Does forward head posture correction improve temporomandibular joint dysfunction? A pilot randomized trial using a cervical extension traction orthotic
-
Shima A. Mohammad Zadeh
Abstract
Context
This pilot study assessed participants adherence rate and the effect size needed to determine the sample size for a full-scale study evaluating the effectiveness of forward head posture (FHP) correction on temporomandibular disorders (TMDs) and symptoms. Moreover, the potential impact of adding FHP correction to a standard conservative protocol for treatment of TMD severity, pain, and pain-free mouth opening range is explored.
Objectives
The primary objective was to investigate the additional effect of FHP correction by a cervical extension traction (CET) orthotic on myogenic TMD symptoms of pain and function.
Methods
A total of 21 participants (19 females) were enrolled and completed the study. The participants’ mean age was 21.99±2.06 years, body mass index (BMI) 22.92±4.27 kg/m2. A randomized clinical trial was conducted with participants who were randomly divided into two groups: 1) an experimental group with 10 participants receiving a FHP CET orthotic and a conservative TMD protocol; and 2) a control group with 11 participants receiving the conservative TMD protocol and a placebo CET device utilizing a standard pillow. Outcome assessments included: TMD severity with Fonseca’s questionnaire, numerical rating scale for pain intensity, maximum mouth opening (MMO), and the craniovertebral angle (CVA) to measure FHP. Assessments were performed at three time points (baseline, 3rd week, 6th week), and three treatment sessions per week for six consecutive weeks were administered.
Results
Both groups achieved a high adherence rate to the study protocol (≥90 %). Within-group analysis for both groups, across the three time points, identified significant differences utilizing Friedman’s test (p<0.001) between measures for orofacial pain, TMD severity, MMO, and CVA. Between-group comparison identified no difference at the follow-up assessments for orofacial pain or MMO measures (p>0.05). The Mann-Whitney U test for between-group comparisons identified a statistically significant difference in CVA at week 3 (p=0.01) and at the 6th week (p<0.001) favoring the experimental group. For the TMD severity score, no difference was found at week 3 (p=0.11) but there was a significant difference between groups at week 6 (p=0.02) favoring the experimental group.
Conclusions
These preliminary findings suggest that adding FHP correction through the application of a CET orthotic might offer short-term selected benefits for chronic TMD symptoms, which would need to be confirmed in a full-scale trial. High adherence rates were found with a moderate effect size that provided data indicating that at least 38 participants would be required for a full-scale study.
Temporomandibular disorders (TMDs) have a high prevalence ranging between 15 and 25 % among young adults and adults globally [1], [2], [3]. TMD features consist of muscle malfunction, abnormal teeth fitting and improper occlusion that results in pain, and a limited opening range of motion that is often accompanied by joint noises “crepitus, clicking or popping” sounds [1], 2], [4], [5], [6]. Studies investigating the prevalence of TMD found that its symptoms often originate at a young age, specifically 10 years old [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. TMD can be clinically classified into two different groups: articular (disc displacement and degeneration) or nonarticular (myogenous TMD) [17]. Several studies reported symptoms to be related to sleep quality, anxiety, stress, and depression [5], 14], 15], [18], [19], [20], whereas other studies have found conflicting results of the cause-and-effect relationship but offer important prevalence data [11], 12], 16], 21].
A predominance of forward head posture (FHP) among different age groups globally revealed that at least more than 50 % of the sample selected in these previous studies had FHP [22], [23], [24], [25], [26]. FHP is defined as a deviation from the normal anatomical relationship in which the head should be vertically but dynamically balanced on the cervical spine, maintaining its physiological lordotic curve [27]. This craniovertebral balance is kept by sustained contraction of deep cervical neck flexor muscle such as rectus capitus, longus colli, and longus capitus [27]. Anatomically, the two regions of the cervical spine and masticatory system are closely linked by the frequent coexistence of neck pain and TMD [28]. Altered masticatory muscle tension has been linked to cervical curvature and can potentially cause cervical paravertebral muscle dysfunction [29]. The relationship between the two conditions of FHP and TMD has been investigated by comparing the craniovertebral angle (CVA) of TMD patients to healthy individuals; on average, TMD patients have a smaller CVA, indicative of a forward head position [30], 31].
Multiple investigations have sought the association between FHP and TMD and have generally inferred the following: 1) FHP can be a risk factor for TMD when any alteration in the head position produces more tension on the masticatory muscles by altering the mandibular position [32], 33]; and 2) TMD might originate from muscular dysfunction rather than an articular derangement. However, the correlation between FHP and TMD is still not clear enough to elucidate the exact preventive and treatment measures that are needed [33]. Arguably, discrepancy in the literature exists on causal and/or association relationships between FHP and TMD due to the lack of proper subgrouping of TMD patients based on their diagnostic subcategories and a lack of standardization of patients’ posture analytical methods [34], [35], [36], [37].
Previously, FHP and TMD patients were, arguably, managed for separate disorders by utilizing soft occlusal splints and a conservative physiotherapy program to improve the TMD symptoms on the one hand [38], [39], [40] and then other studies managed FHP by corrective exercises [34], 41], 42]. However, different therapeutic interventions specifically targeting correction of FHP in the subgroup of patients with FHP and TMD have identified reduced TMD symptoms compared to a focused TMD treatment regimen without FHP corrction [28], 34], 42], 43]. These previous studies included traditional unstandardized correction methods of neck muscles strengthening and stretching exercises [34], posture training [43], manual therapy [28], and Mulligan’s mobilization with movement [42].
It might be beneficial to look at the literature specific to rehabilitation in cervical spine disorder patients without TMD but with significant FHP to identify the best method for rehabilitation of the cervical spine in patients with FHP as a primary biomechanical problem. A systematic review analyzed nine controlled trials that examined cervical extension traction (CET) techniques to restore the cervical lordosis and reduce FHP [44]. It was found that increasing the curvature of the neck through CET as part of a rehabilitation program can reduce pain, reduce disability, and improve functional measurements in both short-term and long-term follow ups [44], 45]. Similarly, in a recent randomized trial, significant improvement in FHP was identified by the incorporation of a CET orthotic called the Denneroll cervical traction orthotic (DCTO) as compared to standard rehabilitation protocols in elderly individuals [22]. This superiority of CET methods to improve FHP in patient populations is generally consistent with the results of the systematic review reported by Oakley et al. [44] In general, CET devices cause a three-point bending force to the cervical spine in which spine tissues anterior to the axis of extension application experience significant tension loads while spine tissues posterior to the axis of rotation will experience compression. Thus, the anterior tension will unload the intervertebral disc and create longitudinal tension loads to be applied to the cervical spine muscles and anterior longitudinal ligament. This will result in considerable visco-elastic creep deformation of spine tissues which effectively increases the cervical lordosis and reduces any FHP [22], 44], 45]. Interestingly, CET methodology has been utilized to effectively treat a variety of chronic neck pain disorders with both loss of the cervical lordotic curvature and FHP, including patients suffering from: myofascial pain syndrome, cervicogenic dizziness, chronic nonspecific neck pain, discogenic radiculopathy, and cervical spondylotic radiculopathy [22], 44], 45]. Of course, patients must be properly screened for indications and contraindications [22], 44], 45].
