Il-Hyung Yang

The short-term treatment effects of face mask therapy in Class III patients based on the anchorage device: miniplates vs rapid maxillary expansion.

OBJECTIVE To compare the short-term treatment effects of face mask therapy with miniplates (FM-MP) and face mask therapy with rapid maxillary expansion appliance (FM-RME) in growing Class III malocclusion patients with maxillary hypoplasia. MATERIALS AND METHODS Twenty patients were allocated into two groups according to the anchorage device: FM-MP group (n  =  10; mean age  =  11.2 ± 1.2 years; miniplates in the zygomatic buttress area) and FM-RME group (n  =  10; mean age  =  10.7 ± 1.3 years; bonded or banded RME). The face mask was applied for 12 to 14 hours/day in both groups with a force of 400 g/side directed 30° downward and forward from the occlusal plane. Lateral cephalograms were taken before (T1) and after FM-MP or FM-RME therapy (T2). Skeletodental and soft-tissue variables were measured. Paired and independent t-tests were performed for statistical analysis. RESULTS Both groups exhibited significant forward movement of point A and posterior repositioning and opening rotation of the mandible from T2 to T1. The FM-MP group showed significant protraction of orbitale (ΔSNO), and the FM-RME group showed a decrease in overbite and an increase in Björk sum. Comparing the amount of changes between the two groups, the FM-MP group displayed greater forward movement of the maxilla than the FM-RME group (ΔSNA, ΔA to N perp, all P < .05). However, the FM-RME group exhibited a greater opening rotation of the mandible (ΔSNB, Björk sum, all P < .01; ΔPog to N-perp, P < .05) and labioversion of the maxillary incisors (ΔU1-FH, P < .05). CONCLUSION FM-MP therapy induces a greater advancement of the maxilla, less posterior repositioning and opening rotation of the mandible, and less proclination of the maxillary incisors than FM-RME therapy.

Comparison of the effects of maxillary protraction using facemask and miniplate anchorage between unilateral and bilateral cleft lip and palate patients.

OBJECTIVE To determine the difference in the effects of facemask with miniplate (FM-MP) anchorage on maxillary protraction in growing cleft patients between unilateral (UCLP) and bilateral cleft lip and palate (BCLP) groups. MATERIALS AND METHODS The samples consisted of a UCLP group (N  =  15, 13 boys and 2 girls; mean age 10.98 years; mean protraction duration 2.37 years) and a BCLP group (N  =  15, all boys; mean age 11.42 years; mean protraction duration 2.36 years), who were treated with the same surgical technique (rotation and advancement flap and double opposing Z-plasty) by one surgeon and with FM-MP by one orthodontist. Lateral cephalograms were taken before (T1) and after FM-MP (T2). Fourteen skeletal and dental variables were measured. Independent and paired t-tests were performed for statistical analysis. RESULTS There were no differences in mean age and values of variables at the T1 stage and in the duration of protraction between the two groups. The BCLP group showed less advancement of point A than the UCLP group (ΔA-vertical reference plane, 2.51 mm vs 4.06 mm, P < .05; ΔA-N perpendicular, 0.79 mm vs 2.26 mm, P < .05; ΔSNA, 0.45° vs 2.85°, P < .01). Since counterclockwise rotation of the palatal plane in two groups was minimal (-0.36° vs -0.87°), no difference was observed with regard to clockwise rotation of the mandible (0.46° vs -0.07°). There were no differences in the degree of labioversion of the maxillary incisor (8.16° vs 7.10°), linguoversion of the mandibular incisor (-2.66° vs -2.14°), and increase in overjet (5.39 mm vs 5.70 mm) between the two groups. CONCLUSION In FM-MP therapy of growing cleft patients under the conditions of this study, the UCLP group shows a more favorable change in maxillary advancement than the BCLP group.

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.

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.

