The Journal of Adhesive Dentistry, 05/2006

Purpose: This study describes a two-photon laser fluorescence microscopy technique developed to evaluate the interfacial micromorphology of the hybrid layer in bonded restorations. Materials and Methods: Micropermeability of the hybrid layer was characterized by means of simultaneously contrasting a dye-containing adhesive with a differently colored dye placed into the pulp chamber and allowed to diffuse toward the different-colored hybrid layer. A fluorescent red dye (rhodamine B) was incorporated into a commercial dentin bonding agent. Class I preparations (margins in enamel) were made on extracted human third molars. The teeth were restored using conventional methods: bonding agent, composite, finishing, and polishing. An aqueous solution of a yellow/green dye (fluorescein) was then placed into the pulp chamber for 3 h, allowing time to diffuse toward the different-colored bonded interface. The teeth were then embedded, sectioned, and microscopically analyzed using two-photon laser microscopy at 40X magnification. Results: Subsurface fluorescent imaging using this technique enabled interfacial micromorphology to be characterized at submicrometer resolution and provided high-contrast images. The quality of surrounding structures and potential presence of gaps were also precisely assessed. Conclusion: Two-photon laser microscopy provided high quality, high-resolution images of the bonded interface and surrounding areas, allowing accurate qualitative and quantitative analysis of the structure and integrity of the hybrid layer. Keywords: fluorescence microscopy, two-photon laser scanning microscope, fluorescent dyes, resin-based bonded interface

Purpose: The present study is a compilation of methodologies developed in order to evaluate the effects of addition of a fluorescent agent, rhodamine B, to resin-based materials. The intent of the work was to develop a systematic methodology that accounts for variables not shown to be of concern in past testing, but may significantly affect interpretation of the resulting images and material properties. Materials and Methods: Different methodologies were specifically developed to evaluate factors affecting the use of the fluorescent agent rhodamine B in the identification of resin-based materials. The influence of dye concentration was evaluated with respect to adhesive polymerization reaction kinetics and bond strength of the resin into which the dye is added. The pH of the dye-solvent solution was also considered. Additionally, the mass and percentage of rhodamine B leached into different media over time was determined. Results: It was demonstrated that a specific dye must be used with caution, and the concentration of a fluorescent agent is important with respect to both the conversion and bond strength of the resin to which the dye is added. An alcoholbased dye solution also produced an extremely high amount of dye leaching from polymerized specimens. The adhesive pH was not altered. Conclusion: The standardized methodology developed here to analyze restoration interfaces using a fluorescent dye can lessen the impact of variables when interpreting results. Keywords: fluorescence microscopy, fluorescent dyes, dental adhesives

Purpose: To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations. Materials and Methods: Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm2 (XL 3000, 3M ESPE); LED at 750 mW/cm2 (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm2 (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37°C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm2. Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set α = 0.05. Results: The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values. Conclusions: Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC. Keywords: light-curing units, microtensile bond strength, adhesive system, resin composite

