Esthetics And Smile Characteristics From The Patient's Perspective, Part II

Objectives:  To quantify layperson's ideal and maximum acceptable deviation for nine smile characteristics through digital technology.  Methods:  Photographs of ideal, symmetric dental configurations were digitally manipulated using Adobe® Photoshop® CS2.  Incisor tooth proportions, central-lateral incisal edge lengths and gingival margins, maxillary central incisor width-length ratio and gingival margins, transverse occlusal cant, overbite, maxillary midline to face, and maxillary-mandibular midline were altered and placed in a gender neutral face, showing the lower portion of the nose to below the mentolabial fold.  The composites of teeth and soft tissue were placed in random image sequences and imported into Quask™ Form Artist to generate the survey, which was administered in Columbus, OH (n=43); Seattle, WA (n=41) and Boston, MA (n=40), supported by power analysis.  An interactive interface allowed raters to move a slider to adjust each variable to their choices.   Rater reliability was assessed by rating every smile twice (26 images total).  Results:  Reliability ranged from ICC=0.88 to 0.47.  The smile became unattractive when the maxillary midline deviated 2.9mm or once the maxillary-mandibular midlines deviated 2.1mm.  Overbite was ideal at 2.0mm and unacceptable at <0.4mm and >5.7mm.  Central incisor crown width:height ratio was ideal at 0.73:1.  The lateral incisor had an ideal lateral:central width ratio of 0.72:1, with a range of 0.53:1 to 0.76:1.  Maxillary central incisor gingival discrepancies were acceptable until >2.0mm.  The ideal lateral incisor gingival margin was ideally 0.4mm incisal to the central.  However, it was acceptable from 2.9mm incisal to 1.2mm gingival to the central gingival margin.  The ideal central-lateral incisor step was 1.4mm and became unattractive >2.9mm.  Transverse maxillary cants became unattractive at 4.0°.  Conclusions:  The range of acceptability for these smile characteristics remains large, and except for midlines, is equal to or greater than what most clinicians envision.