Hyrax Screw Research Articles

Investigation of bone remodeling in gingival crevicular fluid in patients treated with rapid maxillary expansion during pubertal period

Purpose: We aimed to evaluate bone remodeling following 3-month and 6-month retention periods of rapid maxillary expansion (RME) in gingival crevicular fluid (GCF). Materials and Methods: 23 pubertal participants (15 girls- 8 boys, 12-15 years) with maxillary transversal deficiency were enrolled in the study. Following banded-type RME appliance was introduced into the mouth, RME protocol was initiated by turning the Hyrax screw twice daily (morning/evening) with ¼ activation. GCF samples were taken from right maxillary first molars at four different time points (T0: before the appliance was deployed, T1: following active phase, T2: at the end of the 3-month retention period, T3: at the end of the 6-month retention period) using paper strips. Probing depth, gingival index, plaque index, and bleeding percentage at probing were recorded. BALP, OPG, RANKL, and TNF-α levels were measured in GCF samples using ELISA kits. Results: Our study revealed that GCF's BALP and OPG levels remained unchanged over time in tension and pressure regions, and there were no statistically significant differences among regions at each time point (p>0.05). RANKL level was statistically significantly increased in the buccal region (the pressure region) at time T1 (p=0.042). The palatinal region's TNF-α level was statistically significantly higher than the buccal region at T0, T2, and T3 time points (p=0.005, p=0.042, and p=0.006, respectively). Our study showed no correlation between 3-month and 6-month retention periods and biomarkers indicating RME's bone metabolic activities. Conclusions: Further studies with different retention periods and larger sample sizes are suggested.

Mini-Implant Insertion Using a Guide Manufactured with Computer-Aided Design and Computer-Aided Manufacturing in an Adolescent Patient Suffering from Tooth Eruption Disturbance.

Due to dental diseases, anatomical restrictions, and mixed dentition, the reduction in the number of teeth and the displacement of tooth germs pose challenges in orthodontic treatment, limiting anchorage options. The presented case demonstrates an advanced treatment solution using digital CAD/CAM-technologies and medical imaging for the creation of a mini-implant template. A 12-year-old male patient experiencing delayed tooth eruption, multiple impacted germs, and maxillary constriction underwent intraoral scanning and CBCT. Utilizing coDiagnostiXTM Version 10.2 software, the acquired data were merged to determine the mini-implant placement and to design the template. The template was then manufactured through stereolithography using surgical-guide material. Mini-implants were inserted using the produced appliance, enabling safe insertion by avoiding vital structures. Surgically exposed displaced teeth were aligned using a Hyrax screw appliance anchored on the mini-implants for rapid palatal expansion (RPE) and subsequently used as fixed orthodontics to align impacted teeth. The screw was activated daily for 10 weeks, resulting in a 7 mm posterior and 5 mm anterior maxillary transversal increase. Skeletal anchorage facilitated simultaneous RPE and tooth alignment, ensuring accuracy, patient safety, and appliance stability. The presented case shows a scenario in which computer-aided navigation for mini-implant positioning can enhance precision and versatility in challenging anatomical cases.

Interim use of Hyrax Screw Assembly for Single-Step Closure of Small Alveolar Cleft before Anterior Maxillary Distraction Osteogenesis

Anterior maxillary distraction osteogenesis (AMDO) is often used for the correction of maxillary retrognathia in select cleft lip and palate cases. The restoration of alveolar arch continuity is desirable before the initiation of AMDO in these cleft maxillary deformities; however, AMDO is technically difficult in a patient with coexisting alveolar cleft where there is a discontinuity of the defect that presents a challenge in terms of adequate vector control of the movement of the anterior segment and the potential risk of tipping of teeth, which already have compromised anchorage/bone support on the cleft side. The treatment becomes more challenging when ongoing management is compounded by failed previous alveolar cleft grafting procedures, along with the patient’s reluctance to undergo further grafting of alveolar clefts. This technical note demonstrates a novel application of the modification of the Hyrax screw where an initially fully opened Hyrax screw was utilised as an interim assembly for accomplishing the single-step closure of a small alveolar cleft before the commencement of anterior maxillary distraction osteogenesis. This technique may prove to be feasible for patients presenting with alveolar cleft defects of smaller widths of up to 5 mm and relatively well-aligned upper arches. Keywords: Distraction Osteogenesis; Cleft Palate; Cleft Alveolar; Maxillary Osteotomy; India.

