Int. J. Morphol., 26(4):981-987, 2008.

The Mental Foramen Position in Dentate and Edentulous Brazilian’s

Posición del Foramen Mental en Mandíbulas de Brasileños Dentados y Desdentados

*Maise Mendonça Amorim; *Felippe Bevilacqua Prado; *Cynthia Bicalho Borini; **Telmo Oliveira Bittar; ***Maria Cristina Volpato; ***Francisco Carlos Groppo & ****Paulo Henrique Ferreira Caria

AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. The mental foramen in dentate and edentulous Brazilian’s mandible. Int. J. Morphol., 26(4):981-987, 2008.

SUMMARY: The mental foramen has been reported to vary in position in different ethnic groups. Repeated failures during injections and operative procedures involving the mental foramen suggest the presence of local differences in a given population. The aim of the present study was to determine the position of mental foramen (MF) in a sample of one hundred seventy Brazilian adult dry mandible, being 79 edentulous and 91 dentate. The assessment was made, having as it referential, the base of the mandible (BM) and the mandibular symphisis (MS), whereby the comparisons were carried out considering genders, the mandible side (left or right), and dentition (dentate or edentulous). The statistical analysis was performed using multifatorial ANOVA (alpha=5%). It was found the male presented higher values of MF-MS than the female ones and the dentate presented higher values when compared to edentulous ones (p<0.0001). No difference was observed between left and right sides (p=0.2990), as well, as concerning to gender (p=0.152). The most frequent position of MF was in the long axes of the second premolar for male (p<0.0001) and female (p=0.0004). No statistical difference (p>0.05) was found between right and left sides comparing male to female. It was concluded the position of the mental foramen is mainly altered in edentulous subjects as it is consider a symmetric structure in Brazilian population and its most common position is in the long axes of the secondpremolar.

KEY WORDS: Mandibles; Mental Foramen.

INTRODUCTION

The orientation and position of the mental fora- premolar according to the ethnic group studied. The men is important to performing anesthetic block prior to literature shows studies conducted on Asians (Chung et clinical procedures in lower-anterior teeth and also to pre- al., 1995; Igbigbi & Lebona, 2005), Africans (Mbajiorgu serve the integrity of the trunk in surgical et al., 1998; Olasoji et al., 2004; Souaga et al., 2004) and interventions (Julian et al., 1998; Cutright et al., 2003; Caucasians (Cutright et al., 2003). Mwaniki & Hassanali, 1992). The mental nerve injury can cause transitory or permanent sensitive, thermal and The Brazilian population shows high degree of tactile changes (Phillips et al., 1990; Wismeijer et al., miscegenation (IBGE, Brazil, 2000) and the literature on 1997). the location of the mental foramen in this population is very scarce (de Freitas et al., 1975; de Freitas et al., 1976) The location of the mental foramen has been hence does not present any statistical analysis. studied by means of direct measurement on dry mandibles or by using radiographs of dry mandibles or patients The development of implant techniques increased (Phillips et al., 1990; Phillips et al., 1992b; Agthong et the interest in the mandible anatomy, specially the MF al., 2005; Apinhasmit et al., 2006; Captier et al., 2006. localization. Despite this interest a small number of papers has been published on the position of mental foramen in A number of studies have shown difference in the edentulous subjects (Soikkonen et al., 1995; Güler et al., position of the mental foramen in relation to the second 2005; Captier et al.).

* DDS, MSc. Graduate student, Department of Morphology, Anatomy Area, State University of Campinas, Brasil. ** DDS, MSc - Graduate student, Department of Community Health, State University of Campinas, Brasil. *** DDS, PhD - Chairman, Department of Physiological Sciences, State University of Campinas, Brasil. ****DDS, PhD - Associate Professor, Department of Morphology, Anatomy Area, State University of Campinas, Brasil.

981 AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. The mental foramen in dentate and edentulous Brazilian’s mandible. Int. J. Morphol., 26(4):981-987, 2008.

The aim of this paper was to evaluate the position of the mental foramen in dentate and edentulous Brazilian subjects attempting to spot a light to surgical interventions and anesthetic block procedures.

MATERIAL AND METHOD

One hundred and seventy human Brazilian dry mandibles (91 dentate and 79 edentulous) were obtained from the collection of Piracicaba Dental School and Institute of Biology, State University of Campinas – UNICAMP, Brazil. The dentate mandibles presented a mean of at least 14 erupted teeth whereas the edentulous present any. Hundred eighteen mandibles were from male gender and 52 from female. All of them have shown any osseous or dental abnormalities.

