Histochemical examination on the peri-implant bone with early occlusal loading after the immediate placement into extraction sockets.

Early and immediate loading of dental implants has become a routine procedure in dental practices throughout the world, but the histological feature of peri-implant bone has not been fully understood. Therefore, we aimed to elucidate the histological response of peri-implant bone bearing the early occlusal loading using rat models. Four-week-old male Wistar rats were subjected to extraction of their maxillary left first molars and had titanium implants inserted immediately into the post-extraction sockets. In experimental groups at 1 week after placement, implants were loaded for 1 or 2 weeks by adding adhesive resin on the top of the screws. In control groups, no adhesive resin was added to the implants. After 1 or 2 weeks with loading, rats were fixed with an aldehyde solution for histochemical assessment. Newly-formed bone adhered broadly to the implant surface in both the control and experimental groups. The experimental group loaded for 2 weeks showed thicker trabeculae between the implant threads compared to those in the control group. Osteopontin- and osteocalcin-positive cement lines, which are histological hallmarks of bone remodeling, were narrow and smooth in the experimental groups, while featuring a complex meshwork with thick scalloped lines in the control groups. The index of sclerostin-positive osteocytes located close to implants loaded for 2 weeks was significantly lower than in controls, suggesting that osteoblast activity was preserved. Summarizing, our experimental model suggested that early implant loading increases trabecular thickness in the peri-implant bone tissue in a process that involves the regulation of bone remodeling.

Does an Association Exist Between the Presence of Lower Third Molar and Mandibular Angle Fractures?: A Meta-Analysis.

PURPOSE: The current data suggest that the presence of lower third molars predisposes the patient to a greater risk of mandibular angle fracture. Thus, the present review sought to determine whether an association exists between the presence of a lower third molar and the occurrence of a mandibular angle fracture in adults and to assess the influence of third molar position according to the Pell and Gregory classification. MATERIALS AND METHODS: The present study was a systematic review and meta-analysis of analytical observational studies. The present review included all reports of the relationship between mandibular angle fractures and lower third molars. No restriction regarding year, language, or publication status was used. The review protocol was registered at the PROSPERO database (registration no. CRD42016047057). Electronic searches unrestricted for publication period and language were performed in the PubMed, Scopus, SciELO, and Latin American and Caribbean Health Sciences databases. Google Scholar and OpenGrey databases were used to search the "gray literature," avoiding selection and publication biases. The entire search was performed by 2 eligibility reviewers. Association and proportion meta-analyses were planned for the studies with sufficient data. The primary predictor variable was the relationship between the presence of a lower third molar and the development of mandibular angle fractures. The secondary outcome variables were the vertical and horizontal positions of the lower third molar, according to the Pell and Gregory classification and their relationship to the susceptibility to developing a mandibular angle fracture. RESULTS: The search strategies resulted in 411 studies, from which 16 were selected for qualitative and quantitative review. The association meta-analysis included all the selected studies and showed that patients with lower third molars are 3.16 times more likely to develop mandibular angle fractures. The proportion meta-analysis included 5 studies and showed that the overall rate of mandibular angle fractures was 51.58% and that positions III and C are more likely to result in fracture, with a rate of 59.84 and 63.67%, respectively. CONCLUSIONS: The results of the present study have shown that the presence of impacted third molars increases by 3.16 times the risk of mandibular angle fractures in adults, with the greatest risk present when third molars are classified as IIIC according to Pell and Gregory. The available evidence is not sufficiently robust to determine whether third molar presence or the level of impaction is the main causative factor for the occurrence of mandibular angle fractures.

MicroCT assessment of bone microarchitecture in implant sites reconstructed with autogenous and xenogenous grafts: a pilot study.

PURPOSE: To assess bone microarchitecture in maxillary sites grafted with autogenous or xenogenous grafts as well as to demonstrate the usefulness of microCT in dental implant research. MATERIALS AND METHODS: Samples (n = 12) consisting of titanium fixation screws covered by at least 0.5-1 mm of human bone were obtained from 17 sites grafted with autogenous or xenogenous materials and prepared for microCT scanning and conventional histology. Bone histomorphometric parameters were evaluated in three distinct regions (graft region, transitional region, and native bone region). Three-dimensional (3D) bone-to-implant contact (BIC) calculation was performed using microCT data. Histological sections were used to calculate two-dimensional (2D) BIC percentages, which were compared with values obtained from 2D microCT images. RESULTS: Histomorphometric parameters varied according to the type of graft used, but sites reconstructed with autogenous bone showed higher mean values in general. In autograft samples, indices for parameters such as Tb.Th and Tb.Sp were significantly different when the native bone region was compared to the graft region. While a higher mean 3D BIC was found in the native bone region for both graft materials, significant BIC differences were absent when graft types were compared. The 2D BIC percentages obtained from histological and microCT images were similar. CONCLUSIONS: Autografts outperformed the xenogenous material used in this study concerning the histomorphometric parameters assessed. While graft type did not seem to influence 3D BIC, the native bone region showed the highest BIC percentages when compared to the other regions in both graft groups. In addition, 2D BIC ratios were similar regardless of graft material or image source (histological sections x microCT slices). Taken together, our findings suggest that microCT is an effective tool for 2D and 3D histomorphometric and BIC assessments in dental implant research.

