Is the Er:YAG laser affect the surface characteristics and bond strength of Y-TZP?

Abstract This study evaluated the surface characteristics and bond strength of Y-TZP treated with Er:YAG laser at different focal distances. 120 Y-TZP blocks were divided into five groups (n=24), according to the surface treatment: no treatment (C-); sandblasting with silica-coated aluminum oxide particles (C+); and Er:YAG laser application at focal distances of 1mm (Er:YAG-1), 4mm (Er:YAG-4), and 7mm (Er:YAG-7). Surface characteristics were analyzed using Vickers microhardness, confocal laser microscope, scanning electron microscopy (SEM), and X-ray diffractometer (XRD). For the bond strength test, 100 Y-TZP blocks were subdivided into two subgroups (n=10), according to the resin cement used: with (MDP+) or without 10-methacryloyloxydecyl dihydrogen phosphate (MDP-). The Vickers microhardness and surface roughness were analyzed by one-way ANOVA and bond strength by two-way ANOVA and Tukey's test for both (α=0.05). Vickers microhardness differences were not observed between the groups (p>0.05); C+ showed higher surface roughness values. SEM images showed micromorphological differences between the groups. The XRD data detected tetragonal crystals for C- and, for the other groups, tetragonal and monoclinic peaks. For bond strength, no statistically difference significance were observed among the cements with or without MDP (p>0.05) but showed significant difference between the surface treatments (C+ > C- = Er:YAG1 > Er:YAG4 = Er:YAG7) (p<0.05). Suggested that the Er:YAG laser cannot replace conventional treatment with aluminum oxide particles and the presence of MDP in the resin cement had no influence on the bond strength.

Resumo Este estudo avaliou as características de superfície e resistência de união de Y-TZP tratado com laser de Er: YAG em diferentes distâncias focais. Cento e vinte blocos de Y-TZP foram divididos em cinco grupos (n=24), de acordo com a superfície de tratamento: sem tratamento (C-); asperização com partículas de óxido de alumínio revestidas por sílica (C +); e aplicação de laser Er: YAG a distâncias focais de 1 mm (Er: YAG-1), 4 mm (Er: YAG-4) e 7 mm (Er: YAG-7). As características de superfície foram analisadas por meio de microdureza Vickers, microscópio confocal a laser, microscopia eletrônica de varredura (MEV) e difratômetro de raios-X (DRX). Para o ensaio de resistência de união, cem blocos de Y-TZP foram subdivididos em 2 subgrupos (n=10) de acordo com o cimento resinoso utilizado (n=12): com 10-metacriloiloxidecil dihidrogenofosfato (MDP+) ou sem (MDP-). Microdureza Vickers e rugosidade de superfície foram analisadas por ANOVA a 1 fator e a resistência de união por ANOVA a 2 fatores e ambos seguidos de teste complementar de Tukey (α=0,05). Não foram observadas diferenças de microdureza Vickers entre os grupos; C+ apresentou maiores valores de rugosidade superficial. Imagens de MEV mostraram diferenças micromorfológicas entre os grupos. Os dados de DRX detectaram apenas cristais tetragonais para C- e, para os outros grupos, picos de zircônia nas fases tetragonal e monoclínica. Para a resistência de união, não foram observadas diferenças estatisticamente significante entre os cimentos com e sem MDP (p>0.05), mas foram observadas diferenças significativas entre os tratamentos de superfície (C+ > C- = Er:YAG1 > Er:YAG4 = Er:YAG7) (p<0.05). Sugere-se que o laser de Er: YAG não pode substituir o tratamento convencional com partículas de óxido de alumínio e a presença de MDP no cimento resinoso não influenciou na resistência de união.

Is the Er:YAG laser affect the surface characteristics and bond strength of Y-TZP?

This study evaluated the surface characteristics and bond strength of Y-TZP treated with Er:YAG laser at different focal distances. 120 Y-TZP blocks were divided into five groups (n=24), according to the surface treatment: no treatment (C-); sandblasting with silica-coated aluminum oxide particles (C+); and Er:YAG laser application at focal distances of 1mm (Er:YAG-1), 4mm (Er:YAG-4), and 7mm (Er:YAG-7). Surface characteristics were analyzed using Vickers microhardness, confocal laser microscope, scanning electron microscopy (SEM), and X-ray diffractometer (XRD). For the bond strength test, 100 Y-TZP blocks were subdivided into two subgroups (n=10), according to the resin cement used: with (MDP+) or without 10-methacryloyloxydecyl dihydrogen phosphate (MDP-). The Vickers microhardness and surface roughness were analyzed by one-way ANOVA and bond strength by two-way ANOVA and Tukey's test for both (α=0.05). Vickers microhardness differences were not observed between the groups (p>0.05); C+ showed higher surface roughness values. SEM images showed micromorphological differences between the groups. The XRD data detected tetragonal crystals for C- and, for the other groups, tetragonal and monoclinic peaks. For bond strength, no statistically difference significance were observed among the cements with or without MDP (p>0.05) but showed significant difference between the surface treatments (C+ > C- = Er:YAG1 > Er:YAG4 = Er:YAG7) (p<0.05). Suggested that the Er:YAG laser cannot replace conventional treatment with aluminum oxide particles and the presence of MDP in the resin cement had no influence on the bond strength.

