The Influence Of Tubule Density And Area Of Solid Dentin On Bond Strength Of Two Adhesive Systems To Dentin

Purpose: To determine the correlation between the tubule density (TD) and the area occupied by solid dentin (ASD) with the bond strength of one conventional and one self-etching adhesive system to dentin. Materials and Methods: The crown of extracted human third molars was transversally sectioned with a diamond saw to expose either superficial, middle, or deep dentin. The three groups of dentin surfaces were randomly divided and bonded with either Clearfil Liner Bond 2V (LB) or Prime & Bond 2.1 (PB) adhesive systems according to manufacturer's directions. Resin composite buildup crowns (10.0 mm high) were incrementally constructed on the bonded surfaces and the teeth stored in water at 37°C. After 24 h of storage, the teeth were vertically, serially sectioned in both x and y directions to obtain several bonded sticks of approximately 0.7 mm2 cross-sectional area. Each stick was tested in tension in a EMIC DL-500 tester at 0.5 mm/min until failure. After testing, the dentin side of the fractured specimen was gently abraded with a 1000-grit SiC paper, etched with 37% phosphoric acid for 15 s and allowed to air dry. SEM micrographs at 1000X and 4000X magnification were taken to permit calculation of the TD (number of tubules/mm2) and ASD (% of total area) at the site of fracture. Correlation between TD and ASD with the bond strength data was performed by linear regression. All statistical analysis was done with a = 0.05. Results: Overall bond strength (MPa) for LB was 26.0 ± 10.2, and 42.6 ± 15.2 for PB. There was a significant direct relationship between bond strength and ASD for both materials (r2 = 0.20, p < 0.05 and r2 = 0.66, p < 0.01, respectively for LB and PB). PB bond strength dropped significantly as the TD increased (r2 = 0.63, p < 0.05), while LB was not sensitive to TD (r2 = 0.05, p > 0.05). Mean bond strength of PB was significantly higher than LB for both superficial and middle dentin (p < 0.05), while there was no significant difference for deep dentin (p > 0.05). Conclusion: Regional variations in TD and ASD may modify bond strength of both conventional and self-etching adhesive systems. Bonding sites with larger ASD seem to yield higher bond strengths regardless of the type of adhesive system used.34315324Burrow, M.F., Takakura, H., Nakajima, M., Inai, N., Tagami, J., Takatsu, T., The influence of age and depth of dentin on bonding (1994) Dent Mater, 10, pp. 241-246Carrigan, P.J., Morse, D.R., Furst, M.L., Sinai, I.H., A scanning electron microscopic evaluation of human dentinal tubules according to age and location (1984) J Endod, 10, pp. 359-363Fernandes, C.A.O., (2000) Estudo Comparativo da Resistência Adesiva À Dentina Superficial e Profunda Testada Simultaneamente, Empregando-se Dois Sistemas Adesivos, , Thesis, Bauru School of Dentistry, USP, Bauru, SP, BrazilFosse, G., Saele, P.K., Eide, R., Numerical density and distributional pattern of dentin tubules (1992) Acta Odont Scand, 50, pp. 201-210Garberoglio, R., Brännström, M., Scanning electron microscopic investigation of human dentinal tubules (1976) Archs Oral Biol, 21, pp. 355-362Gwinnett, A.J., Quantitative contribution of resin infiltration/hybridization to dentin bonding (1993) Am J Dent, 6, pp. 7-9McCabe, J.F., Rusby, S., Dentine bonding agents - Characteristic bond strength as a function of dentine depth (1992) J Dent, 20, pp. 225-230Nakajima, M., Sano, H., Burrow, M.F., Tagami, J., Yoshiyama, M., Ebisu, S., Ciucchi, B., Pashley, D.H., Tensile bond strength and SEM evaluation of caries-effected dentin using adhesives (1995) J Dent Res, 74, pp. 1679-1688Nery, S., McCabe, J.F., Wassell, R.W., A comparative study of three dental adhesives (1995) J Dent, 23, pp. 55-61Pashley, D.H., Carvalho, R.M., Dentine permeability and dentine adhesion (1997) J Dent, 25, pp. 335-372Pashley, D.H., Ciucchi, B., Sano, H., Carvalho, R.M., Russell, C.M., Bond strength versus dentine structure: A modelling approach (1995) Archs Oral Biol, 40, pp. 1109-1118Pashley, D.H., Ciucchi, B., Sano, H., Yoshiyama, M., Carvalho, R.M., Adhesion testing of dentin bonding agents. A review (1995) Dent Mater, 11, pp. 117-125Pashley, D.H., Clinical correlations of dentin structure and function (1991) J Prosth Dent, 66, pp. 777-781Pashley, D.H., Dentin: A dynamic substrate - A review (1989) Scanning Microsc, 3, pp. 161-174Pereira, P.N.R., Okuda, M., Sano, H., Yoshikawa, T., Burrow, M.F., Tagami, J., Effect of intrinsic wetness and regional difference on dentin bond strength (1999) Dent Mater, 15, pp. 46-53Prati, C., Pashley, D.H., Dentin wetness, permeability and thickness and bond strength of adhesive systems (1992) Am J Dent, 5, pp. 33-38Suzuki, T., Finger, W.J., Dentin adhesives: Site of dentin vs. Bonding of composite resins (1988) Dent Mater, 4, pp. 379-383Tagami, J., Tao, L., Pashley, D.H., Correlation among dentin depth, permeability, and bond strength of adhesive resins (1990) Dent Mater, 6, pp. 45-50Tao, L., Pashley, D.H., Shear bond strengths to dentin: Effects of surface treatments, depth and position (1988) Dent Mater, 4, pp. 373-378Tay, F.R., Gwinnett, A.J., Wei, S.H.Y., The overwet phenomenon: A scanning electron microscopic study of surface moisture in the acid-conditioned, resin-dentin interface (1996) Am J Dent, 9, pp. 109-114Tay, F.R., Sano, H., Carvalho, R.M., Pashley, E.L., Pashley, D.H., An ultrastructural study of the influence of acidity of self-etching primers and smear layer thickness on bonding to intact dentin (2000) J Adhesive Dent, 2, pp. 83-98Yoshiyama, M., Carvalho, R.M., Sano, H., Horner, J., Brewer, P.D., Pashley, D.H., Interfacial morphology and strength of bonds made to superficial versus deep dentin (1995) Am J Dent, 8, pp. 297-302Yoshiyama, M., Sano, H., Ebisu, S., Tagami, J., Ciucchi, B., Carvalho, R.M., Johnson, M.H., Pashley, D.H., Regional strengths of bonding agents to cervical sclerotic root dentin (1996) J Dent Res, 75, pp. 1404-141

