Enhancing systematic reviews in orthodontics: a comparative examination of GPT-3.5 and GPT-4 for generating PICO-based queries with tailored prompts and configurations.

OBJECTIVES: The rapid advancement of Large Language Models (LLMs) has prompted an exploration of their efficacy in generating PICO-based (Patient, Intervention, Comparison, Outcome) queries, especially in the field of orthodontics. This study aimed to assess the usability of Large Language Models (LLMs), in aiding systematic review processes, with a specific focus on comparing the performance of ChatGPT 3.5 and ChatGPT 4 using a specialized prompt tailored for orthodontics. MATERIALS/METHODS: Five databases were perused to curate a sample of 77 systematic reviews and meta-analyses published between 2016 and 2021. Utilizing prompt engineering techniques, the LLMs were directed to formulate PICO questions, Boolean queries, and relevant keywords. The outputs were subsequently evaluated for accuracy and consistency by independent researchers using three-point and six-point Likert scales. Furthermore, the PICO records of 41 studies, which were compatible with the PROSPERO records, were compared with the responses provided by the models. RESULTS: ChatGPT 3.5 and 4 showcased a consistent ability to craft PICO-based queries. Statistically significant differences in accuracy were observed in specific categories, with GPT-4 often outperforming GPT-3.5. LIMITATIONS: The study's test set might not encapsulate the full range of LLM application scenarios. Emphasis on specific question types may also not reflect the complete capabilities of the models. CONCLUSIONS/IMPLICATIONS: Both ChatGPT 3.5 and 4 can be pivotal tools for generating PICO-driven queries in orthodontics when optimally configured. However, the precision required in medical research necessitates a judicious and critical evaluation of LLM-generated outputs, advocating for a circumspect integration into scientific investigations.

3D evaluation of cranial and dentofacial morphological differences between individuals with mouth breathing and nasal breathing.

INTRODUCTION: The present study aimed to identify the morphological differences in cranial and dentofacial structures between individuals with mouth-breathing and nasal-breathing. MATERIALS AND METHODS: The study included 120 individuals, 60 each in the nasal breathing (NB) and mouth breathing (MB) groups. 3D stereophotogrammetry, lateral cephalometric radiographs, and intraoral examination results were recorded by the researchers to determine the morphological differences between the MB group and the NB group. The study utilized cephalometric radiographs for 2D hard tissue measurements and 3D stereophotogrammetric records for linear and angular measurements. RESULTS: Statistically significant differences were found between the NB and MB groups' SNB angles (respectively, 79.3 ± 3.04, 76.6 ± 4.24, and p=0.002). Also, the NB group's SN-GoGn angle was lower than the MB group's (respectively, 31.5 ± 5.12, 36.0 ± 5.55, and p=0.002). Considering the Jarabak ratio, the NB group's Jarabak ratio was higher than the MB group (respectively,65.7 ± 4.16, 62.6 ± 4.10, and p=0.014). In 3D stereophotogrammetry measurements, increased Li-Me' was detected in the MB group than in NB group. CONCLUSION: Mouth breathing results in significant morphological differences that affect the development of both soft tissues and skeletal structures. Orthodontists utilize these characteristic features observed in mouth-breathing anomalies for early diagnosis and consider referring their patients for medical treatment of mouth breathing.

Clinical comparative study on the accuracy of palatal rugae in models obtained by different impression materials and intraoral scanning.

