Effects of insertion angle and implant thread type on the fracture properties of orthodontic mini-implants during insertion

Objective:

To determine the effects of insertion angle (IA) and thread type on the fracture properties of orthodontic mini-implants (OMIs) during insertion.

Materials and Methods:

A total of 100 OMIs (self-drilling cylindrical; 11 mm in length) were allocated into 10 groups according to thread type (dual or single) and IA (0°, 8°, 13°, 18°, and 23°) (n  =  10 per group). The OMIs were placed into artificial materials simulating human tissues: two-layer bone blocks (Sawbones), root (polymethylmethacrylate stick), and periodontal ligament (Imprint-II Garant light-body). Maximum insertion torque (MIT), total insertion energy (TIE), and peak time (PT) were measured and analyzed statistically.

Results:

There were significant differences in MIT, TIE, and PT among the different IAs and threads (all P < .001). When IA increased, MIT increased in both thread groups. However, TIE and PT did not show significant differences among 0°, 8°, and 13° IAs in the dual-thread group or 8°, 13°, and 18° IAs in the single-thread group. The dual-thread groups showed higher MIT at all IAs, higher TIE at 0° and 23° IAs, and longer PT at a 23° IA than the single-thread groups. In the 0°, 8°, and 13° IA groups, none of the OMIs fractured or became deformed. However, in the 18° IA group, all the OMIs were fractured or deformed. Dual-thread OMIs showed more fracturing than deformation compared to single-thread OMIs (P < .01). In the 23° IA group, all OMIs penetrated the artificial root without fracturing and deformation.

Conclusions:

When OMIs contact artificial root at a critical contact angle, the deformation or fracture of OMIs can occur at lower MIT values than those of penetration.

The effects of orthodontic bonding steps on biofilm formation of Streptococcus mutans in the presence of saliva

OBJECTIVE

To investigate the effects of various orthodontic bonding steps on biofilm formation of Streptococcus mutans in the presence of saliva.

MATERIALS AND METHODS

Hydroxyapatite (HA) and orthodontic adhesive (AD) disks were prepared to a uniform size. HA disks were etched with 37% phosphoric acid gel in the etched group (HE). In the primed group (HP), Transbond XT primer was applied to the etched HA surface and light-cured. For biofilm formation, Streptococcus mutans was grown on each specimen in a biofilm medium with either glucose or sucrose in the presence of fluid-phase UWS (F-UWS) or surface adsorbed saliva (S-UWS). The adherent bacteria were quantified by enumeration of the total viable counts of bacteria. Biofilms formed on each surface were examined by scanning electron microscopy.

RESULTS

When glucose was used, both F-UWS and S-UWS suppressed biofilm formation of S. mutans. Compared to HA and HE, biofilm formation was significantly inhibited on HP and AD in the presence of glucose. Biofilm-forming patterns that were inhibited by saliva were restored in a sucrose-containing medium. F-UWS promoted biofilm formation on HA and HE, while S-UWS significantly promoted biofilm formation on HP. S. mutans developed biofilm better on HA and HE than on AD when sucrose was used as the sole carbohydrate source.

CONCLUSIONS

This study suggests that the biofilm development by S. mutans is significantly influenced by the orthodontic bonding procedure. Biofilm formation of S. mutans was inhibited on AD more than other surfaces, irrespective of the presence of saliva or a carbohydrate source.

Comparison of the microhardness and morphology of five different retrograde filling materials in aqueous and dry conditions

The purpose of the present study was to compare the effect of dry and aqueous conditions on the surface morphology and surface hardness of five materials 24 h after being used as fillings without initial setting time in dry condition. The five materials were ProRoot mineral trioxide aggregate (MTA), super EBA, intermediate restorative materials (IRM), zinc oxide eugenol (ZOE), and amalgam. To evaluate microhardness, the five materials were submitted to the Vickers microhardness (VHN) test. We used a scanning electron microscope (Steroscan 440, Leica Cambridge, England) to observe the microstructural morphology of the five different materials. The VHN of MTA soaked in water showed five times lower than that of MTA soaked in dry condition. On the other hand, super EBA was less influenced by the medium of storage compared with the other materials. Scanning electron microscope (SEM) images showed the similar results with microhardness tests. The surface of MTA soaked in water appeared to be unstable compared with that of dry condition while super EBA showed similarly smooth surface in both conditions (aqueous and dry). In conclusion, the physical property of MTA is reduced after storage in water; however, super EBA is less influenced by aqueous condition.

