Interocclusal clearance during speech and in mandibular rest position. A comparison between different measuring methods.

Background And Aim: The interocclusal clearance during speech and in mandibular rest position shows an interindividual variation and influences the stability of prosthodontic reconstruction or orthodontic therapy, especially in patients with deep bite or cover-bite. Exact determination of the vertical dimension, not always a simple matter in practice, is controversially discussed with respect to the methodology. The aim of the present investigation was to compare three methods for determining interocclusal clearance during speech and in mandibular rest position.

Patients And Methods: Extraoral manual registration and electronic registration were used to evaluate 33 malocclusion-free patients. The measurements were repeated to determine the reproducibility. For disturbance-free objectification, the freeway space, i.e. the interocclusal clearance in mandibular rest position, was also recorded cephalometrically.

Results: None of these registration methods displayed clear-cut superiority to the others. Electronic registration is very time-consuming and should be confined to special cases. Sources of error in manual registration are increased movement of the measuring points marked on the skin during mandibular movement and the free handling of dividers.

Conclusions: This method can be used only in connection with mm. consonants. Speaking the word "Ohio" yielded excessively high values in all methods, so that this word has to be rejected as a speech sample. Cephalometric registration produced values with slight interindividual variations. In practice, however, this method is unsuitable for use with orthodontic patients because of the additional radiation exposure involved in producing an additional lateral cephalogram. For good reproducibility, practicing or frequent repeating of the measuring method prior to definitive measuring is essential.