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PREPARATIONS FOR PARTIAL VENEER CROWNS MAXILLARY POSTERIOR THREE QUARTER CROWNS THE STANDARD THREE QUARTER CROWN IS A PARTIAL VENEER CROWN IN WHICH THE.

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Presentation on theme: "PREPARATIONS FOR PARTIAL VENEER CROWNS MAXILLARY POSTERIOR THREE QUARTER CROWNS THE STANDARD THREE QUARTER CROWN IS A PARTIAL VENEER CROWN IN WHICH THE."— Presentation transcript:

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2 PREPARATIONS FOR PARTIAL VENEER CROWNS

3 MAXILLARY POSTERIOR THREE QUARTER CROWNS THE STANDARD THREE QUARTER CROWN IS A PARTIAL VENEER CROWN IN WHICH THE BUCCAL SURFACE IS LEFT UNCOVERED. IT IS THE MOST COMMONLY USED PARTIAL VENEER CROWN. THE STANDARD THREE QUARTER CROWN IS A PARTIAL VENEER CROWN IN WHICH THE BUCCAL SURFACE IS LEFT UNCOVERED. IT IS THE MOST COMMONLY USED PARTIAL VENEER CROWN.

4 OCCLUSAL REDUCTION IS THE FIRST STEP IN PREPARING A TOOTH FOR A THREE QUARTER CROWN. DEPTH ORIENTATION GROOVES ARE CUT ON THE ANATOMIC RIDGES AND GROOVES OF THE OCCLUSAL SURFACE WITH A ROUND END TAPERED DIAMOND. CLEARANCE SHOULD BE 1.5 mm ON THE FUNCTIONAL CUSP ( lingual on maxillary teeth) AND 1 mm ON THE NON FUNCTIONAL CUSP (facial) OCCLUSAL REDUCTION IS THE FIRST STEP IN PREPARING A TOOTH FOR A THREE QUARTER CROWN. DEPTH ORIENTATION GROOVES ARE CUT ON THE ANATOMIC RIDGES AND GROOVES OF THE OCCLUSAL SURFACE WITH A ROUND END TAPERED DIAMOND. CLEARANCE SHOULD BE 1.5 mm ON THE FUNCTIONAL CUSP ( lingual on maxillary teeth) AND 1 mm ON THE NON FUNCTIONAL CUSP (facial)

5 NEXT THE FUNCTIONAL CUSP BEVEL IS MADE. HOLDING THE ROUND-END TAPERED DIAMOND AT A 45 degree ANGLE TO THE LONG AXIS OF THE PREPARATION, 3-5 DEPTH-ORIENTATION GROOVES ARE PLACED ON THE LINGUAL OR OUTER INCLINE OF THE LINGUAL CUSP. THE GROOVES ARE 1.5 mm DEEP AT THE CUSP TIP AND FADE OUT AT THEIR APICAL END.

6 AXIAL REDUCTION IS BEGUN BY REDUCING THE LINGUAL SURFACE WITH A TORPEDO DIAMOND, TAKING CARE NOT TO OVERINCLINE THE LINGUAL WALL. AXIAL REDUCTION IS BEGUN BY REDUCING THE LINGUAL SURFACE WITH A TORPEDO DIAMOND, TAKING CARE NOT TO OVERINCLINE THE LINGUAL WALL. THE CUT IS EXTENDED INTERPROXIMALLY THE CUT IS EXTENDED INTERPROXIMALLY AS THE AXIAL REDUCTION IS DONE, A CHAMFER FINISH LINE IS FORMED. AS THE AXIAL REDUCTION IS DONE, A CHAMFER FINISH LINE IS FORMED.

7 PROXIMAL ACCESS IS GAINED BY USING A SHORT NEEDLE DIAMOND IN AN UP AND DOWN SAWING MOTION. THIS IS CONTINUED FACIALLY UNTIL CONTACT WITH THE ADJACENT TOOTH IS BROKEN. PROXIMAL ACCESS IS GAINED BY USING A SHORT NEEDLE DIAMOND IN AN UP AND DOWN SAWING MOTION. THIS IS CONTINUED FACIALLY UNTIL CONTACT WITH THE ADJACENT TOOTH IS BROKEN. THE GIGIVO FACIAL ANGLE SHOULD NOT BE UNDER EXTENDED; IT IS THE MOST LIKELY AREA OF A THREE QUARTER CROWN TO FAIL. THE GIGIVO FACIAL ANGLE SHOULD NOT BE UNDER EXTENDED; IT IS THE MOST LIKELY AREA OF A THREE QUARTER CROWN TO FAIL.

