Chooryung J. Chung

Nasal Changes after Surgical Correction of Skeletal Class III Malocclusion in Koreans

OBJECTIVE To quantify the changes in the nose after bimaxillary surgery to correct skeletal Class III malocclusion and to test the hypothesis that there is no change in the nasal width following bimaxillary surgical correction of skeletal Class III when a nasal cinch is properly used. MATERIALS AND METHODS Sixty-five adult Korean skeletal Class III patients who had received maxillary advancement/impaction and mandibular set-back surgery in conjunction with an alar base cinch suture were evaluated. The anthropometric variables of the nasal region were measured directly on the soft-tissue surface before and 6 months after surgery. RESULTS After surgery, the alar width and alar base width had increased significantly (P < .001), while the nasal tip projection decreased (P < .001). The nostril morphology also showed widening (P < .001). There was a trend for females with a narrow alar width presurgically to have a larger amount of nasal widening compared with those with a broader alar width (P < .05). CONCLUSION There is a high probability of nasal and nostril widening after bimaxillary surgery for skeletal Class III malocclusion in Koreans despite the careful performance of alar cinch suture. Nevertheless, the authors believe that alar cinch suture was positive in limiting the nasal widening to the minimum and would consider routine application during bimaxillary surgery for skeletal Class III especially for female patients with a narrow nose who are susceptible to these changes.

OPN deficiency suppresses appearance of odontoclastic cells and resorption of the tooth root induced by experimental force application.

Osteopontin (OPN) is a major non‐collagenous bone matrix protein implicated in the regulation of cell function. Although OPN is rich in the cementum of the tooth, the significance of OPN in this tissue is not understood. Tooth root resorption is the most frequent complication of orthodontic tooth movement (TM). The objective of this study was to examine the pathophysiological role of OPN in cementum of the tooth root. For this purpose, the upper right first molar (M1) in OPN‐deficient and wild‐type (WT) mice was subjected to mechanical force via 10 gf NiTi coil spring while the left side molar was kept intact to serve as an internal control. Micro‐CT section and the level of tartrate resistant acid phosphatase (TRAP)‐positive cells on the tooth root surface defined as odontoclasts were quantified at the end of the force application. In WT mice, force application to the tooth caused appearance of odontoclasts around the mesial surface of the tooth root resulting in tooth root resorption. In contrast, OPN deficiency significantly suppressed the force‐induced increase in the number of odontoclasts and suppressed root resorption. This force application also induced increase in the number of TRAP‐positive cells in the alveolar bone on the pressure side defined as osteoclasts, while the levels of the increase in osteoclastic cell number in such alveolar bone were similar between the OPN‐deficient and WT mice. These observations indicate that OPN deficiency suppresses specifically tooth root resorption in case of experimental force application. J. Cell. Physiol. 214: 614–620, 2008.

Morphological characteristics of the symphyseal region in adult skeletal Class III crossbite and openbite malocclusions.

OBJECTIVE To evaluate the relationship of the morphological characteristics of the symphyseal region of adult Class III malocclusion to the differences in overjet and overbite. MATERIALS AND METHODS The basal and symphyseal widths along with the alveolar and symphyseal heights were evaluated using data from the lateral cephalograms of Korean adult male skeletal Class III, divided into crossbite (n = 28) and openbite (n = 41) groups. Korean male normal occlusion samples (n = 32) were used as controls. RESULTS The width of the symphyseal region including the basal width, point B width, Id width, symphyseal thickness, and pogonion width were similar in adult Class III crossbite and normal occlusion groups, but significantly less in the adult Class III openbite group (P < .001). The alveolar height was similar in the adult Class III crossbite and control groups, but significantly less in the adult Class III openbite group (P < .05). However, the symphyseal height was similar in all three groups. CONCLUSIONS An openbite, rather than a negative overjet, is the major factor influencing the symphyseal morphology in an adult Class III malocclusion.

