Abstract
Objectives
The aim of this study was to investigate the association between psychological factors (Personality and Dental anxiety) with self-reported bruxism-related symptoms.
Methods
526 subjects, over 18 years old and not seeking dental treatment, were recruited from the families and acquaintances of dental students from the University of Salamanca. Bruxism activity was estimated by means of a six-item questionnaire aimed at recording common bruxism-related symptoms and clenching/grinding awareness. The Spanish version of the modified dental anxiety scale (MDAS) was used to determine the level of anxiety perceived in 5 typical scenarios of dental assistance. The NEO-FFI inventory was applied to assess personality profiles associated with 5 different factors ( neuroticism , extroversion , openness , agreeableness , and conscientiousness ). Pearson correlations, Student T-tests, and logistic regression modelling were used for the statistical analyses.
Results
Thirty-five point nine percent of this adults sample was classified as being bruxers, where sleep bruxers comprised more than half of the sample at 20.2%. Bruxers tended to perceive more anxiety in all of the situations included within the MDAS, where they exhibited a higher level of phobia towards the teeth scaling and local anaesthetic injection. The risk of being considered a bruxer is reduced with age (OR: 0.99), and increases proportionally for some personality traits, such as neuroticism (OR: 1.06) and extraversion (OR: 1.04), to the MDAS total score (OR: 1.08) and in smokers (OR: 1.61), after controlling for all potentially confounding factors.
Conclusions
Self-reported bruxism is significantly associated to several personality traits (mainly neuroticism and extraversion ) and to the level of dental anxiety (MDAS score).
Clinical significance: Clinicians should be aware of the typical psychological profiles of patients who experience bruxism and the relationship with dental phobias.
1
Introduction
Bruxism is an oral condition of great interest to researchers, clinicians and patients in the dental, neurological and sleep medicine domains. According to Lobbezzo et al. bruxism is a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Bruxism has two distinct circadian manifestations: it can occur during sleep (indicated as sleep bruxism) or during wakefulness (indicated as awake bruxism).
To date, the aetiology of bruxism has not been completely determined, but there is consensus about its multifactorial nature. In the past, peripheral factors like occlusal discrepancies or several morphological deviations in the orofacial region were considered capable of initiating and perpetuating non-functional masticatory movements that try to minimize the impact of such anomalies in the stomatognathic system . However, such factors are now known to play only a minor role, if any. Nowadays, the focus is centred on causes related to pathophysiological and psychological factors.
Recent works support the idea that some psychological factors, such as personality and stress, could modulate the occurrence and severity of such parafunctional behaviour. In the classical study by Ramfjord published in 1961, the role of “neurotic tensions” in the aetiology of bruxism was determined. Latter Olkinuora demonstrated that bruxers were emotionally out of balance and that they tended to develop more psychosomatic disorders, because their personality profile was characterized by perfectionism and an increased tendency towards anger and aggression.
In 1993, Fisher & O’toole reported that the personality of bruxers differed significantly from non-bruxers. In general, it was observed that chronic bruxers are shy, stiff, cautious, and aloof, preferring things rather than people, avoiding compromises, rigid in their ways, affected by feelings of inferiority, impeded in expressing themselves, apprehensive, and given to worrying. A few years later Kampe et al. observed that bruxers, in terms of personality, tended to score higher in somatic anxiety and muscular tension and lower in socialization .
A recent systematic review focussing on the role of psychological factors in the aetiology of bruxism in adults reported the major personality traits that characterize bruxers (eg, aggressiveness, neuroticism, perfectionism , and stress sensitivity ), occurring mainly during wakefulness . Thus, the idea than not all types of personalities are equally susceptible to the bruxism disorder seems to be supported by the literature.
Personality can be defined as the dynamic organization of the psychobiological systems that modulate adaptation to changing environments through several personality traits, which are long-lasting patterns of how we perceive, relate to, and think about oneself, other people and the world as a whole . Since bruxism is likely to be a result of emotional tension and psychosocial disorders that force the subject to respond with a prolonged contraction of his/her masticatory muscles , it could be argued that some personality traits, such as neuroticism , extraversion , and conscientiousness may underlie the behaviour related to bruxism. In addition, more anxiety and phobias have been reported in association with bruxism .
