Comparison of histometric and morphometric analyses of bone height in ligature-induced periodontitis in rats

Induced Periodontitis in Rats With Three Ligature Types: An Exploratory Study

BACKGROUND

The placement of ligatures in the cervical area of rat molars is considered as a predictable model to induce periodontitis.

OBJECTIVES

The present explorative study aimed to compare the efficacy of metal wires (MWs), without or with sandblasting, versus silk ligatures (SLs) in inducing periodontal bone loss in rats.

MATERIALS AND METHODS

Twenty-four Wistar rats were randomly divided into three groups of eight rats that received three different types of ligatures (MW, sandblasted wire [SMW], and SL) around their first right mandibular molar, while the contralateral tooth was left without the ligature and served as a control. Bone loss was assessed by measuring the distance from the cementoenamel junction (CEJ) to the bone crest at the distal aspect of the first molar on central mesiodistal sections generated from micro-CT scans taken 24 and 35 days after ligature placement.

RESULTS

In the SL group, only in two rats the ligatures were retained until the end of the 24-day period; in all other animals, the ligatures were lost at some time point. In the SMW, the ligatures were retained only for the 24-day period. In the MW group, no ligatures were lost. Irrespective of the group or experimental period, the difference in the crestal bone level between ligated and control teeth was in most cases z < 0.20 mm, that is, in 19 out of 25 pairs of teeth. In a few cases, the bone crest was more apically located at the control teeth compared to the ligated ones (four cases each, during both 24- and 35-day experimental periods).

CONCLUSIONS

Bone loss was minimal during the experimental period, with no significant differences between the test and control teeth, or among the three types of ligatures. MWs, not even roughened, do not seem to be a better alternative to SLs for inducing bone loss in the experimental periodontitis model in the rat. This assumption, however, has to be confirmed in a larger, well-powered study.

Alveolar Bone Loss in a Ligature-Induced Periodontitis Model in Rat Using Different Ligature Sizes

OBJECTIVES

 Ligature-induced periodontitis model has been widely used as a preclinical stage for investigating new treatment modalities. However, the effect of different ligature sizes on alveolar bone loss has never been studied. Therefore, we examined alveolar bone loss in this rat model using different sizes of silk ligatures, as well as healing after ligature removal.

MATERIALS AND METHODS

 Left maxillary second molars of Sprague-Dawley rats were ligated with 3-0, 4-0, or 5-0 silk ligatures (n = 4-5/group) for 14 days before harvested maxillae and gingival tissues. For subsequent experiment, animals were ligated for 14 days using the ligature size that induced the most alveolar bone loss before ligature removal and sacrificed at 0, 7 and 14 days (n = 5-6/group). All maxillae and gingival tissues were harvested to evaluate alveolar bone level, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) levels.

STATISTICAL ANALYSIS

 Data was analyzed using SPSS Statistics 23.0 software (SPSS Inc., Chicago, Illinois, United States). Data from all experiments were tested for normality using Shapiro-Wilk test. Data between ligatured and nonligatured teeth were compared using Student's t-test or Wilcoxon signed-rank test. Differences among different ligature sizes were analyzed by analysis of variance followed by multiple comparisons with post-hoc test. A p-value less than 0.05 was considered statistically significant.

RESULTS

 The alveolar bone loss of ligated teeth was substantially higher than that of control after 14 days of ligation. While 3-0 and 4-0 resulted in significantly greater bone loss than 5-0 silk, the 3-0 group had the lowest rate of ligature loss. Therefore, alveolar bone healing postligature removal was investigated further using 3-0 silk. The results showed no significant bone level change at 2 weeks after ligature removal. In term of IL-1β and TNF-α levels, there was no statistically significant difference in IL-1β level between groups at any time point, while TNF-α was undetectable.

CONCLUSION

 These data showed that 3-0 silk was the most effective ligature size in promoting alveolar bone loss comparing with 4-0 and 5-0 silk. During the 2-week period following ligature removal, spontaneous bone healing was not observed.

Chronic exposure to lead acetate promotes changes in the alveolar bone of rats: microstructural and physical-chemical characterization

There are a few data relating to the effects of lead (Pb) exposure on the alveolar bone, which has very distinct morphophysiological characteristics and is of great importance in the oral cavity. In this context, the aim of this study was to investigate the changes promoted after long-term exposure to Pb in the microstructure of the alveolar bone of rats. Twenty adult Wistar rats were exposed to 50 mg/kg/day of lead acetate for 55 days. These animals were euthanized and had their mandible removed. Each mandible was divided into hemimandibles, and the alveolar bone was used for bone lead quantification, crystallinity analysis, microstructure evaluation by the percentage of bone volume (BV/TV), number of trabeculae (Tb.N), thickness of the trabecular (Tb.Th), and trabecular space (Tb.Sp). Morphometric analysis of the exposed root area was also performed. Long-term exposure to Pb resulted in high levels of Pb in the alveolar bone but showed no changes in the organization of crystallinity. The microstructural analyses showed a reduction of BV/TV, Tb.Th, and Tb.N and increase of Tb.Sp parameters, resulting in an increase in the exposed root area and an alveolar bone loss in height. The findings of this study reveal the ability of Pb to alter the alveolar bone microstructure after long-term exposure to the metal, possibly due to changes in tissue homeostasis, contributing to the reduction of bone quality.