Purpose: The purpose of the study was three-fold: 1) to determine the strength of the bond between a number of dual-curing resin cements and dentin treated with corresponding adhesive systems, 2) to determine the effect on bond strength of not light curing the cements, and 3) to investigate whether application of a solution of sodium sulfinate or ascorbic acid would increase the bond strength in the cases where the manufacturer's version of an adhesive system resulted in low bond strength with chemically cured cement, ie, cement cured without light. Materials and Methods: The adhesive systems comprised 5 simplified systems (Adper Scothcbond 1 XT, ED Primer II, Excite DSC, OptiBond Solo Plus, and Prime & Bond NT), and as controls, two three-step etch and rinse systems (Adper Scotchbond Multi-Purpose Plus and Gluma Solid Bond). The corresponding dual-curing resin cements were RelyX ARC, Panavia F 2.0, Variolink II, Nexus 2, Calibra, RelyX ARC, and 2Bond2. The cements were either light and chemically cured or only chemically cured. The adhesive systems were used as recommended by the manufacturers, which for some systems involved inclusion of a so-called activator or catalyst when used with chemically cured cement. Sodium sulfinate and ascorbic acid were applied as a 1% ethanol solution. The bond strengths were measured in shear after storing specimens for 24 h in 37°C water. Results: When the dual-curing resin cements had been both light and chemically cured, the bond strengths increased in this order: Gluma Solid Bond < ED Primer II < Prime & Bond NT < Adper Scotchbond Multi-Purpose Plus < Excite DSC < Adper Scotchbond 1 XT < OptiBond Solo Plus. Omission of light curing of the cements decreased the bond strengths with OptiBond Solo Plus and Prime & Bond NT. The use of activator in conjunction with OptiBond Solo Plus and Prime & Bond NT increased the bond strength to chemically cured cement, but not to the level obtained when the cement was both light and chemically cured. The use of the catalyst of Adper Scotchbond Multi-Purpose Plus did not increase the bond strength with chemically cured cement. Pretreatment with a solution of sodium sulfinate or ascorbic acid increased the bond strength with chemically cured cement in the case of OptiBond Solo Plus, whereas only the solution of sodium sulfinate was effective with Prime & Bond NT. Conclusion: Clinicians should be aware that in situations where a dual-curing resin cement cannot be light cured, some adhesive systems suffer a loss of efficacy, even when respective activators are used. Pretreatment with a 1% ethanol solution of sodium sulfinate may restore much of the lost bond strength. Keywords: activator, adhesion, chemical cure, initiator, photopolymerization

Purpose: To investigate the influence of composite resin consistency and placement technique on proximal contact tightness of Class II composite resin restorations. Materials and Methods: A manikin model (KaVo Dental) was used with an artificial first molar in which a standardized MO preparation was ground. This preparation was duplicated 360 times. Cavities were restored using Clearfil Photo Bond (Kuraray) combined with one of three composite resins of different consistencies: a low-viscosity (X-Flow, Dentsply), a medium-viscosity (Clearfil AP-X, Kuraray) and a high-viscosity composite (Tetric Ceram HB, Ivoclar Vivadent). Each composite was combined with 6 different matrix systems and separation techniques (n = 20). Groups 1 and 2: pre-contoured metal circumferential matrix (KerrHawe 1101-c) in a Tofflemire retainer combined either with hand instrument (OptraContact, Ivoclar Vivadent) or separation ring (Composi-Tight Gold, Garrison Dental Solutions). Group 3: pre-contoured metal sectional matrix (Lite-Flex, Danville Materials) with separation ring. Groups 4 and 5: precontoured metal circumferential dead-soft matrix (Adapt SuperCap, KerrHawe) with or without separation ring. Group 6: flat metal circumferential matrix (OptraMatrix, Ivoclar Vivadent) in a Tofflemire-retainer with hand instrument (OptraContact). Proximal contact tightness was measured using the Tooth Pressure Meter (University of Technology, Delft). To determine the effect of experimental variables on the proximal contact tightness, a multiple linear regression model was constructed. Results: Measurements in group 6 were not possible; therefore, this group was excluded. The use of medium- or high-viscosity instead of a low-viscosity composite resin resulted in statistically significantly tighter proximal contacts (p < 0.01). The use of a separation ring resulted in a large, statistically significant increase (p < 0.001) in contact tightness, while the use of a hand instrument resulted in a small, statistically significant increase of contact tightness (p = 0.017). No statistically significant differences were found when a dead-soft matrix or a sectional matrix was used instead of a Tofflemire (p = 0.159, p = 0.261, resp.). Conclusion: Use of a separation ring when restoring a Class II composite resin restoration has a greater influence on the obtained proximal contact tightness compared to the influence of the consistency of the composite resin. Keywords: proximal contact, Class II composite resin restoration, matrix system, separation ring

