بسم الله الرحمن الرحيم


تحضير مرممة Onlay ذهبية بشكل MOD

The MOD Gold Onlay

Dr. Richard G. Stevenson

Indications


Replacing failed large amalgams/composites/inlays
When an inlay leaves remaining cusps too weak
When cusps may have internal cracks
Occlusal rehabililtation
Contraindications
Cracked tooth syndrome (better to do FGC)
Compromised retention
Esthetic concerns



Preparation design


Steps – MOD onlay preparation

Perform inlay first


56 or 170 bur
2 mm deep, flat pulpal, sharp line angles
6-10 degree taper, narrow at pulpal
Proximal extensions (clear adjacent teeth)
Butt joint margin at occlusal

Proximal Box - MOD Inlay

169L
1 -1.2 mm deep axially
Proximal clearance = 0.5-0.75 (rgs 2)
Axial wall = 3 mm in height minimum
Buccal and Lingual walls one plane
Axial wall straight – no need to curve




Refine Line Angles

Use hatchets/chisels to refine
axiobuccal and axiolingual line angles
Use instrument in two orientations




Reduce cusps


56, 57, 170 etc.
1.5 mm clearance on cusps
1.0 mm clearance for buccal cusp of maxillary onlay
Non-functional cusp
Preserves esthetics (like 3/4 and 7/8 crowns)
Use isthmus depth as a guide






Place shoulders (when indicated)


56, 57, 170, etc.
On buccal cusp of mandibular and lingual cusp of maxillary
Provides for greater bulk of gold on functional cusp
Increased resistance
Reinforced margin (more durable)
1 mm wide and 1 mm in height





QUESTION?

When performing a maxillary MOD onlay, is it necessary to place an offset, as we do in both the 3/4 and 7/8 crowns?


ANSWER:

No. The isthmus, adjacent to the buccal cusp will provide enough bulk of gold to support the thin marginal area.


Finishing bevels

7404
Place 0.5 mm bevel on shoulder
Mandibular buccal cusp
Maxillary lingual cusp
Place 0.5 mm bevel on occlusolingual
Mandibular preparation
Place 0.2-0.3 mm bevel on maxillary buccal cusp




Brief overview of restoration