Archives of Oral Biology

Editorial Board

2010-02-01

HIV protease inhibitors block oral epithelial cell DNA synthesis

2010-02-01

Abstract: Objectives: Anti-retroviral therapy regimens that include HIV protease inhibitors (PIs) are associated with diverse adverse effects including increased prevalence of oral warts, oral sensorial deficits and gastrointestinal toxicities suggesting that PIs may perturb epithelial cell biology. To test the hypothesis that PIs could affect specific biological processes of oral epithelium, the effects of these agents were evaluated in several oral epithelial cell-lines.Design: Primary and immortalized oral keratinocytes and squamous carcinoma cells of oropharyngeal origin were cultured in the presence of pharmacologically relevant concentrations of PIs. Their affects on cell viability, cytotoxicity and DNA synthesis were assessed by enzymatic assays and incorporation of 5-bromo-2′-deoxyuridine (BrdU) into DNA.Results: Viability of primary and immortalized oral keratinocytes as well as squamous carcinoma cells of oropharyngeal origin was significantly reduced by select PIs at concentrations found in plasma. Of the seven PIs evaluated, nelfinavir was the most potent with a mean 50% inhibitory concentration [IC50] of 4.1μM. Lopinavir and saquinavir also reduced epithelial cell viability (IC50 of 10–20μM). Atazanavir and ritonovir caused minor reductions in viability, while amprenavir and indinavir were not significant inhibitors. The reduced cell viability, as shown by BrdU incorporation assays, was due to inhibition of DNA synthesis rather than cell death due to cytotoxicity.Conclusion: Select PIs retard oral epithelial cell proliferation in a drug and dose-dependent manner by blocking DNA synthesis. This could account for some of their adverse effects on oral health.

Fibronectin supports TNF-α-induced osteopontin expression through β1 integrin and ERK in HN-22 cells

2010-02-01

Abstract: The extracellular matrix (ECM), in collaboration with intracellular signal, plays a critical role in the modulation of cellular behavior and function. Herein, we investigated the influence of fibronectin (FN) and tumor necrosis factor-alpha (TNF-α) on OPN expression in HN-22, a human head and neck squamous cell carcinoma (HNSCC) cell line. The data showed that TNF-α significantly increased OPN expression only in the FN-coated condition. Application of function-blocking antibody directed against β1 integrin abolished this OPN induction. Moreover, TNF-α when added together with activating β1 integrin antibody is sufficient to induced OPN expression. The combination effect of FN and TNF-α was significantly deteriorated by a MEK inhibitor, but not NF-κB inhibitor. We further demonstrated that the phosphorylation of ERK1/2 was strongly enhanced by TNF-α and FN compared to the application of either one alone. Synergistic effect on ERK1/2 phosphorylation was also detected by TNF-α and activating β1 integrin antibody, whereas inhibitory antibody to β1 integrin attenuated FN and TNF-α-induced phosphorylation of ERK1/2. Our results indicate that FN coordinates TNF-α-mediated OPN induction via β1 integrin-dependent signaling mechanism that activates ERK. The results suggest the critical role of tumor micro-environment signaling networks on the regulation of cytokine expression profiles during tumor progression.

Expression of Wnt5a in tooth germs and the related signal transduction analysis

L. Peng, G. Dong, P. Xu, L.B. Ren, C.L. Wang, Melissa Aragon, X.D. Zhou, L. Ye — 2010-02-01

Abstract: Objective: Wnt5a is generally considered a non-canonical Wnt family member and plays an important role in the development of several tissues through regulation of cell fate, proliferation, migration, polarity and death. This study investigates its expression mode in human tooth development and the involved cell signal transduction pathways, as they remain unclear.Design: The expression of Wnt5a was analyzed by immunohistochemistry method. Recombinant adenovirus encoding full-length Wnt5a cDNA was constructed to investigate four cell signal pathways and nine dentinogenesis nuclear transcription factors in response to Wnt5a in human dental papilla cells (HDPCs).Results: Immunostaining revealed that Wnt5a was expressed in enamel epithelium cells from the bud stage, and in odontoblast layers and dental papilla tissues from early bell stage of human tooth development onward. Western blot analysis indicated that p42/44 MAPK, p38 MAPK, JNK and AKT signal pathways could be phosphorylated by WNT5A. RT-PCR analysis showed that Wnt5a increased the expression of DLX1, DLX2, LEF1, MSX2, PAX9 and RUNX2 mRNA, but decreased BARX1 and PITX2 mRNA.Conclusions: It was concluded that WNT5A is expressed in human tooth development, and that p42/44 MAPK, p38 MAPK, JNK and AKT signal pathways and DLX1, DLX2, LEF1, MSX2, PAX9, RUNX2 could be activated by Wnt5a.

