Cimetidine Reduces Alveolar Bone Loss in Induced Periodontitis in Rat Molars

Background: There is evidence that histamine released during inflammation plays a role in bone metabolism via the H₂ receptor, stimulating bone resorption. The purpose of this study is to evaluate whether cimetidine, a histamine H₂‐receptor antagonist, interferes with the initiation and progression of induced periodontal disease in rat molars. Methods: Forty male rats received 100 mg/kg body weight of cimetidine (cimetidine group [CimG]) or saline solution (sham group [SG]). Periodontal disease was induced in the maxillary left first molars (PDSG and PDCimG); maxillary right molars were used as non‐ligature controls. After 7, 15, 30, and 50 days, maxillary fragments were embedded in paraffin. The sections were stained with Masson trichrome and hematoxylin and eosin and subjected to the tartrate‐resistant acid phosphatase (TRAP) method. The distances between the cemento‐enamel junction (CEJ) and alveolar process (AP) crest, as well as between the CEJ and junctional epithelium (JE) level, were measured; the number of inflammatory cells was computed. Receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) immunohistochemistry was carried out, and the RANKL/OPG ratio was calculated. Results: In PDSG and PDCimG, a significant increase (P ≤0.05) was observed in CEJ‐AP and CEJ‐JE distances. However, the increases in both distances were significantly less in PDCimG compared with PDSG at 15, 30, and 50 days. Numerous TRAP‐positive osteoclasts were found in the PDSG and PDCimG. In PDCimG, the volume density of inflammatory cells and the RANKL/OPG ratio were significantly lower (P ≤0.05) than in PDSG. Conclusions: Cimetidine exerts a beneficial effect on periodontal disease in rats, decreasing the RANKL/OPG ratio in gingival connective tissue and reducing alveolar bone resorption.     

Lactoferrin Knockout Mice Demonstrates Greater Susceptibility to Aggregatibacter actinomycetemcomitans–Induced Periodontal Disease

Background : Among the innate defense mechanisms in the oral cavity, lactoferrin (LF) is a vital antimicrobial that can modify the host response against periodontopathogens. Aggregatibacter actinomycetemcomitans is the main periodontopathogen of localized aggressive periodontitis. The aim of this study is to evaluate the role of LF during A. actinomycetemcomitans–induced periodontitis. Methods: Differences in the expression levels of cytokines, chemokines, chemokine receptors, and bone loss markers between wild‐type (WT) and LF knockout mice (LFKO^?/?) were evaluated by real time‐PCR. Serum IgG and LF levels were quantified by ELISA. Alveolar bone loss among the groups was estimated by measuring the distance from cemento‐enamel junction (CEJ) to the alveolar bone crest (ABC) at 20 molar sites. Results: Oral infection with A. actinomycetemcomitans increased LF levels in periodontal tissue (P = 0.01) and saliva (P = 0.0004) of wild‐type infected (WTI) mice compared to wild‐type control mice. Pro‐inflammatory cytokines such as interferon‐γ, tumor necrosis factor‐α, interleukin (IL)‐1β, IL‐6, and IL‐12 were increased in the infected LF knockout (LFKO^?/?I) mice compared to the WTI mice, whereas the anti‐inflammatory cytokines IL‐4 and IL‐10 were decreased. Chemokines and chemokine receptors showed different expression patterns between WTI and LFKO^?/?I mice. The LFKO^?/?I mice developed increased bone loss (P = 0.002), in conjunction with increased expression of receptor activator of nuclear factor‐κB ligand and decrease in osteoprotegerin, compared to WTI mice. Conclusions: These results demonstrate that the infected LFKO^?/? mice were more susceptible to A. actinomycetemcomitans–induced alveolar bone loss, with different patterns of immune responses compared to those of WTI mice.     

