Effects of furcation involvement on molar survival in periodontally treated patients / Efectos de la furcación sobre la supervivencia molar en pacientes sometidos a tratamiento periodontal

Objective: This study aims to analyze the survival time of molar tooth according to furcation involvement (FI) classification among periodontally treated patients under a supportive periodontal care program. Materials and Methods: A retrospective study was con-ducted among 77 periodontitis patients with 240 molars who had undergone periodontal therapy that were followed up with supportive periodontal therapy (SPT) for at least five years. Periodontitis patients' data were retrieved from the periodontic clinical record. The clinical parameters of all involved molars and treatment modality were recorded at baseline and SPT. Results: A total of 69 (28.8%) molars were extracted during active periodontal therapy, while 17 (7.1%) were lost during SPT. The 5-year survival rate of molars was 83.5% (95% confidence interval [CI], 76.9-88.4) for FI=0 (n=141), 81.0% (95% CI, 56.9-92.4) for FI=I (n=18), 50.0% (95% CI, 33.8-64.2) for FI=II (n=21), and 25.0% (95% CI, 6.9-48.8) for FI=III (n=4). Additionally, the 10-year survival rate for molars with FI = III was 12.5% (95% CI, 1.0-39.2), which was lower than that of molars with FI = 0 (77.1%; 95% CI, 69.7-83.0). Conclusions: The presence of a high degree of FI classifica-tion, especially Class III, is associated with a lower survival rate of molars among periodontally treated patients. Retention of molars is possible on a long-term basis through a maintenance program of periodontal therapy.

Objetivo: Este estudio tiene como objetivo analizar el tiempo de supervivencia de los molares según la clasificación de implicación de la furcación (IF) entre pacientes tratados periodontalmente bajo un programa de cuidado periodontal de apoyo. Materiales y Métodos: Se realizó un estudio retrospectivo entre 77 pacientes con periodontitis con 240 molares que habían sido sometidos a terapia periodontal y fueron seguidos con terapia periodontal de soporte (TPS) durante al menos cinco años. Los datos de los pacientes con periodontitis se recuperaron de la Historia Clínica de Periodoncia. Los parámetros clínicos de todos los molares involucrados y la modalidad de tratamiento se registraron al inicio y en el TPS. Resultado: Se extrajeron un total de 69 (28,8%) molares durante la terapia periodontal activa, mientras que 17 (7,1%) se perdieron durante la TPS. La tasa de supervivencia de los molares a 5 años fue del 83,5% (intervalo de confianza [IC] del 95%, 76,9-88,4) para FI=0 (n=141), del 81,0% (IC del 95%, 56,9-92,4) para FI=I ( n=18), 50,0% (IC 95%, 33,8-64,2) para FI=II (n=21) y 25,0% (IC 95%, 6,9-48,8) para FI=III (n=4). Además, la tasa de supervivencia a 10 años para los molares con FI = III fue del 12,5 % (IC del 95 %, 1,0-39,2), que fue inferior a la de los molares con FI = 0 (77,1 %; IC del 95 %, 69,7-83,0). Conclusión: La presencia de un alto grado de clasificación FI, especialmente Clase III, se asocia con una menor tasa de supervivencia de los molares entre los pacientes tratados periodontalmente. La retención de los molares es posible a largo plazo mediante un programa de mantenimiento de terapia periodontal.

Morphology of the Second Mesiobuccal Canal in the Maxillary Second Molar / Morfología del Segundo Canal Mesiovestibular en el Segundo Molar Maxilar

SUMMARY: Failure to locate a complete canal system affects the prognosis of root canal treatment. A missed root canal is one of the most common reasons for failed root canal treatment. The prevalence of the second mesiobuccal canal in the maxillary second molar is relatively high and has a variety of configurations. Therefore, knowledge of its morphology is required in clinical endodontics. This review presented the canal in terms of its prevalence, classification, anatomical features, and the method for locating the second mesiobuccal canal in the maxillary second molar. Root canal treatment requires knowledge of tooth morphology, appropriate access preparation, and a thorough examination of the tooth's interior. Thus, clinicians should carefully employ various methods for assessing the anatomy of the entire root canal system to prevent failure in locating the second mesiobuccal canal. This canal can be located by modifying the access cavity design and utilizing specific instruments to improve the second mesiobuccal canal system visualization.

La falta de localización de un sistema completo de canal afecta el pronóstico del tratamiento de éste. La omisión de un tratamiento de canal es uno de los motivos más frecuentes por las que el tratamiento de canal fracasa. La prevalencia del segundo canal mesiovestibular en el segundo molar superior es relativamente alta y tiene una variedad de configuraciones. Por tanto, el conocimiento de su morfología es necesario en endodoncia clínica. Esta revisión presentó el canal en términos de su prevalencia, clasificación, características anatómicas y el método para localizar el segundo canal mesiovestibular en el segundo molar superior. El tratamiento de canal requiere conocimiento de la morfología del diente, una preparación adecuada del acceso y un examen exhaustivo del interior del diente. Por lo tanto, los dentistas deben emplear cuidadosamente varios métodos para evaluar la anatomía de todo el sistema de canales radiculares para evitar fallas en la localización del segundo canal mesiovestibular. Este canal se puede localizar modificando el diseño de la cavidad de acceso y utilizando instrumentos específicos para mejorar la visualización del sistema del segundo canal mesiovestibular.

Microcomputed-Tomographic Analysis of the Root Canal Morphology of the Mandibular First Molars in a Malaysian Subpopulation Using Two Classification Systems / Análisis por Tomografía Microcomputada de la Morfología del Conducto Radicular de los Primeros Molares Mandibulares en una Subpoblación de Malasia Utilizando dos Sistemas de Clasificación

SUMMARY: This work investigated the morphology of the root canal system of the mandibular first molar in a Malaysian subpopulation. Using micro-computed tomography with an isotropic resolution of 22 µm, 140 mandibular first molars were scanned. MIMICS software was used for segmentation, 3-D reconstruction and analysis of the acquired images. The canal configuration was described using Vertucci [supported by the supplementary configurations proposed by Sert & Bayirli (2004)] and Ahmed et al. (2027), coding systems. The chi-square test was used to assess the association between qualitative variables. By non-considering intercanal communications, Vertucci types IV (17.1%) and I (76.4%) were the most frequently reported configurations in the mesial and distal roots, respectively. Of the reported configurations, 24.3% and 4.3% were non-classifiable by Vertucci system in the mesial and distal roots, respectively. Up to 63.6% and 9.3% of the reported configurations were non- classifiable, and type I was the most frequent when considering intercanal communications (7.1% and 76.4% in the mesial and distal roots, respectively). According to Ahmed et al., system, almost half of the sample had more than four digits (47.9%), followed by the 3-digits category (20.71%). In both systems, a significant association was found between the canal configuration and the root type (p<0.001). The mandibular first molar of this Malaysian subpopulation demonstrated a wide range of root canal morphology. When compared to the Vertucci system, the system developed by Ahmed et al., successfully classified all molars configurations despite their level of complexity. The complex canal anatomy of mandibular first molars in this subpopulation warrants special attention during root canal treatment procedures.

