Discussion
The patho-etiology of unerupted third molars remains unresolved and
controversial. In a recent study [14] it was found that over half
(52%) of adults above 18 years had at least one impacted third molar
regardless of the skeletal/dental antero-posterior relationship. Some
have suggested that as modern humans evolved the jaws became diminutive,
leading to end-molar impaction. However, evolutionary history suggests
that the teeth became larger in size through an increased number of
cusps [15] with thicker enamel [16]. Recently, Olsson et al.
[17] reported that although the MSX1 gene is expressed differently
for impacted maxillary third molars, in general, other changes in gene
expression are not found, suggesting an epigenetic mechanism for third
molar impaction. Similarly, Isomura et al. [18] concluded that while
third molar eruption was more similar in monozygotic twins compared to
dizygotic twins, the identification of genetic trends, such as those
encoding for reduced stature, influence third molar treatment options.
In fact, Adeyemo et al. [19] found that subjects with lower third
molar impactions were often shorter in height. In a similar study
[20], insufficient bony dimensions for the eruption of the third
molars were found in teenagers with Class II malocclusions. Because of
these concepts, some believe that extraction of other teeth can result
in favorable treatment outcomes for third molars [21]. In our
present study, Case #6640 appears to support this approach. After the
extraction of four, healthy, first premolars, biomimetic oral appliance
therapy appears to have aided in the eruption of the third molars in an
adult aged 22yrs at the beginning of treatment. Indeed, although the
early extraction of healthy teeth is debatable given the uncertainty of
the developing third molars erupting, it is essential to assess the
third molars’ eruptive potential and provide sufficient functional
space. Park et al. [22] reported spontaneous eruption of a third
molar after extraction of an ankylosed mandibular first molar. In that
case, orthodontic intrusion of the maxillary first molar and
mesialization of the root of the second molar was completed before third
molar root formation.
While a deficiency of retromolar space is a known risk factor for
end-molar impaction, Marchiori et al. [23] investigated delayed
third molar development as a factor leading to impacted wisdom teeth.
They found that a lack of jaw space distal to the second molars was
related to less well-developed third molars, and a severe deficiency of
space was associated with an absence of third molar tooth germ
development in early childhood. In our study, for case #3044 (a
9-year-old male), panoral radiography revealed the absence of developing
#1 and #16 tooth germs (Fig. 9). By the end of treatment, however,
while tooth #16 was found to be congenitally absent, the other three
third molars erupted into occlusion (Fig. 12). This somewhat surprising
outcome might be associated with the use of biomimetic oral appliance
therapy, which putatively increases midfacial bone volume [13].
Tamer et al. [24] consider eruptive issues associated with third
molars ought to be diagnosed and treated early, using orthodontic
repositioning, surgical uprighting or extractions (with or without
transplantation). In this way, induced third molar eruption was reported
by Jung et al. [25]. However, in that case they utilized a
mini-screw placed in the maxilla with cross-arch elastics to induce
eruption prior to exodontia, which contrasts with the biomimetic
approach described in this case, since the third molars erupted
naturally and did not require extraction. Therefore, treatment timing is
an essential factor in the management of third molars.
There is a dearth of literature on the use of devices to recapture
retromolar space to aid in the eruption of third molars. One study
[25] compared mandibular third molar eruption in teenagers with
Class II malocclusions using a Forsus device. They found that the device
led to mesialization of the lower arch, which increased the retromolar
space but there was only little uprighting of the third molars. In
contrast, using biomimetic oral appliance therapy, both Case #5535 and
Case #8476 showed eruption of the third molars in all four quadrants
(Fig. 4 and Fig. 7, respectively). Indeed, both of these cases initially
presented to the dental office with craniofacial pain. Mksoud et al
[26] investigated the correlation of orofacial pain, jaw muscle
pain, headache/migraine to third molar eruption status. They reported
that although impacted third molars are not associated with masticatory
muscle pain or migraines headaches, they can be a cause of chronic
orofacial pain. In our study, Case #5535 was concerned with TMJ
issues and Case #8476 had gross caries masking and/or masquerading as
third molar odontalgia. Both of these cases showed resolution of
craniofacial pain and spontaneous eruption of the third molars (Fig. 4
and Fig. 7, respectively). Indeed, De Bruyn et al. [28] include
adequate eruptive space as one reason for retaining third molar teeth
since approx. one third (32%) can erupt into proper occlusion.
Therefore, this case series describes the use of a novel, biomimetic
midfacial development protocol to illustrate how successful patterns of
third molar eruption might be achieved. Further studies are now
indicated to test the robustness of these initial findings.