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ISSN (Print) 1013-9052
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Treatment of a pseudo Class III relationship in the mixed dentition: A case report
Sahar F. AlBarakati,
BDS, MSc
This
article describes a case report in which a Class III patient was successfully
treated with an inverted labial bow appliance.
The appliance is easy to make, efficient and well tolerated by the
patient. Early treatment of Class III conditions is recommended. The importance of differentiating between
true Class III and pseudo Class III malocclusions is emphasized.
In pseudo Class III malocclusion, Moyers11 suggested
that it is a positional mal-relationship with an acquired neuromuscular reflex
pattern of mandibular closure. Pseudo
Class III malocclusion is usually characterized by Class I or mild Class III
skeletal relationship, retroclined maxillary incisors with upright positioned
lower incisors on the basal bone, incisors in an edge to edge relationship in
centric relation (CR), and an anterior cross bite in centric occlusion (CO).1,8
Graber et al.12 attributed the incisor
interference to the retroclined upper incisors and proclined lower incisors.
During habitual closure to achieve maximum intercuspation, the lingually
inclined maxillary incisors glide down the lingual surfaces of the mandibular
incisors,1 so as to disengage the incisors and bring the posterior
teeth into full occlusion. This results in a forward displacement of mandible
and an anterior crossbite.
A male patient aged 9 years and 6 months, presented with a chief
complaint of the lower anterior teeth overlapping the upper teeth.
The clinical examination revealed a convex profile with a symmetrical face. Class III molar and canine in centric occlusion with the incisors in anterior crossbite, deep bite and fair oral health (Fig. 1). In centric relation (CR), the incisors were in an end-to-end relationship resulting in no overbite and a posterior open bite. The upper right central incisor was unerupted due to the presence of two supernumerary teeth. Tooth size discrepancies demonstrated crowding of -8mm in the upper arch and -2mm in the lower arch. The panoramic radiograph (Fig. 2) demonstrated normal bone and tooth development except for the upper right central incisor (due to the two supernumerary teeth present). Although a functional forward displacement was present from CR to CO, no sign of temporomandibular joint dysfunction was detected. The hand and wrist radiograph indicated that the patient was in a stage before the period of maximum growth spurt (SMI= 1) and the rate of growth was smallest. The lateral cephalometric radiograph analysis (Fig. 2) is shown in Table 1 and illustrates a mild skeletal Class III relationship and retained maxilla with a normal position of the mandible relative to anterior cranial base. There was a tendency of a horizontal growth pattern with skeletal deep bite, an increase in posterior cranial base, and maxillary and mandibular length. The dental relationship suggested severe retrusion of upper central incisors, with mild retraction of lower incisors. The soft tissue relation showed retruded upper and lower lips with an obtuse nasio-labial angle. Diagnosis was a pseudo Class III with functional anterior crossbite and with an impacted upper right central incisor due to the presence of two unerupted supernumerary teeth.
Treatment Objectives
Treatment Plan
Treatment Progress The plan was divided into two stages; the first was directed towards correction of the functional crossbite to enhance facial growth and avoid accentuating the Class III discrepancy, in addition to facilitating the eruption of the right upper central incisor. After eruption of the permanent teeth, the second stage of treatment would be initiated with fixed orthodontic appliances for occlusal adjustment and resolving the crowding problem.
The patient was referred to the maxillofacial surgeon to remove
the supernumerary teeth. The orthodontic
treatment was conducted by the use of a removable appliance with an inverted
labial bow appliance. 3 (Fig. 3)
An upper impression was
taken with an edge to edge construction bite. The removable appliance was made
of an inverted labial bow and acrylic on the lower incisors, Adams clasps on
molars for retention, Z-spring against upper incisors to move them labially,
and a posterior bite plane to elevate the bite. The inverted labial bow and
Z-spring were activated and the appliance was placed inside the mouth. The
patient was asked to wear the appliance full time except during eating. Oral
hygiene instructions were given, and the appliance was checked and activated
every four weeks.
