INTRODUCTION:

The range of mouth opening is a factor that helps in diagnosis of many clinical conditions and has implications in the treatment of maxillofacial disorders. It is necessary to know a normal range of mouth opening that enable the clinician to conduct a oral examination conveniently.[1] A reduction of mouth opening may cause masticatory and social difficulties for the patient and Clinically, a reduction in mouth opening creates problems for the dentist and the mandibular function is performed by means of several diagnostic tests including muscle and joint palpation, occclusal evaluation and radiographic examination.

Since, maximal mouth opening is the combined result of movement of temporo-mandibular joint (TMJ) and action of mandibular musculature and the facial type and also found that individuals with vertically short facial pattern had thick masseter and those with long face had thin masseter [2,3]. The rationale behind finding a maximal mouth opening was that, several studies have found a relation between facial musculature and its effect on arch width and also on facial type [1,2].

Gender differences have been shown, with men having the tendency to open on average five mm more than women.[4] Measurements range from 40 mm to 77 mm in male subjects, with more frequent values around 50-60 mm, and from 32 mm to 75 mm in female subjects, 17 with more frequent values around 45-55 mm.

Clinical measurement of normal range of mouth opening is an important diagnostic tool for evaluation of stomatognathic system, especially in those who have suspected temporomandibular and neurogenic dysfunctions. Maximal mouth opening can also be helpful in providing necessary information for designing of dental instruments or prosthesis [5].During clinical examination, limitation of maximum mouth opening is considered an important sign of a possible diagnosis of Temporal mandibular joint disorder. Limited mouth opening can be associated with TMJ dysfunction, trauma, neuromuscular disorders, odontogenic infection, congenital and developmental anomalies and advanced malignancies.[6]Any restriction in mandibular mobility is commonly accepted as one of the main signs of mandibular dysfunction, and so it is an important criterion for the evaluation of functional state of the masticatory system. In order to make a diagnosis of decreased mouth opening, it is essential that we know the range of normal mouth opening for that particular population.

The maximum opening of the mouth can be measured by interincisal distance. Maximal mouth opening is described as the distance between incisal edge of maxillary central incisor to the incisal edge of mandibular central incisor, when the mouth is opened as wide as possible painlessly.[7]

Therefore, the purpose of the present investigation is to obtain the normal range of mouth opening among children in Chennai. And also to evaluate the possible relationship between mouth opening, age, gender, height, and body weight.

MATERIALS AND METHODS:

The study was approved by the Scientific review board of Saveetha Dental College, Saveetha University. This study consisted of 300 subjects from schools in the Chennai city of India. A convenience sampling was done in 5 Zones of Chennai, involving 60 children from each zone. The children between the ages of three and twelve years were included in the study.

Information that included age and gender, any previous history of trauma, tenderness or clicking sound at rest or during jaw movements and any head and neck disorders. The child was also asked to give information about other types of conditions such as, any systemic diseases, neurological disorders or craniofacial deformities that would affect the maximal mouth opening in children. Information from parents of 450 children were obtained regarding children who fulfilled the below mention of inclusion and exclusion criteria were taken up for the study.

The inclusion criteria were children with no history of trauma, no history of pain in the jaw, face, or neck, either at rest or during function, no history of facial or dental abnormalities, no history of temporomandibular joints sounds, and no dental prosthesis on the anterior teeth.

The exclusion criteria were subjects with severe orthodontic problems (anterior cross bite), neurological disorders and craniofacial deformities, systemic diseases (juvenile rheumatoid arthritis), and neck pain, which have been reported to create limited mouth opening. Because children with these conditions has a chance of limited mouth opening. However, the present study measures the normal range of maximal mouth opening in healthy Indian children. Data contributed by this study will help in maximal mouth opening in healthy children.

The children were randomly selected into three groups based on the age:

Group I : Children of age three to six years

Group II : Children of age six to eight years

Group III: Children of age eight to ten years

Group IV: Children of age ten to twelve years

The maximal mouth opening, body weight, and height were recorded in all four groups. The measurements of were maximal mouth opening correlated with the body weight and height of the children in different age groups.

