The immediate bonding effectiveness of contemporary adhesives is quite favorable, regardless of the approach used. In the long term, the bonding effectiveness of some adhesives drops dramatically, whereas the bond strengths of other adhesives are more stable. This review examines the fundamental processes that cause the adhesion of biomaterials to enamel and dentin to degrade with time. Non-carious class V clinical trials remain the ultimate test method for the assessment of bonding effectiveness, but in addition to being high-cost, they are time- and labor-consuming, and they provide little information on the true cause of clinical failure. Therefore, several laboratory protocols were developed to predict bond durability. This paper critically appraises methodologies that focus on chemical degradation patterns of hydrolysis and elution of interface components, as well as mechanically oriented test set-ups, such as fatigue and fracture toughness measurements. A correlation of in vitro and in vivo data revealed that, currently, the most validated method to assess adhesion durability involves aging of micro-specimens of biomaterials bonded to either enamel or dentin. After about 3 months, all classes of adhesives exhibited mechanical and morphological evidence of degradation that resembles in vivo aging effects. A comparison of contemporary adhesives revealed that the three-step etch-and-rinse adhesives remain the 'gold standard' in terms of durability. Any kind of simplification in the clinical application procedure results in loss of bonding effectiveness. Only the two-step self-etch adhesives approach the gold standard and do have some additional clinical benefits.

http://www.endoexperience.com/documents/DeMunketalDurabiltyofadhesionJDR.pdf

A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results

Bonding to tooth tissue can be achieved through an "etch&rinse," "self-etch" or "glass-ionomer" approach. In this paper, the basic bonding mechanism to enamel and dentin of these three approaches is demonstrated by means of ultramorphological and chemical characterization of tooth-biomaterial interfacial interactions. Furthermore, bond-strength testing and measurement of marginal-sealing effectiveness (the two most commonly employed methodologies to determine "bonding effectiveness" in the laboratory) are evaluated upon their value and relevance in predicting clinical performance. A new dynamic methodology to test biomaterial-tooth bonds in a fatigue mode is introduced with a recently developed micro-rotary fatigue-testing device. Eventually, today's adhesives will be critically weighted upon their performance in diverse laboratory studies and clinical trials. Special attention has been given to the benefits/drawbacks of an etch&rinse versus a self-etch approach and the long-term performance of these adhesives. Correlating data gathered in the laboratory with clinical results clearly showed that laboratory research CAN predict clinical effectiveness. Although there is a tendency to simplify bonding procedures, the data presented confirm that conventional three-step etch&rinse adhesives still perform most favorably and are most reliable in the long-term. Nevertheless, a self-etch approach may have the best future perspective. Clinically, when adhesives no longer require an "etch&rinse" step, the application time, and probably more importantly, the technique-sensitivity are substantially reduced. Especially "mild," two-step self-etch adhesives that bond through a combined micromechanical and chemical interaction with tooth tissue closely approach conventional three-step systems in bonding performance.

Buonocore memorial lecture, adhesion to enamel and dentin: current status and future challenges

Systematic review of the chemical composition of contemporary dental adhesives

Dental adhesion review: Aging and stability of the bonded interface

http://webdelprofesor.ula.ve/odontologia/robertramirez/PDF/1.pdf

State of the art of self-etch adhesives

Classification and potential of composite luting materials

The aim of this study was to evaluate the effect of treating titanium (Ti) with polyphosphoric acid on the attachment and proliferation of human bone marrow derived mesenchymal stem cells (hBMSCs). Cleaned Ti disks were immersed into three different concentrations of polyphosphoric acid solution (0.1, 1, and 10 wt %) and 10 wt % orthophosphoric acid solution for 24 h at 37°C. Ti immersed in distilled water for 24 h at 37°C served as control. The level of polyphosphoric acid that interacted with the Ti surface was determined by measuring the surface P/Ti ratio (atom%/atom%) using X-ray photoelectron spectroscopy. Degrees of cell attachment (1, 3, 5 h after cell seed) and proliferation (1, 3, 5, and 7 days after cell seed) on each treated Ti disk were evaluated by MTS assay. The mean surface P/Ti ratios increased in a polyphosphoric acid concentration dependent manner. A significantly higher cell attachment was found on Ti treated with polyphosphoric acid in contrast to untreated Ti (control) for all three culture periods. MTS assay also revealed that cell proliferation levels significantly increased following a polyphosphoric acid dose dependency. Ti surface treatment with orthophosphoric acid did not influence the cell attachment and proliferation. It was concluded that polyphosphoric acid treatment of Ti enhanced the attachment and proliferation of hBMSCs. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007

Chemical interaction of polyphosphoric acid with titanium and its effect on human bone marrow derived mesenchymal stem cell behavior.

Bisphenol A as degradation product of monomers used in resin-based dental materials

PURPOSE To evaluate the hydrolytic stability of three one-step self-etching adhesives (1-SEAs) bonded to dentin through bond strength testing and ultra-morphological interfacial analysis before and after long-term thermocycling. MATERIALS AND METHODS Eighteen flattened mid-coronal dentin surfaces of extracted human molars were subjected to bonding treatment using three 1-SEAs (Clearfil S3 Bond, Kuraray (S3), G-Bond, GC (GB), Absolute, Dentsply-Sankin (AB)), after which the bonded surfaces were built up with composite. After storage overnight at 37°C, the specimens were sectioned into slabs and further trimmed into an hourglass shape with an interface area of approximately 1 mm2. The specimens were left untouched (control) or were thermocycled for 100,000 cycles. The microtensile bond strength (μTBS) was measured and the ultrastructure of the adhesive/dentin interface characterized using transmission electron microscopy (TEM). RESULTS Long-term thermocycling significantly decreased the μTBS of all one-step adhesives tested (p < 0.05, one way ANOVA and Games-Howell test). TEM revealed a similar interfacial ultrastructure before and after thermocycling for S3. For GB, many voids were observed at the interface after 100,000 thermocycles. Regarding AB, collagen fibrils could no longer be clearly observed upon staining, while the adjacent unaffected dentin was rich in voids. CONCLUSION The bond strength and ultramorphological data demonstrated that the bond of 1-SEAs to dentin degrades with time, although the degree of degradation is obviously material dependent.

Bart Van Meerbeek

Papers

Classification and potential of composite luting materials

Chemical interaction of polyphosphoric acid with titanium and its effect on human bone marrow derived mesenchymal stem cell behavior.

Bisphenol A as degradation product of monomers used in resin-based dental materials

Hydrolytic stability of one-step self-etching adhesives bonded to dentin.

Bonding to enamel using alternative Enamel Conditioner/etchants.