Inclination Of Molars Research Articles

Transverse dentoalveolar development in Chinese children and adolescents: A cross-sectional study using revised Andrews’ Element III analysis

This study investigated the prevalence of maxillary transverse deficiency (MTD) in Chinese children and adolescents using revised Andrews' Element III analysis and studied transverse developmental characteristics of the maxillomandibular complex. Plaster or digital casts of 794 participants aged 7-18 years were evaluated. MTD was diagnosed when the maxilla-mandible width difference, represented by the decompensated maxillary and mandibular first molars, exceeded 4 mm. The average prevalence of MTD among patients aged 7-18 years was 31.1%. Patients with MTD exhibited narrower maxillary and/or wider mandibular arches. Strikingly, 32.3% of participants with posterior crossbite because of local crowding or mandibular deviation were not diagnosed with MTD. Dental compensation, such as a greater buccolingual inclination of the first molars, was common in patients with MTD. Transverse growth of the maxillomandibular complex was completed by 17 years old, with the maxilla undergoing greater transverse growth than the mandible. The physiological buccolingual inclination of first molars was observed in patients without MTD. The 95% reference value of the palatal arch width was 31.9-42.3 mm. The prevalence of MTD is 31.1% among Chinese children and adolescents. However, it is often camouflaged by dental compensation and sagittal discrepancy. The etiology of MTD is uncoordinated width in the maxillomandibular complex, which is not solely attributed to a narrow maxilla but also to an excessively wide mandible. To enhance diagnostic accuracy, individualized measurements of the maxillomandibular complex and a revised dental decompensation formula, rather than posterior crossbite alone, are recommended for transverse diagnosis. A potential presence of MTD is indicated when the palatal arch width is<31.9 mm.

Biomechanical behaviour of tilted abutment after fixed partial denture restoration of CAD/CAM materials

BackgroundFailure to restore missing teeth in time can easily lead to the mesial tilting of the distal abutment teeth. However, a fixed partial denture (FPD) can improve stress conduction and distribution and prevent periodontal injuries. In these more complex cases, it is necessary to consider various factors comprehensively to improve conventional treatment planning and achieve better results.MethodsWe selected a patient with a missing first molar and a mesial inclination of the second molar, leaving inadequate space or bone mass for implant denture restoration, necessitating an FPD for restoration. Three-dimensional finite element analysis (3D-FEA) combined with photoelastic analysis were used to explore how the inclination angle (0 ‒ 30°) and different dental restoration materials (zirconia, lithium disilicate, polymer-infiltrated ceramic network, and resin composite) affect the biomechanical behaviour of FPD‒abutments‒periodontal tissue complex.ResultsThe stress was easily concentrated in the FPD connectors, enamel shoulder collar, periapical area, and root bifurcation. The stress on FPD and the periodontal ligament (PDL) of the second premolar increased with an increase in the elastic modulus of FPD, with an opposite trend in the abutments, the alveolar bone, and the PDL of the second molar. The stress on the FPD and alveolar bone increased with increased inclination angle of the distal abutment. The stress on two abutments and their PDL were positively correlated with the inclination angle in two stages; however, when the inclination angle > 12°, the second premolar and its PDL showed a negative correlation.ConclusionsFPDs can be used for restoration within 24° of distal abutment inclination, but protecting the abutments (< 12° especially) and the periodontal tissue (> 12° especially) must be taken seriously. For this purpose, an FPD material with higher strength is recommended.

Effects On Palatal Surface Area In Mixed Dentition Patients Treated With Leaf Expander And Rapid Palatal Expander, Compared To Untreated Subjects: A Randomised Clinical Trial.