Avaliação da perda óssea utilizando diferentes parâmetros na análise microtomográfica. Estudo em ratos

Resumo Introdução o desafio no uso do Micro-Ct tem sido estabelecer e padronizar padrões adequados para escaneamento e tratamento das imagens, para que se obtenha o máximo desempenho do equipamento, e permitir a comparação dos achados entre diferentes estudos. Objetivo o presente estudo tem como objetivo comparar a porcentagem de volume ósseo em regiões com perda óssea periodontal utilizando diferentes metodologias para definição da área a ser analisada (ROI). Material e método dez ratos foram submetidos à indução de doença periodontal, e, após a eutanásia, as mandíbulas foram escaneadas com cortes de 9 μ e 18 μm de espessura, com passo de rotação de 0.3mm. As imagens foram reconstituídas utilizando o software NRecon, e em seguida, utilizando o software CTAnalyser – CTAn, foram definidas as áreas de interesse (ROI) ao redor dos segundos molares. A primeira área de interesse (ROI1) foi definida em um padrão retangular que se restringiu às regiões interproximais e furca, onde a área total de tecido ósseo foi obtida somando os resultados dos 3 ROIs. A segunda área (ROI2) foi definida no sentido corono/apical ao redor do segundo molar até suas limitações proximais com os dentes vizinhos, onde a porcentagem de tecido ósseo pertencente às raízes foram excluídas das avaliações. As análises foram realizadas com cinco diferentes valores de thresholds (130-50, 130-60, 130-70, 130-80, 130-90 e 130-100). Resultado a análise entre os diferentes ROIs demonstrou que em ambas as análises foi observada a tendência a menor porcentagem de tecido ósseo quanto maior o contraste de tons de cinza utilizado, no entanto, nos resultados obtidos no ROI2 essa diferença não foi estatisticamente significante. Conclusão com os resultados obtidos pode se concluir que a utilização de diferentes thresholds para quantificação óssea, em áreas onde houve doença periodontal, pode trazer resultados divergentes; a definição da área de interesse interfere com os resultados obtidos e que a obtenção de uma área de interesse com a remoção das raízes mostrou-se menos susceptível à variação dos parâmetros de escaneamento.

Imaging Microstructural Damage and Alveolar Bone Loss in Rats Systemically Exposed to Methylmercury: First Experimental Evidence

The alveolar bone is an important mineralized structure of the periodontal support apparatus, and information about the methylmercury (MeHg) effects on the structural integrity is scarce. Therefore, this study aimed to investigate whether systemic, chronic, and low-dose exposure to MeHg can change the alveolar bone microstructure of rats. Adult Wistar rats (n = 30) were exposed to 0.04 mg/kg/day of MeHg or vehicle through intragastric gavage. The animals were euthanized after 60 days, and blood samples were collected for trolox equivalent antioxidant capacity (TEAC), glutathione (GSH), lipid peroxidation (LPO), and comet assays. The mandible of each animal was collected and separated into hemimandibles that were used to determine the total Hg level in the bone and to analyze microstructural damage and alveolar bone loss in terms of trabecular number (Tb.N), trabecular thickness (Tb.Th), bone volume fraction (BV/TV), and exposed root area of the second molars. MeHg exposure triggered oxidative stress in blood represented by lower levels of GSH and TEAC and the increase in LPO and DNA damage of the blood cells. High total Hg levels were found in the alveolar bone, and the microstructural analyses showed a reduction in Tb.N, Tb.Th, and BV/TV, which resulted in an increase in the exposed root area and a decrease in bone height. Long-term MeHg exposure promotes a systemic redox imbalance associated with microstructural changes and alveolar bone loss and may indicate a potential risk indicator for periodontal diseases.

Influence of immunosuppression on the progression of experimental periodontitis and on healthy periodontal tissue: A rat in vivo study

Background. The potent anti-inflammatory and immunosuppressive properties of glucocorticoids (GCs) might influence the progression of some disorders, such as periodontitis. Hence, this study aimed to investigate the influence of dexamethasone (DEX) on the alveolar bone loss (ABL) of healthy and periodontally compromised molars in rats.

