PROSTH

Question 1

A complete denture patient presents to the first postinsertion visit with a chief complaint of soreness of the denture-supporting tissues. The MOST likely cause would be

	A.	excessive vertical dimension.
	B.	overextension of the borders.
	C.	unbalanced occlusion.
	D.	overextended post-palatal seal.
	E.	the denture needs a reline.

Answer 1

A. excessive vertical dimension:

The patient is complaining of generalized soreness is important. This is very common when there is excessive vertical dimension. Patients will often comment that they are having difficulty speaking, eating, and generalized intraoral discomfort. If the occlusion is unbalanced, there will be overloading and mucosal changes on the affected side only. An overextended postpalatal seal will cause the patient to complain of a sore throat. Lastly, overextension of the borders will cause soreness only in the border area.

Question 2

The MOST common cause of porcelain separation from porcelain fused to metal restoration is

A.	contamination of the metal before applying the porcelain.
B.	poorly supported porcelain in the crown.
C.	excessive compressive forces within the porcelain.
D.	all of the above.

Answer 2

A. contamination of the metal before applying the porcelain:

Contamination will cause the porcelain to have a poor fusion to the metal substructure. Contamination can be from an oxide layer, oils, water, etc. Poorly supported porcelain is a cause of failure, but is most common in the anterior region. It is not as common as contamination. Compressive forces are responsible for holding the porcelain and providing the strength of the porcelain.

Question 3

All of the following are advantages to using an immediate full denture EXCEPT one. Which one is the EXCEPTION?

A.	Helps protect the extraction sites during healing
B.	Allows the patient to maintain acceptable esthetics during treatment
C.	Allows the patient to maintain acceptable masticatory function during treatment
D.	Assists in the speech adaptation
E.	Provides less postoperative discomfort

Answer 3

E. Provides less postoperative discomfort:

The fabrication of an immediate denture does have several advantages. It allows the patient to maintain acceptable aesthetics during treatment. The patient is never without teeth. It also provides protection to the extraction sites; the patient is usually required to wear this denture for at least 24 hours after the oral surgery procedure, and the denture provides assistance in speech and masticatory adaptation. However, there can be significant pain following the multiple extraction of teeth and immediate placement of the denture. The temporary dentures will not do anything to assist with pain management.

Question 4

Which of the sounds listed below will bring the mandible closest to the maxilla?

	A.	"V" sounds
	B.	"Th" sounds
	C.	"F" sounds
	D.	"S" sounds
	E.	None of the above

Answer 4

D. “S” sounds:

Phonic sounds are very important to the fabrication of complete dentures. These sounds will help determine the placement of the teeth in the acrylic.

• The “f” and “v” sounds are made between the upper incisors and the posterior of the lower lip.
• If the anterior teeth are set too high, the “v” will sound more like an “f”. Also, if the teeth are placed too low, the “f” will sound more like the “v”.
• The “th” sound will help in the labiolingual placement of the teeth.
• With the “s” sound, the important observation is the relationship between the maxillary and mandibular anterior teeth. When this sound is produced, the anterior teeth should approach each other but never touch.

Question 5

What is the recommended range of occlusal reduction for an all-porcelain restoration?

A.	0.5-1.00 mm
B.	1.0-1.5 mm
C.	1.5-2.00 mm
D.	2.0-2.5 mm

Answer 5

C. 1.5-2mm:

For an ALL CERAMIC crown:

• the incisal reduction should be 1.5 to 2 mm
• 1.2-1.5 mm reduction on the facial surface
• 1 mm on the lingual aspects are preferred.
• All line and point angles should be rounded. -
• The finish line should be 1.0-mm-wide.

For a PFM crown the recommended:

• incisal reduction is 2 mm for adequate material thickness to permit translucency in the completed restoration
• Posterior teeth generally require less (1.5 mm) because esthetics is not as critical.
• A minimum of 1.2mm of facial reduction is required and 1.5mm is preferable.
• Minimum 1mm reduction is required for lingual surface.
• The finish line should be 1 mm-wide.

Question 6

Which of the following statements is TRUE concerning the posterior palatal seal?

A.	It is used only during construction of a full denture and should be removed after the last post operative visit.
B.	The outline is the same for all patients.
C.	It should be used with all maxillary partial denture patients.
D.	It helps prevent food from becoming trapped under the denture.
E.	It should be at least 4 mm thick to provide proper retention.

Answer 6

D. It helps prevent food from becoming trapped under the denture:

It is important to note that the posterior palatal seal plays a significant role in the success of the full maxillary denture. It serves to provide a seal, prevents food from becoming trapped under the denture, helps provide retention, and helps compensate for the shrinkage of the acrylic during the processing of the denture. Landmarks for the posterior palatal seal include the posterior outline, the vibrating line, and the anterior outline, which is formed by the blow line. The posterior palatal seal varies in outline and depth from patient to patient. Typically, the posterior palatal seal comes to a thin taper of about 1.5-2mm, any thicker may trigger the patient’ s gag reflexes.

Question 7

In a complete denture case, which of the following is responsible for the path of the condyles in mandibular movements?

	A.	Centric relation
	B.	The degree of compensating curve
	C.	The amount of horizontal and vertical overlap
	D.	The size and shape of the bony fossa
	E.	The vertical dimension of occlusion

Answer 7

D. The size and shape of the bony fossa:

Condylar guidance is determined by the anatomical configuration of the patient’s condyles and condylar fossae. All of the remaining options are directly related to the teeth, which are missing in the complete denture patient. It is necessary to reproduce the condylar guidance on an articulator so that incisal guidance, the compensating curve, and the occlusal plane can all be developed within acceptable limits of the patient’s anatomically configured condylar guidance.

Question 8

Tooth-borne removable partial dentures with both anterior and posterior abutments for all clasps, and the presence of anterior teeth are classified in Kennedy Class

A.	I.
B.	II.
C.	III.
D.	IV.

Answer 8

C. Kennedy Class III:

is the best-known classification system for partial denture cases. While there probably will not be detailed questions on this system, you should know the major divisions.

• Class I: is bilateral distal extension
• Class II: is unilateral distal extension
• Class III: is the case of spaces with both mesial and distal abutments (tooth-borne partials)
• Class IV is the case of missing bilateral anteriors with posteriors remaining on both sides.

Modifications (Mod), refer to additional edentulous spaces. As an example, a case of bilateral distal extension, and a missing central incisor would be a Class I, Mod I case.

Question 9

Which of the following denture teeth is BEST for a patient with opposing natural dentition?

A.	Monoplane porcelain
B.	Anatomic porcelain
C.	Monoplane plastic
D.	Anatomic plastic

Answer 9

D. Anatomic plastic:

The anatomic teeth will be easiest to articulate properly with the natural dentition, and they will give the patient the best function. Plastic is the material of choice. Monoplane teeth will be difficult to articulate with the natural dentition. Porcelain has been found to be very destructive to the opposing dentition and the residual ridge under the denture.

Question 10

In RPD clasp assemblies, support is located on the _____ third of the tooth, while retention is located on the _____ third.

	A.	occlusal, middle
	B.	occlusal, gingival
	C.	middle, middle
	D.	middle, gingival
	E.	none of the above

Answer 10

B. occlusal, gingival:

As a general rule, support, in the form of the occlusal rest and guiding plane of the clasp assembly, functions primarily in the upper third of the tooth. The middle third is usually the site of reciprocation from the reciprocating arm of the clasp. Retention is usually located in the gingival third, as the retentive arm descends to find an undercut in this third.

Answer: occlusal ⅓ and gingival ⅓.

Question 11

Indirect retention in RPD frameworks is used primarily to

A.	INCREASE retention of the framework.
B.	decrease damaging effects of forces towards tissue.
C.	decrease damaging effects of forces away from tissue.
D.	balance the forces of retentive arms in clasps.

Answer 11

C. decrease damaging effects of forces away from tissue:

Indirect retention is used primarily in distal extension partial dentures. The extension denture base can move away from the tissue base during function, especially chewing of sticky foods. In the maxilla, this movement is downward, and in the mandible it is upward. The denture exerts a strong torquing action on the distal abutment teeth, endangering their periodontal support. This can cause tissue trauma in some patients.

