Analysis of Human Tooth Pulp Chamber Temperature After 670 nm Laser Irradiation: In Vitro Study.

OBJECTIVE: One of the limiting factors of employing laser radiation on dental therapies is the potential of causing thermal injuries to pulp tissues. The purpose of this study was to evaluate intra-chamber temperature increase on extracted human teeth exposed to 670 nm wavelength InGaAlP laser diode radiation. MATERIALS AND METHODS: In vitro intra-chamber temperature measurements of 12 standardized human teeth (incisors, canines, premolars, and molars; n = 3) were taken both before and after laser radiation. A type-K thermocouple fast-response thermocouple wire with a 0.5 mm diameter probe was inserted into the tooth pulp chamber (ICEL-Manaus-brand). The laser device Lasotronic-brand InGaAlP laser diode was used to irradiate tooth enamel, perpendicularly to the external surface for 30 sec, with power of levels of 340, 272, 204, 136, and 68 mW. The measurements were taken at three time points: 0, 30 sec, and 3 min after the laser irradiation. Measurements were repeated 24 h after removal and reinsertion of the probe in the pulp chamber. The temperature gradient (ΔT in °C) was calculated (ΔT = final temperature-initial temperature) for each group. Data of ΔT were statistically analyzed by two-way analysis of variance (ANOVA) at the 95% confidence level and compared by Tukey post hoc test (α = 0.05). RESULTS: ANOVA showed statistically significant differences to the interaction of factors (p < 0.05). The highest ΔT values obtained were observed to incisors with 340 mW, 272 mW; 204 mW of power (respectively 4.7°C, 4.2°C, and 3.1°C); and canines presented the lowest ΔT (0.8°C-0.3°C) with no influence of power output. CONCLUSIONS: Since the thermal increase was observed in this study, especially in incisors, attention should be paid to avoid pulpal damage.

Bond Strength of Abraded and Non-Abraded Bleached Enamel to Resin After Er,Cr:YSGG Laser Irradiation.

OBJECTIVE: The objective of the study was to evaluate the microtensile bond strength (µTBS) of a composite resin to abraded or non-abraded bleached enamel after Er,Cr:YSGG laser irradiation and to observe the fracture patterns of the tested interfaces. MATERIALS AND METHODS: Two hundred twenty-eight bovine incisors were sectioned, resulting in 228 enamel blocks (7 × 4 × 4 mm3) that were divided into 12 groups (n = 19) according to the factors "adhesion" after bleaching (immediate adhesion; after 14 days; and a control group with adhesion on unbleached teeth); enamel "abrasion" (with or without abrasion simulating cavity preparation); and "laser" (with or without Er,Cr:YSGG laser irradiation). Bleached enamel groups were treated with 20% carbamide peroxide, 8 h/day for 21 days. Abrasion was performed with silicon carbide sandpaper. Specimens were restored with adhesive system and a composite resin (Adper Single Bond 2 and Z250; 3M ESPE). After 7 days, specimens were prepared by cutting into 1 mm beans to µTBS test performed in a universal testing machine. Fracture mode analysis was performed by using a stereoscopic loupe. The µTBS data were statistically analyzed by three-way analysis of variance with 95% confidence level and compared by running a Tukey post hoc test (α = 0.05). RESULTS: There was no statistically significant difference between triple interaction and double interactions among factors. There was no significant difference between the factors "adhesion," "abrasion," and "laser." Laser irradiation produced significantly lower bond strength values in irradiated groups compared with the non-irradiated ones. All groups had a high percentage of adhesive failures. CONCLUSIONS: Abrasion provided no benefit to bond strength of composite resins to bleached enamel. Er,Cr:YSGG (20 Hz, 0.5 W, 3.97 J/cm2) treatment reduced the bond strength of composite resins to enamel.

In Vitro Behavior of Osteoblasts on Zirconia After Different Intensities of Erbium, Chromium-Doped: Yttrium, Scandium, Gallium, and Garnet-Laser Irradiation.