Methods. Thirty male rats were randomly assigned to two groups: physiological saline solution (PSS) and DEX. The animals received subcutaneous injections of either 0.5 mL of PSS) (group PSS) or 2 mg/kg of DEX (group DEX) from one day before experimental periodontitis (EP) induction until euthanasia. EP was induced through ligature placement around the mandibular lower first molars at day 0. Contralateral molars remained unligated. Ten animals per period were euthanized on days 3, 7, and 14. Morphometric analysis was performed to access the ABL. Data were statistically analyzed with ANOVA followed by post hoc Tukey tests (P ≤ 0.05).

Results. Higher ABL was observed in both groups on days 7 and 14 than on day 3 (P ≤ 0.05). Concerning periodontitis, higher ABL was observed in group DEX on days 3, 7, and 14 days than group PSS at the same time intervals (P ≤ 0.05). Also, even in the contralateral unligated molars, group DEX exhibited higher ABL on days 3, 7, and 14 days than group PSS at the same time intervals (P ≤ 0.05).

Conclusions. Collectively, it can be concluded that DEX aggravates EP and induces spontaneous ABL in the healthy periodontium.

Fish oil diet effects on alveolar bone loss, in hypercholesterolemic rats

This study evaluated the effects of replacing a saturated fat diet by n-3 polyunsaturated fatty acids (n-3PUFA), on alveolar bone loss in hypercholesterolemic rats with experimental periodontitis (PD).

METHODS

Eight week old Wistar rats were assigned according to dietary intake. Control group (C, n = 15) fed a commercial diet throughout the experiment. Atherogenic group (AT, n = 30) fed AT diet for 3 weeks; thereafter, AT was randomized to receive either a n-3PUFA (n = 15) or to continue with AT (n = 15) diet. Subsequently, PD was induced in all groups by unilateral ligature (L) of the first molar (M1) of the left mandible, non-ligated contralateral molars served as controls. After every week of PD induction, 5 rats per group were euthanized. Serum was collected for lipids assays and hemi-mandibles were subjected to histomorphometric (% upper and lower interradicular bone volume and periodontal ligament height, hPDL) and radiographic analyses (periodontal bone support, PBS, in ligated teeth, between M1-M2).

RESULTS

Rats fed n-3PUFA diet rapidly induced a significant reduction in the serum lipids (p < 0.001). In all rats the ligated teeth showed a greater bone loss as compared with the unligated molars. At the end of the experiment the AT + L was the worst in % lower bone volume (p < 0.01), hPDL and PBS (p < 0.05). In contrast, rats fed n-3PUFA + L was similar to those rats fed C diet (p > 0.05).

CONCLUSION

Alveolar bone and dyslipidemia improved by substituting saturated fat intake for a n-3PUFA rich diet, in hypercholesterolemic rats with PD.

Effects of Low Molecular Weight Heparin on Alveolar Bone Loss in Wistar Rats

This study aimed to assess the effects of low molecular weight heparin (LMWH) on alveolar bone loss (ABL), blood count, and counting of megakaryocytes and adipocytes in male Wistar rats. Forty male 60-day Wistar rats were randomly divided into four groups: Control (C), Periodontal Disease (PD), Heparin (Hp) and Heparin + Periodontal Disease (Hp+PD). LMWH was applied for 60 days at doses of 1 ml/kg/day. Blood samples were collected at baseline, 30 and 60. On day-49, PD and Hp+PD groups were subjected to ligature-induced periodontitis around second upper right molar. The left side was assessed as spontaneous alveolar bone loss. Mean ABL in the side with ligature showed significantly different between C (0.35±0.07 mm) and Hp+DP (0.49±0.09 mm) groups (p<0.001), between PD (0.55±0.11 mm) and Hp (0.32±0.06 mm) groups (p<0.001) and between Hp and Hp+DP groups (p<0.001). No significant differences were found among groups for ABL in the side without ligature. Animal weight, food intake, and water consumption showed no statistically significant difference among groups. Megakaryocytes and adipocytes were counted using optical microscopy and no statistically significant differences were found. Within-groups, there were an increase and a decrease, respectively, in the counting of lymphocytes (p=0.005 for C and p=0.009 for Hp+PD groups only) and leukocytes (p=0.003 for C, p=0.001 for PD, p=0.002 for Hp, and p<0.001 for Hp+PD groups). There was no decrease in the number of platelets in the three collection periods. LMWH was not able to affect ABL, but it may change the blood counting, especially increasing lymphocytes.

