The weakest points in concrete pavement systems are the concrete joints. They are man-made cracks that allow for temperature-related expansion and contraction of concrete slabs. Sealants are commonly used in pavement joints to keep debris, deicing chemicals, and moisture out of the joint. When a joint sealant fails, the pavement can quickly deteriorate; however, when a joint sealant functions well, the pavement maintains its intended performance. Joint sealants are subjected to two forms of mechanical loads in the field: 1) as slabs contract or expand, the sealant is subjected to tension or compression, respectively; and 2) heavy vehicles travel over the joint and deflect the ends of the pavement slabs, causing sealants to shear. Sealants may also be exposed to a range of environmental factors, such as moisture and ultraviolet radiation. In this research project, to simulate the joint sealant performance, samples were made by buttering the three different silicone sealants, namely Sealant 1, Sealant 2, and Sealant 3, between 1" x 1" x 3" Portland Cement Concrete dogbone-shape samples and 0.2" x 1" x 3" glass substrate samples were prepared according to VTM 90 and ASTM C1135, respectively. The tests were carried out employing an Instron Tensile Testing Machine and unique fixtures designed at Virginia Tech to impart mechanical loading. In comparison to Sealant 2, the results demonstrated that Sealant 1 can withstand larger stresses. All the concrete samples failed due to adhesive failure, whereas some of the Sealant 1 glass samples failed due to adhesive failure at low peak loads and others failed due to a combination of adhesive and cohesive failure. Glass samples of Sealant 2 on the other hand showed just cohesive failure. In case of Sealant 3, samples of both ASTM C1135 and VTM #90 showed adhesive failure and failed by showing reasonable strength. / Master of Science / Concrete pavements have a number of man-made joints that separate adjacent slabs. The purpose of these joints is to allow relatively free concrete expansion and contraction owing to changes in temperature and moisture. To ensure longevity of concrete, these joints must be sealed with a long-lasting material that can protect the joints from moisture, dust, and de-icing salts. The focus of this study is on silicone sealants, which have used for years as a joint sealant material. Three different silicone-based sealants were used. And two test methods, VTM-90, and ASTM C1135, were used to conduct the tensile testing. VTM-90 provides the test method to determine bond of silicone sealant to concrete mortar while ASTM C1135 gives the procedure for quantitative measure of tensile adhesion properties of structural sealants. ASTM C1135 In comparison to Sealant 2, the test results showed that Sealant 1 can withstand high loads. All the VTM-90 samples of Sealant 1, 2 and 3, failed because of adhesive failure, whereas some of the Sealant 1 ASTM C1135 samples failed because of adhesive failure at low peak loads and others because of a combination of adhesive and cohesive failure. On the other hand, ASTM C1135 samples of Sealant 2 showed only cohesive failures while Sealant 3 samples showed adhesive failure.

