Induction Of Periodontitis Research Articles

Histopathological evaluation of different methods of experimental induction of periapical periodontitis

This study evaluated histopathologically different methods of experimental induction of periapical periodontitis. The radiographic and microbiological evaluations have been performed in a previous investigation. Fifty-seven root canals from dogs' teeth were assigned to 4 groups. In GI (n=14) and GII (n=14), the root canals were exposed to oral environment for 180 days; in GIII (n=14) and GIV (n=15) the root canals were exposed for 7 days and then the access cavities were restored and remained sealed for 53 days. The root apices of GI and GIII were perforated, whilst those of GII and GIV remained intact. After induction of periapical periodontitis, the dogs were euthanized. Serial sections were obtained and stained with hematoxylin and eosin. Data of the histopathological evaluation were submitted to Kruskal-Wallis and Dunn's tests at 5% significance level. The inflammatory periapical reaction and resorption of mineralized tissues were less intense in GII than in the other groups (p<0.05). There was no histopathological difference among the experimentally induced periapical lesions in the teeth with coronal sealing. On the other hand, when coronal sealing was not performed, greater intensity of induced periapical periodontitis was observed in the teeth with apical perforation.

Microbial distribution in the root canal system after periapical lesion induction using different methods

The aim of this study was to evaluate the microbial distribution in the root canal system after periapical lesion induction in dogs' teeth using different methods. Fifty-two root canals were assigned to 4 groups (n=13). Groups I and II: root canals were exposed to the oral cavity for 180 days; groups III and IV: root canals were exposed for 7 days and then the coronal openings were sealed for 53 days. The root apices of groups I and III were perforated, while those of groups II and IV remained intact. After the experimental periods, the animals were euthanized and the anatomic pieces containing the roots were processed and stained with the Brown & Brenn method to assess the presence and distribution of microorganisms. The incidence of microorganisms at different sites of the roots and periapical lesions was analyzed statistically by the chi-square test at 5% significance level. All groups presented microorganisms in the entire root canal system. A larger number of microorganisms was observed on the root canal walls, apical delta and dentinal tubules (p<0.05), followed by cementum and cemental resorption areas. In spite of the different periods of exposure to the oral environment, the methods used for induction of periapical periodontitis yielded similar distribution of microorganisms in the root canal system.

Periodontal Diseases and Rheumatoid Arthritis: A Coincident Model for Therapeutic Intervention?

There are remarkable similarities in the pathogenesis of periodontal diseases and rheumatoid arthritis. The mechanisms that drive antigen induced sequelae of oxidative stress are discussed in this review. A poorly modulated inflammatory response drives both diseases resulting in oxidative stress induced tissue injury. Immune complex formation in response to the periodontal pathogen Porphyromonas gingivalis triggering the production of ROS in both gingivae and synovium of RA patients has been reported. Elevated antibody levels to several periodontal pathogens in RA patients has implications on both RA and periodontal diseases. Periodontal patients are challenged individuals representing a multifactorial aetiopathogenesis with potential for therapeutic intervention in the context of free radical damage. Subjects with moderate to severe periodontal bone loss are significantly more likely than healthy individuals to have several co-existing systemic conditions resulting in ROS mediated damage. There is potential for dual induction of periodontal disease by existing inflammatory mechanisms of systemic diseases rather than exacerbation of low grade inflammation only; emphasizing the relevance of reducing inflammatory burden for disease control. Therapeutic strategies based on disease mechanisms include combined low dose non-steroidal anti-inflammatory drugs and doxycycline for synergistic reduction of matrix metalloproteinase activity in periodontal tissues and RA; sub-optimal dosing with CMT-8 and a biphosphonate clodronate to reduce pathologically elevated levels of MMPs, elastase and to restore alveolar bone in experimental periodontits demonstrating dual applications. Therapeutic interventions relevant to both diseases discussed in this review, have scope for a double hit in periodontal patients with co-existing RA and vice versa.

