Prevalence of horizontal alveolar changes in edentulous patients: a retrospective tomographic study

Abstract Horizontal bone loss after tooth extraction is a common finding that demands bone reconstruction in various cases. The aim of this study was to assess the horizontal alveolar status in partially and completely edentulous patients using cone-beam computed tomography (CBCT). In total, 1516 CBCT scans of 1404 adult patients were analyzed. Assessment of the images was performed in accordance with the previously published horizontal alveolar change (HAC) classification, which categorizes horizontal bone defects into four classes: HAC 1, HAC 2, HAC 3 and HAC 4 (from the least severe to the most severe condition). Analysis of 1048 scans from partially edentulous patients presented a distribution of 63.55%, 22.14%, 13.36% and 0.95% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Analysis of 468 scans from completely edentulous patient images presented a distribution of 19.87%, 28.63%, 41.67% and 9.83% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Based on these results, as in HAC 4, no cancellous bone was found between the cortical buccal and lingual/palatal bone plates, it seems reasonable to state that the absence of cancellous bone is higher in completely edentulous patients than in partially edentulous patients. Therefore, the absence of cancellous bone seems to be higher in completely edentulous than in partially edentulous patients.

Segmentation methods for micro ct images: a comparative study using human bone samples

Abstract X-ray microtomography (microCT) is a nondestructive technique used to assess bone morphometry. For an accurate analysis, it is necessary to segment the bone tissue from the background images, avoiding under- or overestimation of the real bone volume. Thus, segmentation methods for microCT can influence the accuracy of bone morphometry analysis. The purpose of this study was to compare two different image segmentation methods available on microCT software (subjective and objective) regarding to the human bone morphometric analysis. Sixteen samples containing a fixation screws covered by 0.5-1mm of bone were scanned using the SkyScan 1173 scanner. Three examiners segmented the microCT images subjectively and recorded the threshold values. Subsequently, an objective segmentation was also done. The 3D analysis was performed for both images using the values​ previously determined in CTAn software. Five bone morphometric parameters were calculated (BV/TV, Tb.Th, Tb.N, Tb.Sp, Conn.Den) and used as dependent variables. ANOVA showed no significant differences between the methods concerning BV/TV (p=0.424), Tb.N (p=0.672), Tb.Th (p=0.183), Tb.Sp (p=0.973) and Conn.Den (p=0.204). Intra- and interobserver agreement ranged from satisfactory to excellent (0.55-1 and 0.546-0.991, respectively). Therefore, results obtained with subjective threshorlding were similar to those obtained with objective segmentation. Since objective segmentation does not have human input and it is a truly objective method, it should be the first choice in microCT studies that concern homogeneity and high resolution human bone sample.

Resumo A microtomografia computadorizada (microTC) é uma modalidade de imagem não destrutiva utilizada para avaliar a morfometria óssea. Para análise acurada, faz-se necessário segmentar o tecido ósseo do fundo (background) da imagem, evitando assim, sub ou sobre estimação do volume ósseo real. Desta forma, fica evidente que os métodos de segmentação em análise de microTC podem influenciar a precisão dos cálculos da morfometria óssea. A realização do presente estudo teve como objetivo comparar o desempenho de dois diferentes métodos de segmentação de imagem de microTC, subjetivo e objetivo, através da avaliação dos resultados das análises morfométricas obtidas de ossos humanos. Dezesseis amostras contendo parafusos de fixação cobertos por 0,5- 1 mm de osso humano foram escaneados usando o microtomógrafo SkyScan1173. Três examinadores realizaram a segmentação das imagens de forma subjetiva (visualmente) obtendo seus respectivos valores de threshold. Em seguida, a segmentação objetiva (automática) foi realizada. As análises tridimensionais foram obtidas utilizando os valores determinados por ambos os métodos no software CTAn. Cinco parâmetros morfométricos do osso foram calculados (BV / TV, Tb.Th, Tb.N, Tb.Sp, Conn.Den) e usados ​​como variáveis ​​dependentes. O teste ANOVA não mostrou diferenças estatisticamente significantes entre os métodos comparados: BV / TV (p=0,424), Tb.N (p=0,672), Tb.Th (p=0,183), Tb.Sp (p=0 973) e Conn.den (p=0,204). A concordância intra e interobservardores variou entre satisfatória e excelente (0,55-1 e 0,546-0,991, respectivamente). Portanto, os resultados obtidos com a segmentação subjetiva foram semelhantes aos obtidos com a automática. Entretanto, a segmentação automática dispensa intervenção humana, sendo um método verdadeiramente objetivo e deve ser a primeira escolha em estudos microTC que objetivam avaliar a morfometria óssea humana.