Lower Incisor Inclination Research Articles

Evaluation of four machine learning methods in predicting orthodontic extraction decision from clinical examination data and analysis of feature contribution.

The study aims to predict tooth extraction decision based on four machine learning methods and analyze the feature contribution, so as to shed light on the important basis for experts of tooth extraction planning, providing reference for orthodontic treatment planning. This study collected clinical information of 192 patients with malocclusion diagnosis and treatment plans. This study used four machine learning strategies, including decision tree, random forest, support vector machine (SVM) and multilayer perceptron (MLP) to predict orthodontic extraction decisions on clinical examination data acquired during initial consultant containing Angle classification, skeletal classification, maxillary and mandibular crowding, overjet, overbite, upper and lower incisor inclination, vertical growth pattern, lateral facial profile. Among them, 30% of the samples were randomly selected as testing sets. We used five-fold cross-validation to evaluate the generalization performance of the model and avoid over-fitting. The accuracy of the four models was calculated for the training set and cross-validation set. The confusion matrix was plotted for the testing set, and 6 indicators were calculated to evaluate the performance of the model. For the decision tree and random forest models, we observed the feature contribution. The accuracy of the four models in the training set ranges from 82% to 90%, and in the cross-validation set, the decision tree and random forest had higher accuracy. In the confusion matrix analysis, decision tree tops the four models with highest accuracy, specificity, precision and F1-score and the other three models tended to classify too many samples as extraction cases. In the feature contribution analysis, crowding, lateral facial profile, and lower incisor inclination ranked at the top in the decision tree model. Among the machine learning models that only use clinical data for tooth extraction prediction, decision tree has the best overall performance. For tooth extraction decisions, specifically, crowding, lateral facial profile, and lower incisor inclination have the greatest contribution.

Evaluation of the Best Method for Orthodontic Correction of Skeletal Deep Bites in Growing Patients: A Systematic Review.

This review aimed to evaluate the currently available evidence regarding the best method of correcting deep bites in growing patients. In September 2023, a search was conducted electronically across the following databases: PubMed®, Web of Science™, Scopus®, Embase®, Google™ Scholar, and Cochrane Library. In this systematic review, randomized control trials (RCTs), controlled clinical trials (CCTs), and cohort studies of growing patients with deep bite malocclusion who received treatment with the primary objective of treating the deep bite were included. Risk of bias of the included studies was assessed using two different tools; one tool was applied for RCTs and the other one for the CCTs and cohort studies. One RCT, one CCT, and one cohort study were included (85 patients). The flat fixed acrylic bite plane was superior in terms of duration of treatment when compared to the inclined fixed acrylic bite plane and the utility arch with posterior intermaxillary elastics. Limited evidence indicates that the inclined fixed acrylic bite plane causes a significant increase in the lower incisor inclination and a significant increase in the angle between the mandible and the anterior cranial base (SNB). However, limited evidence indicates that the utility arch with posterior intermaxillary elastics causes a significant decrease in the angle between the maxilla and the anterior cranial base (SNA). Regarding the vertical skeletal changes, it was found that the three methods were comparable; in each case, the vertical dimension of the face increased because of a significant increase in the lower first molar height. There is a need for further studies to strengthen the evidence of the treatment efficacy of the employed methods, with more RCTs to be conducted in this regard.

Comparison of effects of Forsus FRD and miniscrew implant anchorage supported Forsus FRD on lower incisor inclination

Comparison of effects of Forsus FRD and miniscrew implant anchorage supported Forsus FRD on lower incisor inclination

Automated diagnostic classification with lateral cephalograms based on deep learning network model

