Clinical crown height changes in adult patients after non-extraction, orthodontic treatment: a retrospective cohort study.

OBJECTIVE: To assess changes in clinical crown height (CCH) in adult orthodontic patients treated by fixed appliances to distalise the molars. DESIGN: Retrospective case series study. SETTING AND PATIENTS: A total of 30 adults with healthy periodontal tissues who received orthodontic treatment at the Department of Orthodontics, Yokohama, Japan and its related orthodontic clinic were assessed. METHODS: CCH was measured as the distance from the gingival margin to the crown plane perpendicular to the tooth axis. Treatment changes of CCH of each tooth were examined on the labial/buccal and lingual/palatal side. RESULTS: In the upper dentition, on the labial/buccal side, the CCH of the lateral incisors, canines, first premolars, first molars and second molars were increased significantly (P < 0.01), with a median value of 0.41 mm, 0.43 mm, 0.28 mm, 0.43 mm and 0.55 mm, respectively. In contrast on the palatal side, the CCH of the central incisors, first molars, and second molars decreased significantly (P < 0.01), with a median value of -0.41 mm, -0.30 mm and -0.20 mm, respectively. In the lower dentition on the labial/buccal side, the CCH of the first premolars, second premolars and first molars were increased significantly, with a median value of 0.39 mm (P < 0.01), 0.43 mm (P < 0.01) and 0.19 mm (P < 0.05), respectively. The second molars exhibited a significant decrease in CCH with a median value of -0.26 mm (P < 0.05). On the lingual side, the CCH of the central incisors, lateral incisors, canines, first premolars, second premolars and first molars were increased significantly (P < 0.01), with a median value of 0.28 mm, 0.22 mm, 0.31 mm, 0.37 mm, 0.26 mm and 0.28 mm, respectively. CONCLUSION: Significant differences were observed in CCH before and after treatment for many teeth, the average change was less than 0.5 mm. The impact on the long-term health of the periodontal tissue is unknown.

Treatment decision of camouflage or surgical orthodontic treatment for skeletal Class III patients based on analysis of masticatory function.

Background/purpose: Surgical orthodontic treatment is recommended for patients with severe dentoskeletal discrepancies, while camouflage orthodontic treatment is recommended for patients with mild to moderate discrepancies. However, the decision as to which treatment should be chosen is complicated. The purpose of this study was to determine differences in masticatory function in patients who underwent camouflage and surgical orthodontic treatment for skeletal Class III malocclusion, as well as the usefulness of Wits appraisal in treatment decision based on masticatory functional analysis. Materials and methods: The study subjects were 45 patients with skeletal Class III malocclusion (15 cases with camouflage orthodontics and 30 cases with orthognatic surgery) and 12 individuals with normal occlusion. We analyzed the pre-treatment records of electromyographic activities of masseter and temporalis muscles and jaw movements. Results: There were no significant differences in various functional measurements between the camouflage and surgery groups. However, there were significant but not strong correlations between ANB and both masseter muscle activity (r = 0.36, p < 0.01) and expression ratio of abnormal chewing (r = -0.54, p < 0.01). Division of patients into two groups using a cutoff value of -6.0 mm for Wits appraisal showed a significant difference in masseter muscle activity between -6.0 mm or less group and the control (p < 0.01) but none between more than -6.0 mm group and the control. Conclusion: Camouflage orthodontic treatment is inappropriate for patients with relatively severe dentoskeletal discrepancies. Wits appraisal of -6.0 mm is a potentially useful parameter for treatment decision.

Gingival blood flow before, during, and after clenching, measured by laser Doppler blood flowmeter: A pilot study.

