Effect of EDTA Concentrations as Irrigation Solution on Bonding of Fiber Posts into Root Canals with Universal Adhesives.

PURPOSE: To evaluate the effect of different concentrations of ethylene-diamine-tetra acetic acid (EDTA) on bond strength (BS) and nanoleakage (NL) of fiber posts bonded into root canals. MATERIALS AND METHODS: Seventy-two single roots were endodontically treated and divided into six groups (n = 12), according to the combination of the following factors: surface treatment (no irrigation [control], 17% EDTA, or 24% EDTA), and composite cement applied with an adhesive used in a self-etch mode (Single Bond Universal/RelyX Ultimate [SB], 3M Oral Care; Ambar Universal/Allcem [AM], FGM). After fiber post cementation, six 1-mm-thick disks were obtained for each root. Push-out bond strength (BS) was evaluated using 8 specimens per group, and the other 4 specimens were used to examine nanoleakage (NL). Data from BS and NL of each adhesive were evaluated by two-way ANOVA (surface treatment vs root region) and Tukey's test (α = 0.05). RESULTS: The application of 17% and 24% EDTA did not influence the bond strengths of either adhesive. In general, the application of 17% and 24% EDTA increased NL values for both adhesives. CONCLUSION: Pre-treatment with different concentrations of EDTA was not able to improve the adhesion of fiber posts into root canals with universal adhesives..

Assessment of the effect of experimental bleaching agent with nano-bioactive material on postoperative sensitivity: A randomized, triple blind clinical trial.

OBJECTIVES: This clinical study aimed to evaluate the effect of incorporating bioactive nanoparticles (n-Bm) inside an in-office bleaching gel on the risk and intensity of tooth sensitivity (TS) and on bleaching effectiveness. MATERIALS AND METHODS: Sixty-six participants were selected and randomly assigned into two groups: control-only in-office gel and experimental-in-office gel with n-Bm. Teeth were bleached in two sessions (3 × 15-min). TS was recorded using a VAS and NRS. The color change was evaluated by subjective (VITA Classical and VITA Bleachedguide) and objective (Easyshade spectrophotometer) methods at baseline and 30 days after the end of treatment. The TS was evaluated by McNemar, Wilcoxon Signed Rank, and paired t test. The color changes between groups were compared using paired t test (α = 0.05). RESULTS: No significant differences between the groups were observed in the risk (control = 27% [95%IC 18-39]; experimental = 21% [95%IC 13-32]) and intensity of TS, as well as in the color change (p >0.05) for any color measurement. CONCLUSION: The inclusion of n-Bm into the bleaching agents did not affect the whitening effectiveness, as well as the risk and intensity of TS between groups. However, the results of the absolute risk of TS were low for both in-office gels used. CLINICAL SIGNIFICANCE: Despite no significant differences between groups, both experimental bleaching agents present suitable results with low values for TS.

Is There Evidence that Three-step Etch-and-Rinse Adhesives Have Better Retention Rates than One-step Self-etch Adhesives in Noncarious Cervical Lesions? A Systematic Review and Meta-Analysis.

PURPOSE: A systematic review and meta-analysis was conducted to compare the retention rates of 3-step etch-and-rinse (3ER) adhesives with 1-step self-etch (1SE) adhesives in noncarious cervical lesions (NCCLs). The secondary outcomes were marginal integrity and marginal discoloration. MATERIALS AND METHODS: Only randomized clinical trials (RCTs) that compared 1SE with 3ER in NCCLs were included. Controlled vocabulary and keywords were combined in the search strategy for PubMed/Medline, LILACS, BBO, Web of Science, Cochrane Library, grey literature, and IADR abstracts (1990-2018). The Cochrane Risk of Bias tool (RoB) was applied to eligible studies. Meta-analyses were conducted for retention rate and secondary outcomes at different follow-up times, using the random effects model. Heterogeneity was assessed with the Cochran Q test and I2 statistics. The GRADE approach was used to assess the quality of the evidence. RESULTS: After the removal of duplicates, title and abstract screening, 18 studies remained. Of these, 15 studies were used for meta-analysis. Fourteen out of these 15 were judged at "unclear" risk and 1 at "low" risk of bias. No significant differences between groups were observed in the different follow-up periods for retention rates 12 to 24 months (p = 0.66), 24 to 36 months (p = 0.21) and 60 months (p = 0.96). A significant difference in marginal integrity was found at 12 to 24 months (p = 0.04) and in marginal discoloration at 12 to 24 months (p = 0.003). CONCLUSION: There is no evidence that 3-step ER adhesives have better retention rates than 1-step SE adhesives in NCCLs.

