Erbium laser in the debonding of ceramics: a literature review / Laser de érbio na remoção de cerâmicas: uma revisão de literatura

Background: The debonding of crowns and ceramic veneers with laser is already a reality in the clinic. It presents benefits in comparison to traditional removal with the use of a rotating instrument; however, there is still no consolidated protocol and many professionals use it without the necessary scientific basis. Objective: The aim of this work was to perform a literature review on the debonding of indirect ceramic restorations using the Er:YAG and Er,Cr:YSGG lasers to provide clinical professionals and the scientific community a careful analysis, and also to guiding the use of irradiation at laser for such procedures. Methods: Bibliographic searches were performed in the following databases: Pubmed, Web of Science and Google Scholar. According to the inclusion criteria adopted, twenty-seven clinical and in vitro studies were selected in the period from 2007 to 2021. In the present work, the composition of the crowns and facets, as well as the types of cement and the laser irradiation protocols adopted in the selected studies is detailed. Conclusions: It was concluded that the use of erbium lasers for debonding of indirect ceramic restorations proved to be more selective and conservative when compared to removal with a rotary diamond instrument. Furthermore, it was shown to be in more efficient in debonding different types of ceramics. However, there are great variations in the "debonding" protocols, which emphasizes the need for further studies that seek to standardize the irradiation protocols considering the different clinical situations (AU)

Antecedentes: A remoção de coroas e facetas cerâmicas com laser já é uma realidade clínica e apresenta benefícios em relação à remoção tradicional com uso de instrumento rotatório diamantado; entretanto, ainda não existe um protocolo consolidado e muitos profissionais o utilizam sem o embasamento científico necessário. Objetivos: O objetivo deste trabalho foi realizar uma revisão da literatura sobre a remoção de restaurações cerâmicas indiretas utilizando os lasers Er:YAG e Er,Cr:YSGG para fornecer uma análise cuidadosa aos profissionais clínicos e à comunidade científica, além de orientar o uso da irradiação a laser para tal aplicação. Métodos: As buscas bibliográficas foram realizadas, nas seguintes bases de dados: Pubmed, Web of Science e Google Scholar. De acordo com os critérios de inclusão adotados, foram selecionados vinte e sete estudos clínicos e in vitro no período de 2007 a 2021. No presente trabalho, a composição das coroas e facetas, bem como os tipos de cimento e os protocolos de irradiação laser adotados nos estudos selecionados foram detalhados. Conclusão: Concluiu-se que o uso dos lasers de érbio para remoção de restaurações cerâmicas indiretas mostrou-se mais seletivo e conservador quando comparado à remoção com instrumento rotatório diamantado, além de ser eficiente na remoção de diferentes tipos de cerâmicas. No entanto, existem grandes variações nos protocolos de "debonding", o que enfatiza a necessidade de novos estudos que busquem uma padronização dos protocolos de irradiação considerando as diferentes situações clínicas.(AU)

Assessment of the preventive effects of Nd:YAG laser associated with fluoride on enamel caries using optical coherence tomography and FTIR spectroscopy.

