The growth plate is a cartilaginous tissue responsible for the longitudinal growth of long bones. It is a complex tissue composed of chondrocytes whose maturation and proliferation is tightly regulated by a biochemical feedback loop. Injury to this tissue can result in a limb length discrepancy or angular deformity that may lead to life long disability. Given the recent rise in the number of growth plate injuries and the variability in success of current therapies, there is a significant need for a greater understanding of growth plate injury pathology and the development of improved treatment strategies. Cartilage tissue engineering strategies offer an attractive alternative to regenerating growth plate tissue and restoring growth function. Bone marrow-derived stem cells (BMSCs) have been shown to be able to undergo chondrogenic differentiation and in vitro and in vivo and therefore offers an appealing and abundant cell resource for developing tissue engineering strategies for the treatment of growth plate defects. However, the dependence of chondrogenic differentiation and matrix accumulation on monolayer expansion protocols and three-dimensional (3D) culture environment has received little attention. Prior to developing treatment strategies for growth plate injury repair, it is essential to first understand the interconnection between alterations in growth plate morphology and subsequent limb deformities. To that end, we have established a surgical defect model of growth plate injury in Sprague Dawley rats and developed a novel technique to quantitatively monitor growth plate morphology in health and disease using microcomputed tomography (micro-CT) imaging. In an effort to develop a tissue engineering treatment strategy for growth plate injury, the role of monolayer expansion, 3D scaffold, and growth factor regimen in the chondrogenic differentiation of rat BMSCs was also examined. This research study has demonstrated the utility of micro-CT as a non-invasive imaging modality for assessing growth plate injury and repair. This work has also provided an improved understanding of the interrelationship of monolayer expansion, 3D culture environment, and growth factor regimen in BMSC chondrogenic differentiation. Finally, this work suggests that an injectable in situ gelling hydrogel is a feasible method for decreasing limb length discrepancies, however, neither implantation of agarose alone into the defect nor the inclusion of BMSCs fully corrects growth disruption.

Diabetes mellitus is a systemic condition that remains undiagnosed in a large portion of the population, which presents potential challenges for implant-based rehabilitation. Currently, the effects of diabetes on bone healing are not fully understood. Thus prior to employing a model of diabetes in studies of peri-implant healing, it was important to investigate the temporal effects of hyperglycemia on bone healing. Bone healing of femoral drill-defects was compared between streptozotocin-induced hyperglycemic (DB) and normoglycemic (NDC) rats at 5, 10, 15, and 30 days P.O. Quantitative assessment of bone samples using μCT demonstrated a delay in bone formation occurring up to 10 days in DB animals. Histological assessment confirmed these quantitative findings. Additionally, fluorescently stained bone samples indicated possible defects in mineralization of bone in DB group. In summary hyperglycemia affects bone healing at the early stages of bone formation, concurrent with the osteoconduction phase of bone healing.

Diabetes mellitus is a systemic condition that remains undiagnosed in a large portion of the population, which presents potential challenges for implant-based rehabilitation. Currently, the effects of diabetes on bone healing are not fully understood. Thus prior to employing a model of diabetes in studies of peri-implant healing, it was important to investigate the temporal effects of hyperglycemia on bone healing. Bone healing of femoral drill-defects was compared between streptozotocin-induced hyperglycemic (DB) and normoglycemic (NDC) rats at 5, 10, 15, and 30 days P.O. Quantitative assessment of bone samples using μCT demonstrated a delay in bone formation occurring up to 10 days in DB animals. Histological assessment confirmed these quantitative findings. Additionally, fluorescently stained bone samples indicated possible defects in mineralization of bone in DB group. In summary hyperglycemia affects bone healing at the early stages of bone formation, concurrent with the osteoconduction phase of bone healing.

