Evaluation of mandibular growth in a prepubertal Class I and Class II population: a longitudinal analysis.

OBJECTIVE: This study aims to identify the presence, timing, and magnitude of a prepubertal mandibular growth spurt in a Class I and Class II population. METHODS: From the Burlington and Iowa Growth study of the AAOF Craniofacial Growth Legacy Collection, 83 Class I subjects (37 females and 46 males) and 32 Class II subjects (18 males and 14 females) were identified, as having at least seven consecutive annual lateral cephalograms taken from 5 to 11 years of age. Only subjects with a normodivergent facial pattern were considered. A customized cephalometric analysis was performed, and total mandibular length, defined as the distance between Condylion (Co) and Gnathion (Gn), was calculated. RESULTS: Overall, a significant early peak of mandibular growth was present in all the subjects analysed both in Class I (4.69 mm for males and 4.18 mm for females; P < .05) and in Class II (5.85 mm for males and 4.05 mm for females; P < .05). No differences between males and females were found for the timing of this peak (7 years for Class I and Class II females and 7 years for Class I and 6.5 years for Class II males). In males, a significantly larger peak was observed in Class II than Class I subjects (P = .007). LIMITATIONS: The main limitations of this study were the impossibility of using a suitable growth indicator to identify the timing of the early mandibular growth peak and the limited Class II records retrievable. CONCLUSION: This investigation suggests that a prepubertal mandibular growth peak is consistently present in both Class I and Class II males and females of clinically significant magnitude. Despite that, chronological age confirms to be unsuitable to identify this peak.

Longitudinal effects of estrogen on mandibular growth and changes in cartilage during the growth period in rats.

Estrogen is a steroid hormone that induces skeletal growth and affects endochondral ossification of the long tubular bone growth plate during the growth period. However, the effects of estrogen on endochondral ossification of the mandibular condylar cartilage are unclear. In this study, ovariectomized Wistar/ST rats were used to investigate the longitudinal effects of estrogen on mandibular growth. The rats were administered different doses of estrogen. Longitudinal micro-computed tomographic scanning, histological staining and ELISA on plasma growth hormone were performed to examine the effects of estrogen on mandibular growth. The results showed that mandibular growth was suppressed throughout the growth period by estrogen in a dose-dependent manner. In addition, long-term administration of a high dose of estrogen to the rats resulted in significant increase in growth hormone throughout the growth period, significant circularization of cell nuclei in the proliferative layer, intensely staining cartilage matrix in the subchondral bone, and significant suppression of estrogen receptor (ER) alpha and beta expression in the mandibular cartilage. However, regardless of estrogen concentration, in the posterior part of the mandibular cartilage, ER expression extended to both the hypertrophic and proliferative layers. These results indicate that estrogen suppresses mandibular growth throughout the growth period. Additionally, it influences endochondral ossification via its effect on ERs.

Deep learning-based prediction of mandibular growth trend in children with anterior crossbite using cephalometric radiographs.

BACKGROUND: It is difficult for orthodontists to accurately predict the growth trend of the mandible in children with anterior crossbite. This study aims to develop a deep learning model to automatically predict the mandibular growth result into normal or overdeveloped using cephalometric radiographs. METHODS: A deep convolutional neural network (CNN) model was constructed based on the algorithm ResNet50 and trained on the basis of 256 cephalometric radiographs. The prediction behavior of the model was tested on 40 cephalograms and visualized by equipped with Grad-CAM. The prediction performance of the CNN model was compared with that of three junior orthodontists. RESULTS: The deep-learning model showed a good prediction accuracy about 85%, much higher when compared with the 54.2% of the junior orthodontists. The sensitivity and specificity of the model was 0.95 and 0.75 respectively, higher than that of the junior orthodontists (0.62 and 0.47 respectively). The area under the curve value of the deep-learning model was 0.9775. Visual inspection showed that the model mainly focused on the characteristics of special regions including chin, lower edge of the mandible, incisor teeth, airway and condyle to conduct the prediction. CONCLUSIONS: The deep-learning CNN model could predict the growth trend of the mandible in anterior crossbite children with relatively high accuracy using cephalometric images. The deep learning model made the prediction decision mainly by identifying the characteristics of the regions of chin, lower edge of the mandible, incisor teeth area, airway and condyle in cephalometric images.

