Influence of facial width on the perception of lip protrusion and its differences between profile and 3-dimensional video clip.

INTRODUCTION: This study evaluated the influence of facial width on the perception of lip protrusion and investigated the concordance between 2-dimensional (2D) profile images and 3-dimensional (3D) video clips in assessing lip protrusion. METHODS: An Asian female standard head model was created using 3D modeling software. Eight head models were constructed by modifying the standard head model in terms of facial width (broad, neutral, and slim) and lip protrusion (retrusive, straight, and protrusive). Overall, 97 Asian raters rated the lip protrusion from the 2D profiles and 3D rotation video clips of the 9 models. RESULTS: No significant differences were found in the perception of lip protrusion in terms of sex, age, or occupation. Compared with the 2D profiles, the 3D video clips were rated as more protrusive in 8 of the 9 head models, with the retrusive broad, retrusive neutral, straight broad, and straight slim faces showing statistical significance (P <0.01). The rating is significantly higher in slim faces than in broad faces across the 3 groups of 2D profiles (P <0.01). For 3D video clips, the rating was higher in slim faces than in broad faces in all 3 groups, whereas differences were significant in the straight and protrusive groups only (P <0.01). CONCLUSIONS: In this study, 3D video clips were more sensitive to the perception of lip protrusion than were 2D profiles to some extent. The lips were rated relatively more protrusive in a slim face than in a broad face. Therefore, the relationship between facial width and lip protrusion should be considered in orthodontic treatment goals and treatment plans.

Recovery bone formation on radiographic palatal bone dehiscences after incisor retraction with microimplants.

OBJECTIVES: To investigate the difference in labial and palatal alveolar bone thickness and height during the retention period after incisor retraction treatment with microimplant. MATERIALS AND METHODS: A sample of 21 patients (mean age: 17.80 ± 4.38 years) who underwent incisor retraction treatment using microimplants after premolar extraction was investigated. The cone-beam computed tomography images at pretreatment, posttreatment, and retention were used to measure anterior alveolar bone thickness (labial, palatal, and total; at three vertical levels) and height (labial and palatal) and differences in the incisor position during treatment or retention. Repeated-measures analysis of variance with Bonferroni correction was performed to compare the variables at T0, T1, and T2. RESULTS: The maxillary central incisor moved posteriorly by approximately 8.0 mm along with intrusive movement of 1.8 mm after treatment. The alveolar bone thickness significantly decreased on the palatal side and increased on the labial side after treatment. Thereafter, the palatal bone thickness significantly increased and labial bone thickness decreased during the retention period. The palatal interdental bone depressed by incisor retraction showed substantial bone deposition after retention. CONCLUSIONS: Radiographic palatal bone dehiscences on the incisor root and palatal bone depression between the incisor roots were apparent after treatment. This palatal bone loss around the incisor roots noticeably recovered with newly formed bone during retention.

The effect of different mechanical retention forms on shear bond strength of rebonding of ceramic brackets.

The objective of this study is to compare the shear bond strength (SBS) and the morphological characteristics and chemical compositions of the base surface of newly bonded and rebonded ceramic brackets with different mechanical retention bases. Sixty extracted human premolars were divided into the newly bonded and rebonded groups. Ceramic brackets with patterned, laser-etched, and particle-coated patterned bases were randomly bonded to the tooth samples in each group (n=10 per base type). The rebonded brackets exhibited significantly lower SBS than the newly bonded brackets (p<0.05). The main chemical composition of the brackets in both groups was aluminum on the energy-dispersive X-ray spectroscopy. Scanning electron microscopy imaging showed the presence of regular-shaped undercuts or irregular micro-undercuts on the bracket bases which mostly remained intact even after debonding and sandblasting, while coated particles disappeared. The rebonded ceramic brackets with mechanical retention bases exhibited clinically acceptable bond strength regardless of retentive forms.

