Bone fixation with miniplates has recently been used for fixation following sagittal spliting ramus osteotomy. We have observed breakage L-shaped titanium miniplates during the postoprerative observation period. We investigated the breakage cases, and performed biomechanical analysis of stress on L-shaped and straight miniplates in a sagittal spliting ramus osteotomy model, which we developed using CT images and the three-dimensional finite element method.
Breakage was detected in 22 sides (18 patients) in miniplates placed on 123 sides between January 2000 and December 2001. The period between surgery and breakage was less than 3 months in 17 of the miniplates, between 3 and 6 months in 3 miniplates, and greater than 6 months in 2 of them. The breakage, when it occurred, was always at the bending site of the L-shaped miniplates. Stress analysis by the three-dimensional finite element method demonstrated that the stress level was greatest at the upper margin of the bending region in the L-shaped plates.
Although it is thought that there is no difference in the effectiveness of bone union between L-shaped and straight miniplates, the letter may be better in resisting long-term stress on the jaw bone, such as occurs during relapse. (J Osaka Dent Univ 2007 ; 41 : 89-96)

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Analysis of plaster dental models is essential for orthodontic diagnosis. We enhanced traditional calipers to permit measurement of the basal arch length, which is difficult to measure with existing micrometer calipers. We found no difference between data obtained with the new caliper, and that measured with a traditional caliper. We also developed a method to quickly calculate the measured values using a computer, and were able to apply these techniques to many methods of analysis. (J Osaka Dent Univ 2007 ; 41 : 97-99)

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I investigated morphological changes in the facial soft tissues of patients with mandibular prognathism following orthognathic surgery by scanning their faces before and after surgery using a non-contact type three-dimensional scanner. Coordinate data obtained before and after surgery were overlapped by the least square method using a computer, and the differences in swelling at various areas were color-coded. The results showed differences in swelling mainly around the gonial angle. The differences peaked two days after surgery and were the lowest eleven days after surgery. Although the mandible was surgically retracted, soft tissue changes in the mental region were mild immediately after surgery, suggesting that mandibular retraction was cancelled out by soft tissue swelling. As the swelling started to subside 8 days after surgery, the soft tissue retraction became obvious. With the present method, it was possible to visually ascertain the soft tissue changes caused by marked swelling immediately after surgery and the positional changes caused by mandibular retraction. However, it is necessary to differentiate changes caused by swelling from reduction in soft tissue that result from body weight loss during intermaxillary fixation, and the changes in soft tissue thickening that result from increases in body weight after removal of the fixation apparatus. (J Osaka Dent Univ 2007 ; 41 : 101-106)

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In clinical orthodontics, the headgear is used to treat maxillary protrusion, while the chin cap and maxillary protractor are used to treat mandibular protrusion. These devices use orthopedic force to improve jaw discrepancies. Research on these appliances that produce orthopedic force often analyzes the position of the center of resistance and of the center of rotation in the maxillofacial complex. How orthopedic forces affect maxillary and mandibular rotations depends on the location of the pulling force relative to the center of resistance. Past research methods have been very complex. Because simulation models were rarely used, the accurate centers of resistance and rotation were not obtained.
We applied random dot moire patterns to cephalometric radiographs to develop a simple method of pinpointing the center of rotation. (J Osaka Dent Univ 2007 ; 41 : 107-110)

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Analysis of vertical factors in the facial skeleton is important in understanding craniofacial morphology. We measured the maxillofacial complex and occlusal plane on standardized lateral cephalograms of 239 male students and analyzed the potential relation-ship of these measurements with the mandibular plane angle. The ANB and OM angles were compiled for each 5 degree increment in FMA between 15 and 45 degrees. A larger mandibular plane angle was associated with a larger OM angle. No correlation was found between the mandibular plane angle and ANB angle. (J Osaka Dent Univ 2007 ; 41 : 111-113)

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We investigated how the vertical position of the mandibular incisors relates to an acceptable soft tissue profile in 100 Japanese adults. The E-line was used to evaluate esthetics. The subjects were divided into four groups based on the mandibular plane angle, and the distance of the maxillary and mandibular incisors from the Xi-stomion line was calculated for each group.
We found that all subjects had a negative distance from the maxillary central incisor to the Xi-stomion line of between 2.7mm and 3.6mm. The distance from the mandibular central incisors to the Xi-stomion line could be modified by changing the FMA.
These results suggest that it is necessary to consider both the horizontal and vertical positions of the mandibular central incisors to achieve good orthodontic results. (J Osaka Dent Univ 2007 ; 41 : 115-119)

