Expansion Appliance Research Articles

Effect of bone-borne maxillary skeletal expanders on cranial and circummaxillary sutures: A cone-beam computed tomography study.

Miniscrew-assisted maxillary expansion devices are frequently used for patients with calcified midpalatal sutures. This study aimed to evaluate the effects of two bone-borne maxillary expansion appliances on the cranial and circummaxillary sutures by comparing cone-beam computed tomography (CBCT) images before and after transverse maxillary expansion. A total of 81 patients (women = 58, men = 23) were treated with either a C-expander (n = 44) or an ATOZ expander (n = 37). CBCT images were obtained before (T0) and after (T1) maxillary expansion, and the widths of 10 circummaxillary sutures were measured in the sagittal, coronal, and axial planes. The Wilcoxon signed-rank test was used to compare the changes in suture width between the C-expander and ATOZ groups, and statistical significance was set at P < 0.05. The frontonasal, frontomaxillary, pterygomaxillary, nasomaxillary, internasal, intermaxillary, and midpalatal suture widths increased significantly after maxillary expansion in both the ATOZ and C-expander groups (both P < 0.05). The frontozygomatic, zygomaticomaxillary, and temporozygomatic suture widths decreased in the C-expander group (P < 0.05), whereas the frontozygomatic suture width increased significantly in the ATOZ group (P < 0.05). The width changes of the frontozygomatic, zygomaticomaxillary, temporozygomatic, pterygomaxillary, internasal, intermaxillary, and midpalatal sutures differed significantly between the two groups (P < 0.05). Both the C- and ATOZ expanders affected the suture width in the naso-maxillozygomatic region. The C-expander decreased the circum-zygomatic suture widths, whereas the ATOZ expander widened the frontozygomatic suture with no effect on other circummaxillary sutures.

Comparative Experimental Evaluation of Orthodontic Appliances for Maxillary Arch Expansion.

Background/Objectives: The orthodontic treatment of posterior crossbite using appliances for gradual maxillary expansion is crucial to ensure proper transversal jaw relationships as much as occlusal functionality. The aim of this study was to analyze forces and torques generated by different appliances for maxillary expansion. Methods: Measurements were conducted for the Wilson® 3D® Quadhelix (WQH) and Wilson® 3D® Multi-Action Palatal Appliance (WPA) across various sizes and compared to the Remanium® Quadhelix (RQH). Activations were set to 8 mm for the WQH and RQH and 6 and 8 mm for the WPA. Rotations and root torque were simulated via an activation of 10° for arches. A total of eight test series were conducted. Results: The WPA displayed the highest force and torque values for all movements, far surpassing recommended guideline values (expansion 8.5->15.0 N/46.3-86.5 Nmm, rotation 3.1-6.1 N/40.7-61.4 Nmm, torque 3.9-5.1 N/22.4-29.7 Nmm), and the WQH displayed the lowest values (expansion 2.7-12.6 N/11.1-39.6 Nmm, rotation 0.1-1.7 N/23.0-32.2 Nmm, torque 0.9-2.9 N/3.4-10.5 Nmm). Appliances with the smallest transverse dimensions exhibited the highest force and torque maxima. Conclusions: This study underscores the importance of understanding biomechanical principles in orthodontics for minimizing unintended tooth movements, providing detailed insights into the force systems of appliances acting in the transverse plane, and establishing a foundation for future clinical investigations to validate these in vitro findings.

Miniscrew-assisted Rapid Palatal Expansion Before Orthognathic Surgery for a Patient With Laterognathia

In this case report, a 19-year-old male patient with maxillary transverse deficiency, concave profile, and facial asymmetry is presented. In the case of transversal insufficiency, nonsurgical maxillary expansion was performed with the miniscrew-assisted rapid palatal expansion (MARPE) appliance to reduce the number of surgeries and provide both dentoalveolar and skeletal expansion. The periodontal soundness and short-term stability of the maxillary expansion were confirmed both clinically and radiologically. Mandibular prognathism was later corrected with orthognathic surgery. MARPE is an effective approach to the treatment of maxillary transverse deficiencies in adult patients.