The influence of type I diabetes mellitus on the expression and activity of gelatinases (matrix metalloproteinases‐2 and ‐9) in induced periodontal disease

Periodontal disease corresponds to a group of lesions that affect the tooth-supporting tissues present in the dental follicle. Although bacterial plaque is important, the immune response also contributes to the destruction of periodontal tissues. Diabetes mellitus is closely associated with the development, progression and severity of periodontal disease because it not only affects extracellular matrix organization but also the tissue response to inflammation. The objective of the present investigation was to study the influence of diabetes on experimental periodontal disease by evaluating the degradation of extracellular matrix through the analysis of matrix metalloproteinase (MMP)-2 and MMP-9 expression and activity, using immunofluorescence, zymography and real-time reverse transcription-polymerase chain reaction. Wistar rats were divided into normal and diabetic groups and evaluated 0, 15 and 30 d after the induction of periodontal disease by ligature. MMP-2 and -9 were detected in epithelial cells, in the blood vessel endothelium and in connective tissue cells. The same profile of enzymatic expression of MMP-2 and -9 was observed in normal and diabetic animals, with a peak in activity at day 15 of inflammation. However, in diabetic animals, MMP-2 gelatinolytic activity was reduced after the inflammatory stimulus, whereas that of MMP-9 was increased. MMP-2 gene expression decreased with inflammation in both normal groups and groups with diabetes. In contrast, MMP-9 expression increased in normal animals and decreased in diabetic animals after inflammation. The results suggest the involvement of MMP-2 and -9 in the dynamics of periodontal disease and that variation in their expression levels results in differences in tissue organization and wound healing in normal and diabetic animals.

Protective effects of baicalin on ligature‐induced periodontitis in rats

Baicalin is a flavonoid compound purified from the medicinal plant, Scutellaria baicalensis Georgi, and has been reported to possess anti-inflammatory and antioxidant activities. The purpose of this study was to test the ability of baicalin to influence the progression of experimental periodontitis in rats, as well as the expression of cyclooxygenase-2 and inducible nitric oxide synthase. Adult male Sprague-Dawley rats were subjected to placement of a nylon thread around the bilateral lower first molars and killed after 7 d. Baicalin (50, 100 or 200 mg/kg) was supplied to the animals by oral gavage, starting 1 d before the induction of periodontitis. The ligature group consisted of rats subjected to periodontitis and receiving vehicle (0.5% carboxymethylcellulose) alone. The alveolar bone loss and the area fraction occupied by collagen fibers were assessed. The expression of cyclooxygenase-2 and inducible nitric oxide synthase protein in the gingiva were detected by immunohistochemistry and western blotting. Baicalin-treated groups presented with lower alveolar bone loss than that of the ligature group, reaching statistical significance at the dose of 200 mg/kg (p = 0.009). The area fraction of collagen fibers was significantly higher in the baicalin (200 mg/kg)-treated group than in the ligature group (p = 0.047). Baicalin treatment significantly down-regulated the protein expression for cyclooxygenase-2 (p = 0.000) and inducible nitric oxide synthase (p = 0.003), compared with the ligature group. Baicalin protects against tissue damage in ligature-induced periodontitis in rats, which might be mediated, in part, by its inhibitory effect on the expression of cyclooxygenase-2 and inducible nitric oxide synthase. These activities could support the continued investigation of baicalin as a potential therapeutic agent in periodontal disease.

Repair of Experimental Plaque-Induced Periodontal Disease in Dogs

Forty mongrel dogs were used in this study for induction of periodontal disease by placing subgingival silk ligatures affecting maxillary and mandibular premolar teeth during a 12-month period. Experimental premolar teeth received monthly clinical, radiographic, and histometric/pathologic assessments. The results demonstrated significant increases in scores and values of periodontal disease parameters associated with variable degrees of alveolar bone loss. The experimental maxillary premolar teeth exhibited more severe and rapid rates of periodontal disease compared with mandibular premolar teeth. Histometric analysis showed significant reduction in free and attached gingiva of the experimental teeth. Histopathological examination of buccolingual sections from experimental premolar teeth showed the presence of rete pegs within the sulcular epithelium with acanthosis and erosive changes, widening of the periodontal ligament, and alveolar bone resorption. Various methods for periodontal repair were studied in 194 experimental premolar teeth exhibiting different degrees of periodontal disease. The treatment plan comprised non-surgical (teeth scaling, root planing, and oral hygiene) and surgical methods (closed gingival curettage, modified Widman flap, and reconstructive surgery using autogenous bone marrow graft and canine amniotic membrane). The initial non-surgical treatment resulted in a periodontal recovery rate of 37.6% and was found effective for treatment of early periodontal disease based on resolution of gingivitis and reduction of periodontal probing depths. Surgical treatment by closed gingival curettage to eliminate the diseased pocket lining resulted in a recovery rate of 48.8% and proved effective in substantially reducing deep periodontal pockets. Open root planing following flap elevation resulted in a recovery rate of 85.4% and was effective for deep and refractory periodontal pockets. Autogenous bone graft implantation combined with canine amniotic membrane as a biodegradable membrane was used in 18 premolar teeth and failed to improve advanced furcation defects in most teeth.

