The intent of this study was to evaluate any change in the dental arches of adults in the third decade of life after the removal of all third molars in relation to occlusal factors, gender and the status of the third molars prior to extraction. The subjects were 24 healthy students (9 women, 15 men; mean age 23.2; age range 20-32) whose third molars were all removed. All extractions in the lower arch were performed because of impaction and complicating symptoms such as pain and swelling. Full occlusal registrations were performed before the extractions and one year afterwards, including the production of dental casts. The dimensions of the lower dental arch showed a small, but significant, increase one year after the removal of all the third molars. No significant change took place in the lower anterior area during the year. In the maxillary arch (in the lateral and transversal dimensions), the direction of change was similar to that of the lower arch, but smaller than in the mandibular arch. This indicated a minor space gain during the year after the removal of all third molars. The changes in the dental arches did not correlate significantly with changes in craniomandibular disorders (CMDs). It can be concluded that the extraction of an impacted third molar allows at least the second molar to drift posteriorly and laterally in the dental arch. The results give no further indication, in this age group, to extract the lower third molars in order to prevent lower anterior crowding.