External root resorption and rapid maxillary expansion in the short-term: a CBCT comparative study between tooth-borne and bone-borne appliances, using 3D imaging digital technology.

BACKGROUND: The aim of the study was to analyze and compare external root resorption (ERR) in patients treated with tooth-borne (TB) and bone-borne (BB) rapid maxillary expansion (RME). METHODS: The sample included 40 subjects who received tooth-borne RME (TB group, average age: 13.1 ± 1.08 years) or bone-borne RME (BB group, average age: 14.5 ± 1.11 years) and Cone-beam computed tomography (CBCT) scans before treatment (T0) and after 3-month of retention (T1). A specific 3D Imaging technology was used to generate 3D models of posterior dentition (M1 = maxillary first molars, P2 = second premolars, P1 = first premolar) and calculate volumetric data (mean and percentage values) and shape changes, the latter obtained from deviation analysis between the radicular models at different time points. Evaluation of radicular length changes was performed for each tooth. Data were statistically analysed to perform intra-timing and inter-groups comparisons. RESULTS: A significant reduction of radicular volume and length was found in posterior dentition in both groups (p < 0.05), and the M1 (volume) and its palatal root (length) were mostly involved in this response. No differences were found between M1, P1 and P2 (p > 0.05) when volumetric changes were calculated as percentage of the total volume. Deviation analysis revealed that the radicular areas mostly affected by shape change were the apex and bucco-medial side. The amount of ERR was significantly greater in TB group compared to BB group. CONCLUSIONS: BB-RME treatment could reduce the amount of ERR at the post-expansion stage.

Midpalatal suture density ratio after rapid maxillary expansion evaluated by cone-beam computed tomography.

INTRODUCTION: Identifying the stage of midpalatal suture (MPS) fusion is essential for rapid maxillary expansion (RME). The objective of this study was to evaluate the relationship between MPS density ratio and the skeletal response after RME using cone-beam computed tomography (CBCT). METHODS: CBCT scans of 64 patients (age, 13.81 ± 1.68 years; 42 females and 22 males) who underwent RME as part of comprehensive orthodontic treatment were used for this study. Two CBCT records were made at T1 (pre-RME) and T2 (post-RME). MPS density was assessed by gray scale and the skeletal effects through linear measurements: greater palatine foramina, the width of the nasal cavity (NW), infraorbital foramina. The data were collected at 4 different times: baseline, 24 hours, 48 hours, and 4 weeks. RESULTS: There was no statistically significant correlation between MPS density ratio and greater palatine foramina or infraorbital foramina. Negative correlations with MPS density ratio are presented with the difference of age post-RME and pre-RME (r = -0.46, P = 0.033) in males, and NW (r = -0.41, P = 0.007) in females. A significant association between gender and the MPS density ratio was found (P = 0.015) in females. CONCLUSIONS: There is a weak negative correlation between the MPS density ratio and the difference of age post-RME and pre-RME in males and the NW in females. Females presented greater density ratios than males. MPS density ratio through CBCT does not appear to be an adequate parameter to predict the skeletal effect in adolescent patients and young adults.

Three-dimensional skeletal and dentoalveolar sagittal and vertical changes associated with cantilever Herbst appliance in prepubertal patients with Class II malocclusion.

INTRODUCTION: This study aimed to assess sagittal and vertical skeletal and dentoalveolar changes through the use of 3-dimensional imaging in prepubertal Class II malocclusion patients treated with a cantilever Herbst appliance (HA). Condyle-glenoid fossa positional changes were also quantified. METHODS: This retrospective cohort study assessed 22 children (11.2 years ± 1.2) consecutively treated with a cantilever HA for 12 months and 11 untreated children (aged 9.3 ± 0.30 years) that served as controls. Cone-beam computed tomography was performed at baseline (T1) and at the end of the observation period (T2). Movements in the regions of interest were measured as linear displacements from cone-beam computed tomography images through algebraic calculations. A Student t test for independent samples was used for group equivalence testing at T1, and the treatment differences between T2 and T1 were evaluated by 2 analyses of covariance, one considering the expected growth unit as a covariate and the other with an annualized factor. RESULTS: The largest dental movement was a mesial movement of mandibular molars (3.70 mm), whereas the largest skeletal changes consisted of a larger relative length of the mandible (difference of 1.2 mm) in the HA group than in the control group. CONCLUSIONS: Within the study limitations (retrospective cohort, historical control group, and sample size), 3-dimensional imaging suggests that HA corrected Class II malocclusion in a predominantly prepubertal sample through more dental than skeletal changes. The changes were more significant in the sagittal than in the vertical direction. In addition, relative stability in the condyle-fossa relationship was noted.