En este trabajo se investigó la morfología del sistema de conductos radiculares del primer molar mandibular en una subpoblación de Malasia. Utilizando tomografía microcomputada con una resolución isotrópica de 22 µm, se escanearon 140 primeros molares mandibulares. Se utilizó el software MIMICS para segmentar (enmascarar), reconstruir en 3D, visualizar y analizar las imágenes adquiridas. La configuración del canal se describió utilizando Vertucci respaldado por las configuraciones complementarias propuestas por Sert & Bayirli (2004)] y Ahmed et al. (2017, 2020), sistemas de codificación. Se utilizó la prueba de chi-cuadrado para evaluar la asociación entre variables cualitativas. Sin considerar las comunicaciones intercanales, los tipos Vertucci IV (17,1%) y I (76,4%) fueron las configuraciones reportadas con mayor frecuencia en las raíces mesiales y distales, respectivamente. De las configuraciones reportadas, el 24,3 % y el 4,3 % fueron no clasificables por el sistema de Vertucci en las raíces mesial y distal, respectivamente. Hasta el 63,6 % y el 9,3 % de las configuraciones reportadas fueron no clasificables, siendo la tipo I la más frecuente al considerar las comunicaciones intercanales (7,1 % y 76,4 % en las raíces mesiales y distales, respectivamente). Según Ahmed et al. (2017, 2020) en el sistema, casi la mitad de la muestra tenía más de cuatro dígitos (47,9 %), seguido por la categoría de 3 dígitos (20,71 %). En ambos sistemas se encontró una asociación significativa entre la configuración del canal y el tipo de raíz (p<0,001). El primer molar mandibular de esta subpoblación de Malasia demostró una amplia gama morfológica del conducto radicular. En comparación con el sistema Vertucci, el sistema desarrollado por Ahmed et al. (2017, 2020) clasificaron con éxito todas las configuraciones de los molares a pesar de su nivel de complejidad. La compleja anatomía del canal de los primeros molares mandibulares en esta subpoblación merece una atención especial durante los procedimientos de tratamiento de conducto.

Odontometria em molares inferiores: comparação entre radiografia convencional e digital / Odontometry in mandibular molars: a comparison between conventional and digital radiograph

Objetivo:Comparar os métodos radiográficos convencional e digital na Odontometria de molares inferiores. Materiais e Métodos: Foram selecionados 26 dentes e inseridos em recipientes com gesso e serragem para simular o osso alveolar. Após adequado acesso endodôntico, limas K#15 foram posicionadas nos canais mésio-vestibular e distal, 1mm aquém da patência foraminal (CT1). Foi construído um dispositivo em resina, onde fixou-se um medidor de ângulos padronizando a angulação horizontal em 20º para distal. O ângulo vertical foi 0º com distância foco-filme de 30 centímetros. Foi utilizado um aparelho de Rx de 70 KVp e 8 mA e exposição de 0,4 segundos. Para obtenção do CT radiográfico (CT2), posicionou-se o paquímetro na borda inferior do cursor até a ponta da lima. As mesmas medidas foram realizadas nas radiografias digitais obtidas com um sensor CMOS. A ferramenta "régua" foi utilizada determinando-se o CT digital (CT3). O teste de Correlação Intraclasse verificou concordâncias intragrupo e intergrupos e os testes Anova OneWay e Tukey (α = 0,05) foram usados para análise comparativa entre CT1, CT2 e CT3. Resultados: Tanto as medidas convencionais quanto as digitais apresentaram excelente concordância intragrupo (0,9842 e 0,9943, respectivamente). A concordância entre as mensurações para o CT digital foi maior em relação às medidas reais (0,8162) que as medidas do CT convencional (0,6761). A média e desvio padrão para CT1, CT2 e CT3 foram 18,4±1,4; 19,2±1,6 e 18,8±1,2mm, respectivamente. O teste de Tukey indicou diferença estatística entre CT1 e CT2 (p = 0,027); já entre CT1 e CT3 (p = 0,499) e entre CT2 e CT3 (p = 0,314) não houve diferenças significativas. Conclusão: As radiografias digitais propiciaram maior precisão na Odontometria de molares inferiores nas condições experimentais avaliadas.

Objective: To compare conventional and digital radiographic methods in Odontometry of lower molars. Materials and Methods:Twenty-six teeth were selected and inserted into containers with plaster and sawdust to simulate the alveolar bone. After adequate endodontic access, K#15 files were positioned in the mesiobuccal and distal canals, 1 mm below the foraminal patency (CT1).A resin device was constructed, where an angle gauge was fixed, standardizing the horizontal angulation at 20º distally. The vertical angle was 0º with a focus-film distance of 30 cm. An Rx device of 70 KVp and 8 mA, with an exposure time of 0.4 seconds, was used. To obtain the radiographic CT (CT2), the caliper was positioned on the lower edge of the cursor up to the tip of the file. The same measurements were performed on digital radiographs, obtained with a CMOS sensor. The "ruler" tool was used to determine the digital CT (CT3). The Intra-Class Correlation test was used to verify intra-group and intergroup agreements, and the Anova One-way and Tukey tests (α = 0.05) were used for comparative analysis between CT1, CT2, and CT3. Results: Both conventional and digital measurements had excellent intra-group agreement (0.9842 and 0.9943, respectively). The agreement between measurements for digital CT was greater in relation to real measurements (0.8162) than conventional CT measurements (0.6761). The mean and standard deviation for CT1, CT2, and CT3 were 18.4±1.4; 19.2±1.6; and 18.8±1.2, respectively. The Tukey test indicated a statistical difference between CT1 and CT2 (p = 0.027); Between CT1 and CT3 (p = 0.499) and between CT2 and CT3 (p = 0.314) no significant differences were observed. Conclusion:Digital radiographs provided greater precision in the odontometry of lower molars according to the experimental conditions evaluated in this study.