Indirect retention limits the torquing movement by adding rests on teeth more anteriorly. Typically, rests for indirect retention are placed on mesial/occlusal surfaces of premolars, or on cingulum or notch rests of canines. The retention is always placed in a prepared rest seat on the tooth most mesial to the denture fulcrum line, on a tooth with sufficient bony support. Retenative arms are designed with a tapered shape to minimize forces. Located above the height of contour (HOC), the clasps should be passive until the patient tries to remove the appliance. Incisors are seldom used for indirect retention.

Question 12

In a removable partial denture design, the reciprocal arm of a clasp is designed to

A.	run along the mucosa, cross the gingival margin of the abutment tooth and approach the undercut from the gingival direction.
B.	be located below the height of contour.
C.	contact the abutment tooth immediately after the retentive arm reaches its position on the retentive area.
D.	contact the abutment tooth simultaneously with the retentive arm.

Answer 12

D. contact the abutment tooth simultaneously with the retentive arm:

The primary function of the reciprocal clasp is to counter the horizontal forces transferred to the abutment tooth by the retentive arm. The reciprocal arm also serves to stabilize the partial denture along with the other rigid components of the partial denture framework. The reciprocal arm is placed above the height of contour and, therefore, does not act as a direct retainer. The approach arm is designed to run along the mucosa, cross the gingival margin of the abutment tooth and approach the undercut from the gingival direction.

Question 13

What is the proper way to remove a polyvinyl Siloxane® impression for the mouth?

A.	Slow steady pressure
B.	Quick snapping pressure
C.	Walking one side of the impression out and then the other
D.	Apumping up-and-down movement

Answer 13

B. Quick snapping pressure:

A quick snapping motion will allow for minimal distortion of the impression material.

Slow removal or pumping of the impression material will likely cause the material to exceed its modulus of elasticity, which will result in permanent distortion of the impression material. Walking or rocking the impression material out of the mouth will also likely exceed the modulus of elasticity. This permanent distortion of the impression material will result in a poor-fitting cast restoration.

Question 14

Which of the following forces is MOST damaging to a porcelain restoration?

A.	Compressive
B.	Lateral
C.	Tensile
D.	All of the above

Answer 14

B. Lateral forces:

will likely produce shearing forces on a porcelain restoration. Porcelain has very POOR shear strength but is very good against compressive forces. Porcelain restorations rarely will undergo tensile strain, but porcelain’s tensile strength is still better than its shear strength.

Question 15

Which of the following would be considered an indication for a cast post and core?

A.	Perforation of the root
B.	Endodontically treated teeth
C.	Teeth with severe loss of coronal tooth structure
D.	Desire to strengthen the remaining tooth structure
E.	All of the above

Answer 15

C. Teeth with severe loss of coronal tooth structure:

A cast post and core is used in the restoration of endodontically treated teeth. Very often, teeth that have been endodontically treated have lost much of the coronal tooth structure as a result of caries, previously placed restorations, or in preparation of the endodontic access cavity. In this case, a cast post and core is the treatment of choice. It consists of a core, which replaces the part of the destroyed crown, and a post, which fits into the root canal and provides retention for the core. Generally, as a separate procedure, a cast crown is placed over the post and core to restore form, function, and esthetics. It should be noted that this procedure does not strengthen the tooth, but provides only a means of retaining the core.

Question 16

Recall visits for a patient with cast restorations should be at least every

	A.	3 months.
	B.	4 months.
	C.	6 months.
	D.	9 months.
	E.	12 months.

Answer 16

C. 6 months:

Patients who received treatment that included cast restorations should be recalled at least every 6 months. Failing to adhere to this recall schedule could lead to an oversight of recurrent caries or the development of periodontal disease. Patients who completed treatment plans that included more extensive fixed prostheses should consider a more frequent recall schedule (~3 months), especially if periodontal disease was present initially.

Question 17

Which type of major connector should be used for a mandibular removable partial denture in a patient with mobile anterior teeth or periodontal involvement of the anterior teeth?

A.	A lingual plate
B.	A lingual bar
C.	A labial bar
D.	Double lingual bar

Answer 17

A. Lingual plate (LP):

is similar to the lingual bar thinned out to extend onto the lingual surfaces of the teeth with a scalloped edge. Superior border of this major connector (MC) rests on the lingual surfaces of the teeth above the cingula (knife edge). It Must close the interproximal spaces at the level of contact point. Inferior border is placed as low as possible without interfering with the function of the floor of the mouth. It is the MC of choice when there is insufficient vertical space and periodontally compromised teeth.

Lingual bar is the most frequently used major connector (MC), it is half-pear shaped in cross section, the broadest portion of the bar is located at the inferior border. At least 8 mm of vertical space should be available between the Free Gingival Margin (FGM) and the floor of the mouth, allowing for 5 mm height of the bar and 3 mm space between the FGM and the bar.

Double Lingual Bar (Kennedy Bar) provides minimum coverage. It displays characteristics of both lingual bar and plate, it is basically two bars not joined by a continuous sheet of metal. The advantages of this MC design are that it preserves the health of the remaining dentition. The two most common disadvantages are that it may be a potential food trap and may irritate the tongue.

The Labial Bar runs on the facial surface of the mandibular teeth. It is only used when the placement of the lingual major connector is impossible due to the presence of an interference such as large mandibular tori. It is also indicated when teeth have extreme lingual inclination. Advantages: It is MC of choice in situations where other MC cannot be used. The Disadvantages are: Poor patient acceptance, poor aesthetics and uncomfortable to the patient.

Question 18

Ante’s law is associated with the

A.	crown to root ratio.
B.	degree of tipping allowable in an abutment tooth.
C.	degree of taper of the walls of a crown preparation.
D.	amount of curvature acceptable in the plane of occlusion.
E.	degree of periodontal surface area.

Answer 18

E. degree of periodontal surface area:

Ante’s law is a generalized rule that focuses on the periodontal surface area of the abutment teeth and the teeth to be replaced. It states that the pericemental area of the roots of the abutment teeth must equal or surpass the original pericemental surface area of the roots being replaced by the fixed prosthesis. This law is designed to assure that the load on the abutment teeth does not overburden the supporting structures. For example, when a patient may have lost a mandibular right first molar and second premolar, a four-unit FPD would be indicated, as long as the abutments have a healthy periodontium, because the second molar and first premolar abutments have root surface areas approximately equal to those of the missing teeth. However as per Ante’ s law, if the first molar and both premolars are missing, an FPD may be a risk because the missing teeth have a greater total root surface area than the potential abutments (canine and the second molar).

Question 19

The altered cast technique is used to obtain

A.	a static impression of the edentulous ridge.
B.	a static impression of selected supporting areas and an anatomic impression of non-supporting areas.
C.	an anatomic impression of the edentulous ridge.
D.	a preliminary impression.

Answer 19

C. an anatomic impression of the edentulous ridge:

It is possible that the residual ridge will not support a partial denture when the denture is under occlusal loading. This will leave all stress being transferred to the abutment teeth as if the distal extension was cantilevered from the abutment tooth. The objective is to ensure that both the residual ridge and the abutment teeth support the prosthesis, allowing the stresses to be shared between the two support systems. This cannot be achieved by the use of a single impression. The altered cast technique will relate the extension base functionally to the supporting teeth to provide a much more stable denture.

Question 20

In casting a complete gold crown, ________________ softens the alloy and increases malleability for finishing.

	A.	the lost wax technique
	B.	investment
	C.	soldering
	D.	quenching
	E.	crucibles

Answer 20

D. Quenching:

involves rapidly cooling a casting in water, which serves to soften the alloy and increase the malleability for finishing.

The lost wax technique is the overall technique in which a wax mold is invested in ceramic, heated to melt the wax, and molten metal is inserted into the empty space left behind.

Investment can be gypsum-bonded, phosphate-bonded, or silica-bonded depending on the types of metals used.

Soldering is the procedure in which metal components are joined by heating a piece of metal that melts at a temperature slightly lower than the metals that are to be joined together.

Crucibles are the vessel used to hold everything together and should only be used with one type of alloy to prevent contamination.

Question 21

Inadequate interocclusal distance with complete dentures could result in all of the following except:

A.	muscle soreness.
B.	facial distortion.
C.	soreness of the denture-supporting tissues.
D.	a clicking sound during normal conversation.
E.	angular cheilitis.

Answer 21

E. Angular cheilitis.

Excess interocclusal distance (excess freeway space, collapsed occlusal vertical dimension = low VDO) can lead to angular cheilitis, temporomandibular joint damage, facial distortion and loss of muscle tone.

