Doctor of Philosophy / This thesis describes experiments which were carried out at the Institute of Dental Research in Sydney and within the Department of Prosthetic Dentistry at the United Dental Hospital of Sydney between February 1991 and May 1996. The study is concerned with finding practical means of treating chronic atrophic candidosis, also referred to as Candida-associated denture stomatitis and to this purpose two methods of denture disinfection are investigated, namely, sodium hypoclorite denture soak and microwave irradiation. Although the aetiology of denture stomatitis is generally considered to be multifactorial, there is sufficient evidence that Candida species and in particular C. albicans play an important role in the aetiology of the condition. In Chapter 1, therefore, the literature review, which provides relevant background information for the experiments to be described in later chapters, is primarily concerned with Candida species. The characteristics and distribution of Candida species are described and factors affecting the distribution of or Candida are discussed. The literature relating to the cause of chronic atrophic candidosis is vast and consequently a detailed description is given of Candida-associated denture stomatitis in the section concerned with oral diseases caused by Candida and their treatment. Each of the subsequent chapters, contains a brief literature review of material relevant to the subject of the particular chapter. Chapter 2 describes laboratory work to assess the effect of sodium hypochlorite on the adhesion of Candida species to oral surfaces and the ability of Candida to coaggregate with oral streptococci. The results showed that sodium hypochlorite decreased the ability of Candida species to adhere to both inert surfaces and BECs. However, coaggregation of Candida with streptococci was increased. Thus, hypochlorite if used as a denture soak may initially reduce the ability of Candida species to adhere to the denture surface and may therefore assist the treatment of denture stomatitis. The effects of hypochlorite on the characteristics of Candida species that are associated with tissue invasion are described in Chapter 3. The production of acid proteinase, the formation of germ tubes and presence of major cell wall proteins at 43 and 27 kDa are demonstrated. The ability of the whole cells of certain species of Candida to aggregate human platelets was assessed. The results showed that sodium hypochlorite did not affect proteinase production by Candida species but the rate of germ tube formation and the production of Candida cell wall proteins were increased. Hypochlorite did not affect the ability of certain Candida species to aggregate human platelets. Mechanisms to defend the host against candidal invasion are discussed and include platelet aggregation where aggregated platelets release antimicrobial factors that are active against Candida. Chapter 4 describes an in vitro study to test the effects of sodium hypochlorite and microwave irradiation on the survival of Candida species and oral streptococci on denture surfaces. The results showed that 0.02% sodium hypochlorite denture soak for 8 h will eliminate Candida species and reduce the growth of streptococci. However, microwaving of dentures at medium setting for 6 min will eliminate both Candida and streptococci. This information servers as baseline data for clinical assessments described in Chapters 7 and 8. Denture hygiene is an important factor in the prevention and treatment of Candida-associated denture stomatitis. Hence, a clinical study to assess the microbiology of denture plaque is described in Chapter 5. The results showed that denture plaque was composed mainly of Gram-positive streptococci with varying proportions of Gram-positive rods, Gram-negative cocci and rods and is similar to dental plaque. Candida was not always isolated and when detected constituted a very small proportion (< 1%) of the total aerobic bacterial count. The results of an investigation to test the effect of soft denture liners in lower dentures on the colonization of denture surfaces by Candida species and aerobic bacteria are given in Chapter 6. There was no significant difference in Candida /bacterial colonization of dentures with soft denture liners and those without liners. Chapter 7 describes a clinical study to test the efficiency of sodium hypochlorite (0.02%) over-night denture soak as an effective denture disinfecting agent. Treatment of dentures with hypochlorite over a trial period resulted in reductions of Candida and aerobic bacteria and although the reductions were not significant the effect over the trial period could be assessed. A significant finding was that for the palate, treatment with hypochlorite over the trial period prevented an increase in candidal load. Thus, sodium hypochlorite may function as an effective disinfecting agent when used as 0.02% denture soak for a prolonged period. A pilot study to assess the effectiveness of microwaving dentures for ten min (350 W, 240 MHz) as a potential method of denture disinfection is described in Chapter 8. For practical reasons the dentures were microwaved only once only and therefore the effect over a trial period could not be assessed. However, one treatment resulted in significant reductions in the levels of Candida and aerobic bacteria. These findings have indicated that future research should be carried out to test the effect of daily consecutive microwave treatments on candidal and bacterial growth. The general discussion in Chapter 9 summarizes the data presented in the previous chapters and from the findings conclusions are made concerning the prevention and treatment of Candida-associated denture stomatitis. The limitations of this thesis are recognized and some important aspects of the study are recommended for future research.

