J. Dent. 1993; 21: 195-202 195

Two-year clinical evaluation of two dentine-adhesive systems in cervical lesions

B. Van Meerbeek, M. Braem*, P. Lambrechts and G. Vanherle Aspirant, National Fund for Scientific Research of Belgium, Department of Operative Dentistry and Dental Materials, Katholieke Universiteit te Leuven, Belgium and *Dental Propedeutics, Universitair Centrum Antwerpen (RLJCA), Belgium

ABSTRACT Two commercially available dentine-adhesive systems, Tenure and Tripton, were tested in two different cavity designs by placing 132 Class Vcomposite restorations in cervical lesions of 35 patients. In Group& the cervical restorations were placed totally in dentine without any intentional enamel involvement. In Group B, they were placed in dentine with adjacent enamel margins bevelled and acid etched. The retention rate, the evidence of clinical microleakage, and the marginal integrity were monitored over a 2-year period. The results of this clinical investigation indicate a high failure rate when only dentinal bonding was involved. A loss rate of 30% for Tenure and 55% for Tripton was noted in Group A after 2 years of clinical service. However, both adhesive systems used in combination with micromechanical retention on the enamel border (Group B) performed extremely well with only one restoration each having debonded over the 2-year period. Identically, marginal integrity and evidence of clinical microleakage more severely deteriorated with time for the Group A restorations in comparison with their Group B counterparts. In summary, the overall results were more positive for Tenure than for Tripton. It is concluded that micromechanical retention by acid etching of the enamel margin is still indispensable for the clinical success of cervical Class V composite restorations, primarily for retention and clinical microleakage and also, but to a lesser degree, for marginal adaptation.

KEY WORDS: Adhesives, Dentine bonding, Resin composites, Restorative dentistry

J. Dent. 1993; 21: 195-202 (Received 18 June 1992; reviewed 29 July 1992; accepted 14 December 1992)

Correspondence should be addressed to: 8. Van Meerbeek, Department of Operative Dentistry and Dental Materials, Katholieke Universiteit te Leuven, UZ St-Rafael, Kapucijnenvoer 7, 8-3000 Leuven, Belgium.

INTRODUCTION

With the development of numerous dentine-adhesives over the last three decades, the bonding of resin composites to dentine has been approached in different ways. In imitation of the enamel acid-etch technique (Buonocore, 1955) acid-etched dentine was expected to provide micromechanical retention for the restorative composite by penetration of the resin-bonding agent into the opened dentine tubules (Fusayama, 1980). However, the counter- pressure of dentinal fluid and its abundant presence on the bonding site hinder the micromechanical attachment of these hydrophobic resins to the hydrophilic dentine substrate (Torney, 1978; Pashley, 1990). After the failure of this dentine acid-etch technique, bifunctional adhesive

@ 1993 Butterworth-Heinemann Ltd. 0300-5712/93/040195-08

molecules were designed to react chemically with either the inorganic and/or organic constituents of the dentine surface, and, simultaneously, to copolymerize with the restorative resin. However, the generation of a smear layer during cavity instrumentation prevents close dentine- resin contact, which is a prerequisite for any chemical reaction (Kinloch, 1987). In addition, evidence of real chemical adhesion is still lacking, as it has been demon- strated by several spectroscopic studies (Eliades et al., 1990; Edler et al., 1991; Spencer et al., 1992).

As a result, a micromechanical interlocking principle is proposed as the prime mechanism of dentine adhesion (Nakabayashi et al., 1982; Erickson, 1989; Inokoshi et al., 1990; Pashley, 1990; Suzuki et al., 1991). Better wetting

196 J. Dent. 1993; 21: No. 4

ability of the moist dentine structure was achieved by pretreating it with hydrophilic priming agents (Duke, 1991, Sdderholm, 1991). At present, modern dentine- adhesive systems generally use one of two adhesion strategies that use opposite methods of dealing with the smear layer (Van Meerbeek et al., 1992a). One strategy aims to modify or at least preserve the smear layer, while its opponent requires a complete removal of the smear layer. Whether this iatrogenically produced smear layer should be preserved or removed, has to be determined in clinical trials as the ultimate proofs of efficacy for dentine-adhesive systems.

