Influence of Human and Bacterial Enzymes on Resin Restorations: A Review

BACKGROUND: Esthetic satisfaction has been a prime concern for patients. This has led to a surge in the development of esthetic restorations and dental composites in the field of restorative dentistry over the past decade. Resins are the most preferred restorative material. However, their failure rate was observed to be high.

AIM: This review is aimed for clinician, discussing the influence of human and bacterial enzymes on resin restorations.

REVIEW RESULTS: Composite restoration failure is multifactorial with an interplay of mechanical functions such as masticatory forces and abrasion with biological factors such as host modulated and bacterial enzymes. Salivary esterases and bacterial esterases act on the ester-link bond of resin restoration to form byproducts of methacrylic acid and Bis-hydroxy-propoxy-phenyl-propane. Salivary enzymes form microgaps between the resin-tooth interface and provide a suitable environment for bacterial growth. Bacteria colonize the resin-tooth interface to weaken the resin bond strength. The presence of bacteria draws neutrophils into the hybrid layer. The activation and degranulation of neutrophils leads to enzyme secretions that act on bacteria. However, this can also have adverse effects on resin restoration. Acids prompt the activation of matrix metalloproteinases (MMPs). Proteinases secreted by MMPs uncoil the collagen fibrils of the dentin matrix and degrade tooth structure. The salivary esterases, bacterial esterases, neutrophils, and MMPs work synergistically to degrade dental resin material, resin-tooth interface, and dentin. This causes failure of dental resin restorations and secondary caries formation.

CONCLUSION: Biological degradation of resin restorations is inevitable irrespective of the material and techniques used. Salivary esterases such as cholesterol esterase and pseudocholinesterase and cariogenic bacterial esterase can degrade dental resin, weakening the hybrid layer at the resin-tooth interface, affecting the bond strength, and causing failure. Ester-free resin and incorporation of antimicrobial materials, esterase, and MMP inhibitors are strategies that could ameliorate degradation of the restoration.