The effects of surface roughness of composite resin on biofilm formation of Streptococcus mutans in the presence of saliva

The purpose of this study was to investigate the effects of surface roughness of resin composite on biofilm formation of Streptococcus mutans in the presence of saliva. To provide uniform surface roughness on composites, disks were prepared by curing composite against 400-grit silicon carbide paper (SR400), 800-grit silicon carbide paper (SR800), or a glass slide (SRGlass). The surface roughness was examined using confocal laser microscopy. For biofilm formation, S. mutans was grown for 24 hours with each disk in a biofilm medium with either glucose or sucrose in the presence of fluid-phase or surface-adsorbed saliva. The adherent bacteria were quantified via enumeration of the total viable counts of bacteria. Biofilms were examined using scanning electron microscopy. This study showed that SR400 had deeper and larger, but fewer depressions than SR800. Compared to SRGlass and SR800, biofilm formation was significantly increased on SR400. In addition, the differences in the effect of surface roughness on the amount of biofilm formation were not significantly influenced by either the presence of saliva or the carbohydrate source. Considering that similar differences in surface roughness were observed between SR400 and SR800 and between SR800 and SRGlass, this study suggests that surface topography (size and depth of depressions) may play a more important role than surface roughness in biofilm formation of S. mutans .

The effects of humidity and serum on the surface microhardness and morphology of five retrograde filling materials

The purpose of this study was to compare the surface morphology and surface hardness of five materials 24 h after filling, in conditions of 100% humidity, and fetal bovine serum. The five materials were ProRoot Mineral Trioxide Aggregate (MTA), Super-EBA, Intermediate Restorative Materials (IRM), Zinc Oxide Eugenol (ZOE), and Amalgam. The microhardness of these materials was evaluated by Vickers microhardness test, and their morphologies were compared by using scanning electron microscopy (SEM). To evaluate the microhardness, the mixed five materials were measured with Vickers microhardness test. Differences between the experimental groups were analyzed by two-way ANOVA and Duncan's multiple comparison tests. All analyses were performed using the Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL). For the microstructural morphological evaluation, the cross cut and root-end cavity prepared surfaces followed by retrograde filling with five different materials were observed under a Scanning Electron Microscope (Steroscan 440; Leica, Cambridge, England) at ×500. To summarize, Super EBA was less influenced by storage medium than the other materials, especially MTA. However, further long-term studies considering other factors, such as biocompatibility (i.e. cellular toxicity) and retention, are needed to be collaborated with these findings in the clinical context.

Effects of Cleft Type, Facemask Anchorage Method, and Alveolar Bone Graft on Maxillary Protraction: A Three-Dimensional Finite Element Analysis

Objective

To investigate biomechanical effects of cleft type (unilateral/bilateral cleft lip and palate), facemask anchorage method (tooth-borne and miniplate anchorage), and alveolar bone graft on maxillary protraction.

Design

Three-dimensional finite element analysis with application of orthopedic force (30° downward and forward to the occlusal plane, 500 g per side).

Model

Computed tomography data from a 13.5-year-old girl with maxillary hypoplasia.

Intervention

Eight three-dimensional finite element models were fabricated according to cleft type, facemask anchorage method, and alveolar bone graft.

Main Outcome Measure(s)

Initial stress distribution and displacement after force application were analyzed.

Results

Unilateral cleft lip and palate showed an asymmetric pattern in stress distribution and displacement before alveolar bone graft and demonstrated a symmetric pattern after alveolar bone graft. However, bilateral cleft lip and palate showed symmetric patterns in stress distribution and displacement before and after alveolar bone graft. In both cleft types, the graft extended the stress distribution area laterally beyond the infraorbital foramen. For both unilateral and bilateral cleft lip and palate, a facemask with a tooth-borne anchorage showed a dentoalveolar effect with prominent stress distribution and displacement on the upper canine point. In contrast, a facemask with miniplate anchorage exhibited an orthopedic effect with more favorable stress distribution and displacement on the middle maxilla point. In addition, the facemask with a miniplate anchorage showed a larger stress distribution area and suturai stress values than did the facemask with a tooth-borne anchorage. The pterygopalatine and zygomatico-maxillary sutures showed the largest suturai stress values with a facemask with a miniplate anchorage and after alveolar bone grafting, respectively.

