RPD Definitions + Lectures Flashcards
1
Q
Definition of a removable partial denture
A
It is a dental device that restores one or more,
but not all the natural teeth and associated structures, its retention and support are provided by the natural teeth (dental implants) and/or mucosa (and under it the bone). It occupies more space in the mouth than the teeth, the mucosa and the edentulous ridge are also covered, it is connected to the natural teeth, and the patient himself can remove and insert it.
2
Q
Parts of RPD (4)
A
1• Base plate: saddles, connectors, occlusal rests
2• Artificial teeth,
3• Artificial gingiva
4• Retainers:
1) Clasp,
2) Precision attachment (Sliding PA, Bar attachment, Telescopic crown, Ball attachment, joint attachment)
3
Q
Tasks of the RPD (3)
A
1• To restore the functions of the masticatory system (eating, speaking, esthetics of the face – including teeth and gum)
2• To prevent the further damage to the masticatory system (migration and tilting of the teeth, elongation of the opposing teeth, overloading the teeth, damage to TMJ–prophylactic function)
3• It has to provide static and dynamic occlusion, evenly distribute the chewing force to the remaining teeth and the mucosal bony base
4
Q
Indications for RPD (10)
A
1• The number, distribution, position of the teeth in dental arch,
2• Caries and/or periodontal status don’t allow making a fixed denture (or it is not practical to make one).
3• Long bounded saddle, free end saddle.
4• Splinting is necessary.
5• Great atrophy/defect of the edentulous ridge.
6• Patient’s request.
7• Young age (under 18), later fixed denture or implant is possible.
8• General physical or mental status of the patient (tooth preparation can’t be carried out)
9• Temporary treatment before or after implantation
10• FF classes: 2A, 2A/1, 2B, 3, All Kennedy classes
5
Q
Contraindications for RPD (4)
A
1• Patient may faint, spastic - epileptic seizures
2• Bad general condition of the patient
3• Lack of care, patient is unable to clean the denture
4• Special occupations –diver, test pilot, opera singer, artist
6
Q
Advantages relating to fixed denture (5)
A
1• Treatment is reversible
2• Cleaning is simple
3• Support of the lips can be better (missing alveolar process is also replaced)
4• It can be generally modified after tooth extraction (extra artificial tooth can be fitted)
5• Relatively cheap
7
Q
Disadvantages compared to fixed denture (8)
A
1• It occupies and covers bigger area,
2• It can be uncomfortable,
3• Plaque more frequently may accumulate on the surface,
4• Vomiting/Wretching reflex,
5• Occasional relining due to changes in the bony base,
6• Patients relate it to old age
7• Clasp – unesthetic,
8• Crown preparation maybe necessary for fixed-removable dentures
8
Q
Requirements for making an RPD (6)
A
1• Remaining teeth and artificial teeth have to create a functional unit;
2• It must not overload the abutment teeth and mucosa-bony base;
3• It must not harm the teeth, periodontium, mucosa and bone base;
4• It must not change the character of the face;
5• It must not change the habitual OVD and articulation;
6• It must not impair the hygiene of the mouth
9
Q
Forces affecting the denture
A
• vertically: --loading (chewing) --lifting (weight of the upper denture, sticky food) • horizontally: --chewing
10
Q
what is the chewing force
A
• It is the force of all the muscles which elevate the mandible. The force arises b/w the 2 jaws. The average value is 300- 400N, depending on age, sex, status of dentition, and muscles. There may be great differences (acrobats)
11
Q
Support of prosthesis
A
• The transmission of vertical components of chewing force to the tissues of the mouth, and the resistance of these tissues to this force. In other words: The foundation on which the denture rests, and which resists displacement towards the tissues. It comprises the hard and soft tissues that bear the loads of mastication and clenching applied to the denture.
12
Q
Methods of support (3)
A
1• Dental, periodontal: fixed prosthesis or removable bridge
2• Mucosal: full denture, traditional RPD with acrylic base plate without occlusal rests
3• Dento-mucosal, muco-dental: RPD, supported also on teeth
13
Q
Axis of rotation
A
a connecting line between the supporting points on the
abutment teeth adjacent to the edentulous ridge around which the denture can rotate or rock.
14
Q
Primary rotation axis
A
a connecting line between the supporting points on the abutment teeth adjacent to the edentulous ridge. After inserting the denture it may become a real or actual rotational axis.
15
Q
Secondary rotation axis
A
a line between the supporting points of a tooth neighboring and a tooth non-neighboring the edentulous ridge
16
Q
Clasp line/support line
A
a line connecting two occlusal rests of the RPD in an arch segment
17
Q
Load line
A
connects the centric stops in an arch segment. It should be orally from the line of support to avoid the generation of lifting forces on the prosthesis.
18
Q
Lever/loading arm
A
is equal to the distance connecting a possible axis of rotation and a point of loading.
The distance between the impact point of the loading force and the axis of the rotation;
the length of the line segment mounted perpendicular on the rotational axis (and) starting from the loading point.
Or: the distance between the occlusal contact point of furthest artificial tooth from the axis and the rotation axis.
19
Q
Resistance arm
A
the distance between the furthest clasp tip of the retentive arm and the rotational axis. The length of the line segment mounted perpendicular on the rotational axis starting from the furthest clasp finger.
20
Q
Area/poligon of support
A
The area that is bounded by the occlusal rests, or the area determined by the lines of support. Line of support connects the occlusal rests of an arch segment. The polygon of support connects all lines of support. The supporting area must be as big as possible.
To establish such an area at least 3 supports are needed.
21
Q
Area of load
A
The edentulous ridge outside of the supporting area. The smaller the loading area the more stable the RPD is.
