PrPc is temporospatially expressed in molar development of rats

Odontogenesis, tooth development, is derived from two tissue components: ectoderm and neural crest‐derived mesenchyme. Cyto‐differentiation of odontogenic cells during development involves time‐dependent and sequential regulation of genetic programs. This study was conducted to detect molecules implicated in cyto‐differentiation of developing molar germs of rats. Differential display‐PCR revealed that PrP^c was differentially expressed between cap/early bell‐staged germs (maxillary 3rd molar germs) and root formation‐staged germs (maxillary 2nd molar germs) at postnatal day 9. Both levels of PrP^c mRNA and protein expression were higher in the root formation stage than the cap/early bell stage and increased in a time‐dependent manner. Immunofluorescence revealed for the first time that PrP^c was not localized in the enamel organ, but localized in dental follicular cells for the development of the periodontal ligament and cementum as well as odontoblasts, both of which are of neural crest origin. These results suggest that the physiological functions of the PrP^c in tooth development may be implicated in the differentiation of neural crest‐derived mesenchyme including the periodontal tissues for root formation rather than epithelial tissue. Anat Rec, 296:1929–1935, 2013. © 2013 Wiley Periodicals, Inc.     

Alteration in the expression level of calbindin D28k in the periodontal ligament of the rat molar during experimental tooth movement.

The present immunohistochemical study was designed to investigate changes in the distribution and expression level of calbindin D28k in the periodontal ligament during experimental tooth movement in the rat molar to clarify the physiological role of this protein in the ligament. In normal animals, calbindin D28k-like immunoreactivity appeared sparsely in spindle-shaped cells in the alveolar half of the periodontal ligament. Electron microscopic observations showed that these immunoreactive cells were characterized by well-developed rough-surfaced endoplasmic reticulum and phagosomes--which often contained collagen fibers--suggesting that these cells could be categorized as periodontal fibroblasts. Twelve hours following the onset of the experimental tooth movement, cells positive for calbindin D28k increased in number in the periodontal ligament, especially in the alveolar half of the pressured side. Immunoelectron microscopy showed that the calbindin D28k-immunopositive cells had morphological features similar to those of fibroblasts in the normal ligament, and that these cells occasionally made contact with immunonegative macrophage-like cells. Immunopositive cells gradually decreased in number, and the distribution of the cells and intensity of the immunoreactivity returned to normal levels by 14 days following the induction of the experimental tooth movement. The present results suggest that calbindin D28k plays an important role in the homeostasis and cyto-protection of fibroblasts in the periodontal ligament at the initial phase of experimental tooth movement.     

骨膜蛋白基因敲除鼠正畸牙齿移动模型的建立及验证

目的:建立小鼠以及骨膜蛋白（PN）基因敲除小鼠正畸牙齿移动模型,并分析相关信号通路。方法:根据实验条件把小鼠分为4组:C57小鼠未加力组和加力组、PN基因敲除小鼠组上颌加力组和未加力组,每组5只,其中加力组加力5 d。处死后,显微CT扫描上下颌骨,并采用RT-PCR检测牙周膜中相关基因的表达水平。结果:与C57小鼠相比,PN基因敲除小鼠的牙槽骨出现明显的吸收,牙周膜连续性中断破坏。在C57小鼠中,加力组牙周膜中的PN、粘着斑激酶（FAK）和TGF-β1表达水平显著增强（P<0.05）;在基因敲除鼠中,加力组牙周膜中的FAK（P<0.05）和TGF-β1表达水平显著增强（P<0.01）;在同样加力的条件下,C57小鼠与PN基因敲除小鼠相比,TGF-β1显著降低（P<0.05）,FAK表达水平显著升高（P<0.01）。结论:PN是正畸作用下牙周膜的改建过程一个重要分子环节,发挥着转导调控作用,TGF-β1--PN--FAK信号通路参与调控正畸作用下牙周膜的改建过程。     

