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Neuro‐occlusal rehabilitation (N.O.R.) is a discipline of the stomatognathic medicine that defends early treatments of functional malocclusions, such as unilateral crossbite, for the correction of craniofacial development, avoiding surgical procedures later in life. Nevertheless, N.O.R.'s advances have not been proved analytically yet due to the difficulties of evaluate the mechanical response after the treatment. This study aims to evaluate computationally the effect of N.O.R.'s treatments during childhood. Therefore, bilateral chewing and maximum intercuspation occlusion were modelled through a detailed finite element model of a paediatric craniofacial complex, before and after different selective grinding‐alternatives. This model was subjected to the muscular forces derived from a musculoskeletal model and was validated by the occlusal contacts recorded experimentally. This approach yielded errors below 2% and reproduced successfully the occlusal, muscular, functional and mechanical imbalance before the therapies. Treatment strategies balanced the occlusal plane and reduced the periodontal overpressure (>4.7 kPa) and the mandibular over deformation (>0.002 ε) on the crossed side. Based on the principles of the mechanostat theory of bone remodelling and the pressure‐tension theory of tooth movement, these findings could also demonstrate how N.O.R.'s treatments correct the malocclusion and the asymmetrical development of the craniofacial complex. Besides, N.O.R.'s treatments slightly modified the stress state and functions of the temporomandibular joints, facilitating the chewing by the unaccustomed side. These findings provide important biomechanical insights into the use of N.O.R.'s treatments for the correction of unilateral crossbite, but also encourage the application of computing methods in biomedical research and clinical practise. [ABSTRACT FROM AUTHOR]

Unilateral posterior crossbite typically presents as a narrow maxillary arch and a broad mandibular arch on the side of the crossbite. Unwanted overexpansion and iatrogenic crossbite may develop as side effects if conventional rapid maxillary expansion is done in such cases. Thus, unilateral expansion of the maxilla with unilateral posterior crossbite can help us avoid these side effects and improve the transverse relationship between the maxillary and mandibular posterior dentition on the affected side only. In this case report, we describe a mini-implant–supported unilateral expansion of the maxillary arch in a patient with a unilateral posterior crossbite.

Aim and Background: The quad helix is well known for its ability to treat posterior crossbites in children with maxillary deficiency. A few authors have also used it for the treatment of unilateral crossbite due to unilateral maxillary deficiency by incorporating modifications in the appliance. The aim was to treat a unilateral crossbite using a newly modified quad helix., Case Description: An 8-year-old female patient had presented with multiple missing teeth and a unilateral posterior crossbite due to an asymmetric maxillary arch. The amount of unilateral asymmetry was measured using a unique method over the cast. A modified quad helix was cemented to treat the unilateral posterior crossbite, and correction was obtained in 30 days. A Nance palatal arch was cemented which functioned as a space maintainer and a retention appliance., Conclusion: The posterior unilateral crossbite was treated successfully with the modified quad helix., Clinical Significance: This article highlights a new modification of the quad helix for treating unilateral posterior crossbite and a new method of measuring maxillary asymmetry. The modification has been termed as a "bi helix" since it eliminates two helices from the classic quad helix design., How to Cite This Article: D'souza OK, Chalakkal P, de Noronha de Ataide I. A Modification of the Quad Helix: The "Bi Helix". Int J Clin Pediatr Dent 2024;17(7):822-825., Competing Interests: Source of support: Nil Conflict of interest: None Patient consent statement: The author(s) have obtained written informed consent from the patient’s parents/legal guardians for publication of the case report details and related images.Conflict of interest: None, (Copyright © 2024; The Author(s).)

True unilateral posterior crossbite in adults is a challenging malocclusion to treat, especially when we need to correct cross-arch segments with unwanted effects on non-cross segments. Conventional expansion methods are expected to have some shortcomings; the Unilateral dental expander appliance used to restore unilateral cross bite dental arch is an uncommon appliance; for this, a designed new device is needed. This paper aimed to invite a new unilateral dental expander appliance (UDEX) to treat unilateral dental posterior crossbite in adults using available dental material, easy to use and handle, well tolerated by the patient, and biocompatible with oral structure. It could find that in all dental markets and dental clinics--an eighteen-year-old female with bilateral crossbite and upper and lower dental arch crowding. During active orthodontic treatment, a quad-helix expander had broken from one side at soldering between band and wire attachment. The patient did not show up to the clinic for a while due to COVID 19 pandemic lockdown, leading to a true unilateral crossbite at the dental arch's upper left side, especially at the molar premolars area. This unilateral cross bite was treated using a new specially designed expanded appliance as a unilateral posterior cross bite dental maxillary expander. As a result of this study, orthodontic treatment was finished within (15) months, much less than expected. We obtained Class I molar and canine relationships with uncrossed dental arches in both upper arch sides, proper overbite and overjet with well-leveled and aligned teeth as it confirmed by clinical examination and radiographic images (OPG (Orthopantomogram) and cephalometric radiograph (WebCeph analysis digitalized computer program). Conclude from that, the newly designed unilateral dental expander (UDEX) is proven to be useful for treating real unilateral posterior crossbites as single molar or premolar tooth andmultiple joint unilateral crossed posterior teeth. Also, it could easily modify it for future unilateral crossed purposes. This appliance was fabricated using readily available dental material, well tolerated by patients, and reduced the need for excessive patient compliance. An orthodontist could fabricate devices, or cautious laboratory work is required; it can rapidly achieve favorable results. [ABSTRACT FROM AUTHOR]