Effect of maxillary constriction orthodontic correction using a fixed appliance with a screw in teenagers during a growth spurt

Relevance. The research is relevant because of a high prevalence of anterior and posterior crowding in children with mixed and permanent dentition (from 42 to 86 %), for whom the correction of the dentition form and the size is recommended by fixed expanding appliances with a screw. After the teenage growth spurt, the growth and development of jaws end, steady pathological signs form, there are psychological problems in a face and smile selfperception, and the question of the orthodontic treatment duration arises.Purpose. To study the effectiveness of treatment of patients with maxillary premolar area constriction during growth spurt using two modifications of fixed Hyrax expander.Material and methods. We examined 22 male patients aged 10.6 to 13 y.o. (average age 11.2 ± 1.6 years old) with permanent dentition, constriction of the posterior teeth and crowding of incisors, treated with a fixed expander (Hyrax appliance) in the upper jaw during the growth spurt. The patients formed two groups. Group 1 (n = 11) had the Hyrax screw at the level of the upper first premolars, and Group 2 (n = 11) had the Hyrax lock located at the first permanent molars. The patients activated the expander independently by ¼ turn every other day for six months. Then the appliance remained in the mouth for three months. We studied the maxillary expansion results on plaster models before and after six months of the expander fixation using the Tonn, Pont, Korkhaus, Bolton method.Results. The study has established that orthodontic correction of transversal abnormalities with a fixed Hyrax expander affects the maxillary posterior teeth expansion, changes their parameters and improves their movement. At the same time, in Group 1, the width between the first premolars and the first molars reached the norm calculated from the sum of the mesiodistal dimensions of the upper incisors, and in Group 2, the width between the first permanent molars exceeded the normal, and inter-first-premolar distance did not reach the normal values for three months of activation.Conclusion. Fixed Hyrax expander showed the best results if the screw was at the level of first premolars during the teenage growth spurt.

Effect of three different maxillary expansion appliances on root resorption

Aim: The study was to examine rapid maxillary expansion (RME), semi-rapid maxillary expansion (SRME), and slow maxillary expansion (SME) compare the root resorptions occurring in the supporting upper first premolar teeth during treatment by using micro-computed tomography (micro-CT). Methodology: Thirty individuals that required maxillary expansion and upper first premolar tooth extraction were divided into three groups consisting of 10 individuals for RME, SRME, and SME. RME group, first premolar and first molar teeth with hyrax screw were activated ¼ tour twice daily with the banded hyrax appliances. SRME group, acrylic-bonded hyrax appliances were activated ¼ tour per morning and night until the opening of the suture. Upon the opening of the suture, it was activated ¼ tour per every two days until sufficient maxillary expansion was gained. SEM group, quad helix appliances were activated every 20 days. After 12 weeks of the retention period, the upper first premolar teeth were extracted. The teeth were scanned with Micro-CT (SkyScan 1172, Kontich, Belgium), and images were analyzed with a Dell Precision T5500 to determine the resorption crater volumes. Results: In all samples, the resorption craters were concentrated on the buccal surfaces of the tooth roots. The highest resorption craters volume, the total resorption volume, was observed in the RME group, followed by the SRME group, and the least resorption crater volume was detected in the SME group. Conclusion: Since the supporting teeth were exposed to more force on the root surfaces, the most resorption was seen in the RME group. How to cite this article: Topal R, Gündüz Arslan S. Effect of three different maxillary expansion appliances on root resorption. Int Dent Res 2023; 13(1):19-26. https://doi.org/10.5577/idr.2023.vol13.no1.4 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

The Hyrax appliance with tooth anchorage variations in surgically assisted rapid maxillary expansion: a finite element analysis.

