Clinical Evaluation of the Soft-Start (Pulse-delay) Polymerization Technique in Class I and II Composite Restorations

Abstract

The polymerization shrinkage of resin composites may affect restoration quality. A double blind, randomized clinical trial was carried out to compare two curing techniques-Soft-Start (SS) and the plasma arc curing light (PAC). The hypothesis that, delaying the gel point (with SS) improves marginal seal, was tested at alpha=0.05. Also, this report includes two-week, three-month, one-year and two-year results for post-op sensitivity. Twenty informed participants, each needing two Class II and/or complex Class I restorations, gave written consent. All the teeth were trans-illuminated to rule out pre-op crack lines before restoration placement. Clinical RelevanceClass I and II composite restorations placed with a Soft-Start technique showed no significant changes in post-op sensitivity to cold or any decreased signs of marginal stress. 266Operative Dentistry Sensitivity to a standardized cold stimulus was performed preoperatively at 2 weeks and at 3, 12 and 24 months. Patients rated their sensitivity after stimulus by means of a Visual Analog Scale (VAS). In addition, two independent, calibrated investigators evaluated the restorations clinically at each appointment. There were no significant differences in VAS scores between the two groups at any appointment period (two-way ANOVA; p>0.05).Several conditions were defined as indicating marginal stress before the start of the trial. At 24 months, there was no significant difference between the SS and PAC groups.Conclusion: Within the limitations of this study, Class I and II restorations placed with a SS technique did not show significant changes in post-op sensitivity or decreased signs of marginal stress.

Postoperative sensitivity in Class V composite restorations: Comparing soft start vs. constant curing modes of LED

“…The authors concluded that within the limitations of this study, Class I and II restorations placed with a soft start technique did not show significant changes in postoperative sensitivity or decreased signs of marginal stress. [15] These results are similar to the one that we have found. These results may be explained by one study that found that the advantage of initial slow polymerization obtained by the “soft-start” method was offset by a rise in total polymerization shrinkage when final curing was completed at 1130 mW/cm.…”

Effect of filler content of flowable composites on resin-cavity interface

“…It has been reported that the soft-start polymerization method provided twofold advantages: an increase in resindentin bond strength in box-shaped cavities 16) and reduced polymerization shrinkage stress without compromising the degree of conversion into a polymer network 17) . However, Class I and II composite restorations clinically placed with a soft-start technique showed no significant improvements in terms of postoperative sensitivity to cold or reduction in marginal stress 6) . Resin composites vary widely in shrinkage-strain magnitude, and the inverse relationship between filler loading and shrinkage-strain is explained by the corresponding volume fraction of monomers present to undergo polymerization 18) .…”

“…On the longevity of composite resin restorations, clinical trials have shown that they are acceptable for long-term use [1][2][3][4][5][6] . The longevity of a resin restoration is influenced by myriad factors: not only by the various properties of composite resins and adhesives, but also by the restorative technique.…”

Effect of thermocycling and varying polymerization techniques on the restorative interface of class V cavities restored with different composite resin systems

“…Unlike conventional polymerization, whereby the light intensity is fixed, an initial photoactivation of low light intensity followed by high light intensity final photoactivation, would tend to minimize marginal cracks, without compromising the physical and mechanical properties of composite resins. This process is termed Soft-Start polymerization (9). …”