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Revista chilena de anatomía

versión impresa ISSN 0716-9868

Rev. chil. anat. v.18 n.1 Temuco  2000

http://dx.doi.org/10.4067/S0716-98682000000100006 

THE ANATOMY OF THE LINGUAL FORAMEN CANAL AND ITS RELATED
TO THE MANDIBULAR SYMPHYSIS.

ANATOMÍA DEL CANAL Y FORAMEN LINGUAL Y SUS RELACIONES CON LA
SÍNFISIS MANDIBULAR.

 

* Henrique Ayres de Vasconcellos
**

Antônio Eduardo de Siqueira Campos

**

Gerson Hayashi de Almeida

** Mey Lie Tan Maia
*** Pedro Henrique Barros de Vasconcellos

* Department of Anatomy, UERJ- RJ, and Faculty of Medicine of Petropolis, RJ, Brazil.
** Department of Anatomy, UERJ, Brazil.
*** Faculty of Medicine of Petropolis, RJ-Brazil.

SUMMARY: We have measured alveolar and basal midsagittal cross-sections of the symphyseal area of the mandible to determine the relationships between the mandibular lingual foramen (MLF) and its canal to the anterior and posterior surfaces of the mandibular symphysis.

The alveolar-basal length (A), the distance between the anterior end of the foramen canal and buccal (B1), lingual (B2), basal (C) and alveolar (D) surfaces of 116 midsagittal cross-sections (58 dentulous; 58 edentulous) of dried human mandibles were evaluted.

The mean values of the length of the symphysis (A) were 31.87 ± 3.75 mm for dentulous and 23.08 ± 4.40 mm for the edentulous mandibles. The A measurements had the smallest coefficient of variation. The B1, B2, C and D measurements showed small differences between dentulous and edentulous mandibles but higher coefficients of variation. We established morphometric parameters for mandibular symphysis of brazilian mandibles that can be use in planning of oral surgery and implantology compared with other studies.

KEY WORDS: 1. Anatomy; 2. Mandible; 3. Lingual canal; 4. Lingual foramen; 5. Mandibular symphysis.

INTRODUCTION

Studies correlating the structure of the alveolar bone of both maxilla and mandible with the height of the face suggest the importance of the analysis of these bones, specially that of the mandible, for the facial morphology (CAMPOS et al., 1996; Beckmann et al., 1998).

The determination of the bone density of the mandible is now considered to be usefull in the diagnosis of osteoporosis. The data obtained in the study of this bone, can be as precise as femur and spine densitometry (KLEMETTI et al., 1993 ; HORNER et al., 1996).

Patterns of alveolar bone reabsorption, as many as four times more intense in the anterior mandible than in the maxilla, are of special interest in oral implantology (Guerrieri & Miguel, 1982 ; Hobkirk & Watson, 1996).

The intraosseous blood supply of the body of the mandible and maxilla, is centrifugal, in normal conditions, forming plexuses involving both bone and periosteum. In the presence of teeth, the intraosseous vessels send branches that reach the alveolar processes and periodontal plexus.

The intraalveolar arteries and the periodontal plexus, link to vessels of the periosteal plexus and to the vessels of the soft tissues, around the bone, having the loss of the periodontal plexus, in the absence of the tooth. In the presence of abnormal conditions, as in the obstruction of the main nutrient artery, the blood-supply to the bone is inverted, the flux changes direction and the blood flows from outside to inside the bone, producing centripetal circulation (Sharawy & Mish, 1997).

On the lingual surface of the mental area of the mandible, nutrient foramen appear being Mandibular Lingual Foramen (MLF) the more constant and larger diameter, serving as a path to a plexus of vessels and occasionally very small nerves. Branches of the sublingual artery (branch of the lingual artery), and submental artery (branch of the facial artery) or branches resulting from the anastomosis between these vessels, penetrate the foramen reaching a canal inside the bone (Shiller & Wiswell, 1954; Chapnick, 1980; McDONNELL et al., 1994; FREITAS et al., 1994; VASCONCELLOS, et al., 1996).

Only those mandibles where the MLF was present were used in this study. We attempted to describe the functioning of the MLF intra-bone canal and its relationships with the various osseous parameters used in the measurement of the symphysis. This canal is probably responsible for the arterial blood supply of this region and its anatomy has definite surgical implications.

