Residual monomer release from orthodontic adhesives cured with different light sources

Introduction: The aim of this study was to evaluate the residual monomer release from orthodontic adhesives cured with light-emitting diode (LED) and halogen light sources.

Methods: Seven hundred and twenty stainless steel brackets were divided into 3 groups according to the adhesive system used (Transbond XT light-cure adhesive [TXT], Transbond LR capsule [LR], and Light Bond light-cure adhesive paste [LB]), and each group was divided into 2 subgroups according to light-curing procedure (LED or halogen). Brackets were bonded with adhesives onto tooth buccal surfaces and polymerized. Each specimen contained 24 brackets that simulated the oral environment (n = 5). The specimens were immersed in a 75% ethanol/water solution at 37 °C for 10 min, 1 h, 1 d, 7 d, 14 d, and 30 d, respectively. Eluted monomers (Bis-GMA, UDMA, and TEGDMA) were detected using HPLC.

Results: There was residual monomer release at all time periods, and the highest amount of release was observed cumulatively on the 30th day. The cumulative Bis-GMA released from adhesives was not different (p > 0.05). The cumulative TEGDMA released from adhesives was statistically different (p < 0.05). There was no statistical difference between QTH and LED light-curing units for each adhesive (p > 0.05).

Conclusions: The release of residual monomers stays at a high level for a long time after polymerization. The total leaching of residual monomers from the Light Bond light-cure sealant resin plus Light Bond light-cure adhesive paste was higher than that of other materials for both curing units. Different curing units (LED or QTH) did not affect the monomer release from the orthodontic adhesives.     

Effect of adhesive application on the shear bond strength of refrigerated and pre-heated of different composite resins to orthodontic molar tubes

Objective: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel using different temperatures and orthodontic composite resins. Methods: One hundred and twenty metal tubes were bonded to human third molars, which were randomly divided into three groups depending on the composite used: Transbond XT (XT); Transbond Supreme LV (LV); and Light Bond (LB). Each group was divided into four subgroups depending on the temperature (5°, 20°, 40°, and 60°) applied to the composite before cementing. For each experimental subgroup, half the specimens were bonded in combination with XT Primer. After 72?h, a SBS test was performed using a universal testing machine. Statistical analysis was performed using ANOVA, post hoc intergroup comparisons, chi-square test, and linear regression. Two representative molar surfaces from each subgroup were assessed under Scanning electron microscope. Results: The composite type only influenced XT regarding LB. The use of adhesive does not affect the SBS values of any composite. The flowable composites with adhesive containing zirconia (LV) as a filler showed lower SBS when cooled to 5?°C and when increases the temperature from 40?°C. Whether adhesive was used or not, composites with silica as filler (LB) showed lower SBS at 60?°C and increased to 5?°C. Conclusions: For all composites, from 20?°C, SBS values tend to increased and started to decline at 40°C except when adhesive is applied to the quartz-filled composite, which continues to increase, and the silica-filled composite without adhesive, which tend to decreases from 5?°C.     

Are antibacterial component additions in etchants and adhesives effective against Streptococcus Mutans?

The aim was to investigate the antibacterial activity of various acids and adhesives with and without antibacterial components against Streptococcus mutans. The antibacterial activities of 35% phosphoric acid (Ultra-Etch), 37% phosphoric acid with benzalkonium chloride (Etch-37), adhesive with chlorhexidine (Peak Universal Bond) and without any agent (PQ1) were investigated by agar-diffusion test. The inhibition-zones were measured after 48 h of incubation. For the tooth-cavity model test; cylindrical cavities were prepared on occlusal dentin surfaces of human molars and divided into four groups (n = 10 cavity/group). Group 1: Ultra-Etch + Peak Universal Bond, Group 2: Ultra-Etch + PQ1, Group 3: Etch-37 + PQ1 were applied. The fourth group without any agent application served as control. The teeth were immersed in 5.8 × 10⁶ cfu/ml of S. mutans solution to infect the cavities for 72 h before the application of the groups. After 72 h, dentin chips were collected from the cavity walls with burs for bacterial counting. Statistical analysis was performed by ANOVA, Bonferroni and Dunnett C tests (p < 0.05). Ultra-Etch and Etch-37 performed similar antibacterial activities in agar-diffusion test. Both acids showed better antibacterial activity compared to adhesives (p < 0.05). The antibacterial activity of PQ1 and Peak Universal Bond was observed to be inactivated by light-polymerization. According to the tooth-cavity model; Group I, II, and III demonstrated reduction in bacterial number and there was no significant difference between them. Antibacterial component additions in etchant and adhesive did not show superior antibacterial activity against S. mutans in both in vitro tests.     