Organic solvents in varnish can easily cause volatile organic compounds (VOCs) and odorous problems in manufacturing plants of enamel insulated wire. In general, the related process exhaust gases are treated by catalytic incinerators. However, the slight odors in the incinerated exhausts may induce uncomfortable feels to the inhabitants in the vicinity of the plants. Main components of odors are reported to be xylenes and to a lesser extent ketones. This study intended to oxidize the odorous compounds by chemical scrubbing method with either sodium hypochlorite or ozone as an oxidant and hydrogen peroxide as a reducing agent for the elimination of residual chlorine or ozone emitted from the oxidation scrubber. An additional study was the oxidation of aqueous mixed xylenes by sodium hypochlorite. The first part of the study was the chemical oxidation of aqueous xylenes by sodium hypochlorite. Results indicated that more than 95 % of 20 mg/L xylenes could be converted to some oxygenated hydrocarbons with an initial effective chlorine concentration of 180 mg/L at pH 6.5 over a prolonged reaction time of over 120 min. With pH < 3 and a reaction time of 120 min, xylenes could be oxidized to benzene carboxylic acid that precipitated as organic crystalline solids to the reactor bottom. The second part was chemical scrubbing of the odorous gases emitted from the catalytic incinerator. Operation conditions were an effective chlorine concentration of 1,500 mg/L and pH 6.5 for the oxidative scrubbing liquor, and a hydrogen peroxide concentration of 700 mg/L and pH > 12 for the reductive one. Results indicated that on an average, around 59 % of the influent xylenes could be removed, and the scrubbed gas was nearly odorless. 65.0 - 98.5 % of the influent non-aromatic compounds could be removed with trace amounts of chlorinated compounds in the gas were detected. The third one was the treatment of the odorous gases by using ozone as an oxidant and followed by activated carbon adsorption. 18 - 34 mg/m3 of ozone was added to the test gas with initial xylene concentrations of 25 - 55 mg/m3. Results indicated that only around 35 % of the added xylene was removed with ozone contact times of 0.15 - 0.6 min. Although 99.9 % of the residual ozone and odors were removed by the activated carbon, a longer operation time should be tested to verify the performance. Trace amounts of ring cleavage precursors of 2.4-dimethylphenol and ring cleavage products were found in the ozonized gas.

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

Doctor of Philosophy / This thesis describes experiments which were carried out at the Institute of Dental Research in Sydney and within the Department of Prosthetic Dentistry at the United Dental Hospital of Sydney between February 1991 and May 1996. The study is concerned with finding practical means of treating chronic atrophic candidosis, also referred to as Candida-associated denture stomatitis and to this purpose two methods of denture disinfection are investigated, namely, sodium hypoclorite denture soak and microwave irradiation. Although the aetiology of denture stomatitis is generally considered to be multifactorial, there is sufficient evidence that Candida species and in particular C. albicans play an important role in the aetiology of the condition. In Chapter 1, therefore, the literature review, which provides relevant background information for the experiments to be described in later chapters, is primarily concerned with Candida species. The characteristics and distribution of Candida species are described and factors affecting the distribution of or Candida are discussed. The literature relating to the cause of chronic atrophic candidosis is vast and consequently a detailed description is given of Candida-associated denture stomatitis in the section concerned with oral diseases caused by Candida and their treatment. Each of the subsequent chapters, contains a brief literature review of material relevant to the subject of the particular chapter. Chapter 2 describes laboratory work to assess the effect of sodium hypochlorite on the adhesion of Candida species to oral surfaces and the ability of Candida to coaggregate with oral streptococci. The results showed that sodium hypochlorite decreased the ability of Candida species to adhere to both inert surfaces and BECs. However, coaggregation of Candida with streptococci was increased. Thus, hypochlorite