22
Q
Torque
A
is moment or moment of force, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. The torque is the product of the applied force and the length of the lever. Mathematically, torque is defined as the product of force and the lever-arm distance, which tends to produce rotation. Loading force x length of loading arm = resistance force x length of resistance arm.
23
Q
Base plate
A
that part of the denture which is laying on the mucosa. Its parts: saddles, connectors, occlusal rests. It transmits the chewing load to the oral tissues, unites the parts of the partial denture: artificial teeth, flange, and retainers.
• must have suitable strength to withstand chewing force and parafunctional forces, no deformity, precise attachment on the mucosa of the palate
• Thickness:
–Co-Cr alloy -> min. 0.6-0.9 mm
–noble metals (gold) -> thicker
24
Q
Décolletage
A
is a feature of the RPD, when the base plate does not cover the marginal gingiva.
Minimum distances between base plate and marginal gingiva:
UPPER denture: 5-6mm,
LOWER denture: 4-5mm
25
The saddle
is that part of the partial denture, which rests on or covers the edentulous ridge and carries the artificial teeth, artificial gingiva and the anchors/retainers. It transmits the functional load to the mucosal-bony base in case of mixed and mucosal support.
26
Types of saddle
bounded saddle and free-end saddle
27
Tasks of the saddle (3)
1• bear the flange and artificial teeth
2• transmit the functional load to the mucosal- bony base (mixed and mucosal support)
3• take part in the retention of the denture
28
The characteristics of the saddle
* It should cover maxillary tuberosity and retromolar pad (in case of free end saddle), thus the distribution of load is better and the denture is stabilized against horizontal dislodgment, and can be relined
* The distal third of the saddle should be relieved (free end saddle, we should not replace the second molar)
29
Major connector
is the part of a partial denture that connects components on one side of the dental arch with those on the opposite side. It is that part of the denture to which all other components are attached. In the upper jaw it takes part in the support of the RPD, in the lower it has no such function.
• The biggest reduction in case of pure dental support
• It should be stable
• It should not interfere w/ speaking or eating
30
Types of maxillary major connector (4)
1• Palatal strap/butterfly shaped/midpalatal bar
2• Horseshoe shaped plate/U shaped
3• Anterior and posterior bar/ring form/skeletal
4• Full palatal plate
31
Palatal strap/butterfly shaped/midpalatal bar:
Indications (2)
Advantages (5)
Characteristics (4)
1• In case of missing posterior teeth
2• In case of a bulky/big torus palatinus it is not recommended
1• it's rigid enough and has sufficient resistance to deformation
2• it doesn’t cover the rugae palatini
3• it doesn't impair speech, sense of heat, and taste
4• it connects the saddles on a site, where the chewing force is the biggest
5• well tolerated by patients
1• It should be symmetrical with midsagittal plane
2• It should cross median palatine suture perpendicular
3• Minimum width 8 mm
4• Minimum thickness 0.7-0.8 mm, in case of flat palatal vault it may be thin, in case of a gothic (high) palatal vault, it has to be thicker, but narrower
32
Horseshoe shaped plate/U shaped:
Indications (1)
Advantages (2)
Disadvantages (1)
1• In case of missing front teeth
1• Provides good stability
2• Advantageous in case of a big torus palatinus and in case of a strong retching reflex
1• rugae palatini are covered, it covers greater area than the palatal strap
33
Anterior and posterior bar/ring form/skeletal:
Indication (2)
Advantages (1)
Disadvantages (1)
Characteristics (1)
1• In case of multiple bounded saddles, when mainly dental support is given
2• It may not be used in case of long edentulous saddles, because due to its small size the framework may deform
1• smaller segment of the palate is covered
1• Its mesial part may interfere with speech, because of its location and the bars should be obviously thicker than the plate to be rigid enough
1• It has to be planned symmetrical to the midsagittal plane
34
Full palatal plate:
Indication (1)
Advantages (4)
Disadvantages (2)
1• In case of great edentulous ridges, when only few teeth are present
1• It can bear great functional load, provides maximum mucosal support
2• No deformation
3• It resists the most to the horizontal dislodging forces
4• It can be modified easily after incidental tooth removal
1• The connector is heavier than the other forms
2• Patient may not tolerate it well
35
Types of mandibular major connector (4)
1• Lingual bar/Sublingual bar
2• Dental bar/Cingulum bar
3• Kennedy bar
4• Vestibule bar/Labial bar
36
Lingual bar/Sublingual bar:
Definition
Requirements (5)
Cross section
Dimensions of cross section
Distance from marginal gingiva
Distance from the mucosa
• It is the major connector of the lower RPD, it connects the saddles, its shape is a teardrop in cross section
1• It is placed almost always lingually but if teeth are tilted lingually, it can be placed buccally (rare occasion)
2• It is vertically positioned generally. It may be oblique or horizontal in case of shallow floor of the mouth
3• It should not lie on the marginal gingiva
4• It should neither interfere with the function of the floor of the mouth nor disturb its movements
5• must be stable and rigid
* Cross section: teardrop/flattened egg
* Dimensions of cross section: 3x2mm
* Distance from marginal gingiva: 4-5mm
* Distance from the mucosa: 0.2-0.3mm
37
Dental bar/Cingulum bar:
Indication (4)
Contraindication (5)
Size
• Indication:
1- when limited distance is present between the marginal gingiva and the mucolingual fold, shallow floor of the mouth.
2- The teeth have to be long enough
3- good periodontal health.
4- It is a continuous clasp which provides an indirect retention.
