Biomedical subjects

B Van Meerbeek

Publications and source records attributed to B Van Meerbeek.

At least 55 records · Page 3Linked to original sources

PubMed1999

Polymerization shrinkage and elasticity of flowable composites and filled adhesives.

OBJECTIVES: The magnitude and kinetics of polymerization shrinkage, together with elastic modulus, may be potential predictors of bond failure of adhesive restorations. This study examined these properties in visible-light-cured resins, in particular new flowable composites and filled adhesives. METHODS: Polymerization shrinkage values were obtained by digital video imaging before and after light-curing; shrinkage kinetics were obtained by the "deflecting disk" method and the elastic modulus by analysis of the fundamental period of vibration. RESULTS: Flowable composites generally showed higher shrinkage than traditional non-flowable composites, while more densely filled adhesives presented lower shrinkage than lightly filled or unfilled resins. The elastic moduli of flowable composites were in the low-medium range, whilst the hybrid composites showed the highest values and the microfilled the lowest. More densely filled adhesives were more rigid than lightly filled and unfilled adhesives. The kinetics behavior was material dependent, mainly characterized by the coefficient of near-linear contraction between 10 and 40% of the final shrinkage and the time to reach 75% of the final shrinkage. SIGNIFICANCE: The higher shrinkage of flowable composites over that of hybrids may indicate a potential for higher interfacial stresses. However, their lower rigidity may be a counteracting factor. The microfilled composite showed low shrinkage and low rigidity, a combination that may prove less damaging to the interface. As the kinetics parameters tended to be material specific, no specific class of materials should be seen as more stress inducing until studies determine the relative importance of each examined parameter. The performance of adhesive resins as stress buffers also remains unpredictable.

Analysis of Variance↗

PubMed1999

The effect of a re-wetting agent on dentin bonding.

OBJECTIVES: Recently, a new generation of simplified one-bottle dentin bonding systems, sensitive to variations in the degree of substrate moisture, was introduced. This in vitro project compared the dentin bond strengths and interfacial ultra-morphology formed by three one-bottle bonding systems [OptiBond SOLO (ethanol-based), Prime&Bond 2.1 (acetone-based), and Single Bond (ethanol- and water-based)]. The null hypothesis tested was that re-wetting a dried dentin surface with a HEMA aqueous solution would not result in bond strengths, and resin impregnation into demineralized dentin, comparable to those obtained for moist dentin. METHODS: Dentin specimens were assigned to the following three etched surface conditions: moist dentin-control group; dentin dried for 5 s; and dentin dried for 5 s and re-moistened with a commercial 35% HEMA aqueous solution. Mean shear bond strengths were calculated and analyzed with one- and two-way ANOVA. Dentin discs treated with the same combination of surface condition/adhesive were processed and observed under both transmission and scanning electron microscopes. RESULTS: For moist dentin, the morphology of the resin-dentin interfaces showed penetration of the dentin adhesives to the depth of the transition between demineralized and unaffected dentin. Drying dentin for 5 s resulted in a significant decrease in mean bond strengths and an incompletely infiltrated collagen structure with areas of unveiled collagen fibers, regardless of the solvent. Re-wetting dentin with the aqueous HEMA solution re-established the level of bond strengths obtained to moist dentin and resulted in a raise of the fiber network with simultaneous increase in interfibrillar space dimensions. SIGNIFICANCE: The results suggest that the use of an aqueous HEMA solution might compensate for the dryness induced on dentin surfaces by using air blasts from an air syringe, after rinsing off the etchant. As the behavior of the material that contained water was also affected by surface dryness, the percentage of water included in the composition of current ethanol- and water-based adhesives, such as Single Bond, may not be enough to compensate for the collapse of the collagen filigree upon drying.

Analysis of Variance↗

PubMed1999

Evaluation of esthetic parameters of resin-modified glass-ionomer materials and a polyacid-modified resin composite in Class V cervical lesions.

OBJECTIVE: The purpose of this study was to compare the esthetics of 3 resin-modified glass-ionomer materials and 1 polyacid-modified resin composite to the esthetics of a conventional glass-ionomer control material. METHOD AND MATERIALS: One hundred eighty-seven Class V cervical restorations were observed clinically over 18 months. The esthetic index system that was used evaluated color match, translucency or opacity, and surface roughness. RESULTS: The tested materials behaved very dissimilarly and inconsistently. In general, the esthetic results of the resin-modified glass-ionomer materials and the polyacid-modified resin composite were far from optimal. The esthetic appearance of restorations seriously deteriorated during clinical service, mainly because of discoloration of margins, changes in translucency and opacity, and rapidly appearing roughness or dullness on the surface. Both the resin-modified glass-ionomer materials and the polyacid-modified resin composite evaluated in this study performed better esthetically than did the conventional glass-ionomer material. CONCLUSION: Indications for these combination materials are limited to areas where esthetics is not a primary concern but where their ease of application may guarantee a more durable functional result.