Nowadays, there is a lack of research that focuses on evaluating the global personality profile and the level of dental anxiety among bruxers. The present study aims to assess the association between psychological factors (Personality and Dental anxiety) with self-reported bruxism-related symptoms.
2
Methods
A cross-sectional study was carried out on five hundred and twenty-six subjects, over 18 years old and not seeking dental treatment, which were recruited using a snowball technique from the families and acquaintances of dental students from the University of Salamanca during the Christmas holidays in 2015. Students were instructed to collect data from both gender and from distinct age intervals in order to have a broad spectrum of age with balanced gender. A written informed consent was obtained from all individual included within the study, in accordance with the Bioethics Committee of the University of Salamanca. The sample size was estimated for detecting significant differences in personality scores using the t -test for independent groups, with a power of 95% and a significance level of two-side alpha = 0.05, using the data dispersion values from the first 100 subjects of the pilot study (2 units of mean differences and 7 units of common standard deviation), resulting in a minimum of 320 subjects for such bivariate analysis. But in order to maintain enough effective sample size with which to explore the multi-factorial nature of the personality among self-reported bruxers and also for compensating missing data we decided to over recruit the initial sample. In the 526 subjects that comprised the main study, were already included the initial 100 subjects of the pilot study. The final response rate of this survey was 92%.
For all participants, sociodemographic (age, gender, education, and etc.) and behavioural data (brushing habits, smoking and dental attendance patterns) were collected in a face-to-face interview performed by the dental students. Moreover, the prosthodontics status, the number of standing teeth and occlusal units were registered by inspection, for capturing clinical variables that could be potentially related with the psychological background or with the awareness of bruxism or acting as confounding factors for the logistic regression analyses. Given the simplicity of such exploration and that all the students were trained with this methodology from the clinical practices, no calibration was made. Additionally, a self-completed questionnaire, consisting of several items regarding bruxism-related symptoms, dental anxiety and personality traits, was also obtained from all participants. The various sections within this questionnaire are described in the following paragraphs.
Bruxism activity was estimated by means of a six-item questionnaire with good face and content validity , which was previously used by Pintado et al. for similar studies . The items were answered dichotomically with either a ‘yes’ or a ‘no’. The patients were instructed to answer ‘yes’ only if they considered that their habit was frequent enough to be clinically relevant (i.e. more frequent than 3×/week and/or several hours per day).
Subjects classified as bruxers gave a positive response to at least two of the following six items:
- 1
Has anyone heard you grinding your teeth at night?
- 2
Is your jaw ever fatigued or sore on awakening in the morning?
- 3
Are your teeth or gums ever sore on awakening in the morning?
- 4
Do you ever experience temporal headaches on awakening in the morning?
- 5
Are you ever aware of grinding your teeth during the day?
- 6
Are you ever aware of clenching your teeth during the day?
Among bruxers we distinguished between diurnal and nocturnal activities based on the bruxism-related symptoms. Hence we considered awake bruxers if at least one of the affirmative responses to the questionnaire was in the items 5 or 6; whereas the sleep bruxers were those subjects whose all the affirmative responses were in the items 1–4.
The Spanish version of the Modified Dental Anxiety Scale (MDAS) was used to determine, on a 5-point Likert scale format (not anxious = 1 to extremely anxious = 5), the level of anxiety acknowledged by subjects in the 5 common situations during dental office assistance. . To do this, two scoring strategies were used. The total score was obtained by adding up all of the item responses, as recommended by the developers of the MDAS_TS. In addition, we also counted the number of items recorded as very anxious or extremely anxious (coded as 4 and 5, respectively) in order to obtain a useful quantitative variable proportional to the level of dental anxiety (MDAS_SC).