Bulk Fill flow resin contraction using 3D finite element model and calibration by Fiber Bragg Grating measurement.

Contraction due to polymerization of dental resin can cause failure on the adhesive interfaces, can lead to problems such as the appearance of gaps in the interfaces, postoperative sensitivity, pulp damage and the return of the caries. The objective of this work is the study of stresses on the dental adhesive that are generated by the process shrinkage of resin associated with biting forces. A laboratory experiment measured the strains and temperature inside the FiltekTM Bulk Fill Flow resin during the process of polymerization using Fiber Bragg Grating sensors in an ex vivo tooth. From tomographic images a three-dimensional geometric model of the tooth was reconstructed. A pre-tension was calibrated to simulate the residual contraction on the resin 3 D model. Finally, an Finite Element Method analysis was performed to access the adhesive stresses at the interface enamel/dentin with the adhesive, considering as loading the residual polymerization contraction of the dental resin and also biting loads. The model was able to represented the strain obtained in the laboratory experiment. The results of the stress analysis shows that the outer regions of adhesive are more prone to failure, as veried by dental surgeons in clinical practice.

Influence of Alternative Restoration Technique with Different Composite Resins for Flared Root Reinforcement.

PURPOSE: To evaluate the influence of type and viscosity of composite resins used for root reinforcement in the adhesion of glass-fiber posts to flared root canals. MATERIALS AND METHODS: The crowns of 78 uniradicular permanent teeth were removed and the teeth were endodontically treated. After one week, the roots were prepared for root reinforcement and randomly divided into 6 groups (n = 13): positive control group ([PCG] the root canals were not enlarged), negative control group ([NCG] root canals were enlarged, no reinforcement), and in the remaining 4 groups, root canals were enlarged to receive root reinforcement according to a combination of the factors composite resin type (bulk-fill or conventional) and viscosity (flowable or regular). After fiber post cementation, six slices were obtained from each root (2 each from the cervical, middle, and apical thirds). For each group, 7 teeth underwent push-out bond strength testing, and 6 teeth were evaluated for nanoleakage and Vickers microhardness. Bond strength and nanoleakage data were submitted to two-way ANOVA and Tukey's test (α = 0.05), and microhardness data to one-way ANOVA and Tukey's test (α = 0.05). RESULTS: The root reinforcement groups with regular and flowable bulk-fill composite resins showed statistically superior adhesion results (higher bond strength and less nanoleakage) compared to the negative control in all root regions. Microhardness values were higher in the cervical third followed by the middle third. CONCLUSION: Regular or flowable bulk-fill composite resins should be chosen for root reinforcement of flared root canals prior to fiber post cementation.

Effect of Conditioning Protocols and Ultrasonic Application of an Infiltrant Resin in White Spot Lesions.

The aim of this study was to evaluate different conditioning protocols and sonic/ultrasonic application of an infiltrant resin (IR) in artificial white spot lesions (AWSL). the V/L surfaces of 48 molars were induced to an AWSL and divided in 6 groups, according to the conditioning protocols and application technique: 15% hydrochloric acid (HA) + manual application of the IR; HA + 37% phosphoric acid (PA) + manual application of the IR; HA + ultrasonic application (U) of the IR; HA + sonic application (S) of the IR; PA+HA+S; and PA+HA+U. For the Penetration Depth (PD), the crowns were etched with HA for 120s. The IR Icon® (DMG) was applied according to the manufacturer`s instructions. The crowns were dye penetrated (0.1% red fluorophore rhodamine B isothiocyanate for 12h) and bleached with 30% hydrogen peroxide for 12 h. The discs were immersed in a 50% ethanol solution, containing 100 µM of sodium fluorescein. The PD (in µm) was measured using confocal laser scanning microscopy (20x). The bond strength (BS) was performed by michoshear test (0.5 mm/min). Data were submitted to 2-way ANOVA and Tukey (α=0.05). For BS, the interaction was not significant (p>0.05). For PD, the main factors were significant (application - p<0.001; conditioning technique - p=0.003). The ultrasonic application showed the highest PD values. PA+HA presented higher results than HA. The sonic/ultrasonic applications and the use of phosphoric acid prior to hydrochloric acid improved PD of the infiltrant resin. Conditioning protocols or application techniques did not influence BS values.