The role of macrophages in the periodontal regeneration using Emdogain® gel

Emdogain gel is clinically used as a periodontal regenerative material. However, the mechanism of the regeneration has not been completely elucidated. Although many studies have focused on the regenerative effect of Emdogain on connective tissue attachment and alveolar bone, the role of macrophages and the expression of growth factors remains unclear in the regeneration stimulated by Emdogain gel in vivo. The aim of this study was to investigate the effect of Emdogain gel on the expression of cytokines and growth factors by macrophages in vivo using a newly devised rat experimental periodontitis model. Rat experimental periodontitis was induced by elevating a full-thickness gingival flap and ligating silk threads around the first molars of the mandible. At 14 d after inducing experimental periodontitis, Emdogain gel or propylene glycol alginate was applied to the furcation area. The rats were killed 7 and 14 d after treatment with propylene glycol alginate or Emdogain gel. The expression of cytokines and growth factors, and the regeneration of periodontal tissue, were examined by histochemical and immunohistochemical methods. Fourteen days after the induction of periodontitis, the resorption of alveolar bone at furcation was observed and cytokines such as interleukin-1beta, transforming growth factor-beta1, receptor activator of nuclear factor-kappaB ligand, receptor activator of nuclear factor-kappaB and osteoprotegerin were found. In the Emdogain-treatment group, the formation of new acellular cementum and, more remarkably, recovery of the bone, were observed. The new bone formation ratio in the Emdogain treatment group was significantly higher than that of the propylene glycol alginate treatment group. Although the expression of cytokines such as interleukin-1beta, transforming growth factor-beta1, receptor activator of nuclear factor-kappaB ligand and receptor activator of nuclear factor-kappaB was very low, bone morphogenetic protein-2- and bone morphogenetic protein-4-expressing macrophages were observed close to the root, and bone morphogenetic protein-4-expressing macrophages were mainly observed close to the bone surface at the furcation in the Emdogain-treatment group. These results suggest that wound-healing macrophages may express bone morphogenetic protein and play an important role in the regeneration of periodontal tissue at the furcation following the application of Emdogain gel.

Protective effects of Tacrolimus, a calcineurin inhibitor, in experimental periodontitis in rats

Objective Periodontitis is a well-appreciated example of leukocyte-mediated bone loss and inflammation with pathogenic features similar to those observed in other inflammatory diseases, such as arthritis. Since Tacrolimus, is an immunomodulatory drug used for the treatment of some cases of arthritis, we hypothesized that it may modulate periodontal disease. Design Using a murine model of ligature-induced periodontal disease, we assessed the effects of daily administrations of Tacrolimus (1 mg/kg body weight) on bone loss, enzymatic (myeloperoxidase) analysis, differential white blood cells counts, airpouch exudate and cytokine expression for 5–30 days. Results Radiographic, enzymatic (myeloperoxidase) and histological analysis revealed that Tacrolimus reduced the severity of periodontitis. More specifically, Tacrolimus suppressed the expression of serum interleukin (IL-1β), tumour necrosis factor (TNF-α), IL-6, airpouch exudate PGE 2 and leukocytosis usually observed after the induction of periodontitis. Tacrolimus treatment in periodontitis-induced rats conferred protection against the inflammation-induced tissue and bone loss associated with periodontitis, through a mechanism involving IL-1β, TNF-α and IL-6. Conclusions The effects of Tacrolimus on periodontal disease pathogenesis may provide clues to a novel approach to host modulation therapy in destructive periodontal disease.

