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

http://webdelprofesor.ula.ve/odontologia/robertramirez/PDF/17.pdf

Resin composite--state of the art.

Systematic review of the chemical composition of contemporary dental adhesives

Hygroscopic and hydrolytic effects in dental polymer networks.

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization.

Bonding performance of universal adhesives in different etching modes.

Chairside CAD/CAM materials. Part 2: Flexural strength testing.

Bulk-fill resin composites: polymerization properties and extended light curing.

This in vitro study evaluated dentin bond strength and marginal adaptation of direct resin composites according to the manufacturers' instructions and with simulated application errors. One hundred and forty cavities were prepared into disks of freshly extracted human third molars and filled with one resin composite. Dentin adhesives of the third (with self-etching primer: Syntac Classic), fourth (with total etching: Scotchbond Multi-Purpose Plus) and fifth generation (one-bottle adhesive: PrimeB 2) excessive drying after conditioning; 3) drying primers immediately after application and 4) drying primers excessively. After 21 days of storage and 24 hours thermocycling (1150 cycles), replicas were made and push-out testing was performed. Replicas were examined for marginal adaptation using SEM (X200 magnification). Compared with values of the control groups, application errors resulted in dramatically decreased bond strengths and reduced percentages of gap-free margins for all products tested (p < 0.05). Excessive drying after conditioning exhibited significantly less effect for the third generation adhesive than for products requiring total etching/wet bonding.

Anselm Petschelt

Papers

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization.

Bonding performance of universal adhesives in different etching modes.

Chairside CAD/CAM materials. Part 2: Flexural strength testing.

Bulk-fill resin composites: polymerization properties and extended light curing.

Technique sensitivity of dentin bonding: effect of application mistakes on bond strength and marginal adaptation.