# Plywood Jig--A New Technique for Root Canal Curvature Measurement
## 3 Results  
The canal curvature angle average values measured using Jig method and Schneider method for mandibular teeth are 28.23\({}^{\circ}\) (\(\pm\)9.96) and 22.07\({}^{\circ}\) (\(\pm\)9.46) respectively. (Table 1) The smallest/largest average curvature angles measured using Jig method and Schneider technique are 12\({}^{\circ}\)/52\({}^{\circ}\) and 8\({}^{\circ}\)/44\({}^{\circ}\) respectively. Paired \(t\)-test showed that there was highly significant difference between the curvature angle measured using each technique (\(p<0.001\)) (Figure 4 and Table 2). Canal curvature angle average values measured using Jig method and Schneider method for maxillary teeth are 23.40\({}^{\circ}\) (\(\pm\)11.36) and 19.23\({}^{\circ}\) (\(\pm\)11.94) respectively. (Table 1) The smallest/largest average curvature angles measured using Jig method, Schneider technique are 9\({}^{\circ}\)/70\({}^{\circ}\) and 5\({}^{\circ}\)/72\({}^{\circ}\) respectively. Paired \(t\)-test showed that there was highly significant difference between the curvature angle measured using each technique (\(p\) < 0.001). (Table 2)  
The results of radius of curvature measured using Jig method and Schneider method for mandibular teeth are 9.79 mm (\(\pm\)3.65) and 10.55 mm (\(\pm\)3.34) respectively. The smallest/largest average curvature radius measured using Jig method, [PERSON] technique are 2.4 mm/18.4 mm and 2.8 mm/18.4 mm respectively. Paired \(t\) test showed that there was highly significant difference between the curvature angle measured using each technique (\(p\) < 0.001). For maxillary teeth using Jig method 16.06 mm (\(\pm\)8.12) compared to Schneider method 17.51 mm (\(\pm\)7.88). The  
method are that it is reproducible, easy to use as well as efficient, particularly when using radiovisiographic (RVG) images. Precise knowledge of root curvature radius is required to ensure accurate planning of the instrumentation and reduces the impact of the anatomic limitations of various endodontic instruments. By modifying the instrumentation techniques, we can eliminate the disastrous consequences that may occur during root canal preparation, such as loss of working length, apical transportation, creation of elbows, zips, ledges, perforations, and even instrument fracture. [PERSON] proposed a method to determine curvature based on the angle that is obtained by two straight lines [3,4]. The first line runs parallel along the length of the root canal, while the second one runs through the apical foramen till it intersects with the first line at the start of the curvature. The formed angle (a) was named according to the degree of root canal curvature: straight: 5\({}^{\circ}\); moderate: 10-20\({}^{\circ}\); and severe: 25-70\({}^{\circ}\). There are major problems encountered during routine endodontic treatment such as deformation or fracture of instruments. Mechanical preparation errors may come about because of an increase in the canal curvature [8]. Additionally, the file may fracture due to stress arising from contact with the canal surface. Despite their super-elasticity recently developed nickel titanium canal instruments can suffer from cyclic fatigue effect in curved canals, a sharp canal curvature increases the stress on instrument [11, 12, 13]. Recent literature evaluated the importance of stress at 360 degree in extracted teeth, assesses the recently developed NiTi rotary instrumentations, and new dynamic stress assessment technique, which revealed the excellent resistant to cyclic effort [14,15]. The type of canal exhibiting secondary curvature in plane opposite to that of direction of primary curvature as in mesio-buccal canal. The highest mean of curvature in mesio-buccal canal. [PERSON] described the mesio-lingual canal of mandibular molar usually straighter than the mesio-buccal canal [16]. Previous studies reported that most fractures occurred in the apical portion of the canal, because of the presence of a curvature with a small radius [10]. [PERSON] et al.