In vitro evaluation of the cariostatic action of esthetic restorative materials in bovine teeth under severe cariogenic challenge

Considering that caries around restorations is a serious problem in dentistry, and some restorative materials with fluoride may be important in inhibiting these lesions, this research is aimed at performing an in vitro evaluation of the cariostatic action of some esthetic restorative materials. Standardized cavities were prepared in the center of either intact blocks of bovine enamel or with bovine teeth containing early artificial carious lesions. The specimens were restored with a high viscosity glass ionomer cement (Molar Ketac), a resin-modified glass ionomer cement (Vitremer), a polyacid-modified resin composite (Dyract AP) and a conventional resin composite (Z-250). In addition to the restored specimens, four corresponding control groups were evaluated. All groups, except for two control groups, were subjected to a demineralization/remineralization cycling model for 14 days, simulating a situation of severe cariogenic challenge. The blocks were then longitudinally sectioned through the restorations. Mineral loss was evaluated in these specimens using the Knoop microhardness profiles in longitudinal sections at three different distances of the cavities and at eight distinct depths in relation to the external enamel surface. Statistical analysis of the results showed significant differences (p < 0.05) among the groups, although none of the study materials completely inhibited creation of the lesions. Vitremer demonstrated the best cariostatic action in intact bovine enamel. Ketac Molar, in intact or demineralized enamel, and Vitremer, in demineralized enamel, presented intermediate cariostatic potential. Z-250 and Dyract AP did not demonstrate any cariostatic effect. The data suggests that glass ionomer cements demonstrated better cariostatic action compared to the other restorative materials.     

IN VITRO ASSESSMENT OF AN EXPERIMENTAL COAT APPLIED OVER FLUORIDE VARNISHES

Objective:

The time of contact between the product and enamel surface is important in ensuring the efficacy of fluoride varnishes. Thus, some alternatives could avoid fluoride loss to saliva and improve the anticariogenic action of the product. This study evaluated the effect of an experimental coat on the anticariogenic action of fluoride varnishes.

Material and Methods:

Enamel bovine blocks were selected by evaluating surface microhardness and randomized into five groups (n=24): placebo, Duraphat™, Duraphat™ with coat, Duofluorid™ and Duofluorid™ with coat. Twelve blocks from each group were used to analyze calcium fluoride (CaF₂) formed on enamel after treatment. The other 12 blocks were subjected to pH cycling for 7 days. The varnishes were kept on enamel for 6 h. Next, the percentage change of surface microhardness (%SMHC) and mineral loss (ΔZ) were calculated. CaF₂ retained and fluoride present in the pH-cycled solutions were also measured.

Results:

The use of the coat did not decrease %SMHC and ΔZ, but all fluoride varnishes had better results when compared to the placebo (ANOVA and Kruskal-Wallis, respectively). The values from CaF₂ formed were higher compared to the values of CaF₂ retained (non-paired t test, p<0.05). There was a trend to decrease the amount of F in the solutions at the end of pH cycling (Kruskal-Wallis, p<0.05).

Conclusions:

Although the experimental coat increased the formation of CaF₂ on the enamel surface, it did not significantly improve the anticariogenic action of fluoride varnishes.     

SEM ANALYSIS OF THE ACID-ETCHED ENAMEL PATTERNS PROMOTED BY ACIDIC MONOMERS AND PHOSPHORIC ACIDS

Objective:

Although self-etching bonding systems (SES) are indicated to prepare dental enamel for bonding, concerns have been expressed regarding their effectiveness. The aim of this study was to analyze the etching pattern (EP) of nine SES in comparison with 35% and 34% phosphoric acid etchants (FA) on intact (IN) and ground (GR) enamel surface.

Materials and Methods:

Twenty-two human third molars were sectioned in mesial-distal and buccal-lingual directions, and four dental fragments were obtained from each tooth. Half of the fragments were ground using 600-grit SiC paper and the other half remained intact. The fragments were randomly assigned into 22 groups, according to the texture of enamel surface (IN and GR) and the technique to etch the enamel (34% FA, 35% FA, AdheSE primer; Brush & Bond; Clearfil Protect Bond primer; iBond; One-up Bond F; OptiBond Solo Plus primer; Tyrian SPE primer; Unifil Bond primer and Xeno III). Conditioners were applied to IN and GR enamel surfaces, according to the manufacturer''s instructions. Specimens etched with phosphoric acids were washed with water, while the surfaces treated with SES were submitted to alternate rinsing with alcohol and acetone. The specimens were dried, sputter-coated and examined under a scanning electron microscope.

