Interradicular Septum Research Articles

Radiological Evaluation of the Dimensions of Lower Molar Alveoli.

The aim of the present radiological study was to analyze the alveolar bone morphology of the lower molars in physiological conditions. The main goal is to describe the bone anatomy of a hypothetically postextractive site in lower molar area. Computed tomography scans of 100 patients were examined. Axial, paraxial, and Panorex sections were analyzed using a dedicated software. Precise reference points were encoded to make the bone measurements clear and repeatable. The total number of dental sites examined was 235. The mean available bone height was 13.32 ± 3.23 mm in first molars and 11.76 ± 2.82 mm in second molars. The inter-radicular septum was present in 86% out of cases in first molar sites and in 52% in second molar sites. The lingual cortex mean width, at the most coronal point, measured 1.41 ± 0.52 mm in first molar alveoli and 1.67 ± 0.66 mm in second molar alveoli. Proper clinical conditions, for scheduling a postextraction immediate implant placement surgery, involve the presence of 4 bone walls showing and sufficient height and width. The accurate knowledge of alveolus bone morphology of mandibular molars, prior extraction, could be an important guide to avoid potential failures due to nonideal anatomical features to fixture stabilization.

Anatomical and Radiologic Evaluation of the Dimensions of Upper Molar Alveoli.

The aim of the present study was to analyze the alveolar bone morphology of the upper first and second molars. This analysis aims to evaluate the morphology of a hypothetical postextractive site in the upper molar area to diagnose the possibility of immediate postextraction implant placement. Cone-beam CT scans of 100 patients were examined. The measurements were made using a dedicated 3D software. Reference points were identified to allow clear and repeatable measurements. The mean available height was 7.43 ± 3.40 mm for the upper first molars and 7.07 ± 3.09 mm for the upper second molars. The interradicular septum was present in first molars in 74% of cases and 44% of cases in upper second molars. In most cases, the alveolar sites of the upper first and second molars do not present ideal conditions for immediate implant insertion in a correct position. The primary stabilization of a standard-sized dental implant is often difficult because of the minimum apical bone available. In particular, the interradicular septum, which often represents the ideal fixture position, is rarely adequately represented. Preoperative cone-beam scan and the knowledge of anatomical measurements from the present analysis are fundamental before planning immediate postextractive implants in the upper molar area.

One-stage laser-microtextured implants immediately placed in the inter-radicular septum of molar fresh extraction sockets associated with GBR technique. A case series study.

BackgroundThe outcome of one-stage trans-mucosal immediate implants with simultaneous guided bone regeneration (GBR) technique has become highly predictable. Furthermore, when this approach is performed to place one-stage implants into the inter-radicular septum of fresh extraction sockets in the molar region, the risk of incorrect emergence profile and off-angle loading is reduced. The aim of the present study was to clinically evaluate the horizontal hard and soft tissue changes, and radiographically the vertical socket walls remodeling, and the early peri-implant marginal bone loss (EMBL) following the placement of immediate one-stage implants in the inter-radicular septum of molar fresh extraction sockets, associated with a collagen membrane.Material and MethodsTwenty patients were selected to receive a one-stage implant with laser-microtextured collar surface into the inter-radicular septum of a fresh molar extraction sockets, associated with a simultaneous placement of a collagen membrane. Intraoral radiographs and model casts were used for the evaluation. Correlation between the amount of the keratinized tissue thickness (KTT) with EMBL was also analyzed.ResultsAfter 4 months, the vertical radiographic mesial and distal EMBL around implants was of 0.06 ±0.01 mm and 0.04±0.02 mm, respectively, with no statistically significant difference between T0 and T1 (P >0.05). No statistical differences were found also for each radiographic measure used for the examination of implant sites vertical bone changes (p >0.05). Clinically, horizontal changes of the bucco-lingual central width were found statistically significant (p<0.05), whereas no statistical differences were found for bucco-lingual mesial and distal width changes (p >0.05). In addition, no statistically significant correlation between EMBL and the amount of KTT was found (P >0.05).ConclusionsResults suggest that the immediate placement of one-stage laser-microtextured implants could provide advantages in preserving the extraction socket’s hard and soft tissue remodeling, and the peri-implant marginal bone level before the prosthetic loading. Key words:One-stage implant, laser-microtextured collar surface, GBR, collagen membrane.