Objective: To establish a comprehensive diagnostic classification model of lateral cephalograms based on artificial intelligence (AI) to provide reference for orthodontic diagnosis. Methods: A total of 2 894 lateral cephalograms were collected in Department of Orthodontics, Capital Medical University School of Stomatology from January 2015 to December 2021 to construct a data set, including 1 351 males and 1 543 females with a mean age of (26.4± 7.4) years. Firstly, 2 orthodontists (with 5 and 8 years of orthodontic experience, respectively) performed manual annotation and calculated measurement for primary classification, and then 2 senior orthodontists (with more than 20 years of orthodontic experience) verified the 8 diagnostic classifications including skeletal and dental indices. The data were randomly divided into training, validation, and test sets in the ratio of 7∶2∶1. The open source DenseNet121 was used to construct the model. The performance of the model was evaluated by classification accuracy, precision rate, sensitivity, specificity and area under the curve (AUC). Visualization of model regions of interest through class activation heatmaps. Results: The automatic classification model of lateral cephalograms was successfully established. It took 0.012 s on average to make 8 diagnoses on a lateral cephalogram. The accuracy of 5 classifications was 80%-90%, including sagittal and vertical skeletal facial pattern, mandibular growth, inclination of upper incisors, and protrusion of lower incisors. The acuracy rate of 3 classifications was 70%-80%, including maxillary growth, inclination of lower incisors and protrusion of upper incisors. The average AUC of each classification was ≥0.90. The class activation heat map of successfully classified lateral cephalograms showed that the AI model activation regions were distributed in the relevant structural regions. Conclusions: In this study, an automatic classification model for lateral cephalograms was established based on the DenseNet121 to achieve rapid classification of eight commonly used clinical diagnostic items.

Lower incisor inclination and thickness of the alveolar process and mandibular symphysis in the development of gingival recession: A retrospective cohort study

IntroductionRetrospective studies have found conflicting results regarding the relationship between lower incisor inclination and the development of gingival recession (GR) after orthodontic treatment. ObjectiveThis study aimed to investigate the relationship between lower incisor inclination and alveolar process (AP) and mandibular symphysis (MS) thickness in the development of GR. Materials and MethodsFrontal intraoral photography and cephalometric radiography were conducted before (T0) and after (T1) orthodontic treatment of 62 subjects. The presence of GR was considered when the cementoenamel junction was visible in the lower incisor on the frontal intraoral photograph.The circumstances for improvement, stability, and worsening of the gingival situation were based on the reduction, maintenance, and increase in the number of lower incisors with GR before and after treatment. To measure the incisor-mandibular plane angle (IMPA) andthe thickness of the AP and the MS were used the cephalometric radiographs. ResultsMen had a significantly thicker MS than women at T0 and T1 (p < 0.0004).There was a significant reduction of approximately 10% in AP between T0 and T1 (p < 0.0001).Among subjects without GR at T0, 70.4% presented a stable gingival situation at T1. For subjects with 1 lower incisor with GR at T0, 50% showed improvement in the gingival situation at T1, 21.4% remained stable, and 28.6% experienced worsening.Sixteen lateral incisors presented a worsening gingival situation, representing an increase of 129% compared to the central incisors. ConclusionNo relationship was found between lower incisor inclination and the thickness of the AP and MS in the development of GR.

Skeletal and dental effects of serial extractions performed with or without maxillary expansion-A retrospective controlled study.

The study aimed to compare severe crowding treatment's skeletal and dental effects by serial extractions or maxillary expansion and serial extractions in the mixed dentition phase. The retrospective controlled study included lateral cephalograms of 78 subjects aged 8.5 ± 1.4 years, 52 consecutively treated because of severe crowding, and 26 untreated controls matched for baseline age and observational period. Subjects were clustered according to the treatment modality, either serial extraction (EX) or expansion and extraction (EXP-EX) group. Sagittal and vertical skeletal as well as dental cephalometric parameters were assessed at baseline and after the eruption of all permanent posterior teeth, and group comparisons were performed. Both treatment modalities significantly affected the vertical skeletal parameters in terms of decreasing the mandibular and occlusal plane inclination and increasing the facial height index. A distinct treatment effect on the gonial angle was observed, with a significant decrease in its superior part observed in both extraction groups. The annualized changes in the superior part of the gonial angle significantly differ (P = .036) between the Control (-0.04 ± 0.6), EX (-0.44 ± 0.6) and EXP-EX (-0.34 ± 0.5) groups. Upper and lower incisor inclination did not change significantly in any of the groups; however, the interincisal angle at follow-up was significantly smaller in the Control compared with both treated groups. Serial extractions and a combination of maxillary expansion and serial extractions have similar significant skeletal effects, mainly affecting vertical cephalometric parameters if performed during the pre-pubertal growth phase.