A ativação ultrassônica é um dos métodos mais utilizados para aumentar a eficiência mecânica e química dos irrigantes. No entanto, além de possivelmente causar desgastes indesejáveis na parede do canal, questiona-se a eficiência mecânica da irrigação ultrassônica ativada em canais com curvatura acentuada. O presente estudo teve como objetivo avaliar, por meio da microtomografia computadorizada (micro-CT) a influência do grau de curvatura dos canais radiculares nos desgastes dentinários não controlados produzidos pelo uso da Irrigação Ultrassônica Ativada (UAI), no percentual de debris dentinários remanescentes após UAI e o transporte do canal. Foram selecionados canais mesiais de 24 molares inferiores permanentes humanos, sendo 12 dentes com curvatura média de 25,5º (Curvatura Moderada) e 12 dentes com curvatura média de 50,9º (Curvatura Acentuada). Após escaneamento pré-operatório com um Microtomógrafo de raios-X, os canais foram preparados com os instrumentos Mtwo. Os dentes foram divididos em 2 grupos: Grupo CM (n=12) e Grupo CA (n=12). Ambos os grupos receberam irrigação ultrassônica ativada e em seguida foram escaneados novamente. Foram quantificados o volume e a profundidade máxima dos desgastes não controlados das paredes dos canais radiculares, o percentual de debris dentinários remanescentes e o transporte do canal. Foi realizada análise estatística, utilizando o software GraphPad Prism 7, com nível de singnificância de p <0,05. Os resultados mostraram que os grupos, apresentaram resultados semelhantes quanto ao volume de desgaste não controlado, porém o grupo CA apresentou desgastes mais acentuados no terço apical e um maior percentual de debri remanescente nos terços médio, apical e no total do canal radicular, além de promover desvio do canal no terço apical. Este estudo concluiu que curvaturas acentuadas interferem na profundidade do desgaste, na manutenção dos debris e no transporte do canal. / Ultrasonic activation is one of the most widely used supplementary irrigation methods. However, besides Ultrassonic Activated Irrigation (UAI) possibly causes uncontrolled removal of dentin in the root canal walls, it is unknown the efficiency of the ultrasonic irrigation in root canals with severe curvatures. The aim of the present study was evaluate using microcomputed tomography, the influence of the degrees of curvature in the percentage of remaining hard tissue debris, uncontrolled removal of dentin during UAI and root canal transportation. Twenty-four mesial roots of mandibular molars, 12 teeth with a mean curvature of 25.5º (Moderate Curvature) and 12 teeth with a mean curvature of 50.9º (Accentuated Curvature) were selected. After the pre-operative scanning with an X-ray microcomputed tomography, the specimens were prepared to size 35.04. The teeth were divided into two groups: Group CM (n = 12) and Group CA (n = 12). Both groups received ultrasonic irrigation and were scanned again. The maximum deep of the defects, volume of the uncontrolled removal of dentin, the percentage of remaining hard tissue debris and the root canal transportation were quantified. A statistical analysis was performed using GraphPad Prism 7 software, use Mann-Whitney test with a significance level of p <0.05. The results showed that the groups CM and CA had similar results in volume of uncontrolled removal of dentin, but the CA group show maximum deep defects more severe in the apical third, more percentage of hard tissue debri remaining in the middle, apical and total thirds of the canal root canal and a higher transport of the canal in the apical third. This study concluded that severe curves interfered in the maximum depth defects, in the maintenance of the debris and the transport of the canal.

O objetivo do presente estudo foi avaliar, quantitativa e qualitativamente, por meio de microtomografia computadorizada, o percentual de volume e de redução de debris dentinários acumulados (DDA) no sistema de canais radiculares com istmos de raízes mesiais de molares inferiores submetidos à: irrigação por pressão apical positiva; irrigação ultrassônica passiva; finalização do preparo com Self-Adjusting File e finalização do preparo com XP-endo Finisher. Quarenta raízes mesiais de molares inferiores, com curvatura moderada, e presença de dois canais mesiais com istmo único e contínuo verificada por escaneamento em microtomográfo, foram selecionadas. Os canais foram preparados pela técnica de instrumentação reciprocante (WaveOne Small e Primary). Em seguida, a composição dos grupos experimentais foi realizada por meio da técnica