Immediate dentin sealing supports delayed restoration placement

STATEMENT OF PROBLEM: Immediate dentin sealing (IDS) is a new approach in indirect restorations. Dentin is sealed immediately following tooth preparation, prior to impression making. It is not known whether it is still possible to obtain an efficient bond between the resin-coated dentin and the restoration after 2 to 4 months of placement of provisional restorations. PURPOSE: The purpose of this study was to determine if there were differences in microtensile bond strength to human dentin using the IDS technique when comparing 2, 7, and 12 weeks of delay until restoration placement, using 2 different dentin bonding agents (DBAs). Previously published preliminary IDS data were included for comparison. MATERIAL AND METHODS: Fifty freshly extracted human molars were obtained and divided into 10 groups. A 3-step etch-and-rinse DBA (Optibond FL) and a 2-step self-etching DBA (SE Bond) were used. For each DBA, the control (C) specimens were prepared using a direct immediate bonding technique and composite restoration (Z100). Preparation of the other specimens used an indirect approach without dentin prebonding (delayed dentin sealing, DDS) or with immediate dentin sealing (IDS), immediately following preparation. IDS teeth had provisional restorations (Tempfil inlay) placed for 2 weeks (IDS-2W), 7 weeks (IDS-7W), or 12 weeks (IDS-12W) before restoration placement. All teeth were prepared for a nontrimming microtensile bond strength test (MTBS) 24 hours after definitive restoration with composite overlays (Z100). Ten to 11 beams (0.9 x 0.9 x 11 mm) from each tooth were selected for testing. MTBS data obtained from the 10 experimental groups were analyzed with a 2-way analysis of variance (ANOVA, dentin bonding system, and sequence of application) with each tooth (mean MTBS from the 10-11 beams) used as a single measurement. The Tukey HSD post hoc test was used to detect pairwise differences among experimental groups (alpha=.05). Fractured beams were also analyzed under stereoscopic microscope (x 30) and SEM. RESULTS: For both adhesives, the mean microtensile bond strengths of C and all IDS groups were not significantly different and exceeded 45 MPa. DDS groups exhibited lower bond strength than all others sequences (P<.001) with SE Bond at 1.81 MPa significantly lower (P=.026) than Optibond FL at 11.58 MPa. The highest mean microtensile bond strength values were found with Optibond FL at 7 weeks (66.59 MPa) and 12 weeks (59.11 MPa). These were significantly higher than SE Bond in the same conditions with values of 51.96 MPa and 45.76 MPa (P=.001 and P=.003), respectively. Failures in DDS groups were all interfacial and purely adhesive. Both C and IDS-2W groups demonstrated interfacial failure that was typically mixed with both areas of failed adhesive resin and areas of cohesively failed dentin while IDS-7W and IDS-12W failed consistently between the existing resin coating (used during IDS) and the overlaying composite resin. CONCLUSIONS: When preparing teeth for indirect bonded restorations, IDS with a 3-step etch-rinse or a 2-step self-etching DBA (prior to impression making) results in microtensile bond strength similar to that obtained with a freshly placed adhesive. The bond strength is not affected by up to 12 weeks of elapsed time prior to placement of the definitive restoration.     

三种脱敏剂对全酸蚀粘结剂牙本质粘结强度和界面形态的影响

目的:研究、比较三种脱敏剂对全酸蚀粘结剂牙本质粘结强度及其粘结界面形态的影响。方法:选择12个无龋损离体人磨牙,磨除牙合面釉质,用600目碳化硅砂纸在流水下预备出有统一玷污层的牙本质粘结面后,随机分为4组,分别用去离子水(对照组)和3种脱敏剂(Hybrid Coat、Gluma、极固宁)进行脱敏处理后,应用Single Bond 2在面粘结4 mm树脂。然后将每个牙垂直于粘结面切割出12个1.0 mm×1.0 mm×4.0 mm的粘结试件,分别在SEM下观察其粘结界面微观形态并进行微拉伸强度(μTBS)测试。结果:HybridCoat组粘结强度最高((14.81±3.87)MPa,随后依次为去离子水组(13.39±4.67)MPa、Gluma组(12.76±2.96)MPa和极固宁组(10.48±4.32)MPa,各组间两两比较,极固宁组明显低于其他3组(P﹤0.05),其他3组间相比均无显著性差异(P﹥0.05);Hybrid Coat组形成的树脂突大部分>35μm,长而密集;Gluma组形成的树脂突长7～35μm;极固宁组形成的树脂突长20～35μm,较稀疏。结论:Hybrid Coat和Gluma对全酸蚀粘结剂牙本质粘结强度无明显影响,而极固宁则明显降低其粘结强度。     