In-silico evaluation of orthodontic miniscrew-assisted rapid palatal expanders for patients with various stages of skeletal maturation

This study aimed to use a finite element method to assess the stress on the miniscrews, skeletal and dental changes resulting from maxillary expansion using either a tooth-bone-borne (TBB) or a bone-borne (BB) device on patients with various skeletal maturation. Two types of expanders were modeled using SolidWorks. The design of the 2 expanders was similar, with the exception that the BB appliance lacked support for teeth (rods and bands). Both were placed on the palatal bones with the help of 4 miniscrews as bony anchorage. Five skeletal maturation stages were examined using suture maturation classification by Angelieri. A lateral displacement of 0.2 mm was applied to simulate 1 turn of jackscrew per day. The dental and skeletal changes from the treatment were quantified. Stage A sutural maturation exhibited the greatest skeletal movement (0.13 mm/d) with a V-shaped displacement pattern. Stages B and C exhibited a more parallel expansion pattern. Stages D and E exhibited the least amount of skeletal movement with either device. Compared with the BB device, TBB demonstrated greater dental displacement. On average, the BB device exhibited a skeletal-to-dental expansion ratio of 70% from stage A to C compared with 49% with the TBB device. BB device showed more skeletal displacement than TBB, and the latter showed more dental side effects, particularly during stages B and C. The miniscrew-assisted rapid palatal expansion appliance was effective with sutural maturation stages A to C using the classification by Angelieri with a more parallel separation of the midpalatal sutures in stages B and C.

Effect of rapid maxillary expansion on intracranial pressure

ObjectiveThe aim of this study was to evaluate the effects of rapid maxillary expansion on the optic nerve sheath diameter and to examine its possible effects on intracranial pressure. Design20 patients with bilateral crossbite were selected. Hyrax Expander was applied and activated twice daily until the overcorrection was achieved. The optic nerve sheath diameter (ONSD) was measured via ultrasonography before the first activation (T0), then repeated after 1 (T1) and 10 min (T2). At the end of the expansion, ONSD was measured (T3) again, then the screw was activated for the last time, and measurements were repeated after 1 (T4) and 10 min (T5). The Friedman test was performed to compare the changes, and The Wilcoxon Signed-Rank test was done to determine the significant intergroup changes (p < 0.05). ResultsThe ONSD increased significantly 1 min after the activations (T0-T1 and T3-T4) (P < 0.05). The ONSD values measured 10 min after the activations also increased significantly compared to the baseline values (T0-T2 and T3-T5) (P < 0.05). ConclusionThe activation of maxillary expansion appliances increased the optic nerve sheath diameter in adolescents. Therefore, orthodontists should be careful with patients at risk of intracranial hypertension.

Forecasting changes in oral hygiene levels using the API index with different orthodontic appliances

Relevance. The prevalence of various types of orthodontic pathology among the Russian population is quite high. Depending on the region, malocclusion are registered in 30.9% to 76.5% of cases. The high prevalence of orthodontic pathology and the unresolved issues related to both the pathology itself and the presence of concomitant diseases indicate the necessity for personalized methods of prevention and treatment of malocclusion during both the primary and mixed dentitions, which in 70-84% of cases are treated using both removable and fixed orthodontic appliances.Materials and methods. An observational study was conducted to identify factors contributing to the increased intensity of caries among children aged 6 to 11 with orthodontic pathology. The study evaluated the characteristics of hygiene knowledge and skills, as well as the Approximal Plaque Index (API), in children using various orthodontic appliances. To assess hygiene knowledge levels, a survey was administered to two groups of children aged 6-11: those undergoing orthodontic treatment and those who visited the dental clinic for a routine check-up and were diagnosed with orthodontic pathology. The questionnaire included questions about the primary and supplementary tools and practices for daily oral hygiene, the frequency of hygiene activities, and the patients' awareness of the importance of professional oral hygiene.Results. Factors that statistically significantly influence the level of hygiene and the Approximal Plaque Index (API) were identified. A computer program was developed to forecast the dynamics of oral hygiene levels (based on the API index) when using different orthodontic appliances. An algorithm for predicting changes in the API hygiene index was created, considering the use of orthodontic appliances, oral status, adherence to hygiene procedures, presence of harmful habits, and dietary behaviors. Negative factors significantly impacting hygiene levels include bruxism and daily consumption of sweets, while positive factors include adherence to the recommended frequency and duration of tooth brushing (at least twice a day) and the use of a medium-hard toothbrush when permanent teeth are erupting. During orthodontic treatment, additional negative factors impacting hygiene status include gingival bleeding (gingivitis), lack of lip closure, and harmful habits. The study of changes in hygiene levels over one year of treatment with various orthodontic appliances (braces, Haas appliance, SPA) showed that the fixed Haas appliance for treating dental and maxillofacial anomalies is the most favorable orthodontic design for mixed dentition.Conclusion. Factors significantly affecting the level of oral hygiene have been identified. The dynamics of the API hygiene index with various orthodontic appliances have been established. The most favorable appliance for mixed dentition is the HAAS appliance for rapid palatal expansion.

