15. Prosthodontics

Question 1

Dentures

1. 3 indications
2. 3 contraindications
3. 3 advantages
4. 3 disadvantages

Answer 1

1. Multiple missing teeth, fixed pros contraindicated (finances, poor bone/abutment quality, poor prognosis of dentition), provisional post-extraction, low patient motivation for complex treatment, sufficient occlusal contacts
2. Poor prognosis of remaining dentition, untreated/advanced perio disease, TMD, significant malocclusion, signs of pathological wear, functional SDA
3. Simple, removable, restore function and appearance, no tooth destruction, cost effective
4. Plaque retentive factor, denture stomatitis, unaesthetic clasps, compromise abutment teeth

Question 2

Definitions

1. Saddle
2. Flange
3. Survey lines
4. Denture

Answer 2

1. Part that rests on and covers the edentulous areas and carries artificial teeth and gum work
2. Replacement tissue that extends from the gingival margin to the vestibular sulcus
3. Indicate the maximum bulbosity of a tooth in the plane of the path of removal
4. Removable prostheses used to replace missing teeth

Question 3

RPDs 1

1. 2 materials for bases
2. Give 2 indications for each base
3. What is the Kennedy classification
4. What is the Craddock classification
5. What are the clinical stages of RPD design

Answer 3

1. CoCr, acrylic/PMMA
2. CoCr - greater strength, more hygienic design. PMMA - temporary denture, poor OH and likely to be denture additions, cheaper, inadequate support from remaining teeth for tooth borne denture
3. Anatomical classification that describes the number and distribution of edentulous areas presentI.
   I. Bilateral free-end saddles
   II. Unilateral free-end saddles
   III. Unilateral bounded saddle
   IV. Anterior bounded saddle, crossing the midline
4. Simple classification based on support for an RPD
   I. Tooth-bearing/supported (preferred, most comfortable, natural feeling, load transmitted via PDL)
   II. Tissue/mucosa-bearing/supported
   III. Mixed (tooth and mucosa borne)
5. Primary imps, master imps, jaw reg, (framework try in), tooth trial, delivery, review

Question 4

Support

1. Definition
2. 2 ways it can be provided
3. What are rests and how are they described
4. Give 4 functions of rests
5. Describe how rests should be placed
6. Give some key features for a mucosal support denture
7. What is the Every partial denture design

Answer 4

1. Resistance to occlusal directed forces. Prevents/resists movement and distributes the load. Cast or wrought, cast preferred.
2. Utilising hard tissues (teeth, bony undercuts) and large surface coverage (palate)
3. Components that provide mechanical support. Extension of the denture onto a tooth. Described by the part of the tooth that they contact. Rests in CoCr are rigid and strong and connect to base via connectors. PMMA rests are flexible and have poor strength and are mechanically incorporated within the base and loads can cause stress
4. Oppose movement of denture base towards tissue (support), help distribute/direct occlusal loads (down long axis of abutment tooth), provide anterior bracing, involved in reciprocation and indirect retention, determine axis of rotation for free-end saddle RPDs
5. Kennedy I/II - not immediately adjacent to saddles
   Kennedy III/IV - immediately adjacent to saddles
   Craddock I - on tooth surface nearest base
   Craddock III - on tooth surface not closest to base
6. As large an area as possible, base must be 3mm from gingival margin to adduct for soft tissue compressibility
7. Entirely mucosa-borne. Restores arch with contact points, wire stops prevent distal drift of most posterior teeth. Gingival margins not covered

Question 5

Retention

1. Definition and 3 ways retention is achieved
2. 2 types and their definitions
3. Ideal pattern of retention
4. Define retainers
5. How do indirect retainers work
6. Define fulcrum axis
7. How is mechanical retention provided
8. What are guide planes and how do they provide retention
9. What do altered PoIs provide

Answer 5

1. Resistance to vertical displacement. Mechanical, muscular, physical
2. Direct - resistance to vertical displacement of denture. Clasps, guide planes, soft tissue undercuts, precision attachments
   Indirect - resistance to rotation displacement of denture. Provided by placing components to resist rocking
3. Triangular, with one point on opposite side of the arch
4. Components that resist displacement of the denture
5. Resist rotation about the clasp axis by acting on the opposite side to the displacing force.
6. Axis around which a tooth and Craddock III denture tends to rock when the saddles are loaded
7. Clasps and guide planes
8. Retention through friction. Supplementary direct retention. Two or more parallel surfaces on abutment teeth used to limit the PoI and improve retention and stability
9. Retention

Question 6

Clasps

1. What do they do
2. What is key to clasps working effectively
3. How are clasps named
4. What clasp is commonly used for lower teeth
5. What clasp is commonly used for ML/MB undercuts on upper molars
6. What 3 things is clasp efficacy dependent on
7. What material should be used for undercuts of 0.25mm, 0.5mm and 0.75mm
8. What length of clasp is required to engage a 0.25mm undercut