A role for decorin in the structural organization of periodontal ligament

Decorin is a small leucine-rich proteoglycan that interacts with several matrix molecules, including various types of collagen and growth factors, and suppresses the growth of neoplastic cells by an epidermal growth factor (EGF) receptor-mediated pathway. Decorin is abundantly expressed in the periodontal connective tissues during development and tissue maintenance. In periodontal disease, which is one of the most common diseases in the human kind, the level of decorin is decreased in the periodontal connective tissue. Abnormal expression of decorin may also associate with certain inherited disorders that involve increased susceptibility to severe periodontal disease in the early childhood. Therefore, we investigated the periodontal tissues of mice with targeted disruption of the decorin gene. Gross and microscopic analyses showed that decorin-deficient mice appeared to have normal tooth development and eruption, and there were no signs of periodontal disease. However, electron microscopic analysis revealed abnormal morphology and organization of the collagen fibrils in the periodontal ligament. The number of periodontal ligament fibroblasts in the decorin-deficient mice was also increased about two-fold as compared with the wild-type mice. In cell culture, ectopic overexpression of decorin in NIH 3T3 fibroblasts or decorin added exogenously to periodontal fibroblasts suppressed cell growth. However, blocking the EGF receptor tyrosine kinase activity did not prevent the decorin-elicited growth suppression in periodontal fibroblasts. Additionally, decorin did not induce a marked increase in the relative expression of p21 mRNA in periodontal fibroblasts. Therefore, decorin appeared to regulate growth of normal periodontal fibroblasts by a mechanism distinct from that reported for neoplastic cells. The findings demonstrate that decorin plays a role in the organization of collagen fibrils and regulates cell proliferation in the periodontal ligament.     

Osteoclast induction in periodontal tissue during experimental movement of incisors in osteoprotegerin‐deficient mice

Osteoprotegerin (OPG) is a novel secreted member of the tumor necrosis factor (TNF) receptor superfamily that negatively regulates osteoclastogenesis. The receptor activator of the NFKB ligand (RANKL) is one of the key regulatory molecules in osteoclast formation and binds to OPG. In this study, it was suggested that OPG and RANKL are involved in alveolar bone remodeling during orthodontic tooth movement. We examined RANKL localization and osteoclast induction in periodontal tissues during experimental movement of incisors in OPG‐deficient mice. To produce orthodontic force, an elastic band was inserted between the upper right and left incisors for 2 or 5 days, and the dissected maxillae were examined for cytochemical and immunocytochemical localization of tartrate‐resistant acid phosphatase (TRAP), vacuolar‐type H⁺‐ATPase, and RANKL. Compared to wild‐type OPG (+/+) littermates, TRAP‐positive multinucleated cells were markedly induced in the periodontal ligament (PDL) on the compressed side and in the adjacent alveolar bone of OPG‐deficient mice. These multinucleated cells exhibited intense vacuolar‐type H⁺‐ATPase along the ruffled border membranes. Because of accelerated osteoclastic resorption in OPG‐deficient mice, alveolar bone was severely destroyed and partially perforated at 2 and 5 days after force application. In both wild‐type and OPG‐deficient mice, RANKL expression became stronger at 2 and 5 days after force application than before force application. There was no apparent difference in intensity of RANKL expression between OPG (+/+) littermates and OPG‐deficient mice. In both wild‐type and OPG‐deficient mice, expression of RANKL protein was detected in osteoblasts, fibroblasts, and osteoclasts mostly located in resorption lacunae. These results suggest that during orthodontic tooth movement, RANKL and OPG in the periodontal tissues are important determinants regulating balanced alveolar bone resorption. Anat Rec 266:218–225, 2002. © 2002 Wiley‐Liss, Inc.     

