Research Information System
Journal of Oral and Maxillofacial Surgery; 2014: Vol. 72 Issue 9, e30-e31. / 96th Annual Meeting of American Association of Oral and Maxillofacial Surgeons, Hawaii, United States Of America, 8 - 13 October 2014, vol.72, no.9, pp.30-31
Purpose: Lingual nerve (LN) injuries are often associated
with the removal of impacted mandibular thirdmolars
(M3s), and the only barrier in between the two, is the
lingual bone. As such, the lingual bone thickness (LBT)
might be an important risk factor for this kind of injuries.
This study, therefore,was designed to answer the following
clinical question: ‘‘Does the impacted M3’s angulation
affect the lingual bone thickness at the impaction site?’’
Methods: The investigators implemented a retrospective,
radiographic study of the cone-beam computed
tomography (CBCT) scans taken prior to theM3s’ removal.
Using the appropriate coronal CBCT slices, LBT was
measured at three levels: mandibular second molar’s
cement-enamel junction (M2-CEJ), M3’s mid-root level
(M3-MR), and the M3’s same root’s apex level (M3-RA). If
the LBT was <1mm, it was defined as ‘‘thinning’’. Deficiencies
of the lingual bone (fenestration, dehiscence)
exposing lingual soft tissue (and LN) were also noted. These measurements were correlated with the M3
angulation.
The predictor variables were categorized as demographic,
anatomic, and radiographic.The primaryoutcome
variable was the lingual bone thickness in proximity to the
M3. Appropriate descriptive and bivariate statistics were
computed. P-values <0.05 were statistically significant.
Results: The study sample included 200 M3s (149 subjects;
mean age 40.36 15.13). There were 79 males
(53%); 102 M3s were on the left side (51%). 125 M3s had
< 85 degrees of angulation with the occlusal plane
(62.5%). For the LBT at M2-CEJ level, the mean thickness
was 1.40mm (SD=0.87) and the maximum thickness was
4.35mm. For the LBT at M3-MR level, the mean thickness
was 1.07mm (SD=1.03) and the maximum thickness was
5.51mm, and for the LBT at M3-RA level, the mean thickness
was 1.07mm (SD=1.30) and the maximum thickness
was 7.03mm. M3 angulations < 85 degrees (horizontal and
mesioangular) showed statistical difference compared to
the M3 angulations $ 85 degrees (vertical and distoangular)
in LBT at the mid-root level (X2 (1) = 18,41; P < 0,001
(OR 3,6; CI 95%)).
Conclusion: Horizontal and mesioangular mandibular
M3 impactions are 3,6 times more likely to have ‘‘thinning’’
in LBT compared to vertical and distoangular
mandibular M3s at the level of mid-root of M3. Since
LBT thickness of horizontal and mesioangular M3 impactions
are thinner at the mid-root level, an additional care
should be given to protect the LN at these sites in the
management of M3s. These findings may be of prognostic
value and aid in guiding treatment recommendations in
M3 management to prevent LN injury.