For the global personality assessment, the Spanish Version of the NEO-FFI inventory (60-items) was applied to identify the participants’ personality profiles . It was derived from a factor analysis on the scores of the original extended inventory (240 items) developed by Costa & McCrae . The 60 items were divided conceptually into 5 factors ( neuroticism, extroversion, openness, agreeableness and conscientiousness ), which are widely accepted as the five basic domains of the human personality.
These five relatively independent personality dimensions are Neuroticism (i.e. a predisposition towards negative affect expressed through anxiety, depression and hostility), Extroversion (i.e. a desire for both a greater quantity and intensity of interpersonal interaction), Openness (i.e. a tendency to seek new experiences and perspectives), Agreeableness (i.e. a perspective that emphasizes positive qualities in others and offers an accommodating social presence), and Conscientiousness (i.e. a quality associated with persistence and attention-to-detail in goal-directed behaviors).
The responses were coded on a 5-point Likert scale (from strongly disagree = 1 to strongly agree = 5 ). For each factor, the additive score was calculated by adding up the response codes coherently oriented towards the trait being assessed (because some items were inversely set). The potential range of scores of each domain was 0 to 48 points and the average of scores was calculated within subgroups. The higher the scores on a give domain the stronger the personality trait.
The inter-group comparisons for qualitative (nominal and ordinal) and quantitative variables were done using the Chi-squared test and ANOVA test with Post Hoc Bonferroni correction, respectively. Using Pearson coefficients, we studied the linear relationship between the scores obtained for bruxism symptoms, anxiety and personality. Finally, we calculated a forward stepwise logistic regression model as a function of all of the sociodemographic, behavioural and clinical and personality-related variables for predicting the risk of being a self-reported bruxer. The predictive capacity of the model was calculated with the R 2 of Nagelkerke.
The Statistical Package for the Social Sciences v.20. (SPSS Inc., Chicago, IL) was used for the statistical analyses. The cut‐off level for statistical significance was 0.05. We used the STROBE guidelines for reporting this study.
2
Methods
A cross-sectional study was carried out on five hundred and twenty-six subjects, over 18 years old and not seeking dental treatment, which were recruited using a snowball technique from the families and acquaintances of dental students from the University of Salamanca during the Christmas holidays in 2015. Students were instructed to collect data from both gender and from distinct age intervals in order to have a broad spectrum of age with balanced gender. A written informed consent was obtained from all individual included within the study, in accordance with the Bioethics Committee of the University of Salamanca. The sample size was estimated for detecting significant differences in personality scores using the t -test for independent groups, with a power of 95% and a significance level of two-side alpha = 0.05, using the data dispersion values from the first 100 subjects of the pilot study (2 units of mean differences and 7 units of common standard deviation), resulting in a minimum of 320 subjects for such bivariate analysis. But in order to maintain enough effective sample size with which to explore the multi-factorial nature of the personality among self-reported bruxers and also for compensating missing data we decided to over recruit the initial sample. In the 526 subjects that comprised the main study, were already included the initial 100 subjects of the pilot study. The final response rate of this survey was 92%.
For all participants, sociodemographic (age, gender, education, and etc.) and behavioural data (brushing habits, smoking and dental attendance patterns) were collected in a face-to-face interview performed by the dental students. Moreover, the prosthodontics status, the number of standing teeth and occlusal units were registered by inspection, for capturing clinical variables that could be potentially related with the psychological background or with the awareness of bruxism or acting as confounding factors for the logistic regression analyses. Given the simplicity of such exploration and that all the students were trained with this methodology from the clinical practices, no calibration was made. Additionally, a self-completed questionnaire, consisting of several items regarding bruxism-related symptoms, dental anxiety and personality traits, was also obtained from all participants. The various sections within this questionnaire are described in the following paragraphs.
Bruxism activity was estimated by means of a six-item questionnaire with good face and content validity , which was previously used by Pintado et al. for similar studies . The items were answered dichotomically with either a ‘yes’ or a ‘no’. The patients were instructed to answer ‘yes’ only if they considered that their habit was frequent enough to be clinically relevant (i.e. more frequent than 3×/week and/or several hours per day).
Subjects classified as bruxers gave a positive response to at least two of the following six items:
- 1
Has anyone heard you grinding your teeth at night?
