After analysing over 300,000 trays in UK only, we realised that most failure cases were happening at the back of the mouth (second and third molars) where the trays tend to be a little looser. The reason often was that it is tough for some patients to open their mouths wide enough to capture great gingival margins when taking their impressions so the retention of the trays is then compromised. Poor retention means that gel escapes the tray easily and also saliva ingresses diluting the gels further, compromising the results.
With the launch of our Evo4 range, we decided to stop the trays at the first molars (since the first and second molars are not really visible when we smile anyway) and we also added attachments on the 6s in order to ensure optimal retention.
Can we include 7's or 8's in the tray?
We do not recommend including the very back teeth (7s and 8s) in order to improve retention at the back of the trays, however yes - it is possible to request a full arch trays. When booking your patient, simply add your request in the special instructions comment box.
Why is the tray not covering recession areas near the gum line?
We do not cover gum recession areas because exposed dentine does not change colour and it would also make the process a lot more sensitive.