Evaluation of pulp cavity/chamber changes after tooth-borne and bone-borne rapid maxillary expansions: a CBCT study using surface-based superimposition and deviation analysis.

OBJECTIVES: To compare volume and shape changes of pulp chamber of maxillary posterior teeth between tooth-borne and bone-borne maxillary expansions in adolescents. MATERIALS AND METHODS: This study included 36 adolescents with bilateral maxillary crossbite who received tooth-borne rapid maxillary expansion (TB group, average age 14.4 years) or bone-borne rapid maxillary expansion (BB group, average age 14.7 years). Cone beam computed tomography (CBCT) was taken before treatment (T1) and after a 6-month retention period (T2). Volumetric and shape changes of pulp chamber of maxillary first molars and premolars were detected by referring to a specific 3D digital technology involving deviation analysis of T1/T2 CBCT-derived models of pulp chamber. Student's t tests were used to (1) compare T1 and T2 volumes of pulp chambers in TB and BB groups and (2) assess differences between the two groups in the post-treatment volumetric changes and in the percentage of matching of 3D pulp models. RESULTS: All investigated teeth showed a reduction of pulp volume, being this difference significant in both TB (p < 0.0001) and BB (p < 0.0001) groups. The volumetric reduction was greater in the TB group; also, subjects in the TB group showed a lower percentage of matching between T1 and T2 pulp models (p < 0.0001). The area most affected by shape change was that of pulp horns. CONCLUSIONS: TB expander could induce a higher volumetric reduction of pulp chamber of posterior teeth compared with BB expander, in the short term. CLINICAL RELEVANCE: The present findings add new information concerning the effects of RME protocols on pulp tissue.

Evaluation of mandibular changes after rapid maxillary expansion: a CBCT study in youngsters with unilateral posterior crossbite using a surface-to-surface matching technique.

OBJECTIVES: The purpose of this study was to evaluate mandibular asymmetry in youngsters with posterior unilateral crossbite (PUXB), through cone-beam computed tomography and reverse engineering technique, before and after rapid maxillary expansion (RME) treatment. MATERIALS AND METHODS: Forty cone-beam computed tomography (CBCT) images were obtained from all patients at two time points, namely T0 acquired before the placement of a Hyrax expander and T1 after appliance removal. The CBCT scans were segmented and volume rendered into a surface there-dimensional (3D) mesh model. Thereafter, mandibular models were digitally registered by using a "best-fit" algorithm. Surface and volumetric changes, between T0 and T1, were compared by using Student's t tests. RESULTS: A slight increase of 0.45 cm3 of the total mandibular volume was found at T1 when compared with T0 (p < 0.001). The mandibular hemi-volume on the crossbite side (CB) was slightly smaller than the non-crossbite side both at T0 and T1. However, the mean differences of hemi-volume from the CB (crossbite) and non-CB side between T0 and T1 show a decrease of 0.26 cm3 (p < 0.001). Findings for the surface-to-surface deviation analysis demonstrated a fine percentage of matching at T0 which slightly improved at T1 (p < 0.001). CONCLUSIONS: Youngsters affected by PUXB showed a very slight and not statistically significant volumetric and morphological asymmetry between CB side and non-CB side at T0. However, the change in mean differences of 0.26 cm cannot be considered clinically relevant. CLINICAL RELEVANCE: Mandibles in young PUXB patients exhibit only a very mild mandibular asymmetry. Although the statistically significant mean change found right after RME removal cannot be considered clinically relevant, a more consistent sample and a longer follow-up could be of interest in explaining the short-term findings.