MATERIAL AND METHOD

We used 116 dried human mandibles of brazilian adults, withoud deformities, being 58 at least partially dentulous (with incisive teeth) and 58 edentulous. The bones presented characteristics of adult bones, sex and chronological age being unknown. All mandibles presented MLF in the lingual surface of the mental symphysis McDONNELL et al.; VASCONCELLOS et al.).

The mandibles were immersed in a 3% sodium hipochlorite solution for a period of 24 hours. The immersion facilitated the cleaning of the bones complemented by brushing under running water for complete removal of debris to expose MLF and the insertion of geniohyoid and genioglossus muscles (CAMPOS et al., 1996; VASCONCELLOS et al.). After the drying, the bones were examined and MLF and its intraosseous tract identified and explored using a stainless steel wire (gauge 0). After penetrating the canal we accomplished the sagital section of the mandible with a fine electric reciprocal saw to expose the trajectory of the canal explored previously (Fig. 1).


Fig. 1. Diagrams of the identification and intraosseous trajectory exploration of MLF.

The morphometry of the symphysis was obtained from the following measurements : A _ vertical distance between the alveolar crest and the inferior border; B1 _ horizontal distance between the vestibular surface of the mandible and the anterior end of the canal; B2 _ horizontal distance between the lingual surface of the mandible and the anterior end of the canal; C _ vertical distance between the end of the canal and the inferior border; D _ vertical distance between the alveolar crest and the anterior end of the canal (Fig. 2). The measurements were accomplished by the same researcher with a precision caliper (0.01 mm) and recorded at the average of three consecutive measurements.


Fig. 2. Squematic representation of mandibular morphometry: A _ distance between the alveolar crest and basal border ; B1 _ distance between the anterior surface of the mandible and the anterior end of the canal; B2 _ distance between the lingual surface of the mandible and the anterior end of the canal; C _ distance between the anterior end of the canal and the basal border; D _ distance between the alveolar crest and the anterior end of the canal.

Statistical analysis was proceeded using the MS Excel program and mean, standard deviation and coefficient of variation were obtained.

RESULTS

Dentulous Mandibles: In the dentulous mandibles group (n=58) we found one MLF in 35 bones (60.35%); 2 MLF in 20 bones (34.48%) and 3 MLF in 3 bones (5.17%). Some mandibles presented more than one foramen, resulting therefore in 84 intraosseous canals.

Thirty one canals (36.90%) had ascendind and 53 (63.10%) had descending trajectories. We found 78 (92.85%) canals with a single trajectory and 3 (7.15%) with bifurcation.

Edentulous Mandibles: In the edentulous mandibles group (n= 58) we found one MLF in 37 bones (63.79%); 2 MLF in 19 (32.76%) and 3 MLF in 2 (3.45%) bones. Eight-one intraosseous canals were found, out of which 25 (30.90%) had ascending and 56 (69.10%), had descending trajectories. We found 79 (98.75%) canals with a single trajectory and only 1 (1.25%) with a bifurcation.

In Tables I and II we summarize the data concerning statistical analysis of the morphometry, in dentulous and edentulous mandibles, respectively.

Table I. Data of the statistical study of the morphometry of dentulous mandibles, in millimeters: A, B1, B2, C, D; Mean= arithmetic mean; SD= standart deviation; CV%= coefficient of variation.
  Mean SD CV%

A 31.87 3.75 11.76%
B1 06.94 1.94 27.95%
B2 05.78 1.89 36.48%
C 14.40 3.49 24.23%
D 19.83 4.79 24.15%

Table II. Data of the statistical study of the morphometry of edentulous mandibles, in millimeters :A, B1, B2, C, D; Mean= arithmetic mean; SD= standart deviation; CV%= coefficient of variation.
  Mean SD CV%

A 23.08 4.40 19.06%
B1 06.78 2.80 41.29%
B2 05.06 2.36 46.64%
C 14.02 3.37 24.03%
D 10.82 4.99

46.11%


DISCUSSION

Our data showed the morphometric relationships of the MLF canal and some bony landmarks of the symphysis in dentulous and edentulous mandibles. The measurement A (distance between the alveolar crest and basal border) presented a mean of 31.87 mm (± 3.75) for the dentulous and 23.08 mm (± 4.40) for the edentulous mandibles. Individuals with long faces present increased alveolar mandibular height, associated with a narrower shape of the symphysis (Beckmann et al., 1998). The data we obtained for this measurement can be taken as parameters for alveolar height, in the mandibular symphysis of brazilians and can be correlated to other measurement obtained from the face and the mandible itself. Shiller & Wiswell affirm the value of the measurement A to be of 34.25 mm for dentulous mandibles, being close to the values we obtained. KLEMETTI et al. in a study of edentulous mandibles of women in the postmenopause period, affirm the average of the distance A to be of 20 mm (± 4.00) corresponding to the values obtained by our study. Distance A presented the smallest coefficient of variation, as much for the dentulous mandibles (11.76%) as for edentulous ones (19.06%), becoming a parameter to be considered, mainly for the dentulous mandibles.

