The current study evaluates the rotational One Shape single-file system regarding clinical and radiographic outcomes in root canal treatment of infected primary molars.

This randomized clinical trial was carried out on 94 primary molars on children in the age group from 4 to 6 years. The teeth selected for this study were randomly assigned into 2 groups according to the used endodontic preparation system. Group I: 47 primary molars were instrumented with One Shape rotational single-file system. Group II: 47 primary molars were instrumented with stainless steel K-files. All teeth were evaluated clinically and radigraphically for 12 months with periodic recall at 3, 6 and 12 months.

Inclusion Criteria:

• Children categorized as class I or II according to American Society of Anesthesiologists (ASA).
• Children aged between 4 and 6 years with at least one necrotic primary second mandibular molar.
• History of dull toothache over an extended period of time
• History of spontaneous pain or pain at night
• Swelling adjacent to tooth with or without a sinus tract
• Abnormal tooth mobility
• Presence of necrotic pulp tissue or purulent discharge when the pulp chamber was accessed
• Interruption of lamina dura or thickening of periodontal ligament space
• Furcational radiolucency did not surpass half of the distance between the furcation and permanent successor
• Negative findings of internal root resorption
• External root resorption confined to the apical third and with at least two-thirds of the root length was intact

Exclusion Criteria:

• Uncoperative children or parents/legal guardians
• Sever intellectual, behaviour or emotional problems
• Non-restorable tooth crowns
• Root canal obliteration
• Presence of underlying dentigerous or follicular cysts