Orthopaedic treatment in Class II cases—clinical considerations

Regardless of the type of appliance, several systematic reviews and meta-analyses have confirmed the positive effect of mandibular repositioning in correcting Class II malocclusion in children and adolescents with an improved overjet and molar relationship.^10–12 However, several randomised controlled trials have shown that there was no clinically significant difference in patients’ final mandibular position and molar relationship when early Class II functional correction was performed to guide the forward growth of the mandible rather than during adolescence.^13, 14 A systematic review and meta-analysis also concluded that there was no difference in the sagittal position of the mandible between the group for which a functional appliance was not used and the group for which a functional appliance was used.¹⁵ Although there is no consensus regarding the effectiveness of advancing the mandible with functional appliances, it is generally considered safe and remains an important and indispensable treatment method for the early correction of Class II skeletal malocclusion in children and adolescents. For clinical use, it is necessary to understand the indications and limitations of the various functional appliances and to select the appropriate functional appliance based on the specific case.

Mandibular repositioning in adults

Mandibular repositioning is different in adults from growing patients owing to the absence of growth. Treatment of severe Class II malocclusion in adult patients is typically referred for orthognathic surgery. There have been reports of lifelong glenoid fossa remodelling and condylar adaptation,¹⁶ and some orthodontists have attempted to use orthopaedic appliances to reposition the mandible anteriorly in adult patients with Class II mandibular retrusion as a non-surgical alternative. However, the success rates and follow-up periods of these attempts have varied in different studies.^17, 18

There are several key issues that a modern orthodontist needs to consider in clinical practice based on the currently available evidence. When repositioning the mandible, the condyles will inevitably move away from their natural position, and this can increase the activity of the lateral pterygoid muscles. While there is no evidence to support using centric relation position as the ideal jaw position,¹⁹ a patient’s existing and repeatable jaw relationships appear to be the best physiological guide on which to base treatment.²⁰ Therefore, during routine dental procedures, the patient’s natural jaw relationships should be maintained, and condyle–fossa relationships should not be deliberately altered. Although there is controversy surrounding the causal relationship between temporomandibular joint dysfunction (TMD) and condylar position, repositioning the condyle in non-symptomatic healthy adult patients remains to be further studied.¹⁸ The adaptive physiological parameter for each patient needs to be carefully designed and monitored, and sometimes, a mandibular postural muscle relaxer device may help the treatment.²¹ In other words, procedures that significantly deviate the condyles away from their natural and physiological position should be carefully planned and conducted.

Patients with TMD should be handled with extra care when planning for mandibular anterior repositioning. Although in some cases, a spontaneous repositioning of the condyle can be observed after occlusal interferences have been eliminated with the relief of TMD symptoms,²² such as in cases of condylar resorption where the condylar head becomes superiorly and posteriorly displaced after splint therapy or in cases of Class II Division II deep bite after maxillary incisors have been uprighted,²³ it is still not advisable to deliberately position the condyle through orthodontic treatment in order to reduce or eliminate the risk of TMD. While anterior placement of the condyle might be beneficial in certain cases of anterior disc displacement with reduction, simulating the effect of an anterior repositioning splint that captures the displaced disc,^24, 25 in other TMD cases, anterior positioning of the condyle may cause more harm owing to the already poor adaptive capacity of the TMJ. Therefore, it is crucial to conduct a thorough TMD examination and screening before commencing orthodontic treatment. It is also important to address any TMD pain before starting orthodontic treatment and to refer the patient to appropriate healthcare professionals, such as oral surgeons, TMJ specialists or other medical professionals, if necessary.

Clinical practice considerations

Another important consideration for clinicians is undesired dental effects produced by repositioning in skeletally mature patients.²⁶ Since the physiological potential of an individual’s glenoid fossa remodelling and condylar adaptation varies greatly, it is likely that unwanted dental tipping and protrusion will occur in individuals who have less adaptability. In such cases, the sagittal improvement in occlusion is more of a dental compensation, which can lead to unfavourable periodontal outcomes and relapse.^17, 27 This concern was highlighted in a recent safety alert released by both the US Food and Drug Administration and the American Dental Association regarding certain expanders used in non-growing patients in which the dental effects overshadow the skeletal effect, causing unwanted tooth flaring, uneven bites and even tooth loss.^28, 29 Unfortunately, such incidents ended with lawsuits against the inventor of the devices.³⁰

Conclusion

In summary, orthodontic treatment should be based on the latest scientific evidence. When planning mandibular repositioning in adult patients, clinicians need to be cautious in their case selection in order to avoid potential risks that may lead to complaints or lawsuits. It is also important to consider a team approach involving experienced clinicians. Patients should be fully informed and understand the nature of repositioning as an alternative to orthognathic surgery.