Immunocytochemical localization of amelogenins in the deciduous tooth germs of the human fetus

The immunocytochemical localization of amelogenins in the developing deciduous tooth germs of 6-month-old human fetuses was investigated by the protein A-gold method using an antiserum against porcine 25K amelogenin. The inner enamel epithelial cells and underlying matrix showed no amelogenin-like immunoreactivity. Distinct immunoreactivity was initially shown by fine fibrils found beneath the intact basal lamina of preameloblasts at the early differentiation stage. At the late differentiation stage, amelogenin-like immunoreactivity was shown by a fine granular material within the extracellular matrix as well as by the Golgi apparatus, secretory granules, lysosomal structures, coated vesicles, and coated pits of preameloblasts with a disrupted basal lamina. At the formative stage, the localization of immunoreactivity in secretory ameloblasts was similar to that in preameloblasts during the late differentiation stage. However, immunopositive coated vesicles and coated pits were only found at the early stage of matrix formation. The calcified enamel matrix and stippled material showed intense immunoreactivity. Immunocytochemical labeling of the enamel matrix appeared as a gradient, decreasing from the enamel surface to the dentinoenamel junction. No maturation stage of ameloblasts existed in the tooth germs examined. In predentin and dentin, amelogenin-like immunoreactivity was occasionally detected on odontoblasts and their processes, but odontoblasts and cells of the stratum intermedium contained no immunoreactive elements. These findings confirmed that the secretory ameloblast in the human deciduous tooth germ is responsible for the synthesis and secretion of enamel proteins.     

Osteoclast induction in periodontal tissue during experimental movement of incisors in osteoprotegerin-deficient mice

Osteoprotegerin (OPG) is a novel secreted member of the tumor necrosis factor (TNF) receptor superfamily that negatively regulates osteoclastogenesis. The receptor activator of the NFKB ligand (RANKL) is one of the key regulatory molecules in osteoclast formation and binds to OPG. In this study, it was suggested that OPG and RANKL are involved in alveolar bone remodeling during orthodontic tooth movement. We examined RANKL localization and osteoclast induction in periodontal tissues during experimental movement of incisors in OPG-deficient mice. To produce orthodontic force, an elastic band was inserted between the upper right and left incisors for 2 or 5 days, and the dissected maxillae were examined for cytochemical and immunocytochemical localization of tartrate-resistant acid phosphatase (TRAP), vacuolar-type H(+)-ATPase, and RANKL. Compared to wild-type OPG (+/+) littermates, TRAP-positive multinucleated cells were markedly induced in the periodontal ligament (PDL) on the compressed side and in the adjacent alveolar bone of OPG-deficient mice. These multinucleated cells exhibited intense vacuolar-type H(+)-ATPase along the ruffled border membranes. Because of accelerated osteoclastic resorption in OPG-deficient mice, alveolar bone was severely destroyed and partially perforated at 2 and 5 days after force application. In both wild-type and OPG-deficient mice, RANKL expression became stronger at 2 and 5 days after force application than before force application. There was no apparent difference in intensity of RANKL expression between OPG (+/+) littermates and OPG-deficient mice. In both wild-type and OPG-deficient mice, expression of RANKL protein was detected in osteoblasts, fibroblasts, and osteoclasts mostly located in resorption lacunae. These results suggest that during orthodontic tooth movement, RANKL and OPG in the periodontal tissues are important determinants regulating balanced alveolar bone resorption.     

Periostin is expressed within the developing teeth at the sites of epithelial-mesenchymal interaction.

Periostin was originally isolated as an osteoblast-specific factor that functions as a cell adhesion molecule for preosteoblasts and is thought to be involved in osteoblast recruitment, attachment, and spreading. The protein was renamed "periostin" because of its expression in the periosteum and periodontal ligament, indicating a potential role in bone and maintenance of tooth structure. Periostin has structural similarity to insect fasciclin-I and can be induced by TGF-beta and Bmp2. Because tooth and periodontium development is a well-described genetic model for organogenesis governed by a reciprocal set of epithelial-mesenchymal interactions, thought to be controlled by various TGF-beta superfamily members, we investigated whether periostin is present during tooth morphogenesis. Both periostin mRNA and protein expression were analyzed throughout normal tooth development (embryonic day [E] 9.5-newborn) and within both Bmp4- and Msx2-null embryos. Periostin mRNA is initially present within the E9.5 first branchial arch epithelium and then shifts to underlying ectomesenchyme. Both mRNA and protein are asymmetrically localized to the lingual/palatal and buccal side during the early epithelial-mesenchymal interactions. Periostin is also present in dental papilla cells and within the trans-differentiating odontoblasts during the bell and hard tissue formation stages of tooth development. We suggest that periostin plays multiple roles as a primary responder molecule during tooth development and may be linked to deposition and organization of other extracellular matrix adhesion molecules during maintenance of the adult tooth, particularly at the sites of hard-soft tissue interface.     