应用AutoCAD定量分析牙槽骨水平的研究

目的应用AutoCAD计算机辅助设计软件,建立定量分析牙槽骨水平的新方法并对其进行评价。方法用AutoCAD软件在数字曲面体层片上分别测量168颗牙釉牙骨质界到牙槽嵴顶及釉牙骨质界到根尖的面积和线性距离,计算牙槽骨吸收的面积比值和长度比值,对2种比值进行比较分析。结果用AutoCAD测量336个面积和672个线性距离,牙槽骨吸收的面积比值与长度比值之间有很高的相关一致性,Pearson相关系数为0.921(P0.001);不同操作者之间的测量结果无显著差异(P0.05),组内相关系数为0.994(P0.001),Pearson相关系数为0.988(P0.001)。结论在二维图像的X线片中,用AutoCAD软件测量牙槽骨吸收面积比值可作为定量评价牙槽骨水平的新方法。     

MyD88 is essential for alveolar bone loss induced by Aggregatibacter actinomycetemcomitans lipopolysaccharide in mice

Aggregatibacter actinomycetemcomitans is a Gram‐negative bacteria highly associated with localized aggressive periodontitis. The recognition of microbial factors, such as lipopolysaccharide from A. actinomycetemcomitans (_AaLPS), in the oral environment is made mainly by surface receptors known as Toll‐like receptors (TLR). TLR4 is the major LPS receptor. This interaction leads to the production of inflammatory cytokines by myeloid differentiation primary‐response protein 88 (MyD88) ‐dependent and ‐independent pathways, which may involve the adaptor Toll/interleukin‐1 receptor‐domain‐containing adaptor inducing interferon‐β (TRIF). The aim of this study was to assess the involvement of MyD88 in alveolar bone loss induced by _AaLPS in mice. C57BL6/J wild‐type (WT) mice, MyD88, TRIF or TRIF/MyD88 knockout mice received 10 injections of _AaLPS strain FDC Y4 (5 μg in 3 μl), in the palatal gingival tissue of the right first molar, every 48 h. Phosphate‐buffered saline was injected in the opposite side and used as control. Animals were sacrificed 24 h after the 10th injection and the maxillae were removed for macroscopic and biochemical analyses. The injections of _AaLPS induced significant alveolar bone loss in WT mice. In the absence of MyD88 or TRIF/MyD88 no bone loss induced by _AaLPS was observed. In contrast, responses in TRIF^?/? mice were similar to those in WT mice. Diminished bone loss in the absence of MyD88 was associated with fewer TRAP‐positive cells and increased expression of osteoblast markers, RUNX2 and osteopontin. There was also reduced tumor necrosis factor‐α production in MyD88^?/? mice. There was less osteoclast differentiation of hematopoietic bone marrow cells from MyD88^?/? mice after _AaLPS stimulation. Hence, the signaling through MyD88 is pivotal for _AaLPS‐induced osteoclast formation and alveolar bone loss.     

The thickness of facial alveolar bone overlying healthy maxillary anterior teeth

Background: A facial bone (<2 mm) overlying maxillary anterior teeth may be prone to resorptive processes after extraction and immediate implant placement. A thin bone contributes to risk of bone fenestration, dehiscence, and soft‐tissue recession. This study measures the distance between the cemento‐enamel junction (CEJ) and alveolar bone crest and the thickness of facial alveolar bone at points 1 to 5 mm from the bone crest for the six maxillary anterior teeth. Methods : Sixty‐six tomographic scans (31 males and 35 females; aged 17 to 69 years; mean age: 39.9 years) of intact anterior maxilla were randomly selected and evaluated by two calibrated and independent examiners (MG and TP). Results: A high variation of CEJ–bone crest (0.8 to 7.2 mm) was detected. A significantly larger CEJ–bone crest was measured in smokers (P <0.05) and patients who were ≥50 years old (P <0.05). The average bone thickness at 3 mm from the CEJ for the maxillary right central incisor was 1.41 mm and for the maxillary left central incisor was 1.45 mm. For the maxillary right and left lateral incisors, the crestal bone thickness averaged 1.73 and 1.59 mm, respectively. For the maxillary right and left canines, the crestal bone thickness averaged 1.47 and 1.60 mm, respectively. Conclusions : The present study supports the finding of a predominantly thin facial bone overlying the six maxillary anterior teeth. Therefore, it is essential to make informed treatment decisions based on thorough site evaluation before immediate implant placement.     