Crown retention with use of different sealing systems on prepared dentine

The purpose of this in vitro study was to evaluate crown retention after using different sealing systems on prepared dentine. Ca(OH)2 suspension was used in comparison with three adhesive bonding systems (Gluma Desensitizer, Optibond FL, Prompt L-Pop). Extracted human premolars were uniformly prepared with the use of a special parallelometer (11 degrees taper, 4 mm axial length). Groups of 20 teeth each were treated with each sealing system. Then crowns were fabricated and temporarily cemented twice. Finally the abutments were cleaned and the crowns were cemented with a glass-ionomer cement Ketac-Cem. Subgroups of 10 crowns were removed with a universal testing machine following storage in distilled water either for 3 days or for 150 days. Prior to dislodging, the crowns of both groups were subjected to chewing simulation. The mean dislodgement stresses in MPa were between 4.9 and 6.9. A range test of Student-Newmann-Keuls revealed significant differences between Ca(OH)2 and Optibond FL (P < 0.05), while the storage time had no significant effect. The level of microleakage increased significantly with storage time (P < 0.05). It is concluded, that the use of Gluma Desensitizer and Prompt L-Pop did not affect crown retention as compared with Ca(OH)2, thus may be used in combination with glass-ionomer cement to desensitize prepared teeth.     

Microtensile bond strengths of seven dentin adhesive systems.

OBJECTIVES: The purpose of this study was to evaluate the microtensile bond strengths of seven dentin adhesive systems (Solid Bond, EBS-Multi, PermaQuik, One Coat Bond, Gluma One Bond, Prime & Bond NT/NRC and Clearfil Liner Bond 2V) and their respective fracture modes. METHODS: Superficial occlusal dentin of extracted human molars was exposed, finished with wet 600-grit silicon carbide paper, and a block of resin composite bonded with the above adhesives according to the manufacturers' instructions. The teeth were kept in tap water for 24 h at 37 degrees C, sectioned to obtain three or four bar-shaped specimens, which were then shaped to an hour-glass form of 1.2 +/- 0.02 mm diameter. The specimens were stressed at a crosshead speed of 1 mm/min until rupture of the bond. The mean bond strengths were compared using one-way ANOVA and LSD tests. The frequency of fracture modes was compared using Kruskal-Wallis and Mann-Whitney U-tests. RESULTS: Mean microtensile bond strengths ranged from (17.8 +/- 7.0) MPa for Solid Bond to (36.0 +/- 8.1) MPa for Clearfil Liner Bond 2V. The bond strength of Clearfil Liner Bond 2V and PermaQuik (30.8 +/- 8.5 MPa) were not significantly different, and were higher than all other materials. Bond strengths of Solid Bond (17.8 +/- 7.0) MPa, EBS-Multi (18.7 +/- 5.0) MPa, One Coat Bond (21.9 +/- 5.6) MPa, and Gluma One Bond (23.4 +/- 5.2) MPa were not significantly different. SEM examination indicated that Solid Bond, EBS-Multi and One Coat Bond showed no significant difference in failure modes but were significantly different from PermaQuik, Prime & Bond NT/NRC and Clearfil Liner Bond 2V. SIGNIFICANCE: The self-etching primer system, Clearfil Liner Bond 2V, provided the simplest bonding technique, and together with PermaQuik exhibited greatest bond strength to dentin.     