Effectiveness of removable expander appliances in posterior crossbite: A review of the literature

Objective: To evaluate the effectiveness of removable expander appliances in the treatment of posterior crossbite by reviewing and analyzing clinical studies, scientific articles and published case reports. Background: Posterior crossbite is a dental malocclusion characterized by a transverse misalignment of the upper and lower teeth, where the upper teeth bite into the lower teeth. This condition can affect one or more dental organs and if left untreated, can lead to functional and esthetic problems, as well as imbalances in maxillofacial growth. Early correction of posterior crossbite is crucial to avoid future complications such as uneven tooth wear, temporomandibular dysfunction and facial asymmetries, and different treatment methods have been used, including removable appliances. Methodology: The research was structured from a search tree (PubMed, Scielo, Google Scholar, Dialnet, Scopus), with keywords such as: removable expandable appliance; posterior crossbite; removable orthodontics; treatment efficacy AND posterior crossbite; posterior crossbite NOT fixed appliance. Conclusions: Removable expander appliances are an effective option for treating posterior crossbite in children. Studies show that these devices correct malocclusion, promote maxillary growth and improve dental alignment. The effectiveness of the treatment depends on the cooperation of the child and parents. The choice of appliance should be based on a careful evaluation of the patient's needs, considering cooperation, severity of the malocclusion and the preferences of the patient and the orthodontist.

Rapid maxillary expansion appliance in correction of unilateral skeletal crossbite in an adult female patient: A case review

Rapid maxillary expansion appliance in correction of unilateral skeletal crossbite in an adult female patient: A case review

Effects of different expansion appliances and surgical incisions on maxillary expansion: A finite element analysis

PurposeThis study aims to assess the impact of different surgical techniques and three expansion appliances on maxillary expansion in adults using finite element analysis (FEA), with a focus on maxillary displacement and stress on surrounding structures. MethodsSeven different FEA models were created to compare different surgical techniques and three different expansion appliances. Model I represented a bone-supported appliance without surgical assistance. Model II, Model III, and Model IV were surgically assisted rapid palatal expansion (SARPE) models without pterygomaxillary suture disjunction (PMD). Model V, Model VI, and Model VII were SARPE models with PMD. ResultsThe largest displacement at the anterior nasal spine (ANS) was recorded for Model II (2.95 mm). For the posterior nasal spine (PNS), the highest displacement was observed in Models V, VI, VII (2.50 mm), with the lowest in Model III (0.79 mm). Stress analysis revealed the highest stress in Model I, with models featuring PMD displaying nearly zero stress at all anatomical points, highlighting distinct expansion patterns and stress distributions between models with and without PMD. ConclusionSARPE models with PMD demonstrated a parallel expansion of the maxilla with minimal stress, while the miniscrew assisted rapid maxillary expansion (MARPE) model displayed transverse rotation. SARPE models without PMD exhibited a V-shaped expansion pattern. SARPE models with PMD represent an optimal approach for achieving uniform expansion and minimizing stress, with stress levels nearly negligible at all anatomical points in models with PMD.