Conclusion

In this three-dimensional finite element analysis, it would be more advantageous to perform maxillary protraction using a facemask with a miniplate anchorage than a facemask with a tooth-borne anchorage and after alveolar bone graft rather than before alveolar bone graft, regardless of cleft type.

Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis

AIM

The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal.

MATERIALS AND METHODS

A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal.

RESULTS

The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001).

CONCLUSIONS

Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.

Skeletal differences in patients with temporomandibular joint disc displacement according to sagittal jaw relationship

PURPOSE

The present study was designed to analyze the skeletal differences in patients with temporomandibular joint (TMJ) disc displacement (DD), according to the sagittal jaw relationship.

MATERIALS AND METHODS

We implemented a cross-sectional study design and enrolled a sample of Korean women older than age 17 years. The subjects were classified into 3 groups according to the magnetic resonance images of the bilateral TMJs: bilateral normal disc position (BN), bilateral disc displacement with reduction, and bilateral disc displacement without reduction. Each group was subdivided into 2 groups using the mandibular body length to anterior cranial base ratio as a sagittal jaw parameter: normal-size mandible (NM) and oversized mandible (OM). Seventeen variables from the lateral cephalograms were analyzed using 2-way analysis of variance to analyze the differences in skeletal characteristics with respect to the mandible size and TMJ DD status.

RESULTS

The subjects with TMJ DD generally had a short ramus height and clockwise rotation of the ramus and mandible compared with those with BN in both OM and NM groups. However, significant differences were present in the skeletal characteristics of the TMJ DD patients between the NM and OM groups. Significant backward positioning and rotation of the ramus and mandible were found between BN and bilateral disc displacement with reduction or bilateral disc displacement without reduction in the OM group, while those of the ramus and mandible were found between BN and bilateral disc displacement with reduction or bilateral disc displacement without reduction in the NM group.

CONCLUSIONS

The results of our study suggest that the skeletal characteristics associated with TMJ DD are differently represented according to the sagittal jaw relationship.

Effects of periodic fluoride treatment on fluoride ion release from fresh orthodontic adhesives

OBJECTIVE

Periodic fluoride treatment may contribute to the ability of fresh orthodontic adhesives to provide long-term F(-) release. The effects of periodic fluoride treatment on the amount of F(-) release from fresh orthodontic adhesives was investigated.

METHODS

F(-) release was measured from a nonfluoride-releasing composite, a fluoride-releasing composite, a polyacid-modified composite (compomer), and two resin-modified glass-ionomer cements (RMGICs) at 1, 2, and 5 days after one of the following treatments: 225 ppm F(-) solution, 900 ppm F(-) solution, acidulated phosphate fluoride gel (APF), fluoridated dentifrice, and deionised water (control). F(-) release was measured in a 5-day cycle, which was repeated 9 consecutive times. The amount of F(-) release for each group was analysed using the repeated measures analysis of variance. Statistical significance was set at a level of α=0.05.

RESULTS

Periodic fluoride treatment temporarily increased F(-) release in fresh fluoride-releasing orthodontic adhesives, but not in fresh nonfluoride-releasing composite. The order of effective fluoride-release was RMGICs>compomer>fluoride-releasing composite>nonfluoride-releasing composite. The application of APF or 900 ppm F(-) solution was the most effective way to maintain F(-) release from fresh orthodontic adhesives. However, the amount of F(-) release gradually decreased with increasing specimen age.

CONCLUSION

Given the difficulty of routine use of APF at home, the results of this study show that a combination of RMGICs and high-dose fluoride mouth rinse is the most effective protocol to maintain F(-) release from fresh orthodontic adhesives.

CLINICAL SIGNIFICANCE

Most studies have investigated fluoride-uptake abilities using aged materials in which fluoride had been lost for at least 1 month. This study has found that periodic fluoride treatment altered the conventional F(-) release pattern of fresh fluoride-releasing materials and type of fluoride-containing medium plays a more critical role in fluoride recharging of the materials than fluoride concentration. This study will help clinicians to find the most effective fluoride treatment protocol of fresh materials.

Effect of orthodontic bonding steps on the initial adhesion of mutans streptococci in the presence of saliva

OBJECTIVE

To test the hypothesis that orthodontic bonding has no effect on the initial adhesion of mutans streptococci (MS) in the presence of saliva.