Effect of glutamine ingestion on the progression of induced periodontitis: experimental study in rats

Abstract Introduction With glutamine supplementation there is better performance in the body’s defense system. Objective The aim of this study was to analyze the effect of glutamine supplementation on ligand-induced periodontal disease in rats. Material and method 48 selected male Wistar rats were divided into 4 groups (N = 12): control group (CG) including healthy animals receiving daily saline solution via gavage; glutamine group (GG) including healthy animals receiving oral glutamine supplementation by gavage at a dose of 1.5 g / kg / day; periodontitis group (PG) including animals with induced periodontal disease on both upper sides receiving daily saline solution via gavage; experimental group (EG) including animals with induced periodontal disease on both upper sides receiving daily glutamine via gavage at a dose of 1.5 g / kg / day. On the 30th day, all animals were euthanized by excess anesthetic. Result In the various analyses, the EG (116.63 ± 22.50 mm2) compared to the CG (82.32 ± 7.48 mm2) obtained a p<0.05. The PG (143.15 ± 35.24 mm2) compared to the EG group (116.63 ± 22.50 mm2 ) presented a p<0.05. The PG (143.15 ± 35.24 mm2) compared to the CG (82.32 ± 7.48 mm2) presented a p<0.05. The GG (118.09 ± 10.4 mm2) compared to the CG (82.32 ± 7.48 mm2) presented a p>0.05. Conclusion Glutamine supplementation associated with induced periodontal disease demonstrated a smaller amount of bone loss compared to the periodontitis group.

Effect of 15% Alcohol Dependence on Alveolar Bone Loss and TNF-α Secretion in Wistar Rats

The aim of the present study was to evaluate the effect of 15% alcohol dependence on ligature-induced alveolar bone loss and TNF-α secretion in Wistar rats. Thirty-three male Wistar rats aged 45-60 days (mean weight=253 g) were randomly allocated test or control groups. Test group (n=18) received 15% alcohol as liquid intake and control group (n=15) received water during the experimental period. TNF-α was analyzed by ELISA assay in 11 animals per group. After 14 days of alcohol/water intake, alcohol dependency was assessed and silk ligatures were placed around the left second upper molars. Ligature presence and body weight were checked weekly. After 40 days, animals were sacrificed and the maxillae were defleshed for morphometric analysis using standardized images. All animals in the test group displayed signs of alcohol dependency at day 14. No statistically significant differences in final body weight (334.83±21.38 vs. 322.48±30.65 g, p=0.20) were observed between groups. In relation to alveolar bone loss, no statistically significant difference was observed among test and control groups both for ligated teeth (0.76±0.06 vs. 0.74±0.10 mm, p=0.60) and unligated teeth (0.41±0.16 vs. 0.35±0.05 mm, p=0.22). The TNF-α secretion also did not display statistically significant differences between test and control groups (10.78±1.84 vs. 12.13±2.11 pg/mL, p=0.12). It may be concluded that 15% alcohol dependency was not capable to alter alveolar bone loss and TNF-α secretion in Wistar rats.

Effects of alcohol and/or tobacco exposure on spontaneous alveolar bone loss in rat

The aim of the present study was to evaluate the effect of alcohol and/or tobacco exposure on spontaneous alveolar bone loss in Wistar rats. Twenty-four, male, 60 day-old, Wistar rats were assigned to 4 groups: Group 1 received 10 mL/kg of glucose solution (5%). Group 2 received 2 g/kg alcohol (20%). Group 3 was exposed to tobacco smoke (6 cigarettes/60 min). Group 4 received both interventions of groups 2 and 3. Alcohol was given by gastric gavage and cigarette exposure was performed using a forced ventilation chamber. After 30 days, animals were sacrificed and the upper maxillae removed and defleshed. Morphometric analysis of alveolar bone loss (ABL) around the second molar was performed in standardized digital photographs. Statistical analysis was conducted using paired t-test, one-way ANOVA and occurrence of spontaneous periodontal disease (ABL ≥ 0.39 mm) was analyzed by Fisher's exact test. Significant differences in body weight were observed between all groups. Group 2 presented higher body weight as compared to the 3 other groups at 4 weeks (p≤0.05). Mean ABL values were 0.31 mm (±0.08), 0.29 mm (±0.07), 0.33 mm (±0.10), and 0.33 mm (±0.08) for groups 1, 2, 3, and 4, respectively. No significant differences were found among groups. In the analysis of occurrence of periodontal breakdown, alcohol exposure decreased the occurrence of ABL and cigarette exposure increased ABL. The combination of alcohol and cigarette exposure did not differ from the control group. Alcohol consumption decreased the occurrence of periodontal breakdown, while tobacco increased this rate.