Combined use of F22 aligners and intermaxillary elastics in mild skeletal Class II: Two case reports.

INTRODUCTION: The aim of these two case-reports is to illustrate and compare the therapeutic effects of Class II elastics in combination with F22 aligners in an adult and an adolescent patient, respectively. CASE PRESENTATION: Two patients with a mild skeletal Class II malocclusion, associated with mild-to-moderate crowding, presented for orthodontic treatment. The first patient was 12 years old, while the second was 40 years old. In both cases, the goal was to obtain bilateral molar and canine Class I with ideal overjet and overbite, and Class II skeletal relationship improvement in the young patient as well. Both treatments were approached without extractions and using clear aligners (CAs) in combination with Class II elastics, giving the patient the opportunity to take advantage of a therapy that is both comfortable and aesthetic. DISCUSSION: Final records of both cases demonstrate how appropriate analysis and diagnosis enable CAs in conjunction with Class II elastics to be used with considerable efficiency and efficacy for Class II treatment. In the first case, the key to success was exploiting residual jaw growth, while in the second case it was careful orthodontic digital planning. CONCLUSION: In the presence of good patient compliance, CAs associated with Class II elastics provide satisfactory occlusal outcomes if biomechanics and digital set-up are carefully evaluated and executed and if diagnosis is appropriate.

IGF-1 TMJ injections enhance mandibular growth and bone quality in juvenile rats.

OBJECTIVES: Dentofacial orthopaedic treatment of mandibular hypoplasia has unpredictable skeletal outcomes. Although several biomodulators including insulin-like growth factor 1 (IGF-1) are known to contribute to chondrocyte proliferation, their efficacy in modulating mandibular growth has not been validated. The aim of this study was to determine the effect of locally delivered IGF-1 on mandibular growth and condylar bone quality/quantity in juvenile rats. SETTING AND SAMPLE POPULATION: Institutional vivarium using twenty-four 35-day-old male Sprague-Dawley rats. METHODS: PBS or 40 µg/kg (low-dose) IGF-1 or 80 µg/kg (high-dose) IGF-1 was injected bilaterally into the temporomandibular joints of the rats at weekly intervals for four weeks. Cephalometric and micro-computed tomography measurements were used to determine mandibular dimensions. Bone and tissue mineral density, volume fraction and mineral content were determined, and serum IGF-1 concentrations assayed. RESULTS: Intra-articular administration of high-dose IGF-1 contributed to a significant 6%-12% increase in mandibular body and condylar length compared to control and low-dose IGF-1-treated animals. Additionally, IGF-1 treatment resulted in a significant decrease in the angulation of the lower incisors to mandibular plane. Condylar bone volume, bone volume fraction, mineral content and mineral density were significantly increased with high-dose IGF-1 relative to control and low-dose IGF-1 groups. Serum IGF-1 levels were similar between all groups confirming limited systemic exposure to the locally administered IGF-1. CONCLUSION: Local administration of high-dose 80 µg/kg IGF-1 enhances mandibular growth and condylar bone quality and quantity in growing rats. The findings have implications for modulating mandibular growth and potentially enhancing condylar bone health and integrity.

Comparison of spheno-occipital synchondrosis maturation stages with three-dimensional assessment of mandibular growth.

BACKGROUND: This study aimed to compare spheno-occipital synchondrosis (SOS) maturation stages with a three-dimensional assessment of mandibular growth. METHODS: This is a cross-sectional study of a retrospective type, in which cone-beam computed tomography (CBCT) images of 500 patients aged 6 to 25 years (226 males and 274 females) were analyzed. The SOS was evaluated using the four-stage scoring system; completely open, partially fused, semi-fused, or completely fused. The SOS scoring and three-dimensional cephalometric measurements were analyzed by Invivo 6.0.3 software. Descriptive and analytical statistics were performed, and a P-value < 0.05 was considered statistically significant. RESULTS: There was a statistically significant difference in mandibular measurements among SOS maturation stages in both sexes (P < 0.05). The skeletal growth increments of mandibular variables across the SOS stages had higher mean differences between SOS stages 2 and 3 than those between stages 1 and 2 and stages 3 and 4 in both sexes. The mandibular growth curves increased with chronological age (earlier in females) and SOS maturation stages (mostly in stages 1, 2, and 3 than stage 4). CONCLUSIONS: The SOS maturation stages are valid and reliable mandibular skeletal indicators as evaluated with three-dimensional cephalometric mandibular measurements. The findings of growth increments and constructed growth curves of mandibular growth might be helpful in diagnosis and treatment planning.

