An open bite refers to the lack of occlusal contact between teeth and is considered a challenging malocclusion to manage, because relapse often occurs after treatment [1]. When there is no skeletal deformation, the face is normal, and the open bite is limited to the canine, it is known as a dental open bite. Conversely, when the alveolar process is structurally altered, this can result in a condition defined as skeletal open bite, characterized by dolichofacial features, a hyperdivergent maxilla, and a prolonged lower facial height [2]. The terms anterior open bite or posterior open bite are used depending on the region affected by the open bite.

The occurrence of an open bite is considered to be the result of a variety of factors, including vertical overgrowth of the mandible, temporomandibular joint (TMJ) osteoarthritis (OA), dental anatomy, and bad habits [3,4]. In certain cases, TMJ OA can lead to morphological changes in the condyles, which can reduce the ramus height and progressively shift the mandible posteriorly, resulting in an anterior open bite [5-7]. In cases of TMJ OA, it is not easy to determine whether the condylar resorption is active or not, and the possibility of recurrence makes it difficult to determine the appropriate timing and method of treatment [7].

The treatment of open bite has traditionally been orthognathic surgery or extrusion of the anterior teeth; however, nonsurgical treatment has recently become available through the intrusion of the posterior teeth using a skeletal anchorage system (SAS) [8-11]. The intrusion of the posterior teeth facilitates the upward and forward rotation of the mandible, leading to an improved class II facial profile characterized by mandibular retrusion. Hence, this approach is highly effective for addressing skeletal class II malocclusions. We present a case of open bite with TMJ OA that was effectively resolved through orthodontic treatment using SAS.

This study was conducted with the approval of the Institutional Review Board at Chosun University Dental Hospital (CUDHIRB-1901 011 R02), and the requirement for written consent was waived by the board.

1. Diagnosis

A 21-year-old man visited the hospital with a complaint of “being unable to chew using his upper and lower incisors.” Before treatment, the patient had a convex profile and difficulty closing his lips comfortably, and hyperactivity of the mentalis muscle was observed during lip closure (Fig. 1). Intraoral photographs showed upper anterior crowding and a shallow posterior overbite, with an anterior open bite of 15.0 mm and a class I molar relationship with occlusal contact only between the molars (Fig. 1).

Panoramic radiographs showed distally tilted second molars and present third molars (Fig. 1). Analysis of the lateral cephalometric radiograph showed a skeletal class II malocclusion with an sella-nasion–point A angle (SNA) of 81.6°, sella-nasion–point B angle (SNB) of 74.3°, and point A-nasion-point B angle (ANB) of 7.3°, which resulted from mandibular undergrowth or posterior rotation of the mandible (Table 1). The Frankfort-mandibular plane angle (FMA) was 45.3°, indicating a very steep slope (Fig. 1).

An erosive change in the left condyle of the TMJ was detected in cone-beam computed tomography (CBCT) analysis. Subsequently, the patient was referred to the Department of Oral Medicine. Upon clinical examination and CBCT evaluation, a mild erosive change was detected in the left condyle of the TMJ. Without other treatments for TMJ OA, a 6-month follow-up was recommended due to normal mouth opening, jaw mobility, and no pain (Fig. 2A, C). Based on these findings, the patient received a diagnosis of high-angle skeletal class II open bite accompanied by left TMJ OA.

2. Treatment Plan

In this case, orthognathic surgery including posterior nasal spine impaction and mandibular advancement was primarily considered for effective improvement of facial appearance and prevention of open-bite recurrence. To correct the labial inclination and lack of space in the anterior teeth, extraction of the first premolars was decided. A skeletal anchor was planned to flatten the mandibular occlusal plane, which already consists of two planes, and to intrude the maxillary posterior teeth. For stable occlusion after treatment, evaluation of the left TMJ OA was required before treatment.

3. Treatment Progress

Following the diagnosis of TMJ OA from the Department of Oral Medicine, the patient was followed up for 6 months. However, a subsequent CBCT scan revealed further irregularities in the left anterior condyle of the TMJ (Fig. 2B, D). Although additional follow-up was recommended, the patient indicated a strong willingness to accept the possibility of relapse after orthodontic treatment and expressed eagerness to initiate orthodontic therapy. Consequently, orthodontic treatment commenced without an extended observation period.

