lec 4 - principles of design Flashcards
General Rules of Principles of Designing
1) Utilize what’s present.
2) Plan for the future.
3) Minimize framework elements whenever possible.
- Whenever possible, select a design that fits the teeth and soft tissues, rather than choosing one that requires _____________.
- When minimal tooth re-contouring is required, _____________ is minimized and teeth will be less susceptible to plaque adhesion and subsequent caries.
tissue alteration
surface roughness
- When abutments of questionable prognosis are present, a design should be chosen that would enable the partial denture to be adapted if such a tooth were lost.
- An example would be a tooth borne partial denture in which a posterior abutment was periodontally involved. In this instance, a _________________ should be used on the anterior abutment so that torqueing stresses would not compromise its periodontal support upon conversion to a distal extension partial denture.
stress-relieving clasp
- The _________ number of minor connectors should be used. This decreases potential for plaque adhesion. In some distal extension cases, one minor connector may be used for adjacent direct and indirect retainers (e.g. mesial occlusal rest on a first premolar and a cingulum rest on the adjacent canine)
- ____________ can be designed to join proximal plates, rather than having separate minor connectors, whenever possible.
fewest
Cingulum rests
1) Use _______________ support.
* Maximizing the denture base coverage provides greater stress distribution and resistance to displacement by lateral forces. (WHat principle?____________)
- However, the denture base should not be _____________ so that it is not displaced during functional movements. If this occurs the overextension will cause greater rotational forces to be placed on the denture and the abutment teeth.
broad tissue base
snow shoe principle
overextended
2) Distal extension bases should be extended to the ________________________ as these structures provide comfort and a peripheral seal for retention.
retromolar pads and the maxillary tuberosities
1) Minimize requirements for______________ by maximizing other retentive factors (e.g. broad and intimate denture base adaptation, use of guiding planes, indirect retainers, use of minor soft tissue undercuts).
2) Design retentive clasps tips to be ideally placed in the ___________ and modify any heights of contour to eliminate interferences with rigid portions of the direct retainer. This minimizes the torque on teeth and optimizes esthetics.
direct retention
gingival 1/3
3) Consider ____________. The placement of clasp arms are important to prevent area for caries development.
4) The ___________ may affect the choice of retentive clasps, since it affects possible clasp length and hence flexibility.
caries susceptibility
height of tooth
5) Consider the ____________ in the arch. The choice of direct retainer must be evaluated, its position, angulation and tilt.
6) If no retentive undercut can be found it is possible to ____________________ on the tooth. In order to re-contour the tooth properly, the designated surface must be approximately parallel to path of insertion or too much tooth structure will have to be removed.
tooth position
prepare a small retentive area
7) Circumferential retentive arms should be drawn in ___________ on diagnostic casts – the retentive tip not too close (1- 1.5mm) from the free gingival margin and the beginning rigid portion of the clasp low enough to prevent occlusal contact with the opposing tooth and low enough for acceptable esthetics.
8) Bracing arms should be placed in the __________ of the tooth occluso-gingivally. If the height of contour is above the inferior border of the arm, the height of contour should be lowered by preparing a guiding plane on the corresponding axial surface.
ideal position
middle 1/3
9) When there is marked mobility of one or more of the abutments, the use of ____________________ becomes more important. Stress relieving clasp assemblies allow release of the tooth and therefore, result in more of load being transferred to the denture base tissues.
10) I-bars should ___________ from the gridwork and originate from the gridwork approximately one tooth posterior to the replacement tooth adjacent to the abutment. Do not use ______ (less flexible). Do not flatten retentive end of the I-bar, to increase surface contact since the hygienic properties of the clasp will be compromise. A properly designed I-bar should not require an increased ____________ with the tooth.
stress-releasing direct retainers
gently curve
L-bars
contact area
11) Whenever possible, it is advisable to avoid placing rest seats or guiding planes on _____________________. The relatively high creep values and low yield strengths of these materials results in frequent failure under partial denture frameworks. It is better to redesign the partial denture to avoid these restorations or to replace the restorations with onlays or crowns.
12) Avoid placing rest in areas of ____________. Therefore, it is imperative that the clinician check the occlusion intraorally.
direct restorations such as amalgams
heavy occlusal contact
Four direct retainers offer an excellent amount of retention and are most frequently and oftenly used in ___________. Placement is ______________ of arch.
tooth borne cases
max at 2 on each side
3 (Three) Direct Retainers
Less retentive than four direct retainers, most commonly used in ____________.
Class II cases
2 (Two) Direct Retainers
Absolute minimum, usually only used in ____________, unless a rotational path design is selected.
Class I partial dentures
