Which Norm of Mixing Ability Index to Evaluate Deficiency in Masticatory Performance in Young Adults?

BACKGROUND: The two-coloured chewing gum test is widely used to quantify oral mixing ability. Lack of consensual normative reference values limits its interpretation and comparability across studies. OBJECTIVE: To present the methodology establishing normative reference cut-offs for masticatory mixing ability in healthy young adults using two-coloured chewing gums. METHODS: Data from 61 healthy individuals (22.08 ± 2.22 years) who fulfilled anatomical (≥ 7 posterior functional units), psychosocial (GOHAI ≥ 52) and physiological (carrot D50 < 4 mm) criteria for good oral health were considered. Mixing ability was measured after 5 cycles, 20 cycles and 1 min with two different gum types (Hue-Check Gum and Hollywood gum). Outcomes were SD-Hue and Mix%. RESULTS: Mix% increased significantly from 5 to 20 cycles for both gums and approached maximal values after 1 min (p < 0.001). At 20 cycles, mean Mix% was 81.06% (95% CI: 78.46-83.66) for Hollywood and 88.31% (95% CI: 85.44-91.17) for Hue-Check Gum. Corresponding mean SD-Hue values were 0.076 (95% CI: 0.068-0.084) and 0.108 (95% CI: 0.085-0.131), respectively. Normative reference cut-offs at 20 cycles were defined using the lower bound of the 95% CI for Mix% (78.46% for Hollywood and 85.44% for Hue-Check Gum) and the upper bound of the 95% CI for SD-Hue (0.084 for Hollywood and 0.131 for Hue-Check Gum). CONCLUSION: Normative reference cut-offs for the two-coloured chewing gum test are provided for healthy young adults, enabling standardized interpretation of mixing outcomes. However, their applicability across other age groups is needed.