de amostragem estratificada, de acordo com o protocolo de irrigação final ou de finalização de preparo biomecânico, em quatro grupos (n=10): Pressão Apical Positiva (PAP), Irrigação Ultrassônica Ativa (IUP), Self-Adjusting File (SAF), e a XP-endo Finisher (XPF). Os protocolos foram realizados durante 2 minutos com 5,5 mL de hipoclorito de sódio a 2,5%. Os espécimes foram submetidos aos exames microtomográfico inicial, após o preparo e após os protocolos de irrigação final ou de finalização do preparo para análise de DDA. A porcentagem de volume e redução de DDA após os protocolos de irrigação final ou de finalização do preparo biomecânico foram comparados estatisticamente entre os grupos por meio de ANOVA e pós-teste de Tukey, com nível de significância de 5%. Foi possível observar redução de DDA após os protocolos de irrigação final e de finalização do preparo biomecânico em todos os grupos avaliados. Os grupos IUP e XPF apresentaram as menores médias de volume e de percentual de volume (%vol) de DDA (0,05±0,06mm³ e 0,61±0,75%; e 0,08±0,09mm³ e 0,81±1,03%, respectivamente) comparados aos grupos PAP e SAF (0,36±0,13mm³ e 3,73±1,59%; e 0,47±0,23mm³ e 4,31±1,87%, respectivamente) (p<0,05). Ainda, o percentual de redução de DDA foi maior nos grupos IUP e XPF (94,05±7,21% e 89,67±10,96%, respectivamente) quando comparados aos grupos PAP e SAF (45,74±15,76% e 41,26±9,96%, respectivamente) (p<0,05). Não houve diferença estatística entre os grupos IUP e XPF; e entre os grupos PAP e SAF (p>0,05). Qualitativamente, os DDA remanescentes foram localizados principalmente no terço apical após o protocolo com IUP; no terço cervical após protocolo com XPF e nos terços médio e apical após protocolos com PAP e SAF. Conclui-se que os protocolos de irrigação ultrassônica passiva e de finalização do preparo com XP-endo Finisher apresentaram maiores remoções de debris dentinários do sistema de canais radiculares com istmos comparados aos protocolos de irrigação por pressão apical positiva e de finalização de preparo com SAF. / The aim of this study was to evaluate, quantitatively and qualitatively, the percent volume and percent reduction of accumulated hard-tissue debris (AHTD) from root canal system with isthmuses of mesial roots of mandibular molars subjected to different final irrigation and final shaping protocols, using micro-computed tomography (micro-CT) analysis. Forty mesial roots of mandibular molars with moderate curvature and two mesial canals with a single and continuous isthmus detected by micro-CT scanning were selected. The canals were prepared by reciprocating instrumentation technique (WaveOne Small and Primary). Then, the composition of the experimental groups was performed by a stratified sampling method, resulting in four groups (n=10), according to the final irrigation or final shaping protocol: Apical Positive Pressure (APP), Passive Ultrasonic Irrigation (PUI), Self-adjusting File (SAF) and XP-endo Finisher (XPF). The protocols were performed with 5.5 mL of 2.5% NaOCl per canal during 2 minutes. The specimens were subjected to preoperative and following preparation, final irrigation or final shaping micro-CT scanning for AHTD analysis. The percent volume and percent reduction of AHTD after final irrigation or final shaping were statistically compared among groups using ANOVA and post hoc Tukey test with a 5% significance level. It was observed a reduction in the percentage of AHTD after final irrigation or final shaping in all groups. The PUI and XPF groups showed the lowest mean of volume and percent volume (%vol) of AHTD (0.05±0.06mm³ and 0.61±0.75%; and 0.08±0.09mm³ and 0.81±1.03%, respectively) when compared with APP and SAF groups (0.36±0.13mm³ and 3.73±1.59%; and 0.47±0.23mm³ and 4.31±1.87%, respectively) (p<0.05). Furthermore, the percent reduction of AHTD was greater in PUI and XPF groups (94.05±7.21% and 89.67±10.96%, respectively) compared with APP and SAF groups (45.74±15.76% and 41.26±9.96%, respectively) (p<0.05). No statistically significant differences were found when comparing PUI and XPF groups or APP and SAF groups (p>0.05). Qualitatively, the remaining DDA were mainly located in the apical third after the protocol with IUP; the cervical third after protocol XPF and in the middle and apical thirds after protocols PAP and SAF. It may be concluded that the passive ultrasound irrigation and final shaping with XP-endo Finisher protocols showed greater AHTD reduction from root canal system with isthmuses of mesial roots of mandibular molars than apical positive pressure and final shaping with SAF.

