“Does impacted mandibular third molar’s angulation affect the lingual bone thickness?”

Selvi F., Tolstunov L., Brickeen M., Kamanin V.

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

  • Publication Type: Conference Paper / Summary Text
  • Volume: 72
  • Doi Number: 10.1016/j.joms.2014.06.053
  • City: Hawaii
  • Country: United States Of America
  • Page Numbers: pp.30-31
  • Istanbul University Affiliated: No


 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


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.