Hyaluronic acid is required for palatal shelf movement and its interaction with the tongue during palatal shelf elevation.

Palatal shelf elevation is an essential morphogenetic process that results from palatal shelf movement caused by an intrinsic elevating force. The nature of the elevating force remains unclear, but the accumulation of hyaluronic acid (HA) in the extracellular matrix (ECM) of the palatal shelves may play a pivotal role in developing the elevating force. In mammals, HA is synthesized by hyaluronic acid synthases (HAS) that are encoded by three genes (Has1-3). Here, we used the Wnt1-Cre driver to conditionally disrupt hyaluronic acid synthase 2 (Has2) in cranial neural crest cell lineages. All Has2 conditional knockout (cko) mice had cleft palate due to failed shelf elevation during palate development. The HA content was significantly reduced in the craniofacial mesenchyme of Has2 cko mutants. Reduced HA content affected the ECM space and shelf expansion to result in a reduced shelf area and an increased mesenchymal cell density in the palatal shelves of Has2 cko mutants. We examined palatal shelf movement by removal of the tongue and mandible from unfixed E13.5 and early E14.5 embryonic heads. Reduced shelf expansion in Has2 cko mutants altered palatal shelf movement in the medial direction resulting in a larger gap between the palatal shelves than that of littermate controls. We further examined palatal shelf movement in the intact oral cavity by culturing explants containing the maxilla, palate, mandible and tongue (MPMT explants). The palatal shelves elevated alongside morphological changes in the tongue after 24-h culture in MPMT explants of early E14.5 wild type embryos. On the contrary, shelf elevation failed to occur in MPMT explants of age-matched Has2 cko mutants because the tongue obstructs palatal shelf movement, suggesting that reduced shelf expansion could be essential for the palatal shelves to interact with the tongue and overcome tongue obstruction during shelf elevation. Has2 cko mutants also showed micrognathia due to reduced HA content in the mandibular mesenchyme including Meckel's cartilage. Through 3D imaging and morphometric analysis, we demonstrate that mandibular growth results in a significant increase in the vertical dimension of the common oral-nasal cavity that facilitates palatal shelf movement and its interaction with the tongue during shelf elevation.

Prediction of Mandibular Growth Pattern Using Palatoscopy: A Retrospective Model Analysis.

AIM AND OBJECTIVE: To predict and correlate mandibular growth pattern using palatoscopy (average, horizontal, and vertical). MATERIALS AND METHODS: This retrospective study includes 120 archived maxillary casts. One key person and two examiners performed the study; the key person was responsible for coding and collecting casts and radiographs, as well as calibration of the examiners. The key person divided the samples into three craniofacial growth pattern groups (average, horizontal, and vertical) based on Frankfort-mandibular plane angle (FMA), SN-GoGn, and facial axis angle and distributed them to the blinded examiners. Rugae were studied using a modified Thomas and Kotze classification system. After the analysis, the results were decoded and analyzed with the corresponding cephalometric radiographs. RESULTS: Multinomial logistic regression was employed to predict the mandibular growth patterns with the following independent variables: Forwardly directed rugae, number of divergent rugae, predominant shape circular, predominant shape curved, primary rugae, predominant shape wavy, number of convergent rugae, and horizontally directed rugae. CONCLUSION: Palatal rugae patterns predict the growth pattern of the mandible. CLINICAL SIGNIFICANCE: Considering the significant parameters and their correlation with mandibular growth pattern, prediction of mandibular growth patterns can be done noninvasively.

Ontogenetic insights into the significance of mandibular corpus shape variation in hominoids: Developmental covariation between M2 crypt formation and corpus shape.