The clinical and microscopical performance of two dentine-adhesive systems with such opposing adhesion strategies, Tenure (Den-Mat, Santa Maria, CA, USA) and Tripton (GC, Tokyo, Japan), was evaluated in cervical lesions, using two different cavity designs. The retention rate, the evidence of clinical microleakage, and the marginal integrity were recorded over a 2-year period.

MATERIALS AND METHODS

The clinical performance of two dentine-adhesive systems, Tenure (Den-Mat) and Tripton (GC), was evaluated in 132 Class V cervical, either saucer- or wedge-shaped lesions of 35 patients. The distribution of lesions between types of teeth is given in Table I. Two cavity designs were defined. In Group A the cervical restorations were placed totally in dentine without any intentional enamel involvement. In Group B, they were placed in dentine with adjacent enamel margins bevelled and acid-etched. In both groups, the dentine walls were not mechanically roughened prior to etching and bonding. Two trained dentists used both adhesive systems randomly in the two experimental groups, strictly following the instructions of the manu- facturers. All restorative procedures were carried out under rubber dam isolation with a gingival retraction clamp Ivory 2122 SA (Columbus Dental, St Louis, MO, USA) to retract the gingival tissue. A local anaesthetic,

Table 1. Distribution of lesions between types of teeth

Incisors Canines Premolar-s Molars Total

Tenure A Upper jaw

z 1 1 1

Lower jaw Total 6 87

13 2 2: 14 3 31

Tenure 6 Upper jaw 5 2 6 14 Lower jaw 7 5 6

:, 18

Total 12 7 12 1 32

Tripton A Upper jaw 3 Lower jaw 4

: 1: 0 5 2 24

Total 7 3 17 2 29

Tripton B

Upper jaw 7 2 5 Lower jaw 7 5 10 ; :: Total 14 7 15 4 40

Lidocaton 2% (Pharmaton, Lugano, Switzerland), was injected when needed to prevent patient discomfort during the clinical procedures. Following isolation, the cervical lesion and the adjacent enamel were cleaned with a pumice-water slurry using a rubber cup to remove the saliva pellicle or any remaining dental plaque.

For Tenure (Den-Mat, batch number 1140105) in Group A, Tenure Dentine Conditioner (2.5% HNO, + 3.5% Al oxalate; Den-Mat) was applied to the dentine surface with a disposable brush, left on the surface for 60 s, thoroughly rinsed with a water stream, and, finally, dried with compressed air free of oil and water. Equal amounts of Tenure Solution A and B (5% NTG-GMA + 10% PMDM; Den-Mat) were then stirred, and immediately brushed onto the conditioned dentine surface. After lo-20 s of drying, this application was repeated. Visar Seal (Bis- GMA, Den-Mat) was next applied, blown with air to establish a thin, uniform resin layer, and finally cured for 20 s with a visible-light-curing unit (Luxor Lamp, ICI, Macclestield, UK). Herculite XR (Kerr, Romulus, MI, USA) was applied incrementally to restore the cervical lesion to its natural tooth contour. Final contouring and finishing of the restorations were performed using a pinetree-shaped contouring diamond (Komet, Lemgo, Germany) and flexible discs of the Sof-Lex Pop-On set (3M, St Paul, MN, USA). For Tenure in Group B, the technique was similar to that of Group A with the additional steps of bevelling and etching the adjacent enamel with 37% phosphoric acid (Scotchgel, 3M) for 30 s.