Chlorhexidine and proanthocyanidin enhance the long-term bond strength of resin-based endodontic sealer.

The aim of this study was to evaluate the effects of proanthocyanidin (PA) and chlorhexidine (CHX) on the bond strength (BS), failure pattern, and resin-dentin interface morphology of the endodontic sealers EndoREZ and AH Plus after 24 h and 6 months of water storage. A total of 120 prepared bovine roots were divided into six groups: AH Plus, CHX+AH Plus, PA+AH Plus, EndoREZ, CHX+EndoREZ, and PA+EndoREZ. Dentin was treated for 1 or 5 min with 2% CHX or 15% PA, respectively. Roots were filled and stored in water for 24 h or 6 months (n = 10). Root slices were subjected to push-out test and scanning electron microscopy (SEM). Data were compared using two-way ANOVA and student's t-test (α = 5%). BS decreased over time for AH Plus and untreated EndoREZ (p < 0.05). At 24 h, AH Plus had higher BS than EndoREZ (p < 0.001), with no differences among treatments for both sealers (p > 0.05). At 6 months, EndoREZ had higher BS values for CHX and PA than control (p < 0.05). AH Plus had higher BS than EndoREZ (p < 0.001), while with CHX or PA, similar BS was observed in both sealers (p > 0.05). Cohesive and mixed failures were observed in all groups. SEM revealed sealer tags in the root dentin. In conclusion, BS decreased with time and AH Plus had higher BS than EndoREZ in untreated dentin; however, CHX or PA enhanced long-term BS of EndoREZ. Overall, dentin treatment affected failure pattern and resin-dentin interface morphology, particularly for EndoREZ.

Non-contact profilometry of eroded and abraded enamel irradiated with an Er:YAG laser.

Literature has reported positive results regarding the use of lasers in the control of erosive lesions; however, evaluating whether they are effective in the control of the progression of erosive/abrasive lesions is important. Objectives This study aimed to evaluate the effect of the Er:YAG laser irradiation in controlling the progression of erosion associated with abrasive lesions in enamel. Material and methods Bovine incisors were sectioned, flattened and polished. Forty-eight enamel slabs were subjected to treatment in an intraoral phase. Twelve volunteers used an intraoral appliance containing one slab that was irradiated with an Er:YAG laser (5.2 J/cm2, 85 mJ, 2 Hz) and another non-irradiated slab on each side of the appliance, during one phase of 5 d, under a split-mouth design. Devices were subjected to erosive challenges (1% citric acid, 5 min, 3 times a day) and abrasive challenges one h after (brushing force of 1.5 N for 15 s) randomly and independently on each side of the device. Measurements of enamel loss were performed via 3D optical profilometry (µm). We analyzed data using the Kruskal-Wallis and Mann-Whitney tests and morphological characteristics via scanning electron microscopy. Results Following erosive and abrasive challenges, the group that was irradiated with the Er:YAG laser presented less loss of structure than the non-irradiated group. The group that underwent erosion and irradiation did not exhibit a significant difference from the non-irradiated group. Conclusion Irradiation with the Er:YAG laser did not control the loss of structure of enamel subjected to erosion but did control abrasion after erosion.

Influence of laser irradiation on the push-out bond strength between a glass fiber post and root dentin.

STATEMENT OF PROBLEM: A major issue related to the failure of endodontically treated teeth restored with an intraradicular post is gradual debonding of the glass fiber post, resin cement, and dentin. PURPOSE: The purpose of this in vitro study was to evaluate the influence of laser irradiation on the push-out bond strength of glass fiber posts to radicular dentin. MATERIAL AND METHODS: Thirty-two mandibular bovine incisors were endodontically treated and divided into 4 groups according to the surface treatment of the post: silane control (GC); irradiation with Er:YAG (GYAG); irradiation with Er,Cr:YSGG (GCR); and 980-nm diode laser (GDI) application. After surface treatment, the glass fiber posts were cemented with dual adhesive resin cement. To evaluate bond strength, the specimens were subjected to a push-out test at a crosshead speed of 0.5 mm/min using a universal testing machine. Failure mode was analyzed using stereomicroscopy. The surface morphology was evaluated qualitatively after surface treatment by using confocal laser microscopy. The push-out test data (MPa) were analyzed using a linear mixed effects model and the Bonferroni test (α=.05). RESULTS: At the cervical third, no significant differences were observed between the GC and GCR groups (P=1.00), and both of the groups exhibited higher bond strength. At the middle and apical thirds, the GCR group revealed higher bond strength, which was significantly different from that observed in all other groups (P<.05). No statistical differences were observed among the other tested protocols (GC, GYAG, and GDI groups; P=1.00). Adhesive failure was predominant in all groups. CONCLUSIONS: Irradiation with Er,Cr:YSGG improved the bond strength of the cement-post-dentin interfaces.

