Is 2-mm dental midline deviation acceptable?
The training process and background knowledge allow us, dentists to observe more details in teeth. For example, we are sensitive to smile characteristics like dental midline shift, occlusal plane canting, or other asymmetries.
However, not every imperfection can or should be corrected in clinical cases since the actual possibility, the time needed, or the treatment budget is different. Besides, laypeople (or patients) might not notice the minor shifting or canting and hence do not consider them problems that need to be solved.
Finding the harmony between soft tissues and dentition is the primary purpose of esthetic dentistry. Whereas balancing patients’ expectations and the ideal esthetic criteria is another harmony for us to achieve.
Therefore, knowing the acceptable threshold to smile characteristics for laypeople (or patients) can help us propose more customized treatment plans and prevent us provide unrealistic treatment goals. [1]
The followings are the acceptable thresholds for laypeople (or patients) with figures to visualize the situation. (These figures are from Silva, Bruno Pereira, et al.[2] article. Thank you!)
Upper dental midline shift
- ≥2 mm dental midline shift is rated less attractive when compared with the control image and significantly impacts the esthetics. [2, 3]
- Some studies reported 4mm. [4, 5] However, these studies used images with only the lower third of the face for assessment which might bring different results and higher thresholds. [2]
Dental midline canting
- 5 degrees for a dental midline cant can be recognized as a negative impact for most laypeople. [2]
Nose deviation
- ≥4 mm nose deviation is rated less attractive when compared with the control image. [2]
Among all these parameters mentioned, dental midline shifting and canting had the most significant impact, while chin deviation had the least or no impact. [2]
Even though the dental midline seems to be the dominant determinant in facial and dental esthetics, there are still ranges of tolerance that give us the flexibility to adjust our treatment planning and achieve harmony of both esthetics and communication.
Reference:
[1] Ker, A. J., Chan, R., Fields, H. W., Beck, M., & Rosenstiel, S. (2008). Esthetics and smile characteristics from the layperson’s perspective: a computer-based survey study. The Journal of the American Dental Association, 139(10), 1318–1327.
[2] Silva, B. P., Jimenez-Castellanos, E., Martinez-de-Fuentes, R., Greenberg, J. R., & Chu, S. (2013). Laypersons’ perception of facial and dental asymmetries. International Journal of Periodontics & Restorative Dentistry, 33(6).
[3] Johnston, C. D., Burden, D. J., & Stevenson, M. R. (1999). The influence of dental to facial midline discrepancies on dental attractiveness ratings. The European Journal of Orthodontics, 21(5), 517–522.
[4] Kokich Jr, V. O., Asuman Kiyak, H., & Shapiro, P. A. (1999). Comparing the perception of dentists and lay people to altered dental esthetics. Journal of Esthetic and Restorative Dentistry, 11(6), 311–324.
[5] Pinho, S., Ciriaco, C., Faber, J., & Lenza, M. A. (2007). Impact of dental asymmetries on the perception of smile esthetics. American Journal of Orthodontics and Dentofacial Orthopedics, 132(6), 748–753.
[6] Padwa, B. L., Kaiser, M. O., & Kaban, L. B. (1997). Occlusal cant in the frontal plane as a reflection of facial asymmetry. Journal of oral and maxillofacial surgery, 55(8), 811–816.
[7] Geron, S., & Atalia, W. (2005). Influence of sex on the perception of oral and smile esthetics with different gingival display and incisal plane inclination. The Angle Orthodontist, 75(5), 778–784.Chicago