Inadequate interocclusal distance (excessive occlusal vertical dimension = high VDO) leads to a stretched appearance (facial distortion), the lips do not touch when the patient is at rest, elevator muscles cannot complete their contraction, hence, they become sore. This also results in damage to the denture supporting tissues causing their soreness, ischemia and resorption and speech problems (clicking of the teeth when the patient speaks).

Question 22

Shade selection should NOT be conducted under fluorescent light BECAUSE fluorescent light is heavier in which wavelengths?

	A.	Red and yellow
	B.	Blue and violet
	C.	Red and blue
	D.	Blue and green
	E.	None of the above

Answer 22

D. Blue and green:

Shade should ideally be selected under color-corrected light, and under at least one other type of light. Color-corrected light has a balance of wavelengths in equal proportion and represents the same light as natural sunlight. Other types of light can show how the crown will appear in different conditions. Indoor fluorescent lighting tends to have strong blue and green wavelengths. Incandescent lighting will have strong red and yellow wavelengths and will bring out the red and yellow tones of a shade when the crown is observed under that light. It is important to remember that metamerism cannot always be avoided, regardless of using more than one light source during shade selection.

Question 23

Which of the following is NOT TRUE of base metal partial denture frameworks, as compared to gold alloy frameworks?

A.	They are MORE ductile.
B.	They require higher melting temperatures.
C.	They are MORE difficult to grind during adjustment.
D.	They are less expensive.
E.	They are stiffer.

Answer 23

A. They are MORE ductile:

Ductility is the ability of the metal to be drawn into wire. Gold is very ductile, but base metal alloys are much less so. The most common partial denture frameworks are made with base metal alloys. An example of a common brand name is Vitalliumreg. The alloys usually contain nickel, cobalt and chromium in varying degrees. Chromium, in particular, is valuable in helping the alloy to resist tarnish. Base metal alloys tend to be harder and more brittle. They have a high modulus of elasticity (high stiffness), lower yield strength (can break under less force) and are lower weight than are noble alloys. They are more difficult to adjust and polish, and care must be taken in bending base metal clasps. They require special casting equipment and much higher temperatures than gold. Their cost is significantly less than gold. Tin is not commonly used in these frameworks.

Question 24

What is the anatomical landmark commonly used to signify the location for the posterior border of a maxillary denture?

A.	Tensor veli palatini
B.	Fovea palatini
C.	Tuberosity
D.	Vibrating line

Answer 24

B. Fovea Palatini:

They are two small pits or depressions in the posterior palate, one on each side of the midline. They may be useful in identification of the vibrating line because they occur within 2 mm of vibrating line.

Tensor veli palatini: The tendon of the muscle runs across the hamulus to reach the soft palate. It is not clinically discernible.

Tuberosity: An important denture support area. It also provides resistance to horizontal movements of the denture. The denture posterior border extends beyond the tuberosity.

Vibrating line: is not a true anatomical landmark. It is an imaginary line that extends through the hamular notches bilaterally and marks the junction of the movable and immovable tissues of the palate However, it is the maximum posterior limit of the maxillary denture.

Please also note: Hamular Notch - This narrow cleft extends from tuberosity to the pterygoid muscles. Capturing of the hamular notch in the impression is critical to the retention of the maxillary denture. Improper molding of this area could lead to soreness and the loss of retention. The posterior extent of the denture (the vibrating line) runs bilaterally through the hamular notches.

Question 25

Which of the following cements requires the use of a cavity varnish or liner prior to placement? ``` A. Zinc phosphate B. Glass ionomer C. Zinc polycarboxylate D. Zinc oxide/eugenol E. Resin composite ```

Answer 25

A. Zinc phosphate cement: has good compressive strength but has a very low pH at the initial mixing. When zinc phosphate is used as a luting agent, it is recommended that it be mixed in small increments over a large area of a glass slab to dissipate the heat generated during the exothermic reaction. Also, it is recommended that a thin layer of cavity varnish/liner be applied over the preparation prior to cementation of the crown or bridge, especially if the preparation is close to the pulp.

Question 26

Which of the following direct retainers should be considered when esthetics is of concern? A. Intracoronal attachment B. Wrought wire C. Bar clasp D. Circumferential clasp

Answer 26

A. Intracoronal attachment: One of the disadvantages of treatment planning a traditional metal clasp partial is the compromise in esthetics. Many times, it is difficult to place the clasps in an area that is aesthetically pleasing. Patients with this problem should consider a fixed partial denture. In cases where this cannot be the treatment of choice, another option would be to place intracoronal attachments. These can be either semi-precision or precision attachments. This type of attachment is built into the contour of a crown, and it produces both a mechanical and frictional retention.

Question 27

Which of the following is an acceptable reason to use solder on a cast crown? ``` A. To add contact B. To fill in an occlusal opening C. To repair a marginal gap D. All of the above E. None of the above ```

Answer 27

A. to add contact: On occasion, it is necessary to add solder to a cast restoration to increase the contact with the adjacent teeth. In the case of a full cast crown, the entire crown would be heated with solder attached; the solder melts and becomes incorporated as part of the restoration. The solder will melt due to the fact that its melting point is lower than that of alloy in the cast crown. It is important to remember that solder cannot be used to repair marginal gaps. When used as a means to increase the contact between teeth, solder can be modified with a disk or polished down until the proper fit is attached. Also, it is not recommended to be used to fill occlusal openings. These openings or holes may indicate the lack of occlusal reduction.

Question 28

What metal may sometimes cause unsightly "greening" of porcelain? ``` A. Gold B. Silver C. Nickel D. Platinum E. Palladium ```

Answer 28

B. Silver: Gold, platinum, palladium, and silver are the major components of noble metal casting alloy. Zinc, tin, and indium are trace elements useful for aiding the bonding between metal coping and porcelain. Silver and palladium "whiten" the alloy, and alloys with high silver/palladium content are silver/white in appearance. High silver content can cause a detrimental greening of porcelain, as can copper, though copper is not commonly used in these alloys. This is because silver tends to tarnish or have a reaction to moisture overtime.

Question 29

Which of the following describes brightness when color is being discussed? ``` A. Chroma B. Value C. Hue D. Intensity E. Translucency ```

Answer 29

B. Value: The three dimensions of color are its hue, chroma, value, and translucency. Value is the relative lightness (brightness) or darkness of the hue (color). Value decreases as the darkness increases. Chroma is the intensity or saturation of the color tone (hue), i.e. light green or dark green. It is used to describe, the orange or yellow hue of a tooth or a restoration. Hue is the color tone, i.e. red, blue, yellow, green. The term "hue" is the same as the term "color", and it is used to describe the color of a tooth or a prosthesis. As the teeth age, the enamel becomes thinner. The intensity of the basic hue can be different in allowing the dentin to dominate the shade of the tooth. Translucency is the three-dimensional representation of value. Highly translucent teeth tend to be lower in value, since they allow light to transmit through the tooth and pick up the darkness of the oral cavity and the surrounding environment. More opaque teeth allow less light transmittance; they are more reflective in nature and, therefore, appear brighter. The cervical third of a tooth contains the highest chroma and the lowest value, whereas the slightly lower chromas are at the middle third. The transition to transparency at the incisal 1/3rd minimizes the chroma, thereby letting the opulence effects to take place at the incisal edge.

Question 30

What is the BEST way to INCREASE the strength of cold cure acrylic resin used in repairing a broken denture? A. Placing the cold cure resin in hot water B. Placing the cold cure resin in cold water C. Allowing the resin to cure on the bench top D. Placing the cold cure resin in a pressure pot

Answer 30

D. Placing the cold cure resin in a pressure pot: Placing the curing resin under pressure will cause the resin to increase in density. Placing the resin in hot water will cause the reaction to increase and the resin to cure more quickly-but if the water is too hot, the uncured monomer will boil, resulting in voids in the cured resin. If the resin is placed in cold water, the reaction rate will be slowed, but the final product will be the same. Letting the resin cure naturally on the benchtop will not have much effect on the strength.

Question 31

The preparation of a full gold crown involves the occlusal reduction of ``` A. 1 to 1.5 mm. B. 2.0 to 2.5 mm. C. 2.5 to 3.0 mm. D. 3.0 to 3.5 mm. E. none of the above. ```

Answer 31

A. 1 to 1.5 mm: The object of preparing a tooth for a full cast gold crown is to provide a tooth surface free of undercuts, allowing complete seating of the casting and providing sufficient occlusal and proximal reduction for adequate thickness of restorative material. The minimum recommended clearance is 1 mm. It is recommended that occlusal reduction follow normal anatomic contours to conserve tooth structure. Axial reduction should parallel the long axis of the tooth while allowing for the recommended 6 degrees of taper or convergence between opposing axial surfaces.