Differences in facial soft tissue deviations in Class III patients with different types of mandibular asymmetry: A cone-beam computed tomography study.

Objective: : This study assessed the differences in soft tissue deviations of the nose, lips, and chin between different mandibular asymmetry types in Class III patients. Methods: : Cone-beam computed tomography data from 90 Class III patients with moderate-to-severe facial asymmetry were investigated. The sample was divided into three groups based on the extent of mandibular rolling, yawing, and translation. Soft tissue landmarks on the nose, lips, and chin were investigated vertically, transversely, and anteroposteriorly. A paired t test was performed to compare variables between the deviated (Dv) and nondeviated (NDv) sides, and one-way analysis of variance with Tukey's post-hoc test was performed for intergroup comparisons. Pearson's correlation coefficient was calculated to assess the relationship between the soft and hard tissue deviations. Results: : The roll-dominant group showed significantly greater differences in the vertical positions of the soft tissue landmarks between the Dv and NDv than other groups (P < 0.05), whereas the yaw-dominant group exhibited larger differences in the transverse and anteroposterior directions (P < 0.05). Moreover, transverse lip cant was correlated with the menton (Me) deviation and mandibular rolling in the roll-dominant group (P < 0.001); the angulation of the nasal bridge or philtrum was correlated with the Me deviation and mandibular yawing in the yaw-dominant group (P < 0.01). Conclusions: : The three-dimensional deviations of facial soft tissue differed based on the mandibular asymmetry types in Class III patients with similar amounts of Me deviation. A precise understanding of soft tissue deviation in each asymmetry type would help achieve satisfactory facial esthetics.

Mandibular asymmetry types and differences in dental compensations of Class III patients analyzed with cone-beam computed tomography.

OBJECTIVES: To assess differences in dental compensation of the incisors and first molars in skeletal Class III patients with roll-, yaw-, and translation-dominant mandibular asymmetries. MATERIALS AND METHODS: A total of 90 skeletal Class III adult patients (mean age, 22.00 ± 3.31 years; range, 18-37.9 years) with facial asymmetry were enrolled and divided into the roll-, yaw-, and translation-dominant type groups (n = 30 per group). The vertical, transverse, and anteroposterior distances and axial angles of the teeth were measured using cone-beam computed tomography images. The measurements were compared between the deviated and nondeviated sides using a paired t-test and among the three groups using one-way analysis of variance with a Tukey post hoc test. RESULTS: The roll-dominant groups showed the greatest values for the bilateral difference in the vertical position of the maxillary (2.42 ± 1.24 mm) and mandibular molars (2.23 ± 1.28 mm; P < .001). The transverse deviations of the maxillary (2.19 ± 1.51 mm) and mandibular incisors (-2.11 ± 1.39 mm) were greater in the yaw-dominant groups than those of other groups. Regarding tooth axial angle, the yaw-dominant group showed the greatest tipping of the mandibular incisor (-4.13 ± 3.30°; P < .001). CONCLUSIONS: Dental compensation differed depending on the type of facial asymmetry. The roll-dominant type showed more vertical compensation of the posterior teeth, whereas the yaw-dominant type exhibited more tipping of the molars and incisors. By precisely assessing dental compensation in each asymmetry type, sufficient dental decompensation could be achieved.

Differences in positions of cone-beam computed tomography landmarks in patients with skeletal Class III facial asymmetry according to midsagittal planes.