The diffu~ion and permeation of aviation fuel (Avtur) and water in commercial and 'model' polysulphide sealants have been studied using simple gravimetric techniques. For Avtur, the mass uptake behaviour is explicable in terms of normal, Fickian diffusion, and the diffusion coefficient determined has been found to be independent of the experimental method and concentration of the liquid. Water, however, exhibits anomalous diffusion behaviour. Mass uptake by the polysulphides is high and equilibrium is not reached after several months. There is no correlation between the results of permeation, absorption and desorption experiments except at low water concentration ... ,,~ . These anomalies have been explained in terms of the formation of water droplets within the rubber. This study shows that the amount of water absorbed is dependent upon the amount and nature of the curing agent residues. The results have been analysed in terms of the osmotic and water vapour pressure and two equations have been derived which satisfactorily predict the amount of water absorbed at equilibrium. It has been shown that the effect of the water droplets on permeation is negligible, and hence the diffusion coefficient found is a measure of the true rate of diffusion. In contrast, the effect of the droplets on mass uptake experiments is large and the apparent overall diffusion rate is greatly reduced. The apparent diffusion coefficient found is dependent upon the water concentration and the concentration of the water-soluble impurities. An equation has been derived showing the relationship between these variables. The results of this work show that the elastic strength of the rubber has negligible effect in determining the water uptake at equilibrium and the apparent diffusion coefficient. However, deterioration in adhesive and cohesive strength occurs with water uptake. At high uptake some of this loss is irreversible. The deterioration in properties is mainly due to breakage of weak physical bonds and plasticisation effects. -

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: The ability of sealants to prevent caries is directly related to the sealant being retained in teeth. The longer the material remains bonded to the occlusal surface, the more protection it provides to the tooth. Objective: The aim of this in-vitro study was to evaluate the influence of pit and fissure morphologies and sealant viscosity on sealant penetration and micro-leakage. 82 Study Hypothesis: The low viscosity dental sealant will express better penetration ability and less microleakage in permanent molars with any pit and fissure morphology than the high viscosity sealant. Material and methods: Permanent extracted molars (n = 150) were distributed into two groups based on two types of sealant (high and low viscosity) Permanent extracted molars (n = 150) were selected using the International Caries Detection Assessment system (ICDAS) criteria 0-1. Teeth were stored in 0.1-percent thymol and distilled water. Teeth were assigned to three subgroups according to the fissure’s morphology. Enamel was etched with 35-percent phosphoric acid for 30 seconds; two different light cured sealants were placed, Group A: Delton and Group B: Ultra X Plus. Specimens were thermocycled for 500 cycles between two water baths, having a 40°C temperature differential (4°C to 48°C). Teeth were coated with nail varnish and wax, except in the occlusal areas. All specimens were immersed in 1-percent methylene blue dye at 37°C for 24 hours. Specimens were sectioned longitudinally in a bucco-lingual direction, and the sections were photographed and analyzed by a previously trained examiner for fissure morphology, sealant penetration, and microleakage using a standardized grading system. Data were entered and statistically analyzed, at the 5-percent significance level. Results: Viscosity of sealant and morphology of fissures had significant effects on sealant penetration (p < 0.001). The interaction between viscosity of sealant and morphology of fissures was not significant (p = 0.4236). The sealant penetration for Delton was significantly higher than the UltraSeal XT Plus (p < 0.0001). The sealant penetration for fissure I-type was significantly lower than fissures U and V-types (p < 0.0001). Sealant penetration for Y-type was significantly lower than U and V-types (p < 83 0.0001). However, the viscosity of sealant and morphology of fissures did not have significant effect on microleakage (p = 0.5891 and p = 0.4857). The interaction between the viscosity of the sealant material and the morphology of pit and fissures was not significant (p = 0.6657). Conclusion: The results of the present study indicated the viscosity of the sealant and the morphology did not affect the microleakage. On the other hand, the viscosity of sealant affected the penetration ability of dental sealant. The low viscosity dental sealant (Delton) exhibited a better penetration than the high viscosity sealant (UltraSeal XT Plus). As the morphology of pit and fissure directly affected the penetration ability, the fissures types U and V exhibited a better penetration than fissure types Y and I.