O objetivo do presente estudo foi avaliar a anatomia do sistema de canais radiculares (SCR) de 72 primeiros pré-molares superiores (32 unirradiculares, 30 birradiculares com sulcos e 10 trirradiculares), por meio de microtomografia computadorizada (&mu;CT). As amostras foram escaneadas no microtomógrafo SkyScan 1174 v2, e as imagens geradas foram reconstruídas para análise dos parâmetros bidimensionais (número, área, circularidade , diâmetro maior e menor, fator de forma) a 1, 2, 3 mm do forame apical e tridimensionais (volume, área de superfície, índice de estrutura do modelo - SMI, número e localização de canais acessórios), bem como avaliação das características anatômicas externas da raiz (presença, localização, profundidade e extensão do sulco e espessura interna e externa de dentina) e análise qualitativa dos modelos tridimensionais. Os resultados mostraram que o número máximo de canais no terço apical foi três. A 1 mm do forame apical, nos dentes unirradiculares, o diâmetro maior foi, em média, duas vezes maior que o diâmetro menor. O padrão de circularidade demonstrou forma circular com tendência ao achatamento dos canais dos dentes unirradiculares e uma forma mais circular nos canais dos bi e trirradiculares, principalmente nas raízes palatinas. Os resultados do fator de forma confirmaram a forma mais circular dos canais em todos os dentes avaliados. Na análise tridimensional, as maiores médias de volume (14,84±10,78mm³) e área de superfície (83,65±48,26mm²) foram encontradas nos canais radiculares dos pré-molares unirradiculares, e as menores médias de volume (3,78±1,61mm³) e área de superfície (25,11±6,17mm²) foram observadas na raiz disto-vestibular dos primeiros pré-molares superiores trirradiculares. Os valores de SMI foram semelhantes em todas as raízes nos três grupos dentais avaliados, evidenciando uma forma tridimensional cônica com tendência cilíndrica dos canais radiculares. A presença de um canal acessório variou de 45% a 100% no terço apical e de 15% a 100% no terço médio em todas as raízes dos grupos dentais avaliados. Na análise radicular externa, foram encontrados 35 sulcos radiculares (23 únicos e 12 duplos), sendo encontrados na face palatina da raiz vestibular em 100% dos pré-molares superiores birradiculares. A profundidade do sulco apresentou maior valor médio (0,57±0,27mm) na secção transversal correspondente à 1mm acima da metade da extensão total do sulco. O teste de correlação mostrou que nas secções transversais mais cervicais em relação ao suco, quanto maior a sua profundidade, maior é o achatamento e a ocorrência de divisão dos canais radiculares. Os modelos tridimensionais evidenciaram a prevalência da classificação tipo IV de Vertucci. Dessa forma, conclui-se que a &mu;CT possibilitou o estudo detalhado da anatomia interna e externa do SCR em primeiros pré-molares superiores uni, bi e trirradiculares. / The aim of this study was to evaluate the anatomy of the root canal system (RCS) of 72 maxillary first premolars (32 single-rooted, 30 two-rooted with radicular grooves and 10 three-rooted), using computed microtomography (&mu;TC). The specimens were scanned with the SkyScan 1174v2 microtomography device and the images were reconstructed for analysis of two-dimensional parameters (number, area, roundness, major diameter, minor diameter, and form factor) at 1, 2 and 3 mm of the apical foramen, and three-dimensional parameters (volume, surface area, structure model index - SMI, number and location of accessory canals), as well as examination of external anatomic characteristics of the roots (presence, location, depth and extension of the grooves, and internal and external dentin thickness) and qualitative analysis of the three-dimensional models. No more than three canals were found in the apical third. At 1 mm from the apical foramen in single-rooted teeth, mean values of the major diameter were twice as higher than those of the minor diameter. The roundness pattern of the canals revealed a round shape with a tendency to flattening in the single-rooted premolars, and a shape with more accentuated roundness in the two- and three-rooted premolars, mainly in the palatal roots. The form factor results confirmed the more circular shape of all teeth. In the three-dimensional analysis, the highest values of mean volume (14.84±10.78mm³) and surface area (83.65±48.26mm²) were found in the canals of the single-rooted premolars, and the lowest values of mean volume (3,78±1,61mm³) and surface área (25,11±6,17mm²) were observed in the distobuccal root of the three-rooted premolars. The mean SMI values were similar in all roots of the three groups of premolars, indicating a tendency to a 3D cylinder-like geometry of the canals. The presence of one accessory canal ranged from 45 to 100% in the apical third and 15 to 100% in the middle third in all evaluated roots. In the examination of the external root surface, 35 radicular grooves (23 singles and 12 doubles) were found, with prevalence (100%) in the palatal face of the buccal root in two-rooted premolars. The radicular groove depth presented higher mean value (0.57±0.27mm) in the cross-section corresponding to 1 mm above the middle point of the full length of the groove. The correlation test showed that in the cross-sections more coronal to the groove, the greater the depth, the more accentuated the flattening and the greater the occurrence of division of the canals within the root. The analysis of the tree-dimensional models demonstrated the prevalence of Vertucci\'s type IV configuration. In conclusion, the use of &mu;CT provided a detailed evaluation of the internal and external anatomy of the RCS in singlerooted, two-rooted and three-rooted maxillary first premolars.

