Dentin bond strength evaluation between a conventional and universal adhesive using etch-and-rinse strategy

Aim: The aim of this study was to compare the microtensile bond strength (μTBS) and the characteristics of the adhesive interface of Scotchbond Universal - SU – etch-and-rise mode (3M ESPE) and Adper Scotchbond Multi-Purpose - MP (3M ESPE) to dentin over time. Methods: Class I cavity preparations were performed in 60 human molars that were randomly divided according to the dentin bonding system (DBS) used (n=30): (1) Acid conditioning + SU and (2) Acid conditioning + MP. For bonding strength (BS) analysis, 30 teeth (n = 15) were sectioned into sticks and submitted to the microtensile test in a universal testing machine after 24 hours and 12 months. The adhesive interface of the others 30 teeth was analyzed in a confocal microscope after 24 hours and 12 months. The data of μTBS were analyzed by two-way repeated measures ANOVA and Tukey’s HSD (α = 0.05). Results: SU presented the lowest DBS compared to MP (p=0.000). Time did not influenced DBS for both adhesive systems (p=0.177). Confocal microscopy analysis showed no cracks between both adhesive systems tested. Conclusion: The results indicate that MP - μTBS showed a better performance compared to SU in total-etch mode.

Adapted Three-step Restorative Technique: Recovering Dental Substrate Compromised by Complex Erosive Wear in a Young Patient

Clinical Relevance

This article presents the dental restoration of a young female patient complaining of erosive dental wear using a three-step restorative technique, an alternative approach with some novel adjustments.

SUMMARY

For successful tooth wear treatment, determining the etiological systemic and local factors is the main priority before deciding on effective and long-term preventive and/or therapeutic restorative approaches. In addition to professional intervention, achieving optimal outcomes requires patients to control their diet and/or gastric issues, thus minimizing the wear process. However, continuous wear constitutes the most challenging scenario, mainly when it affects young patients’ dentitions. This article describes the dental restoration of posterior teeth with reestablishment of occlusal vertical dimension before treating the anterior teeth, while educating the patient and providing medical monitoring. The three-step restorative technique seems to be properly applicable in cases of significant dental compromise due mainly to erosive wear and is based on direct procedures, which can assure a reliable and feasible approach.

Molecular Response of Pulp Fibroblasts after Stimulation with Pulp Capping Materials

This in vitro study evaluated cell viability and metabolism, nitric oxide release and production of two chemokines and one cytokine by cultured human dental pulp fibroblasts (HDPF) in contact with two glass ionomer cements (Ketac Molar-KM and Vitrebond-VB), Single Bond (SB) and calcium hydroxide (Dycal-DY). Cultures of HDPF were established by means of an explant technique. The specimens were prepared under sterile conditions and in disks measuring 5 mm x 2 mm obtained from a prefabricated mold and placed on a permeable membrane to avoid direct contact with the cells. Cytotoxicity was assessed by Trypan Blue exclusion method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Nitric oxide release in cell supernatant was detected by the Griess Method whereas stromal derived factor-1 alpha (SDF-1α or CXCL12), chemokine (C-X-C motif) ligand 8 [Interleukin 8 (IL-8 or CXCL8)] and interleukin-6 (IL-6) were detected by ELISA. RT-qPCR was employed for gene expression analysis. Statistical analyses were performed by One-way ANOVA followed by Tukey's post hoc test for materials independent of the time, and Two-way ANOVA followed by Bonferroni correction test for the comparisons between materials and experimental time (p<0.05). Cytotoxic tests showed significant differences only for DY. Protein levels and mRNA expression were significantly increased for IL-8 for both periods of time. IL-6 production increased when fibroblasts were stimulated by KM. SDF-1α protein production and mRNA expression were not affected by any of the materials. There was a decrease in nitrate/nitrite levels only for KM. Although DY caused intense cell death and did not stimulate the production of the inflammatory mediators evaluated in this work, it is known that this event seems to be fundamental for the process of repair of the pulp tissue and formation of mineralized barrier. KM and VB increased production of proteins related to the inflammatory process, thus favoring tissue repair. Therefore, although these glass ionomer cements did not lead to large cell death, they should be used with caution.