Acrylic Resins↗

PubMed1999

Hybridization effectiveness of a two-step versus a three-step smear layer removing adhesive system examined correlatively by TEM and AFM.

PURPOSE: The objectives of this study were (1) to compare the hybridization effectiveness of two adhesive systems that are applied in respectively three and two steps, and (2) to determine the best resin-dentin interface preparation technique for atomic force microscopy (AFM). MATERIALS AND METHODS: The resin-dentin interface produced by the three-step OptiBond Dual-Cure (Kerr) and its simplified two-step successor OptiBond Solo (Kerr) was ultramorphologically examined using transmission electron microscopy (TEM) and AFM. Four different methods were used to prepare interface specimens for AFM: (1) polishing to a 0.1-micron finish with a silicon oxide suspension, (2) polishing to a 0.05-micron finish with an aluminum oxide suspension, (3) argon-ion etching, and (4) sectioning with a diamond knife. RESULTS: Both TEM and AFM demonstrated that some collapse of the exposed collagen fibril network, due to gentle postconditioning air-drying of the dentin surface, may not have been totally recovered through hybridization by the two-step adhesive formulation as opposed to the three-step precursor. From the four interface preparation methods, only diamond-knife sectioning revealed sufficient ultramorphologic detail and high resolution that can capitalize on the high resolution offered by AFM. CONCLUSION: First, the findings suggest that simplifying the application procedure of adhesives by combining the primer and adhesive resin into a single application step may reduce hybridization effectiveness. Future research should confirm this effect for other two- versus three-step adhesive systems. Second, diamond-knife sectioning should be used for future topographic imaging and physicomechanical testing of resin-dentin interfaces by AFM.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1998

Marginal adaptation and retention of a glass-ionomer, resin-modified glass-ionomers and a polyacid-modified resin composite in cervical Class-V lesions.

OBJECTIVES: An 18-month follow-up clinical trial of one conventional glass-ionomer (HIFI Master Palette), three resin-modified glass-ionomers (Fuji II LC, Vitremer, 3M Exp. 155) and one polyacid-modified resin composite (Dyract) was conducted to evaluate their clinical effectiveness in Class-V cervical lesions. In addition, the interface between dentin and two resin-modified glass-ionomers and one polyacid-modified resin composite was examined by scanning electron microscopy (SEM). METHODS: After evaluation of the restorations immediately following placement (baseline), all patients were subjected to a strict recall schedule with controls at 6, 12 and 18 months. The clinical effectiveness was recorded in terms of retention and marginal integrity, clinical microleakage, caries recurrence, and tooth vitality. A chi 2-test (p < 0.05) was used to test for significant differences between materials. In case of restoration loss or special defects, a replica was made to examine the surface texture and restoration margins by SEM. In vitro, the interface was examined by SEM after an argon-ion-beam etching technique was used to enhance surface relief and disclose interfacial substructures. RESULTS: Retention appeared to be good for all the materials tested. Marginal discrepancies were localized at the incisal enamel and/or the cervical dentin margin, except for the polyacid-modified resin composite that showed most of the defects at the incisal enamel margin. None of the systems could guarantee margins free of microleakage for a long time. In vitro, the type of dentin pre-treatment defines to a great extent the morphology of the resultant interface between dentin and the restorative material tested. SIGNIFICANCE: In this clinical study, the retention rate of the tested materials was good and even excellent for some products. Perfect marginal adaptation deteriorated too fast. The marginal adaptation of the polyacid-modified resin composite at the enamel site would probably have been better by the use of selective enamel or total acid etching. Marginal sealing remains a problem. Future research should concentrate on improving the marginal adaptation and sealing capacities before a broader clinical use can be advocated.

Acrylic Resins↗

PubMed1998

Immediate versus one-month wet storage fatigue of restorative materials.

