Assessing the Association Between Occlusal Characteristics and Sleep Quality and Stress Levels: A Cross-Sectional Study

Abstract

Malocclusion can arise due to various causes and may impact not only temporomandibular joint (TMJ) disorders but also overall systemic health. This study aimed to evaluate the association of individual occlusal characteristics with sleep quality and stress levels in female college students. Occlusal analysis was conducted using T-Scan III on 84 participants (age: 21.7 ± 2.09), while sleep quality and stress levels were assessed using the Korean version of the Pittsburgh Sleep Quality Index and self-reported stress questionnaires, respectively. Sleep quality was categorized as “good sleeper” (≤5 points) or “poor sleeper” (>5 points). Stress levels were classified as Normal (≤13), Initial stress (14–16), Moderate stress (17–18), or Severe stress (≥19). The results indicated no significant differences in sleep quality based on occlusal characteristics. However, participants with Type A occlusion (posterior contact without anterior contact) exhibited higher stress scores than those with Type B occlusion. Correlation analysis showed a weak negative association between stress scores and occlusion type, but no significant relationship was found between occlusal characteristics, sleep quality, and stress levels. In conclusion, individual occlusal characteristics have limited explanatory power regarding their effects on sleep quality and stress.

1. Introduction

Malocclusion is a condition where abnormalities in the development, morphology, or function of the craniofacial structures, teeth, or periodontal tissues—due to various factors—lead to improper occlusion [1]. As such, malocclusion is one of the most common oral disorders worldwide, with a high prevalence across various populations. It goes beyond a mere misalignment of teeth and has been identified as a critical factor affecting both oral and systemic health [2]. Malocclusion can influence not only masticatory function and temporomandibular joint dysfunction (TMD) but also physical, social, and psychological well-being [2,3,4].

Normal occlusal relationships are essential for efficient masticatory function and help distribute the load on the temporomandibular joint (TMJ) evenly, maintaining muscular and neurological stability [5]. However, when occlusal disharmony occurs, it can impair masticatory function, negatively affect food selection and nutritional status [6], and contribute to various physical issues such as headaches, muscle tension, and cervical imbalance [7,8].

Furthermore, occlusal disharmony is closely linked to mental health problems such as social isolation, depression, and increased stress levels [9]. As a result, the World Health Organization (WHO) has classified malocclusion as a “disabling oral and maxillofacial abnormality” that negatively affects oral and maxillofacial function and structure and social well-being [10,11] and has identified it as a major public health challenge [12,13].

Recent studies have highlighted the correlation between occlusal conditions and nervous system responses, emphasizing that malocclusion can stimulate stress responses through an increased sympathetic nervous system [14]. In cases of unstable occlusion, excessive tension in the masticatory muscles and an increased load on the temporomandibular joint (TMJ) may occur [15]. When these conditions persist, they can lead to physical fatigue and mental anxiety. Such neurological changes may eventually reduce immune function, cause metabolic imbalances, and result in mental fatigue—factors that can contribute to increased stress levels and poorer sleep quality [16].

Moreover, some studies have reported a correlation between malocclusion types, such as anterior open bite, and changes in breathing patterns during sleep, suggesting a potential decline in sleep quality [17]. Structural abnormalities in the oral cavity may cause upper airway narrowing, increasing airway resistance and leading to sleep-related breathing disorders [18]. This mechanism significantly increases the risk of conditions such as obstructive sleep apnea (OSA), characterized by reduced oxygen saturation and fragmented sleep, ultimately impairing deep sleep [19,20]. However, a cross-sectional study conducted among non-obese adult Saudi patients found no significant association between dental occlusion characteristics and the severity of OSA, suggesting that occlusion may not serve as a consistent risk factor across all population groups [21]. These conflicting findings highlight that the relationship between occlusal characteristics and sleep quality or sleep-related disorders remains inconclusive and warrants further investigation.