Effect of conditioning protocols and ultrasonic application of an infiltrant resin in white spot lesions

Abstract The aim of this study was to evaluate different conditioning protocols and sonic/ultrasonic application of an infiltrant resin (IR) in artificial white spot lesions (AWSL). the V/L surfaces of 48 molars were induced to an AWSL and divided in 6 groups, according to the conditioning protocols and application technique: 15% hydrochloric acid (HA) + manual application of the IR; HA + 37% phosphoric acid (PA) + manual application of the IR; HA + ultrasonic application (U) of the IR; HA + sonic application (S) of the IR; PA+HA+S; and PA+HA+U. For the Penetration Depth (PD), the crowns were etched with HA for 120s. The IR Icon® (DMG) was applied according to the manufacturer`s instructions. The crowns were dye penetrated (0.1% red fluorophore rhodamine B isothiocyanate for 12h) and bleached with 30% hydrogen peroxide for 12 h. The discs were immersed in a 50% ethanol solution, containing 100 µM of sodium fluorescein. The PD (in µm) was measured using confocal laser scanning microscopy (20x). The bond strength (BS) was performed by michoshear test (0.5 mm/min). Data were submitted to 2-way ANOVA and Tukey (α=0.05). For BS, the interaction was not significant (p>0.05). For PD, the main factors were significant (application - p<0.001; conditioning technique - p=0.003). The ultrasonic application showed the highest PD values. PA+HA presented higher results than HA. The sonic/ultrasonic applications and the use of phosphoric acid prior to hydrochloric acid improved PD of the infiltrant resin. Conditioning protocols or application techniques did not influence BS values.

Resumo: O objetivo deste estudo foi avaliar diferentes protocolos de condicionamento e a aplicação sônica/ultrassônica de uma resina infiltrante (RI) em lesões de mancha branca produzidas artificialmente (LMBA). As superfícies vestibulares/linguais de 48 molares foram induzidas à formação de LMBA e divididas em 6 grupos, de acordo com os protocolos de condicionamento e técnica de aplicação da resina infiltrante: ácido hidroclorídrico 15% (AH) + aplicação manual da RI; AH + ácido fosfórico 37% (AF) + aplicação manual da RI; AH + aplicação ultrassônica da RI (U); AH + aplicação sônica da RI (S); AF + AH + S; e AF + AH + U. para o grau de penetração (GP), condicionou-se as coroas com AH por 120 s. A RI Icon® (DMG) foi aplicada de acordo com as instruções do fabricante. As coroas foram coradas (rodamina B 0,1% por 12 h) e clareadas com peróxido de hidrogênio 30% por 12 h. os discos foram imersos em solução de etanol 50%, contendo 100 µM de fluoresceína sódica. O GP (em µm) foi mensurado por meio de microscopia confocal a laser (20´). A resistência de união (RU) foi calculada pelo teste de microcisalhamento (0,5 mm/min). Os dados foram submetidos ao teste ANOVA 2 fatores e Tukey (α=0,05). Para RU, a interação não foi significante (p>0,05). Para GP, os fatores principais foram significantes (técnica de aplicação - p<0,001; protocolos de condicionamento - p=0,003). A aplicação U mostrou os maiores valores de GP. AF+AH demonstrou resultados superiores ao grupo AH. As aplicações sônica/ultrassônica e o uso do ácido fosfórico antes do ácido hidroclorídrico aumentaram o GP da resina infiltrante. Os protocolos de condicionamento ou as técnicas de aplicação não influenciaram os valores de RU.

Are Glass-Ionomer Cement Restorations in Cervical Lesions More Long-Lasting than Resin-based Composite Resins? A Systematic Review and Meta-Analysis.

