Optimization of early orthodontic therapy: the potential of preformed elastomeric eruption guidance appliances (EGA) in addressing class ii malocclusions

Introduction

Malocclusion is a condition characterized by the alteration of dental-alveolar relationships, which can be evident already in mixed dentition with an increase in overbite (OVB) and overjet (OVJ) and may persist in permanent dentition, increasing the risk of dental trauma such as, for example, the fracture of the upper incisors1. This phenomenon is particularly seen in second-class malocclusions of 1 division, characterized by increased overjet and overbite, often associated with hypodivergent growth patterns and dental rotations caused by insufficient eruptive guides. At the skeletal level, sagittal alterations may occur, such as mandibular hypoplasia or upper maxillary hyperplasia, which contribute to the clinical situation described2.

To address these issues, interceptive orthodontic therapy is often the first choice in the treatment of malocclusion of growing subjects1,3. However, it is crucial to understand that in almost all patients there will be a need, subsequently, for a second therapeutic phase by means of fixed orthodontics or with transparent aligners, to optimize the therapeutic results, solve inter-arch and intra-arch and achieve proper occlusion4,5. The orthodontist, after a careful diagnosis that considers various factors such as the facial model and the age of the patient, will have to identify the most appropriate treatment for each case, also considering the collaboration of the patient himself3,6. Managing the aesthetic impact of malocclusion is of considerable importance for the growing patient, not only to ensure dental health, but also to preserve psychological well-being1,7.

The purpose of this study is to demonstrate how the use of preformed elastodontic guided eruption appliance (EGA) allows the improvement of OVB and OVJ parameters and has a stable corrective action on dental elements.

Materials and methods

Clinical observation

On the extraoral examination, the patient had a convex facial profile, balanced facial proportion, regular nasolabial angle, and marked sub-labial fossa. The joint examination showed no clinical signs.

During the last stage of the mixed teething, the visit occurred. From a sagittal point of view, a class II tendency was observed at both molar and canine levels, with a OVJ increased by 5 mm. On the transverse side, there was a slight contraction of the upper arch and a slight deviation of the midline to the left, which however disappeared during the opening of the mouth. This showed that the problem was not of a skeletal nature, but functional. As for the vertical plane, an accentuation of the Spee curve was observed in the lower arch, whereas the upper arch had an inverse Spee curve. Parents were also made aware of the need to improve the oral hygiene of the young patient.

Diagnostic values

For a more detailed evaluation, orthopantomography and cephalometric analysis were performed using a latero-lateral teleradiograph. To conduct digital cephalometric measurements, a JPG format X-ray image was uploaded to the OneCeph application (Google Play Store, Google Inc, Mountain View, California) on an Android smartphone (Motorola Moto E13, Motorola Inc, Schaumburg, Illinois)8. The image was calibrated using a reference scale. Subsequently, the same operator identified the necessary skeletal and dental reference points for analysis. Upon completion of the reference point identification, the OneCeph application performed linear and angular measurements, yielding the following values.

Results

The patient showed signs of a double occlusion a year later, one with an OVJ that was still elevated and the other with an OVJ of 2 mm. The OVB had improved, and dental rotations had decreased, suggesting that the device was performing. The upper arch was no longer contracted, the rotations were corrected and the OVJ and OVB were fixed two years after the treatment began. While class relations in class I stabilized, the midline deviation also improved. Furthermore, there was an improvement in the patient’s harmonious facial profile.

Follow-up

To maintain the achieved results and promote the correct intermaxillary growth, the patient continued to use a LM-Activator Low-Long 55. This approach was aimed at supporting the correct intermaxillary relationship and the three-dimensional growth of dentoalveolar processes. The correction of occlusal planes has been ensured over time.

Approximately four years and five months post-therapy, the patient was re-evaluated at the age of 16 years and 11 months. Follow-up results demonstrated a stable occlusion, with Class I relationships observed in both canines and molars across both dental arches.

Aesthetically, the patient’s smile was harmonious with good smile exposure, though slight incisor crowding was noted in both arches. The patient’s profile remained convex.

Cephalometric measurements indicated significant improvements in key reference values. The ANB angle improved to 2.1°, and the Wits appraisal (AOBO) reached 2.2 mm. Maxillary rotation was recorded at 11.5°, while the basal plane angle was 19.4°. The upper incisor to SN angle (UISN) increased to 103.4°, and the IMPA was measured at 95.4°.

These results suggest, as also described by scientific literature, that interceptive treatment with EGA contributed positively to occlusal stability and smile aesthetics, with noted improvements in cephalometric parameters10–13.