Effect of Bleaching Gels on Surface Roughness of Nanofilled Composite Resins

Objectives: The aim of this study was to investigate the superficial texture of composite restorations after different bleaching protocols. Methods: Filtek Supreme (S), Filtek Z350 (F), and Grandio (G) were compared to Opallis (O) and Filtek Z250 (Z) (control microhybrid composites) and to bovine enamel using three different bleaching agents: 35% hydrogen peroxide Whiteness HP (WHP), 35% Whiteness HP MAXX (WMAXX) and 16% carbamide peroxide Whiteness Standard (WS). Six specimens from each composite were treated using each bleaching agent, according to the manufacturers’ instructions. Three random sites were measured for superficial roughness (Hommel Tester T 1000) weekly for each sample. Data were analyzed for each bleaching system using two-way ANOVA and Bonferroni tests at 5% significance level. Results: WHP treatment significantly altered the Filtek Supreme composite over time. When WMAXX was used, Grandio displayed the most significant alterations in surface roughness throughout the evaluation period, which was not observed for the other nanocomposites. Using WS, Filtek Z250 presented significant surface alterations over time, which was not seen in the nanofilled materials. Conclusions: Surface roughness alteration was material and time-dependent. The bleaching gels affected nanofilled and microhybrid composite resins. Enamel was the surface less affected by bleaching. (Eur J Dent 2011;5:173-179)

Management of dental caries guided by the ICDAS-LAA: a 28-month follow-up

Dental caries is a significant oral health issue and public health concern. Currently conceptualized as a dynamic and multifactorial process, caries is a continuum of disease stages, during which tooth damage may be reversed or controlled, depending on lesion progression. The International Caries Detection and Assessment System, when used in conjunction with the Lesion Activity Assessment (ICDAS-LAA), reflects the dynamic caries process and allows the classification of cavitated lesions according to their severity and progression, which is essential to selecting the appropriate treatment. This case report describes the diagnosis and treatment of a patient who had caries in the past and in whom old lesions remained untreated. The ICDAS-LAA was used to assess caries accurately and guide treatment decisions. The patient maintained a dietary journal for 2 weeks to help establish her risk of developing caries. Treatment involved a minimally invasive dentistry approach, which consisted of remineralization via fluoride applications, placement of a composite resin restoration, microabrasion, and periodic maintenance. During the 28-month follow-up period, rigorous control of caries risk factors was achieved, and the results were satisfactory, demonstrating the effectiveness of the ICDAS-LAA in diagnosing and managing carious lesions.

Influence of depth of mesio-occlusodistal preparation and mechanical cycling on fracture resistance of restored premolars

The purpose of this in vitro study was to evaluate the influence of depth (3.0 vs 5.0 mm) of mesio-occlusodistal (MOD) cavity preparation and mechanical cycling on fracture resistance of maxillary premolars restored with resin-based composite (RBC). Seventy premolars were randomly divided into 7 groups (n = 10): NP, no cavity preparation (control); MOD3, 3.0-mm-deep MOD preparation, not restored; MOD3R, 3.0-mm-deep MOD preparation restored with RBC; MOD5, 5.0-mm-deep MOD preparation, not restored; MOD5R, 5.0-mm-deep MOD preparation restored with RBC; MOD3RC, 3.0-mm-deep MOD preparation restored with RBC and subjected to mechanical cycling; and MOD5RC, 5.0-mm-deep MOD preparation restored with RBC and subjected to mechanical cycling under the same conditions as MOD3RC. All specimens were tested using a universal testing machine, resulting in the following mean (SD) values: NP, 224.65 (35.66) kgf; MOD3, 58.92 (15.48) kgf; MOD3R, 95.58 (13.88) kgf; MOD5, 68.06 (10.12) kgf; MOD5R, 98.49 (13.16) kgf; MOD3RC, 83.68 (14.39) kgf; and MOD5RC, 54.25 (11.56) kgf. Analysis of variance and Tukey test showed no statistically significant difference among MOD3, MOD5, and MOD5RC; between MOD5 and MOD3RC; or among MOD3R, MOD5R, and MOD3RC (P > 0.05). MOD3RC had significantly greater fracture resistance than MOD5RC (P < 0.05). NP had the highest fracture resistance of all groups (P < 0.05). The results showed that the depth of the cavity preparation only influenced fracture resistance after mechanical cycling of the specimens.

