Photoelastic stress analysis of different types of anterior teeth splints.

BACKGROUND/AIMS: Traumatic dental injuries are highly prevalent and are considered an important health problem. The aim of this study was to evaluate the in vitro stress distribution around simulated traumatized teeth subjected to different types of splints by photoelastic analysis. MATERIALS AND METHODS: For each group, five models of maxillary and mandibular arches were made in photoelastic resin using prefabricated teeth models, which were fixed and adjusted in a semi-adjustable articulator. All splints were bonded with composite resin on the labial surfaces of the maxillary central incisors, the lateral incisors and the canine teeth, simulating trauma to the 11. The groups were divided according to the type of splint: control-without splint; rigid-brackets and 0.021 × 0.025 inch stainless steel wire; semi-rigid-brackets and 0.016 × 0.016 inch cobalt-chromium wire; fiber-fiberglass ribbon; and flexible-nylon thread. The groups were submitted to an occlusal force in a special device attached to a universal test machine in balanced, protrusive, and lateral occlusions. Then, the incisal edge of the 11 was ground to simulate infra-occlusion, and the tests were performed again. Five points were analyzed around tooth 11 with a polariscope, and the data were submitted to ANOVA and Tukey tests at a 5% level of significance. RESULTS: When centric occlusion was analyzed by comparing normal occlusion to infra-occlusion, all groups showed high stress values in infra-occlusion with statistical differences-except for the control group. When lateral occlusion was analyzed, the nylon splint showed lower statistical differences compared with the control, fiberglass, and rigid splint groups, which did not differ between each other. The semi-rigid splint did not differ from any group. CONCLUSIONS: Fiberglass and semi-rigid splints showed better stress distribution around the traumatized tooth under occlusal loads. The nylon splint showed characteristics of non-stress distribution.

Evaluation of bond strength durability on bleached human dentin.

This study evaluated the effect of aging on the microtensile bond strength (µTBS) between composite resin and human dentin bleached with 35% hydrogen peroxide (HP) or 10% carbamide peroxide (CP). Thirty intact extracted third molars were selected for the study. After the dentin surface was exposed, the smear layer was abraded with silicon carbide paper to ensure standardization. The teeth were randomly divided into 3 groups: 1 (G1), no treatment (control); 2 (G2), dentin bleached with CP (at-home bleaching); and 3 (G3), dentin bleached with HP (in-office bleaching). G2 and G3 were bleached according to the manufacturers' instructions and stored in distilled water for 21 days. The teeth in all 3 groups were then bonded with a dental bonding agent and nanohybrid composite resin. Each tooth was sectioned and divided into groups to allow evaluations at 3 time periods: 24 hours, 6 months, and 12 months. The specimens were stored in distilled water at 37°C ± 1°C until use. The µTBS of the specimens was tested on a universal testing machine. Fracture mode analysis was performed with a stereoscopic loupe. The data were analyzed statistically by 2-way analyses of variance and Tukey tests. After 24 hours, G3 had a significantly lower mean [SD] µTBS value (20.00 [5.67] MPa) than G1 (31.14 [8.83] MPa), but their means were statistically similar at 6 months (29.42 [7.72] MPa vs 22.97 [7.48] MPa, respectively). Tukey tests revealed that there was no statistically significant change in µTBS over time for G2 or G3. After 12 months of aging, only G1 specimens showed statistically lower µTBS values compared with the 24-hour time period (P < 0.05). Based on the results, the durability of the bond between composite resin and dentin is not affected by the choice of bleaching treatment.

Push-Out Bond Strength of Restorations with Bulk-Fill, Flow, and Conventional Resin Composites.

The aim of this study was to evaluate the bond strengths of composite restorations made with different filler amounts and resin composites that were photoactivated using a light-emitting diode (LED). Thirty bovine incisors were selected, and a conical cavity was prepared in the facial surface of each tooth. All preparations were etched with Scotchbond Etching Gel, the Adper Scotchbond Multipurpose Plus adhesive system was applied followed by photoactivation, and the cavities were filled with a single increment of Filtek Z350 XT, Filtek Z350 XT Flow, or bulk-fill X-tra fil resin composite (n = 10) followed by photoactivation. A push-out test to determine bond strength was conducted using a universal testing machine. Data (MPa) were submitted to Student's t-test at a 5% significance level. After the test, the fractured specimens were examined using an optical microscope under magnification (10x). Although all three composites demonstrated a high prevalence of adhesive failures, the bond strength values of the different resin composites photoactivated by LED showed that the X-tra fil resin composite had a lower bond strength than the Filtek Z350 XT and Filtek Z350 XT Flow resin composites.