It is known that a correct transverse maxillary dimension is a key factor for a stable occlusion, which brings functional and esthetic benefits for the patient. In patients presenting maxillary atresia and the completion of bone growth, a highly recommended option for correction is the surgically assisted rapid maxillary expansion (SARME) associated with the Hyrax appliance. The objective of this study was to evaluate the influence of tooth anchorage variations of the Hyrax appliance in SARME through finite element analysis, evaluating which anchorage option might be associated with more effective orthopedic results with less undesired side effects. Five different dental anchoring conditions for the Hyrax appliance were simulated through FE analysis applying premolars and molars as anchorage, having the same force applied by the activation of the Hyrax screw (0.5mm) in all groups. The maxillary displacement results (axes X, Y, and Z) and generated stresses for both teeth and maxillary bone were calculated and represented using a color scale. All groups presented significant bone displacement and stress concentration on anchoring teeth, with the group presenting anchorage in the 1st and 2nd molars showing the greatest maxillary horizontal displacement (axis X) and suggesting the lowest tendency of dental vestibular inclination. Variations in dental anchorage might substantially affect the maxillary bone and teeth displacement outcome. The protocol for the Hyrax apparatus in SARME applying the 1st and 2nd molars as anchorage might generate less tilting and inclination of the anchoring teeth.

Modified Hyrax for Microimplant-Assisted Rapid Palatal Expansion

Temporary anchorage device-assisted rapid maxillary expansion has widened the horizon to treat adults having maxillary transverse deficiency without any surgical procedure. Three-dimensional custom modifications have also been developed, but they can be expensive. A modification of Hyrax screw with the use of lingual sheaths is suggested for microimplant-assisted rapid palatal expansion, which can be an easy to fabricate in-office and economical option.

Effects of rapid and slow maxillary expansion on root resorption: a micro-computed tomography study.

To compare root resorption (RR) after rapid maxillary expansion (RME) and slow maxillary expansion (SME) through micro-computed tomography (micro-CT). Twenty-six subjects who required maxillary expansion and bilateral upper first premolar extraction were randomly assigned to RME (n = 13, mean age: 13.25 ± 0.88 years) or SME (n = 13, mean age: 13.53±1.28 years) group. A hyrax-type acrylic bonded expansion appliance was used. The Hyrax screw was activated ¼ turn twice a day for 20 days in the RME group and ¼ turn every second day for 80 days in the SME group. One randomly selected upper first premolar was extracted in each patient after active expansion. The appliance was left in situ for a 24-week retention period then the contralateral upper first premolar was extracted. Extracted teeth were scanned with micro-CT and the volume of the resorption craters was analysed with a specialized software. Transversal skeletal and dental widths were measured on posteroanterior radiographs taken before and after expansion and retention periods. The resorption craters were concentrated mostly on the buccal surface and middle level in all samples. The total RR in the RME group was less post-expansion (P ≤ 0.05) and more post-retention (P > 0.05) than the SME group. During retention, there was a significant decrease in the total RR in the SME group (P > 0.05) and an increase in the RME group. Both RME and SME groups displayed a similar increase in skeletal transverse dimensions, but inter-molar width increased significantly more in the SME group during the whole experimental period. RME does not have an advantage over SME in terms of skeletal expansion and the amount of RR when a retention period of six months is followed.

Investment casting with FFF (fused filament fabrication)-printed appliances: the intermediate step.