O conhecimento prévio da anatomia interna e externa dos dentes decíduos é de fundamental importância para o sucesso do tratamento endodôntico. O objetivo do presente estudo foi analisar a morfologia das raízes e dos canais radiculares de molares decíduos superiores e inferiores, por meio de microtomografia computadorizada (micro-CT). Foram usados 40 molares decíduos, divididos em quatro grupos, sendo 10 primeiros molares inferiores, 10 segundos molares inferiores, 10 primeiros molares superiores e 10 segundos molares superiores. Os dentes foram escaneados e avaliados quantitativamente por meio de parâmetros bidimensionais no terço apical (número, área, circularidade, maior e menor diâmetro) a 1, 2 e 3 mm do bisel de rizólise e tridimensionais (volume, área de superfície e SMI), assim como a medida da espessura na face interna e externa da dentina e qualitativamente por meio da observação dos modelos tridimensionais. Os resultados mostraram que o número máximo de canais radiculares encontrados por raiz foi 2. Os canais apresentaram valores de SMI entre 1,98 ± 0,45 e 2,74 ± 0.38, sugerindo forma geométrica tridimensional com tendência a um cone. Para a espessura da dentina, observou-se que a espessura da dentina na face interna das raízes foi, em geral, menor que a espessura na face externa. Os valores de espessura interna variaram entre 0,25 e 0,90 mm na raiz mesial e 0,20 e 0,92 mm na raiz distal para os molares inferiores e, 0,14 e 1,00 mm na raiz mesiovestibular, 0,24 e 1,14 mm na raiz distovestibular e 0,26 e 1,54 mm na raiz palatina para os molares superiores. Em relação à espessura externa, a variação foi de 0,35 a 1,45 mm na raiz mesial e 0,32 a 1,52 mm na raiz distal para os molares inferiores e, 0,22 a 1,33 mm na raiz mesiovestibular, 0,28 a 1,40 mm na raiz distovestibular e 0,44 a 2,24 mm na raiz palatina nos molares superiores. Foi observado também, que a extensão da raiz foi sempre maior que a extensão do canal. Dessa forma, conclui-se que as variações anatômicas observadas e os parâmetros obtidos a partir da micro-CT, método não destrutivo, reprodutível e confiável para o estudo de anatomia interna e externa, são importantes para determinar protocolos clínicos nos casos de dentes decíduos. / The previous knowledge of the internal and external anatomy of primary teeth is of fundamental importance for the success of the endodontic treatment. The purpose of this study was to analyze the morphology of the roots and root canals of the upper and lower primary molars, using the microcomputed tomography (micro-CT). Forty primary molars, divided in four groups, ten first lower molars, ten second lower molars, ten first upper molars and ten second upper molars. The teeth were scanned and assessed quantitatively by the observation of two-dimensional parameters in the apical third (number, area, roundness, major and minor diameter) at 1, 2 and 3 millimeters of the resorption bevel and three-dimensional parameters (volume, surface area and SMI), as well as the measurement of internal and external dentin thickness and qualitatively by means of observation of the three-dimensional models. The results showed that the maximum number of root canals found for each root was 2. The canals have SMI values between 1.98 ± 0.45 and 2.74 ± 0.38, suggesting a three-dimensional geometrical shape with a tendency to conical. For the dentin thickness of the internal wall of the roots, in general the values were lower than the ones for the external wall. The values of the internal thickness ranged between 0.25 and 0.90 mm in the mesial root and 0.20 and 0.92 mm in the distal root for the lower molars and 0.14 and 1.00 mm on the mesio-vestibular root, 0.24 and 1.14 mm on the disto-vestibular and 0.26 and 1.54 mm on the palatal for the upper molars. Regarding the external thickness, it ranged between 0.35 and 1.45 mm on the mesial root and 0.32 and 1.52 mm on the distal for the lower molars, and 0.22 and 1.33 mm on the mesio-vestibular, 0.28 and 1.40 mm on the disto-vestibular and 0.44 and 2.24 mm on the palatal root of the upper molars. It was observed that the dentin thickness of the external wall was always higher than the extension of the canal. That way, it can be concluded that the observed anatomical variations and the obtained parameters from the micro-CT, a non-destructive method, reproducible and reliable for the study of internal and external anatomy, are important to define clinical protocols for the primary teeth.