Two-dimensional patterns of human enamel thickness on deciduous (dm1, dm2) and permanent first (M1) mandibular molars

Patrick Mahoney — 2010-02-01

Abstract: Objective: To characterise patterns of enamel thickness on deciduous (dm1, dm2) and permanent first (M1) mandibular molars and evaluate these against functional and morphological interpretative models.Methods: Histological sections of mesial and distal cusps from 69 unworn molars were produced and examined using transmitted light microscopy. Enamel cap area, dentine area, as well as average and linear measurements of enamel thickness were recorded from digital images of the sections using image analysis software. Comparisons were made along the molar row, and between the mesial and distal sections of each tooth, using univariate and multivariate inferential statistics.Results: The enamel cap area, dentine area, and average enamel thickness increased from the anterior to the posterior molars. The greatest proportional increase in linear enamel thickness occurred between the outside surface of the lingual cusps when dm1 was compared to dm2, and between the outside surface of the buccal cusps when dm2 was compared to M1. The enamel cap area increased from the mesial to the distal sections in M1. Dentine area decreased from the mesial to distal sections in dm1. Enamel cap and dentine areas did not change across dm2.Conclusion: Results for the deciduous molars are interpreted within a functional model of mastication, in which the dm2 dissipates less laterally orientated loads compared to dm1. Differences in enamel thickness between dm2 and M1 support previous functional interpretations for this permanent molar. Some mesial–distal results are not easily explained from either a functional or a morphological perspective and suggest an underlying developmental constraint.

Effect of a pulsed CO2 laser and fluoride on the prevention of enamel and dentine erosion

2010-02-01

Abstract: Objective: The hypotheses of this study was that pulsed CO2 laser (λ=10.6μm) treatment in combination (or not) with previous fluoride gel application could increase the resistance of enamel and dentine to erosion, throughout successive erosive challenges.Design: Thirty-two bovine specimens of enamel and of root dentine were flattened, polished and randomly assigned to the following treatments (n=8): fluoride (F), laser (L), fluoride+laser (FL) or no treatment as negative control (C). The treated specimens were submitted to demineralization (0.3% citric acid, pH 2.45, for 5min) and remineralization (artificial saliva, for 60min) cycles, three times a day, for 3 days. Dental surface loss as well as the concentration of calcium, phosphorus and fluoride in the demineralizing solutions were determined after each cycling day. Enamel and dentine were analysed separately using repeated measures ANOVA for ranks (α=0.05).Results: The association between fluoride and laser (FL) resulted in the lowest enamel and dentine surface loss values throughout the cycles, differing significantly from the control group. No clear benefit of FL over the F or L treatments was observed. There was a non-significant trend (p>0.05) for FL to release less calcium, phosphorus and fluoride into the demineralizing solutions when compared to the other groups.Conclusions: Pulsed CO2 laser (λ=10.6μm) alone was not able to prevent enamel or dentine surface losses due to erosion. Laser treatment in combination with fluoride showed some protection, but the effect does not appear to be synergistic.

Measurement of hydroxyapatite density and Knoop hardness in sound human enamel and a correlational analysis between them

Bing He, Shengbin Huang, Junjun Jing, Yuqing Hao — 2010-02-01

Abstract: Objective: The aim of this study was to measure the hydroxyapatite (HAP) density and Knoop hardness (KHN) of enamel slabs and to analyse the relationship between them.Design: Twenty enamel slabs (10 lingual sides and 10 buccal sides) were prepared and scanned with micro-CT. Tomographic images of each slab from dental cusp to dentinoenamel junction (DEJ) were reconstructed. On these three-dimensional (3D) images, regions of interest (ROIs) were defined at an interval of 50μm, and the HAP density for each ROI was calculated. Then the polished surfaces were indented from cusp to DEJ at intervals of 50μm with a Knoop indenter. Finally, the data were analysed with one-way ANOVA, Student's t-test, and linear regression analysis.Results: The HAP density and KHN decreased from the dental cusp to DEJ. Both HAP density and KHN in the outer-layer enamel were significantly higher than those in the middle- or inner-layer enamel (P<0.05). The HAP density showed no significant difference between the buccal and lingual sides for enamel in the outer, middle and inner layers, respectively (P>0.05). The KHN in the outer-layer enamel of the lingual sides was significantly lower than that of the buccal sides (P<0.05); there was no significant difference between the lingual and buccal sides in the middle or inner layer. Linear regression analysis revealed a linear relationship between the mean KHN and the mean HAP density (r=0.87).Conclusion: Both HAP density and KHN decrease simultaneously from dental cusp to DEJ, and the two properties are highly correlated.