Some modifications of orthodontic appliances such as the rapid maxillary expansion (RME) device with a Hyrax screw or Herbst are fabricated using traditional investment casting (lost-wax casting). This is precise but very labor-intensive. New technologies enable us today to use direct selective laser sintering (SLS) to produce freeform metallic structures. These machines are very expensive and only available in specialized laboratories. The aim of this investigation was to combine fused filament fabrication (FFF) 3D printing with wax-based filaments to produce orthodontic appliances via investment casting. For demonstration purposes, a lingual arch, a palatal arch, and an RME appliance were digitally designed based on an intraoral scan. The *.stl files were sliced and printed with a dual-nozzle FFF printer. The object was printed with a wax-based filament especially suited for investment casting, and support structures were printed with water-soluble polyvinyl-alcohol (PVA) filament. The printed objects were cast in metal and finished. All appliances were successfully cast and polished. They were provisionally placed intraorally. The fit was clinically very good and comparable to traditionally crafted appliances. The printing and handling of the parts made of these special filaments is challenging. With this experiment, the successful production of investment casting using FFF printing was shown for the first time.

Cephalometric Analysis of Hard and Soft Tissue Changes Following Anterior Maxillary Osteotomy Distraction in Cleft Maxillary Hypoplasia.

Nonsyndromic unilateral CLAP patients despite the best surgical efforts present with variable degree of maxillary hypoplasia after cleft palate repair. AMOD is an extension of anterior maxillary osteotomy where the resulting segment anterior to the chosen site of vertical corticotomy cut is distracted with the help of hyrax screw through a tooth-borne appliance. To analyze the hard and soft tissue profile changes following AMOD. To determine the ratio of soft tissue changes to the given extent of hard tissue movements. Study group consisted of 25 patients with cleft maxillary hypoplasia reporting to the Department of OMFS, Coorg Institute of Dental Science. The preoperative and postoperative radiographs were taken followed by prediction tracing. In comparison of pre-op and post-op ceph mean improvement in hard tissue profile was seen at N-A by 2.84mm, N-A-Pg by 2.52, ANS-Gn by 2.28mm, N-ANS by 0.68mm, 1-Nf by 0.32 and at PNS-ANS was 4.2mm signifying improvement in middle third of face. Mean improvement in soft tissue profile at G-Sn-Pg angle by 1.2, G-Sn was 3.92mm, nasolabial angle by 10.92, incisor exposure (Stm-1) by 0.24mm and interlabial gap by 0.56mm. On ratio and correlation of soft tissue changes to given extent of hard tissue change, with movement of point A and U1 resulted significant changes in Sn and Ls. Movement of ANS resulted in significant changes in pronasale and columella. In our study significant improvement was seen in hard and soft tissue facial profile. In conclusion, AMOD is one of the emerging techniques to correct cleft maxillary hypoplasia which will have a defined definitive role to play in future.

Alternativa de tratamiento oportuno de mordida cruzada posterior unilateral en dentición primaria y mixta temprana. Serie de casos.

Introducción Las mordidas cruzadas posteriores unilaterales (MCPU) constituyen uno de los tipos de maloclusiones más frecuentes encontrados tanto en dentición primaria como en dentición mixta temprana. Debido a su origen multifactorial su tratamiento se encuentra enfocado no solo en la corrección de la maloclusión, sino en obtener una estabilidad oclusal y funcional a largo plazo que disminuya las alteraciones en el crecimiento y desarrollo del sistema estomatognático en edades tempranas. El objetivo de esta serie de casos es presentar dos alternativas de tratamiento oportuno para esta maloclusión.
 Descripción de los casos El primer caso es un paciente de 8 años de edad con MCPU izquierda quien recibe tratamiento de expansión palatina controlada con un tornillo tipo Hyrax con férula acrílica, en el cual se obtienen resultados favorables en corto tiempo y con estabilidad a largo plazo. El segundo caso es una paciente de 4 años de edad con MCPU derecha a la cual se le realizan Pistas Directas Planas logrando un cambio postural mandibular deseado. 
 Discusión En las alternativas de tratamiento presentadas, varios autores han reportado una serie de beneficios obtenidos a partir del tipo de intervención que no solo logran la corrección de la maloclusión, sino que a su vez alcanzan la mejoría de estructuras que componen el complejo craneofacial, dentro de los cuales se destaca la estabilidad a largo plazo deseada. Estos beneficios se obtienen a través de la alternativa de tratamiento seleccionada, según el diagnóstico y las características clínicas presentadas en cada paciente y justifica la decisión de realizar una intervención temprana especialmente en este tipo de maloclusión.
 Conclusión El tratamiento temprano de la mordida cruzada posterior unilateral debe ser seleccionado según el tipo de dentición y necesidad del paciente, lo que favorece el adecuado crecimiento y desarrollo del sistema estomatognático.
 Palabras Claves 
 Mordida cruzada posterior unilateral, maloclusión, tratamiento oportuno, pistas directas planas, expansión palatina.

