Loss of KDM4B impairs osteogenic differentiation of OMSCs and promotes oral bone aging.

Aging of craniofacial skeleton significantly impairs the repair and regeneration of trauma-induced bony defects, and complicates dental treatment outcomes. Age-related alveolar bone loss could be attributed to decreased progenitor pool through senescence, imbalance in bone metabolism and bone-fat ratio. Mesenchymal stem cells isolated from oral bones (OMSCs) have distinct lineage propensities and characteristics compared to MSCs from long bones, and are more suited for craniofacial regeneration. However, the effect of epigenetic modifications regulating OMSC differentiation and senescence in aging has not yet been investigated. In this study, we found that the histone demethylase KDM4B plays an essential role in regulating the osteogenesis of OMSCs and oral bone aging. Loss of KDM4B in OMSCs leads to inhibition of osteogenesis. Moreover, KDM4B loss promoted adipogenesis and OMSC senescence which further impairs bone-fat balance in the mandible. Together, our data suggest that KDM4B may underpin the molecular mechanisms of OMSC fate determination and alveolar bone homeostasis in skeletal aging, and present as a promising therapeutic target for addressing craniofacial skeletal defects associated with age-related deteriorations.

Loss of KDM4B impairs osteogenic differentiation of OMSCs and promotes oral bone aging / 国际口腔科学杂志·英文版

Aging of craniofacial skeleton significantly impairs the repair and regeneration of trauma-induced bony defects, and complicates dental treatment outcomes. Age-related alveolar bone loss could be attributed to decreased progenitor pool through senescence, imbalance in bone metabolism and bone-fat ratio. Mesenchymal stem cells isolated from oral bones (OMSCs) have distinct lineage propensities and characteristics compared to MSCs from long bones, and are more suited for craniofacial regeneration. However, the effect of epigenetic modifications regulating OMSC differentiation and senescence in aging has not yet been investigated. In this study, we found that the histone demethylase KDM4B plays an essential role in regulating the osteogenesis of OMSCs and oral bone aging. Loss of KDM4B in OMSCs leads to inhibition of osteogenesis. Moreover, KDM4B loss promoted adipogenesis and OMSC senescence which further impairs bone-fat balance in the mandible. Together, our data suggest that KDM4B may underpin the molecular mechanisms of OMSC fate determination and alveolar bone homeostasis in skeletal aging, and present as a promising therapeutic target for addressing craniofacial skeletal defects associated with age-related deteriorations.

Craniofacial and Long Bone Development in the Context of Distraction Osteogenesis.

BACKGROUND: Bone retains regenerative potential into adulthood, and surgeons harness this plasticity during distraction osteogenesis. The underlying biology governing bone development, repair, and regeneration is divergent between the craniofacial and appendicular skeleton. Each type of bone formation is characterized by unique molecular signaling and cellular behavior. Recent discoveries have elucidated the cellular and genetic processes underlying skeletal development and regeneration, providing an opportunity to couple biological and clinical knowledge to improve patient care. METHODS: A comprehensive literature review of basic and clinical literature regarding craniofacial and long bone development, regeneration, and distraction osteogenesis was performed. RESULTS: The current understanding in craniofacial and long bone development and regeneration is discussed, and clinical considerations for the respective distraction osteogenesis procedures are presented. CONCLUSIONS: Distraction osteogenesis is a powerful tool to regenerate bone and thus address a number of craniofacial and appendicular skeletal deficiencies. The molecular mechanisms underlying bone regeneration, however, remain elusive. Recent work has determined that embryologic morphogen gradients constitute important signals during regeneration. In addition, striking discoveries have illuminated the cellular processes underlying mandibular regeneration during distraction osteogenesis, showing that skeletal stem cells reactivate embryologic neural crest transcriptomic processes to carry out bone formation during regeneration. Furthermore, innovative adjuvant therapies to complement distraction osteogenesis use biological processes active in embryogenesis and regeneration. Additional research is needed to further characterize the underlying cellular mechanisms responsible for improved bone formation through adjuvant therapies and the role skeletal stem cells play during regeneration.