Classificação e profundidade de istmos em primeiros molares inferiores: estudo retrospectivo em TCFC / Classification and depth of isthmus in mandibular first molars: retrospective CBCT study

O conhecimento da anatomia dental é de extrema importância para o clínico na busca do sucesso endodôntico. Complexidades anatômicas, como os istmos, podem causar dificuldades durante o tratamento, comprometendo a limpeza, antissepsia e posterior obturação. O primeiro molar inferior é o elemento que apresenta maior incidência de istmos em suas raízes e a TCFC é uma poderosa ferramenta para estudo e diagnóstico destas variações anatômicas. O objetivo deste estudo foi avaliar a incidência, classificação e profundidade do istmo na raiz mesial de primeiros molares inferiores, por meio de um banco de dados de tomografias, utilizando o software visualizador e-Vol DX. Foram analisadas 2000 imagens tomográficas obtidas por meio de um tomógrafo Prexion 3D e selecionados 174 primeiros molares inferiores de pacientes com média de idade de 39,5 anos, sendo 86 do sexo masculino e 88 do sexo feminino; as imagens foram analisadas mm a mm, com auxílio dos recursos 3D do software. Os resultados mostraram que 100% dos dentes apresentaram istmos na região cervical em sua raiz mesial, a profundidade mínima encontrada foi de 0,3 mm; em 6,89% das amostras foram observados istmos em todos os cortes ao longo da raiz; a média de profundidade cervical foi de 2,04 mm, não havendo diferenças nos grupos de idade e sexo (p>0,05). O canal mésio-medial foi encontrado em 5,17% das amostras. Seguindo a classificação de Hsu e Kim (1997), ao longo da raiz a maior incidência foi o tipo I (46,90%), seguida do tipo V (25,98%), tipo II (18,22%), tipo IV (7,18%) e tipo III (1,42%). Mais de 83% das amostras apresentaram 3 ou mais tipos de istmo ao longo da raiz; assim, este estudo propôs uma nova classificação baseada na quantidade de variações, sendo que 27,01% foram classificadas como anatomias complexas (4 ou mais tipos na mesma raiz), 56,90% moderadas (3 tipos) e apenas 16,09% simples (até 2 tipos). A TCFC de alta resolução obtida por meio do Prexion 3D, aliada aos recursos do software visualizador e-Vol DX, proporcionaram uma visualização dos istmos com maior clareza.

Avaliação da profundidade da cárie proximal nos exames radiográfico convencional e digitalizado / Evaluation of the size of proximal caries in radiography and digitized

Introdução: A cárie dentária é uma doença multifatorial que compreende vários fatores biológicos e sociais. A superfície proximal dos dentes é uma região de difícil visualização que pode esconder pequenas lesões cariosas no esmalte dentário, impossibilitando o diagnóstico através de inspeções visuais e táteis. Objetivo: O objetivo deste trabalho foi avaliar a profundidade da cárie proximal nos exames radiográficos convencionais e digitais, comparando as profundidades das lesões consideradas nestes exames às do exame histológico. Método: Foram utilizados exames radiográficos interproximais de 40 dentes humanos, 20 pré-molares e 20 molares, com alterações clínicas em uma das superfícies proximais, como lesões de mancha branca ou acastanhada e pequenas cavitações. Três profissionais especializados em radiologia odontológica com mais de cinco anos de experiência clínica mediram a profundidade das lesões pelos exames radiográfico e digital das amostras. Para obter os resultados, utilizou-se a técnica de análise de variância (ANOVA). Resultados: Constatou-se um nível de significância de 5% nas mensurações dos exames radiográficos convencionais e digitalizados, mostrando a fidelidade das imagens radiográficas em relação a real profundidade da lesão. Conclusão: Conclui-se que os exames de imagem avaliados foram eficientes na determinação da profundidade das lesões de cárie proximal.

Introduction: Dental caries is a multifactorial disease that comprises several biological and social factors. The proximal surface of the teeth is a region of difficult visualization that can hide small carious lesions in the dental enamel, making diagnosis through visual and tactile inspection infeasible. Objective: The objective of this study was to evaluate the depth of proximal caries in the conventional and digitized radiographic examinations, comparing the depths of the lesions considered in these examinations to those of the histological examination. Method: Interproximal radiographic examinations of 40 human teeth, 20 premolars and 20 molars, with clinical alterations on one of the proximal surfaces, such as white or brown spot lesions and small cavitations, were used. Three professionals specialized in dental radiology with more than five years of clinical experience measured the depth of the lesions by radiographic examination of the samples. To obtain the results, we used the technique of analysis of variance (ANOVA). Results: A level of significance of 5% was found in conventional and digitized radiographic measurements, showing the fidelity of the radiographic images in relation to the actual depth of the lesion. Conclusion: It was concluded that the imaging tests evaluated were efficient in determining the depth of proximal caries lesions.

Radix em molares decíduos inferiores: revisão sistemática com metanálise / Radix in lower primary molars: systematic review with meta-analysis

Objective: To estimate the prevalence of three roots in deciduous mandibular molars. Methodology: Electronic searches were carried out in PubMed and Scopus to identify cross-sectional studies published up to September 2023. The Joanna Briggs Institute tool was used to critically appraise the studies. STATA 16.0 was used to generate risk of bias figures and perform the meta-analysis. Results: Eighteen studies evaluating 9,067 patients (8,969 first molars and 10,765 second molars) were included in this review. The overall prevalence of radix in mandibular deciduous molars was 9.61% (3.67% for first molars and 18.72% for second molars). The prevalence rate of teeth diagnosed using Cone Beam Computed Tomography (CBCT) was similar to the diagnoses made using conventional radiographic techniques together (periapical, interproximal and panoramic). Final considerations: Lower deciduous molars with three roots have a prevalence of almost 10%, with a higher prevalence in second molars. The diagnosis of this morphological alteration can be made using conventional radiographic techniques, but the use of CBCT is recommended.(AU)

Objetivo: estimar a prevalência de três raízes em molares inferiores decíduos. Metodologia: foram realizadas buscas eletrônicas na PubMed e Scopus para identificar estudos transversais publicados até setembro/2023. Para a avaliação crítica dos estudos foi utilizada a ferramenta do Instituto Joanna Briggs. STATA 16.0 foi usado para gerar figura do risco de viés e realizar a metanálise. Resultados: dezoito estudos que avaliaram 9.067 pacientes (8.969 primeiros molares e 10.765 segundos molares) foram incluídos nesta revisão. A prevalência global de radix em molares decíduos inferiores foi de 9,61% (3,67% para primeiros molares e 18,72% para segundo molares). A taxa de prevalência de dentes com diagnóstico através de Tomografia Computadorizada Cone Beam (TCCB) foi semelhante aos diagnósticos realizados pelas técnicas radiográficas convencionais em conjunto (periapical, interproximal e panorâmica). Considerações finais: os molares decíduos inferiores com três raízes têm uma prevalência de quase 10%, com maior prevalência em segundo molares. O diagnóstico desta alteração morfológica pode ser feito através das técnicas radiográficas convencionais, porém recomenda-se a utilização de TCCB.(AU)