Purpose: To evaluate the effects of saliva contamination on microtensile bond strengths of all-in-one adhesives to dentin. Materials and Methods: Flat superficial occlusal dentin surfaces of extracted human molars were used and randomly divided into 2 groups depending on two all-in-one adhesives: One-Up Bond F Plus (Tokuyama Dental) and Adper Prompt L-Pop (3M ESPE). For each adhesive, the teeth were allocated to 7 subgroups in which one group was bonded without contamination with saliva, serving as a control. The other groups, either before or after the polymerization of adhesives, were contaminated with saliva and dried; contaminated, dried, and adhesives re-applied; contaminated, rinsed, and the adhesives re-applied. Resin composite was then placed on the treated dentin surfaces. After 24 h storage in distilled water at 37°C, the teeth were sectioned perpendicular to the adhesive interface in x and y directions, obtaining multiple beam-shaped specimens with a cross-sectional area of approximately 1.0 mm2. Specimens were stressed in tension at 1 mm/min until rupture of the bond. Data were analyzed using one-way ANOVA and the Games-Howell test. Results: For both all-in-one adhesives, saliva-contaminated groups showed lower bond strengths than the controls. Re-application of the adhesives after drying or rinsing the saliva off restored the dentin bond strengths to the control levels. Conclusion: Saliva contamination reduced the dentin bond strengths of all-in-one adhesives. Supplementary application of the adhesive after cleaning the saliva from the dentin surface is an empirical recommendation for restoring bond strength. Keywords: all-in-one adhesive, bond strength, microtensile bond test, saliva contamination

Purpose: The aim of this study was to examine the influence of Er:YAG laser on the shear bond strength of three different adhesives to lased dentin. Materials and Methods: Seventy specimens obtained from 35 extracted human molars were embedded in polyester resin and ground with silicon carbide papers. The samples were divided into seven groups. 1. Er:YAG laser (Key Laser 3, KaVo) + Clearfil Protect Bond (Kuraray); 2. Er:YAG laser + Clearfil tri-S Bond (Kuraray); 3. Er:YAG laser + 37% H3PO4 + Single Bond 2 (3M-ESPE); 4. Er:YAG laser + Single Bond 2; 5. conventional method + Clearfil Protect Bond; 6. conventional method + Clearfil tri-S Bond; 7. conventional method + 37% H3PO4 + Single Bond 2. The samples were subjected to shear bond testing 24 h after bonding. Statistical analyses were carried out by two-way ANOVA, t-test, one-way ANOVA, post-hoc Tukey's and Dunnett C test (p = 0.05). Results: Only the Er:YAG laser + Clearfil tri-S Bond group demonstrated significantly higher bond strengths vs conventionally prepared specimens (p < 0.05). There were no significant differences between the shear bond strengths of Single Bond 2 adhesive applied to laser- vs bur-treated specimens (p > 0.05). In laser prepared samples, Clearfil Protect Bond showed the highest scores (p < 0.05), whereas in conventionally prepared groups, no statistical differences were observed between Clearfil Protect Bond and Clearfil tri-S Bond (p > 0.05). Conclusion: Er:YAG laser irradiation did not adversely affect the shear bond strength of Single Bond 2 and Clearfil Protect Bond to dentin, whereas it increased the shear bond strength values of Clearfil tri-S Bond. Keywords: Er:YAG laser, antibacterial adhesive, all-in-one adhesive