Photocatalytic Antibacterial Effect of TiO 2 Film of TiAg on Streptococcus mutans

OBJECTIVE To test through various oxidation procedures the differences in antibacterial activities against Streptococcus mutans (S mutans) of Titanium (Ti) and Titanium silver (TiAg) metals coated with TiO(2). MATERIALS AND METHODS This study examined the photocatalytic antibacterial effects on S mutans of Ti and TiAg ubstrates coated with two crystalline forms of TiO(2) by thermal and anodic oxidation. A bacterial suspension of S mutans was pipetted onto TiO(2)-coated metal specimens and uncoated specimens with ultraviolet A (UVA) illumination for 20 to 100 minutes. The same specimen without UVA was used as the control. The level of colony-forming units of S mutans after UVA illumination was compared with that of the control. RESULTS The level of colony-forming units of S mutans was significantly lower on TiO(2)-coated Ti and TiAg metal specimens after UVA illumination than on uncoated Ti and TiAg specimens. The level of colony-forming units of S mutans was significantly lower on the metals coated by anodic oxidation than on those coated by thermal oxidation. The TiO(2) coating on TiAg had a significantly higher and more rapid antibacterial effect than did the TiO(2) coating on Ti. CONCLUSIONS The antibacterial effect of a TiO(2) film formed by anodic oxidation was superior to that formed by thermal oxidation. The addition of Ag to the Ti specimen indicated a synergistic effect on the photocatalytic antibacterial property against S mutans.

Vertical Control by Combining a Monoblock Appliance in Adult Class III Overclosure Treatment

Monoblock appliances were used in combination with intermaxillary elastics for treatment of adult skeletal Class III patients. The patients showed predisposing upper incisors problems, significant mobility in patient 1 and root resorption in patient 2, which contraindicated direct intrusion of the incisors. Using the monoblock with selective extrusion of the molars, a clockwise rotation was induced to reduce overbite and to achieve a better profile. It was also possible to reduce the excessive force to the upper incisors during and after treatment, which improved incisor mobility to a physiologic extent (patient 1) and prevented further progression of root resorption (patient 2). Stability was high after the 2-year follow-up, which suggests a stable vertical control approach by using the monoblock appliance in combination with a fixed appliance in adults.

Nonsurgical and nonprosthetic camouflage treatment of skeletal Class II open bite with bilaterally missing lower first molars

This report illustrates the successful nonsurgical and nonprosthetic camouflage treatment of a skeletal Class II open bite malocclusion combined with missing mandibular first molars bilaterally. In the mandible, the second and third molars were uprighted and protracted, substituting for the missing first molars. In the maxilla, anterior bodily retraction and full-arch intrusion were achieved following premolar and second molar extraction, which also induced autorotation of the mandible. The treatment outcome and prognosis were confirmed with three-dimensional superimposition techniques, along with long-term stability.

Apical root displacement is a critical risk factor for apical root resorption after orthodontic treatment

OBJECTIVES: To identify risk factors for apical root resorption (ARR) of maxillary and mandibular incisors using mathematical quantification of apical root displacement (ARD) and multiple linear mixed-effects modeling. MATERIALS AND METHODS: Periapical radiographs of maxillary and mandibular incisors and lateral cephalograms of 135 adults were taken before and after orthodontic treatment. ARR was measured on the periapical radiographs, and movement of central incisors was evaluated on the superimposed pre- and posttreatment lateral cephalograms. ARD was mathematically calculated from pretreatment tooth length, inclination change, and movement of the incisal edge. Linear mixed-effects model analysis was performed to identify risk factors for ARR, and standardized coefficients (SCs) were calculated to investigate the relative contribution of the risk factors to ARR. RESULTS: Vertical ARD showed the highest SCs for both maxillary and mandibular incisors. Horizontal ARD showed the second highest SC for mandibular incisors but was not significantly correlated with the ARR of maxillary incisors. When horizontal and vertical ARDs were included in the mixed-effects model, the use of self-ligating brackets was significantly correlated with increased ARR of mandibular incisors. CONCLUSIONS: ARD is a critical factor for ARR after orthodontic treatment. Careful monitoring of ARR is recommended for patients requiring significant ARD of incisors.