OBJECTIVES: Here, we quantify and compare the cross-sectional shape of the mandibular corpus between M1 and M2 during growth in Pan paniscus, Pan troglodytes, and Pongo pygmaeus. The goal is to assess the hypothesis that the shape of the corpus is influenced by the development of permanent molars in their crypts, by examining ontogenetic changes in corpus shape and investigating covariation between corpus shape and M2 and M3 molar crypt forms. MATERIALS AND METHODS: Ontogenetic changes in mandibular corpus shape were assessed using landmarks and semilandmarks, and measurements of length, width, and height were used to quantify molar crypts (M2 and M3 ). Ontogenetic changes in corpus growth from the eruption of M1 to the eruption of M3 were evaluated for each species through generalized Procrustes analysis and principal components analysis in shape-space and form-space. The relationship between corpus shape and molar crypt form was investigated at three different developmental stages using two-block partial least squares (2B-PLS) analysis. RESULTS: The results show clear differences in growth patterns among all three species and provide evidence that species-level differences in mandibular corpus growth occur prior to the emergence of M1 . The results of the 2B-PLS analysis reveal that significant covariance between corpus shape and molar crypt form is limited to the developmental stage marked by the emergence of M1 , with covariance between corpus shape and M2 crypt width. Corpora that are relatively narrower in the inferior portion of the cross section covary with relatively narrower M2 crypts. CONCLUSIONS: These results have important implications for understanding the taxonomic and phylogenetic significance of mandibular corpus shape variation in the hominoid fossil record.

Vertical growth in mono-and dizygotic twins: A longitudinal cephalometric cohort study.

OBJECTIVE: The aims of this longitudinal analysis of untreated monozygotic and dizygotic twins were to investigate vertical changes of the craniofacial structures during growth, to determine the concordance between genetically twins and to assess the genetic component for the various aspects of vertical growth. SETTINGS AND SAMPLE POPULATION: The sample consisted of 34 pairs of untreated monozygotic twins (23 male, 11 female) and 30 untreated dizygotic siblings of multiple birth (8 male, 8 female and 14 mixed) from the Forsyth Moorrees Twin Study (1959-1975); lateral cephalograms taken from 6 to 18 years of age were analysed at 3-year intervals. MATERIALS AND METHODS: Cephalograms were traced, and longitudinal changes between twins in six angular and proportional vertical cephalometric variables (SN-NL, ML-NL, SN-ML, y-axis, PFH/AFH and LAFH/AFH) were analysed with intraclass correlation coefficients and linear regression modelling. RESULTS: The concordance between monozygotic/dizygotic twins at 18 years of age was moderate to high with intraclass correlation coefficient values between 0.51 and 0.66. Additionally, sex differences in concordance at 18 years of age were found for three variables. High heritability (66%-79%) was observed for 5 of the 6 variables (LAFH/AFH, ML-NL, y-axis, SN-ML, PFH/AFH), while SN-NL showed limited heritability (34%). CONCLUSIONS: Although monozygotic/dizygotic twins share at least part of their genetic material, differences in the vertical dimension were found. This supports the complex developmental mechanism of the human face and the varying influence of genetic and environmental factors.

The three-dimensional stable mandibular landmarks in patients between the ages of 12.5 and 17.1 years.

BACKGROUND: With the aid of implants, Björk identified two-dimensional mandibular stable structures in cephalograms during facial growth. However, we do not know what the three-dimensional stable structures are with certainty. The purpose of this study was to identify the most stable mandibular landmarks in growing patients using three-dimensional images. METHODS: The sample was comprised of two cone-beam computed tomography (CBCT) scans taken about 4.6 years apart in 20 growing patients between the ages of 12.5 (T1) and 17.1 years (T2). After head orientation, landmarks were located on the chin (Pog), internal symphysis (Points C, D and E), and mandibular canals, which included the mental foramina (MF and MFA) and mandibular foramina (MdF). The linear distance change between Point C and these landmarks was measured on each CBCT to test stability through time. The reliability of the suggested stable landmarks was also evaluated. RESULTS: The total distance changes between Point C and points D, E, Pog, MF, and MFA were all less than 1.0 mm from T1 to T2. The reliability measures of these landmarks, which were measured by the Cronbach alpha, were above 0.94 in all three dimensions for each landmark. From T1 to T2, the distance changes from Point C to the right and left mandibular foramina were 3.39 ± 3.29 mm and 3.03 ± 2.83 mm, respectively. CONCLUSIONS: During a growth period that averaged 4.6 years, ranging from 11.2 to 19.8 years old, the structures that appeared relatively stable and could be used in mandibular regional superimpositions included Pog, landmarks on the inferior part of the internal symphysis, and the mental foramen. The centers of the mandibular foramina and the starting points of the mandibular canal underwent significant changes in the transverse and sagittal dimensions.

