Simvastatin therapy in cyclosporine A-induced alveolar bone loss in rats

Background and Objective:  Cyclosporine A treatment is important in the therapy of a number of medical conditions; however, alveolar bone loss is an important negative side-effect of this drug. As such, we evaluated whether concomitant administration of simvastatin would minimize cyclosporine A-associated alveolar bone loss in rats subjected, or not, to experimental periodontal disease.
Material and Methods:  Groups of 10 rats each were treated with cyclosporine A (10 mg/kg/day), simvastatin (20 mg/kg/day), cyclosporine A and simvastatin concurrently (cyclosporine A/simvastatin) or vehicle for 30 days. Four other groups of 10 rats each received a cotton ligature around the lower first molar and were treated similarly with cyclosporine A, simvastatin, cyclosporine A/simvastatin or vehicle. Calcium (Ca²⁺), phosphorus and alkaline phosphatase levels were evaluated in serum. Expression levels of interleukin-1β, prostaglandin E₂ and inducible nitric oxide synthase were evaluated in the gingivomucosal tissues. Bone volume and numbers of osteoblasts and osteoclasts were also analyzed.
Results:  Treatment with cyclosporine A in rats, with or without ligature, was associated with bone loss, represented by a lower bone volume and an increase in the number of osteoclasts. Treatment with cyclosporine A was associated with bone resorption, whereas simvastatin treatment improved cyclosporine A-associated alveolar bone loss in all parameters studied. In addition, simvastatin, in the presence of inflammation, can act as an anti-inflammatory agent.
Conclusion:  This study shows that simvastatin therapy leads to a reversal of the cyclosporine A-induced bone loss, which may be mediated by downregulation of interleukin-1β and prostaglandin E₂ production.     

牙周炎性牙槽骨吸收与T细胞间的关系

牙周炎性牙槽骨吸收是常见的牙周组织炎症性破坏性疾病,是导致牙丧失的主要原因。T细胞在牙周炎的发生发展过程中发挥了重要的作用。一方面,牙周致病菌抗原活化T细胞是机体抗牙周致病菌感染所必需;另一方面,活化的T细胞是破骨细胞分化成熟和骨吸收活性的重要调节细胞,也是牙周炎性牙槽骨吸收的损伤细胞。本文就牙周炎性牙槽骨吸收,T细胞在牙周炎性牙槽骨吸收中的作用,T细胞和干扰素一1对破骨细胞的作用等研究进展作一综述。     

The influence of short-term diabetes mellitus and insulin therapy on alveolar bone loss in rats

BACKGROUND: It is well known that the multiple direct and indirect consequences of hyperglycemia in diabetic individuals have been linked to a number of abnormal host effector mechanisms that could lead to an increased risk of developing periodontal disease. OBJECTIVE: The aim of this study was to investigate the effect of short-term experimental diabetes and insulin therapy on the severity of alveolar bone loss in rats, and the effect of experimental periodontitis on glycemic control. METHODS: Seventy-two male Wistar rats were divided into four groups: group I animals were submitted to dental ligature around lower right first molars (ligated); group II consisted of streptozotocin (STZ)-diabetic, ligated rats; group III represented STZ-diabetic, unligated rats; and group IV consisted of insulin-treated (6 U/day), STZ-diabetic, ligated rats. Blood glucose of all diabetic rats was monitored at regular intervals. Standardized digital radiographs were taken after killing at 7, 15 and 30 days to measure the amount of bone loss about the mesial root surface of the first molar tooth in each rat. Results: No significant (p < 0.05) changes in plasma glucose levels of insulin-treated diabetic rats were found among the different examinations after the beginning of insulin therapy. Rats from group II showed significantly greater increases in mean plasma glucose levels at 15 and 30 days after ligature placement compared with rats from group III (p < 0.05). Furthermore, in spite of the significant alveolar bone loss progression that was observed in groups I, II and IV (p < 0.00001; two-way anova), no significant differences among these groups regarding the severity of bone loss (p = 0.77) and no significant interaction between treatment group and time (p = 0.81) were found. CONCLUSIONS: Within the limits of this study, it can be suggested that the severity of periodontal disease was not affected by short-term diabetes, and that experimental periodontitis increased blood glucose levels in uncontrolled diabetic rats.     