Correlation between the cross-sectional morphology of the mandible and the three-dimensional facial skeletal pattern: A structural equation modeling approach

OBJECTIVE: To clarify the relationship between the cross-sectional morphology of the mandible and vertical, transverse, and anteroposterior facial skeletal patterns using statistical shape analysis and structural equation modeling (SEM). MATERIALS AND METHODS: We used 150 cone beam computed tomography (CBCT) images to obtain three-dimensional (3D) facial landmarks and cross-sectional images of the mandible. The morphology of the inner and outer cortices of the mandible was analyzed using statistical shape analysis, including generalized Procrustes analysis and principal component analysis (PCA). Factor analysis was performed to determine factors pertaining to the skeletal measurements and shape variations for the inner and outer cortices, following which a structural equation model was constructed. RESULTS: Using factor analysis, characteristics of the vertical, transverse, and anteroposterior facial skeletal patterns were determined. PCA of the cross-sectional morphology of the mandible revealed 70% of the cumulative proportion by PC1 and PC2 after generalized Procrustes superimpositions. SEM showed complex relationships between the facial skeletal patterns and variations in the cross-sectional morphology of the mandibular cortices. The influence of the transverse factors on the outer cortex as a latent variable was relatively significant ( P = .057). However, the influence of the vertical factors on the outer and inner cortices was not significant. CONCLUSIONS: The transverse skeletal pattern is associated with the morphology of the outer cortex of the mandible.

A 15-year follow up of an orthodontic treatment including a lower incisor extraction and keeping the maxillary canine–premolar transposition

Lower incisor extraction is an effective option for treating lower anterior crowding in patients with a good facial profile, Class I molar occlusion, and narrow upper incisors. This report describes the successful treatment of an adolescent patient with lower anterior crowding and a transposed maxillary canine and premolar treated by extracting a lower incisor and keeping the transposed positions of the teeth. With the use of retainers, treatment results were stable up to the 2-year postretention visit. However, upon a 15-year postretention appointment, the fixed retainer had been removed and the removable retainer was no longer in use, which resulted in relapse of lower anterior alignment. Moreover, the transposed canine had extruded during this period, causing occlusal interference and gingival recession, as well as loss of tooth vitality, which indicates the importance of maintaining orthodontic retainers for long-term stable occlusion.

Changes in occlusal function after extraction of premolars: 2-year follow-up

OBJECTIVE To determine the effects of extraction and the number of teeth extracted on changes in occlusal function by measuring occlusal contact area and force before and after orthodontic treatment with a fixed appliance. MATERIALS AND METHODS Female patients treated with a fixed appliance were divided into nonextraction (n = 36), two maxillary premolar extraction (n = 31), and four premolar extraction (n = 18) groups. Bite pressure-sensitive films were used to analyze the occlusal contact area and force. Measurements were performed before treatment (Pre-Tx), immediately afterward (After-Tx), and 2 years later (2Y After-Tx). The data were analyzed using a linear mixed model and the post hoc Bonferroni test. RESULTS The occlusal contact area and force after treatment decreased significantly compared with Pre-Tx values but were increased 2 years later in all groups. There were no significant differences in occlusal contact area or force during the entire observation period among the three groups (P > .05). The occlusal contact area and force in the nonextraction and two maxillary premolar extraction groups recovered to Pre-Tx levels 2 years later (P > .05). The occlusal contact area in the four premolar extraction group was significantly lower than the Pre-Tx level after 2 years of retention (P < .05). CONCLUSIONS The occlusal contact area and force showed a tendency to decrease immediately after treatment and then gradually increase to pretreatment levels during the observation period. However, the occlusal contact area did not recover fully after 2 years in the four premolar extraction group.