Os objetivos deste trabalho foram avaliar e comparar por 24 meses, a retencao e as caracteristicas superficiais de dois diferentes materiais seladores, Helioseal Clear e Helioseal F ambos da Ivoclar Vivadente, AG - Schaan, Liechtenstein. Participaram desse estudo, 50 criancas de 6 a 8 anos de idade, com no minimo dois primeiros molares permanentes higidos e historia de carie, num total de 153 dentes divididos em dois grupos: GHC(Helioseal Clear) e GHF (Helioseal F). O selamento foi realizado sob isolamento relativo para todos os grupos, após profilaxia previa com jato de bicarbonato (Profident Dabi-Atlante) e agua e, condicionamento com gel de acido fosforico a 34% por 15 segundos. Apos 6, 12, 18 e 24 meses, a avaliacao clinica foi realizada por dois examinadores calibrados. Avaliou-se a retencao e a incidencia de carie nas 5 areas oclusais: OM, OC, OD, OV e OL (DEERY et al.) e; as caracterisiticas superficiais e a retencao considerando a superficie oclusal com o um todo (criterio modificado de RYGE &SNYDER).Nao houve diferenca estatisticamente significante atraves do teste exato de Fisher na taxa de sucesso (p=0,496 a 1,0) ou para a incidencia de carie (p=0,472 a 1,0) entre as areas avaliadas quando comparado o GHC com GHF durante todo o período estudado. Considerando todas as areas juntas e os grupos separados ou, os dois grupos juntos mas as areas separadas, nao houve diferenca estatisticamente significante, respectivamente, pelo teste de Fisher (p=0,170 a 0,534) e do Qui- Quadrado (p=0,058 a p=0,909), quanto ao sucesso na retencao em nenhum periodo. Quanto a analise da superficie oclusal toda quanto a retencao, esta foi maior e estatisticamente significante para o GHC aos 12m (p=0,0345) e 24m (0,0076). Em relacao as caracteristicas superficiais, o GHC so nao apresentou superioridade quanto a descoloracao superficial, durante o periodo estudado. Para as demais caracteristicas, os resultados do teste de Mann-Whitney foram altamente significantes em diferentes periodos (p= 00000 a 0,0421). A frequencia de bolhas nas superficies seladas, determinada pelo teste do Qui-quadrado, foi maior e significante (p=0,000:12 e 18 meses a p=0,002: 6 e 24 meses) no GHF. Portanto, pode-se concluir que quanto a retencao e caracteristicas superficiais, na superfície oclusal toda, o selante Helioseal Clear apresentou melhor desempenho. / The objectives of this study were evaluated and compared for 24 months, the retention and surface characteristic of two different sealing materials, and Helioseal F Clear Helioseal both of Ivoclar Vivadent, AG - Schaan, Liechtenstein. 50 children from 6 to 8 years of age with at least with two sound first permanent molars and caries of history, total of 153 teeth, were divided into 2 groups: GHC (Helioseal Clear) and GHF (Helioseal F). The sealing was done with ruber dam for all groups, after prophylaxis with air-polishing jet (Profident --Dabi Atlante) and water, and acidetching with 34 % phosphoric acid 34% for 15 seconds. After 6, 12, 18 and 24 months, clinical evaluation was evaluated by two calibrated examiners. To evaluate the retention and the incidence of occlusal caries in 5 areas: OM, OC, OD, and OV OL (DEERY et al.). And, the surface characteristics and retention considering the all occlusal surface (modified criterion RYGE & SNYDER ). There was no statistically significant by Fisher\'s exact test in the rate of success (p = 0,496 to 1.0) or the incidence of caries (p = 0,472 to 1.0) between the areas assessed when compared with the GHC GHF throughout the study period. Considering all areas and groups together or separated, the two groups together but separate areas, there was no statistically significant difference, respectively, by Fisher\'s test (p = 0170 to 0534) and Chi-Square (p = 0,058 to 0,909), about the success in holding in any period. The analysis of the entire occlusal surface on retention, it was higher and statistically significant for the GHC to 12m (p = 0.0345) and 24m (0.0076). In relation to surface characteristics, the GHC showed superiority not only on the superficial discoloration over the period studied. For other characteristics, the results of the Mann-Whitney test were highly significant in different periods (p = 00000 to 0.0421). The frequency of bubbles in the sealed surfaces, as determined by Chi-Square was higher e statistically significant difference (p = 0,000:12 and 18 months p = 0,002: 6 and 24 months) in GHF. Therefore,the retention and surface characteristic in the all occlusal surface, the Helioseal Clear sealant showed better performance