Results:

For both IN and GR enamel surfaces, the EP of 34 and 35% FA was deeper and more homogeneous in comparison to EP of SES, except for Tyrian SPE. The acidic monomer action of self-etching systems was more effective on GR enamel.

Conclusion:

Most of the SES are less aggressive than phosphoric acid etchants and their etching effects were reduced on intact enamel surfaces. Uniterms: Dental acid etching; Dental enamel; Electron microscopy.     

56-month clinical performance of Class I and II resin composite restorations

Objective

This study evaluated the 56-month clinical performance of Class I and II resin composite restorations. Filtek P60 was compared with Filtek Z250, which are both indicated for posterior restorations but differ in terms of handling characteristics. The null hypothesis tested was that there is no difference in the clinical performance of the two resin composites in posterior teeth.

Material and Methods

Thirty-three patients were treated by the same operator, who prepared 48 Class I and 42 Class II cavities, which were restored with Single Bond/Filtek Z250 or Single Bond/Filtek P60 restorative systems. Restorations were evaluated by two independent examiners at baseline and after 56 months, using the modified USPHS criteria. Data were analyzed statistically using Chi-square and Fisher''s Exact tests (a=0.05).

Results

After 56 months, 25 patients (31 Class I and 36 Class II) were analyzed. A 3% failure rate occurred due to secondary caries and excessive loss of anatomic form for P60. For both restorative systems, there were no significant differences in secondary caries and postoperative sensitivity. However, significant changes were observed with respect to anatomic form, marginal discoloration, and marginal adaptation. Significant decreases in surface texture were observed exclusively for the Z250 restorations.

Conclusions

Both restorative systems can be used for posterior restorations and can be expected to perform well in the oral environment.     

EFFECT OF LIGHT CURING UNIT ON RESIN-MODIFIED GLASS-IONOMER CEMENTS: A MICROHARDNESS ASSESSMENT

Objective:

To evaluate the microhardness of resin-modified glass-ionomer cements (RMGICs) photoactivated with a blue light-emitting diode (LED) curing light.

Material and Methods:

Thirty specimens were distributed in 3 groups: Fuji II LC Improved/GC (RM1), Vitremer/3M ESPE (RM2) and Filtek Z250/ 3M ESPE (RM3). Two commercial light-curing units were used to polymerize the materials: LED/Ultrablue IS and a halogen light/XL3000 (QTH). After 24 h, Knoop microhardness test was performed. Data were submitted to three-way ANOVA and Tukey''s test at a pre-set alpha of 0.05.

Results:

At the top surface, no statistically significant difference (p>0.05) in the microhardness was seen when the LED and QTH lights were used for all materials. At the bottom surface, microhardness mean value of RM2 was significantly higher when the QTH light was used (p<0.05). For RM1, statistically significant higher values (p<0.05) were seen when the LED light was used. No statistically significant difference (p>0.05) was seen at the bottom surface for RM3, irrespective of the light used. Top-to-bottom surface comparison showed no statistically significant difference (p>0.05) for both RMGICs, regardless of the light used. For RM3, microhardness mean value at the top was significantly higher (p<0.05) than bottom microhardness when both curing units were used.

Conclusion:

The microhardness values seen when a LED light was used varied depending on the restorative material tested.     

INFLUENCE OF ENVIRONMENTAL CONDITIONS ON PROPERTIES OF IONOMERIC AND RESIN SEALANT MATERIALS

Objectives:

The aim of this study was to determine the effect of environmental conditions on the degradation of ionomeric and resin sealant materials.

