This is a pilot diagnostic accuracy study to assess the ability to discriminate in a screening context Stage IV periodontitis from other stages of periodontitis. The index test is the assessment of masticatory dysfunction performed with a questionnaire and a chewing gum test. The reference standard is a full periodontal and functional assessment performed by a trained and calibrated specialist.

This is a pilot diagnostic accuracy study. Data are derived from a cross-sectional study based on a convenience, quota sample of patients referred for dental care to the reception clinic of the Prince Philip Dental Hospital or at the Institute of Advanced Dentistry, the University of Hong Kong between October 2020 and May 2021. The study will be conducted in accordance with the current revision of the Declaration of Helsinki. Informed consent will be obtained from all participants prior to enrollment in the study. This study will follow the Standards for Reporting Diagnostic Accuracy (STARD) guidelines. To limit bias, separate calibrated examiners performed the index test (chewing gum test) and the periodontal examination used for periodontitis stage and grade diagnosis (reference standard).

To evaluate the diagnostic accuracy of masticatory function assessment for Stage IV periodontitis, logistic regression analyses will be conducted in univariate analyses and the area under the receiver operating characteristic curve (AUROC), diagnostic odds ratios (DORs), sensitivity, specificity, positive predictive values and negative predictive values will be calculated.

Multivariate logistic regression models will be applied to develop a screening algorithm for Stage IV periodontitis diagnosis including the masticatory function assessment and other candidate predictors. A backward stepwise selection method will be used (p = 0.05 for inclusion in model; p = 0.05 for removal from model). The standard nomenclature for interpreting low, moderate and high levels of accuracy will be based on sensitivity and specificity as well as the AUROC values: low level = sensitivity or specificity <60%, AUROC ≤ 0.70; moderate level = sensitivity or specificity ranging from 60% to 79%, AUROC ranging from 0.71 to 0.90; high level = sensitivity or specificity ≥ 80%, AUROC>0.90

Inclusion Criteria:

• Periodontitis subjects reporting for care at reception clinic of dental hospital

Exclusion Criteria:

• presence of temporomandibular disorders,
• subjects undergoing orthodontic treatment
• less than 12 teeth;
• subjects having received periodontal treatment in the previous 12 months;
• subjects having received antibiotic medication in the previous 3 months

Convenience, quota sample (equal number of subjects with stage I, II, III and IV periodontitis) of consecutive patients referred for dental care to the reception clinic of the Prince Philip Dental Hospital