Mouth preparation of partial denture

Mouth preparation is fundamental to a successful removable partial denture prosthesis. It contributes to philosophy : the prescribed prosthesis must not only replace what is missing, but also preserve thee remaining tissue and structures that will enhance the prosthesis.

Mouth preparation follows in logical sequence after oral diagnosis and tentative treatment planning. Final treatment planning may be deferred till the response to preparatory procedures can be ascertained.

Objectives of mouth preparation in removeable partial denture 1.To establish a state of health in the supporting and contiguous tissues. 2.To eliminate interferences or obstructions to the placement, removal and function of the prosthesis. 3.To establish an acceptable occlusal scheme. 4.To establish an acceptable occlusal plane.

5. To alter natural tooth form to accommodate the requirements of form and function of the prosthesis.

Mouth preparation

Relief of pain Dental conditions causing pain or discomfort due to caries or defective restoration should be treated as early in the treatment process as possible to eliminate the possibility of an acute episode or pain occurring during the treatment procedure. The gingival tissue should also be treated early to decrease the possibility of periodontal abscesses and other inflammatory responses.

Calculus accumulation should be derided, plaque should be controlled and a preventive dental hygiene program should be started and vigorously monitored.

Extractions The extraction of non-strategic teeth that would present complications or those that might be detrimental to the design of the prosthesis is necessary.

Removal of residual roots Generally all retained roots or root fragments should be removed, especially, if they are in close proximity to the tissue surface or if there is evidence of associated pathological findings.

Malposed teeth Loss of individual tooth or group of teeth may lead to extrusion, drifting or combination of malpositioning of the remaining teeth. In most cases, the alveolar bone supporting the extruded teeth also will be carried occlusally.

Cysts and odontogenic tumors

Exostoses and tori Presence of exostoses and tori compromise the design of the RPD. Modification of denture design at times can accommodate for exostoses, but more frequently resulting in additional stress to the supporting elements and compromised function.

Minor tooth movement Malposed teeth can be corrected by orthodontically repositioning.

1.Orthodontic treatment

2.Placement of cast restoration on the tooth to increase the clinical crown

3.Use of an occlusal onlay as a part of the RPD or as an onlay rest to restore the clinical crown to the plane of occlusion

Preparation of abutment teeth Abutment may be grouped as follows. 1.Those requiring only minor modifications to their coronal portions. 2.Those requiring to have restorations other than complete coverage crowns. 3.Those requiring to have crowns (complete coverage).

Abutment teeth that require only minor modifications include teeth with sound enamel.

Those with small restorations not involved in the RPD.

Sequence of abutment preparation on sound enamel or existing restorations i.Proximal surfaces path of placement should be prepared to provide guiding planes. ii.Tooth contours should be modified, lowering height of contour, so that : i.Origin of circumferential clasp arms may be placed well below the occlusal surface, preferably at the junction of the middle and gingival third.

ii. Retentive clasp terminals may be placed in the gingival third of the crown for better esthetics and better mechanical advantage. iii. Reciprocal clasp arms may be placed on and above a height of contour that is no longer higher than cervical portion of the abutment tooth.

3. After alterations of axial contours and before rest seat preparations are instituted, an impression of the arch should be made irreversible hydrocolloid and cast formed, that is surveyed to determine the adequacy of axial alterations before proceeding with rest seat preparations. If axial surfaces require additional recontouring, it can be done at the same appointment.

4. Occlusal rest areas should be prepared that will direct the occlusal forces along the long axis of the abutment tooth. Mouth preparation should follow removable partial denture design outlined on the diagnostic cast. Proposed changes to the abutment teeth should be made on the diagnostic cast and outlined to indicate the area, amount and angulation of modification to be done.

Preparing guiding planes

Preparing rest seats

Basic types of rest seats : 2 general types of rest seats : 1.Intracoronal. 2.Extracoronal.

Intracoronal rest preparation are prepared in a restoration such as a crown or inlay, they are never in atural tooth structure. Extracoronal rest preparations are placed on natural or restored tooth surfaces.