A 0.022-inch slot self-ligation bracket (Clippy-M; Tomy International) was attached, and an alignment was initiated using a 0.014-inch Nitinol wire. All first premolars were extracted to improve crowding. To intrude the posterior teeth, two mini-implants (LIM plate system; Jeil Medical) were implanted in the midpalatal region at the seventh month of treatment. Lingual sheaths were attached to the palatal surfaces of the first molars in the maxilla, and 0.0.0215×0.028-inch stainless-steel transverse arch lines were connected to expand the width of the posterior teeth. Brackets (DAMON^®; Ormco) with 0.022-inch slots were attached to the palatal side of the upper second molars. Subsequently, an elastic chain was connected to the upper first and second molars in the lever arm to provide intrusive force. After molar intrusion, the bite turbo was placed on the first and second molars of the maxilla to avoid subsequent extrusion of the mandibular molars. After 1 year of treatment, the mandibular extraction space were closed, and the maxillary posterior teeth were partially intruded, resulting in an improvement of the anterior open bite (Fig. 3).

After 1 year 4 months of treatment, the patient expressed satisfaction with the improvement in his facial features. He did not wish to undergo orthognathic surgery. According to the patient’s desires, it was decided to complete only orthodontic treatment, excluding orthognathic surgery, and posterior intrusion and space closure were continued. Although the space was closed after 24 months of treatment, the vertical overbite was shallow. In the finishing stage, the horizontal and vertical overbites were improved by using class 3 and vertical rubber bands. An appropriate occlusion was formed after 28 months of treatment, and orthodontic treatment was finished after the necessity of adjusting the tongue habit to prevent the recurrence of open bite was explained to the patient (Fig. 4).

4. Treatment Result

After treatment, the patient’s vertical overbite improved from −15.0 mm to 1.5 mm, and posterior contact was adequately restored. The protrusion of the lips was reduced, and the tension around the lips was relieved (Fig. 4). Pre- and posttreatment CBCT overlapping images confirmed that the mandible moved upward by 1.9 mm and anteriorly by 0.5 mm (Fig. 5G). Also, backward displacement of the condyles on both sides was observed; this was more severe in the left condyle, which had an irregular surface before treatment. It was confirmed that the chin point of the mandible moved 1.7 mm to the left (Fig. 5). The vertical overbite was slightly reduced after 1 year of posttreatment maintenance (Fig. 6).

A severe skeletal open bite is characterized by a hyperdivergent maxilla and a dolichofacial appearance, as in this patient. In such cases, orthognathic surgery, which involves lifting the posterior part of the maxilla to create space for the mandibular teeth to move anteriorly and upwardly, while rotating the occlusal plane and, in turn, rotating the mandible anteriorly and upwardly to deepen the open bite, can be an effective treatment [12]. However, addressing skeletal high-angle open bites with OA is challenging. Even with orthognathic surgery, posttreatment relapse is frequent, and the prognosis tends to be unfavorable [13].

An alternative method for managing open bites involves intrusion of the posterior teeth using SAS, which can include mini-implants implanted directly into the alveolar bone or palate. This approach can achieve outcomes similar to those of maxillary impaction through orthognathic surgery by counterclockwise rotation of the mandible, which effectively improves the anterior open bite and reduces the anterior facial height [13]. Several studies have reported successful orthodontic treatment using SAS alone to correct occlusion and enhance facial esthetics in patients with anterior open bites and class II malocclusions [10,14,15]. In our case, a patient with a severe anterior open bite initially scheduled for orthodontic treatment with orthognathic surgery achieved satisfactory results with posterior teeth intrusion alone, avoiding the need for surgical intervention. Evaluation of the treatment results demonstrated a significant improvement in the anterior open bite due to intrusion of the maxillary posterior teeth and anterior superior displacement of the mandible.

Research indicates that the recurrence rate of open bite after orthodontic treatment is approximately 10% to 30% [2]. Potential factors contributing to recurrence include tongue size and position, finger sucking, mouth breathing, resorption of the mandibular condyle, and additional mandibular growth, although identifying the exact cause can be challenging [2]. Patient education can address bad habits that may trigger a relapse, but factors such as mandibular condyle resorption and further mandibular growth require thorough evaluation and preventive measures. Special attention is needed for patients with TMJ OA, because changes in the condyle’s morphology can lead to occlusal alterations [13].

