Yuko Tanimoto

Condylar Motion in Patients with Reduced Anterior Disc Displacement

The influence of reduced anterior disc displacement on condylar motion has not been fully examined in young adults. Reduced anterior disc displacement was hypothesized to inhibit condylar motion. Using a six-degrees-of-freedom jaw-tracking system, we recorded bilateral condylar motion during maximum open-close jaw movement and gum-chewing on both sides in ten young adults with unilateral reduced anterior disc displacement and in ten control subjects without temporomandibular disorders. The bilateral condylar motion during both maximum open-close jaw movement and chewing on the disc-displacement side was inhibited in the test group. The condylar motion on the disc-displacement side during chewing on the non-disc-displacement side was also inhibited in the test group. These results suggest that the limitation of condylar motion on the disc-displacement side may influence condylar motion on the non-disc-displacement side during maximum open-close jaw movement, and mastication on the disc-displacement side in young adults.

Occlusal Force and Condylar Motion in Patients with Anterior Open Bite

Patients with open bite often show a weak occlusal force and temporomandibular disorders (TMDs). If these are the main cause of open bite, it may be hypothesized that both pre-pubertal and adult open-bite patients would show a weak occlusal force and abnormal condylar motion. The purpose of this study was to test this hypothesis. Test group subjects consisted of 13 consecutive pre-pubertal and 13 adult patients with anterior open bite. They were compared with age-matched normal subjects. The adult open-bite group showed a weaker occlusal force and a shorter range of condylar motion compared with the control subjects. In the pre-pubertal subjects, however, there were no significant differences in the occlusal force and range of condylar motion between the open-bite and control groups. Therefore, these results suggest that a weak occlusal force or TMDs may not be the main cause of open bite.

Motion of the Human Mandibular Condyle during Mastication

It has been reported that loading to the mandible during closing movement makes the condylar path move more in the superior direction than that during the free closing movement. In this study, the hypothesis was tested that the displacement of the condyle on the chewing side is greater in the direction of the mandibular fossa than that on the non-chewing side. Using a six-degrees-of-freedom jaw movement recording system, we recorded condylar motion in 12 healthy adults without TMD, during the chewing of a large hard gummy jelly. The maximum displacements at the condyle on the chewing side from the maximum intercuspation (CO) position were significantly larger in the superior and medial directions at the initial stage and in the posterior direction at all stages (0.5 mm, 0.5 mm, and 0.6 mm, respectively) than those on the non-chewing side (0.0 mm, 0.1 mm, and 0.1 mm, respectively). This suggests that, in healthy adults, the condyles at CO are located in a position such that excessive load is not applied to the temporomandibular joint when there are the aforementioned displacements.

Correlation between craniofacial and condylar path asymmetry.

PURPOSE The purpose of this study was to examine the correlation between the condylar path length and craniofacial morphology in patients with mandibular prognathism and deviation, and investigate changes in the condylar path length and temporomandibular joint disorders after intraoral vertical ramus osteotomy (IVRO). PATIENTS AND METHODS Sixteen Japanese patients exhibiting mandibular prognathism and deviation were studied. For their correction, all patients underwent IVRO. In the case of patients with severe occlusal cant after cant correction by Le Fort I osteotomy, IVRO was carried out on the same day. The change in craniofacial morphology was assessed with frontal cephalograms and submentovertex radiograms. Condylar path changes were assessed using a 6 degrees of freedom measuring device. All patients were examined with regard to their temporomandibular joint (TMJ) function. RESULTS Before treatment, mandibular deviation was moderately related to the asymmetries of craniofacial morphology and condylar path length. The rate of incidence of TMJ sounds on the deviated side was significantly higher than that on the nondeviated side. After treatment, although the condylar path length as well as condylar position had changed to become bilaterally symmetric, there was still a significant difference during protrusive excursion and maximal open-close movements. TMJ sounds disappeared in 64.3% of patients. CONCLUSION Mandibular deviation was found to be strongly related to the morphologic and functional asymmetries in patients with mandibular prognathism and deviation. The condylar path length and condylar position were improved after the correction of mandibular deviation with IVRO.

Orthodontic treatment of a patient with an impacted maxillary second premolar and odontogenic keratocyst in the maxillary sinus.

An eight-year-, four-month-old girl was brought to the orthodontic clinic of Okayama University Medical and Dental Hospital. The patient had an impacted upper left second premolar because of an odontogenic keratocyst and showed a skeletal Class II jaw base relationship. At the age of six years four months, marsupialization of a cyst was performed at the Okayama University Medical and Dental Hospital because the patient had shown a swelling of the left cheek because of the cyst. The upper left second premolar was located in the roof of the maxillary sinus. The cyst was histopathologically diagnosed as an odontogenic keratocyst. At the age of nine years 10 months and after regaining the space for eruption of the premolar, the impacted premolar erupted without traction. At the age of 12 years five months, edgewise treatment was initiated, which continued for three years. After removing the edgewise appliance, an optimum occlusion was achieved. The occlusion was maintained without recurrence of the keratocyst after a retention period of five years.

Longitudinal craniofacial changes in Japanese adults with untreated maxillary and mandibular protrusions

Abstract This study evaluates the craniofacial change during the third decade of life and compared the changes that occurred in subjects with normal occlusion and untreated malocclusions. 10 cases each of normal occlusion, untreated maxillary protrusion and mandibular protrusion were subjected to cephalometric analysis and model analysis. The mean age at the beginning of the observation (T1) was 24 years, and the observation period (T2) was approximately 13 years in three groups. There was no significant difference in any cephalometric values between T1 and T2 in the normal occlusion group. The SNB angle was slightly decreased, the Y-axis was increased, and upper incisors were lingually inclined in the maxillary protrusion group and increasing of overjet and decreasing of overbite was observed in the mandibular protrusion group. In model analysis, the arch length discrepancy (ALD) and the inter-molar width (IMW) were slightly increased in the lower arch in the normal occlusion group and the upper arch length (AL) had decreased in the mandibular protrusion group. In conclusion, significant differences were found in the changes of several skeletal and dental parameters between normal occlusion and untreated malocclusion subjects in the third decade of life. These changes in the third decade of life should be considered in order to plan the orthodontic treatment and evaluate the long-term stability in the patients with maxillary and mandibular protrusion.