OBJECTIVE: Palatal rugae are frequently used in the evaluation of tooth movement after treatment in orthodontics and as a stable region in superimposition. It is important to note that the impression method and material used to record the rugae region affect the accuracy of the impression. The aim of this study is to compare the accuracy of palatal rugae, in three-dimensional (3D) by employing both conventional and digital impression methods. MATERIALS AND METHODS: In this study, 22 patients (12 females, 10 males) mean age of 13.5 ± 1.7 years old were selected with complete permanent dentition. Three different impressions were taken from the maxillae of the patients: conventional impression using silicone rubber impression material, conventional impression using alginate impression material, and optical impression using an intraoral scanner. The impressions' digital data were analyzed by the GOM Inspect (Version 2018, Braunschweig, Germany), a 3D analysis software. The Root Mean Square (RMS) values of the total ruga region were evaluated in this software. The data were statistically analyzed using the Jamovi program. The Kruskal-Wallis test and Mann-Whitney U test were performed due to the non-normal distribution of the data. RESULTS: There is no statistically significant difference between the comparison points of the right and left rugae's medial and lateral points and total rugae regions' RMS values. Although there was no statistically significant difference, the total RMS values of alginate and digital scan measurements showed closer results than the RMS values of silicone and digital scan measurements. CONCLUSION: The study found that there was no statistically significant difference in the total RMS values of the ruga region between traditional and digital impression methods. CLINICAL RELEVANCE: The treatment period in orthodontics is long. Different impression materials and methods can be used for diagnostic, mid-treatment, and final impressions. For superimpositions and treatment and post-treatment palatal ruga evaluations, traditional and digital impression methods are clinically acceptable and can be used as alternatives to each other.

The effect of layer thickness on the accuracy of the different in-house clear aligner attachments.

OBJECTIVE: The accuracy of the attachments, one of the key components of clear aligner therapy, is important for obtaining more precise tooth movement. The aim of this study was to evaluate the accuracy of the ovoid, hemi-ellipsoid, and vertical rectangular attachments produced by the digital light-processing(DLP) 3-dimensional printing technologies with 25 µm, 75 µm, and 125 µm layer thickness. MATERIALS AND METHODS: The ovoid, hemi-ellipsoid, and vertical rectangular attachments were positioned onto the convex surface of the central incisor by the software. The printing process was carried out by a DLP printer using a commercially printed resin with 25 µm, 75 µm, and 125 µm layer thickness (n = 30, for each group). All test models' digital data was exported into the reverse engineering software for the superimposition. After selecting the 5 comparison points for the ovoid and vertical rectangular attachments, and 6 comparison points for the hemi-ellipsoid attachment, the Root Mean Square (RMS) was evaluated for each group. RESULTS: There is a statistically significant difference between the 25 µm and 125 µm layer thickness of total RMS values in the ovoid, hemi-ellipsoid, and vertical rectangular attachment groups (p = 0.001, p = 0.03, and p = 0.00 respectively). The printing time with the 25 µm layer thickness was 4 times longer than with the 125 µm layer thickness. CONCLUSIONS: This study revealed that the accuracy of the attachments used for in-house clear aligner therapy is affected by the layer thickness of the 3D printer. CLINICAL RELEVANCE: The layer thickness of the 3D printer is a crucial factor in determining attachment accuracy, but its clinical significance is minimal. Clinicians should make informed decisions about the appropriate layer thickness, taking into account their workflow preferences, time constraints, and other practical considerations specific to their clinical practice.

Evaluation of the accuracy of fully automatic cephalometric analysis software with artificial intelligence algorithm.

OBJECTIVE: The aim of this study is to evaluate whether fully automatic cephalometric analysis software with artificial intelligence algorithms is as accurate as non-automated cephalometric analysis software for clinical diagnosis and research. MATERIALS AND METHODS: This is a retrospective archive study using lateral cephalometric radiographs taken from individuals aged 12-20 years. Cephalometric measurement data were obtained from these lateral cephalometric radiographs by manual landmark marking with non-automated computer software (Dolphin 11.8). Again, the same radiographs were made using fully automatic digital cephalometric analysis software OrthoDx™ (AI-Powered Orthodontic Imaging System, Phimentum) and WebCeph (Assemblecircle, Seoul, Korea) with artificial intelligence algorithm, without manual intervention of the researcher and fully automatic markings and measurements were made by the software. RESULTS: According to the consistency test, a statistically significant good level of consistency was found between Dolphin and OrthoDx™ measurements and Dolphin and WebCeph measurements in angular measurements (ICC > 0.75, P < .01, ICC > 0.75, P < 0, respectively. 01). A weak level of consistency was found in linear measurement and soft tissue parameters in both software (ICC < 0.50, P < .05, ICC < 0.50, P < .05), and the difference between measurements was statistically found to be different from "0." CONCLUSION: The results obtained from fully automatic cephalometric analysis software with artificial intelligence algorithms are similar to the results of non-automated cephalometric analysis software, although there are differences in some parameters. To minimize the margin of error in artificial intelligence-based fully automatic cephalometric software, the manual intervention of the observer is needed.