Improvement of the Molar Tube Bond Durability with Preheated Orthodontic Adhesive

This study aimed to evaluate the effect of preheated orthodontic adhesives and thermal cycling on the bond strength of molar tubes. One hundred sixty molar tubes were bonded to acid-etched bovine incisors using a conventional orthodontic adhesive (Transbond XT), two microhybrid (Wave and Permaflo), and a nanofilled (Filtek Z350) flowable composite resins, at room temperature or preheated at 60°C. Transbond XT primer and Single Bond 2 adhesive system were used in association with Transbond XT and the flowable composites, respectively. The specimens were stored in water (37°C) for 24 h, and half of the sample was subjected to thermal cycling for 6000 cycles. Ashear bond strength (SBS) test was performed, followed by the appraisal of the adhesive Remnant Index (ARI). Three-way analysis of variance (ANOVA) and the Tukey test were performed at a significance level of 95% (P < .05). Samples bonded with preheated adhesives showed higher SBS regardless of the aging method. Only samples bonded with preheated conventional orthodontic adhesive maintained their bond strength after thermal cycling for 6000 cycles. Preheating orthodontic adhesives improved the bond strength of molar tubes, but only the preheated conventional orthodontic adhesive was capable of maintaining bond strength after thermal cycling.     

Antibacterial effect of dental cements evaluated using agar diffusion test

Purpose: Secondary caries can occur around the restoration, fixed prosthesis, and orthodontic band margins because of cariogenic bacteria. Long-lasting antibacterial effectiveness of dental cements used contemporarily can reduce this phenomenon. The purpose of this study was to examine the antibacterial activities of nine dental cements (BisCem^®, Super-Bond C&B, Rely X^TM, Panavia^TM F 2.0, Variolink^® II, Unitek^TM Multi Cure, Multilink^® Automix, Clearfil^TM Esthetic Cement, Transbond^TM LR) using agar diffusion test. Materials and methods: The test materials were inserted into the wells of Muller Hinton agar plates inoculated with Streptococcus mutans and Streptococcus salivarious. The diameters of the inhibition zones produced around the materials were measured after 24 h of incubation. Two-Way ANOVA, the Kruskal-Wallis, and the Mann–Whitney U tests at a significance level of p < 0.05 were analyzed for the results. Results: Unitek Multi Cure cement exhibited a significant difference from the control group against both S. mutans and S. salivarious (p < 0.05). While the zone of inhibition of Unitek Multi Cure cement was shorter (8.50 ± 1.77) than the control group (12.63 ± 1.30), Unitek Multi Cure had antibacterial effect against S. mutans and S. salivarious (p < 0.05). S. mutans displayed a significantly lower resistance to Unitek Multi Cure, BisCem, and Superbond C&B than S. salivarious (p < 0.05). Conclusion: Conventional glass ionomer cement, Unitek Multi Cure, exhibited greatest in vitro antibacterial activity against both S. mutans and S. salivarious. Formation of dental caries had been suppressed by the fluoride-releasing GICs.     