PURPOSE: To compare the the loss of retention and color match of glass-ionomer cements (GIC) and resin-based composites (RC) in noncarious cervical lesions. Other secondary outcomes (surface texture, marginal adaptation, marginal discoloration, and secondary caries) were evaluated in a systematic review and meta-analysis. MATERIALS AND METHODS: A comprehensive search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, and Cochrane. We included only randomized clinical trials. The quality of the evidence for each outcome was assessed using the GRADE tool. RESULTS: A total of 1530 articles were identified, but only 19 reports remained for analysis, all of which were judged to possess "unclear" risk of bias. GIC showed higher retention rates in all follow-ups (1 to 3 years, p < 0.0001; at 5 years, p < 0.00001). No difference was observed for marginal discoloration, marginal adaptation and secondary caries in all follow-ups (p > 0.05). RC showed better color match than GIC only at 2 years (p = 0.03). Higher roughness was observed in GIC in all follow-ups (at 1 year p = 0.0003; at 3 years p = 0.0004). Quality of evidence was graded as moderate or low due to unclear risk of bias and imprecision in some outcomes. CONCLUSION: The loss of retention of RMGIC/GIC was inferior to that of RC, but a higher roughness was observed in the RMGIC/GIC when compared to RC in all follow-ups of the clinical studies evaluated. In addition, the color match was better with RC only in the 2-year follow-up when compared to GIC. The quality of evidence was judged as moderate to low in these two outcomes.

Bond strength values of fiberglass post to flared root canals reinforced with different materials.

The aim of this study was to compare in vitro the bond strength (BS) between fiberglass posts and flared root canals reinforced with different materials. The roots of 48 premolars were endodontically treated. After one week, the root canals were prepared to simulate an oversized root canal, except for the positive control group (PCG), which was cemented with a prefabricated fiber post (PFP) compatible with the root canal size, simulating an ideal adaptation. The other samples (n=8/group) were used to test alternative restorative techniques for filling root canals: negative control group (NCG [PFP with a smaller diameter than of the root canal]), composite resin group - CRG, bulkfill group - BFG, self-adhesive cement group - SAG, and glass ionomer group - GIG. The posts were cemented and after 1 week, each root was sectioned transversely into six 1-mm thick discs and the push-out test was done to evaluate the BS. Data were analyzed by two-way repeated measures ANOVA and Tukey's tests (α=0.05). The highest BS value was observed for PCG. The NCG and the GIG groups showed the lowest BS values. Root reinforcement with conventional and bulk-fill composite resins showed the highest BS values; however, the bulk-fill resin was the only treatment able to maintain high BS values in all regions of the root canal. The self-adhesive cement showed intermediate results between CRG and GIG. Root reinforcement with bulk-fill composite resin is an effective option for flared root canals before cementation of a prefabricated fiber post.

Influence of different burs and acid ultrasonic agitation on the bonding of fiber posts to root dentin

Aim: The objective is to evaluate the influence of different burs used to prepare the root canal space and acid ultrasonic agitation on bond strength (BS) between glass fiber posts (GFP) and root dentin. Methods: After endodontic treatment, the root canal spaces of 36 extracted human canines were prepared, according to the rotary instrument used (n=18): carbide bur (CB), provided by the post manufacturer and a diamond bur (DB). In both groups, the fiber posts were cemented with the adhesive system Ambar and resin cement Allcem, following the manufacturer`s instructions. Previously to the cementation procedures, the groups were subdivided into 2 groups (n=9), according to the phosphoric acid application mode: conventional etching (CE) and active etching (AE), performed by ultrasonic tip, both for 15s. Before the cementation procedures and after the acid application, 1 root of each group was randomly selected for ultrastructural morphological evaluation by SEM. After 1 week of the cementation, 8 specimens per group were transversely sectioned into six 1-mm thick slices, the root canal regions (cervical, medium and apical) were identified and the push-out test was performed to evaluate BS. Data were analyzed by 3-way ANOVA and Tukey test (α=0.05). Results: The results showed that the cross-product interaction of all factors was significant (P=0.035). Higher bond strength values were obtained when a DB with conventional etching, instead of CB, was used to prepare the root post space. Conclusion: It may be concluded that the use of diamond burs with conventional etching yields high BS values in all root canal thirds

Bond strength values of fiberglass post to flared root canals reinforced with different materials

