OBJECTIVE: To test the null hypothesis that there is no relationship between the posture of the head and the neck and late lower arch crowding. MATERIALS AND METHODS: The sample comprised 55 subjects (23 female, 32 male), age 12-18 years, with complete permanent dentition and without previous orthodontic treatment. Space conditions were valued by Nance's space analysis on the study models. Craniovertical, craniocervical, and craniohorizontal postural variables were recorded from lateral cephalograms. Student's t-test was performed to assess the differences of the postural angles between the two groups. RESULTS: The results showed that the differences of the postural variables between the two groups are statistically significant. Subjects with more than 2 mm dental crowding had mean craniocervical angles (NSL/CVT, NSL/OPT, NL/CVT, NL/OPT) that were 5 degrees to 6 degrees larger than the subjects with the space conditions smaller than 2 mm (P < or = .01). In addition, the mean craniohorizontal angles (CVT/Hor, OPT/Hor) in the subjects with lower dental crowding were 4 degrees smaller than subjects without dental crowding (P < .05). CONCLUSIONS: The hypothesis is rejected. A clear pattern of association between extended head posture and lower arch dental crowding was found.
OBJECTIVE: To test the null hypothesis that there is no relationship between the posture of the head and the neck and late lower arch crowding. MATERIALS AND METHODS: The sample comprised 55 subjects (23 female, 32 male), age 12-18 years, with complete permanent dentition and without previous orthodontic treatment. Space conditions were valued by Nance's space analysis on the study models. Craniovertical, craniocervical, and craniohorizontal postural variables were recorded from lateral cephalograms. Student's t-test was performed to assess the differences of the postural angles between the two groups. RESULTS: The results showed that the differences of the postural variables between the two groups are statistically significant. Subjects with more than 2 mm dental crowding had mean craniocervical angles (NSL/CVT, NSL/OPT, NL/CVT, NL/OPT) that were 5 degrees to 6 degrees larger than the subjects with the space conditions smaller than 2 mm (P < or = .01). In addition, the mean craniohorizontal angles (CVT/Hor, OPT/Hor) in the subjects with lower dental crowding were 4 degrees smaller than subjects without dental crowding (P < .05). CONCLUSIONS: The hypothesis is rejected. A clear pattern of association between extended head posture and lower arch dental crowding was found.