Old amalgam fillings replacement with indirect CAD-CAM composite restorations
Partial indirect CAD/CAM reconstructions, such as onlays and overlays made by ceramics or composite, are suitable to substitute worn dental amalgam fillings. These old restorations should be carefully examined as dentinal sensitivity to cold and hot might disclose dentinal cracks or cuspal fractures that could determine chronic pulpal disease or pulpal necrosis. The digital workflow in these clinical situation could be a great opportunity for the clinician to replace old fillings with new indirect restorations made by esthetics materials, such as composite or ceramics, thus improving the quality of the entire system, i.e. dental tissues and reconstruction material.
Dental amalgams fillings should be constantly monitored as, in aging process, might present marginal chipping, enamel microfractures or hidden dentinal cracks; sensitivity to cold drinks is one of the features related to the degradation of the restoration, due to a micro-infiltration of bacteria toward the inner part of the tooth, thus stimulating pulpal reactivity.
A proper diagnosis is mandatory and a careful examination of the borders might disclose these problems before an irreversible pulpitis takes place.
Dental amalgams replacement is not a “free of biological costs” process; part of the dentin and of the enamel should be removed, in addition, demineralized dentin should be carefully examined and drilled out. At the end of this process the cavity floor and the cavity walls are composed by a wide area of different type of dentin – reactive and sclerotic ones – in a frame of thin enamel.
Frequently dental cusps are too thin to be preserved and a cuspal coverage indirect reconstruction should be considered as the first choice.
In all these cases, particularly in those needing an indirect reconstruction made by CAD-CAM systems, a preventive sealing of the dentin (IDS) and a proximal box elevation (PBE) are both advisable.
PBE has been proposed in 1994 by Dietschi D & Spreafico R (1) and was confirmed by different studies (2,3,4), also IDS was introduced in late nineties but recently confirmed by Magne et al. (5,6,7) and has been widely accepted as a good clinical practice to prevent post operative sensitivity in the case of indirect restorations. Some studies reported (6,7) a better adhesion of the indirect manufactures to the dentin sealed before the impression procedure.
CAD/CAM chairside restorations have been report as a clinical highly reliable procedure to obtain inlays, onlays and overlays (8,9,10).
In the clinical case presented two dental amalgams should be replaced by indirect restorations; a composite – made for CAD/CAM restoration (Lava Ultimate, 3M, USA) – was chosen and both PBE and IDS was performed before the digital impression.
Proper conditioning of the cavity was accomplished and of the inner part of the CAD/CAM restoration conditioned by a gentle use of sandblasting (50 microns alumina-oxide powder).
A flowable composite was used as a luting agent. The time needed for the whole process was monitored and resulted in two hours and a half.
Main tip: Substitution of old dental amalgam fillings by indirect partial CAD/CAM reconstruction is better accomplished by a previous adhesive preparation of the dentinal substrate by Immediate Dentinal Sealing (IDS) and Proximal Box Elevation (PBE), also named as Deep Margin Relocation.
CAD/CAM indirect partial restorations are suitable to substitute old dental amalgam fillings; proper preparation procedures like PBE and IDS should be at first considered to create a precise cavity base; this feature will help both during the digital impression phase and during the luting process.
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