if used as a denture soak may initially reduce the ability of Candida species to adhere to the denture surface and may therefore assist the treatment of denture stomatitis. The effects of hypochlorite on the characteristics of Candida species that are associated with tissue invasion are described in Chapter 3. The production of acid proteinase, the formation of germ tubes and presence of major cell wall proteins at 43 and 27 kDa are demonstrated. The ability of the whole cells of certain species of Candida to aggregate human platelets was assessed. The results showed that sodium hypochlorite did not affect proteinase production by Candida species but the rate of germ tube formation and the production of Candida cell wall proteins were increased. Hypochlorite did not affect the ability of certain Candida species to aggregate human platelets. Mechanisms to defend the host against candidal invasion are discussed and include platelet aggregation where aggregated platelets release antimicrobial factors that are active against Candida. Chapter 4 describes an in vitro study to test the effects of sodium hypochlorite and microwave irradiation on the survival of Candida species and oral streptococci on denture surfaces. The results showed that 0.02% sodium hypochlorite denture soak for 8 h will eliminate Candida species and reduce the growth of streptococci. However, microwaving of dentures at medium setting for 6 min will eliminate both Candida and streptococci. This information servers as baseline data for clinical assessments described in Chapters 7 and 8. Denture hygiene is an important factor in the prevention and treatment of Candida-associated denture stomatitis. Hence, a clinical study to assess the microbiology of denture plaque is described in Chapter 5. The results showed that denture plaque was composed mainly of Gram-positive streptococci with varying proportions of Gram-positive rods, Gram-negative cocci and rods and is similar to dental plaque. Candida was not always isolated and when detected constituted a very small proportion (< 1%) of the total aerobic bacterial count. The results of an investigation to test the effect of soft denture liners in lower dentures on the colonization of denture surfaces by Candida species and aerobic bacteria are given in Chapter 6. There was no significant difference in Candida /bacterial colonization of dentures with soft denture liners and those without liners. Chapter 7 describes a clinical study to test the efficiency of sodium hypochlorite (0.02%) over-night denture soak as an effective denture disinfecting agent. Treatment of dentures with hypochlorite over a trial period resulted in reductions of Candida and aerobic bacteria and although the reductions were not significant the effect over the trial period could be assessed. A significant finding was that for the palate, treatment with hypochlorite over the trial period prevented an increase in candidal load. Thus, sodium hypochlorite may function as an effective disinfecting agent when used as 0.02% denture soak for a prolonged period. A pilot study to assess the effectiveness of microwaving dentures for ten min (350 W, 240 MHz) as a potential method of denture disinfection is described in Chapter 8. For practical reasons the dentures were microwaved only once only and therefore the effect over a trial period could not be assessed. However, one treatment resulted in significant reductions in the levels of Candida and aerobic bacteria. These findings have indicated that future research should be carried out to test the effect of daily consecutive microwave treatments on candidal and bacterial growth. The general discussion in Chapter 9 summarizes the data presented in the previous chapters and from the findings conclusions are made concerning the prevention and treatment of Candida-associated denture stomatitis. The limitations of this thesis are recognized and some important aspects of the study are recommended for future research.

Thesis (M. D. S.)--University of Hong Kong, 2007.

Thesis (doctoral)--Katholieke Universiteit te Nijmegen.