Women are known to be more vulnerable to these effects due to hormonal fluctuations, particularly estrogen level changes, which influence autonomic nervous system regulation, making them more susceptible to physical and mental stress [22]. University and college students, in particular, may experience heightened stress levels due to academic pressure, social obligations, and changes in daily routines [23]. These psychological factors can interact with occlusal issues, exacerbating both physical and mental health problems.

Therefore, the aim of this study was to measure individual occlusion using T-Scan III^® in female college students and to analyze occlusion characteristics such as occlusion contact time, occlusion balance, and occlusion contact pattern to evaluate the effects of occlusion imbalance on stress level and sleep quality.

2. Materials and Methods

This study was conducted with ethical approval from the Bioethics Committee of OO University (IRB No: CKU-22-01-0308) and included female college students from a university in Gyeonggi Province. The sample size was determined using G*Power 3.1.9.2, with a significance level of 0.05, a medium effect size of 0.41, and a statistical power of 0.95, resulting in a required sample size of 80. To account for a 20% dropout rate, the final target sample was set at 96 participants. The research was conducted between 1 February and 30 June 2023. All subjects who participated in the study underwent occlusion analysis using the T-Scan III^® System and a questionnaire to determine their sleep quality and stress level. After excluding 12 individuals who either did not complete the questionnaire or did not undergo occlusal measurements, the final analysis included 84 participants (age: 21.7 ± 2.09).

2.1. Occlusal Analysis Using the T-Scan III^® System

Occlusal characteristics were analyzed using the T-Scan III^® System (Tekscan Inc., Boston, MA, USA). Before data collection, participants practiced under examiner supervision to ensure consistent measurement. All measurements were conducted with a standardized sensitivity setting, and participants were instructed to maintain centric occlusion for approximately two seconds. Each participant underwent four repeated trials, with the first and last trials excluded and the average value of the remaining trials used for analysis.

The occlusion time (OT), defined as the time from initial tooth contact to complete occlusion, was measured. Based on an established threshold of 0.3 s, occlusion was classified as stable occlusion (OT < 0.3 s) or unstable occlusion (OT ≥ 0.3 s). Occlusal force distribution was also analyzed by dividing the relative occlusal force (%) at maximum intercuspation into four quadrants, assessing balance in the left–right and anterior–posterior regions [24].

Participants were categorized into two occlusal types based on their centric occlusion contact pattern: Type A, where all premolars and molars made contact, but the anterior teeth did not, and Type B, where both premolars and molars, as well as the anterior teeth, made contact [25].

2.2. Assessment of Sleep Quality

Sleep quality over the past month was evaluated using the Korean version of the Pittsburgh Sleep Quality Index (K-PSQI). The PSQI consists of 19 items across seven components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Each component is scored from 0 to 3, and the total PSQI score, ranging from 0 to 21, was used to classify participants into the following categories: Good sleeper, PSQI score ≤ 5; Poor sleeper, PSQI score > 5 [26].

2.3. Assessment of Stress Level

Participants’ stress levels were assessed using a 10-item questionnaire. Each item was rated on a 5-point Likert scale, with scores ranging from 0 (never experienced stress-related emotions in the past month) to 4 (very frequently experienced stress-related emotions). The total stress score was calculated by summing the scores of all 10 items, resulting in a stress index classified into four categories: Normal, 0–13 points; Initial stress, 14–16 points; Moderate stress, 17–18 points; Severe stress, ≥19 points.

2.4. Statistical Analysis

All collected data were analyzed using SPSS 27.0 (IBM Corp., Armonk, NY, USA). A p-value of <0.05 was considered statistically significant. Prior to statistical analysis, normality was assessed using the Shapiro–Wilk test, and homogeneity of variance was evaluated using Levene’s test. Descriptive statistics and frequency analyses were conducted to examine the sleep quality, stress scores, and occlusal characteristics of the participants. Differences in sleep quality and stress scores according to occlusal characteristics were analyzed using the independent t-test. If the assumption of equal variances was not met, then Welch’s t-test was applied. The relationships among occlusal characteristics, sleep quality, and stress levels were assessed using Spearman’s correlation analysis. Spearman’s rank correlation coefficients (p, rho) were interpreted according to commonly accepted guidelines: p (rho) = 0.00–0.19 was considered negligible; 0.20–0.39 was considered weak; 0.40–0.59 was considered moderate; 0.60–0.79 was considered strong; and 0.80–1.00 was considered to show a very strong correlation [27].