Obesity may increase the occurrence of spontaneous periodontal disease in Wistar rats

OBJECTIVE

To evaluate the effect of body weight on the occurrence of spontaneous alveolar bone loss in Wistar rats.

METHODS

Twenty-eight rats were randomly divided in two groups. Control group received standardized rat chow diet and water. Test group received cafeteria (CAF) diet during 17 weeks. Diet was available for both groups ad libitum. Body weight and Lee Index were evaluated. At the end of the experimental period, rats were killed by decapitation and maxillae were defleshed with 9% sodium hypochlorite. Morphometric analysis was performed in digital standard photographs. Presence of spontaneous periodontitis was considered when mean alveolar bone loss was ≥0.51mm (75th percentile). Statistical analysis was performed with chi-square test, Mann-Whitney test and independent samples t-test (significance level P≤0.05).

RESULTS

After 17 weeks of exposure to standard CAF diet, a statistically significant mean difference in body weight (g±SD) (478±43 vs. 580±60) and Lee Index (3.07±0.05 vs. 3.24±0.07) was observed between control and obesity groups, respectively. Median (interquartile range) of alveolar bone loss in control group was 0.344 (0.313-0.367) and 0.491 (0.427-0.506) for buccal and palatal site, respectively. For obese group was 0.308 (0.289-0.354) and 0.549 (0.482-0.616) for buccal and palatal site, respectively. In animals submitted to CAF diet, 20 sites were classified as spontaneous periodontal disease, whereas in control animals, only 8 sites exhibited periodontal breakdown according cut-off point. A significant difference between groups was detected (P=0.009).

CONCLUSIONS

It may be concluded that obesity increases the occurrence of spontaneous periodontal disease in Wistar rats.

Resveratrol decreases periodontal breakdown and modulates local levels of cytokines during periodontitis in rats

BACKGROUND

Resveratrol (3,4',5-trihydroxystilbene) is a naturally occurring product found in numerous plants. Among its biologic properties, resveratrol may promote immunomodulatory effects on the host response. This study investigates the effect of continuous administration of resveratrol on the progression of experimental periodontitis in rats.

METHODS

Periodontitis was induced in rats in one of the first molars chosen to receive a ligature. Animals were assigned to one of two groups: 1) daily administration of the placebo solution (control group) or 2) 10 mg/kg resveratrol (RESV group). The therapies were administered systemically for 30 days: for 19 days before periodontitis induction and then for another 11 days. Then, the specimens were processed for morphometric analysis of bone loss, and the gingival tissue surrounding the first molar was collected for quantification of interleukin (IL)-1β, IL-4, and IL-17 using a multiplexing assay.

RESULTS

Intergroup comparisons of the morphometric outcomes revealed higher bone loss values in ligated molars and unligated teeth in the control group than the RESV group (P <0.05). The immunoenzymatic assay of the gingival tissue showed a lower concentration of IL-17 in the RESV group than the control group (P <0.05), whereas no differences in the IL-1β and IL-4 levels of the groups were observed (P >0.05).

CONCLUSIONS

Continuous administration of resveratrol may decrease periodontal breakdown induced experimentally in rats. In addition, lower levels of IL-17 were found in the RESV group. Future studies are important to confirm the mechanism through which resveratrol exerts its effects.

Correlation analysis of alveolar bone loss in buccal/palatal and proximal surfaces in rats

The aim was to correlate alveolar bone loss in the buccal/palatal and the mesial/distal surfaces of upper molars in rats. Thirty-three, 60-day-old, male Wistar rats were divided in two groups, one treated with alcohol and the other not treated with alcohol. All rats received silk ligatures on the right upper second molars for 4 weeks. The rats were then euthanized and their maxillae were split and defleshed with sodium hypochlorite (9%). The cemento-enamel junction (CEJ) was stained with 1% methylene blue and the alveolar bone loss in the buccal/palatal surfaces was measured linearly in 5 points on standardized digital photographs. Measurement of the proximal sites was performed by sectioning the hemimaxillae, restaining the CEJ and measuring the alveolar bone loss linearly in 3 points. A calibrated and blinded examiner performed all the measurements. Intraclass Correlation Coefficient revealed values of 0.96 and 0.89 for buccal/lingual and proximal surfaces, respectively. The Pearson Correlation Coefficient (r) between measurements in buccal/palatal and proximal surfaces was 0.35 and 0.05 for the group treated with alcohol, with and without ligatures, respectively. The best correlations between buccal/palatal and proximal surfaces were observed in animals not treated with alcohol, in sites both with and without ligatures (r = 0.59 and 0.65, respectively). A positive correlation was found between alveolar bone loss in buccal/palatal and proximal surfaces. The correlation is stronger in animals that were not treated with alcohol, in sites without ligatures. Areas with and without ligature-induced periodontal destruction allow detection of alveolar bone loss in buccal/palatal and proximal surfaces.

