- Email: [email protected]
The social and psychologic factors of bruxism
The socia.1 and psychologic Gina Pingitore, James Petrie,
M.A.,* Vickyann D.D.S.***
Loyola
Chicago,
University,
Chrobak,
factors
of bruxism
D.D.S., M.S.,** and
111.
Bruxism is a destructive habit that is defined as the nonproductive diurnal or nocturnal cl.enching or grinding of the teeth. This study investigated whether the combination of physical abnormalities, type A behavior pattern, and the perceived desirability and controllability of life stress are related to bruxism. The subjects for the study were 125 dental patients who were classiled as bruxers or nonbruxers by a licensed dentist and who completed two measures, the Jenkins Activity Survey, and a modified version of the Holmes and Rahe Life Events Scale. Regression analyses indicate there is a difference in the separate impact of each variable. Type A behavior and physical abnormalities are significant in a stepwise analysis, while stress is not. Stress appears to be significant only in conjunction with type A behavior, and suggests that the combination of type A behavior, and stress is more predictive of bruxism than either of the individual variables. The linear combination of physical abnormalities. type A behavior, and stress is significant, and suggests that it is the best predictor of bruxism. (J PROSTRET DENT1991;65:443-6.)
B
ruxism is an involuntary, parafunctional, excessive grinding, clenching, or rubbing of the teeth. It is a potentially destructive habit that results in tooth wear, damageto the structure of the surrounding teeth, inflammation and recessionof .the gums, increasedrisk of periodontal disease,musclepain, and temporomandibular joint (TMJ) dysfunction.’ These symptoms are also associatedwith headaches,jaw aches, and stiffness or tightening of the shoulders and neck.2 Conservative estimates of the incidence of bruxism range from 5 % to 10% in the adult population.3Many other researchersbelievethat the actual percentageismuch higher and suggestthat mostadults will brux at somepoint in their life.4 Although there is some disagreementin the literature about the incidenceof bruxism,all studiessuggestthat bruxism affects a large portion of the population and that its consequencescan be insidious and highly destructive. Although bruxism has been frequently researchedand well documented in the medical literature since 1901, its etiology remainsdebatable.5To many researchers,bruxism is viewed as the result of physical abnormalities such as mutilated occlusion, excessive cuspal inclinations, and working or balancing interferences6 Yet when other researchersattempted to replicate thesefindings, conflicting and at times opposingconclusionsresulted. For example, Olkinuora7 found no statistical correlation betweenthe incidence of malocclusionand bruxism.
*Ph.D. candidate, Department of Psychology. **Director of Clinics, School of Dentistry. ***Assistant Professor, Department of Fixed School of Dentistry.
10/l/24231 THEJOURNAL
OF PROSTHETIC
DENTISTRY
Prosthodontics,
Table
I. Correlations of physical abnormalities Jaw
Jaw relation (X = 4.1; S.D. = 0.17) T.M.J. (X = 0.23; S.D. = 0.05) Muscle palpation (X =0.58; S.D. = 10)
Muscle
relation
TMJ
palpation
1.00
0.52*
0.51*
-
1.00
037t
-
-
1.00
N = 125.
*p > 0.001. tp > 0.0001.
As a result of inconsistent support for a physical propensity to brux, other researchersproposed that certain psychologicfactors are associatedwith bruxism. Many researchersbelieve that bruxism is related to certain personality characteristics such as aggressiveness,anxiety, hyperactivity, and a need for control.8-10In addition to personality characteristics, other researchers have explored the effect of life events on bruxing. Rugh and Solberg” and Funch and Galei found that bruxism correlated with both experiencedand anticipated life stress,and they suggestedthat life stressplays an important role in the frequency, duration, and severity of bruxism. Review of the literature on bruxism suggeststhat the personality characteristics describedby many researchers suchasMolton and Levin,13are descriptionsof what Freidman and Rosenman14called a type A behavior pattern.” The literature alsosuggeststhat the perception of the desirability and controllability of life stressmay play an important role in bruxism, but only as it relates to the personality characteristicsof the individual. In an attempt to bridge the gap between the psychologic and physical
443
PINGITORE,
Table
II.