Chlorhexidine and proanthocyanidin enhance the long-term bond strength of resin-based endodontic sealer

Abstract The aim of this study was to evaluate the effects of proanthocyanidin (PA) and chlorhexidine (CHX) on the bond strength (BS), failure pattern, and resin-dentin interface morphology of the endodontic sealers EndoREZ and AH Plus after 24 h and 6 months of water storage. A total of 120 prepared bovine roots were divided into six groups: AH Plus, CHX+AH Plus, PA+AH Plus, EndoREZ, CHX+EndoREZ, and PA+EndoREZ. Dentin was treated for 1 or 5 min with 2% CHX or 15% PA, respectively. Roots were filled and stored in water for 24 h or 6 months (n = 10). Root slices were subjected to push-out test and scanning electron microscopy (SEM). Data were compared using two-way ANOVA and student's t-test (α = 5%). BS decreased over time for AH Plus and untreated EndoREZ (p < 0.05). At 24 h, AH Plus had higher BS than EndoREZ (p < 0.001), with no differences among treatments for both sealers (p > 0.05). At 6 months, EndoREZ had higher BS values for CHX and PA than control (p < 0.05). AH Plus had higher BS than EndoREZ (p < 0.001), while with CHX or PA, similar BS was observed in both sealers (p > 0.05). Cohesive and mixed failures were observed in all groups. SEM revealed sealer tags in the root dentin. In conclusion, BS decreased with time and AH Plus had higher BS than EndoREZ in untreated dentin; however, CHX or PA enhanced long-term BS of EndoREZ. Overall, dentin treatment affected failure pattern and resin-dentin interface morphology, particularly for EndoREZ.

Non-contact profilometry of eroded and abraded enamel irradiated with an Er: YAG laser

Abstract Literature has reported positive results regarding the use of lasers in the control of erosive lesions; however, evaluating whether they are effective in the control of the progression of erosive/abrasive lesions is important. Objectives This study aimed to evaluate the effect of the Er:YAG laser irradiation in controlling the progression of erosion associated with abrasive lesions in enamel. Material and methods Bovine incisors were sectioned, flattened and polished. Forty-eight enamel slabs were subjected to treatment in an intraoral phase. Twelve volunteers used an intraoral appliance containing one slab that was irradiated with an Er:YAG laser (5.2 J/cm2, 85 mJ, 2 Hz) and another non-irradiated slab on each side of the appliance, during one phase of 5 d, under a split-mouth design. Devices were subjected to erosive challenges (1% citric acid, 5 min, 3 times a day) and abrasive challenges one h after (brushing force of 1.5 N for 15 s) randomly and independently on each side of the device. Measurements of enamel loss were performed via 3D optical profilometry (μm). We analyzed data using the Kruskal-Wallis and Mann-Whitney tests and morphological characteristics via scanning electron microscopy. Results Following erosive and abrasive challenges, the group that was irradiated with the Er:YAG laser presented less loss of structure than the non-irradiated group. The group that underwent erosion and irradiation did not exhibit a significant difference from the non-irradiated group. Conclusion Irradiation with the Er:YAG laser did not control the loss of structure of enamel subjected to erosion but did control abrasion after erosion.

Effect of a 12-methacryloyloxy-dodecyl-pyridinium-bromide-containing adhesive with different post types on the long-term bond strength to dentin.

