Bruxism is a jaw muscle activity that involves physio-pathological, psycho-social, hereditary and genetic factors. The purpose of this study was to determine the associations between self-reported bruxism, anxiety, and neuroticism personality trait with the rs6313 polymorphism in the gene
Bruxism is a repetitive muscular activity of the jaw characterized by grinding or clenching the teeth and by pulling or pushing the jaw. This can occur during sleep, ‘sleep bruxism’, or when awake, ‘awake bruxism’ (
Worldwide epidemiological data of bruxism reported a prevalence of sleep bruxism of 15.9%, and of awake bruxism of 23.8% (
Several psychological traits that have been reported in individuals with bruxism, such as anxiety and neuroticism personality trait, suggesting an anxious individual, have been linked to the rs6313 polymorphism of the
Owing to the integrated relationship between these variables, the aim of the present study was to investigate the associations between self-reported bruxism, anxiety, and neuroticism personality trait with the rs6313 polymorphism in the gene
A quantitative, descriptive, non-experimental, cross-sectional, multi-center association study was conducted in Northeastern Mexico. The selection of participants was based on the recommendations of the Temporomandibular Disorder (TMD)-RDC guidelines (
This was determined in three ways: i) Clinical diagnosis in order to identify and confirm the presence of signs and symptoms of bruxism; ii) an evaluation of self-reported signs and symptoms through the ‘self-report of bruxism’ questionnaire (
The presence of signs and symptoms of anxiety was evaluated by the Beck Anxiety Inventory (BAI), which was adapted for the Mexican population (
Genomic DNA was isolated from a sample of peripheral blood with EDTA using the QIAcube and the QIAamp® DNA Investigator kit and performed according to the manufacturer's instructions (Qiagen, Hilden, Germany). Genomic DNA was treated with RNase I (Invitrogen, Carlsbad, CA, USA) for 30 min at 37°C to remove traces of RNA. DNA quality and integrity were assessed by standard spectrophotometric and electrophoretic methods, respectively (NanoDrop Technologies, Wilmington, DE, USA). The rs6313 alleles from gene
The descriptive statistical analysis of values and the comparison of the level of perception of bruxism, symptoms of anxiety, and neuroticism personality traits, in individuals with waking bruxism, sleep bruxism, and without bruxism was performed using IBM SPSS (version 22; IBM Corp., Armonk, NY, USA). The EPI-INFO package was used to evaluate the odds ratio (OR) for anxiety and neuroticism. Genotype data analysis was performed using the maxLik (maximum likelihood) statistical program to differentiate the allele frequencies C and T. In addition to the allelic discrimination, the Hardy-Weinberg equilibrium by exact text was determined, and allele association analysis was conducted.
A total of 171 subjects (control, n=59; and cases, n=112) were subdivided into groups that included individuals with self-reported symptoms of sleep bruxism (n=22), awake bruxism (n=46) and combined (n=45), and a control group that reported no signs or related symptoms (n=58). In this study, Cronbach's alpha of the Self-Reported Bruxism Questionnaire (SBQ) was α=0.869. The highest score was reported by combined bruxism, mean = 32.21 (
According to the maxLik statistical program, the four groups were in Hardy-Weinberg equilibrium. In the analysis of genotypic frequency 3×4, the following genotype frequency was observed in the control group (G1, n=60), C/C=8, T/T=22, T/C=30; in the subgroups with bruxism symptoms during sleep (G2, n=22), C/C=5, T/T=8, T/C=9; while awake (G3, n=44), C/C=4, T/T=19; T/C=21; combined (G4, n=46), C/C=9, T/T=18, T/C=19. In this analysis no differences were found (F=4.517, P=0.612). In these results, we can identify that out of the four groups, the one that had the farthest P-value from significance was the control group (P=0.82), unlike the combined bruxism group (P=0.10). For this reason, this group of combined bruxism was used to establish the risk factor of anxiety and neuroticism. The EPI-INFO software package was used and showed a higher risk factor of neuroticism (six levels, 0–5) at level 5 (maximum score) (OR=15.0; CI 1.52–148.32) (
The pathophysiological traits associated with bruxism were quantitatively measured by the SBQ (
The psychological traits evaluated were anxiety and neuroticism, as these, besides being associated with bruxism, have been associated with the
Furthermore, research suggesting a genetic association is scarce, as in the case-control study of Abe
In order to perform genotype analysis, the sample was divided by generations and four groups were established according to self-reported signs and symptoms. The Hardy-Weinberg test was used in this sample; however, when performing the analysis of genotypic homogeneity (genotypes C/C, C/T and T/T) vs. the four groups, (3×4), no trend was observed between the SNP rs6313 and the individuals from the different analyzed groups (F=4.517, P=0.612). In contrast to the subjects from Japan, in this population from northeastern Mexico, there was no significant genetic association found, which is explained by the close relationship between genetic factors and the environment and by its influence to cause individual differences in genes related to personality traits, cognitive skills, and specifically, bruxism (
Corresponding author thanks the CONACYT for its support of the scholarship (337518/285502).
Mean values and standard deviation for self-reported symptoms of bruxism, symptoms of anxiety, and personality trait of neuroticism for case and control group.
Items | Groups | n | Mean | SD |
---|---|---|---|---|
Self-report of bruxism | G1 | 60 | 13.92 | 2.97 |
G2 | 22 | 24.64 | 6.35 | |
G3 | 44 | 23.36 | 5.24 | |
G4 | 46 | 32.21 | 7.5 | |
Total | 172 | 22.60 | 9.04 | |
Anxiety symptoms | G1 | 60 | 8.38 | 8.27 |
G2 | 22 | 9.41 | 7.36 | |
G3 | 44 | 11.50 | 10.34 | |
G4 | 46 | 14.80 | 10.31 | |
Total | 172 | 11.03 | 9.58 | |
Neuroticism trait | G1 | 60 | 2.28 | 1.49 |
G2 | 22 | 3 | 1.66 | |
G3 | 44 | 2.27 | 1.83 | |
G4 | 46 | 3.26 | 1.49 | |
Total | 172 | 2.63 | 1.65 |
SD, standard deviation.
One-way ANOVA between independent groups.
F | P-value | |
---|---|---|
Self-reported bruxism | 97.87 | 0.000 |
Anxiety symptoms | 4.39 | 0.005 |
Neuroticism trait | 4.38 | 0.005 |
Genetic homogeneity analysis 3×4 (1 locus, 2 alleles: 1 and 2).
Alleles | |||||
---|---|---|---|---|---|
Groups | χ2 HW | 1 | 2 | SD | P-value |
G1 control | 0.051 | 0.3621 | 0.6379 | 1 | 0.82 |
G2 case | 0.153 | 0.4545 | 0.5454 | 1 | 0.70 |
G3 case | 0.152 | 0.3152 | 0.6848 | 1 | 0.70 |
G4 case | 2.673 | 0.3778 | 0.6222 | 1 | 0.10 |
Total | 0.51 | 0.3424 | 0.6576 | 1 | 0.82 |
HW, Hardy-Weinberg; SD, standard deviation.
EPI-INFO was used to assess the risk factor of neuroticism.
Strata | Control | Case | OR (1 ref.) | Woolf 95% CI |
---|---|---|---|---|
0 | 6 | 1 | 1.00 | Reference |
1 | 13 | 6 | 2.77 | (0.25–30.54) |
2 | 21 | 9 | 2.57 | (0.26–25.90) |
3 | 7 | 7 | 6.00 | (0.57–63.68) |
4 | 8 | 12 | 9.00 | (0.94–86.53) |
5–6 | 4 | 10 | 15.0 | (1.52–148.32) |