Assessment of thermal alteration during cavity preparation and caries removal efficiency using Er:YAG laser

O objetivo deste estudo foi avaliar a alteração de temperatura durante preparo cavitário em dentina cariada e hígida e a eficiência na remoção de tecido cariado com Er:YAG. Foram utilizados 30 terceiros molares humanos hígidos, doados pelo Banco de Dentes da FORP-USP, os quais tiveram suas raízes removidas e as coroas seccionadas, obtendo-se 60 fragmentos de 2,5mm de espessura. Os espécimes foram divididos em 2 grupos (n=30): dentina cariada e dentina hígida (controle) e em 3 subgrupos (n=10), de acordo com as freqüências de laser aplicadas (4, 6 e 10Hz). Foi empregada energia constante de 200mJ no modo não-contato, focado e sob refrigeração. A indução das lesões artificiais de cárie foi realizada pelo modelo bacteriano, no qual foram utilizadas cepas de Streptococcus mutans. O registro da temperatura foi realizado antes do inicio da irradiação, após 10 segundos e ao final do preparo. Após este procedimento, os fragmentos foram analisados por DIAGNOdent® e microscopia óptica de luz, utilizando-se o software Axio Vision 4.3 LE, para quantificar a remoção de dentina cariada. Para a análise morfológica, 5 espécimes de cada grupo foram aleatoriamente selecionados e preparados para microscopia eletrônica de varredura. Os dados foram submetidos à Análise de Variância α=5% e, quando apropriado, ao teste de Fisher. Os resultados mostraram que todas as freqüências do laser Er:YAG promoveram aumento gradual e significante da temperatura durante o preparo cavitário, independente do substrato. Com relação às freqüências de laser empregadas, observou-se que apenas a de 10Hz promoveu aumento diferencial de temperatura, sendo observado neste subgrupo o maior acúmulo de calor, em ambos os substratos. A análise por Diagnodent® revelou que a remoção de tecido cariado foi semelhante entre os subgrupos de 4 e 6Hz, e maior no de 10Hz. Contudo, por microscopia óptica de luz, os subgrupos de 6 e 10Hz foram estatisticamente iguais e o de 4Hz apresentou os menores valores de remoção de tecido cariado. A avaliação morfológica da superfície e subsuperfície dos espécimes revelou a presença de tecido dentinário desmineralizado em todos os subgrupos estudados. Contudo, em preparos realizados com 4Hz, foi observado que a dentina cariada remanescente apresentava sua estrutura colágena desnaturada. Assim, conclui-se que o aumento da freqüência do laser Er:YAG promove aumento gradativo e significante da temperatura em função do tempo, independentemente do substrato, não atingindo níveis nocivos ao tecido pulpar e uma ablação mais eficiente do tecido dentinário cariado e que a irradiação do tecido dentinário cariado resulta em uma superfície mais uniforme em relação ao tecido dentinário hígido.The aim of this study was to evaluate the thermal alterations during cavity preparation with sound and caries dentin and dentin caries removal efficiency using Er:YAG laser. Thirty humans molars, donated by FORP-USP Teeth Bank, had the root removed and the crown sectioned getting sixty fragments with 2.5-mm thick. The fragments were assigned into two groups (n=30): artificial dentin caries and sound dentin (control group) and 3 subgroups (n=10), according to the irradiation frequency used (4, 6, or 10Hz) at a constant energy level of 200mJ, focused-mode and under refrigeration. The artificial caries lesion was obtained by the bacterial model with was used Streptococcus mutans. Before irradiation, a thermocouple, adapted to the tooth fragment, recorded the initial temperature value (°C); then, the temperature was measured at every 10s during irradiation and after finishing irradiation. A caries detection system (DIAGNOdentTM) and a light microscopy software (Axion VisionTM) was employed to evaluate the demineralized dentin removal. The morphologic analyses used 5 fragments randomly selected from each group and processed for the accomplishment scanning electron microscope. Data were analyzed by ANOVA and Fishers tests (α=5%). The results revealed that the temperature increased gradually over time for all groups, independent the type of substrate. Concerning the frequencies it was observed that irradiation with 10Hz promoted the highest temperature values for both substrates and it was statistical different of remaining frequencies. The caries detection system revealed that the caries removal was similar with 4 and 6Hz, and was superior with 10Hz. However with the light microscopy software the frequency the caries removal was similar with 6 and 10Hz and the frequency of 4Hz presented the lowest caries removal values. The surface and subsurface morphologic analyses revealed the presence of demineralized dentin in all frequencies studied. However in the preparation carried through with 4Hz, the remaining dentine beyond demineralized, presented its collagen structure disorganized. It can be concluded by the present study that the Er:YAG laser frequency increase provides a higher temperature increase for sound and caries dentin, however without reaching harmful levels to the dental pulp, as well a greater caries dentin removal and the caries dentin irradiation provides a regular surface compared with sound dentin

