Internal corrosion in dental composite wear

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Internal corrosion of dental resin composites, driven by water sorption, causes interfacial debonding, filler dissolution, matrix cracking, and subsurface damage.
• This subsurface damage layer facilitates "corrosive-wear," a cycle where wear exposes new surfaces, perpetuating degradation and differing significantly from abrasive wear.
• Current laboratory methods using aqueous or low pH media are slow, failing to adequately simulate in vivo corrosive-wear conditions and leading to poor correlation with clinical data.

Purpose of the Study:

• To develop and validate an accelerated laboratory method for simulating the in vivo corrosive-wear of dental resin composites.
• To evaluate the effectiveness of an alkaline medium (0.1 N NaOH at 60°C) in mimicking the degradation processes observed in clinical settings.
• To assess the resistance of eleven commercial dental composites to simulated corrosive-wear.

Main Methods:

• Eleven commercial dental composites were exposed to 0.1 N NaOH at 60°C for two weeks to induce degradation.
• Following alkaline exposure, materials underwent abrasion using a tooth brushing machine to simulate wear.
• Key parameters evaluated included mass loss, silicon (Si) loss, degradation depth, and wear depth, with Scanning Electron Microscopy (SEM) used for microstructural analysis.

Main Results:

• A highly significant correlation was found among the measured corrosion and wear parameters, indicating the reliability of the method.
• SEM analysis revealed degradation patterns consistent with in vivo worn composites, including interfacial separation, filler dissolution, matrix cracking, and subsurface damage.
• The alkaline medium accelerated the degradation process, successfully mimicking the in vivo corrosive-wear mechanisms.

Conclusions:

• The use of warm 0.1 N NaOH provides an effective and time-efficient method for simulating the in vivo corrosive-wear of dental composites.
• This accelerated testing approach accurately reproduces the subsurface damage and degradation characteristics observed in clinical settings.
• The developed method offers a valuable tool for evaluating the long-term durability and performance of dental restorative materials under corrosive-wear conditions.