CAVITY PREPARATION

Knowledge of the fundamental principles of adhesive dentistry is a prerequisite when working with composite in order to obtain good levels of aesthetic-functional integration of the restoration and long-term duration.Adhesive cavities do not foresee retentions,   internal   sharp  edges shall be avoided and a rounded cavity   has   to   be   prepared   to facilitate the flowing of composite cement. When preparing the cavity for indirect adhesive restorations, the principle of maximum tissue preservation shall be observed and the shape of the cavity depends on the extension of the caries or the presence of pre-existing restorations to be replaced.


The clinical procedure includes two sessions: the first one to prepare and take the impression, and the second one to cement the composite restoration. Adhesive restorations require a conical shape with clear-cut margins and the filling of any undercuts with composite material, in order to avoid excessively invasive preparations. After finishing the preparation, the dentinal substrate is properly treated to protect tooth vitality, if any. Then, after removing the rubber dam, an impression is taken of both the arch to be rehabilitated and of the opposite arch, and the intermaxillary relationship is recorded with wax and face bow, which is what the dental technician needs  to  subsequently  mount the casts on the articulator. Preparations can now be provisionalised with light-curable Eugenol-free provisional cement.

CEMENTATION

At the cementation stage, the artifacts delivered by  the laboratory have already been subjected to a post-polymerization cycle which, thanks to the combination of light, heat and pressure, provides the inlay with physical and mechanical characteristics which are absolutely superior to those of direct restorations.



The already sandblasted and silanized inlays are then cleansed and conditioned with an enamel- dentin adhesive. After removing provisional cement and placing the rubber dam, cavities are cleaned and cleansed so as to remove all residues of dental and cavity surfaces; congruity of artifacts is then checked and cementation procedure is started.



Cavities are sandblasted with particles having a size of 30 microns, at 2 bar pressure, for approximately 10 seconds; etching is performed with 36.5-37.5% orthophosphoric acid for approx. 40 seconds; cleansing with 0.2% chlorhexidine is carried out to inhibit metalloproteinase and after applying the primer/bonding agent (EnaBond, Micerium). A uniform layer of pre-heated composite (37-39 degrees C) is then placed into the cavity, after which the inlay/onlay is seated and kept in situ by exerting constant pressure. Excess cement is removed before its polymerization, and  dental floss is used to remove it also from interproximal areas. Curing with UV radiation is performed on all sides for at least 2 minutes per side, while exerting constant occlusocervical pressure on the prosthetic artifact. Once curing is complete, coarse composite residues on the margins are removed and 40 micron diamond burrs and silicone trimmers are used for finishing. After checking marginal congruity, occlusion is also checked, followed by finishing and polishing.   In another session, final polishing and glossing can be performed under a rubber dam.

DR. ALBERTO PUJIA and ODT. PAOLO RICCIONI