Shelf life effects on the bond strength and microhardness of self-adhesive resin cements.

Background: Among the main advantages of self-adhesive resin cements comprise good aesthetics, strong restoration-tooth bond and biocompatibility. However, some disadvantages, such as high viscosity level, color limitation and short shelf life should be mentioned. Thus, the aim of the current study was to assess bond strength between fiberglass post and root dentin in teeth subjected to self-adhesive resin cements with expired shelf life and hardness. Material and Methods: Sixty (60) single-rooted human teeth were sectioned and divided into 2 groups of different cements: U200 3M and MaxCem Elite Kerr. Each group was divided into 3 subgroups, based on self-adhesive resin cements' shelf life, namely: Within the use-time recommended by the manufacturer or no expiration date; 6 months after opening the aluminum blister; 12 months after opening the aluminum blister. Bond strength was measured through push-out test conducted in universal testing machine; fracture pattern was analyzed, and microhardness was investigated through Knoop test, based on hardness readings. Data were subjected to Shapiro-Wilk normality test; nonparametric test was applied to hardness data, whereas parametric test was applied to bond strength data. Hardness data were subjected to Kruskal-Wallis test, whereas bond strength data were subjected to analysis of variance, which was followed by Tukey test; both tests were conducted at 5% significance level (α = 0.05). Results: There was no statistically significant difference in knoop hardness values recorded for the material / time / root thirds combination (p=0.483). There was no statistically significant difference in bond strength values recorded for the Material / Time / Thirds combination (p=0.237). Conclusions: It was possible concluding that shelf life did not influence material's hardness and bond strength. Key words:Dental cements, Resin Cements, Shelf Life of Products.

Evaluating changes in the color and luminosity of dental enamel after orthodontic treatment: A clinical study.

The aims of this clinical study were to evaluate the Color change - ΔE (based on spectrophotometry and visual analysis) and luminosity - L* (based on spectrophotometry) of dental enamel surface (after orthodontic treatment) around the area where orthodontic brackets were fixed, based on different cementing materials such as a resin (R group) and resin-modified glass ionomer cement (RMGIC group). The split-mouth study initially comprised 14 patients. Orthodontic brackets were fixed to the upper central incisors with resin or RMGIC. The color of the buccal surface of each tooth was measured through spectrophotometry and visual examination before the bracket-fixation process. Four individuals were excluded during the follow-up; thus 10 patients were evaluated (n=10). Brackets were removed after 12 months of orthodontic treatment, tooth color measurement and visual examination were performed again, and Adhesive Remaining Index (ARI) was also measured. ΔE and L* results were subjected to Student's t-test and by repeated-measures analysis of variance, respectively (α=0.05). ARI data were analyzed in percentages. There was statistically significant difference in ΔE between groups; the R group showed statistically higher values of L* after orthodontic treatment. ARI of 2 and 3 prevailed in the RMGIC group, whereas the R group presented 0 and 1. After orthodontic treatment, the RMGIC group presented smaller changes in ΔE, and the increase in the white scale was observed on the enamel surface around the area where brackets were fixed in the R group. The visual analysis did not show color change on the evaluated teeth.

Evaluation of Removal Force in Prosthetic Components of Morse Taper Dental Implants.

The longevity of prosthetic rehabilitation is determined by the stability of the implant and abutment interfaces. True morse taper connections on dental restorations have been effective, however activation force still empirical. This work compared the activation strength and internal contact of Morse taper system according to the removal force. Eighty sets, composed of implants and prosthetic abutments, were evaluated with different internal contact areas; 15.12mm2 (G3.3) and 21.25mm2 (G4.3). The specimens were activated at 0° and 30°, with loads of 10, 20, 40 and 60N. The specimens were submitted to tensile test and the data to ANOVA and Tukey's tests (α=0.05). Representative specimens were examined under SEM. Removal force of G3.3 (2.15±1.33MPa) did not differed to G4.3 (1.99±1.03MPa). The activation at 0º (2.95±0.98MPa) statistically differed to 30º (1.19±0.54MPa). The 60N load was statistically superior for G3.3 and there was no statistical difference between 20N to 60N in G4.3. The values of 10N at 30o and 20N at the long axis of the morse taper implant, independent of the frictional contact area showed the best settlement.