To evaluate palatal surface effects induced by LE and RPE, alongside spontaneous changes in an untreated group, and to compare differences in canine and molar inclination among the three groups. This randomised clinical trial aimed to compare digital models pre- and post-treatment over 12 months in patients receiving tooth-borne Leaf Expander® (LE) and tooth-borne Hyrax-type maxillary expander (RPE) treatments, alongside untreated patients. Analysis included 24 LE patients (13 males, 11 females, mean age 8.5±1.5), 22 RPE patients (10 males, 12 females, mean age 7.9±1.6), and 17 untreated subjects (7 males, 10 females, mean age 8.1±1.2). Inclusion criteria comprised indications for maxillary expansion treatment, mixed dentition, CVMS ≤ 3, erupted first molars, and good oral hygiene. Digital models were obtained using an intraoral scanner pre- and post-treatment. Palatal surface, segmented into anterior, median, and posterior zones, and canine/molar inclination were measured at T0-T1 using VAM software as the primary and secondary endpoint. Statistical analyses involved paired-sample T-tests for intra-group comparisons and ANOVA tests with Bonferroni correction for inter-group comparisons. No significant difference in palatal surface increment was found between the two experimental groups (LE and RPE); both demonstrated a significant increase in palatal surface. The greatest increment occurred in the median palate zone for both experimental groups. The increment in the untreated control group was not significant. Furthermore, the RPE group showed a greater inclination of permanent molars compared to those treated with LE, indicating that expansion with lighter and continuous forces may lead to fewer dental side effects.

Comparative evaluation of buccolingual inclination of molars in low-angle cases and high-angle cases using manual technique- A pilot study

The general feature of occlusal curvature, when viewed from the front, consists of a buccal inclination of the maxillary molars and a lingual inclination of the mandibular molars. The fourth key of Andrew’s six keys of occlusion is related to the curve of Wilson, describing the posterior inclination of the crowns of the lower posterior teeth as a concave curve, setting the molars with a lingual torque. Facial skeletal characteristics of subjects with a vertical growth pattern include increased total face height, especially the lower anterior face height, high mandibular plane angle, clockwise mandibular rotation, short mandibular ramus, and high gonial angle. Opposite aspects are present in subjects with a horizontal growth pattern. This study aimed to measure the buccolingual inclination of maxillary first molars in low-angle and high-angle cases using a manual technique. 20 subjects with permanent dentition were divided into 2 groups. Group I comprises 10 subjects with a low-angle case (proportionally short lower anterior facial height) and group II with a high-angle case (proportionally long lower anterior facial height). The buccolingual inclination of 1st molar was assessed on model casts.The maxillary posterior teeth of subjects with a vertical growth pattern (group II) had a significantly greater buccal inclination compared with those of subjects with a horizontal growth pattern (group I).

Tip, torque and rotation of maxillary molars during distalization using Invisalign: a CBCT study

BackgroundDesirable molar distalization by bodily movement is challenging and can be difficult to achieve. This study investigated changes in molar angulation (mesiodistal tipping), molar inclination (buccolingual torque) and rotation during distalization using clear aligner therapy (CAT).Materials and methodsThis retrospective study included 38 cone beam computed tomographic images (CBCTs) taken for patients treated with molar distalization using CAT. The study evaluated pre- (T0) and post-treatment (T1) CBCTs of 19 adult patients (36.68 ± 13.50 years) who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization. Changes in maxillary molar tip, torque and rotation were measured for 61 molars (183 roots). Paired t-test was used to evaluate the differences between pre- and post-treatment readings. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC).ResultsMolar angulation did not show significant change after distalization (p = 0.158) however, there was significant increase in buccal molar inclination (p = 0.034) and mesiobuccal molar rotation (p < 0.001).ConclusionMolar distalization of 2 mm did not cause significant molar tipping. Maxillary molars showed significant buccal inclination (increased torque) and mesiobuccal rotation after distalization.

Evaluation of Buccolingual Inclinations of First Molars Among Different Vertical Facial Patterns in Class II Division I Subjects.

Background Knowing the characteristics of vertical patterns is crucial to provide the best orthodontic treatment. Cone beam computed tomography (CBCT) offers a valuable tool for evaluating true buccolingual inclinations. The current study investigates the buccolingual inclination of first molars in adult subjects with different vertical facial patterns. Methods CBCT scans of 66 adult patients (31 males, 35 females) with a mean age of 31.6 years (SD: 6.4 years) exhibiting skeletal class II division I maxillomandibular relationships were employed. Participants were categorized into three groups based on linear and angular measurements: normodivergent group (n=22), hypodivergent group (n=22), and hyperdivergent group (n=22). The independent samples t-test and Mann-Whitney U-test were conducted to investigate statistical differences in terms of buccolingual inclination between the three vertical patterns. Results Statistically significant differences were observed in the buccolingual inclinations of both maxillary and mandibular first molars in the hypodivergent group compared to the other groups (p<0.05). Conclusions In patients with class II division I sagittal relationships, the buccolingual inclinations of the first molars exhibit similarities between normodivergent and hyperdivergent groups. However, these inclinations differ significantly in hypodivergent adult subjects.

