Table 4.

Illustrates summary of the key factors that are important in TMD study design and suggested recommendations for reproducible methodology, intending only to provide clinical guidance and serve as a starting point for extensive research. ** All the abbreviations in this table are listed in Supplementary File S2.

Key Factors **		Suggested Recommendation **	Description and Citation of Scientifc Evidence ** (Manuscript)
Population characteristics	Age range	Paediatric cohort: <18 years old Adult cohort: 18–40 years old       41–60 years old       >60 years old	Refer to Section 4.1
	Gender	Either female or only male category for each study. Mixed-gender subjects, depending on aims and objectives of the study
	Racial background	It is noteworthy that skin colour plays an important role in the scattering and absorption of the photonic energy. It can have a great impact on PBM dosimetry
	Optical properties of the target tissue	Identify the consistency, structure, thickness, skin colour and absorption/scattering coefficient of the target tissue	Refer to Section 4.3
	Sample size	Even distribution of the sample size to the intervention and placebo groups Same gender cohort in each study Same racial background cohort in each study and avoid mixed racial background in each study Sample size should be at least 25 in each group	Refer to Section 4.1 and Section 4.2.1
Randomisation and blinding processes		Two independent blind investigators to assess the variables at all timepoints (double-blind) and record the data. Robust randomised process. Parallel arm study design.	Refer to Section 4.2.1
Comparable arms of the study		Placebo/sham PBM, as a comparable arm in TMD study design, is essential to validate the optimal outcome. It assists in providing standarised and reproducible data	[137]
Presented symptoms	Pain: TMJ: pain, arthralgia TMJ-associated areas EO or IO masticatory muscles (or combination) Cervical muscles A combination of any of the above areas, depending on the presented symptoms Functional disability: Limited mouth movements, highlighting the degree of severity. Difficulty in chewing TMJ clicking/or crepitation Jaw protrusion or deviation, during mouth opening or closing Cervical muscles stiffness Anxiety/depression	-Diagnosis of the symptoms, whether they are acute or chronic, as they have a great impact on the laser treatment protocol -Thorough clinical examination to identify the palpable TP (EO and IO), along with the unpalpable TP, which can contribute to TMD symptoms such as tenderness in the cervical muscles -Identifying functional disabilities and their contributions to TMD symptoms -Pre-treatment measurement of mouth opening by 2 independent investigators, utilising 1 or 2 of the assessment tools reported in Table S2 -Assessment of a patient’s anxiety/depression is crucial for all TMD patients, as a routine assessment measure	Refer to Section 4.2.1 and Table S2
Diagnostic criteria		Combining 2 tools: RDC/TMD and diagnostic manual muscle testing (MMT) for cervical muscles assessment	Refer to Section 4.2.2
Standardised laser protocol		Based on gathered evidence-based practice and science, 11 out of 44 studies utilised power meter and placebo/sham PBM; recommendations of PBMT protocols suggested for further research	Refer to Table 4 and Section 4.5
Light device standardisation		Standardised prototype development for each involved light source in the study
Route of delivery of PBM irradiation		Identifying the consistency, structure, thickness, skin colour and absorption/scattering coefficient of the target tissues (optical properties) of each of the following PBM delivery rout(s), prior to setting up the PBM parameter protocols: Transmucosal approach (IO) Transcutaneous approach (EO) Combination of the above approaches	Refer to Section 4.4 and Table 4
Unilateral/bilateral PBM irradiation		Regardless of unilateral or bilateral TMD symptoms, PBM irradiation needs to be applied bilaterally, due to the concept of compensation effects	[147]
Trigger Points (TP)	Affected sites Number of the TP/site	All the TP need to be addressed as follows: EO and IO muscles’ contribution to TMD, including the masticatory muscles, as well as the cervical (palpable or unpalpable). The number of the TP depends on the origin and insertion of each muscle, its location and volume	Refer to Section 4.5.4 and Figure 13
The investigated variables and follow-up timepoints		-Pain -Functional problems -Anxiety/depression -QoL Address these variables at T0 (pre-treatment), mid-treatment and end-treatment, then 1, 3, 6, 12 and 18 months post treatment	Refer to Section 4
Outcome measures		-Qualitative or quantitative or combination assessment tools (Table S2) -Including the synovial fluid assessment is vital, which has not been employed in all the eligible studies of the present review. Therefore, immunological and quantitative synovial fluid analysis, beta-glucuronidase, IgA and IgG demonstrate elevated levels of inflammatory mediators in diseased joints compared with asymptomatic non-diseased joints [124,125] -IMMPACT recommendations [126] -Utilise QoL index	Refer to Table S2 and these citations: [124,125,126]
Reported data		Documentation of essential and desirable PBM parameters is pivotal for reproducibility and standardisation	Refer to Table 2 [135]