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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 29  |  Issue : 3  |  Page : 186-190

Study on evaluation of normal range of maximum mouth opening among Indian adults using three finger index: A descriptive study


1 Department of Oral Medicine and Radiology, New Horizon Dental College and Research Institute, Bilaspur, Chhattisgarh, India
2 Department of Plastic Surgery, Burn and Trauma Centre, Bilaspur, Chhattisgarh, India
3 Department of Community Medicine, Chhattisgarh Institute of Medical Sciences, Bilaspur, Chhattisgarh, India

Date of Submission08-Jan-2017
Date of Acceptance07-Nov-2017
Date of Web Publication20-Nov-2017

Correspondence Address:
Ravleen Nagi
Department of Oral Medicine and Radiology, New Horizon Dental College and Research Institute, Sakri, Bilaspur, Chhattisgarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.JIAOMR_5_17

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   Abstract 

Introduction: Early recognition of decreased or limited mouth opening in many pathological conditions is necessary for prompt diagnosis and to plan the treatment options judiciously. Therefore, it is essential to establish what constitutes normal opening for the population. Aim: This study was designed 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 an Indian population. Materials and Methods: Total 400 healthy participants were studied in the age range of 17 to 60 years and stratified into four groups according to their age ranges. The maximum interincisal distance and width of three fingers (index, middle, and ring fingers) at the first distal interphalangeal folds of both right and left hand were measured using Vernier caliper. Statistical analysis was done using SPSS version 21 software package. Results: Results suggested that mean value and range of MMO for males was 51.00 mm (33.0–68.0 mm) and for females it was 46.3 mm (39.0–58.0 mm). Mean values of MMO correlated significantly with the width of three fingers of left and right hand as shown by Pearson correlation test. Conclusion: The study suggested that three finger index is a convenient and reliable tool for assessing normal MMO and is a most appropriate method to normal from restricted mouth opening.

Keywords: Age, diagnosis, gender, maximum mouth opening, three finger index


How to cite this article:
Nagi R, Sahu S, Gahwai D, Jain S. Study on evaluation of normal range of maximum mouth opening among Indian adults using three finger index: A descriptive study. J Indian Acad Oral Med Radiol 2017;29:186-90

How to cite this URL:
Nagi R, Sahu S, Gahwai D, Jain S. Study on evaluation of normal range of maximum mouth opening among Indian adults using three finger index: A descriptive study. J Indian Acad Oral Med Radiol [serial online] 2017 [cited 2019 Nov 14];29:186-90. Available from: http://www.jiaomr.in/text.asp?2017/29/3/186/218722


   Introduction Top


Assessment of mouth opening is a normal daily practice in clinical dentistry. For all practical purposes, normal mouth opening has been defined as the interincisal distance at maximal mouth opening (MMO).[1] A known range of normal mouth opening is necessary to enable the clinician to conduct a thorough oral examination conveniently. Limitation of mouth opening is one of the early signs of many pathological and traumatic conditions. Early recognition of decreased or limited mouth opening is necessary for a prompt and efficient approach to diagnosis and to plan the treatment options judiciously. To diagnose decreased mouth opening it is essential to establish what constitutes the normal opening for the population.[2] MMO can be defined as the greater distance between the incisal edge of the upper central incisor and the opposing tooth of the lower jaw at the midline when the mouth is open widely.[3] Although this technique is simple and noninvasive, difficulty occurs when different instruments are used to measure mouth opening and when a large population has to be screened. Research has also shown that the measurement of mouth opening varies significantly with age, gender and race.[4],[5],[6],[7],[8] Because the variability in the range of mouth opening is so large, clinicians do not usually have a baseline measurement for a particular individual to determine if there is any limitation in mouth opening. This wide variability may be related to a variety of factors, including differences in body size among participants. To correct this factor, it would be more appropriate to use a measuring method that is directly proportional to the participant's body size.[9] The width of three fingers is directly proportional to the participant's body size, and is a commonly used practice to measure the MMO of the participants.

