Analysis of the palatal rugae following Rapid Maxillary Expansion (RME) by using a 3D-3D superimposition procedure

A sample of 38 Italian subjects (17 males and 21 females, mean age 8.2 +/- 1.2 years, age range 7.2-8.8 years), who underwent active Rapid Maxillary Expansion (RME), was studied to assess the reliability of an intraoral scan and the stability of palatal rugae. An intraoral scanner was used to obtain digital dental models pre- and post-treatment. A 3D-3D superimposition procedure was performed, and the Root Mean Square (RMS) of the distance calculated, to verify the forensic validity of this biometric technique. The Intra-Class Correlation Coefficient (ICC) values for the overall inter- and intra-observer agreement were 0.955 (95% CI: 0.931-0.980; p < 0.001) and 0.936 (95% CI: 0.918-0.975; p < 0.001), respectively. The values for TEM and rTEM tests were 0.423 and 1.2% for intra-observer; 0.637 and 1.7% for inter-observer. Results showed a statistically significant difference in RMS mean point-to-point distance between untreated control and treated subjects (p = 0.002). The RMS values to distinguish the pooled group (untreated and treated with RME) from any mismatch ranged from 0.42 to 0.61. This methodology was highly suitable to detect changes caused by RME. Since some modifications were detected, caution is necessary when palatal rugae are analysed for forensic purposes in subjects who underwent RME.