Correlation
CHROBAK,
AND
PETRIE
of physical and psychologic factors with bruxism
Type A (X = 217; S.D. = 75) Stress (X = 73; S.D. = 64) Mechanical (X = 0.00; S.D. = 2.5) Bruxism
Type A
Stress
1.00 -
0.24t
Mechanical
Bkwxism
0.17* 0.26f
1.00 -
0.27$ 0.267 0.28$
1.00 -
1.00
N = 125. ‘p = 0.02. tp = 0.002. $p = 0.001.
processes associated with bruxism, this study investigates bruxism as it relates to type A behavior, the product of the amount of life stress, and structural features that include the jaw and condylar relationship, muscle palpation, and internal derangement. To investigate this hypothesis, great care has been taken to operationally define type A behavior and stress and to select valid and reliable measures of these variables. A brief description of the definitions and measures used is given to provide a clearer understanding of this investigation.
DEFINITION AND PSYCHOLOGICAL
MEASURES CONSTRUCTS
OF THE
Type A. Freidman and Rosenma@ define type A behavior as an “action-emotion complex that can be observed in any person who is aggressively involved in a chronic, incessant struggle to achieve more and more in less and less time, and if required to do so, against the opposing efforts of other things or other persons.“15 The type A personality consists of six patterns: (1) an intense desire to achieve; (2) a need to compete; (3) a persistent, sustained need for recognition; (4) seemingly continuous involvement in many activities; (5) a habitual propensity to accelerate the rate of execution of all mental and physical functions; and (6) an extraordinary mental and physical alertness. Perhaps the most common impression that the public has of type A behavior can be described as hurried, accelerated, pressured, controlling, demanding, and highly ambitious. This description conjures up the picture of a person who is under high amounts of internally and externally induced stress, is driven to perform, is compelled to achieve, and to do these things quickly. Typical motor behaviors exhibited by type A personalities are excessive, rapid body movements characterized by tense facial and body muscle constriction, explosive speech intonations, hand or teeth clenching, and a general air of impatience. The measurement of type A behavior. The Jenkin’s Activity Survey (JAS) was used to measure type A behavior. It is a reliable (r 0.85) instrument that provides an overall score for type A behavior, plus separate scores for three subfactors: impatience, job involvement, and harddriving and competitive nature. This measure is frequently used and is well documented as a valid, reliable measure of type A behavior.16-18
444
Life stress. Life stress is operationally defined in terms of self-reported life changes, and physical illness.lg In addition, it is necessary to conceptualize life stress in terms of the perceptions of its desirability and controllability. In this investigation, life stress is viewed as a multiplicative relationship between the amount of life changes and physical illnesses and the perceived desirability and controllability of these events. The measurement of life stress. A modified version of Homes and Rahe’s Life Events Perception Scale (LEPS) was used in this investigation.zo This scale consists of questions to which respondents answer “yes” or “no” to a series of 57 items. For items answered “yes,” respondents then indicated their perception of the desirability and controllability of these events by using a 1 to 5 scale (1 = totally desirable/controllable; 5 = totally undesirable/ uncontrollable). To derive stress ratings for each of the 57 items, values of 1 were assigned to “yes” and 0 to “no.” These values were then multiplied by the rating of desirability and controllability. For example, if a patient answered “yes” to item 14 and rated it 3 for desirability and 4 for controllability, the value for this item equals 12. To obtain the total stress score, values were summed across all items.
MATERIAL
AND
METHODS
Subjects in this study were 125 dental patients who were being treated at Loyola University of Chicago Dental Clinic, Department of Fixed Prosthodontics. For the Methodology, each patient completed both the JAS and the modified version of the LEPS. Patients were also asked to answer specific questions designed to determine their awareness of the possibility that they brux. Questions were in a “yes/no” format and included items such as “do you grind your teeth?” “ do you frequently wake up with a headache?,” and “do you notice that your teeth are wearing down?” After the patients completed these measures, each-was evaluated by the same dentist, who was blind to patients’ responses on the psychologic measures. The dental examination included evaluations of the anterior and posterior wear facets and types of occlusion (Angle class I, II, or III). Based on this evaluation, patients were classified as a “bruxer” or “nonbruxer.” Several types of malocclusion were also evaluated. These were eccentric interferences,
MARCH
1991
VOLUME
66
NUMBER
3
TYPE
A BEHAVIOR
AND
BRUXISM
III. Two-by-two contingency table of number of correctly classifiedbruxers and nonbruxers
centric relation prematurities, and the general occlusion schemes. Signs and symptoms of temporomandibular joint (TMJ) disorders were evaluated without attempting to classify derangements other than noting the presence or absence of internal derangement or positive response to muscle palpation. From this evaluation, three scores were derived: a jaw and condylar relationship score, a TMJ score that included evidence of myofacial pain disorder (MPD) and internal derangement, and a muscle palpation score that showed evidence of palpation of the masseter, medial, lateral, and temporal muscles. On the basis of the correlation of these scores, it was decided to sum them and form an overall mechanical index (Table I). This index was then used in all analyses.