The development of the periodontium. A transplantation and autoradiographic study

First molar tooth germs were dissected from one-day-old mice; placed for one hour in McCoy's medium containing 10 μc tritiated thymidine and transplanted subcutaneously into young adult animals of the same strain. Seven, 14, 21 and 28 days after implantation the host animals were sacrificed and the transplants harvested. The transplants were then serially sectioned and autoradiographs prepared. Control sections were prepared of first molar tooth germs in situ, after dissection from the jaws and after labelling with tritiated thymidine. Forty-nine of the 115 transplanted tooth germs continued development with the formation of enamel, dentine, cement, periodontal ligament and bone. In some instances the transplanted tooth germs “erupted” through the skin with the establishment of an epithelial attachment. Examination of control sections showed that the transplants consisted of dental organ, dental papilla and a layer of ectomesenchymal cells continuous with the dental papilla and investing the dental organ. Examination of autoradiographs of the transplants showed labelling of cementoblasts and periodontal ligament fibroblasts, thereby establishing their origin from the ectomesenchymal cells investing the tooth germ.     

Differential Expression of Cyclophilin A and EMMPRIN in Developing Molars of Rats

A complex and intricate cascade of gene expression is essential for late stage tooth development. This study was performed to detect molecules involved in dental hard tissue formation and tooth eruption by comparing gene expression in cap stage molar germs (before eruptive movement and dental hard tissue formation) with that in root formation stage molar germs (after eruptive movement and dental hard tissue formation). DD‐PCR revealed that cyclophilin A (Cyp‐A), a potent chemoattractant for monocytes as well as a ligand for extracellular matrix metalloproteinase inducer (EMMPRIN) was expressed differentially in the two stages molar germs. The levels of Cyp‐A and EMMPRIN mRNA were significantly higher at the root formation stage than at the cap and crown stages of the molar germs. Immunofluorescence showed that Cyp‐A and EMMPRIN were expressed strongly in the follicular cells overlaying the occlusal region of the molar germs at the root formation stage. In contrast, their immunoreactivity was weak in the follicular tissues and was not region‐specific in molar germs at the cap stage. In addition, the MCP‐1 and CSF‐1 mRNA levels increased in parallel to that of Cyp‐A mRNA and the increased number of osteoclasts at the occlusal region. Immunoreactivity against Cyp‐A and EMMPRIN was also observed in the fully differentiated ameloblasts and odontoblasts. This study suggests that Cyp‐A and EMMPRIN play roles in the maturation of dental hard tissue and the formation of an eruption pathway. Anat Rec, 2012. © 2011 Wiley Periodicals, Inc.     

Tooth transplantation in the mouse. I. The use of procion dyes and tritiated proline in a study of syngeneic tooth germ transplantation

