Orthodontics : the art and practice of dentofacial enhancement最新文献

Aim: To compare in vitro the effects on shear bond strength of the application of a dental bleaching and desensitizer agent prior to bonding metallic orthodontic brackets to extracted human teeth.

Method: Sixty therapeutically extracted human premolars without any visible defects were collected and stored in 0.1% thymol solution at room temperature. All teeth were randomly assigned to one of four groups (each n = 15): group I, teeth were treated with bleaching gel containing 10% carbamide peroxide; group II, teeth were treated with a desensitizer containing 26% potassium oxalate; group III, teeth were treated as in group I followed by application of the desensitizer agent as in group II; and group IV, control group. The teeth from all the four groups were then bonded with 0.018-inch Roth premolar brackets. The shear bond strength was tested in a Hounsfield material testing machine.

Results: In group I, 10% carbamide peroxide gel alone did not affect the shear bond strength significantly compared with the unbleached specimens in the control group. The use of the desensitizer agent alone in group II significantly reduced the shear bond strength. In group III, further significant reduction of the mean shear bond strength occurred compared with all the three groups.

Conclusion: The use of 10% carbamide peroxide prior to bonding orthodontic metallic brackets does not significantly alter shear bond strength. Application of desensitizer agent alone or in combination with bleaching agent significantly lowers the shear bond strength of orthodontic brackets. Application of desensitizer agent alone or in combination with bleaching agent does not lower the shear bond strength below the recommended value for orthodontic bonding procedure. As a result, their use is not a contraindication before orthodontic fixed mechanotherapy.

Aim: The relationship of anterior cranial base to midface dimensions in skeletal Class III malocclusions is said to be unclear. The purpose of this retrospective study was to investigate and correlate various cephalometric parameters depicting anterior cranial base and cranial base flexure to maxillary dimensions in skeletal Class III malocclusions.

Methods: Lateral cephalometric radiographs of 60 skeletal Class III subjects aged 16 to 29 years comprising 30 cases with maxillary retrusion (group A) and 30 cases with normal maxillae (group B) were analyzed for 14 variables, along with 60 skeletal Class I controls (group C) matched for both age and sex.

Results: The Bonferroni multiple comparison and ANOVA tests revealed a statistically significant decrease of maxillary (Co-A, Ptm-A, ANS-PNS) and anterior cranial base (S-N, S-Ca) linear dimensions (P < .001) as well as a decrease in N-S-Co (P < .001) and N-S-Ar (P < .05) in group A subjects. Comparison of ratios of the skeletal dimensions to each of the maxillary dimensions showed statistically significant increased values for group A (P < .001). The Pearson correlation coefficient showed a positive correlation between each cranial base parameter and the maxillary parameters (P < .001).

Conclusion: The anterior cranial base dimensions were found to be decreased in only skeletal Class III cases with maxillary deficiencies. Significant decrease of angle N-S-Co may prove diagnostically reliable in maxillary retrusion. Significant positive correlations were found to exist between each cranial base parameter and the maxillary parameters. The strongest correlation was observed between S-N and Co-A, and the weakest with respect to S-Ca and ANS-PNS.

The aim of this paper is to present and debate the treatment of a unilateral canine crossbite using clear aligners (Invisalign). The possibility of combining partial fixed appliances with removable elastics to optimize the final outcome is also described. The advantages of protected movement, due to the presence of the aligners, to jump the occlusion during crossbite correction is also highlighted.

Aim: To detail two different clinical protocols and case studies using mini-implant anchorage developed to respond to certain clinical conditions.

Methods: Two clinical protocols are described to upright mesially tilted mandibular molars. In the first protocol, a single mini-implant is inserted distally to the molar to be uprighted, and an elastic traction chain is applied to the tooth. In the second clinical approach, two mini-implants are inserted mesially. A screw-suspended TMA sectional archwire is applied (Derton-Perini technique). Two cases, descriptive of the two different treatment protocols, are described. In the first case, the mandibular right second premolar was missing and the adjacent first molar needed to be uprighted. A single screw was inserted distally to the first molar, and an elastic chain was applied. In the second case, the mandibular left second molar was missing and the third molar needed to be uprighted. Two mini-implants were inserted mesially and a fully screw-supported sectional archwire was used to upright and bodily mesialize the third molar.

Results: Both uprighting approaches uprighted the molar axis without loss of anchorage.

Conclusion: The two approaches to mandibular molar uprighting, developed as rational responses to different clinical cases, were both found to be effective.

This case report reiterates the fact that selective alveolar decortication in conjunction with periodontal alveolar augmentation with a bone graft indubitably and efficaciously produces rapid orthodontic tooth movement. A 29-year-old woman presented with a Class I malocclusion and increased bidentoalveolar protrusion with increased spacing between the maxillary and mandibular incisors. She readily agreed to selective alveolar decortication in conjunction with periodontal alveolar augmentation with a bone graft when presented with the proposal that her malocclusion could be corrected in one-third the treatment time required for conventional orthodontics. A preadjusted edgewise appliance (Roth prescription, 0.022 x 0.028-inch slot) was placed prior to the surgical procedure. One week later, full-thickness labial and lingual flaps were reflected in the maxillary and mandibular arches. The alveolar bone was selectively decorticated and periodontally augmented with a bone graft. Starting 1 week postsurgically, orthodontic adjustments were carried out every 2 weeks. From bracketing to debracketing, the entire orthodontic treatment took 7 months. The rapid orthodontic tooth movement was attributed to the regional acceleratory phenomenon, triggered by selective alveolar decortication. The subsequent periodontal alveolar augmentation with the bone graft repaired the bony dehiscences and enhanced the bone volume and dramatically improved the patient's soft tissue profile.