Distribution of forces on supporting teeth in the midpalatal expander during “Hyrax” screw pre-load

Purpose: The aim of the study was to determine forces which are transferred to supporting teeth during the treatment with the midpalatal device with Hyrax screw and to evaluate orthodontic and orthopaedic effects based on displacement analysis. Design/methodology/approach: The finite element method (FEM) was used to simulation the midpalatal expansion forces activated by the screw pre-loaded during a turn of 180° which corresponds to daily recommended value. Distribution of expansion forces of Hyrax device was calculated as reaction forces on elastic supports with stiffness corresponding to the teeth working on periodontal ligament in alveolar bone. Findings: On the basis of the displacement analysis was observed the movement of supporting teeth by a value higher than 0.1 mm which corresponds to the recommended daily value. The midpalatal suture splitting forces were determined on the first premolars with a value of 32.8 N and on the first premolars of 44.2 N. Research limitations/implications: The studies did not take into account the shape of palate other craniofacial bones and their stiffness. Practical implications: Adjusting the stiffness of the device to degree of ossification midpalatal suture and teeth mobility. Searching for new solutions which eliminate the negative phenomenon of tilting teeth during the expansion of maxilla and recommending a surgically assisted techniques. Originality/value: The simulation confirmed that treatment with Hyrax screw gives a uniform expansion with values of forces corresponded to stiffness of premolar and molar teeth. The studies have indicated a possibility of tendency to tilting the supporting teeth what is a negative phenomenon.

Influence of Hyrax screw position on dental movement and cortical bone: A study of finite elements.

BackgroundRapid maxillary expansion (RME) has effects on the dental and periodontal structures of the parts involved, which vary according to the design and position of the expansion screw. The purpose of the study was to determine the optimal three-dimensional position of the Hyrax screw to obtain precise control of the dental movement and effect on the bone cortex using the finite element method (FEM).Material and MethodsRME was performed from the patient whom two Cone-Beam computerized tomography scans (CBCT) were obtained: T1 before expansion, and T2 three months after stabilization of RME. The FEM model was designed with T1 and of Hyrax photographs. FEM was obtained by comparing the simulation, T2, and clinical results. Three sagittal screw positions (anterior-middle-posterior) and vertical (upper-medium-low) were evaluated.ResultsA coronal- buccal displacement of premolars and first molars was found which decreased in the occlusal-apical direction, presenting different types of dental movement in the screw positions; besides, a tendency of translational movement in the posterior-high location was observed. In the posterior-high position a higher concentration of efforts and homogeneous deformations in the periodontal ligament and vestibular cortex of the cervical area of first molars, first and second premolars were observed, with variations according to the screw position and the distribution of stresses.ConclusionsThe ideal location of the expansion screw for controlling dental movement and periodontal side effects was the high-posterior position. Key words:Maxillary expansion, dental movement, finite element analysis, orthodontic appliances.

An Innovative Use of Hyrax for the Treatment of Obstructive Sleep Apnea

The number and kind of oral appliances have proliferated in recent years as dentists have responded to the challenge to develop more sophisticated devices for the control of socially disruptive snoring and obstructive sleep apnea (OSA). Oral appliances are appealing because they are simple to use, reversible, portable, and appear to be quite safe. Anterior mandibular positioners are the most commonly used appliances. This article illustrates a simple modification of hyrax screw which can be used as a mandibular advancement device for the treatment of OSA.

Cephalometric changes in nasopharyngeal area after anterior maxillary segmental distraction versus Le Fort I osteotomy in patients with cleft lip and palate.

