The relationship of the nasolabial angle and the superior incisors inclination in relation to the palatal plane during the “ugly-ducking” phase

Vania Célia Vieira de SIQUEIRA, Conceição Eunice CANUTO, Hélio SCAVONE JR, Paulo Eduardo NEGREIROS

During the period of the permanent cuspids eruption, the superior incisors may assume positional changes (“ugly ducking” phase). The nasolabial angle, in his turn, may also be influenced by the magnitude of the anterosuperior teeth protrusion. Therefore, this transversal cephalometric research has been conducted using a sample of 99 roentgenograms of white brasilian children, from both sexes and with normal occlusion, between the ages of 7 to 11 years. The objectives of this investigation were to establish the mean cephalometric values for the nasolabial angle (NLA) and for the superior incisors inclination in relation to the palatal plane (1.PP); to determine if there is sexual dimorphism for these variables; to verify if the mean values of this cephalometric variables exhibited appreciable change between the age periods; to evaluate the possible correlation between these angles and, finally to observe if the “ugly-ducking” period influences these measures. The mean values obtained for NLA at 7, 8, 9, 10 and 11 years of age were, respectively 114,40º (sd=10,15); 112,10º (sd=9,15); 108,76º (sd=9,06); 110,15º (sd=9,64); 110,13º (sd=12,04). For the 1.PP angle the mean values were 68,15º (sd=5,80); 67,81º (sd=3,70); 68,47º (sd=4,52); 68,40º (sd=4,22) and 68,63º (sd=4,70). After applying the student “t” test for comparison of these mean values between sexes, for every one of the age periods, it was verified that there weren’t statistically significant gender differences. Furthermore, the variance analysis indicated a F value of 0,96 for the NLA and 0,091 for 1.PP, demonstrating the lack of statistically significant differences between the age periods analyzed. The Pearson’s correlation coefficients between NLA and 1.PP, indicated values of R=0,14 at 7 years, R=0,14 at 8 years; R=0,41 at 9 years, R=0,18 at 10 years and R= 0,043 at 11 years of age. The total correlation (R=0,06) revealed the lack of statistical significance. Therefore, the authors concluded that NLA and 1.PP variables didn’t exhibit correlation among them and they also didn’t demonstrated significant changes during the age periods studied. These results suggest that the eruption of the superior permanent cuspids don’t exert appreciable repercussions over the vestibulolingual superior incisor inclination and over the nasolabial angle, during the “ugly-ducking” phase.

Keywords: Nasolabial angle. “Ugly-ducking”. Normal occlusion. Mixed dentition.

Wednesday, May 01, 2024 00:14