This study was performed of directly measures and observations, over dry mandibles as it is described: Fig.1. Graphical representation of the measurements obtained in this study. Orientation of the mental foramen (MF) and its position Position of the mental foramen (MF)to the mandibular in relation to the teeth. symphisis (MS) and the base of the mandible (BM) as shown The location of the mental foramen in relation to the in Fig. 1. mandibular teeth was assessed in the dentate mandible and classified in one of the following positions (Tebo & Telford, Mandibles were placed on a standard basal plane 1950): position 1- mesial to the first premolar; position 2- in searching the maximous contact surface when a vertical line with the long axes of the first premolar; position 3- between pressure was applied to the region of the second molars. The the first and second premolar; position 4- in line with the long distance between the center of mental foramen and the axes of the second premolar; position 5- between the second mandibular symphisis (midline of the mandible) was then premolar and the first molar; position 6- at the mesial half of the measured. This measure was performed on a plane parallel first molar. The results were submitted to Qui-square test to the standard basal plane. adopting 5% significance level. The distance between the mental foramen center to the base of the mandible was measured on a vertical straight RESULTS line perpendicular to the standard basal plane passing on the center of the mental foramen. The values obtained for the ICC were higher than The measurements were performed with a digital 0.98; therefore the replicability was considered excellent. pachymeter of 0.01 mm accuracy (Mitutoyo, Japan), by one investigator. Three measurements were conducted with Position of the mental foramen (MF) to the one week interval and submitted to intraclass coefficient mandibular symphisis (MS) and base of the mandible (BM) (ICC) analysis to assess the measurement replicability. Multifactorial ANOVA was performed to analyze the Table I shows the results of the measurements from influence of the variables (gender, side and dental state) mental foramen to the mandibular symphisis (MF-MS) and on the measurements. The significance level adopted was from the mental foramen to the base of the mandible (MF- 5%. BM), according to the side, gender and dental status.

The orientation and position of the mental foramen Data analysis showed that gender (p<0.0001) and was visually inspected. According to its orientation it was dental status (p<0.0001) significantly affected the measure classified as posterior-superior, superior and posterior. The MF-MS; the male mandibles presented higher values than results were submitted to Kruskal-Wallis test with 5% the female ones and the dentate presented higher values when significance level. compared to the edentulous mandibles. No difference was

982 AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. The mental foramen in dentate and edentulous Brazilian’s mandible. Int. J. Morphol., 26(4):981-987, 2008.

Table I. Mean (SD) of the measurements from mental foramen to the mandibular symphisis according to the measures (MF-MS) and from mental foramen to the base of the mandible (MF-BM) (in mm), according performed. to the side, gender and dental status. Right (mm) Left (mm) Orientation of the mental Gender Dental status Mean (±SD) Mean (±SD) foramen (MF) and position in [95% CI] [95% CI] relation to the teeth. 26.9 (±0.30) 26.6 (±0.44) Edentulous (n=28) [26.3 - 27.5] [25.7 - 27.4] Female* Table II shows the results for 27.3 (±0.42) 27.2 (±0.46) Dentate (n=24)** [26.5 - 28.2] [26.3 - 28.1] orientation of the mental foramen. MF-MS No differences (p=0.9682) were 27.7 (±0.33) 27.5 (±0.33) observed in relation to the gender, Edentulous (n=51) [27.1 - 28.4] [26.9 - 28.2] dental status, and side. Male* 28.9 (±0.23) 28.9 (±0.22) Dentate (n=67)** [28.5 - 29.4] [28.4 - 29.3] The position of the mental foramen in relation to the mandibular teeth is shown in 13.5 (±0.31) 13.7 (±0.32) Edentulous (n=28) [12.9 - 14.1] [13.0 - 14.3] Table III. The most frequent Female position of the mental foramen 14.2 (±0.41) 14.2 (±0.39) Dentate (n=24)** [13.4 - 15.0] [13.4 - 14.9] was in line with the long axes of the second premolar for male MF-BM (p<0.0001) and female 13.3 (±0.23) 13.7 (±0.21) Edentulous (n=51) (p=0.0004). No difference [12.8 - 13.7] [13.3 - 14.1] Male (p>0.05) was found between sides 14.2 (±0.21) 14.2 (±0.22) Dentate (n=67)** for both, male and female. [13.8 - 14.6] [13.8 - 14.6] * Significantly differences (p<0.0001) between male and female. **Significantly differences (p<0.0001) Finally, no accessory or between edentulous and dentate. multiple foramens were observed in this study. observed between left and right sides (p=0.2990).

