Histometric analysis of ligature-induced periodontitis in rats: a comparison of histological section planes

The purpose of this study was to analyze the histometry of ligature-induced periodontitis in rats at different histological section depths. Sixteen male adult Wistar rats were randomly assigned to two groups: ligature and control. In the ligature group, rats received a sterile 4/0 silk ligature around the maxillary right 2nd molar. Thirty serial sections containing the 1st and 2nd molars, in which the coronal and root pulp, cementoenamel junction (CEJ) in the mesial side of the 2nd molar, interproximal alveolar bone and connective fiber attachment were clearly visible, were selected for histometric analysis. The histological sections were clustered in groups of 10 sections corresponding the buccal (B), central (C) and lingual (L) regions of the of periodontal tissue samples. The distance between the CEJ in the mesial side of the 2nd molar and the attached periodontal ligament fibers (CEJ-PL) as well as the distance between the CEJ and the alveolar bone crest (CEJ-BC) were determined. From CEJ-PL and CEJ-BC distances measured for each specimen, the measurements obtained in the B, L and C regions were recorded individually and together. Data were submitted to statistical analysis. Significant differences (p<0.001) were observed between the control and ligature groups regarding CEJ-PL (0.05 mm and 0.26 mm, respectively) and CEJ-BC (0.47 mm and 0.77 mm, respectively) measurements. Regarding the depth of the buccal, central and lingual planes, the means of CEJ-PL and CEJ-BC of both groups showed no statistically significant differences (p>0.05). In conclusion, the selection of 10 serial sections of the central region of periodontal tissue samples at any depth can be considered as representative for the evaluation of periodontal ligament fiber attachment and bone loss in ligature-induced periodontitis in rats.

Delayed replantation of rat teeth after use of reconstituted powdered milk as a storage medium

Minimal extraoral dry storage period and moist storage for the avulsed tooth are identified as key steps for the treatment protocol of tooth replantation. Among the possible moist storage media, bovine milk has stood out because of its capacity of preserving the integrity of the periodontal ligament (PDL) fibers. This condition has attracted the attention to investigate the use of powdered milk, which is one of the presentation forms of bovine milk, as a feasible storage medium in cases of delayed tooth replantation. The aim of this study was to evaluate the healing process after delayed replantation of rat teeth stored in reconstituted powdered milk and long shelf-life (ultra high temperature) whole milk. Forty maxillary right rat incisors were assigned to four groups (n = 10): group I - the teeth were extracted and immediately replanted into theirs sockets; group II - the teeth were stored for 60 min in 200 ml of freshly reconstituted powdered milk; group III - the teeth were stored for 60 min in 200 ml of long shelf-life whole milk; group IV - the teeth were kept dry for the same time. All procedures were performed at room temperature. Next, the root canals of teeth in groups II, III, and IV were instrumented, filled with a calcium hydroxide-based paste, and replanted into their sockets. All animals received systemic antibiotic therapy and were killed by anesthetic overdose 60 days after replantation. The pieces containing the replanted teeth were removed, fixed, decalcified, and paraffin-embedded. Semi-serial 6-mu m-thick sections were obtained and stained with hematoxylin and eosin for histomorphological analysis. There was statistically significant difference (P < 0.05) between groups I and IV regarding the presence of replacement resorption and PDL remnants on root surface. The powdered milk and long shelf-life whole milk presented similar results to each other and may be indicated as storage media for avulsed teeth.

Intraoral approach for surgical treatment of Eagle syndrome

Eagle syndrome is symptomatic elongation of the styloid process, or calcification of the stylomandibular ligament. Difficulty with deglutition. phonation. cervical movement. and the sensation of a foreign body in the oropharynx are all symptoms of this syndrome. Its treatment consists of partial removal of the styloid process. leaving it within the range of normality. We describe the technique, report it case, and point Out Sortie of the advantages. such as the simplicity of the procedure, reduced operating time, and lack risks of operative complications. (C) 2008 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Influence of Crown Ferrule Heights and Dowel Material Selection on the Mechanical Behavior of Root-Filled Teeth: A Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of customized composite resin fibreglass posts on the mechanics of restored treated teeth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Histomorphometric evaluation of periodontal compression and tension sides during orthodontic tooth movement in rats