Relationship of buccolingual inclination between the alveolar bone and first molar in different vertical facial types: A CBCT study

BackgroundThis study aimed to investigate the differences in the buccolingual inclination and transverse width of maxillary and mandibular first molars among different vertical facial types. MethodsIn all, 78 samples were divided into three groups based on the GoGn-SN angle: the low-angle group (n = 26, mean age=24.21±5.11), average-angle group (n = 26, mean age=22.66±3.72), and high-angle group (n = 26, mean age=22.23±2.43). Cone beam computed tomography (CBCT) measurements were used to assess the buccolingual inclination of the axis of the maxillary and mandibular first molars, as well as the buccolingual inclination of the alveolar bone, the dental arch width, and the basal bone width. One-way ANOVA, the LSD test, and Pearson correlation analysis were performed. ResultsThe high-angle group showed significantly greater lingual inclination of the maxillary alveolar bone than the low-angle group and average-angle group (p < 0.001; p < 0.05). The difference in buccolingual inclination of the axis of the maxillary first molar and the alveolar bone was significantly greater in the high-angle group than in the low-angle group (p < 0.05). Both the maxillary and mandibular dental arch were significantly narrower in the high-angle group than in the other two groups. The mandibular basal bone was also significantly narrower in the high-angle group than in the low-angle group and average-angle group (p < 0.001; p < 0.01). ConclusionsThe alveolar bone of maxillary first molar in the high-angle group was more palatal inclined than that the low-angle group and the average-angle group, which suggests that orthodontists should pay more attention to the root-bone relationship in the high-angle group during expansion treatment to prevent bone fenestration and dehiscense.

Srovnání změn v dolním zubním oblouku u pacientů léčených konvenčními zámky a samoligujícími zámky

Aim: The aim was to assess the changes in the mandible in patients treated with conventional brackets compared to those treated with self-ligating brackets. In particular, we focused on the degree of transversal changes and the length of therapy. Material and method: The sample included 43 patients; 11 men and 32 women. The mean age was 22.2 years. The patients had complete permanent dentition, were treated without extractions, molars in Angle Class I. The subjects were divided into two groups – conventional brackets, self-ligating brackets. Measurements were performed in scans of cast models made prior to therapy (T1), after removal of fixed appliance (T2), the length of treatment was given in months. The changes in intercanine and intermolar distance were compared in teeth and in relevant points on WALA ridge of the mandible. ORTODONCIE | ročník 33 | č. 2/2024 ODBORNÉ PRÁCE / ORGINAL ARTICLES 29 www.ortodonciejournal.cz | e-mail: redakce@ortodonciejournal.cz, office@ortodonciejournal.cz Results: In lower first molars the change in intermolar width was significant in both groups both at T1 and T2. The change was significantly bigger in the group with self-ligating brackets. The change in intercanine width between T2 and T1 was statistically significant only in the group with self-ligating brackets when measured on canine tips. Measurements at FA points (the most prominent point in the middle of longitudinal axis of the clinical crown) did not prove significant change. At WALA the change between T2 and T1 was significant only in the group with self-ligating brackets and only in first lower molars (clinically the change was small). The change in the distance WALA-FA in first lower molars on the left and on the right between T2 and T1 was statistically significant in both groups, however, it was significantly bigger in the group with self-ligating brackets. The difference in the length of therapy was not statistically significant. Conclusion: In patients with self-ligating brackets there is a greater expansion in first molars and canines. We can also observe more prominent vestibular inclination of canines and first molars. In patien

Evaluation of maxillary dimensional changes in the mixed dentition: clear aligners vs acrylic expanders.