Although many researchers have reported the prevalence of TMD combined with FHP and suggested a relationship between the two conditions, to our knowledge, none have investigated the additional effect resulting from FHP correction on myogenic TMD. Exploring the impact of FHP correction on TMD could be beneficial to strengthen any association and discover an alternative pathway to target TMD. Although clinicians have investigated the association between FHP and TMD reporting various therapy techniques to relieve TMD symptoms [22], 28], 34], 43], few have considered the impact of FHP correction on TMD symptoms. Thus, this study will hopefully reinforce the existing knowledge and will enrich the association between the two conditions, as well as highlight the importance of developing new management plans for TMD when associated with FHP.
Although the CET methodology has proved its efficacy in improving FHP, no study has previously investigated the effect of improving TMD and FHP in patients suffering from myogenic TMD symptoms utilizing a combined approach of standard TMD interventions combined with CET methodology. Thus, the primary aim of this study was to evaluate participant adherence the proper effect size required for a full-scale study, and the additive effect of FHP correction on TMD symptoms utilizing the DCTO combined with a standard TMD treatment protocol.
Methods
Study setting and design
This research was a pilot study with two parallel groups following the CONsolidated Standards Of Reporting Trials (CONSORT) extension for pilot studies (Supplementary Material). It was conducted among a random sample of young adults at the medical campus, University of Sharjah, United Arab Emirates. This study was approved by the Research Ethics Committee of the University of Sharjah (reference number REC-23-12-18-02-P G), and the main study was registered on ClinicalTrials.gov (ID: NCT06156345).
Participants
Participants were recruited through social media (Instagram, WhatsApp, and Snapchat) by sharing the study flyer, and by word of mouth directed toward young adult and adult participants from 18 to 40 years who reported one or more of TMD signs or symptoms and has been diagnosed with TMD as well as having FHP with a CVA angle <55° [46]. Participants were excluded if there was any surgical intervention directed toward the TMJ and if head, neck, or TMJ traumas were reported. Once participants were deemed to be eligible, they were asked to fill in a consent form and complete the baseline evaluation in the treatment room (University of Sharjah, medical campus). The study started after obtaining Ethical Approval in December 2023, participants were recruited in January 2024, and the treatment session started on March 1, 2024 and was completed on May 5, 2024.
Interventions
All participants (both experimental and control groups) were requested to attend the treatment sessions 3 days per week for 6 weeks irrespective of their group randomization. The total treatment time per participant per group ranged from 20 to 28 min per session.
Conservative TMD protocol
All participants (both experimental and control groups) received a conservative TMD protocol that was adopted from Shousha et al. [40] and Bose et al. [47] This conservative protocol consisted of teaching the patient the relaxed jaw position (tongue placed up behind the upper front teeth with a gap between the lower and upper teeth) and stretching exercises for the masseter and lateral pterygoid muscles with a hold of 20–30 s and 3–5 repetitions (Supplementary Material).
DCTO FHP traction and placebo
The DCTO (www.denneroll.com, of PO BOX 5051, Wheeler Height Post Office. Wheeler Heights NSW 2097) was applied in the experimental group to improve FHP, and the traction protocol was adopted from a study by Suwaidi et al. [22] Participants were placed supine with the DCTO placed on the posterior aspect of their neck in the lower-to-mid cervical spine (C6-T1) following previously published protocols [22], 48]. Placement of the peak of the DCTO in the lower cervical spine (C6–T1) creates moderate hyperextension in this region while causing substantial posterior head translation over the orthotic. Patients were encouraged to relax when lying supine, and their movements were restricted with direct supervision from the responsible therapist. Treatment session time began with 3 min of DCTO application per session and patients were encouraged to increase the time by 2–3 min per session until they reached 15–20 min of sustained duration each session (Figure 1).
The Denneroll cervical traction orthotic (DCTO). The participant must lie on a firm surface, such as the floor, and place the peak of the Denneroll just distal to the apex of their cervical lordosis. Shown here is a midcervical spine placement in which the Denneroll and model are on a soft bench for proper photography (reprinted with permission CBP Seminars, Inc.).
In the control group only, a placebo pillow was included in the treatment sessions to ensure that each participant received the same number of interventions and the same approximate time of intervention session as recommended and performed by Moustafa et al., [48], where the time allotted for the placebo pillow was similar to that for the DCTO in the experimental group beginning at 2–3 min per session and increasing the time gradually until they reached 15–20 min. This nonmedical pillow is a relatively firm pillow that applies adequate pressure to the head and neck in a comfortable manner and is shown in Figure 2.
![Figure 2:
The placebo utilized for the control group. The participant was placed supine on a firm surface, and a standard firm pillow was utilized to support the head and neck. This placebo allowed for the same number of interventions and length of treatment sessions [48].](/document/doi/10.1515/jom-2025-0081/asset/graphic/j_jom-2025-0081_fig_002.jpg)
The placebo utilized for the control group. The participant was placed supine on a firm surface, and a standard firm pillow was utilized to support the head and neck. This placebo allowed for the same number of interventions and length of treatment sessions [48].
Outcome measures
The primary outcome measure was the numerical rating score (NRS) from 0 to 10 to record the orofacial pain intensity, where 0 means no pain and 10 is the worst pain experienced ever. The NRS is both reliable and valid with a standard error of measurement of one point and a minimal important change (MIC) of two points [49].