FaceBase 3: analytical tools and FAIR resources for craniofacial and dental research.

The FaceBase Consortium was established by the National Institute of Dental and Craniofacial Research in 2009 as a 'big data' resource for the craniofacial research community. Over the past decade, researchers have deposited hundreds of annotated and curated datasets on both normal and disordered craniofacial development in FaceBase, all freely available to the research community on the FaceBase Hub website. The Hub has developed numerous visualization and analysis tools designed to promote integration of multidisciplinary data while remaining dedicated to the FAIR principles of data management (findability, accessibility, interoperability and reusability) and providing a faceted search infrastructure for locating desired data efficiently. Summaries of the datasets generated by the FaceBase projects from 2014 to 2019 are provided here. FaceBase 3 now welcomes contributions of data on craniofacial and dental development in humans, model organisms and cell lines. Collectively, the FaceBase Consortium, along with other NIH-supported data resources, provide a continuously growing, dynamic and current resource for the scientific community while improving data reproducibility and fulfilling data sharing requirements.

Three-Dimensional Analysis of Age-Related Orbital and Midfacial Bone Remodeling in Asians.

BACKGROUND: Facial bony changes vary among races, yet few studies have been conducted in Asians. OBJECTIVE: To analyze the aging of orbital and midfacial bones in Asians. METHODS: Based on the two-dimensional data obtained from the computed tomography scanner of imaging department, 3D reconstructions were conducted to take measurements (orbital diagonal diameter, orbital width, orbital area, maxillary angle, midfacial height, pyriform angle, pyriform width, and pyriform area). RESULTS: In this retrospective study of 261 subjects, a significant decrease in the orbital diagonal diameter, orbital width, and midfacial height was found in men, whereas women displayed a significant increase in the pyriform width and a significant decrease in maxillary angle and midfacial height by three-dimensional analysis. CONCLUSION: This study verifies the minor female changes in the orbital region and less dramatic male changes in the midfacial region compared with that in Caucasians. Individualized treatment should be performed according to different genders and races. Further exploration of facial bone metabolism may have valuable implications for Asians.

Long-Term Follow-Up on Bone Stability and Complication Rate after Monobloc Advancement in Syndromic Craniosynostosis.

BACKGROUND: Monobloc advancement is a complex procedure used to treat patients with syndromic craniosynostosis. Studies directly addressing the long-term stability of monobloc advancement with distraction osteogenesis are underreported in the literature. The objectives of this study were to assess 5-year midface bone stability following monobloc advancement performed on patients with syndromic craniosynostosis, identify risk factors for relapse, and present strategies for prevention and management of complications. METHODS: An observational retrospective study was performed on consecutive patients with Apert, Crouzon, or Pfeiffer syndrome (n = 23) who underwent monobloc advancement using distraction osteogenesis between 1994 and 2013. A total of 130 lateral cephalograms were used to assess both long-term stability after monobloc advancement with distraction osteogenesis and risk factors for relapse. All serious complications were identified and recorded. The analysis of variance test was used to assess horizontal relapse of the midface and mandibular plane. RESULTS: Cephalometric analysis revealed long-term stability of frontofacial advancement using distraction osteogenesis, regardless of the presence of tested variables. Serious complications arising from monobloc advancement using distraction osteogenesis included cerebrospinal fluid leakage in six patients (26 percent), accompanying meningitis in two patients (8.7 percent), seizures in seven patients (30.4 percent), and impaired visual acuity in one eye of one patient (4.3 percent). CONCLUSION: Frontofacial monobloc advancement with distraction osteogenesis provides long-term midface bone stability. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Disconnect between the developing eye and craniofacial prominences in the avian embryo.

