Effect of different fabrication methods of occlusal devices on periradicular stress distribution: A photoelastic analysis.

STATEMENT OF PROBLEM: Investigations on the effectiveness of new methods for optimizing the fabrication of oral devices are lacking. PURPOSE: The purpose of this in vitro study was to evaluate stress distribution with photoelastic analysis in the periradicular area of teeth supporting occlusal devices fabricated by 5 different processes. MATERIAL AND METHODS: The occlusal devices were fabricated by vacuum thermoforming, heat-polymerized acrylic resin, chemical polymerized acrylic resin, 3-dimensional printing, and milling (computer-aided manufacturing). The devices were evaluated regarding initial fit, number of adjustments for passive fit, and stress distribution under 100-N and 400-N loads in the periradicular locations of posterior teeth. RESULTS: The 3-dimensional printing device did not require any adjustment for initial adaptation to the photoelastic model and presented a little friction with the model. The heat-polymerized acrylic resin device did not seat initially, requiring more sites of adjustment until passive adaptation. At 100-N and 400-N loads, the use of the computer-aided manufacturing occlusal device resulted in the lowest stresses in periradicular areas (0.744 and 1.583, respectively), and the 3-dimensional printing occlusal device produced the highest stresses with a 400-N load application (2.427). The lowest mean of fringe pattern was observed for the computer-aided manufacturing device, and the highest mean of fringe pattern was observed for the vacuum thermoforming device. CONCLUSIONS: The computer-aided design and computer-aided manufacturing milled occlusal device presented the best initial adaptation and transferred lower stresses to the periradicular areas than the other evaluated devices.

Failure load and shear bond strength of indirect materials bonded to enamel after aging.

This study evaluated the failure load and the shear bond strength of 4 block materials indicated for computer-aided design/computer-aided manufacturing (CAD/CAM) of dental veneers: lithium disilicate, feldspathic ceramic, polymer-infiltrated ceramic, and nanohybrid composite. The tested hypothesis was that the material that combined an elastic modulus similar to that of enamel with the highest bond strength values would present the highest failure load. From prefabricated CAD/CAM blocks, disc-shaped specimens (6.0 × 0.7 mm; n = 10) and cylinders (2.4 × 2.5 mm; n = 10) were fabricated for load-to-failure and shear bond strength tests, respectively. Materials were adhesively bonded to flattened bovine enamel surfaces, stored in distilled water at 37°C for 90 days, and subjected to thermocycling (2000 cycles of 5°C to 55°C). Discs of restorative material were bonded to enamel and subjected to an increasing load that was applied perpendicular to the bonding interface until catastrophic failure occurred. A chisel was used to apply an increasing load parallel to the adhesive interface between the enamel and a cylinder of restorative material to measure shear bond strength. Data were subjected to a Weibull analysis and 1-way analysis of variance followed by a Tukey post hoc test (α = 0.05). The type of restorative material significantly affected the (mean [SD]) failure load when bonded to enamel (P = 0.006): polymer-infiltrated ceramic (1167.9 [310.2] N) = feldspathic ceramic (1115.0 [382.0] N) = nanohybrid composite (1067.3 [251.0] N) > lithium disilicate (786.2 [304.5] N). The type of restorative material also significantly affected the (mean [SD]) bond strength to enamel (P < 0.001): lithium disilicate (32.81 [11.19] MPa) = polymer-infiltrated ceramic (27.04 [7.65] MPa) > feldspathic ceramic (21.11 [9.16] MPa) > nanohybrid composite (9.08 [3.66] MPa). The polymer-infiltrated ceramic presented the best performance when bonded to enamel.

Effect of staining and repeated firing on the surface and optical properties of lithium disilicate.