Objective:The present study was designed to compare the effects of two surgical methods, anterior maxillary segmental distraction (AMSD) versus conventional Le Fort I osteotomy, on cephalometric changes of velopharyngeal area of patients with cleft lip and palate.Materials and Methods:This study was conducted on 20 CLP in two groups. The first group had classic Le Fort I maxillary advancement and the second group had AMSD with a modified hyrax as an intraoral tooth-borne distractor. In the second group, 1 week after the surgery, activation of hyrax screw was started with the rate of 2 times a day for about 10 days. Initial and final lateral cephalograms were traced and analyzed by OrthoSurgerX software.Results:The changes in variables evaluating velopharyngeal status showed a significant difference between the two groups. In Group A (conventional), the mean of nasopharyngeal area and Nasopharynx floor length showed a significant increase (P < 0.05) after the surgery, while in Group B (DO), the trend of changes was vice-versa. The changes in SNA, overjet, and soft-tissue convexity were similar in both groups.Conclusion:AMSD can improve facial profile, almost similar to the conventional Le Fort I advancement, while there is a significant decrease in nasopharyngeal; hereby there is no increase in the velopharyngeal sphincter.

A finite element analysis of the effects of different skeletal protraction and expansion methods used in class III malocclusion treatment

This study aims to carry out an in-silico examination of the different skeletal advancement methods used in the treatment of maxillary retrusion patients. Computed tomography images of a young adolescent patient with maxillary retrusion were processed using three-dimensional medical image processing software to obtain a patient-specific model. Three different treatment scenarios were envisaged for the finite element analysis. In the first scenario, rapid maxillary expansion (RME) and face mask (FM); in the second, bone-assisted maxillary advancement and RME, and in the third, hybrid hyrax+mentoplate combination method were used. The hyrax screw was activated by 0.25mm in each model, with a force of 500g in the first scenario and 250g in the second and third scenario for each side. Von Mises stresses and the initial displacements were evaluated when different maxillary protraction methods were applied. We found that similar stress distributions were observed in the skull where the methods of RME/FM model and bone-assisted maxillary advancement were used. These stresses were higher than the hybrid hyrax+mentoplate combination method. When the displacement values were compared, anterior movement was found in the maxilla in the bone-supported model to include the middle face, while maxillary anterior movement of maxilla was detected on the Le Fort 1 level with the hybrid hyrax+mentoplate combination method. Dentoalveolar anterior movement was detected in the RME/FM model. Given the obtained stress distributions and displacement values, it has been observed that the bone-assisted maxillary advancement method provides more skeletal efficiency than the RME/FM and the hybrid hyrax+mentoplate combination methods.

CRANIOFACIAL STRESS PATTERNS AND DISPLACEMENTS AFTER ACTIVATION OF HYRAX DEVICE: FINITE ELEMENT MODELLING

Rapid maxillary expansion is employed for the treatment of cross-bite and deficiency of transversal dimension of the maxilla in patients with and without cleft of palate and lip. For this procedure, generally, different orthodontic appliances and devices generating significant transversal forces are used. The aim of this study is the finite-element analysis of stresses and displacements of the skull without palate cleft and the skull with unilateral and bilateral cleft after activation of the Hyrax orthodontic device. Two different constructions of the orthodontic device Hyrax with different positions of the screw relative palate are considered. In the first case, the screw is in the occlusal horizontal plane, and in the other, the screw is located near the palate. Activation of the orthodontic device corresponds to the rotation of the screw on one-quarter turn. It is established that the screw position significantly affects the distributions of stresses in skull and displacements of the cranium without palate cleft and with unilateral or bilateral palate cleft. Stresses in the bone structures of the craniums without cleft and with cleft are transferred from the maxilla to the pterygoid plate and pharyngeal tubercle if the screw displaces from the occlusal plane to the palate. Depending on the construction of the orthodontic appliance, the maxilla halves in the transversal plane are unfolded or the whole skull is entirely rotated in the sagittal plane. The stresses patterns and displacements of the skull with bilateral palate cleft are almost unchanged after activation of the orthodontic devices with different positions of the screw, only magnitudes of stresses and displacements are changed. The obtained results can be used for design of orthodontic appliances with the Hyrax screw, as well as for planning of osteotomies during the surgical assistance of the rapid maxillary expansion.