Mandibular advancement devices used with morning occlusal guides for treating obstructive sleep apnea-changed incisor inclination and its associated factors.

Mandibular advancement devices (MADs) effectively treat patients withobstructive sleep apnea (OSA). Although the use of morning occlusal guides (MOGs) along with MADs is recommended to prevent dental side effects, there is no evidence to support this. The aim of this study was to evaluate the change in incisor inclination in patients withOSA treated with MADs and MOGs, and to identify its predictive factors. Patients with OSA who received MAD and MOG therapy and had a reduction in their apnea-hypopnea index greater than 50% were analyzed. Cephalometric measurements were performed at baseline and at a 1-year follow-up or longerto assess the dentoskeletal side effects of MAD/MOG treatment. Multivariable linear regression analysis was used to assess the association between the change in incisor inclination and the independent variables that may cause the observed side effects. Among 23 patients enrolled in the study, there was significant upper incisor retroclination (U1-SN: 2.83° ± 2.68°, U1-PP: 2.86° ± 2.46°; P < 0.05) and significant lower incisor proclination (L1-SN: 3.04° ± 3.29°, L1-MP: 1.74° ± 3.13°; P < 0.05). However, no significant skeletal changes were observed. Multivariable linear regression revealed that advancement ≥ 95% of the patients' maximal mandibular protrusion was associated with greater upper incisor retroclination. Increased treatment duration was alsoassociated with increased upper incisor retroclination. No \measured variables were associated with the change in lower incisor inclination. Dental side effects occurred in patients who used MADs with MOGs. The amount of mandibular protrusion by MADs and treatment duration were predictive factors associated with upper incisor retroclination.

Correlation of the inclination of the incisors to the stability of the alignment of the anterior sector, based on PAR index criteria

Introduction: the objective of this study was to evaluate the relationship between incisor inclination at the end of orthodontic treatment with the anterior teeth alignment stability using PAR index. Methods: analytical cross-sectional study, the angle formed between the plane (Silla-Nasion) (U1-NS) and the inclination of the upper incisor and the angle between axial inclination of the lower incisor and mandibular plane (Go-Gn), were measured in 47 initial and final lateral radiographs of patients who finished orthodontic treatment. The anterior sector PAR index was applied to pretreatment (T0), posttreatment (T1) and follow-up (T2) casts. Statistical analysis was performed using frequency and percentage distributions, T test, Anova I, Anova II and Manova; significance p = 0,05. Results: no association was found between upper and lower incisor inclination, alignment stability and PAR weighted score between T2-T1 (p&gt; 0,05). The PAR decreased 75,29% from T0 to T1 and 58,79% from T0 to T2, with a recurrence of 16,5%. There was no association between retainer type and PAR weighted score. From T0 to T2 there was an association between the interaction of the incisor inclination of upper (p = 0,03) and lower (p = 0,04), with the weighted total score of the PAR index. Conclusion: there was no association between the modification of the incisor inclination with the stability of the anterior sector. At the end of orthodontic treatment there was a high level of correction in the anterior-superior and inferior sector, however, there was a recurrence of 16,5%.

Treatment of Class III Malocclusion and Anterior Crossbite with Aligners: A Case Report

The article describes the orthodontically treated case of a 25-year-old patient with skeletal and dental class III malocclusion, anterior crossbite, which caused functional and aesthetic problems, occlusal trauma, and incisor wear. Treatment with transparent aligners was proposed to meet the patient’s needs, using the sequential distalization protocol. While sequential distalization is well documented for class II malocclusion treatment in maxillary arch teeth, further investigations are necessary for class III malocclusions. In fact, lower teeth movements are more complex due to mandibular bone density and the presence of the third molars, which are often extracted to perform distalization. In addition, the use of intermaxillary elastics helps control the proclination of the anterior teeth as a reaction to distalizing forces. At the end of the treatment, the patient reached molar and canine class I and positive overjet and overbite. The inclination of lower incisors and the interincisal angle have improved, resulting in aesthetic and functional enhancement.