Protective effect of topical Cordia verbenacea in a rat periodontitis model: immune-inflammatory, antibacterial and morphometric assays

BACKGROUND

This study evaluated the effects of C. verbenacea essential oil topically administered in a rat periodontitis model.

METHODS

Periodontitis was induced on rats in one of the mandibular first molars assigned to receive a ligature. Animals were randomly divided into two groups: a) non-treatment group (NT) (n = 18): animals received 1mL of vehicle; b) C. verbenacea group (C.v.) (n = 18): animals received 5mg/Kg of essential oils isolated from C. verbenacea. The therapies were administered topically 3 times daily for 11 days. Then, the specimens were processed for morphometric analysis of bone loss. The ligatures were used for microbiological assessment of the presence of Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Porphyromonas gingivalis using PCR. The gingival tissue was collected to Elisa assay of interleukin (IL)-1α and IL-10 levels.

RESULTS

Bone loss was inhibited by C. verbenacea when compared to the NT group (p < 0.05). A decrease in the levels of IL-1α and increase in the IL-10 amounts was observed in the C.v. group as compared to NT group (p < 0.05). A lower frequency of P. gingivalis was found in C.v. group (p < 0.05).

CONCLUSION

C. verbenacea essential oil topically administered diminished alveolar bone resorption, promoting a positive local imbalance in the pro/anti-inflammatory system and reducing the frequency of detection of P. gingivalis.

Effect of obesity on alveolar bone loss in experimental periodontitis in Wistar rats

Obesity has been linked to higher inflammatory status and periodontal breakdown.

Evaluation of the effect of an organic extract obtained from Ipomoea alba L. on experimental periodontitis in rats

The aim of this study was to evaluate the effect of an organic extract obtained from Ipomoea alba L. (Convolvulaceae or OE 1493), on experimental periodontal disease in rats. Periodontitis was induced in thirty six Wistar rats: a first mandibular molar was randomly assigned to receive a ligature, whereas the contralateral molar was left unligated. Animals were randomly assigned to two groups and treated topically, three times a day, for 11 days, as follows: Control Group - vehicle-treated (n = 18), and Test Group - OE 1493-treated (n = 18). The rats were sacrificed on the 12th day. Morphometrical measurements from the cementoenamel junction to the bone crest were performed to determine alveolar bone loss, using standardized photographs. Single- and multi-dose acute toxicity assays were carried out after OE 1493 treatment. Morphometrical analysis demonstrated that topically-administered OE 1493 showed no effect on reducing bone loss when compared with the control group (p > 0.05). In addition, OE 1493 did not present toxicity. Within the limits of this investigation, it may be concluded that OE 1493 did not show any positive influence on the progression of ligature-induced periodontitis in rats, when administered according to the regimen used in the present study.

Influence of different durations of estrogen deficiency on alveolar bone loss in rats

The purpose of this study was to morphometrically evaluate the influence of different durations of ovariectomy-induced estrogen deficiency on alveolar bone loss associated with ligature-induced bone loss in rats. Sixty female Wistar rats were randomly assigned to ovariectomy (OVX test group) or sham operation (SHAM control group). The OVX and SHAM groups were each distributed into three subgroups of ten rats each according to the duration of estrogen deficiency (30, 60 and 90 postoperative days). In all groups, for the last 30 days of the experimental period, cotton ligatures were placed around the cervix of the right upper second molar; the contralateral tooth was left unligated to serve as a control. The maxillary bones were removed, and the alveolar bone loss was analyzed by measuring the distance between the cementoenamel junction and the alveolar bone crest at the buccal site of the right upper second molar. A comparison between the ligated and unligated groups verified the presence of ligature-induced alveolar bone loss (p < 0.05). No significant differences were observed among the unligated groups (p > 0.05). A significant increase in bone loss was observed when ligation occurred 90 days after ovariectomy compared with the sham group (p < 0.05). These results demonstrate that long-term estrogen deficiency affects ligature-induced alveolar bone loss.

Effect of inhaled corticosteroid on TNF-α production and alveolar bone loss in Wistar rats

OBJECTIVE

To evaluate the effect of different concentrations of inhaled budesonide on secretion of tumoral necrosis factor-alpha (TNF-α) and on ligature-induced alveolar bone loss in Wistar rats.

