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Table of Contents   
ORIGINAL RESEARCH  
Year : 2015  |  Volume : 26  |  Issue : 4  |  Page : 361-365
Evaluation of normal range of mouth opening using three finger index: South India perspective study


1 Department of Oral Medicine and Radiology, GITAM Dental College and Hospital, Visakhapatnam, Andhra Pradesh, Karnataka, India
2 Department of Oral Medicine and Radiology, Yenepoya Dental College and Hospital, Mangalore, Karnataka, India

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Date of Submission06-Aug-2014
Date of Decision05-Jan-2015
Date of Acceptance27-Jul-2015
Date of Web Publication20-Oct-2015
 

   Abstract 

Aims: The frequency, with which restricted mouth opening is encountered in the clinical practice, makes it essential to establish what constitutes the normal range. This study was undertaken to evaluate the normal range of mouth opening in adult population in south India. Settings and Design: randomized clinical study conducted on dentate adult patients to evaluate the normal range of mouth openin. Materials and Methods: 500 healthy patients aged between 18-59 were randomly selected and divided into four groups according to their age ranges. The maximum inter-incisal distance and width of right and left three fingers at the first distal inter-phalanges were measured using vernier calipers. Statistical analysis used: ANOVA test, student t test and pearsons correlation test. Results: The mean value and range of maximum mouth opening of 50.3mm±6.26mm for males and 49.9mm±6.74mm for females was recorded. These values were significant and correlated with the width of three fingers. It was found that the greatest mean maximum mouth opening was recorded in youngest age group and lowest was recorded in older age group in both genders. Conclusions: The mean mouth opening value decreases with age and is lesser in females as compared to males of same age. This study demonstrated that individuals in all the four groups were able to vertically align their right and left three fingers between the upper and lower central incisors upto the first distal interphalangeal folds thus suggesting that, width of three fingers can be used as 'tool' to distinguish 'normal' from 'restricted' mouth opening.

Keywords: Age, gender, maximum mouth opening, measuring tool, three finger index

How to cite this article:
Agrawal J, Shenai PK, Chatra L, Kumar PY. Evaluation of normal range of mouth opening using three finger index: South India perspective study. Indian J Dent Res 2015;26:361-5

How to cite this URL:
Agrawal J, Shenai PK, Chatra L, Kumar PY. Evaluation of normal range of mouth opening using three finger index: South India perspective study. Indian J Dent Res [serial online] 2015 [cited 2019 May 21];26:361-5. Available from: http://www.ijdr.in/text.asp?2015/26/4/361/167638


Mandibular movements are complex in nature and vary greatly among persons. The various factors that regulates the motion of the jaws includes contacts of opposing teeth, the anatomy, and the physiology of temporomandibular joints (TMJ), the axes around which the mandible rotates, the action of muscles, and ligaments, and the neuromuscular integration of all these factors. To assess the degree of restricted mouth opening it's essential to first establish the normal range of mouth opening. For all practical purposes, the maximum interincisal distance is taken as mouth opening of an individual. Research has shown that this range varies significantly with the age, gender, body size, and race. The number of relevant studies pertaining to the measurements of mouth opening is limited, and only two documented research work has been reported among Indians. According to the earliest study, carried out by Mezitis et al.[1] in symptom free adults aged 18–70 years, the average maximum interincisal distance was reported to be 52.85 mm for men and 48.34 mm for women.

The most common method used to assess the mouth opening is the measurement of interincisal distance attained during the active mouth opening by the subject. It is a simple and noninvasive technique; however, difficulty arises when different instruments are used to measure linear mouth opening and when a large population is screened. Thus, the most appropriate method would be used for measuring the technique which is directly proportional to subject's body size. The width of three fingers is directly proportional to the subject's body size. Hence, this study was conducted with an aim to consider the applicability of this method as an index to measure the maximum mouth opening (MMO) among different age groups in a population.


   Subjects and Methods Top


The study was undertaken in the department of Oral Medicine and Radiology. A total sample of randomly selected 500 patients from the OPD between the age group of 18–59 years, representing a sample of dentate adults were taken for the study. The study group consisted of 216 females and 284 males. The sample was stratified into four groups according to the age followed by gender stratification. A sample size of 125 per group was determined (n = 500) for a power of 0.80, probability of type I error being 0.05, largest difference between groups of two and expected standard deviation of 6.8. The age groups being 18–29 years (Group 1), 30–39 years (Group 2), 40–49 years (Group 3) and 50–59 years (Group 4).

