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Occlusal indicators are widely used in dental treatment to measure tooth contacts that occur during occlusion. However, the presence of an indicator may affect the mechanics of occlusion and lead to invalid tooth contact data. The objective of this study was to determine the effect of four indicators (Parkell, silk, T-Scan(®) sensor and paper) on surface electromyography (SEMG) activity during occlusion. Twenty-three subjects performed strong bites and maximum clenches onto the four indicators and natural dentition. Surface electromyography recordings of anterior temporalis and superficial masseter activity and the subjects' perception of each indicator were measured. SEMG activity with the T-Scan(®) sensor and paper was significantly different (higher masseter activity; P0·05) compared to that for natural dentition. The Parkell and silk gave no significant differences to natural dentition. Similarly, subjects perceived that T-Scan(®) sensor and paper had the greatest effect on occlusion and were the least comfortable (P0·05). Thus, the very plastic T-Scan(®) sensor and very thick articulating paper both affected SEMG activity during occlusion and, therefore, may not provide valid tooth contact information for dental treatment. In conclusion, occlusal indicators can change SEMG activity during occlusion which may affect the validity of the measurements they provide.

The evolution in time of the relationship between occlusion tooth absence was studied in 204 people in Salamanca, in 1996. The data collected in an oral test (biting in maximal intercuspidation on articulating paper) were analysed using the method called expansion-contraction systems. The results show that the loss of occlusion through time is directly related to the absence of premolars and molars. Incisors and canines occlude more in elderly people. This supports the view of a polarization in the evolution of the occlusion towards canines and premolars whereas tooth absence is polarized towards molars.