Adult circumcision with Shang ring is quick procedure however wound healing takes longer than conventional circumcision in adults. 

A randomised clinical study with a Shang ring versus conventional circumcision showed wound healing time in the Shang ring groups was longer than conventional circumcision (maen +/-SD 19.86 +/-5.24 vs 13.42+/-2.35 days, p<0.001 significant) J Urol 2012

A systematic review and meta-analysis of circumcision with Shang ring vs conventional circumcision. Urology 2015 showed  Overall, 8 randomised controlled trials involving 3314 patients were included. Compared with the conventional circumcision group, Shang circumcision is associated with shorter operative time, lower intraoperative pain score, higher satisfaction with penile appearances, less intraoperative blood loss, lower adverse event rate, and lower wound bleeding rate. Shang circumcision appears to be a safer and more effective choice in comparison with circumcision with stitches for male patients.

One long term study showed scar width is 3.7+/- 1.6 mm (clinical medicine journal 2014)

Healing showed significant wound edges gap after removal of Shang ring and this wound heals by secondary intention, scaring with some cases.  

No study mentioned that how long adult patient feel pain after ring came off.  

Dr. Khan has performed three revision circumcisions with glue after Shang ring circumcision. Glue circumcision provide excellent cosmetic result with less pain and less complications. Patients suffered pain due to secondary healing of gapped wound for three months after Shang ring circumcision.  

This required further studies to conduct addressing this issue in Shang ring circumcision.