Effect of mechanical stimulation by tooth brushing on oxygen tension in dog gingiva

Spatial extent of gingival cell activation due to mechanical stimulation by toothbrushing

BACKGROUND

Mechanical stimulation by toothbrushing enhances gingival fibroblast proliferation and collagen synthesis, and reduces inflammatory cell infiltration. The aim of this study was to investigate the spatial extent of proliferation of fibroblasts and endothelial cells in dog gingiva in response to mechanical stimulation by toothbrushing.

METHODS

All maxillary fourth premolars and mandibular first molars of 6 mongrel dogs were used. Dental plaque was removed with a curet. One of each pair of bilateral teeth (in the same jaw) was assigned to the brushing group, and the corresponding tooth (opposite side) was assigned to the control group. The Bass method was used to brush the limited mesial half of the tooth at 1.96 N for 20 seconds with a fitted plastic stent. Immediately before fixation of tissue, the surface of brushed gingiva was notched to indicate the borderline between the brushed and non-brushed areas. Histometrical analyses of the sections were performed using assays for proliferating cell nuclear antigen (PCNA) and von Willebrand factor.

RESULTS

The numbers of fibroblasts and PCNA-positive fibroblasts in the subepithelial connective tissue adjacent to oral sulcular epithelium significantly increased in brushed gingiva, not only in the brushed area but also in the non-brushed area 0 to 0.5 mm from the notch. Increased numbers of vascular endothelial cells were observed only in the brushed area.

CONCLUSION

The effect of mechanical stimulation by toothbrushing on gingival cell proliferation was not observed more than 0.5 mm from the brushed area. These results indicate that effective activation of gingival cell proliferation requires mechanical stimulation of gingiva in all areas.

Toothbrushing and gingival recession

AIM

To review the hypothesis that toothbrushing leads to gingival recession. Gingival recession develops due to anatomical and pathological factors. The prevalence of recession is dependent on the age and characteristic of the population because it usually presents in individuals with periodontal disease or those who practise zealous or improper oral hygiene methods. Gingival trauma and gingival abrasion from toothbrushing is thought to progress directly to gingival recession. Case studies documenting recession from toothbrush trauma are speculative. Short-term studies suggest that gingival trauma and gingival abrasion may result from toothbrushing, but the direct relationship between traumatic home care and gingival recession is inconclusive. Long-term studies remain elusive or do not support the development of recession following toothbrushing. Nevertheless, tooth abrasion may be an integral part in the aetiology of recession. Toothbrush abrasion also may cause wear at the cemento-enamel junction resulting in the destruction of the supporting periodontium leading to recession.

Effect of mechanical toothbrush stimulation on gingival microcirculatory functions in inflamed gingiva of dogs

The effect of mechanical toothbrush stimulation on gingival microcirculatory functions was examined with and without removal of supragingival plaque in inflamed gingiva of 6 dogs. After removal of the ligatures, 4 treatment modalities: mechanical stimulation by vibration (MS), removal of supragingival plaque (PR), combination (MS+PR) and no treatment (NT), were administered to each quadrant for 2 weeks. Both quadrants with plaque removal showed a marked decrease in the gingival index score, while slight and moderate decreases were observed in NT and MS quadrants, respectively. Changes in gingival crevicular fluid flow, pocket oxygen tension and hemoglobin oxygen saturation in the gingiva were significant in the MS, PR and MS+PR quadrants. Significant treatment-by-time effects were found for all of the parameters of microcirculatory function between NT and MS quadrants, and gingival crevicular fluid flow between PR and MS+PR quadrants, respectively. These findings suggest that mechanical stimulation with a toothbrush may offer an additional benefit to gingival microcirculatory functions in inflamed gingiva.

The effects of thermal and mechanical stimulation on blood flow in healthy and inflamed gingiva in man

The purpose of this study was to compare the state of the microcirculation in healthy gingiva with that in untreated, inflamed gingiva in humans. Reflection photoplethysmography (RP) was used to record blood flow from 13 clinically healthy, attached gingival sites in seven adults and 11 inflamed sites in seven patients. Changes in the pulse amplitude of the RP signal were measured before and after application of thermal (cold and hot water) and mechanical (brushing) stimuli to the gingiva. Hot water and brushing, but not cold water, produced a significant increase in the pulse amplitude in healthy gingiva (p < 0.05, Friedman analysis and Student-Newman Keuls test). None of the stimuli produced a significant change in inflamed gingiva. In neither group of participants was there a significant correlation (Spearman rank correlation coefficient) between vascular responsiveness and age. The results indicated that vasomotor control may be impaired in inflamed gingiva.

Comparisons of modalities of mechanical stimulation with a toothbrush on improvement of oxygen sufficiency in dog gingiva

Mechanical stimulation with a toothbrush was applied to each quadrant of 10 dogs at a force of 200 g for 10 s using following modalities: vibration at attached gingiva, pressurization at attached gingiva, vibration at marginal gingiva and no treatment as a control. Hemoglobin oxygen saturation (SO2) in the gingiva was measured by non-invasive tissue reflectance spectrophotometry. Simultaneously, oxygen tension (pO2) in gingival tissue was monitored with an oxygen microelectrode. Both SO2 and pO2 increased within 10-20 min after stimulation and then slowly returned to the initial level at all treatment sites. The response was most prominent after vibration at attached gingiva. SO2 and pO2 increased by 12% and 42%, respectively, and significant increase continued for 75-85 min. Response after vibration at marginal gingiva was moderate in pO2 and transient in SO2. Pressurization at attached gingiva caused moderate response in SO2, but the increase in pO2 was slight. Control showed little change in both indices. These results suggest that vibration with a toothbrush at attached gingiva may cause a maximal response in improving oxygen sufficiency to gingival tissue.