Accelerated alveolar bone loss in male HLA-B27 transgenic rats: adult onset

OBJECTIVE AND BACKGROUND: HLA-B27 transgenic (TG) rats exhibit severe colitis, arthritis and other inflammatory lesions. Previous studies in female TG rats indicate that they develop severe alveolar bone loss (ABL). Lack of data on male TG rats has left open the question of possible hormonal/sex dependence for the observed ABL. The purpose of the present study was to assess the natural history of ABL in male HLA-B27 rats, compared to age- and sex-matched wild-type Fischer 344 (WT) rats. MATERIALS AND METHODS: Fourteen WT and 11 TG male rats, aged 7-8 weeks, were used. Sacrifice times occurred at 10, 22 and 35 weeks. Animal heads were defleshed and treated to remove organic material, and skulls were stained to locate the cemento-enamel junction. ABL was measured as exposed molar root surface area (mm2) on the right maxilla and right mandible. Blinded measurements were performed using a computer-assisted image analysis system. RESULTS: ABL for the entire TG group was significantly different from the WT group (p < 0.05). There was no significant difference in ABL between WT and TG rats at 10 weeks of age. At 22 and 35 weeks of age TG rats experienced 23% and 37% greater ABL than WT rats, respectively; these differences were statistically significant (p < 0.015). For both TG and WT animals, ABL was significantly different between the three age groups. CONCLUSIONS: These results, consistent with previous findings in female TG rats, suggest that the accelerated ABL found in TG rats is an adult-onset, age-dependent, and sex-independent process.     

Applicability of an image analysis system in alveolar bone loss measurement

Clinical and epidemiological studies in the field of periodontics and endodontics often utilize radiographs to monitor or measure the changes in bone structure and density. Periodontal bone loss or gain can be quantified on a radiograph by measurement of the distance between the bottom of the bony pocket and the apical contour of the involved tooth. The objective of this investigation was to study the accuracy of an image analysis system (IAS) to measure changes in height of the interproximal crest on radiographs. Artificial bone lesions were introduced in a dissectioned part of a human mandible. The distances between crest and apices were measured with a micrometer (MM). Radiographs were produced with horizontal and vertical deviations of 10 degrees. The radiographs were digitized and processed by computer. The landmarks in the digital image were enhanced mathematically and by histogram-based thresholding. The depth of the introduced defect was increased 6 times, followed by the measurement procedure. The IAS produced measurements of crown-apex distances with an accuracy of 0.066 to 0.358 mm. Repeated crest height measurements were recorded with an accuracy of 0.112 to 0.184 mm. Both the histogram-based binarization and the ellipse-fitting type of contour detection could be applied precisely. Misangulation errors during radiographic exposure of 10 horizontal or vertical did not statistically significant influence the IAS-measurements. The IAS can be applied in clinical trials and follow-up studies.     

Topical administration of simvastatin recovers alveolar bone loss in rats

Background and Objective:  Simvastatin, a cholesterol-lowering drug, has been reported to show anabolic effects on bone metabolism. We examined the effects of simvastatin in vitro using cultured rat calvaria cells and in vivo using periodontitis-induced rats.
Material and Methods:  Alkaline phosphatase activity and bone nodule formation were measured in cultured rat calvaria cells. Nylon ligature was placed around the maxillary molars of Fischer male rats for 20 d to induce alveolar bone resorption. After ligature removal, simvastatin was topically injected into the buccal gingivae for 70 d and then microcomputed tomography and histological examinations were performed.
Results:  Simvastatin maintained high alkaline phosphatase activity and increased bone nodule formation in rat calvaria cells in a dose-dependent manner, showing that simvastatin increased and maintained a high level of osteoblastic function. Microcomputed tomography images revealed that treatment with simvastatin recovered the ligature-induced alveolar bone resorption, showing a 46% reversal of bone height. Histological examination clarified that low-mineralized alveolar bone was formed in simvastatin-treated rats.
Conclusion:  These findings demonstrate that simvastatin has the potential to stimulate osteoblastic function and that topical administration of simvastatin may be effective for the recovery of alveolar bone loss in rats.     