For Tripton (GC, batch number UM17-21) in Group A, a thin layer of Tripton Dentine Primer (0.1% poly- hexanide; GC) was applied to all exposed dentine, left for 30 s, and dried with compressed air free of oil and water. A thin, even layer of Tripton Universal Bonding Agent (70% TEG-DMA + 15% UDMA + 10% MPDM + 4% aerosil; GC) was next brushed onto the primed surface using a disposable brush, gently airblown, and finally polymer- ized for 30 s with a visible-light-curing unit (Luxor Lamp, ICI). Placement of the composite Opalux (GC), polymer- ization, and finishing were performed as described for Herculite XR (Kerr). Again for Tripton in Group B, the adjacent enamel was first bevelled and etched with 37% phosphoric acid (Scotchgel, 3M) prior to the application of the Tripton system.

The clinical efficacy of the two adhesive systems was determined by the percentage of lost restorations after 6, 12, and 24 months of clinical service. Retention failures were calculated by dividing the number of lost restorations by the recall total. The evidence of clinical microleakage and the marginal integrity were evaluated clinically using a mirror and a probe, and microscopically with the scanning electron microscope on replica casts. An index system as defined by Vanherle et al. (1986) was used to record the results (Table II).

For the evaluation on the scanning electron microscope XL20 (Philips, Eindhoven, The Netherlands), an impres- sion of the cervical fillings or cavities of lost fillings was

Van Meerbeek et al.: Clinical evaluation of two dentine adhesive systems 197

Table II. Marginal integrity, retention and clinical microleakage in percentages

6-month recall I P-month recall Tenure Tripton Tenure Tripton

Clinical evaluation criteria

24-month recall Tenure Tripton

no marginal defects slight defect at the enamel margin partial loss of the restoration loss of the restoration small chip fracture severe chip fracture small cervical defect severe cervical defect

49 43 14 45 24 16 7 54 IO 20 a 49 21 43 21 15 37 42 31 9 40 45 31 11

0 0 0 0 0 0 0 0 0 0 0 0

13 038 3 13 0 41 ; 30 3 55 3 : g2: ; 0 3 15 4 14 0 6 0 : : :

14 :oo 7 32 23 23 7 28 20 26 3 3: 0 0 0 0 0 0 0 0 0

R clinically acceptable ,257 67 100 62 97 a7 96 59 97 70 97 45 97 R clinically unacceptable 3488 13 038 3 13 441 3 30 3 55 3

M, no discoloration 93 97 67 97 77 92 53 a2 73 97 62 91 M, superficial, localized 7 3 33 3 23 84718 27 3 38 9

discoloration M, deep, generalized 0 0 0 0 0 0 0 0 0 0 0 0

discoloration

*Recall level.

taken with Xantopren Blue (Bayer Dental, Leverkusen, Germany) light body and poured out with Araldite epoxy resin (Ciba Geigy, Dilbeek, Belgium). All replicas were mounted on metal stubs and coated by vaporization with a pure gold layer of nearly 40 nm in an argon-gas environment for 4 min, using an SEM coating unit E-5100’ (Polaron Equipment Ltd, Watford, UK). SEM photo- micrographs of the resin-dentine interface produced by both products were prepared by the method introduced by Inokoshi et al. (1990) and Van Meerbeek et al. (1992a).

RESULTS

The percentage of lost fillings as a function of time is represented inFig. 1 for the two dentine-adhesive systems. The Group A restorations, placed totally in dentine, show a loss rate of 30% for Tenure and even 55% for Tripton after

0 6 12 18 24 30 36

Time (mth)

Fig. 1. Chart showing the percentage of lost fillings as a function of time for both adhesive systems investigated. The two dotted lines represent the ADA guidelines for provisional and for full acceptance of dentine-adhesive systems. -W-, Tripton A; -A-, Tenure A; -El-, Tripton B; -A-, Tenure B.

2 years of clinical service. For Tenure, the first major retention loss of Group A restorations occurred during the first 6 months, with a delayed increment of losses after 1 year of clinical service. For Tripton, most of the Group A restorations were lost during the first 6 months after placement, with a slower loss rate thereafter. When the enamel margins were bevelled and acid etched in Group B, only one filling each debonded for Tenure and for Tripton.

