Cuspal Deflection and Marginal Adaptation in Premolars Restored with Low-Shrinkage Resin Composites

Area of Science:

• Dental Materials Science
• Restorative Dentistry
• Biomaterials Engineering

Background:

• Dental restorations aim to mimic natural tooth structure and function.
• Resin composites (RCs) are widely used but can exhibit polymerization shrinkage, leading to cuspal deflection and marginal gaps.
• Low-shrinkage RCs have been developed to mitigate these issues.

Purpose of the Study:

• To evaluate and compare cuspal deflection and marginal adaptation of conventional and low-shrinkage resin composites in premolar restorations.
• To assess the influence of material formulation on the mechanical behavior of dental restorations.

Main Methods:

• An in vitro study involving 56 maxillary first premolars with standardized MOD cavities.
• Random assignment to four groups (n=14) using Clearfil Majesty Posterior (CMP), Charisma Diamond (CHD), Beautifil II LS (BL), and Filtek Z550 (FZ).
• Cuspal deflection measured using a digital micrometer; marginal adaptation assessed via scanning electron microscopy.

Main Results:

• All groups showed greater cuspal deflection at 5 minutes than at 24 hours.
• Conventional Filtek Z550 (FZ) exhibited significantly higher cuspal deflection than CMP, CHD, and BL at all time intervals (p < 0.001).
• Clearfil Majesty Posterior (CMP) showed the lowest cuspal deflection, with no significant differences among the low-shrinkage RCs.

Conclusions:

• Modifications in resin composite organic matrix or formulation positively influence cuspal deflection and marginal adaptation.
• Low-shrinkage RCs offer reduced cuspal movement, potentially enhancing restoration integrity and clinical success.
• The development of advanced resin composites is crucial for improving the longevity and performance of dental restorations.