🔥 C e r a m i c   I n l a y s 🔥 

Often the definitive choice of the technique - direct or indirect- and the restorative material, is possible only after removal of the carious tissue or the poor restoration when the professional knows the exact quantity and quality of the remnant tooth structure. 

This post demonstrates a ceramic inlay for a carious premolar. Where the removal of carious tissue promoted cusp undermining and compromised the integrity of both marginal ridges. Furthermore, the cavity is relatively deep and presents the occlusal isthmus equal to or greater than half the intercuspal distance. All these factors favor the indication of an inlay - a partial indirect restoration that doesn’t include cusps but may involve one or both proximal surfaces.

👉🏻 Notes this scheme showing the general characteristics of preparation for a ceramic inlay :
1️⃣ taper to allow the insertion of the restoration performed extra-orally “ occlusal divergence “.
2️⃣ rounded internal angles to minimize stress concentration which could lead to the fracture of the restoration or the tooth remnant.
3️⃣ well-defined margins with an angle close to 90 degrees between the internal surface of the preparation and the external surface of the remnant.
4️⃣ proper thickness of the ceramic about 1.5-2 mm, depending on the region.
5️⃣ absence of weakened areas in the tooth remnant, whether related to the presence of unsupported enamel or to the small thickness of the tooth structure. 

First of all, remove all the carious lesion using spherical burs  then follow the steps :
1️⃣ Using a coarse diamond point parallel to the planned insertion axis for the inlay to get the optimal preparation taper. ⛔️ Don’t attempt to manually set the taper by tilting the diamond points, inevitably will result in retentive preparations or more commonly, preparations with excess taper.

2️⃣ A conical diamond point is used to smooth and eliminate retentions in the surrounding buccal and lingual walls.

⛔️ The tip height allows for action along with the whole extent of the wall.
⛔️ If the cusps are undermined it is possible to fill the undercuts with composite, so that the cavity is not extended unnecessarily.

3️⃣ Extend the preparation to the proximal regions after protecting the adjacent teeth with a metal matrix.

⛔️ The large caliber of these points limits their action along the proximal walls, so use thin and tapered diamond points to open the contact areas facilitating the procedures of impression and cementation.
⛔️ The proximal-lingual and the proximal-buccal margins should present an angle of about 90 degrees with the external surface. This is an important feature for the resistance of the remnant and the restoration. Although this is easier on the proximal-lingual margins, on the proximal-buccal margins -because of the outer contour of the crown - a Hollenback reverse curve is necessary for the preparation.

4️⃣ Finishing is accomplished with similar points but with fine and extra-fine grits.

⛔️ This step allows us to correct any small defects and to remove irregularities improving surface smoothness of the walls.
⛔️ When performing the finishing & polishing of the proximal boxes, one must be extremely careful not to compromise the angulation of 90 degrees with the external surface obtained in the proximal-lingual & the proximal-buccal margins. Thus, it is preferable that the points act at the proximal boxes without reaching the region of the margins.

Once the preparation is complete, one can observe that it meets all the aforementioned requirements :
 taper about 12 degrees.
 rounded internal angles.
 sharp edges & a well-defined angle close to 90 degrees.
 enough thickness for the ceramic.
 tooth remnant with adequate strength. 

The next post will give attention to ceramic onlays.
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