Comparison of skeletal and dental effects of two different tooth-tissue–borne types of rapid maxillary expansion appliances: A CBCT retrospective study

Objectives: To compare the skeletal and dental effects of different types of rapid maxillary expansion (RME) appliances using cone-beam computed tomography (CBCT). Materials/methods: This multi-centre study was conducted with a total of 56 patients. The sample consisted of two groups including the McNamara-Type RME (MNR) group with 30 patients (16 females, 14 males, mean age: 13.38 ± 1.16 years) and Full-Coverage RME (FCR) group with 26 patients (10 females, 16 males, mean age:13.78 ± 1.06 years). Twenty-one parameters were measured on CBCT images including 4 maxillary skeletal, 12 maxillary alveolar, and 5 maxillary dental measurements, and the data were analysed using the SPSS 20.0 software. Results: The rates of increase in the palatal maxillary width (PMW) (3), PMW(4), and PMW(6) were significantly higher in the MNR group (P < .05). While the rates of increase in the buccal maxillary width (BMW) (3) and BMW(4) were statistically higher in the MNR group, the rate of increase in BMW (6) was higher in the FCR group (P < .05). The increases in HPW (4), HPW (6), PAA4(°), and PAA6(°), which are parameters about hard palate width (HPW) and palatal alveolar angle (PAA), were also significantly higher in the MNR group (P < .05). The increases in PAW (4) and PAW (6), referring to the widths between the palatal root apices were significantly higher in the MNR group (P < .05).The increase in Slope-6(°) was also higher in the MNR group (P < .05). Conclusion: Expansion in the palatal region on the alveolar level was higher in MNR than in FCR, while expansion in FCR was the highest in the posterior. In both appliances, there was tipping in the buccal direction in both alveolar bone and teeth, and the rate of this tipping was higher in MNR.