Give a rule of thumb for how far the minor connector should extend posteriorly.
Extend buccally within physiologic tolerance of border structures. Mx: cover both Mx tuberosities, extend into the pterygomaxillary notches and provide for adaption along the posterior border, taking care not to extend beyond the soft palate flexure. Mn: bilateral distal extension RPD bases cover the retromolar pads and extend into the retromylohyoid fossae
The minor connector for acrylic resin bases must be totally embedded in the acrylic resin base. What thickness of acrylic resin is necessary between the residual ridge and minor connector to allow adjustment of the base if it should become necessary?
We use 2X28 gage
Nine requirements for an ideal denture base are given in this chapter, list six.
Accuracy of adaptation to the tissue, with minimal volume change
Dense, nonirritating surface capable of receiving and maintaining a good finish
Low specific gravity; light weight in the mouth
Sufficient strength; resistance to fracture or distortion
How is the design of a denture influenced by the classification of the arch being restored?
The type of arch presents various types of coverage forces and occlusion. RPDs opposing natural teeth will require greater support and stabilization because greater functional load demands
Two main types of dentures and why?
Kennedy class I and II-primary support tissue under base, secondary support from abutment teeth
Kennedy class III- all support derived from abutment teeth
Refer to book- Essay question
Definition of Guiding Plane: Two plus vertically parallel surfaces of abutment teeth shaped to direct a prosthesis during placement and removal. They are parallel to path of insertion and preferably the long access of abutment teeth.
Three main functions of guiding plane surfaces contacted by minor connectors:.
Provide one path of placement and removal
Insure intended actions of reciprocal, stabilizing, and retentive components
Eliminate food traps btn. Abutment teeth and denture
Should guiding planes on enamel surface of abut teeth be rounded or flat? Why?
Rounded, to avoid B or Li line angles bc line angles weaken either or both parts of clasp assembly
Direct retainers for tooth supported dentures differ in design from those used in extension base-type dentures. What requirement, in relation to undercut, exists for direct retainer (clasp) on a terminal abut of extension denture when denture base is forced into heavier contact with residual ridge?
Prevent horizontal movement, allow flex of retentive clasp, clasp arm must be freely flexible in any direction. Round, tapered clasp form offer advantages of more uniform flexibility, less tooth contact, and better esthetics.
Name component of RPD that must be rigid. Name flexible parts.
Rigid- Minor connectors that join rests and clasp assemblies to major connector, reciprocal arm clasps
Flexible- retentive arm clasp
Would a fixed partial denture be a better than RPD?
Totally depends on patient preferences and clinical presentation
What method used to replace single missing teeth or missing ant. Teeth
Preferably bridge, implant, maybe nothing
when confronted with K class 1, should you replace premolars with fixed partial?
No, nothing distal as an abutment
Amount of stress transferred to supporting edent ridge and abut teeth in extension based partial are dependent on 4 factors.
Tooth number and position in the arch relative to the edentulous spaces
For a tooth tissue supported prosthesis-the residual ridge for support
Opposing arch tooth positions
Existing and nature of prosthesis support in the opposing arch
Potential for establishing a harmonious occlusion (this one’s retarded but it makes 9 :0)
How is the design of a denture influenced by the classification of the arch being restored.
The main difference is in the type of support-whether that be tissue, tooth, or tooth-tissue.
There are really only two types of removable partial dentures. What are they?
Kennedy class I / II vs Kennedy class III.
Because there are two basic types of removable partial dentures, it is evident that a dentist must consider 1) the manner in which each is supported 2) the method of impression registration 3) the need of or lack of need for indirect retention and 4)the use of a base material that can be readily relined. Write a meaningful essay of 100 words or less about each of these listed considerations.
The answer to this question is pp 146-148. Kinda helpful.
What is a guiding plane?
Defined as two or more parallel, vertical surfaces of abutment teeth, so shaped to direct a prosthesis during placement and removal
What are the three main functions of guiding plane surfaces contacted by minor connectors?
1) to provide for one path of placement and removal of the restoration to eliminate detrimental strain to abutment teeth and framework components during placement and removal 2) to ensure the intended actions of reciprocal, stabilizing, and retentive components to provide retention against dislodgement of the restoration when the dislodging force is directed other than parallel to the path of removal and also to provide stabilization against horizontal rotation of the denture 3) to eliminate gross food traps between abutment teeth and components of the denture
Should guiding planes prepared on enamel surfaces of abutment teeth be rounded or flat, why?