OBJECTIVE: Evaluate the effect of staining and repeated firings on color, translucency and surface proprieties of CAD/CAM lithium disilicate (LD). MATERIAL AND METHODS: One hundred eighty LD discs were made (ISO 6872) and distributed in different groups (n = 20): control (CO)-no treatment; single-step characterization (SC)-crystallization and staining fired together; and double step characterization (DC)-crystallization and then staining. The samples were submitted to two, four, or six firings, resulting in nine groups: COII, COIV, COVI, SCII, SCIV, SCVI, DCII, DCIV, and DCVI. The color and translucency were measured by a reflectance spectrophotometer. Surface roughness (Ra) and Vickers nano-hardness were also measured. ANOVA and Tukey statistical tests were used (α = .05). RESULTS: Only CO and DC demonstrated significant color alterations (ΔE00 > 1.8). SC and DC did not show changes in translucency by the number of firings (P > .05); however, for CO (P = .02) these values increased. Nano-hardness was similar in all groups (P > .05). Ra values indicated differences due to the type of characterization (SC presented the highest values) and number of firings (CO and DC groups) (P < .01). CONCLUSION: SC promoted color, translucency, and roughness stability after repeated firings. CLINICAL SIGNIFICANCE: The single characterization technic in CAD/CAM lithium disilicate presents good color, translucency, and hardness stability, which promote predictable results to monolithic restoration.

Mechanical performance of monolithic materials cemented to a dentin-like substrate.

STATEMENT OF PROBLEM: Studies on the mechanical behavior of restorative materials bonded to tooth structure and considering the properties of the material and the bonding between both substrates are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the hardness, fracture toughness, load-to-failure, cyclic fatigue, and stress distribution of 4 computer-aided design and computer-aided manufacturing (CAD-CAM) materials when bonded to a substrate similar to dentin (G10). MATERIAL AND METHODS: Disks (11×1.2 mm) of lithium disilicate (LD), feldspathic ceramic (FC), polymer-infiltrated ceramic (PC), and a nanohybrid composite resin (NC) were fabricated (n=45) and had their surfaces polished. Microhardness was measured by the Knoop indentation (19.61 N, 12 seconds, n=5). Indented specimens were subjected to biaxial flexural strength testing, and the fracture origin defect was measured to calculate fracture toughness (n=5). Forty disks from each material were adhesively bonded to G10. Half of the specimens were subjected to load-to-failure testing, and remaining specimens (n=20) were subjected to cyclic fatigue (400 N, 106 cycles). The test was suspended every 200 000 cycles, and specimens were examined for cracks, debonding, or catastrophic failure. Obtained data were evaluated by analysis of variance and the Tukey post hoc test (α=.05). Weibull analysis was also performed. A 3D model of the tested specimens was constructed in a design software program, and the stress distribution was evaluated by finite element analysis, with the application of a 100-N load normal to the restoration surface. RESULTS: Hardness values with statistically significant differences were LD (540.4)>FC (474.6)>PC (176.6)>NC (58.26). Fracture toughness vales (MPa.m1/2) and statistical significance were as follows: LD (2.25)=NC (2.46)>FC (1.14)=PC (1.18). Load-to-failure values (N) were LD (2881.6)=FC (2881.6)=PC (3200.6)>NC (2367.5). A specimen each of LD and NC fractured during the fatigue test, and LD and PC had a high percentage of subsurface cracks (55% and 75%, respectively). The FC had the lowest debonding rate after load-to-failure testing and no catastrophic fractures or cracks during fatigue. CONCLUSIONS: The materials tested had different mechanical behaviors depending on the tests performed. Feldspathic ceramic had the best fatigue behavior when cemented to a dentin-like substrate.

Body composition parameters can better predict body size dissatisfaction than body mass index in children and adolescents.