3. Results

3.1. Sleep Quality and Stress Levels of Participants

The average Pittsburgh Sleep Quality Index (PSQI) score among participants was 18.3, indicating poor sleep quality, as all participants had scores exceeding 5. Regarding stress levels, 13.1% of participants had normal stress levels, while 56.0% experienced stress levels high enough to require professional counseling (

Table 1. Sleep quality and stress levels of participants.

Index	Mean ± SD	N (%)
PSQI 1	18.3 ± 4.3
Good (≤5)		0 (0.0)
Poor (>5)		84 (100.0)
Stress Score	18.9 ± 4.7
Normal (≤13)		11 (13.1)
Initial Stress (14–16)		12 (14.3)
Moderate Stress (17–18)		14 (16.7)
Severe Stress (≥19)		47 (56.0)

¹ PSQI, Pittsburgh Sleep Quality Index.

).

3.2. Occlusal Pattern Analysis Using the T-Scan System

The occlusion time measured using the T-Scan system was 0.24 ± 0.17 s. Among the participants, 18.0% exhibited unstable occlusion (occlusion time ≥0.3 s).

Regarding occlusal balance, the relative occlusal force between the left and right sides was 44.9% and 52.8%, respectively, indicating a relatively balanced distribution. However, in the anterior–posterior direction, occlusal force was predominantly concentrated in the posterior region.

In terms of occlusal contact patterns, Type B occlusion, characterized by contact in both premolars and molars, as well as the anterior teeth, was the most prevalent, observed in 82.0% of participants (

Table 2. Distribution of occlusion analysis using T-scan III^® system (N = 84).

Characteristics	Division	N (%)
Occlusion time	<0.3 sec (Stable occlusion)	69 (82.1)
	≥0.3 sec (Unstable occlusion)	15 (17.9)
Occlusion balance I	Left side	39 (46.4)
	Right side	45 (53.6)
Occlusion balance II	Anterior	2 (2.4)
	Posterior	82 (97.6)
Occlusion contact pattern	Type A	14 (16.7)
	Type B	70 (83.3)

Data are presented as frequencies.

).

3.3. Differences in Sleep Quality and Stress Scores According to Occlusal Patterns

A comparison of sleep quality scores based on occlusal characteristics revealed no significant differences in sleep quality scores across occlusal stability, occlusal balance, or occlusal type.

In terms of stress scores, no significant differences were observed between groups based on occlusal stability or occlusal balance. However, participants with Type A occlusion—characterized by posterior occlusion without anterior contact—had higher stress scores compared to those with Type B occlusion (

Table 3. Differences in sleep quality and stress scores according to occlusal characteristics.

Characteristics	PSQI (Mean ± SD)	p-Value	Stress Score (Mean ± SD)	p-Value
Occlusion time
<0.3 (Stable occlusion)	18.4 ± 4.6	0.812	18.8 ± 4.9	0.771
≥0.3 (Unstable occlusion)	18.1 ± 3.0		19.2 ± 3.5
Occlusion balance I
Left side	18.7 ± 5.0	0.485	19.6 ± 4.3	0.180
Right side	18.0 ± 3.7		18.2 ± 4.9
Occlusion balance II
Anterior	19.5 ± 6.4	0.697	23.5 ± 0.7	0.157
Posterior	18.3 ± 4.3		18.8 ± 4.7
Occlusion contact pattern
Type A	19.1 ± 4.2	0.434	21.1 ± 4.3	0.045 *
Type B	18.1 ± 4.4		18.4 ± 4.6

Data are presented as mean ± standard deviation (SD). p values were calculated using the independent t-test. * p < 0.05 indica tes statistical significance.