Objective: This study aimed to clarify differences in the positions of cone-beam computed tomography (CBCT) landmarks according to different midsagittal planes (MSPs) in patients with skeletal Class III facial asymmetry. Methods: Pre-treatment CBCT data from 60 patients with skeletal Class III were used. The patients were classified into symmetric (menton deviations of < 2 mm) or asymmetric (menton deviations of > 4 mm) groups. Six MSPs were established based on previous studies, and three-dimensional analyses were performed for the planes in both the groups. The measurement outcomes were compared statistically. Results: A statistically significant interaction (p < 0.01) was observed between MSPs and facial asymmetry. No significant differences were observed among MSPs in the symmetric group. However, significant differences in linear measurements were identified among MSPs in the asymmetric group. Specifically, the upper facial MSP revealed both maxillary and mandibular transverse asymmetries. On the other hand, anterior nasal spine (ANS)-associated MSP could not identify maxillary asymmetry. Furthermore, the menton deviation was approximately 3 mm lower when estimated using the ANS-associated MSP than that using upper facial MSP. Conclusions: The choice of MSP can significantly affect treatment outcomes while diagnosing patients with asymmetry. Therefore, care should be taken when selecting MSP in clinical practice.

Minimum required length of orthodontic microimplant: a numerical simulation and clinical validation.

INTRODUCTION: This study aimed to determine the minimum required length of microimplants (MIs) to prevent excessive micromotion during MI healing that can lead to MI failure. METHODS: Hypothesizing that the implantation depth of MI in cancellous bone (IDcancel) is the key to the control of micromotion during MI healing, we numerically investigated the minimum IDcancel required to maintain MI micromotion to below the threshold (30 µm) that would threaten MI survival. Twenty MI and bone models were built using MIs of 4 lengths and bone specimens with 5 different cortical bone thicknesses to create IDcancel in the 0.5-5.5 mm. Then, applying a horizontal force of 1.5 N on the MI head, we calculated the micromotion (peak and average MI micromotions) and determined the minimum IDcancel. A clinical test was performed to verify the numerical result by placing 160 MIs in the posterior maxilla and mandible. RESULTS: A strong correlation (r2= 0.694) was found to exist between IDcancel and MI micromotion. A minimum of 2.5 mm of IDcancel was needed to maintain the level of MI micromotion (peak micromotion) <30 µm threshold. The 6-month survival rate of MI was strongly correlated with IDcancel (r2= 0.744) and decreased sharply when IDcancel was ≤2 mm. CONCLUSIONS: The minimum lengths of MIs to provide the minimum IDcancel of 2.5 mm required to promote successful MI healing in the posterior maxilla and mandible are 5.2 and 6.5 mm, respectively.

Use of a novel body mandibular plane (mental foramen-protuberance menti) in analyzing mandibular asymmetry compared with conventional border mandibular plane.

OBJECTIVES: To compare a novel body mandibular horizontal plane (mental foramen-protuberance menti; Body-MHP) with the conventional border mandibular horizontal plane (gonion-menton [Me]; Border-MHP) to assess mandibular body inclination and dental compensation of skeletal Class III patients with and without facial asymmetry. MATERIALS AND METHODS: Retrospective data obtained from diagnostic cone-beam computed tomography of 90 skeletal Class III patients (mean age, 21.67 ± 2.93 years; range, 15.0-30.6 years) were divided into symmetry (n = 30) and asymmetry groups (n = 60). The asymmetry group was subdivided into roll (n = 30) and non-roll types (n = 30). The differences in body inclination and dental measurements (distance and angle) according to two mandibular planes (Body-MHP and Border-MHP) were assessed in the groups and subgroups. RESULTS: Mandibular body inclinations relative to the Body-MHP were not different in the roll-type asymmetric mandible between the sides, while those relative to the Border-MHP were different (P < .001). For the mandibular first molar positions relative to the Border-MHP, the differences in vertical distance between the sides were undermeasured and the inclination differences were overmeasured when compared relative to the Body-MHP. CONCLUSIONS: The Body-MHP demonstrated better bilateral similarity in body inclination compared with the Border-MHP in patients with roll-type facial asymmetry. The novel body mandibular plane ensures an accurate diagnosis for tooth movement and jaw surgery, particularly in the roll-type asymmetric mandible.

Nonsurgical orthodontic correction of facial asymmetry by condylar remodeling and mandibular repositioning following occlusal cant correction with microimplants: a case report.