After three months, the crossbite was completely corrected with
a satisfactory posterior interdigitation. The patient was instructed to wear
the appliance as a night time retainer for three months. Patient was kept under
observation and checked every three months, until completion of permanent teeth
eruption occurred, which took about two years. The sequence of planned
treatment was to start fixed appliances after the eruption of the permanent
teeth, but patient declined due to his satisfaction of the result of the first
stage of treatment. He was referred to extract the wisdom teeth.
The facial and intraoral photographs (Fig. 4) showed an improved
facial profile. The crossbite was corrected with good posterior
interdigitation. All CR - CO shifts were
eliminated and centric occlusion and centric relation were coincident. A
positive overjet was established and deep bite was reduced. Class I canine
occlusion was achieved. The maxillary incisors were proclined producing a
better upper lip prominence. The upper right central incisor had not yet
erupted as at this phase of treatment.
The post-treatment cephalometric radiograph (Fig. 5) illustrated changes in skeletal relation toward Class I skeletal relationship, with slight protrusion of the maxilla and retrusion of the mandible by 1o. There was an increase in ramus height which was reflected on the maxillary-mandibular plane angle. The upper incisors were proclined and the mandibualr incisors were upright over basal bone (Table 1). Two years post treatment photographs (Fig. 6), the radiographs (Fig. 7) revealed the eruption of permanent dentition including the right upper central incisor and a stable occlusion. There was mild anterior crowding in both upper and lower arches. The skeletal relationship was improved to normal range. An increase in the nasiolabial angle and a protrusion of upper and lower incisors were accomplished.
Many authors have recommended early treatment of Class III
malocclusion which exhibited dental and skeletal components that tend to become
worse with age. They believe that early intervention is an advantage in the
early mixed dentition, as well as in the deciduous dentition. Advantages
include correcting anterior crossbite to allow normal dental base development
and subsequent favorable skeletal growth, preventing habits such as bruxism,
eliminating traumatic occlusion, and reducing the length of treatment time with
fixed appliance.17 The optimum period for treatment suggested is between the ages of 6-9 years.5,12,18
Several clinicians however still avoid early correction of the pseudo Class III in the deciduous dentition because of poor stability and unfavorable experiences with behavior of young patients.16 Some practitioners prefer to wait for permanent maxillary incisors to erupt before starting treatment due to the natural tendency of the teeth to erupt in a lingual position during dental arch development.19 The various therapies suggested for the correction of an anterior crossbite and which may correct skeletal problems in young patients include face mask therapy,20 chincaps5 and functional appliances.21 Other alternative treatments include fixed13 and / or removable applainces4, which are effective methods of treating a Class III incisor malrelation. Before any treatment, it must be first established that the malocclusion is treatable. As a general rule, if the patient cannot make contact of the upper and lower incisors on closure, there is no possibility of successful appliance treatment and surgical correction may be considered. The inverted labial bow appliance was used in this case and it proved to be a highly effective interceptive treatment for Class III cases, which are not severe enough to require orthognathic surgery (ANB angle is more than -20). When the mandible closes, the appliance exerts a lingually directed force against the lower anteriors, with the Z-spring against the upper anteriors, thus producing a reciprocal movement. Clinical experience shows the appliance is comfortable and easily adapted and accepted by the young patient. The disadvantage is that the success of treatment will depend on patient cooperation. In the described case, reduced SNA and normal SNB angles were present. This finding is similar to that of Guyer et al.10 who reported that the maxilla was retruded in 25% of the cases. This patient presented with an increased maxillary and mandibular length, which indicated a tendency to a skeletal Class III that could be worsened if not treated early. Upper incisors were protruded and lower incisors were upright, which with other clinical features, distinguish pseudo Class III type of malocclusion. The post-treatment records indicated that the forces were transferred to the mandible and maxilla producing forward movement of the maxilla (SNA = 770), and backward movement of mandible (SNA = 760) (upper incisor - maxillary plane = 1140). Two years post-treatment revealed improvement in skeletal relationships due to growth improvement of the maxilla, that occurred after correction of the Class III malocclusion (ANB = 30, SNA = 800, and SNB = 770). For retention, the appliance is preferable to be used, although the developmental changes that occur in the incisor region (normal overbite) maintain the stability of the results.
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