Material and Methods:

FluroShield, Vitremer, and Ketac Molar disc-shaped specimens (n=18/material) were prepared, polished, subjected to initial hardness and roughness readings. Six discs of each material were randomly assigned to one of three different storage solutions: 0.3% citric acid (CA), demineralization solution (DE), and remineralization solution (RE). The specimens were individually immersed in 3 mL of the test solutions, which were daily changed. After 15 days of storage, new surface roughness and hardness readings were done. Fluoride release in the solutions was measured within 15 days. Data were analyzed by ANOVA and Tukey''s and Contrast tests (α=0.05).

Results:

The storage in CA increased the roughness of Vitremer and Ketac Molar. A significant reduction in hardness was observed for all materials after storage in all solutions. For all materials, the greatest amounts of fluoride release occurred during the 1^st day. FluroShield presented the same patterns of fluoride release in all solutions. Ketac Molar and Vitremer released the highest amounts of fluoride in the CA solution.

Conclusions:

Ionomeric materials are more susceptible to degradation than resin-based materials under acidic conditions. Acidic conditions lead to a higher fluoride release from ionomeric materials.     

Mechanical,antibacterial and bond strength properties of nano-titanium-enriched glass ionomer cement

The use of nanoparticles (NPs) has become a significant area of research in Dentistry.

Objective

The aim of this study was to investigate the physical, antibacterial activity and bond strength properties of conventional base, core build and restorative of glass ionomer cement (GIC) compared to GIC supplemented with titanium dioxide (TiO₂) nanopowder at 3% and 5% (w/w).

Material and Methods

Vickers microhardness was estimated with diamond indenter. Compressive and flexural strengths were analyzed in a universal testing machine. Specimens were bonded to enamel and dentine, and tested for shear bond strength in a universal testing machine. Specimens were incubated with S. mutans suspension for evaluating antibacterial activity. Surface analysis of restorative conventional and modified GIC was performed with SEM and EDS. The analyses were carried out with Kolmogorov-Smirnov, ANOVA (post-hoc), Tukey test, Kruskal-Wallis, and Mann Whitney.

Results

Conventional GIC and GIC modified with TiO₂ nanopowder for the base/liner cement and core build showed no differences for mechanical, antibacterial, and shear bond properties (p>0.05). In contrast, the supplementation of TiO₂ NPs to restorative GIC significantly improved Vickers microhardness (p<0.05), flexural and compressive strength (p<0.05), and antibacterial activity (p<0.001), without interfering with adhesion to enamel and dentin.

Conclusion

GIC supplemented with TiO₂ NPs (FX-II) is a promising material for restoration because of its potential antibacterial activity and durable restoration to withstand the mastication force.     

The roughness, microhardness, and surface analysis of nanocomposites after application of topical fluoride gels

Objectives

Application of acidulated phosphate fluoride (APF) gels has long been considered to cause deterioration of composite surfaces. The aims of this study were to demonstrate that nanocomposite surfaces were not affected by some APF gels and to investigate the possible underlying mechanisms.

Methods

The elemental composition and viscosity of 3 acidulated phosphate fluoride (APF) agents (60 Second Taste Gel, Topex, and Zap) and 1 neutral fluoride agent (pH7 Gel) were analyzed. Subsequently, 320 specimens of 3 nanocomposites (Premisa, Filtek Z350, and Grandio) and a microhybrid composite (Estelite Sigma) with 80 specimens for each composite were randomly divided into 5 groups (n = 16) and treated with 4 fluoride gels as well as distilled water which served as the control. Fluoride gels were applied on composite resin surfaces 4 times, 30 min each time. The roughness and microhardness were measured after treatments. Qualitative examination of the surface degradation of the composites was carried out with Fourier transforming infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).

Results

Topex and Zap did not cause surface changes of composite resins, the possible reason being ascribed to the presence of magnesium aluminum silicate (MAS) clays. In contrast, 60 Second Taste Gel treatments caused significant roughness increase, microhardness decrease, more prominent filler dissolution, and IR spectral changes of Premisa, Filtek Z350, and Grandio. Estelite Sigma was less affected by the 4 fluoride gels.

Significance

The composite surfaces were not affected by Topex or Zap even after extended treatments. These two APF gels may be more suitable for clinical applications.     