Effects of chemical pretreatments on dentin bonding

The aim of this study was to evaluate several chemical pretreatments on the shear bond strength of three dentin bonding agents (DBAs) and to try to correlate dentin morphology with bond strength using scanning electron microscopy (SEM). The DBAs tested were: Gluma Primer in association with Scotchbond DC, Scotchbond DC alone and Clearfil New Bond. Bond strengths of Scotchbond DC and Clearfil New Bond were not significantly modified or reduced by acidic dentin pretreatments. Gluma/Scotchbond adhesion was increased by several treatments but only maleic acid treatment produced shear bond strengths significantly higher than EDTA treatment. SEM evaluation of dentin treatments revealed a wide variety of morphological changes in the dentin surface with partial and complete removal of smear layer by acidic solutions, and only minor modification by amino acid solutions. Only maleic acid was capable of the complete removal of the smear layer and smear plugs coupled with extensive exposure of dentin collagen fibrils.     

The effect of current-generation bonding systems on microleakage of resin composite restorations.

OBJECTIVE: The aim of this study was to determine the microleakage of current-generation dentin bonding systems in Class II resin composite restorations. METHOD AND MATERIALS: Class II (occlusodistal or occlusomesial) cavity preparations with a gingival margin 2 mm apical to the cementoenamel junction were prepared on 70 noncarious, extracted human premolar teeth. Teeth were randomly divided into five groups and treated with different-generation bonding systems (Optibond FL, Gluma One Bond, Clearfil SE Bond, acid etching plus Clearfil SE Bond, and Prompt-L-Pop). All cavities were restored in a posterior resin composite and subjected to 200 thermocycles (at 5 degrees C to 55 degrees C; 30-second dwell time). After immersion in 0.5% basic fuchsin dye for 24 hours, the teeth were sectioned longitudinally and evaluated for dye penetration using a binocular stereomicroscope. RESULTS: There was no statistically significant differences among bonding systems in the degree of microleakage in the occlusal walls. For gingival walls, statistically significant differences were found only between the Clearfil SE Bond and Prompt-L-Pop groups and the Clearfil SE Bond with acid etching and Prompt-L-Pop groups. The greatest microleakage was observed in Prompt-L-Pop specimens. CONCLUSION: Most of the tested dentin bonding systems were able to eliminate microleakage completely in the occlusal walls, but some systems exhibited statistically significant differences in leakage in the gingival walls.     

In vitro cytotoxicity of different desensitizers under simulated pulpal flow conditions

PURPOSE: To evaluate the cytotoxicity of three desensitizers, one nonrinse, and one etch-and-rinse adhesive system applied on dentin specimens of different thickness. MATERIALS AND METHODS: The test materials (A: Admira Protect, B: Gluma Desensitizer, C: Seal&Protect, D: Clearfil Protect Bond, E: Optibond FL) and a positive control (35% H2O2) were applied on 1.0-, 1.5-, and 2.5-mm-thick bovine dentin specimens (each subgroup n = 5) in a dentin barrier test device. The experiments were performed with perfusion (2 ml/h) of the pulpal part of the chamber. The eluates were obtained before (baseline) and 15, 30, 45, 60, and 120 min after application of the adhesives and pipetted onto L-929 fibroblasts. Cytotoxicity of the materials was determined in relation to the baseline value using the MTT assay (succinic dehydrogenase activity). Statistical analysis was performed using ANOVA and Student's t-test. RESULTS: With regard to 1.0-mm dentin specimens, application of Clearfil Protect Bond (D) decreased enzyme activity significantly, while test materials A to C and E were not cytotoxic. However, cytotoxicity of D was limited to up to 15 min and decreased thereafter. Application of the test materials A to E on 1.5- and 2.5-mm dentin samples exhibited no significant cytotoxic effects within 120 min. Generally, ANOVA found significant interactions between the test materials and dentin thickness. However, only for Admira Protect was a significant increase of enzyme activity with increasing dentin thickness observed. CONCLUSION: Desensitizing agents might exhibit cytotoxic potential when applied on dentin less than 1.0 mm thick. The tested desensitizers and the adhesive systems caused similar effects, in which cytotoxicty might be influenced by the duration of perfusion and dentin thickness.     