Dental Pulp Fibroblasts Response after Stimulation with HEMA and Adhesive System

This study evaluated in vitro cell viability and metabolism, nitric oxide release and production of chemokines by cultured human dental pulp fibroblasts (DPF) under contact with HEMA and Single Bond. Cultures of DPF were established by means of an explant technique. Once plated, cells were kept under contact with increasing concentrations of HEMA (10, 100 and 1000 nM) or Single Bond (SB) [10-fold serially diluted in culture medium (10-4, 10-3 and 10-2 v/v)] and also with polymerized SB components. Cytotoxicity was assessed by Trypan Blue exclusion method and MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Nitric oxide release on cell supernatant was detected by Griess Method whereas chemokines (CXCL12 and CXCL8) were detected by ELISA. RT-qPCR was employed for chemokines gene expression analysis. Cytotoxic tests showed significant differences for SB 10-2. None of the tested materials significantly altered NO levels. Protein levels of CXCL12 were significantly decreased only by HEMA. On the other hand, while CXCL12 mRNA remained unaltered, gene expression of CXCL8 had significant decrease with all materials, except for polymerized SB. In conclusion, Single Bond and HEMA at various concentrations, decreased expression and production of molecules involved in inflammatory processes and, therefore, the use of adhesive systems such as pulp capping materials must be viewed with caution due to its large cytotoxic effect when in close contact with the pulp.

Water interaction and bond strength to dentin of dye-labelled adhesive as a function of the addition of rhodamine B

Objective

This study investigated the effect of the fluorescent dye rhodamine B (RB) for interfacial micromorphology analysis of dental composite restorations on water sorption/solubility (WS/WSL) and microtensile bond strength to dentin (µTBS) of a 3-step total etch and a 2-step self-etch adhesive system.

Material and Methods

The adhesives Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) were mixed with 0.1 mg/mL of RB. For the WS/WSL tests, cured resin disks (5.0 mm in diameter x 0.8 mm thick) were prepared and assigned into four groups (n=10): MP, MP-RB, SE, and SE-RB. For µTBS assessment, extracted human third molars (n=40) had the flat occlusal dentin prepared and assigned into the same experimental groups (n=10). After the bonding and restoration procedures, specimens were sectioned in rectangular beams, stored in water and tested after seven days or after 12 months. The failure mode of fractured specimens was qualitatively evaluated under optical microscope (x40). Data from WS/WSL and µTBS were assessed by one-way and three-way ANOVA, respectively, and Tukey’s test (α=5%).

Results

RB increased the WSL of MP and SE. On the other hand, WS of both MP and SE was not affected by the addition of RB. No significance in µTBS between MP and MP-RB for seven days or one year was observed, whereas for SE a decrease in the µTBS means occurred in both storage times.

Conclusions

RB should be incorporated into non-simplified DBSs with caution, as it can interfere with their physical-mechanical properties, leading to a possible misinterpretation of bonded interface.

Influence of Erosive and Abrasive Cycling on Bonding of Different Adhesive Systems to Enamel: An In situ Study

This study evaluated the impact of orange juice on the bond strength (BS) of dentin bonding systems (DBSs) to enamel surface after simulation with an in situ/ ex vivo erosive cycling. One hundred and ninety two bovine enamel fragments (4x4x2mm) were obtained and randomized regarding superficial microhardness and distributed to palatal devices for 8 volunteers, in three phases (one for each DBS), containing 8 blocks, which were, allocated in 4 pairs. Daily, these pairs were subjected extraorally to the following conditions: CONT- neither erosive nor abrasive challenge; ERO- erosive challenge only; ABR- abrasive challenge only and ERO + ABR- with erosive and abrasive challenges. Erosive cycles (immersion in orange juice, 3 times/day/5 min/5 days) or/and abrasive challenges (electric toothbrush, 3 times/day/1 min/5 days) were performed. After these cycles, all specimens were restored with the adhesive systems Adper Scotchbond Multi Purpose (MP), Adper Single Bond 2 (SB) or Clearfil SE Bond (SE), and the composite resin Filtek Z250. After 7 days, sticks (area ≅1 mm2) were obtained and subjected to the microtensile bond strength test (μTBS) at 0.5 mm/min. Data was statistically analyzed by ANOVA and Tukey tests (a=0.05). Failure modes were determined using a digital microscope (40´). DBS was the only statistical significant factor. SE was the unique DBS not affected in any challenge, whereas MP and SB performed according to the scenario. The adhesive and mixed failures were predominant in all groups. Overall performance suggested that BS to enamel after erosive /abrasive challenged by orange juice was not affected and it was material-dependent.

Effect of resin-modified glass-ionomer cement lining and composite layering technique on the adhesive interface of lateral wall

Interface integrity can be maintained by setting the composite in a layering technique and using liners.

Bleaching technique effect on dentin permeability

PURPOSE

To evaluate the effect of bleaching techniques on dentin permeability. The hypothesis was that the bleaching agent associated or not to etching and/or energy source would be able to increase dentin permeability (conductance).