Discussion

The primary objective of the orthodontist, while examining a growing patient, is to assess the development of occlusion to determine whether it is physiological or, on the contrary, may be indicative of a potential malocclusion. Indeed, it is essential to have an in-depth understanding of facial growth, dental and skeletal development, as well as proportional variations1,14. Additionally, it is crucial to examine the direction of dentofacial growth associated with the overall physical development and maturation of the pediatric patient15. Hence, it is the responsibility of the orthodontist to diagnose potential anomalies, including abnormalities in dental arches, alterations in occlusion and jaw relationships and pathological occlusal interferences16,17.

The purpose of interceptive orthodontic therapy is to identify and address the factors contributing to malocclusions, promote harmonious growth and development of maxillaries and minimize the duration of future treatment during permanent dentition3,18.

Typically, the interceptive orthodontic treatment can include one or two phases, followed by definitive treatment during permanent dentition, which can be carried out with fixed appliance or clear aligners9,19.

Treatment timing is a contentious issue in orthodontics1. During the first phase, in mixed dentition, Angle’s class relationships, overbite and overjet relationships are assessed. Early intervention aims to prevent the development of malocclusion and facilitate proper growth of permanent teeth20.

Interceptive and functional orthodontic devices are designed to avoid interfering with the physiological changes associated with the pubertal growth peaks, which are correlated with the eruption of permanent teeth. Consequently, they do not alter the dynamic nature of occlusal adjustments6.

The overjet increase, which can result from rotations of the anterior teeth exerts adverse effects on the growth pattern, potentially compromising the development of skeletal issues. Under such circumstances, mandibular retrusion during growth may persist. As a consequence, upper incisors protrusions and mandible’s retrognathic position can predispose to dental traumas. An increase in overjet leads to a subsequent increase in overbite: as a result of insufficient contact with the opposing arch, the lower incisors will overerupt until they make contact with the palatal mucosa2,21. This situation necessitates early intervention to establish a proper occlusal relationship for long-term maintenance. Additionally, the familial predisposition to skeletal Class II can genetically influence the development of this malocclusion in the patient3. To enhance sagittal and vertical dimensions in a patient, achieving proper eruption of posterior teeth is crucial to positively influence mandibular growth. However, the timing and extent of dental eruption may vary, depending on individual factors such as mandibular resting position and interocclusal free space1,22.

Orthodontic functional appliances employ various mechanisms of action, yet they share the common effect of orthopedically guiding dental eruption and movement. Consequently, the treatment goal is to foster proper mandibular growth in children and correct basal bone growth in all three spatial planes. The principle of functional orthodontics centers on achieving morphological modifications through functional actions, including physiotherapy, exercises, and oral muscle training23,24.

Preformed elastomeric eruption guidance appliances (EGA) are generally employed in interceptive orthodontic therapy to early treat Class II malocclusions. They can be considered dental positioners, due to their capacity to achieve guided movements during dental eruption10,13. These appliances are particularly indicated for patients aged 6 to 12 years old presenting with Class II division 1 malocclusions, characterized by deep bite and increased overjet during the early mixed dentition11. They adhere to similar indications as other functional appliances and primarily comprise a singular elastic structure with intercuspation for both upper and lower teeth25.

Early treatment with EGA devices aims to obtain an ideal sagittal condition by controlling vertical dimension and harnessing eruption forces11,12. These appliances are designed to guide dental eruption and retain permanent teeth in their correct positions throughout the mixed dentition phase, thereby facilitating the attainment of an ideal occlusion through the application of moderate and constant orthodontic forces10,25.

Initially, the teeth are guided towards proper alignment during their eruptive phase. Subsequently, efforts are directed towards achieving optimal spatial positioning within the occlusal plane26.

As mentioned in previous studies, these devices demonstrate effectiveness when employed during the early mixed dentition stage for the treatment of Class II division 1 malocclusions, particularly during the skeletal growth phase of the craniofacial complex10, 11, 12, 13. Indeed, their utilization is expected to yield significant mandibular growth, resulting in subsequent dentoalveolar alterations. These include forward linear movement of lower incisors, retrusion and intrusion of upper incisors and extrusion of posterior segments, while maintaining the position of the skeletal basal components12,27.

The primary features of preformed devices facilitate mandibular growth activation, reduction of labial pressure, arch expansion, and dental alignment. The correction of dental parameters can be achieved through dental disclusion, a process that occurs with the constant utilization of the appliance11,25. Furthermore, the EGA device incorporates frontal slots to address dental rotations. The alteration in incisor inclination leverages the principles of inclined planes. The proper alignment of the upper incisors can positively influence the mandibular growth pattern, extending beyond the mandibular body to involve the mandibular ramus12.