In vitro shear bond strength of self-etching adhesives in comparison to 4th and 5th generation adhesives

PURPOSE: To determine the shear bond strength (SBS) of different established (Resulcin Aqua Prime & Monobond N: RA, Prompt L-Pop III: PLP) and experimental (AC-Bond: AC, AC-Bond + Desensitizer: ACD) self-etching adhesives in comparison to fourth (Optibond FL: FL) and fifth generation (Excite: EX, Gluma Comfort Bond: CB) adhesives. MATERIALS AND METHODS: All adhesives were applied on flat enamel and dentin surfaces and light cured following manufacturers' directions. Tetric Ceram A2 composite cylinders 3.5 mm in diameter and 2.0 mm in height were sheared off (1 mm/min) after thermocycling (5 to 55 degrees C, 5000x). The t-test (5% level, Bonferroni-correction) was used for statistical analysis. RESULTS: SBS in enamel: RA: 27.0+/-5.8 MPa, PLP: 15.9+/-3.4 MPa, AC: 28.1+/-4.4 MPa, ACD: 22.2+/-4.1 MPa, FL: 33.2+/-3.2 MPa, EX: 30.5+/-5.1 MPa, CB: 30.1+/-3.7 MPa. SBS in dentin: RA: 25.8+/-5.7 MPa, PLP: 20.7+/-2.9 MPa, AC: 27.0+/-4.5 MPa, ACD: 20.7+/-3.7 MPa, FL: 34.4+/-3.8 MPa, EX: 30.0+/-4.6 MPa, CB: 27.9+/-2.6 MPa. FL resulted in significantly (p < 0.002) higher SBS in enamel and dentin than RA, AC, ACD, and PLP, and in higher SBS to dentin than CB. In enamel and dentin, RA performed significantly superior to PLP, but was not different from AC and ACD. EX and CB were both on the same level of significance as AC and RA, but showed superior results to ACD and PLP (enamel and dentin). PLP resulted in significantly lower SBS values in enamel and dentin than all the other materials investigated, except ACD in dentin, to which it was equivalent. CONCLUSION: Resulcin Aqua Prime & Monobond N and AC-Bond were not significantly different than established 5th generation products. AC-Bond + Desensitizer and Prompt L-Pop have significantly different SBS from established 4th and 5th generation products. Future studies are required to investigate marginal integrity to determine if self-etching adhesives are an adequate alternative to one- and multi-bottle systems.     

Glutaraldehyde collagen cross‐linking stabilizes resin–dentin interfaces and reduces bond degradation

This study evaluated the stability of resin–dentin interfaces treated with glutaraldehyde‐containing agents, and assessed collagen degradation in dentin matrices treated with Gluma. Microtensile bond strength (μTBS) was evaluated 24 h and 6 months after treatment with three desensitizers (Gluma Desensitizer, Gluma Desensitizer Power Gel, and MicroPrime G) and two etch‐and‐rinse adhesives (Comfort Bond & Desensitizer and iBond TE). Demineralized beams of human dentin were treated with water or Gluma, and the degradation of collagen in these beams was assessed by quantification of the dry mass loss and of the amount of hydroxyproline released from hydrolyzed specimens after 1 or 4 wk. All groups demonstrated significant reduction in μTBS after 6 months, except for Gluma Desensitizer and iBond TE groups, which showed decreases of 7.2% and 10.8%, respectively. The most prevalent failure mode was ‘mixed’. Significantly less hydroxyproline was released from Gluma‐treated beams than from control beams after 4 wk. Beams treated with Gluma yielded significantly less dry mass loss than did beams in the control group. Collagen cross‐linking with glutaraldehyde‐containing agents may assist in the stabilization of resin–dentin bonds by reducing the amount of collagen solubilized from dental matrices in the hybrid layer. In turn, this may contribute to the preservation of adhesive interfaces.     

Resin-dentin bond strength of 10 contemporary etch-and-rinse adhesive systems after one year of water storage

To compare the resin-dentin bond degradation of 10 contemporary etch-and-rinse adhesive systems after one year of water storage, 100 bovine incisors were randomly separated into 10 groups and their superficial coronal dentin was exposed. According to manufacturers' instructions, dentin surfaces were bonded with one of seven two-step etch-and-rinse adhesives or one of three three-step etch-and-rinse adhesives. Composite buildups were constructed incrementally. Restored teeth were sectioned to obtain sticks (0.5 mm2). The specimens were subjected to a microtensile bond strength test after storage in distilled water (at 37°C) for one year. Data (MPa) were analyzed using Kruskal-Wallis and Tukey's tests at α = 0.05. Of the adhesives tested, One Step, All Bond 2, and Optibond FL attained the highest bond strength to dentin after one year in water storage, while Magic Bond DE and Master Bond presented a high number of premature debonded flaws.     

