Open bites have traditionally been challenging to treat, but advances in aligner technology have opened up new possibilities. Based on recent studies and clinical experience, we will explore the key elements for success and some limitations and opportunities.
Diagnosis and Case Selection
The foundation of successful open bite treatment with clear aligners lies in proper diagnosis and case selection. Careful cephalometric analysis remains crucial to determine whether the open bite is primarily dental or skeletal. Recent studies have shown mild to moderate dental open bites tend to be more predictable to treat with aligners than severe skeletal cases. Clinicians should consider the severity of the malocclusion, skeletal pattern, and patient compliance when deciding if aligner therapy is appropriate.
Controlling Vertical Dimension
One of the major advantages of aligners in open bite treatment is their ability to control the vertical dimension. Many orthodontists consider the plastic coverage over posterior teeth to have a bite-block effect, helping to prevent molar extrusion. However, recent studies have challenged the significance of this “bite block effect.” While some vertical control is achievable, the impact may be less pronounced than initially believed. Garnett et al. (2019) found no significant differences in the magnitude of open bite correction between clear aligners and fixed appliances in adult hyperdivergent patients. Both groups showed good vertical control.
Mechanisms of Open Bite Correction
Research has clarified the primary mechanisms of open bite correction with clear aligners. Programmed extrusion of anterior teeth is a crucial component, and retroclination of incisors can contribute significantly to overbite improvement. Some degree of posterior intrusion is often beneficial. The intrusion has become more predictable with the introduction of molar intrusion protocols (like Invisalign’s G4 in 2011). Harris et al. (2020) reported successful open bite closure primarily through mandibular autorotation, lower molar intrusion, and lower incisor extrusion. Recent studies by Finkleman et al. (2024) and Blundell et al. (2023) have shown that incisor extrusion and retroclination are the main contributors to bite closure rather than significant molar intrusion.
- Incisor Movements: Programmed extrusion of anterior teeth, coupled with retroclination, is the most predictable and effective method for closing open bites with aligners. Optimized extrusion attachments on incisors are crucial for achieving these movements.
- Molar Intrusion: Patients with planned molar intrusion show a trend towards more molar intrusion than patients with no molar intrusion incorporated into their Clincheck plan. While we can achieve some molar intrusion, it is limited. Therefore, we should incorporate overtreatment in molar vertical control. The amount of true molar intrusion achievable with aligners is less than we can accomplish with temporary anchorage devices (TADs) or orthognathic surgery.
- Mandibular Autorotation: Some studies have reported slight counterclockwise rotation of the mandible contributing to open bite closure. When we intrude posterior teeth, the mandibular plane angle can decrease with autorotation of the mandible. The combination of incisor extrusion, molar intrusion, and mandibular automation is an effective way to resolve anterior open bites.
Treatment Planning Considerations
Proper treatment planning and biomechanical understanding specific to aligner therapy are critical for predictable outcomes. Recent research suggests that ClinCheck software may overestimate the achievable amount of open bite correction. Blundell et al. (2023) found that only about 66.2% of programmed open bite closure was clinically expressed compared to the ClinCheck prediction. We must consider the importance of overcorrection in the digital plan to achieve the desired clinical outcomes. Recent studies have shown encouraging results, with Finkleman et al. (2024) reporting 100% success in achieving positive overbite in their sample, with an average overbite change of 2.5-3.2mm.
- Attachment Design: Properly designed and placed attachments are critical for achieving the desired tooth movements, especially for extrusion and support of the posterior intrusion. Clinicians should pay close attention to attachment placement and design in their ClinCheck plans.
- Interproximal Reduction (IPR): Strategic IPR can create space for the retraction of anterior teeth, which aids in bite closure. IPR should be carefully planned and executed throughout treatment.
Opportunities and Limitations
Clear aligner therapy offers several opportunities for open bite correction. It can provide a non-surgical alternative for some patients, offers superior esthetics and comfort compared to fixed appliances, and allows for versatile treatment planning. However, clinicians must also be aware of its limitations. Severe skeletal cases may still require surgical intervention or TADs, and success relies heavily on patient compliance. The limited amount of molar intrusion achievable may also impact treatment outcomes in some cases.
Conclusion
Clear aligner therapy offers a promising approach for open bite correction in carefully selected cases. The key to success lies in thorough diagnosis, strategic treatment planning, and leveraging the unique properties of aligners to control the vertical dimension while achieving desired tooth movements. However, clinicians should be aware of the limitations of molar intrusion and the need for potential overcorrection in digital treatment plans. As we refine our techniques and gather more long-term data, the predictability of open bite correction with aligners will likely improve further.
References:
1. Finkleman S, et al. Does planned molar intrusion with aligners assist with closure of anterior open bite? Am J Orthod Dentofacial Orthop. 2024.
2. Blundell HL, et al. Predictability of anterior open bite treatment with Invisalign. Am J Orthod Dentofacial Orthop. 2023;164:674-681.
3. Suh H, et al. Treatment of anterior open bites using non-extraction clear aligner therapy in adult patients. Korean J Orthod. 2022;52:210-219.
4. Harris K, et al. Evaluation of open bite closure using clear aligners: a retrospective study. Prog Orthod. 2020;21:23.
5. Garnett BS, et al. Cephalometric comparison of adult anterior open bite treatment using clear aligners and fixed appliances. Angle Orthod. 2019;89:3-9.
6. Moshiri S, et al. Cephalometric evaluation of adult anterior open bite non-extraction treatment with Invisalign. Dental Press J Orthod. 2017;22(5):30-38.
7. Guarneri MP, et al. Open bite treatment using clear aligners. Angle Orthod. 2013;83(5):913-919.