Postnatal vascular growth is a complex process involving multiple cells types whose functionality is orchestrated by a variety of soluble extracellular growth factors, mechanical stimuli, and matrix derived cues. The central goal for this dissertation project was to elucidate the role of osteopontin, a non-collagenous extracellular matrix protein, in postnatal vascular growth. At the onset, we concluded that the current methods for measurement of vascularity in small animal models were lacking. To address this shortcoming, we pursued micro-CT imaging for analysis of three-dimensional blood vessel architecture. We were able to demonstrate that micro-CT imaging provides an objective, quantitative, and three-dimensional methodology for evaluation of vascular networks that has broad applicability to preclinical studies. Next, we sought to apply the developed imaging techniques, along with other complementary methodologies, to explore the role of osteopontin in postnatal vascular growth. Osteopontin was previously known to elicit survival, migration, and other relevant activities in multiple cell types involved in postnatal vascular growth. Therefore, we sought to determine the in vivo significance of osteopontin in this process. To do so, we compared wild type and Osteopontin-/- mice for (1) their ability to form collateral vessels and functionally recover following acute induction of hind limb ischemia and (2) their capacity for neovascularization, mineralization, remodeling, and the restoration of mechanical properties during fracture healing. Data suggested that OPN is a critical regulator of collateral vessel formation and that this effect is driven by its role in mediating monocyte/macrophage migration and functionality. Secondly, we found that the presence of osteopontin was essential for normal early callus formation, neovascularization, late stage callus remodeling, and restoration of biomechanical strength. Abnormal collagen organization was observed within the remodeling fractures of Osteopontin-/- mice, and we hypothesize that a unifying link between the vascular and bone defects may be related to deficient matrix organization and remodeling. In conclusion, the imaging techniques developed in this thesis provide a novel methodology for quantitative analysis of vascular structures in small animal models. Secondly, this project has yielded an improved understanding of the basic pathophysiological mechanisms that control postnatal blood vessel growth and bone fracture healing.

O objetivo do presente estudo foi avaliar, quantitativa e qualitativamente, por meio de microtomografia computadorizada, o percentual de volume e de redução de debris dentinários acumulados (DDA) no sistema de canais radiculares com istmos de raízes mesiais de molares inferiores submetidos à: irrigação por pressão apical positiva; irrigação ultrassônica passiva; finalização do preparo com Self-Adjusting File e finalização do preparo com XP-endo Finisher. Quarenta raízes mesiais de molares inferiores, com curvatura moderada, e presença de dois canais mesiais com istmo único e contínuo verificada por escaneamento em microtomográfo, foram selecionadas. Os canais foram preparados pela técnica de instrumentação reciprocante (WaveOne Small e Primary). Em seguida, a composição dos grupos experimentais foi realizada por meio da técnica de amostragem estratificada, de acordo com o protocolo de irrigação final ou de finalização de preparo biomecânico, em quatro grupos (n=10): Pressão Apical Positiva (PAP), Irrigação Ultrassônica Ativa (IUP), Self-Adjusting File (SAF), e a XP-endo Finisher (XPF). Os protocolos foram realizados durante 2 minutos com 5,5 mL de hipoclorito de sódio a 2,5%. Os espécimes foram submetidos aos exames microtomográfico inicial, após o preparo e após os protocolos de irrigação final ou de finalização do preparo para análise de DDA. A porcentagem de volume e redução de DDA após os protocolos de irrigação final ou de