FGF23 is mainly synthesized by osteocytes in the regularly distributed osteocytic lacunar canalicular system established after physiological bone remodeling.

This study aimed to evaluate whether the immunolocalization of fibroblast growth factor (FGF) 23 and dentin matrix protein 1 (DMP1) is associated with the spatial regularity of the osteocyte lacunar canalicular system(s) (OLCS). Femora of 12-weeks-old male ICR mice were fixed with 4% paraformaldehyde, decalcified with a 10% EDTA solution and then embedded in paraffin. We have devised a triple staining procedure that combines silver impregnation, alkaline phosphatase (ALPase) immunohistochemistry and tartrate-resistant acid phosphatase (TRAPase) enzyme histochemistry on a single paraffin section. This procedure permitted the visualization of ALPase-positive plump osteoblasts and several TRAPase-positive osteoclasts on those bone matrices featuring irregularly arranged OLCS, and of ALPase-positive bone lining cells on the bone matrix displaying the well-arranged OLCS. As observations proceeded from the metaphysis toward the diaphysis, the endosteal cortical bone displayed narrower bands of calcein labeling, accompanied by increased regularity of the OLCS. This implies that the speed of bone deposition during bone remodeling would affect the regularity of the OLCS. While DMP1 was evenly localized in all regions of the cortical bones, FGF23 was more abundantly localized in osteocytes of cortical bones with regularly arranged OLCS. In cortical bones, the endosteal area featuring regular OLCS exhibited more intense FGF23 immunoreaction when compared to the periosteal region, which tended to display irregular OLCS. In summary, FGF23 appears to be synthesized principally by osteocytes in the regularly distributed OLCS that have been established after bone remodeling.

Histochemical Examination on Periodontal Tissues of Klotho-Deficient Mice Fed With Phosphate-Insufficient Diet.

To elucidate which of elevated serum concentration of inorganic phosphate (Pi) or disrupted signaling linked to αklotho/fibroblast growth factor 23 (FGF23) is a predominant regulator for senescence-related degeneration seen in αKlotho-deficient mice, we have examined histological alteration of the periodontal tissues in the mandibular interalveolar septum of αKlotho-deficient mice fed with Pi-insufficient diet. We prepared six groups of mice: wild-type, kl/kl, and αKlotho-/- mice with normal diet or low-Pi diet. As a consequence, kl/klnorPi and αKlotho-/-norPi mice showed the same abnormalities in periodontal tissues: intensely stained areas with hematoxylin in the interalveolar septum, dispersed localization of alkaline phosphatase-positive osteoblasts and tartrate-resistant acid phosphatase-reactive osteoclasts, and accumulation of dentin matrix protein 1 in the osteocytic lacunae. Although kl/kllowPi mice improved these histological abnormalities, αKlotho-/- lowPi mice failed to normalize those. Gene expression of αKlotho was shown to be increased in kl/kl lowPi specimens. It seems likely that histological abnormalities of kl/kl mice have been improved by the rescued expression of αKlotho, rather than low concentration of serum Pi. Thus, the histological malformation in periodontal tissues in αKlotho-deficient mice appears to be due to not only increased concentration of Pi but also disrupted αklotho/FGF23 signaling.

Surgical Maxillary Advancement Increases Upper Airway Volume in Skeletal Class III Patients: A Cone Beam Computed Tomography-Based Study.

STUDY OBJECTIVES: Although volumetric changes of the upper airway occur following surgical advancement of the maxilla, few studies investigated these changes using three-dimensional imaging techniques. Thus, the goal of this study was to verify whether the surgical advancement of the maxilla affects the volume of the upper airway and to determine any association of these volume changes with sex and age. METHODS: Preoperative and postoperative cone-beam computed tomography (CBCT) scans of 14 patients (8 male and 6 female) who underwent maxillary advancement to correct skeletal class III deformities were assessed to determine the postoperative volumetric changes in the upper airway. Preoperative and postoperative airway volume measurements were compared by means of paired t-test, which was also used to compare airway volume between genders. Pearson correlation coefficient was used to verify whether a correlation between age and upper airway volume was present. RESULTS: Maxillary advancement produced significant upper airway volume increases (mean 20.94%, p < 0.05) on nearly half of our sample. However, sex and age did not seem to influence upper airway volume in our sample of skeletal class III patients. CONCLUSIONS: Surgical advancement of the maxilla may produce significant volume increases in the upper airway of skeletal class III patients regardless of sex and age.