Distribution of nanofillers from a simplified-step adhesive in acid-conditioned dentin

Purpose: This in vitro study examined the interfacial ultrastructure of a nanofilled, simplified-step adhesive (Prime & Bond NT, Dentsply), to determine the distribution of nanofillers within the collagen network of the hybrid layer. Materials and Methods: Twenty-four dentin discs were divided into two groups and bonded using two recommended conditioning techniques: Group I, NRC (Non-Rinse Conditioner), and Group II, Conditioner 36 (colloidal silica thickened: 36% phosphoric acid. Following conditioning, a single coat of adhesive was applied and light-cured. Dentin discs were then bonded to form disc-pairs and processed for TEM examination. Demineralized, ultrathin sections were examined stained or unstained. Non-demineralized sections were used for STEM/EDX analysis of elemental distribution across the resin-dentin interface. In addition, four dentin discs were bonded with a generic adhesive (HEMA/TBBO) for TEM examination of stained collagen and proteoglycans. Results: In unstained sections of both groups, nanofillers from the adhesive layer were congested around patent tubular orifices, but were not found within the interfibrillar spaces of the hybrid layer. EDX analysis of silicon (Si) showed predominant distribution within the adhesive layer and tubular orifices. Phosphorus (P) was present within the hybrid layer and adhesive layer in Group II. Conclusion: It is hypothesized that a aggregation of the nanofillers within the adhesive resulted in filler clusters that are too large to infiltrate the interfibrillar spaces of the hybrid layer; and b retention of ground substance within the demineralized intertubular collagen matrix may also have prevented the infil-tration of the nanofillers