The Effects of a Novel Botanical Agent on Lipopolysaccharide‐Induced Alveolar Bone Loss in Rats

Background: The development of host‐modulatory agents with low risk of adverse effects has been needed to treat periodontitis, a chronic inflammatory disease. A botanical mixture of extracts from two natural substances, Panax notoginseng and Rehmannia glutinosa Libosch, was developed as a novel botanical agent synthesized with anti‐inflammatory effect. The aim of this study is to evaluate the effects of the botanical mixture on the release of inflammatory cytokines and its inhibitory effect on lipopolysaccharide (LPS)‐induced alveolar bone loss (ABL) in a rat model. Methods: Cytotoxicity was assessed by 3‐(4,5‐dimethylthiazol‐2yl)‐5(3‐carboxymethoxyphenol)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium assay using human gingival fibroblast (hGF) and human periodontal ligament (hPDL) cells. Human acute monocytic leukemia cell line and hGF cells were cultured to assay tumor necrosis factor (TNF)‐α and interleukin (IL)‐6, respectively. Microcomputed tomography analysis and immunofluoresence analysis were performed to evaluate the efficacy of the botanical mixture to inhibit the destruction of alveolar bone and connective tissue in a rat model. Results: The botanical mixture is cytotoxic at concentrations exceeding 2.5 mg/mL (P <0.05). Based on the results from cytotoxicity assay, it can be determined that the pharmacologic ranges of the botanical mixture to be used in all subsequent in vitro and in vivo experiments. The botanical mixture reduced the release of TNF‐α and IL‐6 from human monocytic cells and hGF cells in a dose‐dependent manner (P <0.05). The administration of the botanical mixture significantly reduced the alveolar bone loss in a rat model (P <0.05). In groups treated with the botanical mixture, matrix metalloproteinase (MMP)‐9 was detected along the alveolar bone crest (ABC), but not around the gingival connective tissue, while in the group with LPS‐induced ABL, pronounced expression of MMP‐9 around the ABC, periodontal ligament, and gingival connective tissue was found. Conclusions: The botanical mixture showed a potential adjunctive effect in the treatment of periodontitis. However, the present findings are obtained in vitro and in a rat model, so further clinical study is needed for its clinical application.     

In Vivo Inhibition of Porphyromonas gingivalis Growth and Prevention of Periodontitis With Quorum‐Sensing Inhibitors

Background: Autoinducer (AI)‐2 has an important role in biofilm formation in the oral environment. Mature biofilms formed as a result of the cell‐to‐cell communication make it difficult to overcome periodontitis with the use of antibiotics. Previous in vitro studies suggest that quorum‐sensing inhibitors (QSIs) interfere with AI‐2. This study compares the QSI effects resulting from an oral inoculation of Porphyromonas gingivalis in an experimental animal model. Methods: Forty‐five male mice were divided into three groups (n = 15 each): 1) infection; 2) QSI; and 3) control. Infection and QSI groups received oral inoculation of P. gingivalis, whereas treatment with QSIs (furane compound and d ‐ribose) was only performed in the QSIs group. The control group was a negative control not receiving manipulation. After 42 days, mice were sacrificed, and the distance from the alveolar bone crest (ABC) to the cemento‐enamel junction (CEJ) was measured by microcomputed tomography. P. gingivalis DNA was quantified in the soft and hard tissues around the molar teeth by real‐time polymerase chain reaction. Results: Distance from ABC to CEJ was significantly increased in the P. gingivalis infection group compared with the control group (P = 0.02) and significantly decreased in the QSI group compared with the infection group (P = 0.02). The QSI group contained 31.64% of the bacterial DNA count of the infection group. Conclusion: Use of QSIs in the mice infection model showed a reduction of bone breakdown and a decrease in the number of bacteria in vivo, suggesting that QSIs can be a new approach to prevention and treatment of periodontitis.     