METHODS

Fifty 1 mm-thick disks of mid-coronal dentin were obtained from human third molars, which were mounted in a filtration chamber, allowing exposure of a standardized area of 0.282 mm2. All specimens were treated with 35% liquid phosphoric acid for 15 seconds to maximize dentin permeability. Then they were randomly allocated to five different conditions: C: placebo gel (negative control); HP: Whiteness HP Maxx (WM)-35% hydrogen peroxide; PA-HP: WM preceded by phosphoric acid etching for 15 seconds. HP-E: WM associated to a light source and PA-HP-E: WM preceded by phosphoric acid etching for 15 seconds and associated to a light source. The bleaching agent was applied for 10 minutes with intermediate agitation at 5 minutes. In the groups associated with a light source, it was activated for 30 seconds every 5 minutes. Afterwards, the permeability (Lp) was measured using the Flodec device. The data were collected and analyzed with one-way ANOVA and Tukey's test (P< 0.05).

RESULTS

Mean and standard deviation of Lp were: C = 1.92 (1.04); HP = 1.14 (0.29); PA-HP = 14.40 (8.62); HP-E = 4.18 (5.14); PA-HP-E = 27.32 (13.24). Data revealed that phosphoric acid etching could increase the dentin permeability, while the bleaching agent or light curing alone did not.

Prevalence of Enamel Defects in Permanent Teeth of Patients with Complete Cleft Lip and Palate

Objective

To evaluate the prevalence, types, location, and characteristics of enamel defects in anterior permanent teeth of patients with complete unilateral and bilateral cleft lip and palate, as well as the relation with the cleft.

Setting

Hospital for Rehabilitation of Craniofacial Anomalies, Bauru, São Paulo, Brazil.

Participants

Eighty patients of both genders, 12 years and older, with unilateral or bilateral cleft lip and palate.

Methods

A single examiner carried out clinical examination under artificial light with a dental probe and mirror after drying teeth according to the modified DDE index.

Results

Seventy-four of 80 patients presented with at least one tooth affected by enamel defects: 165 of 325 evaluated teeth (50.8%) presented enamel defects, with hypoplasia being the most prevalent (50.7%), followed by diffuse opacity (23.1%) and demarcated opacity (18.4%). The most affected tooth was 21 (36.5%), followed by 11 (34%), located at the middle (40%) and incisal (33%) thirds. Most defects occur at the buccal surface (47.7%), followed by the distal (22.7%), the mesial (19%), and the palatal (10.6%) surfaces. A significant relationship was found between the cleft side and enamel defects.

Conclusion

Upper anterior teeth of patients with complete cleft lip and palate present a high prevalence of enamel defects; the highest percentage on the cleft side suggests that the cleft does influence the occurrence of enamel defects in permanent teeth.

Push-out bond strength and SEM evaluation of a new bonding approach into the root canal

Objective

This study evaluated the performance of different adhesive systems in fiber post placement aiming to clarify the influence of different hydrophobic experimental blend adhesives, and of one commercially available adhesive on the frictional retention during a luting procedure.

Material and Methods

One luting agent (70 Wt% BisGMA, 28.5% TEGDMA; 1.5% p-tolyldiethanolamine) to cement fiber posts into root canals was applied with 4 different adhesive combinations: Group 1: The etched roots were rinsed with water for 30 s to remove the phosphoric acid, then rinsed with 99.6% ethanol for 30 s, and blotdried. A trial adhesive (base to catalyst on a 1:1 ratio) was used with an experimental luting agent (35% Bis-GMA, 14.37% TeGDMA, 0.5% eDMAB, 0.13% CQ); Group 2: A trial adhesive (base to catalyst on a 1:2 ratio) was luted as in Group 1; Group 3: One-Step Plus (OSP, Bisco Inc.) following the ethanol bonding technique in combination with the luting agent as in Group 1; Group 4: OSP strictly following the manufacturer's instructions using the luting agent as in Group 1. The groups were challenged with push-out tests. Posted root slices were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under scanning electron microscopy.

Results

Push-out strength was not significantly influenced by the luting agent (p>0.05). No statistically significant differences among the tested groups were found as Group 1 (exp 1 - ethanol-wet bonding technique)=Group 2 (exp 2 - ethanol-wet bonding technique)=Group 3 (OSP - ethanol-wet bonding technique)=Group 4 (control, OSP - water-wet bonding technique) (p>0.05). The dominating failure modes in all the groups were cohesive/adhesive failures, which were predominantly observed on the post/luting agent interface.