OBJECTIVE: The purpose of this study was to evaluate the thickness of the periodontal ligament of rat molars during orthodontic tooth movement (OTM). METHODS: Thirty Wistar rats were divided into three groups of 10 animals each: GI, GII and GIII and the mice were euthanized at 7, 14 and 21 days, respectively. Experimental subjects were compared to their respective controls by the Mann-Whitney test. Comparison of values between compression and tension sides were performed during the same and different time periods through Analysis of Variance (ANOVA), Kruskal-Wallis test and, subsequently, Tukey's test. RESULTS: Groups GI and GII showed decreased PDL size in the apical regions of the mesiobuccal root and in the cervical region of the distobuccal root. There was also an increased PDL in the cervical regions of the mesiobuccal root, apical region of the distobuccal root and middle region of both roots. CONCLUSION: The reduction and increase in PDL size were seen in the same root, which characterizes tooth inclination. The apical, middle and cervical regions were compared with one another in each time period and at three times: 7, 14 and 21 days. They were also compared in each region, confirming a tipping movement in GI and GII and a gradual decreased intensity between GI to GII, reaching normal dimension in GIII.

Immediate reimplantation of primary teeth: a histological study in dogs

Reimplantation of primary teeth has been the subject of various clinical and histological studies, but very little is known about the effect of this treatment on primary teeth. The aim of the present study was to histologically evaluate the biological response of dog primary teeth after immediate reimplantation. Twelve dogs were divided into two groups according to postoperative time: 1 week and 3 weeks. Twenty-one upper and lower intermediate incisors were extracted and submitted to endodontic treatment, reimplantation and splinting. The 21 homologous teeth not submitted to treatment served as controls. The animals were killed after the respective experimental periods, and the obtained specimens were processed for histological analysis. Most dogs of the 1-week group exhibited the following alterations: gingival epithelium was inserted in the cemento-enamel junction, with a small number of chronic inflammatory cells being observed in the gingival corium; the periodontal ligament was partially reestablished, with a more expressive chronic inflammatory infiltrate being observed in the apical third; small root resorption was observed on the palatine/lingual side in the apical third. In contrast, in 3-week animals, gingival epithelial insertion was predominantly absent on the buccal side, and a moderate chronic inflammatory infiltrate was present; the periodontal ligament generally showed no bone-cementum reinsertion especially on the palatine/lingual side, with an expressive inflammatory infiltrate in the apical region, and large root resorption was mainly observed on the palatine and lingual sides. In conclusion, reimplantation causes histological alterations in the tooth and its supporting periodontal structures that suggest the impossibility of its maintenance.

Tissue reaction to Endométhasone sealer in root canal fillings short of or beyond the apical foramen

Objective: This study evaluated the response of periapical tissues to the endodontic sealer Endomethasone in root canal fillings short of or beyond the apical foramen. Material and Methods: Twenty root canals of premolars and incisors of 2 mongrel dogs were used. After coronal access and pulp extirpation, the canals were instrumented up to a size 55 K-file and the apical cemental barrier was penetrated with a size 15 K-file to obtain a main apical foramen, which was widened to a size 25 K-file. The canals were irrigated with saline at each change of file. The root canals were obturated either short of or beyond the apical foramen by the lateral condensation of gutta-percha and Endomethasone, originating 2 experimental groups: G1: Endomethasone/short of the apical foramen; G2: Endomethasone/beyond the apical foramen. The animals were killed by anesthetic overdose 90 days after endodontic treatment. The individual roots were obtained and serial histological sections were prepared for histomorphological analysis (H&E and Brown & Brenn techniques) under light microscopy. The following parameters were examined: closure of the apical foramen of the main root canal and apical opening of accessory canals, apical cementum resorption, intensity of the inflammatory infiltrate, presence of giant cells and thickness and organization of the apical periodontal ligament. Each parameter was scored 1 to 4, 1 being the best result and 4 the worst. Data were analyzed statistically by the Wilcoxon nonparametric tests (p=0.05). Results: Comparing the 2 groups, the best result (p<0.05) was obtained with root canal filling with Endomethasone short of the apical foramen but a chronic inflammatory infiltrate was present in all specimens. Conclusions: Limiting the filling material to the root canal space apically is important to determine the best treatment outcome when Endomethasone is used as sealer.