INTRODUCTION: This study aimed to investigate the effects of the strong occlusal force on the hemodynamics of gingival microcirculation. METHODS: Eleven adult volunteers with healthy periodontium and normal occlusion participated in this study. Using a noncontact laser Doppler flowmeter placed at the attached gingiva and the interdental papilla of the maxillary first premolar, changes in gingival blood flow (GBF) were examined during and after clenching. RESULTS: When the strong occlusal pressure was applied on the maxillary first premolar by clenching, GBF in the attached gingiva on the buccal side decreased significantly compared with the resting GBF, with medians of 2.3 mL/min/100 g and 5.4 mL/min/100 g, respectively (P <0.05). After the release of the maximum clenching, GBF recovered immediately and transiently increased to a median of 2.4 mL/min/100 g, showing a significant difference to the resting GBF (P <0.05). In contrast, in the interdental papilla, no significant change in GBF was found by clenching. CONCLUSIONS: Ischemia of the buccal attached gingiva associated with strong clenching may be due to compression of the vascular network of the periodontal membrane. Through reactive hyperemia resulting from the release of clenching, it is possible not only that blood flow will be restored to the tissue but that the tissue itself may be damaged by the reperfusion. During active orthodontic treatment, it is suggested that occlusal management to prevent occlusal trauma is important to avoid detrimental effects on periodontal tissues.

Change in clinical crown height in adult patients treated by means of the multi-bracket appliance with extraction of four first premolars.

OBJECTIVE: To evaluate the gingival condition due to adult orthodontic treatment using the clinical crown height (CCH) as an index. DESIGN: Retrospective study. SETTING: Department of Orthodontics at a university. PARTICIPANTS: A total of 21 adult female patients with healthy periodontal tissue were treated by means of the multi-bracket appliance with extraction of four first premolars. METHODS: Three-dimensional (3D) digital dental models were reconstructed to assess the vertical movement of the free gingival margin caused by adult orthodontic treatment. Pre- and post-treatment CCH were measured, and changes in CCH due to treatment were examined. RESULTS: The change in CCH by orthodontic treatment was able to be assessed objectively using 3D digital models of the dental casts. In the upper dentition, a significant reduction in CCH was found on the labial and lingual sides of the central incisor, with a mean of -0.28 mm and -0.34 mm, respectively (P < 0.001). In contrast, a significant increase in CCH was found on the labial side of the lateral incisor with a mean of 0.75 mm (P < 0.001). In the lower dentition, CCH on the lingual side of the canine, the second premolar and the first molar increased significantly (P < 0.001), with a mean of 0.41 mm, 0.45 mm and 0.50 mm, respectively. For the buccal side, the second premolar showed a significant increase in CCH with a mean of 0.61 mm (P < 0.001). CONCLUSION: By using the CCH as an index, it was possible to assess the gingival condition after active orthodontic treatment.

Effects of functional training after orthognathic surgery on masticatory function in patients with mandibular prognathism.

BACKGROUND/PURPOSE: Even after surgical orthodontic treatment, the level of masticatory function in patients with jaw deformities is still lower than that of healthy subjects. The purpose of this study was to evaluate the effects of functional training program using gum chewing exercise after orthognathic surgery on masticatory function in patients with mandibular prognathism. MATERIALS AND METHODS: The study subjects were 16 patients with mandibular prognathism who underwent orthognathic surgery and 8 individuals with normal occlusion. Patients were divided into two groups (training group and non-training group; n = 8 per group). Functional training included gum chewing exercise and patient-education about masticatory function. The training; gum chewing exercise of 5 min twice a day for 90 days, started at 3 months after surgery. For each subject, electromyographic activities of masseter and temporalis muscles during maximum voluntary clenching (MVC) and jaw movement during gum chewing were recorded before and after surgical orthodontic treatment. Two parameters; activity index (AI: ratio of activity of masseter and temporalis muscles) and error index (EI: ratio of the number of abnormal chewing patterns), were used. RESULTS: In the training group, the AI value during MVC increased significantly and the EI value during gam chewing decreased significantly after surgical orthodontic treatment (AI: p < 0.01; EI: p < 0.01), indicating the improvement of activity balance of masseter and temporalis muscles and conversion of the jaw movement from abnormal to normal pattern (p < 0.01). CONCLUSION: Our findings suggested that functional training using the gum chewing and patient-education exercise improved masticatory function in patients with mandibular prognathism.

Mixed-reality simulation for orthognathic surgery.