PROCEDURE FOR MEASURING MOUTH OPENING:

After obtaining informed consent from the school authorities and parents, a clinical examination was performed. Measurement of maximal mouth opening was recorded by asking the subjects to open their mouth as wide as possible twice, while the examiner measured maximum distance from a marked dot on the base of the nose and a second marked dot on the chin at the midline; only the widest maximal mouth opening was retained. The choice of using landmarks other than the teeth was due to the fact that many children in the age group of five to seven years had their central incisors either unerupted or partially erupted. The degree of mouth opening was measured using the distance between the incisal edges of upper and lower anterior teeth. Any deviation of the mandible during the opening was also observed.

During measurement, maximal mouth opening was recorded by asking the subjects to open their mouths as wide as possible, while the examiner measured the maximum distance from the inter incisal edge of the maxillary central incisor to inter incisal edge of mandibular central incisor. For each subject three readings were recorded in millimeters (mm) and the mean value was considered. The maximal mouth opening measurements were taken using a modified Vernier Caliper, while the subjects rested their heads against a wall surface in an upright position and their body weight was recorded in kilograms using a weighing balance. The height was measured, without shoes, in centimeters, using a metric scale. This was followed by palpation directly over the TMJ when the child opened and closed his mouth. The assessment of the extent of the mandibular condylar movement and auscultation of TMJ were done to elucidate any underlying TMJ disorder. This was followed by auscultation and palpation of masticatory and cervical muscles. All measurements were performed by a single examiner to avoid any variance. The measurements of maximal mouth opening were compared in children of different age groups. Similarly a correlation between the maximal mouth opening and body weight and height were also observed.

RESULT:

The MMO was measured in boys and girls aged between three and twelve years [Table 1]. The estimated average means maximal mouth opening ured for children at the age of three to six was 42.04 mm. The estimated average means maximal mouth opening ured for children at the age of six to eight years was 44.95 mm. The estimated average means maximal mouth opening ured for children at the age of eight to ten years was 48.38 mm. The estimated average maximal mouth opening measured for children at the age of ten to twelve year was 52.15 mm.

There was a gradual increase in maximal mouth opening with age, which was found to be statistically significant when compared between three and twelve year olds.

As shown in Table 1 there was a gradual increase in the height and weight of children with age. The maximal mouth opening was also found to increase with age, height and weight of children at different age groups.

Table 1: Mean value of maximum mouth opening (mm), height (cm), weight (kg) of children age from 3 to 12 years

AGE(YEARS)	MMO (mm)	HEIGHT(cm)	WEIGHT (kg)
3 – 6	42.04	110.05	19.24
6 – 8	45.95	124.53	28.46
8 – 10	48.38	139.80	34.84
10 -12	52.15	145.18	39.96

DISCUSSION:

The present study revealed that the maximal mouth opening in South Indian children were 42.04 mm, 45.95 mm, 48.38 mm and 52.15 mm in the age groups of three to six, six to eight, eight to ten, and ten to twelve years, respectively.

The maximal mouth opening has been described as the inter-incisal distance[8,9] Measurement of the inter-incisal distance means measurement of the vertical distance traveled by the mandible. However, as pointed out by Mezitis et al.[4]the functional opening of the mouth is more important, because this is the value that actually affects the chewing and dental treatment. It also helps in maintaining oral health in children.[10,11]. Hence, it is essential to estimate the normal maximal mouth opening. The inter-incisal distance during active opening has been used as the maximal mouth opening measurement in most studies.[9]

Travell and Simons[12] suggested using the first three knuckles(the index, middle, and ring fingers) of the nondominant hand to assess normal maximal mouth opening, and since the value of the width of three knuckles is higher than the value of the width of three fingers, such an approach would probably be more accurate according to the results of this survey. It gives us an intermediate measurement between the width of three and four fingers, as maximal mouth opening seems to be in children. Another difference between this study and the one performed by Lobo Lobo S,[13] be due to the difference between adults and children, is that the percentage of subjects able to open wide enough to position four fingers between the upper and lower incisors is much higher: 36.3% (37 out of 102 subjects) versus 8.6% (12 out of 140 subjects).The disadvantage with this method is that a normal maximal mouth opening in children may be greater than the width of three fingers.

However, Wood and Branco[14] compared direct and extra oral measurements, and suggested that direct measurements using a ruler or Vernier caliper are more precise and accurate. Hence in the present study measurement of maximal mouth opening was done with vernier caliper to ensure accurate resulted.