Unilateral posterior crossbite is a malocclusion disease that involves morpho-functional characteristics of masseter muscle; a normal or increased activity of contralateral muscle and a reduced activity of the ipsilateral muscle during unilateral crossbite have been shown. Since the extracellular matrix plays a key role in in mechano-transduction of transmitting forces during muscle contraction, the aim of the present study was to analyse the behaviour of extracellular matrix in this type of malocclusion through immunofluorescence reactions against laminin, collagen IV, MMP-2 and MMP-9. Our results show an increased expression of Laminin, Collagen IV, and MMP-9 in the contralateral side if compared to the ipsilateral side. No differences have been found in MMP-2 expression between contralateral and ipsilateral muscles. Since the increased expression of Laminin, Collagen IV and MMP-9 is associated with muscle hypertrophy and MMP-2 is associated with muscle atrophy, our results support the existence of a hypertrophic response of contralateral muscle during unilateral posterior crossbite that probably aims to compensate the altered function of the ipsilateral one. [ABSTRACT FROM AUTHOR]

Unilateral posterior crossbite typically presents as a narrow maxillary arch and a broad mandibular arch on the side of the crossbite. Unwanted overexpansion and iatrogenic crossbite may develop as side effects if conventional rapid maxillary expansion is done in such cases. Thus, unilateral expansion of the maxilla with unilateral posterior crossbite can help us avoid these side effects and improve the transverse relationship between the maxillary and mandibular posterior dentition on the affected side only. In this case report, we describe a mini-implant-supported unilateral expansion of the maxillary arch in a patient with a unilateral posterior crossbite. [ABSTRACT FROM AUTHOR]

The evaluation of temporomandibular joint (TMJ) dysfunction using finite element models is a time consuming process that requires extensive technical knowledge. We combined a statistical active appearance model with automated modelling algorithms to biomechanically study the relationship between TMJ malformations and dysfunction in radiographs from 20 paediatric patients with unilateral crossbite. A fitting algorithm (fitting error < 4%) recognised the TMJ shape and adjusted the dimensions of each patient-specific 2D FE model, which was then used to compute 2 different joint movements. Significant functional differences were observed between the crossbite and non-cross bite sides, and the shape-function relation was verified. [ABSTRACT FROM AUTHOR]

Unilateral posterior crossbite is a malocclusion disease that involves morpho-functional characteristics of masseter muscle; a normal or increased activity of contralateral muscle and a reduced activity of the ipsilateral muscle during unilateral crossbite have been shown. Since the extracellular matrix plays a key role in in mechano-transduction of transmitting forces during muscle contraction, the aim of the present study was to analyse the behaviour of extracellular matrix in this type of malocclusion through immunofluorescence reactions against laminin, collagen IV, MMP-2 and MMP-9. Our results show an increased expression of Laminin, Collagen IV, and MMP-9 in the contralateral side if compared to the ipsilateral side. No differences have been found in MMP-2 expression between contralateral and ipsilateral muscles. Since the increased expression of Laminin, Collagen IV and MMP-9 is associated with muscle hypertrophy and MMP-2 is associated with muscle atrophy, our results support the existence of a hypertrophic response of contralateral muscle during unilateral posterior crossbite that probably aims to compensate the altered function of the ipsilateral one.

Introduction: The treatment of a true unilateral posterior crossbite often requires asymmetric maxillary expansion; however, this is challenging to achieve with conventional expansion methods because of several biomechanical limitations. In this paper, we introduce a new protocol for the treatment of a unilateral posterior crossbite in adults based on maxillary orthodontic expansion assisted by corticotomy and low-level laser therapy (LLLT) performed on the crossbite side. Methods: The study sample included 15 adults (8 females, 7 males) affected by a true unilateral posterior crossbite, with a mean age of 21.6 ± 3.1 years at the at the beginning of treatment. After the application of orthodontic appliances (palatal expander and self-ligating brackets), corticomy was performed at the buccal aspect of the crossbite side while LLLT was monthly administered up to the correction of the crossbite. The efficacy of the technique was evaluated through measurements performed on maxillary digital models. Results: All subjects reported successful correction of the posterior unilateral crossbite, and functional occlusion was achieved as well. The average expansion was greater at the crossbite side compared to the unaffected side and such difference was significant at the levels of first premolars (P < 0.05), second premolars (P < 0.05) and first molars (P < 0.05). Conclusion: Orthodontic maxillary expansion assisted by unilateral corticotomy and LLLT was effective in the treatment of the true unilateral crossbite. [ABSTRACT FROM AUTHOR]