Table
RESULTS
Clinical
In order to determine the relationship between bruxism and the physical and psychologic measures, Pearson product-moment correlation coefficients were examined. Table II shows that st:ress, type A behavior, and the mechanical index are significantly related to bruxism, suggesting that each may play an important role in this disorder. To obtain a clearer picture of how these factors may relate to bruxism, a ;stepwise multiple regression analysis was used.21 Only the type A behavior and mechanical index scores were entered into the equation. The stress score failed to meet the default criteria for inclusion. To examine whether the combination of type A behavior and stress provides a fuller description of the bruxism process than does type A behavior alone, the difference between these equations was examined. This involved comparing the goodness-of-fit that was obtained from the combination of standardized type A behavior and stress scores to the goodness-of-fit that resulted from the individual variables. The result of this F ratio indicates that the equation for the combination of type A behavior and stress is different from the equation using each of these individual variables (F&120) = 10, p > 0.01). To test whether bruxism is the result of a linear combination of type A, stress, and physical abnormalities, a “brux-type” score was created. This score was created by converting the total scores for the mechanical index, JAS, and LEPS into standardized t scores and then summing them together. A bivariate regression analysis was employed using the “brux-type” variable defined above as predictive of bruxism. This relationship is significant (Multiple R = 0.35; F(1,123) = 16, p = 0.0001). Finally, decision theory, as discussed by Miller et a1.,22 was used to assess the probability of correctly classifying bruxers and nonbruxers, given this set of variables. A twoby-two contingency table of the number of patients correctly classified a.3a bruxer/nonbruxer is given in Table III. This table shows that the constructs used in this investigation better differentiate nonbruxers than they do hruxers. For nonbruxers, 62% werecorrectly classified(specificity),
The resultsof this investigation suggestseveral items of interest to clinical situations. Since the results of this investigation show that bruxism is not only related to physical abnormalities but also to behavior and life-style, dentists may find that somepatients will continue to brux no matter how much their dental condition is improved. In these patients, the dental materials used in restorative treatment should be resistant to wear and breakage. For instance,porcelain occlusalsurfaceson posterior crownsor large posterior composite resin restorations may be contraindicated. Teeth weakenedby large restorations would also be evaluated as potential cusp fractures due to the force produced by bruxing. The dentition may need to be protected with a prosthesisto be worn during times the patient is most apt to brux. When presenting treatment plans, dentists should be awareof “type A characteristics” so asto enlist patient cooperation. Information should be presentedto patients in personally relevant and salient ways, such as using audiovisual aidsto showthe effects of bruxism. This can help the patient comply with treatment recommendations,especially with the use of splints. Finally, since bruxism may affect the outcome of treatment of TMJ disordersand chronic pain, stepsshould be taken to control parafunctional activity. It may become important to refer patients to a stressor life-style management program if they brux severely and continuously, especially if the patients are highly competitive and are under life stress.These programs, with the appropriate and indicated dental care, can help them develop alternative skills neededto prevent seriousdamageto their teeth and related structure,
THE
JOURNAL
OF l?ROSTHETIC
DENTISTRY
Absent negatives
actual (AN)
Present positives
actual (AP)
Predicted bruxers
False
positives 12
True
positives
Predicted nonbruxers
True
negative 52 64
False
negatives 23 61
38
whereas only 62% of bruxers were correctly classified (sensitivity).