```
• Contraindication:
1- when there are short clinical crowns,
2- diastema,
3- lingually tilted teeth,
4- excessive bone loss around teeth,
5- long edentulous ridges.
```
• Size: 4 x 1.5-2.0mm
38
What is support remote from the saddle?
Aim
* the occlusal rest is on the remote side of the abutment tooth, or on the second tooth from the saddle.
* Primarily used in free end saddle cases
• Aim: to prevent the rotation (rocking, seesaw) and displacement of the denture away from the underlying tissues (gravity on the upper jaw, or sticky food)
39
Advantages of support remote from the saddle (4)
1• It provides an indirect lengthening of the saddle in mesial direction in case of distal free end saddle
2• It prevents the rotation/tilting of the denture
3• It prevents the distal tilting of the abutment tooth
4• It prevents sinking of the saddle on the distal part of the denture
40
Disadvantages of support remote from the saddle (4)
1• The minor connector covers the interdental papilla, difficult self- cleansing of the denture (periodontium!)
2• It needs bigger area in the mouth
3• More complicated construction
4• The connection with the saddle is not so strong, the saddle may be displaced due to horizontal forces more easily (especially in case of greatly resorbed alveolar ridge)
41
Indications of support remote from the saddle (5)
1• the denture may displace due to lifting force
2• the abutment has a long clinical crown
3• the opposing teeth have great chewing force
4• the edentulous ridge tolerates the load well, and the mucosa has a great compressibility
5• it is necessary to extend the saddle in mesial direction (we don’t have to reduce the number of artificial teeth in case of free end saddle)
42
What is support adjacent to the saddle
* the occlusal rest is close to the saddle on the abutment tooth near the edentulous saddle.
* Primarily used in tooth-bounded cases
43
Advantages of support adjacent to the saddle (4)
1• Minor connector (clasp stalk) doesn’t cover an extra area on the abutment tooth (good for the periodontium)
2• Tight connection with the saddle, small possibility for displacement or rotation of the saddle
3• Construction is simple
4• Minor connector is short and strong
44
Disadvantages of support adjacent to the saddle (3)
1• In case of distal free end saddle the denture may rotate around the rest, can sink into the mucosa
2• The abutment tooth (tooth adjacent to the edentulous ridge) may tilt in distal direction
3• In case of two-sided distal edentulous saddles the denture is not stabilized against forces and it could result in displacement away from the underlying tissues
45
Indirect retainer (a.k.a tilt breaker)
those elements of a partial denture which provide resistance to the rotation of the denture around the fulcrum axis. They may be the same elements as direct retainers placed on the opposite side of the fulcrum axis to that on which the displacing saddle is situated (rests, continuous clasps, connectors)
46
Retainer
a component of a partial denture that uses a natural tooth to resist reasonable dislodging forces which may affect the denture in function. The retainer connects the denture to the abutment tooth in a way, that the patient himself can remove the denture. Retainer can be connected to the tooth directly or through a crown or other device. The most commonly used retentive devices are clasps.
47
Retention of the RPD
Means the fixation of the RPD against the forces that would provoke the dislodgment, or lift of the prosthesis from its place. Retention is that property of a denture which resists the outward displacement of the denture, away from the tissues
48
Methods of retention?
types?
- elastic: there is a force present affecting the abutment tooth even if the patient doesn’t chew (harmful for the tooth)
types: wrought wire clasp, acrylic clasp
- rigid: there is no force transmission to the abutment tooth without chewing, it doesn’t cause any harm to the tooth
types: cast clasps, precision attachments, bars, telescopic crowns
49
Rigid retainer
Means that the load affecting the denture is transmitted to the abutment tooth in the same size, because the connection between the saddle and the retainer is stiff, there is no movement of the denture independent from the abutment tooth. The denture can move neither in vertical, horizontal, nor in sagittal direction. Forces from any direction affecting the denture reach the abutment teeth immediately. Retention acts at the moment of load. There is no force transmission to the abutment tooth without chewing; it is the appropriate retention form.
cast clasps, PA, bars, telescopic crowns
50
Elastic retainer
In this case a decreased load is transmitted to the abutment teeth, because the connection between the saddle and the abutment teeth is elastic/non rigid (wrought wire clasp), the partial denture can move/dislodge independent from the abutment tooth. The fixation is not activated immediately at the time of the load.
The wrought wire clasp transmits load to the tooth also, when the denture is in a resting position and sooner or later it may cause the destruction of the parodontium of the abutment and loss of tooth.
51
Types of clasps (2)
- Metal clasps:
elastic (wrought wire clasps)
rigid (cast clasps)
- Acrylic clasps
52
Cast clasp
a metal device, when in contact with a tooth, retains and/or stabilizes a partial denture. Retainer for RPD. Theoretically it provides rigid retention (clasp finger has small flexibility) Freedom of movement is only in one direction, namely along the path of insertion.
53
Requirements of Cast clasp (5)
1• The stop of the terminal position is clearly defined.
2• Bodily encirclement of the abutment tooth.
3• The clasp embraces about 270° the abutment tooth.
4• Gentle insertion and removal.
5• Sufficient friction, in this case with active retention
54
Task of Cast clasp
support and retention-to stabilize the denture against vertical and horizontal dislodging forces
55
Material of Cast clasp (3)
1) generally chrome-cobalt-molybdenum alloy,
2) seldom gold alloy,
3) (titanium)
56
Parts of the cast clasp
a. retentive arm/clasp finger/tip
b. bracing/reciprocal/guiding arm
c. Shoulder and body
e. Minor connector/clasp stalk
d. Occlusal rest
57
Anatomical equator
the biggest outline of the clinical crown, the most prominent part of the axial walls
58
Prosthetic equator
(height of contour, survey line) – the most prominent part of the clinical crown perpendicular to the path of insertion of the RPD, also called survey line, it can be determined with a surveyor. It divides the tooth in two parts:
- -occlusal from the prosthetic equator there is no undercut area, it can be used for support,
- -gingival from this line there is an undercut, which is suitable for retention.