Os objetivos deste trabalho foram avaliar e comparar por 24 meses, a retencao e as caracteristicas superficiais de dois diferentes materiais seladores, Helioseal Clear e Helioseal F ambos da Ivoclar Vivadente, AG - Schaan, Liechtenstein. Participaram desse estudo, 50 criancas de 6 a 8 anos de idade, com no minimo dois primeiros molares permanentes higidos e historia de carie, num total de 153 dentes divididos em dois grupos: GHC(Helioseal Clear) e GHF (Helioseal F). O selamento foi realizado sob isolamento relativo para todos os grupos, após profilaxia previa com jato de bicarbonato (Profident Dabi-Atlante) e agua e, condicionamento com gel de acido fosforico a 34% por 15 segundos. Apos 6, 12, 18 e 24 meses, a avaliacao clinica foi realizada por dois examinadores calibrados. Avaliou-se a retencao e a incidencia de carie nas 5 areas oclusais: OM, OC, OD, OV e OL (DEERY et al.) e; as caracterisiticas superficiais e a retencao considerando a superficie oclusal com o um todo (criterio modificado de RYGE &SNYDER).Nao houve diferenca estatisticamente significante atraves do teste exato de Fisher na taxa de sucesso (p=0,496 a 1,0) ou para a incidencia de carie (p=0,472 a 1,0) entre as areas avaliadas quando comparado o GHC com GHF durante todo o período estudado. Considerando todas as areas juntas e os grupos separados ou, os dois grupos juntos mas as areas separadas, nao houve diferenca estatisticamente significante, respectivamente, pelo teste de Fisher (p=0,170 a 0,534) e do Qui- Quadrado (p=0,058 a p=0,909), quanto ao sucesso na retencao em nenhum periodo. Quanto a analise da superficie oclusal toda quanto a retencao, esta foi maior e estatisticamente significante para o GHC aos 12m (p=0,0345) e 24m (0,0076). Em relacao as caracteristicas superficiais, o GHC so nao apresentou superioridade quanto a descoloracao superficial, durante o periodo estudado. Para as demais caracteristicas, os resultados do teste de Mann-Whitney foram altamente significantes em diferentes periodos (p= 00000 a 0,0421). A frequencia de bolhas nas superficies seladas, determinada pelo teste do Qui-quadrado, foi maior e significante (p=0,000:12 e 18 meses a p=0,002: 6 e 24 meses) no GHF. Portanto, pode-se concluir que quanto a retencao e caracteristicas superficiais, na superfície oclusal toda, o selante Helioseal Clear apresentou melhor desempenho. / The objectives of this study were evaluated and compared for 24 months, the retention and surface characteristic of two different sealing materials, and Helioseal F Clear Helioseal both of Ivoclar Vivadent, AG - Schaan, Liechtenstein. 50 children from 6 to 8 years of age with at least with two sound first permanent molars and caries of history, total of 153 teeth, were divided into 2 groups: GHC (Helioseal Clear) and GHF (Helioseal F). The sealing was done with ruber dam for all groups, after prophylaxis with air-polishing jet (Profident --Dabi Atlante) and water, and acidetching with 34 % phosphoric acid 34% for 15 seconds. After 6, 12, 18 and 24 months, clinical evaluation was evaluated by two calibrated examiners. To evaluate the retention and the incidence of occlusal caries in 5 areas: OM, OC, OD, and OV OL (DEERY et al.). And, the surface characteristics and retention considering the all occlusal surface (modified criterion RYGE & SNYDER ). There was no statistically significant by Fisher\'s exact test in the rate of success (p = 0,496 to 1.0) or the incidence of caries (p = 0,472 to 