Influence of the Period After Ovariectomy on Femoral and Mandibular Bone Density and on Induced Periodontal Disease

This study investigated the influence of the period after ovariectomy on femoral and mandibular bone mineral density (BMD) and on induced periodontal disease. One hundred and twenty-six female Holtzman rats were divided into nine groups: control, sham surgery (SHAM) with and without induction of periodontal disease for 51 and 150 days, and ovariectomy (OVX) with and without induction of periodontal disease for 51 and 150 days. Periodontal disease was induced by placing ligatures on the first lower molars during the last 30 days of each period. BMD was measured by dual-energy x-ray absorptiometry. Vertical bone loss was determined by measuring the distance from the alveolar bone crest to the cemento-enamel junction on the mesial side of the first lower molar. Statistical analyses (Kruskal-Wallis test) revealed a significant difference between the OVX and SHAM groups' global and femoral proximal epiphysis BMD (P <0.001) for 150 days and in the global evaluation for 51 days. For mandibular BMD, no difference was found between the groups of each period. Influence of the period on femoral BMD was found only for the SHAM groups, with lower BMD for the 51-day period compared to the 150-day period (P <0.05). In the global evaluation of the mandible, a lower BMD was found after 51 days. The period was a contributing factor for the vertical bone loss, and it resulted in higher values for the 51-day period (P <0.05). The period influenced the femoral BMD and the vertical bone loss in induced periodontal disease.

Comparison of etoricoxib and indomethacin for the treatment of experimental periodontitis in rats

We investigated the effect of etoricoxib, a selective cyclooxygenase-2 inhibitor, and indomethacin, a non-selective cyclooxygenase inhibitor, on experimental periodontitis, and compared their gastrointestinal side effects. A ligature was placed around the second upper left molars of female Wistar rats (160 to 200 g). Animals (6 per group) were treated daily with oral doses of 3 or 9 mg/kg etoricoxib, 5 mg/kg indomethacin, or 0.2 mL saline, starting 5 days after the induction of periodontitis, when bone resorption was detected, until the sacrifice on the 11th day. The weight and survival rate were monitored. Alveolar bone loss (ABL) was measured as the sum of distances between the cusp tips and the alveolar bone. The gastric mucosa was examined macroscopically and the periodontium and gastric and intestinal mucosa were examined by histopathology. The ongoing ABL was significantly inhibited (P < 0.05) by 3 and 9 mg/kg etoricoxib and by indomethacin: control = 4.08 +/- 0.47 mm; etoricoxib (3 mg/kg) = 1.89 +/- 0.26 mm; etoricoxib (9 mg/kg) = 1.02 +/- 0.14 mm; indomethacin = 0.64 +/- 0.15 mm. Histopathology of periodontium showed that etoricoxib and indomethacin reduced inflammatory cell infiltration, ABL, and cementum and collagen fiber destruction. Macroscopic and histopathological analysis of gastric and intestinal mucosa demonstrated that etoricoxib induces less damage than indomethacin. Animals that received indomethacin presented weight loss starting on the 7th day, and higher mortality rate (58.3%) compared to etoricoxib (0%). Treatment with etoricoxib, even starting when ABL is detected, reduces inflammation and cementum and bone resorption, with fewer gastrointestinal side effects.

Comparison of etoricoxib and indomethacin for the treatment of experimental periodontitis in rats

We investigated the effect of etoricoxib, a selective cyclooxygenase-2 inhibitor, and indomethacin, a non-selective cyclooxygenase inhibitor, on experimental periodontitis, and compared their gastrointestinal side effects. A ligature was placed around the second upper left molars of female Wistar rats (160 to 200 g). Animals (6 per group) were treated daily with oral doses of 3 or 9 mg/kg etoricoxib, 5 mg/kg indomethacin, or 0.2 mL saline, starting 5 days after the induction of periodontitis, when bone resorption was detected, until the sacrifice on the 11th day. The weight and survival rate were monitored. Alveolar bone loss (ABL) was measured as the sum of distances between the cusp tips and the alveolar bone. The gastric mucosa was examined macroscopically and the periodontium and gastric and intestinal mucosa were examined by histopathology. The ongoing ABL was significantly inhibited (P < 0.05) by 3 and 9 mg/kg etoricoxib and by indomethacin: control = 4.08 ± 0.47 mm; etoricoxib (3 mg/kg) = 1.89 ± 0.26 mm; etoricoxib (9 mg/kg) = 1.02 ± 0.14 mm; indomethacin = 0.64 ± 0.15 mm. Histopathology of periodontium showed that etoricoxib and indomethacin reduced inflammatory cell infiltration, ABL, and cementum and collagen fiber destruction. Macroscopic and histopathological analysis of gastric and intestinal mucosa demonstrated that etoricoxib induces less damage than indomethacin. Animals that received indomethacin presented weight loss starting on the 7th day, and higher mortality rate (58.3%) compared to etoricoxib (0%). Treatment with etoricoxib, even starting when ABL is detected, reduces inflammation and cementum and bone resorption, with fewer gastrointestinal side effects.

