Validation of cone beam computed tomography as a clinical imaging method for dentin thickness measurement in the danger zone of mandibular molars / Validação da tomografia computadorizada de feixe cônico como um étodo de imagem clínico para mensuração da espessura dentinária na zona de risco de molares inferiores

Objective: to verify the accuracy of cone beam computedtomography (CBCT) for measuring dentin thicknessin the danger zone of mandibular molars in order to validatethis method to be used as a clinical auxiliary. Materialsand method: dentin thickness of the distal wall ofmesial canals was measured at 2 mm of furcation areain ten mandibular molars before and after preparation ofcervical and middle thirds. CBCT (0.25 mm voxel size)and stereomicroscopy images were acquired twice foreach sample. CBCT axial images and stereomicroscopeimages were evaluated by a calibrated examiner. Statisticalanalysis was performed using Mann-Whitney testin order to investigate whether CBCT images providedtrusted values. Results: mean values of initial (1.23 versus1.24 mm) and final measurements (0.88 versus 0.87mm) obtained with, respectively, CBCT and stereomicroscopemethods did not show statistical differences(P > 0.5). Conclusion: CBCT images provide high accuracyfor measuring dentin thickness in the danger zoneof mandibular molars. (AU)

Objetivo: avaliar a acurácia da tomografia computadorizada de feixe cônico (TCFC) para mensurar a espessura dentinária na zona de risco de molares inferiores e validar este método, a fim de usá-lo como um auxiliar clínico. Materiais e método: a espessura dentinária da parede distal dos canais mesiais foi medida a 2 mm da área de furca em dez molares inferiores, antes e após a preparação dos terços médio e cervical. Foram adquiridas imagens por TCFC (tamanho do voxel de 0,25 mm) e estereomicroscopia. Um examinador treinado e calibrado avaliou as tomografias no plano axial e as imagens de estereomicroscopia. A análise estatística foi realizada com o teste Mann-Whitney, para verificar se as imagens tomográficas forneceram valores comparáveis à estereomicroscopia. Resultados: a média dos valores obtidos, respectivamente, após as mensurações iniciais (1,23 versus 1,24 mm) e finais (0,88 versus 0,87 mm) das imagens de TCFC e estereomicroscopia não mostraram diferença estatisticamente significativa entre os métodos (P > 0,5). Conclusão: a TCFC produz imagens acuradas para a mensuração da espessura dentinária na zona de risco de molares inferiores. (AU)

A methodology to standardize the evaluation of root canal instrumentation using cone beam computed tomography

The evaluation of root canal instrumentation is important to observe the action of endodontic instrumentsin the root canal walls. Aim: This study introduces a method to standardize the acquisition of imagesbefore and after preparing root canals by using cone-beam computed tomography (CBCT). Methods:Sixteen mandibular molars were included in acrylic resin blocks. Samples were inserted in a stablewood box, which was filled with plaster and served as a guide to reinsert the samples. The apparatuswas used for the CBCT examination before and after cervical flaring of root canals. The softwareIcatVision® was used to equalize the images before and after instrumentation with two computersoperating at the same time. The measurements between root canal center and the furcation areawere determined. The statistical analysis was performed using the t-test for paired samples (á=0.05).Results: The values for dentin thickness in the risk zone before and after root canal flaring withGates-Gliden drills were 1.096 (± 0.27) mm and 0.742 (± 0.24) (p<0.01), respectively. Conclusions:The proposed method assures the same positioning of the samples before and after root canalpreparation. It is extremely important, as any mesiodistal or buccolingual movement can producea different topogram for comparison procedures.