Association between Chewing Gum Use and Clinical Signs of Temporomandibular Disorders (TMD) Chewing gum and TMD pain
Jasmin Lappalainen†, Anna Liisa Suominen‡, Nina Zaproudina§, Matti Närhi¶, Kirsi Sipil䆆
†Dental Student, Institute of Dentistry, University of Eastern Finland, Kuopio, Finland
‡ Institute of Dentistry, University of Eastern Finland, Kuopio, Finland
Department of Oral and Maxillofacial Diseases, Kuopio University Hospital, Kuopio, Finland, Public Health Evaluation and Projection Unit, National Institute for Health and Welfare (THL), Helsinki, Finland
§ Institute of Dentistry, University of Eastern Finland, Kuopio, Finland and Kuopio University Hospital, Kuopio, Finland
¶ Institute of Dentistry and General Biology, University of Eastern Finland, Kuopio, Finland
††Research Unit of Oral Health Sciences Faculty of Medicine, University of Oulu, Oulu, Finland, and Medical Research Center, Oulu, Oulu University Hospital, Finland, Institute of Dentistry, University of Eastern Finland, Kuopio, Finland
The present study is part of the Health 2000 Survey, organized by the National Institute for Health and Welfare (THL), the former Public Health Institute (KTL) of Finland (http://www.terveys2000.fi/indexe.html), and partly supported by the Finnish Dental Society Apollonia and the Finnish Dental Association.
(Tutkielma on muokattu lehteen lähetettävän käsikirjoituksen ulkoasuun)
Abstract
Background Temporomandibular disorders (TMD) can be associated with excessive load of temporomandibular joints (TMJs) and masticatory muscles due to parafunctions, such as chewing gum use. Some previous studies indicate that there could be an association between chewing gum use and TMD signs and symptoms. Objectives The aim of this population-based study was to examine the association of chewing gum use with signs of TMD. Methods The data came from the Health 2000 Survey (BRIF8901) conducted in 2000-2001 by the National Institute for Health and Welfare (THL) in Finland. Clinical oral examination was performed for 6,335 participants, of whom 6,318 were examined for signs ofTMD (restricted mouth opening, TMJ sounds and palpation pain in TMJs and masticatory muscles). Of these, 6,136 participants also answered questions
concerning use of chewing gum. The associations of each TMD sign with the use of chewing gum were evaluated using chi-square tests. Logistic regression analyses were used to study these associations, adjusted for age and for level of education and stratified by gender. Results TMD signs, such as restricted mouth-opening in men (odds ratio, OR = 0.5; 95% confidence interval, CI = 0.3-1.0) and women (OR= 0.5; 95% CI = 0.3-0.8) and muscle palpation pain in women (OR = 0.6;
95% CI = 0.4-1.0), were inversely associated with chewing gum use. Conclusion Use of chewing gum appears to be negatively associated with TMD signs. Thus, people having TMD signs may possibly avoid using chewing gum. Keywords pain, TMJ, chewing gum, muscle pain,
temporomandibular disorders, temporomandibular joint disorders.
Background
Temporomandibular disorders (TMD) are dysfunctions of the temporomandibular joints (TMJ), masticatory muscles and related structures.1 TMD signs include TMJ sounds during jaw movements, pain in TMJs and masticatory muscles, and restricted jaw movements1,2.
The aetiology of TMD is multifactorial. Several local and general factors can exist in the background.
Besides anatomical and occlusal characteristics and traumas, TMD can also be associated with excessive load of TMJ and masticatory muscles due e.g. to parafunctions.3,4 The use of chewing gum can be regarded as one form of overloading factor, and further studies are needed to examine its potential role in aggravating TMD signs and symptoms. It should also be noted that a person’s individual adaptability to these aetiological factors, depending on, for example, genetics and biological, e.g. hormonal factors, may affect the individual’s vulnerability to these symptoms.5,6,7,8 TMD are common in the population. In a Finnish population-based study at least one TMD sign was found in 38% of the participants in a clinical examination.9 Using xylitol for caries prevention is a Finnish invention.10 Several different xylitol pastilles and xylitol chewing gums have received the Finnish Dental Association’s recommendation.11 The use of chewing gum is relatively prevalent in the Finnish population. In the Health 2000 Survey, 13 percent of adults reported that they used chewing gum daily.12
Some previous studies indicate that there could be a positive association between chewing gum use and TMD signs and symptoms. Studies have led to the finding that chewing gum use increases the risk of TMD signs13 and symptoms14,15. Furthermore, longer duration of gum chewing has been shown to be connected to increased incidence of TMD signs.13 According to a study by Correia et al., arthralgia and myofascial pain were statistically significantly more common in those who used chewing gum than in non-users.14 It has also been found that during gum chewing the participants’
jaw-movement smoothness is decreased compared to empty chewing.16 Additionally, it has recently been shown that gum chewing is associated with headache, restricted mouth opening and TMJ and masticatory muscle disorders.15
All the studies mentioned above were targeted to special groups. Therefore, additional population- based studies are needed to investigate the relationship between gum chewing and TMD. The comprehensive Finnish population-based Health 2000 Survey offers possibilities to evaluate these associations.
