The effect of IL-1alpha and nifedipine on cell proliferation and DNA synthesis in cultured human gingival fibroblasts

The effect of nifedipine and interleukin-alpha (IL-1alpha) on the cell proliferation and DNA synthesis was studied in human gingival fibroblasts derived from 5 patients who developed gingival overgrowth (nifedipine responders) and 5 patients who did not develop gingival overgrowth (nifedipine non-responders) in response to nifedipine. Epidermal growth factor was used as a positive control. The fibroblasts derived from nifedipine responders tended to have a numerically greater rate of cell proliferation and DNA synthesis (3H-thymidine incorporation) than those from nifedipine nonresponders in the presence of nifedipine and IL-lalpha. Fibroblasts derived from nifedipine responders showed significantly higher cell proliferation rate in the presence of nifedipine and IL-1alpha, than nifedipine or IL-lalpha alone on both the second and the fourth day of incubation (P < 0.05). A combination of IL-1alpha and epidermal growth factor also showed significantly greater cell proliferation than IL-lalpha alone on the second day (P < 0.05). The DNA synthesis rate with a combination of nifedipine and IL-1alpha was higher than that for nifedipine alone on the second day (P < 0.01), and IL-1alpha alone on the fourth day (P < 0.05) in gingival fibroblasts originating from nifedipine responders. These results suggest that the interaction between nifedipine and gingival inflammation might play an important role in the pathogenesis of nifedipine-induced gingival overgrowth.     

Relationship between masticatory function and internal structure of the mandible based on computed tomography findings

INTRODUCTION: The purposes of this study were to investigate bone mineral density as a part of bone construction in human skulls and to examine the relationship between dentofacial morphology and masticatory function by using computed tomography (CT) findings. Changes in bone mineral density in the mandible because of loss of masticatory function were tested in rats by experimentally producing an environment that inhibited mastication by the molars. METHODS: Data for the human study were obtained from 27 modern male Japanese skulls (mean age, 28 years) from the University of Tokyo. Cortical bone thickness (CBT) and CT value (CV) were measured by each CT scan of the first and molars. For the animal study, a metal cap was inserted between the maxillary and mandibular incisors to prevent the molars from biting in 6-week-old male Wistar rats. The rats were killed after 2, 4, or 6 weeks, and bone mineral density was measured in cancellous and cortical bone equivalent to the first molar region by using peripheral quantitative computed tomography. RESULTS: In the human skull study, significant negative correlations were observed between CV in the regions of the buccal side of the second molar and the angle between the Frankfort horizontal and mandibular planes. Significant negative correlations were also observed between the gonial angle and CV in the buccal and basal sides. In the animal study, cancellous bone mineral density began to decline 4 weeks after the start of the experiment in the masticatory hypofunction group compared with the control group. By week 6, cancellous bone density had declined by 11.6% on the buccal side, 16.7% on the lingual side, 12.3% at the bifurcation of the root, and 38.1% at the root apex. Cortical bone density declined by 8% to 12% on the lingual side. CONCLUSIONS: The results support our hypothesis that a functional adaptive response by the mandible to mechanical stress resulting from mastication occurs not only in the muscle insertion area, but also in mandibular alveolar bone in the molar region.     

An ultrastructural analysis of the prototype single-step adhesive applied on enamel and dentin surfaces

A new type of self-etching agent, the single-step adhesive, was developed. The purpose of this study was to investigate the difference in the ultrastructural features of enamel and dentin surfaces following application of the prototype single-step adhesive (EXM618, 3M, MN, USA). Extracted caries-free human premolars were used in this study. Occlusal enamels of teeth--to be used as cut surface specimens--were removed perpendicular to the long axis of the specimens. The mesial and distal surfaces of these teeth, on the other hand, were used as uncut surface specimens in the test. In addition, Mega Bond (Kuraray Medical Inc., Tokyo, Japan) and Xeno CFII Bond (Dentsply Sankin, Tokyo, Japan) were used as controls. After covering half of the tooth surfaces with nail varnish (for control), the other half of each surface was treated with one of the three test adhesives--EXM618, Mega Bond, or Xeno CFII Bond--according to the manufacturer's recommendations. Conditioned enamel and dentin surfaces (i.e., decalcified depth and rugged surface) were observed with a scanning confocal laser microscope (SCLM 1100, Olympus, Tokyo, Japan; henceforth abbreviated as SCLM). Based on the findings of this study, the prototype single-step adhesive EXM618 appears to be suitable for use in dental clinics.     