59
Path of insertion
Path is a term followed by the denture from its initial contact with the surface teeth until it is fully seated.
Determined by surveyor. It helps to find undercut part for the retentive arm and parallel surfaces for the reciprocal arm
60
bracing/reciprocal/guiding arm
an arm of a clasp located in such a manner as to reciprocate any force arising from an opposing clasp arm on the same tooth. It stabilizes the prosthesis against horizontal bodily movement and rotation around vertical axis.
61
retentive arm/clasp finger/tip
a circumferential clasp arm that is a little flexible and engages the infrabulge area at the terminal end of the arm. It ends in a finger that is slender. Ensures the retention of the denture.
62
Occlusal rest
A unit of the partial denture that rests upon the tooth surface to provide vertical support for the denture. It provides a precise terminal stop for the clasp. Transmits the vertical chewing forces exerted on the body of the RPD to the abutment tooth. Stabilizes the denture against the abutment, and restricts displacement in the transverse and sagittal planes. Prevents vertical bodily movement. Limits rotation around sagittal and vertical axes. Due to its function it belongs to the base plate.
63
The position and size of rest seat
- The buccal-lingual width is about 1/3 of the distance between the cusp tips, min. 1.5-2.5mm,
- mesio-distal length 2-2.5mm,
- depth 1-1.5mm.
- The rest and the connector make a right angle.
- Spoon shaped, inside enamel or fillings
64
Minor connectors (clasp stalk)
Definition
Characteristics (6)
It connects the clasp to the body of the prosthesis, It transmits forces falling on the denture base to the clasp, and thereby to the abutment tooth.
• 1) cross section is rounded triangle, 2) it should be strong, 3) perpendicular to baseplate, 4) as short as possible, 5) not lie on the marginal gingiva, 6) not very close to each other
65
Position of minor connectors (2)
1• Connectors adjacent to the denture base (direct)
| 2• Connectors remote from the denture base (indirect)
66
The ideal abutment tooth (7)
1• Free from caries or restorations
2• Undercut buccally, no undercut (flat) lingually,
3• Crown of adequate length
4• Healthy periodontal status,
5• Long root with large surface area,
6• Good vertical and horizontal position within the arch,
7• Stable opposing occlusion
67
Methods to achieve retention area (4)
1• Crown preparation
2• Filling: (amalgam), composite
3• Gold inlay
4• Composite build-up
68
Indications for clasp retaining crown (6)
1• There is not enough surface for retention, support, bracing arm
2• There is not enough mechanical resistance (deep caries, large filling in the tooth)
3• Poor occlusal condition (tilted, rotated, elongated tooth)
4• Big difference between the axes of the teeth (convergence or divergence)
5• Too big undercut, big bulge,
6• Caries prevention
69
Advantage of clasp retaining crown (4)
1- Optimal shape for clasping.
2- Straight, milled surface lingually, for the bracing arm, relating to the path of insertion.
3- Adequate bulge buccally for the retention arm, incidentally slight concave surface under survey line.
4- Adequate place for the occlusal rest
70
Disadvantage of crown preparation (6)
```
1• Sacrifice healthy tooth tissue,
2• Risk of immediate or late pulp damage,
3• Caries, periodontitis,
4• Patient is loaded by the treatment,
5• Cost: Time, material, work
6• Crown must be changed periodically
```
71
Advantages of composite build-up (6)
1• Conservation of healthy tooth structure,
2• No adverse effect on pulp or periodontium,
3• Short treatment time,
4• No technical work,
5• No load on patient,
6• Less cost
72
Advantages of
| Ney 1 / E clasp / circumferential clasp (3)
1- simple,
2- fulfills all requirements (bodily encirclement, good retention),
3- if the connector is close to the saddle, periodontally good
73
Disadvantages of
| Ney 1 / E clasp / circumferential clasp (2)
1- unesthetic,
| 2- not always applicable
74
Indications of
| Ney 1 / E clasp / circumferential clasp (2)
1- mainly bounded saddle and less free end saddle,
| 2- adjacent or remote from the saddle
75
Advantages of
| Ney 2/3 (1)
1- good esthetic
76
Disadvantages of
| Ney 2/3 (5)
1- clasp follows periodontally unfavorable course,
2- smaller retention: possibility for horizontal dislodgment of the denture is bigger;
3- placement of retentive arm can irritate the lip,
4- uncomfortable for the patient,
5- caries under the clasp
77
Indications of
| Ney 2/3
Ney-2: straight teeth with great bulge on buccal and oral surfaces
Ney-3: great bulge on the buccal surface, tilted tooth
78
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Advantages of
Ney 4 (1)
```
1- good esthetic
79
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Disadvantages of
Ney 4 (2)
```
1- stalk follows periodontally unfavorable course,
| 2- possibility for horizontal dislodgment of the denture is bigger
80
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Indications of
Ney 4 (2)
```
1- free edentulous saddle,
| 2- premolar tooth
81
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Advantages of
Ney 5 (4)
```
1- axial loading,
2- minor connector emerges directly from saddle,
3- saddle close and remote support with one clasp,
4- clasp finger doesn’t hurt the bucca at insertion of the denture
82
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Disadvantages of
Ney 5 (3)
```
1- big surface is covered,
2- due to the long arm it may break,
3- retention may be smaller
83
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Indications of
Ney 5 (2)
```
1- alone standing molar teeth,