Simvastatin application to augment facial jaw bone in a dog model: pilot study

Background: Locally injected simvastatin (SIM) has been shown to induce bone growth in rat models. The purpose of this study is to evaluate the effects of locally injected simvastatin in several human‐like clinical situations in a beagle dog model. Methods: Four beagle dogs completed the study and were used in a split‐mouth design. Dehiscence defects of 5 × 3 mm were created bilaterally on the lateral aspect of the mandibular second premolar (PM2) mesial roots including removal of root cementum. At the same surgery, porous hydroxyapatite–collagen grafts with resorbable membranes with or without 10‐mg SIM were placed buccal to the mandibular first molars (M1). One week later, three weekly local injections of 10‐mg SIM in ethanol and contralateral ethanol alone were initiated at three sites through the buccal mucosa: 1) 6 mm apical to the cemento‐enamel junction (CEJ) of the maxillary fourth premolar (PM4; thin bone over root); 2) 6 mm apical to the CEJ of PM2 (dehiscence defect); and 3) 10 mm distoapical to the CEJ of the maxillary canine (edentulous ridge). Dogs were euthanized 2 months after the final injections. Block sections were harvested and specimens were decalcified and stained with hematoxylin and eosin. Histomorphometry was performed using digitized photographs and analyzed with distribution‐free rank tests. Results: Regarding M1, the distance between CEJ and the alveolar crest was significantly more coronal in the SIM group (P = 0.038). Regarding the edentulous ridge, the width of new bone was significantly greater in SIM injection specimens (P = 0.0164). Regarding PM2, buccal bone in the dehiscence defects lacking periosteum was not augmented in the SIM group. Regarding PM4, the total width of bone 5 mm apical to the coronal height of contour (thin buccal bone covering the root) was significantly wider on the SIM side (SIM, 0.63 ± 0.53 mm; contralateral ethanol alone, 0.25 ± 0.19 mm; P = 0.0098). Conclusion: Locally injected SIM has the ability to induce modest amounts of new bone formation in closed injection sites over a periosteal surface.     

Topical and intermittent application of parathyroid hormone recovers alveolar bone loss in rat experimental periodontitis

Tokunaga K, Seto H, Ohba H, Mihara C, Hama H, Horibe M, Yoneda S, Nagata T. Topical and intermittent application of parathyroid hormone recovers alveolar bone loss in rat experimental periodontitis. J Periodont Res 2011; 46: 655–662. © 2011 John Wiley & Sons A/S Background and Objective: Periodontitis is characterized by periodontal tissue inflammation and alveolar bone loss. The intermittent administration of parathyroid hormone (PTH), a major regulator of bone remodeling, has been demonstrated to stimulate osteoblastic activity. Although the systemic administration of PTH has been reported to protect against periodontitis‐associated bone loss, the effect of the topical administration of PTH is unclear. In this study, the effect of intermittent administration of PTH on osteoblastic differentiation was examined in cultured calvaria cells and then the effect of topical and intermittent administration of PTH was determined by measuring the recovery of alveolar bone loss after inducing experimental periodontitis in rats. Material and Methods: Alkaline phosphatase activity and bone nodule formation were measured in fetal rat calvaria cells. Experimental periodontitis was induced by placing nylon ligature around rat maxillary molars for 20 d. After ligature removal (day 0), PTH was topically injected into buccal gingiva three times a week for 10 wk. Micro‐computed tomography analysis and histological examination were performed on days 35 and 70. Results: Intermittent exposure of PTH in calvaria cells increased alkaline phosphatase activity and bone nodule formation by 1.4‐ and 2.4‐fold, respectively. Ligature procedures induced marked alveolar bone loss around the molars on day 0 and greater bone recovery was observed in the PTH‐treated rats on day 70. An increase in osteoid formation on the surface of alveolar bone was detected in the PTH‐treated rats. Conclusion: Intermittent treatment with PTH stimulated osteoblastic differentiation in fetal rat calvaria cell cultures, and topical and intermittent administration of PTH recovered alveolar bone loss in rat experimental periodontitis.     

