Seung-Hak Baek

Factors associated with the success rate of orthodontic miniscrews placed in the upper and lower posterior buccal region

OBJECTIVE To determine the success rate and the factors related to the success rate of orthodontic miniscrew implants (OMI) placed at the attached gingiva of the posterior buccal region. MATERIALS AND METHODS Four hundred eighty OMI placed in 209 orthodontic patients were examined retroactively. The sample was divided into young patients (range 10-18 years, N = 108) and adult patients (range 19-64 years, N = 109). The placement site was divided into three interdental areas from the first premolar to the second molar in the maxilla and mandible. According to soft tissue management, the samples were divided into incision and nonincision groups. Chi-square tests and multiple logistic regression analyses were used. RESULTS The overall success rate was 83.8%. Dislodgement of the OMI occurred most frequently in the first 1-2 months, and more than 90% of the failures occurred within the first 4 months. Sex, age, jaw, soft tissue management, and placement side did not show any difference in the success rate. Placement site, however, showed a significant difference in the mandible of adult patients. There was no difference in the success rate in the maxilla. CONCLUSIONS Placement site is one of the important factors for success rate of OMI.

Tissue-engineered growth of bone by marrow cell transplantation using porous calcium metaphosphate matrices

In this study we investigated not only osteoblastic cell proliferation and differentiation on the surface of calcium metaphosphate (CMP) matrices in vitro but also bone formation by ectopic implantation of these cell-matrix constructs in athymic mice in vivo. Interconnected porous CMP matrices with pores 200 microm in size were prepared to use as scaffolds for rat-marrow stromal-cell attachment. Cell-matrix constructs were cultured in vitro, and cell proliferation and ALPase activities were monitored for 56 days. In addition to their being cultured in vitro, cell-matrix constructs were implanted into subcutaneous sites of athymic mice. In vitro these porous CMP matrices supported the proliferation of osteoblastic cells as well as their differentiation, as indicated by high ALPase activity. In vivo the transplanted marrow cells gave rise to bone tissues in the pores of the CMP matrices. A small amount of woven bone formation was detected first at 4 weeks; osteogenesis progressed vigorously with time, and thick lamellar bones that had been remodeled were observed at 12 weeks. These findings demonstrate the potential for using a porous CMP matrix as a biodegradable scaffold ex vivo along with attached marrow-derived mesenchymal cells for transplantation into a site for bone regeneration in vivo.

Comparison of Stability between Cylindrical and Conical Type Mini-Implants

OBJECTIVE To investigate the mechanical and histologic properties of conical compared with cylindrical shaped mini-implants in terms of the success rate. MATERIALS AND METHODS The samples consisted of cylindrical and conical groups, and commonly had 1.6 mm diameter and 6.0 mm length (Jeil Medical Corporation, Seoul, Korea) placed in beagle dogs. The mechanical study for analyzing maximum insertion torque (MIT), maximum removal torque (MRT), and torque ratio (TR; MRT/MIT) in Sawbones (Pacific Research Laboratories Inc, Vashon, Wash), and the animal study for resonance frequency analysis (RFA) and histomorphometric analysis (bone-to-implant contact and bone area) in two beagle dogs were done. All measurements were statistically evaluated using independent t-tests to determine any difference in MIT, MRT, TR, RFA, bone-to-implant contact (BIC), and bone area (BA) between the cylindrical group and conical group. A P value less than 0.05 was considered significant. RESULTS The conical group showed significantly higher MIT and MRT than the cylindrical group in the mechanical study. However, there was no significant difference in RFA, BIC, and BA between the two groups in the animal and histomorphometric studies. CONCLUSIONS Although the conical shaped mini-implant could induce tight contact to the adjacent bone tissue and might produce good primary stability, the conical shape may need modification of the thread structure and insertion technique to reduce the excessive insertion torque while maintaining the high resistance to removal.

Comparison of frictional forces during the initial leveling stage in various combinations of self-ligating brackets and archwires with a custom-designed typodont system.

INTRODUCTION The purpose of this study was to compare the frictional force (FF) generated by various combinations of self-ligating bracket (SLB) types, archwire sizes, and alloy types, and the amount of displacement during the initial leveling phase of orthodontic treatment, by using a custom-designed typodont system. METHODS Two passive SLBs (Damon 2 [D2] and Damon 3 [D3]), and 3 active SLBs (SPEED [SP], In-Ovation R [IO], Time 2 [T2]), and SmartClip (SM) were tested with 0.014-in and 0.016-in austenitic nickel-titanium (A-Ni-Ti) and copper-nickel-titanium (Cu-Ni-Ti) archwires. To simulate malocclusion status, the maxillary canines (MXCs) were displaced vertically, and the mandibular lateral incisors (MNLIs) horizontally from their ideal positions up to 3 mm with 1-mm intervals. Static and kinetic FFs were measured with a speed of 0.5 mm per minutes for 5 minutes with a testing machine (model 4466, Instron, Canton, Mass). Two conventional brackets (Mini-Diamond [MD] and Clarity [CL]) were used as controls. Analysis of variance and Duncan tests were used for statistical purposes. RESULTS FF was increased in ascending order: D2, D3, IO, T2, SM, SP, CL, and MD in the maxillary typodont; and IO, D2, D3, T2, SP, CL, and MD in the mandibular typodont, regardless of archwire size and alloy type. The A-Ni-Ti wire showed significantly lower FF than did the Cu-Ni-Ti wire of the same size. As the amounts of vertical displacement of the MXCs and horizontal displacement of the MNLIs were increased, FF also increased. CONCLUSIONS These findings suggest that combinations of the passive SLB and A-Ni-Ti archwire during the initial leveling stage can produce lower FF than other combinations of SLB and archwire in vitro.