This study included several secondary outcome measures. First, the anamnestic questionnaire by Fonseca was administered to evaluate TMD symptom severity through 10 questions with their corresponding scores 0, 5, or 10 [50], 51]. The anamnestic questionnaire is considered to be a valid and reliable tool [52]. It has four classifications based on the total score: 1) no TMD between 0 and 15 points; 2) mild TMD symptoms between 20 and 40; 3) moderate TMD symptoms between 45 and 65 points; and 4) severe TMD symptoms between 70 and 100 points.
Furthermore, the CVA via a photographic method utilizing the PostureScreen Mobile app to assess the FHP where an angle less than 55° is generally considered to be FHP. Herein, we followed the assessment protocol by Awatani et al. [53] because this method has been proved to have a high reliability validity. During the procedure, an iPad camera is utilized for the app to take pictures of participants from various directions. When taking the picture, the app reflects a target-like display that turns green when the tablet is level. This ensures that each image is taken at a level and consistent angle. The app then calculates the translations and angulations of different postural regions. For instance, for the CVA in the sagittal plane, the angle is calculated based on a marker placed on the C7 spinous process and one at the tragus of the ear, which are connected by a line that is then measured relative to a horizontal (PostureCo; http://postureanalysis.com/mobile/).
Lastly, clinical examination of the maximum mouth opening (MMO) via Boley gauge measures the width between the upper and lower teeth in mm. All outcome assessments were conducted at baseline, at the end of the third week of treatment, and at the end of the sixth and final week of treatment by the same therapist who applied the intervention protocols to minimize inter-therapist variability.
Sample size
Sample size was determined before conducting the trial based on the outcome of orofacial pain through the NRS based on the calculations designed for pilot studies by Hertzog et al., [54] in which a smaller sample such as 10 participants in each group is sufficient. As a result, 20 participants were sought to be recruited.
Randomization
After the baseline assessment, participants were randomized into group A or B (where A represents the experimental group and B represents the control group) utilizing a permuted block randomization with a 1:1 ratio. Each random block was stored in opaque sealed envelopes consecutively numbered with a third researcher. Once each participant officially joined the study, the researcher opened the subsequent envelope. This study was single-blinded wherein all of the examinations and treatment sessions were performed by one therapist to ensure the fidelity of the treatment, and the participants were blinded about the research group to which they were allocated.
Statistical analysis
When data are presented as continuous data, the Shapiro-Wilk test was conducted to check the normality of the data distribution. When data were not normally distributed, the Mann-Whitney U test was performed to compare between the group, and the Friedman test was utilized to compare the difference across the three time points of the study (baseline, 3 weeks, and 6 weeks). Descriptive statistics of the frequency, median, and interquartile range (IQR) were utilized to report participant demographics, characteristics, and improvement. IBM Statistical Package for the Social Sciences (SPSS) statistics software version 22 (IBM Corp., Armonk, NY) was utilized to perform the analysis with 95 % confidence interval (CI) and a significance level set at 5 %.
Results
A total of 21 participants completed this pilot study. Participants were divided into two groups: experimental and control. The participant flowchart shows the screening of 25 participants and enrollment of 21 only after excluding four participants due to withdrawal (n=3) and not fulfilling the inclusion criteria (n=1); therefore, the 21 participants were split into two groups (experimental with 10 participants and control with 11 participants), and all of them were included in the final results (Figure 3). In the experimental group, 10 participants received both the conservative and the DCTO FHP traction treatments. The 11 participants in the control group received the conservative protocol with a placebo method utilizing a pillow for an equivalent time and interventions as compared to the experimental group. We identified a high adherence rate to the recommended treatment frequency and duration (≥90 %) in both groups, and this was calculated by dividing the number of participants who finished the study by the total number of each group. The study ended when the final participant in either group completed their 6-week follow-up evaluation.
A participant flow chart showing the screening of 25 participants, and enrollment of 21, after excluding four participants due to withdrawal (n=3) and not fulfilling the inclusion criteria (n=1). Therefore, the 21 participants were split into two groups (an experimental group with 10 participants and a control group with 11 participants), and all of them were included in the final results analysis.
The participant characteristics including but not limited to age, weight, height, body mass index (BMI), and gender are shown in Table 1. The two groups were homogenous in their anthropometrics, and there were no significant difference in the three baseline measures between the participants (p>0.05), with the exception of orofacial pain intensity, which was different between the groups (p=0.02); Tables 1 and 2 show this data.
Participants characteristics (n=21).
| Variables | Experimental (n=10) | Control (n=11) | p-Value |
|---|---|---|---|
| Age, years [median (IQR)] | 21.00 (3.00) | 22.00 (2.00) | 0.69 |
| Body mass, kg [median (IQR)] | 59.50 (27.10) | 68.00 (28.00) | 0.94 |
| Height, cm [median (IQR)] | 164.50 (10.30) | 159.00 (12.00) | 0.11 |
| BMI, kg/m2 [median (IQR)] | 22.00 (6.32) | 25.00 (7.01) | 0.48 |
| Gender (female, male) | (9, 1)a | (10, 1)a | 0.12 |
| Educational level (high school, Bachelor’s, postgraduate) | (0, 8, 2)a | (1, 7, 3)a | 0.54 |
| Family history of overweight/obesity (yes, no) | (2, 8)a | (3, 8)a | 0.15 |
-
aNumber of participants. IQR, interquartile range; BMI, body mass index.
Participants baseline measures (n=21).
| Variables | Experimental (n=10) | Control (n=11) | p-Value |
|---|---|---|---|
| Orofacial pain (NRS) | 3.50 (2.00) | 2.00 (1.00) | 0.02 |
| TMD severity score | 45.00 (26.00) | 50.00 (30.00) | 0.97 |
| MMO, mm | 38.50 (14.50) | 43.00 (5.00) | 0.32 |
| CVA, ° | 51.35 (5.70) | 53.30 (5.40) | 0.42 |
-
NRS, numerical rating scale; IQR, interquartile range in (); TMD, temporomandibular joint dysfunction; MMO, maximum mouth opening; CVA, craniovertebral angle.
The Mann-Whitney U test for between-group comparisons identified a statistically significant difference in CVA at the week 3 assessment (p=0.01), which continued until the last assessment (p<0.001). Likewise, for the TMD severity score, there was a significant difference between groups at week 6 (p=0.02) but no difference at week 3 (p=0.11) (Table 3). Figure 4 illustrates the differences between the experimental and control groups in the significant outcome measures at baseline and final assessment time points. Across the three time points, within-group difference revealed a statistically significant difference utilizing Friedman’s test (p<0.001). The steady improvement in all the measures for both groups (orofacial pain, TMD severity, MMO, and CVA) are shown in Table 4.