Yang, Li. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 67-72). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background and Motivation --- p.1 / Chapter 1.2 --- Objectives --- p.2 / Chapter 1.3 --- Contributions --- p.2 / Chapter 1.4 --- Organization of the Dissertation --- p.3 / Chapter 2 --- Carbon Nanotubes as Sensing Elements --- p.4 / Chapter 2.1 --- Introduction --- p.4 / Chapter 2.2 --- Introduction to Carbon Nanotubes --- p.4 / Chapter 2.3 --- Chemical Sensor Applications --- p.6 / Chapter 2.3.1 --- Semiconducting Sensors --- p.7 / Chapter 2.3.2 --- Dielectric Sensors --- p.8 / Chapter 2.3.3 --- Adsorption Based Sensors --- p.9 / Chapter 2.4 --- Dielectrophoresis of CNTs --- p.9 / Chapter 2.4.1 --- Theory and Methodology --- p.10 / Chapter 2.4.2 --- Basic CNTs Sensor Fabrication Process Using DEP Force --- p.13 / Chapter 2.4.3 --- Electronic-Grade Carbon Nanotubes --- p.13 / Chapter 2.4.4 --- Simulation --- p.14 / Chapter 2.5 --- Photodesorption Phenomenon --- p.16 / Chapter 2.5.1 --- Chemical Desorption Process Induced by UV Illumination --- p.16 / Chapter 2.6 --- Summary --- p.19 / Chapter 3 --- Design of NaOCl Sensors Based on EG-CNTs in Microfluidic System --- p.20 / Chapter 3.1 --- Introduction --- p.20 / Chapter 3.2 --- Chemical --- p.20 / Chapter 3.2.1 --- Introduction to Chemical Properties and Reactions --- p.21 / Chapter 3.2.2 --- Reagents --- p.23 / Chapter 3.3 --- Methods for Chemical Detection --- p.23 / Chapter 3.3.1 --- Hypochlorite Detection --- p.23 / Chapter 3.3.2 --- Chlorine Gas Detection --- p.24 / Chapter 3.4 --- Design and Fabrication --- p.26 / Chapter 3.4.1 --- Sodium Hypochlorite Sensor Using Microfluidic System --- p.26 / Chapter 3.4.2 --- Modified Design For Indirect Detection to Chlorine Gas --- p.29 / Chapter 3.5 --- Equipments --- p.30 / Chapter 3.5.1 --- Source Meter --- p.30 / Chapter 3.5.2 --- Pneumatic Pump --- p.31 / Chapter 3.5.3 --- UV Illumination Devices --- p.31 / Chapter 3.5.4 --- Experimental Setup --- p.32 / Chapter 3.6 --- Summary --- p.34 / Chapter 4 --- Results --- p.35 / Chapter 4.1 --- Introduction --- p.35 / Chapter 4.2 --- Processes of the Experiments --- p.35 / Chapter 4.2.1 --- Response to Static Solution --- p.35 / Chapter 4.2.2 --- Response to Fluid Flow --- p.36 / Chapter 4.2.3 --- Response to Gas --- p.36 / Chapter 4.3 --- Noise and Accuracy --- p.37 / Chapter 4.4 --- I-V Characteristics --- p.38 / Chapter 4.4.1 --- EG-CNTs Sensor --- p.38 / Chapter 4.4.2 --- Variation Under UV Illumination --- p.39 / Chapter 4.5 --- Responses to Sodium Hypochlorite Solution --- p.41 / Chapter 4.5.1 --- Typical Responses --- p.41 / Chapter 4.5.2 --- Selectivity --- p.44 / Chapter 4.5.3 --- Sensitivity --- p.45 / Chapter 4.5.4 --- Effect of Injection Flow Rate on Sensor Performance --- p.50 / Chapter 4.5.5 --- Effect of Volume on Sensor Performance --- p.51 / Chapter 4.5.6 --- Continuous Detection --- p.54 / Chapter 4.5.7 --- Operating Power Limit --- p.57 / Chapter 4.6 --- Response to Chlorine Gas by Modified Design --- p.59 / Chapter 4.7 --- Desorption Induced by UV Illumination --- p.60 / Chapter 4.8 --- Summary --- p.63 / Chapter 5 --- Conclusion --- p.64 / Chapter 5.1 --- Future Work --- p.65 / Chapter 5.1.1 --- Selectivity --- p.65 / Chapter 5.1.2 --- Gaseous Chlorine Detection --- p.66 / Chapter 5.1.3 --- UV-LED Induced Desorption --- p.66 / Chapter 5.2 --- Concluding Remarks --- p.66 / Bibliography --- p.67

Introdução: O objetivo do presente estudo foi analisar a citotoxicidade e biocompatibilidade de soluções de hipoclorito de cálcio (Ca(OCl)2) comparadas a soluções de hipoclorito de sódio (NaOCl) in vitro em cultura de fibroblastos 3T3 e in vivo em ratos. Metodologia: Culturas de fibroblastos 3T3 foram expostas a diferentes concentrações de hipoclorito de cálcio e sódio e foi realizado um ensaio de “scratch”. Além disso, a taxa de viabilidade foi analisada utilizando o teste Azul de Trypan. As soluções a 1 e 2,5% foram, também, injetadas no tecido conjuntivo de 18 ratos Wistar de 18 semanas de idade. A reação inflamatória tecidual foi avaliada em 2h, 24h e 14 dias após as injeções e as amostras foram qualitativamente analisadas em microscópio óptico. Análise estatística foi realizada utilizando teste ANOVA e post hoc de Tukey para testes in vitro e Kruskal‐Wallis e post hoc de Dunn para o teste in vivo (α=.05). Resultados: No ensaio de “scratch”, Ca(OCl)2 não apresentou diferença estatística em relação ao controle no período de 24h (p<0.05). NaOCl e Ca(OCl)2 a 0.0075% e 0.005% apresentaram resultados de viabilidade similar ao grupo controle positivo (p > 0.05) no ensaio Azul de Trypan. No teste in vivo, Ca(OCl)2 1% mostrou uma diminuição significativa de neutrófilos entre 2h e 24h (p=0.041) e entre 2h e 14d (p=0.017). Não