Correlation between symphyseal morphology and mandibular length in class 1 malocclusion between males and females: A radiographic study

Mandibular symphysis (MS) morphology is a valuable diagnostic and treatment-planning tool in orthodontics. MS is affected by a number of factors that include neuromuscular factors, vertical jaw relationships, inclination of lower incisors and genetic factors among others. 80 lateral cephalograms (40 – males and 40 – females) were used in the study and mandibular lengths (Schwarz analysis) were measured for males and females separately. Pearson correlation coefficient showed no statistically significant correlation between symphyseal morphology and mandibular length both in males and females. The inter-examiner reliability (IER) showed Cronbach’s Alpha for mandibular length shows a value of .70 implying good agreement. The study concludes there is no correlation between mandibular length and symphysis morphology. Although sexual dimorphism exists.

Determination of treatment options for Class III malocclusions in adult patients based on cephalometric values: a systematic review

Abstract Objective The present systematic review aimed to determine cephalometric values that may be used as a guide in deciding between orthodontic camouflage and orthognathic surgery to treat a Class III malocclusion in adults. In addition, a secondary aim was to identify treatment complications and aesthetic perceptions by laypersons/orthodontists. Methods Without a language restriction, an electronic search of six databases and a hand search of three orthodontic journals were performed until September 2021. All studies comparing orthodontic camouflage and orthognathic surgery in Class III malocclusion patients, were included. Data extraction was carried out independently by two authors with disagreement resolved by a third author. The risk of bias related to individual studies was appraised using a modified version of the STROBE checklist. The results were summarised qualitatively, and no meta-analysis was undertaken due to the high heterogeneity between the studies. Results With the quality of evidence ranging from moderate to high, six retrospective studies were included. A cephalometric analysis comprising the Holdaway angle, overjet, the Wits appraisal, lower incisor inclination, the maxillary-mandibular ratio, overbite, gonial angle and an additional combination were used as a guide. No treatment complications were reported. One study examined the perception of facial profile attractiveness in borderline surgical Class III malocclusions and found no difference in outcome and significant improvements in both camouflage and surgical groups. Conclusion The existing evidence is insufficient to identify a cephalometric parameter threshold in deciding between orthodontic camouflage and orthognathic surgery. PROSPERO database protocol no. CRD42020165164.

Identification of Orthodontic Extraction Predictors in End-On Class II Malocclusion

BJECTIVE: This study was designed to determine the different treatment predictors which help in the extraction and non-extraction decision of an end-on Class II malocclusion case. METHODOLOGY: The pretreatment records of 240 adult subjects aged 15-40 years with bilateral end-on Class II molar relationship were retrospectively selected and categorized under extraction (120) and non-extraction (120) treatment categories. The extraction cases were planned for different combinations of premolar extractions. The independent variables i.e., the cephalometric and orthodontic cast measurements were obtained from the recruited sample. Binary logistic regression analysis was applied using SPSS software. RESULTS: Increased upper and lower incisor inclinations (p &lt; 0.001) and procumbent upper lip (p = 0.004) was statistically significant in the extraction group. According to the regression model, the odds of extraction treatment were 1.12 times greater than non-extraction treatment for every one degree increase in upper and lower incisor inclinations, respectively. The chances of extraction treatment were 1.6 times higher than non-extraction treatment for every 1 mm increase in the distance of upper lip to S-plane. CONCLUSIONS: The upper and lower incisors inclinations and upper lip position are the critical factors affecting the extraction decision in adult patients with end-on Class II molar relationships. Overjet, dental crowding and the vertical growth pattern were found to be clinically insignificant in opting for an extraction treatment plan for such cases. KEYWORDS: Treatment, Angle Class II, tooth extraction, non-extraction