Recently, the demand for correcting facial asymmetry has been increasing, even when the extent of asymmetry is small. This case report describes nonsurgical orthodontic treatment for facial asymmetry in a 13-year-old female patient, facilitated by moving the deviant mandible to the nondeviated side after correcting for relevant dental compensation using microimplants. Mandibular repositioning was attempted using intermaxillary elastics between the microimplants placed into each jaw and guided by resin that was bonded on the maxillary first molar of the deviated side. To enhance mandibular movement, correction of the transverse occlusal cant and buccolingual inclination of the teeth were also performed. After 65 months of gradual treatment, facial symmetry, with favorable occlusion and jaw function, was achieved. These satisfactory results, including a well-balanced face and good occlusal interdigitation, were well maintained at the 53-month follow-up. Direct and functional forces applied against deviant functional forces can reduce facial asymmetry by differential growth or modeling of the condyle.

Evidence-based selection of orthodontic miniscrews, increasing their success rate in the mandibular buccal shelf. A randomized, prospective clinical trial.

BACKGROUND: Skeletal anchorage has made it possible to perform complex orthodontic tooth movements that are difficult or even impossible to achieve with conventional orthodontic treatment. Mandibular buccal shelf miniscrews, used for distalization, play a particularly important role in treatment of Class III malocclusion. Unfortunately, stability of the miniscrews placed in the mandible is still considered at higher risk of failure compared to other intraoral locations. The aim of our study was to determine the influence of the miniscrew size on their long-term stability, occurrence of oral mucosa inflammation and pain lasting over 48 h after implantation. METHODS: 184 Absoanchor® miniscrews (Dentos, South Korea) in two sizes: SH2018-10 (length 10 mm, ø 1.8-2.0 mm) and SH1514-08 (length 8 mm, ø 1.4-1.5 mm) were inserted in the mandibular buccal shelf in 92 Caucasians aged 20-50 years, diagnosed with Class III malocclusion that required en-masse distalization of the mandibular dentition. Data was statistically analyzed with the level of significance set at p = .05. RESULTS: 91.3% of the SH2018-10 and 75% of the SH1514-08 miniscrews were stable, and this difference was statistically significant (p < .05). Inflammation of the oral mucosa was noticed around both types of miniscrews and affected 50% of the SH2018-10 and 26.09% of the SH1514-08 group (p < .05). Pain lasting longer than 48 h after implantation was related to 60.87% and 20.65% of the SH2018-10 and the SH1514-08 miniscrews (p < .05), respectively. Inflammation associated with larger SH2018-10 miniscrews did not affect their stability (p > .05), contrary to the SH1514-08 ones (p < .05). When inflammation was present, the overall success rate declined to 64.29%, from 94.74% noted for TADs without inflammation. According to the log-rank test, smaller TADs failed significantly sooner than the larger ones (p = .002). CONCLUSION: Larger SH2018-10 miniscrews are the anchorage of choice for the mandibular buccal shelf, despite triggering inflammation and long-lasting pain significantly more often than the smaller ones. Therefore, this issue should be discussed with every patient prior to miniscrew use. Trial registration ID: ClinicalTrials.gov Identifier: NCT05280678 Date of Registration: 15/03/2022. Retrospectively registered.

Influence of late removal after treatment on the removal torque of microimplants.

Objective: To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors. Methods: The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque. Results: The mean period of total in-bone stay of microimplants in the postretention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4-5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively. Conclusions: The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

Correlation between insertion torque and peri-implant bone strain during placement of orthodontic mini-implants: A finite element study.