PURPOSE: Recent studies suggest that body mass index is not a reliable enough measurement for body composition in individuals, particularly in older and younger people. However, most research on body image has used the body mass index (BMI) as a physiological predictor of body satisfaction, particularly in children. The aim of this study was to investigate whether body composition is a better predictor of body size dissatisfaction in children than BMI. METHODS: This is a cross-sectional study. Healthy children and adolescents aged 5-19 years, sex male and female, were recruited using a convenience sample in Brazil. BMI was measured according to the international standardization method and body composition was measured by bioelectrical impedance analysis (BIA) with a portable device model (BIA InBodyS10 multi-frequency, USA). Body size dissatisfaction was assessed using the Kakeshita's Figure Rating Scale for Brazilian Children. Data were analyzed with logistic regression analysis. RESULTS: A total of 547 participants were evaluated, including 54% females and 67% Caucasian, with a mean age of 11.4 ± 3.8 years. The mean BMI was 20.5 ± 4.6 kg/m2, and the mean percentages of fat and lean mass were 23.01 ± 10.59% and 72.84 ± 10.03%, respectively. In the multivariable model, only body composition was significantly associated with body size dissatisfaction (odds ratio: 1.849 (1.085-3.149, p = 0.024) and 1.828 (1.043-3.202, p = 0.035), respectively). CONCLUSIONS: Body composition measures can better predict body size dissatisfaction in children and adolescents than BMI. This result may be relevant for the design of future studies on physiological indicators and body satisfaction. LEVEL OF EVIDENCE: Level V, cross-sectional study.

Leishmanicidal candidate LASSBio-1736, a cysteine protease inhibitor with favorable pharmacokinetics: low clearance and good distribution.

1. LASSBio-1736 ((E)-1-4(trifluoromethyl) benzylidene)-5-(2-4-dichlorozoyl) carbonylhydrazine) is proposed to be an oral cysteine protease leishmanicidal inhibitor. 2. This work aimed to investigate plasma pharmacokinetics, protein binding and tissue distribution of LASSBio-1736 in male Wistar rats. 3. LASSBio-1736 was administered to male Wistar rats at doses of 3.2 mg/kg intravenously and 12.6 mg/kg oral and intraperitoneal. The individual plasma-concentration profiles were determined by HPLC-UV and evaluated by non-compartmental and population pharmacokinetic analysis (Monolix 2016R1, Lixoft). Tissue distribution was evaluated after iv injection of 3.2 mg/kg drug by non-compartmental approach. 4. After intravenous administration, Vdss (1.79 L/kg), t ½ (23.1 h) and CLtot (56.1 mL/h/kg) were determined, and they were statistically similar (α =0.05) to oral and intraperitoneal pharmacokinetic parameters. The plasma profiles obtained after intravenous, oral and intraperitoneal administration of the compound were best fitted to a three-compartment and one-compartment open model with first-order absorption. 5. The intraperitoneal and oral bioavailability were around 40 and 15%, respectively. 6. Liver, spleen and skin tissues showed penetration of 340, 130 and 40%, respectively, with t ½ like plasma values. 7. LASSBio-1736 protein binding was 95 ± 2%. 8. The t ½, CLtot and tissue distribution of the compound agreed with the desired drug characteristics for leishmanicidal activity.

Histological evaluation of the repair process of replanted rat teeth after storage in resveratrol dissolved in dimethyl sulphoxide.

BACKGROUND/AIM: The storage media is directly related to the prognosis of avulsed teeth, with resveratrol drawing attention due to its antioxidant and anti-inflammatory proprieties. The aim of this study was to evaluate the repair process in rat teeth following delayed replantation after storage in resveratrol (R) dissolved in dimethyl sulphoxide (DMSO). MATERIALS AND METHODS: The upper right central incisors of 36 rats were divided into 4 groups. In group I, the teeth were extracted and immediately replanted. Group II teeth were stored in 50 mL R+DMSO (0.0512 g/mL), whereas group III teeth were stored in 50 mL pure DMSO, both for a period of 60 minutes. The teeth of group IV were stored dry for 60 minutes. The teeth of groups II, III and IV were then replanted, and the animals were euthanized after 60 days. Longitudinal histological cuts were HE stained for histomorphometric analysis of the periodontal ligament, alveolar bone, cementum and dentin. RESULTS: The analysis of HE stained histological sections showed the following statistical differences: the acute inflammatory process in the epithelial insertion was less prominent in group II than in group III; the organization of the periodontal ligament was better in group I, while the intensity and extension of acute inflammation in the periodontal ligament were better in group I, and worse in group III; the chronic inflammatory infiltrate was less in groups I and IV, and the depth and extent of resorption, as well as the repair of root resorption, were better in group I. CONCLUSIONS: Storage in R+DMSO solution did not inhibit root resorption after delayed replantation in rat teeth. It is concluded that pure DMSO is not a suitable transport medium for avulsed teeth.