Question 32

The first step in taking a face-bow transfer record would be to A. establish centric relation. B. equilibrate the plane of occlusion. C. establish the vertical dimension of occlusion. D. set the articulator condylar inclination. E. establish the location of the hinge axis point.

Answer 32

E. establish the location of the hinge axis point: The face-bow is designed to relate the maxillary cast to the condylar elements of the articulator in the same way that the maxillary arch is related to the temporomandibular joint. The condyles are placed in centric relation through manipulation at the time of occlusal registration with the protrusive relation being verified with a check bite. If the face-bow transfer is done correctly, the arc of closure should be identical to that seen in the patient. Therefore, because this is a record of the patient's maxilla/hinge axis relationship, it is necessary to establish the location of the axis point.

Question 33

Which of the following cements adheres to tooth structure and is very susceptible to moisture contamination? ``` A. Zinc oxide/eugenol B. Zinc phosphate C. Polycarboxylate D. Glass ionomer E. All of the above ```

Answer 33

D. GI: Glass ionomer cement is susceptible to moisture contamination and adheres to tooth structure. Zinc oxide eugenol cement is biocompatible and provides excellent seal. It does not adhere to tooth structure.

Question 34

Selection of mold of anterior prosthetic teeth for an edentulous patient should be based on all of the following except: ``` A. Former casts of patients teeth. B. Patients stated preferences. C. High smile line. D. Interalar distance. E. Occlusal plane position. ```

Answer 34

E. Occlusal plane position: The occlusal plane position will determine the positioning of the prosthetic teeth and not influence their selection. If the patient was satisfied with his or her previous appearance, former casts provide ideal sources of information. Patient preferences are vital in selecting the anterior teeth mold. High smile line that displays a lot of gingiva would benefit from selection of a less tapered mold with a long contact point. It is an observation that the midline of canines are in vertical alignment with the outer edge of the ala of the nose, hence many manufacturers have provided with an interalar guide selector for selecting the mold of the artificial teeth.

Question 35

Posterior palatal seals (post dam) are added to maxillary complete dentures primarily to A. prevent saliva from reducing retention. B. aid in producing "T" sounds. C. reduce flexing of a wide area of acrylic. D. INCREASE retention against torquing forces. E. prevent loosening action from chewing of posterior teeth.

Answer 35

D. INCREASE retention against torquing forces: Pressure exerted on the maxillary anteriors of a complete denture, in an outward direction, causes the denture to torque, or rotate forward out of the mouth. Your patient often uses this action to remove his dentures. The post dam or palatal seal helps create a suction, which resists this force. The post dam presses slightly into soft palate tissue slightly posterior to the hard palate. Its does not prevent saliva from entering. Some small amount of saliva is present normally, and actually increases retention. "T" sounds are produced just behind the lingual surfaces of the maxillary anteriors, not in the soft palate. The thickened portion of acrylic will strengthen the denture slightly, but this is not its purpose. The loosening counteracted by the post dam comes from the rotating action of force on the anteriors, not from chewing on the posteriors. Straight downward force on the posteriors will seat, not dislodge, the denture.

Question 36

A record of protrusive relation is obtained in order to A. adjust the path of the incisal guide pin. B. establish intercondylar distance. C. verify centric relation. D. adjust the condylar inclination of the articulator. E. establish the Bennett angle.

Answer 36

D. adjust the condylar inclination of the articulator: The protrusive record is necessary to set the angle of condylar incline on the articulator in an anterior-posterior direction. The incisal guidance is determined by the location of the anterior teeth and their relation in protrusive movement. The lateral records are used to set the Bennett angle. The intercondylar distance is transferred to the articulator by the use of a face-bow.

Question 37

Indium is known in prosthodontics primarily as a ``` A. contaminant in FPD frameworks. B. component of base metal RPD frameworks. C. metal of high ductility. D. component of wrought wire. E. metal that forms a useful oxide. ```

Answer 37

E. metal that forms a useful oxide: Indium, Tin, and Zinc are sometimes present in trace amounts in noble metal coping alloys for metal/ceramic crowns. The primary metals in these alloys are gold, silver, palladium, and platinum. The trace elements of indium, zinc and tin, form oxides at the metal surface which aids in the bonding of the first layer of opaque porcelain to the metal coping. The only option which addresses oxide is, the others discuss other various characteristics of metal.

Question 38

What would be the major advantage to fabricating immediate full dentures? A. Both the maxillary and mandibular denture can be constructed at the same time. B. The maxillary denture can be constructed first. C. The mandibular denture can be constructed first. D. The ability to duplicate the position of the natural teeth. E. All of the above

Answer 38

D. The ability to duplicate the position of the natural teeth: An immediate complete full denture is designed for placement immediately after removal of the remaining natural teeth. Patients usually receive an immediate denture as their initial prosthesis. Immediate dentures offer several advantages. Because a patient receives the denture immediately after the remaining teeth are removed, the natural teeth serve as a guide for positioning of the denture teeth providing an appearance that is usually excellent. Also, the patient is spared the needless embarrassment of having to appear without teeth. The immediate denture can also protect the surgical site.

Question 39

The following are noble metals used to fabricate metal-ceramic restorations: ``` A. Gold, palladium, and nickel B. Gold, silver, and palladium C. Gold, silver, and platinum D. Gold, platinum, and cobalt E. Gold, platinum, and palladium ```

Answer 39

E. Gold, platinum, and palladium: Noble metals: Gold, platinum, and palladium are considered the noble metals. Silver is not noble as it is reactive and causes “ greening” . High noble alloys are > 60% in weight with a gold content > 40%. Noble alloys have a content in weight > 25% and are usually combined with a non-noble metal. Noble alloys do not have stipulations on the amount of gold present. Non-noble metals: copper, silver, or cobalt. Base metals: Nickel, Chromium, Beryllium, and Titanium.

Question 40

What metal is NOT found in noble metal alloy systems? ``` A. Gold B. Platinum C. Palladium D. Silver E. ALL of the above are found in noble metal alloys ```

Answer 40

E. ALL of the above are found in noble metal alloys: Gold, platinum, palladium, and silver are the major components of noble metal casting alloy. Zinc, tin, and indium are trace elements useful for aiding the bonding between metal coping and porcelain. Silver and palladium "whiten" the alloy, and alloys with high silver/palladium content are silver/white in appearance. High silver content can cause a detrimental greening of porcelain, as can copper, though copper is not commonly used in these alloys.

Question 41

In Kennedy Class I or Class II applications, the indirect retainer should be located on A. The disto-occlusal fossa of the most posterior abutment tooth. B. The lingual surface of incisors. C. A tooth farthest from the fulcrum line, capable of withstanding the dislodging forces. D. Tooth closest to the fulcrum line, capable of withstanding the dislodging forces.

Answer 41

C. A tooth farthest from the fulcrum line, capable of withstanding the dislodging forces: The primary fulcrum line passes through the most posterior abutments on each side of the arch. To prevent displacement of the extension base away from the tissues the indirect retainer must be positioned on the opposite side of the fulcrum line. The greater the distance between the fulcrum line and the indirect retainer, the more effective it will be. Hence, the ideal position would be a tooth farthest from the fulcrum line capable of withstanding the dislodging forces. Rest seats on the distal surface of the most posterior teeth will function as occlusal rests and NOT provide indirect retention. Rest seats on mandibular canines and on maxillary and mandibular incisors for indirect retention are planned only when rests on other favorable locations would be contraindicated.

Question 42

Which of the following statements is TRUE for the selection of a sprue when casting a full gold crown using a centrifugal casting machine? A. Should be placed near the margin of the restoration B. Should be placed at right angles to the surface C. Should be placed in a bulky area D. Should be placed on the occlusal table

Answer 42

C. Should be placed in a bulky area: The sprue must be attached to the pattern at the bulkiest portion so that the molten metal enters at an area that allows easy flow and prevents premature cooling. Angle placement of the sprue should allow the metal to enter without making a sharp turn. If the sprue is attached at right angles to the surface, the incoming metal would bounce and result in turbulence that could produce porosity in the casting. Placement at the margins or at the occlusal surface would compromise the final seat of the restoration when the sprue is eventually cut off.