Aim

This study was conducted with an aim to consider the applicability of this method as an index to measure the MMO among different age groups in an Indian population.


   Materials and Methods Top


This is a descriptive cross-sectional study conducted in a tertiary health care centre in Bilaspur, Chhattisgarh from 1st June 2015 to 31st December 2015. Total 400 healthy participants were studied in the age range of 17 to 60 years. The study group consisted of 238 males and 162 females. The sample was stratified into four groups according to the age followed by gender stratification. A sample size of 100 per group was determined (n = 400) for a power of 0.80, probability of type I error being 0.05. The age groups were 18–29 years (Group 1), 30–39 years (Group 2), 40–49 years (Group 3), and 50–60 years [Group 4]. Informed consents were taken from all study participants fulfilling the inclusion criteria of functional maxillary and mandibular central incisors, normal positioning of anterior teeth, attrition on the incisal edges no more than 1 mm, no dental prosthesis on anterior or first molars, and class I molar relation bilaterally. The exclusion criteria for the study were patients 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.

MMO was measured using standard protocol. Considering the hypothesis that, the width of three fingers at the first inter-phalangeal fold, is proportional to the body size parameter of an individual and is most appropriate technique to measure MMO, the present study was carried out to evaluate its correlation with the MMO. Two measurements were considered using Vernier calipers, MMO and width of three fingers (index, middle, and ring fingers) at the first distal interphalangeal folds of both the right and left hand. Participants were asked to open their mouth maximally till no further opening was possible. The distance from the incisal edge of the upper incisor teeth to the incisal edge of the lower incisor teeth was measured and recorded in millimeters [Figure 1]. The ability to vertically align three fingers up to the first distal interphalangeal folds with the mouth maximally opened was also documented [Figure 2].
Figure 1: Measurement of MMO using Vernier caliper

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

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Statistical analysis

The data was compiled in MS Office Excel. Statistical analysis was done using SPSS version 21 software package (SPSS Statistics for Windows, Version 21.0. Chicago: SPSS Inc.). Comparison of mouth opening, the width of three fingers of right hand, and three fingers of left hand, between all four groups was done by using analysis of variance (ANOVA). Independent sample t-test was used for group difference in relation to MMO, width of right hand and left hand. Pearson correlation test was used to correlate the width of three fingers with mouth opening. The paired t-test was used to find the difference between MMO, the width of three fingers of right hand, and three fingers of left hand. The logistic regression was drawn among tobacco users with age and MMO where tobacco was dichotomous dependent variable. A P value of <0.05 was considered statistically significant.


   Results Top


A total of 400 patients were equally divided according to their age into four groups consisting of 100 patients in each group. The mean MMO and mean width of three fingers of right and left hand in all four groups are illustrated in [Table 1] which also describes standard deviation, P value and 95% confidence interval for mean. The independent sample t-test showed that for width of left hand three fingers, group difference between Group 1 – Group 2 was –2.10 mm ± 0.542), with a P value of 0.000 which was highly significant, difference between Group 1 – Group 3 was –2.71 ± 0.693, with a P value 0.000, which was equally significant and the difference between Group 1 – Group 4 was –2.16 ± 1.010, with a P value of 1.03 (>0.05), hence not significant. For right hand three fingers, group difference between Group 1 – Group 2 was –2.28 mm ± 0.527, with a P value of 0.000 which was highly significant, difference between Group 1 – Group 3 was –2.78 ± 0.675, with a P value of 0.000, which was equally significant and the difference between Group 1 – Group 4 was –3.11 ± 0.963, with a P value of 0.001 (<0.05), hence highly significant. For MMO, the differences between the groups were not significant. Even differences between Group 2 – Group 3, Group 2 – group 4, and Group 3 – Group 4 in relation to MMO, width of right hand and left hand were not statistically significant.
Table 1: Mean MMO and mean width of three fingers of all four groups using independent sample t-test