Assessment of bone loss in periodontitis from panoramic radiographs

Bone loss in chronic periodontitis was assessed from panoramic radiographs by direct measurement from the cemento-enamel junction (CEJ) and by measuring the proportion of the tooth length supported by bone. Mesial and distal bone levels of all available teeth were assessed for 50 patients aged 30-39 years referred for periodontal treatment. 85% and 74% of surfaces were measurable by the proportional and direct techniques, respectively. 27% of surfaces had no bone loss according to the proportional score, whereas 22% had a CEJ to alveolar bone distance of less than 2 mm. In addition, over half the surfaces with a proportional bone loss score of zero had a CEJ to alveolar bone distance of 2 mm or more, and for each proportional bone loss score, there was considerable overlap in the CEJ to alveolar bone distances recorded. The validity of the CEJ to alveolar bone measurements was established by comparison with direct measurements at periodontal surgery. The results support the use of direct measurement from the CEJ to alveolar bone rather than the assessment of the proportion of the tooth length within the bone when investigating bone loss from panoramic radiographs. This population of 30-40-year-old periodontal patients had a mean of 50% of sites with a CEJ to alveolar bone distance of 3 mm or more, and at such sites, there was a mean additional bone loss of 2.1 mm.     

Standardized Rat Model Testing Effects of Inflammation and Grafting on Extraction Healing

Background: Loss of alveolar ridge width and height after tooth extraction is well documented, but models to evaluate ridge preservation are neither standardized nor cost‐effective. This rat model characterizes the pattern of bone turnover and inflammation after extraction and bone grafting with or without local simvastatin (SIM). Methods: Fifty retired‐breeder rats underwent extraction of the maxillary right first molar and standard surgical defect creation under inhalation/local anesthesia. The left side of each animal served as unmanipulated control. Untreated groups (n = 8 to 9 per group) were compared (analysis of variance, t test) at days 0, 7, 14, and 28 for alveolar ridge height and width and for markers of inflammation and bone turnover by microcomputed tomography, histology, and enzyme‐linked immunosorbent assay. Seventeen additional specimens had defects grafted with either bone mineralized matrix (BMM) or a BMM+SIM conjugate. Results: Extraction‐induced bone loss (BL) was noted on buccal, palatal, and interproximal height (P <0.05) and ridge width (P <0.01). Week 1 inflammation positively correlated with ridge height; thereafter, a more intense inflammatory reaction corresponded to reduction in alveolar bone height and density (r = 0.74; P <0.05; Spearman). BMM+SIM preserved the most interproximal bone height (P <0.01), increased ridge width and bone density (P <0.01), enhanced 7‐day prostaglandin E2 (P <0.01), and reduced 28‐day inflammation density (P <0.05). Conclusions: The standard defect used in the current study paralleled human postextraction alveolar BL. Defect grafting, especially BMM+SIM, reduced inflammation and preserved bone.     

N‐acetylcysteine decreases alveolar bone loss on experimental periodontitis in streptozotocin‐induced diabetic rats

Toker H, Ozdemir H, Balc? H, Ozer H. N‐acetylcysteine decreases alveolar bone loss on experimental periodontitis in streptozotocin‐induced diabetic rats. J Periodont Res 2012; 47: 793–799. © 2012 John Wiley & Sons A/S Background and Objective: The purpose of this study was to evaluate the morphometric and histopathological changes associated with experimental periodontitis in diabetic rats in response to systemic administration of N‐acetylcysteine (NAC), a sulfhydryl‐containing thiol antioxidant. Material and methods: Sixty Wistar rats were divided into six experimental groups: nonligated (NL) group; ligature‐only (L) group; streptozotocin‐only (STZ) group; STZ and ligature (STZ + L) group; and systemic administration of NAC and ligature (70 and 100 mg/kg body weight per day, respectively) (NAC70 and NAC100 groups). Diabetes mellitus was induced by 60 mg/kg of streptozotocin. Silk ligatures were placed at the gingival margin of the lower first molars of the mandibular quadrant. The study duration was 30 d and the animals were killed at the end of this period. Changes in alveolar bone levels were clinically measured and tissues were histopathologically examined to assess the differences among the study groups. Results: At the end of the 30‐d study period, alveolar bone loss was significantly higher in the STZ + L group compared with the other groups (p < 0.05). Also, alveolar bone loss in all the NAC groups was significantly lower than in the STZ + L and L groups (p < 0.05). The osteoblastic activity in the NAC100 group was significantly higher than in the other groups (p < 0.05). Conclusion: Within the limits of this study, it can be suggested that NAC, when administered systemically, prevents alveolar bone loss in the diabetic rat model.     