Considering the FM-BM measurement, the dentate mandibles presented higher DISCUSSION values (p<0.0001) than the edentulous ones. No differences were observed in relation to the gender (p=0.1520) and side (p=0.4420). The location of the mental Fig. 2 shows the graphical representation of the variation of mental foramen foramen is an important factor when considering the mental and incisive anesthetic block and surgeries in the outer premolar mandibular region. The present study shows, for the Brazilian population, the location in line with the long axes of the second premolar as the most common position of the mental foramen, followed by the position between the first premolars. These results, in consistence with others (Freitas et al., 1975; Phillips et al.; Fig. 2. The variation of mental foramen in a graphical representation Apinhasmit et al.; Mwaniki & according to the measures from the mental foramen to the mandibular Hassanali 1992; Ari et al., 2005; symphisis (MF-MS) and from to the inferior base of Oguz & Bozkir, 2002 and the mandible (FM-BM); Black circles= minimum and maximal Cutright et al., 2003) show this is measurements. Diagonal hatched square = probable localization area.

983 AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. The mental foramen in dentate and edentulous Brazilian’s mandible. Int. J. Morphol., 26(4):981-987, 2008.

Table II. Orientation of the mental foramen, according to the side, gender and dental status. Obliterated Posterior Posterior-superior Superior Total N (%) N (%) N (%) N (%) N (%) Female 1 (3.6) 3 (10.7) 19 (67.9) 5 (17.9) 28 (100) Right Male 1 (2) 4 (7.8) 39 (76.5) 7 (13.7) 51 (100) Edentulous Female 4 (14.3) 21 (75) 3 (10.7) 28 (100) Left Male 5 (9.8) 37 (72.5) 9 (17.6) 51 (100)

Female 1 (4.2) 20 (83.3) 3 (12.5) 24 (100) Right Male 5 (7.5) 57 (85.0) 5 (7.5) 67 (100) Dentate Female 3 (12.5) 18 (75) 3 (12.5) 24 (100) Left Male 11 (16.4) 52 (76.1) 5 (7.5) 67 (100)

Table III. Position of the mental foramen in relation to the mandibular teeth of dentate mandibles. Position 3 Position 4 Position 5 Total p N (%) N (%) N (%) Female 5 (20.8) 17 (70.8) 2 (8.3) 24 (100) 0.0004 Right side Male 13 (19.4) 48 (71.6) 6 (9.0) 67 (100) < 0.0001 Total 18 (19.8) 65 (71.4) 8 (8.8) 91 (100)

Female 5 (20.8) 17 (70.8) 2 (8.3) 24 (100) 0.0004 Left side Male 16 (23.9) 45(67.1) 6 (9.0) 67 (100) < 0.0001 Total 21 (23.1) 62 (68.1) 8 (8.8) 91 (100)

the most common finding in the majority of the ethnic groups. measure than edentulous mandibles. This difference can A few number of researches has shown these two locations be related to the high variability of the results and small in inverse order as the most common positions for the men- number of edentulous mandibles (2) evaluated by these tal foramen (Olasoji et al.) or with similar percentages of authors. According to the findings of Güler et al. no frequency for Saudis, for white Americans and for differences werefound among genders in the FM-BI Jordanians claimed by others. measure.

As observed previously by Apinhasmit et al. and Considering the means and the respective standard now in the present study this parameter is not influenced deviations for MF-MS measures in dentate mandibles, the by gender. results of the present study were similar to that observed for black Africans, Chinese and Thai subjects (Souaga et Another parameter that seems to show little variance al. and Apinhasmit et al.) and bigger than that related for among races is the orientation of exit of the mental fora- white British, Korean, and black and white Americans men. As shown by others, such as Apinhasmit in Thais, (Chung et al. and Cutright et al.). In the present study, Mwaniki & Hassanali in Kenian Africans, Igbigbi & male mandibles presented bigger MF-MS measures than Lebona in Malawian, and Phillips in mandibles with female ones, similar to the result observed previously by unknown race, the postero-superior direction is the most Apinhasmit et al., however, this outcome was not observed common orientation of exit of the mental foramen. by Chung et al. and Cutright et al.