| 2- tilted tooth
84
Advantages of
| Ring clasp, one arm clasp (3)
1- no extra periodontium coverage by the stalk,
2- good for deep undercut
3- clasp finger looks mesially, it doesn’t hurt the bucca at inserting the denture
85
Disadvantages of
| Ring clasp, one arm clasp (2)
1- caries b/c it covers a big surface,
| 2- it may break because the arm is long
86
Indications of
| Ring clasp, one arm clasp (3)
1- alone standing molars,
2- tilted, rotated teeth,
3- saddle close support
87
Advantages of
| Modified Ney-1 (5)
1- fulfills all requirements (bodily encirclement, good retention),
2- load parallel with the long axis of the tooth,
3- stalk is connected directly to the saddle,
4- periodontium is not covered,
5- saddle close and saddle remote support together
88
Disadvantages of
| Modified Ney-1 (2)
1- unesthetic,
| 2- extensive tooth coverage: caries
89
Indications of
| Modified Ney-1
generally applicable for single tooth or the last tooth in the row
90
Advantages of
| Back-action clasp (4)
1- good retention even in case of less undercut,
2- support remote from the saddle,
3- stabilizes distally tipped tooth,
4- good esthetic
91
Disadvantages of
| Back-action clasp (2)
1- connector covers the interdental papilla,
| 2- less effective against horizontal dislodgment of the denture
92
Indications of
| Back-action clasp (2)
1- for premolars in unilateral and bilateral distal extension PD,
2- support remote from the saddle
93
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Advantages of
G clasp (3)
```
1- mesial support acts as direct saddle extension,
2- direct connection to saddle,
3- good retentive and stabilizing ability and safe encirclement
94
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Disadvantages of
G clasp (2)
```
1- bracing arm close to the occlusal level
| 2- extensive tooth coverage (caries)
95
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Indications of
G clasp (2)
```
1- support remote from the saddle,
| 2- premolars
96
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Advantages of
Bonwill clasp (1)
```
1- good retentive and stabilizing ability and safe encirclement
97
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Disadvantages of
Bonwill clasp (3)
```
1- periodontally unfavorable location of stalk,
2- needs great space for joint shoulders
3- extensive tooth coverage (caries)
98
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Indications of
Bonwill clasp (3)
```
1- support remote from the saddle,
2- unilateral free end saddle on side opposite the denture base,
3- anterior or anterolateral bounded saddle
99
Advantages of
| Roach-clasp (T-bar clasp) (1)
1- good esthetic
100
Disadvantages of
| Roach-clasp (T-bar clasp) (3)
1- periodontally unfavorable location of retentive arm (caries, gingivitis),
2- stability of retentive arm is relatively low,
3- retentive arm may irritate the lip, and indicate parafunctional habits
101
Indications of
| Roach-clasp (T-bar clasp) (1)
1- for premolars or front teeth in uni- or bilateral distal extension prosthesis, when esthetics is important
102
Talon clasp (5)
```
1- Incisor (incisal) rest splint
2- Use very rarily
3- Cover the incisal edge of the teeth
4- Stable
5- No esthetic
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103
Nurse clasp (3)
1- Two retentive arms which look likes a mother’s arm
2- originally for swadged crown
3- good when only one lower elongated canine
104
Rules of Designing the clasp (7)
1• The part above the prosthetic equator takes part in the support and the area under it participates in the retention
2• The clasp should go through at least 3 quadrants
3• The line of the prosthetic equator is close to the anatomic equator (not too high and not too low)
4• We should design retentive areas in case it is not suitable for the retentive arm
5• The end of the clasp tip needs to be 1 mm above the marginal gingiva
6• Co-Cr alloy: 0,12-0,25 mm gold- alloy: 0,25-0,5mm deep undercut place
7• Clasp arm: 1,5-2 mm wide and 1,1 mm thick, semicircular sectioned, tapering towards the tip
105
Steps of RPD with clasp-holding crown and denture preparation on separate impressions/casts (17)
1• History taking, examination, planning, etc.
2• Tooth preparation for crown (temporary crowns)
3• Precision impression
4• Antagonist impression
5• Jaw relation – wax biting, wax rim (occlusal rim)
6• Trial of the crown - framework
7• Shade selection
8• Preparation of the crown
9• Cementation of the crown
10• Impression for the RPD (special tray)
11• Antagonist impression (or you have it already!)
12• Bite registration (again!)
13• Trial insertion of metal framework
14• Trial of wax up the artificial teeth
15• Delivery of the RPD
16• Check ups
17• Maintenance
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RPD with clasp-holding crown and denture preparation on separate impressions/casts (4)
Advantages (4)
Disadvantages (3)
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• Advantages:
1- Crowns are inserted earlier,
2- more comfortable for the patient
3- Crowns do not dislodge during taking the pick-up impression
4- More precise procedure
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• Disadvantages:
1- Time of the treatment is longer
2- 2x impressions
3- 2x jaw registration
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RPD with clasp-holding crown– 2. crowns and denture on one cast
* Metal framework is prepared on the same precision cast, as the crowns
* Trial insertion of metal framework, check the bite registration
* Trial of wax up
* Cementation of crowns, delivery of the denture – denture has to be inserted before the setting of the cement!!