Effects of two metal primers on the shear bond strength of orthodontic molar tubes bonded to silver amalgam restorations of different dimensions

The aim of this study was to evaluate the shear bond strength (SBS) of orthodontic molar tubes bonded to amalgam restorations and enamel with four different area ratios, with and without the use of various metal primers. One hundred and fifty-six sound lower first molars were divided into five groups; control group (CG;n = 12) then divided into three subgroups: A, B, and C. Class V buccal amalgam restorations consisting of 25%(G1), 50%(G2), 75%(G3), and 100%(G4) of the basal areas of the molar tubes. Transbond XT Primer (TXTP;subgroup A), Alloy Primer (AP;subgroup B) and Reliance Metal Primer (RMP;subgroup C) (n = 12). Transbond XT was used as an adhesive material in all groups. Thermocycling was as 5 –55 °C, 1000 cycles. Data were analysed by one-way ANOVA and post hoc least significant difference tests (p < 0.05). Bond failure sites were classified using a modified Adhesive Remnant Index (ARI) system. SBS did not differ significantly among the three intermediate adhesives in subgroups of groups 1, 2, or 3 (p > 0.05); however, SBS was significantly higher in groups 4B and 4C than in group 4A (p < 0.05). Mean SBSs of groups 1 and 2 were significantly higher than others (p < 0.05). Mean SBS of group 3 was higher than that of group 4, but lower than that of the other groups. For ARI, significant relationships between CG and the intermediate adhesive groups were found (p < 0.05). Application of metal primers, such as AP or RMP, to sandblasted amalgam adjacent to etched enamel (25, 50, and 75%) did not improve bond strength significantly compared with the application of TXTP to amalgam and enamel.     

Effect of adhesive application on the shear bond strength of flowable composite resins and APC plus to orthodontic molar tubes

Objectives: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel when using different flowable composite resins and the APC Plus system (APC). Study design: One hundred metal tubes were bonded to human third molars, which were randomly divided into five groups: Tetric EvoFlow (TF); Wave mv Flow (W); Transbond Supreme LV (S); Transbond XT (XT); and APC. For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72?h, an SBS test was performed using a universal testing machine. Two-way analysis of variance (ANOVA) was run for multiple comparison tests and for comparing the mean SBS among the 10 subgroups to evaluate the effect of both the composite and the adhesive factors. Then, a Student-Newman-Keuls test was used for pairwise comparisons using the highest mean SBS group as reference. Adhesive Remnant Index scores were determined for the teeth after failure and compared by χ ²-test. Two representative molar surfaces from the 10 subgroups were assessed under scanning electron microscope. Results: The application of adhesive did not have a significant effect, but there was a marked tendency toward the influence of the factor composite on SBS. The mean SBS of tubes bonded with XT with adhesive was significantly higher than that of those bonded with APC with adhesive, TF with and without adhesive, and S with adhesive. Conclusion: Flowable composites and the APC system without intermediate bonding resin could be conveniently applied for orthodontic tube bonding.     

Adhesion of orthodontic brackets to indirect laboratory-processed resin composite as a function of surface conditioning methods and artificial aging

This study compared the shear bond strength of orthodontic brackets to laboratory-processed indirect resin composites (IRC) after different surface conditioning methods and aging. Specimens made of IRC (Gradia Indirect, GC) (thickness: 2 mm; diameter: 10 mm) (N = 80) were randomly assigned to one of the following surface conditioning methods: C – Control: no treatment; AA – Air-abrasion (50 μm Al₂O₃ particles); DB – Diamond bur and HF – Etching with hydrofluoric acid (9.6%). After adhesive primer application (Transbond XT), orthodontic brackets were bonded to the conditioned IRC specimens using adhesive resin (Transbond XT). Following storage in artificial saliva for 24 h at 37 °C, the specimens were thermocycled (×1000, 5–55 °C). The IRC–bracket interface was loaded under shear in a Universal Testing Machine (0.5 mm/min). Failure types were classified using modified adhesive remnant index criteria. Data were analyzed using two-way ANOVA and Tukey`s HSD (α = 0.05). Surface conditioning method did not significantly affect the bond strength results (p = 0.2020), but aging significantly decreased the results (p = 0.04). Interaction terms were not significant (p = 0.775). In both non-aged and aged conditions, non-conditioned C group presented the lowest bond strength results (MPa) (p < 0.05). In non-aged conditions, surface conditioning with DB (8.03 ± 0.77) and HF (7.87 ± 0.64) showed significantly higher bond strength results compared to those of other groups (p < 0.05). Thermocycling significantly decreased the mean bond strength in all groups (2.24 ± 0.36–6.21 ± 0.59) (p < 0.05). The incidence of Score 5 (all adhesive resin remaining on the specimen) was the highest in HF group without (80%) and with aging (80%) followed by DB (40, 70%, respectively). C groups without and with aging showed exclusively Score 1 type (no adhesive resin on the specimen) of failures indicating the least reliable type of adhesion.     