Clinical examination was performed on selected patients fulfilling the inclusion criteria of occlusion in class I molar relation, completely erupted, and functional maxillary, and mandibular central incisors, anterior teeth with normal positioning, attrition on the incisal edges no more than 1 mm, and no dental prosthesis on upper and lower anterior teeth or first molars. The exclusion criteria for the study were the patient presenting a history of jaw or face pain either at rest or during function, history of bruxism, temporomandibular disorders (TMDs), oral submucous fibrosis, malignancy or exhibiting facial or dental developmental abnormalities.

For all practical purpose pertaining to the measurements of mouth opening, the maximum interincisal distance is taken as MMO of an individual. This distance can be accurately measured with the use of measuring instruments; however, it becomes difficult to use any instrument when a large population is screened. Thus, the most convenient, and appropriate method would be to use a measuring technique which is directly proportional to subject's body size. Considering the hypothesis, that the width of three fingers at the first interphalangeal fold, as the body size parameter of an individual, the present study was carried out to evaluate its correlation with the MMO. Two measurements were considered using Vernier calipers, MMO [Figure 1] and width of three fingers (index, middle and ring fingers) at the first distal interphalangeal folds of both right and left hand [Figure 2]. Measurement of MMO was recorded by asking the subject to open their mouth as wide as possible, while the examiner measured the maximum distance from the incisal edge of the maxillary central incisors to the incisal edge of the mandibular central incisors at the midline. The ability to vertically align three fingers up to the first distal interphalangeal folds with the mouth maximally opened was also documented. The data was analyzed using SPSS version 17 statistical software package (SPSS Statistics for Windows, Version 17.0. Chicago: SPSS Inc.). The comparison of mouth opening, the width of three fingers of right hand, and three finger width of a left hand, between all four groups were done by using analysis of variance (ANOVA). Pearson's correlation test was used to correlate the width of three fingers with mouth opening. A P value of <0.05 was considered statistically significant.
Figure 1: Measurement of maximum mouth opening using Vernier caliper

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Figure 2: Measurement of width of three fingers (index, middle and ring fingers) at the first distal interphalangeal folds using Vernier caliper

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   Results Top


Total of 500 patients was equally divided according to their age into four groups consisting of 125 patients in each group. The mean MMO and mean width of three fingers of both right and left hand in all four groups are summarized in [Table 1]. [Table 1] also describes the standard deviation, P value and 95% confidence interval for mean.
Table 1: Mean MMO and mean width of three fingers in all four group along with their SD and CI

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In Group 1 the MMO was 51 mm ± 0.62 mm and mean width of right hand three fingers was 46 mm ± 0.52 mm. The obtained P value was 0.020 (<0.05). Similarly, when compared to the width of left hand three finger, which was 45 mm ± 0.53 mm, a P value was 0.023 (<0.05) which was equally significant. In Group 2 the mean MMO was 49 mm ± 0.64 mm. The mean width of both right hand three fingers and left hand three fingers was 48 mm ± 0.52 mm and P value was 0.000 (<0.05). In Group 3 the mean MMO was 50 mm ± 0.64 mm, and the mean width of right hand three fingers was 47 mm ± 0.59 mm. The P value for this group was > 0.05 (0.59) which was not significant. However, the mean width of left hand 3 finger was 46 mm ± 0.52 mm and P value was of 0.020 (<0.05). In Group 4 the mean MMO was 49 mm ± 0.70 mm and mean width of the right hand three finger was 48 mm ± 0.56 mm. The P value was 0.000 (<0.05). When compared with the mean width of left hand three fingers which was 48 mm ± 0.53 mm. Similar significant P value of 0.000 (<0.05) was obtained. Using ANOVA test degree of freedom between the group was 3 and within the group was 496 [Table 2]. The statistical results were significant suggesting that all individual were able to align vertically their right and left three fingers at the level of first distal interphalangeal folds during MMO. Using the three fingers width to evaluate the MMO of an individual was an innovative, simple and quick method of assessing and recording the normal mouth opening.
Table 2: Determining df between and within group using ANOVA