Abstract The aim of this study was to compare in vitro the bond strength (BS) between fiberglass posts and flared root canals reinforced with different materials. The roots of 48 premolars were endodontically treated. After one week, the root canals were prepared to simulate an oversized root canal, except for the positive control group (PCG), which was cemented with a prefabricated fiber post (PFP) compatible with the root canal size, simulating an ideal adaptation. The other samples (n=8/group) were used to test alternative restorative techniques for filling root canals: negative control group (NCG [PFP with a smaller diameter than of the root canal]), composite resin group - CRG, bulkfill group - BFG, self-adhesive cement group - SAG, and glass ionomer group - GIG. The posts were cemented and after 1 week, each root was sectioned transversely into six 1-mm thick discs and the push-out test was done to evaluate the BS. Data were analyzed by two-way repeated measures ANOVA and Tukey's tests (α=0.05). The highest BS value was observed for PCG. The NCG and the GIG groups showed the lowest BS values. Root reinforcement with conventional and bulk-fill composite resins showed the highest BS values; however, the bulk-fill resin was the only treatment able to maintain high BS values in all regions of the root canal. The self-adhesive cement showed intermediate results between CRG and GIG. Root reinforcement with bulk-fill composite resin is an effective option for flared root canals before cementation of a prefabricated fiber post.

Effect of the Bis-Dimethylamino Benzydrol Coinitiator on the Mechanical and Biological Properties of a Composite.

To examine the effect of the alternative coinitiator 4,4'bis dimethylamino benzydrol (BZN) in degree of conversion (DC), mechanical and biological properties of experimental composites. The coinitiator BZN was used in three concentrations (0.2, 0.5 and 1.2%), and the coinitiator DMAEMA was used as control at the same concentrations as above. The molar concentration of camphorquinone (CQ) and coinitiators was kept constant (1:1). The composites were manipulated and submitted to microhardness test (VHN), flexural and compressive strength (in MPa), elastic modulus (GPa), DC (FT-IR) and in vitro cytotoxicity (against 3T3 fibroblastic cells) of the experimental resins. Data were subjected to two-way ANOVA and Tukey post-test (α=0.05). The experimental composite resin with BZN showed higher DC values compared to control DMAEMA groups. For the mechanical properties, microhardness values were higher in BZN groups; flexural strength and elastic modulus were similar between all the groups. Compressive strength for groups BZN0.5 and DMAEMA0.5 were not statistically different, being the lowest values attributed to group BZN0.2. The experimental resins with BZN and DMAEMA were considered nontoxic against 3T3 fibroblasts. The inclusion of the coinitiator BZN in experimental composites was considered nontoxic against 3T3 fibroblast cells, without compromising DC and mechanical properties.

Effect of the Bis-Dimethylamino Benzydrol Coinitiator on the Mechanical and Biological Properties of a Composite

Abstract To examine the effect of the alternative coinitiator 4,4'bis dimethylamino benzydrol (BZN) in degree of conversion (DC), mechanical and biological properties of experimental composites. The coinitiator BZN was used in three concentrations (0.2, 0.5 and 1.2%), and the coinitiator DMAEMA was used as control at the same concentrations as above. The molar concentration of camphorquinone (CQ) and coinitiators was kept constant (1:1). The composites were manipulated and submitted to microhardness test (VHN), flexural and compressive strength (in MPa), elastic modulus (GPa), DC (FT-IR) and in vitro cytotoxicity (against 3T3 fibroblastic cells) of the experimental resins. Data were subjected to two-way ANOVA and Tukey post-test (α=0.05). The experimental composite resin with BZN showed higher DC values compared to control DMAEMA groups. For the mechanical properties, microhardness values were higher in BZN groups; flexural strength and elastic modulus were similar between all the groups. Compressive strength for groups BZN0.5 and DMAEMA0.5 were not statistically different, being the lowest values attributed to group BZN0.2. The experimental resins with BZN and DMAEMA were considered nontoxic against 3T3 fibroblasts. The inclusion of the coinitiator BZN in experimental composites was considered nontoxic against 3T3 fibroblast cells, without compromising DC and mechanical properties.