INTRODUCTION: Insertion torque is the amount of torque exerted on the implant to tighten into the bone. We investigated whether insertion torque values could be correlated with the strain level in the peri-implant cortical bone resulting from mini-implant insertion. METHODS: The insertion of a standard size mini-implant (φ 1.4 mm × 7 mm) into maxillary alveolar bone was simulated using the finite element method. A total of 3600 calculation steps were employed to numerically reproduce the mini-implant insertion process and analyze the insertion torque and strain distribution in bone. Special attention was given to the relationship between insertion torque values and strain level in the cortical bone at the final tightening. The strain level was quantified using the following 3 strain parameters: (1) average insertion strain, (2) peak insertion strain recorded near the mini-implant thread tips, and (3) the size of the damage zone in the cortical bone. Correlations between the insertion torque values and these 3 parameters were analyzed using linear regression. RESULTS: Direct proportionality and strong correlation were found between the insertion torque values and each of the 3 strain parameters: average insertion strain (r2 = 0.91), peak insertion strain (r2 = 0.91), and the size of damage zone (r2 = 0.90) in the peri-implant cortical bone. CONCLUSIONS: The results of this finite element method study demonstrated that insertion torque could serve as a reliable indicator of the strain level in the peri-implant cortical bone resulting from mini-implant insertion.

Treatment of severe mandibular deficiency following TMJ ankyloses by distraction osteogenesis and orthodontic treatment with microimplants.

Severe mandibular deficiency caused by temporomandibular joint (TMJ) ankyloses produces functional and aesthetic problems that require complicated long-term treatment. In this case report, we describe the benefits of using microimplant mechanics for controlling the direction of distraction during distraction osteogenesis and for performing the movement of teeth. We also present its remarkable results and long-term stability. A 20-year-old girl presented with a convex profile due to severe mandibular retrognathia after a history of several TMJ surgeries for bilateral TMJ ankyloses. Mandibular distraction osteogenesis (MDO) was performed, and elastics were placed between the microimplants to control the direction of distraction. Subsequently, after retraction of the maxillary anterior teeth and distalisation of the whole mandibular dentition, the facial profile was markedly improved, and good interdigitation was obtained. The six-year follow-up retention and overall stability were satisfactory with good interdigitation and jaw function.

Long-term evaluation of factors affecting removal torque of microimplants.

BACKGROUND: The current study aimed to evaluate factors affecting the long-term stability of microimplants using removal torque and the correlation between removal torque and clinical variables. MATERIALS AND METHODS: This research evaluated 703 microimplants placed in 354 patients (mean age: 30.4 ± 12.1 years). The removal torque was evaluated according to various clinical variables including sex, age, placement site, microimplant size, and placement method (self-drilling versus pre-drilling). Pearson correlation and stepwise multiple linear regression analyses were performed to investigate different variables and their association with removal torque. RESULTS: The mean removal torque was significantly higher in the mandible (4.46 N cm) than in the maxilla (3.73 N cm). The values in the posterior teeth/retromolar areas were significantly higher than those in the anterior teeth area. There were no significant difference in terms of sex. Teenagers had a lower removal torque than older adults in the mandible, but not in the maxilla. Microimplants with a greater length and diameter, except for those with a greater diameter in the maxilla, was associated with a higher removal torque. Regardless of placement torque, the removal torque convergently reached approximately 4 N cm in both placement methods. The removal torque was significantly correlated with screw length in the self-drilling group and with diameter in the pre-drilling group. CONCLUSIONS: Removal torque was related with placement site, age, placement method, and length and diameter of microimplants.

Does maxillary yaw exist in patients with skeletal Class III facial asymmetry?

INTRODUCTION: This study aimed to evaluate maxillary skeletal and dental yaw in patients with skeletal Class III facial asymmetry and investigate its correlation with menton deviation. METHODS: Initial cone-beam computed tomography data from 60 patients with skeletal Class III malocclusion were used. There were 30 patients in both the symmetrical group (menton deviation <2 mm) and the asymmetrical group (menton deviation >4 mm). After reconstruction of 3-dimensional (3D) cone-beam computed tomography data, maxillary yaw and 3D positions of skeletal and dental landmarks were measured and compared between the groups. After that, correlations between menton deviation and the other variables were assessed. RESULTS: No significant difference was noted in maxillary skeletal and dental yaw between the 2 groups. In the assessment of 3D positions, translation of the maxillary bone and maxillary dentition toward the menton deviation was observed (P <0.01). Maxillary skeletal and dental yaw was not significantly correlated with menton deviation in the asymmetrical group. CONCLUSIONS: Maxillary skeletal and dental yaw was not evident in either group. Therefore, when planning maxillary surgery for patients with skeletal Class III facial asymmetry malocclusion, it may be appropriate to shift the focus of decompensation from maxillary yaw to maxillary translation.