The intentional reduction in appliance thickness at the incisor section, characteristic of the device utilized, facilitates posterior segment extrusion while mitigating passive eruption of the anterior teeth10. The management of posterior segment eruption and alteration of the occlusal plane are correlated with post-rotation of the mandible, achieved by condylar distraction within the glenoid cavities11.

A comparable methodology is employed in conventional orthodontic functional therapy, exemplified by the Twin-Block appliance, which incorporates push bite blocks in order to induce mandibular advancement and subsequent rotation28. Even Class II elastics utilized in fixed therapy adopt a similar approach, exerting orthopedic forces on the maxilla to tilt the occlusal planes, thereby generating forces directed posteriorly and inferiorly29.

The trajectory of anterior arch movement plays a pivotal role in controlling overbite by influencing the opening of the gonial angle. The efficacy of therapy conducted using preformed EGA devices is consequently linked to the simultaneous correction of transverse, sagittal, and vertical discrepancies13,25.

EGA therapy enables precise management of early-age patients while also stimulating perioral musculature: preformed devices operate at the level of the lips, activating underlying muscles and promoting sagittal mandibular growth10. The thickness of the material in the anterior region elicits a comparable effect to the Lip Bumper orthodontic device in terms of labial proprioception. Muscle activity is stimulated by oral proprioceptors activated by the soft and transparent biocompatible silicone material. The material thickness located at the lateral zones, unlike Frankel-type appliances, is distanced from the fornix, creating a screen that provides a proprioceptive function to the patient’s lips, cheeks, and tongue throughout device usage. Consequently, this facilitates a continuous tissue conditioning25,30.

Once all therapeutic objectives associated with the active phase of treatment have been achieved, the device can subsequently serve passively as a retainer10.

The primary effects observed in patients on the sagittal plane include mandibular advancement, primarily attributed to positive outcomes at the temporomandibular joint (TMJ) level. This stimulation results in bilateral condylar growth, fostering harmonious spatial arrangement11.

On the frontal plane, an increase in facial height is observed, attributed to the extrusive effect on the anterior group and the intrusive effect on the posterior group13,25.

On the transverse plane, the primary effects pertain to inter-arch relationships and arch width. Specifically, preformed elastomeric EGA devices facilitate a guiding action during tooth eruption, leading to an optimal interocclusal relation. Furthermore, literature supports physiological expansion of dental arches when forces exerted by vestibular and labial musculature are controlled by apposite shields10, 11, 12,26.

Ultimately, EGAs can serve as retainers, ensuring the stable maintenance of tooth position at the occlusal plane achieved until the completion of dental transition12.

Patient cooperation plays a crucial role in achieving optimal results, with the device ideally worn during nighttime hours and for approximately 4–6 hours during the day, as strongly recommended in the literature10, 11, 12.

The utilization of these devices, distinguished by their comfort and convenience in daily use, fosters increased compliance among young patients while allowing for uninterrupted oral hygiene practices10,25. This therapeutic approach represents a substantial advancement in enhancing the quality of orthodontic treatment, particularly for patients afflicted with Class II malocclusion, by providing an effective and comfortable solution11.

The utilization of EGAs can prove highly advantageous in early intervention strategies, as it mitigates or potentially obviates the necessity for subsequent orthodontic interventions during the permanent dentition phase. This, in turn, facilitates a notable reduction in treatment expenditures10, 11, 12, 13,25–26.

Conclusions

The orthodontic treatment of Class II malocclusions with deep overbite and increased overjet using elastomeric guidance appliances is aimed at correcting tooth position, with a focus on the frontal and sagittal planes and occlusal alignment. Therapeutic objectives entail the early and highly effective improvement of deep overbite and incisal relationships, contingent upon full patient cooperation. This therapeutic approach substantially diminishes the duration of subsequent orthodontic treatment phases, involving multibracket fixed appliances or clear aligners. Moreover, in certain instances, it can enable the resolution of malocclusion within a single interceptive orthodontic phase. Preformed elastomeric orthodontic appliances demonstrate particular efficacy in this context, yielding satisfactory outcomes when applied during the mixed dentition phase. The assessment of treatment timing holds paramount importance, with tools such as skeletal growth indicators assuming a pivotal role. Finally, precise diagnosis, meticulous planning, and optimal patient cooperation remain indispensable for the success of the treatment, consistent with every interceptive approach. In conclusion, precise diagnosis, meticulous planning, and high levels of patient cooperation remain essential for the success of the treatment, consistent with any interceptive orthodontic approach.