Michael P. Powers

Changes in soft tissue profile following treatment with the bionator.

The purpose of this study was to determine the changes in the soft tissue profile in patients treated in the mixed dentition with a bionator. Two groups of 30 individuals, between 9 and 12 years old and with Class II, Division 1, malocclusion were matched for age, sex, observation time, and dentofacial characteristics. Patients in the first group were treated with a bionator for an average of 18.7 months, resulting in a Class I molar relationship and reduction of overjet. The second group acted as a control and individuals did not receive any form of orthodontic treatment. Pretreatment and posttreatment cephalograms were analyzed and paired t-tests were used to compare the significance of changes between the two groups. Compared with the control group, the treated group demonstrated 1.97 degrees decrease in ANB, a 3.35 mm increase in anterior facial height, 2.22 degrees decrease in soft tissue profile convexity, and 17.4 degrees increase in mentolabial angle.

An assessment of extraction versus nonextraction orthodontic treatment using the peer assessment rating (PAR) index.

The extraction of teeth for orthodontic purposes has always been a controversial subject in the specialty. The purpose of this study was to assess the outcome of orthodontic treatment in 100 patients treated with the extraction of four premolars and compare it with the outcome of 100 patients treated without extractions, using the peer assessment rating (PAR) index. Records were selected from 1,198 consecutively completed cases treated by a single provider (MGH) between 1981 and 1995. We chose the first 100 finished patients in each group (extraction and nonextraction) who were under the age of 16 and had no deciduous teeth at the start of treatment. The results of this study show that average treatment time for the extraction group was 29.7+/-6.1 months compared with 26.0+/-7.2 months for the nonextraction group. The extraction group had significantly higher initial PAR scores (T1-PAR ext = 30.01+/-8.20 vs. T1 PAR nonext = 25.21+/-8.55), with greater initial maxillary anterior crowding (PAR ext value = 6.05+/-3.85 vs. PAR nonext value = 4.21+/-2.90) and greater initial overjet (PAR ext value = 1.82+/-1.01 vs. PAR nonext value 1.28+/-1.04). All pretreatment differences were significant at the p < or = 0.0001 level. Although significantly different at the beginning of treatment, both groups were statistically identical at the end (PAR T2 ext = 6.18 + 3.04% reduction = 79.4% compared with PAR T2 nonext = 5.64 + 3.08% reduction = 77.6%). In conclusion, the results demonstrate that, given an additional 3 months of treatment, it is possible for an orthodontist to produce dento-occlusal relationships in extraction patients that are as good as those achieved in nonextraction cases.

Micromechanics/structure relationships in the human mandible.

OBJECTIVES A clear understanding of the relationship between the micromechanical properties and orientation of the osteons within the mandible is important to understand mandibular function, fracture repair, treatment of temporo-mandibular joint disorders, the materials and organization of dental implants. The objective of this research was to obtain the micromechanical properties of human mandibular cortical bone as a function of orientation from TMJ to TMJ. METHODS A mandible obtained from a deceased 66 year-old female free of bone disease was used. The mandible was embedded in polymethylmethacrylate. The micromechanical properties analysis was obtained using the UH3 scanning acoustic microscope (SAM; Olympus Co., Tokyo, Japan). The coordinates system is defined such that the inferior border of mandibular is positioned on the x-y plane. x is along the anterior-posterior direction, y is in the horizontal direction and z is in superior-inferior direction. RESULTS The osteonal orientations were almost parallel to the x axis and eventually branched into two directions towards the coronoid process and condylar head. The SAM revealed that almost the whole area of the mandible body was found to be transversely isotropic in the plane perpendicular to the x axis. In the parallel and oblique directions, all data were transversely isotropic with respect to the x axis. Data of the perpendicular osteons were transversely isotropic with respect to the z axis. SIGNIFICANCE Having actual micromechanical properties as a function of orientation in the mandible could provide base line data for: fracture repair; choice of bone replacement materials.

The transmandibular implant: from progressive bone loss to controlled bone growth.