Streptococcus cristatus ArcA interferes with Porphyromonas gingivalis pathogenicity in mice

Xie H, Hong J, Sharma A, Wang B‐Y. Streptococcus cristatus ArcA interferes with Porphyromonas gingivalis pathogenicity in mice. J Periodont Res 2012; 47: 578–583. © 2012 John Wiley & Sons A/S Background and Objective: Porphyromonas gingivalis has been implicated as one of the major pathogens in chronic periodontitis, an infectious disease affecting the majority of the adult population. We have previously demonstrated that a surface protein, arginine deiminase (ArcA), of Streptococcus cristatus represses production of P. gingivalis long fimbriae and interrupts the formation of P. gingivalis biofilms in vitro. Our in vivo studies have also shown that the distribution of P. gingivalis and S. cristatus in human subgingival plaque is negatively correlated. The objective of this study was to determine if S. cristatus ArcA inhibits P. gingivalis colonization and attenuates its subsequent pathogenesis in alveolar bone loss in the murine oral cavity. Material and Methods: A wild‐type strain of S. cristatus (CC5A) and its arcA knockout mutant (ArcAE) were used as initial colonizers in the oral cavity of BALB/cByJ mice. Colonization of P. gingivalis on the existing S. cristatus biofilms was assessed by quantitative PCR, and P. gingivalis‐induced alveolar bone loss was measured 6 wk after P. gingivalis infection. Results: The presence of S. cristatus CC5A, but not its arcA mutant, attenuated P. gingivalis colonization in the murine oral cavity. In addition, P. gingivalis‐induced alveolar bone loss was significantly lower in mice initially infected with S. cristatus CC5A than in those infected with the arcA mutant. Conclusion: This study provides direct evidence that S. cristatus ArcA has an inhibitory effect on P. gingivalis colonization, which may in turn attenuate the pathogenicity of P. gingivalis.     

牙周基础治疗对伴高脂血症牙周炎大鼠血清IL-6及牙槽骨吸收影响的研究

目的:建立慢性牙周炎(chronic periodontitis,CP)合并高脂血症(hyperlipidemia,HL)的SD大鼠模型并对其进行牙周基础治疗,观察血清白介素-6(interleukin 6,IL-6)炎症因子及牙槽骨的影响。方法:SD大鼠随机分为4组,对照组(A)、HL组(B)、CP组(C)、HL+CP组(D);进行相应的建模处理,从建模开始15周后随机处死B组大鼠1只,取颈动脉分叉血管组织进行油红O染色,观察到泡沫细胞形成,则建模成功。再将C/D组随机分为2小组,C1/D1为自然进程组,C2/D2为牙周基础治疗组,进行2次牙周干预,分别于干预前1周、第1次干预后1周、第2次干预后1、3、5周采血,酶联免疫吸附法测定血清IL-6含量。实验结束后处死所有大鼠,取单侧上颌骨,剥离牙龈,进行亚甲基蓝染色,使用电子数显卡尺在徕卡显微镜(16X)下测量离体上颌骨实验牙釉质牙骨质界至牙槽嵴顶(cementoenamel junction and alveolar bone crest,CEJ- ABC)的距离(第一、二磨牙共12个位点)作为牙槽骨吸收值以检测牙槽骨吸收情况。使用SPSS21.0软件对所得数据进行统计学分析。结果:血清IL-6含量C、D组明显高于A组(P<0.05),其中,C1/D1组随时间推移一直呈现上升趋势,C2/D2组则在第2次干预后1周血清IL-6含量达到高峰,随观察时间延长则逐渐下降并低于基线水平(P<0.05);牙槽骨丧失量:C、D组>A组(P<0.001),而C2/D2组较C1/D1组牙槽骨丧失略有改善,但差异无统计学意义;牙槽骨吸收与血清IL-6水平呈Pearson正相关关系(P<0.01)。结论:高脂血症可加重牙周炎病变,牙周干预后短期内表现为机体炎症反应加重,远期则可能因炎症因子水平的降低而减轻全身病变进程。血清IL-6水平升高后,牙周局部表现为牙槽骨的吸收量增加。牙周基础治疗一定程度上可改善伴或不伴有高脂血症的牙周炎大鼠牙槽骨丧失的进程。     