The marginal integrity was seriously affected for both adhesive systems already after 6 months in tivo and further declined after 1 and 2 years (Table II). Again, a clear difference became evident between Group A and Group B. This contrast between the two cavity designs is particularly reflected by the percentage of clinically acceptable restorations (R,,,,). At the 2-year recall, 70% and 45% of the Group A restorations for Tenure and Tripton, respectively, were rated as clinically acceptable, versus 97% of the Group B restorations for both systems (Table ZZ, R,,,,). Although the Group B score for restorations without any marginal defects (R,) is substan- tially higher for Tripton, in comparison with that for Tenure, this difference is less important when all clinically acceptable fillings are taken into account (Table ZZ, R, and R,,,,). A relatively high percentage of small cervical defects (R,) was recorded for both systems in Group B in comparison with their respective Group A restorations. No partial losses of restoration (R,), severe chip fractures (R,J, or severe cervical defects (IQ were recorded (Table II). One exception was the Tenure Group B restoration, which at the l-year recall was recorded as &, but, eventually, was debonded at the 2-year recall (Table ZZ, &). In summary, the overall result was more positive for Tenure than for Tripton, mainly due to the higher loss rate (RJ of the latter.

198 J. Dent. 1993; 21: No. 4

Fig. 2. SEM photomicrograph showing an overall view of a Class V filling restored with the Tenure-Herculite XR combination. High magnification of the composite surface reveals the rather smooth surface appearance, typical of Herculite XR, which is a small-particle hybrid with filler particles smaller than 3 pm. C, Composite; E, enamel; G, gingiva.

Fig. 4. SEM photomicrograph of the dentinal surface of a lost Tenure filling, clearly revealing evidence of cohesive com- posite failure. D, Dentine; E, enamel; G, gingiva.

Regarding the evidence of clinical microleakage (Table Ir), the Group A restorations again scored worse than the Group B restorations. In Group A the percentage of restorations without discoloration (M,) is significantly higher for Tenure than for Tripton. Already at the 6-month recall, Tripton showed a relatively high percentage of superficial, localized discoloration (MJ. After 2 years of clinical service, the Group A restorations demonstrating superficial, localized discoloration (M,) gradually increased versus a rather steady percentage for the Group B restorations. Only superficial, localized discolorations (M,) but no deep,generalized discolorations (M3) were recorded for the two adhesive systems.

Representative photomicrographs taken by scanning electron microscopy are shown in Figs 2-9. Two retained restorations, restored with the Tripton-Opalux com- bination, and the Tenure-Herculite XR combination, respectively, are depicted in Figs 2 and 3. Some evidence

Fig. 3. SEM photomicrograph showing an overall view of a Class Vfilling restored with theTripton-Opaluxcombination. The highly magnified rectangle demonstrates the rather rough surface appearance of Opalux, which is a hybrid composite with filler particles larger than 3 pm. C, Composite; E, enamel; G, gingiva.

Fig. 5. SEM photomicrograph of thedentinal surface of a lost Tripton filling, clearly revealing several remnants of composite material attached to dentine. D, Dentine; E, enamel; G, gingiva.

of cohesive composite failure was occasionally found on the dentine surface of lost restorations, as demonstrated by the photomicrographs ofFigs 4 and5 An excellent (R,) and a defective (R,) marginal adaptation at the cervical- dentine margin are presented in the successive photo- micrographs of Figs 6-9 for the two products.

DISCUSSION

This clinical investigation revealed that neither Tenure nor Tripton was capable of retaining the restorations in cervical lesions for a prolonged time when only dentinal bonding was involved. Their relatively high loss rates in Group A are consistent with those of a similar clinical study, done by van Dijken (1992), in which a loss rate of 32% for the Tenure-Opalux combination and even 73% for the Tripton-Opalux combination were noted at the 2-

Van Meerbeek er al.: Clinical evaluation of two dentine adhesive systems 199

Fig. 6. Excellent (R,) cervical outline of a Tenure restoration. C, Composite; D, dentine; G, gingiva.

