Bonding strength on dentin from primary tooth withamelogenesis imperfecta

Abstract

Objective: Dentin of many teeth with amelogenesis imperfecta (AI)is histologically altered following loss of the overlying hypoplasticenamel and exposure to the oral environment. Such dentin becomeshypermineralized and sclerotic with obliteration of the dentinaltubules, which makes bonding less predictable. This studyexamined the effect of etching time on the microtensile bondstrength (MTBS) of an etch-and-rinse adhesive to dentin fromprimary tooth with AI.Methods: Flat coronal dentin surfaces from six primary molarsaffected by AI were divided into two groups according to theetching time (I) 15 seconds and (II) 30 seconds. Following etching,a two-step etch-and-rinse adhesive, Prime and Bond NT (DentsplyDe Trey) was applied to dentin surfaces, air-dried and light-cured.Composite build-ups were performed using Filtek Z250 (3MESPE) for MTBS testing. Flat dentin surfaces from six extracted,non-carious human primary molars were similarly bonded andwere used as controls. The bonded teeth were sectioned into beamsof 0.8 mm2and stressed to failure under tension at a crossheadspeed of 1 mm/min. Representative fractured beams from eachgroup were prepared for fractographic analysis under scanningelectron microscope (SEM).Results: One-way ANOVA and Tukey’s multiple comparison testsshowed that MTBS of dentin from primary tooth group with AIwas significantly low (15 seconds: 19.8 ± 6.6, 30 seconds: 21.1 ±7.7) compared to sound dentin groups (15 seconds: 31.8 ± 4.8,30 seconds 24.9 ± 5.1). SEM observation of the fractured surfacesrevealed predominantly adhesive failure for dentin in AI groups.The low MTBS observed in AI groups could be attributed to theporous hybrid layer and short resin tags that were retained on thecomposite side of the fractured beams.Conclusion: The bonding efficacy of etch-and-rinse adhesive wascompromised by dentin in AI groups and could not be improved byextending the etching time to 30 seconds.