EFFECT OF 2% IODINE DISINFECTING SOLUTION ON BOND STRENGTH TO DENTIN

Introduction:

Disinfection of dentin surfaces is desirable so long as it does not interfere with subsequent bonding of adhesive resins.

Objective:

To test the null hypothesis that bond strengths to dentin are not affected by previous application of an iodine disinfecting solution.

Materials and Methods:

Twenty-four extracted non-carious molars were selected. Occlusal enamel was removed producing a flat dentin substrate. Test teeth were all treated with 2% Iodine disclosing/disinfecting solution (I₂DDS) for 20 sec and rinsed for 20 sec followed by the application of self- or total- etching bonding systems, generating five adhesive groups (n=3): Single Bond;; Prime & Bond NT; Clearfil SE Bond; Opti-Bond Plus. The control groups (n=3 per adhesive) had no disclosing/disinfectant application prior to adhesive application. A 4-mm thick resin restoration was built up on each tooth for microtensile testing. Statistical analyses between experimental and control groups were performed by student''s t-test (α = 0.05).

Results:

In general, experimental groups (previously treated with I₂DDS) showed significantly lower bond strength values when compared with their respective controls (p<0.05), except for group Prime &Bond I₂ that did not significantly differ from its control (p>0.05).

Conclusion:

Acetone-base adhesive systems seem not to be affected by the application of I₂DDS prior to etching and bonding procedures.     

Extent of the cariostatic effect on root dentin provided by fluoride-containing restorative materials

This study evaluated the extent of the cariostatic effect on root dentin provided by four fluoride-containing restorative systems: Ketac-Fil/ESPE [Ke], Fuji II LC Improved/GC Corp [Fj], Dyract AP/Dentsply [Dy] and SureFil/Dentsply [Su], and one without fluoride: Z250/3M [control]. Ninety-five bovine root dentin fragments (5.0 x 6.0 mm) were obtained, embedded in polyester resin and planed. Cavities (1.5 x 3.5 x 1.0 mm) were made and restored by the five restorative systems (n=19) in a randomized complete block design according to the manufacturers' instructions. After 24 hours, the dentin/restoration surface was polished. The restoration surface and an adjacent area of 3.0 x 3.0 mm were demarcated and submitted to a pH-cycling model. Dentin surface Knoop microhardness values were obtained (5.0-g, 5.0-s) for 10 distances: 50, 100, 150, 300, 600, 900, 1200, 1500, 1800 and 2100 microm from the margin of the restoration. The dentin microhardness means for each restorative material at each distance was considered by the ANOVA multi-factor split-plot method. The interaction between the restorative system and distance was statistically significant (p<0.05). The Tukey test and the regression analysis showed that the means of [Ke] and [Fj] were similar up to 300 microm, the [Ke] means being higher than the [control] at distances 50, 100, 150 and 300 microm. The [Fj] means were higher than the [control] at distances 50, 100 and 150 microm. The microhardness means of [Dy] and [Su] were not statistically different from the [control] and remained steady throughout the studied distances. This study concluded that the extent of the cariostatic effect on root dentin was 300 microm for [Ke] and 150 microm for [Fj]. [Dy] and [Su] did not show any cariostatic effect.     

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.     

The recharge of esthetic dental restorative materials with fluoride in vitro-two years' results.

OBJECTIVES: A range of esthetic restorative dental materials are now available to dental clinicians. The aim of this study was to evaluate the relative fluoride recharge potential of a number of these materials in vitro over two years. METHODS: Disc samples (12 mm x 2 mm) of each of the materials were placed into artificial saliva at neutral pH. The materials tested were: two glass ionomers (Chemfil; Ketac-Fil), two resin-modified glass ionomers (Photac-Fil Aplicap; Vitremer), two compomers (Dyract; Compoglass) and two composites (Heliomolar; Concise). At 13 intervals over a two years period the discs were subjected to a 2 min fluoride recharge by exposure to sodium fluoride (500 ppm F). The pre- and post-recharge fluoride release values were determined using an ion sensitive electrode. RESULTS: At all time intervals the post-recharge fluoride release of the materials was significantly different (MANOVA p<0.0001). The mean values for post-recharge fluoride release after two years were: Chemfil 10.3, Ketac 3.0, Vitremer 9.0, Photac-Fil Aplicap 12.1, Compoglass 5.0, Dyract 3.6, Concise 0.3, Heliomolar 0.2 (units = microgF/cm(2)/h). SIGNIFICANCE: Esthetic fillings vary significantly in their capacity to absorb and re-release fluoride. The glass ionomer-based materials displayed a far greater potential for fluoride recharge than the composites, in which the recharge was virtually negligible. Whilst it cannot be assumed that fluoride release is directly proportional to cariostatic potential, these results suggest that, where possible, glass ionomer-based materials should be used in patients who have a high caries rate.     

