Hyo-Sang Park

Group distal movement of teeth using microscrew implant anchorage.

The purpose of this study was to quantify the treatment effects of distalization of the maxillary and mandibular molars using microscrew implants. The success rate and clinical considerations in the use of the microscrew implants were also evaluated. Thirteen patients who had undergone distalization of the posterior teeth using forces applied against microscrew implants were selected. Among them, 11 patients had mandibular microscrew implants and four patients had maxillary implants, including two patients who had both maxillary and mandibular ones at the same time. The maxillary first premolar and first molars showed significant distal movement, with no significant distal movement of the anterior teeth. The mandibular first premolar and first and second molars showed significant distal movement, but no significant movement of the mandibular incisor was observed. The microscrew implant success rate was 90% over a mean application period of 12.3 +/- 5.7 months. The results might support the use of the microscrew implants as an anchorage for group distal movement of the teeth.

Density of the alveolar and basal bones of the maxilla and the mandible.

INTRODUCTION The purpose of this investigation was to quantitatively evaluate density of the alveolar and basal bones of the maxilla and the mandible. METHODS Sixty-three sets of computed tomographic (CT) images were selected, and bone density was measured with V-Works imaging software (Cybermed, Seoul, Korea). The sample consisted of 23 men (ages, 29 +/- 10.9 years) and 40 women (ages, 25.6 +/- 7.6 years). Cortical and cancellous bone densities at the alveolar and basal bones at the incisor, canine, premolar, molar, and maxillary tuberosity/retromolar areas were measured. RESULTS The cortical bone density of the maxilla ranged approximately between 810 and 940 Hounsfield units (HU) at the alveolar bone except for the maxillary tuberosity (443 HU at the buccal and 615 HU at the palatal alveolar bone), and between 835 and 1113 HU at the basal cortical bone except for tuberosity (542 HU). The cortical bone density of the mandible ranged between 800 and 1580 HU at the alveolar bone and 1320 and 1560 HU at the basal bone. The highest bone density in the maxilla was observed in the canine and premolar areas, and maxillary tuberosity showed the lowest bone density. Density of the cortical bone was greater in the mandible than in the maxilla and showed a progressive increase from the incisor to the retromolar area. CONCLUSIONS These data might provide valuable information when selecting sites and placement methods for miniscrew or microscrew implants in the dental arch.

Sliding mechanics with microscrew implant anchorage.

Three cases are illustrated. One was treated with maxillary microscrew implants, another with mandibular microscrew implants, and the third with both maxillary and mandibular microscrew implants. With the maxillary microscrew implants, the maxillary anterior teeth were retracted bodily with a slight intrusion and all the premolar extraction space was closed without loss of anchorage. Furthermore, the maxillary posterior teeth showed distal movement. The mandibular microscrew implants controlled the vertical position of the mandibular posterior teeth and played an important role in improving the facial profile. The efficacy of sliding mechanics with microscrew implant anchorage on the treatment of skeletal Class II malocclusion is also discussed.

Nonextraction treatment with microscrew implants.

The maxillary and mandibular posterior teeth were retracted with microscrew implants (1.2 mm in diameter and six to 10 mm long) that were placed into the alveolar bone and used as anchorage. The retraction proceeded without adverse reciprocal effects on the reactive part of the conventional mechanics, such as premolar extrusion and flaring of the incisors. The anterior crowding was resolved without any deleterious effect on the facial profile. En masse movement of the posterior teeth and the whole dentition after anterior tooth alignment can reducethe treatment period and maximize the efficiency of the treatment. The microscrew implants were maintained firmly throughout the treatment and were able to provide an anchorage for retraction of whole dentitions. The efficacy and potency of the microscrew implants aid mechanics in the nonextraction treatment of both labial and lingual treatments.

