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National Journal of Maxillofacial Surgery
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Table of Contents
Year : 2021  |  Volume : 12  |  Issue : 1  |  Page : 83-87  

Third molar impaction in different facial types and mandibular length: A cross-sectional study

1 Department of Oral and Maxillofacial Surgery, Government Dental College, Thiruvananthapuram, Kerala, India
2 Department of Oral and Maxillofacial Surgery, Apex Trauma Centre, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
3 Department of Conservative Dentistry and Endodontics, Faculty of Dental Sciences, King George's Medical University, Lucknow, Uttar Pradesh, India

Date of Submission13-Jun-2020
Date of Acceptance23-Oct-2020
Date of Web Publication16-Mar-2021

Correspondence Address:
Dr. Saurabh Kumar Rawat
Department of Oral and Maxillofacial Surgery, Apex Trauma Centre, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow - 226 029, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njms.NJMS_111_20

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Background: The etiology of mandibular third molar impaction is proposed to be mainly due to inadequate space between the distal of the second mandibular molar and the anterior border of the ramus of the mandible. This study was aimed to assess whether an association exists between different facial types and mandibular length to impaction of mandibular third molars.
Materials and Methods: The study consisted of 170 patients who were assessed for facial type clinically based on facial index and mandibular length radiographically on lateral cephalogram. The impaction status was determined clinically and radiographically on orthopantomogram. The facial type was categorized as euryprosopic (broad face), mesoprosopic (normal facial type), leptoprosopic (long face), hypereuryprosopic (extra broad face), and hyperleptoprosopic (extra long face).
Results: Of 170 patients, 18.8% of cases were with hypereuryprosopic profile, 33.5% of cases with euryprosopic profile, 24.7% with mesoprosopic profile, 21.8% with leptoprosopic, and 1.2% with hyperleptoprosopic profile were found. Nearly 42.2% of cases with hypereuryprosopic profile, 52.6% of cases with euryprosopic profile, 53.6% cases of mesoprosopic profile, and 60.3% cases of hyperleptoprosopic and leptoprosopic profile had impacted mandibular third molars. As for mandibular length assessment, 66% cases of short mandibular length, 64.5% cases of normal mandibular length, and 27.9% cases of long mandibular length had impaction.
Conclusion: Within the limitations of the study, it was concluded that, though a higher incidence of impacted third molar was noted in patients with long facial pattern, no significant difference could be established among facial types and their association with impacted mandibular third molars. A significant association was noted between mandibular length and impaction.

Keywords: Euryprosopic, facial type, impaction, leptoprosopic, mandibular third molar, mesoprosopic

How to cite this article:
Hasan K M, Sobhana C R, Rawat SK, Singh D, Mongia P, Fakhruddin A. Third molar impaction in different facial types and mandibular length: A cross-sectional study. Natl J Maxillofac Surg 2021;12:83-7

How to cite this URL:
Hasan K M, Sobhana C R, Rawat SK, Singh D, Mongia P, Fakhruddin A. Third molar impaction in different facial types and mandibular length: A cross-sectional study. Natl J Maxillofac Surg [serial online] 2021 [cited 2022 Dec 4];12:83-7. Available from: https://www.njms.in/text.asp?2021/12/1/83/311357

   Introduction Top

Third molars, also called wisdom teeth, typically erupt between the age of 18 and 24 years.[1],[2] It is found, however, wisdom teeth often fail to erupt (unerupted tooth) or erupt only partially (partially erupted tooth). Unerupted or partially erupted teeth may be impacted, which means they are prevented from completely erupting into the normal functional position, due to a lack of space, obstruction by another tooth, or an abnormal path of eruption.

The facial types may be classified basically into broad facial type (euryprosopic), normal facial type (mesoprosopic), and long facial type (leptoprosopic). Individuals with broad facial type were proposed to have greater horizontal occlusal plane length hence have more space for third molars to erupt, whereas individuals with long facial type would have less space available for third molar eruption due to narrow arches.

A brief guideline document was issued by the National Institute of Clinical Excellence[3] in 2000 regarding prophylactic removal of pathology-free impacted third molars. Several recommendations for further research were given that included study of factors affecting third molar impaction in a bid of optimally predicting third molar impaction. This study was hence aimed at studying facial type and mandibular length as factors that affect impaction of mandibular third and trying to predict at an early age the probability of impaction or eruption of the mandibular third molar.

