Cells at the Edge: The Dentin–Bone Interface in Zebrafish Teeth

Bone-producing osteoblasts and dentin-producing odontoblasts are closely related cell types, a result from their shared evolutionary history in the ancient dermal skeleton. In mammals, the two cell types can be distinguished based on histological characters and the cells’ position in the pulp cavity or in the tripartite periodontal complex. Different from mammals, teleost fish feature a broad diversity in tooth attachment modes, ranging from fibrous attachment to firm ankylosis to the underlying bone. The connection between dentin and jaw bone is often mediated by a collar of mineralized tissue, a part of the dental unit that has been termed “bone of attachment”. Its nature (bone, dentin, or an intermediate tissue type) is still debated. Likewise, there is a debate about the nature of the cells secreting this tissue: osteoblasts, odontoblasts, or yet another (intermediate) type of scleroblast. Here, we use expression of the P/Q rich secretory calcium-binding phosphoprotein 5 (scpp5) to characterize the cells lining the so-called bone of attachment in the zebrafish dentition. scpp5 is expressed in late cytodifferentiation stage odontoblasts but not in the cells depositing the “bone of attachment”. nor in bona fide osteoblasts lining the supporting pharyngeal jaw bone. Together with the presence of the osteoblast marker Zns-5, and the absence of covering epithelium, this links the cells depositing the “bone of attachment” to osteoblasts rather than to odontoblasts. The presence of dentinal tubule-like cell extensions and the near absence of osteocytes, nevertheless distinguishes the “bone of attachment” from true bone. These results suggest that the “bone of attachment” in zebrafish has characters intermediate between bone and dentin, and, as a tissue, is better termed “dentinous bone”. In other teleosts, the tissue may adopt different properties. The data furthermore support the view that these two tissues are part of a continuum of mineralized tissues. Expression of scpp5 can be a valuable tool to investigate how differentiation pathways diverge between osteoblasts and odontoblasts in teleost models and help resolving the evolutionary history of tooth attachment structures in actinopterygians.

Finite Element Analysis of the Effect of Dental Implants on Jaw Bone under Mechanical and Thermal Loading Conditions

Dental implants have been studied over the years to replace missing teeth. One of the conditions for the success of implants is their stability and resistance under the applied forces and minimal tension in the surrounding bone. The purpose of this dissertation is numerical and three-dimensional analysis of jaws with implants under mechanical and thermal loading by the finite element method. For this purpose, implant simulations (including ceramic crown, titanium root, and jaw bone) under dynamic and thermal load have been performed in Abacus software. In this simulation, it is considered that the jawbone is composed of two areas, one area is the superficial bone tissue (cortical) and the other part is the spongy tissue. Implants are usually made of different metals or ceramics with a bone-like structure that are compatible with body tissues. Implants are currently made of titanium metal. Therefore, titanium metal has been used for modeling implants in this dissertation. The implant crown is also considered as a ceramic material. In the simulation, the effect of stresses imposed by the implant on the jawbone is performed. In this simulation, mechanical force is applied to the upper part of the implant and force enters the jawbone through the implant, which causes tension at the junction of the implant to the jawbone. To investigate the effect of thermal loads, different temperature conditions are considered by considering the decrease in temperature and increase in temperature on the tooth surface and its effect on the implant and the jaw bone. After validation and ensuring the accuracy of the modeling, it has been observed that, with increasing mechanical load, the stresses created in all parts of the ceramic coating, titanium implants, and jawbone have increased. It is also observed that the stress created in the titanium implant due to the application of negative heat flux was about twice as much as the stress created due to the application of positive heat flux.

MORPHOLOGICAL RESEARCH USAGE OF BIOPLAST - DENT IN EXPERIMENT

The work represents experimental and morphological studies of regeneration of damaged areas of maxillo-facial bones. Time course of healing of induced defects in the low jaw bone filled with bioplast - dent and was studied in experimental rabbits. On days 7, 14, 21 and 28 four rabbits from each group were killed and the defect investigated by X-ray and histological methods. We stained the micropreparations ith hematoxilineeosine. Bioplast - dent granulate exerted the best effect on bone repair. In experiments with bioplast - dent, bone regenerate replaced up to one half of the area of defect by day 28.

Cisto periodontal lateral e cisto odontogênico botrióide

Cystic jaw bone lesions have been largely studied and discussed since the beginning of their recognition. Although many of them have already been well-defined, some of them go on generating divergent opinions, such as the lateral periodontal cyst (LP C) and the botryoid odontogenic cyst (BOC). The objective of this article is to report two cases of unusual characteristics, one of them is about a lateral periodontal cyst and the other one is about a botryoid odontogenic cyst, presenting considerations as to their clinical, radiographic and histological aspects.

