Latar Belakang: Preparasi saluran akar dengan instrumen putar NiTi dapat menyebabkan crack pada dinding saluran akar.Tujuan: Menganalisa dan membandingkan efek penggunaan instrumen putar NiTi single-file gerakan resiprokal dan kontinyu terhadap terbentuknya crack pada dinding saluran akar. Metode: Tigapuluh dua sampel saluran akar tunggal dipilih secara acak dan dibagi menjadi dua grup (n=16) sesuai dengan instrumen yang digunakan untuk preparasi saluran akar, yaitu instrumen putar NiTi gerakan resiprokal dan gerakan kontinyu. Micro-CT digunakan untuk mengevaluasi crack  sebelum dan setelah preparasi saluran akar. Analisis statistik menggunakan Continuity correction. Hasil: Tidak terdapat perbedaan bermakna antara preparasi saluran akar menggunakan instrumen putar NiTi gerakan resiprokal dan gerakan kontinyu (p>0,05). Crack yang terbentuk ditemukan pada bagian sepertiga apikal saluran akar dengan tipe incomplete crack. Simpulan: Preparasi saluran akar menggunakan instrumen putar NiTi single-file dengan gerakan resiprokal dan kontinyu dapat menyebabkan terbentuknya crack pada dinding saluran akar.

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Background: Root canal preparation with NiTi rotary instrument has the potential to induce cracks in the root canal wall. Objective: To analyze and compare the effects of single-file NiTi rotary continuous and reciprocating instruments in the propagation of cracks in the root canal wall. Methods: Thirty two single root canal samples were randomly assigned into two groups (n=16 per group) according to the system used for root canal preparation : reciprocating instruments and rotary continuous instruments. The samples were scanned through high-resolution micro-computed tomographic imaging to evaluate cracks before and after root canal preparation. The comparison between two groups was analysed statistically using Continuity correction. Results: There was no significant difference in the number of cracks between reciprocating group and rotary continuous group (p> 0.05). Cracks that occured was found in the apical third of the root canal, with incomplete cracks. Conclusion: Root canal preparation with single-file NiTi rotary continuous and reciprocating instruments can induce dentinal cracks in the root canal wall.