The aim of the present study was to examine the association of chewing gum use with TMD signs in a population-based sample of Finnish adults.
Methods
The Health 2000 Survey (BRIF8901) was conducted in 2000-2001 by the National Institute for Health and Welfare in Finland (THL). The main sample covered 8,028 adults aged 30 years or older living in mainland Finland. Of these, 79% (n=6,335) participated in a clinical oral examination, and 6,318 of them where examined for signs of TMD. The data of this study covered 6,136 adults who answered the questions about chewing gum use and also went through the TMD examination. More detailed information about the Health 2000 Survey can be viewed at https://www.thl.fi/fi/tutkimus-ja-
asiantuntijatyo/vaestotutkimukset/terveys-2000-2011. The Health 2000 Survey was approved by the Ethical Committee for Epidemiology and Public Health of the Hospital District of Helsinki and Uusimaa and by the Ethical Committee of the National Public Health Institute (KTL) of Finland. Each participant in the study gave their informed consent.
Assessment of TMD signs
“A standardized clinical oral examination was performed by five calibrated and experienced examiners (dentists), who assessed the signs of TMD. The examiners were trained by experienced specialists in order to increase the reproducibility of the clinical examinations. The clinical examination technique for assessment of the signs of TMD was trained and calibrated, and each examiner’s protocol was videotaped to be reviewed and discussed immediately afterwards.
Reference measurements were performed for 269 participants by the examiner, followed immediately by the reference examiner. The percentage agreement between examiners and the reference examiner was 95% (kappa value 0.56; 95% confidence interval [CI] = 0.34-0.77) for maximum interincisal distance, 84% (kappa value 0.44; 95% CI = 0.35-0.52) for TMJ clicking, 91%
(kappa value 0.21; 95% Cl = 0.13-0.29) for TMJ crepitation, 92% (kappa value 0.26; 95% CI = 0.19- 0.34) for TMJ pain on palpation, and 95% (kappa value 0.47; 95% Cl = 0.41-0.53) for pain on palpation of the masticatory muscles”.17,18
“The assessment of TMD signs included the recording of maximum vertical mouth opening, auscultation of TMJ noises, and palpation of the TMJ and two masticatory muscles (anterior temporalis and superficial masseter). Maximum mouth opening was measured with a ruler and reported as maximum interincisal distance without overbite. It was categorized as limited when less than 40 mm. The mouth opening was measured in both dentate participants and denture wearers.
TMJ clicking and/or crepitation were recorded with gentle digital palpation bilaterally over the TMJ region while the participant opened and closed the mouth. TMJ pain was measured by palpating with a force of about 5 N over the unmoving condyle, and muscle pain by palpating with a force of about 10 N. Attempts were made to standardize the palpation force by exerting the forces on a measuring scale between the examinations. TMJ and muscle pain on palpation were recorded if participants reported pain when asked, or showed a protective response. Except for the maximum interincisal distance, all the findings were recorded separately for both sides, and they were combined and categorized as either present or absent. Five dichotomous variables were formed:
limited maximum mouth opening, TMJ clicking, TMJ crepitation, pain at least in TMJ, and pain in at least one masticatory muscle”.18
Chewing gum use
Information on chewing gum use was obtained using some of the questions regarding the use of sugar products, “How often do you consume the products listed below?”. The participants were asked how often they use chewing gum with or without xylitol (two separate questions) by a scale from 0 to 4, (0 = never, 1 = rarely, 2 = weekly 2-5 times, 3 = daily 1-2 times and 4 = daily 3 times or more). If a participant answered both these questions, only the “higher” answer was recorded.
Potential confounding factors
Age and gender were obtained from the Population Register Centre and level of education was obtained from the interview - these were used as cofactors. Age was categorized into three groups (30-44, 45-59 and 60 + years). Education was categorized into basic, secondary, or higher education.
