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

Dental adhesion review: Aging and stability of the bonded interface

The dentin substrate: structure and properties related to bonding.

Relationship between surface area for adhesion and tensile bond strength — Evaluation of a micro-tensile bond test

The purpose of this study was to investigate marginal microleakage by examining the resin/dentin interface using a cryo-SEM and a silver ion penetration method. Class 5 cervical cavities were restored using an adhesive resin system following treatment with 37% phosphoric acid gel. The cavity wall adaptation was observed using cryo-SEM to avoid specimen damage. This observation showed excellent marginal adaptation of material to cavity walls and no gap formation. However, silver ions had penetrated beneath the resin-impregnated layer when observed with conventional SEM images, which showed the leakage of silver ions between the resin and decalcified tooth structure without gap formation. This study suggests that the bonding monomers of Clearfil Photo Bond were not fully able to penetrate into the demineralized dentin after phosphoric acid etching, thus leaving a porous zone as a microleakage pathway beneath the resin-impregnated layer.

Microporous dentin zone beneath resin-impregnated layer.

SYNOPSIS IN INTERLINGUALE RELATION INTER LE DURITATE, LE DISCOLORATION, E LE INVASION MICROBIAL IN DENTINA CARIOSE.-Frescamente extrahite dentes con carie esseva dissecate verticalmente. In un del partes le superficie sectional esseva examinate pro duritate secundo Knoop e discoloration. Sectiones histologic del altere parte esseva usate pro le detection de evidentia microbiotic. Le resultatos esseva le sequentes: In dentina cariose, mollification precedeva in omne casos le discoloration, e invasion microbial esseva semper le tertie stadio. Le duritate de dentina in le fronte discolorate o microbial esseva inferior in casos acute e superior in casos chronic. Le distantia inter ille frontes e le fronte de mollification esseva plus grande in casos acute e plus micre in casos chronic.

Relationship between Hardness, Discoloration, and Microbial Invasion in Carious Dentin

T HE RESISTANCE OF cementing materials is a factor that prevents cast restorations from being seated correctly. Such a failure in seating restorations, if slight, can be compensated by malleting or burnishing their margins. However, the margins of full crowns are difficult to mallet or burnish in the mouth. In a previous study,l the thickness of the film of cement of Class I, II, and MOD inlays, and full crowns was determined on their cross sections. The best adaptation of full crowns was obtained when they were made by a combination of an alginate indirect method as described by Fusayama,2p” and the improved thermal expansion technique. 3,4 These crowns generally exhibited more than 90 p thickness of cement on their occlusal floors unless some special means were used to relieve the heavy resistance of the cementing substance. Many means have been suggested5-8 for relieving the resistance of cement for the placement of full crowns. Perforation of the center of the occlusal surfaces of crowns to provide an outflow for the cement has been reported as the most effective method.9-11 However, this technique is not convenient because the perforations must be sealed later with gold foils or inlays. Another technique requires relief spaces inside of cast crowns such as reduced inside surfaces by means of dental burs. However, in this procedure the advantage of cast crowns is reduced by the irregular loss of bulk. In this study, the influences of the cementing load, the taper and height of preparations, and relief spaces inside crowns were investigated as they related to the adaptation of full cast crowns during cementation.

Relief of resistance of cement of full cast crowns

The interfacial structure of seven dentin adhesive systems was studied morphologically. Argon ion beam etching of an undecalcified section clearly revealed the resin-impregnated demineralized dentin at the adhesive interface of the seven systems when observed under the scanning electron microscope.

Interfacial structure between dentin and seven dentin bonding systems revealed using argon ion beam etching

3. Popovich, F. and Thompson G. W.: Maxillary diastema: Indications for treatment. Am J Orthod 75:399, 1979. 4. Keene, H. J.: Distribution of diastema in the dentition of man. Am ,J Phys Anthropol 21:437, 1963. 5. Becker, A.: The median diastema. Dent Glin North Am 22:685, 1978. 6. Lindsey, D.: The upper midline space and its relation to the labial frenum in children and adults. Br Dent J 143:327, 1977. 7. Hornwitz, H. S.: A study of occlusal relations in 10 to 12 year old Caucasian and Negro children. Int Dent J 20:593, 1970. 8. Becker, A.: The median maxillary distema: A review of its etiology. Israel J Dent Med 26:21, 1977. 9. Lavelle, C. L. B.: Distribution of diastema in different human population sample. Scand J Dent Res 78:530, 1970.

Hiroyasu Hosoda

Papers

Microporous dentin zone beneath resin-impregnated layer.

Relationship between Hardness, Discoloration, and Microbial Invasion in Carious Dentin

Relief of resistance of cement of full cast crowns

Interfacial structure between dentin and seven dentin bonding systems revealed using argon ion beam etching

Relation of finish to discoloration of composite resins