Answer 6

1. Provide retention by engaging the undercut of a tooth
2. If the clasp arm is seated below the undercut
3. By the direction in which they approach the undercut from
4. Gingivally-approaching I-bar
5. Occlusally-approaching single arm clasp
6. Material, cross-sectional thickness and shape, length
7. 0.25mm - cast CoCr
8. 5mm - wrought gold
9. 75mm - wrought stainless steel
10. At least 15mm

Question 7

Retention 2

1. How is muscular retention achieved
2. How is physical retention achieved
3. How is indirect retention achieved
4. What is reciprocation and how is it achieved
5. What is the RPI system and when is it used
6. What are the RPI components
7. What does the RPI provide

Answer 7

1. Action of surrounding musculature on the shape of the polished surface. Involves patient’s muscular control and denture extension into sulcus
2. Existing forces of adhesion, cohesion, surface tension, atmospheric pressure. Includes closeness of adaptation, extent of base and peripheral seal
3. Extension of the base to provide a fulcrum of a class II lever, preventing rotation. Stability for free-end/very long bounded saddles
4. Movement/force of the opposing element to prevent pressure from the retentive clasp arm acting on the tooth (resistance to lateral movement). Provided via reciprocating (non-retentive) clasp arm (or reciprocal connector) above maximum bulbosity of the tooth remaining in contact with the tooth, prevent horizontal tooth movement caused by action of clasp flexing.
5. Stress reliving clasp system. Used in Craddock III and commonly for Kennedy I/II. Used to reduce load on such teeth
6. Mesial rest, proximal guide plate, gingivally-approaching I-bar clasp
7. Retention, indirect retention (via proximal plate and minor connector) and reciprocation (if gap between plate and connector is less than width of tooth)

Question 8

Connectors

1. What are the 2 types
2. What do major connectors provide
3. Give 2 examples of major connectors and 3 features of each
4. How much space is required for a lingual bar for a lower RPD
5. What do minor connectors do
6. What is bracing

Answer 8

1. Major, minor
2. Major - connect components on one side of arch to components on other

3. Plate - thinner, Kennedy class II, cover gingival margin, good support, retention and tolerance; covers larger surface area. Can provide bracing and indirect retention if used in conjunction with rests
Bar - less mucosal coverage, Kennedy class I/mandibular RPDs, thicker

4. 8mm - 3mm from gingival margin, 4mm for height of bar, 1mm above raised functional depth of FoM
5. Minor - connect components to major connectors
6. Provided by connector, max saddle extension and reciprocating clasp arm. Not required as much if occlusal interferences eliminated

Question 9

Complete Dentures

1. Describe 3 key anatomical areas involved in construction
2. Describe the Cawood and Howell ridge classification
3. What is support
4. Give 2 ways support is provided in the upper and 3 ways it is provided in the lower
5. What is retention
6. Give 3 ways retention is provided
7. What is stability
8. Give 2 ways stability is provided
9. What is the neutral zone
10. Give 3 ways how retention and stability can be optimised

Answer 9

1. Hamular notch - area between distal surface of tuberosity and hauler process of medial pterygoid plate; ideal site for distal border, helps with post seal
   Retromolar pad - triangular pad of soft tissue at the posterior end of the lower edentulous ridge. Support
   Retro-mylohyoid space - space at distal end of lingual sulcus, posterior to mylohyoid. Aids in retention and stability
2. I - dentate; II - post-extraction; III - broad alveolar process; IV - knife-edge; V -flat ridge (no alveolar process); VI - submerged ridge (loss of basal bone)
3. Resistance to vertical movement of denture (occlusal directed forces).
4. Upper - hard palate, residual ridge. Lower - residual ridge, buccal shelf, retromolar pad
5. Resistance to displacement in a vertical direction
6. Peripheral seal, contact area between denture and tissues, denture extension, close fit, viscosity/volume of saliva (adhesion cohesion)
7. Resistance to horizontal movement
8. Stable/flat occlusal plane, denture teeth in neutral zone, correct denture extension. Influenced by forces acting on the polished and occlusal surfaces and form of supporting tissues
9. Area where muscular displacing forces are in balance. Ideal tooth position where displacing forces of cheeks and lips are balanced with the opposing displacing forces of the tongue
10. Maximum extension of denture base, close adaptation to mucosa, teeth in neutral zone, correct shape of polished surfaces, good border seal, balanced occlusion

Question 10

Impressions

1. Define impression
2. Give 3 features of a good primary impression
3. Give 2 primary impression materials
4. Name 4 poor denture-bearing areas
5. Give 2 other names for master impressions
6. Give 3 features of a good master impression
7. What are the aims of master impressions
8. Give 2 master impression materials
9. What is the function of occlusal stops
10. What is the function of border moulding

Answer 10

1. Reverse/negative form of the tissue
2. Cover denture-bearing area, create good peripheral seal, provide adequate surface detail suitable to produce a satisfactory cast
3. Alginate - mucostatic, cheap, easy to use, elastic, poor tear resistance
   Impression compound - non-elastic, mucocompressive, difficult to use
4. Atrophic mandibular ridge, flabby ridge, tori, high frenal attachments, dry mouth
5. Secondary, definitive
6. Cover denture-bearing area, create good peripheral seal, provide good surface detail suitable to produce a satisfactory cast
7. Record maximum denture-bearing area and functional width and depth of sulcus and develop effective border seal
8. Alginate - accurate, good surface detail
   Polyether (Impregum) - dimensionally stable, very accurate, hydrophilic
9. Allow accurate correction of posterior borders of tray by pre-forming impression material, improving peripheral seal
10. Full the functional sulcus (depth of sulcus during normal movement)

