Dental Institute, Queen Mary University of London
Friday Morning, 301E
The relationship between root growth and eruption is poorly understood. The aim of this retrospective cross-sectional study was to describe eruption levels of human mandibular teeth in terms of root stage and age. The sample was 944 panoramic dental radiographs from children aged 3-16 years. Left mandibular teeth (excluding M3) were assessed for eruption level and root stages described by Moorrees, Fanning and Hunt. Eruption levels were defined as tooth within bone, cusp tips at or just above the alveolar bone level (AE), partially erupted (PE) and fully erupted. The distribution of tooth stage and age was described for AE and PE for each tooth type and data were pooled for boys and girls. Mean age for M1 was 5.20 (SD 0.80, N=110) and 6.00 (SD 0.90, N=49) for AE and PE respectively. Values for M2 were 10.35 (SD=1.26, N= 112) and 11.93 (SD= 1.48, N=46). The oldest child with no fully erupted tooth was 7.68 years. The youngest child with a fully erupted tooth (M1) was 4.87 and with seven fully erupted teeth was 10.69 years. The modal root stage at AE for molars and incisors was R1/4 and R1/2 respectively. Modal stage for the canine and premolars was R3/4. The modal root stage at PE for most teeth was R3/4 with the exception of M1 (R1/2) and canine (Rc). These findings show a wide range of root stage and age for eruption levels and that M2 erupts relatively later in root formation terms compared to M1.