The basic education category included those with no formal vocational training or senior secondary education, secondary education included those who had completed vocational training or passed the matriculation examination and higher education comprised degrees or diplomas from higher vocational institutions, polytechnics and universities. 18
Statistical analyses
The associations of each of the five TMD signs with the use of chewing gum were evaluated using chi-square tests in IBM SPSS Statistics. Logistic regression analyses were used to study the associations of use of chewing gum with the risk of having separate TMD signs, adjusted for age and for level of education and stratified by gender.
Results
Description of the study participants is presented in Table 1. All TMD signs were statistically significantly more prevalent in women than in men (p<0.001). In women the most common sign was muscle palpation pain (19.7%) and in men TMJ clicking (12.9%). The frequency of reported chewing gum use was statistically significantly higher in women than in men (p<0.001).
The use of chewing gum was inversely associated with restricted mouth opening and muscle palpation pain in both genders and with TMJ crepitation in women. The highest prevalences of restricted mouth opening, muscle palpation pain and TMJ crepitation were recorded among those reporting never using chewing gum (Table 2).
When adjusted for age group and level of education, an inverse association of frequent use of chewing gum with restricted mouth opening was observed in both genders, and with muscle palpation pain in women, (Table 3).
Discussion
The results of the present study indicate that infrequent use of chewing gum is associated with an increase of two TMD signs: restricted mouth opening and masticatory muscle palpation pain. After confounding factors were considered in logistic regression, restricted mouth- opening in both genders and muscle palpation pain in women were still significantly associated with infrequent chewing gum use. These two TMD signs were both most common in those who never use chewing gum.
When comparing the present study to earlier studies, these have all observed TMD signs, at least partly, by clinical examination. The present study is population-based, whereas earlier studies were targeted to smaller, specific groups such as university or high school students.
In contrast to the present results, earlier studies indicate that people using chewing gum have greater risk for TMD signs and symptoms than non-users. 13,14,15
In comparison to some earlier studies, the assessment of chewing gum use is more inaccurate in the present study. Only the frequency of chewing gum use was recorded, but not e.g.
the length of time of gum use, as for example in the study of Tabrizi et al. 201413, a cross-sectional study of 200 participants including university students and employees. In their study, instead of self-reported chewing gum use, the study group was advised to use chewing gum an exact time per day. The control group (n=100) consisted of non-users. The incidence of TMJ clicking and TMJ pain was higher in those who used chewing gum. The study of Correia et al. 201414 was a single- centre, randomized study with 50 participants (university students). Chewing gum use was self- reported, but in addition to weekly using times, the number of using times per day was also recorded. The study of Mejersjö et al. 201615 was performed with high school students (n=124).
Chewing gum use and the prevalence of TMD symptoms were investigated by self-reported questionnaires. In addition to questionnaires, clinical examination of the TMD signs was
performed on 116 of the participants. In that study, chewing gum use was statistically significantly associated with headache, restricted mouth-opening and stiffness of the masticatory muscles and TMJs.
Having TMD signs such as restricted mouth-opening or muscle pain can possibly lead to avoidance of chewing gum use, which may at least partly explain the inverse associations found in the present study compared to previous ones. This can be one of the reasons why it seems as if non-users have a greater risk for TMD signs than users. Because this is a cross-sectional study, it remains unknown whether the participants with TMD signs had used chewing gum more often earlier in their lives. Possibly, earlier chewing gum use could be one of the background or aggravating factors for the restricted mouth-opening or muscle pain, and thus had led to avoidance of the habit.
Because the present study is part of the extensive, population-based Health 2000 Survey, it was possible to obtain data concerning TMD signs in the Finnish adult population as a whole. This is one of the major strengths of the study. It was also possible to use many outcome variables, such as the main signs of TMD and a number of confounding factors, due to extensive data material. Assessment of TMD signs clinically instead of using mere self-reported questions was another strength of the study. Furthermore, repeatability of the clinical examination was good, excluding the recording of TMJ crepitation (kappa value 0.21) and TMJ palpation pain (kappa value 0.26). However, for practical reasons, not all the TMD signs evaluated in the clinical
examinations could be included in the present study. Such signs are, for example, pain during mandibular movements, as well as palpation pain in other masticatory muscles in addition to masseter and temporalis. It should be noted that the data of this study does not support making TMD diagnoses, but only observes TMD signs. Also, for practical reasons, the clinical examinations were performed by general dentists rather than specialists, which may have caused some
inaccuracy in the measurements. When behavioral assessment is based on self-reports, recall bias is always a concern. When participants are asked to inform how often they use chewing gum, the information is based on their memory. Information about not using chewing gum at all is more reliable. Thus, it is more important to ascertain whether there is chewing gum use at all than to enquire how often.