OBJECTIVE: This in vitro study characterized and monitored, by Optical Coherence Tomography (OCT) and Fourier Transformed Infrared Spectroscopy (FTIR), the effects of the association of acidulated phosphate fluoride gel (APF-gel) and Nd:YAG (neodymiun:yttrium-aluminum-garnet) laser, as sequencial treatments, in the prevention of incipient enamel caries lesions. METHODS: 120 human enamel samples were randomized into 3 groups (n = 40): APF-gel (1.23% F-, 4 min.); Laser+APF (Nd:YAG laser irradiation-0.6W, 84.9J/cm2, 10Hz, followed by APF-gel); and APF+Laser (APF-gel followed by laser irradiation). The samples were subjected to a 15-day pH-cycling, evaluated by OCT (quantification of optical attenuation coefficient-OAC) and FTIR (analysis of carbonate and phosphate content) before treatments, after treatments, and on the 5th, 10th and 15th days of pH-cycling. The statistical analysis was performed (α = 5%). RESULTS: The Optical Attenuation Coefficient (OAC) assessed by OCT increases with the progression of demineralization, and the Laser+APF presented the highest values of OAC in 10th and 15th days of pH-cycling. Nd:YAG decreased the carbonate content after treatment regardless of the application order of the APF-gel, while APF-gel did not interfere in the composition of enamel. The carbonate content was also changed in the first 5 days of the pH-cycling in all groups. CONCLUSION: Nd:YAG laser irradiation before or after the application of APF-gel did not influence the appearance of incipient caries lesions, showing no synergistic effect. Regardless of the application order of the APF-gel, laser irradiation reduces the carbonate content of the enamel, which also changes during the demineralization process. However, irradiation before the application of APF-gel increased the speed of progression of the lesions, which positively impacts public health as it can prevent caries disease, even in high risk individuals. OCT and FTIR are suitable for assessing this effect.

Osteoporosis evaluation through full developed speckle imaging.

Osteoporosis is a disease characterized by bone mineral density reduction, weakening the bone structure. Its diagnosis is performed using ionizing radiation, increasing health risk. Optical techniques are safer, due to non-ionizing radiation use, but limited to the analyses of bone tissue. This limitation may be circumvented in the oral cavity. In this work we explored the use of laser speckle imaging (LSI) to differentiate the sound and osteoporotic maxilla and mandible bones in an in vitro model. Osteoporosis lesions were simulated with acid attack. The samples were evaluated by optical profilometry and LSI, using a custom software. Two image parameters were evaluated, speckle contrast ration and patches ratio. With the speckle contrast ratio, it was possible to differentiate sound from osteoporotic tissue. From speckle patches ratio it was observed a negative correlation with the roughness parameter. LSI is a promissory technique for assessment of osteoporosis lesions on alveolar bone.

The effects of photodynamic therapy with blue light and papain-based gel associated with Urucum, on collagen and fibroblasts: a spectroscopic and cytotoxicity analysis.

Papacarie Duo™ is clinically used and has proven effectiveness; however, it is necessary to improve its antimicrobial action. The combined treatment of Papacarie Duo™ with Urucum (Bixa Orellana) could create a potential tool for dental caries treatment; its extract obtained from the seeds' pericarp contains a water-soluble primary pigment (cis-bixin) with smaller amounts of other carotenoids. The dicarboxylic acid salts of cis-norbixin and trans-norbixin occur in heated alkaline solutions. To analyze the absorption spectra and cytotoxicity (with human dermal fibroblasts) in different concentrations of Urucum, associated or not with Papacarie Duo™, we performed this in vitro study. The effects of pure Urucum, Papacarie Duo™, and PapaUrucum™ on the microstructure of collagen were also analyzed. The application of papain-based gel with Urucum did not present cytotoxicity, its exhibit UV absorption spectrum peak around 460 ± 20 nm. Also, it showed that the compound used did not alter the chemical structure of collagen. Consequently, this product could be used as a chemomechanical method to remove dentin caries as well as being a potential product for antimicrobial photodynamic therapy (aPDT) application.

Evaluation of Intra Root Canal Er,Cr:YSGG Laser Irradiation on Prosthetic Post Adherence.