Segundo Conducto Mesiovestibular en Molares Superiores: Prevalencia y Análisis Anatómico Mediante Tomografía Computarizada de Haz Cónico / Second Mesiobuccal Canal in Maxillary Molars: Prevalence and Anatomical Analysis Through Cone Beam Computed Tomography

El objetivo de este estudio fue utilizar la Tomografía Computarizada de Haz Cónico (TCHC) para investigar la configuración anatómica, prevalencia y distribución del conducto mesiovestibular Dos (MV2) en molares superiores de una subpoblación chilena, considerando variables como la presencia del conducto MV2, la clasificación de Vertucci, el género y edad. Estudio observacional de corte transversal. La muestra consistió en Tomografías Computarizadas de Haz Cónico tomadas en la clínica odontológica de la Universidad Andrés Bello (Viña del Mar). Se calculó el tamaño muestral utilizando la fórmula de población conocida, lo que resultó en 262 tomografías. Los examinadores se calibraron utilizando el coeficiente Kappa de Cohen, para luego analizar las variables mediante un estudio imagenológico utilizando el software I-CAT Visión. Se analizaron 439 primeros y segundos molares superiores. La prevalencia del conducto MV2 en primeros molares fue del 63,74 %, mientras que, en segundos molares, fue del 20,04 %. La prevalencia en primeros molares fue mayor en hombres (73,86 %) que en mujeres (58,62 %), mientras que, en segundos molares, fue del 15,81 % en mujeres y del 28,41 % en hombres. En relación con la edad, en los primeros molares la diferencia fue significativa en el rango de 18 a 40 años (66,49 %). En cuanto al tipo de configuración según Vertucci (2005), el 70 % de los primeros molares presentó una configuración Tipo II, y un 23,65 % Tipo IV, con resultados similares en los segundos molares. El presente estudio demostró que los conductos MV2 son frecuentes en la población analizada, especialmente en los primeros molares, y que la configuración Tipo II es la más prevalente. Además, se observó una mayor prevalencia en hombres y en el rango de 18 a 40 años. Estos hallazgos proporcionan información relevante sobre la anatomía radicular en la población y pueden contribuir a mejorar los resultados de tratamiento.

SUMMARY: The aim of this study was to use Cone-beam Computed Tomography (TCHC) to investigate the anatomical configuration, prevalence, and distribution of the Second Mesiobuccal (MB2) canal in upper molars of a Chilean subpopulation, considering variables such as the presence of MB2 canal, Vertucci classification, gender, and age. Cross-sectional observational study. The sample consisted of TCHC scans taken at the dental clinic of Universidad Andrés Bello (Viña del Mar). The sample size was calculated using the formula for known population, resulting in 262 scans. The examiners were calibrated using Cohen's Kappa coefficient, then the variables were analyzed through an imaging study using I-CAT Vision software. 439 first and second upper molars were analyzed. The prevalence of MB2 canal in first molars was 63.74 %, while in second molars, it was 20.04 %. The prevalence in first molars was higher in males (73.86 %) than in females (58.62 %), while in second molars, it was 15.81 % in females and 28.41 % in males. Regarding age, in first molars the difference was significant between the age range of 18 to 40 years (66.49 %). Regarding the type of configuration according to Vertucci, 70 % of the first molars had Type II configuration, and 23.65 % had Type IV, with similar results in second molars. The present study demonstrated that MB2 canals are frequent in the analyzed population, especially in first molars, and Type II configuration is the most prevalent. Additionally, a higher prevalence was observed in males and in the age range of 18 to 40 years. These findings provide relevant information about root anatomy in the studied population and can contribute to improving treatment outcomes.

Analysis of the Internal and External Morphology of the Mandibular First Molar in a Chilean Sub-Population Using Cone-Beam Computed Tomography / Análisis de la Morfología Interna y Externa del Primer Molar Mandibular en una Subpoblación Chilena Mediante Tomografía Computarizada de Haz Cónico

SUMMARY: The mandibular first molar (MFM) commonly presents two roots with two canals in the mesial root and one or two canals in the distal root. However, morphological variations have been described in different populations, which must be considered when planning endodontic treatment. The aim of this study was to analyze the internal and external morphology of the MFM in a Chilean sub-population using cone-beam computed tomography (CBCT) images. An in vivo cross-sectional, descriptive, and observational study was conducted using CBCT exams from 351 right and left MFM. The data were analyzed by descriptive statistics using the Chi- Square test for categorical variables, Fisher's exact test, the Mann-Whitney U non-parametric test for two independent samples, and the Wilcoxon non-parametric test for related samples. Of the total sample, 1 root was observed in 2.27 % of the cases, 2 roots in 93.73 %, and 3 roots in 4 %. In relation to the number of canals, 71.23 % of the MFM showed 3 root canals, 16.81 % 4 canals, 9.69 % 2 canals, and 2.28 % 1 canal. Of all the studied cases, 2.3 % had a C-shaped anatomy. In terms of morphology, using Zhang's classification, variant 3 was observed in 71.23 %, variant 4 in 12.82 %, variant 1 in 9.67 %, variant 6 in 4 %, and variant 8 in 2.28 %. In conclusion, the morphology of the MFM is variable in a Chilean sub-population, and these variations must be considered before and during endodontic therapy. CBCT proved to be an effective tool for the in vivo study of tooth morphology.

El primer molar mandibular (MFM) comúnmente presenta dos raíces con dos canales en la raíz mesial y uno o dos canales en la raíz distal. Sin embargo, se han descrito variaciones morfológicas en distintas poblaciones, las que se deben tener en consideración al momento de planificar el tratamiento endodóntico. El objetivo de este estudio fue analizar la morfología interna y externa del MFM en una sub población chilena mediante el uso de imágenes de tomografía computarizada Cone Beam (CBCT). Se realizó un estudio transversal, descriptivo y observacional in vivo empleando exámenes CBCT de 351 MFM tanto derechos como izquierdos. Los datos se analizaron mediante estadística descriptiva empleando la prueba Chi-Cuadrado para variables categóricas, el test exacto de Fisher, la prueba no paramétrica de U-Mann-Whitney para dos muestras independientes y la prueba no paramétrica de Wilcoxon para muestras relacionadas. Del total de la muestra se observó 1 raíz en un 2.27 % de los casos, 2 raíces en 93.73 % y 3 raíces en un 4 %. En relación al número de canales un 71.23 % de los MFM mostraron 3 canales radiculares, un 16.81 % 4 canales, un 9.69 % 2 canales y un 2.28 % 1 canal. Del total de los casos estudiados un 2.3 % se presentó anatomía en forma de C. En relación a la morfología, empleando la clasificación de Zhang, se observó en un 71.23 % la variante tipo 3, en un 12.82 % la variante tipo 4, en un 9.67 % la variante tipo 1, en un 4 % variante tipo 6 y en un 2,28 % variante tipo 8. En conclusión, la morfología del MFM es variable en una subpoblación chilena y estas variaciones deben ser consideradas antes y durante la terapia endodóntica. El CBCT demostró ser una herramienta eficaz para el estudio in vivo de la morfología dentaria.

