Objective:To describe the procedures for management of the non-vital teeth with open apices using mineral trioxide aggregate(MTA). Methods:Six non-vital teeth with open apices in 6 patients aged 10～20 years old were treated with MTA. After a rubber dam was applied, a large access was made for debridement of the canal. Calcium hydroxide paste was placed in the canal for 1 week for disinfection. After the calcium hydroxide was rinsed from the canal at the subsequent appointment, a mixture of MTA powder with sterile water was carried into the canal with an amalgam carrier. The mix was condensed to the apical extent using pluggers to create a 3-4 mm apical plug. To ensure proper setting of MTA, a moist cotton pellet was placed in the canal over the material and the tooth was temporized, The remainder of the canal was obturated with gutta-percha and sealer or bonded composite resin was placed in the access cavity at next visit. Results:The patients had no abnormal symptoms and signs after apical plug. Radiograph demonstrated all open apices healing 6 months after obturation. Conclusion:MTA is effective and convenient in the management of non-vital teeth with open apices.

Objective The beam data is compared with those obtained from Monte Carlo (MC)simulation and measurement to investigate their feasibility and reliability for X-ray small fields.MethodsThe beam data,including the total scatter factor (Scp),percentage depth dose (PDD) was acquired byneasurement and calculation with the field size ranging from 0.5 cm × 0.5 cm to 10 cm x 10 cm.The resultswere compared and analyzed.Results All the data is most consistent for the fields size of ≥3.5 cmx 3.5cm,but they are obvious different for the fields size of ≤ 3.0 cm × 3.0 cm.The measurements seem toreliable using the chambers of CC04 and CC13 for the fields size of ≥2.0 cm x 2.0 cm.Conclusions It isdemonstrated that the accurate measurements and calculations of Scp and PDD can be obtained for the fieldssize of ≥2.0 cm ×2.0 cm,but they needed morc rcscarchcs for thc smaller fields.