The present study adds to understanding of the association between chewing gum use and TMD signs. Although causal inferences cannot be drawn due to the cross-sectional design of the study, the results do support earlier studies indicating that TMD signs and chewing gum use are statistically significantly associated, although inversely in our study. Therefore, the most interesting result of this study is that chewing gum users had less TMD findings than non-users.
There are many confounding factors; in addition to the factors observed in this study, it is
important to bear in mind e.g. individual variation, for example in occlusion, dental status,
strength of masticatory muscles and function of TMJs. Apart from normal anatomical variation and traumas, diseases such as rheumatism or muscular dystrophy can affect the presence of TMD signs. However, in conclusion, there is a need for a longitudinal study to evaluate the causality between TMD signs and symptoms and chewing gum use.
References
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An association between temporomandibular disorder and gum chewing. Gen Dent 2014;62:33-36
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Table 1. Description of the Study Participants (n=6136).
Total n (%)
Men n (%)
Women n (%)
P-value
TMJ¶ pain onpalpation †† p < 0.001*
All 6136(100.0) 2790(100.0) 3346(100.0)
No 5895(96.1) 2723(97.6) 3172(94.8)
Yes 241(3.9) 67(2.4) 174(5.2)
Restricted mouth opening ‡‡ p < 0.001*
Missing 57(0.9) 40(1.4) 17(0.5)
No 5531(90.1) 2580(92.5) 2951(88.2)
Yes 548(8.9) 170(6.1) 378(11.3)
Muscle pain on palpation §§ p < 0.001*
Missing 1(0.0) 1(0.0) 0(0.0)
No 5263(85.8) 2576(92.3) 2687(80.3)
Yes 872(14.2) 213(7.6) 659(19.7)
TMJ Clicking ¶¶ p < 0.001*
Missing 2(0.0) 0(0.0) 2(0.1)
No 5178(84.4) 2431(87.1) 2747(82.1)
Yes 956(15.6) 359(12.9) 597(17.8)
TMJ Crepitation ††† p < 0.001*
Missing 2(0.0) 0(0.0) 2(0.1)
No 5641(91.9) 2642(94.7) 2999(89.6)
Yes 493(8.0) 148(5.3) 345(10.3)
Chewing gum use ‡‡‡ p < 0.001*
Missing 0(0.0) 0(0.0) 0(0.0)
Never 2088(34.0) 929(33.3) 1159(34.6)
Rarely** 2091(34.1) 1130(40.5) 961(28.7)
Weekly 2-5 times 1116(18.2) 450(16.1) 666(19.9)
Daily 1-2 times 522(8.5) 175(6.3) 347(10.4)
Daily ≥3 times 319(5.2) 106(3.8) 213(6.4)
Level of education p < 0.001*
Missing 17(0.3) 8(0.3) 9(0.3)
Basic† 2368(38.6) 1040(37.3) 1328(39.7)
Secondary‡ 1991(32.4) 1066(38.2) 925(27.6)
Higher§ 1760(28.7) 676(24.2) 1084(32.4)
Age(years) p < 0.001*
Missing 0(0.0) 0(0.0) 0(0.0)
30-45 2120(34.6) 1002(35.9) 1118(33.4)
45-60 2151(35.1) 1031(37.0) 1120(33.5)
60+ 1865(30.4) 757(27.1) 1108(33.1)
† No formal vocational training or senior secondary education.
‡ Completed vocational training or passed the matriculation examination.
§ Degrees or diplomas from higher vocational institutions, polytechnics, and universities.
¶ Temporomandibular joint.
†† Pain on palpation in right, left or both sides during mouth opening (at least one of the temporomandibular joints).18
‡‡ Distance between the incisal edges of the upper and lower front teeth less than 40 mm.18
§§ Pain on palpation in right, left or both sides in masseter superficialis or temporalis anterior muscle (at least in one muscle).18
¶¶ Clicking and ††† crepitation during mouth opening.18
‡‡‡ Use of either xylitol or non-xylitol chewing gum.
* Chi-square test between genders.
** Maximally once a week
Table 2. Prevalence (%) of Clinical Signs of Temporomandibular Disorders in Men and Women by Chewing Gum Use among 6136 Finnish adults.