Mann-Whitney U test comparing experimental to control group.
| Variables | Week 0 (baseline) | Week 3 | Week 6 |
|---|---|---|---|
| Orofacial pain (NRS) | 0.02 | 0.82 | 0.54 |
| TMD severity score | 0.97 | 0.11 | 0.02 |
| MMO, mm | 0.32 | 0.97 | 0.42 |
| CVA | 0.42 | 0.01 | <0.001 |
-
NRS, numerical rating scale; TMD, temporomandibular joint dysfunction; MMO, maximum mouth opening; CVA, craniovertebral.
Box plots of total TMD score and CVA between groups. Comparing both groups at the baseline (W0) and upon completion of the study (W6) revealed an improvement in the experimental group compared to the control group upon completion of their 6-week intervention program.
Friedman’s test for within-group differences. Each number under the weeks reflects the mean ranks while the difference between each variable across the intervention period is reflected by the p value.
| Variables | Orofacial pain (NRS) (mean rank) | TMD severity score (mean rank) | MMO (mean rank) | CVA (mean rank) | p-Value | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| W0 | W3 | W6 | W0 | W3 | W6 | W0 | W3 | W6 | W0 | W3 | W6 | ||
| Experimental group | 3.30 | 1.95 | 1.40 | 8.50 | 5.15 | 3.35 | 6.65 | 8.10 | 9.70 | 8.60 | 10.20 | 11.10 | <0.01 |
| Control group | 2.59 | 1.86 | 1.55 | 8.95 | 5.55 | 4.59 | 6.18 | 8.18 | 8.55 | 9.36 | 10.05 | 10.59 | <0.001 |
-
NRS, numerical rating scale; TMD, temporomandibular joint dysfunction; MMO, maximum mouth opening; CVA, craniovertebral. W0, week zero; W3, third week; W6, sixth week.
Discussion
The purpose of the study was to assess participants’ adherence rate as well as to detect the effect size needed to determine the actual sample size essential for a larger-scale study evaluating the effectiveness of FHP correction on TMD symptoms. Moreover, this study aimed to explore the potential impact of adding FHP correction in the conservative protocol on TMD severity, pain, and pain-free mouth opening range utilizing the DCTO. The findings showed that both groups had a high level of adherence. In clinical settings, it is necessary to investigate a patient’s adherence or compliance because there is a lack of definitions and standards for satisfactory compliance in research, which are seen as deficiencies in research methodology [55]. Conservative care relies heavily on the participants’ interest to volunteer for studies on the consequences of research materials and their dedication to carry out treatment regimens [56]. Still, after enrolling in a clinical trial, some participants fail to adhere [57].
The results of this study met the accepted compliance threshold, which is also known as the “80 % rule” in biomedical research, which is a baseline for treatment program compliance [58]. Our finding of a high adherence rate in this study is crucial because scientific journals are often reluctant to publish studies with lower adherence rates [59]; this finding alone indicates an important factor to take into consideration. On the other hand, our study identified an effect size of 0.53 that requires a total of 38 participants (19 in each group) to be recruited for a larger-scale study. The results of this pilot study indicate that the addition of FHP correction, along with the conservative protocol, has a noticeable effect on TMD severity after 6 weeks. CET, through the use of the DCTO, was found to improve FHP, reduce the TMD severity score, and improve CVA simultaneously in the experimental group. Moreover, both groups experienced notable improvements after completing the treatment period since the conservative TMD protocol was introduced to both groups; thus, a significant improvement was reported compared to the measurements prior to the intervention sessions. However, the experimental group was superior to the control group in reducing TMD.
Some previous literature findings are consistent with this study’s results while others were not, likely due to methodological differences. For instance, a study by El-Hamalawy [34] added FHP correction along with a TMD conservative protocol that improved different aspects of pain, MMO, and CVA. However, this study had a single group without a control group to compare to and TMD severity was not measured; rather, they relied on MMO and pain to report TMD improvement [34]. Similarly, Oleksy et al. [28] investigated the effect of cervical spine rehabilitation including but not limited to manual cervical traction on TMD relying on pain and the Helkimo clinical dysfunction index to report on TMD presence. Here, there was a notable reduction in pain with improvement in FHP and a reduction of the disability index score in the experimental group [28]. Likewise, Calixtre et al. [60] and La Touche et al. [61] inferred positive significant changes in their single group regarding MMO and pain when cervical mobilizations were performed on patients with TMD [60], 61]. Each of these previous studies’ findings were in alignment with our current pilot project in terms of TMD improvement rather than other symptomatic features. Hence, this pilot was more targeted to report TMD based on a scale to be more cohesive, allowing for clearer comparisons and reduced variability in reporting. Therefore, this approach would seem to enhance the clarity of the findings and infer better interpretation of TMD improvements across different patients between the two groups.
It was reported earlier by Xiao et al. [36] that people with TMD tend to show an increase in FHP and thus this study involved TMD patients, each of whom presented with FHP to be comparable with similar clinical/biomechanical features. Additionally, another study stated that there is a high negative correlation between TMD and FHP in which TMD patients presented with greater FHP [31]. This was further supported by Lamba et al., [62] who reported that an increase of CVA has a negative effect on the vertical mandibular opening where it was improved following intervention. Physiologically, CET has been found to have a positive effect on blood circulation, soft tissue flexibility, as well as reducing muscle tension [44], 45], 48], 63]; arguably, this should enhance mandibular function. Furthermore, correcting lower cervical vertebrae hypolordosis in TMD patients by restoring the gravitational alignment would prevent muscle-joint deviations [64]. Herein, the use of CET with the DCTO was found to have improved FHP alignment compared to a standard protocol and in previous studies; thus, it seems that the DCTO was a viable component in the experimental group management protocol [22].