Therapeutic Effects of Melatonin on Alveolar Bone Resorption After Experimental Periodontitis in Rats: A Biochemical and Immunohistochemical Study

Background: The present study aims to investigate the effects of systemic melatonin administration on alveolar bone resorption in experimental periodontitis in rats. Methods: Twenty‐four male Sprague‐Dawley rats were divided into three groups (control, experimental periodontitis [Ped], and experimental periodontitis treated with melatonin [Mel‐Ped]). For periodontitis induction, first molars were ligatured submarginally for 4 weeks. After ligature removal, rats in the Mel‐Ped group were treated with a daily single dose of 10 mg/kg body weight melatonin for 15 consecutive days. At the end of the study, intracardiac blood samples and mandible tissues were obtained for histologic, biochemical, and radiographic analysis. Serum markers related to bone turnover, calcium, phosphorus, bone alkaline phosphatase (b‐ALP), and terminal C telopeptide of collagen Type I (CTX) were analyzed. Myeloperoxidase levels were determined in gingival tissue homogenates, and receptor activator of nuclear factor‐kappa B ligand (RANKL) activation was analyzed in the mandible samples stereologically. Alveolar bone loss was also evaluated radiographically in the mandible samples of each group. Results: Melatonin treatment decreased serum CTX levels and increased b‐ALP levels. Serum calcium and phosphorus levels were not statistically different among groups (P >0.05). Alveolar bone resorption and myeloperoxidase activity were statistically higher in the Ped group compared to the Mel‐Ped group (P <0.05). Immunohistochemical staining of RANKL and osteoclast activity were significantly lower in the Mel‐Ped group compared to the Ped group (P <0.05). Conclusion: This study reveals that melatonin treatment significantly inhibits regional alveolar bone resorption and contributes to periodontal healing in an experimental periodontitis rat model.     

Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats

Liu Y‐F, Wu L‐A, Wang J, Wen L‐Y, Wang X‐J. Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats. J Periodont Res 2010; 45: 714–719. © 2010 John Wiley & Sons A/S Background and Objective: Nicotine reportedly is a risk factor for periodontitis, but accurate data regarding nicotine‐induced alveolar bone loss is lacking. The aim of this study was to quantitatively assess alveolar bone loss in ligature‐ and nicotine‐induced periodontitis in rats using micro‐computerized tomography (micro‐CT). Material and Methods: Thirty‐six adult male rats were treated by placing silk ligatures around the cervixes of the right second maxillary molar; the contralateral tooth was untreated. After ligation, the animals were randomly divided into three groups: group A received intraperitoneal injections of saline solution, group B received 0.83 mg of nicotine/kg/d, and group C received 1.67 mg of nicotine/kg/d. Six animals in each group were killed on days 14 and 28 after ligature placement, and then micro‐CT examinations were conducted. Results: In all groups, bone mineral density (BMD), bone volume fraction (BVF), trabecular number (Tb.N) and trabecular thickness (Tb.Th) values of the ligated sides were significantly lower than those of the unligated sides (p < 0.001), whereas alveolar bone height loss (ABHL) and trabecular separation (Tb.Sp) of the ligated sides were significantly higher than those of the unligated sides (p < 0.001). Compared with the control group, nicotine administration increased the ABHL value and decreased the BMD, BVF and Tb.Th values of both sides in a dose‐dependent manner (p < 0.05). Conclusion: Our results confirmed that ligature could cause significant loss in the trabecula of alveolar bone, and daily administration of nicotine resulted in further bone loss and microstructure deterioration.     