A simple and innovative device to position and stabilize the expansion screw during removable appliance fabrication

Precise positioning and stabilization of the expansion screw are crucial steps in fabricating a removable expansion appliance. The current method of inserting the plastic handle of the screw into a wax-filled well in the working model is unwieldy and often unsatisfactory. We present a simple device that is easy to construct and effective for the purpose. It permits adjustments in the depth and angulation of the screw and secures it firmly during appliance fabrication.

Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children.

Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children.

Retrospective Clinical Analysis of the Effectiveness of Skeletally Anchored Appliances for Maxillary Expansion

(1) Background: Skeletally anchored appliances for maxillary expansion are a less invasive alternative to surgery and are increasingly often selected as a method of treatment. The purpose of this study was to retrospectively evaluate the efficacy of maxillary expansion using distractors supported by temporary orthodontic implants (TOIs) in patients of differing sex and age. (2) Methods: The study group consisted of patients treated with distractors anchored to TOIs between July 2019 and June 2022. The group was divided into adolescent and the adult patients. Effectiveness was evaluated one and two weeks after installation of the distractors and the results were analyzed statistically. (3) Results: In total, 39 patients were treated, of which 21 were women and 18 men, ranging in age from 11 to 42. A group of 8 girls and 9 boys younger than 18 years were included. The presence of diastema at the first follow-up visit was observed in all girls and in 8 of the boys, as well as in 7 women and in none of the men. At the second visit, no diastema was found in one woman, but was noted in 3 men (p = 0.007). At the completion of distraction, diastema was observed in all the girls and in 12 women, as well as in 8 out of 9 boys and in 3 men (p = 0.015). (4) Conclusions: The effectiveness of the distraction procedure in adolescents is positive, regardless of sex. However, in adults, the procedure has limited effectiveness in males.

MISMARPE protocol: minimally invasive surgical and miniscrew-assisted rapid palatal expansion

ABSTRACT Objective: The purpose of this article is to present the MISMARPE technique, a new minimally invasive surgical procedure to treat maxillary transverse atresia in adult patients under local anesthesia and on an outpatient basis. Technique description: The technique consists of miniscrew-assisted rapid palatal expansion (MARPE) associated with a minimally invasive approach using maxillary osteotomies, latency and activation periods until the desired expansion is achieved. The present MISMARPE technique was performed in 25 consecutive cases with a success rate of 96%, yielding good skeletal outcomes with minimal trauma. The expander appliances, with their anchorage types, and a description of the surgical steps of the MISMARPE technique are presented. Conclusion: MISMARPE is a new and effective alternative for less invasive treatment of maxillary transverse deficiency in adults, compared to conventional surgery. Emphasis is placed on the importance of systematic and well-established protocols, for executing the procedures safely and predictably.

Evaluation of Palatal Thickness for the Placement of MARPE Device among a Cohort of Iraqi-Kurdish Population: A Retrospective CBCT Study.

This study aimed to evaluate and compare palatal thickness in adults for the placement of mini-implants for miniscrew-assisted rapid palatal expansion (MARPE) appliances using cone-beam computed tomography (CBCT) in a sample of Iraqi-Kurdish people. CBCT scans from 68 Kurdish patients, aged between 18 and 30 years, were assessed retrospectively. Of these, 37 were males and 31 were females. The measurements were performed at 3 mm from the mid-palatal suture. T-zone was selected for the anterior points, at the level of the palatal cusps of 2nd premolars, and the posterior point at the level of mesio-palatal cusps of 1st molars bilaterally. Palatal thickness of males and females bilaterally, as well as anterior and posterior areas, were measured and compared. An independent t-test was applied for comparison for normally distributed data, and the Mann-Whitney test was utilized for nonnormally distributed data. Additionally, Bonferroni correction was implemented for p-value adjustment. The mean palatal thickness at the anterior area was 6.06 mm for males, 6.17 mm for females on the right side, 5.94 mm for males, and 5.99 mm for females on the left side. The mean palatal thickness at the posterior area was almost the same for both genders (4.40 mm for males and 4.44 mm for females) on the right side, 4.35 mm for males, and 4.54 mm for females on the left side. Statistically, no significant difference was recorded between males and females, as well as right and left sides in both anterior and posterior regions; however, a very highly statistically significant difference (p < 0.001) was recorded when comparing total thickness, including both hard and soft tissue, between anterior and posterior regions. CBCT proves a highly effective modality in assessing palatal thickness and suggesting ideal locations for orthodontic mini-screw placement. Our examination of palatal thickness in a sample of Iraqi-Kurdish individuals revealed no statistical difference between genders or sides, but significant variations were noted between anterior and posterior thicknesses. Comprehensive clinical and pre-expansion CBCT evaluations are crucial for precisely determining the optimal placement of MARPE devices in each patient, ensuring successful outcomes.