* Review
* Maintenance
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RPD with clasp-holding crown– 2. crowns and denture on one cast
Advantages (2)
Disadvantages (3)
Conditions (3)
• Advantages:
1- Quick process,
2- only one impression
• Disadvantages:
1- Crowns will be cemented later (provisional crowns)
2- Crowns may not fit exactly identical on the teeth as on the die – it is a source of error at making the metal framework
3- Delivery is more complicated
• Conditions:
1- first impression has to be perfect and extend to all the details, which are necessary for the crowns and for the denture
2- Crowns have to fit perfect on the teeth, same position on the teeth and on the cast
3- Technician has to preserve the the details important for the denture base
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RPD with clasp-holding crown– 3.
* Pickup impression with the framework of the crowns
* Impression of the opposing arch, if it is not preserved in the lab
* Bite registration
* Trial finished crowns and metal framework
* Trial of wax up
* Cementation of crowns, delivery of the denture – denture has to be inserted before the setting of the cement!!
* Review
* Maintenance
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RPD with clasp-holding crown– 3
Advantages (2)
Disadvantages (3)
• Advantages:
1- gingival marginalis and mucosa is well visible around the crowns (same if the crowns are cemented and take the impression after that),
2- clasps will be prepared direct on the crowns
• Disadvantages:
1- Crowns will be cemented later (provisional crowns removal, re-cementation)
2- Crowns may dislodge in the pick up impression– it is a source of error at making the metal framework
3- delivery is more complicated
111
Interlock
types (4)
It is a milled structure, which completes the precision attachment. It contains a stabilizing arm that partially encircles the abutment. This arm helps to insert the prosthesis, and in end-position provides the axial loading of the abutment tooth. The crown has an oral stabilizing surface (seating guide) with a cervical shoulder, and a groove on the approximal side remote from the saddle.
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Types:
1-Custom made
2-Prefabricated
3-Can be activated
4-No activation possible
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112
Mode of retention in precision attachment (3)
1• Frictional:
- metal-metal
- metal-plastic inset
2• Spring loaded frictional with a split inside
3• Frictional with an active retention element
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Placement of precision attachments (5)
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1- Extracoronal
2- Intracoronal
3- paracoronal
4- Interproximal
5- Built in a pontic
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Precision attachments
Interlocking device, one component of which is fixed to an abutment or abutments and the other is integrated into a fixed or removable prosthesis in order to stabilize and/or retain it. The effectiveness is based mainly on friction between the female and male parts, it can be combined with additional elements, like spring, stud. The friction is provided by the good fit between the parallel surfaces of the primary and secondary parts.
115
Extracoronal positioned precision attachments
Advantages (3)
Disadvantages (2)
Examples (2)
--Advantages:
1- we do not need to remove more tooth substance than regularly during tooth preparation
2- the abutment crown will not be overcontoured, esthetic is not impaired
3- the attachment length necessary for frictional retention is maintained
--Disadvantages:
1- without an interlock there is no axial loading, splinting the teeth also helps to achieve favorable loading
2- cleaning is difficult, periodontal damage
--Examples:
• Preci-vertix system
• Ot-Cap system
(Activation by changing the plastic clip)
116
Intracoronal positioned precision attachments
A recess/box must be prepared into the abutment to receive the attachment
117
Intracoronal positioned precision attachments
Advantages (2)
Disadvantages (3)
Example (1)
--Advantages:
1- more axial loading
2- the gingival part is easy to clean
--Disadvantages:
1- we have to remove tooth substance from the abutment, therefore it is not generally applicable, rather only on molar teeth.
2- The retainer crown will be often overcontoured.
3- Intracoronal females will collect food and present problems when the patient attempts to seat the prosthesis
--Example:
1- Biloc system (Activation possible)
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Bar attachments
Consist of a horizontal bar/rod with a sleeve that slide over it. The bar is attached to crowns; its cross section may be different (cylindrical, egg shaped, U shaped, rectangular). The sleeve is built in the denture. Retention is provided by friction, mechanical tools (plastic insets), or combination of these.
* Bar – male element, sleeve – female element
* Distance from the mucosa: at least 1.5-2.0mm
119
Types of bar attachments (cross- section of a bar) (4)
1- Rounded: cylindrical (classified as joint attachments)
2- Egg-shaped – Dolder bar
3- „U” shaped
4- Rectangular
120
Ball attachment
Definition
Advantages (4)
Disadvantages (4)
cap-post system. a structure which is similar to a press-stud. It has two parts: patrix/primary part similar to a ball cemented into the root of the tooth, and the matrix/secondary part, which covers the previous, and clicks on it. It is called also house. It is used in hybrid dentures.
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--Advantages:
1- Simple fabrication
2- Only a root is enough
3- No problem with the place
4- Easy to recover
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--Disadvantages:
1- Only in root-canal obturated teeth
2- Inadequate retention
3- Caries danger
4- Risk of the fracture of remained tooth structure
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Joint attachments
Aim
Consequence
Types (2)
Disadvantages (5)
* Aim: to protect the abutment tooth from the loading that affects the denture. They allow various degrees of movement between the body of the prosthesis and the abutment teeth, at loading first the denture sinks; the load affects the teeth later
* Consequence: the denture moves up and down during function, it results a great atrophy of the jaws
Types:
1. Pure hinge joint – rigid attachment, allows only rotation around a transversal axis
2. Resilient hinge joint – allows first a vertical bodily movement and then a rotation around a transverse axis
Disadvantages:
1- complicated constructions,
2- they may have a failure easily
3- results great atrophic changes in the jaw
4- since it is moving always parafunction can start
5- it may damage the periodontium of the abutment teeth
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Bolt (passive)
We use it rather for psychological and safety reasons additionally to some main precision attachment. No retentive function
123
Methods for producing RPD with precision attachments (2)
1. We take two impressions, and make two models
| 2. We take one impression, and use one model
124
Pick-up impression
records the situation of a dental appliance in the mouth relating to the teeth or other structures. Generally, the aim of the pick-up impression to record the exact position of the fix part of a denture, namely the primary crowns or a bridge.