Problematically, there is still disagreement in the literature regarding the relationship between TMD, mastication muscle dysfunction, and altered posture, and it is obvious that better-controlled trials with proper diagnoses, larger sample sizes, and objective posture measurements are needed [37], 65], 66]. Importantly, gaps in the understanding of these relationships persist due to the complexity of the contributing variables and the multimodal nature of TMD. However, there is a general connection between altered sagittal cervical posture and TMD, and this is supported by a variety of literature on the topic [36], 37], [67], [68], [69]. For example, the correlation between myogenic TMD and altered posture has been found to be strong but weak between other types of TMD [37]. Biomechanically, FHP causes posterior cranial rotation and stretching of the infrahyoid muscles, which increases the activity of the masticatory muscles and cranial extensors [36]. This in turn can lead to overuse, strain, and pain. In this scenario, the masticatory muscles pull on the mandible keep the mouth closed, while the infrahyoid muscles attempt to bring the mandible down and back [36]. This ongoing conflict between muscles that depress and elevate the mandible is called parafunction. Thus, interventions that aim to reduce tension in these muscle groups through restoration of normal alignment of the CVA and cervical lordosis on a stable shoulder girdle can rebalance these muscles [67], [68], [69]. Numerous studies have demonstrated that TMD patients frequently present with an excessive FHP, accompanied by shortening of the sternocleidomastoid and posterior cervical extensor muscles [36], 37], [67], [68], [69]. When the head tilts forward, the field of vision decreases, and the upper cervical lordosis increases to extend the field of view [37]. Therefore, postural changes in the cervical region can lead to TMD by altering the position of the mandible, changing the stress-strain relationship between the anterior and posterior muscles and the alteration of the cervical lordosis. We propose that the application of CET via the DCTO in the current investigation likely rebalances the cervical spine connective tissue biomechanics by improving the sagittal head postural position.
Limitations and future work recommendations
As is the case for all pilot investigations, it must be emphasized that a comprehensive large-scale study is required to test and/or enhance the generalizability of the reported findings in this pilot study, and this should present short-term as well as long-term follow-up such as 1–2 years. A broader study will allow further participant inclusion and better evaluation of the measured outcomes. Although our two groups were homogenous in their demographics, because pain level was heterogenous in this study, future studies are recommended to attain full matching in the groups’ baseline measure as well. Similarly, although we did not design our study to be restricted to a young adult age range, due to our university demographics, the participants included in our trial were in their second decade of life. As a result, a broader age range in future trials is recommended and needed to properly evaluate the findings of this pilot project.
Additionally, although this pilot investigation did not include a safety analysis or a satisfaction evaluation between the groups, a previous pilot investigation identified high satisfaction and no reports of injuries in the participants receiving the DCTO in a multimodal program for the treatment of cervicogenic headaches [70]. Still, we recommend that future investigations include both a safety analysis and a satisfaction analysis for further understanding of this type of intervention. Lastly, future trials should explore any potential differences in gender responsiveness to the provided treatment interventions because this study consisted of mostly females.
Conclusions
This pilot study inferred high adherence rates in both groups with a moderate effect size of 0.53 where only 38 participants will be required for a larger-scale study at alpha level 0.05 and statistical power of 0.80. Moreover, we identified that adding FHP correction through the Denneroll cervical traction orthotic to a conservative TMD protocol might provide an initial short-term benefit in selected TMD outcomes. These preliminary pilot trial findings need to be tested in a full-scale, properly powered trial with long-term follow-up before any significant conclusions can be made regarding this treatment regimen for this unique population of TMD sufferers.
Acknowledgments
The authors would like to acknowledge all the participants of the study.
-
Research ethics: This study was approved by the Research Ethics Committee of the University of Sharjah (reference number REC-23-12-18-02-P G) and was registered on ClinicalTrials.gov (ID: NCT06156345).
-
Informed consent: Informed consent was obtained from all individuals included in this study.
-
Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
-
Use of Large Language Models, AI and Machine Learning Tools: None declared.
-
Conflict of interest: DEH teaches rehabilitation methods to physicians and is the CEO of a company that distributes the DCTO product to physicians in the United States. All other authors state no conflict of interest.
-
Research funding: This research was funded by the Office of the Vice Chancellor for Research and Graduate Studies, University of Sharjah, United Arab Emirates.
-
Data availability: The data that support the findings of this study are available from the corresponding author (TS) upon reasonable request.
References
1. Ali, KFM, Fatima, A, Ilyas, F, Ali Khan, MW, Abbassi, ZA. Impact of anxiety and depression on temporomandibular joint disorders among sample of dental undergraduates of Karachi. J Pak Dental Assoc 2016;25:49–143.Search in Google Scholar
2. Chang, C, Wang, D, Yang, M, Hsu, W, Hsu, M. Functional disorders of the temporomandibular joints: internal derangement of the temporomandibular joint. Kaohsiung J Med Sci 2018;34:223–30. https://doi.org/10.1016/j.kjms.2018.01.004.Search in Google Scholar PubMed PubMed Central