1.0) between the areas assessed when compared with the GHC GHF throughout the study period. Considering all areas and groups together or separated, the two groups together but separate areas, there was no statistically significant difference, respectively, by Fisher\'s test (p = 0170 to 0534) and Chi-Square (p = 0,058 to 0,909), about the success in holding in any period. The analysis of the entire occlusal surface on retention, it was higher and statistically significant for the GHC to 12m (p = 0.0345) and 24m (0.0076). In relation to surface characteristics, the GHC showed superiority not only on the superficial discoloration over the period studied. For other characteristics, the results of the Mann-Whitney test were highly significant in different periods (p = 00000 to 0.0421). The frequency of bubbles in the sealed surfaces, as determined by Chi-Square was higher e statistically significant difference (p = 0,000:12 and 18 months p = 0,002: 6 and 24 months) in GHF. Therefore,the retention and surface characteristic in the all occlusal surface, the Helioseal Clear sealant showed better performance

Pneumothorax, or a collapsed lung, is a serious medical condition resulting when air or fluid escapes the lung into the chest cavity and prevents the lung from inflating. Few viable means of sealing the damaged and leaking tissues are currently available, leading to longer hospital stays, multiple interventions, and increasing costs of care. The motivation of this dissertation is to engineer a novel polysaccharide-based therapeutic surgical sealant, which can be utilized to seal trauma-induced damage to the outer lining of the lung, i.e. pleura, preventing or reversing lung collapse to restore normal breathing function. The use of polysaccharides, such as alginate and hyaluronan, has become increasingly prevalent in biomedical and tissue engineering applications due to the ability to add functionality through chemical modification, allowing for tunable mechanical and physical properties. These hydrophilic polymer chains can be crosslinked to form hydrogels, which can retain large volumes of water and can mimic the properties of tissues found within the body. In this work, polysaccharide hydrogel sealants were engineered with well-regulated gelation and mechanical properties, and further modified to achieve adhesion to biological tissues. This was accomplished by mimicking the mechanical and physical properties of the complex tissues, and crosslinking the hydrogels in situ using a visible light-initiated system. Methacrylated alginate and oxidized alginate were successfully synthesized and utilized to fabricate adhesive sealant patches, which can adhere and seal damaged tissues in vivo. Methacrylation was implemented to allow covalent photo-crosslinking between adjacent polymer chains in solution. Here, a novel anhydrous chemistry was developed to allow for precise control over the degree of methacrylation and thus tune the mechanical properties of the resulting hydrogels by modulating the number of crosslinkable side-groups attached to the polysaccharide chain. To increase the adhesive properties of the resulting hydrogels, oxidation of the polysaccharide chain was subsequently implemented to form functional aldehyde groups capable of protein interactions through the formation of imine bonds on biological tissue surfaces. To test the performance of this multifunctional material, burst pressure testing was executed, revealing the relationship between the two distinct chemical modifications performed and the mechanical and adhesive properties of the resulting sealant. In addition, methacrylated alginate was utilized to synthesize therapeutic, drug-encapsulating hydrogel nanoparticles, which when incorporated within the polysaccharide-based surgical sealant allow for local drug release. The ability to control drug release at the site of application further broadens the potential uses of this surgical sealant patch and will be discussed further within this dissertation.

