O.O. Gbolahan1, B.B. Osinaike2, C.I. Udoye3 and O.W. Olawole4

  1. Dept. of Oral and Maxillofacial Surgery, College of Medicine, University of Ibadan/UCH, Ibadan.
  2. Department of Anaesthesia, College of Medicine, University of Ibadan/UCH, Ibadan
  3. Department of Restorative Dentistry, University of Nigeria Teaching Hospital, Enugu, Enugu State.
  4. Dept. of Dental and Maxillofacial Surgery, Federal Medical Centre, Birnin Kebbi, Kebbi State, Nigeria


Background: Maximum mouth opening (MMO) is an important parameter in the assessment of several clinical situations and its measured value is documented to have racial, gender, age and anthropometric variation.

Objective: To determine the maximal mouth opening and its predictors among the different major ethnic groups in Nigeria.

Methods: Study subjects were 449 adults (232 males, 215 females), age range 18-74 years from the three major ethnic groups in Nigeria. MMO measurements and anthropometric parameters were recorded. Data analysis was done using SPSS Version 22 and variables subjected to univariate analysis to determine association and a linear regression model was performed to determine variables that could predict maximum mouth opening with pvalue set at < 0.05.

Result: The overall mean MMO across the ethnic groups was 49.33 ± 7.91mm. Mean MMO for the Yoruba ethnic group, 53.06 ± 6.27 mm was found to be significantly higher than values obtained for Hausa tribe 52.77 ± 8.06 mm and Igbo tribe 47.59 ± 8.61 mm (p=<0.001). Age, weight and height were observed to correlate significantly with MMO. A multivariate linear regression model revealed that age and height were independent predictors of maximum mouth opening across the ethnic groups.

Conclusion: There is ethnic variation in MMO among the 3 major ethnic groups in Nigeria with mean MMO values of 53.96 (± 6.27 mm), 52.77 (± 8.06 mm) and 47.59 (± 8.61 mm) for the Yoruba, Hausa and Igbo ethnic groups respectively. Age and height are important predictors of MMO.

Keywords: Maximum mouth opening, Ethnicity, Weight, Height, Gender


Dr. O.O. Gbolahan
Dept. of Oral and Maxillofacial Surgery,
College of Medicine,
University of Ibadan/UCH,
Email: gbolahanlere@yahoo.com


Maximum Mouth Opening (MMO) can be described as the distance between the incisal edges of the maxillary and the mandibular central incisors when the mouth is maximally opened.1,2

Assessment of mouth opening is carried out routinely during clinical examination by a number of dental, medical and surgical specialties. Range of mouth opening is used in the assessment of the stomathognathic system and is a significant factor in the diagnosis of many clinical conditions.3-7 It is also essential in the evaluation of therapeutic interventions following treatment of various conditions affecting the stomathognathic system like temporomandibular joint disorders.8 Range of mouth opening can also be used in predicting possible difficulties that may be associated with a number of procedures involving the stomathognathic system and can as well have implications for the management and treatment of patients.9-12

Mouth opening can be limited by a wide range of conditions that include odontogenic and nonodontogenic orofacial infections, trauma, neuromuscular disorders, temporomandibular joint diseases, congenital and developmental anomalies and oral neoplastic conditions among others.13-16 Normal maximum mouth opening varies with age, race and gender.13 There is need to know the normal range of mouth opening for a particular population before abnormal or limitation in mouth opening can be properly appreciated.3 A number of authors in different studies have characterized the mouth opening of their population and have been able to establish the normal and abnormal range for their population.3- 15 Few studies have been done in Nigeria on maximum mouth opening, these studies relied on population sample from specific regions of the country.17,18 Studies however have shown that degree of mouth opening can be affected by ethnicity.16,19 There are three major ethnic groups in Nigeria (Yoruba, Hausa and Igbo) with about 250 other ethnic groups commonly referred to as minor ethnic groups.20 To the best of our knowledge, no previous study had been conducted to determine the maximum mouth opening among the different ethnic groups in Nigeria. Therefore, this study aims to determine the maximum mouth opening and its predictors among the three major ethnic groups in Nigeria. Findings from this study will be useful in characterizing the mouth opening among Nigerians and also serve as baseline for researchers in future.