TMJ† pain on palpation
‡
n=6136
Restricted mouth opening §
n=6079
Muscle pain on
palpation ¶ n=6135
TMJ clicking ††
n=6134
TMJ crepitation ‡‡
n=6134 Use of chewing
gum§§
Men n=2790
Women n=3346
Men n=2750
Women n=3329
Men n=2789
Women n=3346
Men n=2790
Women n=3344
Men n=2790
Women n=3344 n (%)
All 67(2.4) 174(5.2) 170(6.2) 378(11.4) 213(7.6) 659(19.7) 359(12.9) 597(17.9) 148(5.3) 345(10.3) never 15(1.6) 74(6.4) 89(9.9) 201(17.6) 94(10.1) 313(27.0) 122(13.1) 207(17.9) 52(5.6) 145(12.5) rarely 33(2.9) 40(4.2) 62(5.5) 90(9.4) 70(6.2) 169(17.6) 150(13.3) 160(16.6) 61(5.4) 90(9.4) weekly 2-5times 12(2.7) 30(4.5) 12(2.7) 55(8.3) 32(7.1) 101(15.2) 53(11.8) 126(18.9) 20(4.4) 67(10.1) daily 1-2times 3(1.7) 19(5.5) 5(2.9) 19(5.5) 9(5.1) 52(15.0) 22(12.6) 63(18.2) 8(4.6) 23(6.6) daily ≥3 times 4(3.8) 11(5.2) 2(1.9) 13(6.1) 8(7.5) 24(11.3) 12(11.3) 41(19.2) 7(6.6) 20(9.4) P-value *
(Chi-square test)
0.278 0.191 <0.001 <0.001 0.011 <0.001 0.919 0.778 0.847 0.014
† Temporomandibular joint.
‡ Pain on palpation in right, left or both sides during mouth opening (at least one of the temporomandibular joints).18
§ Distance between the incisal edges of the upper and lower front teeth less than 40 mm.18
¶ Pain on palpation in right, left or both sides in masseter superficialis or temporalis anterior muscle (at least in one muscle).18
††Clicking and ‡‡ crepitation during mouth opening.18
§§ Use of either xylitol or non-xylitol chewing gum.
* Chi-square test between chewing gum use and TMD signs separately in men and women.
Table 3. Adjusted* associations of Chewing Gum Use with Occurrence of Signs of Temporomandibular Disorders (TMD) separately in 6119 Finnish Men and Women.
OR= Odds Ratio, 95%CI = 95% Confidence Interval, Ref. = Reference category, * = for Age Group and Level of Education
† Temporomandibular joint.
‡ Pain on palpation in right, left or both sides during mouth opening (at least one of the temporomandibular joints).18
§ Distance between the incisal edges of the upper and lower front teeth less than 40 mm.18
¶ Pain on palpation in right, left or both sides in masseter superficialis or temporalis anterior muscle (at least in one muscle).18
††Clicking and ‡‡ crepitation during mouth opening.18
§§ Use of either xylitol or non-xylitol chewing gum.
* Chi-square test between chewing gum use and TMD signs separately in men and women.
Use of chewing gum §§ TMJ† pain on palpation‡ Restricted mouth opening§ Muscle pain on palpation¶ TMJ Clicking†† TMJ Crepitation‡‡
Men Women Men Women Men Women Men Women Men Women
OR (95% CI)
never (ref.) - - - - - - - - - -
rarely 1.6(0.8-3.1) 1.0(0.6-1.5) 0.9(0.6-1.3) 0.7(0.6-1.0) 0.9(0.6-1.3) 0.9(0.7-1.1) 1.0(0.8-1.4) 1.0(0.7-1.2) 1.0(0.7-1.5) 1.0(0.7-1.3) weekly 2-5times 1.4(0.6-3.3) 1.2(0.7-2.0) 0.5(0.3-1.0) 0.7(0.5-1.1) 1.2(0.8-2.0) 0.8(0.6-1.1) 0.9(0.6-1.3) 1.1(0.9-1.5) 0.9(0.5-1.6) 1.2(0.9-1.7) daily 1-2times 0.9(0.2-3.3) 1.6(0.9-2.8) 0.6(0.2-1.5) 0.5(0.3-0.8) 0.9(0.4-1.9) 0.9(0.6-1.2) 1.0(0.6-1.6) 1.1(0.8-1.5) 0.9(0.4-2.0) 0.8(0.5-1.3) daily ≥3 times 2.0(0.6-6.4) 1.4(0.7-2.9) 0.4(0.1-1.5) 0.6(0.3-1.0) 1.3(0.6-2.8) 0.6(0.4-1.0) 0.9(0.4-1.6) 1.2(0.8-1.8) 1.4(0.6-3.2) 1.2(0.7-2.0) P-value *
(Chi-square test)
0.549 0.082 0.023 0.002 0.594 0.037 0.559 0.195 0.760 0.733