Dentine microhardness after different methods for detection and removal of carious dentine tissue

There are several methods for identifying carious dentinal tissue aiming to avoid removal of healthy dentinal tissue.

Objectives

The purpose of this study was to test different methods for the detection of carious dentinal tissue regarding the amount of carious tissue removed and the remaining dentin microhardness after caries removal.

Material and methods

The dentin surfaces of 20 bovine teeth were exposed and half of the surface was protected with nail polish. Cariogenic challenge was performed by immersion in a demineralizing solution for 14 days. After transverse cross-section of the crown, the specimens were divided into four groups (n=10), according to the method used to identify and remove the carious tissue: "Papacárie", Caries-detector dye, DIAGNOdent and Tactile method. After caries removal, the cross-sectional surface was included in acrylic resin and polished. In a microhardness tester, the removed dentin thickness and the Vickers microhardness of the following regions were evaluated: remaining dentin after caries removal and superficial and deep healthy dentin.

Results

ANOVA and Tukey''s test (α=0.05) were performed, except for DIAGNOdent, which did not detect the presence of caries. Results for removed dentin thickness were: "Papacárie" (424.7±105.0; a), Caries-detector dye (370.5±78.3; ab), Tactile method (322.8±51.5; bc). Results for the remaining dentin microhardness were: "Papacárie" (42.2±10.5; bc), Caries-detector dye (44.6±11.8; abc), Tactile method (24.3±9.0; d).

Conclusions

DIAGNOdent did not detect the presence of carious tissue; Tactile method and "Papacárie" resulted in the least and the most dentinal thickness removal, respectively; Tactile method differed significantly from "Papacárie" and Caries-detector dye in terms of the remaining dentin microhardness, and Tactile method was the one which presented the lowest microhardness values.     

Effects of bleaching with carbamide peroxide gels on microhardness of restoration materials

The objective of this in vitro study was to quantitatively assess the effects of bleaching with 10 and 15% carbamide peroxide (CP) on restoration materials by performing superficial microhardness analysis. Acrylic cylindrical containers (4 x 2 mm) were filled with the following restoration products: Charisma (Heraues Kulzer, Vila Santa Catarina, S?o Paulo, Brazil), Durafill VS (Heraeus Kulzer), Vitremer (3M, Sumaré, S?o Paulo, Brazil), Dyract (Dentsply, Petrópolis, Rio de Janeiro, Brazil), and Permite C (SDI, S?o Paulo, S?o Paulo, Brazil). Sixty samples were prepared of each restoration material. Twenty samples received bleaching treatment with 10% CP, 20 samples received bleaching treatment with 15% CP, and 20 samples were kept submerged in artificial saliva, which was replaced daily. The treatment consisted of immersion of the specimens in 1 cm3 of CP at 10 and 15% for 6 hours per day during 3 weeks, whereupon the test specimens were washed, dried, and kept immersed in artificial saliva for 18 hours. Then the test and control specimens were analyzed using a microhardness gauge. The Knoop Hardness Number (KHN) was taken for each test and control specimen at five different locations by applying a 25 g force for 20 seconds. The values obtained were transformed into KHNs and the mean was calculated. The data were submitted to statistical analysis by analysis of variance and Tukey test, p < .05. The means/standard deviations were as follows: Charisma: CP 10% 38.52/4.08, CP 15% 34.31/6.13, saliva 37.36/4.48; Durafill VS: CP 10% 18.65/1.65, CP 15% 19.38/2.23, saliva 18.27/1.43; Dyract AP: CP 10% 30.26/2.81, CP 15% 28.64/5.44, saliva 33.88/3.46; Vitremer: CP 10% 28.15/3.04, CP 15% 17.40/3.11, saliva 40.93/4.18; and Permite C: CP 10% 183.50/27.09, CP 15% 159.45/5.78, saliva 215.80/26.15. A decrease in microhardness was observed for the materials Dyract AP, Vitremer, and Permite C after treatment with CP at 10 and 15%, whereas no effect on either of the two composites (Charisma and Durafill) was verified. CLINICAL SIGNIFICANCE The application of the carbamide peroxide gels at 10 and 15% did not alter the microhardness of the composite resins Charisma and Durafill. In situ and clinical studies are necessary to enable one to conclude that the reduction in microhardness of the materials effectively results in clinical harm to the restorations.     

