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Oral Maxillofac Surg (2014) 18:271–277 DOI 10.1007/s10006-013-0430-5 REVIEW ARTICLE Orthodontic treatment of anterior open bite: a review article—is surgery always necessary? Isabelle Reichert & Philipp Figel & Lindsay Winchester Received: 14 May 2013 / Accepted: 29 July 2013 / Published online: 16 August 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract Introduction Anterior open bite cases are very difficult to treat satisfactorily because of their multifactorial aetiology and their very high relapse rate. Dependent on the origin of the anterior open bite malocclusion and the patient’s age, there are several treatment possibilities ranging from deterrent appliances, high-pull headgear, fixed appliances with and without extractions to orthognathic surgery, and skeletal anchorage with miniplates or miniscrews. Methods The gold standard treatment of skeletal anterior open bite cases is the combined approach of orthodontic treatment with fixed appliances and orthognathic surgery. In recent years, temporary anchorage devices (TAD) have been developed to correct anterior open bites orthodontically. With the introduction of TAD as an effective treatment modality, orthognathic surgery may be avoidable in selected anterior open bite cases. Conclusion This is a relatively new technique and to date there remains a lack of evidence of long-term stability of anterior open bite closure with TAD. Keywords Anterior open bite . TAD . Orthognathic . Skeletal anchorage . Relapse I. Reichert (*) : L. Winchester Orthodontic Department, Queen Victoria Hospital NHS Foundation Trust, Holtye Road, East Grinstead, West Sussex RH19 3DZ, UK e-mail: [email protected] P. Figel School of Oral and Dental Sciences, Bristol Dental Hospital and School, University of Bristol, Lower Maudlin Street, Bristol BS1 2LY, UK Introduction The anterior open bite (AOB) malocclusion is one of the most challenging malocclusions to treat due to the high frequency of relapse [1–6]. It is defined as no vertical overlap of the incisors when buccal segment teeth are in occlusion. This paper aims to review and summarize the different orthodontic treatment modalities that can be used for the management of AOB as an alternative to surgery, together with the evidence for their effectiveness. The early 1960s to the mid-1970s are called the “era of tongue thrusts,” because the malocclusion was often thought to be caused by tongue thrust [6]. Before the 1970s, the orthodontic treatment mainly consisted of dentoalveolar changes and/or modification of habits [7]. AOB has a multifactorial aetiology including skeletal, dental, respiratory, neurologic, and habitual components [1, 8]. It can be broadly described as being skeletal or dental in origin [9]. A high-angle skeletal pattern with increased Frankfort Mandibular Plane Angle can lead to an AOB when the vertical component of growth disproportionally exceeds the horizontal component of growth. Labial tooth eruption cannot compensate for the increase in inter-occlusal distance with, in severe cases, only the posterior molars in occlusion. Patients with an AOB may have some or all of the following cephalometric features: pronounced ante-gonial notching, recessive chin, reduced inter-incisal angle, reduced inter-molar angle, and increased lower anterior facial height. It is believed that soft tissues also play a role in AOB. Incompetent lips might lead to a tongue thrust, to make an oral seal while swallowing, influencing the dentoalveolar position of the anterior segments by intruding them. Digit sucking often results in an AOB, by preventing vertical incisor eruption, with associated posterior cross bites caused by increased cheek pressure and lowered tongue position, resulting in narrowing of the arch. Prolonged mouth breathing due to increased tonsillar or adenoidal 272 obstruction may be a contributory factor which can cause increased vertical growth [8]. The indications for treatment are generally aesthetic and functional improvement. Patients with a severe AOB often have difficulties incising food as well as speech problems including lisps. Closure of an AOB usually helps with eating but there is only little evidence that it might help with speech [8, 9]. The literature shows a variety of treatment possibilities to close AOB, depending on respective diagnoses. High-pull Headgear, chin cups, various types of bite blocks, functional appliances, fixed appliances with or without extractions, and multi-loop edgewise archwires are some examples of the treatment modalities [10]. Difinitive treatment in cases of skeletal aetiology frequently involves a combined approach of orthodontic treatment with fixed appliances and orthognathic surgery. In the majority of cases, the surgery includes a Le Fort I osteotomy with posterior maxillary impaction or bimaxillary osteotomy [8, 9]. Orthognathic surgery for the management of AOB can be notoriously unstable. Several studies have compared different orthognathic treatment to close an AOB and their relapse rates. In 