Method: Twelve healthy men and 12 healthy women with no missing tooth participated. Surface EMG was recorded from the masseter and temporalis muscle. As a control measurement, intercuspal position was maintained to produce a natural (habitual) clenching record (NCR) while the occlusal contact area and point were recorded by means of silicone material. Subsequently, the occlusal contact area was recorded with the narrative instruction for minimum clenching record (MCR), light clenching record (LCR), and strong clenching record (HCR).
Result: While the EMG activity (%MVC) increased modestly from MCR to LCR (from 9.3 ± 2.0% to 11.5 ± 1.5%), the occlusal contact area increased rapidly (from 17.2 ± 11.3 mm2 to 26.8 ± 15.6 mm2) (P<0.05). Both EMG activity and occlusal contact area increased gradually from LCR to NCR (to 17.7 ± 2.0% and to 31.4 ± 14.2 mm2, respectively). Finally, EMG activity still increased from NCR to HCR (to 44.5 ± 3.7%) (P<0.05) but the occlusal contact area remained stable (to 36.8 ± 16.6 mm2). Occlusal contact point at anterior, left posterior, right posterior, and total area were not significantly differences between each task.
Conclusion: This study showed that adequate narrative instructions while recording the bite can result in largely stable EMG-levels and occlusal contact area, and they may contribute to taking a stable occlusal recording in natural dentition.