Characterization of excess hard tissue occurring in the mesio-buccal surface of the mandibular first molar in microphthalmic mouse

OBJECTIVE: The aim of the present study was to characterize the excess hard tissue on the mandible of the microphthalmic mouse having a mutation at the mitf locus. DESIGN: Homozygous mutant (mi/mi) and wild-type (+/+) mice were obtained by mating a breeding pair (strain name, B6C3Fe a/a-Mitf(mi)/J). We used mi/mi and +/+ mice at ages 6, 7, 8, 9, 28, and 49 days for micro-computed tomographic and histologic analyses. RESULTS: Excess hard tissue was found on the mesio-buccal surface of the mandibular first molar in all 11mi/mi mice, but none was found in the 8mi/+ or 14 +/+ mice. The excess hard tissue was located in the mental foramen connected to the mandibular canal. The mandibular canal passed near the basal part of the incisor and the root of the mandibular first molar due to aberrant development of the teeth and mandible. The excess hard tissue contained predentine immunostained for dentine sialoprotein, a marker for early stages of dentinogenesis, which was first observed at about 7 days of age. Dentine, predentine, pulp, and root-like structures were observed in the excess hard tissue, but neither enamel nor enamel organ was observed. CONCLUSION: Odontogenic cells in the basal part of the incisor and/or the mandibular first molar with the ability to develop into odontoblasts and pulp cells appeared to migrate through the mandibular canal to the mental foramen, where they developed into odontoblasts and pulp-like cells, and then formed dentine and predentine-like structures.     

Immobilization of simulated reducing agent at the surface of SiO2 fillers in dental composite resins

To reduce the leachability of reducing agents from composite resins, immobilization of a simulated reducing agent at the surface of SiO2 fillers was examined. SiO2 plates were immersed in 2% 3-aminopropyltriethoxy silane/ethanol solution, and then immersed in dimethyl sulfoxide with 0.25 wt% 4-dimethyl amino benzoic acid (DMABA), 2.0 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, and 0.5 wt% N-hydroxysuccinimide. Wide-scan spectrum of X-ray photoelectron spectroscopy did not detect carbon contamination. However, narrow scan detected an O=C-N peak at 399.8 eV, suggesting that DMABA could be immobilized on silane-coupled SiO2 plates. Further, surface plasmon resonance analysis indicated the adsorption of MMA at the surface of reducing agent-immobilized plate.     

Age-related differences in expression of vascular endothelial growth factor by periodontal ligament cells in vitro

The purpose of this study was to evaluate age-related differences in expression of vascular endothelial growth factor (VEGF) by periodontal ligament (PDL) cells. PDL cells were obtained from Wistar male rats weighing approximately 150 g each in the young group and 350 g each in the old group. PDL cells derived from upper and lower incisors were seeded in 35-mm culture dishes after primary culture. For cell proliferation assays, cells were detached and counted at 1, 3, 5, 7, 11 and 14 days after culture. VEGF mRNA expression was analyzed with TaqMan. The number of cells in both groups increased day by day, but the rate of increase in the young group was higher than that in the old group. VEGF mRNA expression in the young group increased from 3 to 14 days, but in the old group increased only slightly over the same time period. Expression ratios in the young group were higher than those in the old group, and there were significant differences between the young and old groups at 7 and 14 days of culture. In conclusion, the data revealed that PDL cells varied with age, and suggest that in view of such changes in cell proliferation and VEGF mRNA expression, age should be taken into consideration in periodontal treatment.     

The effects of loading locations and direct retainers on the movements of the abutment tooth and denture base of removable partial dentures

The purpose of this study was to evaluate the degree and amount of movement of the abutment tooth and denture base influenced by the direct retainer of distal extension removable partial denture and the location of functional loading, then to suggest direct retainer design with minimal adverse effect and with optimum functional loading location for residual tissue. The displacement of the abutment tooth and inclination of the denture base were determined, with 30 N as work load utilizing simulation model and strain gauge system, about two types of direct retainers with mesial or distal rest and nine loading points on denture base. Displacement and inclination was determined with the one-way analysis of variance and Scheffe's multiple test was performed. The results revealed that type of direct retainer influenced on the magnitude rather than direction of the abutment tooth displacement. The distal displacement of abutment tooth was significantly less in Type M clasp (with mesial rest and connection) than in Type D clasp (with distal rest and connection) (p<0.05). The location of loading points influenced both of the magnitude and direction of the abutment tooth and denture base movement. Posterior and lingual loading resulted in significantly distal displacement of abutment tooth (p < 0.05).     