Enhanced susceptibility to periodontitis in an animal model of depression: reversed by chronic treatment with the anti‐depressant tianeptine

To test the hypothesis that the olfactory bulbectomy model of depression in rats could influence susceptibility to ligature-induced periodontitis, and that chronic treatment with the anti-depressant drug tianeptine could attenuate this effect. Tianeptine was given twice daily (10 mg/kg, i.p.) during the entire experiment, starting 29 days before induction of olfactory bulbectomy and periodontitis. Olfactory bulbectomized (OB) rats and sham-operated rats were given saline in a similar manner. Periodontal disease was assessed when the ligatures had been in place for 21 days. Two hours before decapitation, rats were injected with lipopolysaccharide (LPS;100 microg/kg, i.p.) to induce a robust immune and stress response. Compared with sham-operated controls, OB rats developed significantly more periodontal bone loss, exhibited characteristic behavioural responses in a novel open field test, and showed a decreased expression of glucocorticoid receptors (GRs) in the hippocampus. LPS provoked a significantly larger increase in circulating levels of the stress hormone corticosterone and the cytokine transformation growth factor (TGF)-1beta but smaller tumour necrosis factor (TNF)-alpha levels. Tianeptine treatment of OB rats significantly inhibited peridodontal bone loss, normalized behavioural responses, enhanced TGF-1beta levels, and abolished TNF-alpha decrease, but did not attenuate the increased corticosterone response and the decreased hippocampal GR expression. These experimental results are consistent with an emerging literature showing that life stress, anxiety, depression, pathological grief, and poor coping behaviour may dysregulate regulatory mechanisms within the brain involved in immune regulation, and thereby alter immune responses and influence the susceptibility/resistance to inflammatory disorders.

Dietary Supplementation of Omega-3 Fatty Acid and Circulating Levels of Interleukin-1β, Osteocalcin, and C-Reactive Protein in Rats.

In this study, we evaluated the effects of two different regimes of dietary supplementation of omega-3 fatty acid on serum levels of interleukin-1 beta (IL-1β), osteocalcin (OC), and C-reactive protein (CRP) in experimental periodontitis. Experimental periodontitis was induced by repeated injections of Escherichia coli lipopolysaccharide (LPS). Thirty-nine adult male Sprague-Dawley rats were divided into four study groups as follows: an LPS positive control group; a saline (negative) control group; and two different groups with omega-3 fatty acid dietary supplementation, one in which we gave the supplement subsequent to disease induction (TO3) and the other in which the agent was started prior to and continued subsequent to LPS injections (P + TO3). In the TO3 group, omega-3 fatty acid administration was performed for 14 days following induction of experimental periodontitis. In the P + TO3 group, omega-3 fatty acid was given for 14 days prior to the start of LPS injections and was continued for another 14 days subsequent to the induction of experimental periodontitis. On day 15 of the first LPS injection, serum samples were obtained and rats were sacrificed. Serum samples were analyzed for IL-1β, OC, and CRP concentrations by enzyme-linked immunosorbent assay. Defleshed jaws were analyzed morphometrically for alveolar bone loss. Data were evaluated statistically by non-parametric tests. LPS injection resulted in statistically significantly more bone loss compared to the saline control group (P <0.05). None of the omega-3 fatty acid administration groups showed evidence that this fatty acid was effective in preventing LPS-induced alveolar bone loss. TO3 and P + TO3 groups revealed significantly higher IL-1β and OC levels than the LPS group (P <0.05). The study groups exhibited no significant differences in the serum CRP levels. Omega-3 fatty acid administration does not seem to influence circulating levels of CRP. The significantly increased serum OC level observed in both omega-3 fatty acid regimes is curious and could have an effect on bone turnover, as could the further significant increase in serum IL-1β, which could counteract any osteoblastic induction by OC through promotion of osteoclast activity. The lack of a therapeutic benefit of omega-3 fatty acid in this study, despite the effects on OC and IL-1β, is difficult to explain, and further studies are required to more fully assess the potential role of this fatty acid in periodontal treatment.