PURPOSE: In clinical prosthetics procedures, including endodontics and post fixation, the presence of a smear layer can reduce the post bond strength. An Er,Cr:YSGG laser, which emits at 2780 nm, can promote a smear-layer-free surface due to the ablation process. Considering these aspects, the purpose of this work was to evaluate the influence of Er,Cr:YSGG laser irradiation using either a radial or an axial fiber tip on the bond strength of three resin cements to the fiber-reinforced composite posts. MATERIALS AND METHODS: Ninety recently extracted single rooted human teeth had their root canal instrumented and were randomly distributed into nine experimental groups, in which three resin cements (total-etching Variolink II, self-etching Panavia F, and self-adhesive RelyX Unicem Aplicap) and three root canal treatments (no treatment, laser irradiation using the radial fiber tip, laser irradiation using the axial fiber tip) were used. Specimens were then sectioned into three sections (cervical, middle, and apical thirds) with two slices on each section. A push-out test was performed on each slice, and the values were recorded as MPa. The push-out data were analyzed by a Ryan-Joiner normality test followed by a two-way ANOVA test and Tukey pairwise comparison. The statistical analysis was performed on each third section separately, with a 5% significance level. RESULTS: Laser irradiation with axial fiber tip significantly increased the post bond strength of RelyX Unicem Aplicap on middle third of specimens (p < 0.001) when compared to other root canal treatments (unlased or irradiated with radial tip). Considering the Panavia resin cement, laser irradiation with either axial or radial tips promoted a significant increase on the post bond strength of middle third when compared to unlased specimens (p < 0.001); however, laser irradiation did not influence the post bond strength of Variolink resin cement. CONCLUSIONS: The use of the Er,Cr:YSGG laser for clinical prosthetics procedures enhances the post bond strength of Panavia and RelyX Unicem Aplicap resin cements, mainly at middle third of roots, and does not interfere with the bond strength of Variolink resin cement. For the RelyX Unicem Aplicap system, the use of axial tip is most advantageous and can be recommended for future clinical application.

Evaluation of the accuracy between splinting and non-splintingimpression techniques for multiple implants

Introduction: Among the determinant factors for the implant-supported prosthesis longevity is the exact and comprehensive process of impression which results is the passive prosthesis fitting. Objective: To compare the accuracy of transfer coping impression techniques with or without splinting, after the isolation of the factors associated to the passive fitting. Method: Based on the control group composed by an edentulous mandibular master model (self-cured acrylic resin) with four external hexagon parallel implants splinting with a metallic bar, four customized open trays were constructed with self-cured acrylic. Ten impressions were made with condensation silicone ( Xantopren ®), poured with type IV plaster ( Durone ®), and then divided into two groups: Group 1 (n=5) ­ non-splinting multi unit transfer copings; and Group 2 (n=5) ­ splinting multi unit transfer copings with a bar constructed with self-cured acrylic resin ( Palavit G ®) and dental floss, with the aid of an addition silicon mold ( Elite Double ® Zhermack) . Next, the bar was cut and splinted again. The ten transfer molds were measured at the center of the labial surface of each implant with the aid of Stereoscopic Magnifying Glass ( Physis ®) with x60 magnification. The results were tabulated and submitted to non-parametric statistics through Kruskal-Wallis test (p<0.05). Results: The means were: 22.44 µm (±7) for control group, 26.86 µm (±10) for direct splinting, and 24.70 µm (±13) for direct non-splinting technique. Conclusion: No statistically significant differences were found between the tested techniques.

Introdução: Entre os fatores determinantes para a longevidade de uma prótese implanto suportada, está o processo exato e meticuloso de moldagem dos implantes osseointegrados, implicando diretamente no assentamento passivo da prótese. Objetivo: Comparar a precisão das técnicas de moldagem com e sem união dos transferentes isolando os fatores que podem estar associados ao ajuste passivo. Métodos: A partir de um grupo controle composto por um modelo mestre (em resina acrílica quimicamente ativada) mandibular desdentado com quatro implantes de conexão externa posicionados paralelamente e unidos por uma barra metálica. Foram confeccionadas dez moldeiras em resina acrílica quimicamente ativada (todas abertas). Dez impressões foram feitas com silicone de condensação Xantopren ®, e vertidas com gesso tipo IV, Durone ®, divididas em dois grupos: Grupo 1 (n=5) ­ Pilares multi unit não unidos e Grupo 2 (n=5) ­ Pilares multi unit unidos por uma barra confeccionada com fio dental e resina acrílica autopolimerizável, Palavit G ®, através de um molde de silicone de adição, Elite Double ® Zhermack . Em seguida, a barra foi seccionada e reunida. Os dez modelos de transferência foram mensurados no centro da face vestibular de cada um dos implantes através de uma lupa estereoscópica ( Physis ®) com ampliação de 60 vezes. Os resultados foram tabulados e submetidos à análise estatística não paramétrica, teste Kruskal-Wallis (p<0,05). Resultados: As médias aritméticas encontradas foram de 22,44 µm (±7) para grupo controle, 26,86 µm (±10) para técnica direta com esplintagem e 24,70 µm (±13) para técnica direta sem esplintagem. Conclusão: Não foi identificado diferenças estatísticas significantes entre as técnicas experimentadas.