Effect of adhesive application on the shear bond strength using different cementing agents in molar and premolar attachments

Objectives: The purpose of the study was to evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic brackets and tubes to acid-etched human enamel when using different cementing agents. Study Design: One hundred and sixty metal attachments (80 tubes and 80 brackets) were bonded to human third molars and premolars that were randomly divided into identical groups of four: Transbond XT (XT); Wave MV Flow (WF); APC Plus System (APC); and Fuji Ortho LC (LC). For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72?h, a SBS test was performed using a universal testing machine. Statistical analysis was performed using ANOVA with Bonferroni post hoc comparisons, χ² tests, and linear regression modeling. Adhesive remnant index scores were determined for the teeth after failure. Representative tooth surfaces from each subgroup were assessed under SEM. Results: Considering that each cement was observed, each of them showed similar SBS when the adhesive system was applied as when the adhesive was not applied. By comparing all cements together, it was noted that if an adhesive is not applied, all cements have similar values. If an adhesive is applied, cement XT, WF, and APC showed significantly higher SBS values than LC did. The tubes showed higher SBS than the brackets did in cements XT and WF with or without an adhesive, as well as APC Plus with an adhesive. Conclusions: The use of an adhesive system in bonding brackets and tubes does not influence the SBS obtained, independently of the cement.     

Antimicrobial activity,effects on Streptococcus mutans biofilm and interfacial bonding of adhesive systems with and without antibacterial agent

ObjectivesThis study evaluated the antimicrobial activity (by agar disk diffusion test, AD), viability of S. mutans biofilm (VB), and effect on resin-dentin interface (RDI) of six adhesive systems.MethodsThree adhesives containing antibacterial components (Gluma 2Bond (G2B)/glutaraldehyde, Clearfil SE Protect (CSP)/MDPB and Peak Universal Bond (PUB)/chlorhexidine) and the corresponding adhesives with similar composition, but without antibacterial agents (Gluma Comfort Bond, GCB; Clearfil SE Bond, CSB and Peak LC Bond, PLB) were evaluated. AD was determined measuring the extent of halo formation following application of adhesives and control groups (light cured or not) to cultures of four strict anaerobic and four facultative bacteria. For VB, a UA159 biofilm was grown on adhesive-coated hydroxyapatite discs for five days, collected and processed to count the number of viable cells. For RDI analysis, adhesives were applied according to manufacturers' recommendations and teeth were restored with resin composite, sectioned to obtain bonded slices and visualized by SEM.ResultsAn inhibition halo was observed for G2B (strict anaerobic/light cured and not light cured), CSP (strict anaerobic and facultative/light cured and not light cured) and PUB (strict anaerobic and facultative/not light cured). PUB when light cured produced an inhibition halo on L. casei and S. mutans only. G2B and CSP significantly reduced the viability of S. mutans. Adhesives containing antimicrobial compounds had no detectable effect on RDI.ConclusionThe MDPB-containing bonding agent showed better results of inhibition for all oral pathogens tested and a decrease of viability of Streptococcus mutans biofilm, among the adhesives tested.     

