Influence of specimen size and regional variation on long-term resin-dentin bond strength.
OBJECTIVE
Verify whether the dimension of a bonded specimen stored prior microtensile testing and its regional variation may affect the resin-dentin bond strength (BS) over time.


METHODS
Thirty human third molars had a flat dentin surface exposed and all peripheral enamel removed. Two adhesive systems (Single-Bond and One-Step) were applied and composite resin crowns (Z250) were constructed. Teeth were divided into three groups (n = 5). Group A specimens were sectioned to obtain sticks to be tested in tension (0.5 mm/min) immediately. Group B specimens were stored in water for 6 months, before sectioning and testing. Group C specimens were sectioned; the sticks were stored for 6 months and tested. In groups A and B, the origin of the sticks, periphery and inner regions was controlled. Bond strength (BS) was expressed as an index that considers cohesive failures and estimated values of premature debonded specimens. One-way ANOVA and Tukey's test (alpha = 0.05) were used to compare groups A, B and C, and a second analytical approach (A and B) employed a two-way ANOVA (time versus regional differences) for each adhesive system.


RESULTS
For Single-Bond (SB), the BS for specimens in group A was higher than for groups B and C. For One-Step (OS), the BS in group A was higher than for B, which was in turn higher than for C. In the second group approach, no difference was found when the test was performed immediately; however, after 6 months, the inner sticks from group B showed significantly higher BS.


CONCLUSIONS
(1) The amount of decrease in BS is dependent on the specimen size; (2) the decrease in BS was greater for peripheral specimens than more centrally located specimens.
Loguercio
Alessandro D
AD
School of Dentistry, University of Oeste de Santa Catarina, Joaçaba, SC, Brazil. aloguercio@hotmail.com
Uceda-Gomez
Ninoshka
N
Carrilho
Marcela Rocha de Oliveira
MR
Reis
Alessandra
A
D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D003442:Crowns; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003804:Dentin; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D008963:Molar; D019279:Resin Cements; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D019231:Tooth Preparation, Prosthodontic
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D008689:Methacrylates; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate