Figure 2 - 'Six keys to occlusion' are present (after Andrew); a perfect smile
From the following article
Occlusion:
Orthodontics and occlusion
S J Davies, R M J Gray, P J Sandler & K D O'Brien
British Dental Journal 191, 539 - 549 (2001) Published online: 24 November 2001
doi:10.1038/sj.bdj.4801229
