(i) Subjects: Sixty subjects who will be undergoing third molar surgery (hereafter known as 'cases') will be recruited from The Queen Mary Hospital and The Prince Philip Dental Hospital and sixty, aged and sex matched controls who will not be undergoing surgery in the next 3 months, nor have undergone surgery in the past year (hereafter known as 'controls') will also be recruited from the Outpatients department of the same hospital.