Class III Malocclusion with Posterior Crossbite and Anterior Open Bite Treated with
Extraction, Expansion and Habit Control:
A Case Report and Review of the Literature.

Kourosh Mehrnia, AA* ; Sappho Tzannetou, DDS, MA**;
Sergio Ferreira, DDS***; Russel Toppi, DDS****; Stella Efstratiadis, DDS*****

ABSTRACT
A case report of a 13-year old Hispanic female with Class III malocclusion and 8.5 mm anterior crossbite, bimaxillary protrusion, and minimum crowding in the maxillary arch. Extraction of all four first premolars and a rapid maxillary expander with a habit breaker in the maxillary arch was employed for orthodontic open bite is presented. There was an associated bilateral posterior correction. (Col Dent Rev 2:15, 1997)

INTRODUCTION

In 1831, the type of malocclusion known today as open bite was described, probably for the first time in a scientific manner, by Carabelli in "Handbuch der Zahnheil-Kunde". Carabelli termed it "Mordex apertus", from its most prominent symptom.6,25 Angle, in "Malocclusion of the teeth" (1907), considered open bite as only a part of his first class of malocclusion. He stated that open bite is an infra-occlusion of the anterior teeth and also predicted that a large percentage of the cases treated will result in failure.6,25 Furthermore, Epker stated that open bite is not an ordinary or distinctive abnormality but rather a syndrome presenting a spectrum of characteristics making it difficult to subclassify.5

Open bite early malocclusion causes functional, esthetic and psychological problems to patients. The functional problems consist of impairment of deglutition, mastication and speech which can create unfavorable psychological child development. In the mixed dentition the prevalence of the open bite is approximately 17%.24 It may be caused by partial eruption of the incisors due to abnormal size of lymphoid tissue provoking alterations in the tongue's posture, persistency of infantile swallow and the occurrence of oral habits. According to the study done by Weiser25 in the Orthodontic Clinic of Columbia University, out of the 1028 cases of malocclusions that were examined, 52 (5%) were associated with an open bite. Among the 52 cases, 23 were classified as Class I (44%), 11 as Class II (21%), and 17 as Class III (32%). Similarly, Swinehart's19 study demonstrated that among the open bite malocclusions, 55% were classified as Class I while 40% were Class II and the rest were Class III (angle). Comparable results were reported by T.J. Cangialosi.2 Several studies revealed that the incidence of open bite decreases with age,7,23,24 stabilizing at about 2% in Caucasian and 16% in African-American teens.11

Anterior open bite can be dentoalveolar or skeletal in nature. Anterior open bite caused by aberrant habits, such as digit sucking and tongue thrust is usually dentoalveolar and therefore is more readily corrected by orthodontic treatment alone. This is particularly true when the patient is diagnosed at an early age and the associated habits can be eliminated.20 Many patients with open bite are mouth breathers and have a lowered nasal permeability. Dry rhinitis is also very frequent in these patients and sputtering consonants are very difficult for them to pronounce.6

Generally, vertical dentofacial dysplasias are the most difficult to correct and maintain. The tendency of anterior teeth to relapse towards their pretreatment vertical relationship following treatment is well recognized. This occurs with deep bite as well as open bite malocclusions.20

CASE REPORT

The case of a female patient with Class III malocclusion associated with bilateral posterior cross bite and anterior open bite is presented. Extraction of the four first premolars and orthodontic mechanotherapy with a rapid maxillary expansion appliance and habit breaker restored function and improved facial esthetics.
HISTORY AND GENERAL CLINICAL PICTURE
The patient presented to the orthodontic clinic as a healthy postmenarcheal female with the chief complaint, "I cannot close my mouth." The patient's chronological age was 13 years and 2 months. Her medical and dental histories were non-contributory. A thumb sucking habit and tongue interposition were present.