CLINICAL PECULIARITIES OF WOUND HEALING IN THE POSTOPERATIVE PERIOD OF SURGICAL TREATMENT OF ALVEOLAR PROCESS ATROPHY OF THE UPPER JAW AND PART OF THE LOWER JAW IN POSTMENOPAUSAL WOMEN

Introduction. Atrophy of the alveolar process of the upper jaw and part of the lower jaw is often observed after the tooth extraction. It is known that the atrophy of bone tissue is most likely observed in the first 12 months after the tooth extraction. According to the Koln classification, atrophy of the bone tissue of the jaws can be vertical, horizontal and combined. The aim of surgical treatment of jaw bone tissue atrophy is to increase the size in the area of alveolar process of the upper jaw and part of the lower jaw to further restoration of masticatory function, in particular with the use of dental implants. The aim of the study: to study the dynamics of wound healing in postmenopausal women with osteopenia after surgical treatment of jaw bone tissue atrophy using osteoplastic material and ossein-hydroxyapatite compound. Materials and methods of the study. There were observed 63 postmenopausal women with osteopenia, aged from 50 to 59 years, with atrophy of the maxillary and mandibular alveolar process, who were performed surgical treatment. During surgery, patients were divided into 3 groups: Group I – 23 patients with atrophy of the alveolar process of the upper jaw and part of the lower jaw with osteopenia, with the reduced bone tissue density, who were treated surgically for bone tissue atrophy using the method worked out by us. Group II – 23 patients with atrophy of the alveolar process of the upper jaw and part of the lower jaw with osteopenia, with the reduced bone density who were performed surgical treatment of atrophy of the jaw bone tissue using osteoplastic material of animal origin. Group III – 23 patients with atrophy of the alveolar process of the upper jaw and part of the lower jaw with the indices of bone tissue density within normal limits, who were performed surgical treatment of atrophy of the jaw bone tissue using osteoplastic material of animal origin. The results of the study. A total of 69 edentulous areas on the upper and lower jaws were examined after surgery for the treatment of jaw bone tissue atrophy. Examination of the postoperative wound was performed during the 3rd, 9th, and 14th day in the absence of complaints from patients during this period, as well as in the presence of signs of complications. Discussion of the results. According to the offered by us method of decortication of the bone tissue of the jaws, which was used to treat patients of group I, the blood supply to the postoperative area and infiltration of bone material with blood due to provoked by decortication of bone tissue bleeding, are improved. Impregnation of bone material with blood promotes angiogenesis in the postoperative area, increasing cellular activity during wound healing. It is known that due to the absence of sufficient blood supply, tissue necrosis occurs [8,9]. In patients of groups II and III the complete healing of the postoperative wound with primary tension took longer than in patients of group I. Also, in 3 patients of group II and in 1 patient of group III the wound dehiscence in the postoperative area was observed. Conclusions. As a result of the performed observations of wound healing after surgical treatment of jaw bone tissue atrophy in patients of groups I, II and III, the least complications were observed in patients of group I in the early postoperative period.

Is the Jaw Bone Micro-Structure Altered in Response to Osteoporosis and Bisphosphonate Treatment? A Micro-CT Analysis

The aim of the study was to quantify the micro-architectural changes of the jaw bone in response to ovariectomy, exposed or not to bisphosphonate treatment. A total of 47 Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and exposed to osteoporosis preventive treatment for eight weeks either with bisphosphonates (alendronate, ALN; group OVX-ALN) three days/week at a dose of 2 mg/kg or with saline solution (untreated control condition; group OVX). The bone morphometric parameters of the trabecular jaw bone were assessed using ex vivo micro-computed tomography. The regions of interest investigated in the maxilla were the inter-radicular septum of the second molar and the tuber. The regions quantified in the mandible included the three molar regions and the condyle. A one-way analysis of variance followed by pairwise comparison using Tukey’s HSD and the Games–Howell test was conducted to explore significant differences between the groups. In the maxilla, OVX decreased the bone volume in the inter-radicular septum of the second molar. Bisphosphonate treatment was able to prevent this deterioration of the jaw bone. The other investigated maxillary regions were not affected by (un)treated ovariectomy. In the mandible, OVX had a significant negative impact on the jaw bone in the buccal region of the first molar and the inter-radicular region of the third molar. Treatment with ALN was able to prevent this jaw bone loss. At the condyle site, OVX significantly deteriorated the trabecular connectivity and shape, whereas preventive bisphosphonate treatment showed a positive effect on this trabecular bone region. No significant results between the groups were observed for the remaining regions of interest. In summary, our results showed that the effects of ovariectomy-induced osteoporosis are manifested at selected jaw bone regions and that bisphosphonate treatment is capable to prevent these oral bone changes.