Displacement pattern of the maxillary arch depending on miniscrew position in sliding mechanics.

INTRODUCTION: This clinical study was performed to evaluate the anteroposterior and vertical displacement patterns of the maxillary teeth in sliding mechanics depending on the position of interradicular miniscrews after the extraction of premolars. METHODS: Thirty-six women requiring maximum incisor retraction because of bialveolar protrusion were divided into 2 groups: group A (n = 18), miniscrew between the premolar and the molar, and group B (n = 18), miniscrew between the premolars. Cephalometric measurements for skeletal and dental changes were made before and after space closure. RESULTS: In both groups, significant incisor retraction with intrusion of the root apex was noted, with no significant change in the first molar position. Group B displayed significantly greater intrusion at both the incisal tip (1.59 ± 1.53 mm) and the root apex (2.89 ± 1.59 mm) than did group A. In spite of the mean reduction of the vertical skeletal measurements, we failed to find significant skeletal changes. CONCLUSIONS: Miniscrews provided firm anchorage for anterior retraction. Selection of the placement site appeared to be an important determinant for the resultant displacement pattern of the incisor segment. Discriminative intrusion or retraction might be obtained via strategic miniscrew positioning.

Effects of blood contamination on microtensile bond strength to dentin of three self-etch adhesives.

This study evaluated the effects of blood contamination and decontamination methods during different steps of bonding procedures on the microtensile bond strength of two-step self-etch adhesives to dentin. Sixty extracted human molars were ground flat to expose occlusal dentin. The 60 molars were randomly assigned to three groups, each treated with a different two-step self-etch adhesive: Clearfil SE Bond, AdheSE and Tyrian SPE. In turn, these groups were subdivided into five subgroups (n = 20), each treated using different experimental conditions as follows: control group-no contamination; contamination group 1-CG1: primer application/ contamination/primer re-application; contamination group 2-CG2: primer application/contamination/wash/dry/primer re-application; contamination group 3-CG3: primer application/adhesive application/light curing/contamination/ adhesive re-application/light curing; contamina- tion group 4-CG4: primer application/adhesive application/light curing/contamination/wash/ dry/adhesive re-application/light curing. Composite buildup was performed using Z250. After 24 hours of storage in distilled water at 37 degrees C, the bonded specimens were trimmed to an hourglass shape and serially sectioned into slabs with 0.6 mm2 cross-sectional areas. Microtensile bond strengths (MTBS) were assessed for each specimen using a universal testing machine. The data were analyzed by two-way ANOVA followed by a post hoc LSD test. SEM evaluations of the fracture modes were also performed. The contaminated specimens showed lower bond strengths than specimens in the control group (p < 0.05), with the exception of CG1 in the Clearfil SE group and CG2 and CG3 in the Tyrian SPE group. Among the three self-etch adhesives, the Tyrian SPE group exhibited a significantly lower average MTBS compared to the Clearfil SE Bond and AdheSE (p < 0.05) groups. Based on the results of the current study, it was found that blood contamination reduced the MTBS of all three self-etch adhesives to dentin, and water-rinsing was unable to overcome the effects of blood contamination.

Midpalatal miniscrews for orthodontic anchorage: factors affecting clinical success.

INTRODUCTION: The purpose of this study was to investigate the success rate of midpalatal miniscrews used for orthodontic anchorage and the factors affecting clinical success. METHODS: One hundred twenty-eight consecutive patients (101 female, 27 male; mean age, 23.4 years), who received a total of 210 miniscrews in the midpalatal suture area, were examined. Success rates were determined according to 10 clinical variables. RESULTS: The overall success rates were 88.20% for the total number of patients and 90.80% for the total number of miniscrews. There were no significant associations among success rate and sex, total period of treatment with miniscrews, diameter of miniscrews, types of tooth movements, and variables that represent sagittal and vertical skeletal relationships (ANB, FMA, and Sn-GoGn). The operator's learning curve, patient's age, area (midpalatal or parapalatal), and splinting significantly influenced the success rates. After adjusting for other variables, only 1- splinting-showed a significant effect on the success rate. CONCLUSIONS: The joining of 2 miniscrews by splinting, placement of the miniscrew in the midpalatal suture, patient's age (especially >15 years), and operator's skill were factors influencing the clinical success of orthodontic miniscrews in the palate.

Distalization of the entire maxillary arch in an adult.

Many appliances are available to move maxillary molars distally. First molars have routinely been moved distally with nickel-titanium coil springs and nickel-titanium wire before the eruption of the second molars. However, when first molars are moved distally after the eruption of the second molars, they tend to move slowly, and anchorage loss increases. In adults, the midpalatal area is appropriate for placing titanium miniscrews for orthodontic anchorage. This case report demonstrates the ability of midpalatal miniscrews to control anchorage while distalizing the entire maxillary dentition in an adult, with improvements in lip profile resulting from the retraction of anterior teeth followed by a good response of the lips. This report suggests that absolute anchorage can be established by placing miniscrews in the palate and that miniscrew anchorage can serve as anchorage for the distal movement of an entire arch.