Microbial profile of ligature-induced periodontitis in rats

2010-02-01

Abstract: Objective: The aim of this study was to evaluate the composition of the biofilm accumulated around ligatures in rats by checkerboard DNA–DNA hybridization using probes made from human oral bacterial species.Methods: 12 Wistar rats were selected for this study. One of the mandibular first molars of each animal received a ligature, while the contralateral tooth was left unligated to be used as a control. Forty-two days later, the ligatures and one sample of biofilm from each unligated teeth were analyzed by checkerboard DNA–DNA hybridization for 40 human periodontal species. The area of bone loss in the furcation area was determined histometrically.Results: The unligated teeth did not present any of the bacterial species tested. Twenty five species were detected in the ligatures. Streptococcus- and Actinomyces-like species were found in high mean counts, followed by Fusobacterium-, Prevotella nigrescens- and Parvimonas micra-like species and Porphyromonas gingivalis- and Aggregatibacter actinomycetemcomitans-like species. Greater bone loss was observed in the furcation area of the ligated than of the unligated group (p<0.0001).Conclusion: At 42 days, the ligature biofilm in rats presents various bacterial species that hybridize to probes of periodontal bacterial species commonly observed in human.

Presence and quantification of mast cells in the gingiva of cats with tooth resorption, periodontitis and chronic stomatitis

2010-02-01

Abstract: Objective: Mast cells are tissue-dwelling granule-containing immune cells that play a pivotal role in the pathogenesis of inflammation and other processes. The three most common orodental disorders in cats are periodontitis, feline resorptive lesions (FRL), and chronic gingivostomatitis (FCGS). The presence and density of mast cells in the gingiva has been established in healthy cats but not in cats affected by FRL, FCGS or periodontitis. The aim of the present study was to document and quantify the presence of mast cells in the gingiva adjacent to teeth affected by FRL, FCGS or chronic periodontitis.Methods: Samples from the gingiva of 32 cats affected by FRL, FCGS or periodontitis were obtained and compared to samples obtained from 7 specific pathogen-free (SPF) cats. Evaluation of mast cells and the inflammatory infiltrate were performed on hematoxylin and eosin, and toluidine blue stained sections.Results: Mast cells densities were significantly increased in gingival tissues adjacent to teeth affected by FRL, FCGS or periodontitis in comparison to SPF samples. There were no significant differences between gingival tissues of the FRL, FCGS and periodontitis groups. However, the relative inflammatory score in the FRL group was significantly lower as compared to the FCGS or periodontitis groups, yet with similar density of mast cells.Conclusion: In the gingiva of cats affected with FRL, FCGS or periodontitis, there is an increase in the number of mast cells. The high number of mast cells in the FRL group and concurrent mild inflammatory reaction suggests the notion that mast cells may potentially play role in the pathogenesis of FRL.

Age- and sex-related changes of mandibular condylar cartilage and subchondral bone: A histomorphometric and micro-CT study in rats

Kai Jiao, Juan Dai, Mei-Qing Wang, Li-Na Niu, Shi-bin Yu, Xiao-Dong Liu — 2010-02-01

Abstract: Objective: To quantify the age- and sex-related changes in the rat condylar cartilage and subchondral bone.Methods: SD rats were obtained at the ages of 2, 3, 4, 5, 6 and 7 months. For each sex, the temporomandibular joints tissue blocks from four rats were subjected to histological assessment of cartilage thickness and subchondral bone architecture; for the remaining three rats, the mandibular condyles were delivered for gross measurement and evaluation of the mineralization and architecture properties of the subchondral bone by means of micro-CT.Results: Rapid decrease of cartilage thickness but increase of subchondral bone density occurred respectively from 2 to 3 and 3 to 4 months old in female and 2 to 4 and 3 to 5 months old in male (P<0.05), whereas rapid changes of subchondral bone architecture occurred from 3 to 4 months old in both sexes (P<0.05). The significant enlargement of condyle size occurred at 4 or 5 months old in female but at 5 or 6 months in male (P<0.05).Conclusion: This study demonstrated that the rapid developmental changes of rat condylar cartilage and subchondral bone primarily occurred before 4 months of age, resulting in thinner cartilage but larger and thicker subchondral bone, and they were followed by rapid growth in condylar size. Sex differences were identified that the endochondral ossification of fibrocartilage and formation of subchondral bone were faster in female than in male rats, leading to the earlier enlargement of condyle in female than in male.