A robust methodology for the quantitative assessment of the rat jawbone microstructure

Micro-computed tomography can be applied for the assessment of the micro-architectural characteristics of the cortical and trabecular bones in either physiological or disease conditions. However, reports often lack a detailed description of the methodological steps used to analyse these images, such as the volumes of interest, the algorithms used for image filtration, the approach used for image segmentation, and the bone parameters quantified, thereby making it difficult to compare or reproduce the studies. This study addresses this critical need and aims to provide standardized assessment and consistent parameter reporting related to quantitative jawbone image analysis. Various regions of the rat jawbones were screened for their potential for standardized micro-computed tomography analysis. Furthermore, the volumes of interest that were anticipated to be most susceptible to bone structural changes in response to experimental interventions were defined. In the mandible, two volumes of interest were selected, namely, the condyle and the trabecular bone surrounding the three molars. In the maxilla, the maxillary tuberosity region and the inter-radicular septum of the second molar were considered as volumes of interest. The presented protocol provides a standardized and reproducible methodology for the analysis of relevant jawbone volumes of interest and is intended to ensure global, accurate, and consistent reporting of its morphometry. Furthermore, the proposed methodology has potential, as a variety of rodent animal models would benefit from its implementation.

Providing Flaxseed Oil but Not Menhaden Oil Protects against OVX Induced Bone Loss in the Mandible of Sprague-Dawley Rats.

Higher intakes of polyunsaturated fatty acids (PUFA) are associated with benefits at several skeletal sites in postmenopausal women and in rodent models, but the effect of PUFA-containing oils on tooth-supporting alveolar bone of the mandible has not been studied. Moreover, direct comparison of the effect of flaxseed oil (a source of alpha-linolenic acid (ALA)) and menhaden oil (a source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) is unknown. One-month old female Sprague-Dawley rats (n = 48) were randomized to and fed a diet containing flaxseed oil or menhaden oil from one to six months of age. At three months of age, rats were randomized to receive SHAM or ovariectomy (OVX) surgery (n = 12/diet). The inter-radicular septum below the first molar of the mandible was imaged at 6 months of age (study endpoint) using micro-computed tomography (μCT) at a resolution of 9 μm. As expected, OVX significantly reduced percent bone volume (BV/TV), connectivity density (Conn. D.), trabecular number (Tb. N.), and increased trabecular separation (Tb. Sp.) compared to SHAM rats (p < 0.001). However, post hoc analysis revealed these differences were present in rats fed menhaden oil but not those fed flaxseed oil. These results suggest that providing flaxseed oil, possibly through its high ALA content, provides protection against the OVX-induced alveolar bone loss in rats.

Immunohistochemical localization of tenascin-C in rat periodontal ligament with reference to alveolar bone remodeling.

We investigated the immunohistochemical localization of tenascin-C in 8-week-old rat periodontal ligaments. Tenascin-C immunoreactivity was detected in zones along with cementum and alveolar bone, and more intensely on the resorption surface of alveolar bone than on the formation surface. On the resorbing surface, tenascin-C immunoreactivity was detected in Howship's lacunae without osteoclasts, and in the interfibrous space of the periodontal ligaments, indicating that this molecule works as an adhesion molecule between bone and fibers of periodontal ligaments. Upon experimental tooth movement by inserting elastic bands (Waldo method), the physiological resorption surface of alveolar bone under compressive force showed enhanced bone resorption and enhanced tenascin-C immunoreactivity. However, on the physiological bone formation surface under compressive force, bone resorption was seen only occasionally, and no enhanced tenascin-C immunoreactivity was noted. In an experiment involving excessive occlusal loading to rat molars, transient bone resorption occurred within interradicular septa, but no enhanced tenascin-C immunoreactivity was seen in the periodontal ligaments. These results indicate that tenascin-C works effectively on the bone resorbing surface of physiological alveolar bone remodeling sites, rather than on the non-physiological transient bone resorbing surface. Fibronectin immunoreactivity was distributed evenly in the periodontal ligaments under experimental conditions. Co-localization of tenascin-C and fibronectin immunoreactivity was observed in many regions, but mutually exclusive expression patterns were also seen in some regions, indicating that fibronectin might not be directly involved in alveolar bone remodeling, but may play a role via interaction with tenascin-C.