Influence of apical foramen widening and sealer on the healing of chronic periapical lesions induced in dogs' teeth

Objective. The aim of this study was to evaluate the influence of apical foramen widening on the healing of chronic periapical lesions in dogs' teeth after root canal filling with Sealer 26 or Endomethasone.Study design. Forty root canals of dogs' teeth were used. After pulp extirpation, the canals were exposed to the oral cavity for 180 days for induction of periapical lesions, and then instrumented up to a size 55 K-file at the apical cemental barrier. In 20 roots, the cemental canal was penetrated and widened up to a size 25 K-file; in the other 20 roots, the cemental canal was preserved (no apical foramen widening). All canals received a calcium hydroxide intracanal dressing for 21 days and were filled with gutta-percha and 1 of the 2 sealers: group 1: Sealer 26/apical foramen widening; group 2: Sealer 26/no apical foramen widening; group 3: Endomethasone/apical foramen widening; group 4: Endomethasone/no apical foramen widening. The animals were killed after 180 days, and serial histologic sections from the roots were prepared for histomorphologic analysis. Scores were assigned according to preestablished histomorphologic parameters and analyzed statistically by Kruskal-Wallis and Mann-Whitney U tests.Results. Regarding new cementum formation, repair of cementum and bone resorption areas, presence of microorganisms, inflammatory cell infiltrate and periodontal ligament conditions, significantly better periapical healing was obtained when foramen widening was done and Sealer 26 was used.Conclusion. Apical foramen widening and calcium hydroxide-containing sealer were more favorable to the healing of chronic periapical lesions. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:932-940)

Tissue reaction of the EndoREZ in root canal fillings short of or beyond an apical foramenlike communication

This study evaluated the response of periapical tissues to the endodontic sealer EndoREZ in root canal fillings short of or beyond the apical foramenlike communication. Twenty root canals of premolars and incisors of 2 mongrel dogs were used. After coronal access and pulp extirpation, the canals were instrumented up to a size 55 K-file and the apical cemental barrier was penetrated with a size 15 K-file to create an apical foramenlike communication, which was widened to a size 25 K-file. The canals were irrigated with saline at each change of file. The root canals were obturated either short of or beyond the apical foramenlike opening by the lateral condensation of gutta-percha and EndoREZ, originating 2 experimental groups: G1, EndoREZ/short of the apical foramenlike opening, and G2, EndoREZ/beyond the apical foramenlike opening. The animals were killed by anesthetic overdose 90 days after endodontic treatment. The individual roots were obtained and serial histological sections were prepared for histomorphological analysis (H&E and Brown and Brenn techniques) under light microscopy. The following parameters were examined: closure of the apical foramenlike communication and apical opening of accessory canals, apical cementum resorptions, intensity of the inflammatory infiltrate, presence of giant cells, and thickness and organization of the apical periodontal ligament. Each parameter was scored 1 to 4, 1 being the best result and 4 the worst. Data were analyzed statistically by the Wilcoxon nonparametric tests (P = .05). Comparing the 2 groups, the best result (P = .05) was obtained with root canal filling with EndoREZ short of the apical foramenlike opening. In conclusion, limiting the filling material to the root canal space apically was important to determine the best treatment outcome when EndoREZ was used as the sealer. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: e94-e99)

Cytotoxicity of Portland Cement with Different Radiopacifying Agents: A Cell Death Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A dominant function of p38 mitogen-activated protein kinase signaling in receptor activator of nuclear factor-kappa B ligand expression and osteoclastogenesis induction by Aggregatibacter actinomycetemcomitans and Escherichia coli lipopolysaccharide

Background and Objective: Lipopolysaccharide from gram-negative bacteria is one of the microbial-associated molecular patterns that initiate the immune/inflammatory response, leading to the tissue destruction observed in periodontitis. The aim of this study was to evaluate the role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in lipopolysaccharide-induced receptor activator of nuclear factor-kappa B ligand (RANKL) expression by murine periodontal ligament cells.Material and Methods: Expression of RANKL and osteoprotegerin mRNA was studied by reverse transcription-polymerase chain reaction upon stimulation with lipopolysaccharide from Escherichia coli and Aggregatibacter actinomycetemcomitans. The biochemical inhibitor SB203580 was used to evaluate the contribution of the p38 MAPK signaling pathway to lipopolysaccharide-induced RANKL and osteoprotegerin expression. Stable cell lines expressing dominant-negative forms of MAPK kinase (MKK)-3 and MKK6 were generated to confirm the role of the p38 MAPK pathway. An osteoclastogenesis assay using a coculture model of the murine monocytic cell line RAW 264.7 was used to determine if osteoclast differentiation induced by lipopolysaccharide-stimulated periodontal ligament was correlated with RANKL expression.Results: Inhibiting p38 MAPK prior to lipopolysaccharide stimulation resulted in a significant decrease of RANKL mRNA expression. Osteoprotegerin mRNA expression was not affected by lipopolysaccharide or p38 MAPK. Lipopolysaccharide-stimulated periodontal ligament cells increased osteoclast differentiation, an effect that was completely blocked by osteoprotegerin and significantly decreased by inhibition of MKK3 and MKK6, upstream activators of p38 MAPK. Conditioned medium from murine periodontal ligament cultures did not increase osteoclast differentiation, indicating that periodontal ligament cells produced membrane-bound RANKL.Conclusion: Lipopolysaccharide resulted in a significant increase of RANKL in periodontal ligament cells. The p38 MAPK pathway is required for lipopolysaccharide-induced membrane-bound RANKL expression in these cells.