Early class III treatment with maxillary protraction-miniscrew-assisted rapid palatal expansion (MARPE) and mandibular miniplates

ObjectiveProtaction of maxilla is usually the more commonly and less invasive treatment approach for skeletal Class III with a hypoplastic maxilla. The aim of this study was the comparison of the skeletal and dental effects of two treatment protocols for maxillary protaction: a)MARPE in combination with facemask (FM) b)MARPE and mandibular miniplates (MM). PatientsThirteen patients (6 facemask, 7 mandibular miniplates) were investigated by means of pre- and posttreatment cephalograms and Conebeam Computer Tomographies (CBCTs). The two groups matched with regard to initial cephalometric and CBCTs values. The treatment objectives were to correct the transversal and antero-posterior maxillay deficiency. ResultsBoth groups showed a significant movement of A-point (FM group:+2.86 ± 0.94—p = 0.028; MM: 4.08 ± 0.64—p = 0.018). Also Both groups showed a significant change in ANB°, Wits appraisal and UL-ELine (mm). Upper and lower incisor inclination did not change significantly during treatment in both groups. ConclusionsBoth treatments achieve comparable rates of maxillary protaction and expansion, without dentoalveolar side effects. However, it is important to consider age, the type of growth of the patient (high angle vs low angle) and the cooperation of patients and parents to one or another treatment. Consequently, the timing of treatment seems to be more important.

Tooth Position in Wind Instrument Players: Dentofacial Cephalometric Analysis.

Background: Specific dentofacial characteristics in wind instrumentalists should be taken in consideration when analyzing physiological and anatomical issues regarding the musician’s embouchure, posture, and biomechanics during musical performance. Objectives: To compare tooth cephalometric characteristics between wind instrument players and string players (overjet, overbite, lower facial height, facial convexity, lower incisor inclination, and interincisal angle). Methods: In total, 48 wind instrumentalists (67%) and 24 string instrumentalists (33%). These musicians performed lateral tele-radiography and the correspondent linear and angular measurements of the dentofacial cephalometric analysis. Statistical comparison of wind and string instrumentalists was made by using an independent t-test. Results: Small variations on the analyzed parameters were found between the wind and string instrument groups. Based on the cephalometric analysis the variable interincisal angle was statistically significant (p < 0.05), when comparing the wind and string instrument group. Conclusions: Knowledge of the overjet and overbite value permits a substantial analysis on the tooth position of wind instrument players, where both of these parameters are increased and greater than the norm value. The cephalometry was an added value on the interpretation of possible factors that lead to the position of the central incisors of wind instruments. Till some extent in this group of musicians the applied forces during the embouchure mechanism on the anterior teeth and the existing perioral forces promote an equilibrium on the vector of forces. This study findings demonstrate that when evaluating the two samples, wind and string instruments there are different dentofacial configurations, however the only statistically significant differences that were found are related to the interincisal angle (p < 0.05).

Association of hard and soft tissue factors with gingival recession in orthodontically treated patients: A retrospective study

Orthodontic treatment is thought as a contributory factor in the development of recession. The objective of this study was to determine the factors associated with a gingival recession in patients who underwent orthodontic mechano-therapy. A retrospective chart review of 72 post-orthodontic cases done at the dental clinics of Aga Khan University hospital that were treated from 2009 to 2017. After evaluating dental records patients were recruited based on inclusion and exclusion criteria. Patients were divided into two groups based on the presence or absence of gingival recession on posttreatment photographs. Patients in each group were further assessed on the following factors: (1) Lower incisor inclination (IMPA). (2) Tissue thickness on the facio-lingual dimension. (3) Alveolar bone height. (4) Alveolar bone thickness. The mean age of patients at the start of treatment was 16.56±5.66years. Gingival recession was found in 40.3% of our patients while 59.7% of patients had no recession found after orthodontic treatment. Univariable logistic regression was applied for factors associated with a gingival recession following orthodontic treatment which showed that the odds ratio of gingival recession in thin gingival biotype are 14.4 times more than in thick gingival biotype. Multivariable regression analysis showed that the cases had 10.2 times more recession in thin biotype than those in the thick gingival biotype while adjusting for pre- and posttreatment alveolar heights following orthodontic treatment and with a confidence interval [95% CI=2.69 to 38.40]. It was concluded from this study that 40% of patients developed gingival recession in one or more teeth during orthodontic treatment. Among different factors pre-treatment, gingival biotype of patients and male gender were the factors that were more associated with the development of gingival recession.