Microtensile bond strengths of composite to dentin treated with desensitizer products

PURPOSE: This study was designed to analyze the influence of desensitizing procedures on dentin bond strength. MATERIALS AND METHODS: Forty bovine incisors were used, divided into four groups (n = 10): G1: control; G2: Gluma Desensitizer (Heraeus Kulzer); G3: Oxa-Gel (Art-Dent); G4: low-intensity laser (MMOptics). The buccal surface was wet ground flat with 180-, 400- and 600-grit silicon carbide abrasive paper to expose midcoronal dentin and create a uniform surface. After the application of the desensitizing agents to the exposed dentin, the specimens were etched with 35% phosphoric acid for 30 s, and an adhesive (Single Bond) was applied and light cured. A 4-mm high crown of composite resin (Filtek Z250) was then built up. Specimens were trimmed to an hourglass shape with cross sections of 1 mm2. Each specimen was individually fractured by a microtensile testing machine at a crosshead speed of 0.5 mm/min. The data, recorded in MPa, were analyzed with one-way ANOVA and the Duncan test (p = 0.05). RESULTS: Specimens treated with dentin desensitizers (except Gluma) yielded significantly lower mean bond strengths than nontreated control specimens. The mean values in MPa (+/- SD) were: G1: 13.4 (6.2); G2: 13.2 (4.8); G3: 7.15 (4.3); G4: 7.21 (4.6). CONCLUSIONS: Among the desensitizing agents studied, only Gluma Desensitizer did not detrimentally influence the bond strength values. It is a useful material for dentin desensitization.     

In-vitro Shear Bond Strength of Self-etching versus Traditional Adhesives for Orthodontic Luting

OBJECTIVE: To determine the enamel shear bond strength (SBS) of various established (Resulcin Aqua Prime & Monobond N [RA], Prompt L-Pot III [PLP]) and experimental (AC-Bond [AC], AC-Bond + Desensitizer [ACD]) self-etching adhesives in comparison to fourth (Total Etch, Primer and Bonding have separate liquids; OptiBond FL [FL]) and fifth-generation (Total Etch, Primer and Bonding "One Bottle"; Excite [EX], Gluma Comfort Bond [CB]) adhesives. MATERIALS AND METHODS: All adhesives were applied on flattened human enamel surfaces following the manufacturers' instructions and light-cured using a quartz-tungsten-halogen curing device. 3.5 x 2.0 mm Tetric Ceram A2 composite cylinders were sheared off (Zwick Universal-testing-machine 1445, 1 mm/min) after thermocycling (5-55 degrees C, 5000x). Normal distribution was tested for all groups and analysis of variance was conducted. The t-test (5% level, Bonferroni-correction) was used for statistical analysis to evaluate intergroup differences. RESULTS: Shear bond strength in enamel: Resulcin Aqua Prime & Monobond N: 27.0 +/- 5.8 MPa, Prompt L-Pop III: 15.9 +/- 3.4 MPa, AC-Bond: 28.1 +/- 4.4 MPa, AC-Bond + Desensitizer: 22.2 +/- 4.1 MPa, OptiBond FL: 33.2 +/- 3.2 MPa, Excite: 30.5 +/- 5.1 MPa, Gluma Comfort Bond: 30.1 +/- 3.7 MPa. OptiBond FL demonstrated significantly higher SBS (p < 0.002) in enamel than Resulcin Aqua Prime & Monobond N, AC-Bond, AC-Bond + Desensitizer and Prompt L-Pop III. Resulcin Aqua Prime & Monobond N performed significantly better than Prompt L-Pop III, but did not differ from AC-Bond or AC-Bond + Desensitizer. The SBS values of Excite and Gluma Comfort Bond were both on the same level of significance as AC-Bond and Resulcin Aqua Prime & Monobond N, but the former showed superior results to AC-Bond + Desensitizer and Prompt L-Pop III. Prompt L-Pop III yielded significantly lower SBS-values than all the other products evaluated. CONCLUSION: Resulcin Aqua Prime & Monobond N and AC-Bond did not differ significantly from established 5th-generation products. Further in-vivo studies are required to investigate intra-oral stability and resistance against changing forces and force directions.     

