Tridimensional Evaluation of the Interfacial Gap in Deep Cervical Margin Restorations: A Micro-CT Study

Area of Science:

• Dental Materials Science
• Restorative Dentistry
• Biomaterials Engineering

Background:

• Deep class II cavities present challenges for achieving optimal marginal seal.
• Margin elevation techniques are employed to manage deep cervical margins.
• The choice of restorative material significantly impacts the longevity of dental restorations.

Purpose of the Study:

• To evaluate the tridimensional interfacial gap of class II cavities restored with different nanohybrid resin composites.
• To assess the impact of cyclic fatigue on the marginal seal of these restorations.
• To compare the performance of flowable resins, nanohybrid composites, and bulk-fill composites on enamel and dentin margins.

Main Methods:

• Standardized class II cavities were prepared on 48 premolars with margins above and below the cement-enamel junction (CEJ).
• Restorations were performed using a two-step self-etch adhesive and divided into six groups based on material and technique.
• Microcomputed Tomography (Micro-CT) was used to analyze interfacial gaps before and after 1,000,000 cycles of simulated chewing (50 N).

Main Results:

• Restoration technique and chewing simulation significantly affected interfacial gaps on dentin margins (p<0.001), but not on enamel.
• Flowable resins showed a smaller baseline gap on dentin but a larger gap after chewing simulation, particularly with a 2mm layer.
• Nanohybrid and bulk-fill composites demonstrated more stable marginal integrity on dentin after cyclic loading compared to flowable resins.

Conclusions:

• No significant differences in interfacial gap volume were observed on enamel margins across all tested materials.
• On dentin margins, while flowable resins initially provided a better seal, they were more susceptible to degradation under simulated chewing forces.
• Material selection optimizing marginal seal is crucial for managing deep class II cavities and enhancing clinical outcomes, especially concerning dentin margins.