Tooth germs of first molars from four- to six-day old mice were transplanted heterotopically into the connective tissue under the dorsal skin of adult syngeneic recipients. The rate of the transplants was studied by histologic staining, vital staining with procion dyes, and autoradiography. Together these methods provided the following picture of the development of the transplant. Extraction of the tooth germ severs its vascular connections and disturbs the nutritional environment of the tooth so that many cells undergo necrosis and degeneration. The resulting inflammatory response clears the transplant of necrotic tissue, leaving a fibrous pulp of low cellularity and an extensively disrupted odontoblastic layer; the enamel organ is reduced to only a few epithelial cells. In the second week following transplantation, however, the surviving cells start to proliferate and the tissues of the transplant begin to reorganize. Reorganization starts at the apical foramen and spreads to the rest of the tooth. The central pulp is penetrated by new blood vessels, its cellular content is reestablished, and its morphology returns to normal. Odontoblasts start producing dentin which at first is highly irregular and contains many cells (osteodentin). Later the dentin formation becomes more and more regular and the dentin assumes its normal tubular structure. New enamel is not formed at any time after transplantation. The cells of the enamel organ undergo squamous metaplasia and form epithelial cysts. Abortive root formation is observed but typical roots never develop. Rudiments of periodontal ligament develop rarely. The transplants are enclosed in a capsule of connective tissue. It is concluded that the heterotopically transplanted tooth germs maintain their capability to recover, develop, and differentiate in syngeneic recipients. Although almost all of the developmental processes continue in the transplant after a period of adjustment, some of them are abortive.     

Elastic system fibers in rat incisor periodontal ligament - immunohistochemical study using sections of fresh-frozen un-demineralized tissues

The aim of this study was to examine the localization and distribution of the components of elastic system fibers in the periodontal ligament of continuously erupting rat incisors in an effort to understand the mechanism of the eruption of the tooth. Sections of fresh-frozen, un-demineralized incisors of the rat mandible were prepared for immunohistochemical localization of elastin, fibrillin-2 and microfibril-associated glycoprotein-1 (MAGP-1). The structure of the periodontal ligament was well preserved in sections of fresh-frozen tissues. At the basal region of the ligament, intense immunolabelling for fibrillin-2 and MAGP-1 was observed as dot-like structures (transversely sectioned fibers) mainly on the tooth side of the ligament close to the cementum. These dot-like structures gradually increased in number towards the incisal area and were distributed throughout the tooth side of the ligament. This pattern of distribution was the same as that of reported oxytalan fibers. Elastin-immunopositive fibers were also detected in the ligament, although the labelling was limited and distribution was sparse. In conclusion, both fibrillin-2 and MAGP-1 immunopositive fibers may serve as a scaffold for deposition of tropoelastin during elastogenesis in the periodontal ligament. They may also provide guidance for the migration of fibroblasts to the occlusive side, which generates contractile forces for the movement of the tooth for continuous eruption of incisors.     

Immunohistochemical localization of heat shock protein 25 (HSP 25) during root formation of the rat molar

The present study investigated the immunohistochemical localization of heat shock protein 25 (HSP 25) of rat molar teeth during root formation. Most, probably all, cells of the epithelial rest of Malassez (ERM cells) had immunoreaction for laminin, a marker protein for basement membrane. During root formation, HSP 25 immunoreactivity was observed in odontoblasts, cells at the subodontoblastic layer, and those in close proximity to the acellular cementum. HSP 25-immunopositive cells at the subodontoblastic layer were present only at the apical region. Most HSP 25-immunoreactive cells in close proximity to the cementum lacked laminin immunoreactivity. However, at postnatal day 28 a small number of cells showed immunoreaction for both HSP 25 and laminin at the cervical and bifurcational regions. Under the electron microscope, most HSP 25-immunoreactive cells along the surface of the cementum were round and contained rich organelles such as mitochondria and rough endoplasmic reticulum. They lay between fiber bundles of the periodontal ligament. The localization and morphological features of these HSP 25-immunoreactive cells resemble those of cementoblasts. On the other hand, HSP 25-immunoreactive cells at the cervical region were oval and contained few cell organelles. They were closely apposed to each other, and separated from the surrounding tissues with basal lamina. These features were similar to those of mature ERM cells. In contrast, cells with microvillus-like processes and relatively rich mitochondria, which were similar to immature ERM cells, had no immunoreaction for HSP 25. These results suggest that HSP 25 may be involved in shape alterations of ERM cells, cementoblasts, and odontoblasts during differentiation.     