Nd:YAG laser effect in caries prevention of primary and permanent dentition: in vivo and in vitro study

O presente estudo teve por objetivo avaliar longitudinalmente in vivo e in vitro os efeitos do laser Nd:YAG na prevenção de cárie oclusal na dentição decídua e permanente. Foram selecionadas 52 crianças de alto risco à cárie (7,6 ± 1,4 anos). Os primeiros molares decíduos foram distribuídos entre os grupos controle negativo, controle positivo 1 (flúor fosfato acidulado - FFA) e controle positivo 2 (verniz fluoretado - VF). Os segundos molares decíduos e primeiros molares permanentes foram divididos entre os grupos experimentais: selante, irradiação laser (100mJ/5Hz-0,5W), irradiação laser + FFA e irradiação laser + VF. Os tratamentos foram aleatoriamente distribuídos entre os grupos experimentais e controles nos 4 quadrantes da cavidade bucal do paciente. Os pacientes foram submetidos a exames clínicos e radiográficos em 3, 6, 9, 12, 18 e 24 meses após o tratamento. As avaliações foram realizadas por três examinadores calibrados \"cegos\" aos tratamentos (K=0,92). Durante o período de avaliação os dentes decíduos esfoliados foram coletados e utilizados para os testes de microdureza, microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva de raios-X (EDS), espectroscopia de infravermelho com transformada de Fourier (FTIR) e microscopia óptica (MO). 35 pacientes finalizaram o estudo e os dados das avaliações clínicas foram submetidos aos teste Q de Cochran (&alpha;=0,1%) e Tukey (&alpha;=5%). Na dentição decídua, foi observado que o laser e o selante proporcionaram as menores incidências de lesões de cárie do que o grupo controle negativo (p<0,05). À partir de 12 meses, foi observado um aumento das lesões de cárie do grupo laser, que se igualou aos demais grupos aos 24 meses. Na dentição permanente foi observado que o selante apresentou menores índices de formação de cárie do que os demais grupos (p<0,05). Entretanto, à partir de 12 meses de acompanhamento, foi observado um aumento significativo das lesões de cárie formadas neste grupo. Os dados do FTIR foram submetidos aos testes ANOVA one-way (&alpha;=0,1%) e Tukey (&alpha;=5%). Foram observadas menores concentrações de carbonato (CO3) no grupo laser (0,98±0,06) e as maiores concentrações no controle negativo (1,47±0,31) e no laser + FFA (1,51±0,29). A avaliação morfológica do esmalte foi realizada pela análise em MEV, sendo observado que todas as amostras apresentaram-se ligeiramente mais lisas quando comparadas as irradiadas somente com laser. No EDS não foram observadas diferenças na % de Ca, P e F entre todos os grupos estudados. Os dados de microdureza e MO foram submetidos aos testes Kruskall-Wallis (&alpha;=0,1%) e Tukey (&alpha;=5%). Na microdureza foi observado que o selante (249,86 ± 7,15) e a irradiação laser isolada (262,44±22,69) apresentaram os maiores valores de dureza em comparação ao controle - (128,35±25,19). Na MO foi observada menor área de esmalte desmineralizado no grupo laser isolado (5,35%±5,38) e laser + FFA (10,35% ±0,88) quando comparado ao controle - (72,56%±12,86). Pode-se concluir que o laser Nd:YAG, independente de sua associação com fluoretos, promoveu um efeito preventivo para cárie oclusal de até 12 meses na dentição decídua (semelhante ao selante) e até 9 meses na permanente após sua aplicação.The aim of this study was to evaluated the effect of Nd:YAG laser irradiation alone or combined to fluoride on the occlusal surface of primary and permanent teeth. 52 children (age 7.6 ± 1.4 years) were selected to this study. The four quadrants in the subjects were randomly assigned to receive the controls and experimental treatments. 1st primary molar was the negative control, Acidulated Phosphate Fluoride (APF - positive control 1) or fluoride varnish (FV - positive control 2). 2nd primary molar and 1st permanent molar received resin sealant, laser irradiation (100mJ/5Hz-0.5W), APF + laser irradiation or FV + laser irradiation. Patients were followed-up to 24 months to evaluate the presence of white-spot lesions and/or caries cavities by three calibrated observers (k=0.92). Primary teeth that naturally exfoliated (in 1 year period) were collected, storage in deionized water and the surface area submitted to scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and electron spectroscopy for chemical analysis (EDS). The occlusal subsurface was analyzed by cross-section Knoop microhardness and light microscopy to evaluate the caries lesions status. 35 patients completed the 24 months evaluation period. The clinical data were submitted to Cochran Q (&alpha;=0.1%) and Tukey (&alpha;=5%) tests. Primary teeth clinical results: laser alone group presented lower caries formation compared to negative control group (p<0.05). However the laser preventive effect decreased after 12 months. Permanent teeth clinical results: the sealant group presented lower caries formation compared to the remaining groups (p<0.05). However the sealant preventive effect decreased after 12 months. FTIR data were analyzed by one-way ANOVA (&alpha;=0.1%) and Tukey (&alpha;=5%) tests. Cross-section Knoop microhardness and light microscopy data were analyzed by Kruskall-Wallis test (&alpha;=0.1%) followed by Tukey test (&alpha;=5%). The images obtained with SEM and the percentage of elements calcium, phosphorus and fluoride were qualitatively evaluated by comparing the irradiated area with the control surface. FTIR analysis showed lower concentration of CO3 on lased group (0.98±0.06). Higher [ ] of CO3 were observed on negative control group (1.47±0.31) and laser combined with fluoride (1.51±0.29). SEM analysis revealed that control samples showed a slightly smoother surface compared to lased groups. The EDS analysis revealed no difference in the Ca, P and F % among all studies groups. For microhardness was observed that sealant and laser irradiation alone (262.44±22.69) showed significant higher values compared to control - group (128.35±25.19). For light microscopy, it was observed significant lower caries lesion formation in laser alone (5.35%±5.38) and laser combined to APF (10.35% ±0.88) to the negative control group (72.56%±12.86). Within the limitations of this study it can be concluded that Nd:YAG laser irradiation over one year period for primary dentition and over 9 months for permanent dentition, regardless fluoride association, modified enamel surface to successfully inhibits caries formation