Effect of Sodium Alendronate on Alveolar Bone Resorption in Experimental Periodontitis in Rats

Bisphosphonates are potent inhibitors of bone resorption and were shown to inhibit bone resorption in experimental periodontitis by unknown mechanisms. We studied the effect of the aminobisphosphonate sodium alendronate (SA) in experimental periodontitis. Wistar rats were subjected to ligature placement around the second upper left molars. Animals were treated with SA 0.01 to 0.25 mg/kg subcutaneously (sc), either 1 hour before (prophylactic) or starting 5 days after (therapeutic) periodontitis induction and daily until the rats were sacrificed (11 days). Controls received saline. Animals were weighed daily. Alveolar bone loss was measured as the difference (in millimeters) between the cusp tip and the alveolar bone. The periodontium and the surrounding gingivae were examined at histopathology, and the neutrophil influx into the gingivae was assayed using myeloperoxidase activity. The local bacterial flora was assessed through culture of the gingival tissue in standard aerobic and anaerobic media. Alveolar bone loss was significantly and dose dependently inhibited by SA either as a prophylactic or therapeutic treatment compared to the control. SA reduced tissue lesion at histopathology, with partial preservation of the periodontium, coupled to decreased myeloperoxidase activity compared to the control. The reduced neutrophil influx was also shown in carrageenan-induced peritonitis, used as a control experiment for this parameter. SA also significantly inhibited the growth of pigmented bacilli and Fusobacterium nucleatum, which are important in the pathogenesis of periodontal disease. SA also inhibited the in vitro growth of isolated Peptostreptococcus sp. Sodium alendronate preserves alveolar bone resorption and has anti-inflammatory and antibacterial activities in experimental periodontitis.

The Influence of Loss of Bone Mass on Induced Periodontal Disease: A Radiographic and Densitometric Study of Female Rats

Changes in mineral density in the mandibular and femoral bones (BMD) after estrogen deficiency caused by ovariectomy (OVX) and the influence of these changes on induced periodontal disease were evaluated in female rats. Forty-eight female Holtzman rats (90 days old) were randomly divided into five groups: 0: control (N = 9); 1: SHAM without induced periodontal disease (N = 11); 2: SHAM with induced disease (N = 10); 3: OVX without induced disease (N = 9); and 4: OVX with induced disease (N = 9). In groups 2 and 4, the first lower molars were tied with ligatures for 30 days 120 days after surgery. After 5 months the animals were sacrificed to measure global mineral density (BMD) and that of the sub-regions of the mandible and femur by dual energy x-ray absorptiometry (DXA). The extent of vertical bone loss was evaluated with digital radiography by measuring the distance from the bone crest to the cemento-enamel junction at the mesial of the first lower molar. Results of the femur (Kruskal-Wallis test) showed a significant difference (P <0.001) between the groups SHAM and OVX in bone density values for all regions. Comparison between the groups in relation to the BMD of the mandible, both in the sub-regions and global revealed no differences (P >0.05). The vertical bone loss measured for the groups with induced disease was similar (P = 0.713). Differences between the groups were found in the bone mineral density BMD of the femur but not of the mandible. OVX had no influence on induced periodontal disease.

Lipid peroxidation: a possible role in the induction and progression of chronic periodontitis

