MOD onlay Continued »
provides space for a bulk of metal to reinforce the occlusal margin on the functional cusp. The MOD amalgam is
now removed to form an inlay cavity with sharp, crisp internal line angles. The boxes should just break the contact with the adjacent mesial tooth to reduce the amount of gold visible. The distal box does not need to be quite as conservative with the buccal extensions as this is a non-visible area. Proximal flares are added
to the proximal boxes within the tip of the flare diamond. This flare is then taken onto the base of the box to form a gingival bevel. Finally, the proximal and
gingival flares are continued on to the palatal shoulder to form a shoulder bevel preparation and over the buccal cusp to produce an
Fig 7
The lower gold onlay has the same buccal preparation, but a bevel over the lingual cusp similar to the bevel over the buccal cusp of the maxillary onlay
Fig 8
For added retention, grooves can be placed at the internal line angles and on the buccal cusp tip
“Advantages of the onlay over the inlay include better
resistance and retention form” Paul Tipton
occlusal-buccal bevel. Unlike three-quarter crowns,
no occlusal offset is required as occlusal rigidity near the thin
buccal margin comes from the inlay preparation and bulk of gold. The MOD onlay preparation on mandibular
posterior teeth differs from the maxillary in the same way as in the three-quarter prepara- tions described in the previous article, thus making it a less aesthetic and conservative restoration and one that is not as often used. The next article in this
series deals with the all-ceramic crown.
Ireland’s Dental magazine 21
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