Technique sensitivity of dentin bonding: Effect of application mistakes onbond strength and marginal adaptation

This in vitro study evaluated dentin bond strength and marginal adaptation of direct resin composites according to the manufacturers' instructions and with simulated application errors. One hundred and forty cavities were pre pared into disks of freshly extracted human third molars and filled with on e resin composite. Dentin adhesives of the third (with self-etching primer: Syntac Classic), fourth (with total etching: Scotchbond Multi-Purpose Plus ) and fifth generation (one-bottle adhesive: Prime&Bond 2.1) were used for bonding. Simulated application mistakes were as follows: 1) prolonged etchi ng; 2) excessive drying after conditioning; 3) drying primers immediately a fter application and 4) drying primers excessively. After 21 days of storag e and 24 hours thermocycling (1150 cycles), replicas were made and push-out testing was performed. Replicas were examined for marginal adaptation usin g SEM (X200 magnification). Compared with values of the control groups, application errors resulted in dramatically decreased bond strengths and reduced percentages of gap-free m argins for all products tested (p<0.05). Excessive drying after conditionin g exhibited significantly less effect for the third generation adhesive tha n for products requiring total etching/wet bonding.