3. Jain, S, Chourse, S, Jain, D. Prevalence and severity of temporomandibular disorders among the orthodontic patients using Fonseca’s questionnaire. Contemp Clin Dent 2018;9:31–4. https://doi.org/10.4103/ccd.ccd_689_17.Search in Google Scholar PubMed PubMed Central
4. Alomar, X, Medrano, J, Cabratosa, J, Clavero, JA, Lorente, M, Serra, I, et al.. Anatomy of the temporomandibular joint. Sem Ultrasound CT MRI 2007;28:170–83. https://doi.org/10.1053/j.sult.2007.02.002.Search in Google Scholar PubMed
5. Collins, T. Temporomandibular joint disorders. InnovAIT Educ Inspir Gen Pract 2020;13:475–83. https://doi.org/10.1177/1755738020925858.Search in Google Scholar
6. McNeill, C. History and evolution of TMD concepts. Oral surgery, oral medicine, oral pathology. Oral Radiol Endodontol 1997;83:51–60. https://doi.org/10.1016/S1079-2104(97)90091-3.Search in Google Scholar PubMed
7. Magnusson, T, Egermark, I, Carlsson, GE. A longitudinal epidemiologic study of signs and symptoms of temporomandibular disorders from 15 to 35 years of age. J Orofac Pain 2000;14:310–9.Search in Google Scholar
8. Loster, JE, Osiewicz, MA, Groch, M, Ryniewicz, W, Wieczorek, A. The prevalence of TMD in Polish young adults. J Prosthodont 2017;26:284–8. https://doi.org/10.1111/jopr.12414.Search in Google Scholar PubMed
9. de Paiva Bertoli, FM, Bruzamolin, CD, Pizzatto, E, Losso, EM, Brancher, JA, de Souza, JF. Prevalence of diagnosed temporomandibular disorders: a cross-sectional study in Brazilian adolescents. PLoS One 2018;13:e0192254. https://doi.org/10.1371/journal.pone.0192254.Search in Google Scholar PubMed PubMed Central
10. Graue, AM, Jokstad, A, Assmus, J, Skeie, MS. Prevalence among adolescents in Bergen, Western Norway, of temporomandibular disorders according to the DC/TMD criteria and examination protocol. Acta Odontol Scand 2016;74:449–55. https://doi.org/10.1080/00016357.2016.1191086.Search in Google Scholar PubMed
11. Zwiri, AMA, Al-Omiri, MK. Prevalence of temporomandibular joint disorder among North Saudi University students. CRANIO® 2016;34:176–81. https://doi.org/10.1179/2151090315Y.0000000007.Search in Google Scholar PubMed
12. Al-sanabani, J. Prevalence of temporomandibular joint disorders among Yemeni University students: a prospective, cross-sectional study. Int J Oral Craniofac Sci 2017;3:053–9. https://doi.org/10.17352/2455-4634.000032.Search in Google Scholar
13. AlShaban, KK, Gul Abdul Waheed, Z. Prevalence of TMJ disorders among the patients attending the Dental Clinic of Ajman University of Science and Technology–Fujairah Campus, UAE. Int J Dent 2018;2018:1–6. https://doi.org/10.1155/2018/9861623.Search in Google Scholar PubMed PubMed Central
14. Lee, J-Y, Kim, Y-K, Kim, S-G, Yun, P-Y. Evaluation of Korean teenagers with temporomandibular joint disorders. J Korean Assoc Oral Maxillofac Surg 2013;39:231. https://doi.org/10.5125/jkaoms.2013.39.5.231.Search in Google Scholar PubMed PubMed Central
15. Kmeid, E, Nacouzi, M, Hallit, S, Rohayem, Z. Prevalence of temporomandibular joint disorder in the Lebanese population, and its association with depression, anxiety, and stress. Head Face Med 2020;16:19. https://doi.org/10.1186/s13005-020-00234-2.Search in Google Scholar PubMed PubMed Central
16. Kim, M-R, Graber, TM, Viana, MA. Orthodontics and temporomandibular disorder: a meta-analysis. Am J Orthod Dentofacial Orthop 2002;121:438–46. https://doi.org/10.1067/mod.2002.121665.Search in Google Scholar PubMed
17. Xiang, T, Tao, Z-Y, Liao, L-F, Wang, S, Cao, D-Y. Animal models of temporomandibular disorder. J Pain Res 2021;14:1415–30. https://doi.org/10.2147/JPR.S303536.Search in Google Scholar PubMed PubMed Central
18. Natu, VP, Yap, AU-J, Su, MH, Irfan Ali, NM, Ansari, A. Temporomandibular disorder symptoms and their association with quality of life, emotional states and sleep quality in South-East Asian youths. J Oral Rehabil 2018;45:756–63. https://doi.org/10.1111/joor.12692.Search in Google Scholar PubMed
19. Ye, C, Xiong, X, Zhang, Y, Pu, D, Zhang, J, Du, S, et al.. Psychological profiles and their relevance with temporomandibular disorder symptoms in preorthodontic patients. Pain Res Manag 2022;2022:1039393. https://doi.org/10.1155/2022/1039393.Search in Google Scholar PubMed PubMed Central
20. Özdinç, S, Ata, H, Selçuk, H, Can, HB, Sermenli, N, Turan, FN. Temporomandibular joint disorder determined by Fonseca anamnestic index and associated factors in 18- to 27-year-old university students. CRANIO® 2020;38:327–32. https://doi.org/10.1080/08869634.2018.1513442.Search in Google Scholar PubMed
21. Valesan, LF, Da-Cas, CD, Réus, JC, Denardin, ACS, Garanhani, RR, Bonotto, D, et al.. Prevalence of temporomandibular joint disorders: a systematic review and meta-analysis. Clin Oral Invest 2021;25:441–53. https://doi.org/10.1007/s00784-020-03710-w.Search in Google Scholar PubMed
22. Suwaidi, ASAl, Moustafa, IM, Kim, M, Oakley, PA, Harrison, DE. A comparison of two forward head posture corrective approaches in elderly with chronic non-specific neck pain: a randomized controlled study. J Clin Med 2023;12:542. https://doi.org/10.3390/jcm12020542.Search in Google Scholar PubMed PubMed Central
23. Arooj, A, Aziz, A, Khalid, F, Hussain Iqbal, M, Binte Ashfaq, H. Forward head posture in young adults: a systematic review. The Therapist (J Therap Rehabilitation Sci 2022;3:32–5. https://doi.org/10.54393/tt.v3i1.38.Search in Google Scholar
24. Singh, S, Kaushal, K, Jasrotia, S. Prevalence of forward head posture and its impact on the activity of daily living among students of Adesh University – a cross-sectional study. Adesh Univ J Med Sci Res 2020;2:99. https://doi.org/10.25259/AUJMSR_18_2020.Search in Google Scholar
25. Ramalingam, V, Subramaniam, A. Prevalence and associated risk factors of forward head posture among university students. Indian J Public Health Res Dev 2019;10:775. https://doi.org/10.5958/0976-5506.2019.01669.3.Search in Google Scholar
26. Ashok, K, Purushothaman, V, Muniandy, Y. Prevalence of forward head posture in electronic gamers and associated factors. Int J Aging Health Mov 2020;2:19–27.Search in Google Scholar