To compare changes in upper arch dimension and molar inclination between Invisalign First (IF) and removable acrylic expander (RE) treatments during the mixed dentition period. Seventeen patients meeting inclusion criteria underwent IF treatment and were age matched with a group that received treatment with a removable acrylic expander (RE). Intercanine width (ICW), intermolar width, arch depth, buccolingual inclination of the first molars (MI), surface area (SA) and volume (VAP) of the anterior palate, and expansion were compared before and after treatment. The predictability of expansion was calculated for the IF group. Analysis of variance and Kruskal-Wallis tests were used to assess differences. The ICW increased significantly by 2.14 mm in the IF group and 3.49 mm in the RE group, with no significant intergroup difference. Both groups exhibited significant increases in intermolar width (P < .05), except for intermolar distopalatal width in the IF group (P = .246). Mesiobuccal rotation of the first molar was observed with IF treatment. Although SA and VAP increased in both groups, the changes were not significant for the IF group (P > .05). The RE group exhibited significantly higher increases (P < .05), with an SA increase of 34.32 mm2 and VAP increase of 119.15 mm3. MI changes were in the opposite directions. The prediction accuracy of expansion was 70.28% for canines and 34.12% for first molars. Both appliances effectively expanded the intercanine region in growing patients. Expansion predictability was lower in first molars than in canines for the IF group. Removable acrylic expanders could be a choice of preference for expansion targeted to the molar region.

Analysis of changes and correlation in condyle-fossa relationship after maxillary skeletal expansion.

To investigate the changes in condyle-glenoid fossa relationship after maxillary skeletal expansion (MSE) and to verify the correlation between the condyle positional changes and expansion effect. In this study, 20 patients (mean age 21.1 ± 5.7 years, 8 male, 12 female) with maxillary transverse deficiency (MTD) were treated with the MSE appliance, which contained molar bands and a expander with four micro-implants. The CBCT images were taken before expansion (T0), after expansion (T1) and after 6 months of maintenance (T2). The posterior TMJ space (PS), superior TMJ space (SS), anterior TMJ space, coronal lateral TMJ space (CLS), coronal medial TMJ space (CMS), condyle axis angle, maxillary basal bone width (BWM), inter-molars width, nasal bone width, molar inclination and molar palatal cusp height (U6H) were measured using Dolphin Imaging. At T1, compared with T0, the PS and SS significantly increased by 0.41 mm (P = .008) and 0.3 mm (P = .007). But only the SS significantly increased by 0.21 mm (P = .025) at T2. There was a significant difference of 0.37 mm (left-right, P = .014) between the left and right SS at T0, but no significant difference at T1 and T2. The increased BMW showed weak positive correlations with the change of PS (P = .015) and CMS (P = .031), and the decreased U6H showed weak negative correlations with the change of PS (P = .015) and CLS (P = .031) at T1. The use of MSE led to an increase in the SS and PS, which were weakly correlated with BWM and U6H. But this effect in the TMJ space gradually diminished after 6 months of maintenance, and the symmetry of the condyle-fossa relationship was preserved.

FIVE-YEAR RADIOGRAPHIC FOLLOW-UP OF ASYMPTOMATIC IMPACTED THIRD MOLAR TEETH WITH COMPLETED APICAL ROOT DEVELOPMENT

Third molar teeth can stay impacted due to systemic factors, space deficiency, pathology or an anatomical obstacle. The positions, angles, follicle sizes, and impaction statuses of impacted third molars can change over time. The purpose of this study is to investigate changes in the position, inclination, angle, and follicular width of impacted third molars at the end of a 5-year follow-up on panoramic radiographs. Retrospective analyses of a total of 98 impacted third molar teeth were carried out on panoramic radiographs taken at 5-year intervals for 31 patients who presented to the Department of Oral and Maxillofacial Radiology at Faculty of Dentistry for various reasons between 2013 and 2021. The mean angle of the examined impacted third molars with the occlusal plane was 26.725±27.31° at the beginning of the 5-year follow-up and 26.399±28.46° at the end of the follow-up. There was a 5° angular change(inclination) in 4(8.2%) impacted molars. In the examinations of the panoramic radiographs taken at 5-year intervals, no pathologic change around any impacted third molar or resorption in neighboring teeth was observed. There were inclination changes in 2(4%) of the impacted molars and position changes in 11(22.4%). The changes may be occur in the position, inclination, angle, and follicular width of asymptomatic impacted teeth in time. It is important that asymptomatic impacted teeth can be followed radiographically to evaluate the effects of changes in position, inclination, angle and follicle width over time on the impacted tooth and surrounding tissues and to prevent complications that may occur after a possible impacted third molar extraction.