Optimal microimplant sites in the mandibular retromolar area: mesh analysis of cortical bone thickness and density in CBCT images / Sitios de microimplantes óptimos en el área retromolar mandibular: análisis de malla del grosor y densidad del hueso cortical en imágenes CBCT

SUMMARY: This study was performed to identify optimal microimplant sites in the mandibular retromolar area by measurement and analysis of cortical bone thickness and density. Forty-nine records of cone-beam computed tomography were selected from 173 patients. Invivo 5.2 software was used to measure the thickness and density of 25 sites on a mesh in the mandibular retromolar area. Pearson correlation, Spearman correlation, and binary logistic regression analyses were performed to explore correlations between retromolar measurements and patient characteristics. The LSD test was used to identify optimal microimplant sites in this area. One-way ANOVA, with post hoc SNK test, was used to compare optimal microimplant sites among the retromolar area, the distobuccal bone of the second molar, and a location between the first and second molars. The mean thickness and density of mandibular retromolar cortical bone were 2.35 ± 0.76 mm and 530.49 ± 188.83 HU, respectively. In the mandibular retromolar area, the thickness and density of cortical bone increased from the lingual to buccal sides, and from the distal to mesial. Among 25 sites, S5C1 had the greatest thickness and density; it exhibited greater thickness and density, compared with the distobuccal bone of the second molar and the site between the first and second molars. For distal uprighting of mesially tipped molars, we recommend placement of microimplants into the retromolar distobuccal site; for distalization of mandibular dentition, we recommend placement of microimplants into the retromolar mesiobuccal site (S5C1) or 2 mm from the mesial direction of the second molar distobuccal site (B).

RESUMEN: Este estudio se realizó para identificar los sitios óptimos de microimplantes en el área retromolar mandibular mediante la medición y el análisis del grosor y la densidad del hueso cortical. Se seleccionaron 49 registros de tomografía computarizada de haz cónico de 173 pacientes. Se utilizó el software Invivo 5.2 para medir el grosor y la densidad de 25 sitios en una malla en el área retromolar mandibular. Se realizaron análisis de correlación de Pearson, correlación de Spearman y regresión logística binaria para explorar las correlaciones entre las mediciones retromolares y las características del paciente. La prueba de LSD se utilizó para identificar los sitios óptimos de microimplantes en esta área. Se utilizó ANOVA unidireccional, con prueba SNK post hoc, para comparar los sitios óptimos de microimplante entre el área retromolar, el hueso distobucal del segundo molar y una ubicación entre el primer y el segundo molar. El grosor y la densidad medios del hueso cortical retromolar mandibular fueron 2,35 ± 0,76 mm y 530,49 ± 188,83 HU, respectivamente. En el área retromolar mandibular, el grosor y la densidad del hueso cortical aumentaron desde el lado lingual al bucal y desde el distal al mesial. Entre los 25 sitios, S5C1 se determinó el mayor espesor y densidad; presentó mayor grosor y densidad, en comparación con el hueso distobucal del segundo molar y el sitio entre el primero y el segundo molar. Para rectificación distal de molares con punta mesial, recomendamos la colocación de microimplantes en el sitio retromolar bucal; para la distalización de la dentición mandibular, recomendamos la colocación de microimplantes en el sitio retromolar mesiobucal (S5C1) o 2 mm desde la dirección mesial del sitio distobucal del segundo molar (B).