Comparison of Rapid Maxillary Expansion and Alternate Rapid Maxillary Expansion and Constriction Protocols with Face Mask Therapy.

This study compared dentoskeletal and soft tissue changes with face mask (FM) therapy. Rapid maxillary expansion (RME) and alternate rapid maxillary expansion and constriction (Alt-RAMEC) protocols were used with the two different types of expansion appliance, and their effects on the treatment outcome were investigated. The study consisted of 79 (37 and 42 patients in the RME and Alt-RAMEC groups with FM, respectively) patients who had received FM treatment. The effects of the RME/FM (20 female, 17 male) and Alt-RAMEC/FM (14 female, 28 male) protocols were evaluated using lateral cephalometric films. The chronological ages of the RME/FM and Alt-RAMEC/FM groups were 11.58 and 11.99 years, respectively. In addition, both groups were divided into two subgroups based on the design of the expansion appliance (Spolyar or full coverage type). Differences in all parameters were analyzed using Student's t-tests. The maxilla significantly moved forward in both the RME/FM and Alt-RAMEC/FM groups (p<0.001). No significant skeletal differences were observed between the groups. Sagittal movement of the upper incisors significantly increased, and the lower incisors significantly retruded in both groups. While similar skeletal changes were found between the Spolyar and full-coverage appliance groups, the upper incisors protruded significantly more in the full-coverage type. RME/FM and Alt-RAMEC/FM therapies were found to be efficient for maxillary protraction and resulted in similar skeletal changes. A full-coverage expansion appliance produced a more upper incisor protrusion than a spherical-type appliance.

Long-term evaluation of soft-tissue changes after miniscrew-assisted and conventional rapid palatal expansion using voxel-based superimposition of cone-beam computed tomography scans

This study aimed to evaluate the soft-tissue changes in the long-term after miniscrew-assisted rapid palatal expansion (MARPE) and conventional rapid palatal expansion (RPE) appliances compared with a matched control group using voxel-based superimposition of cone-beam computed tomography (CBCT) scans. A total of 180 CBCTs for 60 patients at 3-time points were evaluated: pretreatment (T1), postexpansion (T2), and posttreatment (T3) for 3 groups: (1) MARPE, (2) RPE, and (3) controls (time-period T1 to T3: MARPE, 2 years 8 months; RPE, 2 years 9 months; control, 2 years 7 months). The voxel-based superimposition technique was used to superimpose the CBCT scans, after which the soft-tissue surfaces were extracted from the superimposed T1-CBCT, T2-CBCT, and T3-CBCT scans. Nine landmarks were identified on the CBCT scans: nasion, A-point, pogonion, right and left alar base, right and left zygoma, and right and left gonion. The coordinates of the 9 parameters were obtained in the x-axis, y-axis, and z-axis for the CBCT scans and subjected to statistical analyses. The changes in the soft-tissue surfaces were also evaluated by color-coded maps for short-term (T2) and long-term (T3) changes. The mean changes from T1 to T2 and T1 to T3 were tested against no change within the groups by paired t test, and the mean changes among the 3 groups were compared with analysis of variance F test with Tukey's Honest significant difference used for adjusting P values for multiple testing. In the short term, both MARPE and RPE led to a significant downward movement of pogonion, left gonion, and lateral movement of the right and left alar base compared with controls at T2 (P<0.05). In addition, MARPE led to a significant downward movement of right gonion than controls at T2 (P<0.05). Moreover, RPE led to a significant downward and forward movement of A-point and downward movement of the right and left alar base than controls at T2 (P<0.05). However, in the long-term, there were no significant differences in the soft-tissue changes among the MARPE, RPE, and control groups. MARPE and RPE do not lead to significant soft-tissue changes in the long term when compared with controls.