Is YouTubeTM an adequate source of oral hygiene education for orthodontic patients?

INTRODUCTION: The present study aims to assess the quality, reliability and content of the information provided by the YouTubeTM videos on oral hygiene during orthodontic treatment, to reveal the efficacy of the videos for patients and to help dentists who use this platform as a source to guide their patients accurately. METHOD: In the beginning, it was found that the most common search term on oral hygiene during orthodontic treatment in Google Trends was 'how to clean braces'. A total of 150 videos containing keywords were reviewed, and 56 videos were assessed within the scope of the study. Videos were analysed for reliability score, content analysis and GQS criteria. RESULTS: According to the results, the mean video length was statistically significantly greater in rich-content videos than in poor-content videos (p = 0.024). In addition, the reliability score of rich-content videos was statistically significantly higher than that of poor-content videos (p = 0.026). Likewise, the GQS of rich-content videos was statistically significantly higher than that of poor-content videos (p < 0.001). However, the number of views, the number of likes, the number of dislikes, the number of comments, the number of days since upload, the interaction index and the view rate did not statistically significantly differ by content categories (p > 0.05). CONCLUSION: The present study concluded that the YouTubeTM videos providing oral hygiene education for patients receiving or scheduled for orthodontic treatment had poor content and overall medium quality. The instantaneous data collection was one of the study's limitations.

Evaluation of an automated approach for facial midline detection and asymmetry assessment: A preliminary study.

OBJECTIVE: To examine the level of agreement between the conventional method and a machine-learning approach to facial midline determination and asymmetry assessment. SETTINGS AND SAMPLE POPULATION: The study included a total of 90 samples (53 females; 37 males) with different levels of mandibular asymmetry. MATERIALS AND METHODS: Two researchers placed predefined soft tissue landmarks individually on selected facial frontal photographs and created 10 reference lines. The midsagittal line was determined as perpendicular to the midpoint of the bipupillary line, and the same two reference lines and facial landmarks were automatically determined by the software using machine-learning algorithms, and researchers created the other 8 reference lines using the facial landmarks that were determined automatically by the software. In the following stage, 2 linear and 10 angular measurements were made by a single researcher on 270 photographs, and the consistency and differences between the measurements were evaluated with a one-sample t test, an intraclass correlation coefficient (ICC) and Bland-Altman Plots. RESULTS: The level of agreement of measurements between the researchers and the software was low for eight parameters (ICC˂0.70). The one-sample t test revealed that differences between the software and researcher measurements of lip canting and pronasale deviation were not statistically significantly different (P > .05). Aside from the body inclination difference in Group 3 (samples with a mandibular body inclination difference >6°), there was no clinically significant difference (˂3°) between the measurements of the two methods. CONCLUSIONS: Machine-learning algorithms have the potential for clinical use in asymmetry assessment and midline determination and can help clinicians in a manual approach.

Three-dimensional evaluation of social smile symmetry.

OBJECTIVE: To evaluate the social smile symmetry using three-dimensional (3D) stereophotogrammetric images. MATERIALS AND METHODS: The study was conducted with 3D facial images of 30 individuals (age range 13-25 years). The rest position was considered as the reference image and the social smile image was aligned on this image using the best-fit alignment method. The spatial differences between the same points established on both images using 3D analyses were determined for right and left points in X, Y, and Z planes. RESULTS: The highest difference related to spatial distance in right and left points was -0.56 mm (95% confidence interval [CI], -1.19, 0.06 mm) between right and left commissure (Com) points. The difference was not significant, and the Bland-Altman upper and lower limits were -3.85 mm and 2.71 mm, respectively. The highest difference for the transversal plane was found in Com points, similarly to the spatial distance (mean: 0.50 mm, 95% CI, -2.62, 1.02 mm). The differences between the changes in the left and right points in the Y and Z plane were not significant (P > .05). CONCLUSIONS: The social smile was observed to show asymmetry in varying amounts in the different directions. Asymmetry increases in some cases, specifically for the corners of the mouth.