OBJECTIVE: This study investigated the osteoblastic behavior to yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) surface after different intensities of erbium, chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation treatment. MATERIALS AND METHODS: Y-TZP blocks were randomized divided into 4 groups to Er,Cr:YSGG laser irradiation: group G1 = control (no laser irradiation); group G2 = 1.5 W; group G3 = 3.0 W; group G4 = 5.0 W, with air-water irrigation. The irradiated surface roughness (Sa and Ra) topography was evaluated. MC3T3-E1 osteoblast cells were cultured and seeded onto the treated surfaces at a plate density of 1 × 10 cells/mL. At the third and seventh days cell proliferation was measured by the colorimetric assay methods. The specimens were prepared to scanning electron microscope to observe adhesion and morphology of cells. RESULTS: MTT assay showed adhesion and proliferation of MC3T3-E1 cells in all groups. Compared with group G1 (control), the group G2 had a proliferation 1.4% higher (P > 0.05), the group G3 had a proliferation 3.1% higher (P < 0.05) and group G4 had a proliferation 4.5% higher (P < 0.01). After 7 days there was no difference among the groups (ANOVA, Newman-Keuls). CONCLUSIONS: Er,Cr:YSGG laser irradiation may have contributed to the greater and earlier cell spreading that was observed with the Y-TZP without alterations on surface topography.

Influence of cavity preparation with Er,Cr:YSGG laser and restorative materials on in situ secondary caries development.

OBJECTIVE: The aim of this study was to evaluate the influence of cavity preparation and restorative materials containing fluorides in the prevention of secondary caries lesion development in situ. METHODS: A total of 120 blocks obtained from human teeth were divided into two groups and standardized cavities were prepared using diamond burs (DB) or Er,Cr:YSGG-laser [20 Hz, 4.0W, 55% water, 65% air (LA)]. They were divided into three subgroups according to the restorative material (n=20): glass-ionomer cement (GI), resin modified glass-ionomer (RM) or composite resin (CR). Blocks were fixed in palatal intra-oral appliances worn in situ by 20 human volunteers, who dropped 20% sucrose solution eight times daily. After 21 days, blocks were removed and restorations were cross-sectioned to evaluate microhardness [Knoop hardness number (KHN)] underneath enamel surface from 30 to 200 µm. Factors "cavity preparation," "restorative materials," and "depth" were evaluated by three way ANOVA, followed by Tukey test (p<0.05). RESULTS: The results showed lower microhardness in cavities prepared with DB than in cavities prepared with LA. At 30 µm, there were no statistical significant differences with regard to "cavity preparation" or "restorative materials" factors. In depth evaluation, the enamel microhardness progressively increased as a function of depth for the GI groups. In the groups prepared with LA at 60 µm/90 µm, there were no significant differences between GI and RM materials, whose microhardnesses were significantly higher than that of CR. CONCLUSIONS: Cavity preparation using Er,Cr:YSGG laser increases caries resistance of enamel walls, and reduce caries lesion depth development regardless of fluoride presence in the restorative material. CR showed higher caries lesion development than GI, and RM showed intermediate results.

The influence of erbium:yttrium-aluminum-garnet laser ablation with variable pulse width on morphology and microleakage of composite restorations.