Influence of resin cement and thermocycling on milled lithium disilicate ceramic microshear bond strength.

The aim of this study was to compare the microshear bond strength of different resin cements to CAD/CAM-created lithium disilicate ceramics after 24 hours and after 1 year (10,000 thermocycles). Forty (40) ceramic bars were subjected to pretreatment comprising airborne abrasion with aluminum oxide particles, etching with 10% hydrofluoric acid and Monobond N application. Bars were divided into 4 groups (n = 10), based on cement type: light-cured Variolink Esthetic LC (VLC) and dual-cured Variolink N (VN) at two different times: after 24 hours and after 1 year. Silicone molds were used to prepare cement cylinders on a ceramic surface. The set was stored in distilled water at 37ºC, for 24 hours or subjected to 10,000 thermocycles. The molds were removed and microshear bond strength was tested. Data were submitted to two-way analysis of variance and Tukey's test (α = 0.05). Based on the comparison between cement values at different aging times (p = 0.035), VN after 24 hours (27.10 ± 0.92) and after 1 year (20.62 ± 1.25) presented significantly higher values than VLC after 24 hours (14.79 ± 0.76) and after 1 year (6.61 ± 0.81). Bond strength recorded for both cements after 24 hours (VN: 27.10 ± 0.92 and VLC: 14.79 ± 0.76) was significantly higher than the one recorded after 1 year (VN: 20.62 ± 1.25 and VLC: 6.61 ± 0.81). The thermocycling reduced the values observed for both investigated cements; bond strength was greater for dual-cure resin cement than for light-cured resin cement.

O objetivo nesse estudo foi comparar a resistência de união de diferentes cimentos resinosos à cerâmica de dissilicato de lítio processada por CAD/CAM após 24 horas e após 1 ano (10.000 termociclos). Foram utilizadas 40 barras cerâmicas com tratamento prévio por jateamento com óxido de alumínio, condicionamento com ácido fluorídrico 10% e aplicação do Monobond N. As barras foram divididas em 4 grupos (n=10) de acordo com o tipo de cimento: fotopolimerizável Variolink Esthetic LC (VLC) e dual Variolink N (VN) em diferentes tempos: após 24 horas e 1 ano. Matrizes de silicone foram usadas para preparar cilindros de cimento na superfície cerâmica. O conjunto foi armazenado em água destilada a 37ºC por 24 horas ou submetidos protocolo de termociclagem com 10.000 ciclos. As matrizes foram removidas e o teste de microcisalhamento realizado. Os dados foram avaliados por análise de variância a dois fatores e teste de Tukey (α=0,05). Ao comparar os valores dos cimentos em diferentes tempos de envelhecimento (p=0,035), observou-se que VN, após 24 horas (27,10 ± 0,92) e 1 ano (20,62 ± 1,25) apresentou valores significativamente superior a VLC após 24 horas (14,79 ± 0,76) e 1 ano (6,61 ± 0,81). A resistência para ambos os cimentos após 24 horas (VN: 27,10 ± 0,92 e VLC: 14,79 ± 0,76) foi significativamente superior que 1 ano (VN: 20,62 ± 1,25 e VLC: 6,61 ± 0,81). A termociclagem promoveu diminuição nos valores de ambos os cimentos estudados e o cimento resinoso dual mostrou maior resistência de união que o cimento resinoso fotopolimerizável.

Evaluation of enamel roughness after the removal of brackets bonded with different materials: In vivo study.