Evaluation of the desensitizing effect of Gluma Dentin Bond on teeth prepared for complete-coverage restorations.

This clinical trial assessed the ability of Gluma Dentin Bond to inhibit dentinal sensitivity in teeth prepared to receive complete cast restorations. Twenty patients provided 76 teeth for the study. Following tooth preparation, dentinal surfaces were coated with either sterile water (control) or two 30-second applications of Gluma Dentin Bond (test) on either intact or removed smear layers. Patients were recalled after 14 days for a test of sensitivity of the prepared dentin to compressed air, osmotic stimulus (saturated CaCl2 solution), and tactile stimulation via a scratch test under controlled loads. A significantly lower number of teeth responded to the test stimuli for both Gluma groups when compared to the controls (P less than .01). No difference was noted between teeth with smear layers intact or removed prior to treatment with Gluma.     

The effect of dentin desensitizer on shear bond strength of conventional and self-adhesive resin luting cements after aging

This study tested the impact of Gluma Desensitizer on the shear bond strength (SBS) of two conventional (RelyX ARC, Panavia 21) and two self-adhesive (RelyX Unicem, G-Cem) resin luting cements after water storage and thermocycling. Human third molars (N=880) were embedded in acrylic resin. The buccal dentin was exposed. Teeth were randomly divided into four main groups, and the following cements were adhered: 1) RelyX ARC, 2) Panavia 21, 3) RelyX Unicem, and 4) G-Cem. In half of the teeth in each group, dentin was treated with Gluma Desensitizer. In the conventional cement groups, the corresponding etchant and adhesive systems were applied. SBS of the cements was tested after 1 hour (initial); at 1, 4, 9, 16, and 25 days of water storage; and at 1, 4, 9, 16, and 25 days of thermocycling. SBS data were analyzed by one-way analysis of variance (ANOVA); this was followed by the post hoc Scheffé test and a t-test. Overall, the highest mean SBS (MPa) was obtained by RelyX ARC (ranging from 14.6 ± 3.9 to 17.6 ± 5.2) and the lowest by Panavia 21 in combination with Gluma Desensitizer (ranging from 0.0 to 2.9 ± 1.0). All tested groups with and without desensitizer showed no significant decrease after aging conditions compared with baseline values (p>0.05). Only the Panavia 21/Gluma Desensitizer combination showed a significant decrease after 4 days of thermocyling compared with initial values and 1 day thermocycling. Self-adhesive cements with Gluma Desensitizer showed increased SBS after aging conditions (ranging from 7.4 ± 1.4 to 15.2 ± 3) compared with groups without desensitizer (ranging from 2.6 ± 1.2 to 8.8 ± 2.9). No cohesive failures in dentin were observed in any of the test groups. Although self-adhesive cements with and without desensitizer presented mainly adhesive failures after water storage (95.8%) and thermocyling (100%), conventional cement (RelyX ARC) showed mainly mixed failures (90.8% and 89.2%, after water storage and thermocyling, respectively). Application of the Gluma Desensitizer to dentin before cementation had a positive effect on the SBS of self-adhesive cements.     

Effects of Different Re-Wetting Techniques on Dentin Shear Bond Strengths

Purpose: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid‐etching. The purpose of this study was to compare the dentin shear bond strengths of two single‐bottle adhesives (one acetone‐based and one ethanol‐based) applied under different etched‐dentin conditions: dry, wet, or dry and re‐wetted with different solutions. Materials and Methods: Bovine incisors (N = 120) were mounted in acrylic, polished to 600‐grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot‐dried, air‐dried, or air‐dried and re‐wetted with different solutions (distilled water, Gluma Desensitizer, Aqua‐Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light‐cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. Results: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re‐wetted with Gluma Desensitizer, re‐wetted with Aqua‐Prep, or never dried. Differences between these surface conditions were not statistically significant for either material. CLINICAL SIGNIFICANCE Different dentin surface conditions and re‐wetting techniques affected bond strengths for adhesives studied. Aqua‐Prep and Gluma Desensitizer can be successfully used as re‐wetting agents. The use of a re‐wetting agent may be beneficial when dentin is dried after acid‐etching and rinsing.     

