The Prevalence and Related Symptoms of Enamel Cracks : A Clinical Survey

Abstract

Enamel cracks, although generally regarded as a minor symptom in tooth fracture occurring with an external injury, are frequently detected in teeth without any history of injury. These cracks may be recognized as multiple thin lines that run parallel to the tooth axis. Although the cracks might cause several clinical problems such as secondary caries, esthetic disorders, tooth fracture and pulp diseases, they are frequently neglected and their causes and frequencies have not yet been fully studied. Therefore, this clinical survey investigated the frequency of enamel cracks and related symptoms. Eighty patients ranging from teenagers to those in their eighties, all underwent a clinical tooth examination. In each age group, 10 patients were investigated. The enamel cracks were divided into three types (A, B and C) based on differences in the progression of the crack: an enamel crack that was easily confirmed by a simple observation was classified as level C, those confirmed by observation through a magnifying glass were level B, and those confirmed using an activator light and a magnifying glass were level A. Cold air was used to assess the thermal sensitivity of cracked teeth. The results demonstrated that there was a tendency of increased crack incidence with aging, and the incidence was 100% in subjects≧50 years of age. A high incidence was observed in teeth restored with composite resin or a metal inlay restoration in comparison to non-restored teeth in subjects <40 years of age. Level A cracks were the most frequent in young subjects, whereas the frequencies of cracks of levels B and C increased with aging. The frequency of cracked teeth sensitive to cold air was 13.0-16.7% in 20- to 69-year-old subjects, and was not different among various age groups. In conclusion, this study clearly demonstrated age-dependent progression of enamel cracks, suggesting that operative procedures may trigger the formation and/or propagation of enamel cracks. Enamel cracks could be related to the pain response upon cold stimulus, although the frequency of sensitive teeth was not dependent on crack progression.