Segmentation Methods for Micro CT Images: A Comparative Study Using Human Bone Samples.

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.

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.

Peri-implant bone innervation: histological findings in humans.

PURPOSE: The aim of the present study was to describe nerve fibres around osseointegrated implants in humans. MATERIALS AND METHODS: Twelve mechanically failed implants, retrieved from 10 patients were collected from three dental centres over a period of 5 years. After implant removal, decalcified semi-thin sections (0.5 µm) were stained with thionic methylene blue for light microscopic analysis. In addition, an ultrastructural analysis was performed on serial ultra-thin sections (0.06 µm) using transmission electron microscopy. RESULTS: Both myelinated and unmyelinated nerve fibres could be identified inside the Haversian canals of the osteonal bone near the implant threads. Myelinated fibres were also located at the woven bone around the implant. However, no differentiated nerve endings could be observed around the implants. CONCLUSIONS: This study shows the presence of nerve fibres in human peri-implant bone. Previous studies in animals showed that those fibres participate in the process of bone modelling and remodelling. Yet, the role of peri-implant bone innervation in the osseoperception phenomenon cannot be ruled out since the mechanism of mechanoreception in bone is not fully understood.

Aplicabilidade dos enxertos em bloco de origem xenógena nas reconstruções ósseas: relato de caso clínico com avaliação tomográfica e histológica após seis meses / Applicability of xenogenous onlay grafts in bone reconstruction: case report with tomographic and histologic evaluation after six months

O osso autógeno é considerado padrão-ouro para reconstrução óssea em bloco e sustentação dos implantes dentários, mas limitações na disponibilidade e aumento na morbidade são associados a este material. Assim, o osso xenógeno em bloco vem sendo abordado como um substituto viável ao osso autógeno nos casos de recontorno vestibular do rebordo ósseo. Este caso clínico demonstrou a técnica de utilização deste material. Uma paciente de 52 anos de idade e com deficiência estética significativa na região anterior superior recebeu enxerto sintético em bloco fixado com parafusos apropriados. Após seis meses, quatro implantes foram instalados e permitida a osseointegração por mais seis meses. Tomografias computadorizadas foram realizadas antes (T0), após a cirurgia de enxertia do bloco (T1), e após o tempo de consolidação (T2), com as mudanças nos contornos volumétricos sendo comparadas em programa apropriado. Análises histológicas também foram realizadas ao redor do osso do parafuso removido. A estabilidade volumétrica do material foi considerada compatível com a literatura publicada após seis meses. Houve neoformação óssea ao redor do enxerto xenógeno com atividade de remodelação óssea.

Autogenous bone is considered the gold standard material for bone block reconstruction and dental implant supporting, but limited availability and morbidity are associated to this material. Thus, exogenous block substitutes have been studied for such bone augmentation. This case report describes the potential application of this material. A 52 years-old patient with significant deficit at the anterior region received a synthetic block secured with appropriate screws. Six months later, four dental implants were placed and osseointegration allowed for more six months. CBCT scans were performed at baseline (T0), after block grafting (T1), and after consolidation phase (T2). Volumetric changes were compared in the recommended software. Histological analyses were performed around the retrieved screws. The volumetric stability of this material after six months was considered compatible with the already published literature. Bone neoformation was seen around the xenograft with associated bone remodeling

Peri-implant bone tissue assessment by comparing the outcome of intra-oral radiograph and cone beam computed tomography analyses to the histological standard.

OBJECTIVES: The present study aims to identify radiographic methods revealing data that are most representative for the true peri-implant bone as assessed by histology. MATERIALS AND METHODS: Eighty implants were placed in 10 minipigs. To assess matching between different image modalities, measurements conducted on intra-oral digital radiographs (IO), cone beam computer tomography (CBCT) and histological images were correlated using Spearman's correlation. Paired tests (Wilcoxon test) were used to determine changes in the bone parameters after 2 and 3 months of healing. RESULTS: Significant correlations between bone defect depth on IO and histological slices (r= + 0.7, P<0.01), as well as on CBCT images and histological slices (r= + 0.61, P<0.01), were found. CBCT and IO images deviate, respectively, 1.20 and 1.17 mm from the histology regarding bone defects. No significant correlations were detected between fractal analysis on CBCT, intra-oral radiography and histology. For bone density assessment, significant but weaker correlations (r= + 0.5, P<0.01) were found for intra-oral radiography vs. histology. Significant marginal bone-level changes could be observed after 3 months of healing using intra-oral radiography. CONCLUSIONS: This study allowed linking radiographic bone defect depth to the histological observations of the peri-implant bone. Minute bone changes during a short-term period can be followed up using digital intra-oral radiography. Radiographic fractal analysis did not seem to match histological fractal analysis. CBCT was not found to be reliable for bone density measures, but might hold potential with regard to the structural analysis of the trabecular bone.

The influence of gender and bruxism on human minimum interdental threshold ability

OBJECTIVE: To evaluate the influence of gender and bruxism on the ability to discriminate minimum interdental threshold. MATERIAL AND METHODS: One hundred and fifteen individuals, representing both genders, bruxers and non-bruxers, with a mean age of 23.64 years, were selected for this study. For group allocation, every individual was subjected to a specific physical examination to detect bruxism (performed by three different examiners). Evaluation of the ability to discriminate minimum interdental threshold was performed using industrialized 0.010 mm-, 0.024 mm-, 0.030 mm-, 0.050 mm-, 0.080 mm- and 0.094 mm-thick aluminum foils that were placed between upper and lower premolars. Data were analyzed statistically by multiple linear regression analysis at 5% significance level. RESULTS: Neither gender nor bruxism influenced the ability to discriminate minimum interdental threshold (p>0.05). CONCLUSIONS: Gender and the presence of bruxism do not play a role in the minimum interdental threshold.

The influence of gender and bruxism on human minimum interdental threshold ability.

OBJECTIVE: To evaluate the influence of gender and bruxism on the ability to discriminate minimum interdental threshold. MATERIAL AND METHODS: One hundred and fifteen individuals, representing both genders, bruxers and non-bruxers, with a mean age of 23.64 years, were selected for this study. For group allocation, every individual was subjected to a specific physical examination to detect bruxism (performed by three different examiners). Evaluation of the ability to discriminate minimum interdental threshold was performed using industrialized 0.010 mm-, 0.024 mm-, 0.030 mm-, 0.050 mm-, 0.080 mm- and 0.094 mm-thick aluminum foils that were placed between upper and lower premolars. Data were analyzed statistically by multiple linear regression analysis at 5% significance level. RESULTS: Neither gender nor bruxism influenced the ability to discriminate minimum interdental threshold (p>0.05). CONCLUSIONS: Gender and the presence of bruxism do not play a role in the minimum interdental threshold.