ANTICARIOGENIC POTENCIAL OF ACIDULATE SOLUTIONS WITH LOW FLUORIDE CONCENTRATION

Objectives:

The aim of this study was to verify the anticariogenic effect of acidulate solutions with low NaF concentration, using pH-cycling model and bovine enamel.

Material and methods:

Enamel blocks were submitted to the surface microhardness (SMH) test and randomly divided in 12 experimental and one placebo groups. The blocks were submitted to pH cycling for 7 days, with daily applications once/day of 0.05% NaF and 0.1% NaF and twice/day of 0.02% NaF solutions. Four different pH: 4.0, 5.0, 6.0 and 7.0 were used. Next, SMH test was again used to determine the surface microhardness percentage change (%SMH). Data obtained for %SMH were homogeneous and passed through variance analyses and Tukey''s test (5%) as far as fluoride concentrations and pH.

Results:

The results showed that pH influenced %SMH in 0.02% NaF and 0.05% NaF solutions with pH 4.0, which had less mineral loss compared to pH 7.0 (p<0.05). The 0.02% NaF - pH 4.0, and 0.05% NaF – pH 7.0 groups showed similar results (p>0.05). A dose-response relationship was observed among the tested solutions, with better anticariogenic effect for the 0.1% NaF solution.

Conclusion:

The results suggest that the addition of citric acid to acidulate mouth rinses reduce mineral loss.     

Initial in situ secondary caries formation: effect of various fluoride-containing restorative materials

This study evaluated the effects of various restorative materials (Ariston pHc; Dyract; Vitremer; Tetric Ceram; Compoglass F, F2000; Hytac and Ketac Molar) on initial secondary caries formation in situ. Eighty-eight enamel slabs from sound human molars were sterilized (ethylene dioxide) and embedded in epoxy resin. Standardized tooth preparations were filled with the various restorative materials according to manufacturers' recommendations. One specimen from each group was inserted into one of two buccal aspects of an intraoral appliance worn by 11 volunteers for four weeks, day and night. Oral hygiene was performed without additional fluoride application. During meals and oral hygiene procedures, the appliances were stored in sucrose solution (10%). After in situ exposure, the samples were prepared for microradiographic assessment. Mineral content and lesion depth were evaluated by a dedicated software package (TMR 1.24). Lesion depth and mineral loss of the carious lesions close to Ariston pHc was significantly lower when compared to distant parts of the same lesions (p < 0.05; t-test, Bonferroni-Holm correction). All other materials containing fluoride showed no caries protective effect on surrounding enamel (p > 0.05; t-test, Bonferroni-Holm correction). A hydroxyl-, calcium- and fluoride-containing restorative material hampers demineralization next to the restoration, whereas, fluoride release of various fluoride-containing restorative materials does not affect demineralization of adjacent enamel in situ.     

Radiographic evaluation of furcal perforations sealed with different materials in dogs' teeth

Objective

The objective of this work was to evaluate, using radiographic images, the behavior of four materials used to repair root perforations in dogs'' teeth.

