Thank you to Drs Yan and Tian for the comments and question regarding Part 2 of our work regarding arch-width and buccal corridor changes.
Drs Yan and Tian suggested that there will always be bias with the use of VAS ratings and that perhaps the eyes of the subjects could have been covered on the assessment photographs so that the assessors could focus directly on the smile. VAS ratings were indeed used in this work. They have previously been used by many authors and have been described and used many times in other articles appearing in the peer-reviewed literature. When planning this work, we discussed providing everything from the full face, with or without partial blocking out, to an edited smile, with or without the surrounding perioral tissues. We first decided that natural smiles from orthodontic patients would be used rather than computer-generated artificial smiles. Ultimately, we decided to present the whole face, because the assessment of the smile is undertaken naturally in public with the view of everything, including facial shape, eye positions and color, as well as skin and hair quality, color, and style. On reflection, we are still happy that this method does provide at least 1 way in which to validly view the smile in relation to its natural surroundings.
The correspondents also questioned the order in which the images were viewed by the assessors. On reflection, we are happy with the set order that was given to each reviewer and do not believe that it would introduce any more bias than other methods.
They also pointed out that the “number of years in practice” seemed to affect the ratings of orthodontists and dentists, and they were concerned that there was only 1 dentist in the 21- to 30-year group and that the distribution of subjects into the year groups was not even. That would of course be a real problem if one were statistically testing differences in means for various classification groups. The subjects were placed into these year groups simply for descriptive purposes. Differences in those means were not used for this part of the assessment, however. Instead, continuous correlations were run against “years in practice,” with all raters included, so that the numbers in each group were then not so important.
Finally, Drs Yan and Tian asked why the ratio (percentage) of the last molar buccal corridor to the total smile width is smaller on average than the ratio of the canine buccal corridor to the total smile width (Table III). Perhaps they misunderstood the material presented in that table. These are buccal corridor percentages of the total smile width, and in most cases, one would expect the distance from the last molar to the commissure to be less than the distance from the canine to the commissure. Hence, the last molar buccal corridor would make up a smaller percentage of the total smile width.