Three-dimensional analysis of tooth movements after palatal miniscrew-supported molar distalization.

INTRODUCTION: The aim of this prospective clinical study was to evaluate the dentoalveolar effects of a palatal miniscrew-supported molar distalization appliance using a 3-dimensional reverse engineering method. METHODS: This study sample comprised 21 patients at an average age of 13.6 years with a bilateral Class II molar relationship. Distalization was performed using skeletal anchorage. Dental casts were obtained just before treatment and after appliance removal, and they were scanned with a 3-dimensional dental scanner. The digital dental cast images were aligned. Four points and 2 lines were determined on each tooth, and the correlations between tooth movements and the linear and angular changes were analyzed 3 dimensionally. RESULTS: In the sagittal direction, the first molars showed a mean linear movement of 4.10 ± 1.57 mm, with distal tipping of 11.02°; the central incisors showed a mean distal movement of 0.95 ± 0.40 mm, with retroclination of 1.59 ± 0.59°. In the vertical direction, only the first molars showed intrusion, with a mean value of -0.59 ± 0.50 mm. Rotation of the first molars was 4.92° ± 3.09°. The second molars had the greatest rotation. The highest correlation among tooth movements was found between the first and second molars. CONCLUSIONS: Through support from the anterior palatal region, the maxillary first molars were distalized without anchorage loss. Furthermore, movement was observed in all 3 planes of space with reduction from the posterior to the anterior in the maxillary arch.

Effects of rapid maxillary expansion on facial soft tissues : Deviation analysis on three-dimensional images.

OBJECTIVE: Changes in soft tissue in various morphological regions of the face immediately after rapid maxillary expansion (RME) were examined using three-dimensional (3D) deviation analyses. PATIENTS AND METHODS: A total of 50 patients were included in the study; 25 patients (11 female and 14 male) presented with a unilateral or bilateral posterior crossbite malocclusion requiring RME. In addition, 25 patients (13 female and 12 male) were included as a control group. The mean ages of the study group and control group were 9.8 years (range 8.1-12.6 years) and 9.6 years (range 8.3-12.2 years), respectively. The 3D stereophotogrammetric images acquired immediately before the appliance was cemented and after expansion had been completed in the treatment group were compared using Rapidform software. The 3D deviation analyses were made for the complete face and in the upper and lower face, upper and lower lips and nose regions. The amount of negative and positive deviations and the mean deviations were examined on the facial meshes for the 95th percentiles. RESULTS: Immediately after RME, the mean absolute deviation over the complete face was 0.54 ± 0.16 mm. The mean change for the upper face was 0.42 ± 0.17 mm (mean positive deviation: 0.37 ± 0.17 mm; mean negative deviation: -0.48 ± 0.18 mm). The mean absolute deviation was 0.62 ± 0.28 mm in the upper lip and 0.60 ± 0.34 mm in the lower lip. In the nose area, the absolute deviation was 0.41 ± 0.21 mm (mean positive deviation: 0.39 ± 0.16 mm; mean negative deviation: -0.43 ± 0.26 mm). CONCLUSIONS: Changes in facial soft tissues in the upper face, lower face, nasal soft tissues, and lower and upper lip regions were observed after RME.

Reproducibility of the lip position at rest: A 3-dimensional perspective.