Resumo Analisar o efeito do co-iniciador alternativo 4,4'bisdimetilaminobenzidrol (BZN) no grau de conversão (GC) e nas propriedades mecânicas e biológicas de resinas compostas experimentais. O co-iniciador BZN foi utilizado em três concentrações (0,2, 0,5 e 1,2), e o co-iniciador DMAEMA como controle, nas mesmas concentrações acima. A concentração molar entre canforoquinona (CQ) e os co-iniciadores foi mantida constante (1:1). As resinas compostas foram manipuladas e submetidas aos testes de microdureza (VHN), resistência à compressão e flexural (em MPa), módulo de elasticidade (em GPa), GC (em %, por meio de espectroscopia micro-Raman e FTIR com KBr), citotoxicidade in vitro (frente às células fibroblásticas 3T3) das resinas experimentais. Os resultados foram submetidos ao teste ANOVA 1 fator e pós-teste de Tukey (α=0,05). As resinas compostas experimentais com o BZN apresentaram GC e propriedades mecânicas satisfatórias, além de serem consideradas atóxicas a fibroblastos 3T3. A inclusão do co-iniciador BZN à resina composta foi considerada não tóxica frente a células fibroblásticas 3T3 e sem comprometer o grau de conversão e as propriedades mecânicas da mesma.

Effect of Dentin Moisture and Application Mode of Universal Adhesives on the Adhesion of Glass Fiber Posts to Root Canal.

PURPOSE: To evaluate the effect of dentin moisture and application mode of universal adhesives on bond strength (BS) and nanoleakage (NL) of fiber posts bonded to root dentin. MATERIALS AND METHODS: The roots of 96 extracted human canines were treated endodontically, and the fiber posts were cemented according to the combination of the following factors: dentin moisture (dry and wet), cementation system [Single Bond Universal/RelyX ARC (SBU) and Prime&Bond elect/Enforce (PBE)], and adhesive application [active (A) and passive (P)] in accordance with the manufacturer's instructions. After one week, the specimens were transversely sectioned into six 1-mm-thick disks. From each group, 8 specimens were subjected to the push-out BS test and the other 4 specimens underwent NL analysis. For both tests, the data were subjected to 3-way repeated measures ANOVA and Tukey's tests (α = 0.05). RESULTS: For BS and NL, the cross-product interaction of all factors was significant (p < 0.05). Lower BS was observed under P application independent of the dentin moisture; for A application, SBU showed higher BS than did PBE in both moisture conditions. Nanoleakage was present in all groups and ranged from 22.9% to 36%. CONCLUSION: The active application of universal adhesives improves the adhesion in fiber post cementation, independent of dentin moisture condition.

Is the bonding of self-adhesive cement sensitive to root region and curing mode?

OBJECTIVES: To evaluate the influence of two curing techniques on the degree of conversion (DC) of resin cements and on bond strength (BS) of fiber posts in different regions of root dentin. MATERIAL AND METHODS: Twenty single-rooted premolars were endodontically treated, and the post spaces were prepared. The roots were randomly divided into two groups (n=10), according to the activation mode of the resin cement RelyX™ U200 (3M ESPE Saint Paul, MN, USA): conventional (continuous activation mode) and soft-start activation mode (Ramp). The posts (WhitePost DC/FGM) were cemented according to the manufacturer's recommendations and, after one week, the roots were cross-sectioned into six discs each of 1-mm thickness, and the cervical, medium, and apical thirds of the root canals were identified. The DC was evaluated under micro-Raman spectroscopy and the BS was evaluated by the push-out test. The data were analyzed by two-way ANOVA and Tukey's test (α=0.05). RESULTS: Neither the activation mode nor the root regions affected the DC of the resin cement. Higher BS was achieved in the soft-start group (p=0.036); lower BS was observed in the apical third compared to the other root regions (p<0.001). Irrespective of the activation mode and root region, the mixed failure mode was the most prevalent. CONCLUSION: The BS of fiber posts to root canals can be improved by soft-started polymerization. The DC was not affected by the curing mode.

Is the bonding of self-adhesive cement sensitive to root region and curing mode?

Abstract Objectives To evaluate the influence of two curing techniques on the degree of conversion (DC) of resin cements and on bond strength (BS) of fiber posts in different regions of root dentin. Material and Methods Twenty single-rooted premolars were endodontically treated, and the post spaces were prepared. The roots were randomly divided into two groups (n=10), according to the activation mode of the resin cement RelyX™ U200 (3M ESPE Saint Paul, MN, USA): conventional (continuous activation mode) and soft-start activation mode (Ramp). The posts (WhitePost DC/FGM) were cemented according to the manufacturer’s recommendations and, after one week, the roots were cross-sectioned into six discs each of 1-mm thickness, and the cervical, medium, and apical thirds of the root canals were identified. The DC was evaluated under micro-Raman spectroscopy and the BS was evaluated by the push-out test. The data were analyzed by two-way ANOVA and Tukey’s test (α=0.05). Results Neither the activation mode nor the root regions affected the DC of the resin cement. Higher BS was achieved in the soft-start group (p=0.036); lower BS was observed in the apical third compared to the other root regions (p<0.001). Irrespective of the activation mode and root region, the mixed failure mode was the most prevalent. Conclusion The BS of fiber posts to root canals can be improved by soft-started polymerization. The DC was not affected by the curing mode.