Question 43

What is the major reason for using cast crowns as abutments for clasp-retained RPDs? ``` A. To INCREASE abutment strength B. To add needed crown length C. To allow for precision attachments D. To provide proper form and contour E. To reduce carious lesions caused by poor hygiene under clasps ```

Answer 43

D. To provide proper form and contour: If a removable partial denture is to be fabricated to fit a crown, the crown can be designed to have ideal abutment tooth form. This can include flat guiding planes, deep, well-designed occlusal rest, good retentive gingival undercut, etc. In brief, the crown can be a perfect abutment at a level of perfection never found in natural teeth Crowns may or may not increase abutment strength. They tend to strengthen weak teeth, such as endodontically treated teeth, but may weaken other teeth due to tooth structure loss during preparation. Crowns can add additional crown length. This may be positive or negative. For example, greater crown length increases crown/root ratio. Crowns are needed for use on precision attachments, which generally fit into slots of prepared crowns. They may also reduce the rate or progression of caries under clasps, though decay may still occur at the crown margin if the hygiene is poor. However, these last few reasons are not the primary reason for fabricating a crown for use with a removable partial denture.

Question 44

In complete denture fabrication, it is critical that centric relation records be accurately taken to ensure that A. centric occlusion can be in harmony with centric relation. B. a face-bow record can be taken accurately only after centric relation has been established. C. vertical dimension of rest is in the same position as centric relation. D. centric relation must be accurately recorded so that the Bennett angle can be measured. E. centric relation and maximum intercuspal position are synonymous.

Answer 44

A. centric occlusion can be in harmony with centric relation: Complete denture occlusions have certain common factors in their designs. In most cases, the teeth in the upper and lower dentures contact in "centric occlusion" when the mandible is in centric jaw relation to the maxillae. Tooth contacts in this relationship are established to optimally distribute stresses over the entire denture base supporting area to preserve the supporting structures that must carry the loads during function.

Question 45

The physiologic rest position is BEST defined as A. the position when all of the mouth's supporting muscles of mastication are in their resting position. B. maximum intercuspal position. C. centric relation. D. movement of the mandible from the first slight premature tooth contact to the maximum intercuspal position.

Answer 45

A. The physiologic rest position of the mandible is when the mandibular musculature is in a state of minimal tonic contraction, to maintain posture and overcome the force of gravity. When the mandible is in this position, the teeth are not usually in contact. The interocclusal distance between the incisal and occlusal surfaces of the maxillary and mandibular teeth is normally between 2 to 6 mm.

Question 46

Where are the GREATEST occlusal forces found in the mouth? A. Incisor region B. Bicuspid region C. First molar region D. Second molar region

Answer 46

D. Second molar teeth: because they are closest to the temporomandibular joints (TMJ). Every joint in the body acts as an integral component of a lever system. Levers are the most efficient work principles known to man, especially Class I levers. Class I levers are situated with the load on one end, the fulcrum or pivot point in the center of the lever arm, and the effort applied to the end of the lever opposite from the load. Class II levers are situated with the fulcrum under one end, the effort applied upward under the other end, and the load pressing down in the middle of the lever arm. Class III levers are those in which the fulcrum lies underneath one end, the effort applied is located in the middle of the lever arm and is being applied upwards, and the load is situated at the end opposite the fulcrum and is applying a force downwards. When we bite an apple, the work is getting done in the location of the front teeth, effort is being applied in an upward direction at the middle of the lever arm and fulcrum is at the jaw joint (F). This is a class III lever. This is not as efficient as a class II lever and hence forces are lesser than that will be produced when the mandible acts as a class II lever. When we chew with our molars (W), mandible works as a class II lever: The fulcrum is still at the temporomandibular joint (TMJ), but now the food ("load") is approximately in the middle of the lever arm and the effort is being applied upward and is at the far end of the lever arm from the fulcrum. For example, when using a nutcracker to open a nut. Placing a nut near the hinge of the device would generate greater force than placing the nut near the opening of the nutcracker. The second molars are closest to the fulcrum (TMJ), hence the greatest occlusal forces should be generated at the second molars.

Question 47

Which of the following is NOT a disadvantage of addition silicone? A. High cost B. Poor dimensional stability C. Hydrophobicity D. Difficulty in pouring the impression

Answer 47

B. Poor dimensional stability: ``` Addition silicones such as vinyl polysiloxanes are: PROS - dimensionally stable - have a short setting time CONS - expensive - extremely hydrophobic. Due to their hydrophobicity and poor wetting, bubbles can easily form when pouring. Hydrophilic formulations have been recently introduced to circumvent these disadvantages. ```

Question 48

The decision to incorporate a tooth as an abutment in a fixed partial bridge should be based upon all of the following EXCEPT one. Which one is the EXCEPTION? ``` A. History of endodontic treatment B. Periodontal condition C. Tooth alignment D. Crown to root ratio E. The number and shape of the roots ```

Answer 48

A. History of endodontic treatment: It is important to consider all of the choices listed, with the exception of whether the tooth has been endodontically treated. If the tooth is restorable, the periodontal condition is stable, and the crown to root ratio is acceptable, then a crown can be placed. Endodontically treated teeth can be restored in a number of ways, including post and core or core buildup followed by the placement of a single crown or an abutment tooth for a bridge.

Question 49

Retention form of crowns on short crown preps can be INCREASED through all of the following EXCEPT A. stronger cement. B. INCREASED parallelism of walls. C. grooves. D. all of the above INCREASE retention form.

Answer 49

A. stronger cement: It may seem like the question is splitting hairs or is excessively picky, but this concept is often tested. While strong cement can increase the retention of a crown, cement properties are not part of the retention form of the preparation. Parallel walls (Choice B) increase retention form, as do vertical grooves (Choice C) in the preparation. Both make it harder to dislodge the crown in a vertical direction. Conical preps on short teeth, in particular, have low retention.

Question 50

All are advantages to condensation silicone impression material EXCEPT one. Which one is the EXCEPTION? ``` A. Records surface detail well B. Pleasant odor and taste C. Excellent elastic properties D. Good shelf life E. Impression can be kept for a long time before pouring cast ```

Answer 50

E. Impression can be kept for a long time before pouring cast: CONDENSATION SILICONES: impression materials have several advantages. These materials are less expensive than the polyvinyl siloxanes and polyethers. PROS - excellent shelf life - can be stored unused for approximately one year before they start to break down. - pleasant odor and a taste that patients tolerate well, which allows practitioners to capture detail in impressions CONS - dimensionally unstable if they are not poured immediately, within 30 minutes of removal from the patient's mouth. They will shrink because of the evaporation of ethanol, which is a by-product of the polymerization process.

Question 51

Which of the following is NOT a characteristic of zinc phosphate cement, when used for luting? A. The mixing reaction is highly exothermic. B. The mixing is begun with one very small powder increment. C. The mixing is done rapidly on a chilled glass slab. D. The consistency for luting is thinner than the base consistency.

Answer 51

C. The mixing is done rapidly on a chilled glass slab: This choice is correct because mixing of the cement is performed slowly in small increments on a chilled glass slab. The mixing of zinc phosphate powder and liquid is highly exothermic (heat-producing) (Choice A). It is mixed on a large cooled glass slab. Before dispensing the liquid, the powder is divided into six-seven small even portions. Following the dispensing of the liquid, each of the portions of the powder is mixed one at a time (Choice B) slowly and carefully (Choice C). This action slows the setting reaction. More powder can then be added in increasingly large increments until the desired consistency is reached. This consistency is thinner than that of zinc phosphate base mixture (Choice D. Fresh zinc phosphate has a low pH (acidic) and can be a pulpal irritant. Preparations are often coated with several coats of varnish before cementation with zinc phosphate.

Question 52

Which statement is TRUE concerning use of rubber base (polysulfide) material for partial denture impressions? A. Impressions are usually completed in a stock tray. B. Impressions can stay unpoured for 3-4 hours without distortion. C. Impression material should have a uniform thickness. D. Impression material should generally exceed 5 mm in thickness for adequate strength. E. None of the above

Answer 52

C. Impression material should have a uniform thickness: Polysulfide material is relatively accurate and inexpensive. It provides a very smooth surface for the cast. It MUST be used in a CUSTOM tray to minimize its thickness. Beyond 3 mm of thickness, it loses accuracy. Therefore, it is never used in a stock tray, which would have very thick areas of polysulfide after setting. Thickness is not needed for strength; instead, thickness is avoided for accuracy (1-1.5 mm of thickness is considered adequate or acceptable). Polysulfide rubber base distorts rapidly and should always be poured soon after impression (within 1 hour maximum, but some sources will say within 10-15 minutes for best results). Because of that, these impressions are never sent to an outside dental laboratory unpoured. The material distorts and tears easily, so it should be handled with care before completing the casts to ensure the most accurate pour possible.