   Materials and Methods Top

This was a cross-sectional study carried out on patients who reported to the Department of Orthodontics, Government Dental College, Trivandrum, Kerala. The study was approved by the Institutional Ethics Committee. Orthopantomogram (OPG) and lateral cephalogram were required for our study which are taken for routine orthodontic treatment plan. One hundred and seventy patients were assessed for their facial type, mandibular length, and impaction status of lower third molar teeth.

Individuals above 18 years were included in this study with exclusion criteria being gross facial asymmetry and patients who had undergone orthognathic surgery.

Following anatomic landmarks were used in this study-

Clinical landmarks

  1. Soft-tissue nasion
  2. Soft-tissue menton
  3. Soft-tissue zygion.

Radiographic landmarks

  1. Gonion (Go)
  2. Gnathion (Gn).

With the above points in mind, each patient was assessed for clinical measurements: (measured using digital sliding Vernier calipers)

  1. Facial height: Soft-tissue nasion to soft-tissue menton [Figure 1]
  2. Facial width: Zygion to zygion [Figure 2].
Figure 1: Facial height in female's frontal view. Facial height measured from soft-tissue nasion (Point in midline of nasal root at frontonasal suture, the most concave aspect of bridge of nose in center line) to soft-tissue menton (most inferior point on chin) – (a) leptoprosopic, (b) mesoprosopic, and (c) brachyprosopic

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Figure 2: Facial width in female's frontal view – zygion right (most lateral point of each zygomatic arch) to zygion left – (a) leptoprosopic, (b) mesoprosopic, and (c) brachyprosopic

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Cephalometric measurements: measured using scale and protractor [Figure 3]
Figure 3: Cephalometric tracing and landmarks. Mandibular length measured on the lateral cephalogram as a distance between gonion to gnathion. (Go: Gonion – the constructed point of intersection of the ramusa plane and the mandibular plane, Gn: Gnathion – Most anteroinferior point on the symphysis of the chin)

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  1. Mandibular length:[4] linear measurement from Go to Gn

  2. Range: males: 82–90 mm and females: 77–85 mm

  3. Facial index: Calculated as explained by Martin and Saller[5] in 1957 which is also cited by Rakosi et al.[6] in Colour Atlas of Dental Medicine Orthodontics.

Following interpretations are withdrawn from the formula-

Facial Index= facial height ×100/facial width

  1. Hypereuryprosopic-<78.9%
  2. Euryprosopic-79–83.9%
  3. Mesoprosopic-84–87.9%
  4. Leptoprosopic-88–92.9%
  5. Hyperleptoprosopic->93%.

For simplicity sake in further discussion, hypereuryprosopic and euryprosopic facial types are referred to as brachyfacial (broad face) and those with hyperleptoprosopic and leptoprosopic facial types are referred to as dolicofacial (long face).

Third molar status

The eruption status of the lower third molar was determined both clinically and radiographically on a OPG.

Statistical analysis

Data were analyzed using computer software Statistical Package for the Social Sciences version 11.0 (SPSS 11.0. Chicago, USA: SPSS Inc.). Data were expressed in its mean and standard deviation. Independent t-test was used as parametric test to compare parametric data. The association between categorical variables was conducted using Chi-square test. For statistical evaluations, a two-tailed probability of value, <0.05 and <0.01 was considered statistically significant.

   Results Top

The study consisted of 170 patients (67 males and 103 females). Of these, 85 (50%) individuals were aged between 18 and 20 years of age and 58 (34.1%) were aged between 21 and 23 years and 27 patients (15%) were >23 years of age [Table 1] and [Table 2].
Table 1: Distribution according to gender (n=170)

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Table 2: Distribution according to age

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Coming to the issue under question, it was noted that the participants with leptoprosopic and hyperleptoprosopic profiles together had higher percentage of impaction (60.3%) though no statistically significant association could be established. However, there was a statistically significant association between the facial type and impaction among males alone, with 66% of leptoprosopic males having impacted third molars [Table 3].
Table 3: Association between facial index and impaction based on gender

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There was a significant association noted in mandibular length and impaction overall as well among males and females separately. Individuals with short and normal mandibular length showed very high percentage of impaction (66% and 64.5%, respectively), while those with long mandibular length had comparatively low rates of impaction (27.9%) [Table 4].
Table 4: Association between mandibular length and impaction based on gender