Fig. 7. Excellent (R,) cervical outline of a Tripton restoration.

Fig. 8. Defective (R,) cervical outline of a Tenure restoration showing gross potential for marginal microleakage. C, Composite; D, dentine; G, gingiva.

Fig. 9. Defective (R,) cervical outline of a Tripton restoration showing gross potential for marginal microleakage. C, Composite; D, dentine; G, gingiva.

year recall. With reference to the American Dental Association guidelines (Council on Dental Materials. Instruments and Equipment, 1991) for cervical Class V restorations without reliance on cavity preparation design, including bevels, or features for micromechanical reten- tion, both of these adhesive systems failed to satisfy the standard of provisional acceptance by having a loss rate exceeding 5% at the l-year recall (Fig. I). Similarly, full acceptance will not be granted at the future 3-year recall, since both adhesive systems suffer from a loss rate higher than 10% already after 2 years of clinical service. The major loss rate during the first 6 months of clinical service for both systems might be attributed to direct detachment of the restorative resin from the cavity wall, probably due to a degree of polymerization shrinkage, exceeding the developing dentine bond strength. The delayed failure, after the l-year recall for Tenure and continuing after the 6-month recall for Tripton, indicates a gradual deteriora- tion of the dentine bond by environmental factors, probably related to microleakage with hydrolysis of the dentine bond, and to tooth flexure, which would dislodge the cervical lesion (Lee and Eakle, 1984; Kemp-Scholte, 1989; Braem et al., 1992). Furthermore, these restorations

meet with considerable problems in achieving suitable margins. Excellent margins were only recorded for 10% and 8% of the Tenure and Tripton Group A restorations, respectively (Table II). The higher percentage (20%) of the Tenure restorations having small cervical defects, in comparison with that of their Tripton counterparts (3%), can be clarified by the lower percentage of lost Tenure restorations. Absence of a deep, generalized discoloration in any of the restorations, thereby satisfying the ADA guidelines concerning clinical microleakage, can be explained by the high loss rate in Group A. These debonded restorations would probably have presented evidence of severe clinical microleakage just before their failure.

When both adhesive systems were used in combination with micromechanical retention on the enamel border, the clinical result was substantially improved. Not only was the percentage of lost restorations limited to 3%, i.e. one filling, but both systems also guaranteed a more reliable marginal adaptation than did Group A (Table Zr). Both systems provided clinically acceptable restorations in 97% of all Group B restorations. However, the relatively high R, code, which records small cervical defects. for

200 J. Dent. 1993; 21: No. 4

Fig. 70. Photomicrograph of the resin-dentine interface produced byTenure, which is disclosed after argon-ion beam etching. A low-viscosity resin (L) was cured on top of the adhesive resin instead of a respective resin composite. The small white dots represent the inorganic microfiller particles of the low-viscosity resin. A hybrid or resin-impregnated dentine layer (R) of about 1 urn connects the deep dentine layers with the low-viscosity resin (L). Resin tags (T) penetrated the opened dentine tubules I, Inter-tubular dentine; P, peritubular dentine.

both systems in Group B in comparison with Group A, might indicate that these Group B restorations are primarily bonded by superior enamel bonding rather than by dentinal bonding. The presence of these inad- equate cervical margins might induce marginal leakage and, thus, compromise the lifespan of these cervical restorations.