PURPOSE In a prospective study, 146 consecutive transmandibular implant (TMI) patients were treated according to revised surgical and prosthetic protocols to induce and control bone growth. Revisions included 1) placement of transosseous posts and cortical screws between the mental foramina so that two threads extended beyond the alveolar crest of the mandible without protruding through the mucosa and 2) fabrication of an implant-borne prosthesis that rested on the retromolar pads with a gap of 2 mm between the denture base and the mucosal tissues in the saddle areas. PATIENTS AND METHODS Measurements of the height of the mandible were made using a digital millimeter calliper and panoramic radiographs, with the enlargement calculated for each radiograph. The follow-up period ranged from 18 to 51 months. RESULTS Bone growth was present in 131 of the 146 patients whereas the bone resorption was arrested in the remaining patients. Increase in bony apposition varied from 9 mm in patients with severe mandibular atrophy to 2 mm in patients with mild atrophy. CONCLUSION The revised surgical and prosthetic protocols for TMI insertion and rehabilitation are advocated to prevent further alveolar resorption and to promote bone growth in patients with mandibular atrophy.

Evidence of correction of open bitemalocclusion using active vertical corrector treatment

This study used a cephalometric analysis that isolated tipping and bodily tooth movements of the upper and the lower incisors and measured vertical skeletal changes in the anterior region of the maxilla and mandible to evaluate the outcome of two-phase nonextraction treatment for open bite malocclusion. Twenty-nine subjects treated with an active vertical corrector (AVC) followed by fixed 022 orthodontic appliances were selected by one orthodontist from his private practice. All subjects lacked vertical incisor contact at the start of treatment and had adequate initial, end of phase 1, and deband lateral cephalograms. Each subject in the treated group was matched by age and sex with an untreated subject from the Broadbent Bolton Collection, Cleveland, OH. Data were collected for three time intervals; phase 1 treatment with the AVC (T1 to T2), phase 2 fixed-appliance treatment (T2 to T3), and over the total treatment period (T1 to T3). Analysis of the data showed no statistically significant (P < or = .002) changes between treated subjects and controls for any variables during the phase 1 (T1 to T2) or phase 2 (T2 to T3) treatment intervals. However, overbite was significantly improved compared with controls (P < or = .002) during the T1 to T3 time interval. It was concluded that two-phase treatment with the AVC followed by fixed orthodontic appliance treatment results in a statistically significant increase in incisor overbite. The observed increase in overbite was the result of small but clinically significant changes in relative mandibular vertical growth, bodily incisor movement toward the occlusal plane, and lingual tipping of the lower incisors.

The transmandibular implant: A 2-year prospective study**

Thirteen consecutive patients with complaints of dysfunction and pain associated with a mandibular denture were treated with the transmandibular implant. The implant was placed from a submental approach with an atraumatic surgical technique. No load was placed on the implant for 12 weeks. Patients were evaluated for pain, paresthesia, healing of the submental wound, soft tissue response, radiographic change, and mobility of the implant for a period of 2 years. Patient satisfaction was recorded at the 1- and 2-year examinations. The results demonstrate the reliability and reparability of the transmandibular implant system.

Histomorphometric Comparison of Transmandibular Implant and Titanium Implant

This study was a histomorphometric comparison of the transmandibular implant (TMI) system and titanium implant using a confocal laser scanning microscope (CLSM). Two dogs were used. In each dog, 16 implant holes were made in the bilateral mandibular angle. Four cortical screws in the TMI, four titanium plasma spray (TPS) implants, and four hydroxyapatite (HA) coating implants were inserted and four holes were left as a control. Two dogs were sacrificed at 3 and 6 months. The samples were cut longitudinally and examined under CLSM. The contact rate of trabecular bone was smaller than that of cortical bone in all implants. The contact rates in TMI at 3 and 6 months was significantly smaller than those of TPS and HA and there was no difference between TPS and HA. Although the contact rate of TMI was low, only a small contact area may be enough for TMI because of its box form structure.