Photodynamic Therapy Associated with a Blue Dye Papain-Based Gel and Evaluation of Its Degradation of Type I Collagen Fibers.

OBJECTIVE: The aim of this in vitro study was to evaluate the degradation of type I collagen fibers after treatment with a papain-based gel associated with a blue dye (PapaMBlue™) for use in antimicrobial photodynamic therapy. MATERIALS AND METHODS: For such, 60 bioabsorbable membrane sponge discs were used. Group 1 was the negative control group. In groups 2, 3, and 4, the papain-based gel PapaMBlue gel was applied all over the samples for 4 min and irradiated using red laser (660 ± 10 nm) with 15, 30, and 40 J/cm2, respectively. In group 5, the papain-based gel was applied all over the samples for 4 min. In group 6, the photosensitizing dye was applied all over the samples for 4 min. The compositional analysis of the samples was performed using ATR-FTIR (attenuated total reflectance-Fourier transformed infrared spectroscopy). The data were statistically analyzed using ANOVA and Tukey's test (p < 0.05). RESULTS: Neither classic Papacarie™ nor the modified product with a photosensitizing agent (PapaMBlue) promoted collagen degradation. CONCLUSIONS: The irradiation of methylene blue added to papain gel with red light did not alter the chemical structure of type I collagen.

Comparison between open and closed-tray impression techniques on the implant transfer accuracy / Comparação das técnicas de moldagem com moldeira aberta e fechada na precisão da transferência de implantes

Objective: This in vitro study aimed to determine and compare the dimensional accuracy of open and closed-tray impression techniques for implantsupported prosthesis. Material and Methods: On a edentulous master model, four external hexagonal implants were parallelly installed and associated with four multi unit coping transfers and four multi unit rotational caps. A master superstructure was constructed and splinted all implants (control group). Five customized trays were constructed to perform ten open (n=5) and closed-tray (n=5) impressions. The obtained models were submitted to the dimensional analysis on three points in the center of the labial face of each implant (A, B, C, and D) with the aid of Stereoscopic Magnifying Glass with x60 magnification. The vertical misfit between the metallic structure and the implant analogues was measured on each point. The obtained results were submitted to Dixon's normality test and KruskalWallis test for independent samples p < 0.05) with the aid of Bioestat 5.0 software. Results: The means and standard deviation were: open tray technique ­ 24.6474 ± 14.8883 µm; closed-tray technique ­ 26.2257 ± 9.7421 µm; and control group 22.445 ± 7.7106 µm. Conclusion: The accuracy of open and closed-tray impression techniques showed no statistically significant differences and both techniques were effective for implant transfer. (AU)