Exodontia de primeiro molar superior permanente em criança: relato de caso / Clínico maxillary first permanent molar extraction in a child: case report

Entre as perdas precoces de um elemento dental ocorre em grande frequência a do primeiro molar permanente, que normalmente tem o seu irrompimento por volta dos 6 anos de idade, e são propensos a serem acometidos por lesões cariosas que se não cuidadas precocemente pode-se levar a perda do elemento dental. Há também outros agentes que ocasionam a perda do elemento como o trauma de baixa intensidade, tais como, os cálculos dentários, os hábitos bucais deletérios e principalmente a falta de motivação de higiene oral. Diante disto, este trabalho visa a apresentação de um caso clínico de um paciente de 9 anos de idade, sem alterações sistêmicas, com grande destruição coronária no dente 26. Os exames de imagens foram colaboradores para diagnóstico e definição da extração. Foi realizada a exodontia em campo aberto. O paciente foi instruído quanto à higiene bucal e futuramente encaminhado para um tratamento ortodôntico. Conclui-se que o Cirurgião Dentista tem papel fundamental no diagnóstico e tratamento dessas alterações dentais, enfatizando a importância do tratamento restaurador de lesões cariosas precocemente, remoção de qualquer agente irritante de baixa intensidade e na motivação da higiene bucal(AU)

Among the early loss of a dental element, the loss of the first permanent molar occurs very frequently, which usually has its eruption around the age of 6 years, and they are prone to be affected by carious lesions that, if not treated early, can if it leads to loss of the dental element. There are also other agents that cause the loss of the element, such as low-intensity trauma, such as dental calculi, deleterious oral habits and especially the lack of motivation for oral hygiene. Therefore, this work aims to present a clinical case of a 9-year-old patient, without systemic alterations, with great coronary destruction in tooth 26. The imaging exams collaborated for the diagnosis and definition of the extraction. The extraction was performed in an open field. The patient was instructed about oral hygiene and later referred for orthodontic treatment. It is concluded that the Dental Surgeon has a fundamental role in the diagnosis and treatment of these dental alterations, emphasizing the importance of an early restorative treatment of carious lesions, removal of any low-intensity irritant and in the motivation of oral hygiene(AU)

Maxillary Molar Root Canal Morphology Using Cone-Beam Computed Tomography: An Epidemiological Study from Shandong Province, China / Morfología del Conducto Radicular del Molar Maxilar Mediante Tomografía Computarizada de Haz Cónico: Un Estudio Epidemiológico de la Provincia de Shandong, China

SUMMARY: The objective of this study was to evaluate the maxillary molar root canal morphology in individuals from the Shandong province, China, using cone-beam computed tomography (CBCT) and classify it based on Ahmed et al. (2017) classification system to obtain a reference for clinical diagnosis and treatment. From December 2020 to June 2021, we screened CBCT data of 1,619 patients at the Jinan Stomatological Hospital who had been indicated for CBCT because of various oral abnormalities. The root and root canal morphologies of all teeth were statistically analyzed, and the root canal morphology was classified based on Ahmed et al. (2017) classification system. In the maxillary molars, three roots were the most common, accounting for 99.24 % and 74.61 % of all maxillary first and second molars, respectively. Two roots were the second most common, accounting for 0.66 % and 17.29 % of all maxillary first and second molars, respectively. Root morphology variation, e.g., fusion or furcation defect, was present in 22 (0.76 %) maxillary first molars and 765 (25.39 %) maxillary second molars, with the most common being mesiobuccal and distobuccal root fusion. Detection rates of a second mesiobuccal canal (MB2) in the maxillary first and second molars were 48.5 % and 26.5 %, respectively. Among age groups, the frequency of MB2 was the highest in the 15-24-year-old group and lowest in the 55-64-year-old group. Bilateral MB2 root canals were present in 64.8 % and 48.4 % of the maxillary first and second molars, respectively. Men and women accounted for 60.6 % and 67.8 % of the maxillary first molars, respectively, and 51.7 % and 45.6 % of the maxillary second molars, respectively. According to Ahmed et al. (2017) classification of root canal morphology, 18 and 22 root canal configurations were found in 1,453 right maxillary first molars and 1,444 left maxillary first molars, respectively. The right maxillary first molars showed three two-rooted, 14 three-rooted, and one four-rooted type. The left maxillary first molars showed two one-rooted, six two-rooted, and 14 three-rooted types. According to Ahmed et al. (2017) classification of root canal morphology, 43 and 45 root canal configurations were found in 1,507 right maxillary second molars and 1,506 left maxillary second molars, respectively. The right maxillary second molars showed 17 one-rooted, 16 two- rooted, eight three-rooted, and two four-rooted types. The left maxillary second molars showed 19 one-rooted, 13 two-rooted, 12 three- rooted, and one four-rooted type. This study showed that the maxillary molar root canal morphology is diverse in the Shandong province. Ahmed et al. (2017) classification system provides a clear description of the root canal morphology. CBCT can be used to study complex root and root canal morphologies.