Tratamento de Classe II utilizando Propulsor mandibular PowerScope II: Relato de caso clínico

A Classe II de Angle, além de ser uma das más oclusões mais procuradas para tratamento, é também um grande desafio para os ortodontistas. Quando um paciente se apresenta com deficiência mandibular e ainda em fase de crescimento, os aparelhos funcionais, geralmente, são escolhidos para a correção deste problema. Porém, em algumas situações, a falta de colaboração do paciente no uso destes aparelhos, especialmente os removíveis, podem comprometer o resultado do tratamento ortodôntico. Com a evolução dos aparelhos propulsores mandibulares, vários modelos funcionais começaram a surgir no mercado e, dentre estes, o PowerScope, um propulsor fixo híbrido. Entretanto, um dos efeitos esperados de todos os propulsores, sejam eles removíveis ou fixos, além da remodelação dento-alveolar, é a inclinação labial excessiva dos incisivos inferiores. Desta forma, o objetivo desse estudo foi demonstrar o uso do PowerScope II, na correção de Classe II de Angle em um paciente de 12 anos com deficiência mandibular, braquifacial e com incisivos superiores e inferiores vestibularizados. Após planejamento detalhado, optou-se por utilizar aparatologia fixa com prescrição Roth 0,022”, seguida pelo PowerScope II e mini parafusos inferiores bilaterais, como forma de ancoragem, para conter a vestibularização excessiva dos incisivos inferiores. Ao fim do tratamento o paciente manteve o perfil convexo com correção da má oclusão pela compensação dentoalveolar e conseguiu um bom controle de inclinação dos incisivos inferiores. Assim, pode-se concluir que a utilização desse dispositivo associado aos mini parafusos de ancoragem permitem uma abordagem conservadora em tratamentos de Classe II.

Therapeutic effectiveness of AdvanSync2 at different stages of skeletal maturity in skeletal Class II malocclusion: A single-blind clinical trial

Objectives: AdvanSync2 (Ormco, Glendora, California, USA) is a molar-to-molar fixed Class II corrector, based on the philosophy of Herbst which allows the bonding of the both upper and lower arches simultaneously along with fixed functional therapy. The purpose of this study was to cephalometrically compare the skeletal and dentoalveolar effects of AdvanSync2 in the correction of Class II malocclusions in circumpubertal and post-pubertal patients. Materials and Methods: Forty-eight samples were selected and divided into two groups based on their CVMI staging, Group A, i.e., at CVMI Stages 2 and 3 (18 girls and six boys) and Group B, i.e., CVMI Stages 4, 5, and 6 (19 girls and five boys). Cephalograms taken at pre- and post-AdvanSync2 stages were compared and analyzed. Results: The results showed that there was a significant increase in mandibular length in both groups. Both the groups also showed sagittal maxillary restriction, maxillary molar distalization, and retroclination of maxillary incisors. On comparison between Group A and Group B, there was no statistically significant differences in terms of maxillary position, size of maxilla, as well as upper and lower incisor inclinations in Group A except for improvement of mandibular position (SNB; P ≤ 0.01) and greater amount of chin growth (B -Pg; P ≤ 0.01) with respect to Group B. Conclusion: AdvanSync2 can be used as an effective fixed functional appliance in post-pubertal group for sagittal mandibular correction in skeletal Class II patients.

Comparison of Dentoskeletal Changes, Esthetic, and Functional Efficacy of Conventional and Novel Esthetic Twin Block Appliances among Class II Growing Patients: A Pilot Study.