2000, Proffit et al. found that maxillary impaction was less prone to relapse (7 % overbite decrease) than two jaw surgery (12 % overbite decrease) [11]. Teittinen et al. also examined the relapse rate of patients with previous maxillary impaction only compared with patients with maxillary impaction and mandibular counterclockwise rotation to close AOB. All of the patients who had a maxillary impaction only showed a positive overbite 3.5 years after treatment but in three cases with bimaxillary surgery the open bite recurred. A vertical relapse of the maxilla was noticed in both groups (one and two jaw surgery); in the bimaxillary group, the changes were statistically significant [12]. It may also be possible to close an AOB surgically by counter clockwise rotation of the mandible. This has been considered by many as unpredictable due to the risk of lengthening the pterygomasserteric sling. Frey et al. noticed greater relapses when the counter clockwise rotation of the mandible was used as operation method [13]. Bisase et al. reported that the closure of AOB by mandibular counter clockwise rotation are at least as stable as AOB closed by maxillary impaction and recommended this method in class II cases with retrusive mandible and chin [5]. Van Sickels reviewed the literature on closure of AOB with counter clockwise movement of the mandible, presented three cases with variation of stability, and concluded that counter clockwise rotation of the mandible should be used with caution. He noted that larger and more rigid plates and screws can help to prevent the early stability but there is no doubt that skeletal AOB are prone to relapse independent of the applied surgical method [14]. In the last few years, as an alternative to treating a skeletal AOB by orthognathic surgery, skeletal anchorage devises Oral Maxillofac Surg (2014) 18:271–277 have been developed. Skeletal anchorage is being used for molar intrusion to correct an AOB [2–4, 15–21]. Deterrent appliances In young patients where the AOB is related to a digit sucking habit the open bite closes naturally after stopping the habit. Passive orthodontic appliances such as the Hayrake appliance (Fig. 1) can help in stopping thumb-sucking habit and allow spontaneous improvement. High-pull headgear The use of a high-pull headgear (Fig. 2) is a common approach for the management of AOB treatment, intruding upper molars that are considered to be extruded and therefore causing the AOB [6]. Some authors also reported some vertical control by minimizing the clockwise rotation or even resulting in a counterclockwise rotation of the mandible [22, 23]. It is often combined with functional and fixed appliances. Posterior bite blocks Posterior bite blocks are usually made of acrylic and fit between the maxillary and mandibular teeth. They can be spring loaded or provided with magnets and are usually used in the early treatment of AOB cases. By impeding eruption of the posterior teeth, this allows an upward and forward autorotation of the mandible [9, 24, 25]. Maxillary intrusion splints which cover the whole of the maxillary dentition are also used with high-pull headgear in cases where it is intended to intrude the whole of the maxillary dentition, such as gummy smile cases, which have a degree of vertical maxillary excess. Iscan et al. conducted a study in which they compared the effectiveness of passive posterior bite blocks of two different heights (5 and 10 mm), with an untreated control group of AOB cases. It was revealed that the downward and backward rotation of the mandible continued in the control group increasing lower face height significantly, whereas in the treated groups the mandible rotated upward and forward and produced a positive overbite [25]. Functional appliances Removable functional appliances combined with high-pull headgear can be used in growing patients where the AOB is associated with a class II malocclusion. This combination helps to correct the anteroposterior discrepancy while controlling the vertical dimension [9]. In our practice, we usually use a Clark Twinblock as the functional appliance of choice combined with high-pull headgear for the management of AOB with a skeletal II pattern. This removable functional appliance has two bite blocks, Oral Maxillofac Surg (2014) 18:271–277 273 Fig. 1 a An 11-year-old female patient with a digit sucking associated AOB. b Patient with fitted Hayrake appliance (deterrent appliance). c Occlusal changes 3 months after wearing Hayrake appliance upper and lower, which work together to posture the lower jaw forward. In Class II AOB cases where the Twinblock is used in combination with high-pull headgear the upper appliance has an expansion screw to widen the arch and always has tubes positioned occlusally between premolars and molars to fit the headgear (Fig. 3). Fig. 2 Patient wearing high-pull headgear The open bite-bionator is a removable appliance with posterior bite blocks to inhibit the extrusion of the posterior teeth. Fig. 3 a Patient with Clark Twinblock with flying tubes to insert a Headgear. b Patient