Association between teeth agenesis and Angle's classes in an Italian population.

BACKGROUND Teeth agenesis or hypodontia consists of the developmental absence of one or more teeth. Many studies confirm that this condition is almost frequent in general population; the prevalence reported is between 2.7% and 11.3%. This condition shows a multifactorial etiology: genetic factors, hereditary factors, environmental factors, local or general infective processes, radiations, drugs and traumas. The aim of this observational study was to evaluate the prevalence of tooth agenesis in a sample of orthodontic healthy patients considering each Angle malocclusion. METHODS 900 patients from a University clinic and three private practices were analyzed through intra and extra oral photographs, orthodontic study casts, panoramic radiographs and lateral cephalograms. The following inclusion criteria were applied: non-syndromic patients, without previous orthodontic, prosthetic treatment or extractions. Patients' clinical data consisted in general and dental anamnesis, intra and extra oral photographs, orthodontic study casts, digital panoramic radiographs and lateral cephalograms. The whole sample was divided into four groups (A-B-C-D) in relation with Angle's malocclusion and dental agenesis registered. RESULTS The whole sample presented a mean prevalence of the condition of 8.80%. Class II/2 is the most affected malocclusion with 20.37% of the patients affected by the condition, followed by class III (11.19%), class II/2 (8.05%) and class I (6.62%). The Chi-square test demonstrated a statistically significant different distribution of the condition between the four groups (p-value = 0.0059). The four groups presented also different patterns of missing teeth. CONCLUSIONS We found a significantly different distribution of the condition in the different malocclusions with class II/2 presenting the higher prevalence of tooth agenesis (20.37%). The most frequent teeth affected by agenesis in the entire sample are respectively: mandibular second premolars (32.40%), followed by the maxillary lateral incisors (27.70%) and the maxillary second premolars (15.50%).