El objetivo de este estudio fue evaluar la morfología del conducto radicular del molar superior en individuos de la provincia de Shandong, China, utilizando tomografía computarizada de haz cónico (CBCT) y clasificarla con base en el sistema de clasificación de Ahmed et al. (2017) para obtener una referencia para diagnóstico clínico y tratamiento. Desde diciembre de 2020 hasta junio de 2021, analizamos los datos de CBCT de 1619 pacientes en el Hospital Estomatológico de Jinan a quienes se les indicó CBCT debido a diversas anomalías orales. Las morfologías de la raíz y del conducto radicular de todos los dientes se analizaron estadísticamente, y la morfología del conducto radicular se clasificó según el sistema de clasificación de Ahmed et al. (2017). En los molares superiores, tres raíces fueron las más comunes, representando el 99,24 % y el 74,61 % de todos los primeros y segundos molares superiores, respectivamente. Dos raíces fueron las segundas más comunes, representando el 0,66 % y el 17,29 % de todos los primeros y segundos molares superiores, respectivamente. La variación de la morfología de la raíz, por ejemplo, fusión o defecto de furcación, estuvo presente en 22 (0,76 %) primeros molares superiores y 765 (25,39 %) segundos molares superiores, siendo la fusión radicular mesiovestibular y distovestibular la más común. Las tasas de detección de un segundo canal mesiovestibular (MB2) en los primeros y segundos molares superiores fueron del 48,5 % y 26,5 %, respectivamente. Entre los grupos de edad, la frecuencia de MB2 fue más alta en el grupo de 15 a 24 años y más baja en el grupo de 55 a 64 años. Los conductos radiculares MB2 bilaterales estaban presentes en el 64,8 % y el 48,4 % de los primeros y segundos molares superiores, respectivamente. En los hombres y en las mujeres representaron el 60,6 % y el 67,8 % de los primeros molares superiores, respectivamente, y el 51,7 % y el 45,6 % de los segundos molares superiores, respec- tivamente. Según la clasificación de la morfología del conducto radicular de Ahmed et al. (2017) se encontraron configuraciones de conducto radicular 18 y 22 en 1453 primeros molares superiores derechos y 1444 primeros molares superiores izquierdos, respectivamente. Los primeros molares superiores derechos mostraron tres tipos de dos raíces, 14 de tres raíces y uno de cuatro raíces. Los primeros molares superiores izquierdos mostraron dos tipos de una raíz, seis de dos raíces y 14 de tres raíces. Según la clasificación de la morfología del conducto radicular de Ahmed et al. (2017) se encontraron configuraciones de conducto radicular 43 y 45 en 1507 segundos molares superiores derechos y 1506 segundos molares superiores izquierdos, respectivamente. Los segundos molares superiores derechos mostraron 17 tipos de una raíz, 16 de dos raíces, ocho de tres raíces y dos de cuatro raíces. Los segundos molares superiores izquierdos mostraron 19 de una raíz, 13 de dos raíces, 12 de tres raíces y uno de cuatro raíces. Este estudio mostró que la morfología del conducto radicular del molar superior es diversa en la provincia de Shandong. El sistema de clasificación de Ahmed y colaboradores proporciona una descripción clara de la morfología del conducto radicular. CBCT se puede utilizar para estudiar morfologías complejas de raíces y conductos radiculares.

Descripción de la morfología del sistema de canales radiculares del primer molar maxilar mediante tomografía computarizada cone-beam en una población chilena / Description of the morphology of the root canal system of the maxillary first molar using cone-beam computed tomography in a Chilean population

Describir la morfología del sistema de canales radiculares del primer molar maxilar en una población chilena mediante exámenes de tomografía computarizada Cone-Beam (CBCT). Se realizó un estudio observacional descriptivo en el cual se utilizaron los exámenes CBCT de pacientes que fueron atendidos en un Centro de Radiología Maxilofacial privado durante el período comprendido entre Enero y Diciembre del año 2018 en la ciudad de Temuco, Chile, los cuales fueron observados de manera independiente por dos investigadores previamente calibrados. Se observaron 199 exámenes CBCT. En la raíz mesiobucal,predominaron las morfologías tipo II, I y IV de Vertucci respectivamente, mientras que en la raíz distobucal y palatina predominó la morfología tipo I. El canal MB2 estuvo presente en el 62,3 % de los casos, con una prevalencia significativamente mayor en pacientes jóvenes. En la mayoría de los primeros molares maxilares de los habitantes de la ciudad de Temuco se observaron tres raíces separadas y la presencia de cuatro canales. Se determinó una alta frecuencia del canal MB2 en la raíz MB.

SUMMARY: The objective of this study was to describe the morphology of the root canal system of the maxillary first molar in a Chilean population through Cone-Beam computed tomography (CBCT) examinations. A descriptive observational study was carried out in which the CBCT examinations of patients who were treated in a private maxillofacial radiology center during the period between January and December 2018 in Temuco, Chile, were used which were observed independently by two previously calibrated researchers. In this analysis 199 CBCT exams were observed. In the mesiobuccal root, Type II, I and IV morphologies predominated respectively, while in the distobuccal and palatal root, Type I morphology predominated. The MB2 canal was present in 62.3 % of cases, with a higher prevalence in young patients. Three separate roots and the presence of four canals were observed in most of the maxillary first molars of the patients in Temuco. A high frequency of the MB2 canal was determined in the root MB.

Effects of early unilateral mandibular first molar extraction on condylar and ramal asymmetry / Efectos de la extracción temprana del primer molar mandibular unilateral sobre la asimetría condilar y ramal

SUMMARY: Craniofacial symmetry is an important factor in creating a harmonious facial appearance. Genetic and external factors may cause the formation of mandibular asymmetry. The aim of this study was to evaluate vertical mandibular asymmetries in adolescents who had unilateral mandibular first permanent molar (FPM) teeth extracted at an early age. The study group consisted of 60 subjects (30 females, 30 males with a mean age of 16.18±1.04 years) who had their mandibular permanent first molar tooth extracted before the age of 12, and the control group consisted of 60 healthy subjects (30 females, 30 males with a mean age of 16.23±0.92 years). Condylar asymmetry index (CAI), ramal asymmetry index (RAI), and condylar-ramal asymmetry index (CRAI) were calculated using panoramic radiographs of the subjects. Independent samples t-test was used to evaluate the differences between groups. CAI, RAI, and CRAI values were similar between male and female subjects in both control and study groups, and no statistically significant difference was found (p>0.05). No statistically significant difference was observed between the group who had their mandibular first permanent molar teeth extracted at an early age and the control group (p>0.05). CAI values were relatively higher in both groups, but there was no significant difference between the CAI, RAI, and CRAI values between the groups.

