Success rate of microimplants in a university orthodontic clinic

Introduction. The purpose of this study was to examine the success rate and find factors affecting the clinical success of microimplants used as orthodontic anchorage. Methods. Seventy-three consecutive patients (25 male, 48 female; mean age, 22.45 years) with a total of 139 screw implants of 2 types were examined. Success rate was determined according to 18 clinical variables. Results. The overall success rate was 87.8%. The clinical variables of microimplant factors (type), patient factors (sex, skeletal and dental relationships, overbite, jaw involved, side involved and site involved), and treatment factors (type of insertion, time of loading, purpose of microimplant insertion, mode of loading, type of anchorage used, direction of forces applied) did not show any statistical difference in success rates. Mandibular angle, vertical position of implant placement, oral hygiene status, and inflammation showed significant difference in success rates. Conclusions. Proper case selection and following the recommended protocol are extremely essential to minimise failures.

Influence of first premolar extraction on mandibular third molar angulation

OBJECTIVE

To compare the angular changes in the developing mandibular third molars in both first premolar extraction and nonextraction cases and to determine whether premolar extraction results in a more mesial movement of the mandibular buccal segment and causes favorable rotational changes in the mandibular third molar tilt, which can enhance later eruption of the third molars.

MATERIALS AND METHODS

Pretreatment (T1) and posttreatment (T2) panoramic radiographs were taken of 25 subjects who had been treated by the extraction of all the first premolars and 25 subjects who had been treated with nonextraction. The horizontal reference plane was used to measure and compare the changes in the angles of the developing mandibular third molars.

RESULTS

The mean uprighting of the mandibular third molars seen in the extraction group was 8.2 +/- 5.4 degrees on the left side and 6.3 +/- 6.5 degrees on the right side following treatment (T2 - T1). For the nonextraction group the mean difference was 1.3 +/- 4.3 degrees on the left side and 1.7 +/- 5.4 degrees on the right side. There was a statistically significant difference between the groups (P = .012 on the right side and P < .001 on the left side).

CONCLUSIONS

Premolar extractions had a positive influence on the developing third molar angulations. Nonextraction therapy did not have any adverse effects.

Maxillary protraction with and without maxillary expansion: a finite element analysis of sutural stresses

INTRODUCTION

In this finite element study, we compared the stress patterns along the various craniofacial sutures with maxillary protraction with and without expansion.

METHODS

Two 3-dimensional analytic models were developed, 1 simulating maxillary protraction and the other simulating maxillary protraction with expansion. The model consisted of 108799 10 node solid 92 elements (tetrahedron), 193633 nodes, and 580899 degrees of freedom.

RESULTS

The overall stresses after maxillary protraction with maxillary expansion were significantly higher than with a facemask alone. The magnitude of stress on the craniofacial sutures with maxillary protraction alone was in the range of a few millinewtons per square millimeter, whereas, with maxillary protraction with maxillary expansion, the stresses ranged from a few newtons per square millimeter to a few hundred newtons per square millimeter. The pattern of stress distribution also differed with the 2 treatment modalities as did the sutures experiencing maximum and minimum stresses.

CONCLUSIONS

The osteogenic potential of such low stresses after maxillary protraction can be questioned. High stresses generated in various craniofacial sutures after maxillary protraction with expansion are responsible for disrupting the circummaxillary sutural system and presumably facilitating the orthopedic effect of the facemask.

Skeletal response to maxillary protraction with and without maxillary expansion: a finite element study

INTRODUCTION

The purpose of this finite element study was to evaluate biomechanically 2 treatment modalities-maxillary protraction alone and in combination with maxillary expansion-by comparing the displacement of various craniofacial structures.

METHODS

Two 3-dimensional analytical models were developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry young skull. AutoCAD software (2004 version, Autodesk, San Rafael, Calif) and ANSYS software (version 10, Belcan Engineering Group, Cincinnati, Ohio) were used. The model consisted of 108,799 solid 10 node 92 elements, 193,633 nodes, and 580,899 degrees of freedom. In the first model, maxillary protraction forces were simulated by applying 1 kg of anterior force 30 degrees downward to the palatal plane. In the second model, a 4-mm midpalatal suture opening and maxillary protraction were simulated.

RESULTS

Forward displacement of the nasomaxillary complex with upward and forward rotation was observed with maxillary protraction alone. No rotational tendency was noted when protraction was carried out with 4 mm of transverse expansion. A tendency for anterior maxillary constriction after maxillary protraction was evident. The amounts of displacement in the frontal, vertical, and lateral directions with midpalatal suture opening were greater compared with no opening of the midpalatal suture. The forward and downward displacements of the nasomaxillary complex with maxillary protraction and maxillary expansion more closely approximated the natural growth direction of the maxilla.

CONCLUSIONS

Displacements of craniofacial structures were more favorable for the treatment of skeletal Class III maxillary retrognathia when maxillary protraction was used with maxillary expansion. Hence, biomechanically, maxillary protraction combined with maxillary expansion appears to be a superior treatment modality for the treatment of maxillary retrognathia than maxillary protraction alone.

Idiopathic failure of eruption of multiple permanent teeth: report of 2 adults with a highlight on molecular biology

Multiple unerupted teeth with no obvious etiology is a rare dental anomaly. Various local and systemic factors have been implicated in the failure of eruption of multiple permanent teeth. But the localization of the genetic defect in the phenotype of failure of eruption is largely unknown at present. Our aims in this article were to consolidate and organize the available information regarding the molecular biology of tooth eruption and to corroborate the current evidence with the report of 2 adult cases of failure of eruption of multiple permanent teeth without a known cause.