Shear bond strength of resin composite to remineralized caries affected dentin using chicken eggshell powder

Objective Evaluate the shear bond strength of composite resin bonded to carious like dentin lesions remineralized by chicken eggshell powder solution (CESP). Materials and methods Thirty-six freshly extracted human third molars were used. The occlusal surfaces were grinded removing all enamel and exposing a flat surface of dentin. A 5 × 5 mm window was made and specimens were divided randomly into three equal groups (12 each). Group I (sound dentin as control group) no further treatment was done. Groups II and III, artificial demineralized dentin like lesions were induced by immersion for 96 h in a specially prepared acidic buffer solution (pH 4.2). In specimens of group II (demineralized dentin), no further treatment was done. For group III remineralization was induced by immersion in 3% eggshell powder solution for 12 min and incubated at 37° twice daily with 12 h intervals between both immersions for seven consecutive days. Light curing resin composite cylinders with universal bonding agent were formed with the aid of polymer tubes (4 mm diameter 4 mm height). All specimens were thermo-cycled for 500 cycles from 5 to 55°C. Shear bond strength test was done using universal testing machine with crosshead speed of 0.5 mm/min until failure occurred. Analysis of mode of failure was done by examining fractured surfaces of debonded specimens under stereomicroscope. Results Group I (normal sound dentin) recoded a significant highest mean value of shear bond strength at 19.38 ± 5.22 MPa followed by group III (remineralized dentin) at 12.94 ± 3.03 MPa which is statically significant higher mean shear bond strength value than group II (demineralized dentin) which recorded mean shear bond at 8.98 ± 3.32. Statistically significant difference was found when comparing mode of failure between three groups; group I showed the highest number of cohesive and mixed failures followed by group III, while group II showed no cohesive failures. Overall, more pronounced adhesive and mixed failures were found regardless of grouping also strong positive significant relation between mode of failure and shear bond strength (maximum load) was found. Conclusion Shear bond strength of composite resin to specimens treated with CESPS showed increase in bond strength values. Treated remineralized specimens with CESPS showed significantly higher number of cohesive/mixed modes of failure compared to demineralized specimens.