Ovariectomy-associated changes in interradicular septum and in tibia metaphysis in different observation periods in rats

In order to standardize an experimental model to study the effects of absence of ovarian hormones in maxillary bones compared with long bones, the aim of this research was to analyze the influence of ovariectomy (OVX) on rat alveolar bone and tibiae, in different observation periods. Thirty-six female rats were ovariectomized or sham operated. After 60, 90 or 120 days, the animals were sacrificed and their hemimandibles, maxillae and tibiae were removed and routinely prepared for hematoxylin and eosin staining. The percentage of bone matrix area in bone septum in the first molar furcation region, and in tibial metaphysis was calculated, and data were submitted to statistical analysis (p<0.05). As regards the histomorphometrical analysis in jaw bones, there was no statistical difference between groups, while the effects of ovariectomy on tibiae were seen as early as 60 days. According to the methods used, there was no significant influence of absence of ovarian hormones on interradicular septum of mandibular or maxillary first molars in the periods studied, despite the reduction in bone matrix area in tibia metaphysis as early as 60 days.

Stabilization of tooth movement by administration of reveromycin A to osteoprotegerin-deficient knockout mice

In this study, mechanical stress in the form of tooth movement was applied to osteoprotegerin-deficient knockout mice, which served as an animal model for juvenile Paget's disease. To compare and evaluate bone turnover and response of the surrounding bony tissue, we administered reveromycin A. We also investigated the ability of reveromycin A to control osteoclastic activity in juvenile Paget's disease. Eight-week-old male osteoprotegerin-deficient knockout and wild-type mice were injected with reveromycin A (15 mg/kg of body weight) intraperitoneally twice daily. An elastic module was inserted interproximally between the maxillary left first and second molars. Administration of reveromycin A to osteoprotegerin-deficient knockout mice reduced tooth movement distances, increased bone volumes at the interradicular septum, decreased osteoclast counts, and reduced serum alkaline phosphatase and tartrate resistant acid phosphatase. Reveromycin A administration also caused a temporal shift in peak Runx2 staining in osteoprotegerin-deficient knockout mice so that the overall staining time course was similar to that observed for wild-type mice. Reveromycin A administration in osteoprotegerin-deficient knockout mice inhibited bone resorption and normalized bone formation. As a result, normal bone turnover was obtained.

Immunolocalization of sclerostin synthesized by osteocytes in relation to bone remodeling in the interradicular septa of ovariectomized rats

This study aimed at elucidating whether estrogen deficiency would affect the synthesis of an osteocyte-derived factor, sclerostin, in the mesial region of alveolar bone. Eight 9-week-old Wistar female rats were ovariectomized (OVX) and eight other rats were Sham-operated (Sham). After 4 weeks, the interradicular septa of mandibular first molar were embedded in paraffin and then histochemically examined. Sclerostin-positive osteocytes were located in the superficial layer of the mesial region of Sham bones, whereas the OVX mesial region showed less sclerostin-reactive osteocytes. There was no significant difference in the distribution of estrogen receptor α and terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling -positive cells in the groups studied. The Sham mesial region featured many osteoclasts, and OVX specimens showed numerous osteoclasts in association with intense immunolabeling of the receptor activator of the nuclear factor kB ligand. Contrary to the observations in Sham specimens, a complex meshwork of cement lines was seen in the OVX mesial region, accompanied by an irregularly distributed osteocytic lacunar-canalicular system. In conclusion, estrogen deficiency appears to inhibit osteocyte-derived sclerostin synthesis in the mesial region of the interradicular septum, in a process that seems to be mediated by accelerated bone remodeling rather than by direct effects on osteocytes.

Influência da largura do septo inter-radicular sobre a estabilidade dos mini-implantes

OBJETIVO: este estudo teve como objetivo avaliar a influência da largura do septo inter-radicular no local de inserção de mini-implantes autoperfurantes sobre o grau de estabilidade desses dispositivos de ancoragem. MÉTODOS: a amostra consistiu de 40 mini-implantes inseridos entre as raízes do primeiro molar e segundo pré-molar superiores de 21 pacientes, com o intuito de fornecer ancoragem para retração anterior. A largura do septo no local de inserção (LSI) foi mensurada nas radiografias pós-cirúrgicas e, sob esse aspecto, os mini-implantes foram divididos em dois grupos: grupo 1 (áreas críticas, LSI&lt;3mm) e grupo 2 (áreas não críticas, LSI&gt;3mm). A estabilidade dos mini-implantes foi avaliada mensalmente pela quantificação do grau de mobilidade e a partir dessa variável foi calculada a proporção de sucesso. Avaliou-se também: a quantidade de placa, altura de inserção, grau de sensibilidade e período de observação. RESULTADOS: os resultados obtidos demonstraram que não houve diferença estatisticamente significativa para o grau de mobilidade e proporção de sucesso entre os mini-implantes inseridos em septos de largura mesiodistal crítica e não crítica. A proporção de sucesso total encontrada foi de 90% e nenhuma variável demonstrou estar relacionada ao insucesso dos mini-implantes. No entanto, observou-se maior sensibilidade nos pacientes cujos mini-implantes apresentavam mobilidade, e que a falha desses dispositivos de ancoragem ocorria logo após sua inserção. CONCLUSÃO: a largura do septo inter-radicular no local de inserção não interferiu na estabilidade dos mini-implantes autoperfurantes avaliados neste estudo.