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Pearson's correlation test showed positive correlation between all three variables of study [Table 2]. Using paired t-test it was observed that the mean difference between MMO and left hand three fingers (1.23 ± 3.55), and between right and left hand three finger (0.91 ± 1.422) was highly significant, however, mean difference between MMO and right hand three fingers (0.32 ± 3.389) was not significant [Table 3].
Table 2: Correlation between mean MMO and width of left hand three fingers (LH) and right hand three fingers (RH) using Pearson correlation test

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Table 3: Determining mean of MMO and width of left hand three fingers (LH) and right hand three fingers (RH) using paired t-test

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ANOVA showed that the degree of freedom between the group was 3 and within the group was 396 [Table 4]. In this study, it was noticed that males had mean MMO of 51.0 mm. The younger male group (Group 1) had mean MMO of 51.48 mm and older (Group 4) had 51.08 mm whereas in case of females the mean MMO was 46.3 mm. The younger age group (Group 1) had mean MMO of 45.69 mm whereas older age group had mean MMO of 48.44 mm [Table 5]. Logistic regression was drawn among tobacco usage with age and MMO in this study where tobacco was a dichotomous dependent variable and age and MMO were independent variables.
Table 4: Determining df between and within group using ANOVA

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Table 5: Mean MMO of males and females in all four groups

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   Discussion Top


In dentistry, various conditions such as TMDs, maxillofacial trauma, oral malignancies, oral submucous fibrosis, and craniofacial syndromes are associated with restricted mouth opening. The treatment of these disorders is to restore the mouth opening to normal. Therefore, it is necessary to establish a normal value. This study was designed with an aim to find a method of assessing MMO using a tool that is directly proportional to body size. Various studies have recommended the individual's ability to fit the first three fingers (index, middle, and ring fingers) vertically positioned between the upper and lower central incisors with the mouth maximally open to assess MMO.[10],[11] Mouth opening is influenced by age, gender, and race. In our study, a sample size of 400 was selected and divided into four groups and it was observed that mean MMO in case of males was greatest for younger age [Group 1] and lowest for older age [group 4] but for females it was greatest for group 2. Similar results were observed in other studies that MMO decreases with increasing age because as age advances there is increase in fibrous tissues and the mucosa loses its elasticity leading to decrease in MMO.[5],[8],[12]

Regarding the normal mouth opening in males and females various research work has been mentioned in literature and it ranges from 40–74 mm in males and 35–70 mm in females.[3],[5],[8],[12] Gallagher et al. conducted a study in an Irish population and found that MMO was 43.3 in males and 41.1 in females.[3] Mezitius et al. studied 1160 Greek adults and found MMO of 52.85 mm in males and 48.34 in females.[5] In the present study, it was found that the mean value and range of MMO for males was 51.00 mm (33.0–68.0 mm) and for females it was 46.3 mm (39.0–58.0 mm). Results suggested that males have more MMO than females; this may be due to greater mandibular length or greater muscle strength leading to the ability to open mouth maximally in males. However, Pullinger et al. found that MMO was more in the female than males. This is because they studied angle of opening at temporomandibular joint (TMJ) and it was found to be increased in females. Moreover, females have greater joint laxity than males.[13]

Several methods have been used to measure the MMO. Most commonly interincisal distance between the incisors is measured with the mouth open maximally to assess the MMO. Majority of researchers measure active mouth opening but some have also found that passive mouth opening is superior to active mouth opening. Dijkstra et al. found that variable force is required to produce passive mouth opening and this method is associated with error.[14] In addition, Wood and Bronco concluded that intraoral measurements using a ruler were more precise and accurate and this method was also easy, quick, and precise.[1] In the present study, interincisal distance between the incisors with mouth open maximally and width of three fingers at interpharyngeal fold were measured by Vernier caliper in millimeter and positive correlations were obtained between the MMO and width of left hand and right hand three fingers. The study also suggested that width of fingers is directly proportional to participant's body size, hence, this method could be used as an appropriate tool to assess MMO.

