A number of mechanisms (both mechanical and chemical) have been proposed as the cause of dentin adhesion. Extensive research in Japan during the past 10 years has shown that strong, long-lived bonds between resin and living dentin will form when a monomer such as 4-META, which contains both hydrophilic and hydrophobic chemical groups, penetrates the tissue and polymerizes in situ. This resin-impregnation creates a transitional “hybrid” layer, that is neither resin nor tooth, but a hybrid of the two. The thin layer of resin-reinforced dentin locks the two dissimilar substances together on a molecular level, sealing the surface against leakage and imparting a high degree of acid resistance.
"This process allows for the primer (which contains hydrophilic acrylic monomers that can re-wet dentin to prevent collagen collapse) to be initially applied and then followed by the application of the adhesive resin. This allows the more hydrophobic adhesive to infiltrate into the created micro-pores, producing a matrix that mechanically interlocks the resin to the dentin or enamel, and produces what has become known as the hybrid layer . In the etch and rinse technique, the primer and adhesive can be combined into a single bottle. "
[Show abstract][Hide abstract] ABSTRACT: To survey the recent literature from the late 1980s to recent years in order to assess the relationship between resin degradation, catalyzed by biological factors, and clinical failure outcomes such as marginal breakdown.
The literature shows that degradation occurs in many manufacturers' products despite varied vinyl acrylate compositions. The authors examine salivary enzyme activity and their ability to degrade the polymeric matrix of resin composites and adhesives, as well as oral microorganisms that can promote demineralization of the tooth surface at the marginal interface. A survey of recent research relating matrix metalloproteinase (MMPs) to the degradation of the exposed collagen at the dentin adhesive interface is also discussed in the context of marginal breakdown.
The literature provides strong support that together, the above factors can breakdown the marginal interface and limit the longevity of resin composite restorations. The authors have found that the field's current understanding of resin biodegradation in the oral cavity is just beginning to grasp the role of bacteria and enzymes in the failure of resin-based restorations.
Knowledge of these biodegradation processes is pertinent to areas where innovative strategies in the chemistry of restorative materials are anticipated to enhance the longevity of resin composites.
Dental materials: official publication of the Academy of Dental Materials 09/2013; 30(1). DOI:10.1016/j.dental.2013.08.201 · 3.77 Impact Factor
"Satisfactory bonding to enamel can be achieved using the acid-etching technique , but dentine bonding is more difficult to achieve due to the wet tubular structure, permeability properties, and organic composition of dentinal substrate . Recently there has been increasing interest in the incorporation of fillers into dentine adhesive systems, but the importance of filler particles is somewhat controversial  . These fillers may include from conventional glass or silica fillers to nanometer-sized aerosil silica . "
[Show abstract][Hide abstract] ABSTRACT: In this laboratory study shear bond strengths of three filled and one unfilled adhesive systems to enamel and dentine were compared. Forty-eight extracted intact noncarious human mandibular molars were randomly assigned to two groups of 24 one for bonding to enamel and the other for bonding to dentine. Buccal and lingual surfaces of each tooth were randomly assigned for application of each one of filled (Prime & Bond NT (PBNT), Optibond Solo Plus (OBSP), and Clearfil SE Bond (CSEB)) and unfilled (Single Bond (SB)) adhesive systems (
). A universal resin composite was placed into the translucent plastic cylinders (3 mm in diameter and 2 mm in length) and seated against the enamel and dentine surfaces and polymerized for 40 seconds. Shear bond strength was determined using a universal testing machine, and the results were statistically analyzed using two-way ANOVA, one-way ANOVA,
-test, and Tukey HSD post hoc test with a 5% level of significance.There were no statistically significant differences in bond strength between the adhesive systems in enamel, but CSEB and SB exhibited significantly higher and lower bond strength to dentine, respectively, than the other tested adhesive systems while there were no statistically significant differences between PBNT and OBSP.
International Journal of Dentistry 11/2012; 2012(2):858459. DOI:10.1155/2012/858459
"The removal of the smear layer exposes the peritubular and intertubular substrates thus allowing penetration of resin and formation of hybrid layer. The resin cement resisted the dye penetration better than the other two sealers because of formation of the hybrid layer. "
[Show abstract][Hide abstract] ABSTRACT: This study was designed to evaluate the apical seal of root canals obturated with resin cement as a root canal sealer and compare with that of the glass ionomer and zinc oxide eugenol sealers using a cold lateral condensation gutta-percha technique.
Successful root canal treatment requires three-dimensional obturation of the root canal system with nonirritating biomaterials. None of the available materials are capable of providing a fluid tight seal.
The prepared teeth were randomly divided into three groups of 15 each to be obturated using three different sealers. Group I: zinc oxide eugenol (Tubliseal), Group II: Glass ionomer (Ketac Endo), and Group III: resin cement (C & B Superbond). All the specimens were stored in 100% relative humidity at 37° for 24 h. The specimens were placed in 2% methylene blue dye for 48 h and sectioned. The dye penetration was evaluated under a stereomicroscope.
The "Kruskal" Wallis test was carried out to test the equality of mean. All the specimens showed dye leakage, and there was a statistically significant difference (P < 0.0001) among the groups. The specimens in Group III showed a minimal leakage and the specimens in Group I showed a maximum leakage.
Resin cement sealed the root canals significantly better when compared with zinc oxide eugenol and glass ionomer sealers.
Journal of Conservative Dentistry 07/2012; 15(3):274-7. DOI:10.4103/0972-0707.97958
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