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Biomedical subjects

Koichiro Komatsu

Publications and source records attributed to Koichiro Komatsu.

7 recordsLinked to original sources
PubMed2006

Effects of an intravenous infusion of Ringer's solution on eruption rates of incisor teeth in anesthetized rats.

OBJECTIVE: The vasculature within the socket is reportedly involved in determining the position of continuously erupting teeth. Thus, loss of body fluid in anesthetized rats, which would affect the vascular physiology, should influence tooth movement. We investigated the effects of an infusion of Ringer's solution on the systemic arterial blood pressure, regional blood flow at the base of the incisor, and axial tooth movement in anesthetized rats to determine the cause of tooth displacement. MATERIAL AND METHODS: In the experimental group, the animals received intravenous infusions of Ringer's solution at 27 microl/min for 13 h. In the control group, the animals did not receive the infusion. RESULTS: The infusion of Ringer's solution suppressed an increase of the mean arterial blood pressure from 86 to 80 mmHg and a decrease of the regional blood flow from 170 to 217 mV, and increased the eruption rate from 267 to 361 microm/13 h during the experimental period. There was a positive correlation between the eruption rate and regional blood flow, and a negative correlation between the blood pressure and regional blood flow. CONCLUSIONS: These results suggest that an infusion of Ringer's solution can cause an increase in the regional blood flow, resulting in increased fluid volume, elevated intra-socket pressure, and increased eruptive movement. It is possible that the regional vascular volume and/or pressure within the socket play an important role in determining the position of the incisor.

Animals↗
PubMed2006

Mechanical behavior of bovine periodontal ligament under tension-compression cyclic displacements.

In the present study, the mechanical response of bovine periodontal ligament (PDL) subjected to displacement-controlled tension-compression harmonic oscillations and subsequent rupture was examined. Specimens including dentine, cementum, PDL, and alveolar bone were extracted from different depths and locations of bovine first molars. They were immersed in a saline solution at room temperature and clamped on their bone and dentine extremities. The samples were tested at +/-35% of the PDL's width, with a frequency of 1 Hz. The mechanical parameters evaluated were hysteresis, phase lag, and the modulus of the stress-stretch ratio curves in tension and compression. The tensile strength and the corresponding stretch ratio were also recorded. Stress-stretch ratio curves indicated a non-linear, time-dependent response with hysteresis and preconditioning effects. The hysteresis and phase lag in compression were much higher than in tension, suggesting that the dissipated energy was higher in compression than in tension. The root depth and location did not play essential roles for the tension or compression data, with the exception of limited statistical differences for tensile strength and corresponding stretch ratio. Thus, biological variability in the specimens, as a result of different bone contours, PDL width, and fiber orientation, did not affect the energy-absorbing capacity of the PDL. The evolution of the stress rate with stress demonstrated a constant increase of stiffness with stress. The stiffness values were twofold higher in tension than in compression. The data also showed that the stiffness of the PDL was comparable with data reported for other soft tissues.

Analysis of Variance↗
PubMed2005

Effects of local injections of vasoactive drugs on eruption rate of incisor teeth in anaesthetized rats.

OBJECTIVES: Previous studies have suggested that the vasculature in the dental pulp and periodontal tissues plays an important role in producing the eruptive force in continuously erupting incisors. The aim of the present study was to investigate the effects of local injections of vasoactive drugs on regional blood flow within the socket in association with axial tooth movements to clarify the role of the local vascular system on tooth eruption. DESIGN: Twenty-two male Wistar rats, weighing 309+/-21 g (S.D.), were immobilized with halothane anaesthesia. We measured the regional blood flow within the socket using a laser Doppler flowmeter, and the axial movements of the mandibular incisor using a displacement detector. The local injections of the vasoactive drugs, adrenaline (0.001, 0.01, and 0.1 microg/kg body weight) and acetylcholine (0.05, 0.5, and 5 microg/kg), into the base of the incisor were performed by a microinjector at a rate of 1 microl/kg body weight. RESULTS: The injections of various doses of adrenaline decreased the mean regional blood flow and eruption rate dose-dependently, while those of acetylcholine increased the mean regional blood flow and eruption rate dose-dependently. The changes in the regional blood flow and eruption rate were transient. Significant correlations (p<0.001) were obtained between the maximum and minimum values in the regional blood flow and in the eruption rate following injections of various doses of adrenaline and acetylcholine. CONCLUSION: These results support the hypothesis that the eruptive force of the rat incisor is closely related to the vasculature within the socket.