Effect of photobiomodulation on the stability and displacement of orthodontic mini-implants submitted to immediate and delayed loading: a clinical study.

The aim of this study was to evaluate the effect of photobiomodulation (PBM) on the stability and displacement of orthodontic mini-implants (MIs) submitted to loading. Forty-eight and 35 mini-implants (1.5 × 8 × 1 mm) were assessed for stability and displacement, respectively (19 patients). MIs were allocated according to the intervention in 1-PBM + immediate loading (IL), 2-PBM + delayed loading (DL) (four weeks after implantation), 3-IL only, and 4-DL only. PBM (Therapy XT, DCM) was implemented using a red emission (660 nm, 4 J/cm2, 0.1 W, 20 s) immediately after implantation (day 0) and infrared emissions (808 nm; 8 J/cm2, 0.1 W, 40 s) in the following appointments every 48-72 h during two weeks (days 2, 4, 7, 9, 11, and 14). Loading of 150 gF was applied during three months for all MIs. The stability was assessed by resonance frequency analysis (Osstell ISQ), and images from Cone beam computed tomography were evaluated to determine the amount of the displacement of the MI's head. MIs from the PBM groups presented lower loss of stability (P = 0.0372). When the analysis considered the loading protocol as an additional variable, group two showed the lowest loss of stability, being significantly different from groups that did not receive PBM (P = 0.0161). There was no difference between groups two and four during the period without loading (P > 0.05). DL groups presented lower loss when the effective period of loading was assessed, independently of the application of PBM (P < 0.0001). All groups showed displacement of the MIs head without significant differences (P > 0.05). DL potentiated the effect of PBM, decreasing the loss of stability.

Presurgical Preparation of Infants With Unilateral Cleft Lip and Palate: The SAC-PP-MR Innovative Technique.

In this article, we demonstrate an effective, cheap, and fast way to shape the nasal alar cartilage in patients with unilateral cleft lip and palate. This technique straightens the vomer and brings the philtrum, columella, premaxilla, and the maxillary frenum to the midsagittal plane, while the alveolar ridges are shaped and positioned. This reduces the lip and palatal cleft to zero even in a 4-week period.

Buccal bone plate thickness after rapid maxillary expansion in mixed and permanent dentitions.

INTRODUCTION: Rapid maxillary expansion (RME) might cause buccal displacement of anchor teeth. Dislocation of teeth outside their alveolar process can damage the periodontium; for this reason, maxillary expansion using deciduous teeth as anchorage in the mixed dentition might be suggested. The aim of this study was to compare changes of buccal bone plate thickness on the maxillary permanent first molars after RME in the mixed and permanent dentitions with different types of anchorage. METHODS: Two groups of patients were evaluated with cone-beam computed tomography before and after RME. Group E (21 patients) underwent RME using deciduous teeth as anchorage; group 6 (16 patients) underwent RME using permanent teeth as anchorage. The Wilcoxon test was used to compare changes between the time points in the same groups, and the Mann-Whitney U test was used to compare differences between the groups. RESULTS: In group E, generally, no statistically significant reduction was found in buccal bone plate thickness between the time points. In group 6, most measurements showed significant reductions in buccal bone plate thickness (P <0.05) between the time points, with a maximum decrease of 1.25 mm. CONCLUSIONS: RME in the mixed dentition with the appliance anchored to deciduous teeth did not reduce the buccal bone plate thickness of the maxillary permanent first molars, except for the mesial roots on both sides. RME in the permanent dentition caused a reduction of the buccal bone plate thickness of the maxillary permanent first molars when they were used as anchorage in the permanent dentition.

Metabolic effects of treatment in patients with obstructive sleep apnea: a systematic review.