The aims of this in vivo study were to evaluate the effect of bonding with resin-modified glass ionomer cement (RMGIC) and to assess enamel surface roughness before and after the removal of brackets bonded with composite or RMGIC from the maxillary central incisors. Fifteen orthodontic patients were selected for the study. For each patient, the teeth were rinsed and dried, and brackets were bonded with composite (Transbond XT) and RMGIC (Vitremer Core Buildup/Restorative). At the conclusion of orthodontic treatment, their brackets were removed. Dental replicas were made of epoxy resin in initial conditions (before bonded) and after polishing with an aluminum oxide disc system. Adhesive remnant index (ARI) and surface roughness was measured on the dental replicas and data were evaluated statistically by Mann-Whitney and paired t-test, respectively. No bracket debonding occurred during patients' treatment periods. It was verified that the ARI values of the two maxillary central incisors were similar (p = 0.665). For both bonding materials, the ARI value of 3 was predominant. After polishing, surface roughness was similar in the composite and RMGIC groups (0.245 µm and 0.248 µm, respectively; p = 0.07). In both groups, enamel surface roughness values were significantly lower after polishing compared with the initial condition (p < 0.001). RMGIC promoted efficiency in cementing brackets without fail during treatment; the choice of composite or RMGIC materials was not a factor that influenced the roughness of the enamel surface, however, polishing led to smoother surfaces than those found at the beginning of the treatment.

Sensitivity to bitter and sweet taste perception in schoolchildren and their relation to dental caries.

PURPOSE: The objective of the present study was to evaluate whether sensitivity to bitter taste and perception of sweet taste have an influence on dental caries in urban and rural areas. MATERIALS AND METHODS: The caries experience in 181 children, aged 12 years, from rural and urban areas of southern Brazil, was assessed according to World Health Organization guidelines. Sensitivity to the bitterness of phenylthiocarbamide was determined using the Harris­Kalmus procedure, and the sweet taste thresholds of sucrose were measured by Nilsson and Holm's method. RESULTS: The caries index (DMFT > 0) was 3.73 (SD = 2.26) in the rural area and 3.51 (SD = 2.14) in the urban area. The sensitivity to bitter taste and sweet taste perception showed significant association with the gender of schoolchildren (P = 0.04). Girls were predominant in the high sweet perception taster group (62.3%) and the bitter taster group (59.4%). No significant difference in sweet perception status could be observed between the groups of low and high caries severity. The genetic ability to taste bitterness significantly influenced the levels of caries only in children from the urban area (P = 0.005). Bitter non-tasters presented higher severity of caries. A positive correlation was observed between sensitivity to bitter taste and sweet taste perception among children in the rural (r = 0.42, P = 0.002) and urban areas (r = 0.36, P = 0.001). CONCLUSIONS: These findings suggest that the bitter non-tasters are more susceptible to dental caries than the tasters in the urban area.

Comparison of microleakage in human and bovine substrates using confocal microscopy.

Microleakage in human and bovine teeth was compared. Cavities were prepared on the buccal surface in 20 human and 20 bovine teeth (3 mm x 2 mm in depth). The teeth were divided into 4 groups (n = 10) according to the substrate and adhesive (CLEARFIL SE Bond-CF or Scotchbond 1-SB1). Resin composite (Wave) was applied in two increments, each cured for 30 sec. Specimens were stored in 100% relative humidity at 37 degrees C for 24 hr and submitted to 1,000 thermal cycles, followed by immersion in 0.6% aqueous rhodamine for 48 hr. Specimens were rinsed and sectioned at the center. Microleakage length was measured and the score recorded using the following scale: 0-none, 1-up to enamel junction, 2-up to pulp wall, 3-in pulp wall, 4-beneath pulp wall. Percentage of leakage penetration into the cavity was submitted to an ANOVA and Tukey's test (5%) and the scores submitted to the Kruskal-Wallis and Dunn's multiple comparison tests (5%). When bovine teeth were used, SB1 (87.76%) showed a statistically higher penetration mean than CF (66.22%). When human teeth were used, no difference was found between SB1 (47.35%) and CF (36.01%). When scores were analyzed, SB1 showed no difference to CF. The differences found should be taken into consideration when evaluating adhesive microleakage using bovine teeth.

Analysis of Molecular Changes Induced By Mineral Trioxide Aggregate On sPLA2.

The aim of this study was to analyze the effects of MTA on the structure and enzymatic activity of sPLA2 in order to provide subsidies for improvement in the formulation of the product. MTA powder was incubated for 60 min in the presence of sPLA2 and was analyzed by chromatography, electrospray mass (ESI-MS) and small-angle X-ray scattering (SAXS). It was find that the elution profile, retention time, and fragmentation of sPLA2 were altered after treatment with MTA. Calcium was the MTA component that most amplified the inflammatory signal. Significant interactions were found between MTA and sPLA2, which could aid in our understanding of the mechanisms of action of MTA during the inflammatory process and it may facilitate the structural modification of MTA, thereby improving its biological safety and consequently the rate of the treatment success.