Acetylcholine↗
PubMed2004

The biomechanical properties of the healing periodontium of replanted rat mandibular incisors.

One of the most important aspects in tooth replantation seems to be restoration of the tooth support function of the healing periodontal ligament (PDL). We examined the support function, as measured by the mechanical properties, of the healing PDL at 7, 14, and 21 days after replantation of the left mandibular incisor in rats. From each dissected left mandible, a transverse section(650 microm in thickness) of the incisor was cut through an axis near the labial alveolar crest. Each section was intrusively loaded at a rate of 5 mm min(-1), and the shear stress-strain curve for the PDL was analyzed. Mechanical measures of the healing PDL showed gradual improvement after replantation. By 21 days, the mechanical strength returned to 53% of the control value; the extensibility, to 85%; the stiffness, to 61%; and the toughness, to 52%. The healing PDL exhibited reattachment of fibers in the middle region of the PDL, and the birefringent collagen fibers appeared to have regained the functional orientation by 14 days. The ratios occupied by the birefringent collagen fibers in the tooth-related, middle, and bone-related areas of the healing PDL gradually improved and returned to 78, 51, and 48% of the respective control values by 21 days. These results suggest that the support function of the healing PDL is gradually restored and that the biomechanical restoration is closely related to the reorganization and reorientation of collagen fiber bundles in replanted rat incisors.

Analysis of Variance↗
PubMed2003

Restoration of mechanical strength and morphological features of the periodontal ligament following orthodontic retention in the rat mandibular first molar.

Biomechanical properties and morphological features of the periodontal ligament (PDL) in the rat mandibular molars were examined during orthodontic retention. Seventy-three male rats of the Wistar strain, 8 weeks of age, were used for biomechanical analysis and six rats for morphological analysis. An elastic band was inserted between the mandibular first and second molars for 4 days; after removal of the elastic band the interdental space was filled with resin for 4 and 8 days. The maximum shear stress, tangent modulus, and failure strain energy density of the PDL of the first molar in the experimental animals decreased markedly following application of an orthodontic force. They increased rapidly and were restored completely to the control levels by the 8th day after retention. Light microscopy showed severe compression and extension of the PDL in the experimental animals on the 8th day after retention. Birefringent collagen fibre bundles running across the compressed and expanded PDL were observed, although they appeared to be thinner with less insertions into the alveolar bone or cementum in the experimental animals than in the controls. This suggests that the periodontal collagen fibres were partially reorganized and rearranged during retention. The reorganization and rearrangement of periodontal collagen fibres seemed to be partly related to the restoration of mechanical strength of the rat molar PDL during the 8 days of retention.

Alveolar Process↗
PubMed2002

Polarized light microscopic analyses of collagen fibers in the rat incisor periodontal ligament in relation to areas, regions, and ages.

We prepared decalcified sagittal sections (20 microm thick) from the incisal, middle, and basal regions of the mandibular incisor of male Wistar rats aged 2, 6, 12, and 24 months, and examined the sections using polarized light microscopy. Most of the birefringent fibers appeared to run obliquely across the periodontal ligament. Birefringent fibers running parallel to the long axis of the incisor were also found in the intermediate area of the ligament. Similar fiber architecture was observed in all four age groups. Quantitative analysis showed that the retardation values of collagen were higher in the bone- and tooth-related areas and lower in the intermediate area of the ligament. The values for the bone- and tooth-related areas increased from the basal toward the incisal regions in all four age groups. Age-related changes in the retardation values were found only in the incisal region of the incisor. In the incisal region, the values for the bone- and tooth-related areas increased markedly from 2-24 months of age, whereas those for the intermediate area increased slightly but significantly with age. Our findings indicate that the degrees of molecular organization and alignment of collagen fibers in the bone- and tooth-related areas of the ligament are higher than those in the intermediate area and increase near the incisal region and with age. It is also suggested that the collagen fibers in the intermediate area remain immature along the long axis of the incisor throughout the life span of the animal.

Age Factors↗