A novel murine model for chronic inflammatory alveolar bone loss

Oz HS, Ebersole JL. A novel murine model for chronic inflammatory alveolar bone loss. J Periodont Res 2009; doi: 10.1111/j.1600-0765.2009.01207.x. © 2009 John Wiley & Sons A/S
Background and Objective:  Chronic inflammatory bowel disease (IBD) demonstrates some similarities to the dysregulated chronic immunoinflammatory lesion of periodontitis. Trinitrobenzene sulphonic acid (TNBS) and dextran sodium sulphate (DSS) administered to rodents have been shown to elicit inflammatory responses that undermine the integrity of the gut epithelium in a similar manner to IBD in humans. The objective of this study was to evaluate the ability of these chemicals to elicit periodontal inflammation as a novel model for alveolar bone loss.
Material and Methods:  Mice were treated by oral application of TNBS twice a week, or with DSS in the diet over a period of 18 weeks. Alveolar bone loss was assessed on the defleshed skull using morphometric measures for area of bone resorption.
Results:  The TNBS-treated animals tolerated oral administration with no clinical symptoms and gained weight at a similar rate to normal control animals. In contrast, DSS exerted a systemic response, including shortening of colonic tissue and liver enzyme changes. Both TNBS and DSS caused a localized action on periodontal tissues, with alveolar bone loss observed in both maxilla and mandibles, with progression in a time-dependent manner. Bone loss was detected as early as week 7, with more severe periodontitis increasing over the 18 weeks ( p  < 0.001). Young (7-month-old) and old (12-month-old) mice with severe combined immunodefiency were treated with TNBS for a period of 7 weeks and did not develop significant bone loss.
Conclusion:  These data show that oral administration of TNBS or DSS provokes alveolar bone loss in concert with the autochthonous oral microbiota.     

Retrospective longitudinal study of the rate of alveolar bone loss in humans using bite-wing radiographs

Abstract This study investigates the possible use of unstandardized bite-wing radiographs to determine the rate of alveolar bone loss over long periods of lime. A total of 100 pairs of bite-wing radiographs obtained from patients of two general dental practitioners were read on a 3M Reader, normally used for reading microfilm. For the purpose of measurement, two reference points were selected on the teeth; the highest point on the occlusal surface of the crown, the mesial and distal points of the cemento-enamel junction. Both vertical and horizontal bone loss was measured. Initially bone levels on 20 full mouth bite-wing radiographs on all posterior teeth were measured, then in the next 80 cases, an abbreviated index was used. The bone heights were first examined at the beginning and then at the end of a 10–year time span. The percentages of measurable distances were 28% and 57%. From the Occlusal measurement point and the C E J measurement points, reasons for unreadability were also recorded. The annual rate of horizontal boneless was 0.06 mm and 0.04 mm from the Occlusal reference point and the CEJ reference point. The rates for the vertical bone loss were 0.05 and 0.03 mm. In order to study whether there was a constant loss over a period of time, bone levels were measured for 10 successive years. The findings suggest that the bone loss rate per year fluctuated. The study suggests that the bite-wing radiographs can be used in longitudinal studies of periodontal disease and can provide important information on the natural history of the disease.     

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目的研究能够快速建立稳定、可靠、重复性好的大鼠实验性牙周炎模型的方法,摸索建模的最佳时间并对比研究结扎与非结扎区域的牙槽骨破坏情况。方法本研究于2010年7月至2011年1月在中国医科大学基础医学院微生物学实验室及口腔医学院中心实验室完成。将18只SD大鼠随机分为对照组和4周、8周实验组。采用牙颈部结扎合并口腔接种牙周致病菌的方法,建立大鼠实验性牙周炎模型。分别于4周、8周时进行牙周检查,并利用放射影像和体视显微镜检查对比大鼠的牙周骨组织破坏情况。结果4周和8周实验组大鼠结扎区都出现牙龈红肿,探诊出血,均可探及较深的牙周袋。对照组和4周、8周实验组大鼠上颌三颗磨牙平均骨丧失量分别为（357．63±284．96）μm、（929．56±366．43）μm和（941．80±354．87）μm。与对照组相比,4周和8周实验组大鼠上颌磨牙的骨丧失量均显著增加,差异有统计学意义（P〈0．05）,但4周与8周实验组之间差异无统计学意义（P〉0．05）。结论采用牙颈部结扎合并口腔接种牙周致病菌的方法,4周左右即可形成稳定可靠的大鼠牙周炎模型。大鼠的牙周骨破坏在4周之后速度减缓。     

Validation of a dental image analyzer tool to measure alveolar bone loss in periodontitis patients