Immediate finishing is a highly desirable property of restorative materials. In general, the resin composites, the polyacid-modified resin composites and resin-modified glass-ionomers are finished immediately after light-curing. For the conventional glass-ionomers a waiting period of 24 h is recommended. Therefore, the objective of this study was to investigate whether immediate finishing and application of cyclic loading under water spray on resin-modified glass-ionomers, a conventional glass-ionomer, a polyacid-modified resin composite and a resin composite are reflected in their Young's modulus and fatigue resistance after 1-month wet storage compared with a control group that could mature untroubled for 1 month. From this study, it could be concluded that there is a material-dependent response on immediate finishing. For the conventional glass-ionomer, the waiting period of 24 h is highly advisable. The resin composite suffered more than the other test materials. A second statement is that one must be cautious by the extrapolation of findings obtained on quasi static tests (Young's modulus) towards dynamic properties (flexural fatigue limit).

Biocompatible Materials↗

PubMed1998

The clinical performance of adhesives.

OBJECTIVES: Traditional mechanical methods of retaining restorative materials have been replaced to a large extent by tooth conserving adhesive restorative techniques. Because adhesives have been evolving so rapidly for the last few years, the timing is right for evaluating the clinical status of present day adhesives. DATA SOURCES: Current literature with regard to the clinical performance of adhesives has been reviewed. An overview of currently available adhesive systems is provided and a categorization of these adhesives according to their clinical application procedure and their intended mechanism of adhesion is proposed. Parameters of direct relevance to the clinical effectiveness of adhesives are discussed in relation to the clinical effectiveness of today's adhesives. CONCLUSIONS: The clinical performance of present day adhesives has significantly improved, allowing adhesive restorations to be placed with a high predictable level of clinical success. Most modern adhesive systems are superior to their predecessors, especially in terms of retention that is no longer the main cause of premature clinical failure. Recent adhesives also appear less sensitive to substrate and other clinical co-variables. As the remaining major shortcoming of modern adhesives, none of these modern systems however appears yet to be able to guarantee hermetically sealed restorations with margins free of discoloration for a long time.

Adhesiveness↗

PubMed1998

Monomethacrylate co-monomers for dental resins.

Polymerisation shrinkage is widely recognised as a major drawback of resin based dental restoratives. Bis-GMA is often employed as the principal dimethacrylate monomer. Due to its high viscosity, Bis-GMA is normally mixed with large proportions of low viscosity glycol dimethacrylates. The purpose of this study was to determine whether the polymerisation shrinkage of Bis-GMA-based resins would be lower if alternative monomethacrylate co-monomers were used in place of conventional dimethacrylate co-monomers as viscosity modifiers. Conventional resins used were ethyleneglycol dimethacrylate and triethyleneglycol dimethacrylate; the alternative monofunctional co-monomers were tetrahydrofurfuryl methacrylate, hydroxypropyl methacrylate and isobornyl methacrylate. Model resins containing 54% mol/mol of co-monomer in Bis-GMA and 1% w/w of benzoyl peroxide as initiator were heat-cured at 70 degrees C for 8 h. Polymerisation shrinkage, degree of conversion and concentration of remaining methacrylate groups were calculated from density changes obtained gravimetrically. Other properties evaluated were Young's modulus, water uptake and viscosity of the monomer mixtures. The Bis-GMA-based resins exhibited lower shrinkage when mixed using the monomethacrylates rather than with conventional glycol dimethacrylates. Among the alternative co-monomers, tetrahydrofurfuryl methacrylate conferred the best balance of all measured properties.

Absorption↗

PubMed1998

A TEM study of two water-based adhesive systems bonded to dry and wet dentin.

To keep the exposed collagen scaffold penetrable to resin, it has been recommended that the conditioned dentin surface be maintained in a visibly moist condition, a clinical technique commonly referred to as wet bonding. In this study, resin-dentin interfaces produced with two water-based adhesive systems--OptiBond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M)--were compared by transmission electron microscopy, following the application of either a dry- or a wet-bonding technique. The hypothesis advanced was that the ultramorphology of the hybrid layer would differ depending on which bonding method was applied. A morphologically well-organized hybrid layer of collagen fibrils intermingled with resin in tiny interfibrillar channels was consistently formed by the OPTI system. The SBMP system was found to produce a hybrid layer with a more variable ultrastructure, less distinctly outlined collagen fibrils, and a characteristic electron-dense phase located at its surface. No major differences in hybrid layer ultrastructure were observed when the two adhesive systems investigated were bonded to either dry or wet dentin. When the adhesives were dry-bonded, no ultrastructural evidence of collapsed demineralized collagen, incompletely or not at all infiltrated by resin, could be detected. In addition, when the two adhesives were bonded to wet dentin, no signs of overwetting phenomena, that would have indicated that water was ineffectively removed, were apparent. It has been hypothesized that the amount of water provided with the hydrophilic primer solution of either of the two adhesive systems investigated suffices to re-hydrate and re-expand the gently air-dried and collapsed collagen network. Further research should be directed to determine whether this hypothesized self-rewetting effect can be extrapolated to other adhesive systems that provide water-based primers.