Objetivos: O presente estudo in vitro objetiva determinar e comparar a precisão dimensional das técnicas de transferência de implantes direta e indireta para próteses implantossuportadas. Material e Métodos: a partir de um modelo mestre mandibular desdentado, foram instalados paralelamente quatro implantes hexágonos externos associados a quatro componentes multi unit e quatro capas multi unit rotacionais. Confeccionou-se uma infraestrutura mestre metálica unindo todos os elementos, considerando o conjunto como grupo controle (GC). Ao todo, fabricaram-se cinco moldeiras individuais para realizar 10 moldagens mediante as técnicas direta e indireta (n= 5), sendo os modelos obtidos submetidos à análise dimensional e estatística. Com uma lupa estereoscópica binocular com ampliação de 60 x, estabeleceram-se três pontos no centro da face vestibular de cada um dos implantes (A, B, C e D) por amostra. Em cada ponto, mensurou-se o desajuste vertical entre a estrutura metálica e os análogos. Os resultados obtidos foram submetidos ao teste de normalidade de Dixon e teste de Kruskal- Wallis para amostras independentes (p< 0,05) com o auxílio do software Bioestat 5.0. Resultados: médias aritméticas e desvio padrão identificados no grupo moldagem direta (24,6474 ± 14,8883 µm) e moldagem indireta (26,2257 ± 9,7421 µm) em comparação com o modelo mestre (22,445 ± 7,7106 µm). Conclusão: Pôde-se concluir que não houve diferenças estatísticas significativas entre as técnicas na precisão da transferência de implantes, sendo ambas igualmente eficientes. (AU)

Mercury Amalgam Diffusion in Human Teeth Probed Using Femtosecond LIBS.

In this work the diffusion of mercury and other elements from amalgam tooth restorations through the surrounding dental tissue (dentin) was evaluated using femtosecond laser-induced breakdown spectroscopy (fs-LIBS). To achieve this, seven deciduous and eight permanent extracted human molar teeth with occlusal amalgam restorations were half-sectioned and analyzed using pulses from a femtosecond laser. The measurements were performed from the amalgam restoration along the amalgam/dentin interface to the apical direction. It was possible to observe the presence of metallic elements (silver, mercury, copper and tin) emission lines, as well as dental constituent ones, providing fingerprints of each material and comparable data for checking the consistence of the results. It was also shown that the elements penetration depth values in each tooth are usually similar and consistent, for both deciduous and permanent teeth, indicating that all the metals diffuse into the dentin by the same mechanism. We propose that this diffusion mechanism is mainly through liquid dragging inside the dentin tubules. The mercury diffused further in permanent teeth than in deciduous teeth, probably due to the longer diffusion times due to the age of the restorations. It was possible to conclude that the proposed femtosecond-LIBS system can detect the presence of metals in the dental tissue, among the tooth constituent elements, and map the distribution of endogenous and exogenous chemical elements, with a spatial resolution that can be brought under 100 µm.

Papain gel containing methylene blue for simultaneous caries removal and antimicrobial photoinactivation against Streptococcus mutans biofilms.

This study intended to evaluate the effects of a papain-gel with a red-light absorbing pigment (methylene blue - MB) to mediate photodynamic therapy (PDT) against Streptococcus mutans biofilms. The PapaMBlue was compared with free MB to generate reactive oxygen species using fluorescence probes (SOSG and HPF). PDT (660-nm light) was carried out against S. mutans biofilms grown on either plastic dishes or on collagen membrane and assayed by CFU, live-dead staining using confocal microscopy, transmission electron microscopy and H&E staining for collagen films. Cytotoxicity and subcellular localization was studied in human fibroblasts. Sponges of bioabsorbable type I collagen membrane were exposed to papain based gel, irradiated with laser and analyzed about their integrity by ATR-FTIR. The PapaMBlue produced higher amounts of singlet oxygen and hydroxyl radicals than free MB, possibly due to better disaggregation of the dye in solution. The PapaMBlue antimicrobial effects on biofilms proved to be capable of reducing the S. mutans. Both MTT and PrestoBlue assays showed higher cell viability and metabolism scores in fibroblasts treated with PapaMBlue and MB, possibly due to stimulation of mitochondrial activity and that collagen triple helix is unaffected. The PapaMBlue is equally effective as MB in destroying S. mutans biofilms growing on plastic or collagen without affecting fibroblasts.

Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components.

The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

Effect of papain-based gel on type I collagen--spectroscopy applied for microstructural analysis.

