Effect of Composite Insertion Technique on Cuspal Deflection Using an In Vitro Simulation Model

Abstract

SUMMARY Objective The objective of this study was to investigate, by simulation, the effect of conventional composite resin insertion techniques on cuspal deflection using bonded typodont artificial teeth. The deflection produced by a new low-shrinkage composite was also determined. Materials and Methods Sixty standardized MOD preparations on ivorine maxillary premolars were prepared: group A at 4 mm depth and group B at 6 mm depth. Each group was further subdivided according to composite insertion technique (n=6), as follows: 1) bulk insertion, 2) horizontal increments, 3) tangential increments, and 4) a modified tangential technique. Preparations were microetched, acid-cleaned, and bonded with adhesive resin to provide micromechanical attachment before restoration with a conventional composite (Spectrum TPH3, Dentsply). Two additional subgroups at 4 mm and 6 mm depth (n=6) were restored in bulk using low-shrinkage composite (Filtek LS, 3M/ESPE). All groups received the same total photo-polymerization time. Cuspal deflection was measured during the restorative procedure using two Linear Variable Differential Transformers attached to a data acquisition system. Results The average cuspal deflections for group A were 1) 40.17 ± 1.18 μm, 2) 25.80 ± 4.98 μm, 3) 28.27 ± 5.12 μm, and 4) 27.33 ± 2.42 μm. The deflections in group B were 1) 38.82 ± 3.64 μm, 2) 50.39 ± 9.17 μm, 3) 55.62 ± 8.16 μm, and 4) 49.61 ± 8.01 μm. Cuspal flexure for the low-shrinkage composite was 11.14 ± 1.67 μm (group A: 4 mm depth) and 16.53 ± 2.79 μm (group B: 6 mm depth). Conclusions All insertion techniques using conventional composite caused cuspal deformation. In general, deeper preparations showed increased cuspal deflection—except in the case of bulk insertion, which was likely affected by decreased depth of cure. Cuspal movement using low-shrinkage composite was significantly reduced.

Fracture resistance of endodontically treated maxillary premolars restored by silorane-based composite with or without fiber or nano-ionomer

“…The deep endodontic access preparation in MOD cavity was found to increase cuspal deflection significantly 5,37. The slow polymerization reaction and lower shrinkage stress of silorane-based composite might be responsible for the decreased cuspal deflection in MOD-prepared vital premolars27,37,38 and subsequently for the increased strength.…”

“…The slow polymerization reaction and lower shrinkage stress of silorane-based composite might be responsible for the decreased cuspal deflection in MOD-prepared vital premolars27,37,38 and subsequently for the increased strength.…”

Polymer-Based Direct Filling Materials

“…However, at least for conventional composites, because of the C-factor vs. stress correlation, the use of incremental placement is still recommended to minimize the bonded surface on each increment, reducing the relative C-factor in each increment, and therefore, reducing overall stress [60]. This was indeed observed in several in vitro studies [60, 74]. In one of them, the deflection of aluminum molds of various thicknesses was measured for conventional composites placed in a single or multiple increments, with the results showing that the single increment technique always resulted in greater wall deflection [72].…”

Incremental Filling Technique and Composite Material—Part II: Shrinkage and Shrinkage Stresses

“…However, these restoratives have polymerization shrinkage as an inherent problem that may cause residual stresses in the tooth, even when not in function. 1,2 Clinical signs that have been associated with polymerization shrinkage stress include inadequate adaptation at tooth/restoration interface, micro-cracking, postoperative sensitivity, microleakage, and secondary caries. 3,4 These issues are often responsible for replacement of composite restorations in posterior teeth.…”