Relationships of beta-blockers and anxiolytics intake and salivary secretion, masticatory performance and taste perception

2010-02-01

Abstract: Objective: Assess the influence of salivary flow on physiological parameters of the stomatognathic system in patients who take beta-blockers or anxiolytic medications.Design: Sixty patients were divided into three groups based on the following criteria: Group 1, control (n=20; no use of medication); Group 2, use of antihypertensive beta-blockers (n=20); and Group 3, use of benzodiazepine anxiolytics (n=20). Salivary flow was assessed by determining stimulated and non-stimulated flow/minute. The quantification of the sense of taste was determined on a visual analogue scale (VAS) using solutions of 0.9% NaCl (salty), 50% sucrose (sweet), 20% unsweetened coffee (bitter) and 4.2% vinegar (sour). The DMFT index (number of decayed/missing/filled teeth) was determined by a calibrated examination, following the criteria of the World Health Organization (WHO). Masticatory performance was assessed with an Optosil comminution test and Rosim–Ramler equation.Results: The results did not reveal a significant correlation between salivary flow and masticatory performance (p>0.05). We observed significant decreased non-stimulated salivary flow for Group 2 (p=0.05) when compared to controls. However, taste perception was not influenced by salivary secretion amongst groups. Furthermore, we observed a significant negative correlation between non-stimulated salivary flow and DMFT in Group 1 (p=0.02; r=−0.52).Conclusions: Patients under beta-blockers therapy presented reduced non-stimulated salivary flow when compared to controls, without influencing the sense of taste or masticatory performance. The use of anxiolytics did not affect salivary flow and taste perception in the studied sample.

Imbalance of oxidative/anti-oxidative status induced by periodontitis is involved in apoptosis of rat submandibular glands

2010-02-01

Abstract: Objective: Epidemiologic studies suggest a relationship between periodontitis and salivary gland dysfunction. A rat periodontitis model was used to investigate whether a causal relationship exists between periodontitis and pathological changes of submandibular glands.Design: Fourteen male Wistar rats (8 weeks old) were divided into two groups (n=7/group): a control group and periodontitis group. Periodontitis was induced by ligature placement around the mandibular first molars. Serum levels for reactive oxygen metabolites, anti-oxidant and tumour necrosis factor (TNF)-α were measured at baseline, 2 and 4 weeks. At 4 weeks, the levels of 8-hydroxydeoxyguanosine were determined to evaluate oxidative damage of submandibular glands. Expression of TNF-α mRNA and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) as well as histological findings were also evaluated in the submandibular glands.Results: The rats with experimental periodontitis showed increase in the levels of serum reactive oxygen metabolites and TNF-α, and a decrease of anti-oxidant power in a time-dependent manner. At 4 weeks, these rats also had significantly increased levels of 8-hydroxydeoxyguanosine and TNF-α, and increased number of TUNEL-positive cells and vacuolisation in the submandibular glands compared to the control rats.Conclusions: Imbalance of circulating oxidative/anti-oxidative status may be involved in vacuolisation and apoptosis of submandibular glands in the rat periodontitis model.

Physical and biological properties of yam as a saliva substitute

Moon-Soo Park, Ji-Youn Chang, Yoon-Young Kim, Jeong-Hyun Kang, Hong-Seop Kho — 2010-02-01

Abstract: Objective: The purpose of this study was to investigate the viscosity and wettability of a water-soluble extract of yam and its effects on lysozyme and peroxidase activities.Design: Human whole saliva, yam tuber, hen egg-white lysozyme, and bovine lactoperoxidase were used. Viscosity was measured with a cone-and-plate digital viscometer, while wettability was determined by measuring the contact angle. Lysozyme activity was determined by the turbidimetric method. Peroxidase activity was determined using the NbsSCN assay. Hydroxyapatite beads were used as a solid-phase.Results: The viscosity of the yam solution was proportional to its concentration, with diluted yam solutions at 1:5 and 1:10 in simulated salivary buffer displaying similar viscosity values to unstimulated whole saliva and stimulated whole saliva, respectively. The contact angle of yam solution was not significantly different according to the tested materials or yam concentrations. Contact angles of yam solutions on acrylic resin were higher than those of human saliva. Yam affected lysozyme and peroxidase activities, and those effects were different on the hydroxyapatite surface versus in solution. Hydroxyapatite-adsorbed yam increased subsequent adsorption of lysozyme and peroxidase.Conclusion: We objectively confirmed the similarity of the viscoelastic properties of yam and human saliva, suggesting a role for yam in the development of effective saliva substitutes.