Effect of tin–chloride pretreatment on bond strength of two adhesive systems to dentin

Objectives

To determine the effect on resin composite-to-dentin bond strength of incorporation of an acidic tin–chloride pretreatment in two adhesive systems.

Materials and methods

Human molars were ground to expose mid-coronal dentin. For microtensile bond strength (μTBS) testing, dentin was treated with Optibond FL or Clearfil SE according to one of six protocols (n?=?22/group). Group 1: Phosphoric acid etching, Optibond FL Prime, Optibond FL Adhesive (manufacturer’s instructions; control); Group 2: Tin–chloride pretreatment, Optibond FL Prime, Optibond FL Adhesive; Group 3: Phosphoric acid etching, tin–chloride pretreatment, Optibond FL Prime, Optibond FL Adhesive; Group 4: Clearfil SE Primer, Clearfil SE Bond (manufacturer’s instructions; control); Group 5: Phosphoric acid etching, Clearfil SE Primer, Clearfil SE Bond; and Group 6: Tin–chloride pretreatment, Clearfil SE Primer, Clearfil SE Bond. The molars were then built up with resin composite (Clearfil Majesty Esthetic). After storage (1 week, 100  % humidity, 37 °C) the μTBS was measured and failure mode was determined. Additionally, pretreated dentin surfaces were evaluated using SEM and EDX. The μTBS results were analyzed statistically by a Welch Two Sample t-test and a Kruskal–Wallis test followed by exact Wilcoxon rank sum tests with Bonferroni–Holm adjustment for multiple testing (α?=?0.05).

Results

When Optibond FL was used, partial or total replacement of phosphoric acid with tin–chloride decreased μTBS significantly. In contrast, when Clearfil SE was used, inclusion of a tin–chloride pretreatment in the adhesive procedure increased μTBS significantly.

Conclusions

Tin–chloride pretreatment had a beneficial influence on the bond promoting capacity of the MDP-containing adhesive system Clearfil SE.     

A comparative study of fluoride uptake from dentin bonding agents and glass-ionomer cements in permanent and primary tooth enamel.

OBJECTIVE: Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount of fluoride release of these materials is still uncertain. The aim of this study was to determine the amount of fluoride uptake in primary and permanent tooth enamel from 1 conventional glass-ionomer cement (Fuji II), 1 resin-modified glass-ionomer cement (Fuji II LC), and 2 fluoride-releasing dentin bonding agents (Liner Bond 2 and Optibond) in vitro. METHOD AND MATERIALS: One hundred sixty caries-free primary and permanent molar teeth were assigned to the study. Materials were applied according to the manufacturer's instructions to standard windows created on the enamel surfaces. The amount of fluoride uptake by enamel was investigated by using a specific fluoride electrode and acid-etching biopsy technique. RESULTS: The amount of fluoride taken up from Fuji II and Fuji II LC by permanent and primary tooth enamel was found to be statistically significant. However, no significant fluoride uptake from Optibond and Liner Bond 2 was found. CONCLUSION: Fuji II and Fuji II LC glass-ionomer materials seemed to provide more effective fluoride release than did Optibond and Liner Bond 2 in permanent and primary enamel.     

Effects of different re-wetting techniques on dentin shear bond strengths

PURPOSE: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid-etching. The purpose of this study was to compare the dentin shear bond strengths of two single-bottle adhesives (one acetone-based and one ethanol-based) applied under different etched-dentin conditions: dry, wet, or dry and re-wetted with different solutions. MATERIALS AND METHODS: Bovine incisors (N = 120) were mounted in acrylic, polished to 600-grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot-dried, air-dried, or air-dried and re-wetted with different solutions (distilled water, Gluma Desensitizer, Aqua-Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light-cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. RESULTS: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re-wetted with Gluma Desensitizer, re-wetted with Aqua-Prep, or never dried. Differences between these surface conditions were not statistically significant for either material.     