Influence of chloramine-T disinfection on elastomeric impression stability.

OBJECTIVE: The aim of this study was to evaluate the stability of elastomer through detail reproduction and its dimensional stability (DS) after disinfection with 0.2% chloramine-T. MATERIALS AND METHODS: The elastomeric impression dental materials used in this study were polydimethylsiloxane (Oranwash L), polyvinyl siloxane (Express), polysulfide (Permlastic), and polyether (Impregum Soft). The entire press procedure was performed on a matrix in accordance with the ISO 4823. Detail reproduction was analyzed using an optical microscope (Stereozoom Microscope) over the 20-µm line with 25 mm of length at a magnification of ×4. DS was measured using an optical microscope (Scanning Tunneling Microscope) by subtracting the distance between the lines X and X' over the 20-µm line on the matrix (DM) from the distance between the lines on the impression material (DI) divided by DM and multiplied by 100 establishing the equation: DS = ([DI - DM]/DM) ×100; then, 100% was added to the results of the equation. The detail reproduction values were subsequently subjected to descriptive analysis by percentage (%), and the DS values (%) were submitted to Kolmogorov-Smirnov test, two-way ANOVA (material × disinfectant), and Tukey's test (α = 0.05). RESULTS: All elastomeric impression materials showed 100% of detail reproduction, regardless of the disinfection procedure. Polysulfide (not disinfected) and polysulfide and polydimethylsiloxane (after disinfection with 0.2% chloramine-T) showed the smaller mean values of DS. CONCLUSION: According to the stability properties analyzed, chloramine-T can be used for disinfection of elastomer molds.

Root canal treatment of a fused mandibular incisor using cone-beam computed tomography as a diagnostic aid.

Tooth fusion consists of the union of crowns by the enamel and/or dentin. We describe a case of a patient who presented with a fistula in the apical portion of teeth 32 and 33. Clinically, tooth 32 showed increased crown width in relation to other teeth in the same arch. Radiographic examination evidenced fusion of tooth 32 with a possible supernumerary tooth. Cone-beam computed tomography was used to confirm the radiographic findings and revealed incomplete apex formation of the supernumerary tooth. The fused tooth was subjected to root canal treatment. Calcium hydroxide was used as intracanal medication, changed for every 30 days, for 4 months. Subsequently, the mesial canal received an apical plug of mineral trioxide aggregate mixed with distilled water. At 2 years of follow-up, the tooth showed signs of tissue repair.

Microtensile Bond Strength and Microhardness of Composite Resin Restorations Using a Sonic-Resin Placement System.

The aim of this study was to evaluate the efficacy of applying sonic energy on microtensile bond strength and microhardness after the restoration process. A total of 40 human third molars were extracted. Class II cavities were prepared and restored with composite SonicFill or Filtek Z350 XT with and without the application of sonic energy. After the teeth were stored in water for 24 h, the teeth were sectioned into sticks (1.0 mm2) and subjected to tensile testing. For a depth Knoop hardness test, the samples were cut and indentations were made sequentially from the surface of the samples to the bottom of the samples in three intervals of 1 mm each. The samples were then subjected to a load of 50 g for 10 s. The results from the tensile (factors: placement system and composite) and hardness (factors: placement system, composite and depth) tests were subjected to the Kolmogorov-Smirnov normality test, followed by analysis of variance and Tukey's test (5% significance). For the placement system factor, higher bond strength was observed for the cavities that were restored with sonic energy (p < 0.001). For depth Knoop hardness, the hardness at 1 mm depth was significantly greater than that at 3 mm depth just for the restorations with Filtek Z350 XT composite without the application of sonic energy. Therefore, the use of sonic energy during the restorative process improved bonding, yet it did not markedly affect the depth hardness for both composites.

Surface detail reproduction and dimensional accuracy of molds: influence of disinfectant solutions and elastomeric impression materials.