Investigação das propriedades mecânicas de cimentos resinosos duais convencionais e autoadesivos em macro e nanoescala / Investigation of mechanical properties of conventional and self-adhesive resin cements in macro and nanoscale

Objetivo: O objetivo desse estudo foi avaliar e comparar as propriedades mecânicas dos cimentos resinosos duais convencionais e autoadesivos em macro e nanoescala. Métodos: Foram confeccionados 15 espécimes de cada marca de cimentos resinosos, AllCem (FGM), RelyX ARC (3M/ESPE) e RelyX U200 (3M/ESPE), para cada teste realizado (flexão de três pontos, compressão e nanoindentação) de acordo com as instruções dos fabricantes. Os espécimes foram fotoativados com aparelho Optilux Demetron (Kerr) por 40 segundos e armazenados em frascos escuros a 37ºC por 24 horas. Foram obtidos os resultados de resistência flexural, resistência à compressão, dureza e de módulo de Young para os diferentes testes mecânicos. Os dados foram avaliados pelos testes ANOVA, múltiplas comparações de Tukey HSD para análise dos valores de resistência, dureza e módulo de elasticidade entre os diferentes cimentos resinosos e ANOVA dois critérios e múltiplas comparações de Games Howell para análise dos módulos de Young entre os diferentes experimentos. Resultados: Os resultados revelaram que o AllCem obteve os maiores valores de resistência flexural e compressão axial (129±22,01 MPa; 243,71±29,75, respectivamente) e o RelyX U200 os menores valores (82,35±19,83 MPa; 134,57±48,93 MPa, respectivamente). Os valores de dureza não diferiram entre os cimentos estudados. No teste de flexão os valores de módulo de Young não diferiram entre os cimentos resinosos. No teste de compressão axial o AllCem apresentou módulo de Young estatisticamente maiores que dos demais cimentos. Para nanoindentação AllCem e RelyX U200 apresentaram maiores valores de módulo de Young que RelyX ARC. Os valores de módulo de Young diferiram significativamente entre todos os experimentos (p<0.05). Conclusão: Os valores das propriedades dos cimentos resinosos podem ser influenciados pelo tipo de experimento (macro- ou nanoescala) realizado.(AU)

Aim: The aim of this study was to evaluate and compare the mechanical properties of conventional and self-adhesive dual resin cements in macroscale and nanoscale. Methods: Fifteen specimens of each brand of resin cement ­ AllCem (FGM), RelyX ARC (3M/ ESPE), and RelyX U200 (3M/ESPE) ­ were made for each test performed in this study (three point bending, compression, and nanoindentation) according to the manufacturer's instructions. The specimens were photoactivated with Optilux Demetron (Kerr) for 40 seconds and stored in the dark at 37°C for 24 hours. Subsequently, they were submitted to flexural strength and axial compression tests at a speed of 1 mm/min, as well as to the Berkovich nanoindentation test. The results of flexural strength, compressive strength, hardness, and Young's modulus were obtained for the different mechanical tests. Data were evaluated by ANOVA tests; multiple comparisons of Tukey HSD to analyze the values of strength, hardness, and Young's modulus among the different resin cements; and ANOVA two criteria and multiple comparisons of Games Howell to analyze the Young's modulus within the different experiments. Results: The results showed that AllCem obtained the highest values of flexural strength and axial compression (129±22.01, 243.71±29.75 MPa, respectively), while RelyX U200 presented the lowest values (82.35 ± 19.83, 134.57 ± 48.93 MPa, respectively). The hardness values did not differ among the studied cements. In the flexural test, the Young's modulus values did not differ between the resin cements. In the axial compression test, AllCem presented a Young's modulus that was statistically higher than the other cements. In the nanoindentation test, AllCem and RelyX U200 presented higher values for Young's modulus than RelyX ARC. Young's modulus values differed significantly among all experiments (p <0.05). Conclusion: The values of resin cement properties can be influenced by the type of experiment (macroscale and nanoscale) performed.(AU)

An in situ evaluation of the polymerization shrinkage, degree of conversion, and bond strength of resin cements used for luting fiber posts.