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   Discussion Top

Mandibular third molar impaction is a commonly encountered condition, with various studies suggesting incidences ranging from 9.5% to 23% (Hellman,[7] Bjork et al.,[8] Haralabakis,[9] Dachi and Howell[10]). Such impacted third molars have been found to be a cause of various pathosis such as caries, infections (pericoronal and periapical), caries, and periodontal problems associated with second molars, odontogenic cysts, and tumors. Such problems indicate the extraction of these teeth, which again is associated with complications related to their removal such as nerve injuries, periodontal defects distal to second molars which together constitute a great social burden. Some investigators have even advocated prophylactic removal of the third molars to prevent such pathologies (Henry[11] and Laskin[12]), and there are investigators such as Henry and Morant[13] who even advocated enucleating the third molar germ at age as early as 8 years.

Hence, it is very important that factors that affect the impaction of third molars be studied and efforts made to predict this condition at an early age so that early intervention may be possible to reduce the postoperative complications as well as various associated pathologies. At the same time, it has been noted that these teeth that seem to be impacted at earlier ages may gain a normal position later on in life (Hattab,[14] Kruger et al.,[15] and Ventä et al.[16]). Keeping these facts in mind, it is important to not only predict impaction but also predict if a presently asymptomatic impacted tooth would eventually erupt to normal occlusion if given time.

This study was done with an effort to make such prediction possible, with a hypothesis that individuals with brachyfacial pattern of growth would have lesser impaction rates as compared to individuals with dolicofacial pattern of growth.

Another factor studied was the association between mandibular length and incidence of impaction with hypothesis that individuals with longer mandibular length would have lesser chances of impaction compared to individuals with shorter mandibular lengths.

Individuals of age 18 years and above were considered for this study based on the various studies[17],[18],[19] which suggested that mandibular growth after puberty is not appreciable, and if the third molar is not fully erupted and properly positioned at the age of 17 years, it is highly probable that it might remain impacted. The mean age of individuals in this study was 21.2 years with standard deviation of 3.2 years.

Bjork et al.[8] noted that, in cases of mandibular third molar impaction, the alveolar arch space behind the second molar was reduced in 90% of cases.

The second most influential factor was mandibular length. A short mandibular length predisposed to mandibular third molar impaction.[20] However, according to a study by Eröz et al.,[21] the mandibular length was shorter in the long-face facial type, consistently supporting the hypothesis that dolichofacial patients have an increased risk of third molar impaction. In our study, it was found that participants with longer mandibular length had a low percentage of impaction as compared to those with short mandibular length, and this difference was found to be highly significant (P = 0.00) on overall basis as well as in males and females separately. The results are in agreement with Bjork et al.,[8] Richardson,[22] and Broadbent.[23]

The purpose of this study was to assess the existence of such association between the facial type and mandibular length with impaction. The results obtained showed a higher percentage of impactions among dolicofacial types, but a significant difference in association could be demonstrated only among males (P = 0.046). Similar results were reported by Breik and Grubor[24] who found incidence of impaction to be twice as high in long facial pattern participants compared to those with broad facial pattern. These findings are consistent with studies of Olive and Basford,[25] Richardson,[22] who found that impaction was related to retrognathic and prognathic skeletal base patterns.

Nanda[26] also noted that the amount of time of growth differed between different facial types. It was shown that brachyfacial patients exhibited a prolonged period of facial growth in contrast to dolichofacial patients. This may also account for the greater amount of resorption of the anterior border of the ramus.