finalização do preparo biomecânico foram comparados estatisticamente entre os grupos por meio de ANOVA e pós-teste de Tukey, com nível de significância de 5%. Foi possível observar redução de DDA após os protocolos de irrigação final e de finalização do preparo biomecânico em todos os grupos avaliados. Os grupos IUP e XPF apresentaram as menores médias de volume e de percentual de volume (%vol) de DDA (0,05±0,06mm³ e 0,61±0,75%; e 0,08±0,09mm³ e 0,81±1,03%, respectivamente) comparados aos grupos PAP e SAF (0,36±0,13mm³ e 3,73±1,59%; e 0,47±0,23mm³ e 4,31±1,87%, respectivamente) (p<0,05). Ainda, o percentual de redução de DDA foi maior nos grupos IUP e XPF (94,05±7,21% e 89,67±10,96%, respectivamente) quando comparados aos grupos PAP e SAF (45,74±15,76% e 41,26±9,96%, respectivamente) (p<0,05). Não houve diferença estatística entre os grupos IUP e XPF; e entre os grupos PAP e SAF (p>0,05). Qualitativamente, os DDA remanescentes foram localizados principalmente no terço apical após o protocolo com IUP; no terço cervical após protocolo com XPF e nos terços médio e apical após protocolos com PAP e SAF. Conclui-se que os protocolos de irrigação ultrassônica passiva e de finalização do preparo com XP-endo Finisher apresentaram maiores remoções de debris dentinários do sistema de canais radiculares com istmos comparados aos protocolos de irrigação por pressão apical positiva e de finalização de preparo com SAF. / The aim of this study was to evaluate, quantitatively and qualitatively, the percent volume and percent reduction of accumulated hard-tissue debris (AHTD) from root canal system with isthmuses of mesial roots of mandibular molars subjected to different final irrigation and final shaping protocols, using micro-computed tomography (micro-CT) analysis. Forty mesial roots of mandibular molars with moderate curvature and two mesial canals with a single and continuous isthmus detected by micro-CT scanning were selected. The canals were prepared by reciprocating instrumentation technique (WaveOne Small and Primary). Then, the composition of the experimental groups was performed by a stratified sampling method, resulting in four groups (n=10), according to the final irrigation or final shaping protocol: Apical Positive Pressure (APP), Passive Ultrasonic Irrigation (PUI), Self-adjusting File (SAF) and XP-endo Finisher (XPF). The protocols were performed with 5.5 mL of 2.5% NaOCl per canal during 2 minutes. The specimens were subjected to preoperative and following preparation, final irrigation or final shaping micro-CT scanning for AHTD analysis. The percent volume and percent reduction of AHTD after final irrigation or final shaping were statistically compared among groups using ANOVA and post hoc Tukey test with a 5% significance level. It was observed a reduction in the percentage of AHTD after final irrigation or final shaping in all groups. The PUI and XPF groups showed the lowest mean of volume and percent volume (%vol) of AHTD (0.05±0.06mm³ and 0.61±0.75%; and 0.08±0.09mm³ and 0.81±1.03%, respectively) when compared with APP and SAF groups (0.36±0.13mm³ and 3.73±1.59%; and 0.47±0.23mm³ and 4.31±1.87%, respectively) (p<0.05). Furthermore, the percent reduction of AHTD was greater in PUI and XPF groups (94.05±7.21% and 89.67±10.96%, respectively) compared with APP and SAF groups (45.74±15.76% and 41.26±9.96%, respectively) (p<0.05). No statistically significant differences were found when comparing PUI and XPF groups or APP and SAF groups (p>0.05). Qualitatively, the remaining DDA were mainly located in the apical third after the protocol with IUP; the cervical third after protocol XPF and in the middle and apical thirds after protocols PAP and SAF. It may be concluded that the passive ultrasound irrigation and final shaping with XP-endo Finisher protocols showed greater AHTD reduction from root canal system with isthmuses of mesial roots of mandibular molars than apical positive pressure and final shaping with SAF.