DIAGNOSIS
The patient had a Class III molar relationship on the left side and Class I on the right in the permanent dentition. She also had a bilateral posterior crossbite and 8.5 mm anterior open bite (Figure 1). Approximately 2 mm of crowding was present on the maxillary arch and 1 mm on the mandibular. The upper midline was deviated to the left side.

Figure 1: Pre-treatment intraoral photograph revealing
patient's marked open bite (8.5mm) and bilateral
posterior crossbite.

The panoramic radiograph demonstrated that all the teeth were present and all third molars were developing.

The cephalometric analysis demonstrated a Class I skeletal pattern. The incisors were proclined and the mandibular and palatal plane angles were higher than normal (mandibular plane angle was 37o, maxillary plane angle was 31.5o). Furthermore, the patient presented with long anterior facial height in relation to posterior facial height, and long lower facial height in relation to upper facial height.

The soft tissue profile was convex.

PLAN OF TREATMENT
Because of the bimaxillary protrusion, anterior open bite and lack of space in the maxillary arch, extraction of the four first premolars was necessary. The sequence of the orthodontic mechanotherapy was as follows:

1. Splitting of the mid palatal suture with a hyrax appliance
combined with a tongue crib to control the habit.
2. Extraction of four first bicuspids.
3. Leveling and alignment of dental arches.
4. Closure of extraction spaces and correction of the anterior
open bite.
5. Establishment of a stable, functional and esthetic occlusion.

TREATMENT PROGRESS
A Hyrax appliance with a tongue crib was inserted and two activations per day initiated (Figure 2). After three weeks of screw activation the posterior crossbites were corrected and the appliance was locked for five months. At this point the expander/tongue crib appliance was removed, and the maxillary and mandibular arches were banded and bonded. All four first bicuspids were extracted. Second molars were banded to increase anchorage and establish the best possible functional occlusion.

Figure 2: Patient with palatal expander (hyrax) combined
with crib to control the habit. The large midline diastema
comfirming a successful splitting of the palatal suture.

The canines were retracted with elastic power chain. When they were fully retracted, the incisors were retracted en masse with closing loop arch wires. During incisor retraction, anterior bite closure was observed.

The patient was very cooperative and all appliances were removed 31 months after initiation of treatment. On the day of debanding, a positioner was delivered to finish the treatment. The patient was instructed to wear the positioner actively four hours during the day and at night. Eight months later, maxillary and mandibular Hawley type retainers were delivered.

TREATMENT RESULTS
The photographs demonstrate the correction of the open bite and the establishment of a normal Class I occlusion (Figures 3&4). Cephalometric evaluation revealed successful retraction of the maxillary and mandibular incisors and improvement of the soft tissue profile.

Figure 3: Post-treatment intraoral frontal photograph.

Figure 4: Post-treatment facial photograph
demonstrating an extremely pleased patient.

FINAL EVALUATION
This patient who presented with a Class III (Angle) malocclusion associated with anterior open bite and bilateral posterior crossbite that was successfully treated with expansion, habit control and extraction therapy. The correction of the malocclusion was achieved with a notable improvement in the patient's self-esteem. The following conclusions may be drawn from the treatment of this patient:

1. The use of a habit breaker type appliance can be an important aid in correction of a severe open bite.
2. The extraction therapy may allow correction of the open bite through retraction and extrusion of the maxillary and mandibular incisors.

DISCUSSION

Anterior open bite is a vertical dysplasia which is caused by several factors. More specifically development of open bite malocclusion can be attributed to genetic and environmental factors.9,14 Heredity contributes to the development of vertical skeletal dysplasias. According to Cangialosi,2 there are great differences in the skeletal patterns of normal and open bite patients. The following are some of the differences:

1. Posterior face height is shorter and overall anterior face height is
longer in open bite subjects.
2. Lower face height is greater in relation to upper anterior face height in persons with open bite.
3. The mandibular plane angle and the gonial angle are larger in persons with open bite.