Background and Objective:  Radiographs are an essential adjunct to the clinical examination for periodontal diagnoses. Over the past few years, digital radiographs have become available for use in clinical practice. Therefore, the present study investigated whether measuring alveolar bone loss, using digital radiographs with a newly constructed dental image analyzer tool was comparable to the conventional method, using intra-oral radiographs on film, a light box and a Schei ruler.
Material and Methods:  Alveolar bone loss of the mesial and distal sites of 60 randomly selected teeth from 12 patients with periodontitis was measured using the conventional method, and then using the dental image analyzer tool, by five dentists. The conventional method scored bone loss in categories of 10% increments relative to the total root length, whereas the software dental image analyzer tool calculated bone loss in 0.1% increments relative to the total root length after crucial landmarks were identified.
Results:  Both methods showed a high interobserver reliability for bone loss measurements in nonmolar and molar sites (intraclass correlation coefficient ≥ 0.88). Also, a high reliability between both methods was demonstrated (intraclass correlation coefficient nonmolar sites, 0.98; intraclass correlation coefficient molar sites, 0.95). In addition, the new dental image analyzer tool showed a high sensitivity (1.00) and a high specificity (0.91) in selecting teeth with ≥ 50% or < 50% alveolar bone loss in comparison with the conventional method.
Conclusion:  This study provides evidence that, if digital radiographs are available, the dental image analyzer tool can reliably replace the conventional method for measuring alveolar bone loss in periodontitis patients.     

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.     

The influence of thyroid hormones on periodontitis-related bone loss and tooth-supporting alveolar bone: a histological study in rats

Background and Objective: Recent studies have pointed to potentially periodontal risk indicators, however no information is available on the impact of changes in thyroid hormone levels on the progression of periodontitis and on the quality of alveolar bone. Thus, the aim of the present study was to evaluate histologically, in rats, the influence of thyroid hormones on the rate of periodontal bone loss resulting from ligature placement and on the quality of tooth‐supporting alveolar bone. Material and Methods: Thirty‐six male Wistar rats were randomly assigned to the following groups: healthy (control, n = 12), hypothyroidism (n = 12) and hyperthyroidism (n = 12). Once alterations were confirmed by total serum levels of triiodothyronine and thyroxine, ligatures were randomly placed around one of the first mandibular molars. Thirty days later, the animals were killed and specimens routinely processed for serial decalcified sections. The parameters assessed were periodontitis‐related bone loss, quality of tooth‐supporting alveolar bone and the number of cells positive for tartrate‐resistant acid phosphatase (TRAP), a marker of bone resorption. Results: At the ligated sites, intergroup analysis revealed that hypothyroidism significantly increased the bone loss resulting from ligature‐induced periodontitis (p = 0.02) and the number of TRAP‐positive cells on the linear surface of bone crest (p = 0.01). In addition, no significant differences were detected regarding the quality of the bone (p = 0.24) or the number of TRAP‐positive cells in the area of the interradicular bone for ligated teeth among the groups (p = 0.17). Conclusion: It may be concluded that decreased serum levels of thyroid hormones may enhance periodontitis‐related bone loss, as a function of an increased number of resorbing cells, whereas the tooth‐supporting alveolar bone seems to be less sensitive to alterations in hormone levels.     

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.     

Spontaneous alveolar bone loss after 4NQO exposure in Wistar rats

ObjectiveThis study evaluated the effect of an experimental carcinogenic, 4-Nitroquinoline 1-oxide (4NQO), in the spontaneous alveolar bone loss (ABL) in an animal model.DesignTwenty-two male Wistar rats were included in this study. They were randomly divided into two groups: the control group (n = 10) received food and water ad libitum, and the test group (n = 12) receive the same food; however, 25 ppm of 4NQO was diluted in the drinking water. All animals were euthanized after 20 weeks, and the tongues were removed and analyzed macroscopically to determine the presence of oral mucosal lesions. All specimens were paraffin-embedded and histological sections were obtained. The microscopic analysis was based on routine procedure (haematoxylin and eosin stain). The analysis of spontaneous ABL was performed by a calibrated examiner using standardized photographs and imaging software. Differences in spontaneous ABL were assessed among the three resulting groups: control, 4NQO with oral squamous cell carcinoma (OSCC), and 4NQO without OSCC.ResultsIn the 4NQO-treated group, nine animals developed OSCC. The animals in the 4NQO with OSCC group presented significantly more spontaneous ABL (0.65 ± 0.21 mm) than the control group (0.34 ± 0.05) (p < 0.001). The animals in the 4NQO without OSCC group showed a mean spontaneous ABL of 0.47 ± 0.13 mm, which was not statistically significant different when compared to the control group (p = 0.096).ConclusionsIt was concluded that the presence of OSCC enhanced spontaneous ABL in Wistar rats when compared to control animals. Additionally, it was shown that, solely, administration of 4NQO may not be considered responsible for alveolar bone destruction.