STATEMENT OF PROBLEM: The behavior and magnitude of the deformations that occur during polymerization and the behavior of the luting agents of glass fiber posts inside the root canal require quantification. PURPOSE: The purpose of this in vitro study was to investigate the in situ polymerization shrinkage, degree of conversion, and bond strength inside the root canal of resin cements used to lute fiber posts. MATERIAL AND METHODS: Thirty maxillary canines were prepared to lute fiber posts. The teeth were randomly divided into 2 groups (n=15) according to the cementation system used, which included ARC, the conventional dual-polymerized resin cement RelyX ARC, and the U200 system, a self-adhesive resin cement, RelyX U200. Two fiber optic sensors with recorded Bragg gratings (FBG) were attached to each post before inserting the resin cement inside the root canal to measure the polymerization shrinkage (PS) of the cements in the cervical and apical root regions (µÎµ). Specimens were sectioned (into cervical and apical regions) to evaluate bond strength (BS) with a push-out test and degree of conversion (DC) with micro-Raman spectroscopy. Data were statistically analyzed with 2-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05). RESULTS: The ARC and U200 system showed similar PS values (-276.4 ±129.2 µÎµ and -252.1 ±119.2 µÎµ, respectively). DC values from ARC were higher (87.5 ±2.7%) than those of U200 (55.9 ±9.7%). The cervical region showed higher DC values (74.8 ±15.2%) and PS values (-381.6 ±53.0 µÎµ) than those of the apical region (68.5 ±20.1% and -146.9 ±43.5 µÎµ, respectively) for both of the resin cements. BS was only statistically different between the cervical and apical regions for ARC (P<.05). CONCLUSIONS: The ARC system showed the highest PS and DC values compared with U200; and for both of the resin cements, the PS and DC values were higher at the cervical region than at the apical region of the canal root. BS was higher in the cervical region only for ARC.

Active and Passive Application of the Phosphoric Acid on the Bond Strength of Lithium Disilicate.

The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey's post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p<0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was concluded that the active application of 37% PA after 9.6% HA increases the microshear bond strength values between the resin cement and lithium disilicate ceramic.

Active and Passive Application of the Phosphoric Acid on the Bond Strength of Lithium Disilicate

Abstract The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey's post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p<0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was concluded that the active application of 37% PA after 9.6% HA increases the microshear bond strength values between the resin cement and lithium disilicate ceramic.

Resumo O objetivo desse estudo foi avaliar o efeito da aplicação passiva ou ativa do ácido fosfórico após o tratamento com ácido hidrofluorídrico na resistência de união ao microcisalhamento entre cimento resinoso e dissilicato de lítio. Trinta discos foram confeccionados com IPS Emax 2 (10 mm de espessura e 10 mm de diâmetro). Os espécimes foram divididos em três grupos (A: aplicação do ácido hidrofluorídrico 9,6%; AF: aplicação do ácido hidrofluorídrico 9,6% + limpeza com ácido fosfórico 37% em modo passivo; AFF: aplicação do ácido hidrofluorídrico 9,6% + limpeza com ácido fosfórico 37% no modo ativo). Para o teste de microcisalhamento, quatro tygons (0,9 de diâmetro e 0,2 mm de altura) foram preenchidos com cimento resinoso (RelyX Ultimate) e dispostos sobre os discos de cerâmica. Após o teste, os modos de fratura foram examinados por microscopia eletrônica de varredura. Os dados foram analisados estatisticamente por ANOVA e pós-teste de Tukey (α=0,05). Os valores de resistência de união foram significativamente superiores para o grupo AFF (11,0±2,5 MPa), comparado ao grupo A (8,1±2,6 MPa) (p<0,002), mas este não estatisticamente diferente do grupo AF (9,4±2,5 MPa). Concluiu-se que a aplicação ativa do ácido fosfórico 37% após o uso do ácido hidrofluorídrico 9,6% aumenta a resistência de união entre o cimento resinoso e a cerâmica de dissilicato de lítio.