Conclusions

The results of this study support the hypothesis that the proposal to replace water with ethanol to bond fiber posts to the root canal using highly hydrophobic resin is plausible, but this seems to be more the proof of a concept than a clinically applicable procedure.

Effect of conventional and resin-modified glass-ionomer liner on dentin adhesive interface of Class I cavity walls after thermocycling

OBJECTIVE

The aim of this in vitro study was to analyze the effect of glass-ionomer cement as a liner on the dentin/resin adhesive interface of lateral walls of occlusal restorations after thermocycling.

MATERIALS AND METHODS

Occlusal cavities were prepared in 60 human molars, divided into six groups: no liner (1 and 4); glass-ionomer cement (GIC, Ketac Molar Easymix, 3M ESPE) (2 and 5); and resin-modified glass-ionomer cement (RMGIC, Vitrebond, 3M ESPE) (3 and 6). Resin composite (Filtek Z250, 3M ESPE) was placed after application of an adhesive system (Adper Single Bond 2, 3M ESPE) that was mixed with a fluorescent reagent (Rhodamine B) to allow confocal microscopy analysis. Specimens of groups 4, 5 and 6 were thermocycled (5°C-55°C) with a dwell time of 30 seconds for 5000 cycles. After this period, teeth were sectioned in approximately 0.8-mm slices. One slice of each tooth was randomly selected for confocal microscopy analysis. The other slices were sectioned into 0.8 mm × 0.8 mm beams, which were submitted to microtensile testing (MPa). Data were analyzed using two-way ANOVA and Tukey test (p<0.05).

RESULTS

There was no detectedstatistical difference on bond strength among groups (α<0.05). Confocal microscopy analysis showed a higher mean gap size in group 4 (12.5 μm) and a higher percentage of marginal gaps in the thermocycled groups. The RMGIC liner groups showed the lowest percentage of marginal gaps.

CONCLUSIONS

Lining with RMGIC resulted in less gap formation at the dentin/resin adhesive interface after artificial aging. RMGIC or GIC liners did not alter the microtensile bond strength of adhesive system/resin composite to dentin on the lateral walls of Class I restorations.

Effect of bleaching gels on surface roughness of nanofilled composite resins

OBJECTIVES

The aim of this study was to investigate the superficial texture of composite restorations after different bleaching protocols.

METHODS

Filtek Supreme (S), Filtek Z350 (F), and Grandio (G) were compared to Opallis (O) and Filtek Z250 (Z) (control microhybrid composites) and to bovine enamel using three different bleaching agents: 35% hydrogen peroxide Whiteness HP (WHP), 35% Whiteness HP MAXX (WMAXX) and 16% carbamide peroxide Whiteness Standard (WS). Six specimens from each composite were treated using each bleaching agent, according to the manufacturers' instructions. Three random sites were measured for superficial roughness (Hommel Tester T 1000) weekly for each sample. Data were analyzed for each bleaching system using two-way ANOVA and Bonferroni tests at 5% significance level.

RESULTS

WHP treatment significantly altered the Filtek Supreme composite over time. When WMAXX was used, Grandio displayed the most significant alterations in surface roughness throughout the evaluation period, which was not observed for the other nanocomposites. Using WS, Filtek Z250 presented significant surface alterations over time, which was not seen in the nanofilled materials.

CONCLUSIONS

Surface roughness alteration was material and time-dependent. The bleaching gels affected nanofilled and microhybrid composite resins. Enamel was the surface less affected by bleaching.

Short-term in situ/ex vivo study of the anticariogenic potential of a resin-modified glass-ionomer cement associated with adhesive systems

OBJECTIVE

As resin-modified glass-ionomer cement (RMGIC) is an adhesive material, its association to dentin bonding agents (DBAs) was previously proposed. This study investigated the adjunctive behavior of an RMGIC with etch-and-rinse bonding systems under in situ/ex vivo cariogenic challenge.

METHOD AND MATERIALS

Bovine enamel blocks (3 3 3 3 2 mm) were randomly assigned to group VP, Vitremer + its own primer (3M ESPE); group VSB, Vitremer + Single Bond (3M ESPE); and group VPB, Vitremer + Prime and Bond 2.1 (Dentsply). Two blocks of each group were randomly placed in an acrylic palatal appliance, so each appliance included six blocks. Volunteers (n = 10) wore these appliances according to given instructions to promote a sucrose challenge eight times/day for 15 days. After this period, the blocks were removed from the devices and cleaned, and demineralization was assessed through longitudinal microhardness analysis (Knoop indenter, 25 g/5 s). Data were submitted to three-way ANOVA and Tukey test (P < .05).