INTRODUCTION: Growth retardation was frequently observed in obstructive sleep apnea (OSA) patients but the complex mechanisms causing this condition are still unclear. Several findings suggested growth catch-up after surgical treatment but other studies did not confirm the results, showing no improvement in OSA patients after tonsillectomy and adenoidectomy (T&A). The aim of the present study was to systematically review scientific literature of the relationships between OSA and metabolic changes involving growth hormone (GH) axis before and after treatment in patients. EVIDENCE ACQUISITION: Different databases were searched without limitations up to August 2017. Additionally, the bibliographies of the finally selected articles were hand searched to identify any relevant publications that were not previously identified. EVIDENCE SYNTHESIS: From the 37 studies collected from all the databases based on their title and abstract, only 12 studies actually fulfilled the selection criteria. From the twelve finally selected articles, eight focused on growth mediators, two evaluated endothelial mediators, one focused on neurocognitive function and mediators and one focused on local inflammation. CONCLUSIONS: OSA children present lower levels of growth mediators (IGF-I and IGFBP-3) thus indicating growth retardation, significantly higher cardiovascular disease risk and decreased cognitive functions when compared to controls. T&A seems to improve all the above mentioned functions with great impact on general health.

Cephalometric landmark identification consistency between undergraduate dental students and orthodontic residents in 3-dimensional rendered cone-beam computed tomography images: A preliminary study.

INTRODUCTION: The aim of this study was to compare 3-dimensional landmark consistency and precision in skeletal structures in groups with different levels of experience with 2-dimensional cephalometrics. METHODS: Sixteen observers, all undergraduate or graduate students, were divided into 4 groups with different levels of experience in 2-dimensional landmarking and no previous experience in 3 dimensions. Group 1 consisted of 4 third-year dental students with no experience in cephalometric landmarking. Groups 2, 3, and 4 consisted of first-, second-, and third-year graduate students, with increasing levels of experience. The participants located 18 landmarks in 12 surface models of cone-beam computed tomography scans of patients on 3 separate occasions. The average of all examiners locating each landmark was defined as the centroid. The mean of the distances of each located point to the centroid of that landmark was used as the mean consistency (MC), and the standard deviation (SD) was used as the precision. Analysis of variance and post hoc Tukey comparisons between groups were done. RESULTS: The MC and SD values across landmarks, patients, and examiners were 1.03 ± 1.14 mm. The MC and SD were 0.89 ± 0.83 mm for group 1 with no experience, 1.02 ± 0.95 mm for group 2, 1.17 ± 1.60 mm for group 3, and 1.05 ± 1.00 mm for group 4. Significant differences were found among the groups. CONCLUSIONS: Comparing the observer groups studied, the undergraduate dental school students without previous experience in bidimensional cephalometrics obtained the best values in volumetric landmark location. Graduate students with increasing amounts of experience did not perform as well. These results and conclusions should be interpreted with caution because the number of subjects in each group was small.

Digital evaluation of nasal changes induced by rapid maxillary expansion with different anchorage and appliance design.

BACKGROUND: Scientific evidence showed that rapid maxillary expansion (RME) affects naso-maxillary complex, increasing nasal width and volume. This study aimed to evaluate nasal changes induced by rapid maxillary expansion with different anchorage and appliance design by using low dose and cone beam computed tomography. METHODS: A total of 44 patients (20 males, mean age 8y 8 m ± 1y 2 m; 24 females mean age 8y 2 m ± 1y 4 m) were included in the investigation and divided into three groups according to the appliance: Hyrax-type expander anchored to permanent teeth, modified Hyrax-type expander anchored to deciduous teeth, modified Haas-type expander anchored to deciduous teeth. Maxillary expansion was performed until overcorrection and the expander was passively kept in situ for 7 months at least. All patients had three-dimensional imaging before expansion (T0) and after the retention period (T1). Nasal floor width, nasal wall width, maxillary inter-molar width were measured by means of Mimics software. The paired sample t-test was employed to assess the significance of the differences between the time points; the analysis of variance test (ANOVA) was used to compare differences between groups. RESULTS: The statistical analysis revealed significant differences between T0 and T1 for each recorded measurement in each group; no significant differences were found by comparing groups. CONCLUSIONS: Rapid maxillary expansion produces a significant skeletal transverse expansion of nasal region in growing patients. No significant differences in nasal effects are expected when the appliance is anchored onto deciduous teeth, with or without the palatal acrylic coverage.

