The purpose of the study is evaluate the histological changes of the dentinal-pulp complex and root resorption in maxillary premolars with intrusive orthodontic movement under a low power laser effects.

Orthodontics movements can cause inflamatory changes in the pulp and external inflamatory root resorption, different methods have been suggested to control that changes as the use of the low power laser. The objective of this study is to evaluate the low power laser effect on the inflamatory pulpar change and inflamatory external root resorption in maxillary premolars with intrusive orthodontic movements of 4 ounces during 12 weeks. Total sample were 34 healthy teeth, 16 were used to evaluate the normal standar and 18 were divided in two groups, the experimental group with the low power laser effect had a dose of 18 joules after activations of the orthodontic intrusion and the control group had a simulated effect in the same orthodontic movement. Teeth were extacted after 12 weeks and histological changes were evaluated in the dentinal-pulp complex and the pesence of external inflamatory root resorption. Findins suggest that low power. Laser decreased the inflamatory changes of the dentinal - pulp complex and the severity of the external inflamatory root resorption.

Inclusion Criteria:

• Patients with first premolar extraction indicated
• Patients with no sistemic diseases
• Healthy premolars with completed root and no trauma or restoration

Exclusion Criteria:

• Sistemics diseased
• Restoration, trauma in first premolars
• root uncompleted