Studies were carried out to assess MMO in children. In these studies, no significant differences were found between MMO between males and females in children. Gender has no influence in children. This may be due to children not having attained sexual maturity of adults. Moreover, there are differences in the skeletal age and growth stage of children.[15] Landtwig stated that in children MMO increases more with stature and weight than with age as growth is not continuous in children but there are periods of rapid growth and slow growth.[9] Agerberg observed significant correlations between body height and age (not weight).[6] In children MMO should be measured after cessation of growth and could be used in an individual where mouth opening is restricted due to pathology but main limitation of three finger index to assess MMO in children arises when the anterior teeth are missing, traumatized, or incompletely erupted.[11] Attempts should be made to avoid movements of soft tissues during measurements. All these may lead to inaccuracy of results.


   Conclusion Top


This study suggested that three finger index is a convenient and reliable tool for assessing normal maximum mouth opening. It is a most appropriate method to distinguish normal from restricted mouth opening. Even in children MMO was found to correlate with body height and weight and was found to be simple method to assess MMO. In future, more studies on large sample sizes should be encouraged and studies should be focused on TMJ disorders and other pathologic conditions that influence mouth opening.

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

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Wood GD, Branco A. A comparison of three methods of measuring maximal opening of the mouth. J Oral Surg 1979;37:175.  Back to cited text no. 1
    
2.
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. 2
    
3.
Gallagher C, Gallagher V, Whelton H, Cronin M. The normal range of mouth opening in an Irish population. J Oral Rehabil 2004;30:110-6.  Back to cited text no. 3
    
4.
Boozer CH, Ferraro EF, Weinberg R. The effects of age, race and sex on the interincisal measurement. Ann Dent 1984;43:5.  Back to cited text no. 4
    
5.
Mezitis M, Rallis G, Zachariades N. The normal range of mouth opening. J Oral Maxillofac Surg 1989;47:1028.  Back to cited text no. 5
    
6.
Agerberg G. Maximal mandibular movements in young men and women. Sven Tandlak Tidskr 1979;67:81-100.  Back to cited text no. 6
    
7.
Landtwing K. Evaluation of the normal range of vertical mandibular opening in children and adolescents with special reference to age and stature. J Maxillofac Surg 1979;6:157.  Back to cited text no. 7
    
8.
Cox SC, Walker DM. Establishing a normal range for mouth opening: Its use in screening for submucous fibrosis. Br J Oral Maxillofac Surg 1997;35:40-2.  Back to cited text no. 8
    
9.
Landtwing K. Evaluation of the normal range of vertical mandibular opening in children and adolescents with special reference to age and stature. J Maxillofac Surg 1978;6:157-62.  Back to cited text no. 9
    
10.
Travell JG, Simons DG: Masseter muscle. The trismus muscle. In: Travell JG, Simons DG, editors. Myofascial pain and dysfunction. The trigger point manual. The upper extremities. Baltimore, MD: Williams and Wilkins; 1983. p. 219-35.  Back to cited text no. 10
    
11.
Zawawi KH, AI-Badawi EA, Lobo Lobo S, Melis M, Mehta NR. An index for the measurement of normal maximum mouth opening. J Can Dent Assoc 2003;69:736-40.  Back to cited text no. 11
    
12.
El Abdin H, Al-Shalan T, Al-Bisher G. Normal mouth opening in Saudi population. Saudi Dent J 1991;3:99-101.  Back to cited text no. 12
    
13.
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. 13
    
14.
Dijkstra PU, Bont LGM, Stegnenga B, Boering G. Angle of mouth opening measurement: Reliability of a technique for a temporomandibular joint mobility assessment. J Oral rehabil 1995;22:263.  Back to cited text no. 14
    
15.
Sousa LM, Nagamine HM, Chaves TC, Grossi DB, Regalo SC, Oliveira AS. Evaluation of mandibular range of motion in Brazilian children and its correlation to age, height, weight, and gender. Braz Oral Res 2008;22:61-6.  Back to cited text no. 15
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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