The model of halfring to dental braces intended to treat for the palatal suture expansion

Abstract One of the most common stomatognathic system dysfunctions on the skeletal level is the maxilla’s narrowing. Orthodontic treatment of defects occurs by using a Biderman appliance with a Hyrax screw. The appliance is placed in the jaw through the cemented rings on the premolars and molar teeth. The cement-mounting ring includes fluorine, still released to the tooth enamel, having a protective effect. Where the cement begins to crumble, it gradually weakens to maintain the ring and begins to move, or to slide up the tooth. Then, it is re-cemented, tightly filling the space between the ring and the tooth. As a result, the aim of the project was to present new conception rings whose use does not lead to a lack in enamel. The proposed new design was created in such a way that the halfring design makes it impossible to slip from a single tooth in the jaw. The project was designed to propose the shape and material of the biocompatible and durable material for the load. The comparative tension analysis and movements of the turnbuckle of the three used stainless steel (AISI 304, AISI 316L, AISI 430) have been performed by means of the finite element method (FEM).

Does pterygomaxillary disjunction in surgically assisted rapid maxillary expansion influence upper airway volume? A prospective study using Dolphin Imaging 3D

Surgically assisted rapid maxillary expansion has been used for the treatment of transverse maxillary deficiency. This prospective study aimed to evaluate the effect of this surgery (with or without pterygomaxillary disjunction) on the upper airway volume. The patients were randomly divided into two groups: without pterygomaxillary disjunction (−PD) and with pterygomaxillary disjunction (+PD). Eleven patients per group were estimated to obtain a representative sample (90% of power and 95% of confidence level). Volumetric images of cone beam computed tomography scans were obtained preoperatively, immediately after Hyrax screw stabilization and 6 months after Hyrax screw stabilization. Volumetric measurements of the nasal cavity, maxillary sinuses, nasopharynx, and oropharynx, and of the minimum oropharynx cross-sectional area were obtained using Dolphin 3D Imaging Software. The final sample consisted of 25 adult individuals (+PD group, n=12; −PD group, n=13). In the +PD group, we observed a statistically significant increase immediately after Hyrax screw stabilization for the nasopharynx volume (P=0.003), oropharynx volume (P=0.007) and oropharynx cross-sectional area (P=0.001). Pterygomaxillary disjunction resulted in a significant (P <0.05) increase in volumetric measurements of the nasopharynx and minimum oropharynx cross-sectional area 6 months after the expander device stabilization.

Assessment of the dental and skeletal effects of fan-type rapid maxillary expansion screw and Hyrax screw on craniofacial structures.

Aims and Objectives:The purpose of the study was to assess the skeletal and dental effects of fan-type rapid maxillary expansion (RME) appliance and Hyrax RME appliance on the craniofacial structures.Materials and Methods:The sample of the study included 12 patients with constricted maxillary arches. Acrylic bonded type of attachment was used for both groups. Changes in sagittal, vertical, and transverse relationship were assessed with lateral and frontal cephalograms, respectively. Intercanine and intermolar widths were measured with stone models. Pre- and immediate post-treatment records were statistically analyzed with Wilcoxon signed-rank test. The differences between the groups were evaluated using Mann–Whitney U-test. Since the data pertaining to intercanine width and intermolar width were normally distributed, parametric test of significance (unpaired t-test) was used to compare them.Results:Results showed that Hyrax presented with significantly greater increments for both nasal cavity width and maxillary width when compared to fan-type RME. Both groups had retroclination of incisors. The increase in the intercanine width was almost similar in both groups.Conclusion:Fan-type RME caused only minimal expansion of the intermolar width when compared to the Hyrax. The ratio between the intercanine and intermolar width expansion was nearly 4:1 in the fan-type RME and 0.75:1 in Hyrax.