A study on kinetic frictional properties in Begg/KB orthodontic appliances at posterior sites

In Begg and KB techniques, the kinetic frictional force generated between their characteristic orthodontic appliances at posterior sites and the orthodontic wire affects the efficiency of tooth movement. We compared the kinetic frictional force between the recent orthodontic appliances for posterior sites: the by-pass loop-KB buccal tube system (loop-KB tube system) and the conventional by-pass clamp-round buccal tube system (clamp-round tube system), and elucidated the frictional properties of the loop-KB tube system. We used 016"/018" round wires (016/018 round) and 022" × 016" ribbon wire (022 ribbon) with anchorage bend/curve applied. The results obtained were as follows:

In vitro comparison of subjective image quality of the pana digital intraoral x-ray imaging system and conventional intraoral radiography in caries detection

The aim of this study was to evaluate observer performance with a charge coupled device-based intraoral X-ray imaging system, Pana Digital system, in comparison with conventional film-based radiography (Ektaspeed Plus). A total of 118 teeth mounted in plaster were radiographed using both the Pana Digital system and conventional film. The occlusal and approximal surfaces of the resultant images were evaluated by six observers in relation to the caries depth. For the verification of the caries depth, the teeth surfaces were rated histologically by two examiners according to the same rating scores used for the X-ray imaging assessment. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of the two image modalities were calculated together with Cohen's kappa values. No significant difference was found in any diagnostic parameters at any thresholds between the two modalities. The Kappa values for the Pana Digital system showed relatively lower levels than those of conventional film in occlusal caries assessment, whereas no apparent differences were found between the two modalities in any scores of depth for approximal caries assessment. The results of the present study, in which there was no discrepancy in diagnostic abilities, suggested that the Pana Digital system could play a useful role in clinical caries diagnosis.     

Effects of Nd:YAG and CO2 laser treatment and ultrasonic scaling on periodontal pockets of chronic periodontitis patients

BACKGROUND: The aim of the present study was to compare the effectiveness of Nd:YAG and CO2 laser treatment to that of ultrasonic scaling used as monotherapies by examining clinical parameters, subgingival microflora, and interleukin-1 beta (IL-1beta) in gingival crevicular fluid (GCF). METHODS: Eighteen patients, each of whom had 2 or more sites with probing depth measuring > 5 mm, were included this clinical trial. The 41 sites were randomly assigned treatment with either Nd:YAG laser alone (n = 14, 100 mj, 20 pps, 2.0 W, 120 seconds), CO2 laser alone (n = 13, 2.0 W, 120 seconds), or ultrasonic scaling alone (n = 14, maximum power, 120 seconds). At baseline and at 1, 4, and 12 weeks, clinical measurements (plaque index, PI; gingival index, GI; probing depth, PD; clinical attachment level, CAL; and bleeding on probing, BOP) were performed and subgingival plaque and GCF sampled. A quantitative analysis of Porphyromonas gingivalis was carried out using real-time polymerase chain reaction (PCR) procedures. The amounts of IL-1beta were estimated by an enzyme-linked immunosorbent assay (ELISA). RESULTS: Decreased inflammation and PD were observed in all 3 groups after treatment. A microbiological analysis indicated significant decreases in P. gingivalis in the Nd:YAG and scaling groups at 1, 4, and 12 weeks compared to baseline (P < 0.05). The amount of GCF significantly decreased in the Nd:YAG and scaling groups at 12 weeks. The amount of IL-1beta increased in the CO2 group from baseline to 1 week (P < 0.05). The Nd:YAG group tended to show a decrease in IL-1beta from 1 to 12 weeks, although these data were not statistically significant. CONCLUSIONS: Our data suggest that Nd:YAG laser and ultrasonic scaling treatments showed significant improvements regarding the clinical parameters and subgingival microflora compared to the baseline, but no significant difference was observed between the 3 groups.