This study compared the surface detail reproduction and dimensional accuracy of molds after disinfection using 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to those of molds that were not disinfected, for four elastomeric impression materials: polysulfide (Light Bodied Permlastic), polyether (Impregum Soft), polydimethylsiloxane (Oranwash L) andpolyvinylsiloxane (Aquasil Ultra LV). The molds were prepared on a matrix by applying pressure, using a perforated metal tray. The molds were removed following polymerization and either disinfected (by soaking in one of the solutions for 15 minutes) or not disinfected. The samples were thus divided into 16 groups (n=5). Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy to assess the 20-µm line over its entire 25 mm length. The dimensional accuracy results (%) were subjected to analysis of variance (ANOVA) and the means were compared by Tukey's test (a=5%). The 20-µm line was completely reproduced by all elastomeric impression materials, regardless of disinfection procedure. There was no significant difference between the control group and molds disinfected with peracetic acid for the elastomeric materials Impregum Soft (polyether) and Aquasil Ultra LV (polyvinylsiloxane). The high-level disinfectant peracetic acid would be the choice material for disinfection.

Este estudo comparou a reprodução de detalhes da superficie e estabilidade dimensional de moldes obtidos após desinfecção utilizando hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a moldes que não foram desinfetados com quatro elastomeros: polissulfeto (Light Bodied Permlastic), polieter (Impregum Soft), silicona reação por condensação (Oranwash L) e silicona reação por adição (Aquasil Ultra LV). Os moldes foram preparados sobre matriz contendo linhas de 20, 50 e 75 µm realizado sob pressão com moldeira de metal perfurada. Os moldes foram removidos após a polimerização e desinfetados (utilizando uma das soluções por imersão, armazenados em frascos fechados durante 15 minutos) ou não desinfetados. Assim, as amostras foram divididas em 16 grupos (n=5). A reprodução detalhes da superficie e a precisão dimensional foram avaliadas usando microscopia óptica na linha 20 µm com 25 mm de comprimento, de acordo com a norma ISO 4823. Os resultados de precisão dimensional (%) foram submetidos a análise de variancia (ANOVA) e as médias comparadas pelo teste de Tukey com 5% de nivel de significancia. A linha de 20 µm foi completamente reproduzida por todos os elastomeros, independentemente do processo de desinfecção. Nao houve diferenga estatisticamente significativa entre o grupo controle e moldes desinfetados com acido peracético para os elastomeros Impregum Soft (polieter) e Aquasil Ultra LV (silicona reação por adição). O desinfetante de alto nivel ácido peracético seria o material de escolha para a desinfecção.

Evaluating changes in the color and luminosity of dental enamel after orthodontic treatment: A clinical study

Abstract The aims of this clinical study were to evaluate the Color change - ΔE (based on spectrophotometry and visual analysis) and luminosity - L* (based on spectrophotometry) of dental enamel surface (after orthodontic treatment) around the area where orthodontic brackets were fixed, based on different cementing materials such as a resin (R group) and resin-modified glass ionomer cement (RMGIC group). The split-mouth study initially comprised 14 patients. Orthodontic brackets were fixed to the upper central incisors with resin or RMGIC. The color of the buccal surface of each tooth was measured through spectrophotometry and visual examination before the bracket-fixation process. Four individuals were excluded during the follow-up; thus 10 patients were evaluated (n=10). Brackets were removed after 12 months of orthodontic treatment, tooth color measurement and visual examination were performed again, and Adhesive Remaining Index (ARI) was also measured. ΔE and L* results were subjected to Student's t-test and by repeated-measures analysis of variance, respectively (α=0.05). ARI data were analyzed in percentages. There was statistically significant difference in ΔE between groups; the R group showed statistically higher values of L* after orthodontic treatment. ARI of 2 and 3 prevailed in the RMGIC group, whereas the R group presented 0 and 1. After orthodontic treatment, the RMGIC group presented smaller changes in ΔE, and the increase in the white scale was observed on the enamel surface around the area where brackets were fixed in the R group. The visual analysis did not show color change on the evaluated teeth.