In the amniote embryo, the upper jaw and nasal cavities form through coordinated outgrowth and fusion of craniofacial prominences. Adjacent to the embryonic prominences are the developing eyes, which abut the maxillary and lateral nasal prominences. The embryos of extant sauropsids (birds and nonavian reptiles) develop particularly large eyes in comparison to mammals, leading researchers to propose that the developing eye may facilitate outgrowth of prominences towards the midline in order to aid prominence fusion. To test this hypothesis, we performed unilateral and bilateral ablation of the developing eyes in chicken embryos, with the aim of evaluating subsequent prominence formation and fusion. Our analyses revealed minor interaction between the developing craniofacial prominences and the eyes, inconsequential to the fusion of the upper beak. At later developmental stages, the skull exhibited only localized effects from missing eyes, while geometric morphometrics revealed minimal effect on overall shape of the upper jaw when it develops without eyes. Our results indicate that the substantial size of the developing eyes in the chicken embryo exert little influence over the fusion of the craniofacial prominences, despite their effect on the size and shape of maxillary prominences and components of the skull.

Stem cells of the suture mesenchyme in craniofacial bone development, repair and regeneration.

Development of the skeleton is mediated through two distinct ossification mechanisms. Craniofacial bones are formed mainly through intramembranous ossification, a mechanism different from endochondral ossification required for development of the body skeleton. The skeletal structures are quite distinct between the two, thus they are likely to have their unique stem cell populations. The sutures serve as the growth center critical for healthy development of the craniofacial skeleton. Defects in suture morphogenesis cause its premature closure, resulting in development of craniosynostosis, a devastating disease affecting 1 in ~2,500 individuals. The suture mesenchyme has been postulated to act as the niche of skeletal stem cells essential for calvarial morphogenesis. However, very limited knowledge is available for suture biology and suture stem cells (SuSCs) have yet to be isolated. Here we report the first evidence for identification and isolation of a stem cell population residing in the suture midline. Genetic labeling of SuSCs shows their ability to self-renew and continually give rise to mature cell types over a 1-year monitoring period. They maintain their localization in the niches constantly produce skeletogenic descendants during calvarial development and homeostastic maintenance. Upon injury, SuSCs expand drastically surrounding the skeletogenic mesenchyme, migrate to the damaged site and contribute directly to skeletal repair in a cell autonomous fashion. The regeneration, pluripotency and frequency of SuSCs are also determined using limiting dilution transplantation. In vivo clonal expansion analysis demonstrates a single SuSC capable of generating bones. Furthermore, SuSC transplantation into injured calvaria facilitates the healing processes through direct engraftments. Our findings demonstrate SuSCs are bona fide skeletal stem cells ideally suited for cell-based craniofacial bone therapy as they possess abilities to engraft, differentiate.(Presented at the 1980th Meeting, April 16, 2019).

Using texture analysis of head CT images to differentiate osteoporosis from normal bone density.

OBJECTIVES: To investigate the use of texture analysis for the detection of osteoporosis on noncontrast head CTs, and to explore optimal sampling regions within the craniofacial bones. METHODS: In this IRB-approved, retrospective study, the clivus, bilateral sphenoid triangles and mandibular condyles were manually segmented on each noncontrast head CT, and 41 textures features were extracted from 29 patients with normal bone density (NBD); and 29 patients with osteoporosis. Basic descriptive statistics including a false discovery rate correction were performed to evaluate for differences in texture features between the cohorts. RESULS: Sixteen texture features demonstrated significant differences (P < 0.01) between NBD and osteoporosis in the clivus including 4 histogram features, 2 gray-level co-occurrence matrix features, 8 gray-level run-length features and 2 Law's features. Nineteen texture features including 9 histogram features, 1 GLCM features, 2 GLRL features, 5 Law's features and 2 GLGM features demonstrated statistically significant differences in both sides of the sphenoid triangles. A total 24 texture features demonstrated statistically significant differences between normal BMD and osteoporosis in the left sphenoid and a total of 31 texture features in the left condyle. Furthermore, a total of 22 texture features including 6 histogram features, 3 GLCM features, 9 GLRL features, 2 Law's features and 2 GLGM features demonstrated statistically significant differences in both sides of the mandibular condyles. CONCLUSION: The results of this investigation suggest that specific texture analysis features derived from regions of interest placed within multiple sites within the skull base and maxillofacial bones can distinguish between patients with normal bone mineral density compared to those with osteoporosis. This study demonstrates the potential utility of a texture analysis for identification of osteoporosis on head CT, which may help identify patients who have not undergone screening with traditional DXA.