Three-dimensional analysis of posterior tooth inclinations in transverse and sagittal relationships: A cross-sectional study

To compare tooth inclinations in different sagittal skeletal patterns and transverse maxillary relationships three-dimensionally. A cross-sectional study carried out with 132 three-dimensional digital models in the complete permanent dentition divided into six groups (n=22); three groups with maxillary atresia: G1- skeletal class I, G2- skeletal class II and G3-skeletal class III; three groups without maxillary atresia: G4- skeletal class I; G5- skeletal class II and G6- skeletal class III. The comparison between the skeletal pattern was performed by the non-parametric tests of Kruskal Wallis and Dunn and between the groups by the non-parametric test of Mann Whitney. Subjects with skeletal class II and maxillary atresia had a greater lingual inclination of the maxillary teeth than those with class I and III; Subjects with skeletal class II without atresia had a less lingual inclination of the mandibular molars than the other classes (p<0.05). The maxillary premolars showed no variation in dental inclination with atresia, independent of the skeletal class in G1, G2, and G3 (p>0.05). The mandibular premolars showed that the groups without atresia G4, G5, and G6 presented no significant difference (p>0.05). Lower premolars in skeletal class III malocclusion individuals with atresia had a more negative inclination than the others. There is a difference in the inclination of posterior teeth between individuals with and without maxillary atresia and skeletal classes I, II, and III.

Three-dimensional finite element analysis of the uprighting movement of mandibular mesially inclined second molars

The mesially inclined mandibular second molar can be supported upright by the microimplant anchorage. This study established the finite element model to analyze the displacement trend and periodontal ligament (PDL) stress distribution of the uprighting mandibular second molar with the microimplant under different conditions. A 3-dimensional model of the mandible and dentition was established. The mesial inclination of the mandibular second molar was 30°, 45°, and 60°. Microimplants were implanted between the buccal side of the second premolar and the first molar and in the distal part of the mandibular second molar, respectively. Six groups were set, each loaded with 0.5 N of force. The second molar initial displacement trend and PDL stress distribution were evaluated. The PDL stress of mandibular second molars in all groups was within the physiological limit, and the PDL stress of mandibular second molars in the distal implant groups was lower than that of mandibular second molars in the mesial implant groups. PDL stress concentration in the cervical area. Tooth displacement decreased as the mesial inclination angle of the second molars increased. The sagittal displacement of mesial implant groups was larger, and there was a tendency of mesiobuccal torsion when standing uprighting; the vertical displacement of distal implant groups was larger, and there was a tendency of distal lingual torsion when standing uprighting. Distal microimplant has a better extrusion effect on the mesially inclined second molar, whereas mesial microimplant has a better effect on the distal movement. The optimal orthodontic force for microimplant traction on mesially inclined second molars is 0.5-0.8 N.

Miniscrews position for a tissue bone borne palatal C-expander affects the displacement pattern of nasomaxillary complex: a finite element study

This study aimed to evaluate the difference in expansion patterns based on the position of miniscrews for a tissue-bone-borne palatal C-expander using a finite element method. Ten expansion models were examined, each representing a different position of miniscrews on the palate. Models A and B had miniscrews symmetrically placed 7 mm and 15 mm below the cementoenamel junction (CEJ), respectively. Models C to J had miniscrews positioned in a triangular manner at 7 mm and 15 mm below CEJ. Stress, displacement, angular changes of the bone and teeth, and changes in the nasomaxillary complex were measured using elastoplastic behavior models through static-nonlinear simulation employing an implicit method. The anterior and posterior parts of paramidpalatal suture area were identified as ANT, TPS-M, and TPS-L, and their ratio was assessed. Model A, which featured three miniscrews located 7 mm below the CEJ, exhibited the least molar inclination and the smallest amount of skeletal expansion. Model I, with two miniscrews placed between the first and second molars, demonstrated the greatest lateral displacement at point N on the nasal cavity wall, along with the smallest ratio of ANT to TPS-M or TPS-L. This finding suggests that the posterior expansion of the palate in relation to the anterior expansion was maximized. The results of this study indicate that strategic positioning of miniscrews is effective in achieving various expansion patterns based on the targeted correction areas within the nasomaxillary complex.