Ablation Rate and Morphology of Superficial and Deep Dentin Irradiated with Different Er:YAG Laser Energy Levels

Objective: In this study we evaluated the ablation rate of superficial and deep dentin irradiated with different Er:YAG laser energy levels, and observed the micromorphological aspects of the lased substrates with a scanning electron microscope (SEM). Background Data: Little is known about the effect of Er: YAG laser irradiation on different dentin depths. Materials and Methods: Sixty molar crowns were bisected, providing 120 specimens, which were randomly assigned into two groups ( superficial or deep dentin), and later into five subgroups (160, 200, 260, 300, or 360 mJ). Initial masses of the specimens were obtained. After laser irradiation, the final masses were obtained and mass losses were calculated followed by the preparation of specimens for SEM examination. Mass-loss values were subjected to two-way ANOVA and Fisher's least significant difference multiple-comparison tests (p < 0.05). Results: There was no difference between superficial and deep dentin. A significant and gradual increase in the mass-loss values was reached when energies were raised, regardless of the dentin depth. The energy level of 360 mJ showed the highest values and was statistically significantly different from the other energy levels. The SEM images showed that deep dentin was more selectively ablated, especially intertubular dentin, promoting tubule protrusion. At 360 mJ the micromorphological features were similar for both dentin depths. Conclusion: The ablation rate did not depend on the depth of the dentin, and an energy level lower than 360 mJ is recommended to ablate both superficial and deep dentin effectively without causing tissue damage.Research Support Foundation of the State of Sao Paulo (FAPESP)[2005/1680-9]Research Support Foundation of the State of Sao Paulo (FAPESP)[2004/15612-2

Thermal effects and morphological aspects of human dentin surface irradiated with different frequencies of Er:YAG laser