The use of matrix metalloproteinase (MMPs) inhibitors, such as 12-methacryloyloxy-dodecyl-pyridinium-bromide (MDPB), might improve the adhesion of glass-fiber (GF) and polyfiber (PF) posts to root dentine. This study assessed the effect of an MDPB-containing adhesive on the long-term bond strength of GF or PF posts to bovine dentine. Bovine endodontically treated roots were randomly divided into six groups, according to the post type and adhesive system used, as follows: GF serrated post + MDBP-free adhesive; GF serrated post + MDPB-containing adhesive; GF smooth post + MDBP-free adhesive; GF smooth post + MDPB-containing adhesive; PF post + MDBP-free adhesive; PF post + MDPB-containing adhesive. Specimens were stored in water for 6 months, thermocycled (500 cycles wk-1 ), and submitted to the pull-out test and failure pattern analysis. The cement-dentin interface was evaluated using scanning electron microscopy. The pull-out data were analyzed using anova and Tukey's test (α = 0.05). No significant interaction between the type of post and the adhesive system was found. Polyfiber posts showed lower bond strength than GF posts, whether serrated or smooth, and the bond strength of the serrated and smooth GF posts was not significantly different. Adhesive failures were predominant in all groups. The type of retainer influenced the bond strength, and MDPB-containing adhesive did not improve the long-term bond strength of posts to dentine.

Effect of Er:Yag laser on dentin demineralization around restorations.

The aim of this study was to evaluate the effect of cavity preparation with Er:YAG laser on dentin adjacent to restorations submitted to cariogenic challenge in situ, by subsuperficial microhardness analysis. Bovine incisors were sectioned, flattened, and polished, resulting in 40 dentin slabs. The slabs were randomly assigned to four groups (n = 10), according to the cavity preparation method: I-high-speed handpiece (control); II-Er:YAG laser (160 mJ; 3 Hz); III-Er:YAG laser (260 mJ; 3 Hz); IV-Er:YAG laser (300 mJ; 3Hz). Cavities were restored with composite resin, and the specimens were fixed in intra-oral appliances, which were worn by 10 volunteers for 14 days for simulating cariogenic challenge in situ. During the experimental period, 20% sucrose solution was dripped over each specimen 6 times a day. Samples were removed, sectioned, and examined for subsuperficial Knoop microhardness at 100, 200, and 300 µm from the restoration and at 30 µm from dentin surface. Split-plot analysis of variance showed no significant difference among the cavity preparation techniques (p = 0.1129), among distances (p = 0.9030), as well as no difference in the interaction between the main factors (p = 0.7338). It was concluded that the cavity preparation with Er:YAG laser did not influence on dentin microhardness submitted to cariogenic challenge in situ.

Fracture Strength of Weakened Anterior Teeth Associated to Different Reconstructive Techniques.

This study evaluated the fracture strength of endodontically treated teeth submitted to reconstructive techniques through dynamic and static tests. Forty human anterior teeth were divided into 4 groups (n=10): GNW (non-weakened) - root restored with glass fiber post (GFP), GW - weakened root restored with GFP, GDA - weakened root restored with direct anatomic GFP, and GIA - weakened root restored with indirect anatomic GFP. The teeth were endodontically treated considering that experimental groups (GW, GDA and GIA) simulated weakened roots for restoration with GFP using different techniques. The GFP was luted with resin cement and the coronal portion was restored with composite resin and metallic crowns. All samples were submitted to chewing simulation at 60 cycles/min in a total of 300,000 cycles. The survival samples were further exposed to compressive loading at a crosshead speed of 1.0 mm/min in a universal testing machine. The load was applied at 135° to the long axis of the tooth until failure. Data were analyzed by ANOVA (a=0.05). After chewing simulation were observed: GNW: 100% of survival roots; GW: 70% of survival roots, and GDA and GIA: 80% of survival roots. The mean fracture strength values (N) were 280.6 (GNW), 239.0 (GW), 221.3 (GDA), and 234.1 (GIA) without significant difference among the groups (p=0.7476). The results suggested similar fracture strength in both weakened and non-weakened teeth regardless the reconstructive technique of root internal wall. Higher incidence of catastrophic fracture was observed in weakened teeth without restoration of the root internal wall.

Fracture Strength of Weakened Anterior Teeth Associated to Different Reconstructive Techniques

Abstract This study evaluated the fracture strength of endodontically treated teeth submitted to reconstructive techniques through dynamic and static tests. Forty human anterior teeth were divided into 4 groups (n=10): GNW (non-weakened) - root restored with glass fiber post (GFP), GW - weakened root restored with GFP, GDA - weakened root restored with direct anatomic GFP, and GIA - weakened root restored with indirect anatomic GFP. The teeth were endodontically treated considering that experimental groups (GW, GDA and GIA) simulated weakened roots for restoration with GFP using different techniques. The GFP was luted with resin cement and the coronal portion was restored with composite resin and metallic crowns. All samples were submitted to chewing simulation at 60 cycles/min in a total of 300,000 cycles. The survival samples were further exposed to compressive loading at a crosshead speed of 1.0 mm/min in a universal testing machine. The load was applied at 135° to the long axis of the tooth until failure. Data were analyzed by ANOVA (a=0.05). After chewing simulation were observed: GNW: 100% of survival roots; GW: 70% of survival roots, and GDA and GIA: 80% of survival roots. The mean fracture strength values (N) were 280.6 (GNW), 239.0 (GW), 221.3 (GDA), and 234.1 (GIA) without significant difference among the groups (p=0.7476). The results suggested similar fracture strength in both weakened and non-weakened teeth regardless the reconstructive technique of root internal wall. Higher incidence of catastrophic fracture was observed in weakened teeth without restoration of the root internal wall.