).

3.4. Correlation Between Occlusal Patterns, Sleep Quality, and Stress Scores

Correlation analysis revealed the following relationships: Occlusal balance (left–right) had a moderate positive correlation with occlusal stability (occlusion time) and a weak correlation with occlusal type. Sleep quality and stress scores exhibited a moderate correlation (r = 0.48), indicating that poorer sleep quality was associated with higher stress levels. Stress scores and occlusal type showed a weak negative correlation, suggesting a slight inverse relationship between occlusal type and stress levels. Apart from the weak correlation between occlusal type and stress scores, no significant relationships were observed between occlusal patterns, sleep quality, and stress scores (

Table 4. Correlation among occlusal characteristics, sleep quality, and stress scores.

Variables	Occlusion Time	Occlusion Balance I	Occlusion Balance II	Occlusion Contact Pattern	PSQI	Stress Score
Occlusion time	1
Occlusion balance I (L-R)	0.31 **	1
Occlusion balance II (A-P)	−0.13	0.01	1
Occlusion contact pattern	−0.13	−0.29 **	0.14	1
PSQI	0.02	−0.04	−0.02	−0.09	1
Stress score	0.22	−0.13	−0.20	−0.24 *	0.48 **	1

Spearman’s correlation coefficient (r) values are presented. p < 0.05 (*), p < 0.01 (**), indicating statistical significance.

).

4. Discussion

This study aimed to evaluate the association between individual occlusal characteristics and sleep quality and stress levels in female college students. The results indicated no significant correlation between occlusal stability or occlusal balance and sleep quality. However, participants with Type A occlusion—characterized by posterior contact without anterior contact—exhibited significantly higher stress scores than those with Type B occlusion, which involves contact in both the posterior and anterior regions. Despite the relatively small sample size of the Type A group, the difference in stress scores was statistically significant. However, the Type A occlusal pattern was not significantly associated with sleep quality.

In this study, occlusal characteristics were objectively analyzed using the T-Scan III^® System, a tool with proven reliability and validity [28,29]. Occlusal stability refers to a state in which the alignment and contact of teeth are maintained consistently, serving as a crucial factor in efficient masticatory function and oral health maintenance. The results showed no significant correlation between occlusal stability and stress levels. This may be attributed to the multifaceted nature of stress, which is influenced by various psychosocial factors [30], suggesting that occlusal stability alone may not be sufficient to explain stress levels.

When evaluating the distribution of occlusal contact in the left–right and anterior–posterior directions, the balance distribution ratios were found to be 46.4% and 54.6%, respectively, indicating a relatively symmetrical distribution. Additionally, most participants exhibited a posterior occlusion pattern. These findings suggest that the absence of significant correlations between occlusal balance and sleep quality or stress levels may be due to the fact that most participants in this study exhibited no issues with occlusal balance.

The finding that participants with Type A occlusion, characterized by the absence of anterior contact, exhibited higher stress scores is consistent with previous studies [14,16]. This result can be interpreted as occlusal imbalance increasing masticatory muscle tension and imposing additional strain on the temporomandibular joint (TMJ), which in turn stimulates the sympathetic nervous system and induces stress. Occlusal instability and psychological stress are recognized as major contributors to masticatory muscle dysfunction and temporomandibular disorders (TMDs), and prior studies have reported that occlusal imbalance can lead to excessive tension and discomfort in the neuromuscular system [31]. When anterior contact is absent, occlusal forces are not distributed evenly during mastication, potentially concentrating stress on specific areas and exacerbating occlusal imbalance. This imbalance may contribute to increased tension in the masticatory muscles, neuromuscular discomfort, and, over time, elevated stress levels.