Mandibular Catch-Up Growth in Pierre Robin Sequence: A Systematic Review.

OBJECTIVE: The concept of mandibular catch-up growth is often quoted in the literature regarding Pierre Robin sequence (PRS). We endeavored to perform a systematic review of whether the literature supports this concept. DESIGN: Systematic review. INTERVENTIONS: A PubMed-based systematic review of the English literature was performed of articles objectively measuring mandibular growth or position after nonoperative management of PRS. MAIN OUTCOME MEASURES: Rate and end point of mandibular length, ramus length, gonial angle, and maxillomandibular discrepancy. RESULTS: The initial search delivered 607 English-language abstracts. Of these, 16 met inclusion criteria. Eight articles evaluating 143 patients followed longitudinal patient data and therefore allowed comparison of growth rates to controls. Ten articles evaluating 228 patients presented cross-sectional data and therefore could only evaluate a single time point. Two of the 8 longitudinal studies reported faster than normal growth of mandibular length in a significant portion of their cohort. Five of 8 reported equal growth rates. One of 16 studies reported that mandibular length of patients with PRS normalized compared to controls. Two of 16 studies reported no difference in maxillomandibular discrepancy between PRS and controls, whereas 10 reported a posteriorly displaced mandible relative to the maxilla in PRS. Significant differences in control groups, patients, and age existed between studies. CONCLUSIONS: While the concept of catch-up growth in PRS is often quoted, a minority of objective studies suggest increased mandibular growth rates in isolated PRS. Even fewer studies suggest that the maxillomandibular discrepancy in PRS completely resolves.

Mandibular growth in survivors of pediatric parotid gland carcinoma treated with interstitial brachytherapy.

BACKGROUND: The aim of the study was to present long-term results of mandibular growth in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy. PROCEDURE: Twenty-five survivors of pediatric parotid gland carcinoma treated with iodine-125 seed interstitial brachytherapy were included for quantitative analysis, including three dimensional (3D) cephalometry and measurement of mandibular volume. RESULTS: 3D cephalometry showed that the median fore-and-aft increments of the lengths of the condyle, the ramus, and the body of the mandible were 1.23, 0.19, and 1.66 mm for the affected side, respectively, and were 1.37, 1.95, and 3.42 mm for the unaffected side, respectively. The difference in increments of the ramus was statistically significant between the affected side and the unaffected side (P = 0.003; P < 0.05). Moreover, mandibular volume measurements showed that the median fore-and-aft increments of the volumes of the condyle, the ramus, and the body of the mandible were 290.62, 220.14, and 1706.40 mm3 for the affected side, respectively, and were 269.15, 370.40, and 1469.86 mm3 for the unaffected side, respectively. The difference in increments was statistically significant between the affected side and the unaffected side for the ramus (P = 0.005; P < 0.05) and the body (P = 0.043; P < .05). CONCLUSION: Mandibular growth was affected by interstitial brachytherapy, especially for the ramus, in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy. Nevertheless, the impact was mild in these survivors.

Evaluation of Skeletal and Dental Effects of Lower Lingual Arches.