Bisphosphonate Inhibits Bone Turnover in OPG−/− Mice Via a Depressive Effect on Both Osteoclasts and Osteoblasts

Osteoclast differentiation and functioning are strictly controlled by RANKL expressed on osteoblast membrane surfaces, but whether osteoclasts exert control over osteoblasts remains unclear. In the present study, we examined the effect of an osteoclast inhibitor, a bisphosphonate (BP), on the response of maxillary bone to mechanical stress in a high-turnover osteoporosis model (OPG(-/-) mice, a model of juvenile Paget disease). Mechanical stress was induced by use of orthodontic elastics to move the maxillary first molar. BP was administered once per day beginning 5 days before elastic insertion. Relative to wild type (WT), in the OPG(-/-) mice tooth movement distance was greater, resorption of the interradicular septum occurred to a greater extent, the osteoclast count was higher, and serum alkaline phosphatase (ALP) was higher. However, administration of BP to OPG(-/-) mice reduced tooth movement distance, increased bone volume at the interradicular septum, decreased the osteoclast count, and reduced serum ALP. BP administration also caused a temporal shift in peak Runx2 staining in OPG(-/-) mice, such that the overall staining time course was similar to that observed for WT mice. We conclude that BP administration not only inhibited osteoclast activity in OPG(-/-) mice but also systemically and locally inhibited osteoblast activity. It is possible that osteoclasts are able to exert some negative control over osteoblasts.

Predictable drill-free screw positioning with a graduated 3-dimensional radiographic-surgical guide: A preliminary report

Mini-implants are placed in restricted sites, requiring an accurate surgical technique. However, no systematic study has quantified technique accuracy to reliably predict the surgical risks. Therefore, a graduated 3-dimensional radiographic-surgical guide (G-RSG) was proposed, and its inaccuracy and risk index (RI) were estimated. The sample consisted of 6 subjects (4 male, 2 female), who used mini-implant anchorage. Ten drill-free screws (DFS) were placed by using the G-RSG. The central point of the mesiodistal septum width (SW) was the selected implant site on the presurgical radiograph. The distances between DFS and the adjacent teeth (5-DFS and 6-DFS) were measured to evaluate screw centralization and inaccuracy degree (ID). These distances were statistically compared by independent t tests, and inaccuracy was determined by the expression ID = (5-DFS - 6-DFS)/2, which represents deviation of the mini-implant's final position regarding the central point initially selected. Then SW, ID, and screw diameter (SØ) were combined to estimate the surgical risk with RI expressed by RI = SØ/SW - ID. The 5-DFS and 6-DFS distances were not significantly different. The ID of the G-RSG was 0.17 mm. The low ID ensured a safe RI (<1) in spite of the restricted SW. The G-RSG accuracy allowed fine prediction of the final DFS position in the interradicular septum, with a low RI, which is a helpful tool to estimate surgical risks.

Anatomically Guided Implant Site Preparation Technique at Molar Sites

Immediate postextraction implant placement in the areas of multiradicular teeth is a difficult procedure in view of having to place the implant in an ideal position without jeopardizing its initial stability. The surgeon often faces the problem of directing the initial osteotomy in the medial portion of the alveolus with the difficulty of engaging the inter-radicular septum of the extraction socket. The drill may slip continually leading to an inaccurate site preparation, and consequently to a deficient implant insertion. The fixture is often placed directly into either one of the extraction sockets of the tooth to be replaced. The anatomically guided site preparation technique is a very useful tool to perform implant placement in the areas of multiradicular teeth. This approach of implant insertion consists of a progressive preparation of the implant site using the anatomy and geometry of the root of the multiradicular teeth to be extracted as a reference and as an aid to engage the inter-radicular septum. This places the implants in a favorable and proper position from a biomechanical and occlusal standpoint. The objective of this article is to describe the anatomically guided implant site preparation technique as an aid to favorably place dental implants in multiradicular teeth postextraction.