A novel silane system as a primer for orthodontic bonding—A pilot study

AimTo determine the adhesion strength (measured as shear bond strength, SBS) of orthodontic brackets using two experimental silane-based primer systems and compare and contrast their effect.Materials and methodsSixty acid-etched premolars were randomly assigned into 4 study groups (n=15). In group 1, brackets were bonded without primer but using Transbond XT adhesive; in group 2, Transbond XT primer was applied and bracket bonded; in group 3, an experimental silane-based primer of 1.0 vol% of 3-acryloxypropyltrimethoxysilane (ACPS) was applied before bonding; in group 4, an experimental silane-based primer of 1.0 vol% of ACPS+0.5% bis-1, 2-(triethoxysilyl) ethane (BTSE) was used. The adhesion strength (measured as shear bond strength) was recorded using a universal testing machine. Failure types were classified according to the Adhesive Remnant Index (ARI). Contact angles of the primers were measured on an enamel slab.Data was analyzed by ANOVA and Tukey's multiple comparison post hoc analysis.ResultsThe mean adhesion strength results were high in group 4: 15.8±1.6 MPa followed by group 3: 12.5±1.5 MPa, group 2: 11.9±1.1 MPa and the lowest in group 1: 08.1±0.7 MPa. A significant difference in adhesion strength was observed between all the groups except for group 3 and group 4 (p<0.01).The ARI score was distributed largely to 0 and 1. One instance of enamel fractures was recorded in group 1. The contact angle measurements suggested that the lowest value with the experimental primer containing (ACPS+BTSE) was, <5° followed by Transbond XT, 41.86±4.56°.ConclusionThe experimental silane primer systems were hydrophilic in nature and demonstrated higher adhesion strength compared to traditional orthodontic primers.     

The effects of self-etch bio-active dental adhesive systems on bacterial microleakage

The aim of this in vitro study was to evaluate the effects of bio-active and non-bio-active self-etch adhesive sytems on bacterial microleakage of class II box cavities with restoration margins in dentin. Two bio-active (Clearfil Protect Bond and F1 Bond II) and two nonbio-active (Clearfil SE Bond and Clearfil s3 Bond) adhesive systems were selected for the study. Eighty mesial and distal class II box cavities were prepared on fourty sound human third molar teeth. The teeth were then divided into four groups with 10 teeth in each group. Groups were restorated using different adhesive systems. The restored specimens were immersed into a culture medium containing streptococcus mutans for bacterial microleakage test. Serial sections of the specimens were used to evaluate the bacterial lekage by using light microscope. The data obtained from the test of bacterial microleakage was evaluated using 2-way mixed analysis of variance (p < 0.05). Statistical analysis showed significant differences between the groups (p < 0.05). Nevertheless it was observed that none of the tested adhesive systems including the bio-active ones were successfull in eliminating bacterial microleakage.     

Influence of Different Solvents on the Morphology of the Hybrid Layer Using Two-Step Etch-and-Rinse Adhesives

To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layer's morphology.

Four one-bottle etch-and-rinse adhesive systems containing different solvents—Group A: Scotchbond 1XT?– 3 M ESPE, Group B: XP – Bond? – Dentsply, Group C: Prime&;Bond NT® – Dentply, and Group D: One Coat Bond® - Coltène Whaledent—were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used.

The hybrid layer thickness average found was 3.23 µm (±0.53) in Group A, 3.13 µm (±0.73) in Group B, 2.53 µm (±0.50) in Group C, and 1.84 µm (±0.27) in Group D. Prime&;Bond NT® presented a more inconsistent hybrid layer.

The solvent seems to play a significant role in hybrid layer structure and thickness.     

Antimicrobial Activity of Ozone against Pathogenic Oral Microorganisms on Different Denture Base Resins

ABSTRACT

The present study aimed to evaluate the antimicrobial effect of gaseous ozone against specific oral pathogens on denture base resins. 1080 round samples were prepared (10mm-diameter, 2mm-thickness). Candida albicans, Streptococcus mutans, Streptococcus gordonii, and Aggregatibacter actinomycetemcomitans, polyamide-Deflex, heat-cured polymethyl-methacrylate (PMMA)-QC-20, and cold-cured-PMMA-Meliodent. The doses and durations: 25, 50 and 100µg/ml, 5, 10, 20, 30 minutes. For Cell viability (CV) MTT was used. 100µg/ml was most effective dose for C. albicans, S .gordonii, and A. actinomycetemcomitans were in heat-cured-PMMA and polyamide for S.mutans. For polyamide, lowest CV was 43% in S.mutans and A.actinomycetemcomitans. CV of heat-cure and cold-cure PMMA were 31% and 32% in S.gordonii, respectively. CV was similar for all resins and durations in S.mutans and A.actinomycetemcomitans and for polyamide for C.albicans and for heat-cure PMMA for S.gordonii. 30-min ozone application killed 80% of all microorganisms in all resins except for C.albicans in polyamide (65% cell death) and cold-cure PMMA (57% cell death). Optimal dose/duration combination was 100 µg/ml-10 min. Gaseous ozone can be considered as an effective cleansing agent for denture base resins.     