Purpose: To evaluate strength and morphology of the interface created on enamel and dentin by Panavia F 2.0 (P, Kuraray), RelyX Unicem (RU, 3M ESPE), and Maxcem (M, Sybron-Kerr), applied under two standardized clinically realistic seating pressures. Materials and Methods: Composite overlays (Paradigm MZ100, 3M ESPE) were luted on flat enamel or dentin surfaces of 48 extracted molars. During the initial 5-min self-curing period, a pressure of either 20 or 40 g/mm2 was maintained on the overlay. Curing was completed by light irradiation from the top of the overlay for 20 s. Microtensile sticks and specimens for SEM observations were obtained from the luted teeth. Bond strength data from enamel and dentin (MPa) were analyzed with separate two-way ANOVAs in order to assess the effect of cement type, luting pressure, and their interactions. Tukey's test was used for post-hoc comparisons (α = 0.05). Results: The bond strengths (MPa) to dentin were: P 20 g/mm2 7.5 ± 3.7, 40 g/mm2 10.9 ± 4.5; RU 20 g/mm2 6.8 ± 2.6, 40 g/mm2 14.5 ± 5.3; M 20 g/mm2 4.1 ± 1.8, 40 g/mm2 5.2 ± 1.6. The bond strengths (MPa) to enamel were: P 20 g/mm2 25.2 ± 9.0, 40 g/mm2 30.7 ± 8.6; RU 20 g/mm2 10.7 ± 4.9, 40 g/mm2 11.1 ± 5; M 20 g/mm2 7.3 ± 3.1, 40 g/mm2 7.9 ± 3.2. Cement type, luting pressure, and the interaction of these two factors had significant influences on dentin bond strength, with RU and P outperforming M. RU and P significantly benefited from the increase in luting pressure. In enamel, the type of cement was a significant factor for adhesion, with P yielding the highest and M the lowest strength. The measured bond strengths corresponded with the morphological results. Conclusion: Interfacial strength and adaptation of self-etching and self-adhesive dual-curing cements are enhanced if a seating force greater than finger pressure is maintained throughout the initial self-curing period. Keywords: self-etching resin cement, self-adhesive resin cement, seating force, microtensile bond strength, scanning electron microscope, interface

Purpose: To test the null hypothesis that three self-adhesive luting materials had the same microtensile bond strength when used to lute ceramic IPS Empress II disks to the dentin of perfused teeth. Materials and Methods: Occlusal enamel and the roots of 9 human third molars were removed and crown segments connected to a perfusion system (30 cm H2O). Nine ceramic disks (IPS Empress II) were prepared, conditioned with 5% HF (20 s), rinsed with water, and air dried. A primer silane agent was applied (Monobond-S) for 60 s and air dried. Teeth were bonded to disks using one of three materials: Multilink System, RelyX Unicem, or Panavia F light. Specimens were vertically sectioned to obtain square bars. Each bar was fixed to a rigid custom-made tensile device and submitted to tensile force until debonding. Microtensile bond strength (µTBS) was given in MPa. Because the means of bonded areas (BA) were different between groups, it was impossible to compare µTBS results directly. Thus, the regression line TBS(MPa) = -2.15 + [19.92 / BA (mm2)] was calculated to correlate µTBS results and BA. Residuals (difference between the value estimated by the regression line and the actual value) were stored as "distances". ANOVA was performed to examine the statistical significance of differences between means distances of the groups', and the Tamhane's post hoc test was used to locate eventual differences. Results: The number of bars used in the analysis was n = 147. Residuals should not be statistically different if the null hypothesis (represented by the regression line) was credible. ANOVA showed statistically significant differences between the distances of the groups' means (p < 0.00001). Tamhane's post hoc test (p < 0.05) showed that different group means were RelyX < Multilink < Panavia F. Conclusion: The null hypothesis was rejected: materials showed different tensile bond strengths. Panavia F obtained highest bonding values, followed by Multilink System. RelyX Unicem, the only material that does not require pretreatment of dentin, achieved the lowest TBS values under these study conditions. Keywords: self-adhesive luting, ceramic, IPS Empress II, microtensile

Traumatic fracture of anterior teeth is one of the common dilemmas facing the dentist during daily practice. Classical treatment of a fractured tooth involving the pulp includes the use of post and core with or without a crown, or extraction of the remaining part of the fractured tooth and replacement with a three-unit fixed partial denture or an implant. With the improvement of adhesive systems, reattachment of the fractured tooth fragment became possible as a mode of treatment that immediately improves the esthetic quality of the restored tooth. This article presents a clinical technique for the restoration of a fractured maxillary central incisor, by reattaching the labial enamel fragment using a metallic post and resin composite restoration. One-year clinical evaluation revealed successful results for this technique. Keywords: traumatic injury, reattachment, adhesive system, resin composite