Estudos têm avaliado a eficiência de diferentes tipos de laser no aumento da resistência ácida e na redução da solubilidade do esmalte dentário. O objetivo do presente estudo clínico longitudinal foi avaliar o comportamento do laser de CO2 associado, ou não, à aplicação tópica de fluoreto acidulado na prevenção de lesões de cárie em fossas e fissuras de primeiros molares permanentes parcialmente irrompidos. Foram selecionadas 61 crianças de alto risco a cárie dentária, de 6 a 8 (7,1 ± 0,8) anos de idade, apresentando os quatro primeiros molares permanentes parcialmente irrompidos e hígidos. Cada primeiro molar recebeu aleatoriamente um dos tratamentos avaliados nas fossas e fissuras: (L) - laser de CO2 (0,066J/cm2); (FL) - gel fluoretado acidulado a 1,23% e laser de CO2 (0,066J/cm2); (V) - verniz fluoretado a 5%; (S) selante (controle). Os dentes foram avaliados aos 3, 6, 12 e 18 meses após a realização dos tratamentos, por meio de exame visual direto e avaliador calibrado e \"cego\" aos tratamentos (Kappa 0,70). Foi utilizado o indíce ICDAS-II para avaliação da manutenção da higidez, presença de lesão de mancha branca ativa e de lesões cavitadas em esmalte e/ou dentina. Para avaliação da retenção do selante, foram utilizados os critérios visuais modificados de Yildiz et al. (2004). Foi aplicada a análise de sobrevida de Kaplan-Meyer. O hazard ratio dos tratamentos foram estimados utilizando-se shared frayilt models com distribuição gama, considerando-se o paciente como conglomerado. O modelo também evidenciou que a correlação intra-paciente foi significante (p = 0,0022), com covariância de 0,8425 (erro padrão = 0,3208). Clinicamente, não houve diferença significante entre os tratamentos (L), (LF) e (V) após 18 meses de avaliação. Para o tratamento (S), observou-se a maior taxa de desenvolvimento de lesões de cárie. Após análise longitudinal de 18 meses, pode-se concluir que a aplicação do laser de CO2, independentemente do uso associado ao fluoreto, foi eficiente na prevenção de lesões de cárie em fossas e fissuras de molares parcialmente irrompidos, em crianças de alto risco à cárie. / Studies have evaluated the efficiency of different laser systems in increasing strength and reducing the acid solubility of dental enamel. The aim of this longitudinal clinical study was to evaluate the CO2 laser combined or not to the topical application of acidulated fluorides in preventing caries in pits and fissures of partially-erupted first permanent molars. It were selected 61 children at high caries-risk, with 6-8 (7.1 ± 0.8) years old, with the four first permanent molars partially erupted and healthy. Each first molar randomly received one of the tested treatments in pits and fissures: (L) - CO2 laser (0.066 J/cm2), (FL) - acidulated fluoride gel 1.23% and CO2 laser (0.066 J/cm2) (V) - 5% fluoride varnish, (S) - sealant (control). The teeth were evaluated at 3, 6, 12 and 18 months after treatment, through direct visual examination and by a calibrated operator blinded to the treatments (Kappa 0.70). The ICDAS-II index was used to assess the soundness of tooth structure, presence of white spot lesions and cavitated enamel and/or dentin lesions. The Yildiz et al. (2004) visual modified criteria was used to evaluate the retention of sealant. The Kaplan-Meyer survival analysis was used. The hazard ratio of the treatments was estimated using frayilt shared models with gamma distribution, considering the patient as a conglomerate. The model also showed that intra-patient correlation was significant (p = 0.0022), with covariance of 0.8425 (standard error = 0.3208). Clinically, there was no significant difference between (L), (LF) and (V) treatments after 18 months of evaluation. For (S) treatment, there was a higher rate of caries development. After long-term analysis of 18 months, it can be concluded that the application of CO2 laser, regardless of use with fluoride, was effective in preventing caries in pits and fissures of partially-erupted molars in children at high caries-risk.

Tissue sealants of a liquid based formulation are widely studied in biomedical research with many starting to gain FDA approval. To date, little investigation has been put toward methods of application for tissue sealant materials, more specifically a powder based formulation. The focus of this research was to develop and prototype a powder spray device capable of administering powder based formulations with a long-term goal of integrating the device within the clinical setting. Powders can be administered in a variety of dry forms. These forms can range from non-homogenous nanoscale particles to homogeneous micro and nano-scale spheres. Incorporation of therapeutics within the powder makes this method of application favorable for the prevention or maintenance of disease. Pneumatic conveying is the transport of granulated solids using gas and is the principal basis from which the powder spray gun was designed. Fluidization aids were added to the device in order to increase powder flow properties. Analysis of spray field, spray rate, characterization of powder and ex-vivo testing was performed. All results suggest that the powder spray device is applicable for the deposition of powder based tissue sealants in a clinical setting.

