STEPS OF MOUTH PREPERATION
1- Completion of required surgical procedures:
-

Conditions requiring surgery include:

-

Ext...
Designed so that its components join the teeth as functional units .
- This include:
1- multiple buccally positioned clasp...
3- Enhance retentive undercuts
c) Rest Seat preparation
1- For posterior teeth
2- For anterior teeth
d) Precision attachme...
1- Prepare guide surfaces
2- Lower survey lines to improve clasp location
3- Carry out embrasure widening
4- Create retent...
Guide Surfaces
Checking orientation
of the bur to the path
of insertion on the
surveyed cast.
Guide Surfaces
Cylindrical d...
surface, the head of
hand piece is tipped
slightly towards the
centre of the tooth
and moving the bur
back and forth.
Embr...
rounded.
Rests in posterior teeth
. This shape follows the outline of the
mesial or distal fossa of the occlusal
surface o...
. The deepest part of the occlusal rest
preparation should be in the center
of the fossa of the tooth.
Rests in posterior ...
smoothed.
Rests
Cingulum Rest seat

in

. Is usually prepared on the cingulum of a maxillary canine.
. The rest seat is an...
Cingulum rest in anterior teeth, clinical treatment options

. Continue cutting gingivally by moving
the tool mesially and...
wheel or green stone to prepare a
a U-shaped notch 1.5 to 2 mm inside
the proximal corner.
Incisal rests in anterior teeth...
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Mouth preperation

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Clinical Removable Prosthodontics
Forth Year