- 2
Is your jaw ever fatigued or sore on awakening in the morning?
- 3
Are your teeth or gums ever sore on awakening in the morning?
- 4
Do you ever experience temporal headaches on awakening in the morning?
- 5
Are you ever aware of grinding your teeth during the day?
- 6
Are you ever aware of clenching your teeth during the day?
Among bruxers we distinguished between diurnal and nocturnal activities based on the bruxism-related symptoms. Hence we considered awake bruxers if at least one of the affirmative responses to the questionnaire was in the items 5 or 6; whereas the sleep bruxers were those subjects whose all the affirmative responses were in the items 1–4.
The Spanish version of the Modified Dental Anxiety Scale (MDAS) was used to determine, on a 5-point Likert scale format (not anxious = 1 to extremely anxious = 5), the level of anxiety acknowledged by subjects in the 5 common situations during dental office assistance. . To do this, two scoring strategies were used. The total score was obtained by adding up all of the item responses, as recommended by the developers of the MDAS_TS. In addition, we also counted the number of items recorded as very anxious or extremely anxious (coded as 4 and 5, respectively) in order to obtain a useful quantitative variable proportional to the level of dental anxiety (MDAS_SC).
For the global personality assessment, the Spanish Version of the NEO-FFI inventory (60-items) was applied to identify the participants’ personality profiles . It was derived from a factor analysis on the scores of the original extended inventory (240 items) developed by Costa & McCrae . The 60 items were divided conceptually into 5 factors ( neuroticism, extroversion, openness, agreeableness and conscientiousness ), which are widely accepted as the five basic domains of the human personality.
These five relatively independent personality dimensions are Neuroticism (i.e. a predisposition towards negative affect expressed through anxiety, depression and hostility), Extroversion (i.e. a desire for both a greater quantity and intensity of interpersonal interaction), Openness (i.e. a tendency to seek new experiences and perspectives), Agreeableness (i.e. a perspective that emphasizes positive qualities in others and offers an accommodating social presence), and Conscientiousness (i.e. a quality associated with persistence and attention-to-detail in goal-directed behaviors).
The responses were coded on a 5-point Likert scale (from strongly disagree = 1 to strongly agree = 5 ). For each factor, the additive score was calculated by adding up the response codes coherently oriented towards the trait being assessed (because some items were inversely set). The potential range of scores of each domain was 0 to 48 points and the average of scores was calculated within subgroups. The higher the scores on a give domain the stronger the personality trait.
The inter-group comparisons for qualitative (nominal and ordinal) and quantitative variables were done using the Chi-squared test and ANOVA test with Post Hoc Bonferroni correction, respectively. Using Pearson coefficients, we studied the linear relationship between the scores obtained for bruxism symptoms, anxiety and personality. Finally, we calculated a forward stepwise logistic regression model as a function of all of the sociodemographic, behavioural and clinical and personality-related variables for predicting the risk of being a self-reported bruxer. The predictive capacity of the model was calculated with the R 2 of Nagelkerke.
The Statistical Package for the Social Sciences v.20. (SPSS Inc., Chicago, IL) was used for the statistical analyses. The cut‐off level for statistical significance was 0.05. We used the STROBE guidelines for reporting this study.
3
Results
As depicted in Table 1 , the sample was comprised of adults aging between 18 and 94 years old (mean age = 43.7 ± 19.0 years), equally distributed by gender, with a high educational level (51.1% university degrees), and living in urban areas (65.4%). In terms of behavioural traits, 77% of the sample was non-smokers, generally showed good oral health habits (71.1% brushed their teeth at least twice a day), and 42.4% regularly visited the dentist ( Table 1 ). Regarding the prosthodontics status, the majority of the sample did not wear any type of dental prosthesis (65.2%) and on average had 11.5 ± 4.1 occlusal units (antagonistic fixed teeth in contact during the maximal intercuspal position).
