Case Description and Diagnosis
A 14-year-old patient was referred to assess the potential for
comprehensive orthodontic treatment. It was noted that the patient was
in the late mixed dentition with an atypical Class II indefinite
malocclusion. The overjet was determined to be 2mm and the maxillary
incisors covered approximately 25% of the mandibular incisors in the
vertical plane. Although the maxillary and mandibular midlines were
coincident with each other, both dental midlines were located 2mm to the
right side of the facial midline. The right-side molar relationship was
Class III, however, the right-side canine relationship was half-unit
Class II. The crown of the mandibular right first permanent molar (46)
was also deemed to have a significant mesial tip. The mandibular right
second primary molar (85) was not clinically visible, and there was no
record of this tooth being extracted. Due to the presence of the
mandibular left second primary molar (75), the left-side molar
relationship had a mild Class II tendency and the left-side canine
relationship was Class I. A posterior lingual crossbite was present on
the left-side and no associated functional shift from the retruded
contact position to the position of maximum intercuspation was evident
(Figure 1).
A panoramic radiograph (Figure 2a) revealed ankylosis and severe
submergence of the 85 along with displacement and impaction of the
developing 45. It appeared that the ankylosis and submergence of the 85
had disrupted the alveolar development in this region, which in turn
resulted in the localised distortion of the posterior teeth in the
fourth quadrant. Despite the highly unusual radiographic appearance in
this area, no current or previous pain or discomfort was reported by the
patient. It was also noted that the mandibular left second premolar (35)
was congenitally missing and the mandibular left second primary molar
(75) was over-retained with significant remaining root structure. The 75
showed no evidence of infraocclusion and was clinically sound and
non-mobile. All third molars were present in the crown stage of
development.
A lateral cephalograph and subsequent cephalometric analysis revealed
that the patient had a horizontal skeletal Class I relationship, a
brachyfacial vertical facial morphology and normal angulation of the
maxillary and mandibular incisors. Soft tissue analysis determined that
the facial features were symmetrical, along with a pleasing facial
profile and competent lip function (Figure 2b).
The relevant diagnostic findings are summarized in Table 1 and as a
prioritized problem list in Table 2. Due to the severe submergence of
the 85 and impaction of the 45, the patient was referred to an oral and
maxillofacial surgeon for assessment of this area and to plan the
required surgical management. Several potential treatment options were
considered (Table 3). Each of these treatment options have been
summarised and compared along with their specific advantages and
disadvantages (Table 4).
Following extensive communication between the orthodontist, general
dentist and the oral and maxillofacial surgeon, it was determined that
the most predictable treatment option involved removal of the submerged
85 and the impacted 45. The oral and maxillofacial surgeon indicated
that removal of the ankylosed 85 would necessitate significant bone
removal and the impacted 45 would be likely to be damaged during in this
process. In addition, surgical exposure and subsequent orthodontic
traction with a gold chain to disimpact the 45 was expected to be both
prolonged and challenging. As the 35 was also congenitally missing, a
decision was also required regarding the over-retained 75. Given that
the mandibular third molars were developing and that over-retained
primary teeth generally have reduced longevity compared to healthy
permanent teeth, removal of the 75, uprighting of the 46 and complete
orthodontic space closure through bilateral mandibular molar
mesialisation was recommended. This treatment option would require the
use of temporary anchorage devices (TADs) to ensure maximum
predictability of these challenging orthodontic tooth movements.
Complete orthodontic space closure in the mandibular arch through
bilateral mandibular molar mesialisation would be associated with the
numerous potential benefits for the patient. Firstly, this option would
eliminate the need for future prosthodontic replacement for the
congenitally missing 35 and the irretrievable 45. The process of
orthodontic tooth movement has been shown to be osteo-inductive and has
the ability to regenerate atrophic alveolar bone resulting from
congenital absence of teeth and/or iatrogenic issues. Effective
mandibular molar mesialisation would also protect the harmonious
pre-treatment incisor angulation and lip positions whilst also creating
significant space for spontaneous future eruption of the developing
third molar teeth into functional positions.