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In the present study, it was observed that, the males are exhibiting mean MMO of 50.3 mm. The younger male group exhibited MMO of 50.8 mm, and the least value of 49.2 mm was noticed in the older male group. The female patients exhibited the mean MMO of 49.9 mm. When dividing them according to age, the mean MMO was 51.2 mm for Group 1 and 49.8 mm for Group 4, suggesting reduced the mouth opening as compared to males of the same age [Table 3].
Table 3: Mean MMO of males and females in all four groups

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   Discussion Top


Research has shown that the mouth opening measurement varies significantly with the age, gender, and stature along with geographical and ethnic variation hence it becomes the essential to establish what parameters to be taken into consideration for evaluating normal mouth opening for the population. The summary of studies conducted in the different geographical area using various methods are enumerated in [Table 4].
Table 4: Summary of studies conducted to evaluate the MMO in various geographical areas

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Review of literature reported by various investigators hence demonstrated the large variability in the range of mouth opening, ranging 40–77 mm in males and 32–75 mm in females.[1],[2],[4],[5],[7],[8],[9],[10] In the present study, it was found, that the mean value, and the range of MMO was 50.3 mm ± 6.26 mm (32.0–72.0 mm) for males and lesser value of 49.9 mm ± 6.74 mm (38.0–67.0 mm) for females which was in the range provided by the other studies done in other part of the world.[5],[8],[9],[10] In all earlier reported studies along with the present one, it was found, that the men exhibit marginally greater mean mouth opening then females, this may be due to greater mandibular length in males than in females or due to greater muscle strength in men allowing their maximum jaw opening. By contrast to our study and those reported above, Pullinger et al. stated in his study, that females have greater range of mouth opening and suggested the difference in behaviour of mouth opening may be due to greater joint laxity in females.[11] This observation could be the reason for the higher frequency of TMD, which is constantly seen in women as compared to men in general surveys.

The 500 sample in the present study was stratified into four groups according to age. It was found that the greatest mean MMO was recorded for younger age (Group 1) in both males and females, whereas the lowest was recorded in older age (Group 4). These findings were similar to those reported by other investigators.[1],[2],[4],[5],[8],[10],[11] The variation in mouth opening with respect to the age, and gender could be related to either altered mobility of TMJ or difference in body size. When interincisal distance is used as the measurement method, mouth opening measurement should increase with the age due to the attrition of incisal edge of anterior teeth. On the contrary as the age advances owing to dehydration and increase in fibrous tissue, the facial musculature loses elasticity and resiliency, often leading to the restricted mouth opening.[12]

Although the numerous method of measuring mouth opening is described in the literature, unfortunately, they are seldom used in daily practice. In the present study, the interincisal distance was measured using Vernier caliper based on the study carried out by Cox and Walker [5] in 700 Nepalese. Despite of documentation of several studies for the evaluation of mouth opening, no baseline measurement was established for an individual to determine if there was any limitation in mouth opening. Hence, the most appropriate method is to use a measuring method that is directly proportional to the subject's body size. A study conducted by Zawawi et al.[8] in 2003 on 140 Tufts University students, suggested a strong positive correlation between MMO, and width of three fingers at first interphalangeal folds. The study also suggested that the width of three fingers is directly proportional to the subject's body size and can be used as a reliable index for evaluation of mouth opening. As the sample size of Zawawi study was very less to consider the width of three fingers as measuring index, and based on the fact that variation in mouth opening exist in various ethnic group, the present study was conducted. Hence in present study, apart from measuring the normal mouth opening in adult population, ability of each subject to vertically position three fingers between the upper and lower incisors during MMO was assessed and the results were significantly correlated. This observation seems to validate our hypothesis that the width of three fingers can be used as a “tool” to evaluate the normal MMO. The ability of placing the three fingers in the mouth is a simple, and quick method of assessing and recording the normal mouth opening of the individual. This method can be used as an index to distinguish “normal” from “restricted” mouth opening.

The present study was conducted on adult patients, similar studies were carried out by several authors worldwide [Table 2]. However, only two studies were reported in Indian population. In a North India study conducted by Mathur and Jha [3] in 1993, it has been found that the average MMO s for males and females were 50.3 mm and 44.9 mm. Another South Indian study by Rangnathan et al.[6] in 2001, the same were found to be 47.5 mm and 44.6 mm for males and females respectively. In the present study, the MMO values for males and females were reported higher than the two Indian studies. This variation may be attributed to the facial dimensions of the studied population with different ethnicity, body weight and size.