OBJECTIVE: A lower lingual arch is usually recommended as a holding device to maintain arch length and to prevent mesial migration of the mandibular first molars. Despite its widespread use, comparatively little is known about the effects of a lower lingual holding arch on preservation of lower arch dimensions and tooth position and the impact of the device on mandibular growth. The aim of this study is to evaluate the skeletal and dental effects of the lower lingual holding arch with regard to arch dimension, positions of mandibular molars and incisors, and usual mandibular growth. STUDY DESIGN: Thirty-four children (18 males and 16 females) who needed space maintainers were included in the present study. The patients were divided into two groups according to whether they were missing second primary molars on one or both sides. Group I comprised 16 children (8 males and 8 females, average age 8.8 ± 0.9 years) with a missing second primary molar on one side; Group II comprised 18 children (10 males and 8 females, average age 8 ± 0.7 years) with extractions on both sides. Lateral cephalograms, dental pantomograms, and study casts of the patients were taken at the beginning and the end of the study period. Average treatment time was 20.4 ± 4 months. RESULTS: Lower incisors moved forward and Incisor Mandibular Plane Angle (IMPA°) increased in both treatment groups. Statistically significant differences between the groups were found when comparing pre-treatment and post-treatment arch dimension and position of mandibular molars. Results were better for lingual arches with extraction on one side than with extraction on both sides Conclusions: A lingual arch seems to be an effective tool for maintaining arch length, and was not found to impair mandibular growth.

Genetic and environmental impact on mandibular growth in mono- and dizygotic twins during adolescence: A retrospective cohort study.

INTRODUCTION: This study aimed to discover the genetic and environmental factors that contribute to the mandibular development of untreated monozygotic and dizygotic twins. MATERIAL AND METHODS: The sample, taken from the Forsyth Moorrees Twin Study, included 52 untreated monozygotic twins (36 male, 16 female) and 46 untreated dizygotic twins (23 male, 23 female). At the ages of 12 and 17, lateral cephalograms were collected and traced to assess total mandibular length, mandibular ramus length, mandibular corpus length, gonial angle, SNB, and bony chin prominence. The genetic and environmental components of variation were assessed using multilevel mixed-effects structural equation modelling. RESULTS: At 12 years of age, high additive genetic influences were observed for total mandibular length (74%), gonial angle (76%), SNB (41%), and bony chin prominence (64%), whereas strong dominant genetic components were observed for corpus length (72%), and mandibular ramus length was under unique environment influence (54%). At 17 years of age, only total mandibular length (45%), ramus length (53%), gonial angle (76%), and bony chin prominence (68%) were under strong additive genetic control, while the remainder were under strong dominant genetic control. CONCLUSIONS: Although monozygotic and dizygotic twins share at least a portion of their DNA, additive, dominant, or environmental components were discovered during adolescence. Nonetheless, by the age of 17, the majority of the mandibular traits are under either additive or dominant genetic impact.

Comparative assessment of two-phase class II treatment with Activator or Bionator followed by fixed appliances: A retrospective controlled before-and-after study.

AIM: Two-phase treatment for children with Class II malocclusion with several functional appliances is still performed by many orthodontists, while the Activator and the Bionator appliances are two of the most popular ones. Aim of this study was to compare the skeletal and dentoalveolar effects of treatment with these two appliances. METHODS: Class II children treated with Activator or Bionator in the first phase, followed by a phase of fixed appliances were included. Skeletal and dentoalveolar parameters were assessed from lateral cephalograms and analysed with linear regressions at 5%. RESULTS: A total of 89 patients (mean age 10.0 years; 47% female) were included. During the first phase, Bionator increased less the SNB (difference in mean treatment-induced changes [MD] -0.7°; 95% confidence interval [CI] -1.3 to -0.2°; P=0.01) and decreased less the ANB angle (MD 0.6°; 95% CI 0 to 1.1°; P=0.03) compared to Activator. Activator slightly increased the facial axis and Bionator reduced it (MD -1.6°; 95% CI -2.3 to -0.8°; P<0.001). Compared to Activator, the Bionator retroclined more the upper incisors (MD -2.4°; 95% CI -4.6 to -0.2°; P=0.03) and increased more the interincisal angle (MD 2.9°; 95% CI 0.5 to 5.4°; P=0.02). After the second phase (6.2 years after baseline), the only differences were a reduced facial axis (MD -1.3°; 95% CI -2.2 to -0.3°; P=0.008) and an increased maxillary rotation (MD 0.9°; 95% CI 0 to 1.8°; P=0.04) with Bionator compared to Activator. CONCLUSION: Similar dentoalveolar effects were seen overall with two-phase treatment with either appliance, with Bionator being associated with more vertical increase compared to Activator.

Prediction of Pubertal Mandibular Growth in Males with Class II Malocclusion by Utilizing Machine Learning.