In patients with symptoms of temporomandibular disorders (TMDs) prior to orthodontic treatment, it is usually recommended that a diagnosis and evaluation of the TMJ be performed to ensure a stable occlusal relationship, efficient orthodontic treatment, and good maintenance after treatment. CBCT is commonly used in the evaluation of TMJ OA to assess the health and condition of the condyle, with a specific focus on the extent of cortical bone coverage [16]. However, the cortical bone may not be fully developed in growing individuals, particularly in males, whose growth continues into their early 20s [16,17]. Therefore, to mitigate the risk of recurrence, assessing TMDs and the growth of the mandibular condyle is crucial before initiating orthodontic treatment in patients with open bite [16,17]. The patient in this case was 21 years old during the initial examination and did not present any symptoms such as TMJ pain or discomfort. However, a CBCT scan revealed mild erosive changes in the left condyles. It was challenging to definitively determine whether these findings indicated incomplete cortical bone development during the later stages of growth or if they were indicative of mild TMJ OA. To gain more clarity, we decided to monitor the extent of cortical bone coverage on the condyle through a 6-month follow-up observation period. After this 6-month follow-up, it became evident that the irregularities in the patient’s condyle had progressed despite the absence of significant clinical symptoms at that time. We recommended continued follow-up, but the patient opted for immediate orthodontic treatment without an adequate follow-up period.

Although the relationship between occlusion and TMJ OA remains a topic of debate, there is general consensus that severe malocclusion can indeed have an impact on TMJ OA [18]. Indeed, in cases of TMJ OA with minimal symptoms, orthodontic treatment could be considered if it is deemed necessary. In this case, monitoring condylar changes is important for determining the appropriateness of orthodontic intervention. In cases in which OA is either already present or potentially a concern, enhancing the occlusal relationship through orthodontic treatment in a cautious and minimally invasive manner becomes paramount. This approach helps eliminate factors that could exacerbate or contribute to TMJ OA. Using SAS in orthodontic treatment offers the advantage of achieving a gradual modification of the occlusal relationship when compared with more invasive orthognathic surgery. Consequently, this method is considered highly suitable for addressing patients with open bite who have TMJ OA.

Although the treatment yielded positive results, there was a change in the condyle’s position after treatment, accompanied by some relapse during the 1-year observation period after orthodontic treatment (Fig. 5, 6). The recurrence is believed to have resulted from the patient’s initial low tongue position and habitual tongue thrusting caused by severe open bite, as well as the progress of TMJ OA. On CBCT at 6-month follow-up before orthodontic treatment was initiated, an increasing irregularity of the left condyle and change in the condylar position was observed. In the comparisons before and after treatment, more posterior migration of the left condyle, which required attention from the initial diagnosis, was observed (Fig. 5). Thankfully, there was no manifestation of TMJ OA. Therefore, to prevent such complications, it would be more desirable to proceed with orthodontic treatment after TMJ stabilization [19].

In conclusion, it is important to recognize that condylar changes resulting from TMJ OA can lead to an open bite. When orthodontic treatment is administered to patients with TMJ OA, predicting the outcome can be challenging because of the unstable condyle position and constantly changing bite. In this case, we successfully corrected the anterior open bite in the patient by using SAS to intrude the maxillary posterior teeth and by extracting the premolars to reposition the anterior teeth posteriorly. However, it is essential to be aware that if an adequate stabilization period is not observed, there is a potential risk of migration of the posterior condyle. Consequently, it is imperative to conduct a comprehensive evaluation before treatment and initiate diligent measures to prevent relapse after treatment.

No potential conflict of interest relevant to this article was reported.

The datasets used in this study are available from the corresponding author upon reasonable request.

This study was supported by research funds from Chosun University Dental Hospital, Korea, 2021.

Conceptulatiin: SHL. Data curation: SGK. Writing original draft: SRJ, SYL. Visualization: SYL, HJP. Writing review and editing: SRJ, HMK, HJP.