Estudos têm avaliado a eficiência de diferentes tipos de laser no aumento da resistência ácida e na redução da solubilidade do esmalte dentário. O objetivo do presente estudo clínico longitudinal foi avaliar o comportamento do laser de CO2 associado, ou não, à aplicação tópica de fluoreto acidulado na prevenção de lesões de cárie em fossas e fissuras de primeiros molares permanentes parcialmente irrompidos. Foram selecionadas 61 crianças de alto risco a cárie dentária, de 6 a 8 (7,1 ± 0,8) anos de idade, apresentando os quatro primeiros molares permanentes parcialmente irrompidos e hígidos. Cada primeiro molar recebeu aleatoriamente um dos tratamentos avaliados nas fossas e fissuras: (L) - laser de CO2 (0,066J/cm2); (FL) - gel fluoretado acidulado a 1,23% e laser de CO2 (0,066J/cm2); (V) - verniz fluoretado a 5%; (S) selante (controle). Os dentes foram avaliados aos 3, 6, 12 e 18 meses após a realização dos tratamentos, por meio de exame visual direto e avaliador calibrado e \"cego\" aos tratamentos (Kappa 0,70). Foi utilizado o indíce ICDAS-II para avaliação da manutenção da higidez, presença de lesão de mancha branca ativa e de lesões cavitadas em esmalte e/ou dentina. Para avaliação da retenção do selante, foram utilizados os critérios visuais modificados de Yildiz et al. (2004). Foi aplicada a análise de sobrevida de Kaplan-Meyer. O hazard ratio dos tratamentos foram estimados utilizando-se shared frayilt models com distribuição gama, considerando-se o paciente como conglomerado. O modelo também evidenciou que a correlação intra-paciente foi significante (p = 0,0022), com covariância de 0,8425 (erro padrão = 0,3208). Clinicamente, não houve diferença significante entre os tratamentos (L), (LF) e (V) após 18 meses de avaliação. Para o tratamento (S), observou-se a maior taxa de desenvolvimento de lesões de cárie. Após análise longitudinal de 18 meses, pode-se concluir que a aplicação do laser de CO2, independentemente do uso associado ao fluoreto, foi eficiente na prevenção de lesões de cárie em fossas e fissuras de molares parcialmente irrompidos, em crianças de alto risco à cárie. / Studies have evaluated the efficiency of different laser systems in increasing strength and reducing the acid solubility of dental enamel. The aim of this longitudinal clinical study was to evaluate the CO2 laser combined or not to the topical application of acidulated fluorides in preventing caries in pits and fissures of partially-erupted first permanent molars. It were selected 61 children at high caries-risk, with 6-8 (7.1 ± 0.8) years old, with the four first permanent molars partially erupted and healthy. Each first molar randomly received one of the tested treatments in pits and fissures: (L) - CO2 laser (0.066 J/cm2), (FL) - acidulated fluoride gel 1.23% and CO2 laser (0.066 J/cm2) (V) - 5% fluoride varnish, (S) - sealant (control). The teeth were evaluated at 3, 6, 12 and 18 months after treatment, through direct visual examination and by a calibrated operator blinded to the treatments (Kappa 0.70). The ICDAS-II index was used to assess the soundness of tooth structure, presence of white spot lesions and cavitated enamel and/or dentin lesions. The Yildiz et al. (2004) visual modified criteria was used to evaluate the retention of sealant. The Kaplan-Meyer survival analysis was used. The hazard ratio of the treatments was estimated using frayilt shared models with gamma distribution, considering the patient as a conglomerate. The model also showed that intra-patient correlation was significant (p = 0.0022), with covariance of 0.8425 (standard error = 0.3208). Clinically, there was no significant difference between (L), (LF) and (V) treatments after 18 months of evaluation. For (S) treatment, there was a higher rate of caries development. After long-term analysis of 18 months, it can be concluded that the application of CO2 laser, regardless of use with fluoride, was effective in preventing caries in pits and fissures of partially-erupted molars in children at high caries-risk.