Expression of Basement Membrane Components in the Dental Papilla Mesenchyme of Monkey Tooth Germs—An Immunohistochemical Study

The present work, which employs indirect immunoperoxidase methods, demonstrates electron microscopic localization of three major basement membrane (BM) components—type IV collagen, laminin, and heparan sulfate proteoglycan—at the early stages of odontogenesis in tooth germs of the Japanese macaque (Macacafuscata). Intense immunostaining for each examined component occurred at the interface between the inner enamel epithelium and the dental papilla mesenchyme. At higher magnification, immunoreaction products were observed both in the lamina densa and lamina fibroreticularis. Fuzzy substances occurring very close to the lamina fibroreticularis manifested moderate immunoreactivity. In addition, immunostaining took place in the dental papilla mesenchyme. The dental papilla cells located close to the BM demonstrated immunoreactive material mainly on plasma membranes facing the BM. Reaction products were also observed in large concavities formed in some areas of the cell surfaces; and small, immunopositive vesicles occurred close to the plasma membrane. Immunoreaction products could be found in the cisternae of the rough endoplasmic reticulum of some mesenchymal cells.

These findings suggest that dental papilla mesenchymal cells may produce the three major BM components and those of the components that are incorporated into the dental BM—particularly into the lamina fibroreticularis—during tooth development.     

牙胚组织中可分离得到大量间充质干细胞

背景：已经有研究从牙髓、牙囊和牙周组织中分离得到间充质干细胞。牙胚是牙的前体,能否从中直接分离间充质干细胞,目前未知。 目的：从人流产胎儿牙胚中分离间充质干细胞,检测其生物学特征。 方法：无菌条件下挖出水囊流产胎儿牙床中的整个牙胚,剪碎后分别用胶原酶Ⅱ和胰酶消化,过滤除去颗粒物后,细胞悬液用培养液洗涤,培养、扩增得到贴壁细胞,进行细胞形态学观察、免疫表型测定和多向分化功能鉴定。 结果与结论：经过3次传代后,从单个胎儿牙胚中即可获得超过10⁷形态均匀的、梭形贴壁细胞,其表达CD105、CD73、CD90和CD44等表面标志,不表达CD34、CD45标志;在体外向成骨、成脂分化,在体内可以分化为软骨细胞。提示用贴壁法可从人胎儿牙胚中分离得到大量的间充质干细胞。     

Immunoexpression of aquaporin-1 in the rat periodontal ligament during experimental tooth movement

This study examined the immunoexpression pattern of aquaporin-1 (AQP1), first identified as a water channel protein, in the periodontal ligament of rat molars during experimental tooth movement to clarify its role in periodontal responses in an overloaded model by the insertion of a piece of elastic band. In the control group without any treatment, the cementoblasts and osteogenic cells as well as the vascular endothelial cells showed AQP1 immunoreaction. In the experimental group, hyalinized tissue and intensely AQP1 positive amorphous structures which were identified as degenerated endothelial cells by immunoelectron microscopy, occurred at the compression side on Days 1 and 3. AQP1 immunoreaction came to be stronger in the intact endothelial cells around the hyalinized tissue. The hyalinized tissue had almost disappeared by Day 5 when many macrophages reactive to acid phosphatase activity appeared. The periodontal width on Day 7 became almost the same as that in the control group. These findings indicate that the hyalinized tissue and damaged AQP1 positive endothelial cells are phagocytized by macrophages which have temporally migrated, and suggest that the surviving endothelial cells with intense AQP1 reaction are involved in periodontal regeneration by capillary sprouting.     

Periostin, a novel marker of intramembranous ossification, is expressed in fibrous dysplasia and in c-Fos-overexpressing bone lesions

