Latar Belakang: Penelitian mengenai pengaruh pelebaran korona saluran akar terhadap tingkat ketepatan apex locator hanya sedikit. Tujuan: Membandingkan ketepatan lokasi foramen apikalis pada dua tipe apex locator dan menilai pengaruh pelebaran koronal saluran akar. Metode: Panjang kerja 16 gigi premolar satu mandibula diukur secara visual, menggunakan dua jenis apex locator saat sebelum dan setelah dilakukan pelebaran korona saluran akar. Hasil: Berbeda bermakna ketepatan pada tiap jenis apex locator setelah dilakukan pelebaran korona, namun tidak berbeda bermakna pada keduanya setelah pelebaran koronal saluran akar. Kesimpulan: pelebaran korona saluran akar meningkatkan ketepatan apex locator mengukur lokasi foramen apikalis.

---

Background: Only a few studies on the effect of coronal preflaring to the accuracy of apex locator.

Objective: To compare the accuracy of two types of apex locators and evaluate the influence of coronal preflaring in them.

Method: working length of sixteen first mandibular bicuspids were measured visually, using two types apex locator at before and after coronal preflaring.

Result: statistically significant of two type apex locators at before and after coronal preflaring, no statistically significant at both types after coronal preflaring.

Conclusion: coronal preflaring will increase the accuracy of apex locator in locating the apical foramen.