Intrusion of overerupted maxillary molars with miniscrew implant anchorage: a radiographic evaluation.

The aim of this retrospective study was to quantitatively evaluate the treatment effects of intrusion of overerupted maxillary molars using miniscrew implant anchorage and to investigate the apical root resorption after molar intrusion. The subjects included 30 patients whose average ages were 35.5±9.0 years. All patients had received intrusion treatments for overerupted maxillary molars with miniscrew anchorage. There were 38 maxillary first molars and 26 maxillary second molars to be intruded. Two miniscrews were inserted in the buccal and palatal alveolar bone mesial to the overerupted molar. Force of 100-150 g was applied by the elastic chains between screw head and attachment on each side. Lateral cephalograms and panoramic radiographs taken before and after intrusion were used to evaluate dental changes and root resorption of molars. Only 6 of the 128 miniscrews failed. The first and second molars were significantly intruded by averages of 3.4 mm and 3.1 mm respectively (P<0.001). The average intrusion time was more than 6 months. The crown of the molars mesially tilted by averages of 3.1 degrees and 3.3 degrees (P<0.001) for first and second molars. The amounts of root resorption were 0.2-0.4 mm on average. The intrusion treatment of overerupted molars with miniscrew anchorages could be used as an efficient and reliable method to recover lost restoration space for prosthesis. Radiographically speaking, root resorption of molars was not clinically significant after application of intrusive forces of 200 to 300 g.

Measurement of cortical bone thickness in adults by cone-beam computerized tomography for orthodontic miniscrews placement.

The purpose of this study was to investigate the cortical bone thickness of the inter-dental area of both jaws for orthodontic miniscrew placement. The cone-beam computerized tomography images of 32 non-orthodontic adults with normal occlusion were taken to measure the cortical bone thickness in both jaws. One-way analysis of variance (ANOVA) was used to analyze the differences in cortical bone thickness. Buccal cortical bone in the mandible was thicker than that in the maxilla. In the maxilla, cortical bone thickness was thicker in the buccal side than in the palatal side. Buccal cortical bone thickness in the mandible was thickest at the site distal to the first molar, and in the maxilla it was thickest at the site mesial to the first molar, while in the palatal side of maxilla it was thickest at the site mesial to the second premolar. The changing pattern of cortical bone thickness varies at different sites. In the buccal side of maxilla, the thinnest cortical bone thickness was found to be at 4 mm level from the alveolar crest, while the thickest was at 10 mm level (except for the site mesial to the first premolar). The buccal cortical bone thickness at the sites mesial or distal to the first molar in the mandible and palatal cortical bone thickness of maxilla tended to increase with increasing distance from the alveolar bone.

[Implant restoration for patients with congenital missing teeth].

OBJECTIVE: To evaluate the treatment plan, clinical outcome and related problems in patients with congenital missing teeth. METHODS: From November 2000 to February 2009, thirty seven patients with congenital missing teeth underwent thorough diagnostic workup, treatment planning and an interdisciplinary approach to ensure optimal treatment in Department of Implant Dentistry, Peking University, School and Hospital of Stomatology. A standard follow-up protocol was conducted for all the patients. RESULTS: The enrolled cases in this study were classified in to 3 types: single tooth missing, multiple teeth missing and edentulous. Among them single tooth missing was found in 21 cases, multiple teeth missing was found in 12 cases and 4 cases were edentulous. 120 implants were placed and restored in 37 patients with the mean follow-up 39.3 months (10-109 months) after prosthetic functioning. Two implants lost after function about 6 months and the remaining implants functioned well until the last review. No adverse complications such as pain and nerve trauma was observed and the mean bone resorption was 1.91 mm. CONCLUSION: An interdisciplinary approach ensures optimal treatment for patients with congenital missing teeth. Implant restorations provide an alternative way with predictable clinical results.

[Evaluation of palatal bone thickness in adults with normal occlusion for orthodontic miniscrews placement].

OBJECTIVE: To investigate the palatal bone thickness in adult with normal occlusion. METHODS: The cone beam computerized tomography records of 32 adults with normal occlusion (16 males and 16 females), mean age (30.1 ± 6.5) years, were used to measure the bone thickness at midpalatal area and the right and left palatal sides. Coronal slices at 3 mm intervals were generated. Slice 1 was the coronal slice through the posterior border to the incisive foramen, while Slice 7 was the coronal slice 18 mm away from the incisive foramen. At each coronal slice, the midpalatal sites were Site M and the sites on the exterior margin of the hard palatal were Site D. Four equally divided parts on the line linking Site M to Site D were named Site A, B, C from the interior to the exterior respectively. Palatal bone thickness were measured at these sites. RESULTS: Significant differences were noted from Slice 1 to Slice 7, the bone thickness of palate tended to decrease from the front to the back. The thickest site at hard palatal was 12.6 mm, locating at Site D of Slice 1, while the thinnest site was 2.7 mm, locating at Site B of Slice 7. The palatal bone thickness ranged from 10.5 mm (maximum) to 5.8 mm (minimum) at Slice 2 and Slice 3. No statistical significance was found between the left and right sides (P > 0.05). CONCLUSIONS: The favorable sites for miniscrew placement were the anterior region of the hard palate in adult. The length of miniscrew ranged from 5 mm to 10 mm can be placed from 6 mm posterior to the incisive foramen.

[Clinical application of miniscrew implant for maximum anchorage cases].

OBJECTIVE: The purpose of this study was to evaluate the efficiency of the self-drilling miniscrew implant for maximum anchorage cases. METHODS: The study comprised 5 patients whose ages ranged from 14 to 31 years. All patients presented with. Class II skeletal pattern, maxillary protrusion or bimaxillary protrusion. Maximum molar anchorage and first premolar extraction were required. In the stage of anterior teeth retraction, self-drilling miniscrew implants were inserted into the buccal alveolar bone between maxillary second premolar and first molar. Sliding mechanics with 150 - 200 g force was used to retract anterior teeth. The cephalometric films before and after retraction were measured. RESULTS: Dental protrusion and facial profile were improved significantly in all patients. The edge of upper incisors was retracted 6.4 mm and anchor molar moved anteriorly 0.3 mm averagely. All miniscrew implants remained stable during treatment and peri-implant soft tissue remained healthy. CONCLUSIONS: Self-drilling minisrcew implant could be used as an efficient method for anchorage control and an alternative choice of extra-oral forces.