Question 53

Immediate dentures over time become ill-fitting BECAUSE of the recontouring and healing of the ridge. At what point after insertion should the denture be relined? ``` A. 3 to 4 months B. 5 to 8 months C. 8 to 10 months D. At least 1 year after delivery E. It is NOT critical when you reline the denture ```

Answer 53

C. 8 to 10 months: An immediate denture is a denture that is inserted immediately upon extraction of the remaining teeth (usually the anterior teeth). Often the fit, appearance, and comfort cannot be predicted. This is because a wax try-in cannot be completed in advance to show you how the denture will look, how well the patient will be able to function, and how well the denture will fit. After approximately 8 to 10 weeks, an immediate denture will require a definitive reline or should be replaced with a new denture. This is because during the healing phase, the bone and gingiva will undergo remodeling and shrinkage, leading to an ill-fitting denture. Immediate dentures often require tissue conditioning or temporary liners during the healing phase.

Question 54

A patient who wears a complete mandibular denture presents to your office with the chief complaint of burning sensation in the lower anterior region. The MOST likely cause would be A. excessive pressure on incisive foramen. B. excessive pressure on mandibular tori. C. premature occlusal contacts. D. excessive pressure on the mental foramen. E. insufficient interocclusal space.

Answer 54

D. excessive pressure on the mental foramen: A patient wearing a complete mandibular denture who experiences excessive pressure from the mandibular buccal flange in the region of the mental foramen may complain of burning, tingling, or numbness in the anterior region of the mouth and the lower lip. This is the result of impingement on the mental nerve. This occurs when there is excessive resorption of the mandibular residual ridge causing the mental foramen to be located near the crest of the bone. Relief may be required in the mandibular denture base in this region.

Question 55

The distobuccal extension of a mandibular impression for a complete denture is limited primarily by the action of which muscle? ``` A. Medial pterygoid B. Masseter C. Buccinator D. Superior constrictor E. Lateral pterygoid ```

Answer 55

B. Masseter: The insertion of the masseter is on the lateral side of the ramus and angle of the mandible. If you poke your finger into the distofacial vestibule of the mandible and push backwards, you will bump into the most anterior section of the masseter. This muscle will thicken on contraction and bulge slightly forward. An overextended mandibular denture will be dislodged by this action. The superior constrictor will limit the distolingual extension of the denture. The medial pterygoid is medial to the mandible and will not contact the distobuccal flange. The lateral pterygoid muscle inserts on the condyloid process of the mandible, so it will not interfere with the fit of dentures. The buccinator will be medial to the masseter at this point, but lateral to the denture base and does not exert force at the distofacial corner of the denture.

Question 56

A patient wearing a mandibular complete denture that is underextended and is short of the retromolar pad may experience which of the following? A. Apposition of bone on the ridge B. Significant resorption C. Irritation of the soft tissue under the denture base ridge D. No net effect will be seen on the alveolar ridge E. None of the above

Answer 56

B. Significant resorption: Mandibular dentures do not rely on suction, but rather covering as much as possible of the basal bone. If the denture were underextended, this would decrease the tissue-bearing surfaces. The bone beneath the retromolar pad is resistant to resorption, and it does provide a small amount of border seal. If the denture is short of this area, an overloading of the mucosa can occur, leading to resorption of the ridge below this tissue.

Question 57

The maxillary major connector type MOST susceptible to undesirable flexing or deformation is the A. Palatal strap. B. Anterior-posterior palatal strap. C. Horseshoe connector. D. Complete palate.

Answer 57

C. Horseshoe connector: Horseshoe connectors consist of a thin sheet of metal covering the palatal surfaces of the remaining teeth and extending on the palatal tissues for 6-8 mm. When vertical force is applied to its ends it flexes or deforms. Hence, not indicated for distal extension situations and when cross arch stabilization is desired. It is indicated when several maxillary anterior teeth are to be replaced. Also, indicated in patients with a large, inoperable palatal torus or an overactive gag reflex where full palatal coverage may not be ideal. Palatal straps cross the palate and are designed to be 8mm wide, as a result, they are rigid. Because the strap is located in two or more planes it offers great resistance to bending and twisting forces. Anteroposterior palatal strap crosses the midline similar to the palatal strap. Each strap should be 8mm wide. The structural encirclement provided by both the straps enhances its rigidity. The shape of the major connector also contributes to its resistance to flexure. Complete palate provides maximum rigidity and support. However, it also has the greatest tissue coverage.

Question 58

The BEST finish line for a full gold cast metal A. a butt joint. B. a shoulder with a small bevel. C. a chamfer D. a knife-edge.

Answer 58

C. chamfer: For a cast metal restoration, a chamfer will provide the best thickness of gold with the most predictable duplication in the laboratory process. A shoulder with a small bevel and a knife-edge do not provide a consistent thickness of gold and often will not produce accurate duplication in the laboratory process. A butt joint can be a good margin for an anterior porcelain crown but proves to be quite poor for cast restorations.

Question 59

Which of the following features, when added to a crown preparation, provides the BEST additional retention? A. A pinhole B. A retentive groove C. A box D. A pothole

Answer 59

C. A box: From most to least retentive: Box> retentive groove> pinhole > pothole Mechanical retention, preparation shape, parallelism, and cement combine to keep the crown restoration in place.

Question 60

The activator in cold cure resin for denture fabrication is ``` A. bis-GMA. B. hydroquinone. C. tertiary amine. D. benzoyl peroxide. E. methyl methacrylate. ```

Answer 60

C. tertiary amine: Acrylic denture resin comes in two forms: cold curing and heat curing. Both contain methyl methacrylate polymer powder, methyl methacrylate monomer liquid, a cross-linking agent, such as ethylene, a catalyst, benzoyl peroxide, and an inhibitor for the monomer, hydroquinone. Once the catalyst, benzoyl peroxide, is activated, polymerization begins. The difference between cold curing and heat curing is what activates the catalyst. In heat cured acrylics: the benzoyl peroxide is activated by: heat. In cold cured acrylics, the benzoyl peroxide is activated by: a chemical activator (accelerator), which is a tertiary amine.

Question 61

A patient presents at the first appointment after insertion of a full denture case with generalized soreness on the crest of the mandibular ridge. The MOST common cause would be A. rough surface. B. inaccurate denture base. C. poor posterior palatal seal. D. premature occlusal contacts.

Answer 61

D. premature occlusal contacts: At the post-op visit, the patient should report back to the dentist any complaints of discomfort or difficulty in function with the denture. The first post-insertion visit should be 24 hours after delivery. Before you start to relieve an area of the denture base, it is important to check the occlusion. If the occlusion is not correct, relieving the denture base will not solve the problem. The patient may still experience the same discomfort after the adjustment. Further occlusal refinement will allow for better distribution of the forces along the edentulous ridge. Other things to look out for during the 24 hour post-op check would be to assess for cheek biting, sore throat/dysphagia, clicking, soreness along the vestibule, or a burning sensation.

Question 62

When considering reversible hydrocolloids, the sol-gel transformation occurs through a ``` A. Constant temperature. B. A physical change. C. Imbibition. D. Syneresis. E. A chemical change. ```

Answer 62

B. physical change: Reversible hydrocolloid is a hydrophilic (water loving), highly accurate impression material. It changes states between solid (gel) and liquid (sol). Note that the sol refers to solution, not solid (the sol is the liquid form -- it is thick and viscous). The change occurs as a physical change, as higher temperatures cause the solid to liquefy, and cooler temperatures cause it to solidify. (Choice A mentions a temperature that is constant.) It is placed on the tooth preparation in a tray, in the heated liquid form (sol), and the tray is then cooled with running water, which causes solid (gel) formation. The gel impression is poured in stone. This change is physical, not chemical (Choice E), and is reversible at high temperatures. Note that imbibition (Choice C) is the taking in of extra water by the hydrocolloid, while syneresis (Choice D) is water release. Both of these processes will distort the impression, and should be avoided; however, they are not responsible for the sol-gel change. Formation of a hydrocolloid sol (liquid) comes from temperature increase, not reduction.