wearing Clark Twinblock with high-pull headgear 274 Acrylic portion extends from the lower lingual part into the upper region as a lingual shield; the labial bow is positioned at the height of correct lip closure. Defraia et al. examined 20 patients with a high angle skeletal relationship treated with the bitebionator and compared the MPA to a nontreated control group. The treated group showed a significant smaller palatal planemandibular plane angle (−1.9°) and greater overbite (+1.5 mm). He concludes that early treatment with the open-bite bionator produces an improvement of intermaxillary divergences [26]. The Fränkel 4 has been advocated in cases where the open bite occurs partly from faulty postural activity of the orofacial musculature. It is a removable functional appliance which works by allowing vertical eruption of upper and lower incisors and retraction of the upper incisors. Some authors have established that the wear of the Frankel can change the mandibular rotation from downward and backward to upwards and forwards. A randomized clinical trial conducted by Erbay et al. evaluates the effects of Fränkel’s function regulator appliance on the treatment of Angle Class I skeletal AOB malocclusion, with results indicating that a spontaneous downward and backward growth direction of the mandible, that were observed in the control group, could be changed to a upward and forward direction by Fränkel 4 therapy [27]. Vertical chincup This appliance is occasionally used in growing patients to try to reduce excessive vertical growth by redirecting the condylar growth, but has fallen out of favour in recent years due to poor evidence of its efficacy. In 1978 Pearson treated twenty growing patients with backward rotational tendencies and AOB by extracting four first premolars, wearing a vertical pull chin cup for at least 12 hours a day while waiting for the remaining teeth to erupt. The AOB were all closed and the mandibular plane angles reduced an average 3.9° [28]. Torres et al. [29] investigated the dentoalveolar and soft tissue changes produced by a removable appliance associated with high-pull chin cup therapy in children with an Angle Class I AOB. They compared the outcome of patients treated with a control group and the results showed no significant differences in the level of molar eruption or in lower anterior face height, which suggests that the vertical control expected from the chin cup therapy did not occur [29]. Oral Maxillofac Surg (2014) 18:271–277 Fixed appliances with anterior box-elastics induce the extrusion of the anterior incisors, which is only helpful when the incisors are not already extruded by natural compensation [8] and is often unstable. The additional use of straight-pull Headgear to distalize the molars is contraindicated as it opens the bite, by inducing molar extrusion. Class II or III elastics should be used with caution because of the undesired side effect of molar extrusion [9]. Schudy elastics (elastics with an anterior vertical component) however have been reported as helpful in these cases as they allow an additional anterior extrusion component of force. The retroclination of proclined upper and lower incisors closes the AOB [30].The stability of AOB correction by orthodontic fixed appliances will depend on the adaptation of the soft tissues to the new dental arrangement of the teeth. Extractions of premolars and orthodontic space closure with fixed appliances are a possible treatment option of AOB correction. The mesial movement of the molar teeth can result in a reduction of the mandibular plane angle with a resultant closure in the AOB and the incisors can be retracted, resulting in uprighting and relative extrusion [30] (Fig. 4). A study by Lopez-Gavito et al. dealt with the stability of open bite cases treated with fixed appliances, headgear, and elastics. Cephalometric radiographs of 41 patients with at least 3 mm of open bite were evaluated at three different points in time, pretreatment, immediately post-treatment, and 10 years post-retention. They found that 35 % of the patients had an open bite of 3 mm or more, whereas 65 % showed relatively stable results [31]. Another study by Zuroff et al. increased the sample size (64 patients) and differentiated between three groups, based on the amount of pretreatment overbite. A contact group (incisal overlap and incisal contact), an overlap group (incisal overlap and no incisal contact), and the open bite group (no incisal overlap). At ten years post-retention, 60 % of the open bite subjects did not have incisor contact. On the other hand, in the whole sample, the largest vertical relapse was 2.4 mm, and no one had negative incisor overlap [10]. Fixed appliances AOB can also be closed by using upper and lower fixed appliances with vertical intermaxillary elastics to extrude the anterior incisors. In addition to the fixed appliance, a transpalatal arch and a high pull headgear to intrude the upper molars can be used. Fixed appliances alone should be used in cases where the open bite is of dental but not skeletal