INTRODUCTION: In this study, we evaluated the reproducibility of the lip position at rest in 3 dimensions using reverse engineering software and stereophotogrammetric images. METHODS: We used 3dMD Flex (3dMD, Atlanta, Ga) to obtain 60 stereophotogrammetric images from the same participant. Thirty images were obtained in 3 sessions on the same day, and the procedure was repeated 6 weeks later for 30 more images. The surface-base registration, the segmentation of the upper and lower lips, and the 3-dimensional deviation analysis were performed with Geomagic Control (3D Systems, Rock Hill, SC) software. The Shapiro-Wilk test, paired sample t test, Bland-Altman plots, and Wilcoxon signed rank test were used for statistical analysis at a significance level of P <0.05. RESULTS: The deviations of the upper lip on the first images were between 0.16 and 1.39 mm. The mean total deviation was 0.25 ± 0.12 mm. The mean deviation of the lower lip was 0.34 ± 0.17 mm. The deviations were observed between -1.96 and 1.97 mm. When the mean positive (P = 0.633 and P = 0.171, respectively) and the mean negative (P = 0.771 and P = 0.842, respectively) deviations of the upper and lower lips were analyzed, there was no significant difference between the 2 time points. CONCLUSIONS: The results suggest that the rest position can be reproduced within a small range both on the same day and between the sessions. More research with larger samples is needed to confirm these results.

Social smile reproducibility using 3-D stereophotogrammetry and reverse engineering technology.

OBJECTIVE: To assess the range of social smile reproducibility using 3-D stereophotogrammetry and reverse engineering technology. MATERIALS AND METHODS: Social smile images of white adolescents (N  =  15, mean age  =  15.4 ±1.5 years; range  =  14-17 years) were obtained using 3dMDFlex (3dMD, Atlanta, Ga). Each participant was asked to produce 16 social smiles at 3-minute intervals. All images were obtained in natural head position. Alignment of images, segmentation of smile area, and 3-D deviation analysis were carried out using Geomagic Control software (3D Systems Inc, Cary, NC). A single image was taken as a reference, and the remaining 15 images were compared with the reference image to evaluate positive and negative deviations. The differences between the mean deviation limits of participants with the highest and the lowest deviations and the total mean deviations were evaluated using Bland-Altman Plots. RESULTS: Minimum and maximum deviations of a single image from the reference image were 0.34 and 2.69 mm, respectively. Lowest deviation between two images was within 0.5 mm and 1.54 mm among all participants (mean, 0.96 ± 0.21 mm), and the highest deviation was between 0.41 mm and 2.69 mm (mean, 1.53 ± 0.46 mm). For a single patient, when all alignments were considered together, the mean deviation was between 0.32 ± 0.10 mm and 0.59 ± 0.24 mm. Mean deviation for one image was between 0.14 and 1.21 mm. CONCLUSIONS: The range of reproducibility of the social smile presented individual variability, but this variation was not clinically significant or detectable under routine clinical observation.

Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry.

OBJECTIVE: To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined. MATERIALS AND METHODS: Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS: The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Pro parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2. CONCLUSIONS: Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics.

Evaluation of the Relationship between Curve of Spee, WALA-FA Distance and Curve of Wilson in Normal Occlusion.

OBJECTIVE: To test the hypotheses that (i) there is a significant correlation between the curve of Spee (COS), basal arch (WALA ridge) to dental arch distance (WALA-FA distance) and curve of Wilson (CW) and that (ii) the deepening of the COS is affected by the CW and the WALA-FA distance. METHODS: Mandibular models of 50 patients aged between 20 and 35 years were scanned with TRIOS. The xyz coordinate system was determined, and a reference occlusal plane was generated. The depth of the COS, the CW, and WALA-FA distance were measured using an engineering software. RESULTS: The greatest difference in the measurement of the depth of the COS between the right and left was found to be 0.41±0.50 mm in the first molar teeth. On the basis of the results of Pearson correlation analysis, there was no strong correlation between the depth of the COS, the CW, and the WALA-FA distance. CONCLUSION: It was shown that there was no strong correlation between the depth of COS, CW, and WALA-FA distance. The CW and WALA-FA distance could not be effective in the deepening of the COS.

Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3-dimensional simulation and modeling program.