RESULTS

No treatment was able to completely avoid demineralization. All materials showed a statistically significant difference in mineral loss when the microhardness on the outer enamel was compared with deeper regions (P < .05).

CONCLUSION

Association of the tested RMGICs with etch-and-rinse DBAs did not seem to be more beneficial against caries than the conventional treatment with RMGIC.

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

In vitro interactions between lactic acid solution and art glass-ionomer cements

Objectives:

Production of acids such as lactic acid contributes to establish a cariogenic environment that leads to dental substrate demineralization. Fluoride plays an important role in this case and, as fluoride-releasing materials, glass-ionomer cements are expected to contribute to minimize deleterious reactions. This study evaluated interactions of glass-ionomer cements used in atraumatic restorative treatment (ART-GICs) with an aqueous lactic acid solution, testing the null hypotheses that no changes occur in the pH of the solution or on the surface roughness and mass of the ART-GICs when exposed to lactic acid solution over a 6-week period.

Material and Methods:

Ketac Molar, Fuji IX, Vitro Molar and Magic Glass were tested, and compared to Filtek Z250 and Ketac Fil Plus as control groups. Six specimens of each material were made according to manufacturers' instructions. The pH of the solution and roughness and mass changes of each specimen were determined over 6 weeks. Each specimen was individually stored in 2 mL of 0.02 M lactic acid solution for 1 week, renewing the solution every week. pH of solution and mass of the specimens were monitored weekly, and surface roughness of the specimens was assessed before and at the end of the 6-week acid challenge. pH and mass data were analyzed statistically by repeated measures using one-way ANOVA and Tukey's post-hoc tests for each material. Paired t-tests were used for roughness analysis. Tukey's post-hoc tests were applied to verify differences of final roughness among the materials. Significance level was set at 5%.

Results:

The null hypotheses were partially rejected. All materials were able to increase the pH of the lactic acid solution and presented rougher surfaces after immersion, while mass change was minimal and generally not statistically significant.

Conclusions:

These findings can be helpful to predict the performance of these materials under clinical conditions. A protective action against the carious process with significant surface damage due to erosion may be expected.

Influence of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and bond strength

STATEMENT OF THE PROBLEM

Adhesive systems can spread differently onto a substrate and, consequently, influence bonding.

PURPOSE

The purpose of this study was to evaluate the effect of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and microtensile bond strength (MTBS).

MATERIALS AND METHODS

Twenty-four molars were sectioned mesiodistally to expose flat buccal and lingual halves. Standardized drop volumes of adhesive systems (Single Bond [SB] and Prime & Bond 2.1 [PB2.1]) were applied to dentin according to the manufacturer's instructions. Teeth halves were randomly divided into groups: 1A-SB/parallel to gravity; 1B-SB/perpendicular to gravity; 2A-PB2.1/parallel to gravity; and 2B-PB2.1/perpendicular to gravity. The bonded assemblies were stored in 37 degrees C distilled water for 24 hours and then sectioned to obtain dentin sticks (0.8 mm2). The adhesive layer thickness was determined in a light microscope (x200), and after 48 hours the specimens were subjected to MTBS test. Data were analyzed by one-way and two-way analysis of variance and Student-Newman-Keuls tests.

RESULTS

Mean values (MPa +/- SD) of MTBS were: 39.1 +/- 12.9 (1A); 32.9 +/- 12.4 (1B); 52.9 +/- 15.2 (2A); and 52.3 +/- 16.5 (2B). The adhesive systems' thicknesses (microm +/- SD) were: 11.2 +/- 2.9 (1A); 18.1 +/- 7.3 (1B); 4.2 +/- 1.8 (2A); and 3.9 +/- 1.3 (2B). No correlation between bond strength and adhesive layer thickness for both SB and PB2.1 (r = -0.224, p = 0.112 and r = 0.099, p = 0.491, respectively) was observed.

CONCLUSIONS

The differently oriented dentin surfaces and the regional variation of specimens on the adhesive layer thickness are material-dependent. These variables do not influence the adhesive systems' bond strength to dentin. CLINICAL SIGNIFICANCE Adhesive systems have different viscosities and spread differently onto a substrate, influencing the bond strength and also the adhesive layer thickness. Adhesive thickness does not influence dentin bond strength, but it may impair adequate solvent evaporation, polymer conversion, and may also determine water sorption and adhesive degradation over time. In the literature, many studies have shown that the adhesive layer is a permeable membrane and can fail over time because of its continuous plasticizing and degradation when in contact with water. Therefore, avoiding thick adhesive layers may minimize these problems and provide long-term success for adhesive restorations.