Fracture load of complete-arch implant-supported prostheses reinforced with nylon-silica mesh: An in vitro study.

STATEMENT OF PROBLEM: Complete-arch implant-supported prostheses without a framework have a high risk of failure: a straightforward and inexpensive reinforcement material, such as nylon mesh, could improve their longevity. PURPOSE: The purpose of this in vitro study was to evaluate a nylon-silica mesh compound on the fracture strength of acrylic resin and the fracture load of complete-arch implant-supported prostheses. MATERIAL AND METHODS: Twenty-four complete mandibular arch implant-supported prostheses were divided into 2 groups according to cantilever length (molar and premolar) and subdivided into another 2 subgroups according to the presence or absence of reinforcing mesh. The specimens were submitted to a maximum load-to-fracture test in a universal testing machine, with a 100-N load cell, a 2 mm/min crosshead speed, and a spherical metal tip diameter of 4 mm at different points (molar and premolar). These were submitted to 1-way analysis of variance for repeated measurement and the post hoc Tukey multiple comparison test (α=.05). RESULTS: The mean maximum load ±standard deviation for the molar group was 393.4 ±95.0 N with reinforcement and 305.4 ±76.3 N without reinforcement (P=.02); and for the premolar group was 1083.3 ±283.7 N with reinforcement and 605.3 ±90.5 N without reinforcement (P=.001). CONCLUSIONS: Reinforcement with nylon mesh increased the mean maximum load of implant-supported complete-arch prostheses at both cantilever lengths. The cantilever to the premolar (5 mm) presented the highest maximum load values to fracture.

Influence of plasma-based dry etching on the bond strength of Y-TZP ceramic.

The aim of this study was to evaluate the bond strength between an yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic and a luting agent when submitted to plasma etching surface treatment before and after thermocycling (TC) with 3000 cycles of 5°C-55°C. The null hypothesis was that the surface treatments and thermocycling would not influence the bond strength. A total of 160 Y-TZP ceramic blocks in 2 sizes (10 size 1 and 10 size 2 blocks in each group) were distributed into 8 groups: group C (control), no surface treatment; group C-TC, TC without prior surface treatment; group SAO, sandblasting with aluminum oxide (Al2O3); group SAO-TC, sandblasting with Al2O3 followed by TC; group SAOS, sandblasting with silica-coated Al2O3; group SAOS-TC, sandblasting with silica-coated Al2O3 followed by TC; group PE, plasma etching; and group PE-TC, plasma etching followed by TC. In each group, size 1 blocks were cemented to size 2 blocks to fabricate specimens for microshear bond strength testing (n = 10 per group). Cementation followed surface treatments (except in control groups) and preceded any TC. All specimens were cemented using a luting agent that contained 10-meth-acryloyloxydecyl dihydrogen phosphate (MDP). The specimens were submitted to a microshear bond strength test and the means were analyzed with a 2-factor analysis of variance and Tukey test. Group PE showed the highest bond strength value before thermocycling (17.31 MPa). After thermocycling, the highest value was observed in the SAO-TC group (9.73 MPa), and statistically significant differences were observed between SAOS-TC and SAO-TC (P < 0.05) and PE-TC and SAO-TC (P < 0.05). Plasma etching improved the bond strength values between the Y-TZP ceramic and MDP-containing luting agent before thermocycling. After thermocycling, all groups showed lower bond strength values.

The influence of traumatic occlusion on the repair process for teeth following subluxation.