Contemporary concepts of sliding mechanics explain that friction is inevitable. To overcome this frictional resistance, excess force is required to retract the tooth along the archwire (ie, individual retraction of canines, en masse retraction of anterior teeth), in addition to the amount of force required for tooth movement. The anterior tooth retraction force, in addition to excess force (to overcome friction), produces reciprocal protraction force on molars, thereby leading to increased anchorage loading. However, this traditional concept was challenged in recent literature, which was based on the finite element model, but did not bear correlation to the clinical scenario. This article will reinforce the fact that clinically, friction increases anchorage loading in all three planes of space, considering the fact that tooth movement is a quasistatic process rather than a purely continuous or static one, and that conventional ways of determining the effects of static or dynamic friction on anchorage load cannot be applied to clinical situations (which consist of anatomical resistance units and a complex muscular force system). The article does not aim to quantify friction and its effect on the amount of anchorage load. Rather, a new perspective regarding the role of various additional factors (which is not explained by contemporary concept) that may influence friction and anchorage loading is provided..

Aim: To examine whether specific hard and soft tissue had any effect on smile characteristics and to ascertain the opinions of laypersons and clinicians in evaluating facial attractiveness among different occlusions.

Method: Photographs of posed smiles, along with profiles and full faces, of 76 patients with different occlusions were captured, and a lateral cephalogram of each subject was traced. These photographs were judged by a panel of 10 clinicians and 10 laypersons on a 5-point visual analog scale. Quantitative measurements were carried out on the smile images for 14 smile characteristics. The effect of hard and soft tissue on these characteristics was also examined.

Results: The upper vermilion lip thickness was affected by Pt.A-UI and E-line to upper lip, while the lower vermilion lip thickness was affected by lower anterior facial height. FMA had a significant positive effect on gingival display (P ≤ .05). This meant that an increase in FMA also caused the gingival display to increase. The nasolabial angle showed a significant positive effect on incisal display, while FMA showed a negative effect on intercanine width. Lower facial height and FMA had a significant negative effect on the smile index. A correlation was found between the judgments of clinicians and laypersons. Both judged Class I relationships to be the most attractive.

Conclusion: FMA was found to have a positive effect on the amount of gingival display. It was also observed that patients with Class II Division 1 relationships had the thickest lips compared with patients having other types of occlusions. Class III patients exhibited no gingival display on smile. Patients with Class I showed the maximum smile width, while patients with Class III showed the least amount of buccal corridor.

Aim: To compare incisal axial inclination and alveolar bone changes after intrusion using segmented (Burstone) and utility (Ricketts) arches.

Methods: The sample comprised 252 incisors in 39 patients (18 to 25 years of age). Eighteen patients were treated using utility arches, and 21 patients were treated using segmented arches. Lateral cephalograms were taken to evaluate incisal movements. CT scans with a slice thickness of 1 mm were exposed, and SSD-3D and MPR images were reconstructed. For all maxillary and mandibular incisors, changes of alveolar bone height; changes of labial and lingual alveolar bone thickness at apical level (A1 and A2), 3 mm coronal from the apex (A3 and A4), and 6 mm coronal from the apex (A5 and A6); and development of dehiscence and fenestration were evaluated after 5 months of intrusion.

Results: Except for the retroclination of maxillary incisors in the Burstone group, all incisors experienced proclination. The greatest alveolar bone height loss was noted in the buccal alveolar bone height of the maxillary incisors in the Burstone group and the mandibular incisors in the Ricketts group (P < .05). There were decreases of alveolar bone thickness in both groups; however, the Ricketts group showed more bone decrease. These differences were significant for the maxilla (A1, A2, A4, and A6) and the mandible (A1 and A3) (P < .05).

Conclusion: Using segmented arches (Burstone) under controlled biomechanical conditions minimizes the undesirable adverse effects of intrusion forces compared with utility arches (Ricketts).

Aim: An onplant is an orthodontic anchorage device fixed to the bone surface with osseointegration. Compared with implants, the onplant has fewer limitations regarding placement and is less invasive. The purpose of this study was to clarify the effect of bone-surface treatment and the fixing method of a newly designed smaller-sized onplant and establish a prospective surgical procedure for placement of the onplant.

Methods: Thirty-eight onplants were placed in six beagle dogs. The bone surface was planed where the cortical bone was thick and reducible (bone-planed). Where the cortical bone was thin and uneven, a filling was inserted in the space between the onplant and bone (filled). The onplant was fixed to the bone in one of two ways: using a membrane that covered the onplant and fixing the membrane with titanium pins (membrane-fixed) or fixing the onplant directly to the bone using the same titanium pins (pin-fixed).

Results: Twelve weeks later, all the onplants were osseointegrated. The bone-planed group showed significantly (P < .05) larger shear stress than the filled groups. In the bone-planed group, the pin-fixed group showed significantly (P < .05) larger shear stress than the membrane-fixed group. The shear stresses were considered strong enough to function in orthodontic treatment.

Conclusion: The effect of the bone-surface treatment and the onplant-fixing method on the shear stress was clarified, and the findings in the present study may be useful for the improvement of surgical procedures for orthodontic onplants.

This report describes a combined orthodontic and surgical treatment approach for a severe skeletal Class III malocclusion in a young Indian woman with serious esthetic concerns. The case required significant surgical correction in the anteroposterior and vertical planes, involving surgeries in both the maxilla and the mandible. The case required the use of mini-implant anchorage in the presurgical phase as well as postorthodontic prosthodontic rehabilitation to replace missing posterior teeth to restore the occlusal table.