Effect of surface treatments on the spreading velocity of simplified adhesive systems

Objectives:

To determine the roughness of glass surfaces submitted to different treatments and to correlate it with the spreading velocity of two adhesive systems.

Materials and Methods:

Glass slides were used as substrates to evaluate the spreading velocity of Single Bond and Prime & Bond NT adhesive systems. Six different surface treatments were compared: 1) no treatment; 2) silanization (SL); 3) sandblasting (SB); 4) SB + SL; 5) 10% hydrofluoric acid treatment (HF); 6) HF + SL. Before and after treatments, surface roughness was measured by a profilometer (Ra, μm). Drop volumes (10 μl) of the adhesive systems were deposited onto substrates with a micropipette to observe materials spreading during 30s. Data were expressed in mm/s as spreading velocity. Statistical significances among groups were analyzed using one-way and two-way-ANOVA designs and the SNK test.

Results:

Significant differences in spreading velocity were found between materials (p < 0.001) and among treatments (p < 0.001). Silanization decreased the spreading velocity for both adhesives in comparison to groups where it was not performed (p < 0.05). Differences in roughness were found only for SB surfaces that were rougher than the others (p < 0.05). Silanization decreased the roughness of SB surfaces (p < 0.05). Linear regression did not indicate any correlation between spreading velocity and roughness (R = 0.173).

Conclusions:

Although surface treatments yielded different roughness, they did not provide differences in the spreading velocity of the simplified bonding systems studied. Silanization decreased bonding systems' spreading velocities.

Effect of the number of coats of simplified adhesive systems on microleakage of dentin-bordered composite restorations

AIM

This study tested the null hypothesis that there is no difference on microleakage of dentin-bordered composite restorations using single or double coats of adhesive from one-bottle adhesive systems.

METHODS AND MATERIALS

The enamel surface was removed from freshly extracted bovine teeth, and standardized Class V cavities (3 x 3 x 1.5 mm) were made at the cervical areas of buccal surfaces. Teeth were restored and grouped according to type of adhesive systems [Prime Bond 2.1 (PB2.1), Prime & Bond NT (PBNT), and Single Bond (SB)] and to the number of coats (one or two) to be used. The restorations were polished and immersed in a 0.5% aqueous solution of basic fuchsin for four hours. Teeth were then sectioned and the most infiltrated section of each tooth was selected under magnification, scanned, and quantitatively analyzed using a computer program. Data were analyzed using two-way analysis of variance (ANOVA) and Student-Newman-Keuls (a=0.05).

RESULTS

Groups without filler content (PB2.1 and SB) showed no difference in microleakage using single or double coats. However, PBNT (with nanofiller) showed statistically less microleakage when only one coat was applied. The influence of the number of coats of the adhesive systems on dentin margin microleakage was material dependent.

CONCLUSION

All adhesive systems demonstrated microleakage, however, it could be minimized using two coats of non-filled or one coat of a filled adhesive system.

Effect of adhesive systems associated with resin-modified glass ionomer cements

The bonding of resin-modified glass ionomer cements to dentin remains a challenge in clinical routine. In an attempt to improve this property, different materials and techniques have been proposed. This study investigated the shear bond strength of resin-modified glass ionomer cements (Vitremer, 3M/ESPE and Fuji II LC Improved, GC) to human dentin using two one-bottle adhesive systems (Prime & Bond 2.1, Dentsply and Single Bond, 3M/ESPE). The restored specimens were stored in deionized water for 24 h at 37 +/- 1 degrees C, and then the bonded surfaces were tested in shear strength using a Universal testing machine at a crosshead speed of 0.5 mm min(-1). Bond strength means were recorded and failure modes were assessed with a stereomicroscope at 40x magnification. Data were submitted to two-way anova and multiple comparisons were performed using a Tukey statistical test (P < 0.05). Fuji II LC Improved yielded higher bond strength (P < 0.05) than Vitremer in all experimental conditions. No statistically significant differences (P > 0.05) were observed among the proposed dentin surface treatments, although a slight decrease in bond strength was observed when phosphoric acid was used alone. Bond strengths of the resin-modified glass ionomer cements to dentin seemed to be more material-dependent than surface treatment-dependent. It may be concluded that the one-bottle adhesive systems tested in this study did not improve the bond strength of the resin-modified glass ionomer cements to dentin.