Preliminary three-dimensional analysis of tooth movement and arch dimension change of the maxillary dentition in Class II division 1 malocclusion treated with first premolar extraction: conventional anchorage vs. mini-implant anchorage

Objective This study aimed to compare the effects of conventional and orthodontic mini-implant (OMI) anchorage on tooth movement and arch-dimension changes in the maxillary dentition in Class II division 1 (CII div.1) patients. Methods CII div.1 patients treated with extraction of the maxillary first and mandibular second premolars and sliding mechanics were allotted to conventional anchorage group (CA, n = 12) or OMI anchorage group (OA, n = 12). Pre- and post-treatment three-dimensional virtual maxillary models were superimposed using the best-fit method. Linear, angular, and arch-dimension variables were measured with software program. Mann-Whitney U-test and Wilcoxon signed-rank test were performed for statistical analysis. Results Compared to the CA group, the OMI group showed more backward movement of the maxillary central and lateral incisors and canine (MXCI, MXLI, MXC, respectively; 1.6 mm, p < 0.001; 0.9 mm, p < 0.05; 1.2 mm, p < 0.001); more intrusion of the MXCI and MXC (1.3 mm, 0.5 mm, all p < 0.01); less forward movement of the maxillary second premolar, first, and second molars (MXP2, MXM1, MXM2, respectively; all 1.0 mm, all p < 0.05); less contraction of the MXP2 and MXM1 (0.7 mm, p < 0.05; 0.9 mm, p < 0.001); less mesial-in rotation of the MXM1 and MXM2 (2.6°, 2.5°, all p < 0.05); and less decrease of the inter-MXP2, MXM1, and MXM2 widths (1.8 mm, 1.5 mm, 2.0 mm, all p < 0.05). Conclusions In treatment of CII div.1 malocclusion, OA provided better anchorage and less arch-dimension change in the maxillary posterior teeth than CA during en-masse retraction of the maxillary anterior teeth.

In vivo comparison between the effects of chemically modified hydrophilic and anodically oxidized titanium surfaces on initial bone healing.

Purpose The aim of this study was to investigate the combined effects of physical and chemical surface factors on in vivo bone responses by comparing chemically modified hydrophilic sandblasted, large-grit, acid-etched (modSLA) and anodically oxidized hydrophobic implant surfaces. Methods Five modSLA implants and five anodized implants were inserted into the tibiae of five New Zealand white rabbits (one implant for each tibia). The characteristics of each surface were determined using field emission scanning electron microscopy, energy dispersive spectroscopy, and confocal laser scanning microscopy before the installation. The experimental animals were sacrificed after 1 week of healing and histologic slides were prepared from the implant-tibial bone blocks removed from the animals. Histomorphometric analyses were performed on the light microscopic images, and bone-to-implant contact (BIC) and bone area (BA) ratios were measured. Nonparametric comparison tests were applied to find any significant differences (P<0.05) between the modSLA and anodized surfaces. Results The roughness of the anodized surface was 1.22 ± 0.17 µm in Sa, which was within the optimal range of 1.0-2.0 µm for a bone response. The modSLA surface was significantly rougher at 2.53 ± 0.07 µm in Sa. However, the modSLA implant had significantly higher BIC than the anodized implant (P=0.02). Furthermore, BA ratios did not significantly differ between the two implants, although the anodized implant had a higher mean value of BA (P>0.05). Conclusions Within the limitations of this study, the hydrophilicity of the modSLA surface may have a stronger effect on in vivo bone healing than optimal surface roughness and surface chemistry of the anodized surface. Graphical Abstract

Effect of tooth displacement and vibration on frictional force and stick-slip phenomenon in conventional brackets: a preliminary in vitro mechanical analysis