Resumo Este estudo avaliou a resistência à fratura de dentes tratados endodonticamente submetidos a diferentes técnicas de reconstrução por meio de testes dinâmico e estático. Quarenta dentes humanos anteriores foram divididos em 4 grupos (n=10): GNW (não fragilizado): raiz restaurada com pino de fibra de vidro (PFV), GW: raiz fragilizada restaurada com PFV, GDA: raiz fragilizada restaurada com PFV anatômico direto, e GIA: raiz fragilizada restaurada com PFV anatômico indireto. Os dentes foram tratados endodonticamente considerando que nos grupos experimentais (GW, GDA e GIA) simulou-se fragilização radicular das raízes para restauração com PFV utilizando diferentes técnicas. Os PFV foi cimentados com cimento resinoso e a porção coronária foi restaurada com resina composta e coroa metálica. Todas as amostras foram submetidas a simulação de mastigação em 60 ciclos/min totalizando 300,000 ciclos. As amostras sobreviventes foram submetidas a teste de compressão com velocidade de 1,0 mm/min em máquina universal de ensaio. A carga foi aplicada a 135° em relação ao longo eixo do dente até a falha do dente. Os dados foram analisados por ANOVA (a=0,05). Após a simulação da mastigação foi observado: GNW: 100% de sobrevivência das raízes; GW: 70% de sobrevivência das raízes, e GDA e GIA: 80% de sobrevivência das raízes. O valor médio de resistência à fratura (N) foi de 280,6 (GNW), 239,0 (GW), 221,3 (GDA) e 234,1 (GIA) sem diferença significante entre os grupos (p=0,7476). Os resultados sugerem similar resistência à fratura em ambos os dentes fragilizados ou não-fragilizados em relação à técnica de reconstrução das paredes radiculares internas. Elevada incidência de fraturas catastróficas foram observadas nos dentes fragilizados sem a restauração das paredes radiculares internas.

Evaluation of Mechanical Properties of Glass Fiber Posts Subjected to Laser Surface Treatments.

OBJECTIVE: The aim of this study was to evaluate the influence of laser irradiation on flexural strength, elastic modulus, and surface roughness and morphology of glass fiber posts (GFPs). BACKGROUND DATA: Laser treatment of GFPs has been introduced to improve its adhesion properties. MATERIALS AND METHODS: A total of 40 GFPs were divided into 4 groups according to the irradiation protocol: GC-no irradiation, GYAG-irradiation with erbium:yttrium-aluminum-garnet [Er:YAG], GCR-irradiation with erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG), and GDI-irradiation with diode laser. The GFP roughness and morphology were evaluated through laser confocal microscopy before and after surface treatment. Three-point bending flexural test measured flexural strength and elastic modulus. Data about elastic modulus and flexural strength were subjected to one-way ANOVA and Bonferroni test (p < 0.05). The effect of roughness was evaluated using the linear mixed effects model and Bonferroni test (p < 0.05). RESULTS: Laser treatment changed surface roughness in the groups GCR (p = 0.000) and GDI (p = 0.007). The mean flexural strength in GYAG (995.22 MPa) was similar to that in GC (980.48 MPa) (p = 1.000) but different from that in GCR (746.83 MPa) and that in GDI (691.34 MPa) (p = 0.000). No difference was found between the groups GCR and GDI (p = 0.86). For elastic modulus: GYAG (24.47 GPa) was similar to GC (25.92 GPa) (p = 1.000) but different from GCR (19.88 GPa) (p = 0.002) and GDI (17.20 GPa) (p = 0.000). CONCLUSIONS: The different types of lasers, especially Er,Cr:YSGG and 980 ηm diode, influenced the mechanical properties of GFPs.