aetiology. Fig. 4 Patient wearing fixed appliances and Schudy elastics Oral Maxillofac Surg (2014) 18:271–277 Multi-loop Edgewise Archwire technique Kim et al. described the use of the Multi-loop Edgewise Archwire technique for AOB closure treatment [6]. They used a 16×22 stainless steel edgewise ideal archwire in an edgewise bracket system, with no prescription for torque, angulation or tip. Vertical and horizontal control and decreasing the load and deflection rate were achieved through bending loops into the archwires. The loops are L-shaped and are positioned between every interbracket distance distal to the lateral incisors (five loops in each quadrant). This appliance works by uprighting the molars and extruding the anterior teeth subsequent to the alteration of the occlusal plane. Heavy intermaxillary elastics are used to close the AOB by extruding the anterior segments. The disadvantage of this technique is that the majority of correction was realized by the extrusion of the anterior teeth, not by the intrusion of molars. The extrusion of anterior teeth is prone to relapse [16]. Temporary anchorage devices In recent years, titanium miniplates and miniscrews have been used as skeletal anchors to correct AOB orthodontically (Fig. 5). The use of skeletal anchorage offers more treatment options for orthodontists and this has a particular application in the correction of AOB [32]. Some workers claim that the use of skeletal anchors can obviate the need for orthognathic surgery in the management of AOB cases. The studies of Umemori et al. [33] demonstrated the effective intrusion of mandibular molars by using titanium miniplates for anchorage. In two severe AOB cases, two titanium L-shaped miniplates were fixed on each side at the buccal cortical bone around the apical regions of the lower first and second molars. By using elastic threads as orthodontic force, the lower molars were intruded and open bite was significantly improved. One month after the fixation of the plates force application was started. Upper and lower teeth were bonded with a straight wire fixed appliance. Intrusion was completed after 5 months, and after 18 months, the fixed appliance and the Fig. 5 TAD in place (between LL6 and LL7) to intrude molars 275 miniplates were removed. Class I occlusion was achieved with a normal overbite and overjet and the mandibular plane angle declined from 41° to 39.5°and 41.9° to 37.7°, respectively, mainly due to a decreased posterior vertical dimension. The lower molars were intruded 3.5 and 5 mm, respectively, and the occlusal plane was counterclockwise rotated by 4°, 2°, and 3, 1°, respectively. The author concludes that implants as anchorage to simplify the orthodontic treatment can be successfully used to intrude the molars in AOB cases. Nevertheless, there is no evidence in long-term follow-up controlled randomized studies that confirm these theses. Erverdi et al. [20] proposed the zygomatic buttress area as an anchorage site for maxillary molar intrusion and reported the closure of AOB. In his case report from 2006, an L-shaped implant was fixed with three bone screws in the zygomatic buttress area with the tip exposed and used for intrusive force application. The orthodontic appliance consisted of two acrylic bite blocks connected with two palatal arches and wire attachments on each buccal side, which were used for force application. The force application commenced 7 days after implant insertion. Two 9.0-mm NiTi coil springs were placed bilaterally between the tip of the implant and the outer wire creating an intrusive force of 400 g. The molars were impacted 3.6 mm and the mandibular plane showed 4.0° of counterclockwise outer rotation. After the gained intrusion, upper and lower fixed appliances for alignment of the upper and lower arches were fitted and the intrusion was maintained with wire ligation between the implants and the molar tubes throughout the treatment. The intrusion of 3.6 mm was maintained after the treatment with fixed appliances, whereas the counterclockwise rotation relapsed during later stages of the treatment. This was caused mainly by the progressive extrusion of the lower molar teeth. A slight posterior open bite Caused by the acrylic bite blocks was observed when the intrusion appliance was first removed. The upper molar were fixed to the zygomatic implant and not free to extrude and therefore the open bite was closed by the extrusion of the lower molars (occlusal plane angle 14.0° to 21.0°).This paper shows within the limitation of a single case report, that zygomatic anchorage can be successfully used for molar intrusion. Further studies with larger samples and assessment of long-term stability are required. Sherwood et al. [2] intruded maxillary molars with miniplate anchorage described by three case reports. The patients were treated with orthodontic fixed appliances and Tshaped miniplates which were surgically placed between the first and second molars and fixed with two 5-mm miniscrews each. Loading began 8 weeks after surgery. Intrusion mechanics were continued for 5.5 months until the AOB were closed. These case reports lack longer-term follow up. In skeletal AOB cases, in which the aim is to close an AOB by intruding the posterior teeth, miniplates and miniscrews are being used and undesirable side effects of extrusion of anterior teeth avoided. 