BACKGROUND/AIM: Traumatic occlusion (TO) can cause morphofunctional alterations that interfere in the homeostasis of the periodontium. The aim of this study was to assess the influence of TO on the periodontal repair process for teeth following subluxation. MATERIALS AND METHODS: Ninety Wistar rats aged 12 weeks were divided into three groups: control (C), subluxation (S) and subluxation with traumatic occlusion (S+TO). Subluxation was created with an impact force of 900 cN applied by a tensiometer and TO was created with a direct composite resin filling. Healing after two experimental periods of 7 and 21 days was assessed histologically. The Kruskal-Wallis and Dunn post hoc tests were used for group comparison. RESULTS: At 7 days, there was a significant increase in periodontal ligament (PDL) width and amorphous fundamental substance, as well as a significant bone area reduction in groups S and S+TO. After 21 days, there was a significant PDL width increase in group S+TO, and in the percentage of collagen fibres in group S, whereas group S+TO showed a 52% bone area reduction compared to the same group at 7 days. Subluxation with or without TO caused only superficial root resorption. However, only group S+TO showed damage to the repair process of resorbed root areas after 21 days. CONCLUSION: TO can increase damage to the PDL after subluxation and it can also delay the repair process after PDL damage.

Effect of interim cement application on bond strength between resin cements and dentin: Immediate and delayed dentin sealing.

STATEMENT OF PROBLEM: Despite the advances in materials and techniques, adhesion to dentin is challenging because of the complex composition of dentin's mineral, organic, and fluid phases. PURPOSE: The purpose of this in vitro study was to evaluate the bond strength of 2 different resin cements (conventional and self-adhesive) with or without previous dentin sealing and the effect of interim cement. MATERIAL AND METHODS: Forty-five molars were embedded into acrylic resin blocks and a flat dentin surface was exposed. Twenty teeth (n=5 per group) were treated with the conventional resin cement associated with etch-and-rinse or self-etch adhesive approaches, applied before (immediate dentin sealing) or after (delayed dentin sealing) the application/removal of interim cement. Another 25 teeth (n=5, per group) were treated with self-adhesive resin cement with (self-etch mode [immediate dentin sealing or delayed dentin sealing]) or without adhesive application. Furthermore, in the self-adhesive resin cement group, the application of polyacrylic acid for dentin etching before cementation was evaluated. Composite resin blocks were cemented onto flat, treated dentin surfaces, and the assemblies were sectioned into bar-shaped specimens for microtensile bond strength testing. The data were subjected to 1-way ANOVA followed by the post-hoc Tukey test (α=.05). The failure patterns were classified as cohesive, adhesive, or mixed. RESULTS: The application of adhesive before interim cement (immediate dental sealing) promoted the highest values of bond strength for both resin cements (P<.001). For self-adhesive resin cement, polyacrylic acid-enhanced bond strength after the application of interim cement. CONCLUSIONS: The application of dental adhesive immediately after tooth preparation (immediate dentin sealing) and before the use of an interim cement promoted the highest values of bond strength to dentin with the resin cements tested.

Fluorination of zirconia surfaces impairs bonding to resin cement.

The aim of this study was to evaluate the fluorination of a zirconia surface as an alternative treatment for bonding to resin cement; the null hypothesis was that fluorination would not improve adhesion values. Four different surface treatments were performed on the surface of yttria-stabilized tetragonal zirconia polycrystal discs (N = 80): Ctrl (control), no treatment; SB, sandblasting with 50-µm alumina particles; SBS, sandblasting with 30-µm silica-modified alumina particles and application of silane; and SF, fluorination with sulfur hexafluoride-containing plasma. The surface roughness (Ra) of each group was measured after surface treatment. Dual-cure resin cement was inserted into cylindrical matrices, and 2 cylinders (0.7 × 3.0 mm) were cemented to each ceramic disc surface. Half of the specimens were thermocycled, and microshear bond strength tests were performed. The SBS group presented the highest median values of surface roughness, while the Ctrl group presented the lowest values. Without thermocycling, the median bond strength of the SF group was statistically similar to those of the sandblasted groups (SB and SBS). After thermocycling, all specimens from the Ctrl and SF groups presented as failures, and their bond strength was considered null. The SB and SBS groups presented decreased bond strengths. Failures were classified as predominantly mixed at the adhesive interface. The fluorination of the zirconia ceramic surface with sulfur hexafluoride as a source gas did not promote stable bond strengths to resin cement. After aging, adhesion was possible only after sandblasting of the ceramic surface.

Treatment of Extrusive Luxation in Permanent Teeth: Literature Review with Systematic Criteria.