implications
SUMMARY This investigation attempted to find a correlation among bruxism, physical abnormalities, the type A behavior pattern, and the perception of the desirability and controllability of stress.Resultsfrom regressionanalysissuggestthe possibility that certain behavioral-emotional patterns and physical conditions may increasethe likelihood to brux. 445
PINGITORE,CHROBAK,ANDPETRIE
CONCLUSION As argued in previous literature, the etiology of bruxism is debatable. While the data presented here do not resolve this debate, they do provide greater insight into the relationship between the psychologic and physical factors of bruxism. To fully understand bruxism, further research is needed. Since other research has documented significant effects of stress on bruxism, a clearer understanding of the effect of this factor is needed. It may be important to assess stress using different measures or to define stress in terms other than life changes and illnesses. Nevertheless, this study shows that both physical and psychologic factors are associated with bruxism. REFERENCES 1. Ware JC, Rugh JD. Destructive bruxism: sleep stage relationship. Sleep 1988;11:172-81. 2. Hudxinski LG. Use of portable electromyograms in determining and treating chronic nocturnal bruxism. Sot Personality Rep Abstr 1986;23:442-3. 3. Wigdorowicz-Makowerowa N, Grodzki C. Frequency and etiopathogenesis of bruxism (English abstract). Czasopismo Stomatol 1972; 25:1109-12. 4. Solberg WK, Woo MW, Houston JB. Prevalence of mandibular dysfunction in young adults. J Am Dent Assoc 1979;98:25-34. 5. Glacos AG, Rao SM. Bruxism: acriticalreview. Psycho1 Bull 1976;84:76781. 6. Meklas JF. Bruxism: diagnosis and treatment. J Acad Gen Dentistry 1971;19:31-6. 7. Olkinuora M. Bruxism: a review of the literature on and a discussion of studies of bruxism and ita psychogenesis and some new psychological hypotheses. Suomen Hammaslaakaarin Toimituksia 1969; 65:31225.
Availability
of
JOURNAL
8. Olkinuora M. Psychosocial aspects in a series of bruxists compared with a group of non-bruxiste. Suomen Hammaslaariseuran Toimituksia 1972;68:200-8. 9. Schulte J. Bruxism: a review and clinical approach to treatment. Northwest Dentistry 1982;SeptO&13-8. 10. Rugh J, Harlan J. Nocturnal bruxism and temporomandibular disorders. Adv Nemo1 1988;49:329-41. 11. Rugh JD, Solberg WK. Psychological implications in temporomandibular pain and dysfunction bruxist behavior. Oral Sci Rev 1976;1:3-10. 12. Funch DP, Gale EN. Factors associated with nocturnal bruxism and its treatment. J Behav Med 1980;3:385-97. 13. Molton C. Levin L. A osvcho-odontahgic investigation of patients with bruxism. kcta Odor&i &and 1966;24:373-91. 14. Freidman M, Rosenman RH. Association of specific overt behavior pattern with blood and cardiovascular findings. JAMA 1959;169:128696. 15. Freidman M, Rosenman RH. Type A behavior and your heart. New York: Alfred A. Knopf, 1974. 16. Matthews K, Haynes S. Type A behavior pattern and coronary disease risk. Am J Epidemiol 1986;123:923-66. 17. Rappaport N, McAnuIty D, Brantley P. Exploration of the Type A behavior pattern in chronic headache sufferers. J Consult Clin Psycho1 1988;5&621-3. 18. Yarnold P, Bryant F. A note on measurement issues in Type A research; let’s not throw out the baby with the bath water. J Pers Assess 1989; 52410-g. 19. Dohrenwand BS, Dohrenwand BP. Stress and life events: their nature and effects. New York: John Wiley & Sons Inc, 1974. JF. Life event perception scale. Portland, Ore: 1983. 20. Christensen 21. Hays W. Statistics. 4th ed. New York: Holt, Rinehart and Winston, 1988. 22. Miller TQ, Turner CA, Tindale RS, Posavac EJ. Disease-based spectrum bias in referred samples and the relationship between Type A behavior and coronary artery disease. J Clin Epidemiol 1988;41:1139-49. Reprint requests to: Ms. GINA PINCITORE DEPARTMENT OF PSYCHOLOCZY, DAMEN LOYOLA UNIVERSITY CHICAGO, IL 60626
back
issues,
HALL
1985-1989
Back issues of THE JOURNAL OF PROSTHETIC DENTISTRY are available for purchasefrom the publisher, Mosby-Year Book, Inc., at a cost of $6.50per issue.(Foreign postageis not included.) The following quantity discounts are available: 25% off on quantities of 12 to 23, and one third off on quantities of 24 or more. Pleasewrite to Mosby-Year Book, Inc., Subscription Services, 11830Westline Industrial Drive, St. Louis, MO 63146-3318,or call (314)453-4351for information on availability of particular issuesfor that period from 1978to 1989.If unavailable from the publisher, photocopiesof complete issuesare available from University Microforms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)761-4700.