MATERIALS AND METHODS

Hydroxyapatite (HA) and orthodontic adhesive (AD) disks were prepared to a uniform size. HA disks were etched with 37% phosphoric acid (HE, etched group). Some of the HE disks were coated with Transbond XT primer and light cured (HP, primed group). Transbond Plus SEP was applied to a third set of HA disks, dried, and light cured (SEP, self-etching primer group). Adhesion assays were performed using two MS strains in the presence of fluid-phase or surface-adsorbed unstimulated whole saliva (UWS). The MS adhesion patterns were examined by scanning electron microscopy.

RESULTS

MS adhesion was influenced by the bonding steps and the presence of UWS. UWS treatment decreased MS adhesion. However, surface-adsorbed UWS resulted in slightly less inhibition of MS adhesion than fluid-phase UWS. MS adhesion was significantly greater for HE than for the other groups. There were interaction effects between the UWS treatment and surface groups. MS adhesion to HP and AD was significantly diminished in the presence of surface-adsorbed or fluid-phase UWS compared with adhesion to HA, HE, or SEP.

CONCLUSION

The hypothesis is rejected. Our results suggest that MS adhesion is significantly influenced by the bonding procedure used, and the application of conventional primers for the bracket bonding can inhibit MS adhesion to tooth surfaces in the presence of UWS.

Dentofacial characteristics of women with oversized mandible and temporomandibular joint internal derangement

INTRODUCTION

To analyze dentofacial characteristics of temporomandibular joint internal derangement (TMJ ID) in orthodontic patients with oversized mandible (skeletal Class III pattern).

MATERIALS AND METHODS

The sample consisted of 66 women whose mandibular body length to anterior cranial base ratio is greater than 1.12. They were divided into three groups based on magnetic resonance images of bilateral TMJs: bilateral normal disk position (BN), bilateral disk displacement with reduction (DDR), and bilateral disk displacement without reduction (DDNR). Thirty-five cephalometric variables regarding their lateral cephalograms were analyzed by Kruskal-Wallis test to evaluate differences in dentofacial morphology among the three groups.

RESULTS

Subjects with TMJ ID had a clockwise rotation of the ramus, with backward position of mandible, labial tipping of mandibular incisors, and protrusion of upper and lower lips. However, TMJ ID did not significantly influence vertical skeletal relationships. Most of the significant dentofacial changes were found between BN and DDR, and dentofacial changes between DDR and DDNR were minimal.

CONCLUSIONS

This study suggests that dentofacial changes associated with TMJ ID begin to appear when TMJ ID develops to DDR from BN in patients with oversized mandible.

Comparison of ultraviolet light-induced photocatalytic bactericidal effect on modified titanium implant surfaces

PURPOSE

Titanium dioxide (TiO2), a photocatalyst, is known to decompose various organic compounds under ultraviolet (UV) illumination by generating various radicals, which is useful for killing bacteria. The purpose of the present study was to evaluate the photocatalytic bactericidal effects of variously treated titanium surfaces on Streptococcus sanguinis SL1.

MATERIALS AND METHODS

Specimens were fabricated from grade 4 commercially pure titanium, 10 mm in diameter and 2 mm in thickness. Three different surfaces were prepared: anodized (AO) at 270 V, heat-treated (HT), and machined (MA). Surface analysis was performed using confocal laser scanning microscope, scanning electron microscopy, and thin-film x-ray diffractometry. The antibacterial activities were assessed by comparing adhesion and survival rates of S sanguinis on various surfaces under UV illumination.

RESULTS

The AO surface was rougher than the HT and MA surfaces. The AO surface showed TiO2 peaks of anatase structure, while the HT surface showed TiO2 peaks of rutile structure in x-ray diffractometry. HT and AO surfaces showed significantly decreased bacterial adhesion under UV illumination (AO and HT > control, AO > MA). In addition, bacterial adhesion decreased more significantly with extended UV illumination time. With respect to survival rates of bacteria, AO and HT showed a significant reduction over time compared to MA. The photocatalytic bactericidal effect was maximal on the AO titanium, followed by HT and MA.

CONCLUSIONS

The photo-induced bactericidal efficacy of TiO2 films is dependent on their surface characteristics.

