Abstract
Aims: To determine the real not radio graphical proximity of mandibular third molar tooth to the inferior dental canal (IDC) using panoramic radiograph. Materials and Methods: 144 mandibular third molars were evaluated by panoramic radiography. The teeth were grouped into erupted vs. un erupted further subdivided by tooth angulations. The real distance from the most inferior aspect of the mandibular third molar tooth to the superior border of the inferior alveolar canal (IAC) was calculated regarding to the reference object used. Descriptive statistics were performed as well as a t test was performed to compare erupted and unerupted teeth, and ANOVA was used to determine a significant difference where exists based upon tooth angulations. In addition, intra observer analysis was done to ensure the standardization of the radiologist interpretation. Results: The mean distance from erupted mandibular third molar teeth to the inferior alveolar canal was 0.23mm. This distance was significantly different from unerupted teeth (P = .000). The mean values for unerupted teeth were negative values which indicated that the apices of all teeth measured was below the superior border of the canal –1.26 mm and as follows: Mesioangular–1.32 mm, vertical – 1.34 mm and –1.04mm for horizontal impactions. Statistically there was no significant positional difference between the impaction groups (P = .835). In general there was a significant difference in third molar position between those age equal and less than 22 years old and those equal and over 23 years old. Conclusions: Unerupted mandibular third molar teeth (mostly vertical impaction) are closer to the inferior alveolar canal than erupted teeth and persons in general of an age equal or less than 23 years old have a closer lower third molar to mandibular canal than other ages and there is no significant relation between this age group and any of impaction types.
Highlights
The removal of impacted mandibular third molars teeth means teeth that fail to erupt into its functional position,(1) is oneAl – Rafidain Dent J Vol 16, No1, 2016 of the most common surgical procedures performed and can be complicated by inferior alveolar nerve (IAN) damage. [2] Anatomically, the mandibular nerve lies inAl –Saffar AB the inferior dental canal which is enclosed within a tube of dense bone
The tube is seen on radiographs as two parallel radiopaque lines; one representing the roof of the canal and other the canal floor.[3]. Many authors have reported the incidence of post-operative dysaesthesia or impairment of sensory perception including paraesthesia and/or anesthesia of the IAN after extraction of third molars. [4,5,6,7] Temporary injuries in 0.4–5.5% and permanent nerve damage in 0.1–1.0% of cases of third molar extraction have been reported
Various preoperative radiographic techniques to evaluate the relationship between the mandibular third molar and the inferior dental canal (IDC) can be used, these include: intra-oral radiographs, OPGs, cross sectional tomography, scan graphs, and CTs;(3,12) the panoramic radiography is the optimum method for radiological assessment for mandibular third molar teeth prior to their removal,(6) as well as it offers both excellent anatomical assessments and excellent evaluations of jaw fractures, tooth development, with availability of modifications to handicapped patients as well as those with gag reflex sensitivity.[13]
Summary
The removal of impacted mandibular third molars teeth means teeth that fail to erupt into its functional position ,(1) is oneAl – Rafidain Dent J Vol 16, No1, 2016 of the most common surgical procedures performed and can be complicated by inferior alveolar nerve (IAN) damage. [2] Anatomically, the mandibular nerve lies inAl –Saffar AB the inferior dental canal which is enclosed within a tube of dense bone. [5] Injury to IAN has been related to deeply impacted teeth and to roots in close approximation to the IDC; [3] a pre-operative radiographic assessment is required to identify approximation of IDC to third molar to minimize the risk of postoperative dysaesthesia .(8) Rood and Shehab described 7 diagnostic signs to predict nerve injury when evaluating patients for possible extraction of third molars when the roots appear to be in close proximity to the mandibular canal (most importantly, darkening of the root, interruption of the white line of the IAC, and diversion of the IAC). [9] The radiographical relationship of the root apex of mandibular third molars to IDC was assessed and categorized according to the following criteria: 1- Adjacent : The superior border of the canal was either touching the roots apices or within 2 mm below them. Many authors have reported the incidence of post-operative dysaesthesia or impairment of sensory perception including paraesthesia and/or anesthesia of the IAN after extraction of third molars. [4,5,6,7] Temporary injuries in 0.4–5.5% and permanent nerve damage in 0.1–1.0% of cases of third molar extraction have been reported. [5] Injury to IAN has been related to deeply impacted teeth and to roots in close approximation to the IDC; [3] a pre-operative radiographic assessment is required to identify approximation of IDC to third molar to minimize the risk of postoperative dysaesthesia .(8) Rood and Shehab described 7 diagnostic signs to predict nerve injury when evaluating patients for possible extraction of third molars when the roots appear to be in close proximity to the mandibular canal (most importantly, darkening of the root, interruption of the white line of the IAC, and diversion of the IAC). [9] The radiographical relationship of the root apex of mandibular third molars to IDC was assessed and categorized according to the following criteria: 1- Adjacent : The superior border of the canal was either touching the roots apices or within 2 mm below them. 2- Superimposed : The canal was superimposed over part of the roots which appeared less radiopaque than the remaining radiological root's images. 3- Notching: Radiolucent band at the apex of the roots, a break in the continuity of the upper radio dense border, and narrowing at the expense of the top of the canal. 4- Grooving: Radiolucent band across the root above the apex ,interruption of both superior and inferior borders of the canal and narrowing of the canal space. 5- Perforation: Radiolucent band crossing the root above the apex with loss of both superior and inferior borders of the canal at the area where they cross the roots and constriction of the canal maximal in the middle of the root. 6- None: A relationship between the canal and the root apices could not be decisively assessed. [3]More studies confirmed an association between these specific radiographic findings and IAN paresthesia.[6,10] Nortje et al [11] who Proximity of Mandibular Third Molar to Mandibular Canal reviewed 3612 panoramic radiographs and found the position of the IDC was either touching or within 2 mm of the apices of molar teeth in 46.7% of the subjects; in
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