La simetría craneofacial es un factor importante para crear una apariencia facial armoniosa. Factores genéticos y externos pueden causar la formación de asimetría mandibular. El objetivo de este estudio fue evaluar las asimetrías mandibulares verticales en adolescentes a quienes se les extrajo el primer molar permanente (FPM) mandibular unilateral a una edad temprana. El grupo de estudio consistió en 60 sujetos (30 mujeres, 30 hombres con una edad media de 16,18±1,04 años) a quienes se les extrajo el primer molar mandibular permanente antes de los 12 años, y el grupo control consistió en 60 sujetos sanos (30 mujeres, 30 hombres con una edad media de 16,23±0,92 años). El índice de asimetría condilar (CAI), el índice de asimetría ramal (RAI) y el índice de asimetría condilar-ramal (CRAI) se calcularon utilizando radiografías panorámicas de los sujetos. Se utilizó la prueba t de muestras independientes para evaluar las diferencias entre los grupos. Los valores de CAI, RAI y CRAI fueron similares entre los hombres y las mujeres tanto en el grupo control como en el de estudio, y no se encontraron diferencias estadísticamente significativas (p>0.05). No se observaron diferencias estadísticamente significativas entre el grupo al que se le extrajo el primer molar permanente mandibular a una edad temprana y el grupo control (p>0,05). Los valores de CAI fueron relativamente más altos en ambos grupos, pero no hubo diferencias significativas entre los valores de CAI, RAI y CRAI entre los grupos.

Banda ortodôntica como alternativa de tratamento conservador provisório para primeiros molares permanentes com hipomineralização molar incisivo (HMI): relato de caso / Orthodontic banding as an alternative provisional conservative treatment for permanent first molars with incisor molar hypomineralization (IMH): case report

Introdução: a Hipomineralização Molar Incisivo (HMI) é um defeito qualitativo de desenvolvimento de esmalte que pode ocasionar fraturas pós-eruptivas (FPE), lesões de cárie e sensibilidade. Objetivo: relatar o tratamento de HMI severa através da cimentação de bandas ortodônticas para preservação da estrutura dentária em primeiros molares permanentes inferiores com FPE. Relato do caso: criança do sexo feminino, 10 anos de idade, apresentou-se com queixa de hipersensibilidade e fratura dentária associada à restauração prévia. Clinicamente, observou-se presença de HMI severa, com FPE associada à lesão de cárie em dentina nas superfícies oclusal e vestibular do dente 36 e restauração insatisfatória com cimento de ionômero de vidro (CIV) na superfície vestibular do dente 46 que apresentava opacidades demarcadas branco-creme. Radiograficamente, observou-se ausência de comprometimento pulpar. Após manejo por meio de abordagens não-invasivas (controle de biofilme e dieta e aplicação de verniz fluoretado), o tratamento proposto foi a cimentação de banda ortodôntica com CIV modificado por resina (Riva Light Cure®, SDI) nos dentes 36 e 46 para maior longevidade das restaurações. O tratamento restaurador atraumático (TRA) foi realizado no dente 36 previamente à cimentação da banda ortodôntica. Resultados: após o tratamento, a criança não relatou dor ou desconforto e as restaurações mantiveram-se intactas. A mãe da criança foi orientada quanto à importância de acompanhamento periódico a cada 4 meses. Conclusão: a cimentação das bandas ortodônticas com CIV possibilitou o manejo conservador de molares permanentes com HMI severa, com manutenção de sua funcionalidade oclusal, saúde pulpar e gengival, proporcionando melhor qualidade de vida à paciente.

Introduction: molar Incisor Hypomineralization (MIH) is a qualitative developmental enamel defect that can cause posteruptive enamel breakdown (PEB), caries lesions, and sensitivity. Objective: to report the treatment of a child with severe MIH through the cementation of orthodontic bands in lower first permanent molars with PEB to preserve tooth structure. Case report: female child, 10 years old, presenting hypersensitivity complaints and tooth fracture associated with previous restoration. Severe MIH was observed, with PEB associated with dentin caries on the occlusal and buccal surfaces of tooth #36 and unsatisfactory glass ionomer cement (GIC) restoration on the buccal surface of tooth #46 which had creamy-white marked opacities. There was no pulp involvement radiographically. After management through non-invasive approaches (biofilm and diet control and application of fluoride varnish), the proposed treatment was the cementation of an orthodontic band with resin-modified GIC (Riva Light Cure®, SDI) on teeth #36 and #46 to long-term lifespan restorations. Atraumatic restorative treatment (ART) was performed on tooth #36 prior to the cementation of the orthodontic band. Results: after treatment, the child did not report pain or discomfort and the restorations remained intact. The child's mother was instructed about the importance of periodic follow-up visits every 4 months. Conclusion: the cementation of orthodontic bands with GIC allowed the conservative management of permanent molars with severe MIH, maintaining their functional occlusion, pulpal and gingival health, providing a better quality of life to the patient.

The groove configuration of mandibular molars of malaysians of mongoloid ancestry / Configuración del surco de los molares mandibulares de los malayos de ascendencia mongoloide

Aim: Variation in dental structures is widely accepted as a combination of multiple factors such as gender, environmental effects and genetics. However, the characterization of similarities and differences in dental morphology has been lacking in relation to the factors mentioned. This study aims to assess and compare the variations in traits in mandibular molars and the influence of gender and ethnicity in affecting these traits amongst the Malaysian population of Mongoloid ancestry. Materials and Methods: Our study population was 180 dental casts of patients, from 15 to 40 years old, comprising 56 Malays and 124 Chinese; 60 were males and 120 were females. Traits like groove pattern, number of cusps, protostylids and deflecting wrinkles were observed, scored, and recorded. Results: This study revealed that the most common mandibular first molar (M1) was characterized by 5 cusps and displayed 'Y' groove pattern, while the most common mandibular second molar (M2) had 4 cusps and exhibited a groove pattern that resembled a '+'. Notably, all the traits studied were bilaterally symmetrical, except for the groove pattern of M1, while sexual dimorphism was observed in groove patterns of M2. Conclusions: This study found that M1 had a preponderance of 5 cusps with 'Y' groove pattern, while M2 were typically 4-cusped with '+' groove pattern.

Objetivo: La variación en las estructuras dentales es ampliamente aceptada como el resultado de una combinación de múltiples factores como el género, los efectos ambientales y la genética. Sin embargo, ha faltado la caracterización de similitudes y diferencias en la morfología dental en relación a los factores mencionados. Este estudio tiene como objetivo evaluar y comparar las variaciones en los rasgos de los molares mandibulares y la influencia del género y la etnia al afectar estos rasgos entre la población malaya de ascendencia mongoloide. Materiales y Métodos: Nuestra población de estudio fue de 180 modelos dentales de pacientes, de 15 a 40 años,conformados por 56 malayos y 124 chinos; 60 eran hombres y 120 eran mujeres. Se observaron, puntuaron y registraron rasgos como el patrón de surcos, el número de cúspides, los protostílidos y las arrugas desviadas. Resultados: Este estudio reveló que el primer molar mandibular más común (M1) se caracterizaba por 5 cúspides y mostraba un patrón de ranura en 'Y', mientras que el segundo molar mandibular más común (M2) tenía 4 cúspides y exhibía un patrón de ranura que se parecía a un ' +'. En particular, todos los rasgos estudiados eran bilateralmente simétricos, excepto el patrón de surco de M1, mientras que se observó dimorfismo sexual en los patrones de surco de M2. Conclusión: Este estudio encontró que M1 tenía una preponderancia de 5 cúspides con un patrón de ranura en 'Y', mientras que M2 tenía típicamente 4 cúspides con un patrón de ranura '+'.