Precision and accuracy of suggested maxillary and mandibular landmarks with cone-beam computed tomography for regional superimpositions: An in vitro study.

INTRODUCTION: Our objective was to identify and evaluate the accuracy and precision (intrarater and interrater reliabilities) of various anatomic landmarks for use in 3-dimensional maxillary and mandibular regional superimpositions. METHODS: We used cone-beam computed tomography reconstructions of 10 human dried skulls to locate 10 landmarks in the maxilla and the mandible. Precision and accuracy were assessed with intrarater and interrater readings. Three examiners located these landmarks in the cone-beam computed tomography images 3 times with readings scheduled at 1-week intervals. Three-dimensional coordinates were determined (x, y, and z coordinates), and the intraclass correlation coefficient was computed to determine intrarater and interrater reliabilities, as well as the mean error difference and confidence intervals for each measurement. RESULTS: Bilateral mental foramina, bilateral infraorbital foramina, anterior nasal spine, incisive canal, and nasion showed the highest precision and accuracy in both intrarater and interrater reliabilities. Subspinale and bilateral lingulae had the lowest precision and accuracy in both intrarater and interrater reliabilities. CONCLUSIONS: When choosing the most accurate and precise landmarks for 3-dimensional cephalometric analysis or plane-derived maxillary and mandibular superimpositions, bilateral mental and infraorbital foramina, landmarks in the anterior region of the maxilla, and nasion appeared to be the best options of the analyzed landmarks. Caution is needed when using subspinale and bilateral lingulae because of their higher mean errors in location.

New algorithm for semiautomatic segmentation of nasal cavity and pharyngeal airway in comparison with manual segmentation using cone-beam computed tomography.

INTRODUCTION: Our objectives were to assess reliability, validity, and time efficiency of semiautomatic segmentation using Segura software of the nasal and pharyngeal airways, against manual segmentation with point-based analysis with color mapping. METHODS: Pharyngeal and nasal airways from 10 cone-beam computed tomography image sets were segmented manually and semiautomatically using Segura (University of Alberta, Edmonton, Alberta, Canada). To test intraexaminer and interexaminer reliabilities, semiautomatic segmentation was repeated 3 times by 1 examiner and then by 3 examiners. In addition to volume and surface area, point-based analysis was completed to assess the reconstructed 3-dimensional models from Segura against manual segmentation. The times of both methods of segmentation were also recorded to assess time efficiency. RESULTS: The reliability and validity of Segura were excellent (intraclass correlation coefficient, >0.9 for volume and surface area). Part analysis showed small differences between the Segura and manually segmented 3-dimensional models (greatest difference did not exceed 4.3 mm). Time of segmentation using Segura was significantly shorter than that for manual segmentation, 49 ± 11.0 vs 109 ± 9.4 minutes (P <0.001). CONCLUSIONS: Semiautomatic segmentation of the pharyngeal and nasal airways using Segura was found to be reliable, valid, and time efficient. Part analysis with color mapping was the key to explaining differences in upper airway volume and provides meaningful and clinically relevant analysis of 3-dimensional changes.

Short-term treatment effects produced by the Twin-block appliance: a systematic review and meta-analysis.

OBJECTIVE: To evaluate dental, skeletal, and soft tissue effects during Twin-block treatment. METHODS: A systematic search of several electronic databases (Medline, PubMed, Embase, all EBM reviews, and Web of Science) was conducted until July 2013, as well as a limited grey-literature search (Google Scholar). Human cephalometric studies that used a Twin-block appliance in a non-extraction and non-surgical approach were selected. A comparable control group of untreated subjects was required. Two authors independently reviewed and extracted data from the selected studies. Risk of bias was assessed. The type of meta-analysis was selected based on heterogeneity. RESULTS: Ultimately 10 articles were included. Proclination of lower incisors, retroclination of upper incisors, distal movement of upper molars and/or mesial movement of lower molars, increase in mandibular length, and/or forward movement of the mandible were consistently reported. Clinically significant restraint of maxillary growth was not found. Although the mandibular body length is increased, the facial impact of it is reduced by the simultaneous increment of the face height. Changes of lower face height and occlusal plane inclination varied, suggesting that vertical dimension can be manipulated in patients who would benefit from lower molar extrusion. As for lip position, there is not enough evidence to suggest clear lip position changes. CONCLUSIONS: Changes associated with a Class II correction were identified. Most of the changes individually were of limited clinical significance, but when combined reached clinical importance. No long-term changes were available.