Efficacy of Recombinant Human BMP2 and PDGF-BB in Orofacial Bone Regeneration: A Systematic Review and Meta-analysis.

With the rapid development of tissue engineering therapies, there is a growing interest in the application of recombinant human growth factors (rhGFs) to regenerate human orofacial bones. However, despite reports of their ability to promote orofacial bone regeneration in animal experiments, their benefits in human clinical treatments remain unclear. Furthermore, the appropriate concentrations or indications of a specific rhGF remain ambiguous. Therefore it is essential to collect data from diverse clinical trials to evaluate their effects more precisely. Here we reviewed randomized clinical trials (RCT) that focused on the utilization of rhGFs in orofacial bone regeneration. Data from included studies were extracted, pooled and then quantitatively analyzed according to a pre-established protocol. Our results indicate that all current concentrations of rhBMP-2 produces insufficient effect on promoting either tooth extraction socket healing, sinus augmentation or reconstruction of alveolar clefts. However, 0.3 mg/ml rhPDGF-BB promotes the healing of tooth extraction sockets, though the effect does not reach a level of statistical significance. Summarily, we recommend concentrations of 0.3 mg/ml rhPDGF-BB only for the healing of tooth extraction sockets.

Is There a Possible Association between Skeletal Face Types and Third Molar Impaction? A Retrospective Radiographic Study.

OBJECTIVE: Third molar impaction is seen much more than impaction of any other tooth as they are the last teeth to erupt. Inadequate retromolar space and the direction of eruption may be contributing factors. The aim of this study was to investigate the relationship between third molar impaction and different skeletal face types. SUBJECTS AND METHODS: Panoramic and lateral cephalometric radiographs of 158 orthodontic patients (aged 19-25 years) were retrieved from the archived records of the Necmettin Erbakan University Faculty of Dentistry, Konya, Turkey. Third molar impaction was classified on the basis of Winter's classification. The skeletal facial type was determined by a measure of the angle created by the lines Ba-Na and Pt-Gn. The mean was 90 ± 2 and this value was regarded as mesofacial. An angle of > 93° was regarded as brachyfacial and an angle of < 87° as dolichofacial. RESULTS: The overall presence of mandibular and maxillary third molar impactions was 65.2 and 38.6%, respectively. Although there was a statistically significant difference between different skeletal facial types and mandibular third molar impaction (p < 0.05), no statistically significant differences were observed between different skeletal facial types and maxillary third molar impaction (p > 0.05). Brachyfacials demonstrated a lower prevalence of third molar impaction than dolichofacials. CONCLUSIONS: Different skeletal face types were associated with mandibular third molar impaction. Brachyfacials, who have a greater horizontal facial growth pattern than dolichofacials, showed a lower prevalence of impacted mandibular third molars.

Midfacial changes in the coronal plane induced by microimplant-supported skeletal expander, studied with cone-beam computed tomography images.

INTRODUCTION: Our objectives were to evaluate midfacial skeletal changes in the coronal plane and the implications of circummaxillary sutures and to localize the center of rotation for the zygomaticomaxillary complex after therapy with a bone-anchored maxillary expander, using high-resolution cone-beam computed tomography. METHODS: Fifteen subjects with a mean age of 17.2 ± 4.2 years were treated with a bone-anchored maxillary expander. Pretreatment and posttreatment cone-beam computed tomography images were superimposed and examined for comparison. RESULTS: Upper interzygomatic distance increased by 0.5 mm, lower interzygomatic distance increased by 4.6 mm, frontozygomatic angles increased by 2.5° and 2.9° (right and left sides), maxillary inclinations increased by 2.0° and 2.5° (right and left sides), and intermolar distance increased by 8.3 mm (P <0.05). Changes in frontoethmoidal, zygomaticomaxillary, and molar basal bone angles were negligible (P >0.05). CONCLUSIONS: A significant lateral displacement of the zygomaticomaxillary complex occurred in late adolescent patients treated with a bone-anchored maxillary expander. The zygomatic bone tended to rotate outward along with the maxilla with a common center of rotation located near the superior aspect of the frontozygomatic suture. Dental tipping of the molars was negligible during treatment.