According to Moss and Salentijn,13 an open bite tendency can be detected at an age before becoming evident clinically. Their study shows that in open bite cases, the foramen ovale is placed lower on the logarithmic spiral than for any other group studied.

The open bite malocclusion that is associated with increased vertical measurements, commonly known as "long face syndrome" is difficult to treat with conventional orthodontic treatment alone. As a result, vertical skeletal dentoalveolar deformities of adults are best treated with orthognatic surgery associated with orthodontic therapy.1,4,21 According to Nahoum,15 patients whose ratio of upper facial height to lower facial height is below 0.65 are poor candidates for conventional orthodontic treatment and require surgical consideration. Surgery is generally done when growth is complete to decrease the chance of relapse.

The amount of eruption of the teeth can also be used to differentiate between the skeletal open bite and environmental (habitual) open bite. In skeletal open bite, the anterior teeth are likely to be normally erupted or in some cases overerupted. However, in habitual open bite they are undererupted due to the interference of the habit.2

Dentoalveolar or habitual open bite is caused by habits such as digit sucking, tongue thrust, mouth breathing or a combination of all these. These habits influence the growth and development of the dentoalveolar processes and contribute to their disharmonies. To see how they contribute to this problem, we will consider each one separately:

1. Digit sucking: Prolonged digit sucking can lead to interrupted vertical development of the alveolar process, lateral constriction of the maxilla due to the increase activity of the perioral muscle forces and a more inferior posturing of the tongue. This situation, in the majority of the cases results in posterior crossbite, high palate, extrusion of the posterior teeth and the anterior displacement of the maxilla. If this condition remains for too long, the alteration may persist, even after the habit has been eliminated. Generally, finger sucking is considered normal in the first four years of life. During this period, finger sucking plays an important role in the child's emotional development and therefore, one should not try to break the habit because there is a strong tendency that it will be dropped as the child matures.3 Development of teeth in the deciduous dentition or early mixed dentition due to a habit may be self corrected after thumb sucking ceases. Malocclusions of the late mixed or permanent dentition, caused by thumb sucking are not self corrected and orthodontic treatment is necessary for their correction.12 There seems to be a strong association between atypical swallowing, tongue thrust and persistent sucking habits.

2. Tongue habit: According to Tisdale,22 most open bite cases are associated, to some extent, with a tongue habit. In dentoalveolar open bite, the tongue habit is the primary factor in developing the open bite condition. If the open bite is skeletal a tongue habit acts as a secondary factor which helps to maintain or exacerbate the condition. Many clinicians, such as Ricketts,16 Subtelny,17,18 Neff and Kydd10 support the second opinion meaning that tongue thrust is a secondarily obligatory adjustment to accomplish the necessary seal which is needed for swallowing. Tongue thrust may start as a curious penetration of the tongue into a space caused by the loss of one or more deciduous anterior teeth. By the time the permanent teeth erupt, the thrust has become a habit. This action exerts an enormous amount of pressure on the newly erupting teeth and could prevent their contact leading to an open bite condition.

3. Mouth breathing: In mouth breathing, in order to produce an oral respiration, the mandible is postured inferiorly with the tongue protruded and resting against the oral floor. It is this postural alteration that induces dental and skeletal modifications similar to those caused by thumb sucking. Furthermore, this may cause excessive eruption of the posterior teeth, leading to an increase in the vertical dimension of the face and result in development of the anterior open bite.3
CONCLUSION

According to Hellman,8 orthodontists have success in treatment of open bite malocclusions only in 50% of the cases. Thus, thorough extraoral and intraoral examination of the patient and careful study of the records (casts, facial and dental photographs and cephalometric radiographs) are very important in leading the orthodontists to the correct diagnosis and appropriate treatment planning for each individual patient with a severe open bite malocclusion. It may be stated that improvement in many instances is all that can be expected and there are times when even any degree of improvement is problematic.

Fortunately, in this case the patient had a successful treatment of her malocclusion which restored her function, improved her facial esthetics and elevated her self-esteem.

REFERENCES

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