Considering the improvement of biomaterials that facilitate atraumatic restorative techniques in dentistry, a papain-based gel can be used in the chemomechanical removal of decayed dental tissue. However, there is no information regarding the influence of this gel on the structure of sound collagen. The aim of the present study was to investigate the adsorption of a papain-based gel (Papacarie(TM)) to collagen and determine collagen integrity after treatment. A pilot study was first performed with 10 samples of type I collagen membrane obtained from bovine Achilles deep tendon to compare the influence of hydration (Milli-Q water) on infrared bands of collagen. In a further experiment, 10 samples of type I collagen membrane were used to evaluate the effects of Papacarie(TM) on the collagen microstructure. All analyses were performed using the attenuated total reflectance technique of Fourier transform infrared (ATR-FTIR). The results demonstrated that the application of Papacarie(TM) does not lead to the degradation of collagen and this product can be safely used in minimally invasive dentistry. As the integrity of sound collagen is preserved after the application of the papain-based gel, this product is indicated for the selective removal of infected dentin, leaving the affected dentin intact and capable of re-mineralization.

Dental enamel irradiated with a low-intensity infrared laser and photoabsorbing cream: a study of microhardness, surface, and pulp temperature.

OBJECTIVE: The aim of this study was to assess the effect of low-intensity infrared laser light (λ=810 nm, 100 mW/cm(2), 90 sec, 4.47 J/cm(2), 9 J) with or without indocyanine green cream fluorinated or not fluorinated, using Knoop surface microhardness analysis. BACKGROUND DATA: Lasers can be used as tools for the prevention of tooth enamel demineralization. METHODS: The surface and pulp temperatures of the human deciduous tooth enamel were measured. For the analysis of surface hardness, a total of 48 specimens were prepared and randomly assigned into six groups (n=8/group): C (+), which received laser light; C(-), which received no treatment; cream (IV); cream and fluoride (IVF); cream and light (IVL); and cream and fluoride and light (IVFL). The specimens were subjected to treatment before demineralizing challenge by pH cycling. To analyze the surface and pulp temperatures, the samples were divided into the following groups (n=10): C(+), IVL, and IVFL. RESULTS: The hardness analysis indicated that the groups that received irradiation had less hardness reduction following the demineralizing challenge (p<0.001), with IVFL and IVL presenting the lowest percentages of surface microhardness loss at 3.98% and 9.3%, respectively. Surface temperature analysis indicated a maximum increase of 74°C and a mean of 45.25°C and 45.95°C for the IVL and IVFL groups, respectively. Pulp temperature analysis indicated a higher mean increase of 2.40°C±0.65 in the IVL group. CONCLUSIONS: These results suggest that the combination of cream and laser light possibly promoted protein denaturation of the tooth enamel organic matrix, which possibly decreased the loss of hardness without causing pulp damage.

Influence of Er,Cr:YSGG laser on CaF2 -like products formation because of professional acidulated fluoride or to domestic dentifrice application.

This study evaluated the synergy of professional acidulated fluoride gel (APF) or fluoridated dentifrice application combined with Er,Cr:YSGG laser irradiation on the formation of CaF2 -like products (CaF2 ), in vitro. Thus, 272 bovine enamel slabs were randomly distributed among eight groups: G1: untreated enamel; G2: treated with fluoridated dentifrice (NaF, 1,100 µgF/g); G3: treated with acidulated phosphate fluoride gel (APF, 1.23% F(-) ); G4: irradiated with Er,Cr:YSGG laser at 8.5 J/cm(2) ; G5 and G6: combination of pre-irradiation with Er,Cr:YSGG followed by dentifrice or APF application, respectively; G7: combination of dentifrice application followed by Er,Cr:YSGG irradiation; G8: combination of APF application followed by Er,Cr:YSGG irradiation. After treatments, samples were evaluated by scanning electron microscopy, and the content of CaF2 was determined by an ion specific electrode. Both APF and dentifrice application promoted the formation of CaF2 on enamel, whereas Er,Cr:YSGG irradiation promoted an increase of roughness of the enamel, increasing the surface area. Laser irradiation before fluoridated products increased the content of CaF2 formed when compared to groups that APF or dentifrice were applied isolated. However, the content of CaF2 formed when irradiation was performed after APF or dentifrice was not statically significant when compared to the control groups. In conclusion, Er,Cr:YSGG laser increases the formation of CaF2 on enamel when the irradiation is performed before the application of APF or dentifrice. The association of laser with APF is most promissory for caries prevention because of the higher concentration of CaF2 formation and also the chemical changes promoted by laser irradiation demonstrated in literature.