Adhesives↗

PubMed1998

The influence of direct composite additions for the correction of tooth form and/or position on periodontal health. A retrospective study.

The aim of this in vivo study was to evaluate the influence of 5- to 6-year-old direct composite additions on the marginal periodontal tissues. Composite additions were directly placed on 79 intact maxillary anterior teeth in 19 patients (12 to 19 years) by one operator using an ultrafine midway-filled densified resin composite. All patients were recalled 5 to 6 years later for a periodontal evaluation. Plaque index, gingivitis index, and probing depth were measured at the buccal-approximal sites of all unilaterally restored teeth (n=51). An intra-individual comparison was made between the periodontal health of the treated versus the intact sites. The plaque index (P=0.029) and gingivitis index (P=0.008) were significantly higher for the treated sites compared to the intact sites. The difference in probing depth nearly reached the level of significance (P=0.059). In conclusion, 5-to 6-year-old direct composite additions have a negative influence on marginal periodontal health, which consisted of increased plaque retention, gingival inflammation, and periodontal destruction.

Adolescent↗

PubMed1998

Five-year clinical performance of porcelain veneers.

OBJECTIVE: The overall clinical performance of porcelain veneers was evaluated at 5 years. METHOD AND MATERIALS: Porcelain veneers were placed on 87 maxillary anterior teeth in 25 patients (19 to 69 years) by a single operator following a standardized clinical procedure. At the 5-year recall, esthetics, marginal performance, vitality, fracture rate, and patient satisfaction were recorded. RESULTS: At recall, 93% of the veneers were satisfactory without intervention. The remaining 7% presented clinically unacceptable problems such as recurrent caries, porcelain fracture, severe clinical microleakage, or pulpal reaction. The retention rate of the porcelain veneers was 100%, and the maintenance of esthetics was perfect. Only 14% of the veneers presented excellent marginal adaptation over the entire outline of the restoration; however, the impact of the slight marginal defects on the clinical performance was negligible. CONCLUSION: Labial porcelain veneers offer a reliable and effective procedure for the conservative treatment of discolored, malformed, and malaligned anterior teeth.

Adult↗

PubMed1997

Epoxy-embedded versus nonembedded TEM examination of the resin-dentin interface.

When transmission electron microscopy (TEM) is used to evaluate resin-dentin interface specimens for completeness of hybridization, the epoxy resin embedding medium that normally facilitates ultrathin sectioning may produce a secondary or artifactual hybrid layer. This secondary hybrid layer, composed of epoxy resin rather than adhesive resin, may fill the pores that remain as evidence of incomplete resin infiltration, obscuring the fact that they ever existed. In this study, resin-dentin interfaces produced by two dentin adhesive systems, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), were comparatively investigated by TEM in epoxy-embedded and nonembedded nondemineralized sections. The hypothesis advanced was that no difference in ultramorphology of the hybrid layer would result from either specimen preparation method. The two adhesive systems were applied to four mid-coronal dentin disks per manufacturer's instructions. One half of each sample was processed following common procedures for TEM sample preparation with epoxy embedding, whereas the other half was not embedded but instead immersed in hexamethyldisilazane (HMDS), dried and mounted so that it protruded from a base of cold-cure acrylic resin. Each sample was then sectioned using a diamond knife in an ultramicrotome. With either means of preparation, a hybrid layer with a relatively uniform electron density and a loose collagen fibril arrangement with electron lucent interfibrillar channels was formed by OPTI. At the base of the hybrid layer, collagen fibrils were anchored in the underlying unaffected dentin, and no microporosities or gaps were observed. Similarly, whether SBMP was embedded or nonembedded, it was found to have a hybrid layer of variable electron density and an electron dense phase localized at the surface of the hybrid layer. No porosities were evident at the base of the hybrid layer. Thus, with either of the two adhesive systems, no ultrastructural difference in hybrid layer formation was observed between epoxy-embedded and nonembedded sections, and no direct evidence of ineffective resin-infiltration of the demineralized collagen scaffold was found.