27. Gonzalez, HE, Manns, A. Forward head posture: its structural and functional influence on the stomatognathic system, a conceptual study. CRANIO® 1996;14:71–80. https://doi.org/10.1080/08869634.1996.11745952.Search in Google Scholar PubMed
28. Oleksy, Ł, Kielnar, R, Mika, A, Jankowicz-Szymańska, A, Bylina, D, Sołtan, J, et al.. Impact of cervical spine rehabilitation on temporomandibular joint functioning in patients with idiopathic neck pain. BioMed Res Int 2021;2021:1–13. https://doi.org/10.1155/2021/6886373.Search in Google Scholar PubMed PubMed Central
29. Häggman-Henrikson, B, Lampa, E, Marklund, S, Wänman, A. Pain and disability in the jaw and neck region following whiplash trauma. J Dent Res 2016;95:1155–60. https://doi.org/10.1177/0022034516653598.Search in Google Scholar PubMed
30. Lee, W-Y, Okeson, JP, Lindroth, J. The relationship between forward head posture and temporomandibular disorders. J Orofac Pain 1995;9:161–7.Search in Google Scholar
31. Monalisa Pattnaik, MPT, Mohanty, P. Relationship between temporomandibular joint dysfunction, forward head posture and severity of neck pain in subjects with neck pain and temporomandibular joint dysfunction. IOSR J Dent Med Sci 2020;19:1–10.Search in Google Scholar
32. Salkar, RG, Radke, UM, Deshmukh, SP, Radke, PM. Relationship between temporomandibular joint disorders and body posture. Int J Dent Health Sci 2015;2:1523–30.Search in Google Scholar
33. Saddu, SC. The evaluation of head and craniocervical posture among patients with and without temporomandibular joint Disorders- A comparative study. J Clin Diagn Res 2015;9:ZC55–8. https://doi.org/10.7860/JCDR/2015/12830.6343.Search in Google Scholar PubMed PubMed Central
34. El-Hamalawy, FA. Forward head correction exercises for management of myogenic tempromandibular joint dysfunction. J Am Sci 2011;7:71–7.Search in Google Scholar
35. Yuan, YAO, Li-li, XU, Shuai, FAN. Control study of forward head posture between patients with temporomandibular disorders and healthy people. Shanghai J Stomatol 2021;30:173.Search in Google Scholar
36. Xiao, C-Q, Wan, Y-D, Li, Y-Q, Yan, Z-B, Cheng, Q-Y, Fan, P-D, et al.. Do temporomandibular disorder patients with joint pain exhibit forward head posture? A cephalometric study. Pain Res Manag 2023;2023:1–11. https://doi.org/10.1155/2023/7363412.Search in Google Scholar PubMed PubMed Central
37. Minervini, G, Franco, R, Marrapodi, MM, Crimi, S, Badnjević, A, Cervino, G, et al.. Correlation between temporomandibular disorders (TMD) and posture evaluated through the diagnostic criteria for temporomandibular disorders (DC/TMD): a systematic review with meta-analysis. J Clin Med 2023;12:2652. https://doi.org/10.3390/jcm12072652.Search in Google Scholar PubMed PubMed Central
38. Shousha, T, Alayat, M, Moustafa, I. Effects of low-level laser therapy versus soft occlusive splints on mouth opening and surface electromyography in females with temporomandibular dysfunction: a randomized-controlled study. PLoS One 2021;16:e0258063. https://doi.org/10.1371/journal.pone.0258063.Search in Google Scholar PubMed PubMed Central
39. Seifeldin, SA, Elhayes, KA. Soft versus hard occlusal splint therapy in the management of temporomandibular disorders (TMDs). Saudi Dent J 2015;27:208–14. https://doi.org/10.1016/j.sdentj.2014.12.004.Search in Google Scholar PubMed PubMed Central
40. Shousha, TM, Soliman, ES, Behiry, MA. The effect of a short term conservative physiotherapy versus occlusive splinting on pain and range of motion in cases of myogenic temporomandibular joint dysfunction: a randomized controlled trial. J Phys Ther Sci 2018;30:1156–60. https://doi.org/10.1589/jpts.30.1156.Search in Google Scholar PubMed PubMed Central
41. Kirupa, K, Mary, SMD, Nithyanisha, R, Kumar, SN. A study on the effectiveness of scapular retraction exercises on forward head posture. Indian J Public Health Res Dev 2020;11:284–9.Search in Google Scholar
42. Sawant, R, Heggannavar, A, Metgud, S, D’Silva, P. Immediate effect of mulligan’s mobilization with movement on forward head posture and postural sway in temporomandibular joint dysfunction: an experimental study. Ind J Phys Ther Res 2021;3:107. https://doi.org/10.4103/ijptr.ijptr_57_19.Search in Google Scholar
43. Wright, EF, Domenech, MA, Fischer, JR. Usefulness of posture training for patients with temporomandibular disorders. J Am Dent Assoc 2000;131:202–10. https://doi.org/10.14219/jada.archive.2000.0148.Search in Google Scholar PubMed
44. Oakley, PA, Ehsani, NN, Moustafa, IM, Harrison, DE. Restoring cervical lordosis by cervical extension traction methods in the treatment of cervical spine disorders: a systematic review of controlled trials. J Phys Ther Sci 2021;33:784–94. https://doi.org/10.1589/jpts.33.784.Search in Google Scholar PubMed PubMed Central
45. Moustafa, IM, Diab, AA, Harrison, DE. The efficacy of cervical lordosis rehabilitation for nerve root function and pain in cervical spondylotic radiculopathy: a randomized trial with 2-year follow-up. J Clin Med 2022;11:6515. https://doi.org/10.3390/jcm11216515.Search in Google Scholar PubMed PubMed Central
46. Oakley, PA, Moustafa, IM, Haas, JW, Betz, JW, Harrison, DE. Two methods of forward head posture assessment: radiography vs. posture and their clinical comparison. J Clin Med 2024;13:2149. https://doi.org/10.3390/jcm13072149.Search in Google Scholar PubMed PubMed Central
47. Bose, GNSC, Vora, K, Inbasekaran, D. An additive effect of lateral pterygoid muscle release technique in temporo mandibular joint dysfunction (TMJD). Int J Eng Technol 2018;7:607–10.Search in Google Scholar
48. Moustafa, IM, Diab, AA, Harrison, DE. The effect of normalizing the sagittal cervical configuration on dizziness, neck pain, and cervicocephalic kinesthetic sensibility: a 1-year randomized controlled study. Eur J Phys Rehabil Med 2017;53:57–71. https://doi.org/10.23736/S1973-9087.16.04179-4.Search in Google Scholar PubMed
49. Young, IA, Dunning, J, Butts, R, Mourad, F, Cleland, JA. Reliability, construct validity, and responsiveness of the neck disability index and numeric pain rating scale in patients with mechanical neck pain without upper extremity symptoms. Physiother Theory Pract 2019;35:1328–35. https://doi.org/10.1080/09593985.2018.1471763.Search in Google Scholar PubMed