MATERIALS AND METHODS

Forty-two animals were randomly divided in four groups. Control group (G1) did not receive any procedure. For the other 3 groups, alveolar bone loss was induced by placement of ligatures around the upper second molar. The contralateral molar was considered intra-group control. Group 2 (G2) was nebulized with saline solution (NaCl 0.9%). Groups 3 and 4 (G3 and G4) were nebulized with 30 μg and 100 μg budesonide, respectively. Administration of drugs was performed daily for 14 days. Blood samples were collected from all animals for analysis of TNF-α. The maxillae from G2, G3 and G4 were removed and defleshed with 9% sodium hypochlorite. Morphometric analysis of bone loss was performed in digital standard photographs. Statistical analysis was performed with one-way ANOVA, followed by Tukey HSD or Scheffé multiple comparison's test (significance level P ≤ 0.05).

RESULTS

Mean alveolar bone loss values for teeth with ligature were 0.72, 0.70 and 0.77 mm for Groups 2, 3 and 4, respectively. No statistically significant differences were found amongst groups with or without ligature. The production of TNF-α was 60% higher in the presence of ligature (G1 vs. G2/G3/G4). No effect was observed in TNF-α secretion after inhalation of budesonide.

CONCLUSION

Inhaled budesonide in different concentrations did not alter alveolar bone loss and TNF-α secretion in male Wistar rats.

Methodological model of chronic stress associated with ligature-induced periodontitis in rats: a radiographic study

This study evaluated the time efficiency of stress associated with ligature-induced periodontitis in rats. Sixty adult Wistar rats, housed in temperature-controlled rooms and receiving water and food ad libitum, were randomly separated into stress (n = 30) or control groups (n = 30). All animals were anesthetized, and nylon ligatures were placed at the gingival margin level of the maxillary right second molars. After the induction of periodontitis, rats in the stress group were subjected to physical restraint for 12 hours daily. The animals were euthanized after 7, 15 and 30 days by anesthetic overdose (10 animals per group per period). The right hemimaxillae were stored in formalin solution for 48 hours. Parallel radiographic images of the hemimaxillae were taken and processed following standard procedures. Radiographic examination was performed by a blinded and previously calibrated investigator. Bone height level was measured, and data were submitted to analysis of variance and post hoc Bonferroni tests (p < 0.05). Rats in the stress group had greater bone loss than those in the control group at 7 and 15 days post-induction (p < 0.05). After 30 days, there was no statistically significant difference between the groups (p > 0.05). Restraint stress modulates the short-term progression of periodontal disease in rats. Therefore, the 12-hour daily physical restraint stress model in rats applied for up to 15 days is suitable for the investigation of the combined effect of ligation and restraint stress on periodontal degradation.

Evaluation of two morphometric methods of bone loss percentages caused by periodontitis in rats in different locations

Objective

The present study evaluated morphometrically bone loss percentages in experimental periodontitis in rats, comparing different locations (lingual mandible, palatal maxilla and buccal maxilla) and two evaluation methods (distance and area methods).

Material and Methods

Ligatures were placed around the maxillary right second molar and around the mandibular right first molar in 14 female Wistar rats. The contralateral molars served as intragroup controls. After 4 weeks, the rats were sacrificed and their mandible and maxilla were removed. The specimens were dissected and stained with methylene blue dye. Bone loss was evaluated by two different methods on the surfaces of the defleshed jaw. In the first method, the distance from the cementoenamel junction (CEJ) to the alveolar bone crest was measured in the roots of teeth associated with ligature. In the second method, the area of bone loss was determined using the alveolar tissue bone, CEJ and the proximal region of roots associated with the ligature as reference. The data were converted to bone loss percentages caused by ligature: (ligated – unligated) x 100/ligated.

Results

When comparing the distance and area methods, no statistically significant difference was observed (p>0.05). Both methodologies indicated that the maxilla presented greater bone loss than the mandible and it was more accentuated on the buccal side than on the palatal side (p<0.05).

Conclusion

The findings of this study show that both the area and the distance methods can be used to evaluate bone loss caused by ligature placement in rats, and suggest applying the morphometric methodology to the maxilla on the buccal side.

Influence of bisphosphonates on alveolar bone density: a histomorphometric analysis

This study is a histomorphometrical analysis of the influence of the bisphosphonate alendronate on alveolar bone density. Eighteen male Wistar rats were randomly assigned to a control group (n = 9) that received no medication and an experimental group (n = 9) that received oral alendronate (1 mg/kg) from birth until euthanization at 3 months of age. Semi-serial 4-µm-thick transverse sections were obtained from the region between the roots of the left maxillary first molar, stained with hematoxylin and eosin, and examined with a Zeiss Axioskop II optical microscope for histomorphometric analysis. The images were captured with a digital camera coupled with the microscope and connected to a computer, and were analyzed using Image J 1.34s image-analysis software. A 1,200-point grid was positioned onto each digitized image. The number of intersection points of grid lines in the bone tissue was counted. The ratio between the number of points in the bone tissue and the total number of points of the grid (1,200) was used to determine the bone density of the analyzed tissue. Data from the control and experimental groups were compared and analyzed statistically by the Student's t-test (p = 0.05). There was no statistically significant difference (p = 0.3754) in the alveolar bone density between the control and alendronate-treated animals. It may be concluded that the bisphosphonate alendronate did not alter the morphology of the alveolar bone, maintaining its structural tissue characteristics in healthy animals.