   Conclusion Top

It may be said that the patients with dolicofacial pattern had a higher percentage of impaction though a significant association could not be established. There was a definite and significant association noted between mandibular third molar impaction and mandibular length. Further research is suggested to study these factors and other factors associated with the impacted mandibular third molars.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Garcia RI, Chauncey HH. The eruption of third molars in adults: A 10-year longitudinal study. Oral Surg Oral Med Oral Pathol 1989;68:9-13.  Back to cited text no. 1
Hugoson A, Kugelberg CF. The prevalence of third molars in a Swedish population. An epidemiological study. Community Dent Health 1988;5:121-38.  Back to cited text no. 2
National Institute for Clinical Excellence. Guidance on the Extraction of Wisdom Teeth. London: National Institute for Clinical Excellence; 2000. Technology Appraisal Guidance. Available from: http://www.nice.org.uk. [Accessed on 2018 Oct 10].  Back to cited text no. 3
Bell WH, Profit WR, White RP. Surgical Correction of Dentofacial Deformities. Vol. 1. Philadelphia: W.B. Saunders Company; 1980.  Back to cited text no. 4
Martin R, Saller K. Lehrbuch der Anthropologie im Systematischer Darstellung, Bd 1. Stuttgart: G. Fischer; 1957.  Back to cited text no. 5
Rakosi T, Jonas I, Graber T. Cephalic index. In: Rakosi T, Jonas I, Graber T, editors. Orthodontic Diagnosis. Colour Atlas of Dental Medicine. 1st ed. Germany: Thieme; 1993.  Back to cited text no. 6
Hellman M. Our third molar teeth: Their eruption, presence and absence. Dent Cosmos 1936;78:750-62.  Back to cited text no. 7
Bjork A, Jensen E, Palling M. Mandibular growth and third mo-lar impaction. Acta Odont Scand 1956;14:231-72.  Back to cited text no. 8
Haralabakis H. Observation on the time of eruption, congenital absence, and impaction of the third molar teeth. Trans Eur Orthod Soc 1957;33:308-9.  Back to cited text no. 9
Dachi SF, Howell FV. A survey of 3,874 routine full-mouth radiographs. I. A study of retained roots and teeth. Oral Surg Oral Med Oral Pathol 1961;14:916-24.  Back to cited text no. 10
Henry CB. Prophylactic odentectomy of the developing mandibular third molar. Am J Orthod Oral Surg 1938,24:72.  Back to cited text no. 11
Laskin DM. Evaluation of third molar problem. J Am Dent Asso 1971;82:824-8.  Back to cited text no. 12
Henry CG, Morant GM. A preliminary study of the eruption of mandibular third molar tooth in man based on measurement obtained from radiographs, with special reference to the problem of predicting cases of ultimate impaction of tooth. Biometrika 1936;28:378-427.  Back to cited text no. 13
Hattab FN. Positional changes and eruption of impacted mandibular third molars in young adults. A radiographic 4-year follow-up study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:604-8.  Back to cited text no. 14
Kruger E, Thomson WM, Konthasinghe P. Third molar outcomes from age 18 to 26: Findings from a population-based New Zealand longitudinal study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92:150-5.  Back to cited text no. 15
Ventä I, Turtola L, Ylipaavalniemi P. Radiographic follow-up of impacted third molars from age 20 to 32 years. Int J Oral Maxillofac Surg 2001;30:54-7.  Back to cited text no. 16
Akinbami BO, Didia BC. Analysis of body variables, mandible and dental arch variables in the prediction of lower third molar impaction. J Contemp Dent Pract 2010;11:1-10.  Back to cited text no. 17
Berge TI. Inability to work after surgical removal of mandibular third molars. Acta Odontol Scand 1997;55:64-9.  Back to cited text no. 18
Brodie AP. The growth of alveolar bone and the eruption of teeth. Oral Surg Oral Med Oral Path 1948;1:342-8.  Back to cited text no. 19
Forsberg CM. Tooth size, spacing, and crowding in relation to eruption or impaction of third molars. Am J Orthod Dentofacial Orthop 1988;94:57-62.  Back to cited text no. 20
Eröz UB, Ceylan I, Aydemir S. An investigation of mandibular morphology in subjects with different vertical facial growth patterns. Aust Orthod J 2000;16:16-22.  Back to cited text no. 21
Richardson ME. The etiology and prediction of mandibular third molar impaction. Angle Orthod 1977;47:165-72.  Back to cited text no. 22
Broadbent BH. The influence of third molar on alignment of teeth. Am J Orthod Oral Surg 1943;29:312-20.  Back to cited text no. 23
Breik O, Grubor D. The incidence of mandibular third molar impactions in different facial types. Aust Dent J 2008;53:320-4.  Back to cited text no. 24
Olive RJ, Basford KE. Tranverse dento-skeletal relationships and third molar impaction. Angle Orthod 1981;51:41-7.  Back to cited text no. 25
Nanda SK. Patterns of vertical growth of face. Am J Orthod Dentofac Orthop 1988,93:103-16.  Back to cited text no. 26


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4]


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