The mandibular foramen (MF) corresponds to the opening of mandibular canal through which it penetrates the inferior alveolar vascular-nervous bundle [
The correct identification of MF is important to avoid complications not only during the performance of surgical procedures involving the region of lingula, but also in the inferior alveolar nerve anesthesia [
The purpose of this research was to study, in macerated adult human mandibles, the height of the lingula and provide morphometric data for its location considering aspects such as shape of the lingula, gender, and race. We intend to contribute to guide maxillofacial surgeons to perform a surgical procedure involving the region of lingula safer, preventing complications.
One hundred thirty-two macerated mandibles of Brazilian adult individuals, of both sexes, Amerindian and Caucasian, belonging to the Department of Morphology and Genetics, UNIFESP (São Paulo, Brazil), were used. Edentulous mandibles and/or those that did not contain information on sex, age, and race were excluded from this study. Only wholly or partially dentate hemimandibles that had at least one molar in the hemiarcade that are being studied were included.
Regarding the shape, the lingula was classified into four types, according to Tuli et al. [
Medial view of the ramus of mandible. (a) Illustration of the height of the lingula (h). (b) Illustration of the distances measures: MN-L, A-L, P-L, and MB-L.
To perform these measurements, we used a digital caliper. The variables such as gender and race were analyzed. The data obtained were tabulated and analyzed using ANOVA and
Additionally we calculated the ratio of the lingula to obtain the anteroposterior position of lingula on the ramus of mandible, using the following formula:
The total was 253 hemimandibles, 96 Amerindian males (AM), 69 Caucasian males (CM), 62 Amerindian females (AF), and 26 Caucasian females (CF). In the statistical tests, we have not included the assimilated shape due to the small number of samples obtained.
Considering the height of the lingula, only in Amerindian males we found a statistically significant difference between truncated and nodular shape. The average values for males were similar in Amerindian and Caucasian individuals and higher than those found for females. Caucasian females showed average values lower than Amerindian females. Furthermore, the height for the nodular shape in Caucasian females was the lowest value found and the height for assimilated shape in Caucasian males was the highest value found.
Average height of the lingula (in millimeters) and average of the following measurements: mandibular notch to lingula (MN-L); anterior margin of ramus of mandible to lingula (A-L); posterior margin of ramus of mandible to lingula (P-L); mandibular base to lingula (MB-L) (in millimeters), for Amerindian and Caucasian males and females,
Amerindian male | Caucasian male | Amerindian female | Caucasian female | Total mean | |
---|---|---|---|---|---|
Height | |||||
Truncated | 8.18 | 8.82 | 7.76 | 7.23 | 8.29 |
Triangular | 8.41 | 8.44 | 7.47 | 6.76 | SD ± 1.99 |
Nodular | 9.33 | 9.19 | 8.01 | 6.54 | |
Assimilated | — | 9.38 | — | — | |
Mean | 8.50 | 8.89 | 7.78 | 7.00 | |
|
0.04 |
0.48 | 0.79 | — | |
SD | ±1.79 | ±2.06 | ±1.87 | ±2.12 | |
|
|||||
MN-L | |||||
Truncated | 17.59 | 16.75 | 16.75 | 16.81 | 17.29 |
Triangular | 18.36 | 17.4 | 16.26 | 14.96 | SD ± 2.57 |
Nodular | 17.95 | 17.50 | 16.12 | 16.38 | |
Assimilated | — | 21.08 | — | — | |
Mean | 17.90 | 17.35 | 16.53 | 16.43 | |
|
0.45 | 0.56 | 0.95 | — | |
SD | ±2.70 | ±2.49 | ±2.50 | ±1.88 | |
|
|||||
A-L | |||||
Truncated | 18.00 | 17.8 | 18.39 |
17.34 | 17.76 |
Triangular | 19.66 | 18.35 | 18.59 |
16.69 | SD ± 2.69 |
Nodular | 16.52 | 16.98 | 16.39 |
13.79 | |
Assimilated | — | 12.77 | — | — | |
Mean | 18.18 | 17.47 | 17.97 | 16.57 | |
|
<0.0001 |
0.29 | 0.005 |
— | |
SD | ±2.46 | ±2.96 | ±2.40 | ±2.88 | |
|
|||||
P-L | |||||
Truncated | 16.10 | 15.75 | 14.76 | 13.63 | 15.28 |
Triangular | 15.68 | 14.44 | 14.04 | 11.17 | SD ± 2.31 |
Nodular | 16.80 | 15.86 | 14.83 | 12.86 | |
Assimilated | — | 14.17 | — | — | |
Mean | 16.13 | 15.41 | 14.67 | 13.22 | |
|
0.23 | 0.05 | 0.56 | — | |
SD | ±2.27 | ±2.10 | ±2.13 | ±1.85 | |
|
|||||
MB-L | |||||
Truncated | 32.90 | 36.16 | 32.58 | 30.77 | 33.30 |
Triangular | 34.80 | 35.80 | 31.38 | 29 | SD ± 4.14 |
Nodular | 32.87 | 35.03 | 30.68 | 28 | |
Assimilated | — | 31.01 | — | — | |
Mean | 33.47 | 35.46 | 31.97 | 30.16 | |
|
0.07 | 0.51 | 0.33 | — | |
SD | ±3.79 | ±3.48 | ±4.72 | ±2.57 |
(—) could not be calculated;
Regarding the distance between lingula and mandibular notch (MN-L), we observed that the highest value found was for assimilated shape in CM and the lowest was for triangular shape in CF. In general, in all types of lingula in AM, the average values found were higher and in CM were lower.