Question 63

Which of the following is NOT TRUE about RPD clasp assemblies? A. The reciprocating arm is shorter than the retentive. B. The reciprocating arm is always placed on the lingual side. C. The reciprocating arm is located MORE coronally than the retentive arm. D. The reciprocating arm flexes less than the retentive.

Answer 63

B. The reciprocating arm is always placed on the lingual side: Clasp assemblies consist of a rest (occlusal, cingulum, etc.), guiding plane minor connectors, a retentive arm and a reciprocating (stabilizing) arm. The retentive arm requires a counterbalancing stronger, less flexible reciprocating arm in order for the retention to be effective. Reciprocating arms are shorter, broader, less flexible, located in the middle third, and are usually placed on the lingual side. Retentive arms are longer, thinner, more flexible, located in the gingival third, and are usually placed on the buccal side. However, tooth form might dictate that the retention is on the lingual and reciprocation on the buccal. There is no absolute rule for this, and it will ultimately be dictated by what the patient needs.

Question 64

The MOST common place for failure in a porcelain fused to metal crown is A. at the opaque layer. B. within the porcelain. C. at the porcelain metal interface. D. within this metal.

Answer 64

B. within the porcelain: Porcelain fused to metal restorations are widely used today in dentistry. The reason is that the combination of porcelain and metal when fused is much stronger than an-all porcelain restoration. True adhesion occurs between the metal and porcelain, creating a very strong bond. The bond strength is so strong that failure of the restoration is most likely in the porcelain rather than at the porcelain-metal interface. Failure within the metal - would be extremely rare.

Question 65

In a patient with less than 7mm of clearance between the lingual frenum and the free gingiva of the lower incisors, what is the BEST major connector to use in a removable partial denture? A. Lingual bar B. Lingual plate C. Double lingual bar D. Labial bar

Answer 65

B. Lingual plate (LP): is similar to the lingual bar thinned out to extend onto the lingual surfaces of the teeth with a scalloped edge. Superior border of this major connector (MC) rests on the lingual surfaces of the teeth above the cingula (knife edge). Inferior border is placed as low as possible without interfering with the function of the floor of the mouth. It is the MC of choice when there is insufficient vertical space and periodontally compromised teeth. Lingual bar is the most frequently used major connector (MC), it is half-pear shaped in cross section, the broadest portion of the bar is located at the inferior border. At least 8 mm of vertical space should be available between the Free Gingival Margin (FGM) and the floor of the mouth, allowing for 5 mm height of the bar and 3 mm space between the FGM and the bar. Double Lingual Bar (Kennedy Bar) provides minimum coverage. It displays characteristics of both lingual bar and plate, it is basically two bars not joined by a continuous sheet of metal. The advantages of this MC design are that it preserves the health of the remaining dentition. The two most common disadvantages are that it may be a potential food trap and may irritate the tongue. The Labial Bar runs on the facial surface of the mandibular teeth. It is only used when the placement of the lingual major connector is impossible due to the presence of an interference such as large mandibular tori. It is also indicated when teeth have extreme lingual inclination.

Question 66

The MOST common cause of porcelain fracture in a porcelain fused to metal pontic is ``` A. excessive vertical overlap. B. excessive horizontal overlap. C. detrimental chewing habits. D. incorrect design of metal backing. E. incorrect design of facing. ```

Answer 66

D. incorrect design of metal backing: The design of the metal framework is very critical when it comes to fabrication of the pontic. If the metal is not stiff enough, the framework could flex. Any deformation of the framework can lead to chipping and fracture of the porcelain. In addition, the location of the external metal-porcelain junction is important. Excessive vertical overlap (overbite), and excessive horizontal overlap, can cause problems with the function of the appliance, but they are not the primary cause of porcelain fracture. Incorrect design of facing, may present issues for soft tissue, but again not the main issue for porcelain. Finally, chewing habits cannot be linked to a pontic design.

Question 67

Optimum length for the root section of a cast post and core is A. 1/3 to 1/2 of the root. B. 1/2 to 2/3 of the root. C. 2/3 to 3/4 of the root. D. GREATER than 3/4 of the root.

Answer 67

C. 2/3 to 3/4 of the root: The cast post and core is used in the endodontically treated tooth to replace missing coronal tooth structure for crown fabrication. The post must be secure within the root, but not excessively weaken the root. Likewise, the post must not extend too far apically, where it might interfere with the apical gutta percha seal. Ideal post length is estimated as 2/3 to 3/4 of the total root length. This gives the proper balance between retention and remaining root strength. Less than this amount will result in increased chance of loss of post. More than this amount can result in an increased chance of root fracture. At least 3-4 mm of well-sealed gutta percha should remain at the end of the preparation. Any less will endanger the apical seal. Any more is likely to interfere with the ability to extend the post 3/4 of the way down the root.

Question 68

During the fabrication of a fixed partial denture for the mandibular arch, the opposing permanent maxillary first molar is extruded 3 mm beyond the plane of occlusion. The BEST way to correct this would be to A. extract the tooth and replace it with a fixed partial denture restored to a satisfactory occlusion. B. intrude the tooth to a satisfactory plane of occlusion. C. reduce and reshape the maxillary 1st molar. D. restore the maxillary 1st molar with a cast restoration to a satisfactory plane of occlusion. E. equilibrate the maxillary molar to the new occlusion at the time the mandibular prosthesis is cemented.

Answer 68

D. restore the maxillary 1st molar with a cast restoration to a satisfactory plane of occlusion: If you were to try to reduce and reshape the occlusal length of the maxillary first molar by 3 mm, you would end up violating the thickness of the enamel of the tooth. The patient may also experience pulp sensitivity or exposure. It would be recommended that you restore the molar with a casting in order to develop the proper plane of occlusion. If you were to try to reduce and reshape the tooth after the fixed partial denture is in place, you would again be removing the enamel to the level of the dentin, thereby leaving the tooth unprotected. Intrusion of molars is a difficult procedure and is not recommended.

Question 69

Several days after the delivery of a fixed partial denture that was cemented with glass ionomer cement, the patient returns to the office complaining of post-treatment sensitivity. What is the MOST likely cause? A. Irritation from the cement B. Desiccation of the prepared dentin surface C. Poor biocompatibility with tooth structure D. Recurrent decay

Answer 69

B. Desiccation of the prepared dentin surface: The primary advantage of using glass ionomer cement is that it releases a significant amount of fluoride, which increases the resistance of enamel and dentin to acid dissolution and acts as a bacteriostatic agent. Additionally, the biocompatibility of glass ionomer is very good with tooth structure. The main disadvantage of glass ionomer cement is its sensitivity to moisture conditions making it critical that the gain or loss of water is minimized during the first 24 hours. Significant desiccation of the dentin prior to cementation and/or bacterial contamination is thought to be the main cause of post-treatment sensitivity in regards to glass ionomer cements. During cementation, proximal contacts, occlusion, intaglio surface, and margins need to be verified for an ideal fit.

Question 70

All of the following are indications of the lingual plate mandibular major connector except A. Insufficient vertical space B. When remaining teeth have suboptimal periodontal support C. When removal of tori is not possible D. Patients with poor oral hygiene

Answer 70

D. Patients with poor oral hygiene Lingual plate is indicated when there is insufficient vertical space (less than 8 mm) between the gingival margins of the teeth and floor of the mouth. When lingual plate is properly designed and contoured it provides excellent rigidity without interfering with functional movements. Lingual plate aids in stabilizing and evenly distributing the forces on the remaining teeth. Hence, it is indicated when the remaining teeth have lost periodontal support and require splinting. Lingual plate is indicated for patients where removal of tori is not possible. Moderate relief must be provided to prevent tissue irritation. Extensive coverage of the lingual plate causes enamel decalcification and soft tissue irritation in patients with poor oral hygiene, hence it is contraindicated when there is poor oral hygiene.

Question 71

Use of a cavity varnish is especially recommended before cementation using ``` A. polycarboxylate. B. reinforced ZOE. C. glass ionomer. D. zinc phosphate. E. calcium hydroxide. ```

Answer 71

D. Zinc phosphate: has a low pH and can be a pulpal irritant. Preparations are often sealed with several coats of cavity varnish (Copalitereg) to seal dentinal tubules and reduce the acidic effects on the pulp. Cavity varnish is not used under ZOE (Choice B). ZOE has a eugenol base, which is soothing, not irritating, to the pulp. Choice A, Polycarboxylate cement (Durelonreg) also has a low pH, but the large polyacrylic acid molecules do not enter the dentinal tubules readily, and therefore it is surprisingly non- irritating. Glass ionomer (Choice C) is generally non-irritating and is not preceded by varnish. Calcium Hydroxide (Choice E) is an example of a liner that can be used to help protect the pulp from chemical irritants. It helps the tooth repair, in hopes that RCT is not necessary. It is placed under dental adhesives, varnishes, fillings, etc. (Ex - Dycalreg).