OBJECTIVE To evaluate the effects of tooth displacement and vibration on frictional force and stick-slip phenomenon (SSP) when conventional brackets were used with a levelling/alignment wire. MATERIALS AND METHODS The samples consisted of six groups (n = 10 per group) with combinations of tooth displacement (2mm lingual displacement [LD], 2mm gingival displacement [GD], and no displacement [control]) and vibration conditions (absence and presence at 30 Hz and 0.25 N). A stereolithographically made typodont system was used with conventional brackets and elastomeric ligatures. After application of artificial saliva, static/kinetic frictional forces (SFF/KFF) and frequency/amplitude of SSP were measured while drawing a 0.018-inch copper nickel-titanium (Cu-NiTi) archwire at a speed of 0.5mm/min for 5 minutes at 36.5 degree celsius. Two-way analysis of variance and independent t-test were performed. RESULTS Tooth displacement increased SFF and KFF (control < LD < GD, all P < 0.001) and reduced SSP frequency (control > [LD, GD], P < 0.01). Vibration reduced SFF, KFF, and SSP amplitude in the control group (P < 0.05, P < 0.05, and P < 0.001, respectively), but not in the LD and GD groups. SSP frequency was increased by vibration in the control, LD, and GD groups (all P < 0.001), and it was lower in the LD and GD groups than in the control group (P < 0.01). CONCLUSIONS When conventional brackets and a 0.018-inch Cu-NiTi archwire were used in the tooth displacement conditions (LD and GD), vibration did not significantly reduce SFF, KFF, or SSP amplitude.

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.

Postsurgical Relapse in Class III Patients Treated With Two-Jaw Surgery: Conventional Three-Stage Method Versus Surgery-First Approach.

AbstractThe aim of this study was to investigate the pattern, amount, and distribution of postsurgical relapse in skeletal Class III patients treated with two-jaw surgery (TJS) using conventional three-stage method (CTM) and surgery-first approach (SFA). A total of 38 patients who underwent the nonextraction approach and TJS (LeFort I posterior impaction and mandibular setback) were divided into CTM and SFA groups (all n = 19/group). Lateral cephalograms were taken before treatment (T0), at 1 month before surgery (T1), immediately after surgery (T2), and at debonding (T3) for CTM patients and at T0, T2, and T3 stages for SFA patients. Cephalometric measurements and statistical analyses were performed. There were no significant differences in the cephalometric variables at all stages except maxillary incisor inclination (U1-UOP) and overbite at T0 between 2 groups. They also did not exhibit significant differences in the amounts of surgical movement except for advancement of the maxilla. The mandible in both groups was rotated slightly clockwise by surgery and counterclockwise during T2–T3 without a significant difference. Distribution of cases with “high relapse” (>30%) and “low relapse” (<30%) of the mandible differed for 2 groups (P < 0.05). SFA group had more “high relapse” cases than CTM group (57.9% versus 26.3%). Postsurgical relapse of the mandible had a positive relationship with the amount of mandibular setback in SFA group (P < 0.01) and clockwise rotation of the proximal segment of the mandible in both groups (P < 0.05 and P < 0.01). The results suggest that SFA might be an effective alternative to CTM if the cause of “high relapse” including amounts of mandibular setback and clockwise rotation of the proximal segment of the mandible during surgery can be controlled.

Influence of temporomandibular joint disc displacement on craniocervical posture and hyoid bone position

INTRODUCTION The purpose of this study was to evaluate craniocervical posture and hyoid bone position in orthodontic patients with temporomandibular joint (TMJ) disc displacement. METHODS The subjects consisted of 170 female orthodontic patients who consented to bilateral magnetic resonance imaging of their TMJs. They were divided into 3 groups based on the results of magnetic resonance imaging of their TMJs: bilateral normal disc position, bilateral disc displacement with reduction, and bilateral disc displacement without reduction. Twenty-five variables from lateral cephalograms were analyzed with 1-way analysis of variance to investigate differences in craniocervical posture and hyoid bone position with respect to TMJ disc displacement status. Pearson correlation coefficients were calculated to analyze the relationships between craniofacial morphology and craniocervical posture or hyoid bone position. RESULTS Subjects with TMJ disc displacement were more likely to have an extended craniocervical posture with Class II hyperdivergent patterns. The most significant differences were found between patients with bilateral normal disc position and bilateral disc displacement without reduction. However, hyoid bone position in relation to craniofacial references was not significantly different among the TMJ disc displacement groups, except for variables related to the mandible. Pearson correlation coefficients indicated that extended craniocervical posture was significantly correlated with backward positioning and clockwise rotation of the mandible. CONCLUSIONS This suggests that craniocervical posture is significantly influenced by TMJ disc displacement, which may be associated with hyperdivergent skeletal patterns with a retrognathic mandible.