The development of a method of assessing swelling following third molar surgery.

A method of measuring post-operative facial swelling following third molar surgery should satisfy the following criteria. Firstly, the accuracy should be assessed, secondly the measurement should be in volume units, and thirdly the method should be both practical and ethical in the clinical situation and not limited by static apparatus. No published method satisfies all of these criteria. In an attempt to develop a satisfactory method, direct physical measurements using a face bow, ultrasound and portable stereophotogrammetry were investigated. None of these three methods was limited by static apparatus. Portable stereophotogrammetry could not be used because of variations in posing for which a correction could not be applied. Repeated measurements on non-operated subjects showed that the face bow was more accurate than the ultrasound method at a single measurement site. Therefore, the face bow method was developed to give volume measurements in cubic centrimetres by using nine measurement sites at the intersections of a square grid located over the swelling. The mean difference between two readings taken on separate occasions on non-operated subjects was -0.94 cc (s.d. +/- 1.90). The mean swelling measured at twenty third molar operation sites was 23.19 cc. It is concluded that this face bow method satisfies the criteria laid down.