Skeletal Anchorage Augmentation in Extraction/Nonextraction Orthodontic Treatment: A Randomized Clinical Study.

To evaluate and compare skeletal, dental, and soft tissue parameters by therapeutic extraction of first premolar and nonextraction distalization of maxillary and mandibular arches in bimaxillary proclination using the skeletal anchorage system. About 40 orthodontic patients undergoing extraction or nonextraction treatment are enrolled in a randomized clinical trial. Participants are randomly assigned to either the extraction or nonextraction group and receive treatment augmented with skeletal anchorage. Mini implants were placed in the extraction group for retraction and infra-zygomatic crest (IZC) and buccal shelf screws were placed in the nonextraction group for distalization. Comparison between the ages of the patients among both Groups showed no significant difference. A significant difference is observed in dental and soft tissue parameters before and after the treatment in group A, whereas skeletal parameters also showed significant changes along with dental and soft tissue parameters in group B. There is a significant change in the position of incisors by retraction and facial profile improves gradually in group A while for group B, a marked change in lower facial height was even seen. On comparing both the groups, a highly significant difference can be seen with respect to the amount of incisor retraction and change in molar inclination. The time taken for retraction of incisors is less in comparison to distalization. With this, we can easily avoid premolar extraction, and in cases of impacted third molars distalization as when indicated can be helpful as a part of the nonextraction treatment plan.

Ectopic Eruption of the Maxillary Permanent First Molar: A Brief Review and Clinical Case Report

The Ectopic Eruption of the Maxillary Permanent First Molar (EEMPFM) is an eruption anomaly, characterized for the maxillary permanent first molar’s impaction in the distal surface of the deciduous second molar. The etiology is related with change of the axial axis of eruption of the permanent first molar associated with missing space in the maxilla. The diagnosis is the combination of clinical and complementary examination. There are two types of Ectopic Eruption: the reversible and the irreversible. The irreversible type requires orthodontics treatment, because it causes root resorption of the deciduous second molar, causing its premature loss. For the treatment, procedures can be used with the aim of promoting distal inclination of the ectopic first molar, using separator elastics, removable or fixed appliances. The aim of this work is to report a clinical case of a patient of 9 years and 6 months old, female gender, who attended the Clinic presenting EEMPFM of the maxillary right permanent first molar. The treatment was a removable appliance composed with an acrylic base plate with clasps and a finger spring activated against a resin button bonded on the mesiobuccal cusp of the maxillary right permanent first molar. The correction of this anomaly was obtained with 35 days of treatment. Therefore, the sequence of procedures from diagnosis to the indication of an adequate treatment method is fundamental to obtain satisfactory results.

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

BackgroundThe 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.MethodsPatients 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.ResultsIn 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).ConclusionsRME 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.

EFFECTS OF 2x4 APPLIANCE AND NiTi OPEN SPRING ON MIXED DENTITION

Background/Objectives: The mixed dentition period is the best time to guide the occlusion and intercept a malocclusion. Among the preventive orthodontic procedures, space recovery is considered extremely important for the biogenesis of the occlusion to follow its normal course. Several orthodontic appliances indicated for space recovery in mixed dentition are mentioned in the literature and among them, mechanics with a fixed 2x4 partial appliance.This study aimed to evaluate changes in the dimensions of the upper arch after using a 2x4 fixed partial appliance with expanded CuNiTi wires and open NiTi springs. Material and Methods: Twenty-four children (±9 years) were assessed who had no space for the eruption of permanent teeth in the upper arch, treated with a 2x4 fixed partial appliance. Lateral teleradiography imaging, panoramic radiography and cast models were used before and after the treatment. The results were compared to a control group of 24 children who did not receive treatment and had their documents assessed for growth-related changes. The following changes were evaluated: dimension of arch perimeter, arch depth, intermolar distance, and inclination and displacement of permanent upper molars and incisors. Student’s t-test was used to assess the differences between pre- and post-treatment times, with significance level of 5%. Results: Increases were observed in arch perimeter (p=0) and arch depth (p=0) due to a distal movement of the crown (p=0) and the root of molars (p=0.004), and maintenance of the spatial position of the incisors, without protrusion (p=0.37) or vestibular movement (p=0.13). Limitations: the limitation of the present study was not to randomize the sample and not to use a control group identical to the group that received treatment. Conclusion: 2x4 fixed partial appliance was effective for the recovery of mixed dentition space, increasing the arch perimeter and depth through a distal movement of the upper molar and maintenance of incisor position.