Altered distribution of extracellular matrix proteins in the periodontal ligament of periostin-deficient mice.

Verifying whether periostin affects the distribution of type I collagen, fibronectin and tenascin C in the periodontal ligament (PDL) is important to contribute to a more thorough understanding of that protein's functions. In this study, we have histologically examined incisor PDL of mandibles in 20 week-old male wild-type and periostin-deficient (periostin-/-) mice, by means of type I collagen, fibronectin, tenascin C, proliferating cell nuclear antigen, matrix metallo-proteinase (MMP)-1 and F4/80-positive monocyte/macrophage immunostaining, transmission electron microscopy and quantitative analysis of cell proliferation. Wild-type PDL featured well-arranged layers of collagen bundles intertwined with PDL cells, whose longitudinal axis ran parallel to the collagen fibers. However, cells in the periostin-/- PDL were irregularly distributed among collagen fibrils, which were also haphazardly arranged. Type I collagen and fibronectin reactivity was seen throughout the wild-type PDL, while in the periostin-/- PDL, only focal, uneven staining for these proteins could be seen. Similarly, tenascin C staining was evenly distributed in the wild-type PDL, but hardly seen in the periostin-/- PDL. MMP-1 immunoreactivity was uniformly distributed in the wild-type PDL, but only dotted staining could be discerned in the periostin-/- PDL. F4/80-positive monocyte/macrophages were found midway between tooth- and bone-related regions in the wild-type PDL, a pattern that could not be observed in the periostin-/- PDL. In summary, periostin deficiency may not only cause PDL collagen fibril disorganization, but could also affect the distribution of other major extracellular matrix proteins such as fibronectin and tenascin C.

Altered distribution of bone matrix proteins and defective bone mineralization in klotho-deficient mice.

In an attempt to identify the histological properties of the klotho-deficient (kl/kl) bone matrix, bone mineralization and the localization of Ca(2+)-binding bone matrix proteins - osteocalcin, dentin matrix protein-1 (DMP-1) and matrix Gla protein (MGP) - were examined in kl/kl tibiae. While a widespread osteocalcin staining could be verified in the wild-type bone matrix, localization of the same protein in the kl/kl tibiae seemed rather restricted to osteocytes with only a faint staining of the whole bone matrix. In wild-type mice, MGP immunoreactivity was present at the junction between the epiphyseal bone and cartilage, and at the insertion of the cruciate ligaments. In kl/kl mice, however, MGP was seen around the cartilaginous cores of the metaphyseal trabeculae and in the periphery of some cells of the bone surface. DMP-1 was identified in the osteocytic canalicular system of wild-type tibiae, but in the kl/kl tibiae this protein was mostly found in the osteocytic lacunae and in the periphery of some cells of the bone surface. Mineralization of the kl/kl bone seemed somewhat defective, with broad unmineralized areas within its matrix. In these areas, mineralized osteocytes along with their lacunae and osteocytic cytoplasmic processes were found to have intense osteocalcin and DMP-1 staining. Taken together, it might be that the excessive production of Ca(2+)-binding molecules such as osteocalcin and DMP-1 by osteocytes concentrates mineralization around such cells, disturbing the completeness of mineralization in the kl/kl bone matrix.

Sclerostin is differently immunolocalized in metaphyseal trabecules and cortical bones of mouse tibiae.

Sclerostin, an osteocyte-derived molecule, has been reported to serve as a negative regulator of osteoblastic activity as well as bone remodeling. However, there is no report that verified the regional difference for sclerostin synthesis, and in this study we have investigated immunolocalization of sclerostin by comparing dentin matrix protein (DMP) 1, an osteocyte-derived factor broadly expressed in tibial metaphyses and cortical bone. In metaphyseal primary trabecules, a site of bone modeling, strong DMP1-reactivity was observed in osteocytic lacunar-canalicular system (OLCS), while faint staining for sclerostin was visible only in a few osteocytes. In secondary trabecules, in which bone remodeling begins, some osteocytes showed intense sclerostin-immunopositivity, though there were many DMP1-positive osteocytes. In cortical bone, there were more osteocytes reactive for sclerostin, when compared with those in the secondary trabecules. Silver impregnation verified that immature, primary trabecules contained randomly-oriented OLCS, while mature, cortical bone showed geometrically well-arrangement of OLCS. Taken together, though DMP1 is broadly synthesized in bone, sclerostin appears to be abundantly synthesized in regular OLCS of cortical bone, but less produced in irregular OLCS as seen in primary trabecules, indicating the regional difference for sclerostin synthesis.