Early Orthodontic Intervention in Cleft Lip-Palate and Noncleft Children with Developing Class III Malocclusion: A Clinical Study.

Orthopedic correction of skeletal class III malocclusion in a growing patient is crucial as it can circumvent future surgical procedures. The aim of the study is to evaluate the dental and skeletal effects of early orthodontic intervention of developing class III malocclusion. A final sample of 38 children in the age-group of 6-14 years having skeletal class III malocclusion was selected. Subjects were divided into two groups; group I-included 18 children (male-10, female-8) with surgically repaired cleft lip and palate and group II-20 children (male-14, female-6) without any cleft lip and palate. Cemented rapid maxillary expansion (RME) appliances with 11 mm hyrax screws were used in all patients. Elastic traction forces were applied to the reverse-pull headgear worn by the patients. Both pre- and posttreatment records along with lateral cephalograms were taken. The pre- and posttreatment mean and standard deviation measurements of the angular and linear observations were statistically analyzed with Statistical Package for the Social Sciences (SPSS) software (version 13) and were correlated through independent t-test and paired t-test. Following headgear therapy, improvement was greater in the cleft group than noncleft group with greater advancement of maxilla along with clockwise rotation of mandible in clefts. Protraction mechanics with expansion can be employed successfully in repaired cleft lip and palate and noncleft prepubertal children having developing class III malocclusion, showing concave profile, and retrusive maxilla. Accurate diagnosis and understanding of the individual growth pattern are crucial in the early interception of a class III malocclusion to achieve a more favorable facial profile. Sahoo SS, Dash JK, Sahoo PK, et al. Early Orthodontic Intervention in Cleft Lip-Palate and Noncleft Children with Developing Class III Malocclusion: A Clinical Study. Int J Clin Pediatr Dent 2023;16(5):716-723.

Skeletal and Dentoalveolar Changes With Mandibular Expansion in Growing Children.

Introduction The primary objective of this study was to quantitatively analyze the skeletal and dentoalveolar parameters following the mandibular expansion with a banded appliance. It was also part of the study to evaluate the amount of dental expansion and assess the change in the intermolar and individual first molar angulation. The basal bone parameters were compared to assess the skeletal effect of removable mandibular expansion appliance therapy. Methods In this retrospective cone beam computed tomography (CBCT) study, a total of 80 subjects with mandibular expansion therapy were screened. After imposing inclusion/exclusion criteria, 70 patients (40 females and 30 males) with a mean age of 8.8±1.24 years and 4.79±3.59 months were included. The mean expansion period was 3.04±1.61 months. Skeletal parameters such as buccal cortical thickness, buccal bone width, and cortical density were measured at 2mm from the alveolar crest, mid-root, and apex region in the coronal slice at the level of the mesiobuccal root of the first molar. Expansion parameters such as intermolar width, intermolar angulation, and individual molar angulation were also measured in the same slice. Finally, basal bone parameters such as inter-mental foramina distance and anterior arch perimeter were recorded. Results No significant difference (p>0.05) was found for most skeletal parameters following the expansion, except for the mid-root buccal bone width (p<0.05). On average, 4.54±2.53 mm of dental expansion (p<0.05) was achieved at the first molar region. Individual molar angulation showed a statistically significant difference (right = 7.46±7.91°, left = 7.53±7.18°, p=<0.05). The basal bone parameters showed no significant difference (p>0.05). Conclusions The mandibular expansion device leads to an increase in intermolar distance. The amount of expansion achieved with such devices is due to the buccal tipping of the molars. Skeletal effects such as cortical thickness, buccal bone width, or changes in the basal bone dimensions should not be expected with mandibular expansion therapy.