Four novel RUNX2 mutations including a splice donor site result in the cleidocranial dysplasia phenotype

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder caused by haploinsufficiency of the RUNX2 gene. In this study, we analyzed by direct sequencing RUNX2 mutations from eleven CCD patients. Four of seven mutations were novel: two nonsense mutations resulted in a translational stop at codon 50 (Q50X) and 112 (E112X); a missense mutation converted arginine to glycine at codon 131 (R131G); and an exon 1 splice donor site mutation (donor splice site GT/AT, IVS1 + 1G > A) at exon 1–intron junction resulted in the deletion of QA stretch contained in exon 1 of RUNX2. We focused on the functional analysis of the IVS1 + 1G > A mutation. A full‐length cDNA of this mutation was cloned (RUNX2Δe1) and expressed in Chinese hamster ovary (CHO) and HeLa cells. Functional analysis of RUNX2Δe1 was performed with respect to protein stability, nuclear localization, DNA binding, and transactivation activity of a downstream RUNX2 target gene. Protein stability of RUNX2Δe1 is similar to wild‐type RUNX2 as determined by Western blot analysis. Subcellular localization of RUNX2Δe1, assessed by in situ immunofluorescent staining, was observed with partial retention in both the nucleus and cytoplasm. This finding is in contrast to RUNX2 wild‐type, which is detected exclusively in the nucleus. DNA binding activity was also compromised by the RUNX2Δe1 in gel shift assay. Finally, RUNX2Δe1 blocked transactivation of the osteocalcin gene determined by transient transfection assay. Our findings demonstrate for the first time that the CCD phenotype can be caused by a splice site mutation, which results in the deletion of N‐terminus amino acids containing the QA stretch in RUNX2 that contains a previously unidentified second nuclear localization signal (NLS). We postulate that the QA sequence unique to RUNX2 contributes to a competent structure of RUNX2 that is required for nuclear localization, DNA binding, and transactivation function. J. Cell. Physiol. 207: 114–122, 2006.

Use of Flowable Composites for Orthodontic Bracket Bonding

OBJECTIVE To test the bonding characteristics of four flowable composites for orthodontic bracket bonding. MATERIALS AND METHODS Metal brackets were bonded to acid-etched human enamel using four flowable composites (Grandio Flow, GF; UniFil Flow, UF; UniFil LoFlo Plus, UL; and DenFil Flow, DF), an orthodontic bonding system (Transbond XT, TX), and a restorative composite (Filtek Z250, FZ). After 24 hours of storage in water at 37 degrees C, a shear bond strength (SBS) test was performed. After debonding, the adhesive remnant index (ARI) was assessed. In addition, the flow and flexural strength of the materials were examined. RESULTS The SBS for the flowable composites ranged between 7.2 and 8.3 MPa, and TX showed a significantly higher value (mean 10.9 MPa). The flowable composites also demonstrated a significantly superior flowability, yet inferior flexural strength (except for DF) than TX and FZ. Two flowable composites (GF and UL) produced significantly higher ARI scores than TX and FZ, which represented a larger resin remnant on the enamel surfaces after debonding. CONCLUSION When considering the SBS and ARI scores obtained in this study, flowable composites with no intermediate bonding resin could be conveniently applied for orthodontic bracket bonding.

Treatment effects and anchorage potential of sliding mechanics with titanium screws compared with the Tweed-Merrifield technique.

The purposes of this study were to quantify the treatment effects of titanium screws on en-masse retraction of 6 anterior teeth and to compare the anchorage potential of treatment with titanium screws with the Tweed-Merrifield technique, which requires patient compliance with a high-pull J-hook. Sixteen nongrowing patients (14 women, 2 men; ages, 22.5 +/- 4.8 years) who had been treated orthodontically for bialveolar protrusion were selected. All patients had 2 maxillary first premolars extracted, 13 had mandibular first premolars extracted, and 3 had second premolars extracted. Maxillary titanium screws were placed in all patients to provide anchorage for retraction of 6 anterior teeth. Screws were placed in 8 patients to apply intrusive force to the mandibular posterior teeth. To compare the anchorage potential with a high-pull J-hook, 14 nongrowing patients (11 women, 3 men; ages, 22.9 +/- 4.0 years) who were treated with the Tweed-Merrifield technique and had an excellent compliance with a high-pull J-hook were used. There was more anchorage loss of the maxillary posterior teeth in the Tweed-Merrifield group than in the titanium screw group. Both groups had excellent vertical control of the maxillary posterior teeth. There was a skeletal effect on the maxilla--reduction of A-point in the titanium screw group; this contributed to improvement of the facial profile. Treatment time in the titanium screw group was less compared with the Tweed-Merrifield technique. The success rate for the titanium screws was 87% in 25.6 +/- 5.5 months. These results suggest that titanium screws can provide acceptable and reliable anchorage and might produce skeletal effects on the maxilla.