Low caloric value of ethanol itself increases alveolar bone loss in ligature-induced periodontitis in male rats

This study aimed at morphometrically evaluating the influence of variable caloric values of ethanol consumption on alveolar bone loss in periodontitis in male rats. Thirty-six male rats were randomized into four groups of nine rats each, as follows: Test group A (low) - rats were fed an ethanol-containing liquid diet (ethanol representing 22% of total caloric value); Control group A -rats were fed a pair-fed control diet (ethanol replaced by isocaloric amounts of carbohydrate); Test group B (high) -rats were fed an ethanol-containing liquid diet (ethanol representing 36% of total caloric value); Control group B -rats were fed a pair-fed control diet for Test B. Following anesthesia, cotton ligatures were placed around the cervix of the right upper second molar. At eight weeks, the maxillary bones were removed and alveolar bone loss was analyzed by measuring the distance between the cementoenamel junction and the alveolar bone crest at buccal and palatal sites of the upper second molar. The unligated groups showed no significant differences between the bone loss values observed for the low and high caloric values of ethanol (p > 0.05). In the ligated groups, the rats receiving low caloric values of ethanol showed significantly greater bone loss compared to the isocaloric rats (p < 0.05); however, the rats receiving high caloric values of ethanol showed no significant differences compared to the controls. Analysis of the results demonstrated that, in male rats, ethanol itself affected ligature-induced bone loss when representing a low value in the total caloric value.

Effect of neonatal clomipramine in the pathogenesis of ligature-induced periodontitis in Lewis rats

OBJECTIVE

The aim of this study was to verify the association between an endogenous depression model and the development of ligature-induced periodontitis in rats.

MATERIAL AND METHODS

Nine male Lewis rats received 30 mg/kg clomipramine from neonatal day 8 to day 21 (depressed group), while 13 control Lewis rats were left untouched (control group). On day 150, ligatures were placed around the 2nd upper molars in both groups, i.e. the contralateral molar of the intra-group control. On day 190, the rats were killed and the maxillae were defleshed. The distance between the cemento-enamel junction and the alveolar bone crest was measured by a blinded examiner using standardized digital photographs.

RESULTS

The depressed rats showed hyperactivity in open field on day 142 and greater attempts to escape on day 143 compared to controls. The other behavioral data did not show statistically significant differences between the groups (Mann-Whitney, p>0.05). In teeth with ligature, mean alveolar bone loss varied from 0.51 to 0.60 and from 0.63 to 0.64 mm for tests and controls, respectively (t-test, p>0.05). In teeth without ligature, these values varied from 0.38 to 0.43 and 0.42 to 0.45 mm in the test and control groups, respectively (t-test, p>0.05).

CONCLUSION

Induced depression did not alter ligature-induced bone loss in Lewis rats.

Effect of body weight in the pathogenesis of ligature-induced periodontal disease in Wistar rats

OBJECTIVE

The aim of this study was to compare ligature-induced alveolar bone loss between obese and non-obese rats.

MATERIAL AND METHODS

Thirty female Wistar rats were randomly divided into two groups: a test group comprising 14 rats fed with a "cafeteria diet" for 120 days in order to gain weight and a control group comprising 16 regularly fed rats. Ligatures were placed around the 2nd upper molars, and the contralateral teeth served as intra-group controls. After 30 days, the animals were killed and the maxillae were removed. Sodium hypochlorite was used to prepare the specimens, and the cementum-enamel junction was stained with methylene blue 1%. Morphometric analysis of alveolar bone loss was by standardized digital photographs and the distance between the cementum-enamel junction and the alveolar bone crest was measured using the software Image Tool 3.0.

RESULTS

Body weight differed statistically between test and controls (268.6 and 242.4 g, respectively). Test animals demonstrated a mean (SD) alveolar bone loss of 0.51 (0.11) mm and in the controls 0.52 (0.14) mm in teeth with ligatures. No statistically significant differences were observed (ANOVA+Tukey), except for teeth with and without ligatures in both groups.

CONCLUSIONS

The establishment and progression of alveolar bone loss in rats was not influenced by body weight in the present study.