276 Several case reports have shown that, at least in the short term, in the maxilla or the mandible implanted miniplates aid intrusion of upper and lower molars up to 3–5 mm while also achieving counterclockwise rotation of the mandible [2, 33, 34]. This treatment enables the orthodontist to close AOB without extruding the front teeth, which are prone to relapse and root resorption [16]. Miniplates are more versatile than screws because they can be placed where anchorage is needed the most. They have the virtue of three-dimensional stability because they are held in place by 3 or more screws. Placing them well away from tooth roots avoids root injury or avoids interference with root movement [2]. Before starting active tooth movement a latency of one week after insertion is required. The miniplates are usually removed a week before debond [8, 16]. Sugawara et al. examined the amount of relapse after SAS (sketelal anchorage system) in 9 adult open bite patients who had been successfully treated. They all had a fixed appliance combined with SAS to intrude the first and second mandibular molars bilaterally. Three lateral cephalometric radiographs per patient have been taken; before the SAS placement (T1), at debond of fixed appliances (T2) and at 1 year post-debond (T3) to calculate the amount of intrusion. The average amount of intrusion was 1.7 mm at the first and 2.8 mm at the second molar respectively. The average amount of relapse was 0.5 mm at first and 0.9 mm at second molar respectively. There was no statistically significant difference between the changes at T1-T2 and T1-T3. Sugawara et al. concluded that the average relapse rates were 27.2 % at the first molars and 30.3 % at the second molars. Therefore he suggests an overcorrection of intrusion [16]. Baek et al. examined the long-term stability of AOB correction by intrusion of the maxillary posterior teeth with miniscrew implants. 9 Patients with diagnosed AOB were treated with fixed appliances combined with molar intrusion by miniscrew implants. Lateral cephalometric radiographs were taken before and after treatment, 1 and 3 years posttreatment. The maxillary first molar was on average intruded by 2.39 mm and showed a relapse rate of 23 % at the 3-year follow-up. The authors noticed that 80 % of the relapse occurred during the first year of retention. An incisor overbite relapse rate of 17 % with no significant recurrence between the 1- and 3-year follow-up were noticed. Baek et al. concluded that most relapse occurs during the first year of retention [35]. Miniplates do however have a number of disadvantages. There are limited areas for their insertion, they are expensive and require two surgical procedures for insertion and removal [36]. Miniscrews on the other hand are used routinely in orthodontics as skeletal anchorage for tooth movement, are cheap and easy to use and can often be placed under local anaesthetic. Some recently published case reports have shown that teeth can be successfully intruded with miniscrews as Oral Maxillofac Surg (2014) 18:271–277 skeletal anchorage [15, 19, 36]. Miniscrews inserted into the maxillary posterior buccal bone can be useful for posterior intrusion and therefore used for AOB closure. Additionally, the use of miniscrews for intrusion during active growth favours counterclockwise rotation of the mandible improving the vertical and anteroposterior discrepancy [19]. Conclusions The Orthodontist has a number of treatment modalities available for the management of mild to moderate AOB cases. With the introduction of TAD as an effective treatment modality, orthognathic surgery may be avoidable in selected AOB cases. This is a relatively new technique and to date there remains a lack of evidence of long-term stability of AOB closure with TAD. Several case reports have illustrated the successful use of TAD in nongrowing skeletal open bite cases that may previously have been treated with orthognathic surgery. The treatment of AOB with skeletal anchorage devices have several advantages compared with single or bimaxillary jaw surgery providing lower cost, less invasiveness, and less complicated low morbidity treatment. Further studies in skeletal anchorage devices need to be conducted to ascertain the long-term stability and effectiveness of this method as a treatment in the management of AOB cases. Conflict of interest The authors declare that they have no conflict of interest. References 1. Greenlee GM et al (2011) Stability of treatment for anterior open-bite malocclusion: a meta-analysis. Am J Orthod Dentofac Orthop 139(2):154–69 2. Sherwood K (2007) Correction of skeletal open bite with implant anchored molar/bicuspid intrusion. Oral Maxillofac Surg Clin North Am 19(3):339–50, vi 3. 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