Relationship between surface topography and energy density distribution of Er,Cr:YSGG beam on irradiated dentin: an atomic force microscopy study.

OBJECTIVE: The aim of this study was to assess by atomic force microscopy (AFM) the effect of Er,Cr:YSGG laser application on the surface microtopography of radicular dentin. BACKGROUND: Lasers have been used for various purposes in dentistry, where they are clinically effective when used in an appropriate manner. The Er,Cr:YSGG laser can be used for caries prevention when settings are below the ablation threshold. MATERIALS AND METHODS: Four specimens of bovine dentin were irradiated using an Er,Cr:YSGG laser (λ = 2.78 µm), at a repetition rate of 20 Hz, with a 750-µm-diameter sapphire tip and energy density of 2.8 J/cm(2) (12.5 mJ/pulse). After irradiation, surface topography was analyzed by AFM using a Si probe in tapping mode. Quantitative and qualitative information concerning the arithmetic average roughness (Ra) and power spectral density analyses were obtained from central, intermediate, and peripheral areas of laser pulses and compared with data from nonirradiated samples. RESULTS: Dentin Ra for different areas were as follows: central, 261.26 (±21.65) nm; intermediate, 83.48 (±6.34) nm; peripheral, 45.8 (±13.47) nm; and nonirradiated, 35.18 (±2.9) nm. The central region of laser pulses presented higher ablation of intertubular dentin, with about 340-760 nm height, while intermediate, peripheral, and nonirradiated regions presented no difference in height of peritubular and interperitubular dentin. CONCLUSION: According to these results, we can assume that even when used at a low-energy density parameter, Er,Cr:YSGG laser can significantly alter the microtopography of radicular dentin, which is an important characteristic to be considered when laser is used for clinical applications.

Nd:YAG laser in caries prevention: a clinical trial.

BACKGROUND AND OBJECTIVE: It is widely known that Nd:YAG can increase enamel resistance to demineralization; however, there are no studies that report the application of Nd:YAG associated with topical application of fluoride in vivo. The aim of this study was to evaluate the effects of the Nd:YAG laser, when associated with the topical application of acidulated phosphate fluoride (APF), for preventing enamel demineralization in vivo. MATERIALS AND METHODS: A double-blind crossover experimental design was used, in which 121 teeth of 33 volunteers were selected. In all volunteers, the right side teeth were selected for Nd:YAG laser+APF application (lased group) and the left side teeth were kept as control group (only APF application). Nd:YAG laser was applied at 60 mJ/pulse, at a repetition rate of 10 Hz and fluence of 84.9 J/cm(2); after that, topical APF was applied for 4 minutes. Recalls were made after 1 year in order to evaluate the formation of white-spot lesions or caries cavities. RESULTS: After 1 year, this in vivo experiment showed a reduction of 39.2% in caries incidence in lased group when compared with the control. The number of white-spots or caries cavities decreased significantly (P = 0.0043) in the Nd:YAG laser group; the formation of white-spots was significantly less (P = 0.0031) when compared with the number of lesions in the control group. CONCLUSION: Combined Nd:YAG laser and topical fluoride treatment was effective for reducing the incidence of caries in vivo.

Adhesion after erbium, chromium:yttrium-scandium-gallium-garnet laser application at three different irradiation conditions.