O objetivo do presente estudo foi avaliar a anatomia do sistema de canais radiculares (SCR) de 72 primeiros pré-molares superiores (32 unirradiculares, 30 birradiculares com sulcos e 10 trirradiculares), por meio de microtomografia computadorizada (&mu;CT). As amostras foram escaneadas no microtomógrafo SkyScan 1174 v2, e as imagens geradas foram reconstruídas para análise dos parâmetros bidimensionais (número, área, circularidade , diâmetro maior e menor, fator de forma) a 1, 2, 3 mm do forame apical e tridimensionais (volume, área de superfície, índice de estrutura do modelo - SMI, número e localização de canais acessórios), bem como avaliação das características anatômicas externas da raiz (presença, localização, profundidade e extensão do sulco e espessura interna e externa de dentina) e análise qualitativa dos modelos tridimensionais. Os resultados mostraram que o número máximo de canais no terço apical foi três. A 1 mm do forame apical, nos dentes unirradiculares, o diâmetro maior foi, em média, duas vezes maior que o diâmetro menor. O padrão de circularidade demonstrou forma circular com tendência ao achatamento dos canais dos dentes unirradiculares e uma forma mais circular nos canais dos bi e trirradiculares, principalmente nas raízes palatinas. Os resultados do fator de forma confirmaram a forma mais circular dos canais em todos os dentes avaliados. Na análise tridimensional, as maiores médias de volume (14,84±10,78mm³) e área de superfície (83,65±48,26mm²) foram encontradas nos canais radiculares dos pré-molares unirradiculares, e as menores médias de volume (3,78±1,61mm³) e área de superfície (25,11±6,17mm²) foram observadas na raiz disto-vestibular dos primeiros pré-molares superiores trirradiculares. Os valores de SMI foram semelhantes em todas as raízes nos três grupos dentais avaliados, evidenciando uma forma tridimensional cônica com tendência cilíndrica dos canais radiculares. A presença de um canal acessório variou de 45% a 100% no terço apical e de 15% a 100% no terço médio em todas as raízes dos grupos dentais avaliados. Na análise radicular externa, foram encontrados 35 sulcos radiculares (23 únicos e 12 duplos), sendo encontrados na face palatina da raiz vestibular em 100% dos pré-molares superiores birradiculares. A profundidade do sulco apresentou maior valor médio (0,57±0,27mm) na secção transversal correspondente à 1mm acima da metade da extensão total do sulco. O teste de correlação mostrou que nas secções transversais mais cervicais em relação ao suco, quanto maior a sua profundidade, maior é o achatamento e a ocorrência de divisão dos canais radiculares. Os modelos tridimensionais evidenciaram a prevalência da classificação tipo IV de Vertucci. Dessa forma, conclui-se que a &mu;CT possibilitou o estudo detalhado da anatomia interna e externa do SCR em primeiros pré-molares superiores uni, bi e trirradiculares. / The aim of this study was to evaluate the anatomy of the root canal system (RCS) of 72 maxillary first premolars (32 single-rooted, 30 two-rooted with radicular grooves and 10 three-rooted), using computed microtomography (&mu;TC). The specimens were scanned with the SkyScan 1174v2 microtomography device and the images were reconstructed for analysis of two-dimensional parameters (number, area, roundness, major diameter, minor diameter, and form factor) at 1, 2 and 3 mm of the apical foramen, and three-dimensional parameters (volume, surface area, structure model index - SMI, number and location of accessory canals), as well as examination of external anatomic characteristics of the roots (presence, location, depth and extension of the grooves, and internal and external dentin thickness) and qualitative analysis of the three-dimensional models. No more than three canals were found in the apical third. At 1 mm from the apical foramen in single-rooted teeth, mean values of the major diameter were twice as higher than those of the minor diameter. The roundness pattern of the canals revealed a round shape with a tendency to flattening in the single-rooted premolars, and a shape with more accentuated roundness in the two- and three-rooted premolars, mainly in the palatal roots. The form factor results confirmed the more circular shape of all teeth. In the three-dimensional analysis, the highest values of mean volume (14.84±10.78mm³) and surface area (83.65±48.26mm²) were found in the canals of the single-rooted premolars, and the lowest values of mean volume (3,78±1,61mm³) and surface área (25,11±6,17mm²) were observed in the distobuccal root of the three-rooted premolars. The mean SMI values were similar in all roots of the three groups of premolars, indicating a tendency to a 3D cylinder-like geometry of the canals. The presence of one accessory canal ranged from 45 to 100% in the apical third and 15 to 100% in the middle third in all evaluated roots. In the examination of the external root surface, 35 radicular grooves (23 singles and 12 doubles) were found, with prevalence (100%) in the palatal face of the buccal root in two-rooted premolars. The radicular groove depth presented higher mean value (0.57±0.27mm) in the cross-section corresponding to 1 mm above the middle point of the full length of the groove. The correlation test showed that in the cross-sections more coronal to the groove, the greater the depth, the more accentuated the flattening and the greater the occurrence of division of the canals within the root. The analysis of the tree-dimensional models demonstrated the prevalence of Vertucci\'s type IV configuration. In conclusion, the use of &mu;CT provided a detailed evaluation of the internal and external anatomy of the RCS in singlerooted, two-rooted and three-rooted maxillary first premolars.