Concerning the measurements, the FM-BI measures The difference between genders was also found in of the dentate mandibles studied are in the same range the edentulous mandibles for the MF-MS measure, which observed by other studies (Phillips et al.; Oguz et al.; are in agreement with that of Güler et al., but with less Agthong et al.; Apinhasmit et al.). Contrary to the findings individual variability. of Agthong et al., dentate mandible showed bigger FM-BI

984 AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. The mental foramen in dentate and edentulous Brazilian’s mandible. Int. J. Morphol., 26(4):981-987, 2008.

As observed for the FM-BI measures, the dentate the measures as shown by the standard deviation in some mandibles showed bigger MF-MS measures, which can studies (Apinhasmit et al. and Chung et al.). This variability be related to the mechanic forces of mastication and the could be due to individual variability or to the instrument consequent osseous deposition response for consolidation of measurement. Although Brazilian population presents of the mandibular symphisis region, as the factors a high degree of miscegenation (IBGE, 2000), little associated to the alveolar osseous growth that follows the variability was found among measurement sample. anterior teeth eruption (Hylander, 1984; Kaifu, 1997). Therefore, the atrophic processes that took part in the Concerning the ethnic factor, the Brazilian edentulous mandibles with alveolar resorption may population sample studied presents results more similar to be responsible for the lower measures observed in these Africans and Chinese, with bigger measures than other specimens. ethnic groups.

In addition, muscle forces, facial biotype, teeth size, Although the inferior third of is related as the shape and size of neurocranium, diet habits, the head most asymmetric portion of the (Türp et al., 1998; position, environmental influences, and socioeconomic Melnik, 1992), this statement wasnot observed in the factors, along with ethnic characteristics and racial parameters related to the mental foramen analyzed in the miscegenation could also change the mastication function present study, which corroborate the findings of Captier et and mandibular morphology (Bogin & Rios 2003; Prado al. for dentate and edentulous subjects. & Caria 2007). In conclusion the position of the mental foramen is The differences observed among studies may be altered in edentulous when compared with dentate subjects. related to different methodology, such as measurements Mental foramen is a symmetric structure in Brazilian on skull photographs (Chung et al.) or different skull marks population being most commonly located in the long axes - center versus anterior or inferior border of the mental of the second premolar as it was previously described by foramen or abscense of skull marks information (Cutright). others elsewhere. Thus, our findings are in consistence with previous studies described before showing little variations Another important factor is the great variability of for Brazialian etnhology.

AMORIM, M. M.; PRADO, F. B; BORINI, C. B.; BITTAR, T. O.; VOLPATO, M. C.; GROPPO, F. C. & CARIA, P. H. F. Posición del foramen mental en mandíbulas de brasileños dentados y desdentados. Int. J. Morphol., 26(4):981-987, 2008.

RESUMEN: El foramen mental ha sido reportado variablemente en diferentes posiciones, según los grupos étnicos. Repetidos errores durante el procedimiento anestésico, que involucran al foramen mental, sugieren la presencia de diferencias locales en una determinada población. El objetivo del presente estudio fue determinar la posición del foramen mental (MF) en una muestra de 170 mandíbulas secas de la población brasileña, siendo 79 desdentadas y 91 dentadas. La evaluación fue hecha teniendo como referencia la base de la mandíbula (BM) y la sínfisis mandibular (MS). La comparación fue dada y llevada por géneros, según el lado de la mandíbula (izquierdo o derecho) y la dentición (dentada o desdentada). El análisis estadístico fue realizado usando el test multifactorial ANOVA (alpha 5%). Mandíbulas masculinas presentaron valores mayores que el grupo femenino y las mandíbulas dentadas presentaron valores superiores, cuando fueron comparadas con las mandíbulas desdentadas (p<0.0001). Ninguna diferencia fue observada entre los lados derecho e izquierdo (p=0.2990), como tampoco para los géneros masculino y femenino (p=0.152). La posición más frecuente de MF para las mandíbulas masculinas fue a lo largo del eje del segundo premolar (p<0.0001), así como para las mandíbulas femeninas (p=0.0004). No fueron encontradas diferencias estadísticamente significativas (p>0.05) entre los lados derecho e izquierdo, comparando mandíbulas masculinas y femeninas. Se concluye que la posición del foramen mental es principalmente alterada en sujetos desdentados, es conside- rada una estructura simétrica en la población brasilera y más comúnmente localizado a lo largo del eje del segundo premolar.

PALABRAS CLAVE: Mandíbulas; Foramen Mental.

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