INTRODUCTION: The aims of this study were to use 3-dimensional simulation and modeling programs to evaluate the effects of bimaxillary orthognathic surgical correction of Class III malocclusions on pharyngeal airway space volume, and to compare them with the changes in obstructive sleep apnea measurements from polysomnography. METHODS: Twenty-five male patients (mean age, 21.6 years) with mandibular prognathism were treated with bilateral sagittal split osteotomy and LeFort I advancement. Polysomnography and computed tomography were performed before surgery and 1.4 ± 0.2 years after surgery. All computed tomography data were transferred to a computer, and the pharyngeal airway space was segmented using SimPlant OMS (Materialise Medical, Leuven, Belgium) programs. The pretreatment and posttreatment pharyngeal airway space determinants in volumetric, linear distance, and cross-sectional measurements, and polysomnography changes were compared with the paired samples t test. Pearson correlation was used to analyze the association between the computed tomography and polysomnography measurements. RESULTS: The results indicated that setback procedures produce anteroposterior narrowing of the pharyngeal airway space at the oropharyngeal and hypopharyngeal levels and the middle and inferior pharyngeal volumes (P <0.05). In contrast, advancement of the maxilla causes widening of the airway in the nasopharyngeal and retropalatal dimensions and increases the superior pharyngeal volume (P <0.05). Distinctively, bimaxillary orthognathic surgery induces significant increases in the total airway volume and the transverse dimensions of all airway areas (P <0.05). Significant correlations were found between the measurements on the computed tomography scans and crucial polysomnography parameters. CONCLUSIONS: Bimaxillary orthognathic surgery for correction of Class III malocclusion caused an increase of the total airway volume and improvement of polysomnography parameters. A proposed treatment plan can be modified according to the risk of potential airway compromise or even to improve it with 3-dimensional imaging techniques and polysomnography.

Radiofrequency heating and magnetic field interactions of fixed partial dentures during 3-tesla magnetic resonance imaging.

OBJECTIVE: This study evaluated the heating and magnetic field interactions of fixed partial dentures in a 3-Tesla (3T) magnetic resonance imaging (MRI) environment. STUDY DESIGN: Three substructure materials (Co-Cr, Ni-Cr, ZrO2) were used to fabricate twelve 4-retained bridges and 12 crowns. Specimens were evaluated at 3T for radiofrequency heating and magnetic field interactions. One-way analysis of variance (ANOVA) test was used to compare continuous variables of temperature change. Significance was set at P < .05. Translational attraction and torque values of specimens were also evaluated. RESULTS: None of the groups exhibited excessive heating (mean temperature change, < 1.4 °C), with maximum increase at the end of the T-1. Moreover, in all groups, only relatively minor magnetic field interactions that would not cause movement in situ were observed. CONCLUSION: The study findings indicated that patients with fixed partial dentures (single crown or bridge) fabricated from Co-Cr, Ni-Cr, and zirconia substructures may safely undergo MRI at up to 3T.

Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study.

OBJECTIVE: The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging. METHODS: The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage. RESULTS: At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity. CONCLUSIONS: Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.

Nasal cavity volume changes after rapid maxillary expansion in adolescents evaluated with 3-dimensional simulation and modeling programs.

INTRODUCTION: The purpose of this study was to evaluate the effects of rapid maxillary expansion on nasal cavity volume by using 3-dimensional simulation and modeling programs. METHODS: The study group consisted of 15 patients (9 boys, 6 girls; mean age, 13.86 years) with maxillary constriction. Computed tomography scans were obtained before treatment and 6 months after the end of expansion. All computed tomography data were transferred to a computer, and the nasal cavity and maxillary teeth were segmented by using the Mimics and Simplant Ortho software programs (both, Materialise, Leuven, Belgium). Paired samples t tests were used to compare pretreatment and posttreatment nasal cavity volumes and maxillary areas. Data analysis was performed by using the software program SPSS for Windows (version 15.00; SPSS, Chicago, Ill). RESULTS: Rapid maxillary expansion treatment induced significant increases in nasal cavity volume (P ≤ 0.001) and maxillary transverse dimensions (P ≤ 0.001). CONCLUSIONS: Both anterior-to-posterior and coronal-to-cranial expansions were observed after rapid maxillary expansion treatment, with the direction of expansion most likely affected by resistance from the cranial bones.