Abou-Atme et al.[13] in 2008 reported MMO measurement in children. On review, the difference in correlation between MMO and three finger width, in adults and children was related to incomplete body growth seen in children. Growth is a continuous phenomenon with a period of rapid growth and the period when growth is slow, it's not always necessary that, as age increases, a different part of the body also increases proportionally. Hence, it is reliable that the measurement should be done after cessation of growth. It is also been stated by few authors that MMO increases significantly with stature as compare to that with age.[8],[14],[15] It is, therefore, reasonable to consider height, and weight of individual to estimate the MMO then their age. Three fingers index either right, or left hand can be used as a parameter to judge normal mouth opening in person, where mouth opening is reduced due to pathology. The limitation of using this three finger as “index” for assessing MMO arises in children and when the incisors are absent, traumatized, restored, or incompletely erupted.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Mezitis M, Rallis G, Zachariades N. The normal range of mouth opening. J Oral Maxillofac Surg 1989;47:1028-9.  Back to cited text no. 1
    
2.
El-Abdin H, Al-Shalan T, Al-Bisher G. Normal mouth opening in the Saudi population. Saudi Dent J 1991;3:99-101.  Back to cited text no. 2
    
3.
Mathur RM, Jha T. Normal oral flexibility – A guideline for SMF cases. J Indian Dent Assoc 1993;64:139-43.  Back to cited text no. 3
    
4.
Chima O, Obiechina AE. Mouth opening among Nigerians. Odontostomatol Trop 1995;18:22-4.  Back to cited text no. 4
    
5.
5Cox SC, Walker DM. Establishing a normal range for mouth opening: Its use in screening for oral submucous fibrosis. Br J Oral Maxillofac Surg 1997;35:40-2.  Back to cited text no. 5
    
6.
Rangnathan K, Devi U, Josua E, Bhardwaj A, Roobam T, Vishwanathan R. Mouth opening, cheek flexibily, and tongue protrusion, parameters of 800 normal patients in Chennai, south India – A baseline study to enable assessment of alteration in oral submucus fibrosis. J Indian Dent Assoc 2001;72:78-80.  Back to cited text no. 6
    
7.
Gallagher C, Gallagher V, Whelton H, Cronin M. The normal range of mouth opening in an Irish population. J Oral Rehabil 2004;31:110-6.  Back to cited text no. 7
    
8.
Zawawi KH, Al-Badawi EA, Lobo SL, Melis M, Mehta NR. An index for the measurement of normal maximum mouth opening. J Can Dent Assoc 2003;69:737-41.  Back to cited text no. 8
    
9.
Placko G, Bellot-Samson V, Brunet S, Guyot L, Richard O, Cheynet F, et al. Normal mouth opening in the adult French population. Rev Stomatol Chir Maxillofac 2005;106:267-71.  Back to cited text no. 9
    
10.
Yao KT, Lin CC, Hung CH. Maximum mouth opening of ethnic Chinese in Taiwan. J Dent Sci 2009;4:40-4.  Back to cited text no. 10
    
11.
Pullinger AG, Liu SP, Low G, Tay D. Differences between sexes in maximum jaw opening when corrected to body size. J Oral Rehabil 1987;14:291-9.  Back to cited text no. 11
    
12.
Winkler S. Essentials for Complete Denture Prosthodontics. 2nd ed. New Delhi: A.I.T.B.S Publishers; 2009.  Back to cited text no. 12
    
13.
Abou-Atme YS, Chedid N, Melis M, Zawawi KH. Clinical measurement of normal maximum mouth opening in children. Cranio 2008;26:191-6.  Back to cited text no. 13
    
14.
Ingervall B. Variation of the range of movement of the mandible in relation of facial morphology in children. Scand J Dent Res 1970;78:533-43.  Back to cited text no. 14
    
15.
Muto T, Kanazawa M. The relationship between maximal jaw opening and size of skeleton: A cephalometric study. J Oral Rehabil 1996;23:22-4.  Back to cited text no. 15
    

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Correspondence Address:
Jayshree Agrawal
Department of Oral Medicine and Radiology, GITAM Dental College and Hospital, Visakhapatnam, Andhra Pradesh, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.167638

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