A new method to evaluate the positional stability of a self-drilling miniscrew.

OBJECTIVES: To evaluate the positional stability of miniscrews during orthodontic treatment change in cone-beam computed tomography (CBCT). SETTING AND SAMPLE POPULATION: Twenty adult volunteers were enrolled. METHODS: In all participants, at least two maxillary first premolars were extracted because of protrusion. Each volunteer received six miniscrews in the maxilla, including two loaded miniscrews to retract anterior teeth and four unloaded miniscrews. CBCT scans were obtained at the beginning of space closure (T1) and approximately 11.8 months later (T2). Three-dimensional miniscrew models were constructed at T1 and T2, and the central axes were calculated using a principal component analysis (PCA) technique. Finally, we measured and compared the angle change of all the miniscrews from T1 to T2. RESULTS: The angle change values of the unloaded and loaded miniscrews were 1.64 ± 1.25° and 1.67 ± 1.15°, respectively. No significant differences in the angle change were observed. CONCLUSION: Cone-beam computed tomography images revealed both the unloaded and loaded miniscrews to be positionally stable during en-masse retraction in this study.

Stable region for maxillary dental cast superimposition in adults, studied with the aid of stable miniscrews.

OBJECTIVES: To identify a stable and reproducible reference region to superimpose serial maxillary dental models in adult extraction cases. SETTING AND SAMPLE POPULATION: Fifteen adult volunteers were enrolled. METHODS: To reduce protrusion, bilateral maxillary first premolars were extracted in all volunteers. Each volunteer received six miniscrews, including two loaded miniscrews used to retract anterior teeth and four unloaded miniscrews. Impressions for maxillary models were taken at T1 (1 week after miniscrew placement) and T2 (17 months later). Dental models were created and then scanned using a laser scanner. Stability of the miniscrews was evaluated, and dental models were registered using stationary miniscrews. The palatal region, where deviation was within 0.5 mm in all subjects, was determined to be the stable region. Reproducibility of the new palatal region for 3D digital model superimposition was evaluated. RESULTS: Deviation of the medial 2/3 of the palatal region between the third rugae and the line in contact with the distal surface of the bilateral maxillary first molars was within 0.5 mm. Tooth movement of 15 subjects was measured to evaluate the validity of the new 3D superimposition method. Displacements were 8.18 ± 2.94 mm (central incisor) and 2.25 ± 0.73 mm (first molar) measured by miniscrew superimposition, while values of 7.81 ± 2.53 mm (central incisor) and 2.29 ± 1.03 mm (first molar) were measured using the 3D palatal vault regional superimposition method; no significant difference was observed. CONCLUSION: The medial 2/3 of the third rugae and the regional palatal vault dorsal to it is a stable region to register 3D digital models for evaluation of orthodontic tooth movement in adult patients.

The submental artery island flap for head and neck reconstruction.

BACKGROUND: Following excisional surgery for head and neck cancer, most complex defects are reconstructed using microvascular free tissue transfer. These methods offer many advantages; however, they are of increasing complexity with attendant risks of flap loss and donor site problems. The submental artery island flap is a recently described local flap that may be used for reconstruction of the lower and middle thirds of the face and oral cavity, and offers the advantages of simplicity, reliability and excellent cosmesis. We have been using this flap as an alternative to free tissue transfer, and in this paper we present our series of 11 cases, after a review of the recent literature, anatomy and surgical technique. The advantages and limitations of the use of this flap are presented. METHODS: A consecutive series of 11 patients in which this reconstruction was performed was reviewed retrospectively, and the results studied. Advantages and disadvantages of this reconstructive method were determined to define appropriate indications and contra-indications for its use. RESULTS: We have used this flap in 11 patients for post-excisional soft tissue reconstruction of the head and neck, both as skin and as a mucosal replacement. In all but two patients the results were satisfactory, with excellent cosmesis when used as skin replacement. One patient required secondary debulking and one had complete flap loss. In all, the donor site was satisfactory. CONCLUSIONS: The Submenal Artery Island Flap is a useful addition to the reconstructive surgeon's options and has definite advantages over distant flaps in terms of ease of dissection, final cosmetic appearance and donor site appearance.