Biomechanical effect of mandibular advancement device with different protrusion positions for treatment of obstructive sleep apnoea on tooth and facial bone: A finite element study.

BACKGROUND: The mandibular advancement device (MAD) is widely used for obstructive sleep apnoea (OSA) treatment, and several studies have demonstrated its effectiveness. However, no comprehensive studies have yet examined the biomechanical safety of the MAD. OBJECTIVES: The objective of this study was to analyse the biomechanical effect of different protrusion positions of a MAD on the teeth and facial bones. METHODS: The posterior restorative forces due to the stretched mandibular muscles were measured by pressure sensors attached to the experimental mandibular advancement device for mandibular protrusions of 10-70% of the maximum protrusion of the subject. A detailed three-dimensional biomechanical model of the study subject, constructed from computed tomography scans, was used in finite element analysis, with loading conditions calculated from the measured posterior restorative forces. The outcome measures were the principal stresses on the periodontal ligaments (PDL) and cancellous bone, and the pressure at the PDL surfaces. The measurements were used to analyse the risk of the tooth movement, tooth root resorption, and bone resorption. RESULTS: The lowest and highest restorative forces occurred at 40% and 70% of maximum protrusion, respectively. The highest risk of tooth movement occurred at the mandibular molar teeth. The mandibular second molar teeth had the highest risks of root and bone resorption. CONCLUSIONS: Mandibular advancement at 70% of maximum protrusion induces risks of tooth root resorption and bone resorption. The mandibular second molars were subjected to the highest stresses. Stress on the teeth and facial bones was the lowest at 40% of maximum mandibular advancement.

Vascularization in Craniofacial Bone Tissue Engineering.

Craniofacial bones, separate from the appendicular skeleton, bear a significant amount of strain and stress generated from mastication-related muscles. Current research on the regeneration of craniofacial bone focuses on the reestablishment of an elaborate vascular network. In this review, current challenges and efforts particularly in advances of scaffold properties and techniques for vascularization remodeling in craniofacial bone tissue engineering will be discussed. A microenvironment of ischemia and hypoxia in the biomaterial core drives propagation and reorganization of endothelial progenitor cells (EPCs) to assemble into a primitive microvascular framework. Co-culture strategies and delivery of vasculogenic molecules enhance EPCs' differentiation and stimulate the host regenerative response to promote vessel sprouting and strength. To optimize structural and vascular integration, well-designed microstructures of scaffolds are biologically considered. Proper porous structures, matrix stiffness, and surface morphology of scaffolds have a profound influence on cell behaviors and thus affect revascularization. In addition, advanced techniques facilitating angiogenesis and vaculogenesis have also been discussed. Oxygen delivery biomaterials, scaffold-free cell sheet techniques, and arteriovenous loop-induced axial vascularization strategies bring us new understanding and powerful strategies to manage revascularization of large craniofacial bone defects. Although promising histological results have been achieved, the efficient perfusion and functionalization of newly formed vessels are still challenging.

Biomaterials for Craniofacial Bone Regeneration.

Functional reconstruction of craniofacial defects is a major clinical challenge in craniofacial sciences. The advent of biomaterials is a potential alternative to standard autologous/allogenic grafting procedures to achieve clinically successful bone regeneration. This article discusses various classes of biomaterials currently used in craniofacial reconstruction. Also reviewed are clinical applications of biomaterials as delivery agents for sustained release of stem cells, genes, and growth factors. Recent promising advancements in 3D printing and bioprinting techniques that seem to be promising for future clinical treatments for craniofacial reconstruction are covered. Relevant topics in the bone regeneration literature exemplifying the potential of biomaterials to repair bone defects are highlighted.

Patterns of Change in Facial Skeletal Aging.