The competing modes of action of these adhesive systems are clearly illustrated in the photomicrographs of Figs 10 and II. Their respective resin-dentine interface was made observable by scanning electron microscopy after an argon-ion beam etching procedure (Van Meerbeek et al., 1992a). When Tenure was used, the iatrogenic smear layer and smear plugs were completely removed by the conditioning pretreatment, thus allowing the adhesive resin to penetrate the dentinal tubules (Fig. 10). Simul- taneously, the intertubular dentine-surface layer was decalcified and subsequently impregnated with resin to a depth of 1 urn, which created the resin-impregnated dentine layer. This transition zone of dentinal components interdiffused by in situ polymerized resin serves as a hybrid junction between the deep solid dentine and the covering restorative material. When the loosely bound layer of unorganized smear debris was modified or at least retained, as for Tripton, the tubule orifices remained obstructed with globular particles without the formation of a hybrid layer (Fig. 11). Its adhesive mechanism is supposedly based on the reinforcement or the fixation of this natural seal of the dentinopulpal complex to the underlying dentine. Penetrating the smear layer with the hydrophilic polyhexanide primer (Cosmocil CQ, GC) is intended to allow micromechanical as well as chemical electrostatic bonding to the dentinal substrate. The polyhexanide additive is also effective in decontaminating

Fig. 1 7. Photomicrograph of the resin-dentine interdiffusion zone when Tripton was used. The dentine tubules are obliterated with unorganized material forming smear plugs (S). No resin-impregnated dentine layer and resin tags are visible. The slight separation between the dentine surface layer and the adhesive resin (A) demonstrates the poor wetting ability and, thus, the weak adhesive capacity of Tripton. L, Low-viscosity resin; I, inter-tubular dentine; P, peritubular dentine.

the cavity preparation by its antibacterial properties. However, a slight separation between the dentine-surface layer and the bonding resin (Fig. I I), which was probably caused by the high vacuum during the SEM procedures, might well reveal poor wetting ability and, thus, weak adhesive capacity of this adhesive resin. Comparing both opposing interfacial ultrastructures (Figs 10 and II), the adhesive failure of the Tripton interface may account for the higher loss rate of Tripton in Group A compared to that of Tenure.

Factors other than the adhesive system or the cavity design and related to tooth flexure may have contributed to the high rate of retention failures in Group A (Lee and EakIe, 1984; Heymann et al., 1991; Bream et al., 1992; Van Meerbeek et al., 1992b). Because extensive incisal or occlusal loads induce compressive and tensile stresses at the enamel-dentine junction in the cervical region, as is known from the aetiology of cervical erosive and abrasive lesions (Lee and Eakle, 1984) cervical composite restora- tions are subject to the same stresses, certainly when adhesive dentistry is involved. With regard to the type of restorative materials presently used, Herculite XR is an ultrafine midway-tilled densified composite with filler particles smaller than 3 urn (Fig, 2) and a Young’s modulus of elasticity of 16042 (? 162) MPa, whereas Opalux (GC) is a fine compact-filled densilied composite with tiller particles larger than 3 urn (Fig. 3) and a relatively high modulus of elasticity (EM) of 22336 (+ 629) MPa (Braem et al., 1986; Willems, 1992). In a previous study, Scotchbond 2 (3M) in combination with the microtilled resin composite Silux Plus (3M) (EM = 9382 f 155 MPa) and Clearfil New Bond (Kuraray, Osaka, Japan) combined with Clearfll Ray (Kuraray) (EM = 27384 + 327 MPa) were clinically evaluated in