Fibrous dysplasia is a benign bone disease caused by a mutation in the gene for the stimulatory guanine nucleotide-binding protein Gs alpha, leading to high cyclic adenosine monophosphate levels. Histologically, fibrous dysplasia is characterized by the production of fibrous tissue accompanied by the deposition of ectopic type I collagen and other bone-associated extracellular matrix proteins, as well as by irregular woven intramembranous bone onto which type I collagen-containing Sharpey fibers are often attached. Fibrous dysplasia is also characterized by high expression of c-Fos/c-Jun, known targets for cyclic adenosine monophosphate signaling. In this study, we examined the expression of the bone-related extracellular matrix protein, periostin, and its known receptor, integrin alpha v beta 3 (CD51/61), in normal bones as well as in fibrous dysplasia. Immunohistochemistry and in situ hybridization studies revealed that periostin was expressed in the extracellular matrix during intramembranous but not endochondral ossification, as well as in the fibrous component of fibrous dysplasia; and all cells adjacent to periostin-positive regions expressed CD51/61. Importantly, periostin was abundantly localized to Sharpey fibers. To investigate the contribution of c-Fos, we examined transgenic mice overexpressing c-fos, which develop sclerotic lesions closely resembling those found in fibrous dysplasia. In all lesions, transformed osteoblasts expressed high levels of periostin, whereas normal osteoblasts did not. Our results show that periostin is a novel marker for intramembranous ossification, and is a good candidate as a diagnostic tool and/or a therapeutic target in fibrous dysplasia. Moreover, the Gs alpha-cyclic adenosine monophosphate-c-Fos pathway might represent one mechanism of periostin up-regulation in fibrous dysplasia, resulting in altered collagen fibrillogenesis characteristic of this disease.     

Detection of acid-sensing ion channel 3 (ASIC3) in periodontal Ruffini endings of mouse incisors

The acid-sensing ion channel 3 (ASIC3), a member of the epithelial sodium channel/degenerin (ENaC/DEG) superfamily, has been reported to participate in acid sensing, mechanosensation, and nociception. However, no information is available regarding the precise localization and function of this molecule in the periodontal ligament, which contains abundant sensory nerves originating from the trigeminal ganglion. The present study examined the expression of ASIC3 in the lingual periodontal ligament of mouse incisors by immunohistochemistry. Furthermore, the expression of ASIC3 in the trigeminal ganglion - which innervates the periodontal ligament - was investigated at protein (immunohistochemistry and quantitative analysis) and mRNA levels (RT-PCR technique and in situ hybridization histochemistry). Immunohistochemistry for ASIC3 was able to demonstrate dendritic profiles of the periodontal Ruffini endings in the mouse incisors. No thin fibers terminating as nociceptive free nerve endings exhibited ASIC3 immunoreactivity. Double immunofluorescent staining revealed ASIC3 immunoreaction in the axoplasm but not in the ordinary Schwann cells - including the associated terminal Schwann cells. Observation of the trigeminal ganglia showed variously sized neurons expressing ASIC3 immunoreaction; the most intense immunopositivity was found in the small and medium-sized neurons, as confirmed by in situ hybridization histochemistry using a specific cRNA probe. Quantitative analysis on trigeminal ganglion neurons showed that 38.0% of ASIC3 neurons could be categorized as medium-sized neurons which mediate mechanotransduction. These findings suggest that ASIC3 functions as a molecule for mechanosensation in the periodontal Ruffini endings.     

牙周膜厚度对舌侧矫治中下颌第1磨牙近中移动的影响

目的 研究舌侧矫治中下颌第1磨牙近中移动过程,牙周膜厚度因素对牙齿及牙周组织应力和位移的影响。方法 基于逆向工程技术的方法,分别建立牙周膜厚度为0.15、0.2、0.25、0.3、0.35 mm的等牙槽骨高度的牙齿—牙周膜—牙槽骨三维模型,在舌侧矫治中倾斜、旋转及整体移动载荷作用下,分析牙周膜、牙根及牙槽骨表面的应力和位移状况。结果 由牙周膜厚度差异引起的牙周膜、牙根以及牙槽骨表面最大应力极大值与极小值之比分别为1.46、2.06、6.72,牙根、牙槽骨表面的最大位移极大值与极小值之比分别为1.65、1.50;对应不同的牙周膜厚度值,牙根及牙周组织最大应力部位在牙根、根分叉以及牙颈间变动。结论 临床治疗中,应注意观察牙颈、根分叉以及牙根部位的变化,针对牙周膜厚度较小的患者,整体移动更有利于牙齿及牙周组织的健康。