Cone beam computed tomography-based evaluation of the relationship between the inferior alveolar canal and the cortical plates and the mandibular molar roots in the saudi subpopulation / Evaluación basada en tomografía computarizada de haz cónico de la relación entre el canal alveolar inferior y las placas corticales y las raíces de los molares mandibulares en la subpoblación saudita

Aim: To assess the distance between the inferior alveolar canal and the roots of the mandibular second molar and the mandibula and cortex in a Saudi Arabian subpopulation through existing CBCT images. Materials and Methods: This retrospective study was performed based on 120 patients CBCT images in five age groups.The distances (D1 and D2) between the buccal cortex (BC), lingual cortex (LC), and mandibular molars and the distances (D3) between the root apices and inferior alveolar nerve canal (IANC) were measured for each dental root on the right and left of the mandible with the help of Vision iCAT software. A radiology specialist with a gap of 15 days twice carried out the measurements. Statistical analysis was carried out with the help of SPSS 24. to analyse variability Chi-square analysis was done, and the p value was fixed at > 0.05. To check inter-person variability, Cohen's variability was fixed at 0.8. Results: The distance between the outer surface of the buccal cortical plate and the buccal root surface ranged between 3.8 and 5.7 mm, whereas the distance between the root apices of the mandibular molars and the IANC ranged between 4.8 and 3.5 mm. The distance from the outer surface of the lingual cortical plate to the lingual root surface varied between 1.2 and 2.8 mm. The mean distance between the root apices and IANC increased with age, more so in males than females. Conclusions: Even though this study was conducted on a small sample size, it will help the dental practitioners in planning endodontic procedures, surgical extractions, and implant placements, and it should be repeated with a higher number of images.

Objetivo: Evaluar la distancia entre el canal alveolar inferior y las raíces del segundo molar mandibular, y la mandíbula y la corteza en una subpoblación de Arabia Saudita a través de imágenes CBCT existentes.Materiales y Métodos: Este estudio retrospectivo se realizó con base en imágenes CBCT de 120 pacientes en cinco grupos de edad. Las distancias (D1 y D2) entre la corteza bucal (BC), la corteza lingual (LC) y los molares mandibulares y las distancias (D3) entre los Se midieron los ápices radiculares y el canal del nervio alveolar inferior (IANC) para cada raíz dental a la derecha e izquierda de la mandíbula con la ayuda del software Vision iCAT. Un especialista en radiología, con un intervalo de 15 días, realizó dos veces las mediciones. El análisis estadístico se realizó con la ayuda del SPSS 24. Para analizar la variabilidad se realizó un análisis de Chi-cuadrado y el valor p se fijó en > 0,05. Para comprobar la variabilidad entre personas, la variabilidad de Cohen se fijó en 0,8. Resultados: La distancia entre la superficie exterior de la placa cortical bucal y la superficie de la raíz bucal osciló entre 3,8 y 5,7 mm, mientras que la distancia entre los ápices radiculares de los molares mandibulares y el IANC osciló entre 4,8 y 3,5 mm. La distancia desde la superficie exterior de la placa cortical lingual hasta la superficie de la raíz lingual varió entre 1,2 y 2,8 mm. La distancia media entre los ápices de las raíces y la IANC aumentó con la edad, más en hombres que en mujeres. Conclusión: Aunque este estudio se realizó con un tamaño de muestra pequeño, ayudará a los odontólogos a planificar procedimientos de endodoncia, extracciones quirúrgicas y colocación de implantes, y debe realizarse con más números.

Evaluation of the occlusal contact area of molar dental implants comparing two different thicknesses (16 µm and 200 µm) of articulating occlusal papers and forces (200 and 250 N): a pivot in vitro study

Introduction: The goal of this pilot study was to evaluate the differences between checking occlusion on implants crowns using 16 or 200 µm thickness of articulating occlusal paper, and to compare the stained occlusal area between the groups after bite forces of 200 and 250 N. Methods: It was included 10 casts of articulated-type IV gypsum, 10 NiCr crowns, articulating occlusal papers (16 µm and 200 µm thick), and a compression test machine. Compressive forces (200 and 250 N.mm) were applied on models, to check the occlusal contact area of fixed and cemented crowns. The contact areas on the crowns were measured through images obtained by the scanning electron microscope. Statistical tests were performed considering the significant level of 5% (p≤0.05). Results: The stains found using 200 µm of articulating paper were higher than those with 16 µm, independent of the force applied. However, the stains obtained in lower teeth with different strengths (200 and 250N) marked with 16 µm articulating paper were not possible to score. The articulating paper variable had significant statistical results (p=0.002), while the variables force (p=0.443) and articulating paper-force interaction (p=0.607) were not significant. The mean area found in staining using the 200 µm and 16 µm papers was, respectively, 8.3380 mm2 and 3.4759 mm2. Conclusion: It was possible to confirm that 200 µm of articulating occlusal paper showed better and significant results to stain the occlusal area, permitting a more accurate adjustment independent of the force applied.

Combined micro-apical surgery and vital pulp therapy in mandibular second molars with external root resorption caused by impacted teeth / 华西口腔医学杂志

OBJECTIVES@#This study aimed to establish a new treatment of the mandibular second molars with external root resorption caused by impacted teeth to preserve the affected teeth and their vital pulps.@*METHODS@#For mandibular second molars clinically diagnosed as external root resorption caused by impacted teeth, debridement and removal of the root at the resorption site via micro-apical surgery and direct capping of the pulp with bioactive material on the surface of the root amputation via vital pulp therapy were performed immediately after the impacted teeth were extracted.@*RESULTS@#The external root resorption of the affected tooth was ceased. It was asymptomatic with intact crown, normal pulp, periapical alveolar bone reconstruction, normal periodontal ligament, continuous bone sclerosis, and no periapical translucency in radiographic examination at the 1-year postoperative follow-up, thus showing good prognosis.@*CONCLUSIONS@#Simultaneous combination of micro-apical surgery and vital pulp therapy after extraction of impacted teeth could successfully preserve mandibular second molars with ERR caused by impacted teeth and their vital pulps.

Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force / 中华口腔医学杂志

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.