Van Meerbeek et al.: Clinical evaluation of two dentine adhesive systems 201

function of retention in cervical Class V lesions (Van Meerbeeket al., 1992b). Comparing these four systems, the Scotchbond 2/Silux Plus (3M) combination performed most favourably with a loss rate of only 13% in Group A at the 2-year recall, followed by the Clearfil (Kuraray) combination with a loss rate of 21%, and, finally, both adhesive systems presently investigated with 30% losses for Tenure (Den-Mat) and 55% losses for Tripton (GC). Hence, except for the Clearfil (Kuraray) combination, the clinical results improved as the moduli of elasticity of the resin composites declined. Moreover, microfilled composites compress rather than dislodge during tooth flexures (Bayne et al., 1991). These findings are consistent with those of Heymann et al. (1991). Evidence of bruxism and malocclusion was often recorded for patients with Group A retention failures, although their Group B restorations were still in place at the 2-year recall. Moreover, Feilzer et al. (1987) defined a configuration factor as a measure for stress relief of polymerization contraction by resin flow depending on the cavity shape and size. Cervical Class V lesions with a high ratio of bonded surface to free, flow-active surface offer the least potential of all restoration classes for contraction-stress relaxation, so resin composites with maximum flow capacities are recommended to restore the natural, vestibular tooth contour. Interestingly, a high correlation (r = 0.86) was found by Kemp-Scholte (1989) between the modulus of elasticity and a marginal leakage factor in the sense of the higher the modulus of elasticity of the resin composite used, the more cervical gaps occurred. There- fore, microfilled resin composites, with their inherently high elasticity and flow reservoir, are definitely the materials of choice for cervical Class V restorations, as far as retention is concerned.

With regard to the location of restored teeth, retention failures occurred more frequently for Group A restorations placed in mandibular teeth than those in maxillary teeth with eight (89%) mandibular versus one (11%) maxillary lost restoration(s) for Tenure (Den-Mat), and 11 (69%) mandibular versus five (31%) maxillary lost restorations for Tripton (GC). The greater difficulty in moisture control and the possibly greater tooth flexure due to the lingual tooth inclination in the mandibular arch accounts for this substantial difference in retention (Heymann et al., 1991). The highest loss rate was noted for restored molars (67%), followed by incisors (30%) and canines (29%), and the lowest for premolars (22%). The difficulty in restoring cervical lesions in molars rather than factors related to tooth flexure is the main reason for the higher losses of molar restorations. As incisors and canines are often the only remaining, natural lower teeth in older dentitions, they have to withstand the total occlusal load during function.

It is concluded that the dentine-adhesive systems presently investigated suffer from a high loss rate already after 6 months of clinical service when only dentinal bonding is involved. Additional retentive measures like enamel bevelling and acid etching suffice to remedy this

retention failure but do not guarantee stable marginal integrity and microleakage resistance for cervical composite restorations with either system. An adhesive system that conditions the intertubular dentine surface layer after removal of the smear layer appears to perform better than a system that modifies the disorderly layer of smear debris without complete removal, at least for Tenure and Tripton.

References Bayne S. C., Heymann H. O., Sturdevant J. R. et al. (1991)

Contributing co-valables on clinical trials. Am. J. Dent. 4,241-250.

Braem M., Lambrechts P., Van Doren V. et al. (1986) The impact of composite structure on its elastic response. J. Dent. Res. 65, 648-653.

Braem M., Lambrechts P. and Vanherle G. (1992) Stress- induced cervical lesions. J. Prosthet. Dent. 67, 718-722.

Buonocore D. H. (1955) A simple method of increasing the adhesion of acryl filling materials to enamel surfaces. J. Dent. Res. 34, 849-853.

Council on Dental Materials, Instruments and Equipment. (1991) Revised Acceptance Program ADA Guidelines.

Duke E. S. (1991) Adhesion and tooth-colored restoratives. Curr. Opin. Dent. 1, 163-171.

Edler T. L., Krikorian E. and Thompson V. P. (1991) FTIR surface analysis of dentin and dentin bonding agents. .J. Dent. Res. 70, 458 (abstr. 1534).

Eliades G., Palaghias G. and Vougiouklakis G. (1990) Surface reactions of adhesives on dentin. Dent. Mater. 6,208-216.

Erickson R. L. (1989) Mechanism and clinical implications of bond formation for two dentin bonding agents. Am. J. Dent. 2, 117-123.

Feilzer A. J., de Gee A. J. and Davidson C. L. (1987) Setting stress in composite resin in relation to configuration of the restoration. J. Dent. Res. 66, 1636-1639.