• Computational models simulate the occlusal imbalance with relative errors below 6%. • Centric occlusion simulations shows the functional imbalance of crossbite patients. • Crossbite patients present asymmetrical strains and shifts in jaw and maxilla. • Facial asymmetry and the unilateral crossbite relationship is proved. • Computational analyses demonstrate functional matrix hypothesis principles. The occlusion effect on the craniofacial development is a controversial topic that has attracted the interest of many researchers but that remains unclear, mainly due to the difficulties on measure its mechanical response experimentally. This mechano-morphological relationship of the craniofacial growth is often explained by the periosteal and capsular matrices of the functional matrix hypothesis (FMH); however, its outcomes have not been analytically demonstrated yet. This computational study aims, therefore, to analytically demonstrate the mechano-morphological relationship in the craniofacial development of children with unilateral crossbite (UXB) using the finite element (FE) method. The craniofacial complex asymmetry of ten children, five of whom exhibit UXB, was 3D-analysed and compared with the biomechanical response computed from a FE analysis of each patient's occlusion. Due to the complexity of the geometry and the multitude of contacts involved, the inherent limitations of the model were evaluated by comparing computed occlusal patterns with those recorded by an occlusal analysis on 3D printed copies. Comparison's outcomes proved the reliability of our models with just a deviation error below 6% between both approaches. Out of validation process, computational results showed that the significant elongation of mandibular branch in the contralateral side could be related to the mandibular shift and increase of thickness on the crossed side, and particularly of the posterior region. These morphological changes could be associated with periodontal overpressure (>4.7 kPa) and mandibular over deformation (0.002 ε) in that side, in agreement with the periosteal matrix's principles. Furthermore, the maxilla's transversal narrowing and the elevation of the maxillary and zygomatic regions on the crossed side were statistically demonstrated and seem to be related with their respective micro displacements at occlusion, as accounted by their specific capsule matrices. Our results were consistent with those reported clinically and demonstrated analytically the mechano-morphological relationship of children's craniofacial development based on the FMH's functional matrices. This study is a first step in the understanding of the occlusion's effect on the craniofacial development by computational methods. Our approach could help future engineers, researchers and clinicians to understand better the aetiology of some dental malocclusions and functional disorders improve the diagnosis or even predict the craniofacial development. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction: True unilateral posterior crossbite can be efficiently treated by using asymmetric expansion appliances that essentially exert unilateral expansion forces thereby minimizing iatrogenic overexpansion of the normal pretreatment side., Aim: To evaluate and compare the stresses and displacements generated by four different types of asymmetric maxillary expansion appliances in true unilateral crossbite using the finite element method., Materials and Methods: A CBCT image of the skull was obtained from a 12-year-old female patient with a true unilateral posterior crossbite on the right side, for the FEM study. Asymmetrically split acrylic plate with jackscrew (ASAPJ), NORD crossbite expander, Asymmetric Maxillary Expansion appliance (AMEX), Asymmetrical Rapid Maxillary Expansion (ARME) appliances were simulated with a given force specific to the appliance. Von Mises stresses, displacements in the x, y, z-axis, and changes in the axial inclination were evaluated and compared on the selected skeletal and dental landmarks., Results: Overall ARME seemed to generate the highest asymmetric von Misses stress on skeletal landmarks followed by NORD; ASAPJ and lowest by the AMEX. ARME also produced the highest asymmetric expansion followed by AMEX; NORD and lowest with the ASAPJ. NORD produced the minimum extrusion and buccal tipping of the canine and 1st molar followed by ASAPJ; AMEX and maximum by the ARME., Conclusion: Each of the four appliances expanded the maxillary arch more on the crossbite side as compared to the non-crossbite side, but the pattern of stress distribution, displacement and change in the axial inclination were unique for each appliance., (Copyright © 2022 CEO. Published by Elsevier Masson SAS. All rights reserved.)

