Flute and Shank Dimensions of Reciprocating Instruments before and after Simulated Root Canal shaping.

AIM: This study analyzed the effect of the dimensions of the flute and shank in the first 4 mm of instrument tips on the deformation and dimensional changes of reciprocating instruments after root canal shaping (RCS). MATERIALS AND METHODS: The reciprocating instruments used were Reciproc® R25, R40, and R50; WaveOne® Small, Primary, and Large; and Unicone® #20, #25, and #40. Scanning electron microscopy images of the first 4 mm of the tip were acquired at 30× magnification before and after simulated curved root canals were shaped. Each instrument was used only once. The images were transferred to the AxioVision® software to measure the flute area (µm2), shank area (µm2), flute length (µm), and cross-sectional diameter (µm). Student's t test for paired samples was used to compare differences before and after RCS, and analysis of variance followed by the Tukey test, to compare differences between instruments of similar sizes. The instruments were classified according to deformations after RCS. RESULTS: Reciproc® instruments had larger flutes and smaller shanks. The Reciproc® R40 had significant differences in cross-sectional diameter at 0.5 mm from the tip. Reciproc® had no plastic deformations. Unicone® #20 instruments had significant differences in cross-sectional diameter at 1.5 and 3.0 mm from the tip, and #25 instruments had differences at 1.5 and 3.0 mm and in length of the second and third flutes. One #20 and three #40 instruments had plastic deformations. The differences in length of the first and fourth flutes of WaveOne® Primary and in cross-sectional diameter at 2.0 mm from the tip of WaveOne® Large were significant. Two of three WaveOne® Large instruments had plastic deformations. CONCLUSION: Reciproc® instruments had greater flute areas and lengths and smaller shanks than Unicone® and WaveOne® instruments of similar sizes. Reciproc® instruments had a greater flute-to-shank ratio. WaveOne® instruments had the lowest flute-to-shank ratio. Unicone® instruments had the most plastic deformations. Instruments with larger flutes and smaller shanks had fewer plastic deformations after curved RCS. CLINICAL SIGNIFICANCE: The knowledge of mechanical behavior before choosing the endodontic instrument may avoid fracture, regardless of the clinical condition, and it is essential to the success of root canal treatment.

Nonconventional Therapeutic Protocol for Type III Dens Invaginatus.

INTRODUCTION: This study discusses a nonconventional therapeutic protocol for type III dens invaginatus. This condition is a disorder of dental development, caused by the invagination of enamel into coronal and/or radicular dentin structure. This promotes several structural alterations within the dental organ, which offers challenges and difficulties to perform the endodontic treatment when needed. This article reports a clinical case where a conservative approach was adopted to preserve the invagi-nated tooth, and endodontic treatment was performed in the main necrotic canal. Following 21 years of observation, a complete root formation could be seen, with dental pulp preservation of the pulpotomized tooth. Considering the reported difficulties for the treatment of dens invaginatus, conservative measures, such as pulpotomy to preserve the remaining dental pulp may be an excellent alternative to allow less invasive procedures, thus avoiding endodontic surgery. This study discusses a nonconventional therapeutic protocol for type III dens invaginatus. A conservative approach adopted preserved the invaginated tooth, and root canal treatment was performed in the main necrotic canal. Following 21 years of observation, there was complete root formation, with dental pulp preservation of the pulpotomized tooth.