Resumo Os objetivos deste estudo clínico foram avaliar a alteração de cor - ΔE (baseada em espectrofotometria e análise visual) e luminosidade - L* (baseada em espectrofotometria) da superfície do esmalte dentário (após tratamento ortodôntico) ao redor da área onde os braquetes ortodônticos foram fixados, com base em diferentes materiais de cimentação, como resina (grupo R) e cimento de ionômero de vidro modificado por resina (grupo RMGIC). Estudo boca dividida foi inicialmente composto por 14 pacientes. Os braquetes ortodônticos foram fixados nos incisivos centrais superiores com resina ou RMGIC. A cor da superfície vestibular de cada dente foi mensurada por espectrofotometria e avaliada por exame visual antes do processo de fixação dos braquetes. Quatro indivíduos foram excluídos durante o acompanhamento; assim, 10 pacientes foram avaliados (n=10). Os braquetes foram removidos após 12 meses de tratamento ortodôntico, a mensuração da cor do dente e o exame visual foram realizados novamente, e o Índice de Remanescente do Adesivo (IRA) também foi mensurado. Os resultados ΔE e L* foram submetidos ao teste t de Student e à análise de variância para medidas repetidas, respectivamente (α=0.05). Os dados do ARI foram analisados em porcentagens. Houve diferença estatisticamente significativa no ΔE entre os grupos; o grupo R apresentou valores estatisticamente maiores de L* após o tratamento ortodôntico. O IRA 2 e 3 prevaleceu no grupo RMGIC, enquanto o grupo R apresentou 0 e 1. Após o tratamento ortodôntico, o grupo RMGIC apresentou menores alterações no ΔE e o aumento da escala branca foi observado na superfície do esmalte ao redor da área onde os braquetes foram fixados no grupo R. A análise visual não mostrou mudança de cor nos dentes avaliados.

Evaluation of Removal Force in Prosthetic Components of Morse Taper Dental Implants

Abstract The longevity of prosthetic rehabilitation is determined by the stability of the implant and abutment interfaces. True morse taper connections on dental restorations have been effective, however activation force still empirical. This work compared the activation strength and internal contact of Morse taper system according to the removal force. Eighty sets, composed of implants and prosthetic abutments, were evaluated with different internal contact areas; 15.12mm2 (G3.3) and 21.25mm2 (G4.3). The specimens were activated at 0° and 30°, with loads of 10, 20, 40 and 60N. The specimens were submitted to tensile test and the data to ANOVA and Tukey's tests (α=0.05). Representative specimens were examined under SEM. Removal force of G3.3 (2.15±1.33MPa) did not differed to G4.3 (1.99±1.03MPa). The activation at 0º (2.95±0.98MPa) statistically differed to 30º (1.19±0.54MPa). The 60N load was statistically superior for G3.3 and there was no statistical difference between 20N to 60N in G4.3. The values of 10N at 30o and 20N at the long axis of the morse taper implant, independent of the frictional contact area showed the best settlement.

Resumo A longevidade da reabilitação protética é determinada pela estabilidade das interfaces implante e pilar. Conexões de cone Morse em restaurações dentárias têm se mostrado eficazes, porém a força de ativação ainda é empírica. Este trabalho comparou a força de ativação e contato interno do sistema cone Morse de acordo com a força de remoção. Oitenta conjuntos, compostos por implantes e pilares protéticos, foram avaliados com diferentes áreas de contato interno; 15,12mm2 (G3.3) e 21,25mm2 (G4.3). Os corpos-de-prova foram ativados a 0° e 30°, com cargas de 10, 20, 40 e 60N. Os corpos de prova foram submetidos ao ensaio de tração e os dados aos testes ANOVA e Tukey (α=0,05). Espécimes representativos foram examinados em MEV. A força de deslocamento do G3.3 (2,15±1,33MPa) não diferiu do G4.3 (1,99±1,03MPa). A ativação a 0º (2,95±0,98MPa) diferiu estatisticamente para 30º (1,19±0,54MPa). A carga de 60N foi estatisticamente superior para G3.3 e não houve diferença estatística entre 20N a 60N no G4.3. Os valores de 10N em 30o e 20N no longo eixo do implante cone morse, independente da área de contato friccional apresentaram o melhor assentamento.