446
MARCH
1991
VOLUME
66
NUMBER
3
M.A.,* Vickyann D.D.S.***
Loyola
Chicago,
University,
Chrobak,
factors
of bruxism
D.D.S., M.S.,** and
111.
Bruxism is a destructive habit that is defined as the nonproductive diurnal or nocturnal cl.enching or grinding of the teeth. This study investigated whether the combination of physical abnormalities, type A behavior pattern, and the perceived desirability and controllability of life stress are related to bruxism. The subjects for the study were 125 dental patients who were classiled as bruxers or nonbruxers by a licensed dentist and who completed two measures, the Jenkins Activity Survey, and a modified version of the Holmes and Rahe Life Events Scale. Regression analyses indicate there is a difference in the separate impact of each variable. Type A behavior and physical abnormalities are significant in a stepwise analysis, while stress is not. Stress appears to be significant only in conjunction with type A behavior, and suggests that the combination of type A behavior, and stress is more predictive of bruxism than either of the individual variables. The linear combination of physical abnormalities. type A behavior, and stress is significant, and suggests that it is the best predictor of bruxism. (J PROSTRET DENT1991;65:443-6.)
B
ruxism is an involuntary, parafunctional, excessive grinding, clenching, or rubbing of the teeth. It is a potentially destructive habit that results in tooth wear, damageto the structure of the surrounding teeth, inflammation and recessionof .the gums, increasedrisk of periodontal disease,musclepain, and temporomandibular joint (TMJ) dysfunction.’ These symptoms are also associatedwith headaches,jaw aches, and stiffness or tightening of the shoulders and neck.2 Conservative estimates of the incidence of bruxism range from 5 % to 10% in the adult population.3Many other researchersbelievethat the actual percentageismuch higher and suggestthat mostadults will brux at somepoint in their life.4 Although there is some disagreementin the literature about the incidenceof bruxism,all studiessuggestthat bruxism affects a large portion of the population and that its consequencescan be insidious and highly destructive. Although bruxism has been frequently researchedand well documented in the medical literature since 1901, its etiology remainsdebatable.5To many researchers,bruxism is viewed as the result of physical abnormalities such as mutilated occlusion, excessive cuspal inclinations, and working or balancing interferences6 Yet when other researchersattempted to replicate thesefindings, conflicting and at times opposingconclusionsresulted. For example, Olkinuora7 found no statistical correlation betweenthe incidence of malocclusionand bruxism.
*Ph.D. candidate, Department of Psychology. **Director of Clinics, School of Dentistry. ***Assistant Professor, Department of Fixed School of Dentistry.
10/l/24231 THEJOURNAL
OF PROSTHETIC
DENTISTRY
Prosthodontics,
Table
I. Correlations of physical abnormalities Jaw
Jaw relation (X = 4.1; S.D. = 0.17) T.M.J. (X = 0.23; S.D. = 0.05) Muscle palpation (X =0.58; S.D. = 10)
Muscle
relation
TMJ
palpation
1.00
0.52*
0.51*
-
1.00
037t
-
-
1.00
N = 125.
*p > 0.001. tp > 0.0001.
As a result of inconsistent support for a physical propensity to brux, other researchersproposed that certain psychologicfactors are associatedwith bruxism. Many researchersbelieve that bruxism is related to certain personality characteristics such as aggressiveness,anxiety, hyperactivity, and a need for control.8-10In addition to personality characteristics, other researchers have explored the effect of life events on bruxing. Rugh and Solberg” and Funch and Galei found that bruxism correlated with both experiencedand anticipated life stress,and they suggestedthat life stressplays an important role in the frequency, duration, and severity of bruxism. Review of the literature on bruxism suggeststhat the personality characteristics describedby many researchers suchasMolton and Levin,13are descriptionsof what Freidman and Rosenman14called a type A behavior pattern.” The literature alsosuggeststhat the perception of the desirability and controllability of life stressmay play an important role in bruxism, but only as it relates to the personality characteristicsof the individual. In an attempt to bridge the gap between the psychologic and physical
443
PINGITORE,
Table
II.