LPS Induces Greater Bone and PDL Loss in SPARC-null Mice

Individuals with periodontal disease have increased risk of tooth loss, particularly in cases with associated loss of alveolar bone and periodontal ligament (PDL). Current treatments do not predictably regenerate damaged PDL. Collagen I is the primary component of bone and PDL extracellular matrix. SPARC/Osteonectin (SP/ON) is implicated in the regulation of collagen content in healthy PDL. In this study, periodontal disease was induced by injections of lipopolysaccharide (LPS) from Aggregatibacter actinomycetemcomitans in wild-type (WT) and SP/ON-null C57/B16 mice. A 20-mu g quantity of LPS was injected between the first and second molars 3 times a week for 4 weeks, whereas PBS control was injected into the contralateral maxilla. LPS injection resulted in a significant decrease in bone volume fraction in both genotypes; however, significantly greater bone loss was detected in SP/ON-null maxilla. SP/ON-null PDL exhibited more extensive degradation of connective tissue in the gingival tissues. Although total cell numbers in the PDL of SP/ON-null were not different from those in WT, the inflammatory infiltrate was reduced in SP/ON-null PDL. Histology of collagen fibers revealed marked reductions in collagen volume fraction and in thick collagen volume fraction in the PDL of SP/ON-null mice. SP/ON protects collagen content in PDL and in alveolar bone in experimental periodontal disease.

Fracture strength of flared bovine roots restored with different intraradicular posts

Objective: The aim of this study was to evaluate the fracture strength and failure mode of flared bovine roots restored with different intraradicular posts. Material and Methods: Fifty bovine incisors with similar dimensions were selected and their roots were flared until 1.0 mm of dentin wall remained. Next, the roots were allocated into five groups (n=10): GI-cast metal post-and-core; GII-fiber posts plus accessory fiber posts; GIII-direct anatomic post; GIV-indirect anatomic post and GV-control (specimens without intraradicular post). A polyether impression material was used to simulate the periodontal ligament. After periodontal ligament simulation, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min in a servo-hydraulic testing machine (MTS 810) applied at 135 to the long axis of the tooth until failure. The data (N) were subjected to ANOVA and Tukey's post-hoc test (alpha=0.05). Results: GI and GIV presented higher fracture strength (p<0.05) than GII. GIII presented intermediate values without statistically significant differences (p>0.05) from GI, GII and GIV. Control specimens (GV) produced the lowest fracture strength mean values (p<0.05). Despite obtaining the highest mean value, GI presented 100% of unfavorable failures. GII presented 20% of unfavorable failures. GIII, GIV and GV presented only favorable failures. Conclusions: Although further in vitro and in vivo studies are necessary, the results of this study showed that the use of direct and indirect anatomic posts in flared roots could be an alternative to cast metal post-and-core.

Cell death and quantitative reduction of rests of Malassez according to age

Background and Objective: Rests of Malassez are clusters of epithelial cells that remain in the periodontal ligament throughout life. However, it has been reported that the number of these structures decreases with age, and some epithelial cells undergo apoptosis in rests of Malassez of young and adult rats. Therefore, the purpose of the present study was to investigate the incidence of epithelial cell death and the quantitative changes in the rests of Malassez in rat molars of different ages.Material and Methods: Fragments containing the upper molars of rats aged 29, 45 and 120 d were fixed, decalcified and embedded for analysis by light microscopy. In the sections stained by hematoxylin and eosin, the number of rests of Malassez and the number of nuclei of these epithelial structures were obtained. Moreover, the nuclei exhibiting typical features of cell death were also counted in each rest of Malassez. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method for detection of cell death was also carried out.Results: In all groups examined, some rests of Malassez exhibited epithelial cell nuclei with typical features of apoptosis and some of them were also TUNEL positive. From 29 to 120 d of age in rats, the quantitative analysis showed a significant decrease in the total number of rests of Malassez in the cervical, middle and furcation regions of the periodontal ligament. Moreover, a significant decrease of epithelial cell nuclei was concomitant to an increase in the frequency of cell death in the oldest rats.Conclusion: These results suggest that epithelial cell death by apoptosis may be, at least in part, responsible for the reduction in the number of rests of Malassez according to age.