3.0 Replacement of Missing Teeth Flashcards
constant pushing of the dental arch
State of dynamic equilibrium
When a tooth is lost, the ___________ of the dental arch is disrupted, and there is a subsequent realignment of teeth as a new state of ______ is achieved. Teeth adjacent to or opposing the edentulous space frequently move into it.
structural integrity
equilibrium
Opposing tooth or teeth may ______ into the vacated space.
supra-erupt
MISSING TEETH MAY BE REPLACED BY 3 TYPES OF PROSTHESES
- RPD
- FPD
- IMPLANT SUPPORTED FPD
FACTORS INVOLVED WHEN CHOOSING PROSTHESIS (5)
- Biomechanical
- Periodontal
- Esthetic
- Financial factors
- Patient’s wishes
it is indicated for:
(1) Spaces greater than 2 posterior teeth.
(2) Anterior spaces greater than 4 incisors.
(3) Spaces that include canine and 2 other contiguous teeth i.e. CI, LI & canine; LI, canine, and 1st PM; canine & both PM.
(4) Edentulous space with no distal abutment exception with cantilever FPD.
(5) Bilateral edentulous spaces with more than 2 teeth missing on one side.
REMOVABLE PARTIAL DENTURE (RPD)
FPD is preferred by majority and can provide long life of function if: (3)
- Abutment teeth is sound periodontally.
- Span is short and straight.
- Retainers are well designed and executed.
- There should be no gross soft tissue defect in the edentulous ridge. If there is, it may be possible to augment the ridge with ____ to enable the construction of a fixed prosthesis.
- This treatment is reserved for patients who are both highly motivated and able to afford this special procedure. If the patient does not meet these criteria, a __________ should be considered.
grafts
removable partial denture
- It creates a poor environment for any crown. The margins of the retainers will be at great risk from recurrent caries, limiting the life span of the prosthesis. However, it can also hinder the success of a removable partial denture.
- In either case, the patient must be made aware of the high risk involved. The risk may be minimized through home fluoride application and frequent recall, but it cannot be eliminated.
Dry mouth
a conservative restoration that is reserved for use on defect-free abutments in situations where there is a single missing tooth, usually an incisor or premolar.
RESIN-BONDED TOOTH SUPPORTED FPD – Maryland Bridge
ideally suited for use where there are insufficient numbers of abutment teeth or inadequate strength in the abutments to support a conventional fixed partial denture and when patient attitude and/or a combination of intraoral factors make a removable partial denture a poor choice.
IMPLANT SUPPORTED FPD
This prosthesis utilizes a standard pontic form, accommodating an edentulous ridge with moderate resorption and no gross soft tissue defects. Because it requires a shallow preparation that is restricted to enamel, it is especially useful in younger patients whose immature teeth with large pulps are poor candidates for endodontic-free abutment preparations.
RESIN-BONDED TOOTH SUPPORTED FPD – Maryland Bridge
________ can be accommodated only if there is enough tooth structure to allow a change in the normal alignment of axial reduction. This is limited by the need to restrict most of the reduction to enamel.
Tilted abutments
It is limited only by the availability of alveolar bone with satisfactory density and thickness in a broad, flat ridge configuration that will permit implant placement.
Span length
A single tooth can be replaced by a single implant, saving defect-free adjacent teeth from the destructive effects of retainer crown preparations. A span length of two to six teeth can be replaced by multiple implants, either as single unit restorations or as implant-supported fixed partial dentures.
SINGLE TOOTH IMPLANT FPD
In cases in which the choice between a fixed partial denture and a removable partial denture is not clear cut, two or more treatment options should be presented to the patient along with their advantages and disadvantages. The dentist is in the best position to evaluate the physical and biologic factors present, while the patient’s feelings should carry considerable weight on matters of esthetics and finances.
CASE PRESENTATION
- The question for treatment should be left to the patient’s wishes – if he or she perceives no functional, occlusal, or esthetic impairment, it would be a dubious service to place a prosthesis.
- Teeth adjoining an edentulous space usually move, but not always. When occasional has beaten the odds, recognize it, congratulate patient for being fortunate, and tend to his or her other needs.
NO PROSTHETIC TREATMENT
Every restoration must be able to withstand the constant occlusal forces to which it is subjected. This is of particular significance when designing and fabricating a fixed partial denture because the forces that would normally be absorbed by the missing tooth are transmitted, through the pontic, connectors, and retainers, to the abutment teeth. Abutment teeth are therefore called upon to withstand the forces normally directed to the missing teeth in addition to those usually applied to the abutments.
ABUTMENT EVALUATION
Roots and supporting tissues should be evaluated for 3 factors:
- Crown-root ratio
- Root configuration
- Periodontal ligament area
a measure of the length of tooth occlusal to the alveolar crest of bone compared with the length of root embedded in the bone. As the level of the alveolar bone moves apically, the lever arm of the portion out of bone increases, and the chance for harmful lateral forces increases.
Crown-root ratio
The optimum crown-root ratio for a tooth to be used as a fixed partial denture abutment
2:3
maximum ratio that is acceptable for a prospective abutment under normal circumstances.
1:1
Occlusal force exerted against prosthetic appliances has been shown to be considerably less than that against natural teeth: (3)
o 26.0 lbs for RPD
o 54.5 lbs for FPD
o 150.0 lbs for natural teeth
- an important part of the assessment of an abutment’s suitability from a periodontal standpoint.
- Roots that are broader labiolingually than they are mesiodistally are preferable to roots that are round in cross section.
ROOT CONFIGURATION
Different root configurations (4)
Normal (Cynodont)
Hypotaurodont
Mesotaurodont
Hypertaurodont
- ________ have a greater surface area and are better able to bear added stress.
Larger teeth
- In addition to increased load placed on the periodontal ligament by a long-span FPD, longer spans are less ____.
- Bending or deflection varies ____ with the cube of the length and ____ with the cube of the occlusogingival thickness of the pontic.
- Compared with a FPD single tooth pontic, a two-tooth pontic will bend __ as much, while a three-teeth pontic will bend ___ as much as a single pontic.
rigid
directly
inversely
8x
27x
- Preparations should be modified accordingly to produce ____________ and _____________.
G ____________, including some on the facial and lingual surfaces, are commonly employed for this purpose.
greater resistance
structural durability
Multiple grooves
G ___________ are sometimes used as a means of overcoming problems created by unfavorable crown-root ratios and long spans.
G There are several criteria that must be met if a _____ (remote from the edentulous space) abutment is to strengthen the fixed partial denture and not become a problem itself.
Double abutments
secondary
G __________ has its effect on the stresses occurring in a fixed partial denture.
G When pontics lie outside the __________________, the pontics act as a ____ arm, which can produce a ________ movement.
G This is a common problem in replacing all four maxillary incisors with a fixed partial denture, and it is most pronounced in the arch that is pointed in the anterior.
Arch curvature
interabutment axis line
lever
torqueing
FPD with the pontic _____ fixed to the retainers provides desirable strength and stability to the prosthesis while minimizing the stresses associated with the restoration
rigidly
A problem that occurs with some frequency is a mandibular second molar abutment that has tilted mesially into the space formerly occupied by the first molar.
TILTED MOLAR ABUTMENTS
Replacing canines can be difficult because the canine often lies outside the interabutment axis.
CANINE-REPLACEMENT FPD
- has an abutment or abutments at one end only, with the other end of the pontic remaining unattached.
- This is a potentially destructive design with the lever arm created by the pontic, and it is frequently misused.
CANTILEVER FPD
