Third molar agenesis in modern humans with and without agenesis of other teeth

Abstract

Background The number of teeth in the human dentition is of interest both from developmental and evolutionary aspects. The present case-control study focused on the formation of third molars in modern humans aiming to shed more light on the most variable tooth class in the dentition. Methods For this reason, we investigated third molar formation in a sample of 303 individuals with agenesis of teeth other than third molars (agenesis group) and compared it to a sex and age matched control group of 303 individuals without agenesis of teeth other than third molars. Results The prevalence of third molar agenesis in the agenesis group was 50.8%, which is significantly higher than the 20.5% in the control group (p < 0.001). The chance of a missing third molar in the agenesis group was increased by 38.3% (p < 0.001), after controlling for the agenesis in other teeth factor. When considering the amount of missing third molars per individual, a clear tendency towards more missing third molars was evident in the agenesis group compared to the control group. The frequency of bilaterally missing third molars in the agenesis group was 29% in the maxilla, as well as in the mandible, which is about three times higher than the frequency of unilaterally missing third molars (p < 0.001). In the control group, bilaterally missing third molars occurred in 8.6% in the maxilla and 8.9% in the mandible. Conclusion The present results indicate that genetic factors involved in tooth agenesis affect also the dentition as a whole. Furthermore, the third molars are more vulnerable to factors involved in agenesis of other teeth and they are more often affected as a whole. These findings seem to be associated with the evolutionary trend in humans towards reduced molar number.

Differential associations of rheumatoid arthritis and periodontitis or tooth loss: A cross‐sectional study

“…Functional dentition was defined as having ≥20 natural permanent teeth, and non‐functional dentition was defined as having ≤19 natural permanent teeth independent of their condition or position (Sheiham & Steele, 2001). Third molars were excluded because of the frequent occurrence of their absence and malposition, which makes the depths reached by probing clinically useless (Scheiwiller et al, 2020).…”

Radiographic Evaluation of Third Molar（M3）Agenesis in Indian Population

“…The order of frequency of agenesis reported in the previous studies are 1>2>3>4 and 1>2>4>3, first quadrant third molar is the most common agenesis reported tooth (4,6,8) . If there is any M3 agenesis present then there is thirteen times more chance of agenesis of other teeth (5,9) . M3 agenesis is less or more considered as a physiological variation or evolutionary adaptation in the jaws rather than developmental disturbance (9) .…”

“…If there is any M3 agenesis present then there is thirteen times more chance of agenesis of other teeth (5,9) . M3 agenesis is less or more considered as a physiological variation or evolutionary adaptation in the jaws rather than developmental disturbance (9) . M3 are the best biological indicator for assessment of juvenile age and they provide forensic specimen (10) .…”

Radiographic assessment of the prevalence and pattern of impacted teeth in Kanyakumari population using orthopantomogram- A retrospective study

“…But anthropological records showed alterations in size of skull and reduction in volume of masticatory muscle due to evolution which leads to minimal lower face projection with the tooth size remaining the same [1] . Eventually third molars can be seen missing as a result of modern agenesis [2] . Similarly overcrowded or impacted teeth are evident due to arch length deficiency and several other factors [3] .…”