Early tooth movement with a clear plastic appliance in rats

In this preliminary study, we investigated early histologic changes of paradental tissues in response to a clear plastic appliance in rats. Fifteen rats were divided into 3 groups. Group I was the untreated controls; group II received a clear plastic appliance made from a model, with the maxillary left first molar repositioned mesially 0.5 mm from the origin; and group III had a closed-coil spring to move the molar mesially. Specimens were prepared in parasagittal sections, and changes in paradental tissues were evaluated on days 1, 4, and 7 by light microscopy. In group II, the periodontal ligament (PDL) was compressed in the bifurcation and apical areas of the roots of the molar. On day 7, the PDL of the apical and distal aspects of the roots and the bifurcation area showed further compression, with the PDL of the roots stretched along the mesial side. In group III, a disorganized and compressed PDL in the mesial cervical half and interradicular septum was observed, and the stretched fibers were at the distal aspects of the roots after days 4 to 7. Early histologic changes in response to the clear plastic appliance were intrusion and distal tipping despite the intended mesial movement. In this rat model, the observed histologic changes were subject to the direction and magnitude of forces generated by the clear aligner.

Expression of receptor activator of nuclear factor kappa B ligand relates to inflammatory bone resorption, with or without occlusal trauma, in rats

Receptor activator of nuclear factor kappa B ligand (RANKL) is an important factor in osteoclast differentiation, activation and survival; however, its involvement in inflammatory bone resorption, with or without occlusal trauma, is unclear. The purpose of the present study was to investigate the distribution of RANKL-expressing cells in rat periodontium during lipopolysaccharide-induced inflammation with or without occlusal trauma. Lipopolysaccharide was injected into rat gingiva of the lower left first molar to induce inflammation. In addition, the occlusal surface of the upper left first molar of rat was raised by placing a gold inlay to induce occlusal trauma in the lower left first molars. The distribution of RANKL-expressing cells was immunohistochemically observed. In the inflammatory model, many osteoclasts were observed at the apical inter-radicular septum on day 5 and they were reduced by day 10. On the other hand, in the inflammatory model with occlusal trauma, many osteoclasts were still observed on day 10. RANKL expression was similar to the changes in osteoclast number. The expression of RANKL increased in endothelial cells, inflammatory cells and periodontal ligament cells. These findings clearly demonstrated that RANKL expression on endothelial cells, inflammatory cells and periodontal ligament cells is involved in inflammatory bone resorption and the expression is enhanced by traumatic occlusion. These results suggest that RANKL expression on these cells is closely involved in the increase of osteoclasts induced by occlusal trauma.

Bone formation as a potential motive force of tooth eruption in the rat molar

The objectives of this anatomical study were to (1) determine if significant bone growth occurs in the base of the alveolar bony crypt of the first mandibular molar to move the tooth through the eruption pathway; (2) determine if the osteogenesis in the crypt correlates with the published chronological gene expression of bone morphogenetic protein-2 (BMP-2) in the dental follicle; and (3) determine chronologically and regionally the crypt bone activity. To accomplish this, the alveolar bony crypts of rat mandibular molars from postnatal days 3 to 18 were processed and examined by scanning electron microscopy (SEM). In addition, mandibles and teeth of ages 12-18 were prepared for light microscopy. SEM demonstrated that bone formation occurs in the basal (apical) portion of the alveolar bony crypt at day 3, whereas bone resorption concurrently is ongoing in the coronal region of the crypt. By day 9, the crypt is beginning to be reduced in depth as the result of basal bone formation, and by day 14, the base of the crypt immediately under the tooth is almost completely filled with bone to form the interradicular septum. At day 18, the tooth erupts as bone formation likely elevates the molar. Bone growth in the basal area of the crypt correlates with a previous study showing enhanced BMP-2 expression in the dental follicle. Thus, SEM indicates that the motive force of tooth eruption likely is bone formation at the base of the alveolar crypt and this osteogenesis may relate to BMP-2 production in the dental follicle.

Relationship between Porotic Changes in Alveolar Bone and Spinal Osteoporosis

Epidemiological studies have shown that post-menopausal women who do not use an estrogen supplement have fewer teeth than those who do. We hypothesized that changes in the dentition of post-menopausal women might be due to alveolar bone alterations by estrogen deficiency. To clarify this, we analyzed the microstructural alveolar bone changes in ovariectomized monkeys and compared these with their lumbar bone mineral density. The % of baseline bone mineral density showed a significant decrease in the ovariectomized group as compared with the controls. The second-molar interradicular septa in ovariectomized monkeys showed a significantly decreased nodes number, cortices number, and an increased structural model index value. More pores were seen in the ovariectomized group at the top of the septa. This study demonstrated that, in such monkeys, estrogen deficiency led to fragility of the trabecular structure of the molar alveolar bone, and such fragility was inversely correlated with lumbar bone mineral density.