The guide planes should be rounded. The reason for this is to avoid creating buccal or lingual line angles that could be produced in flat guide planes. These line angles would weaken the clasp assembly that contacts it.
Guide planes should be one half the width of the distance between the tips of adjacent buccal and lingual cusps or about one third of the buccal lingual width of the tooth.
Direct retainers for tooth supported dentures differ in design from those used in extension base type dentures. What requirement, in relation to an undercut, exists for the direct retainer on a terminal abutment of an extension denture when the denture base is forced in to heavier contact with the residual ridge
Must be able to flex sufficiently to dissipate stresses that otherwise would be transmitted directly to the abutment tooth as leverage. Some dentists prefer stress-breakers, others believe wrought wire are the best for this.
Name the components of a removable partial denture that must be rigid. Name the components in which flexibility is desirable
The rigid ones are major connectors, minor connectors and reciprocal clasp arms (the stabilizing components). The flexible ones are direct retainers (retentive clasps) in tooth supported and for distal extensions partial dentures.
Would you agree that a fixed partial, where indicated, should be the restoration of choice, in lieu of a removable partial? Give an example and explain.
Sorry, my clinical judgment at this point is a little lacking. The book doesn’t answer this question and I guess I’ll email this to Dr Olin. My guess is this question is just trying to make the point that each situation is going to be different depending on the health of the remaining teeth, the patient (ie dexterity, finances, etc), the disease process in the patient (ie rampant caries), etc.
What method should usually be used to replace single missing teeth or missing anterior teeth? Justify your answer.
A fixed partial denture (from chapter 14)
When confronted with a Kennedy class I arch in which all molars and first premolars are missing, should one consider replacing the first premolars with fixed partials rather than restoring the spaces with a removable restoration? Why?
The answer, of course, would be dependent on the clinical situation. However, if the 2nd premolars turned out to be weak abutments on their own, the splinting of the canine and 2nd premolar by a fixed partial denture can provide adequate support for abutment. The answer is yes-the first premolar should be restored by a fixed partial.
The amount of stress transferred to the supporting edentulous ridges and the abutment teeth in extension base partial dentures is dependent on four factors. One is the length of the lever arm or denture bases. Identify the other three and describe how each influences this stress transfer.
1) direction and magnitude of the force 2) the quality of resistance (support from the remaining natural teeth and edentulous ridge) 3) the design characteristics of the partial denture.
A systematic approach to developing the design for any removable partial denture was presented and discussed. Outline the steps presented in this approach.
determine how the partial denture is to be supported (ie rests and tissue stops)
connect the tooth and tissue support units (ie major and minor connectors)
determine how the rpd is to be retained (ie clasps)
connect the retention units to the supporting units
outline and join the edentulous area to the already established design components
In evaluating the potential support that abutment teeth can provide, what specific characteristics of the teeth should you consider?
1) periodontal health 2) crown and root morphologies 3) crown to root ratio 4) bone index area 5) location of the tooth in the arch 6) relationship of the tooth to other support units aka length of the edentulous span 7) the opposing dentition
In evaluating the potential tissue support that the edentulous ridges can provide in extension base situations, what specific characteristics should be considered
1) the quality of the residual ridge 2) the extent to which the residual ridge will be covered by the denture base 3) the type and accuracy of the impression registration 4) the accuracy of the denture base 5) the design characteristics of the component parts of the partial denture framework 6) the anticipated occlusal load
In developing the design for an extension base rpd, what component parts are used to connect the supporting units? What specific characteristics should each of these components have to effectively distribute functional stresses to the supporting units?
Major connectors should be properly located in relation to gingival and moving tissues and should be designed to be rigid. Rigidity in a major connector is necessary to provide proper distribution of forces to and from the supporting components. Minor connectors should be located in interproximal spaces to provide adequate bulk of material without impinging on the tongue.
In developing a design for an extension base rpd, when does one determine how the denture is to be retained? What are the keys to selecting successful clasp designs
Retainers for distal extension rpds have to be able to flex or disengage when the denture base moves toward the tissue when in function. Thus, the retainer may act as a stress breaker. Clasps that act as stress breakers, rather than a mechanical stress breaker, provide the same stress relief without compromising the horizontal stabilization of the rpd. The clasp must be freely flexible in all planes-rounded tapered clasps are the best. Therefore, the wrought wire circumferential or a carefully designed bar clasp can be used.