125
Pick-up cast/die
Through pouring the pick-up impression with dental stone/plaster one get the pick-up cast, which shows the relationship of the fix part to the other parts of the mouth/die.
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Telescopic attachment/double crown system
Definition
Mechanism of retention (3)
Indication (2)
consists of two crowns: the inner/primary crown or coping is cemented to the prepared abutment tooth, while the outer/secondary crown is incorporated (or cast together) in the denture. Telescopic system provides great stability for the prosthesis, the retention and support is solved in one retainer. It provides load parallel to long axis of the abutment tooth.
- Mechanism of retention: 1. Friction 2. Cohesion
3. Vacuum
- Indication: Class FF 2A/1, 3
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Telescopic attachment/double crown system
Advantages (6)
Disadvantages (3)
--Advantages:
1- axial load direction is central -> protection of the residual dentition,
2- lateral load component is rather insignificant
3- Point of load attack has a favorable location: near to the gingival margin
4- one anchor ensures support and retention and prevention of rotation
5- safe bodily encirclement
6- simple to keep perfect OH
--Disadvantages:
1- great amount of tooth substance is lost during the preparation to have enough space -> risk of pulp damage
2- if not enough tooth structure removed -> crown will be too big -> not esthetic
3- parallel surface needed -> difficult preparation
128
Types of telescopes (3)
1. Cylindrical
2. Conical
3. Cylindro-conical
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Conus telescopic system, conical telescopic crowns
Definition
Indication (2)
The axial walls of the primary telescopes converge in occlusal direction in a 4-6°, i.e. the primary crown has a conical shape. There is efficient retention only in the end position of the secondary crowns, even a minor elevation results in ceasing of the retention (when the axial surface of the primary (and inner walls of secondary) has a 4º conicity towards the occlusal surface. The retention of this type is the smallest.)
• Indication:
1. Impaired periodontal tissues
2. Relatively high clinical crown
130
Cylindrical/paralel telescopic crown
Definition
Indication (2)
The axial walls of the primary telescopes are parallel, i.e. the primary crown has a cylindrical shape. The friction and the retention is the biggest in this case among the different types, in some cases even too intensive, and
so it can overload the periodontal tissues of the abutment teeth. (longer term: all the axial surfaces of the primary and secondary crowns are parallel to one another, and also parallel to the axis of each incorporated tooth.)
• Indication:
1. Healthy periodontal tissues
2. Clinical crown is relatively short
131
Cylindroconical telescopic crown
is the combination of the other types (parallel and conical). The axial walls of the primary telescopes are parallel in the gingival region, in a 3mm height, and in the more occlusal region they converge in the occlusal direction, i.e. the primary crown has a cylindrical shape in the gingival region, while in the occlusal region it has a conical form. There is an adequate retention even in a slightly elevated position of the secondary crown, while the conical part facilitates the insertion of the denture.
132
Delayed dental support/resilient telescope
There is an about 0.5mm gap between the occlusal surfaces of the primary and secondary crowns in the rest position of the denture, the denture will be also dentally supported at chewing and after the primary sinking of the denture in two-three weeks.
- Consequence of neglecting this theory results in a denture which is supported only by the teeth, and rocking on the teeth.
- with Stannic foil (0.3-0.6 mm)
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Steps of telescope retained acrylic based RPD construction (12)
1. Patient history, Physical examination, preliminary treatment plan
2. Pretreatments – definite treatment plan
3. Abutment preparation tapered in 5-8 degree, more tooth substance should be removed
4. precision impression
5. (bite registration)
6. Construction of primary crowns, Fraser technology
7. Positional impression (pick up impression and functional) with the primary crowns in their places on the abutments are made, with an individual tray
8. Bite registration, shade selection
9. Trial denture
10. Construction of secondary crowns
11. (Try in)
12. Final insertion
134
Steps of construction telescope retained RPD with metal frame (12)
1. Patient history, Physical examination, preliminary treatment plan
2. Pretreatments – definite treatment plan
3. Abutment preparation tapered in 5-8o, more tooth substance should be removed, chamfer preparation is preferred, precision impression
4. (bite registration)
5. Construction of primary crowns, Fraser technology
6. Bite registration shade selection
7. Positional impression with the primary crowns in their places on the abutments are made, with an individual tray
8. Trial denture
9. Construction of secondary crowns
10. Try in of secondary crowns with metal frame
11. Final insertion
12. Control
135
Dental, Periodontal support
is, when the vertical components of masticatory force are transmitted only to the tooth/periodontium.
136
Indication of Dental, Periodontal support (4)
1. the remaining teeth have a doubtful prognosis due to periodontal or endodontic reasons, especially if they have a strategically important position (canine, last tooth in molar region)
2. A missing bone or mucosa, defect of the alveolar process (we have to replace the lost alveolar process, but a bridge is not a solution because of esthetic, functional, or hygienic causes)
3. financial reason (insurance doesn’t cover it)
4. general health of the patient
137
Mucosal support
is, when the vertical components of masticatory force are transmitted only to the mucosal bony basement.