In this study, stress levels were assessed using a self-reported questionnaire, which reflects participants’ subjective perceptions of stress but is inherently susceptible to response bias and situational influences. Notably, the stress questionnaire was administered immediately after the occlusal evaluation, raising the possibility that participants’ awareness of their occlusion or the testing context may have influenced their responses. Furthermore, the number of participants with Type A occlusion was relatively small (n = 14), which limits the generalizability of the observed differences and should be considered a limitation of this study.

Furthermore, some studies have reported that occlusal imbalance may be closely related to brain function and neural activity [32,33]. Masticatory movements, tooth contact, and occlusal changes in the oral and maxillofacial region can influence neural activity in the motor and sensory cortices by altering proprioceptive input from the periodontal ligaments and the temporomandibular joint (TMJ). These neural changes have been reported to occur even in response to relatively minor occlusal alterations, such as occlusal interference, intraoral appliances, or implant prostheses [33]. These findings suggest that occlusal imbalance may not be merely a localized oral condition but may involve potential mechanisms that affect systemic health, including neurological function and psychological responses such as stress and anxiety. The study sample might be biased towards individuals where occlusal characteristics have a stronger impact on stress than sleep quality.

Contrary to previous studies that reported associations between occlusal imbalance and reduced sleep quality or sleep apnea [17,18,20], the present study did not find a statistically significant difference in sleep quality based on occlusal characteristics. The mean PSQI score for participants with Type A occlusion was 19.1 ± 4.2 (range, 11–26), while the Type B group recorded a mean score of 18.1 ± 4.4 (range, 9–25). Although the Type A group showed a slightly higher average score, the considerable overlap in standard deviations and within-group variability indicates that this difference is not meaningful. Furthermore, sleep quality was assessed using a self-reported questionnaire, which inherently reflects subjective perceptions and may be influenced by individual interpretation and response bias. Additionally, all participants in this study had PSQI scores exceeding 5, categorizing them uniformly as poor sleepers. This homogeneity in sleep quality across the sample may have limited the ability to detect differences based on occlusal patterns and should be acknowledged as a limitation when interpreting the findings.

Women are known to be more vulnerable to stress due to increased autonomic nervous system sensitivity caused by hormonal fluctuations [22]. Moreover, college students are prone to elevated stress levels resulting from academic pressure, social relationships, and changes in lifestyle patterns [23]. These psychological factors may interact with occlusal characteristics, potentially amplifying stress responses. Since stress is also closely linked to lifestyle factors such as irregular sleep patterns, excessive caffeine intake, and heavy academic stress [34], future research should analyze the interaction between such lifestyle factors and occlusal characteristics.

The limitations of this study include the fact that the subjects were limited to female college students, which limits the generalization of the results. In addition, it was difficult to clearly identify the association between occlusal characteristics and stress because it was designed as a cross-sectional study. Finally, there is a possibility of subjective bias when using self-reporting tools to assess sleep and stress. Therefore, future studies are needed that include a wider range of ages and genders and utilize objective physiological indicators. In addition, a longitudinal study is needed to explore the temporal sequence and potential directional relationship between occlusal changes and stress responses.

Nevertheless, the findings of this study suggest that occlusal characteristics may be associated with psychological factors, such as stress. Accordingly, dental professionals should evaluate not only tooth alignment but also anterior occlusal contact and overall occlusal balance. Such a comprehensive approach may aid in the early identification and management of occlusion-related factors that could influence mental health outcomes, including perceived stress and sleep disturbances.

5. Conclusions

This study assessed the relationship between occlusal characteristics, sleep quality, and stress levels among female university students. The results revealed no significant correlation between occlusal stability, occlusal balance, occlusal type, and sleep quality. However, participants with Type A occlusion, characterized by posterior contact without anterior contact, showed significantly higher stress scores compared to those with Type B occlusion, which involves both posterior and anterior contact. This finding suggests that while occlusal imbalance may not have a clear association with sleep quality, certain occlusal types may contribute to increased stress levels. Therefore, further research that comprehensively evaluates psychological factors, lifestyle habits, oral parafunctional behaviors, and environmental influences is necessary to better understand the complex interactions between occlusion, sleep quality, and stress.