Polymorphisms in the Matrilin-1 Gene and Risk of Mandibular Prognathism in Koreans

Previous linkage analysis of an Asian population proposed possible candidate genes for mandibular prognathism, such as Matrilin-1 (cartilage matrix protein). To investigate the association between the single-nucleotide polymorphisms (SNPs) in Matrilin-1 and mandibular prognathism, we investigated three sequence variants (-158 T>C, 7987 G>A, 8572 C>T) in 164 mandibular prognathism patients and 132 control individuals with a normal occlusion. The results showed that the 8572 TT genotypes in Matrilin-1 showed increased risk of mandibular prognathism (OR = 9.28, 95% Cl = 1.19~197.57, P < 0.05), whereas the 7987 AA genotype showed a protective effect for mandibular prognathism (OR = 0.16, 95% Cl = 0.05~0.47, P < 0.05). Genotyping results showed that the Matrilin-1 polymorphism haplotype TGC (ht4; 158T, 7987G, and 8572C alleles) had a pronounced risk effect for mandibular prognathism compared with controls (OR = 5.16, 95% Cl = 2.03~13.93, P < 0.01). The results suggest that polymorphisms in Matrilin-1 could be used as a marker for genetic susceptibility to mandibular prognathism.

Stability of Mandibular Setback Surgery With and Without Presurgical Orthodontics

PURPOSE The purpose of this study was to compare stability after mandibular setback surgery in patients with skeletal Class III malocclusion with and without presurgical orthodontics. MATERIALS AND METHODS This retrospective cohort study included consecutive patients with skeletal Class III malocclusion who underwent only mandibular surgery. Patients treated with the surgery-first approach without presurgical orthodontics (SF group) were compared with a control group (conventional surgery with presurgical orthodontics; CS group) using lateral cephalograms taken preoperatively, immediately postoperatively, and at the time of debonding. Predictor variables (group and timing), outcome variables (cephalometric measurements over time), and other variables, such as baseline characteristics, were evaluated to determine the difference in stability of mandibular positions such as the B point. RESULTS Sixty-one patients were enrolled in this study (CS group, n = 38; SF group, n = 23). Baseline demographic variables were similar in the 2 groups except for orthodontic treatment period. The mean setback of the mandible at the B point was similar (CS group, 8.7 mm; SF group, 9.1 mm; difference, P > .05), but the horizontal relapse in the SF group (2.4 mm) was significantly greater than in the CS group (1.6 mm; P < .05). Patients with a horizontal relapse greater than 3 mm comprised 39.1% of the SF group compared with 15.8% of the CS group (P < .05). CONCLUSION Mandibular sagittal split ramus osteotomy without presurgical orthodontic treatment was less stable than conventional orthognathic surgery for mandibular prognathism. Before performing a surgery-first approach, skeletal stability needs to be considered.

Effect of garlic on bacterial biofilm formation on orthodontic wire.

OBJECTIVE To examine the effect of garlic extract on the biofilm formation by Streptococcus mutans on orthodontic wire and on glucosyltransferase gene expression. MATERIALS AND METHODS Growth inhibition of oral bacteria was tested after 50 µL of garlic extract was placed on an agar plate. The minimum inhibitory concentration (MIC) of garlic extract on S mutans growth was first determined. After cultivating streptococci in biofilm medium (BM)-sucrose with garlic extract and orthodontic wire, adenosine triphosphate (ATP) measurement and viable cell counting was performed from the bacteria attached on the wire. Scanning electron microscopy (SEM) analysis of morphology was observed on bacterial cells attached to orthodontic wire. The effect of garlic extract on gene expression was evaluated using quantitative real-time polymerase chain reaction (PCR) of glucosyltransferase. RESULTS Though garlic extract had a clear antibacterial effect on all microorganisms, it also enhanced S mutans attachment on orthodontic wire. Low concentration of garlic extract also increased glucosyltransferase gene expression of S mutans. CONCLUSIONS Despite its antibacterial function, garlic extract increases biofilm formation by S mutans to orthodontic wire, likely through upregulation of glucosyltransferase expression. Garlic extract may thus play an important role in increased bacterial attachment to orthodontic wires.