How does one know if indirect retention needs to be incorporated into the design? If needed, where should it be located, and what component parts would be included in the design to serves as indirect retainers?
Indirect retention is placed in situations where a fulcrum line exists. Fulcrum lines exist only where a distal extension is present (ie no fulcrum line exists in a kennedy class III-Dr. James said this is a classis test question). Indirect retention should be placed as far anterior (and at a right angle) to the fulcrum line, on a tooth that is capable of withstanding the forces placed on it. Therefore a canine or premolar should be used. An incisal or cingulum rest seat should be used. This describes the first purpose of indirect retention-to prevent rotation of the rpd about the fulcrum line. The second purpose of indirect retention is in support of the major connector- for example, a long lingual bar can be prevented from settling into the tissue if indirect retention is incorporated. Remember-a lingual plate is not an indirect retainer, it is located on inclined tooth surfaces which make it an ortho appliance.
What is the final step in the proposed systematic approach to design? Should this design characteristic have any special requirements? If so, what are they?
The final step was to outline and join the edentulous area to the already established design components (see question 15). The amount of flexure of the distal extension will affect the retentive clasp requirements. For example, if the edentulous ridge is greatly resorbed, the span is especially long, or excessive occlusal load is placed on the extension, greater flexure of the clasp will be required. These examples will also be important in considering how the minor connector will contact the abutment tooth adjacent to the extension in order to prevent torque on that abutment tooth. There is a good diagram on page 149 explaining this phenomenon that is difficult to explain in words.
What is a splint bar?
As answered in a previous question-missing anterior teeth are best replaced with a fixed partial. However, some situations exist in which several missing anterior teeth need to be replaced with the rpd (ie replacing a long span of anterior teeth). When this is the case-the splint bar acts as the major connector to connect the abutment teeth in a long span in order to provide support to the replaced anterior teeth. There is a good picture on page 159 to get an idea of what it looks like.
Draw a splint bar from a frontal, horizontal, and sagittal view. Label the dimensions and relationship of the bar to the tissue and the abutments.
The splint bar should be round or ovoid. As viewed from above, the splint bar should be in a straight line between the abutments. In a sagittal section, a rounded pear shape makes point contact with the ridge (prevents rotational torque). The bar should be placed slightly lingual to the ridge to provide esthetic arrangement of the artificial teeth.
What purposes are served by use of splint bars where indicated?
Enhances longevity of the teeth being replaced and stability of the rpd. Basically, just think of it as a sturdy structure for a long span of artificial teeth to rest on. If flexure of the long span occurs, this prevents the fracture of the span. Kinda like a sturdier grid work that is between two abutments.
A decision has been made to use a splint bar from canine to canine. Will this decision influence the design of the framework? If so, how?
The major design difference in using a splint bar is that the bar actually serves as the major connector, so the traditional major connector is not needed.
For what reasons must a splint bar be convex, rather than concave, adjacent to the residual ridge?
The splint bar needs to be concave in order for the patient to be able to keep it clean (flossing). Think of the hygienic pontic we learned about-same principles.
Is a 13 guage splint bar adequate for a span from canine to canine? Why or why not?
NO-long spans require more rigid bars (10 guage)
Describe and define an internal clip attachment
The internal clip attachment differs from the splint bar in that the internal clip provides both support and retention from the connecting bar. See figure 10-17 on page 161 for picture. Basically, a connecting bar is placed (for example) between two canines and is raised slightly off of the edentulous ridge. Then, a nylon or metal ‘clip’ is secured in the tissue contacting side of the rpd. The clip is contoured to fit the bar and kinda snaps around the bar. The use of the bar and clip provides support, stability, and retention for the anterior modification area and it may allow one to eliminate both occlusal rests and retentive clasps on the adjacent abutment teeth.
The internal clip attachment must be used in conjunction with some type of bar supported by abutment teeth. What is the cross-sectional shape of such a bar? What advantages accrue from using such a design for a restoration?
The previous question answered this one except that the bar should be round and straight in order for the clip to be able to engage it.