Finite element analysis of sagittal screw expander appliance in the treatment of anterior maxillary hypoplasia.

The skeletal anterior crossbite is a common malocclusion in clinic. However, there have been no reports on the maxillary sagittal expansion to correct the premaxillary hypoplasia, which greatly influences the facial morphology and masticatory function, using finite element analysis. In the present study, a three-dimensional finite element model of craniomaxillofacial complex with maxillary sagittal hypoplasia is constructed and the treatment for premaxillary hypoplasia by the sagittal screw expander appliance is simulated. The hypoplasia of the left premaxilla is more serious than that of the right and thus the size of the left part of premaxillary expander baseplate is designed to be larger than that of the right part and the loading is applied at 10° leftward to the sagittal plane and 30° forward and downward to the maxillary occlusal plane. The displacements or equivalent stress distributions of the maxilla, teeth and their periodontal ligaments, are analyzed under the loads of 5.0N, 10.0N, 15.0N, and 20.0N. Consequently, as the load increases, the displacements or equivalent stresses of the maxilla, teeth and their periodontal ligaments all increase. Almost the whole premaxilla markedly move forward, downward, and leftward while other areas in the craniomaxillofacial complex remain almost static or have little displacement. The equivalent stress concentration zone of the maxilla mainly occurs around and in front of the incisive foramina. The displacements of left premaxilla are generally greater than those of the right under the loading forces. The maximum equivalent stress on the teeth and their periodontal ligaments are 2.34E-02MPa and 2.98E-03MPa, respectively. Taken together, the sagittal screw expander appliance can effectively open the premaxillary suture to promote the growth of the premaxilla. An asymmetrical design of sagittal screw expander appliance achieves the asymmetric expansion of the premaxilla to correct the uneven hypoplasia and obtains the more symmetrical aesthetic presentation. This study might provide a solid basis and theoretical guidance for the clinical application of sagittal screw expander appliance in the efficient, accurate, and personalized treatment of premaxillary hypoplasia.

Stress distribution and displacement with four different types of MARPE on craniofacial complex: A three-dimensional finite element analysis

Various designs of mini-implants assisted rapid palatal expander (MARPE) appliances can impact treatment effectiveness through their biomechanical effects. The purpose of the study was to study the stress distribution and displacement with four different designs of the MARPE appliance on the craniofacial complex. A 3D finite element model of the craniofacial complex was created from CBCT DICOM data, comprising four distinct groups. Each group consisted of one 4-hole expansion screw positioned between the second premolar and first molar in all models. Group 1 used four single-cortical mini-implants (1.5×8mm) engaging only the palatal cortex. Group 2 employed four mini-implants (1.5×11mm) engaging both the palatal and nasal cortices. Group 3 had monocortical implants on the palatal slopes, while Group 4 was similar to group 3 with implants in the acrylic wings. Comparisons between groups were made for anchorage (groups 1 and 2), mini-implant position (groups 1 and 3) and surface effect (groups 3 and 4). Von Mises stresses and displacements at various skeletal and dental points were evaluated using ANSYS software. The highest stresses were observed in the maxillary, pterygoid and zygomatic bones, as well as in the mid- palatal suture in all four groups. Downward and forward rotation of the craniofacial complex was noted. Group 2 showed greater skeletal expansion than group 1. Among groups 1 and 3, group 3 showed a better stress distribution. Group 4 showed less dentoalveolar rotation than group 3. The MARPE appliances had an impact on the craniofacial complex with stresses on the mid-palatal suture, maxillary bone, pterygoid bones and anterior teeth. Clockwise rotation of the maxilla, zygomatic bones and dentition was noted, while the pterygoid bones and pterygoid suture were displaced backwards. MARPE with bicortical anchorage produces better skeletal expansion. Placing implants on the palatal slopes with acrylic wings results in better skeletal expansion with less clockwise rotation of the dentition.