IMPORTANCE: Research in facial aging has focused on soft-tissue changes rather than bony changes despite evidence of the importance of underlying bony structural changes. Research has also been limited by comparing different patients in separate age groups rather than the same patients over time. OBJECTIVE: To longitudinally document patterns of change in the facial skeleton and determine a consistent methodology for measuring these changes. DESIGN, SETTING, AND PARTICIPANTS: Case series study of university hospital system records using facial computed tomographic (CT) images timed at least 8 years apart in adults initially aged 40 to 55 years with no history of facial surgery who required repeated facial imaging that included the entire midface and cranium. MAIN OUTCOMES AND MEASURES: Face CTs were analyzed for 3-dimensional constructions and 2-dimensional measurements to document changes in glabellar, piriform, and maxillary angles and piriform height and width. RESULTS: Fourteen patients (5 men, 9 women; mean [SD] age, 51.1 [5.8] years) with mean (SD) follow-up of 9.7 (1.4) years were eligible for 2-dimensional analysis, which revealed statistically significant decreases in mean (SD) glabellar angles (from 68.8° [7.6°] to 66.5° [8.6°]) and maxillary angles on both the right (from 82.5° [6.3°] to 81.0° [7.1°]) and left (from 83.0° [5.8°] to 81.0° [7.0°]), as well as increases in mean (SD) piriform width (from 24.5 [1.6] mm to 25.5 [1.3] mm). Nine patients (3 men, 6 women; mean [SD] age, 51.4 [6.3] years) with mean (SD) follow-up imaging at 9.6 (1.5) years were eligible for 3-dimensional analysis, which revealed statistically significant decreases in mean (SD) maxillary angles (from 56.5° [6.6°] to 51.6° [7.6°]) and piriform angles (from 50.8° [3.4°] to 49.1° [3.4°]). Statistically significant differences between the sexes were also noted: Initial mean (SD) glabellar angle for men was 61.7° (5.7°) vs 72.7° (5.4°) for women, with final values of 57.9° (4.9°) vs 71.2° (6.0°). Mean (SD) maxillary angle initial values were 87.8° (6.1°) (right) and 87.1° (4.9°) (left) for men, with 79.6° (4.3°) and 80.6° (5.0°) for women, respectively. Final values were 87.0° (4.4°) and 86.9° (4.1°) for men and 77.7° (6.1°) and 77.7° (6.2°) for women, respectively. Mean (SD) piriform height for men was 35.0 (2.0) mm initially and 35.5 (2.1) mm finally, vs 31.3 (2.8) and 31.6 (3.0) mm for women, respectively. CONCLUSIONS AND RELEVANCE: Our pilot study of repeated CT images of patients over several years supports previous studies of bony facial aging and further characterizes these changes. This study is the first, to our knowledge, to document bony changes of the face in the same group of patients at different time points to better characterize facial aging. We also detail an improved methodology to study bony aging to contribute to additional research in the field. LEVEL OF EVIDENCE: NA.

Analysis of Craniofacial Remodeling in the Aging Midface Using Reconstructed Three-Dimensional Models in Paired Individuals.

BACKGROUND: Aging leads to a panoply of changes of facial morphology. The present study was conducted to analyze modifications of the facial skeleton with aging, using high-resolution imaging and comparing the same individuals at two time points. METHODS: The electronic medical record system was reviewed since its inception in 2001 for patients for whom two computed tomographic scans of the midface were obtained at least 9 years apart. The computed tomographic scans were converted into three-dimensional craniofacial models for each patient, using the initial and the follow-up computed tomographic scan data. The models were used to highlight areas of bone growth and bone resorption using a color scale and to perform a cephalometric analysis. RESULTS: Seven patients with a mean age of 61 years and computed tomographic scans on average 10.3 years apart were included. Bone resorption was consistently present (100 percent) at the pyriform aperture and the anterior wall of the maxilla. Resorption was noted at the superocentral (71 percent), inferolateral (57 percent), and superomedial (57 percent) aspects of the orbital rim. Resorption occurred earlier at the inferolateral orbital rim followed by the superomedial orbital rim in later decades of life. Paired-analysis of change in the orbital rim height and width demonstrated a mean decrease over time but was not significant. CONCLUSION: Bone remodeling in the same individual, over a period of 10 years, was characterized by resorption at the pyriform aperture; anterior wall of the maxilla; and superocentral, superomedial, and inferolateral aspects of the orbital rims.