The aim of this paper is to present and debate the treatment of a unilateral canine crossbite using clear aligners (Invisalign). The possibility of combining partial fixed appliances with removable elastics to optimize the final outcome is also described. The advantages of protected movement, due to the presence of the aligners, to jump the occlusion during crossbite correction is also highlighted. [ABSTRACT FROM AUTHOR]

14 children with unilateral posterior crossbites (PCB) participated in this study and 14 children with Angle's class I occlusion. Body posture analysis was made by a video recording technique. The results showed greater tilt in the angles of head tilt in PCB children when compared to neutral occlusion children. We also observed that head tilt followed the side of crossbite. Such results suggest that unilateral PCB could be related to the development of head tilt on the same side of the crossbite. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the stability of orthodontically corrected unilateral posterior crossbite in patients treated either by rapid maxillary expansion or with slow expansion devices in the early (mean age 7.2 years, n = 50) or late mixed dentition (mean age 9.9 years, n = 50). Materials and Methods: The observation periods were approximately 8 years for the early treatment groups and 6.5 years for the late treatment groups. The measurements were made on plaster casts at the following time points: before treatment (T1), after crossbite correction (T2), at the end of active orthodontic treatment (T3), and about 2 years after the end of active treatment (T4). Midline deviation and the skeletal classification of the malocclusion were also evaluated. Results: Almost 80% of the treated patients showed long-term stability of the corrected unilateral posterior crossbite. More than 70% of the patients were treated tor the mandibular midline deviation. At the end of active treatment, 50% of the patients showed a skeletal Class Ill craniofacial morphology. Conclusions: The results emphasize that determination of the correct treatment approach for the individual patient is the basic principle underlying the therapeutic success in unilateral crossbite cases. In patients where a broad lower arch is a cofactor in the etiology of the lateral crossbite, the treatment approach should be focused on both arches and not be limited to the constricted upper arch. [ABSTRACT FROM AUTHOR]

• PCA-based method identified the midplane compensating the asymmetry of children's skull. • 3D workflow proposed improves the analytical study of craniofacial development. • Morphological 3D analysis displayed malformations in the cranial base and soft tissues. • Unilateral chewing could lead to the abnormal growth of both the maxilla and jaw. • Maxilla and jaw malformations seem to be correlated in patients with unilateral crossbite. Craniofacial asymmetry is a common growth disorder often caused by unilateral chewing. Although an early orthodontic treatment would avoid surgical procedures later in life, the uncertainty of defining the accurate sagittal midplane potentially leads to misdiagnosis and therefore inaccurate orthodontic treatment plans. This novel study aims to 3D-diagnose craniofacial complex malformations in children with unilateral crossbite (UXB) considering a midplane which compensates the asymmetric morphology. The sagittal midplane of 20 children, fifteen of whom exhibited UXB, was computed by a PCA-based method which compensates the asymmetry mirroring the 3D models obtained from cone-beam computed tomography data. Once determined, one side of the data was mirrored using the computed midplane to visualize the malformations on the hard and soft tissues by 3D-computing the distances between both halves. Additionally, 31 skull's landmarks were manually placed in each model to study the principal variation modes and the significant differences in the group of subjects with and without UXB through PCA and Mann-Whitney U test analyses respectively. Morphological 3D-analysis showed pronounced deformities and aesthetic implications for patients with severe asymmetry (jaw deviation > 0.8 mm) in whole craniofacial system, while initial signs of asymmetry were found indistinctly in the mandible or maxilla. We detected significant (p < 0.05) malformations for example in mandibular ramus length (0.0086), maxillary palate width (0.0481) and condylar head width (0.0408). Craniofacial malformations increased the landmarks' variability in the group of patients with UXB over the control group requiring 8 variation modes more to define 99% of the sample' variability. Our findings demonstrated the viability of early diagnosis of craniofacial asymmetry through computing the accurate sagittal midplane which compensates the individual's asymmetrical morphology. Furthermore, this study provides important computational insights into the determination of craniofacial deformities which are caused by UXB, following some empirical findings of previous clinical studies. Hence, this computational approach can be useful for the development of new software in craniofacial surgery or for its use in biomedical research and clinical practice. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Dysfunctional deviations such as dysfunctional swallowing and chewing manifest as transverse arch discrepancies giving rise to positional asymmetry of the condyles and glenoid fossae with a more or less significant skeletal impact. This results almost inevitably in asymmetric occlusion in the sagittal dimension. Drawing on clinical cases, we will show which treatment strategies to adopt and which occlusal criteria to observe for finishing and stability., (Copyright © 2017. Published by Elsevier Masson SAS.)

Objectives: The aim was to investigate mandibular third molar (3M)'s maturation in the crossbite and normal sides by two- and three-dimensional analyses using cone beam computed tomography (CBCT)., Materials and Methods: A retrospective study was performed using CBCT of 25 patients (16 females and 9 males; mean age: 16.8 ± 2.9 years) with unilateral posterior crossbite. The formation stages and the volume of the mandibular 3Ms were evaluated by means of CBCT data of the patients without knowing the crossbite side of the patients., Results: Statistically no significant differences were found in the development of the 3Ms between the crossbite and the control sides, whereas the volume of 3M was found to be less in the crossbite side than in the normal side (P = 0.021)., Conclusions: A volume of 3M was found to be less in the crossbite side than in the normal side.