In vitro Streptococcus mutans biofilm formation on surfaces of chlorhexidine-containing dentin bonding systems

This in vitro study evaluated the influence of chlorhexidine diacetate (CDA) when blended within dentin bonding systems (DBSs) on Streptococcus mutans (S. mutans) biofilm formation.One commercially available 0.2% wt CDA-containing DBS (Peak Universal Bond) and five experimental 0.2% wt CDA-containing DBS formulations (experimental Adper Scotchbond 1XT plus experimental resins, R₂, R₃, R₄, R₅) were assessed vs their no-CDA containing counterparts. Twenty-eight DBSs disks were prepared for each group (6.4 mm×1.0 mm) and cured for 80 s at 800 mW/cm² in a nitrogen atmosphere. A modified Drip-Flow Reactor was used to grow S. mutans biofilms on specimen surfaces for 24 h and adherent, viable biomass was evaluated using a tetrazolium salt assay (MTT). Two specimens from each of the tested materials were processed with LIVE/DEAD stain and observed using laser confocal microscopy (CLSM) while two disks from each group were examined by using scanning electron microscopy (SEM).MTT assay, CLSM and SEM observations showed that CDA addition decreased, increased or did not change S. mutans biofilm formation. The lowest biofilm formation was obtained with Peak Universal Bond and R₅ (with and without CDA).It may be concluded that the chemical composition of DBSs determines their ability to promote or hamper biofilm formation. Therefore, CDA addition may be helpful in modulating biofilm formation provided that DBS formulation is tuned and optimized.     

Effect of a Self-Etching Adhesive System Containing a Novel Antimicrobial Polymer (QAMP) on Inhibiting Carious Lesions by Evaluating the Mechanical Properties of the Resin–Dentin Interface

The objective of this study was to assess the in vitro effect of a quaternary ammonium methacrylate polymer (QAMP) incorporated into a self-etching adhesive system on inhibiting caries by evaluating the mechanical properties of the adhesive interface. Twenty-four human third molars were distributed into: Clearfil? SE Bond containing 5% QAMP (experimental group), Clearfil? Protect Bond (positive control), and Clearfil? SE Bond (negative control). Teeth of each group were divided according to the method for producing artificial caries lesions: pH-cycling or microbiological assay. All samples were sectioned and polished in order to obtain hardness (H) and Young's modulus (E) values by nanoindentation test in the hybrid layer and dentin. Data were analyzed by ANOVA and Games Howell's post hoc test (α = 0.05). Regarding the hybrid layer, Clearfil? SE Bond containing QAMP demonstrated H and E values statistically higher than Clearfil? SE Bond in both pH-cycling and microbiological experiments. Considering dentin, Clearfil? SE Bond containing QAMP showed H and E values statistically higher than Clearfil? Protect Bond and Clearfil? SE Bond in the pH-cycling method and then Clearfil? SE Bond concerning the microbiological method. In general, Clearfil? SE Bond containing QAMP provided better mechanical properties for the resin–dentin interface after cariogenic challenges.     

The bonding effect of adhesive systems and bulk-fill composites to sound and caries-affected dentine

Purpose: To investigate the influence of adhesive type and increment thickness on shear bond strength of flowable bulk-fill resin composites compared with a flowable conventional resin composite, in both sound and caries-affected dentine.

Methods: Shear bond strength was tested in 100 extracted human molars with coronal dentine caries. Half of the teeth were restored with Adper? Easy Bond and the other half with Adper? Single Bond Plus. Bonded surfaces were restored with Filtek? Ultimate Flow and two bulk-fill composites (SDR and X-tra base) (n = 10 teeth for each subgroup). Restorations of 4 mm were performed with incremental or bulk-fill technique. The shear bond was determined and statistically analysed using three-way ANOVA and Bonferroni multiple comparison post hoc tests (p ≤ 0.05). Dentine–resin interfaces were evaluated by scanning electron microscopy.

