Changes in Smile Proportions Concomitant to Extraction and Non- Extraction Orthodontia (A Comparative Study)

Document Type : Original Article


1 BDS 2006, Faculty of Oral and Dental Medicine. Ain Shams University.

2 Professor of Orthodontics, Head of orthodontic department –Faculty of Dental Medicine for Girls- Al-Azhar University.

3 Professor of Orthodontics, Orthodontic department –faculty of Dental Medicine for Girls Al-Azhar University


Objective: An attractive, well-balanced smile is a paramount treatment objective of modern orthodontic therapy. The purpose of this study was to compare changes in smile proportions among extraction and non-extraction therapy cases and to correlate them with the accompanying hard and soft tissue changes. Material and Methods: A sample of 24 patients with an age range of 14.3-24.9 years, requiring fixed orthodontic treatment was divided into group I (extraction therapy cases) and group II (nonextraction therapy cases). Dentofacial characteristics of the 2 groups were obtained from close up smile photographs and lateral cephalometric analyses before and after treatment. independent student “t” test to compare between both groups before and after treatment, Paired student “t” test to evaluate the change within the same group and Pearson’s correlation analysis to evaluate correlations between selected parameters. Results: After
treatment, maxillary incisor display showed significant increase in the nonextraction group also, maxillary gingival display showed significant increase in the extraction group (P < 0.05). When the two groups were compared, after treatment, the extraction group showed significant higher values in the posterior corridor ratio and maxillary gingival display (P < 0.05). The posterior corridor ratio was negatively correlated with lower anterior facial height (r = -0.579).The amount of incisor display during smile was positively correlated with the inclination of maxillary incisors in relation to the skull
base U1/SN (°) (r = 0.499) and with maxillary incisors protrusion measured as U1/NA distance (r = 0.676). Conclusion: the results revealed that the extraction therapy cases showed higher values in the posterior corridor ratio and maxillary gingival display than the non extraction therapy cases. The significant relationship of incisor protrusion and inclination with the amount of incisor display and the significant relationship of lower anterior facial height with the posterior corridor ratio must be considered when planning orthodontic treatment