Success rate and risk factors associated with mini-implants reinstalled in the maxilla.

OBJECTIVE: To determine the difference in the success rate for two types of oral installed mini-implants (OMIs): one type of initially installed OMI and a new implant of the same type that is reinstalled. MATERIALS AND METHODS: The subjects consisted of 58 patients (19 male, 39 female; mean age = 21.78 +/- 5.85 years) who had received at least one OMI (self-drilling type, conical shape with 2.0-mm upper diameter and 5-mm length) in the attached gingiva of the upper buccal posterior regions for maximum anchorage during en masse retraction. If an OMI failed, a new one was immediately installed in the same area after 4 to 6 weeks or in an adjacent area immediately. The total number of initially installed OMIs (II-OMI) was 109 and the total number of reinstalled OMIs (RI-OMI) was 34. Statistical analysis was performed using chi2 test, Kaplan-Meier method, log-rank test, and Cox proportional hazards regression model. RESULTS: The success rate and mean duration were 75.2% and 10.0 months, respectively, for II-OMI and 66.7% and 6.4 months, respectively, for RI-OMI. Age, vertical skeletal pattern, and site and side of implantation were not related to the success rates of II-OMI and RI-OMI. Log-rank test showed that II-OMI in males and Class III malocclusions were more prone to failure. The relative risk of II-OMI failure in Class III malocclusions as opposed to Class I malocclusions was 5.36 (95% confidence interval, 2.008 to 14.31, P = .001). CONCLUSION: The success rate of the II-OMI was not statistically different from that of the RI-OMI. Sex and ANB angle might be more important factors for better II-OMI results.

Obstructive sleep apnea patients with the oral appliance experience pharyngeal size and shape changes in three dimensions.

Pharyngeal size and shape differences between pre- and posttrials of a mandible-protruding oral appliance were investigated using cine computerized tomography (CT). Fourteen patients diagnosed with obstructive sleep apnea whose apnea-hypopnea index was higher than 5 and arousal index higher than 20 underwent a second overnight sleep study to evaluate the effectiveness of the oral appliance. Three-dimensional changes in pharyngeal shape measured on cross-sectional CT images during two respiratory cycles after oral appliance delivery were estimated by three variables: (1) lateral dimension, (2) anterior-posterior dimension, and (3) cross-sectional area at five vertical levels. Apnea indices improved significantly when the appliance was used. During apnea, measurements at retropalatal and retroglossal levels decreased most. However, the cross-sectional area of these levels appeared to increase significantly (P < .05) with the appliance in place during wakefulness. The oral appliance appears to enlarge the pharynx to a greater degree in the lateral than in the sagittal plane at the retropalatal and retroglossal levels of the pharynx, suggesting a mechanism for the effectiveness of oral appliances that protrude the mandible.

The efficient use of midpalatal miniscrew implants.

The midpalatal suture area with thin, keratinized soft tissue and sufficient cortical bone is an optimal site for miniscrew implantation. Even though the midpalatal area has its own anatomical limitations, it can be overcome by bonding extension arms to the miniscrews. This technique also enhances screw stability, thus producing a successful outcome. Among many applications, midpalatal miniscrew implants can be effectively used for intrusion of upper molars with reduced treatment time and enhanced patient comfort.

Vertical alveolar bone distraction at molar region using lag screw principle.

PURPOSE: Recently, alveolar bone distraction has been widely used and several devices have been developed for this purpose. However, there are some disadvantages in each device, especially for distraction of posterior alveolar ridge. The purpose of this study was to develop a new device for vertical alveolar bone distraction at the molar region and to show the results of its clinical application. MATERIALS AND METHODS: The mechanism of device is based on lag screw principle and the device consists of the following 4 components; distraction screw, hole implant fixture, supporting plate, and temporary short implant and/or neighboring natural teeth. The distraction screw suspended at the supporting plate is inserted into the internal thread of the hole implant fixture placed at alveolar transport segment. If the distraction screw turns at the supporting plate, the hole implant fixture with transport segment moves to the supporting plate without vertical movement of the screw at the supporting plate like a lag screw. After an animal experiment using 4 beagle dogs, the device was clinically applied in 4 patients before implant insertion. RESULTS: The distraction of the alveolar bone could be successfully performed in all patients without any complications. The direction of distraction with this device could be adjustable, and the alveolar bone could be distracted not only vertically but also horizontally. Moreover, the surgical technique is simple with no need for a second surgery, and there is no occlusal disturbance from the device. CONCLUSIONS: The new device for alveolar bone distraction using lag screw principle can be used effectively in the molar region.