50. Karthik, R, Hafila, MIF, Saravanan, C, Vivek, N, Priyadarsini, P, Ashwath, B. Assessing prevalence of temporomandibular disorders among university students: a questionnaire study. J Int Soc Prev Community Dent 2017;7:S24–9. https://doi.org/10.4103/jispcd.JISPCD_146_17.Search in Google Scholar PubMed PubMed Central
51. Nomura, K, Vitti, M, de Oliveira, AS, Chaves, TC, Semprini, M, Siéssere, S, et al.. Use of the Fonseca’s questionnaire to assess the prevalence and severity of temporomandibular disorders in Brazilian dental undergraduates. Braz Dent J 2007;18:163–7. https://doi.org/10.1590/S0103-64402007000200015.Search in Google Scholar
52. Campos, JADB, Carrascosa, AC, Bonafé, FSS, Maroco, J. Severity of temporomandibular disorders in women: validity and reliability of the Fonseca Anamnestic Index. Braz Oral Res 2014;28:16–21. https://doi.org/10.1590/S1806-83242013005000026.Search in Google Scholar
53. Awatani, T, Enoki, T, Morikita, I. Reliability and validity of angle measurements using radiograph and smartphone applications: experimental research on protractor. J Phys Ther Sci 2017;29:1869–73. https://doi.org/10.1589/jpts.29.1869.Search in Google Scholar PubMed PubMed Central
54. Hertzog, MA. Considerations in determining sample size for pilot studies. Res Nurs Health 2008;31:180–91. https://doi.org/10.1002/nur.20247.Search in Google Scholar PubMed
55. Rand, CS. Issues in the measurement of adherence. In: The handbook of health behavior change. New York, NY: Springer Publishing Company; 1990:102–10 pp.Search in Google Scholar
56. Sung, NS, Crowley, WF, Genel, M, Salber, P, Sandy, L, Sherwood, LM, et al.. Central challenges facing the national clinical research enterprise. JAMA 2003;289:1278–87. https://doi.org/10.1001/jama.289.10.1278.Search in Google Scholar PubMed
57. Robiner, WN. Enhancing adherence in clinical research. Contemp Clin Trials 2005;26:59–77. https://doi.org/10.1016/j.cct.2004.11.015.Search in Google Scholar PubMed
58. Ellis, S, Shumaker, S, Sieber, W, Rand, C. Adherence to pharmacological interventions: current trends and future directions. Control Clin Trials 2000;21:S218–25. https://doi.org/10.1016/s0197-2456(00)00082-9.Search in Google Scholar PubMed
59. Sackett, DL. Evidence-based medicine. Semin Perinatol 1997;21:3–5. https://doi.org/10.1016/s0146-0005(97)80013-4.Search in Google Scholar PubMed
60. Calixtre, LB, Grüninger, BLda S, Haik, MN, Alburquerque-Sendín, F, Oliveira, AB. Effects of cervical mobilization and exercise on pain, movement and function in subjects with temporomandibular disorders: a single group pre-post test. J Appl Oral Sci 2016;24:188–97. https://doi.org/10.1590/1678-775720150240.Search in Google Scholar PubMed PubMed Central
61. La Touche, R, Fernández‐de‐Las‐Peñas, C, Fernández‐Carnero, J, Escalante, K, Angulo‐Díaz‐Parreño, S, Paris‐Alemany, A, et al.. The effects of manual therapy and exercise directed at the cervical spine on pain and pressure pain sensitivity in patients with myofascial temporomandibular disorders. J Oral Rehabil 2009;36:644–52. https://doi.org/10.1111/j.1365-2842.2009.01980.x.Search in Google Scholar PubMed
62. Lamba, D, Pant, S, Chandra, G, Joshi, A, Dalakoti, D. Effect of deep cervical flexor strengthening on vertical mandibular opening on subjects with forward head posture. Physiother Occupational Ther 2012;6:22.Search in Google Scholar
63. Katz, EA, Katz, SB, Fedorchuk, CA, Lightstone, DF, Banach, CJ, Podoll, JD. Increase in cerebral blood flow indicated by increased cerebral arterial area and pixel intensity on brain magnetic resonance angiogram following correction of cervical lordosis. Brain Circ 2019;5:19–26. https://doi.org/10.4103/bc.bc_25_18.Search in Google Scholar PubMed PubMed Central
64. Vilar, EL, Bezerra, JLSP, Façanha, CGL, Pontes, RB. Terapia postural e manual nas disfunções temporomandibulares. Rev Bras Odontol 2018;75:1. https://doi.org/10.18363/rbo.v75.2018.e1090.Search in Google Scholar
65. Chaves, TC, Turci, AM, Pinheiro, CF, Sousa, LM, Grossi, DB. Static body postural misalignment in individuals with temporomandibular disorders: a systematic review. Braz J Phys Ther 2014;18:481–501. https://doi.org/10.1590/bjpt-rbf.2014.0061.Search in Google Scholar PubMed PubMed Central
66. de Oliveira-Souza, AIS, de, O, Ferro, JK, Barros, MMMB, Oliveira, DA. Cervical musculoskeletal disorders in patients with temporomandibular dysfunction: a systematic review and meta-analysis. J Bodyw Mov Ther 2020;24:84–101. https://doi.org/10.1016/j.jbmt.2020.05.001.Search in Google Scholar PubMed
67. Taghizadeh Delkhoush, C, Purzolfi, M, Mirmohammadkhani, M, Sadollahi, H, Tavangar, S. The linear intra-articular motions of the temporomandibular joint in individuals with severe forward head posture: a cross-sectional study. Musculoskelet Sci Pract 2024;70:102908. https://doi.org/10.1016/j.msksp.2024.102908.Search in Google Scholar PubMed
68. Joy, TE, Tanuja, S, Pillai, RR, Dhas Manchil, PR, Raveendranathan, R. Assessment of craniocervical posture in TMJ disorders using lateral radiographic view: a cross-sectional study. CRANIO® 2019;39:391–7. https://doi.org/10.1080/08869634.2019.1665227.Search in Google Scholar PubMed
69. Ozmen, EE, Unuvar, BS. Evaluation of head posture in patients with temporomandibular joint disorders: a cross-sectional study. Rev Assoc Med Bras (1992) 2025;71:e20241474. https://doi.org/10.1590/1806-9282.20241474.Search in Google Scholar PubMed PubMed Central
70. Moustafa, IM, Diab, A, Shousha, T, Harrison, DE. Does restoration of sagittal cervical alignment improve 417 cervicogenic headache pain and disability: a 2-year pilot randomized controlled trial. Heliyon 2021;7:e06467. https://doi.org/10.1016/j.heliyon.2021.e06467.Search in Google Scholar PubMed PubMed Central
Supplementary Material
This article contains supplementary material (https://doi.org/10.1515/jom-2025-0081).
© 2025 the author(s), published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 International License.