Radiographic assessment of external root resorption associated with jackscrew-based maxillary expansion therapies: a systematic review.

OBJECTIVE: To evaluate in adolescents and young adults if jackscrew-based maxillary expansion therapies result in external root resorption as measured in vivo via any radiological method. METHODS: The authors conducted a systematic search of several electronic databases (MEDLINE, EMBASE, PubMed, Scopus, CINAHL, Evidence Based Medicine Reviews, LILACS) with the assistance of a senior librarian specialized in Health Sciences database searches through 25 August 2013, as well as a limited grey-literature search (Google Scholar). Human, in vivo studies of adolescents or young adults with transverse maxillary deficiency undergoing non-surgical maxillary expansion therapy through the use of a jackscrew-based maxillary expander with a radiographical assessment of root resorption were selected for full article review. Additionally, manual searches of reference lists of relevant articles were completed to identify additional publications not identified by electronic searches. The lowest levels of evidence accepted for inclusion were case-control studies or consecutively treated series of cases. Two authors independently reviewed and extracted data from selected studies. RESULTS: A total of 83 original articles were identified from the electronic database and limited grey-literature searches. Once selection criteria were applied, only three articles satisfied all inclusion criteria, and individual analysis of the selected articles was undertaken. CONCLUSIONS: Two-dimensional periapical radiographs do not fully reveal the amount of external root resorption associated with maxillary expansion therapy, except for frank apical root resorption. Three-dimensional cone-beam computed tomography radiography displays statistically significant root volume loss associated with maxillary expansion therapy. However, when considering volume-loss percentages, no statistical significance was found.

Medium-term effects of rapid maxillary expansion on nasal cavity and pharyngeal airway volumes considering age as a factor: A retrospective study.

OBJECTIVES: The medium-term effects of rapid maxillary expansion (RME) on nasal cavity (NC) and upper airway (UA) dimensions based on chronological age are still unclear. This retrospective study evaluated the medium-term changes occurring in the NC and pharyngeal airways (PA) after RME in two distinct age-based cohorts of patients. METHODS: This retrospective study included 48 subjects who underwent RME grouped in two cohorts: a 6-9-year-old group (EEG group: early expansion group - 25 subjects) and an 11-14-year-old group (LEG group: late expansion group - 23 subjects). NC and PA volumes were analyzed from CBCT imaging segmentation before RME (T0) and twelve months after RME (T1). The amount of maxillary expansion (PW) and minimal cross-sectional area (CSmin) were also considered. RESULTS: All PAs' volumetric sub-regions, CSmin and PW showed a significant volumetric increment (p < 0.05). Inter-group comparisons showed significant differences (p < 0.05) for nasopharynx and CSmin parameters (p < 0.05), while no significant changes were recorded for the other UA's sub-regions and PW (p > 0.05). According to a deviation analysis, part of the UA increase (more marked for the nasopharynx area) may have occurred due to reduced adenotonsillar tissues, which were larger in the EEG group. CONCLUSIONS: Twelve months after treatment, clinicians should not expect changes in the UAs dimensions to be solely related to treatment effects of RME; instead, normal craniofacial growth changes and spontaneous regression of the adenotonsillar tissue could represent the most significant factors influencing UAs changes. CLINICAL SIGNIFICANCE: From the clinical perspective, the results of the present study encourage caution when considering the therapeutic effects of RME on airways dimensions.

Tooth-Bone-Borne vs Bone-Borne Rapid Maxillary Expanders on Dentoskeletal Changes.