INTRODUCTION: Extrusive luxation is a traumatic dental injury caused by the action of oblique forces, characterized by partial displacement of the tooth out of its socket. The ideal treatment for this type of trauma involves repositioning the tooth in its socket. However, in cases where the tooth cannot be repositioned, different options may be considered, such as intentional reattachment and orthodontic intrusion. The aim is to review the literature on the extrusive luxation of permanent teeth while assessing the risks of complications for two methods of delayed treatment for extrusive luxation. MATERIALS AND METHODS: An electronic search from August 2005 to August 2014 was performed by two reviewers independently, and conflicts were resolved by a third reviewer. The databases used were PubMed and Scopus; the reviewers performed a manual search of the following journals: Dental Traumatology, American Journal of Orthodontics, and Clinical Oral Investigation. RESULTS: After removing the duplicate studies, 328 articles were found. Out of these, 321 were rejected as not addressing the proposed research topic. In addition, five articles were excluded because apical repositioning was used for treatment. Therefore, four articles formed the basis of the study. CONCLUSION: Factors, such as root formation, the degree of tooth mobility, and the presence of tooth vitality were decisive for the choice of treatment. However, both treatments were effective and showed favorable results, i.e., without periodontal and root damage. CLINICAL SIGNIFICANCE: Knowledge of the risks of complications among two methods of delayed treatment for extrusive luxation, as well as other important factors to take into consideration when choosing a treatment assists dentists in improving the prognostic.

Effect of an experimental silica-nylon reinforcement on the fracture load and flexural strength of bisacrylic interim partial fixed dental prostheses.

STATEMENT OF THE PROBLEM: Materials used in the fabrication of interim restorations usually have mechanical properties inferior to those used in definitive prostheses. Various techniques may be used to reinforce these materials. PURPOSE: The purpose of this in vitro study was to evaluate the fracture strength of interim partial fixed dental prostheses (FDPs) with and without an experimental silica-nylon reinforcement placed in different orientations (horizontal or vertical) before and after thermocycling and to evaluate the flexural strength of the bisacrylic resin used for fabricating these prostheses. MATERIAL AND METHODS: For fracture strength testing, 72 four-unit interim partial FDPs were fabricated from bisacrylic resin and divided into 3 groups: no reinforcement, horizontal reinforcement, and vertical reinforcement. Half of the specimens from each group were thermocycled before testing (1000 cycles between 5°C and 55°C) (n=12). An increasing load was applied to the center of the prosthesis until fracture. The flexural strength of bisacrylic resin reinforced with the experimental mesh was measured by using a 3-point bending test with 25×10.5×3.3 mm bars of resin, with or without thermocycling. The results were evaluated with analysis of variance and Kaplan-Meier survival analysis (α=.05). RESULTS: The results showed that incorporating the experimental silica-nylon reinforcement in a horizontal orientation provided the highest values of fracture strength for the 4-unit partial FDPs. Reinforcement also enhanced the flexural strength values of bisacrylic resin bars. CONCLUSION: Silica-nylon reinforcement is an effective method of increasing the strength of interim restorations.

Orthodontic Extrusion as Treatment Option for Crown-Root Fracture: Literature Review with Systematic Criteria.

OBJECTIVE: To review the literature searching for a consensus for the choice of orthodontic extrusion as treatment for crown-root fracture. MATERIALS AND METHODS: An electronic search was performed in the databases PubMed, Cochrane Central Register of Controlled Trials and Scopus and a manual search of the Journal Dental Traumatology. RESULTS: Forty articles were found in PubMed and 38 in Scopus and after removal of duplicate sample 51 contained articles. Of these, 48 were excluded for not having orthodontic treatment, no follow-up or follow-up less than 6 months, or not report the presence of crown-root fracture. In manual search in Dental Traumatology 20 articles were found, but none of them met the prerequisites established. So, three articles formed the basis of the study. CONCLUSION: The choice of how to treat orthodontic extrusion of crown-root fracture was effective and stable, without root and periodontal changes. Factors, such as root formation and presence of pulp vitality were decisive for determining the stages of treatment, however, there is no consensus based on scientific evidence about these protocols.