138
Disadvantages of Mucosal support (6)
1• Abutment teeth receive load also in rest position of the mandible: damage to periodontium -> tooth loss
2• There is a transverse load on the abutment teeth: damage to periodontium -> tooth loss
3• Even, steady sinking of the denture – in different extent in different patients, natural teeth will be overloaded
4• Clasps may sink into the marginal gingiva
5• Teeth and periodontium is covered in a great surface self-cleaning of the teeth is impossible
6• The denture is sinking and rising (moves vertically): covered teeth will wear off, caries develop
139
Indication of Mucosal suppot
We prepare this type of prosthesis (acrylic base) as a provisional treatment, or in some special cases of subtotal edentulousness
140
Mixed, dento-mucosal or muco-dental support
In this case the teeth and the mucosa- bone base take part together in the support and retention of the RPD. When the number and/or position of the remaining teeth doesn’t allow dental support, the vertical components of the masticatory force are transmitted to the teeth and the mucosal bony base (also the hard palate in the upper jaw).
141
Surveyor
instrument to determine the relative parallelism of surfaces of the teeth on the cast, with its help we can determine the insertion path of the denture and the prosthetic equator (height of contour, survey line) of the teeth. Main parts: small table, vertical spindle with tool holder for analyzing rod, carbon marker and undercut gauge.
142
Precision mechanical retainers
They are supporting and retention elements, where the
primary and secondary parts fit together closely and precisely after joined together. The effectiveness based mainly on friction between the female and male parts. The friction is provided by the good fit between the parallel surfaces of the primary and secondary parts. The positive and negative portions have precisely corresponding parallel surfaces, which fit together tightly.
143
Partial edentulousness
The dental status, when one or more teeth are missing from the dental arch, but there is at least one tooth/root present.
144
Real, actual rotation axis
is that primary rotation axis around which the inserted denture may sink, tilt or rock.
145
Master cast, working cast
Master cast (die) is an accurate replica of the prepared tooth surfaces, residual ridge areas, or other parts of the dental arch reproduced from an impression from which prosthesis is to be fabricated. In some cases, the technician makes a copy/duplicate about the master cast, to use it for preparing a metal framework or other appliance, or to avoid injury to the master cast. The working cast is an accurate reproduction of a master cast; used in preliminary fitting of a casting. For casting the metal framework, the working cast is prepared in investment material.
146
Hybrid denture/overdenture/subtotal denture
a removable complete denture constructed over natural teeth, roots or dental implants and uses them for support and possibly for retention, it is supported both by mucosa and by a few remaining natural teeth.
Indication: subtotal edentuolusness (1-3 standing teeth/implants)
147
Constructive elements
The part of overdenture, which serves the support and optionally the retention of the denture on the remaining teeth, roots or implants. Usually individually fabricated by dental technician.
148
Retentive elements
Such constructive elements, which serve not only the support of the overdenture, but also the retention.
149
Reline/rebase of denture
a procedure used to resurface the tissue side of a removable dental prosthesis with new base material, thus producing an accurate adaptation to the denture foundation area.
150
Milling technology
with this technology are the parallel surfaces of the precision attachments prepared, they can be regarded as active surveyors.
151
Subtotal edentulousness
Type of the partial edetulousness, when the patient has only one to three standing teeth.
152
Immediate denture
Is a denture which is finished for the time of tooth extractions, immediately after extracting the teeth it can be inserted into the patient’s mouth.
153
Decreased occlusal vertical dimension
If the physical OVD decreased after the completed eruption of the permanent teeth due to tooth wear or tooth loss.
154
Kennedy Class I
Bilateral Posterior Edentulous Areas, bilateral edentulous areas located posterior to all remaining teeth
155
Kennedy Class II
Unilateral Posterior Edentulous Area, unilateral edentulous area located posterior to all remaining teeth
156
Kennedy Class III
Unilateral edentulous area bounded by anterior and posterior natural teeth
157
Kennedy Class IV
A single, but bilateral (crossing the midline) edentulous area located anterior to remaining teeth.
158
Direct retainer
those elements of a removable partial denture which serve to provide resistance to bodily translation of the denture away from the supportive tissues, when it is subject to the action of gravity or occlusal forces. They are anchored on the teeth or other fixed appliances (crown, bridge, ball retention). These are: clasps, and precision attachments.
159
FF 1A
There can be one or more primary fulcrum lines, but after the prosthesis is inserted none of these becomes an actual rotational axis, torque does not arise on the axis of rotation, and the prosthesis doesn’t sink in any direction. Dental support is possible.
160
FF 1B
There can be one or more primary fulcrum lines from which one can become a real axis of rotation after the prosthesis is inserted. The moment of rotation is small, so the sinking of the tooth supported denture can be compensated for. There is a torque, but it can be compensated for, if we use more abutments for the anchorage. Fix prosthesis can be made.
161
FF 2A
There can be only one primary fulcrum line, but one or more secondary fulcrum lines. After inserting the denture, the primary axis of rotation may turn in an actual axis of rotation, and the denture rotating around this axis may sink in one direction. Tooth and mucosa support. The remaining teeth or the edentulous ridge is in one block. A removable partial denture can be made.
162
FF 2A/1
There is only one fulcrum line, and this primary fulcrum line becomes a real axis of rotation after the denture is inserted, the denture rotating around this axis, may sink in one direction. Mucosa and tooth supported. Long edentulous ridge, subtotal edentulousness. A removable partial denture can be made.
163
FF 2B
There can be two or more primary fulcrum lines, from which one may become a real axis of rotation after the denture is inserted. The denture rotating around this axis may sink in one direction. The remaining teeth aren’t situated in one block, combination of free end saddle and short span ridges. A removable partial denture can be made.
164
FF 3
There can be one or more primary fulcrum lines from which one or more may become a real axis of rotation after the denture is inserted, the denture rotating around them can sink in two directions, and it may rock. Mucosa and tooth supported. Very long edentulous ridges, teeth are situated diagonal. A removable partial denture can be made.