Correlation
CHROBAK,
AND
PETRIE
of physical and psychologic factors with bruxism
Type A (X = 217; S.D. = 75) Stress (X = 73; S.D. = 64) Mechanical (X = 0.00; S.D. = 2.5) Bruxism
Type A
Stress
1.00 -
0.24t
Mechanical
Bkwxism
0.17* 0.26f
1.00 -
0.27$ 0.267 0.28$
1.00 -
1.00
N = 125. ‘p = 0.02. tp = 0.002. $p = 0.001.
processes associated with bruxism, this study investigates bruxism as it relates to type A behavior, the product of the amount of life stress, and structural features that include the jaw and condylar relationship, muscle palpation, and internal derangement. To investigate this hypothesis, great care has been taken to operationally define type A behavior and stress and to select valid and reliable measures of these variables. A brief description of the definitions and measures used is given to provide a clearer understanding of this investigation.
DEFINITION AND PSYCHOLOGICAL
MEASURES CONSTRUCTS
OF THE
Type A. Freidman and Rosenma@ define type A behavior as an “action-emotion complex that can be observed in any person who is aggressively involved in a chronic, incessant struggle to achieve more and more in less and less time, and if required to do so, against the opposing efforts of other things or other persons.“15 The type A personality consists of six patterns: (1) an intense desire to achieve; (2) a need to compete; (3) a persistent, sustained need for recognition; (4) seemingly continuous involvement in many activities; (5) a habitual propensity to accelerate the rate of execution of all mental and physical functions; and (6) an extraordinary mental and physical alertness. Perhaps the most common impression that the public has of type A behavior can be described as hurried, accelerated, pressured, controlling, demanding, and highly ambitious. This description conjures up the picture of a person who is under high amounts of internally and externally induced stress, is driven to perform, is compelled to achieve, and to do these things quickly. Typical motor behaviors exhibited by type A personalities are excessive, rapid body movements characterized by tense facial and body muscle constriction, explosive speech intonations, hand or teeth clenching, and a general air of impatience. The measurement of type A behavior. The Jenkin’s Activity Survey (JAS) was used to measure type A behavior. It is a reliable (r 0.85) instrument that provides an overall score for type A behavior, plus separate scores for three subfactors: impatience, job involvement, and harddriving and competitive nature. This measure is frequently used and is well documented as a valid, reliable measure of type A behavior.16-18
444
Life stress. Life stress is operationally defined in terms of self-reported life changes, and physical illness.lg In addition, it is necessary to conceptualize life stress in terms of the perceptions of its desirability and controllability. In this investigation, life stress is viewed as a multiplicative relationship between the amount of life changes and physical illnesses and the perceived desirability and controllability of these events. The measurement of life stress. A modified version of Homes and Rahe’s Life Events Perception Scale (LEPS) was used in this investigation.zo This scale consists of questions to which respondents answer “yes” or “no” to a series of 57 items. For items answered “yes,” respondents then indicated their perception of the desirability and controllability of these events by using a 1 to 5 scale (1 = totally desirable/controllable; 5 = totally undesirable/ uncontrollable). To derive stress ratings for each of the 57 items, values of 1 were assigned to “yes” and 0 to “no.” These values were then multiplied by the rating of desirability and controllability. For example, if a patient answered “yes” to item 14 and rated it 3 for desirability and 4 for controllability, the value for this item equals 12. To obtain the total stress score, values were summed across all items.