Structural biomechanics of the craniomaxillofacial skeleton under maximal masticatory loading: Inferences and critical analysis based on a validated computational model.

BACKGROUND: The trend towards optimizing stabilization of the craniomaxillofacial skeleton (CMFS) with the minimum amount of fixation required to achieve union, and away from maximizing rigidity, requires a quantitative understanding of craniomaxillofacial biomechanics. This study uses computational modeling to quantify the structural biomechanics of the CMFS under maximal physiologic masticatory loading. METHODS: Using an experimentally validated subject-specific finite element (FE) model of the CMFS, the patterns of stress and strain distribution as a result of physiological masticatory loading were calculated. The trajectories of the stresses were plotted to delineate compressive and tensile regimes over the entire CMFS volume. RESULTS: The lateral maxilla was found to be the primary vertical buttress under maximal bite force loading, with much smaller involvement of the naso-maxillary buttress. There was no evidence that the pterygo-maxillary region is a buttressing structure, counter to classical buttress theory. The stresses at the zygomatic sutures suggest that two-point fixation of zygomatic complex fractures may be sufficient for fixation under bite force loading. CONCLUSIONS: The current experimentally validated biomechanical FE model of the CMFS is a practical tool for in silico optimization of current practice techniques and may be used as a foundation for the development of design criteria for future technologies for the treatment of CMFS injury and disease.

The fate of buccal bone around dental implants. A 12-month postloading follow-up study.

INTRODUCTION AND AIM: Buccal bone thickness is considered to be an important factor during implant surgery. Its resorption might have an effect on the soft tissue stability and eventually on implant survival. This study aimed to investigate the resorption of the buccal bone over the first 12 months after implant loading. MATERIALS AND METHODS: Twenty-four subjects (47 implants) were included. The buccal bone thickness was measured during implant surgery at several distances from the implant shoulder using a specifically designed device which allows buccal bone thickness measurements without the elevation of a muco-periostal flap. These measurements were repeated after 12 months of loading. Sixteen implants were placed flapless and 31 with the elevation of a flap. Of the latter, 19 were placed following a one-stage protocol and 12 following a two-stage protocol. RESULTS: The mean reduction in buccal bone thickness, when all groups pooled, was 0.26, 0.36, 0.35 and 0.27 mm at the shoulder and 2, 4 and 6 mm apically. Implants with initial bone thickness <1mm (thin buccal plate) did not lose significantly more bone than those with an initial thickness ≥1mm (thick bone plate) except in the 'open-flap, one-stage' group (P = 0.009). A flapless procedure leads to less bone resorption compared to an open-flap procedure (P = 0.03). However, the number of surgeries (one stage vs. two stages) did not influence the rate of bone resorption (P = 0.23). CONCLUSION: Within the limitations of this study, one might question the necessity of having a thick bone plate at the vestibular site of the implant.

Pressure Bearing Device Affects Extraction Socket Remodeling of Maxillary Anterior Tooth. A Prospective Clinical Trial.

BACKGROUND: Extraction socket remodeling and ridge preservation strategies have been extensively explored. PURPOSE: To evaluate the efficacy of applying a micro-titanium stent as a pressure bearing device on extraction socket remodeling of maxillary anterior tooth. MATERIALS AND METHODS: Twenty-four patients with a extraction socket of maxillary incisor were treated with spontaneous healing (control group) or by applying a micro-titanium stent as a facial pressure bearing device over the facial bone wall (test group). Two virtual models obtained from cone beam computed tomography data before extraction and 4 months after healing were 3-dimenionally superimposed. Facial bone wall resorption, extraction socket remodeling features and ridge width preservation rate were determined and compared between the groups. RESULTS: Thin facial bone wall resulted in marked resorption in both groups. The greatest palatal shifting distance of facial bone located at the coronal level in the control group, but middle level in the test group. Compared with the original extraction socket, 87.61 ± 5.88% ridge width was preserved in the test group and 55.09 ± 14.46% in the control group. CONCLUSIONS: Due to the facial pressure bearing property, the rigid micro-titanium stent might preserve the ridge width and alter the resorption features of extraction socket.