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I investigated changes in the surface area of facial soft tissue after orthognathic surgery using a non-contact type three-dimensional scanner. The faces of five patients with mandibular protrusion were morphologically analyzed before surgery, during hospitalization, and at each visit after discharge using a non-contact type three-dimensional scanner. To ascertain the relationship between the postoperative day and changes in facial surface area, coordinate data before and after surgery were fit by the least square method using numerical analysis software.
In all patients, the surface area was greatest at either two or three days after surgery, and it markedly decreased within ten days of surgery. When swelling was at its peak, the facial surface area was approximately 1.4 times greater than the preoperative values. Changes were observed up to approximately 120 days after surgery. Chronological data were plotted to visualize postoperative changes in facial surface area. The results showed that when assessing changes, it is necessary to differentiate changes caused by swelling from those caused by other factors, such as decreases in soft tissue caused by body weight loss during intermaxillary fixation and increases in soft tissue from body weight gain after intermaxillary fixation. (J Osaka Dent Univ 2007 ; 41 : 121-124)

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Viruses are associated with many different tumors. Epstein-Barr virus (EBV) is prevalent in Burkitt lymphoma and pharyngeal carcinoma, and human papillomavirus (HPV) is found in cervical carcinoma. How are these viruses related to well-differentiated oral squamous cell carcinoma (WDOSCC)? In the present study, EBV and HPV were detected in WDOSCC by the using the in situ polymerase chain reaction (PCR). Formalin-fixed, paraffin-embedded sections of 30 well-differentiated oral squamous cell carcinoms, 10 oral leukoplakis and 10 epulides were used for detection of EBV DNA and HPV DNA by the in situ PCR reaction method. MY 09/11 and BamHIW primers were utilized for detection of HPV DNA and EBV DNA, respectively. EBV DNA was detected in the central regions of the tumor nests in all WDOSCC. EBV DNA signals were positive mainly in the upper layer of the non-neoplastic epithelium included in the tumor tissues and also positive in the infiltrating lymphocytes in the stroma of the tumor tissues. However, although HPV DNA signals were not observed in the lymphocytes in the stroma of the tumor tissues, they were detected in all of the WDOSCC in the same pattern as that of the EBV DNA signals. To some extent, a mixed infection of EBV and HPV seemed to be a risk factor associated with carcinogenesis of WDOSCC. (J Osaka Dent Univ 2007 ; 41 : 125-131)

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Computer analysis was done on the following Powell parameters of the facial profiles of Japanese TV and movie actresses : nasofrontal angle, nasofacial angle, nasomental angle, mental-cervical angle, nasolabial angle, N-Sn/N-Me, Sn-Me/N-Me, G-Sn/G-ME, Sn-Me/G-Me and Sn-stms/stmi-Me. The average nasofrontal angle was 146.7°, which is about 17° greater than the upper limit of Powell's ideal value. The average nasofacial angle was 27.2°, which is about 3° smaller than the lower limit of Powell's ideal value. The average nasomental angle was 136.2°, which is about 4° greater than the upper limit of Powell's ideal value. The average mental-cervical angle was 87.2°, which is within Powell's ideal range. There were no significant differences between Japanese actresses and Caucasians.
The average nasolabial angle for the Japanese was 118°, which was comparable with the upper limit of Powell's ideal value. The average N-Sn/N-Me was 44.4%, which is slightly greater than Powell's ideal value. The average Sn-Me/N-Me was 55.6%, which is slightly smaller than Powell's ideal value. Because the reproducibility of measurements based on the nasion is markedly higher than that of measurements based on the glabella, this value is believed to serve as a reference when evaluating the facial balance of Japanese. The average G-Sn/G-Me was 51%, which is slightly larger than Powell's ideal value. The average Sn-Me/G-Me was 49%, which is slightly smaller than Powell's ideal value of 50%. The average Sn-stms/stmi-Me was 50.1%, which matched Powell's ideal value.
The above findings indicate that when applying Powell's ideal values to Japanese, it is necessary to make slight corrections to the angle parameters. It is also necessary to set the lower facial heights below the subnasale (Sn) slightly lower than the ideal Caucasian value, and to maintain the ratio of distance from the Sn to the stomion superius against that from the stomion inferius to the menton at 1 : 2. (J Osaka Dent Univ 2007 ; 41 : 133-135)

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Many anesthetics influence intracranial environmental factors such as cerebral blood flow (CBF). Although it has been reported that CBF is closely associated with general anesthetics and nitric oxide (NO), no study has investigated the link between NO and cerebrospinal fluid (CSF) circulation. To examine this issue, we conducted a CSF quantification experiment in six adult cats by the ventriculo-cisternal perfusion (VCP) method using a nitric oxide synthase (NOS) inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME). Continuous mean arterial pressure (MAP) was monitored throughout the experiment. We administered VCP to see how it affected CSF circulation. Regional CBF (r-CBF) was measured with a laser blood flow meter. We calculated CSF production and absorption based on Vf (the rate of CSF formation) and Va (the rate of CSF reabsorption). To investigate the influence of NO, we administered L-NAME at 30mg/kg as a single dose followed by infusion at the rate of 1mg/kg/min.
We found that L-NAME administration significantly increased MAP. However, there were no changes in r-CBF. L-NAME administration did not affect V or Va. Although the acute inhibition of NOS by L-NAME increased MAP, it did not influence the circulatory kinetics of either CSF or r-CBF. However, the decrease in blood flow in the choroid plexus, as reported by Faraci et al., was not consistent with the homeostasis of CSF production. (J Osaka Dent Univ 2007 ; 41 : 137-142)

