Palatal rugae morphology is associated with variation in tooth number.

This observational study compared palatal rugae morphology in adolescent subjects with normal tooth number and tooth agenesis. Maxillary dental study casts were used to compare rugae number, length and shape. Each study group contained 60 subjects (30 females and 30 males) mean age 13.4 (SD, 1.55) in control and 13.56 (SD, 1.54) years in tooth agenesis groups (p = 0.576). Mean number of missing tooth units in the tooth agenesis group was 2.1. Mean number of primary rugae in the whole sample was 4.35 (SD, 0.98) on the right and 4.33 (SD, 0.92) on the left with no significant differences (p = 0.236 and p = 0.404, respectively). However, the number of secondary rugae on the left (p = 0.006) and fragmentary rugae on the right (p = 0.004) was significantly increased in the tooth agenesis group. The shape of left primary rugae 2 and 3 also differed between groups, tending towards a wavy pattern in the control group and curved in the tooth agenesis group (p = 0.012 and p = 0.004, respectively). In addition, primary rugae 3 was more convergent (p = 0.008) whilst left primary rugae 3 and 5 were orientated in an antero-posterior direction (p = 0.04 for both rugae) in the tooth agenesis group. Subgroup analysis also identified significant associations between patterns of tooth agenesis and rugae number, in addition to shape of primary rugae. The identification of significant differences in rugae pattern between subjects with normal tooth number and agenesis suggests potential commonality in signal pathway disruption during establishment of these structures.