Reactive oxygen species (ROS) are implicated in the destruction of the periodontium during inflammatory periodontal diseases. The imbalance in oxidant/antioxidant activity may be a key factor in the damaging effects of ROS. This study aimed to determine the lipid peroxidation levels in gingival crevicular fluid and saliva, and glutathione (GSH) and glutathione peroxidase (GPx) in saliva in patients with chronic periodontitis. Gingival crevicular fluid and saliva were collected from 13 patients and 9 healthy control subjects during the preliminary study, and from 21 patients during the subsequent study. Lipid peroxidation level, GSH level and GPx activity were determined by spectrophotometric assay. The preliminary study found that when comparing patients to healthy controls, the gingival crevicular fluid samples produced the following results, respectively: higher lipid peroxidation concentration (microm) (by sites: 167.55 vs. 53.71, p < 0.0001; by subjects: 151.99 vs. 50.66, p < 0.005) and total amount (pmol) (by sites: 93.02 vs. 8.47, p < 0.0001, by subjects: 80.44 vs. 7.84, p < 0.0005). In saliva samples, lower GSH concentration (microm) (373.04 vs. 606.67, p < 0.05), higher lipid peroxidation concentration (microm) (0.66 vs. 0.13, p < 0.0005), and no difference in GPx activity were found in patients than in those of healthy controls. The subsequent study showed statistically significant (p < 0.05) improvement of clinical periodontal parameters (plaque index, gingival index, probing attachment level, probing pocket depth and gingival crevicular fluid volume), decreases in gingival crevicular fluid lipid peroxidation levels (concentration and total amount) at the sites after the completion of phase 1 periodontal treatment. Similarly, the periodontal treatment resulted in a significant decrease of lipid peroxidation concentrations (p < 0.05), increase in GSH concentration (p < 0.001), and no change in GPx activity in saliva samples. The increased levels of lipid peroxidation may play a role in the inflammation and destruction of the periodontium in periodontitis.

Protective effects of etoricoxib, a selective inhibitor of cyclooxygenase‐2, in experimental periodontitis in rats

The purpose of the present study was to evaluate the effect of a potent selective cyclooxygenase-2 (COX-2) inhibitor, etoricoxib, on the prevention of alveolar bone loss in experimental periodontitis induced in rats. Ninety Wistar rats were separated into three experimental groups. Cotton ligatures were placed at the gingival margin level of lower right first molars. The rats were randomly assigned to one of the following groups: control received a daily oral dose of 1 ml/kg of saline solution; Eto1 received 6 mg/kg of etoricoxib; Eto2 received 12 mg/kg of etoricoxib. Serum levels of etoricoxib and white blood cells were determined. Standardized digital radiographs were taken after death at 3, 5, 10, 18 and 30 days to measure the amount of bone loss at the mesial root surface of the first molar tooth in each rat. One-way analysis of variance (anova) indicated that groups treated with both doses of etoricoxib had significantly (p < 0.05) less alveolar bone loss when compared to controls. Furthermore, etoricoxib treatment significantly inhibited the leukocytosis observed 3 days after the induction of periodontitis. These data provide evidence that systemic therapy with etoricoxib can retard alveolar bone loss in a ligature-induced periodontitis model in rats.

The effect of spironolactone on experimental periodontitis in rats

Elevated levels of tumour necrosis factor (TNF) have been found in patients with adult periodontitis. Animal studies have shown that TNF plays an important role in the pathogenesis of periodontitis. New findings suggest that the aldosterone-inhibitor spironolactone possesses an anti-TNF effect. The purpose of the study was to determine the anti-TNF effect of spironolactone in an endotoxic shock rat model and to disclose the effect of oral administration of spironolactone on the development of experimental periodontitis in rats. The study was divided in two parts. Part 1: oral administration of spironolactone (100 mg/kg) followed by intravenous lipopolysaccharide (1 mg/kg) infusion 45 min later. Blood samples were taken before and 90 min after lipopolysaccharide infusion to determine the TNF levels in spironolactone treated and non-treated rats. Part 2: oral administration of spironolactone [100 mg/(kg day)] starting 2 days prior to induction of experimental periodontitis established by peridental ligatures. Morphometrical and radiographical registrations of alveolar bone destruction were carried out to determine the effect of spironolactone on the progression of experimental periodontitis. In part 1 the endotoxic shock model showed a significant reduction in TNF levels in the spironolactone-treated group compared to the non-treated group, suggesting that spironolactone acts as a TNF inhibitor. In part 2 spironolactone-treated rats did not demonstrate significantly less alveolar bone destruction compared to non-treated rats. The insignificant effect of spironolactone treatment could be explained by the fast metabolism of spironolactone and that spironolactone does not completely inhibit TNF production in rats. Moreover, many other cytokines and mediators involved in alveolar bone destruction may account for the lacking response to spironolactone.