Effect of dentin desensitizers and cementing agents on retention of full crowns using standardized crown preparations

STATEMENT OF PROBLEM: Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. PURPOSE: This research controlled crown preparation surface area and evaluated the effect of various dentin desensitizers and conventional cementing agents on the in vitro retentive strength of cast crowns. METHODS AND MATERIAL: Freshly extracted human molars were prepared for a standardized crown preparation (26 degrees total convergence, 4 mm axial height) with a custom-made pantograph. Dentin desensitizers included none (control), a polymerizable material (All-Bond 2), and a nonpolymerizable desensitizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck's), glass ionomer (Ketac-Cem), resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test condition (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative humidity using a universal testing machine at a crosshead speed of 1.27 mm/min. The proportion of cement retained on the tooth and casting after debonding was quantified according to treatment. Statistical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05.Results. Resin cement exhibited the highest retentive strength and all dentin treatments resulted in significantly different retentive values (All-Bond 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma (4.12 +/- 0.37 MPa)). Retention of resin-modified glass ionomer was between the resin cement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.81 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer values were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0. 20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 MPa). Zinc phosphate had the lowest retention values: control (1.68 +/- 0. 08 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The majority of cement was retained on the debonded tooth surface versus the casting, with the exception of zinc phosphate when used with dentin pretreatments. CONCLUSION: Controlled crown surface areas reduced the variation in strength values permitting high discrimination among retention values of desensitizer/cement combinations. In all but 1 combination, Gluma desensitizer significantly decreased crown retention. With resin cement and resin-modified glass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.     

Immediate dentin sealing of onlay preparations: thickness of pre-cured Dentin Bonding Agent and effect of surface cleaning

This study evaluated the thickness of Dentin Bonding Agent (DBA) used for "immediate dentin sealing" of onlay preparations prior to final impression making for indirect restorations. In addition, the amount of DBA that is removed when the adhesive surface is cleaned with polishing or air abrasion prior to final cementation was evaluated. For this purpose, a standardized onlay preparation was prepared in 12 extracted molars, and either OptiBond FL (Kerr) or Syntac Classic (Vivadent) was applied to half of the teeth and cured in the absence of oxygen (air blocking). Each tooth was bisected in a bucco-lingual direction into two sections, and the thickness of the DBA was measured under SEM on gold sputtered epoxy resin replicas at 11 positions. The DBA layer of each half tooth was treated with either air abrasion or polishing. The thickness of the DBAs was then re-measured on the replicas at the same positions. The results were statistically analyzed with non-parametric statistics (Mann-Whitney U test and Kruskal-Wallis test) at a confidence level of 95% (p=0.05). The film thickness of the DBA was not uniform across the adhesive interface (121.13 +/- 107.64 microm), and a great range of values was recorded (0 to 500 microm). Statistically significant differences (p<0.05) were noted, which were both material (OptiBond FL or Syntac Classic) and position (1 to 11) dependent. Syntac Classic presented a higher thickness of DBA (142.34 +/- 125.10 microm) than OptiBond FL (87.99 +/- 73.76 microm). The higher film thickness of both DBAs was at the deepest part of the isthmus (the most concave part of the preparation), while the lowest was at the line angles of the dentinal crest (the most convex part of the preparation). OptiBond FL presented a more uniform thickness around the dentinal crest of preparation; Syntac Classic pooled at the lower parts of the preparation. The amount of DBA that was removed with air abrasion or polishing was not uniform (11.94 +/- 16.46 microm), and a great range of values was recorded (0 to 145 microm). No statistically significant differences (p<0.05) were found either between different DBAs (OptiBond FL or Syntac Classic) or between different treatments (air abrasion or polishing). As far as the effect of different treatments at different positions, polishing removed more DBA from the top of the dentinal crest, but the difference was not statistically significant. Air abrasion removed less DBA from the corners of the dentinal crest (Positions 4 and 6) than the outer buccal part of the preparation (Positions 1 and 2). Neither air abrasion nor polishing removed the entire layer thickness of the DBA in the majority of the cases.