This study reports the effects on micromorphology and temperature rise in human dentin using different frequencies of Er:YAG laser. Sixty human dentin fragments were randomly assigned into two groups (n = 30): carious or sound dentin. Both groups were divided into three subgroups (n = 10), according to the Er:YAG laser frequency used: 4, 6, or 10 Hz (energy: 200 mJ; irradiation distance: 12 mm; and irradiation time: 20 s). A thermocouple adapted to the tooth fragment recorded the initial temperature value (degrees C); then, the temperature was measured after the end of the irradiation (20 s). Morphological analysis was performed using images obtained with scanning electron microscope. There was no difference between the temperatures obtained with 4 and 6 Hz; the highest temperatures were achieved with 10 Hz. No difference was observed between carious and sound dentin. Morphological analyses revealed that all frequencies promoted irregular surface in sound dentin, being observed more selectively ablation especially in intertubular dentin with tubule protrusion. The caries dentin presented flat surface for all frequencies used. Both substrates revealed absence of any signs of thermal damage. It may be concluded that the parameters used in this study are capable to remove caries lesion, having acceptable limits of temperature rise and no significant morphological alterations on dentin surface. Microsc. Res. Tech. 2012. (c) 2012 Wiley Periodicals, Inc.CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior), Brazi

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 6 months, EndoREZ had higher BS values for CHX and PA than control (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

Effect of erbium:yttrium-aluminum-garnet laser energies on superficial and deep dentin microhardness

This study evaluated the microhardness of superficial and deep dentin irradiated with different erbium:yttrium-aluminum-garnet (Er:YAG) laser energies. Seventy-two molars were bisected and randomly assigned to two groups (superficial dentin or deep dentin) and into six subgroups (160 mJ, 200 mJ, 260 mJ, 300 mJ, 360 mJ, and control). After irradiation, the cavities were longitudinally bisected. Microhardness was measured at six points (20 A mu m, 40 A mu m, 60 A mu m, 80 A mu m, 100 A mu m, and 200 A mu m) under the cavity floor. Data were submitted to analysis of variance (ANOVA) and Fisher`s tests (alpha = 0.05). Superficial dentin presented higher microhardness than deep dentin; energy of 160 mJ resulted in the highest microhardness and 360 mJ the lowest one. Values at all points were different, exhibiting increasing microhardness throughout; superficial dentin microhardness was the highest at 20 A mu m with 160 mJ energy; for deep dentin, microhardness after irradiation at 160 mJ and 200 mJ was similar to that of the control. The lowest energy increased superficial dentin microhardness at the closest extent under the cavity; deep dentin microhardness was not altered by energies of 160 mJ and 200 mJ.Foundation of the State of Sao Paulo (FAPESP), Brazil[2005/01680-9

Influence of Er:YAG Laser Frequency on Dentin Caries Removal Capacity

The purposes of this study were to evaluate in vitro the influence of different frequencies of Er:YAG laser on the human dentin caries removal capacity. Thirty fragments obtained from third molars were randomly assigned into three groups (n = 10) according to the laser frequency used: 4, 6, and 10 Hz. The caries lesion (+/-1 mm deep) was induced before the irradiation by S. mutans cultures for 6 weeks. The specimens of all groups were irradiated with 200 mJ of energy in noncontact and focused mode under constant refrigeration (water flow: 2.5 mL/min). Quantitative analysis of the caries removal was performed by DIAGNOdent (TM) and the Axion Vision (TM) software. Qualitative analysis was performed by Scanning electron microscope (SEM) and light microscope (LM). Data were analyzed by ANOVA and Fishers` tests. The DIAGNOdent (TM) revealed that the caries removal was similar with 4 and 6 Hz and was superior with 10 Hz (P < 0.05). The analysis with Axion Vision (TM) software revealed that the caries removal was similar with 6 and 10 Hz and the 4 Hz group promoted the lowest caries removal. Through SEM morphologic analysis, some specimens irradiated with 4 Hz presented, under the demineralized dentin, a disorganized collagenous matrix. The LM images revealed that all frequencies used promoted irregular caries removal, being observed over preparations with 6 and 10 Hz. It can be concluded that the increase of Er:YAG laser frequency provided a higher dentin caries removal without selectivity to the disorganized dentin. Microsc. Res. Tech. 74:281-286, 2011. (C) 2010 Wiley-Liss, Inc.CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)-Brazi