Survival analysis of orthodontic mini-implants

INTRODUCTION

Survival analysis is useful in clinical research because it focuses on comparing the survival distributions and the identification of risk factors. Our aim in this study was to investigate the survival characteristics and risk factors of orthodontic mini-implants with survival analyses.

METHODS

One hundred forty-one orthodontic patients (treated from October 1, 2000, to November 29, 2007) were included in this survival study. A total of 260 orthodontic mini-implants that had sandblasted (large grit) and acid-etched screw parts were placed between the maxillary second premolar and the first molar. Failures of the implants were recorded as event data, whereas implants that were removed because treatment ended and those that were not removed during the study period were recorded as censored data. A nonparametric life table method was used to visualize the hazard function, and Kaplan-Meier survival curves were generated to identify the variables associated with implant failure. Prognostic variables associated with implant failure were identified with the Cox proportional hazard model.

RESULTS

Of the 260 implants, 22 failed. The hazard function for implant failure showed that the risk is highest immediately after placement. The survival function showed that the median survival time of orthodontic mini-implants is sufficient for relatively long orthodontic treatments. The Cox proportional hazard model identified that increasing age is a decisive factor for implant survival.

CONCLUSIONS

The decreasing pattern of the hazard function suggested gradual osseointegration of orthodontic mini-implants. When implants are placed in a young patient, special caution is needed to lessen the increased probability of failure, especially immediately after placement.

Surface Characteristics of Orthodontic Materials and Their Effects on Adhesion of Mutans streptococci

Objective: To test the hypothesis that there are no significant differences in the adhesion of mutans streptococci (MS) to various orthodontic materials based on their surface characteristics.

Materials and Methods: Surface roughness (SR) and surface free energy (SFE) characteristics were investigated for nine different orthodontic materials (four orthodontic adhesives, three bracket raw materials, hydroxyapatite blocks, and bovine incisors) using confocal laser scanning microscopy and sessile drop method. Each material, except the bovine incisors, was incubated with whole saliva or phosphate-buffered saline for 2 hours. Adhesion assays were performed by incubating tritium-labeled MS with each material for 3 or 6 hours.

Results: Orthodontic adhesives had higher SFE characteristics and lower SR than bracket materials. Orthodontic adhesives showed a higher MS retaining capacity than bracket materials, and MS adhesion to resin-modified glass ionomer and hydroxyapatite was highest. Extended incubation time increased MS adhesion, while saliva coating did not significantly influence MS adhesion. SFE, specifically its dispersive and polar components, was positively correlated with MS adhesion, irrespective of saliva coating.

Conclusions: The hypothesis is rejected. This study suggests that SFE characteristics play an important role in the initial MS adhesion to orthodontic materials.

Early stature prediction method using stature growth parameters

BACKGROUND

The creation of an accurate growth prediction method for human stature at a stage of growth has been an interesting challenge in medical science and human biology.

AIM

The aim of this study was to develop a non-radiographic final stature prediction method that is applicable in the early pubertal growth period.

SUBJECTS AND METHODS

Randomly selected 12-year serial stature growth data for 400 Koreans were fitted with two nonlinear growth curves: Preece and Baines model 1 (PB1) and Jolicoeur-Pontier-Pernin-Sempe (JPPS) functions. Five biological parameters, including take-off (TO) related parameters, were derived by differentiation of the two curves, respectively. Those five variables were composed into a multiple linear regression equation for final stature prediction. In the cross-validation subjects, TO-related variables were estimated by linear interpolation from the partial growth data prior to estimation age, then incorporated into the prediction equation.

RESULTS

The final stature prediction model had excellent validity and accuracy when applied to the cross-validation samples. Prediction accuracy increased according to increasing years after take-off.

CONCLUSIONS

This study suggests that a final stature prediction method using multiple regression analysis that includes biological parameters can predict stature growth with sufficient validity and accuracy. Incorporation of TO-related parameters allowed us to develop earlier growth evaluation and prediction methods compared with other previous methods.

Experimental antimicrobial orthodontic adhesives using nanofillers and silver nanoparticles

OBJECTIVES

Experimental composite adhesives (ECAs) containing silica nanofillers and silver nanoparticles were compared with two conventional adhesives (composite and resin-modified glass ionomer [RMGI]) to analyze surface characteristics, physical properties and antibacterial activities against cariogenic streptococci.

