Seung-Hyun Kyung

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.

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 operators learning curve, patients 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, patients age (especially >15 years), and operators skill were factors influencing the clinical success of orthodontic miniscrews in the palate.

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.

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.

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.

Fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts

The purpose of this study was to investigate the fracture resistance of crown-root fractured teeth repaired with dual-cured composite resin and horizontal posts. 48 extracted human premolars were assigned to control group and three experimental groups. Complete crown-root fractures were experimentally induced in all control and experimental teeth. In the control group, the teeth (n=12) were bonded with resin cement and endodontically treated. Thereafter, the access cavities were sealed with dual-cured composite resin. In composite resin core - post group (n=12), the teeth were endodontically treated and access cavities were sealed with dual-cured composite resin. In addition, the fractured segments in this group were fixed using horizontal posts. In composite resin core group (n=12), the teeth were endodontically treated and the access cavities were filled with dual-cured composite resin without horizontal posts. In bonded amalgam group (n=12), the teeth were endodontically treated and the access cavities were sealed with bonded amalgam. Experimental complete crown-root fractures were induced again on repaired control and experimental teeth. The ratio of fracture resistance to original fracture resistance was analyzed with KruskalWallis test. The results showed that teeth in control and composite resin core - post group showed significantly higher resistance to re-fracture than those in amalgam core group (