Purpose: This study compared the insertion and thickness of the cortical bone, the parallelism of the midpalatal suture, and the skeletal transverse dimension using a microimplant-assisted rapid palatal expansion (MARPE) with those produced by bone-anchored maxillary expander (BAME) in adults. Patients and Methods: The sample comprised 18 patients (mean age, 29.9±9.4 years) selected for the MARPE group and 18 (mean age 24.8±6.8 years) selected for the BAME group. Cone-Beam computed tomography scans taken just before and after the expansion. Results: After treatment, there was a significant palatal depth decrease. In addition, maxillary and mandibular width were increased in both groups. Regarding the cortical bone insertion and cortical bone width, it is shown an increase in both groups but those changes are not significant. However, the anterior suture opening effect occurs more frequently in the BAME than in the MARPE device. There are no differences in the frequency of opening of the midpalatal suture in the cases treated with MARPE and BAME, in both cases the most frequent opening morphology is parallel, independently of midpalatal suture maturation. Conclusion: There are no differences in the use of MARPE or BAME in the parallelism of the middle palatal suture, the cortical bone insertion, and thickness according to the maturation stages of the midpalatal suture but significantly increases the transverse dimensions of the maxillary skeleton.

Trial data for precision analysis of a three-dimensional mandibular mechanical advantage.

The data presented in this manuscript describe craniofacial landmark coordinate values, muscle and load moment arm lengths, and mechanical advantage rates for constructing a three-dimensional model of masticatory muscles. Cone-beam computed tomography scans from 30 subjects (aged 12-19 years, 16 females) were used. Thirty-six craniofacial landmarks were identified. Subsequently, the moment arms for 7 muscles and their corresponding load moment arms at incisor and molar positions were determined. Then, the three-dimensional mechanical advantage for each muscle and tooth position was calculated as the ratio of muscle moment arm to load moment arm. This procedure was repeated three times by a main examiner and once by two other examiners. The Friedman test and the square root of the 'method of moments' variance estimator were used to compare data among examiners and calculate random errors, respectively. Although the values for the craniofacial landmark coordinates and biomechanical variables are very close, differences were found between measurements, especially in the interexaminer comparisons. Values served as the basis for reliability (intraclass correlation coefficient) and errors (average mean of absolute differences) analysis in the research paper titled "A three-dimensional method to calculate mechanical advantage in mandibular function: Intra- and interexaminer reliability study," published in the Journal of Orofacial Orthopedics.

3D occlusal changes of upper first molars after rapid maxillary expansion on permanent versus deciduous teeth: a retrospective multicenter CBCT study.

BACKGROUND: The purpose of this study was to compare the three-dimensional dental changes for the maxillary first molars and the overall skeletal effects achieved after expansion between the rapid maxillary expansion (RME) appliance attached to two different anchor units, the maxillary deciduous molars and the maxillary permanent first molars. METHODS: Patients were retrospectively selected according to the anchorage unit used for RME: deciduous upper second molars (RME-E group; 10 M, 10 F; mean age 8.4 ± 1.1 years) and first upper permanent molars (RME-6 group; 10 M, 10 F; mean age 12.6 ± 1.8 years). CBCT scans were obtained before treatment start (T1) and after retention and removal of the expander (T2). Images were analyzed using a new three-dimensional intra-hemi-maxillary reference system. 3D landmarks were marked to calculate all changes on maxillary first permanent molars; mesio-distal and buccal-lingual inclination and rotation, as well as intermolar and interforaminal distances were calculated. The Wilcoxon test was used to compare within-group changes, whereas the Mann-Whitney test was used to compare between-group differences, with the significance level set at 0.05. RESULTS: In the RME-E group, significant distorotation and lingual inclination of the first permanent molars at T2 were observed (p < 0.01); in the RME-6 group, only the buccolingual inclination of the crossbite side after RME was resulted statistically significant (p < 0.01). In both groups, intermolar and interforaminal values increased significantly (p < 0.01). Intergroup analysis showed a significantly higher distorotation and reduced buccal inclination of maxillary first permanent molars in the RME-E group after RME (p < 0.01). CONCLUSIONS: RME is effective in treating maxillary transverse hypoplasia; RME anchored too deciduous teeth spontaneously reduces buccal inclination and increases distorotation of maxillary first permanent molars, whereas anchorage to permanent molars is associated with increased buccal inclination, albeit with little clinical significance.