The goal of this study was to create a novel machine learning (ML) model that can predict the magnitude and direction of pubertal mandibular growth in males with Class II malocclusion. Lateral cephalometric radiographs of 123 males at three time points (T1: 12; T2: 14; T3: 16 years old) were collected from an online database of longitudinal growth studies. Each radiograph was traced, and seven different ML models were trained using 38 data points obtained from 92 subjects. Thirty-one subjects were used as the test group to predict the post-pubertal mandibular length and y-axis, using input data from T1 and T2 combined (2 year prediction), and T1 alone (4 year prediction). Mean absolute errors (MAEs) were used to evaluate the accuracy of each model. For all ML methods tested using the 2 year prediction, the MAEs for post-pubertal mandibular length ranged from 2.11-6.07 mm to 0.85-2.74° for the y-axis. For all ML methods tested with 4 year prediction, the MAEs for post-pubertal mandibular length ranged from 2.32-5.28 mm to 1.25-1.72° for the y-axis. Besides its initial length, the most predictive factors for mandibular length were found to be chronological age, upper and lower face heights, upper and lower incisor positions, and inclinations. For the y-axis, the most predictive factors were found to be y-axis at earlier time points, SN-MP, SN-Pog, SNB, and SNA. Although the potential of ML techniques to accurately forecast future mandibular growth in Class II cases is promising, a requirement for more substantial sample sizes exists to further enhance the precision of these predictions.

Evaluation of optimal single-photon emission computed tomography reference value and three-dimensional mandibular growth pattern in 54 Chinese unilateral condylar hyperplasia patients.

BACKGROUND: The research aimed to evaluate the optimal Single-Photon Emission Computed Tomography (SPECT) cut-off value in differentiating condylar growth activeness, to observe 3-dimensional (3D) mandibular growth pattern, and to explore the potential correlation between 3D measurement parameters and SPECT uptake ratios in Chinese unilateral condylar hyperplasia (UCH) patients. METHODS:  Data of fifty-four Chinese UCH patients were analyzed retrospectively. All patients underwent SPECT within 1 month before or after the first CT examination (CT1); and received a second CT examination at least 12 months later (CT2). Data from CT scans were analyzed by comparing bilateral differences between CT1 and CT2. The sensitivity and specificity of SPECT were calculated by the receiver operating characteristic (ROC) curve. Pearson's correlation analysis was performed to investigate whether the mandibular growth was correlated with SPECT value. RESULTS: SPECT had a sensitivity of 68.00% and a specificity of 72.41%, with an area under the ROC curve being 0.709. The optimal SPECT cut-off value for evaluating condylar activity has been determined to be 13%. In patients with an active growing condyle, there was a significant increase in Co-Gn and Co-Go, but not in Go-Gn, Go-MF, or MF-Gn. Pearson's correlation analysis revealed no correlation between 3D measurement parameters and differences in relative condylar uptake ratios. CONCLUSION: SPECT showed good diagnostic performance in UCH with the cut-off value of 13%. For those with an active growing condyle, the mandible grows diagonally and vertically, while the relative condylar uptake ratio was not directly related to mandibular growth.

Treatment of Skeletal Class II Division 1 Using Twin Block Myofunctional Appliance.

Myofunctional appliances are customarily used to treat Class II malocclusions in growing children to alter their growth. Functional appliances are widely accepted to enhance skeletal relationships in the short term efficiently. It utilizes muscular forces by muscles to make dental and skeleton modifications. The myofunctional appliance might be removable or fixed. The variation of mode and method of action depends on the design, but the forces created by the muscles' stretching provide their effect. According to research, the effectiveness of functional appliances as a therapy for Class II malocclusion might be influenced by mandibular growth patterns. Their low skeletal maturation influence outweighs the primary dentoalveolar impact of the twin block myofunctional orthodontic appliances. Class II malocclusions can benefit by using myofunctional appliances in specific clinical situations, such as when the patient is still developing. These devices make the fixed appliance phase easier to use, but their effectiveness depends heavily on the patient's compliance. In this case, an 11-year-old female expressed concern about the forward positioning of her upper front teeth when she visited the department of orthodontics. Twin block, a myofunctional appliance, was used to manage it, and then fixed orthodontic treatment was used to fine-tune the occlusion. This case report illustrates the design and treatment effects.