Bonding Effectiveness of Universal Adhesive to Intracoronal Bleached Dentin Treated with Sodium Ascorbate

Abstract This study evaluated the effect of restorative protocol with sodium ascorbate on the shear bond strength (SBS) of a universal adhesive to intracoronal bleached dentin. One hundred-and-twenty bovine dentin fragments were randomly divided into 12 groups (n=10), according to the bleaching procedure (unbleached and bleached) and restorative protocol (no treatment, 10% sodium ascorbate -10SA, 35% sodium ascorbate -35SA and two-step etch-and-rinse -ER or one-step self-etch -SE Scotchbond universal adhesive approaches). Four whitening sessions were performed using 35% hydrogen peroxide. The samples from control groups were kept in relative humidity at 37 °C. Immediately after bleaching procedures, the assigned antioxidant solution was applied on dentin and restorative procedures were performed following either the ER or the SE approach. After 24 h, the specimens were subjected to SBS test. Data (MPa) were analyzed by ANOVA and Tukey's test (?=0.05). Lower SBS values were found for bleached specimens (8.54 MPa) compared with those unbleached (12.13 MPa) (p<0.05). The bond strength of the sodium ascorbate-treated groups was higher than those untreated, regardless of the strategy employed (p<0.05). Groups restored without sodium ascorbate showed lower bond strength values for both ER (8.32 MPa) and SE (8.28 MPa) adhesive strategies. The group treated with 10SA submitted to ER approach (10.14 MPa) was similar to untreated groups (p>0.05). It may be concluded that bond strength of composite resin to intracoronal dentin was affected by restorative protocol and reduced by bleaching.

Resumo Este estudo avaliou o efeito do protocolo restaurador empregando ascorbato de sódio na resistência ao cisalhamento do adesivo universal à dentina intracoronária clareada. Cento e vinte fragmentos de dentina bovina foram aleatoriamente divididos em doze grupos (n=10), de acordo com o procedimento clareador (clareados e não clareados) e protocolo restaurador (sem tratamento, ascorbato de sódio 10% (10AS), ascorbato de sódio (35AS) e estratégia de condicionamento total de dois passos (ER) ou estratégia autocondicionante de um passo (SE) com o sistema adesivo Scotchbond universal. Quatro sessões de clareamento foram realizadas empregando peróxido de hidrogênio a 35%. Os espécimes do grupo controle foram mantidos em umidade relativa a 37 °C. Imediatamente após os procedimentos de clareamento, as soluções antioxidantes selecionadas foram empregadas na dentina e os procedimentos restauradores foram realizados seguindo as estratégias ER ou SE. Após 24 h, os espécimes foram submetidos ao teste de resistência ao cisalhamento. Os dados (MPa) foram analisados pela ANOVA e teste de Tukey (?=0,05). Os menores valores de resistência ao cisalhamento foram encontrados para os espécimes clareados (8,54 MPa) comparados com aqueles não clareados (12,13 MPa) (p<0,05). A resistência de união dos grupos tratados com ascorbato de sódio foi maior que aqueles não tratados (p<0,05), independentemente da estratégia empregada. Grupos restaurados sem ascorbato de sódio demonstraram menores valores de resistência de união para ambas as estratégias adesivas ER (8,32 MPa) e SE (8,28 MPa) (p<0,05). O grupo tratado com ascorbato de sódio a 10% submetido à estratégia ER (10,14 MPa) foi similar ao não tratado (p>0,05). Pode ser concluído que a resistência de união da resina composta à dentina intracoronária foi afetada pelo protocolo restaurador e reduzida pelo clareamento.

Bonding Effectiveness of Universal Adhesive to Intracoronal Bleached Dentin Treated with Sodium Ascorbate.

This study evaluated the effect of restorative protocol with sodium ascorbate on the shear bond strength (SBS) of a universal adhesive to intracoronal bleached dentin. One hundred-and-twenty bovine dentin fragments were randomly divided into 12 groups (n=10), according to the bleaching procedure (unbleached and bleached) and restorative protocol (no treatment, 10% sodium ascorbate -10SA, 35% sodium ascorbate -35SA and two-step etch-and-rinse -ER or one-step self-etch -SE Scotchbond universal adhesive approaches). Four whitening sessions were performed using 35% hydrogen peroxide. The samples from control groups were kept in relative humidity at 37 °C. Immediately after bleaching procedures, the assigned antioxidant solution was applied on dentin and restorative procedures were performed following either the ER or the SE approach. After 24 h, the specimens were subjected to SBS test. Data (MPa) were analyzed by ANOVA and Tukey's test (?=0.05). Lower SBS values were found for bleached specimens (8.54 MPa) compared with those unbleached (12.13 MPa) (p<0.05). The bond strength of the sodium ascorbate-treated groups was higher than those untreated, regardless of the strategy employed (p<0.05). Groups restored without sodium ascorbate showed lower bond strength values for both ER (8.32 MPa) and SE (8.28 MPa) adhesive strategies. The group treated with 10SA submitted to ER approach (10.14 MPa) was similar to untreated groups (p>0.05). It may be concluded that bond strength of composite resin to intracoronal dentin was affected by restorative protocol and reduced by bleaching.