Microtensile bond strength between indirect composite resin inlays and dentin: effect of cementation strategy and mechanical aging.

PURPOSE: To evaluate the microtensile bond strength of indirect resin composite inlays to dentin using two cementation strategies, before and after mechanical aging. MATERIALS AND METHODS: Standardized inlay cavities (bucco-lingual width: 3 mm; depth: 4 mm) were prepared in 32 human premolars. The teeth were embedded in self-curing acrylic resin up to 3 mm from the cementoenamel junction, impressions were made using a polyvinyl siloxane material, master dies were obtained using type 4 stone, and inlay composite resin restorations were fabricated (Sinfony, 3M ESPE). The teeth were randomly allocated into 4 groups according to the cementation strategy (conventional [C] and simplified [S]) and aging (mechanical cycling [MC] and not aged): C[G1]: Adper SingleBond + RelyX ARC without aging; CMC[G2]: conventional cementation + mechanical cycling (106 cycles, 88 N, 4 Hz, ± 37°C); S[G3]: self-adhesive resin cement (RelyX U-100) without aging; SMC[G4] self-adhesive cementation + mechanical cycling. Intaglio surfaces of composite inlays were treated by tribochemical silica coating in G1 and G2, while G3 and G4 received no surface treatment. Non-aged specimens were stored in a moist environment at ca 37°C for the same period as MC (3 days). Non-trimmed beam specimens (bonding area = 1 mm²) were produced by serial cutting, and microtensile testing was performed (0.5 mm/min). RESULTS: Two-way ANOVA showed that the microtensile bond strength was affected only by cementation strategy (p < 0.0001). Tukey's test showed that groups G1 (35.1 ± 9.1) and G2 (32.7 ± 10.7) presented significantly higher bond strength values than G3 (8.7 ± 6.3) and G4 (5.2 ± 4.6). CONCLUSION: The use of a conventional adhesive technique and tribochemical silica coating resulted in higher µTBS than the one-step simplified cementation, even after mechanical cycling.

Histological changes in pulp-dentin complex in tooth subjected to traumatic occlusion and subluxation.

Background: This study evaluated the influence of traumatic occlusion in the dentin-pulp complex a molar teeth submitted to subluxation. Material and methods: Ninety Wistar rats were divided into groups Naïve (N), Subluxation (S) and Subluxation with traumatic occlusion (STO) and submitted to histological analysis after 7 and 21 days. A quantitative analysis was submitted to one-way ANOVA and Tukey's post-hoc test, and Chi-square and Bonferronís post-hoc test. Results: S and STO showed a significant increase in blood vessels area (p < 0.0005), amorphous fundamental substance (p < 0.0005) and reactionary dentin formation (p < 0.0005), as well as a decrease in the nuclear profile (p < 0.0005), odontoblast layer (p = 0.013 and p < 0.0005) by day 7 when compared with N. These changes normalized by day 21, except for the reactionary dentin (p < 0.0005) in both S and STO groups. Interestingly, the STO group exhibited significant changes in the increase of pulp calcification (p < 0.0005), presence of tubules with nuclei (p < 0.0005), and inflammatory infiltrate (p < 0.0005), as well reduction of nuclear profile (p < 0.0005), odontoblast layer (p < 0.0005) compared with N and S at day 21. Conclusions: STO impaired the defence response and decreased pulp regeneration capacity by increasing the inflammatory infiltrate and pulp calcification, and decreasing the nucleated cell number in the odontoblast layer and central pulp.

Zirconia-porcelain bonding: effect of multiple firings on microtensile bond strength.