Micron-scale human enamel layer characterization after orthodontic bracket debonding by intensity-based layer segmentation in optical coherence tomography images.

In clinical orthodontic practice, fixed brackets are widely used for tooth movement and adjustments. Although years of research and development have improved the workability of fixed orthodontic brackets, there are still controversies regarding its plausible destructive influence on the enamel surface of tooth. This, in turn, makes the quantitative assessment of the enamel surface after specific orthodontic treatment procedures important in order to opt for the most effective treatment procedure. Through this study, we show the practical applicability of optical coherence tomography (OCT) as a non-ionizing and nondestructive assessment tool for measuring enamel loss after each step of orthodontic bracket bonding. Two-dimensional and volumetric OCT images are used for the evaluation of the tooth enamel. From the depth intensity profile analysis of cross-sectional OCT images, the changes in the individual internal layer thickness are calculated. A software algorithm was developed to evaluate the structural connectivity in the enamel for analyzing enamel loss on the tooth surface and for detecting enamel abrasion. An intensity-based layer segmentation algorithm is also developed to analyze and evaluate enamel wear in the tooth after each step. Using the proposed algorithms, the total enamel present after each treatment procedure was measured and tabulated for analysis.

Considerations for vertical control with microimplants in a idiopathic condylar resorption patient: A case report.

Idiopathic condylar resorption (ICR) is a rare, destructive temporomandibular joint disease characterised by progressive resorption of the condyles. This case report presents a record of an orthodontically treated patient with ICR with favourable posttreatment remodelling of the condyles. An 18-year-old woman sought treatment for ICR. A severe Class II high-angle facial pattern with resorption of bilateral condyles was evident. The treatment plan was determined after careful examination of condylar radiographs and comprised forward rotation of the mandible through full-arch intrusion with microimplants after extraction of the four premolars. The treatment was completed in 35 months, and the patient was noted to have a straight profile, good interdigitation and slightly increased condylar volume. Two years after retention, the condyles were stable, and the patient's profile and occlusion remained acceptable despite a mild relapse of the mandibular position. ICR was successfully corrected with orthodontic treatment. Counter-clockwise mechanics applied during the ICR remission period not only improved facial aesthetics but were also suitable for condylar unloading.

Estimation of the prevalence of malocclusion on the basis of nationwide oral health examinations of pre-adolescent and adolescent students during 2012-2017.

OBJECTIVE: To investigate the prevalence of malocclusion with respect to grade, sex, and year among Korean pre-adolescent and adolescent students during 2012-2017. METHODS: A total of 165,996 students (first grade [E1, 6-7 years of age], fourth grade [E4, 9-10 years], seventh grade [M1, 12-13 years], and tenth grade [H1, 15-16 years]) were selected by stratified sampling method and underwent the nationwide oral health examination performed by the Ministry of Education, Republic of Korea. The malocclusion assessments based on dentists' judgments were "no malocclusion," "needs orthodontic treatment (N-OTx)," and "under orthodontic treatment (U-OTx)." The sum of N-OTx and U-OTx cases was determined as the number of students with malocclusion. After analyzing the prevalence of malocclusion according to grade, sex, and year-by-year differences, Pearson correlation analyses and two-way analyses of variance were performed. RESULTS: The prevalence of malocclusion was 18.7%, which increased with the grades (E1 [8.3%] < E4 [15.8%] < M1 [22.9%] < H1 [25.3%], p < 0.001). However, there was no significant difference in the prevalence of malocclusion in each grade group for the period (p > 0.05) without significant correlation (E1, ρ = 0.129; E4, ρ = -0.495; M1, ρ = 0.406; H1, ρ = -0.383; all p > 0.05). The prevalence of malocclusion within each grade group over the six-year period was more prominent in the female (p < 0.0001). CONCLUSIONS: Further studies are necessary to modify the malocclusion assessment method to account for specific types of malocclusion in pre-adolescent and adolescent students.