Fusayama T. (1980) New Concepts in Operative Dentistry. Chicago, Quintessence.

Heymann H. O., Sturdevant J. R., Bayne S. et al. (1991) Examining tooth flexure effects on cervical restorations: a two-year clinical study. J. Am. Dent. Assoc. 122, 41-47.

Inokoshi S., Hosoda H., Harnirattisai C. et al. (1990) A study on the resin-impregnated layer of dentin. Part I: A comparative study on the decalcified and undecalcified sections and the application of argon ion beam etching to disclose the resin-impregnated layer of dentin. Jap. J. Conserv. Dent. 33, 427-442.

Kemp-Scholte C. M. (1989) The Marginal Integrity of Cervical Composite Resin Restorations. Thesis, Amsterdam.

Kinloch A. J. (1987) Adhesion and Adhesives: Science and Technology. London, Chapman & Hall.

Lee W. C. and Eakle W. S. (1984) Possible role of tensile stress in the etiology of cervical erosive lesions of teeth. J. Prosthet. Dent. 52, 374-380.

Nakabayashi N., Kojima K. and Masuhara E. (1982) The promotion of adhesion by the infiltration of monomers into tooth substrates. J. Biomed. Mater. Res. 16, 265-273.

Pashley D. H. (1990) Interactions of dental materials with dentin. Trans. Am. Acad. Dent. Mater. 3, 55-73.

Sdderholm K. J. M. (1991) Correlation of in vivo and in vitro performance of adhesive restorative materials: a report of the ASC MD156 task group on test methods for the adhesion of restorative materials. Dent. Mater. 7, 74-83.

202 J. Dent. 1993; 21: No. 4

Spencer P., Byerley T. J., Eick J. D. et al. (1992) Chemical Vanherle G., Verschueren M., Lambrechts P. et al. (1986) characterization of the dentin/adhesive interface by Fourier Clinical investigation of dental adhesive systems. Transform Infrared Photoacoustic Spectroscopy. Dent. Part I: an in-&o study. J. Prosthet. Dent. 55, Mater. 8, 10-15. 157-163.

Suzuki M., Kato H. and Wakumoto S. (1991) Vibrational analysis by Raman spectroscopy of the interface between dental adhesive resin and dentin. J. Dent. Res. 70, 1092-1097.

Van Meerbeek B., Inokoshi S., Braem M. et al. (1992a) Morphological aspects of the resin-dentin interdiffusion zone with different dentin-adhesive systems. J. Dent. Res. 71, 1530-1540.

Torney D. (1978) The retentive ability of acid-etched dentin. J. Prosthet. Dent. 39, 169-172.

van Dijken J. W. V. (1992) Two-year clinical evaluation of four new dentin bonding agents. J. Dent Res. 71, 662 (abstr. 1177).

Van Meerbeek B., Braem M., Lambrechts P. et al. (1992b) Evaluation of two adhesive systems in cervical lesions. J. Prosthet. Dent (accepted).

Willems G. (1992) Multi Standard Criteria for the Selection of Potential Posterior Composites. Thesis, Leuven.

1st European Dental Materials Conference Relevance of Material Laboratory Tests to Clinical Performance Amsterdam, The Netherlands 16-20 August 1993 For further information and registration details please contact: Prof. Dr C.L. Davidson, ACTA, Louwesweg 1, 1066 EA Amsterdam, The Netherlands. Fax: +31 20 6692726.

Annual Conference British Association of Teachers of Conservative Dentistry (BATCD) Sheffield, United Kingdom 16-17 September 1993 Guest speakers

??Professor Derry Shanley ??Professor Richard Johns ??Mr Michael Pendlebury ??Dr Graham White

For further details please contact: Mr R B Winstanley, Department of Restorative Dentistry, Claremont Crescent, Sheffield SIO 2TA, UK. Tel: 0742 670444 ext 3055.