8 THE AXIAL WALL AND CHAMFER ARE FINISHED WITH TORPEDO BUR OF THE SAME SIZE AND CONFIGURATION. THE AXIAL WALL AND CHAMFER ARE FINISHED WITH TORPEDO BUR OF THE SAME SIZE AND CONFIGURATION. PROXIMAL GROOVES ARE APPROXIMATELY THE SIZE OF A NO. 171L BUR. GROOVE SHOULD BE PLACED AS FAR FACIALLY AS POSSIBLE WITHOUT UNDERMINING THE FACIAL SURFACE, PARALLELING THE LONG AXIS OF A POSTERIOR TOOTH PROXIMAL GROOVES ARE APPROXIMATELY THE SIZE OF A NO. 171L BUR. GROOVE SHOULD BE PLACED AS FAR FACIALLY AS POSSIBLE WITHOUT UNDERMINING THE FACIAL SURFACE, PARALLELING THE LONG AXIS OF A POSTERIOR TOOTH

9 A FLARE IS A FLAT PLANE THAT REMOVES EQUAL AMOUNTS OF THE FACIAL WALL OF THE GROOVE AND THE OUTER SURFACE OF THE TOOTH. IT IS CUT FROM THE GROOVE OUTWARD WITH THE TIP OF A FLAME DIAMOND TO PREVENT OVER EXTENSION. THE FLARE SHOULD BE SMOOTHENED WITH A CARBIDE BUR MATCHING THE CONFIGURATION OF THE FLAME DIAMOND. A FLARE IS A FLAT PLANE THAT REMOVES EQUAL AMOUNTS OF THE FACIAL WALL OF THE GROOVE AND THE OUTER SURFACE OF THE TOOTH. IT IS CUT FROM THE GROOVE OUTWARD WITH THE TIP OF A FLAME DIAMOND TO PREVENT OVER EXTENSION. THE FLARE SHOULD BE SMOOTHENED WITH A CARBIDE BUR MATCHING THE CONFIGURATION OF THE FLAME DIAMOND.

10 THE OCCLUSAL OFFSET, A 1 mm WIDE LEDGE ON THE LINGUAL INCLINE OF THE FACIAL CUSP. IT IS MADE WITH A NO.171L BUR. THE OCCLUSAL OFFSET, A 1 mm WIDE LEDGE ON THE LINGUAL INCLINE OF THE FACIAL CUSP. IT IS MADE WITH A NO.171L BUR. A 0.5 mm BEVEL ALONG THE BUCCO- OCCLUSAL FINISH LINE, PERPENDICULAR TO THE PATH OF INSERTION A 0.5 mm BEVEL ALONG THE BUCCO- OCCLUSAL FINISH LINE, PERPENDICULAR TO THE PATH OF INSERTION

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13 POSTERIOR PARTIAL VENEER VARIATIONS A THREE-QUARTER CROWN PREPARATION WITH PROXIMAL BOXES IS MORE RETENTIVE THAN A STANDARD PREPARATION WITH GROOVES. BUT BOXES ARE VERY DESTRUCTIVE. THEY CAN BE JUSTIFIED ONLY IF THERE HAS BEEN PREVIOUS CARIES OR RESTORATIONS. A THREE-QUARTER CROWN PREPARATION WITH PROXIMAL BOXES IS MORE RETENTIVE THAN A STANDARD PREPARATION WITH GROOVES. BUT BOXES ARE VERY DESTRUCTIVE. THEY CAN BE JUSTIFIED ONLY IF THERE HAS BEEN PREVIOUS CARIES OR RESTORATIONS.

14 A THREE-QUARTER CROWN PREPARATION ON A MANDIBULAR MOLAR OR PREMOLAR HAS MANY FEATURES FOUND IN THE PREPARATION OF THE MAXILLARY TOOTH. THE BIGGEST DIFFERENCE IS THE LOCATION OF THE OCCLUSAL FINISH LINE ON THE FACIAL SURFACE, GINGIVAL TO OCCLUSAL CONTACTS. THERE IS NO NEED FOR AN OFFSET ON THE LINGUAL INCLINES OF THE BUCCAL CUSPS. A THREE-QUARTER CROWN PREPARATION ON A MANDIBULAR MOLAR OR PREMOLAR HAS MANY FEATURES FOUND IN THE PREPARATION OF THE MAXILLARY TOOTH. THE BIGGEST DIFFERENCE IS THE LOCATION OF THE OCCLUSAL FINISH LINE ON THE FACIAL SURFACE, GINGIVAL TO OCCLUSAL CONTACTS. THERE IS NO NEED FOR AN OFFSET ON THE LINGUAL INCLINES OF THE BUCCAL CUSPS.

15 THE SEVEN-EIGHTS CROWN IN A THREE- QUARTER CROWN WHOSE VERTICAL DISTO- OCCLUSAL MARGIN IS POSITIONED SLIGHLTLY MESIAL TO THE MIDDLE OF THE BUCCAL SURFACE. THE SEVEN-EIGHTS CROWN IN A THREE- QUARTER CROWN WHOSE VERTICAL DISTO- OCCLUSAL MARGIN IS POSITIONED SLIGHLTLY MESIAL TO THE MIDDLE OF THE BUCCAL SURFACE.  ESTHETICS ARE GOOD.  RESISTANCE IS BETTER THAN THAT OF THE THREE QUARTER CROWN.  EASY TO DO.  CLEANING BY THE PATIENT ARE ALSO FACILITATED.