Mouth preperation

  1. 1. STEPS OF MOUTH PREPERATION 1- Completion of required surgical procedures: - Conditions requiring surgery include: - Extraction of unrestorable teeth , teeth with insufficient periodontal support - Elimination of tori or prominent exostosis. - Removal of hyperplastic tissue - Ridge augmentation, vestibular extension and implant placement should be performed early. - Surgical reduction of maxillary tuberosities to provide adequate restorative space 2- Periodontal Therapy - Should be done early in treatment plan - Periodontal scaling and root planning to eliminate local factor. - Elimination of pockets and periodontal flap when necessary . - Gingivoplasty and gingivectomy - Remaining natural teeth with dead periodontal support and stabilization for RPD and resistance of abutment to applied force This includes: Fixed Splinting - include completion of partial coverage restoration. - Fixed splinting of posterior teeth a- teeth distal to canine  anteroposterior resistance b- teeth mesial to canine  mediolatral resistance Disadvantages of fixed splinting: -Inability to adequately clean splinted unit (inability to floss)  leading to inadequate oral hygiene -High cost Splinting with removable partial denture
  2. 2. Designed so that its components join the teeth as functional units . - This include: 1- multiple buccally positioned clasp arm 2- lingual plating 3) Conditioning of abused oral tissues: May develop due to ill-fitting or poorly occluding old RPD so tissue must get rest and treatment in the following sequence: 1.Patient education and oral hygiene instruction 2.Removal of the dentures from the oral cavity 3.Oral hygiene measures 4.Use of tissue conditioners 5.Modifications to existing prosthesis 6.Provisional prosthesis or Interim prosthesis 4) Conservative treatment : Include  -Restorative fillings - Crowning Endodontic treatment 5) Prosthetic Therapy a) Occlusal equilibration analysis. 1- Correction of irregular occlusal plane. 2- Correction of malaligned occlusal plane. 3- Verifying the occlusion 4- Treatment of traumatic vertical overlap b) Teeth reshaping 1- Development of guiding planes 2- Change the height of contour
  3. 3. 3- Enhance retentive undercuts c) Rest Seat preparation 1- For posterior teeth 2- For anterior teeth d) Precision attachment OCCLUSSAL EQUILIBRATION ANALYSIS: 1-correction of irregular occlusal plane (occlusal plane discrepancies) , this includes: *supra eruption (over eruption) *infra eruption *tipping Phases of mouth preparation for removable partial dentures I- Phase . Periodontal . Operative . Endodontic . Orthodontic . Surgical II-Phase . Involves the alteration of tooth contours to allow the proper fit and functioning of the proposed removable partial denture. Suggested clinical sequence for tooth preparations
  4. 4. 1- Prepare guide surfaces 2- Lower survey lines to improve clasp location 3- Carry out embrasure widening 4- Create retentive undercut. 5- Prepare rest seats 1- Guide surfaces . Are prepared on proximal surfaces of abutments adjacent to edentulous spaces. . Proximal guide surfaces should be about as wide the distance between tips of buccal & lingual cusps. Guide Surfaces A guide surface should be prepared by even reduction of the tooth surface maintaining its contour and not as flat surface. Guide Surfaces A proximal guide surface should be 2-3mm high and about as wide the distance between the buccal and lingual cusps.
  5. 5. Guide Surfaces Checking orientation of the bur to the path of insertion on the surveyed cast. Guide Surfaces Cylindrical diamond bur is moved back and forth around involved tooth surface Lowering Survey Lines Lowering survey lines by reduction of tooth bulbosity will improve clasp placement by allowing :1. The origin of clasp arm to be placed well below the occlusal surface. Restoring abutments with cast restorations (surveyed crowns) Indications . Large carious tooth . Weak tooth because of large restorations . Recurrent caries . Abutment with inadequate contours or required contouring will expose the dentine. Lowering Survey Lines Using Cylindrical bur. The bur is placed against the involved
  6. 6. surface, the head of hand piece is tipped slightly towards the centre of the tooth and moving the bur back and forth. Embrasure widening Achieved by enlarging the lingual embrasure with a narrow tapered diamond bur. Rest seat preparation Functions of Rests . Acts as a stop to prevent injury to and overdisplacement of soft tissues under partial denture bases. . Maintains the attached clasp assembly its proper surveyed position. . Acts as an indirect retainer. Rest seats in Posterior teeth . The outline form is basically triangular with the base of the triangle at the marginal ridge and apex extending toward the center of the tooth. . The apex of the triangle should be
  7. 7. rounded. Rests in posterior teeth . This shape follows the outline of the mesial or distal fossa of the occlusal surface of the tooth. . The length varies from one third to one half the mesiodistal length of the tooth (3-4mm). Rests in Posterior teeth . The bucco-lingual width should be at least one half the distance between the cusp tips( one third the bucco-lingual width of the tooth). . The floor of the occlusal rest should be inclined slightly toward the center of the tooth ( concave or spoon shape). Rests in Posterior teeth . The angle formed by the inclination of the floor of the rest preparation and the vertical projection of the greatest contour of the proximal surface of the tooth should be less than 90 degrees. Rests in Posterior teeth
  8. 8. . The deepest part of the occlusal rest preparation should be in the center of the fossa of the tooth. Rests in posterior teeth, clinical treatment options 1- The preparation is started by first reducing and rounding the middle third of the marginal ridge using a round bur of an appropriate size ( no.6 for molars, no.4 for premolars). Clinical Treatment Options 2- This is followed by deepening the of the adjacent fossa which is then blended into the reduced marginal ridge. Clinical Treatment Options 3- Verify the depth of the preparation by having the patient close on a small piece of red utility wax placed over the preparation. Clinical Treatment Options 4- Once complete, the preparation should be examined to ensure that no interferences to the path of insertion have been created and any small enamel “lips” should be
  9. 9. smoothed. Rests Cingulum Rest seat in . Is usually prepared on the cingulum of a maxillary canine. . The rest seat is an inverted U shape. . The lingual surface of the tooth makes up the inner wall, while the outer wall of the U-shaped notch starts at the apex of the cingulum and inclines gingivally toward the center of the tooth to meet the inner wall of the preparation. Cingulum Rest Seat . The outline form should be in the shape of crescent and for a smooth curve from one marginal ridge to the other. . The deepest portion should be in the center of the tooth over the cingulum. Cingulum rest in anterior teeth, clinical treatment options . An inverted cone carbide bur, round high speed diamond bur (no.2). . Start the preparation incisal to the cingulum. The flat side of the cutting instrument should follow the incline of the lingual surface of the tooth cutting towards the apex of the tooth. Anterior teeth
  10. 10. Cingulum rest in anterior teeth, clinical treatment options . Continue cutting gingivally by moving the tool mesially and distally in an arc to form the notch. . Care should be used not to create an undercut. Incisal Rests . Usually used on mandibular canines, the rest seat consists of a small inverted U-shaped notch on the incisal surface just inside the proximal corner of the tooth with the deepest part of the preparation toward the center of the tooth mesio-distally. Incisal Rests . The notch should be rounded and carried slightly over the labial surface to provide positive seating. . The enamel, lingual to the notch, may be prepared to accommodate some of the bulk of the minor connector. Incisal Rests in anterior teeth, clinical treatment options . Use a small knife-edged diamond
  11. 11. wheel or green stone to prepare a a U-shaped notch 1.5 to 2 mm inside the proximal corner. Incisal rests in anterior teeth, clinical treatment options . Move the cutting instrument in an inverted U-shaped motion and extend the cut to the labial and lingual surfaces of the tooth. . Use it to partially prepare the lingual surface to accommodate the minor connector.

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