A twin block appliance used for correction of skeletal Class II malocclusion suffers from undesirable dental effects and bulkiness. To overcome these limitations and the need for more esthetic appearance of this appliance, an esthetic twin block was designed and used in patients. This study aimed to compare dentoskeletal changes and esthetic and functional efficacy in patients treated with conventional and newly designed esthetic twin block (CTB and ETB) appliances using cephalometric measurements and a questionnaire. A pilot study with a 2-arm parallel-randomized double-blind clinical trial was conducted on 24 patients (20 males, 4 females) in the age group of 11-13 years. Subjects were treated with CTB (group 1 [G1]: n=12; mean age=11.67±0.49 years) and ETB (group 2 [G2]: n=12; mean age=11.75±0.62 years) appliances. A modified Pancherz analysis was performed to evaluate skeletal and dental changes. The esthetic and functional efficacy was evaluated by a questionnaire using Likert scale. Wilcoxon and Mann-Whitney U tests were employed for intra and intergroup comparisons respectively (p<0.05). In G1, a significant increase in lower incisor inclination was observed (p<0.05) whereas it was insignificant in G2. The changes were predominantly skeletal in G2 whereas they were both skeletal and dental in G1. ETB was found to be esthetically and functionally acceptable in all the patients while CTB patients were esthetically conscious, lacked confidence and had discomfort and difficulty in eating, chewing and speaking. ETB had greater skeletal effects with a reduced tendency of lower incisor proclination, was esthetically acceptable, and functionally more comfortable than the CTB.

Craniofacial morphology of wind and string instrument players: a cephalometric study

BackgroundPlaying an instrument may promote a parafunctional behavior within the cranio-cervical-mandibular-complex with unknown repercussions. The aim of this study was to find any association between the dental inter-arch relationship and the practice of a wind or string instrument.MethodsA sample of 77 musicians, divided in two groups of wind (n = 50) and string instrumentalists (n = 27), had a lateral cephalogram taken to compare six cephalometric parameters following the Rickett’s analysis (maxilla position, mandible position, facial type, skeletal class, upper incisor and lower incisor inclination). The Fisher test was performed to compare, with a 95% statistical confidence, if both groups have similar frequency distributions for each cephalometric parameter.ResultsNo statistical differences were found for the maxilla position, mandible position, facial type, skeletal class and upper incisor inclination. Statistical differences were found for the lower incisor inclination (p = 0.011).ConclusionsPlaying a wind instrument showed to have little orthopaedic influence at the craniofacial morphology, on contrary it may influence the lower incisor inclination with its osseous base.

Lower Incisor Inclination in Relation to Head Posture, Tongue and Hyoid Positions

Objectives: To investigate the relationship between head posture, hyoid bone, tongue position and lower incisor inclination. Materials and Methods: The study sample consisted of 98 subjects (35 males, 63 females), who had a mean age of 17.7 years in the permanent dentition and with a skeletal Class I relationship. Lower incisor inclination, craniovertical, craniocervical and craniohorizontal postural variables, tongue and hyoid position and airway measurements were evaluated on lateral cephalograms taken in natural head position. The study sample was divided into two groups according to lower incisor inclination (48 had IMPA&amp;lt;90 ⁰ with a mean degree of 88.09 and 50 had IMPA&amp;gt;90 ⁰ with a mean degree of 102.84) and a Student-t test was performed to compare and describe head posture, tongue and hyoid bone positions.Results: The subjects with upright incisors had a more posteriorly positioned hyoid bone relative to the mandibular symphysis compared with the subjects with flared incisors (p&amp;lt;0.05). Tongue length was greater in the flared incisor group than in the upright incisor group (p&amp;lt;0.05). In relation to head posture measurements, the upright incisor group had 3-3.5° larger cranio-cervical angles (NSL-OPT, NSL-CVT, NL-OPT, NL-CVT angles, p&amp;lt;0.05) than the flared incisor group. The airway measurements revealed no statistically significant difference between the groups.Conclusions: The position of the hyoid bone, tongue length and craniocervical head posture showed significant differences between upright and flared lower incisors.