Background:Orthodontic forces are often followed by the biological response of dental pulp. The present study was conducted to assess effect of orthodontic forces on pulp tissues. Materials & Methods: 58 patients required maxillary first premolar extraction for orthodontic purposes were treated with a cantilever spring made of 16 × 22 steel wire to apply intrusive force to upper first premolars (Group I) and the opposing teeth were considered as control group (Group II). Results: Inflammation at 7 days in group I was none seen in 60% and mild in 40% 34% and in group II was none seen in 80% and mild in 20%. At 1 month was none seen in 100% in both groups. Fibrous tissue at 7 days was none seen in 100% teeth in both groups and at 1 month was none seen in 40% in group I and 100% in group II and mild in 60% in group II. Vascular dilatation at 7 days was none seen in 60% and moderate in 40% in group I and none in 55% and moderate in 45% in group II. Vascular dilatation at 1 month was none in 60% and mild in 40% in both groups. The difference was significant (P< 0.05). Conclusion: Mild intrusive force in closed apex teeth causes no significant histologic changes in both groups.