Acid Etching, Dental↗

PubMed1997

The 5-year clinical performance of direct composite additions to correct tooth form and position. I. Esthetic qualities.

The aim of the study was to evaluate the esthetic performance of direct composite additions in correcting tooth form and position at 5 years. Composite additions were directly placed using the acid-etch technique and enamel bonding on 87 intact maxillary anterior teeth in 23 young patients (12-19 years old). The restorations were made by one operator using an ultrafine midway-filled densified restorative composite. Color slides were made at baseline and 5 years. At the 5-year recall, esthetic performance was assessed clinically by two evaluators at chair-side in subterms of color match, translucency/opacity, surface roughness, and anatomical form. Five additional examiners scored esthetics on the 5-year slides. Of the restorations, 89% were still esthetically satisfactory after 5 years of clinical service. The remaining restorations needed replacement, mainly because of severe loss of anatomical form, to a lesser degree because of severe color mismatch. Central incisors and small unilateral restorations generally showed the best results concerning color match (68% and 74%, respectively) and surface smoothness (84% and 100%, respectively). The slide scores on color match and translucency/opacity were generally similar or somewhat better than the direct clinical scores; however, the difference were not statistically significant (P > 0.05). As far as surface roughness is concerned, the results were significantly better (P < 0.05) when recorded indirectly than by direct clinical evaluation. In conclusion, direct composite additions are a valuable and effective procedure for esthetic and conservative treatment of malformed and misaligned anterior teeth. Loss of anatomical form due to wear points to a shortcoming of the composite material used, with which a durable esthetic result cannot always be guaranteed in the long term.

Adolescent↗

PubMed1997

The 5-year clinical performance of direct composite additions to correct tooth form and position. II. Marginal qualities.

The aim of the study was to evaluate the marginal performance of direct composite additions for the correction of tooth form and position at 5 years. Composite additions were directly placed using the acid-etch technique and enamel bonding on 87 intact maxillary anterior teeth in 23 young patients (12-19 years old). The restorations were made by one operator using an ultrafine midway-filled densified restorative composite. Color slides were made at baseline and 5 years. At the 5-year recall, marginal performance was assessed by two evaluators in terms of marginal adaptation and retention, clinical microleakage, and caries recurrence. Marginal adaptation and clinical microleakage were judged on the vestibular, palatal, and proximal planes. In addition, these planes were divided into a cervical and an incisal part. No caries recurrence was noted at 5 years and no restoration was lost. Concerning marginal adaptation, only four restorations (5%) presented a severe incisal chipping and needed replacement. The restorations showed a significantly (P < 0.05) higher percentage of perfect margins incisally (37%) than cervically (15%). Canines showed the best cervical marginal adaptation (29% with perfect margins), the best results being with small unilateral restorations. Concerning clinical microleakage, 7% of the restorations were rated as clinically unacceptable due to severe marginal discoloration. Clinical microleakage was significantly more often (P < 0.05) found among smokers. In conclusion, an ultrafine midway-filled densified composite is indicated for use in stress-bearing areas in the anterior region. The type and location of the restoration are determining factors for marginal integrity.

Adolescent↗

PubMed1997

Comparative physico-mechanical characterization of new hybrid restorative materials with conventional glass-ionomer and resin composite restorative materials.

The recently developed hybrid restorative materials contain the essential components of conventional glass ionomers and light-cured resins. The objective of this study was to determine several physical and mechanical properties of eight such materials in comparison with two conventional glass ionomers, one micro-filled, and one ultrafine compact-filled resin composite. The two resin composites and two of the three polyacid-modified resin composites could be polished to a higher gloss than the conventional as well as the resin-modified glass ionomers. After abrasion, surface roughness increased for all materials, but not at the same extent, being the least for the conventional resin composites and one polyacid-modified resin composite, Dyract. In contrast to the later resin composites, of which the surface roughness is principally determined by the presence of protruding filler particles above the resin matrix, roughness of conventional and resin-modified glass ionomers results from both protruding filler particles and intruding porosities. The mean particle size of the hybrid restorative materials fell between the smaller mean particle size of the resin composites and the larger one of the conventional glass ionomers. The micro-hardness and Young's modulus values varied substantially among all eight hybrid restorative materials. For all the resin-modified glass-ionomer restorative materials, the Young's modulus reached a maximum value one month after mixing and remained relatively stable thereafter. The Young's modulus of the conventional and the polyacid-modified resin composites decreased slightly after one month. The conventional glass-ionomer materials undoubtedly set the slowest, since their Young's modulus took six months to reach its maximum. The flexural fatigue limit of the hybrid restorative materials is comparable with that of the micro-filled composite. From this investigation, it can be concluded that the physico-mechanical properties vary widely among the eight hybrid restorative materials, indicating that these materials probably have yet to achieve their optimum properties. Their mechanical strength is inadequate for use in stress-bearing areas, and their appearance keeps them from use where esthetics is a primary concern.