In the present study which included South Indian children aged three to twelve years, a positive correlation was found between maximal mouth opening, age, height, and body weight. The present study reported a gradual increase in maximal mouth opening in the different age groups of children. The maximal mouth opening steadily increases after birth until adolescence[8,9,12,13]and then gradually decreases as aging progresses.[6] Similar findings were observed in studies conducted by Ingervall [15], L and twig[16], Sousa[17] and Henrikson[18]. On other hand, Lukas Muller[19] found a correlation between maximal mouth opening values in relation to height and weight in all age group. The same characteristic of a small but there is a increase of maximal mouth opening with age accompanied by large range in every age group was also observed by Hirsh et al. [20] who assessed a sample of children from 10 to 17 years. There is a slight increase of mouth opening with age in children and adolescents is increases by growth of mandible. Growth results in increasing in mandibular length which influences the linear incisal measurement. The study is done in Zurish population and found that data findings is predominant in caucasian population.[21,22]. In this present study, data findings is found predominant in trividaian population.

It was observed in the present study that male children had a greater maximal mouth opening than female children. Only few reports describe gender difference in maximal mouth opening in children.[19-22] In a longitudinal study done by Ingervall female 10-year old subjects showed values of maximal mouth opening similar to adult females but the same was not true for male participants.[20]

In the present study it was seen that children who are taller had a greater maximal mouth opening than other children. The study Jalis Fatima et al [23] conducted correlating maximal mouth opening, weight, height and facial type of all age group. They found that the maximal mouth opening was mostly directly propotional to age, height and weight in euryproscopic face type children when compared to mesoproscopic face type and leptoproscopic face type. Pearson correlation coefficient showed a positive correlation of 0.27 between maximal mouth opening and height, which is in concordance with the findings of Landtwig,[16] and Ingervall.[15]. A higher correlation of 0.45 for the children was seen in his study.

Children who weighed more had a greater maximal mouth opening than other children. This is in contradictory to the study conducted by Youssef S[24] in Saudi Arabia who found that maximal mouth opening was inversely proportional to body weight of children. The findings in the present study could be attributed to the fact that Dravidian children may have more tendency to use their temperomandibular joint or the genetic make which could have contributed to the wide opening of mouth.

Head position also plays a very important role in determining the measurement of maximal mouth opening [19]. Values of maximal mouth opening were seen to vary in forward, natural or retracted head positions in a study conducted by Machado BC et al., [25]. Thus, in the present study, maximal mouth opening was measured with the head of the subjects in an upright position and rested against a firm wall surface, so as to eliminate the possible influence of different head positions on values of maximal mouth opening.

If mouth opening is limited it can lead to improper maintenance of oral hygiene. This causes higher incidence of both dental caries and periodontal diseases. To overcome this difficulty chewable tooth brush can be used.[26]

Assessment of the mouth opening is an important part of the clinical examination for a clinician or physician involved in the treatment of head and neck disorders [27]. A study was conducted correlating temporomandibular joint ankylosis and maximal mouth opening among Chennai population.[28]. In order to diagnose an abnormality, knowledge of the normal condition is essential. The study, in combination with clinical condition, serves as an available approach for clinical decision making, to diagnose severe diseases related to the function of the masticatory system.[29].

CLINICAL IMPLICATION OF PRESENT STUDY:

After knowing the average range of normal maximal mouth opening, it can help the clinician to know if there is any limitation in mouth opening of any individual and can also help in evaluating the improvement during or after treatment.

CONCLUSION:

The present study revealed that the maximal mouth opening in Indian children were 42.04 mm, 45.95 mm, 48.38 mm and 52.15 mm in the age groups of three to six, six to eight, eight to ten, and ten to twelve years, respectively. Age has a significant influence on the maximal mouth opening values. Maximal mouth opening increases with age. A definite correlation exists between maximal mouth opening and height and weight. Maximal mouth opening is found to increase as height and weight increases.

RECOMMENDATIONS:

Future studies are to be conducted involving larger number of children belonging to various ethnic groups. Designing of dental instrument and prosthesis can be done depending on the average mouth opening of children in a particular population.

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Received on 15.12.2017 Modified on 27.01.2018

Research J. Pharm. and Tech. 2018; 11(3): 1092-1096.

DOI: 10.5958/0974-360X.2018.00205.6