Comparison of the left and right first molar alveolar bone levels. Estimated mean percentage difference between the linear measurements of alveolar bone loss (m-AB, f-AB and d-AB) of the upper right and left first molars. Significant left-right differences were noted in the distal alveolar bone loss for all groups, while the only significant between-group difference occurred between sham and EGF. Error bars represent the standard error of the mean difference. *P < 0.05 and **P < 0.01.