Histologic Evaluation of Three Methods of Periodontal Root Surface Treatment in Humans

Removing subgingival plaque and calculus is a major goal of periodontal treatment. Few attempts have been made to evaluate the use of lasers for root surface debridement in periodontal therapy. The aim of the present study was to compare, histologically, the effects of hand instrumentation, ultrasonic instrumentation, and CO2 lasers on the root surfaces of teeth treated in situ. A total of 33 teeth scheduled for extraction due to severe periodontal disease were divided into three groups. In the first group, teeth were treated by ultrasonic bactericidal curettage (UBC) with an ultrasonic scaler; in the second group, teeth were treated by hand instrumentation; and in the third group, after hand instrumentation, roots were lased by a CO2 laser. The samples were then processed for histological examination. In the first and second groups, plaque and calculus were present in interradicular septa, lacunae, and surface concavities. In the third group, surfaces of specimens treated by a low-power defocused CO2 laser showed areas devoid of cementum, with completely sealed dentinal tubules, and no bacterial cell remnants. The CO2 laser treatment, used at low power and in the defocused mode, combined with traditional mechanical instrumentation, could improve root surface debridement of periodontally involved teeth. More extensive, long-term studies are needed to confirm this hypothesis.

Investigation of periodontal ligament reaction upon excessive occlusal load – osteopontin induction among periodontal ligament cells

The purpose of the present study was to investigate the reaction of the periodontal ligament to excessive occlusal loading by observing the histological changes and osteopontin induction. The possibility of ligand for receptor activator of nuclear factor kappaB (RANKL) participation in osteopontin induction was also discussed. The precise mechanism of periodontal ligament breakdown by excessive occlusal loading remains unclear. We established an experimental model for excessive occlusal loading in vivo. Osteopontin is known to be produced upon mechanical loading and is considered to induce the migration of osteoclasts to the resorption site. RANKL is one of the essential factors for osteoclast maturation and induces the constitutive induction of intracellular osteopontin in vitro. The occlusal surface of the upper left first molars of rats was raised by steel wire bonding in order to induce occlusal trauma. The destruction of the periodontal ligament was observed and the production of osteopontin and RANKL by periodontal ligament cells was detected via immunohistochemistry. Our model produced wide-ranging destruction of the periodontal ligament. From day 3 to day 7, prominent compression of the periodontal ligament and osteoclast migration were observed at the apical interradicular septum. Osteopontin was detected in some osteoclasts, surrounding fibroblasts, and osteoblasts adjacent to the compression area. RANKL was observed from day 1 to day 7 around the osteoblasts and osteoclasts. Our model was useful for the detailed investigation of periodontal ligament breakdown during excessive occlusal loading. Although intracellular osteopontin was produced in osteoclasts with intermittent occlusal loading, the role of this protein in the cells was not clear. No correlation between RANKL distribution and osteopontin production in osteoclasts could be found.

Three-dimensional Changes of the Mandible and Alveolar Bone in the Ovariectomized Rat Examined by Micro-focus Computed Tomography

To clarify the changes of the mandible and alveolar bone in postmenopausal osteoporosis, we examined the changes of structure in mandible and alveolar bone of ovariectomized (OVX) rats. Twelve female Wistar rats (25-week old) were divided into two groups equally. Nine weeks after ovariectomy, we examined the mandibles of OVX and sham control (Sham) rats by micro-focus computed tomography (μCT). Bone volume and trabecular thickness in OVX group were significantly less than those in Sham group, while the trabecular separation in OVX group was significantly wider than that in Sham group. Three-dimensional images from the μCT of the mandible demonstrated a reduced bone volume of the mandibular body in the region of the first molar as well as the inter-radicular septum of the first molar in OVX group. The incisor alveolar bone at the interface between the incisor and the bone marrow in OVX group was significantly thinner than that in Sham group. However, there was no significant difference in the thickness of the medial side of the incisor alveolar bone that did not contain or face the bone marrow. These findings demonstrate that the mandibular bone loss in the OVX rats is predominant adjacent to the bone marrow, suggesting bone loss in postmenopausal osteoporosis occurs mainly at the endosteal surface in mandible.