Therapeutic Versus Prophylactic Plus Therapeutic Administration of Omega‐3 Fatty Acid on Endotoxin‐Induced Periodontitis in Rats

The aim of the present study was 1) to evaluate the possible effects of therapeutic usage of omega-3 fatty acid on the gingival tissue levels of prostaglandin E2 (PGE2), prostaglandin F2alpha (PGF2alpha), platelet activating factor (PAF), and leukotriene B4 (LTB4) in endotoxin-induced periodontitis in rats and 2) to investigate whether prophylactic usage provides any additional benefits to therapeutic doses of omega-3 fatty acid. Experimental periodontitis was induced by repeated injection of Escherichia coli lipopolysaccharide (LPS). Thirty-six adult male Sprague-Dawley rats were divided into four study groups: 1) saline controls; 2) LPS; 3) therapeutic omega-3 fatty acid (TO3); and 4) prophylactic plus therapeutic omega-3 fatty acid (P + TO3) groups. In TO3 group, omega-3 fatty acid was given for 15 days following induction of experimental periodontitis. In P + TO3 group, omega-3 fatty acid was started 15 days before baseline, and then periodontitis was induced at baseline and omega-3 fatty acid was continued for 15 days after baseline. On day 15 after baseline, all rats were anesthetized and sacrificed. PGE2, PGF2alpha, and LTB4 levels in gingival tissue samples were analyzed by enzyme immunoassay and PAF levels were analyzed by radioimmonoassay. Data were evaluated statistically by using parametric tests. LPS injection resulted in significant amount of bone loss (P<0.05). Neither therapeutic nor prophylactic plus therapeutic administration of omega-3 fatty acid with the doses and duration of therapy used in the present study was effective in preventing endotoxin-induced alveolar bone loss. TO3 group exhibited significant decreases in the gingival tissue levels of PGE2, PGF2alpha, LTB4, and PAF compared to the LPS group (P<0.05). PGE2 and PGF2alpha levels in TO3 group were similar to those of the saline group (P>0.05), while LTB4 and PAF levels were statistically higher than the saline group (P<0.05). Prophylactic plus therapeutic usage of omega-3 fatty acid provided similar levels of all these mediators to those of the saline controls (P>0.05). Therapeutic omega-3 fatty acid significantly reduced the gingival tissue levels of PGE2, PGF2alpha, LTB4, and PAF in experimental periodontitis. Furthermore, prophylactic usage of omega-3 fatty acid provided additional beneficial effects to the therapeutic administration by decreasing the gingival tissue levels of these mediators to levels of healthy tissue. These findings should be verified by longitudinal clinical trials investigating clinical and biochemical periodontal parameters to better define the possible role of omega-3 fatty acids in periodontal treatment.

Effects of Tumor Necrosis Factor-α Inhibitors Pentoxifylline and Thalidomide on Alveolar Bone Loss in Short-Term Experimental Periodontal Disease in Rats.

Pentoxifylline (PTX) and thalidomide (TLD) have been shown to inhibit cytokine synthesis, mainly tumor necrosis factor (TNF)-α, in different inflammatory conditions. We studied the effects of these cytokine inhibitors in an experimental model of periodontitis. Wistar rats were subjected to a ligature placement around the second upper right molars. Alveolar bone loss was evaluated by the sum of the distances between the cusp tip and the alveolar bone along the axis of each molar root, subtracting from the contralateral side. Histopathological analysis was based on cell influx, amount of alveolar bone, and cementum integrity. Animals were weighed daily, and total and differential peripheral white blood cell counts were performed at 6 hours and 1, 7, and 11 days after induction of periodontitis. Groups were treated with saline (positive control), PTX, or TLD 1 hour before and daily up to 11 days after induction of periodontitis. Alveolar bone loss was inhibited 42%, 54%, and 69% by PTX at 5, 15, and 45 mg/kg, and 25%, 25%, 42%, and 54% by TLD at 5, 15, 45, and 90 mg/kg, respectively, as compared to the control (P <0.05; analysis of variance). Histological analysis showed that PTX and TLD reduced cell influx and alveolar bone and cementum destruction. PTX and TLD also reversed peripheral lymphomonocytosis but not weight loss, as compared to controls. These data showed that both PTX and TLD reduced alveolar bone loss in periodontitis. The data showed a protective effect of PTX and TLD on experimental periodontitis, suggesting a role for TNF-α in the pathophysiology of periodontitis. J Periodontol 2004;75:162-168.