Surgery-first approach in skeletal class III malocclusion treated with 2-jaw surgery: evaluation of surgical movement and postoperative orthodontic treatment.

The purpose of this study was to evaluate the surgical movement and postoperative orthodontic treatment (POT) of the surgery-first approach for the correction of skeletal class III malocclusion. The samples consisted of 11 patients with skeletal class III malocclusion who underwent nonextraction treatment and 2-jaw surgery (Le Fort I osteotomy impaction of the posterior maxilla, IPM; bilateral sagittal split ramus osteotomy setback of the mandible). The wafer was removed 4 weeks after surgery. Mean (SD) durations of POT and total treatment were 8.91 (3.14) and 12.18 (3.57) months, respectively. Lateral cephalograms were obtained during the initial examination (T0), immediately after surgery (T1), and after debonding (T2). Sixteen variables were measured. Paired t-test was performed for statistical analysis. The maxilla rotated clockwise, and the nasolabial angle increased by IPM (FH-palatal plane angle, FH-occlusal plane angle, P < 0.01; nasolabial angle, P < 0.05) and well maintained during POT. The mandible was repositioned backward by bilateral sagittal split ramus osteotomy setback of the mandible (SNB, Pog-N perp, P < 0.001) and relapsed forward during POT (SNB, P < 0.01; Pog-N perp, P < 0.05). U1-SN decreased by IPM (P < 0.001) and relapsed labially owing to class III mechanics during POT (P < 0.01); eventually, no significant difference was found between T0 and T2 stages. Although IMPA increased by POT, there was no significant difference between T0 and T2 stages. The mandible seems to relapse forward immediately after wafer removal and before labioversion of the lower incisors. Accurate prediction of POT is crucial in controlling dental alignment, incisor decompensation, arch coordination, and occlusal settling. Long-term wearing and selective grinding of the wafer for labioversion of the lower incisors and use of miniplates/miniscrews to control the inclination of the upper incisor and to prevent relapse of the mandible are needed.

Effects of the diameter and shape of orthodontic mini-implants on microdamage to the cortical bone.

INTRODUCTION The purpose of this study was to investigate the effects of the diameter and shape of orthodontic mini-implants (OMIs) on microdamage to the cortical bone during implant placement. METHODS Twenty-eight self-drilling OMIs (Biomaterials Korea, Seoul, Korea; length, 6 mm; diameters, 1.5 and 2 mm; cylindrical and tapered shapes; classified as 1.5C, 2C, 1.5T, and 2T) were placed with a surgical device in the tibias of 7 New Zealand white rabbits (mature males; mean age, 6 months; mean weight, 3.1 kg). Four OMIs of each type per rabbit were placed randomly. Maximum insertion torque (MIT) was measured. Immediately after placement of the OMIs, the block of bone with the OMI was harvested. Cortical bone thickness was measured by using microcomputed tomography, and histomorphometric analyses of the number of cracks (NC), accumulated crack length (ACL), maximum radius of the crack (MRC), and longest crack (LC) were performed. Kruskal-Wallis and Mann-Whitney U tests with the Bonferroni adjustment were done for statistical analyses. RESULTS Increased diameter (1.5C<2C and 1.5T<2T) and tapering (1.5C<2T) resulted in increased values of MIT, NC, and LC (P <0.01, respectively). Similarly, with increased diameters (1.5C and 1.5T<2C and 2T), there were increases of ACL and MRC (P <0.001, respectively). However, there were no differences in the values of MIT, NC, ACL, MRC, and LC between the cylindrical and tapered OMIs with the same diameters (1.5C and 1.5T, 2C and 2T). CONCLUSIONS OMIs with larger diameters and tapered shapes caused greater microdamage to the cortical bone; this might affect bone remodeling and the stability of the OMIs.

Hard and soft tissue changes after correction of mandibular prognathism and facial asymmetry by mandibular setback surgery: Three-dimensional analysis using computerized tomography

OBJECTIVE To investigate the 3-dimensional (3D) changes in the hard and soft tissues of skeletal class III malocclusion (CIII) patients with or without facial asymmetry by mandibular setback surgery (MSS). STUDY DESIGN Seventeen adult CIII patients treated with MSS (bilateral sagittal split ramus osteotomy) who had 3D computerized tomography taken 1 month before (T0) and 6 months after (T1) MSS, were allocated into group 1 (symmetry, menton deviation (MD) <4 mm; n = 8) or group 2 (asymmetry, MD >4 mm; n = 9). The landmarks and variables were measured with Rapidform 2006 (Inus Technology). RESULTS Mandibular prognathism was significantly corrected in both groups. Facial asymmetry in group 2 was significantly corrected not only in the lower lip and chin but also in the philtrum deviation and mouth corner of the deviated side. The hard and soft tissue changes were more related in the horizontal and anteroposterior aspects than in the vertical one. CONCLUSION Three-dimensional evaluation showed a significant difference in the hard and soft tissue changes between symmetric and asymmetric MSS.