16 THE REVERSE THREE- QUARTER CROWN IS USED ON MANDIBULAR MOLARS TO PRESERVE AN INTACT LINGUAL SURFACE. THE REVERSE THREE- QUARTER CROWN IS USED ON MANDIBULAR MOLARS TO PRESERVE AN INTACT LINGUAL SURFACE. IT IS USEFUL ON FIXED PARTIAL DENTURE ABUTMENTS WITH SEVERE LINGUAL INCLINATIONS. IT IS USEFUL ON FIXED PARTIAL DENTURE ABUTMENTS WITH SEVERE LINGUAL INCLINATIONS.

17 THE PROXIMAL HALF CROWN IS A THREE-QUARTER CROWN THAT IS ROTATED 90 degrees WITH THE DISTAL RATHER THAN THE BUCCAL SURFACE LEFT INTACT. THE PROXIMAL HALF CROWN IS A THREE-QUARTER CROWN THAT IS ROTATED 90 degrees WITH THE DISTAL RATHER THAN THE BUCCAL SURFACE LEFT INTACT.

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19 ANTERIOR THREE QUARTER CROWNS CREATE A CONCAVE LINGUAL REDUCTION INCISAL TO THE CINGULUM. IT IS NECESSARY TO CREATE 0.7 mm OR MORE CLEARANCE WITH OPPOSING TEETH. CREATE A CONCAVE LINGUAL REDUCTION INCISAL TO THE CINGULUM. IT IS NECESSARY TO CREATE 0.7 mm OR MORE CLEARANCE WITH OPPOSING TEETH. TO ENSURE ADEQUATE REDUCTION DEPTH ORIENTATION CUTS ARE MADE ON THE LINGUAL SURFACE. TO ENSURE ADEQUATE REDUCTION DEPTH ORIENTATION CUTS ARE MADE ON THE LINGUAL SURFACE.

20 INCISAL REDUCTION IS DONE WITH THE SMALL WHEEL DIAMOND. IT PARALLELS THE INCLINATION OF THE UNCUT INCISAL EDGE AND BEARLY BREAKS THROUGH THE LABIOINCISAL LINE ANGLE. INCISAL REDUCTION IS DONE WITH THE SMALL WHEEL DIAMOND. IT PARALLELS THE INCLINATION OF THE UNCUT INCISAL EDGE AND BEARLY BREAKS THROUGH THE LABIOINCISAL LINE ANGLE.

21 THE DIAMOND IS KEPT PARALLEL WITH THE INCISAL TWO-THIRDS OF THE LABIAL SURFACE TO INITIATE THE PATH OF INSERTION OF THE PREPARATION. THE DIAMOND IS KEPT PARALLEL WITH THE INCISAL TWO-THIRDS OF THE LABIAL SURFACE TO INITIATE THE PATH OF INSERTION OF THE PREPARATION. THE INSTRUMENTS COMES FROM THE LINGUAL, TO MINIMIZE DISPLAY OF METAL LATER. AN UP AND DOWN MOTION IS USED WITH CARE NOT TO NICK THE ADJACENT TOOTH OR LEAN THE DIAMOND TOO FAR INTO THE CENTRE OF THE PREPARED TOOTH THE INSTRUMENTS COMES FROM THE LINGUAL, TO MINIMIZE DISPLAY OF METAL LATER. AN UP AND DOWN MOTION IS USED WITH CARE NOT TO NICK THE ADJACENT TOOTH OR LEAN THE DIAMOND TOO FAR INTO THE CENTRE OF THE PREPARED TOOTH

22 THE AXIAL REDUCTION IS COMPLETED AND THE FINISH LINE IS ACCENTUATED WITH A TORPEDO DIAMOND. THE AXIAL REDUCTION IS COMPLETED AND THE FINISH LINE IS ACCENTUATED WITH A TORPEDO DIAMOND. THE GROOVES ARE PLACED AS FAR LABIALLY AS POSSIBLE WITHOUT UNDERMINING THE LABIAL ENAMEL PLATE. THE GROOVES ARE PLACED AS FAR LABIALLY AS POSSIBLE WITHOUT UNDERMINING THE LABIAL ENAMEL PLATE.

23 ON THE FACIAL ASPECT OF EACH GROOVE, A FLARE IS STARTED AT THE GINGIVAL END WITH THE THIN TIP OF A FLAME DIAMOND. ON THE FACIAL ASPECT OF EACH GROOVE, A FLARE IS STARTED AT THE GINGIVAL END WITH THE THIN TIP OF A FLAME DIAMOND. THE GROOVES ARE CONNECTED WITH AN INCISAL OFFSET, STAYING A UNIFORM DISTANCE FROM THE INCISAL EDGE. THE GROOVES ARE CONNECTED WITH AN INCISAL OFFSET, STAYING A UNIFORM DISTANCE FROM THE INCISAL EDGE.

24 A 0.5 mm WIDE BEVEL IS PLACED ON THE LABIOINCISAL FINISH LINE. A 0.5 mm WIDE BEVEL IS PLACED ON THE LABIOINCISAL FINISH LINE.

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