Material and Methods

Second and third premolars of 6 dogs were used. The 48 teeth were randomly divided into 4 groups (n=12) and the perforations were sealed with one of the following materials: MTA, AH Plus, Vitremer and gutta-percha. Dogs were submitted to general anesthesia, teeth were radiographed and pulp was accessed. Perforations were done, at the maximum curve of the pulp floor, sealed and the accessed coronal cavity was filled with glass ionomer cement (Vidrion R). After 90 days, the dogs were sacrificed and the last x-ray image was taken. Images were analyzed for the presence/absence of periodontal lesions at the perforation region. Data were analyzed statistically by chi-square test at 5% significance level.

Results

There were no statistically significant differences (p≥0.05) among AH Plus, Vitremer and gutta-percha groups. MTA produced the smallest number of periodontal lesions (p<0.05).

Conclusions

It may be concluded that none of the tested materials was able to preserve the integrity of the periodontal tissues in the furcation region, and the use of MTA resulted in the least formation of adjacent periodontal bone lesions revealed by the radiographic comparisons.     

Effect of surface treatment on the micro-shear bond strength to zirconia

The constant quest for finding the ultimate esthetic dental restorative material has led to numerous alternatives. These materials, in addition to possessing optical properties simulating natural teeth, should also have physical properties that can withstand the harsh oral environment. Due to their greater toughness, zirconium oxide materials have been used as a core material for all-ceramic restorations.

Objective

The objective of this study was to evaluate the resin-composite micro-shear bond strength to zirconia using different techniques of surface treatment.

Materials and methods

Fully sintered zirconia (LAVA, 3M-ESPE, Seefeld, Germany) discs were used in combination with resin-composite (Filtek Supreme, 3M-ESPE, Seefeld, Germany) discs and divided into four groups of surface treatments. The micro-shear bond strength was measured by applying an axial load on the bonded interface until failure occurred. Failure load (N) was determined and the samples were examined under a SEM and the failure type was identified. One-way analysis of variance (ANOVA) was used to analyze the data with the level of significance α = 0.05.

Results

Data analysis revealed significant difference between the different tested surface treatments with the group using sandblasting and coated with an experimental primer showing the highest failure load and a cohesive fracture pattern.

Conclusion

Within the limitations of this in vitro study the use of an experimental primer achieved a better bond strength in combination with air-abrasion particles.     

Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

Objective

The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models.

Material and Methods

Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer''s instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were sectioned into samples with area between 0.85 and 1.25 mm² that were submitted to µTBS testing, using a universal testing machine (EMIC) at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests.

Results

For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p<0.05). No statistical difference between restorative systems was shown for Class I cavity model (p>0.05), or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05). Regarding fracture pattern, there was no statistical difference among groups (p=0.0713) and 56.3% of the fractures were adhesive.

Conclusion

It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.     

Six-month evaluation of a resin/dentin interface created by methacrylate and silorane-based materials

Objectives:

This study aimed to compare the micro-tensile bond strength of methacrylate resin systems to a silorane-based restorative system on dentin after 24 hours and six months water storage.

Material and Methods:

The restorative systems Adper Single Bond 2/Filtek Z350 (ASB), Clearfil SE Bond/Z350 (CF), Adper SE Plus/Z350 (ASEP) and P90 Adhesive System/Filtek P90 (P90) were applied on flat dentin surfaces of 20 third molars (n=5). The restored teeth were sectioned perpendicularly to the bonding interface to obtain sticks (0.8 mm²⁾ to be tested after 24 hours (24 h) and 6 months (6 m) of water storage, in a universal testing machine at 0.5 mm/min. The data was analyzed via two-way Analysis of Variance/Bonferroni post hoc tests at 5% global significance.

Results:

Overall outcomes did not indicate a statistical difference for the resin systems (p=0.26) nor time (p=0.62). No interaction between material x time was detected (p=0.28). Mean standard-deviation in MPa at 24 h and 6 m were: ASB 31.38 (4.53) and 30.06 (1.95), CF 34.26 (3.47) and 32.75 (4.18), ASEP 29.54 (4.14) and 33.47 (2.47), P90 30.27 (2.03) and 31.34 (2.19).

Conclusions:

The silorane-based system showed a similar performance to methacrylate-based materials on dentin. All systems were stable in terms of bond strength up to 6 month of water storage.