METHODS

Surface roughness and surface free energy (SFE) characteristics were measured using confocal laser scanning microscopy and the sessile drop method. Shear bond strength and bond failure interface were analyzed to compare the physical properties. Antimicrobial activities were analyzed by a bacterial adhesion assay, a disk diffusion test, and an optical density measurement of bacterial suspension containing each adhesive.

RESULTS

ECAs had rougher surfaces than conventional adhesives due to the addition of silver nanoparticles. ECAs had more similar SFE characteristics to composite than to RMGI. Bacterial adhesion to ECAs was less than to conventional adhesives, which was not influenced by saliva coating. Bacterial suspension containing ECAs showed slower bacterial growth than those containing conventional adhesives. There was no significant difference in shear bond strength and bond failure interface between ECAs and conventional adhesives.

SIGNIFICANCE

This study suggests that ECAs can help prevent enamel demineralization around their surfaces without compromising physical properties.

Quantitative analysis of adhesion of cariogenic streptococci to orthodontic raw materials

INTRODUCTION

Knowledge of adhesion patterns of cariogenic streptococci to orthodontic materials can provide valuable information on the cause of enamel demineralization during orthodontic treatment. The purpose of this study was to investigate the adhesion of 2 cariogenic streptococci strains to 7 orthodontic raw materials (3 light-cured orthodontic adhesives, 3 bracket raw materials, and hydroxyapatite) with respect to bacterial species, incubation time, and saliva coating.

METHODS

Each material was incubated with unstimulated whole saliva or phosphate-buffered saline solution for 2 hours. Binding assays were then performed by incubating tritium-labeled cariogenic streptococci with each raw material for 3 or 6 hours.

RESULTS

The degree of adhesion varied by material type. Generally, adhesion of cariogenic streptococci was significantly higher for bonding adhesives than for bracket materials, and adhesion to resin-modified glass ionomer was the highest. A longer incubation time generally increased bacterial adhesion, whereas saliva coating did not significantly influence bacterial adhesion.

CONCLUSIONS

Bonding adhesives around brackets should be removed carefully during the bonding procedure to avoid enamel decalcification.

Initial effect of multiloop edgewise archwire on the mandibular dentition in Class III malocclusion subjects. A three-dimensional finite element study

The purpose of this study was to compare the effect of a multiloop edgewise archwire (MEAW) with a plain ideal archwire (IA) on distal en masse movement of the mandibular dentition. A three-dimensional finite element model (3D FEM) of the mandibular dentition, without third permanent molars, was constructed to include the periodontal membrane (PDM), alveolar bone, standard edgewise bracket (0.018 x 0.025 inch), stainless steel IA (0.016 x 0.022 inch), and MEAW (0.016 x 0.022 inch). Stress distribution and displacement of the mandibular dentition were analyzed when Class III intermaxillary elastics (300 g/side) and 5 degree tip-back bends from the first premolar to the second molar were applied to the IA and the MEAW for distal en masse movement of the mandibular dentition. Compared with the IA, the discrepancy in the amount of tooth displacement was less and individual tooth movement with the MEAW was more uniform and balanced. There was minimal vertical displacement or rotation of the teeth with the MEAW when compared with the IA. The MEAW seems to have advantages for distal en masse movement of the mandibular dentition.

Patient compliance and locus of control in orthodontic treatment: a prospective study

INTRODUCTION

Increased understanding of orthodontic patients will improve communication between dentist and patient; this is important for an optimal treatment outcome. In this prospective study, we addressed the relationship between patient compliance and locus of control (LOC) characteristics and evaluated posttreatment changes in LOC profiles.

METHODS

Two types of LOC questionnaires, the Rotter internal control scale (RICS) and the Nowicki-Strickland external control scale (NSECS), were given to 561 patients before conventional orthodontic treatment. After orthodontic treatment, the same questionnaires were readministered, and patient compliance was evaluated by an orthodontist and 3 dental hygienists. LOC scores were calculated at the end of the examination period. The difference in LOC between the good and poor compliance groups, and the posttreatment changes in LOC were evaluated.

RESULTS

There was no significant difference in RICS and NSECS profiles between the good and poor compliance groups. NSECS decreased significantly after orthodontic treatment, but there were no significant changes in RICS.

CONCLUSIONS

Patient compliance appears to be a complex factor that cannot be predicted by LOC evaluation before orthodontic treatment. Patients who underwent orthodontic treatment showed decreased external control dispositions.