With respect to distance from anterior margin of ramus of mandible to lingula (A-L), we observed a statistically significant difference for Amerindian males between truncated and triangular shapes, truncated and nodular shapes, and triangular and nodular shapes and for Amerindian females between truncated and nodular shapes, and truncated and triangular shapes. In truncated shape, we observed that the averages found for AM, CM, AF, and CF suffered no great variations, presenting themselves relatively similar; however, we observed change in this standard in triangular and nodular shapes, where CF exhibit much lower averages than those found for AM, AF, and CM. The highest average was found for AM in triangular shape and the lowest average was found for CF in nodular shape.
Regarding the distance from posterior margin of ramus of mandible to lingula (P-L), we observed that AM, AF, and CM showed similar averages and higher ones than those found for CF. The highest average was found for AM in nodular shape and the lowest average was found for CF in triangular shape.
Regarding the distance from mandibular base to lingula (MB-L), we have found that CM showed averages considerably higher than AM, AF, and CF in all types of lingula and CF showed the lowest values. The highest average was found for CM in truncated shape and the lowest was found for CF in nodular shape, being observed as a difference of 8.16 mm between these two averages.
Regarding the lingula ratio, we observed that the position of the lingula changes slightly according to the shape of lingula, sex, and race. Assimilated shape in Caucasian males was the type where the lingula occupied a most anterior portion of ramus of mandible and triangular shape in Amerindian males was the type where the lingula occupied a most posterior position.
In general terms, the nodular shape appeared to be occupied a most anterior portion of ramus of mandible and triangular shape most posterior in all individuals (Table
Lingula ratio found for each shape of lingula in Amerindian male, Caucasian male, Amerindian female, and Caucasian female.
Amerindian male | Caucasian male | Amerindian female | Caucasian female | |
---|---|---|---|---|
Truncated | 0.52 | 0.53 | 0.55 | 0.55 |
Triangular | 0.60 | 0.55 | 0.56 | 0.59 |
Nodular | 0.49 | 0.51 | 0.52 | 0.51 |
Assimilated | — | 0.47 | — | — |
(—) could not be calculated.
For AM, the nodular and triangular shapes were located in the superior third of ramus of mandible and only the truncated shape was located in the middle third. For CM, all types were located in the superior third. For AF, only nodular shape was located in the superior third; the truncated and triangular shapes were located in the middle third. For CF, all shapes were located in the middle third.
We observed that in all cases the lingula was located near the intersection line between the superior and middle thirds, no wider than 1 mm, except in nodular shape for CF, which was in the middle third, 2 mm away from the intersection line between the superior and middle thirds.
Analyzing gender differences, we observed that there was a statistically significant difference for the truncated shape in the height of the lingula and in MN-L, P-L, and MB-L distances; for the triangular shape in MN-L, P-L, and MB-L distances, regarding the nodular shape, only A-L distance showed no difference between sexes (Table
Truncated | Triangular | Nodular | ||||
---|---|---|---|---|---|---|
M × F | C × A | M × F | C × A | M × F | C × A | |
Height | 0.026 |
0.91 | 0.136 | 0.46 | 0.0001 |
0.88 |
MN-L | 0.199 | 0.21 | 0.030 |
0.99 | 0.021 |
0.811 |
A-L | 0.787 | 0.27 | 0.765 | 0.32 | 0.151 | 0.064 |
P-L |
<0.0001 |
0.03 |
0.004 |
0.04 |
0.010 |
0.432 |
MB-L | 0.004 |
0.09 | 0.0008 |
0.46 | 0.001 |
0.055 |
Analyzing differences between Amerindian and Caucasian individuals, we observed that there was a statistically significant difference only in P-L distance for truncated and triangular shapes. Additionally, we found statistically significant difference between Amerindian and Caucasian males in P-L (
Morphometric data on the lingula and its location were studied in different researches, addressing different populations (Table
Mean values (in millimeters) for height and the following measurements: mandibular notch to lingula (MN-L); anterior margin of ramus of mandible to lingula (A-L); posterior margin of ramus of mandible to lingula (P-L); mandibular base to lingula (MB-L) reported by other authors.