Question 72

Proper location of a lingual bar major connector for a mandibular RPD is A. coronal to the gingival margin. B. at the gingival margin. C. at least 2 mm below the gingival margin. D. at least 4 mm below the gingival margin. E. at least 8 mm below the gingival margin.

Answer 72

D. at least 4 mm below the gingival margin: The two major types of mandibular major connectors are the lingual bar and lingual plate. The lingual bar is a thick, narrow bar, which connects the two sides, and is placed at least 4 mm below the gingival margin. In this way, it does not impinge on gingival tissue, and acts less as a food and plaque trap. Higher than this will damage gingiva, while much lower may be too low in cases of severe resorption. The lingual plate is the other type, where a thin fan-like section of framework rises out of the lingual bar to cover the lower lingual surfaces of the anterior teeth. The major advantage of this design is that it uses the remaining anterior teeth (often all six), to help spread out torquing forces from the rising of the denture away from the tissue surface. It is not a splint, as it does not actually connect the teeth. It does not aid phonation (speech), as the presence of the metal will cause the patient to make slight speech adjustments. It generally leads to poorer, not better hygiene, as the lingual bar is easier to maintain plaque-free. A labial bar mandibular partial exists, but is extremely rare, as it is almost always possible to keep the major connector on the lingual side. One indication for the labial bar is large inoperable mandibular tori. This might occur in a medically compromised patient who cannot tolerate the surgery to remove the tori. There is never a reason to combine a lingual and labial major connector.

Question 73

Which pontic design should NOT be used in areas of aesthetic concerns? ``` A. Sanitary B. Modified ridge lap C. Concave design D. Saddle E. Conical ```

Answer 73

A. Sanitary: The design of the pontic must assure that there is minimal contact between the gingival portion and the ridge and is compatible to the esthetic considerations. A hygienic pontic does not approximate the ridge. The gingival portion is at least 3 mm off the ridge, and its surface is convex faciolingually and mesiodistally. Because this pontic does not come into contact with the ridge, it provides easy access for cleaning, so the patient can maintain good oral hygiene. This design should be limited to areas where aesthetics is not a concern.

Question 74

The main advantage of using zinc phosphate in cementation of a cast gold crown is ``` A. good compressive strength. B. lack of irritation. C. film thickness. D. low initial pH. E. high initial pH. ```

Answer 74

A. good compressive strength: The primary advantage of zinc phosphate cement is its excellent compressive strength. Its solubility and film thickness is very similar to polycarboxylate. However, it also has the undesirable characteristic of being irritating to the pulp due to a very low pH (3.5) during the initial mixing and setting. Applying two coats of a cavity varnish to the prepared tooth can minimize the penetration of the acid into the dentinal tubules.

Question 75

Purely rotational movement of the mandibular condyle is possible when the mandible is in which position? ``` A. Postural position B. Centric relation C. Centric occlusion D. Maximum intercuspation E. Physiologic rest position ```

Answer 75

B. CR: The rotation of the mandible around a terminal hinge axis is possible only when the mandible is retruded in centric relation. This is a purely rotational movement of the two rami around a horizontal axis connecting the two condyles, and is only possible during the first part of mandibular opening while the jaws maintain a centric relation. Centric jaw relation is the most posterior position of the mandible relative to the maxillae when the mandible is retruded maximally. This is a bone-to-bone relationship between the maxillae and mandible with only a few teeth contacting initially prior to moving into maximum intercuspal position. The physiologic rest position is the position of the mandible when all of its supporting muscles (eight muscles of mastication plus the supra- and infrahyoids) are in their resting posture. The physiologic rest position is further defined as the mandibular position when the person's head is upright, the muscles of mandibular movement are in equilibrium, and the condyles are in an unstrained position. When the mandible is in its physiological rest position, there is a space between the occlusal surfaces of the maxillary and mandibular teeth called the interocclusal distance or freeway space. This space is normally 2 to 6 mm between the incisal and occlusal surfaces of the maxillary and mandibular teeth.

Question 76

The distolingual extension of a mandibular impression for a complete denture is limited primarily by the action of which muscle? ``` A. Medial pterygoid B. Masseter C. Buccinator D. Superior constrictor E. Lateral pterygoid ```

Answer 76

D. Superior constrictor: The superior constrictor connects to the buccinator at the pterygomandibular raphe. It then heads both superiorly and inferiorly from that point. The inferior section will pass down past the distolingual section of the denture, going in the direction of the lower pharynx. Medial pterygoid will be posterior and lateral to this point. Buccinator will be more anterior and superior. Masseter will be lateral to the mandible, and it affects only the distofacial section of the denture. Lateral pterygoid will be far superior to this point.

Question 77

The MOST serious contraindication for fabrication of a fixed partial denture restoration is ``` A. tilted crowns. B. non-parallel abutments. C. bilateral distal extension edentulous spaces. D. endodontically treated abutments. E. rotated abutments. ```

Answer 77

C. bilateral distal extension edentulous spaces: Distal extension cases are not likely to be treated with fixed partial dentures. If several teeth in the distal area need replacement, there will be no distal abutment for the FPD, and too many pontics for a cantilever to be successful. Cantilevered FPD's with long lever arms either result in loss of retention or damage to the support of the abutment teeth. While a one-tooth pontic can be often cantilevered on two sound abutments, you cannot, for example, cantilever 4 missing posterior teeth on two abutments. Tilted crowns (Choice A) are not always contraindications to FPDs. These crowns may need recontouring or endodontic treatment (Choice D) to be used as abutments. Similarly, non-parallel teeth (Choice B) may need adjustment in order to create a path of insertion for the prosthesis. Endodontically treated teeth do not pose special problems in FPD fabrication. Many endodontic teeth should receive full coverage restoration as a matter of course. Rotated abutments (Choice E) are not necessarily a problem either, as the reduction process can recontour them, and the crown restoration can restore normal contour and anatomy.

Question 78

A polysulfide rubber impression material should be poured up immediately BECAUSE A. initial polymerization shrinkage is high. B. the volatile by-products will evaporate. C. they absorb moisture from the air and expand. D. they will distort quickly over time.

Answer 78

D. they will distort quickly over time: Polysulfides exhibit a greater dimensional stability and tear strength than hydrocolloid. However, they should be poured as soon as possible after impression making as delays can result in clinically significant dimensional change. However, the pungent sulfide smell and long setting time present challenges during use on patients. The setting time can be reduced in hot and humid conditions; however, this also results in severe distortion of the final set. Care must also be taken during handling as it can also permanently stain clothing.

Question 79

The two impression materials that produce ethanol and water as a byproduct are: A. Polysulphide and Condensation silicone B. Condensation silicone and Addition siliconereg C. Polysulfide and Polyether D. Polyether and condensation silicone

Answer 79

A. Polysulphide and Condensation silicone: Condensation silicone and polysulphide. The byproduct of this reaction is ethyl alcohol and water.

Question 80

Which of the following movements is potentially MOST damaging to porcelain fused to gold restorations? A. Working interferences B. Non-working interferences C. Premature occlusion D. All of the above are equally damaging to porcelain fused to metal restorations.

Answer 80

B. Non-working interferences: Non-working interferences are the most damaging to porcelain fused to metal restorations. This type of movement will create the greatest shearing forces on the restoration, and porcelain has very poor shear strength. Premature occlusion is not as damaging to the restoration because porcelain has good compressive strength. Working interferences will also provide shearing forces, but the forces will be less, due to proximity to the center of rotation around the condyle.

Question 81

The major reason for treatment planning a 3/4 crown over full coverage is ``` A. less expensive to fabricate. B. less chair time. C. provides a metal occlusal contact. D. to conserve tooth structure. E. less local anesthesia needed. ```

Answer 81

D. to conserve tooth structure: The 3/4 crown allows for the maximal conservation of tooth and is the restoration of choice when there is favorable crown to root ratio, average crown length, and normal esthetics. It should not be used in situations where there is extensive loss of tooth structure and the existing enamel walls are severely weakened. Also, it is contraindicated with patients who have a high caries index.