Long-term stability of surgical orthodontic treatment for patients with asymmetric mandibular prognathism: a retrospective comparison study on surgical methods

ABSTRACT Purpose To consider long-term postoperative stability, and its contributing factors in surgical orthodontic treatment for asymmetric mandibular prognathism by comparing a sagittal split ramus osteotomy (SSRO) and a combination of Le Fort I osteotomy and SSRO. Materials and Methods Patients with asymmetric mandibular prognathism had undergone SSRO (14 patients; one-jaw surgery group) or a combination of Le Fort I osteotomy and SSRO (15 patients; two-jaw surgery group) were enrolled. Cephalometric analyses were performed at five time points: initial visit (T0), pre-surgery (T1), several months after surgery (T2), start of retention (T3) and more than 5 years after surgery (T4). Factors were evaluated by measuring two groups at each time point, comparing changes in measurements during each time period, correlating mandibular changes between each period, and correlating changes in lower first molar and ramus inclination with T2-T4 measurements. Results The two-jaw surgery group had significantly smaller transverse changes of menton (Me) at T3–T4 and T2–T4 compared to the one-jaw surgery group. In the one-jaw surgery group, transverse changes in Me at T2–T4 were positively correlated with changes in transverse inclination of mandibular ramus at the deviated side observed at T1–T2. Vertical change of pogonion at T2–T4 was positively correlated with change in bucco-lingual inclination of lower first molar at T0–T1. Conclusions Two-jaw surgery is suggested to be more effective than one-jaw surgery in achieving long-term stability of mandibular position in the transverse and anteroposterior dimensions after surgical orthodontic treatment for asymmetric mandibular prognathism. Long-term follow-up is necessary to monitor potential mandibular relapse.

A study of transverse maxillomandibular discrepancy and dental compensation in early mixed dentition with skeletal Class III malocclusion without posterior crossbite.

To evaluate transverse maxillomandibular discrepancy and dental compensation in first molar areas in 7- to 9-year-old children with skeletal Class III malocclusion without posterior crossbite using cone-beam computed tomography (CBCT). The sample of this retrospective study consisted of 60 children (7 to 9 years old), who were divided into the skeletal Class III malocclusion group (study group, skeletal Class III malocclusion without posterior crossbite, N = 31) and the Class I occlusion group (control group, Class I occlusion with one or two impacted teeth, N = 30). CBCT data were obtained from the database of the Department of Radiology of Hospital of Stomatology, Shandong University. For three-dimensional reconstruction of the head, the dental arch width, basal bone width, and buccolingual inclination angle were measured using MIMICS 21.0 software. Independent-sample t tests were used to compare the two groups. The mean age of the children was 8.18±0.83years. The width of the maxillary basal bone was significantly smaller in the skeletal Class III malocclusion group (59.75 ± 3.14 mm) than in the Class I occlusion group (62.39 ± 3.01 mm) (P < 0.01). The mandibular basal bone width was significantly larger in the skeletal Class III malocclusion group (60.00 ± 2.56 mm) than in the Class I occlusion group (58.19 ± 2.42 mm) (P < 0.01). The difference in the width of the maxillary and mandibular bases in the skeletal Class III malocclusion group (-0.25 ± 1.73 mm) was significantly different from that in the Class I occlusion group (4.20 ± 1.25 mm) (P < 0.01). However, there was no significant difference in the upper or lower dental arch width between the two groups (P > 0.05). The buccal inclination of the maxillary molars in the skeletal Class III malocclusion group (31.4° ± 8.9°) was significantly higher than that in the Class I occlusion group (17.64° ± 7.3°) (P < 0.01), as was the lingual inclination angle of mandibular molars (45.24° ± 8.3° vs. 37.96° ± 10.18°; P < 0.01). Transverse maxillary and mandibular discrepancies in the posterior area and transverse dental compensation were found in the early mixed dentition of patients with skeletal Class III malocclusion without posterior crossbite. This suggests that even in the absence of posterior crossbite, maxillary expansion can be attempted to correct the maxillomandibular transverse discrepancy.