Evaluation of dentin hardness and bond strength at different walls of class II preparations.
OBJECTIVE
The aim of this study was to evaluate the Knoop hardness number (KHN) of dentin and the microtensile bond strength (microTBS) at different walls of MOD preparations, and the correlation between microTBS and the KHN of dentin.


METHODS
Human molars with MOD preparations were allocated into 3 groups according to the preparation wall (axial, gingival, pulpal). Each tooth was sectioned into halves, resulting in two similar preparation walls: one was used for measuring the KHN of dentin and the other for microTBS testing. Flat surfaces of the respective walls were obtained by cutting away adjacent walls. For the KHN measurement, twelve indentations were performed along the preparation wall (50 g/15 s). For microTBS testing, specimens were distributed into 3 groups according to the adhesive system (Adper Single Bond Plus/SB, Clearfil SE Bond/SE, Adper Prompt/AP). Composite blocks were built over surfaces; specimens were sectioned (3 slabs/wall) and trimmed to an hourglass shape (1 mm(2)).


RESULTS
The KHN of dentin walls was significantly different (ANOVA/Tukey); pulpal wall > axial wall > gingival wall. The effect of preparation walls on microTBS was dependent on the bonding system (2-way ANOVA/Tukey's test). SB had higher bond strength than the other systems at the gingival wall; and higher than SE at the axial wall. At the pulpal wall, SE presented a higher mean compared to AP. A significant negative correlation between microTBS and KHN was observed at the gingival wall.


CONCLUSIONS
It could be concluded that dentin structure can affect bond strengths, but the impact of the substrate varies according to the type of adhesive system.
Cavalcanti
Andrea Nóbrega
AN
School of Dentistry, School of Medicine adn Public Health of Bahia (EBMSP), Cabula, Salvador, BA, Brazil. dea.cavalcanti@uol.com.br
Mitsui
Fabio Hiroyuki
FH
Lima
Adriano Fonseca de
AF
Mathias
Paula
P
Marchi
Giselle Maria
GM
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000033:anatomy & histology*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D010755:Organophosphates / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength
C489661:Adper Prompt Self-Etch; C438313:Clearfil SE Bond; D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D010755:Organophosphates; D019279:Resin Cements; C511238:Single Bond Plus; D017438:Bisphenol A-Glycidyl Methacrylate