The objective of this study was to evaluate the influence of various pulse widths with different energy parameters of erbium:yttrium-aluminum-garnet (Er:YAG) laser (2.94 mum) on the morphology and microleakage of cavities restored with composite resin. Identically sized class V cavities were prepared on the buccal surfaces of 54 bovine teeth by high-speed drill (n = 6, control, group 1) and prepared by Er:YAG laser (Fidelis 320A, Fotona, Slovenia) with irradiation parameters of 350 mJ/ 4 Hz or 400 mJ/2 Hz and pulse width: group 2, very short pulse (VSP); group 3, short pulse (SP); group 4, long pulse (LP); group 5, very long pulse (VLP). All cavities were filled with composite resin (Z-250-3 M), stored at 37 degrees C in distilled water, polished after 24 h, and thermally stressed (700 cycles/5-55 degrees C). The teeth were impermeabilized, immersed in 50% silver nitrate solution for 8 h, sectioned longitudinally, and exposed to Photoflood light for 10 min to reveal the stain. The leakage was evaluated under stereomicroscope by three different examiners, in a double-blind fashion, and scored (0-3). The results were analyzed by Kruskal-Wallis test (P > 0.05) and showed that there was no significant differences between the groups tested. Under scanning electron microscopy (SEM) the morphology of the cavities prepared by laser showed irregular enamel margins and dentin internal walls, and a more conservative pattern than that of conventional cavities. The different power settings and pulse widths of Er:YAG laser in cavity preparation had no influence on microleakage of composite resin restorations.

Implant surface analysis and microbiologic evaluation of failed implants retrieved from smokers.

The aim of this study was to evaluate the microbiota and surface of failed titanium dental implants from 4 manufacturers. Twelve mobile dental implants were retrieved from 10 smokers after 3 to 10 years of functional loading. Before implant removal, microbial samples were taken and evaluated using polymerase chain reaction. After implant removal, analyses of the failed implant surfaces were performed using scanning electron microscopy and energy-dispersive spectrometer x-ray. Periodontal pathogens such as Aggregactibacter actinomycetemcomitans, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Treponema denticola were detected in all implants in different proportions. Surface analysis showed varying degrees of surface roughness between the samples and the presence of proteinaceous material, appearing mainly as dark stains. Foreign carbon, oxygen, sodium, calcium, aluminum, and silicon elements were also found. Although no material-related causes of implant failure were detected, several periodontal pathogens were identified independently of the surface topography or manufacturer.

Estudo in vitro da resistência à traçäo de um adesivo dentinário associado a uma resina composta direta para dentes posteriores utilizando duas técnicas de fotopolimerizaçäo: luz visível e laser de argônio / In vitro study of the tensile bond strength of a dentin bonding system associated with posterior teeth restorative composite resin using two techniques of polimerization ? visible-light and argon laser

Foi estudado, através da avaliaçäo da resistência à força de traçäo em dentina bovina, um sistema adesivo associado à uma resina composta para dentes posteriores utilizando duas técnicas de fotopolimerizaçäo: luz visível e laser de Argônio. Foram confeccionados 60 corpos-de-prova através do desgaste vestibular de incisivos bovinos incluídos em resina acrílica. Foi utilizado o sistema adesivo Single Bond (3M), que é um sistema adesivo monocomponente com um copolímero ácido polialcenóico, associado à uma resina composta direta para dentes posteriores (Filtek P60 - 3M). As superfícies dentinárias foram tratadas de acordo com a orientaçäo do fabricante. Esses 60 dentes, incluídos e desgastados, foram divididos em 4 grupos de 15 dentes: no grupo1 a fotopolimerizaçäo do adesivo foi realizada durante 10segundos com luz visível (Curing Light - 3M) com densidade de potência de 410mWcm e a fotopolimerizaçäo da resina foi realizada durante 20segundos com luz visível/ no grupo2 a fotopolimerizaçäo do adesivo e da resina foi realizada durante 10segundos com laser de Argônio (AccuCure 3000 - LaserMed) com potência de 150mW/ no grupo3 a fotopolimerizaçäo do adesivo e da resina foi realizada durante 10segundos com laser de Argônio (AccuCure 3000 - LaserMed) com potência de 200mW e no grupo 4 a fotopolimerizaçäo do adesivo e da resina foi realizada durante 10segundos com laser de Argônio (AccuCure 3000 - LaserMed) com potência de 250mW. Para o preenchimento total da matriz cônica de teflon com 3mm de altura, foi utilizada a técnica incremental onde a resina composta foi polimerizada em camadas, em média de 1 mm cada...