Results: For both adhesives, the highest shear bond strength values were obtained for sound dentine. In sound dentine, the highest bond strength observed with Easy Bond when used in 2-mm increments of SDR. In caries-affected dentine, Single Bond in combination with SDR displayed significantly lower bond strength.

Conclusion: There was no significant difference in shear bond strength between the incremental and bulk-fill groups for molars with sound dentine when the etch-and-rinse adhesive system was used; however, for the self-etch adhesive system, incremental application caused higher bond strength than bulk application.     

A comparative study on monomer elution and cytotoxicity of different adhesive restoration materials

This study evaluated monomer release and cytotoxicity of different adhesive restoration materials used for dental restorations. The extracts (1, 2, and 7 days) of three types of adhesive dental restoration materials, [Quixfill (QF), Silorane Restorative (SR), and Ketac N 100 Restorative (KR)], and the adhesive resins, [XP Bond (XP), Silorane Primer (SP), Ketac N 100 Primer (KP), and Silorane Bond (SB)] were analyzed using high performance liquid chromatography/mass spectrometry (HPLC-MS). The cytotoxicity levels were determined at different time points (24, 48, and 72 h) of cell culture using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay. All adhesive resin materials showed monomer release at varying amounts with the highest release after 7 days. The lowest amount of release was observed in QF and the highest with KP. Bis-Phenol A (BPA) was not detected in SP and KR that contain bisphenol-A diglycidyl ether dimethacrylate (bis-GMA). Decamethylpenthasiloxane (D5) was not eluted from SR. Except for SR and QF, all other adhesive restoration materials showed different degrees of toxicity along with different monomer release kinetics. The correlation between the monomer release and cytotoxicity of the materials indicated that the cytotoxicity of the materials increased with the monomer release (Spearman’s rho correlation coefficient – r). The correlation after 48 h was statistically significant (r = ?0.342, p = 0.017).     

Adhesion of cast metal alloy and lithium disilicate copings luted to different core build-up materials with self-adhesive resin cement

This study evaluated the shear bond strength of two coping materials (non-nickel chrome-based cast alloy and lithium disilicate ceramic (IPS Empress) to four different core foundation materials (resin composite, cast metal alloy, lithium disilicate, and dentin), luted with adhesive resin cement (RelyX Unicem). Specimens (N = 56) were fabricated and divided into eight groups (n = 7 per group). Each coping material was luted with self-adhesive resin cement (RelyX Unicem) to the core materials. Bond strength was measured in a Universal Testing Machine (0.5 mm/min). Data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s HSD tests (alpha = 0.05). Both core (p = 0.000) and coping material type (p = 0.000) significantly affected the mean bond strength (MPa) values. Interaction terms were also significant (p = 0.001). The highest bond strength results were obtained when lithium disilicate was bonded to lithium disilicate (21.48) with the resin cement tested. Lithium disilicate in general presented the highest bond results when bonded to all core materials tested (16.55–21.38) except dentin (3.56). Both cast alloy (2.9) and lithium disilicate (3.56) presented the lowest bond results on dentin followed by cast-alloy-cast alloy combination (3.82).     

Analysis of Damage on the Streptococcus mutans Immersed in Ozonated Water: Preliminary Study for Application as Mouth Rinse

Ozonated water has been demonstrated to induce significant results in terms of the elimination of microorganisms. The present study assessed the damage to Streptococcus mutans after exposure to ozonated water; the ozone generator was adjusted to provide an outlet concentration of 60 mg/L, the samples were submitted to different ozonation times 1, 2, 4, 6, and 10 mi. Scanning electron microscopy and atomic force images were obtained to identify damage to the bacteria, followed by reactive oxygen species (ROS) evaluation and microbial viability. The results showed a significant reduction in viability and the images evidenced the generation of gaps on the microbial wall and surface layer alterations. Ozone can induce significant damage to S. mutans, thus suggesting that the use of ozonated water to prevent carious lesion formation is extremely promising.