BACKGROUND: Mandibular motion tracking system (ManMoS) has been developed for orthognathic surgery. This article aimed to introduce the ManMoS and to examine the accuracy of this system. METHODS: Skeletal and dental models are reconstructed in a virtual space from the DICOM data of three-dimensional computed tomography (3D-CT) recording and the STL data of 3D scanning, respectively. The ManMoS uniquely integrates the virtual dento-skeletal model with the real motion of the dental cast mounted on the simulator, using the reference splint. Positional change of the dental cast is tracked by using the 3D motion tracking equipment and reflects on the jaw position of the virtual model in real time, generating the mixed-reality surgical simulation. ManMoS was applied for two clinical cases having a facial asymmetry. In order to assess the accuracy of the ManMoS, the positional change of the lower dental arch was compared between the virtual and real models. RESULTS: With the measurement data of the real lower dental cast as a reference, measurement error for the whole simulation system was less than 0.32 mm. In ManMoS, the skeletal and dental asymmetries were adequately diagnosed in three dimensions. Jaw repositioning was simulated with priority given to the skeletal correction rather than the occlusal correction. In two cases, facial asymmetry was successfully improved while a normal occlusal relationship was reconstructed. Positional change measured in the virtual model did not differ significantly from that in the real model. CONCLUSIONS: It was suggested that the accuracy of the ManMoS was good enough for a clinical use. This surgical simulation system appears to meet clinical demands well and is an important facilitator of communication between orthodontists and surgeons.

Orthodontic skeletal anchorage using a palatal external plate.

We have developed the Anchor-Lock external plate system, which is fitted on the palate for the purpose of orthodontic skeletal anchorage. The aim of this study was to introduce the Anchor-Lock and assess its success rate. The Anchor-Lock is composed of titanium screws of 2·0-mm diameter and a titanium plate of 1·0-mm thickness. The external plate is rigidly interlocked with the heads of the screws, which are implanted trans-mucosally into palatal bone. Three types of Anchor-Lock are available. These were applied to 137 orthodontic patients (104 females and 33 males) aged 10-54 years. Two types of plate were used, a straight-shaped plate applied to the hard palate and to the anterior palate and a double-Y-shaped plate applied after tooth-borne rapid maxillary expansion. Success rate of the Anchor-Lock was 92·0% overall. No significant difference in success rate was found by age or sex of patients. Type or screw length of the Anchor-Lock did not affect success rate significantly. Success rate was significantly increased by the use of the surgical stent. The Anchor-Lock was effectively applied to distalize and/or intrude the upper molars. The Anchor-Lock system appears suitable for clinical use as an alternative to conventional screw- and plate-type orthodontic implants.

Real-time orthognathic surgical simulation using a mandibular motion tracking system.

We developed a new orthognathic surgical simulation system able to predict both occlusal correction and mandibular repositioning in three dimensions. This system uniquely integrates the real motion of the dental cast model with the virtual motion of the reconstructed cranio-facial model. The skeletal change of the mandibular osteotomy is simulated on the PC monitor while the occlusal change is confirmed by checking the cast model on the simulator. The simulation process is easily repeated and the operator can make several attempts to determine the final mandibular position. The occlusal relationship at the simulated mandibular posture is registered and the occlusal wafer splint, which ensures intermaxillary fixation, is fabricated on the simulator. This surgical simulation system appears to satisfy clinical demands well and is an important facilitator of communication between orthodontists and surgeons. Here, we outline the system and apply it to a demonstration case of orthognathic surgery.

Analysis of the TMJ intraarticular space variation: a non-invasive insight during mastication.

The analysis of the loading of the temporomandibular joint (TMJ) appears important for the study of joint failure. Reconstruction and animation of the TMJ with real anatomic and kinematic data is currently the only method allowing a non invasive, in vivo, three-dimensional, dynamic, real-time quantitative insight into the relationship between the articulating surfaces of a joint. It consists of the software reconstruction of the joint anatomy from tomography data and the application to it of the corresponding real movement data recorded with a tracking device. Because of the physical properties of the TMJ soft tissues, the reduction of the joint space can indicate compressive loads during function. Analyses of the variation of the TMJ space in ten asymptomatic subjects during unilateral mastication showed a TMJ space that was significantly smaller during closing than during opening (p<0.05) and significantly smaller on the balancing than on the working joint (p<0.05). This occurs especially in the medial part of the posterior slope of the articular eminence at the end of the closing phase (p<0.01). Furthermore, the minimum TMJ space at the end of closing increased from the beginning to the end of food comminution (p<0.01).