The aim of this study was to investigate whether distinct cooling of low fluence erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation would influence adhesion. Main factors tested were: substrates (two), irradiation conditions (three), and adhesives (three). A 750 microm diameter tip was used, for 50 s, 1 mm from the surface, with a 0.25 W power output, 20 Hz, energy density of 2.8 J/cm(2) with energy per pulse of 12.5 mJ. When applied, water delivery rate was 11 ml/min. The analysis of variance (ANOVA) showed that laser conditioning significantly decreased the bond strength of all adhesive systems applied on enamel. On dentin, laser conditioning significantly reduced bond strength of etch-and-rinse and one-step self-etch systems; however, laser irradiation under water cooling did not alter bonding of two-step self-etching. It may be concluded that the irradiation with Er,Cr:YSGG laser at 2.8 J/cm(2) with water coolant was responsible for a better adhesion to dentin, while enamel irradiation reduced bond strength, irrespective of cooling conditions.

Three-dimensional finite element thermal analysis of dental tissues irradiated with Er,Cr:YSGG laser.

In the present study, a finite element model of a half-sectioned molar tooth was developed in order to understand the thermal behavior of dental hard tissues (both enamel and dentin) under laser irradiation. The model was validated by comparing it with an in vitro experiment where a sound molar tooth was irradiated by an Er,Cr:YSGG pulsed laser. The numerical tooth model was conceived to simulate the in vitro experiment, reproducing the dimensions and physical conditions of the typical molar sound tooth, considering laser energy absorption and calculating the heat transfer through the dental tissues in three dimensions. The numerical assay considered the same three laser energy densities at the same wavelength (2.79 microm) used in the experiment. A thermographic camera was used to perform the in vitro experiment, in which an Er,Cr:YSGG laser (2.79 microm) was used to irradiate tooth samples and the infrared images obtained were stored and analyzed. The temperature increments in both the finite element model and the in vitro experiment were compared. The distribution of temperature inside the tooth versus time plotted for two critical points showed a relatively good agreement between the results of the experiment and model. The three dimensional model allows one to understand how the heat propagates through the dentin and enamel and to relate the amount of energy applied, width of the laser pulses, and temperature inside the tooth.

Influência da utilização de selantes na microinfiltração de restaurações de classe V de resina composta condensável / Influence of sealants on microleakage of class V restorations with packable composite resin

O objetivo deste estudo foi avaliar a microinfiltração que ocorre nas restaurações classe V de resina composta condensável e selantes de superfície com e sem carga. Cinqüenta cavidades classe V com margem em esmalte foram preparadas em dentes incisivos bovinos no seu terço médio e foram restauradas com resina condensável SureFil (Dentsply-Caulk). Após o acabamento e polimento, as restaurações foram divididas em cinco grupos (n = 10): (A) sem selante; (B) aplicação do selante Fortify (Bisco Inc.) sem condicionamento ácido; (C) aplicação do selante Fortify (Bisco Inc.) com condicionamento ácido; (D) aplicação do selante Fortify Plus (Bisco Inc.) sem condicionamento ácido; (E) aplicação do selante Fortify Plus (Bisco Inc.) com condicionamento ácido. Os dentes foram termociclados, e o nitrato de prata foi utilizado com traçador. Os resultados indicaram que houve diferença estatisticamente significativa entre o selante sem carga e o grupo controle (5%), embora os valores obtidos entre os selantes com e sem carga não tenham sido estatisticamente diferentes. Concluiu-se que o selante sem carga tem a melhor performance na redução da microinfiltração

[Structuralization of a human teeth bank]. / Estruturação de um Banco de Dentes Humanos.

A Human Teeth Bank (HTB) is a nonprofit institution, associated to a college, to a university or to some other institution. Its purpose is to fulfill academic needs, by supplying human teeth for research or for preclinical laboratory training of students, thus eliminating the illegal commerce of teeth that still takes place in dental schools. It is also up to an HTB to work for the elimination of cross-infection caused by indiscriminate handling of extracted teeth. In order to work properly, an HTB should have a strict control of its internal procedures, which include separation and stocking of teeth, as well as an appropriate maintaining of donors' and beneficiaries' records. In this article, we discuss the functions that an HTB can perform, and how the Human Teeth Bank, School of Dentistry, University of S o Paulo, works and organizes itself today.