Virulence of major periodontal pathogens and lack of humoral immune protection in a rat model of periodontal disease

Oral Diseases (2010) 16 , 686–695 Objective: This study was designed to test the hypothesis that periodontal pathogens Tannerella forsythia and Porphyromonas gingivalis are synergistic in terms of virulence potential using a model of mixed‐microbial infection in rats. Materials and methods: Three groups of rats were infected orally with either T. forsythia or P. gingivalis in mono‐bacterial infections or as mixed‐microbial infections for 12 weeks and a sham‐infected group were used as a control. This study examined bacterial infection, inflammation, immunity, and alveolar bone loss changes with disease progression. Results: Tannerella forsythia and P. gingivalis genomic DNA was detected in microbial samples from infected rats by PCR indicating their colonization in the rat oral cavity. Primary infection induced significantly high IgG, IgG2b, IgG1, and IgG2a antibody levels indicating activation of mixed Th1 and Th2 immune responses. Rats infected with the mixed‐microbial consortium exhibited significantly increased palatal horizontal and interproximal alveolar bone loss. Histological examinations indicated significant hyperplasia of the gingival epithelium with moderate inflammatory infiltration and apical migration of junctional epithelium. The results observed differ compared to uninfected controls. Conclusion: Our results indicated that T. forsythia and P. gingivalis exhibit virulence, but not virulence synergy, resulting in the immuno‐inflammatory responses and lack of humoral immune protection during periodontitis in rats.     

Enhanced alveolar bone loss in a model of non-invasive periodontitis in rice rats

Oral Diseases (2012) 18 , 459–468 Objective: The rice rat (Oryzomys palustris) develops periodontitis‐like lesions when fed a diet rich in sucrose and casein (H‐SC). We aimed to establish whether this model can accurately mimic the development of human periodontitis. Materials and Methods: For this purpose, 28‐day‐old rice rats (15/group) were assigned to standard (STD) or H‐SC diets and sacrificed after 6, 12, and 18 weeks. Jaws were processed for morphometric, histometric, histologic, histomorphometric, and micro‐CT analyses. Results: We found a progressive increase in horizontal alveolar bone loss (ABL) with age in maxillae of rats fed the STD diet as determined by morphometry. The H‐SC diet exacerbated horizontal ABL at the palatal surface at 12 and 18 weeks. Furthermore, increased vertical ABL was detected in mandibles and maxillae of rats fed the H‐SC diet for 12 and/or 18 weeks by histometry and micro‐CT. Remarkably, the H‐SC diet significantly increased bone remodeling at the interproximal alveolar bone of mandibles from rats fed for 6 weeks, but not in those fed for longer periods. Conclusions: These findings indicate that the H‐SC diet induced a transient increase in alveolar bone remodeling, which is followed by ABL characteristic of moderate periodontitis.     

Radiographic study of the prevalence of periodontal bone loss in Australian school-aged children attending the Royal Dental Hospital of Melbourne

OBJECTIVES: To investigate the prevalence of alveolar bone loss around the first permanent molars, and first and second deciduous molars in Australian school-aged children attending the Royal Dental Hospital of Melbourne. METHOD: Nine hundred and ninety-five records were examined for useable bitewing radiographs. From these, radiographs of 542 Australian school children aged 5-12 years were used. The cervical-enamel junction (CEJ) to the alveolar bone crest (ABC) distance was measured using the transparent ruler on the magnifier. Each inter-dental site that was readable was scored as one for the following categories: not available (NA); no bone loss (NBL)- the CEJ-ABC was < or =2 mm; questionable bone loss (QBL): the distance from the CEJ-ABC was >2 and <3 mm; and definite bone loss (DBL): the distance from the CEJ to ABC was > or =3 mm. RESULTS: Seventy-one children (13.0%) were found to have 83 DBL sites, as determined by bone levels >3.0 mm from the CEJ. Seventy children had QBL lesions only, 50 children had DBL only and 21 children had both. The overall prevalence of bone loss was 26%. Second deciduous molars were found to be the most affected teeth with almost 75% lesions being distal. These teeth comprised 50% of the DBL lesions. Children of Asian-Far Eastern origin had a higher percentage of sites with bone loss compared with children of Caucasian origin, being 29.5% and 19.7%, respectively, but lower than that of children of Middle-Eastern origin (35.2%). When the data were analysed with relation to age, there was no relationship between age and prevalence of bone loss. CONCLUSION: In the population studied, there was an overall prevalence of periodontal bone loss of 26% and DBL of 13% in an Australian school-aged group. Calculus was detected infrequently and, where present, was associated with bone loss.