Purpose: To validate the rationale of using a conventional light-curing resin-based composite (RBC) to lute thick indirect restorations by measuring mini-interfacial fracture toughness (mini-iFT). Materials and Methods: Freshly exposed dentin of extracted third molars (n = 64) was immediately sealed with a thin layer of an experimental RBC with a 50 wt% or 75 wt% (IDS) filler load. Two- or 6-mm-thick CAD/CAM composite blocks were luted onto IDS using either pre-heated light-cure or dual-cure luting RBC, with the latter having served as control. Samples were cut into sticks, upon which a notch was prepared at the interface between IDS and luting RBC, prior to being submitted to a 4-point bending test to determine mini-iFT. The results were analyzed using a mixed linear model (LME). Failure mode at the fractured interface was determined using scanning electron microscopy (SEM). Results: LME revealed that mini-iFT was not significantly affected by the composite block thickness (p = 0.39), but by the luting RBC (p < 0.0001) and the IDS RBC filler load (p = 0.0011). Mini-iFT was higher with 50 wt% filler-loaded RBC IDS and when luted using the light-curing RBC. Conclusion: This work provides the proof of concept that 2- and 6-mm-thick indirect restorations can safely be adhesively luted with pre-heated conventional light-cure RBC under controlled light-irradiation conditions. This strategy even seems beneficial in terms of mini-iFT compared to using a dual-cure luting RBC. IDS with lower filler content also appeared more favorable. Keywords: adhesion, composite resin, computer-aided design/computer-aided manufacturing (CAD/CAM), dental cement, dual cure, interfacial fracture toughness, light cure, resin-based luting composite.

Purpose: Mild and intermediately strong 2-step self-etch adhesives (2SEa) have been shown to bond efficiently to dentin. In general, their bonding efficiency to enamel is inferior to that of etch & rinse adhesives (E&Ra). On the other hand, their application procedure is less elaborate, and consequently leaves less room for application mistakes. The aim of this randomized controlled trial was to evaluate the clinical performance of an intermediately strong 2SEa, as compared with that of a 3-step E&Ra after 6 years of clinical functioning. Materials and Methods: 239 non-carious cervical lesions in 50 patients were restored with the nanohybrid composite Herculite XRV (Kerr), bonded in random order either with the 2SEa Optibond XTR (‘O-XTR’, Kerr) or the gold-standard control 3E&Ra Optibond FL (‘O-FL’, Kerr). The restorations were recalled after 1, 2 and 6 years of clinical service and examined for retention, marginal adaptation, marginal discoloration, caries occurrence, and postoperative sensitivity. Statistical analysis was performed using a logistic regression model with generalized estimating equations (2-way GEE model). Results: The patient recall rate at 6 years was 94%. The overall clinical success rate was 81.9% and 80.9% for O-XTR and O-FL, respectively. In total, 42 restorations (21 O-XTR, 21 O-FL) failed because of retention loss, severe abfraction/abrasion/erosion, severe marginal defects and/or discoloration, and/or caries. A retention rate of 92.9% and 88.9% was recorded for O-XTR and O-FL, respectively. Progressive marginal deterioration was observed over the 6-year period. Small clinically acceptable marginal defects were recorded in about 70% of the restorations (O-XTR: 69.9%; O-FL: 74.1%). Regarding marginal discoloration, 37% of the O-XTR and 30.2% of the O-FL restorations showed superficial clinically acceptable marginal discoloration. Six O-XTR and 4 O-FL restorations exhibited caries at the restoration margin. No significant difference was observed between the two groups for any of the evaluated parameters (p > 0.05). Conclusion: After 6 years of clinical service, Class-V restorations bonded with the 2SEa performed clinically equally well as those bonded with the 3E&Ra. Keywords: randomized clinical trial, RCT, Class V, bonding, adhesion, clinical effectiveness

The importance of the interdental anatomy of a class-2 direct composite restoration is one of the most underestimated topics in direct posterior composite restorations. The proximal emergence profile of the restoration and the contact area should be designed to maximize arch continuity and to minimize food impaction. Other restorative criteria that must be fulfilled are marginal adaptation compatible with the dental and periodontal integrity, and geometry of the marginal ridge compatible with the mechanical integrity of the restoration under load. Shortcomings will result in masticatory discomfort, caries, periodontal problems and undesired movement of teeth. In vitro and in vivo studies showed that the use a contoured sectional metal matrix band with a separation clamp results in the tightest contact point. However, this matrix system also has shortcomings and does not give the expected result in all class-2 cavities. The variation in depth, width of the box, distance between the cervical cavity margin and the adjacent tooth requires customization of the interproximal space. In order to realize this, sectional matrix bands with several profiles of curvature, variation of wedges and separation clamps, and the use of teflon tape are required. In addition, dentists should follow a protocol allowing them to build a proximal composite surface that fulfills the required restorative criteria. Pre-wedging, space evaluation, interproximal clearance, correct selection, positioning and stabilization of the matrix band are important steps in this protocol. Keywords: class-2, composite resin restoration, matrix system, proximal contact point, proximal emergence profile

Abstract: Tooth-cavity preparation contributes to a large extent to the quality of the direct posterior composite restoration, the so-called hidden quality of the restoration. Indeed, the effect of a poor cavity design is not immediately visible after placement of the restoration. To correctly prepare a cavity for a posterior composite restoration, the tooth to be restored should first be profoundly biomechanically analyzed. Here, the forces that work on the tooth during occlusion and articulation, and the amount and quality of the remaining tooth structure determine the cavity form. In addition, the dental tissues must be prepared in order to receive the best possible bond of the adhesive and subsequent restorative composite. A well-finished cavity preparation enables the restorative composite to adapt well, providing a good marginal ?seal to the direct benefit of the clinical lifetime of the posterior composite restoration. Finally, it is highly recommendable to isolate the teeth with rubber-dam before starting with the cavity preparation, as this increases the visibility of the operating field and allows the operator to work in a more precise way.