Skeletal sagittal and vertical facial types and electromyographic activity of the masticatory muscle.

OBJECTIVE To investigate the electromyographic activities of the anterior temporal (T) and masseter (M) muscles in different facial skeletal types. MATERIALS AND METHODS The samples consisted of 105 subjects (38 males and 67 females; mean age 22.0 +/- 6.7 years) and were classified into six groups according to the values of ANB and SN-GoMe: group 1 for Class I malocclusion and normodivergent type (n = 27), group 2 for Class I and hyperdivergent type (n = 20), group 3 for Class II and normodivergent type (n = 10), group 4 for Class II and hyperdivergent type (n = 23), group 5 for Class III and normodivergent type (n = 12), and group 6 for Class III and hyperdivergent type (n = 13). Temporal muscle activity (TMA), masseter muscle activity (MMA), and T/M ratio were evaluated at resting and clenching status. RESULTS Although there was no significant difference in resting MMA among all groups, group 6 showed a higher resting TMA than did other groups and a significant difference in resting T/M ratio compared with groups 1 and 3. There were no significant differences in clenching TMA and MMA among all groups. Although all groups showed a significant increase of TMA and MMA from resting to clenching status, group 6 showed a significant decrease of clenching T/M ratio compared with resting T/M ratio. CONCLUSIONS The results suggest that the more Class III and the more hyperdivergent type, the higher resting TMA and the lesser increase of clenching MMA than expressed by other groups. Significant differences existed in TMA and MMA according to sagittal and vertical facial skeletal types.

New treatment modality for maxillary hypoplasia in cleft patients. Protraction facemask with miniplate anchorage.

OBJECTIVE To present cleft patients treated with protraction facemask and miniplate anchorage (FM/MP) in order to demonstrate the effects of FM/MP on maxillary hypoplasia. MATERIALS AND METHODS The cases consisted of cleft palate only (12 year 1 month old girl, treatment duration = 16 months), unilateral cleft lip and alveolus (12 year 1 month old boy, treatment duration = 24 months), and unilateral cleft lip and palate (7 year 2 month old boy, treatment duration = 13 months). Curvilinear type surgical miniplates (Martin, Tuttlinger, Germany) were placed into the zygomatic buttress areas of the maxilla. After 4 weeks, mobility of the miniplates was checked, and the orthopedic force (500 g per side, 30 degrees downward and forward from the occlusal plane) was applied 12 to 14 hours per day. RESULTS In all cases, there was significant forward displacement of the point A. Side effects such as labial tipping of the upper incisors, extrusion of the upper molars, clockwise rotations of the mandibular plane, and bite opening, were considered minimal relative to that usually observed with conventional protraction facemask with tooth-borne anchorage. CONCLUSIONS FM/MP can be an effective alternative treatment modality for maxillary hypoplasia with minimal unwanted side effects in cleft patients.

Comparison of treatment outcome and stability between distraction osteogenesis and LeFort I osteotomy in cleft patients with maxillary hypoplasia.

The purpose of this study was to compare treatment outcome and relapse between maxillary advancement surgery with LeFort I osteotomy and maxillary distraction osteogenesis in patients with cleft lip and palate with maxillary hypoplasia. The sample consisted of a maxillary advancement surgery with LeFort I osteotomy group (group 1, N= 14, mean age, 21.7 years) and a maxillary distraction osteogenesis group (group 2, N = 11, mean age, 16.3 years). Lateral cephalograms were taken and traced at presurgery (T0), postsurgery (T1), and postretention (T2). Nine hard and four soft tissue cephalometric variables were measured. Differences in measurements at each stage, treatment outcome (T1-T0), and relapse (T2-T1) were compared between groups with independent t test. Because the amount of surgical movement could affect the amount of relapse, a difference in relapse between two groups was compared by analysis of covariance with the amount of surgical movement as a covariant. Although the amounts of forward movements of A point (P < 0.01), upper incisor (P < 0.001), and upper lip (P < 0.001) during T1-T0 were greater in group 2, there were no significant differences in the amounts of relapse (T2-T1) between the two groups. During T1-T0, counterclockwise rotation of the palatal plane was observed in group 2 as a result of downward movement of posterior nasal spine (PNS) at T1, whereas group 1 had clockwise rotation of palatal plane at T1 because of downward movement of anterior nasal spine (ANS). The amounts of relapse (T2-T1) in vertical movements of PNS and upper incisor were significantly different between the two groups (P < 0.05). The amount of required maxillary advancement, vector control of palatal plane, and vertical position of upper incisor would be important factors when planning a surgical treatment in patients with cleft lip and palate with midface hypoplasia.