Question 11

Registration, trial and delivery

1. What are 3 objectives of the registration visit
2. What are the stages in registration
3. What should be assessed during trial
4. What should be checked during delivery
5. What are 4 components of denture stomatitis and how is it managed

Answer 11

1. Determine occlusal plane and jaw relationship, define shape of maxillary rim and position of lower teeth and select shade and mould
2. Adjust upper record block, mark lip line and occlusal plane, measure VD, establish face height, identify lower tooth position, perform reg, select appropriate tooth
3. Extension, retention, stability, occlusion, appearance. Upper centrals 10mm anterior to incisive papilla, occlusal plane parallel to ala-tragus line
4. Function, aesthetics, 3 denture surfaces, satisfactory occlusal contacts, extension, retention, stability, incisal plane orientation, occlusal plane orientation, OVD, porosity, undercut areas, sharp areas, comfort, looseness, appearance, speech, extension, retention, stability, occlusion, occlusal planes, OVD, FWS, 3 denture surfaces, function
5. Candidal infection, poor denture hygiene, night-time wear, high sugar intake, systemic factors (iron deficiency, steroid use, xerostomia). Mx - denture hygiene, miconazole gel to fitting surface, systemic fluconazole if indicated

Question 12

Problem solving

1. What 2 things does a post dam help
2. Give 3 reasons for looseness
3. Give 3 reasons for pain
4. Give 3 reasons for aesthetic problems
5. Give 3 reasons for eating problems
6. Give 3 reasons for speech problems

Answer 12

1. Retention, stability
2. Tori, flabby ridge, high renal attachment, recent extractions, incorrect peripheral extension, teeth not in neutral zone, unbalanced articulation, hyposalivation
3. Over-extension, blebs, residual monomer, poor fit, excessive post dam, retained roots, bruxism, premature occlusal contact, non-balanced occlusion, locked/wedged occlusion, rough fitting surface, errors in occlusion
4. Shade, shape, position, alignment
5. FWS, looseness, pain, chewing at side
6. Incisors to palatal, incorrect OJ/OB, palatal PMMA too thick, lack of retention, reduced OVD

Question 13

Complete Dentures 2

1. What is Hanau’s quint
2. What are the 5 determinants of Hanau’s quint
3. What is Christianson’s phenomenon
4. How can it be resolved
5. Define balanced occlusion
6. Define balanced articulation

Answer 13

1. 5 determinants or variables affecting occlusal contacts
2. Occlusal plane orientation, condylar guidance (30d), incisal guidance (10-15d), cusp angle/height, compensating curve
3. A gap occurring in the natural dentition of between the opposing flat occlusal rims when the mandible is protruded (posterior open bite). Can lead to instability in F/F.
4. Compensating curves, monoplane occlusion, correct condylar angle and incisal angle
5. Simultaneous contact between upper and lower teeth on both sides (bilateral) and in anterior and posterior occlusal areas of the jaw when jaw is static. Dependent on Hanau’s quint
6. Continuing contacts of as many artificial teeth as possible in all excursive movements away from and into ICP. Teeth are arranged siuch that there are simultaneous bilateral balancing contacts on both working and non-working sides during excursive movements

Question 14

Setting teeth

1. Give 5 techniques for setting teeth
2. Why are low cusped teeth preferred
3. What is a benefit of cusp less teeth
4. Give 3 features of acrylic and porcelain teeth

Answer 14

1. Low cusped teeth, cusp less, monoplane occlusion, lingualised occlusion, crossbite
2. Efficient at breaking up food
3. Allow excursive movement without occlusal interference; useful for flat ridge, poor natural retention, wandering ICP
4. Acrylic - chemical bond with denture base, silent in function, flexible, tough but soft (low abrasion resistance)
   Modified acrylic - higher abrasion resistance
   Porcelain - require mechanical retention with denture base (metal pins/silane coupling agent), possible noise in function, more brittle, hard (high abrasion resistance)

Question 15

Overdenture

1. What is it
2. Give 3 advantages
3. Give 3 disadvantages
4. Rank teeth in order of ideal abutment teeth for overdentures

Answer 15

1. Denture that derives support from one or more abutments or implants - seated over the top of these
2. Preserve alveolar bone around retainer tooth, improved support, retention and stability, preservation of proprioception via PDL, psychological benefit of maintaining natural teeth
3. RCT likely required, increased fracture risk, more maintenance required by patient and dentist, roots prone to caries, base may be required to be thinned to avoid excessive bulk in the region of the retained tooth
4. Canines > molars > premolars > incisors
   Ideally bilateral and symmetrical with minimum of one tooth space between them; healthy attached gingiva, good perio support, no mobility