MATERIAL
AND
METHODS
Subjects in this study were 125 dental patients who were being treated at Loyola University of Chicago Dental Clinic, Department of Fixed Prosthodontics. For the Methodology, each patient completed both the JAS and the modified version of the LEPS. Patients were also asked to answer specific questions designed to determine their awareness of the possibility that they brux. Questions were in a “yes/no” format and included items such as “do you grind your teeth?” “ do you frequently wake up with a headache?,” and “do you notice that your teeth are wearing down?” After the patients completed these measures, each-was evaluated by the same dentist, who was blind to patients’ responses on the psychologic measures. The dental examination included evaluations of the anterior and posterior wear facets and types of occlusion (Angle class I, II, or III). Based on this evaluation, patients were classified as a “bruxer” or “nonbruxer.” Several types of malocclusion were also evaluated. These were eccentric interferences,
MARCH
1991
VOLUME
66
NUMBER
3
TYPE
A BEHAVIOR
AND
BRUXISM
III. Two-by-two contingency table of number of correctly classifiedbruxers and nonbruxers
centric relation prematurities, and the general occlusion schemes. Signs and symptoms of temporomandibular joint (TMJ) disorders were evaluated without attempting to classify derangements other than noting the presence or absence of internal derangement or positive response to muscle palpation. From this evaluation, three scores were derived: a jaw and condylar relationship score, a TMJ score that included evidence of myofacial pain disorder (MPD) and internal derangement, and a muscle palpation score that showed evidence of palpation of the masseter, medial, lateral, and temporal muscles. On the basis of the correlation of these scores, it was decided to sum them and form an overall mechanical index (Table I). This index was then used in all analyses.
Table
RESULTS
Clinical
In order to determine the relationship between bruxism and the physical and psychologic measures, Pearson product-moment correlation coefficients were examined. Table II shows that st:ress, type A behavior, and the mechanical index are significantly related to bruxism, suggesting that each may play an important role in this disorder. To obtain a clearer picture of how these factors may relate to bruxism, a ;stepwise multiple regression analysis was used.21 Only the type A behavior and mechanical index scores were entered into the equation. The stress score failed to meet the default criteria for inclusion. To examine whether the combination of type A behavior and stress provides a fuller description of the bruxism process than does type A behavior alone, the difference between these equations was examined. This involved comparing the goodness-of-fit that was obtained from the combination of standardized type A behavior and stress scores to the goodness-of-fit that resulted from the individual variables. The result of this F ratio indicates that the equation for the combination of type A behavior and stress is different from the equation using each of these individual variables (F&120) = 10, p > 0.01). To test whether bruxism is the result of a linear combination of type A, stress, and physical abnormalities, a “brux-type” score was created. This score was created by converting the total scores for the mechanical index, JAS, and LEPS into standardized t scores and then summing them together. A bivariate regression analysis was employed using the “brux-type” variable defined above as predictive of bruxism. This relationship is significant (Multiple R = 0.35; F(1,123) = 16, p = 0.0001). Finally, decision theory, as discussed by Miller et a1.,22 was used to assess the probability of correctly classifying bruxers and nonbruxers, given this set of variables. A twoby-two contingency table of the number of patients correctly classified a.3a bruxer/nonbruxer is given in Table III. This table shows that the constructs used in this investigation better differentiate nonbruxers than they do hruxers. For nonbruxers, 62% werecorrectly classified(specificity),
The resultsof this investigation suggestseveral items of interest to clinical situations. Since the results of this investigation show that bruxism is not only related to physical abnormalities but also to behavior and life-style, dentists may find that somepatients will continue to brux no matter how much their dental condition is improved. In these patients, the dental materials used in restorative treatment should be resistant to wear and breakage. For instance,porcelain occlusalsurfaceson posterior crownsor large posterior composite resin restorations may be contraindicated. Teeth weakenedby large restorations would also be evaluated as potential cusp fractures due to the force produced by bruxing. The dentition may need to be protected with a prosthesisto be worn during times the patient is most apt to brux. When presenting treatment plans, dentists should be awareof “type A characteristics” so asto enlist patient cooperation. Information should be presentedto patients in personally relevant and salient ways, such as using audiovisual aidsto showthe effects of bruxism. This can help the patient comply with treatment recommendations,especially with the use of splints. Finally, since bruxism may affect the outcome of treatment of TMJ disordersand chronic pain, stepsshould be taken to control parafunctional activity. It may become important to refer patients to a stressor life-style management program if they brux severely and continuously, especially if the patients are highly competitive and are under life stress.These programs, with the appropriate and indicated dental care, can help them develop alternative skills neededto prevent seriousdamageto their teeth and related structure,
THE
JOURNAL
OF l?ROSTHETIC
DENTISTRY
Absent negatives
actual (AN)
Present positives
actual (AP)
Predicted bruxers
False
positives 12
True
positives
Predicted nonbruxers
True
negative 52 64
False
negatives 23 61
38
whereas only 62% of bruxers were correctly classified (sensitivity).