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We compared the retentive force characteristics of electroformed telescope crowns with those of Akers clasps, magnetic attachments, and cone crown telescope attachments by analyzing the retentive force-displacement curve during vertical dislodgement using a tensile testing machine. The displacement before (DBP) and after (DAP) the peak retentive force was measured, and the retentive energy before (EBP) and after (EAP) the peak were calculated. Magnetic attachments and cone crown telescope attachments are considered more effective retainers for protecting the abutment teeth. We found that the DBP, EBP and EAP for the Akers clasp were significantly greater than for the magnetic attachment, electroformed telescope crown or cone crown telescope. No significant differences were found between the electroformed telescope crown and magnetic attachments in terms of the peak retentive force, DBP, DAP and EBP. We concluded that the 2-degree electroformed telescope crown could be used as an effective retainer for the protection of abutment teeth. (J Osaka Dent Univ 2007 ; 41 : 143-149)

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Volatile anesthetics such as isoflurane and sevoflurane induce cardioprotection mimicking ischemic preconditioning. It has been reported that isoflurane-induced myocardial preconditioning is dependent on phosphatidylinositol-3-kinase (PI 3 K)/Akt signaling which plays a central role in reperfusion injury salvage kinase cascade. It remains unclear whether this signaling cascade is involved in sevoflurane-induced preconditioning. Isolated perfused guinea pig hearts were subjected to 30 min global ischemia and 120 min reperfusion (CTL). Sevoflurane-induced preconditioning was elicited by administration of sevoflurane for 10 min at one minimum alveolar concentration (1 MAC) with 10 min washout before ischemia (SEVO). Contractile recovery was monitored by left ventricular developed pressure (LVDP) and left ventricular end-diastolic pressure (LVEDP). Infarct size (IS) was determined by triphenyltetrazolium chloride (TTC) stain. Phosphorylation of Akt, a downstream target of PI 3 K, was assessed by western blot. After ischemia-reperfusion, SEVO had higher LVDP and lower LVEDP versus CTL. Infarct size was significantly reduced in SEVO compared to CTL (44±8% versus 23±7%). Akt phosphorylation was not increased during ischemia or at 10 min after reperfusion, which is in contrast to the findings previously demonstrated in isoflurane-induced preconditioning. Other reperfusion injury salvage kinases, such as mitogen-activated protein kinase/extra-cellular signal-regulated kinases (MEK) and extra-cellular signal-regulated kinase (ERK), may be more important in sevoflurane-induced preconditioning. (J Osaka Dent Univ 2007 ; 41 : 151-159)

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We developed a method for placing functional dentures in rats. A replication denture core was prepared using a plaster model of the maxilla of the animal before its molars were extracted. A denture was then prepared by positioning the core to a model of maxilla after the teeth had been extracted, and pouring cast pattern resin into the gap. Denture function was evaluated by measuring masticatory performance using grains of raw rice, and by monitoring masseter electromyography during mastication. The results suggested that the dentures functioned efficiently during chewing, thus confirming the suitability of this maxillary denture model in rats. (J Osaka Dent Univ 2007 ; 41 : 161-167)

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We attempted to clarify how stable occlusal positioning in the molar region influence tongue movement during swallowing. M-mode ultrasonography was used to measure the tongue movement of eight healthy dentulous subjects when they swallowed 10 grams of a gel style pudding. Time-course changes in vertical tongue movement were recorded in the mediodorsal region of the tongue at the position of the mandibular first molars. Measurements were done with no splint (NS), a full-jaw splint (FS), a splint maintaining molar occlusion (MS) and a splint maintaining occlusion only on the anterior teeth (AS). The duration the tongue contacted the palate was measured between the time it touched the roof of the palate and the time it disengaged.
Since the time of contact for the NS subjects was not significantly different from that of the FS subjects, we concluded that changes in vertical dimension caused by wearing the splint did not affect the duration of contact. However, when compared with NS, the FS, and the MS, the AS did reduce contact time (p<0.05). This is probably because when the AS was in place the mandible was unstable because of loss of occlusal support in the molar region. This seemed to make it more difficult with the AS to maintain the tongue pressed to the palate as compared with NS, the FS and the MS. (J Osaka Dent Univ 2007 ; 41 : 169-172)

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