ABSTRAK Latar Belakang: Preparasi saluran akar oval memiliki tantangan tersendiri karenabentuknya yang ireguler sehingga file tidak dapat berkontak dengan seluruhdinding. Penelitian ini bertujuan untuk membandingkan luas dinding saluran akaroval yang tidak terpreparasi dengan gerakan sirkumferensial filing. Metode: Tigapuluh dua gigi premolar mandibula diisi tinta cina kemudian dipreparasi menjadidua kelompok: Mtwo® dan ProTaper Next®. Luas sisa tinta cina dianalisisdengan Adobe Photoshop CS6 dan ImageJ. Hasil: Tidak terdapat perbedaanbermakna antara kedua kelompok, namun ProTaper Next® meninggalkan arealebih sedikit dibandingkan Mtwo®. Kesimpulan: Mtwo® dan ProTaper Next®tetap meninggalkan area yang tidak terpreparasi pada saluran akar oval.ABSTRACT Background: Mechanical preparation of oval root canal has its own challengedue to the irregular shape leaving some area uninstrumented. This studycompared uninstrumented area of oval root canal with circumferential filingusing two different files. Methods: Thirty-two mandibular premolars were dyedwith china ink and divided into two groups, Mtwo® and ProTaper Next®. Theuninstrumented areas were analized using Adobe Photoshop CS6 and ImageJ.Results: There were no significant difference between two files, thou ProTaperNext® left less uninstrumented areas than Mtwo®. Conclusion: Mtwo® andProTaper Next® left uninstrumented areas in oval root canal.;Background: Mechanical preparation of oval root canal has its own challengedue to the irregular shape leaving some area uninstrumented. This studycompared uninstrumented area of oval root canal with circumferential filingusing two different files. Methods: Thirty-two mandibular premolars were dyedwith china ink and divided into two groups, Mtwo® and ProTaper Next®. Theuninstrumented areas were analized using Adobe Photoshop CS6 and ImageJ.Results: There were no significant difference between two files, thou ProTaperNext® left less uninstrumented areas than Mtwo®. Conclusion: Mtwo® andProTaper Next® left uninstrumented areas in oval root canal.;Background: Mechanical preparation of oval root canal has its own challengedue to the irregular shape leaving some area uninstrumented. This studycompared uninstrumented area of oval root canal with circumferential filingusing two different files. Methods: Thirty-two mandibular premolars were dyedwith china ink and divided into two groups, Mtwo® and ProTaper Next®. Theuninstrumented areas were analized using Adobe Photoshop CS6 and ImageJ.Results: There were no significant difference between two files, thou ProTaperNext® left less uninstrumented areas than Mtwo®. Conclusion: Mtwo® andProTaper Next® left uninstrumented areas in oval root canal.;Background: Mechanical preparation of oval root canal has its own challengedue to the irregular shape leaving some area uninstrumented. This studycompared uninstrumented area of oval root canal with circumferential filingusing two different files. Methods: Thirty-two mandibular premolars were dyedwith china ink and divided into two groups, Mtwo® and ProTaper Next®. Theuninstrumented areas were analized using Adobe Photoshop CS6 and ImageJ.Results: There were no significant difference between two files, thou ProTaperNext® left less uninstrumented areas than Mtwo®. Conclusion: Mtwo® andProTaper Next® left uninstrumented areas in oval root canal.