implications
SUMMARY This investigation attempted to find a correlation among bruxism, physical abnormalities, the type A behavior pattern, and the perception of the desirability and controllability of stress.Resultsfrom regressionanalysissuggestthe possibility that certain behavioral-emotional patterns and physical conditions may increasethe likelihood to brux. 445
PINGITORE,CHROBAK,ANDPETRIE
CONCLUSION As argued in previous literature, the etiology of bruxism is debatable. While the data presented here do not resolve this debate, they do provide greater insight into the relationship between the psychologic and physical factors of bruxism. To fully understand bruxism, further research is needed. Since other research has documented significant effects of stress on bruxism, a clearer understanding of the effect of this factor is needed. It may be important to assess stress using different measures or to define stress in terms other than life changes and illnesses. Nevertheless, this study shows that both physical and psychologic factors are associated with bruxism. REFERENCES 1. Ware JC, Rugh JD. Destructive bruxism: sleep stage relationship. Sleep 1988;11:172-81. 2. Hudxinski LG. Use of portable electromyograms in determining and treating chronic nocturnal bruxism. Sot Personality Rep Abstr 1986;23:442-3. 3. Wigdorowicz-Makowerowa N, Grodzki C. Frequency and etiopathogenesis of bruxism (English abstract). Czasopismo Stomatol 1972; 25:1109-12. 4. Solberg WK, Woo MW, Houston JB. Prevalence of mandibular dysfunction in young adults. J Am Dent Assoc 1979;98:25-34. 5. Glacos AG, Rao SM. Bruxism: acriticalreview. Psycho1 Bull 1976;84:76781. 6. Meklas JF. Bruxism: diagnosis and treatment. J Acad Gen Dentistry 1971;19:31-6. 7. Olkinuora M. Bruxism: a review of the literature on and a discussion of studies of bruxism and ita psychogenesis and some new psychological hypotheses. Suomen Hammaslaakaarin Toimituksia 1969; 65:31225.
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of
JOURNAL
8. Olkinuora M. Psychosocial aspects in a series of bruxists compared with a group of non-bruxiste. Suomen Hammaslaariseuran Toimituksia 1972;68:200-8. 9. Schulte J. Bruxism: a review and clinical approach to treatment. Northwest Dentistry 1982;SeptO&13-8. 10. Rugh J, Harlan J. Nocturnal bruxism and temporomandibular disorders. Adv Nemo1 1988;49:329-41. 11. Rugh JD, Solberg WK. Psychological implications in temporomandibular pain and dysfunction bruxist behavior. Oral Sci Rev 1976;1:3-10. 12. Funch DP, Gale EN. Factors associated with nocturnal bruxism and its treatment. J Behav Med 1980;3:385-97. 13. Molton C. Levin L. A osvcho-odontahgic investigation of patients with bruxism. kcta Odor&i &and 1966;24:373-91. 14. Freidman M, Rosenman RH. Association of specific overt behavior pattern with blood and cardiovascular findings. JAMA 1959;169:128696. 15. Freidman M, Rosenman RH. Type A behavior and your heart. New York: Alfred A. Knopf, 1974. 16. Matthews K, Haynes S. Type A behavior pattern and coronary disease risk. Am J Epidemiol 1986;123:923-66. 17. Rappaport N, McAnuIty D, Brantley P. Exploration of the Type A behavior pattern in chronic headache sufferers. J Consult Clin Psycho1 1988;5&621-3. 18. Yarnold P, Bryant F. A note on measurement issues in Type A research; let’s not throw out the baby with the bath water. J Pers Assess 1989; 52410-g. 19. Dohrenwand BS, Dohrenwand BP. Stress and life events: their nature and effects. New York: John Wiley & Sons Inc, 1974. JF. Life event perception scale. Portland, Ore: 1983. 20. Christensen 21. Hays W. Statistics. 4th ed. New York: Holt, Rinehart and Winston, 1988. 22. Miller TQ, Turner CA, Tindale RS, Posavac EJ. Disease-based spectrum bias in referred samples and the relationship between Type A behavior and coronary artery disease. J Clin Epidemiol 1988;41:1139-49. Reprint requests to: Ms. GINA PINCITORE DEPARTMENT OF PSYCHOLOCZY, DAMEN LOYOLA UNIVERSITY CHICAGO, IL 60626
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MARCH
1991
VOLUME
66
NUMBER
3