Acrylic Resins↗

PubMed1997

Effects of a self-etching primer on enamel shear bond strengths and SEM morphology.

PURPOSE: To study a dental adhesive system containing a self-etching primer, by evaluating the enamel shear bond strengths and comparing the SEM interfacial morphology. MATERIALS AND METHODS: 100 flat enamel bonding sites were prepared to 600-grit on proximal surfaces of caries-free human molars. The bonding surfaces were treated with Clearfil Liner Bond 2 as recommended by the manufacturer, or combined with various acidic etchants. A composite rod (Clearfil Photo Anterior) was applied to the bonding area in two increments in a Teflon mold and polymerized for 100 s. After 24 h of water storage, the specimens were thermocycled and the shear bond strengths measured using an Instron testing machine. Forty extra molar crowns were roughened and treated with Clearfil Liner Bond 2 and alternative etchants, as described. A low-viscosity resin was bonded to the occlusal surfaces of these crowns, which were further demineralized and deproteinized. Field-Emission SEM examinations were carried out to evaluate the effects of different treatments on enamel surfaces. RESULTS: The mean shear bond strengths were in the range of 18.1 MPa to 25.9 MPa, without significant differences between pairs of means. The failures were predominantly of the adhesive type. The use of alternative etchants resulted in the deepest etching patterns. The use of Clearfil Liner Bond 2, according to manufacturer's directions, resulted in a poorly-defined etching pattern. Regardless of the alternative etchant used, the use of the self-etching primer did not affect the mean enamel shear bond strength.

Acid Etching, Dental↗

PubMed1996

Restorative therapy for erosive lesions.

More needs to be learned about the etiology of erosion lesions before they can be accurately diagnosed, confidently treated and, more importantly, prevented. The treatment is dependent on the location and the degree of erosion. The decision to treat an erosion lesion should be based on careful consideration of the etiology and progression of the condition. Reasons for restoring noncarious enamel/dentin lesions are discussed and various therapeutic measures are provided. Preventive and restorative therapeutic measures for noncarious abrasive/ erosive lesions are proposed such as: a change of dietary or behavior patterns; application of desensitization products; intensive fluoride therapy with or without iontophoresis; brushing with desensitizing dentifrices; adhesive penetration with dentin bonding agents; glass ionomers and compomers; resin composites; composite or porcelain veneers; crown and bridge work; occlusal adjustments and nightguard fabrication if the abfraction factor coincides. The clinical durability of restorative therapy and important clinical factors related to the restoration of multifactorial defects are discussed.

Composite Resins↗

PubMed1996

Correlative transmission electron microscopy examination of nondemineralized and demineralized resin-dentin interfaces formed by two dentin adhesive systems.

The resin-dentin interface formed by two dentin adhesives, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), was ultramorphologically examined by transmission electron microscopy (TEM). Ultrastructural information from nondemineralized and demineralized sections was correlated. It was hypothesized that the different chemical formulations of the two adhesives would result in a different morphological appearance of the hybrid layer. Ultrastructural TEM examination proved that each of the two dentin adhesive systems was able to establish a micromechanical bond between dentin and resin with the formation of a hybrid layer. However, the interfacial hybridization process that took place to produce this resin-dentin bond appeared to be specifically related to the chemical composition and application modes of both systems. OPTI consistently presented with a hybrid layer with a relatively uniform ultrastructure, electron density, and acid resistance. These three parameters were found to be more variable for the hybrid layer formed by SBMP. Characteristic of SBMP was the identification of an amorphous phase deposited at the outer surface of the hybrid layer. Although both adhesive systems investigated follow a total-etch concept, their specific chemical formulations result in different interfacial ultrastructures that are probably related to different underlying bonding mechanisms. The clinical significance of these morphological findings, however, is still unknown.

Acid Etching, Dental↗