Experimental resin-based dual-cured calcium aluminate and calcium titanate materials for vital pulp therapy

Abstract: This paper evaluates the physicochemical and biological properties of experimental resin-based dual-cured calcium aluminate (CA) and calcium titanate (CTi) materials for vital pulp therapy (VPT). The experimental dual-cured materials were obtained as two pastes: a) Bis-EMA 10, PEG 400, DHEPT, EDAB, camphorquinone, and butylated hydroxytoluene; and b) fluoride ytterbium, Bis-EMA 10, Bis-EMA 30, benzoyl peroxide, and butylated hydroxytoluene. The materials were divided into six groups based on the added calcium component: MTA (MTA®, Angelus); CLQ (Clinker-Fillapex®, Angelus); CA (calcined at ,1200°C in pastes a and b); CA800 (calcined at 800°C in paste a); CA1200 (calcined at 1,200°C in paste a); and CTi (paste a). The real-time degree of conversion and rate of polymerization (n = 3), diametral tensile strength (n = 10), hydrogen potential (n = 15), calcium ion release (n = 10), water sorption and solubility (n = 10), and cell viability (n = 6) were evaluated. One- and two-way ANOVA and Tukey's post hoc test were used in the analysis of the parametric data, and Kruskal-Wallis and Dunn's multiple tests were used to analyze the nonparametric data (α = 0.05). CLQ, CA800 and CA1200 had the highest diametral tensile strength. The water solubility of MTA was similar to that of CA800, CA1200 and CTi. CA800 and CA1200 resulted in cell viabilities similar to those of MTA and CLQ. The experimental dual-cured CA-based material that calcined at 800°C showed physicochemical and biological properties suitable for VPT, and similar to those of MTA.

Influence of Surface Treatments and Adhesive Systems on Lithium Disilicate Microshear Bond Strength.

The purpose of this study was to evaluate the microshear bond strength of ceramic prosthetic structures reinforced by lithium disilicate cemented with resin cement under conditions of different surface treatments and adhesive systems. Seventy-two rectangular blocks of lithium disilicate (6.5 mm long × 5 mm wide × 1 mm thick) were fabricated, air abraded with 50-µm Al2O3 particles and divided into six groups (n=12) depending on the surface pretreatments. The groups were as follows: 10HF/S/SBM: 10% hydrofluoric acid etched for 20 s (10HF) + silane (S) + Adper Scotchbond Multi-Purpose (SBM); 10HF/S/SB: 10HF + S + Single Bond Universal (SB); 10HF/SBM; 10HF/SB; S/SBM and S/SB. Two 1-mm-long plastic tubes were placed on the specimens, filled with RelyX ARC resin cement and cured for 20 s per tube. The plastic tube was removed, and the microshear bond strength was tested. Data were submitted to analysis of variance and Tukey's tests (α=0.05). Fractured specimens were observed under optical microscopy. For both adhesives, the bond strengths (MPa) of groups treated with acid-etching and silane (10HF/S/SB: 24.82, 10HF/S/SBM: 24.90) were higher (p<0.001) than those of groups treated with acid-etching (10HF/SB: 16.47, 10HF/SBM: 19.94) only or only silane (S/SB: 18.42, S/SBM: 13.24). All groups showed a predominance of failure adhesive. The silanization should be a clinical step in cementing ceramic structures reinforced by lithium disilicate, even with the application of universal adhesive that contains silane in its formulation.

The influence of concentration of HEMA on degree of conversion and cytotoxicity of a dental bonding resin.

BACKGROUND: This study evaluated the influence of 2-hydroxyethyl methacrylate (HEMA) on the degree of conversion (DC) and cytotoxicity of a dental bonding resin (DBR). METHODS: A monomer mixture based on 61.9 wt% of bisphenol A glycidyl methacrylate (Bis-GMA), 36.9 wt% of triethylene glycol dimethacrylate (TEGDMA), and photoactivated using a binary system based on camphoroquinone (0.4 wt%) and ethyl 4-dimethylamine benzoate (0.8 wt%) was used as DBR. Different groups were obtained with addition of HEMA in crescent concentrations. DC was accessed by Real time Fourier Transform infrared spectroscopy. The cytotoxicity was evaluated with MTT assay. The DC and cytotoxicity were analyzed by one-way ANOVA followed by Tukey's Test (P<0.05). RESULTS: A decrease in the DC was observed in the group with higher amount of HEMA. All tested-extracts were cytotoxic and there was an increased cytotoxic effect with higher HEMA addition. CONCLUSIONS: Higher amount of HEMA in the DBR resulted in adverse effects, with more cell toxicity and lower degree of conversion.