| SOCIODEMOGRAPHICS | Mean | SD |
|---|---|---|
| Age(years) | 43.7 | 19.0 |
| Age groups | N | % |
| <=34 years | 210 | 39.9 |
| 35–64 years | 236 | 44.9 |
| >=65 years | 80 | 15.2 |
| Gender | ||
| Women | 262 | 49.8 |
| Men | 264 | 50.2 |
| Educational level | ||
| Secondary School | 130 | 24.7 |
| High School | 127 | 24.1 |
| University | 269 | 51.1 |
| Residence | ||
| Urban | 344 | 65.4 |
| Rural | 182 | 34.6 |
| Behaviour | N | % |
| Brushing | ||
| once/day | 152 | 28.9 |
| twice or more/day | 374 | 71.1 |
| Smoking habit | ||
| yes | 121 | 23.0 |
| no | 405 | 77.0 |
| Visits to dentist | ||
| Regular | 223 | 42.4 |
| Problem-based | 303 | 57.6 |
| Clinical Variables | N | % |
| Prosthodontic Status | ||
| Complete Denture | 37 | 7.0 |
| Removable Partial Dentures | 48 | 9.1 |
| Tooth-supported fixed partial dentures | 98 | 18.6 |
| Natural dentition | 343 | 65.2 |
| Occlusal status | Mean | SD |
| Number of Standing teeth in maxilla | 12.1 | 3.9 |
| Number of Standing teeth in mandible | 12.2 | 3.7 |
| Number of Occlusal Units | 11.5 | 4.1 |
In Table 2 , the responses regarding the self-reported bruxism activities and strategies are depicted. The most prevalent activities identified from the 6-item questionnaire for assessing bruxism were: item n°6: clenching the teeth during the day (30.2%) and item n°4: experiencing temporal headaches on awakening in the morning (27.6%). According to these responses, 35.9% of the sample was classified as being bruxers, and in particular sleep bruxers (20.2% of the sample). Among the bruxers, 70% believed that their symptoms were stress-related and 21.7% had worn occlusal splints, which are mostly effective at reducing related symptoms (78%). More than 60% of the bruxers acknowledged that they had teeth and joint damage due to bruxism activity, but only 22.8% of them recognised the need for treatment.
| Anamnestic Questionnaire Regarding Bruxing Activity | Prevalence of affirmative respondents | |
|---|---|---|
| Self-report Bruxism according to Pintado et al. | N | % |
| 1. Has anyone heard you grinding your teeth at night? | 110 | 20.9 |
| 2. Is your jaw ever fatigued or sore on awakening in the morning? | 127 | 24.1 |
| 3. Are your teeth or gums ever sore on awakening in the morning? | 123 | 23.4 |
| 4. Do you ever experience temporal headaches on awakening in the morning? | 145 | 27.6 |
| 5. Are you ever aware of grinding your teeth during the day? | 58 | 11.0 |
| 6. Are you ever aware of clenching your teeth during the day? | 159 | 30.2 |
| Prevalence of Self-reported Bruxim | N | % |
| Non Bruxers (less than two affirmative items) | 337 | 64.1 |
| Mild Bruxers (two or three affirmative items) | 113 | 21.5 |
| Hard Bruxers (4–6 affirmative items) | 76 | 14.4 |
| Type of Self-reported bruxism | N | % |
| Non bruxers | 337 | 64.1 |
| Awake bruxers (affirmative responses including items n° 5 or n° 6) | 83 | 15.8 |
| Sleep bruxers (only affirmative responses to items n°1–4) | 106 | 20.2 |
| Symptoms management strategies in bruxers (n = 189) | ||
| Do you know the occlusal splint for reducing such symptoms? | 111 | 58.7 |
| Drugs intake for reducing such symptoms | 22 | 11.6 |
| Perceived Treatment needs | 43 | 22.8 |
| Do you believe your symptoms are Stress-related | 133 | 70.4 |
| Which tissues are being damaged because of the bruxism activity | ||
| Teeth | 129 | 68.3 |
| Joint | 114 | 60.3 |
| Gums | 77 | 40.7 |
| Have you ever wear an occlusal splint | 41 | 21.7 |
| If Yes, Was it effective in reducing your symptoms? | 32 | 78.0 |
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