PURPOSE: To determine the bond strength between zirconia and porcelain with varying numbers of veneer firing cycles. MATERIALS AND METHODS: Fifty specimens of zirconia veneered with feldspathic ceramic were submitted to one (1-firing), two (2-firings), three (3-firings), four (4-firings), or five (5-firings) firing cycles to sinter the porcelain. After the respective number of firings, the specimens were embedded into acrylic resin and sectioned into bars with a 1-mm2 cross-sectional area. The microbars were bonded to a special device and attached to a universal testing machine (Emic DL 1000). Microtensile bond strength testing (MTBS) was performed at 0.5 mm/min. The maximum load for fracture was recorded (N) and the microtensile bond strength was calculated in MPa. Data were analyzed using one-way ANOVA and Tukey's test (α = 0.05). The Weibull modulus and characteristic strength was also calculated for each experimental group. RESULTS: Specimens submitted to a single firing cycle presented the lowest bond strength values (14.1 MPa), two firing cycles provided intermediate bond strength values (15 MPa) and the other groups presented equivalently high values (18.1 - 18.4 MPa). The Weibull modulus did not change between the groups. CONCLUSION: More than three firing cycles of a veneer ceramic provided higher bond strengths between zirconia and the veneering ceramic.

Bond Strength and Surface Roughness of Two Ceramics After Metal Bracket Debonding.

Objective: The aims of this study were to compare the bond strength between metallic brackets and two different glass ceramics and to evaluate the ceramic surface roughness after different finishing protocols. Methods: The surface roughness of lithium disilicate and resin matrix ceramic samples was measured (initial). All samples were treated with hydrofluoric acid and silane and bonded to metallic brackets with orthodontic cement adhesive. Shear bond strength tests were performed using a universal testing machine (n=12). The surface roughness was measured again (intermediate, n=6) after removing the remaining cement adhesive from the ceramic surfaces with a diamond or 24-blade bur after polishing the ceramic surfaces (final, n=6). Results: The resin matrix ceramic had the highest bond strength. The rotatory instrument used for the removal of cement adhesive did not affect the surface roughness of the resin matrix ceramic or lithium disilicate (p=0.985 and p=0.504, respectively), but did affect the evaluation time (p<0.001) for both restorative materials. The intermediate roughness was the highest. For the resin matrix ceramic, polishing promoted a final surface roughness similar to the initial condition; however, changes in the surface shape of this ceramic could be visibly observed when using a 24-blade bur. Conclusion: The bond strength of metallic brackets bonded on resin-matrix ceramics is higher than bonding on lithium disilicate. The use of diamond burs for the removal of the remaining adhesive from the resin matrix ceramics is highly recommended.

Fiber post cementation strategies: effect of mechanical cycling on push-out bond strength and cement polymerization stress.

PURPOSE: To evaluate the effect of mechanical cycling and cementation strategies on the push-out bond strength between fiber posts and root dentin and the polymerization stresses produced using three resin cements. MATERIALS AND METHODS: Eighty bovine mandibular teeth were sectioned to a length of 16 mm, prepared to 12 mm, and embedded in self-curing acrylic resin. The specimens were then distributed into 8 groups (n = 10): Gr1 - Scotchbond Multi Purpose + RelyX ARC; Gr2 - Scotchbond Multi Purpose + RelyX ARC + mechanical cycling; Gr3 - AdheSE + Multilink Automix; Gr4 - AdheSE + Multilink Automix + mechanical cycling; Gr5 - phosphoric acid + RelyX U100 (self-adhesive cement); Gr6 - phosphoric acid+ RelyX U100 + mechanical cycling; Gr7 - RelyX U100; Gr8 - RelyX U100 + mechanical cycling. The values obtained from the push-out bond strength test were submitted to two-way ANOVA and Tukey's test (p = 0.05), while the values obtained from the polymerization stress test were subjected to one-way ANOVA and Tukey's test (α = 0.05). RESULTS: Mechanical cycling did not affect the bond strength values (p = 0.236), while cementation strategies affected the push-out bond strength (p < 0.001). Luting with RelyX U100 and Scotch Bond Multi Purpose + RelyX ARC yielded higher push-out bond strength values. The polymerization stress results were affected by the factor "cement" (p = 0.0104): the self-adhesive cement RelyX U100 exhibited the lowest values, RelyX ARC resulted in the highest values, while Multilink Automix presented values statistically similar to the other two cements. CONCLUSION: The self-adhesive cement appears to be a good alternative for luting fiber posts due to the high push-out bond strengths and lower polymerization stress values.