Distances B1 and B2 inform the relationship of the anterior end of the MLF canal and the vestibular and lingual surfaces of the mental symphysis. It is important to mention that the end of the canal is related to the medulary bone, so the parameters established with these measurements can also be related to that portion of the bone. For Peterson et al. (1996) the values of the minimum distances between osseointegrated implants and the vestibular (0.50 mm) and lingual (1.00 mm) plates, and the inferior border of the mandible (2.00 mm) are of clinical importance. Our results show the average of the measurements B1 for dentulous (6.94 ± 1.94 mm), B1 for edentulous mandibles (6.78 ± 2.80 mm), B2 for dentulous mandibles (5.78 ± 1.89 mm), B2 for edentulous mandibles (5.06 ± 2.36 mm) which can be useful for implant planning (Tables I and II). Although B1 and B2 have not presented significant differences among the average values for dentulous and edentulous mandibles, the variation of the edentulous ones was higher. We believe B1 and B2 can provide parameters for the analysis of the mineral bone content of the mandible, using this bone in the diagnosis of osteoporosis specially in dentulous women in the postmenopause period (KRALL et al., 1996). Another aspect to be considered is the possibility of a fracture caused by the loss of the bone resistance due to fatigue of the compact bone (BOYCE et al., 1997). The evaluation of measurements B1 and B2 can help establish ideal implant diameters and the risk of mandibular fractures following implant installation.

The C and D values correlate the end of the MLF canal to the basal and alveolar borders, respectively. The average values for C were similar for dentulous and edentulous mandibles (14.40 ± 3.49 mm and 14.02 ± 3.37 mm, respectively). For measurement D we found differences between the average values of dentulous and edentulous mandibles (19.83 ± 4.79 mm and 10.82 ± 4.99 mm). Also, there was a higher coefficient of variation for edentulous mandibles.

We believe that the values can help to establish parameters for both dentulous and edentulous mandibles. Those can also be correlated with the quantification of the mineral bone content, in local and systemic pathologies. The information obtained can be helpful when surgical procedures in the symphysis are concerned, specially genioplasties and implants.

We also believe our data to be important because it establishes a morphological pattern for brazilians, permiting comparisons with the existing specialized literature (Hildebolt, 1997; Karras & Wolford, 1998; Klemetti & Kolmakow, 1997).

RESUMEN: Se realizó un estudio de 116 hemimandíbulas humanas (58 dentadas y 58 edentadas) pertenecientes al Laboratorio de Anatomía del Movimiento, del Departamento de Anatomía de la Universidade do Estado do Rio de Janeiro. A través de cortes en la región de la sínfisis mandibular se determinaron las relaciones entre foramen y canal lingual de la mandíbula y las superficies anterior y posterior de la sínfisis. Se midió el largo alvéolo-basal (A), la distancia entre el término del canal y las superficies bucal (B1), lingual (B2), basal (C) y alveolar (D) de las hemimandíbulas. Los valores medios del largo de la sínfisis (A) presentaron el mayor coeficiente de variación. Las medidas B1, B2, C y D mostraron pequeñas diferencias entre mandíbulas dentadas y edentadas, pero un alto coeficiente de variación. Fueron establecidos valores morfométricos para sínfisis de mandíbulas de individuos brasileños, de tal modo que puedan ser utilizados en la planificación de cirugías e implantes orales oseointegrados y además permitan correlacionar estos valores con los obtenidos por otros autores.

PALABRAS CLAVE: 1. Anatomía; 2. Mandíbula; 3. Canal lingual; 4. Foramen lingual; 5. Sínfisis mandibular.

REFERENCES

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Correspondence to:
Prof. Dr. Henrique Ayres de Vasconcellos
Caixa Postal 46523
20562-970 - Rio de Janeiro - Brazil
Tel: 55 21 5876133 ; Fax: 55 21 2663792.
E-mail: havasc@uerj.br

Recibido : 28-02-2000

Aceptado: 04-04-2000