# Regional cutaneous and muscle sensitivity does not mediate changes in active mouth opening in temporomandibular disorders: a cross-sectional study

## TL;DR

This study found that tissue sensitivity does not explain reduced mouth opening in people with temporomandibular disorders.

## Contribution

The study is the first to show that mechanosensitivity does not mediate active mouth opening changes in TMD patients.

## Key findings

- TMD patients had reduced mouth opening and lower pressure pain thresholds compared to healthy controls.
- Tissue mechanosensitivity did not mediate the reduction in active mouth opening in TMD patients.
- No association was found between pain thresholds and mandibular-related disability or mental health outcomes.

## Abstract

Background: One of the main goals of treatment in temporomandibular
disorder (TMD) patients is to improve mouth opening range of motion. However, it
is not clear which factors influence its alteration. The aim of this study was to
compare differences in mechanosensitivity, mouth opening and psychosocial
factors, between people with and without TMD, to evaluate if changes observed in
active mouth opening are mediated by an increase in tissues’ mechanosensitivity,
and to evaluate factors related to mandibular-related disability. Subjects with
and without TMD were recruited. Methods: Cross-sectional study conducted
in Spain. The measured variables were the Craniofacial Pain and Disability
Inventory (CF-PDI), pain intensity, pressure pain thresholds (PPT) at local
points; active and passive mouth opening; the Short-Form 12 questionnaire
(SF-12); the State-Trait Anxiety Inventory (STAI); and the Neck Disability Index
(NDI). Multivariable regression and mediation models were constructed.
Results: A total of 179 subjects (85 with TMD) were included. Subjects
with TMD had less mouth opening range of motion, and lower PPT. Tissues’
mechanosensitivity did not mediate the reduction in active mouth opening in
subjects with TMD (overall indirect effect, 0.98; 95% confidence interval, −0.87
to 3.12). Finally, no variable showed an association with CF-PDI.
Conclusions: Subjects with TMD seem to have decreased mouth opening, and
greater mechanosensitivity of masticatory muscles, when compared with healthy
controls. Tissues’ mechanosensitivity does not seem to mediate the reduction of
active mouth opening in subjects with TMD, and there seems to be no relationship
between PPT measures, mental health outcomes, the NDI and mandibular-related
disability.