Influence of Temperature on the Spreading Velocity of Simplified-Step Adhesive Systems

BACKGROUND

Flowability and viscosity vary for different adhesive systems owing to differences in their composition. These characteristics can be modified by environmental temperature.

PURPOSE

The purpose of this study was to determine the influence of temperature on the spreading (flow capacity) of simplified-step adhesive systems.

MATERIALS AND METHODS

Spreading velocities of adhesive systems (Adper Single Bond and Single Bond Plus [3M ESPE, St. Paul, MN, USA]; Prime & Bond 2.1 and Prime & Bond NT [Dentsply Indústria e Comércio Ltda, Petrópolis, RJ, Brazil]; Adper Prompt [3M ESPE]; and One Up Bond F [Tokuyama Corp, Tokyo, Japan]) were analyzed at intervals of 10, 15, 20, and 30 seconds at both 25 degrees C and 37 degrees C by placing 10 microL drops on a glass slide surface with an inclination of 45 degrees. The spreading of each adhesive system was measured in millimeters per second.

RESULTS

Data were analyzed by two-way analysis of variance and Student-Newman-Keuls tests. Regression analysis was used to determine a correlation between spreading velocity and time. Statistical significance was considered at a confidence level of 95%. Temperature influenced the spreading velocity, increasing it for Single Bond and Prime & Bond 2.1 and decreasing it for Adper Prompt (p < .05). No differences on spreading were observed for the other adhesives studied (p >.05). Regression analysis of each adhesive system demonstrated an inverse correlation between mean spreading velocity and time (R2 = .999) on both temperatures.

CONCLUSIONS

Temperature increases yielded an increase of spreading for Single Bond and Prime & Bond 2.1. The influence of temperature on the spreading velocity was material dependent.

CLINICAL SIGNIFICANCE

Environmental temperature can influence the rate of spreading of the adhesive system in clinically relevant times and may influence adhesive thickness on cavity walls.

Effect of one-bottle adhesive systems on the fluoride release of a resin-modified glass ionomer

A dhesive systems associated to resin-modified glass ionomer cements are employed for the achievement of a higher bond strength to dentin. Despite this benefit, other properties should not be damaged. This study aimed at evaluating the short-time fluoride release of a resin-modified glass ionomer cement coated with two one-bottle adhesive systems in a pH cycling system. Four combinations were investigated: G1: Vitremer (V); G2: Vitremer + Primer (VP); G3: Vitremer + Single Bond (VSB) and G4: Vitremer + Prime & Bond 2.1 (VPB). SB is a fluoride-free and PB is a fluoride-containing system. After preparation of the Vitremer specimens, two coats of the selected adhesive system were carefully applied and light-cured. Specimens were immersed in demineralizing solution for 6 hours followed by immersion in remineralizing solution for 18 hours, totalizing the 15-day cycle. All groups released fluoride in a similar pattern, with a greater release in the beginning and decreasing with time. VP showed the greatest fluoride release, followed by V, with no statistical difference. VSB and VPB released less fluoride compared to V and VP, with statistical difference. Regardless the one-bottle adhesive system, application of coating decreased the fluoride release from the resin-modified glass ionomer cements. This suggests that this combination would reduce the beneficial effect of the restorative material to the walls around the restoration.

Effect of the number of thermocycles on microleakage of resin composite restorations

Thermocycling simulates, in vitro, thermal changes that occur in the oral cavity. The aim of this study was to evaluate the influence of the number of cycles on microleakage. Class V cavities (1.5 mm deep, 3 mm in height and 3 mm in width) were prepared in bovine teeth, restored with a Single Bond/Z250 restorative system (3M/ESPE) and then divided into five groups of ten teeth each: group 1 was not thermocycled (control group), and groups 2, 3, 4 and 5 were thermocycled 500, 1,000, 2,500 and 5,000 times, respectively (5º-55º ± 2ºC, 15 s dwell time). The teeth were immersed in 0.5% basic fuchsin aqueous solution for 24 h, sectioned and the sections with the highest degree of microleakage were selected, scanned and the extent of dye penetration was measured by the ImageTool program. The results submitted to one-way ANOVA showed no significant differences between the groups (p > 0.05). The averages of microleakage values in millimeters were: group 1 (3.92); group 2 (3.13); group 3 (4.48); group 4 (4.33) and group 5 (3.42). Thus, it was concluded that there is no relation between the increase of the number of cycles and the increase in microleakage.