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

Periodontal ligament and peri-implant bone innervation in humans: a basis for physiological integration of oral implants

This thesis is composed of 2 literature reviews and 6 scientific studies focusing on the mechanosensory function related to periodontal ligament (PDL) and peri-implant region. The scientific research first started with the exploration of PDL nerve fibre distribution in humans (1) and the investigation of special PDL structures, namely the epithelial rests of Malassez (ERM) (2). This was followed by the histological search for mechanoreceptors in the peri-implant tissue of humans (3). Besides these histological approaches, more clinically accessible tools were investigated as possible indication for physiological changes of bone, especially dental radiographs which are daily used in clinic. Thus, morphological aspects of peri-implant bone were assessed by cone beam computed tomography (CBCT) and intra-oral (IO) radiography, using histological imaging as gold-standard (4). Finally, the influence of implant treatment on mandibular anatomy and innervation was investigated using 3D CBCT images. For this, the variability of neurovascular canals in the mandibular bone had first to be addressed (5, 6). PDL innervation and mechanoreceptors have been extensively describedaccording to their morphology, neurophysiological aspects, spatial arrangement and functional significance (chapter 2) . Yet, researches exploring the 3D reconstruction of the PDL and mechanoreception function at cellular and molecular levels are expected to further our understanding of mechanosensory function in teeth. Three-dimensional volume reconstruction from 2D histological slices showed some potential in visualising the complex PDL anatomy, spatial arrangement and interrelationship among the different PDL structures (chapter 2) . Regarding nerve fibre distribution in human PDL, bundles of nerve fibres were mostly found at the alveolar related part of the PDL and in the vicinity of blood vessels (chapter 3) . The highest number of fibres was found at the buccal and mesial region as well as at the root apex. The diameter of PDL fibres ranged between 2-15µm, and those that were myelinated and in the range of 5-6µm were most frequently seen in the human PDL. Overall, the lingual region showed higher concentration of nerve fibres of larger diameter (8-9µm). The highest concentration of isolated fibres was found at the intermediate region between apex and tooth fulcrum, and this in the cemental part of the PDL. Other PDL special structures such as ERM and cementicles have been described in the literature, however their role in the PDL function is not fully understood (chapter 4) . An altered ERM morphology after tooth autotransplantation suggested that this structure isrelated to PDL regeneration. Additional studies are needed to confirm this finding and to research the likely influence of this finding in PDL regeneration treatments. For the first time in humans, myelinated and unmyelinated nerve fibres were shown in the peri-implant bone mostly localized in the Haversian canals close to the bone-implant interface (chapter 5) . However in this study, no structure even resembling a mechanoreceptor was observed in the peri-implant region, which does not explain why some PDL mechanoreceptor functions are partially restored after implant treatment. . Therefore, the exact location and mechanism of the structures that would be responsible for those functions remains mostly unknown in fully implant rehabilitated patients. Regarding peri-implant bone tissue estimations, significant correlations could be observed between bone levels histologically assessed and bone levels measured on IO radiographs and CBCT images (chapter 6) . Tissue parameters as measured on IO radiographs correlate significantly with some histomorphometric parameters. However, such correlation could not be established for CBCT images. An increased bone loss (>2mm) seemed more likely to occur at low density bones (Using3D CBCT scans, the anatomical variability of neurovascular canals of the mandible was addressed, not only between modern humans from different time-periods and different geographical regions, but also between mandibles of human and non-human primates. This contributed to an elaborate overview about neurovascular canal anatomy and the relation with adjacent tooth roots (chapter 7) . Geographically, anatomical features which characterize some populations could be related to potential surgicaland pathological risks. Furthermore, the incisive canal is suggested tobe a unique feature of human mandibles (chapter 7) . Considering some study limitations, this thesis suggested that neurovascular canals do not change significantly after tooth extraction and that the resorption rate of mandibular bone after implant treatment in the first years after tooth extraction seemed to be about 50% less than the rate reported in literature (chapter 8) . To conclude, PDL and peri-implant tissue were assessed to understand the underlying mechanisms of osseoperception influencing the oral implant rehabilitation. A special focus was also given to the innervation of those tissues, their functional relation and spatial arrangement with other adjacent structures.status: publishe

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

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

<div><p>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.</p></div