houve diferença estatística entre os grupos para linfócitos/plasmócitos e macrófagos. Conclusão: Ca(OCl)2 mostrou resultados favoráveis de viabilidade e induziu um baixo nível de resposta inflamatória tecidual, apresentando, assim, citotoxicidade e biocompatibilidade aceitáveis para uma solução irrigadora. / Introduction: The aim of the present study was to analyze cytotoxicity in vitro on cultured 3T3 fibroblasts and inflammatory tissue reaction in vivo on rats to calcium hypochlorite (Ca(OCl)2) solutions compared with sodium hypochlorite (NaOCl) solutions. Methods: Cultured 3T3 fibroblasts were exposed to different concentrations of calcium and sodium hypochlorite and a scratch assay was performed. The viability rate was analyzed with Trypan Blue assay. A. The 1 and 2.5% solutions were still injected into the subcutaneous tissues of eighteen male Wistar rats aged 18 weeks. Inflammatory tissue reaction was evaluated at 2h, 24h and 14 days after the injections and the samples were qualitatively analyzed through a light microscope. Statistical analysis was assessed by ANOVA and Tukey post hoc test for in vitro assays and by Kruskal-­‐Wallis and Dunn post hoc test for in vivo assay (α=.05). Results: In scratch assay, Ca(OCl)2 showed no statistically significant difference to control group at 24h (p<0.05). 0.0075% and 0.005% NaOCl and Ca(OCl)2 presented results similar to positive control group (p > 0.05) on Trypan Blue assay. In in vivo assay, 1% calcium hypochlorite group showed a significant decrease of neutrophils at 2h and 24h (p=0.041) and 2h and 14d (p=0.017). There was no statistically significant difference for lymphocytes/plasmocytes and macrophages among groups. Conclusions: Ca(OCl)2 showed favorable results of viability and induced an low level of inflammatory response, thus presenting an acceptable cytotoxicity and biocompatibility for an irrigant solution.

Orientador: Milton Carlos Kuga / Resumo: O objetivo do presente estudo foi avaliar a incidência de resíduos nas paredes dentinárias dos canais radiculares após a energização da solução de hipoclorito de sódio a 2,5% (NaOCl a 2,5%), por meio de ativação ultrassônica passiva (PUI) ou sônica (XP Endo Finisher, XP Clean ou Easy Clean). Quarenta caninos humanos extraídos, obtidos do Banco de dentes da Faculdade de Odontologia de Araraquara (FOAr/UNESP), foram previamente radiografados e selecionados com anatomia radicular semelhantes. Na sequência, as raízes foram padronizadas, a partir do ápice radicular, com a extensão de 17 mm e realizado o preparo químico e mecânico do canal radicular até o instrumento F5 (ProTaper; Dentsply, Petrópolis, RJ, BR), conforme a técnica recomendada pelo fabricante. Entre cada troca de calibre de instrumento, foi realizada a irrigação com 5 mL de NaOCl a 2,5%. Concluído esta fase, as raízes foram incluídas em silicone de alta densidade, previamente adaptadas em frascos de Eppendorf de 2,0 mL. Posteriormente, estas mesmas raízes foram removidas do silicone e seccionadas longitudinalmente no sentido mésio-distal. O segmento do canal radicular da face palatina será demarcado em 3 pontos distintos, correspondentes aos terços cervical, médio e apical. Após, as raízes foram remontadas no padrão de silicone e os canais radiculares submetidos a irrigação final com o NaOCl a 2,5% e energizados com um dos seguintes métodos: G1- Xp Endo Finisher; G2- XP Clean, G3- Easy Clean ou G4- PUI (Ativação Ultr... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of the study was to evaluete the occurrance of dentin walls residue of after energyzing a solution of sodium hypochloritorite in 2,5%(NaOCL a 2,5%), by Passive Ultrassonic Irrigation (PUI) or sonic (XP Endo Finisher, XP Clean ou Easy Clean). Forty extracted human canines, obtained from a tooth bank at the Dentristy School in Araraquara (FOAr/UNESP) were previously radiographed and selected with similar root anatomy. After that, the roots will be standardized from the root apex, with 17mm extension and chemical and mechanical preparation will be carried out until the F5 instrument, according to the technique recommended by the manufacture. Among each instrument caliber shift, irrigation was carried out with 5 ml of NaOCl at 2,5%. When this step was over, the roots were included in high density silicone, previously adapted in 2.0 ml eppendorf. After wards these were removed from the silicone and split lengthwise, mesiobuccal from. The palatine face root canal segment will be demarcarted in 3 distinc points, correspondent to the cervical, medium an apical thirds. After that, the roots were reassembled under the silicone pattern and the root canals were submitted to a final irrigation with NaOCl at 2,5% energized with one of the following methods: G1 XP Endo Finisher, G2: XP Clean, G3: Easy Clean and G4: PUI (Passive Ultrasonic Irrigation). Next, to roots were analyzed through scanning electron microscopy, assessing cervical, medium and apical thirds in arder to evaluate ... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:24:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-09Bitstream added on 2014-06-13T19:11:07Z : No. of bitstreams: 1 rosa_pcf_me_sjc.pdf: 2680312 bytes, checksum: d4fad1db60829c4daa185168c5bf357e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os cones de guta-percha precisam passar por um processo de desinfecção química rápida antes da obturação. Algumas soluções são capazes de agir em 1 minuto, mas se este período de imersão for prolongado, alterações podem ser causadas na estandardização dos cones, dificultando a adaptação ao canal radicular. Essa pesquisa avaliou as alterações morfológicas, em microscopia eletrônica de varredura (MEV), que ocorrem na superfície dos cones de guta-percha em períodos excedidos aos preconizados. Clorexidina 2% (CLX), hipoclorito de sódio 2,5% (NaOCL), ácido peracético 2% (AP) e solução de ácido peracético 0,25% (SAP) foram as soluções utilizadas nos períodos de 1 minuto, 30 minutos, 6 horas e 12 horas. Os grupos foram divididos de acordo com a solução e período de desinfecção (n=12). Os resultados indicaram que houve diferença estatística significante entre as soluções e períodos testados. Em 1 minuto, todas as soluções não diferiram do controle. Após 30 minutos, a SAP alterou significativamente a morfologia dos cones. O teste de espectrometria de energia dispersiva (EDS) indicou que todas as substâncias e períodos alteram a composição química dos cones de gutapercha. A relação da desinfecção na microinfiltração da obturação também foi avaliada nos grupos que sofreram desinfecção por 12 horas. O grupo da SAP apresentou diferença estatística significante em relação ao controle, pois 100% das suas raízes apresentaram infiltração. Os demais grupos da CLX, NaOCL e AP, embora sem diferença estatística significante, tiveram respectivamente 9, 8 e 8 do total de 12 das suas raízes com infiltração. Conclui-se que o processo de desinfecção pode causar alterações morfológicas se o período de imersão for excedido e que, além de alterarem a composição química dos cones de guta-percha, estas soluções podem influenciar no selamento da obturação / The gutta-percha points must go through a fast chemical disinfection process before obturation. Some solutions are able to work in 1 minute, but if this immersion period is prolonged, changes can be caused on the points standardization, hampering the adaptation to root canal. This study evaluated the morphological changes, in scanning electron microscopy (SEM), which occur on the surface of gutta-percha points in periods beyond the recommended. 2% chlorhexidine (CLX), 2.5% sodium hypochlorite (NaOCl), 2% peracetic acid (PA) and peracetic acid solution 0.25% (PAS) were used for 1 minute, 30 minutes, 6 hours and 12 hours. The groups were divided according to disinfecting solution and period (n = 12). The results indicated a statistically significant difference between the solutions and periods tested. In one minute, none of the solutions differed from control. After 30 minutes, PAS has significantly changed the morphology of the points. The energy dispersive x-ray test (EDS) showed that all substances and periods, alter the chemical composition of the gutta-percha points. The ratio of the disinfection on microleakage of the filling was also evaluated. The SAP 12 hours group had a statistically significant difference compared to the control and the other groups, since 100% of their roots showed infiltration. Groups of 12 hours period of CHX, NaOCl and PA, although without significant difference, had respectively 9, 8 and 8 out of 12 of its roots with infiltration. It is concluded that the disinfection process can cause morphological changes if the immersion period is exceeded and that, besides altering the chemical composition of gutta-percha points, these solutions can influence on the hermetic sealing of the root canal