Authors | References | Population | Height | MN-L | A-L | P-L | MB-L |
---|---|---|---|---|---|---|---|
Monnazzi et al. | [ |
— | 5.82 | 16.38 | 16.5 | 14.63 | 27.09 |
|
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Kim et al. | [ |
Koreans | — | 15.1 | 17.4 | — | — |
|
|||||||
Sekerci and Sisman | [ |
Turkish | 7RF |
13.95RF |
15.97RF |
12.43RF |
30.93RF |
|
|||||||
Jansisyanont et al. | [ |
Thai | 8RM |
16.9RM |
20.9RM |
18.2RM |
— |
|
|||||||
Gite and Padhye | [ |
Indian | — | 16.2 | — | — | — |
|
|||||||
Samanta and Kharb | [ |
North Indian | 5.5 | 15.4 | 20 | 15 | — |
|
|||||||
Woo et al. | [ |
Koreans | 10.51 | 19.82 | 18.6 | 16.1 | — |
|
|||||||
Shah et al. | [ |
Indian | — |
18.19L |
— |
— |
— |
|
|||||||
Nicholson | [ |
East Indian | 8.6R |
— |
— |
— |
— |
|
|||||||
Viravudth and Plakornkul | [ |
Thai | 8.7R |
— |
— |
— |
— |
Unreported or with different measurement: (—); left: L; right: R; male: M; female: F; mean:
Sekerci et al. [
Amerindian females showed mean values higher than Caucasian females in height and in all distances, except in MN-L. Amerindian and Caucasian males showed similar values in height and in all distances, except MB-L in which Caucasian males showed higher average values. We found significant differences in P-L and MB-L between Amerindian and Caucasian males and in A-L, P-L, and MB-L between Amerindian and Caucasian females. According to our results, there was significant difference between Caucasian and Amerindian females in the anteroposterior location of the lingula; however, the distance from the lingula to the mandibular notch was quite similar.
Sekerci and Sisman [
In our study, the distance from the mandibular notch to the lingula (MN-L), distance that helps surgeons to find the lingula [
In our study, the distance from the anterior margin of the mandible to the lingula (A-L) with highest average value was found in triangular shape for Amerindian males (19.66 mm), and the lowest average value was found in assimilated shape for Caucasian males (12.77 mm). The average values found for females, in our study, were higher than those reported for the Turkish [
The distance from the posterior margin of the mandible to the lingula (P-L) was lower in the Turkish population [
Regarding the distance from the mandibular base to the lingula (MB-L), the values found for the Turkish population [
The lingula ratio (LR) provides relevant data to aid in surgical planning. We note that, in general, lingulas with triangular shape are located slightly more posterior than lingulas with nodular shape, which can determine change in the level where the osteotomy should be performed in bilateral SSRO or the inferior alveolar nerve block, since the lingula marks the entrance of the inferior alveolar neurovascular bundle. The LR ranged from 0.47 for assimilated shape to 0.60 for triangular shape. The value reported in the literature for LR varied from 0.53 [
As additional data for location of the lingula, we divided the ramus of mandible into three thirds: superior, middle, and inferior to analyze its superoinferior position. We observed that in all cases the lingula was located near the intersection line between the superior and middle thirds, except for the nodular shape in Caucasian females, who was in the middle third, 2 mm away from the intersection line, between the superior and middle thirds. The lingula was usually located in the middle third in females and in the superior third in males.
Based on our results, we emphasize that in planning a surgery involving the region of lingula, such as sagittal split ramus osteotomy (SSRO) technique, the surgeon must take into account aspects such as gender, race, and shape of lingula. Another important issue that should be considered is a possible anatomical variation in the medial region of the ramus of mandible, where there may be an accessory mandibular foramen located above the lingula [
Alves and Cândido [
This research provides additional data on height of the lingula and morphometric data for its location considering aspects such as shape of the lingula, gender, and race, information that had not been reported in the literature to date.
Comparing men and women, we found that the height of the lingula and the measured distances change according to the shape of the lingula (truncated, triangular, or nodular) determining variations in the lingula position. These changes were not so marked when comparing Amerindian and Caucasian individuals. Despite the gender, differences are more apparent than the differences between races; both of them must be taken into account in surgical procedures performed in the lingula region or inferior alveolar nerve block.
The mean values found for the height of the lingula, in our study, were determined according to the gender, race, and the lingula shape, showing great variability. This data has great clinical relevance, since it can be used as a parameter to carry out surgical procedures performed in the lingula region or inferior alveolar nerve block.
Considering the anteroposterior position, we conclude that the lingula was positioned slightly posterior to the center of the width of the ramus of mandible. Regarding the superoinferior position, the lingula was located in the superior or middle third of the ramus, in general, 1 mm away from the intersection line of these two thirds.
Based on our study and on the literature data, we suggest that the length of horizontal osteotomy in bilateral SSRO should be between 13 mm and 24 mm; however, we emphasize that a careful study considering gender and ethnic group makes procedures involving the region of lingula safer.
The authors declare that they have no conflict of interests.
This study was supported by Department of Morphology and Genetics, UNIFESP, São Paulo, Brazil.