Crown lengthening surgery and transurgical restoration

Introduction: The crown lengthening surgery and the transurgical restoration are alternative procedures to enable the restoration of teeth inaccessible to the conventional techniques and restore the lost biological space. Objective: This study aimed to present clinically the reconstruction of a right maxillary second molar through crown lengthening surgery associated with transurgical restoration with composite resin in a patient treated in the Integrated Clinics of the University of Ribeirão Preto. Case report: Patient E.H.C.V., female, aged 51 years, attended the dental clinic of the University of Ribeirão Preto. The anamnesis showed a favorable health history and the clinical examination showed great tooth crown destruction of tooth #17. The treatment planning included the crown lengthening periodontal surgery with regularization of alveolar bone on the buccal surface of tooth #17, rubber dam isolation, the restauration of the compromised area with composite resin, and suture in the same session. After 7 days, the sutures were removed and the restoration polished. Conclusion: It can be concluded that the use of this technique is a viable, fast, and satisfactory solution, with good results, favoring the health and aesthetics, returning function and better social life to the patient.

Combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine.

OBJECTIVE: This study evaluated the combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine. DESIGN: Sixty slabs of bovine root dentine (2×2×2mm) were eroded with citric acid 0.3% (pH 3.2) during 2h and then kept in artificial saliva during 24h. Specimens were randomly assigned in 6 groups (n=10), to receive the following treatments: fluoride varnish; fluoride varnish+Er:YAG laser; fluoride varnish+Nd:YAG laser; non-fluoride varnish; non-fluoride varnish+Er:YAG laser; non-fluoride varnish+Nd:YAG laser. The Er:YAG (100mJ, 3Hz) and Nd:YAG (70mJ, 15Hz) were applied for 10s. Specimens were subjected to further erosive challenges with citric acid 0.3% 4×/day, during 1min, for 5 days, remaining in artificial saliva between cycles. Dentin permeability was then assessed. Two-way ANOVA demonstrated no significant interaction between laser and varnish (p=0.858). RESULTS: No effect was also detected for the main factor varnish (p=0.768), while permeability of eroded root dentin was significantly lower when such substrate was laser-irradiated, no matter the laser source (p<0.001). CONCLUSIONS: This study concluded that Er:YAG and Nd:YAG lasers can be employed to control the permeability of eroded root dentin, regardless of fluoride varnish application.

Effect of Fluoride Varnish Combined with Er:YAG Laser on the Permeability of Eroded Dentin: An In Situ Study

This study evaluated the combined effect of fluoride varnish and Er:YAG laser on the permeability of eroded bovine root dentin. After initial erosive challenge followed by a remineralization period, the specimens were divided in two groups according to the treatment - fluoride varnish and non-fluoride varnish - and were subdivided according to the irradiation protocol: Er:YAG laser (100 mJ, 3 Hz, 12.8 J/cm2per pulse, non-contact and defocus mode) and non-irradiated. After a lead-in period, 7 volunteers wore a palatal device containing 4 specimens that were subjected to erosive challenges. At the first experimental phase, 4 volunteers used specimens treated with fluoride varnish and fluoride varnish+Er:YAG laser and 3 volunteers used specimens treated with non-fluoride varnish and non-fluoride varnish+Er:YAG laser. After a washout period, volunteers were crossed to treatments, characterizing a 2x2 crossover experiment. At the end of the experimental phase, the quantitative response variable was obtained by permeability analysis and the qualitative response by scanning electron microscopy (SEM). Two-way ANOVA and Tukey-Kramer's test revealed that specimens treated with fluoride varnish+Er:YAG laser showed the lowest permeability and a significant difference was found between this group and the others. When varnish (fluoride/non-fluoride) was applied in the absence of Er:YAG laser, higher permeability was found when compared to the laser-treated groups. SEM evaluations showed partially or completely obliterated dentinal tubules when specimens were treated with fluoride varnish+Er:YAG laser. It may be concluded that Er:YAG laser was able to control the permeability of eroded root dentin and the combination with fluoride varnish increased laser action.

