An investigation of the adequacy of interproximal matrices commonly used with posterior composite restoratives.
Abstract The adequacy of six interproximal matrix systems commonly used during the placement of Class II composites has been assessed in vitro . The results indicate that none of the matrix systems investigated can be considered to be ideal.
A randomized clinical trial on proximal contacts of posterior composites.
OBJECTIVE
The objective of this study was to investigate clinical changes in proximal contact strength inserting Class II composite resin restorations according to one of three randomly assigned protocols.


MATERIALS AND METHODS
Seventy-one Class II restorations (MO/DO) were placed by two calibrated operators. Restorations were randomly assigned to one of three groups: one using a circumferential and two a sectional matrix system with separation rings. Proximal contacts were measured by one independent observer with a Tooth Pressure Meter immediately before treatment, and directly after finishing the restoration.


RESULTS
Compared to the situation before treatment groups with a sectional matrix system resulted in a statistical significant stronger mean proximal contact strengths (p<0.05), whereas the use of a circumferential matrix system with hand-instrument resulted in a lower proximal contact strength (p<0.05).


CONCLUSION
Class II posterior composite resin restorations placed with a combination of sectional matrices and separation rings resulted in a stronger proximal contact than when a circumferential matrix system was used.
New finishing instruments for composite resins.
The trimming of composite resin restorations encompasses gross finishing, contouring, fine finishing, and polishing. A series of aluminum oxide-coated flexible disks have been marketed and are suitable for that purpose. However, their use is confined to directly accessible convex surfaces. For precise finishing of small delineated areas, and for concave and occlusal surfaces, rigid rotary instruments are necessary. The currently used stones and tungsten carbide burs are ineffective with microfilled composite systems. Thus, a series of finishing burs coated with 40- and 15-microns diamond chips were evaluated because of the superior grinding effectiveness as compared with existing instruments. Surface roughness measurements, and qualitative and quantitative SEM evaluations, indicate that these fine and superfine diamond finishing burs produce surfaces on composite resins as smooth as tungsten carbide burs and stones. At the same time, they cause less surface and subsurface damage or marginal fractures on composite resin restorations. The three-year clinical experience is generally favorable. Further quantitative clinical studies are warranted.