Resumo Esse estudo avaliou o feito combinado do verniz fluoretado ao laser de Er:YAG na permeabilidade da dentina radicular erodida. Fragmentos de dentina radicular bovina, foram submetidos a um desafio erosivo inicial com ácido cítrico, que foi seguido por um período de remineralização. Posteriormente, os espécimes foram divididos em relação aos tratamentos: verniz (fluoretado e não fluoretado) e subdivididos de acordo com a irradiação: laser de Er:YAG (100 mJ, 3 Hz, 12.8 J/cm2 por pulso, sem contato e modo não focado) e não irradiado. Após um período de lead in, 7 voluntários utilizaram um dispositivo palatino contendo 4 espécimes que foram submetidos a desafios erosivos. Na primeira fase do experimento, 4 voluntários utilizaram dispositivos com fragmentos tratados com verniz fluoretado e verniz fluoretado+laser de Er:YAG e 3 voluntários utilizaram espécimes tratados com verniz não fluoretado e verniz não fluoretado+laser de Er:YAG. Depois de um período de wash-out, os voluntários foram cruzados em relação aos tratamentos, caracterizando um experimento cross-over 2x2. Ao final de cada fase experimental, a variável resposta quantitativa foi obtida através da análise de permeabilidade e a qualitativa por microscopia eletrônica de varredura (MEV). A ANOVA dois critérios e teste de Tukey-Kramer revelou que as amostras tratadas com verniz fluoretado+laser de Er:YAG mostraram menor permeabilidade e uma diferença significativa foi encontrada entre este grupo, quando comparado aos demais grupos. Quando o verniz (fluoretado/não fluoretado) foram aplicados na ausência do laser de Er:YAG maiores valores de permeabilidade foram encontrados quando comparados com os grupos irradiados com o laser. A MEV demostrou túbulos dentinários parcialmente ou completamente ocluídos quando as amostras foram tratadas com verniz fluoretado+laser de Er: YAG. Pode-se concluir que o laser de Er:YAG foi capaz de controlar a permeabilidade da dentina radicular erodida e essa ação é aumentada quando o laser está associado ao verniz fluoretado.

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

OBJECTIVE: This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. METHODS: Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). RESULTS: Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). CONCLUSIONS: The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.

Surface roughness of composite resins subjected to hydrochloric acid.

The purpose of this study was to determine the influence of hydrochloric acid on surface roughness of composite resins subjected to brushing. Sixty samples measuring 2 mm thick x 6 mm diameter were prepared and used as experimental units. The study presented a 3x2 factorial design, in which the factors were composite resin (n=20), at 3 levels: microhybrid composite (Z100), nanofilled composite (FiltekTM Supreme), nanohybrid composite (Ice), and acid challenge (n=10) at 2 levels: absence and presence. Acid challenge was performed by immersion of specimens in hydrochloric acid (pH 1.2) for 1 min, 4 times per day for 7 days. The specimens not subjected to acid challenge were stored in 15 mL of artificial saliva at 37 oC. Afterwards, all specimens were submitted to abrasive challenge by a brushing cycle performed with a 200 g weight at a speed of 356 rpm, totaling 17.8 cycles. Surface roughness measurements (Ra) were performed and analyzed by ANOVA and Tukey test (p≤0.05). Surface roughness values were higher in the presence (1.07±0.24) as compared with the absence of hydrochloric acid (0.72±0.04). Surface roughness values were higher for microhybrid (1.01±0.27) compared with nanofilled (0.68 ±0.09) and nanohybrid (0.48±0.15) composites when the specimens were not subjects to acid challenge. In the presence of hydrochloric acid, microhybrid (1.26±0.28) and nanofilled (1.18±0,30) composites presents higher surface roughness values compared with nanohybrid (0.77±0.15). The hydrochloric acid affected the surface roughness of composite resin subjected to brushing.

Effects of various irrigation/aspiration protocols on cleaning of flattened root canals.

This study aimed to evaluate, by means of scanning electron microscopy (SEM), the cleaning of flattened root canals, varying irrigation/aspiration protocols during biomechanical preparation. Thirdy human mandibular incisors were distributed into three groups (n = 10) according to the aspiration/irrigation protocols: conventional, conventional + brush, and apical negative pressure irrigation. Irrigation procedure was performed with 5 mL of 1% NaOCl at each change of instrument; final irrigation was conducted with 17% EDTA for 5 min. After biomechanical preparation, the roots were sectioned and prepared for SEM analysis. The images obtained were evaluated under 35× and 1,000× magnification by three calibrated examiners, following a double-blind design. All data were analyzed using Kruskal-Wallis and Dunn's post hoc tests (α = 0.05). Canals wherein the conventional method and apical negative pressure irrigation were employed revealed less debris, statistically different from the conventional + brush group (p < 0.05). Regarding the presence of smears, apical negative pressure irrigation was more effective in cleaning, showing lowest scores (p < 0.05), compared with the other tested protocols. Comparing each root canal third revealed that the apical portion was difficult to clean as all the tested protocols showed similar high scores (p > 0.05), both for the presence of debris and smear layer. In conclusion, although none of the studied irrigation/aspiration protocols have completely cleaned flattened root canals, apical negative pressure irrigation was more effective in smear layer removal, whereas the conventional + brush protocol was the least effective in removing the debris and smear layer.