‘N-Angle’: Clinical Indicator for Predictable Insertion of Ramal Bone Screws

Abstract

Introduction: The primary concern in the placement of ramal bone screws is the blind nature of the procedure, as there is a thick, mobile layer of soft tissue over the bone; also, the ramus is not a uniplanar structure but is swerving like a propeller blade. The purpose of this study was to evaluate the possibility of establishing clinical guidelines based on visible dental and soft-tissue landmarks for safe, reliable, and accurate insertion of ramal bone screws. Aims and Objectives: Our primary objective was to evaluate the angle formed between the appropriate direction of ramal-implant placement and the line tangential to the buccal surfaces of the first and second permanent molars. Our secondary objective was to evaluate the average distance of the neurovascular bundle from the tip of the bone screw. Materials and Methods: We obtained 80 cone beam computed tomography (CBCT) samples, marked reference lines and points on selected axial and coronal sections, and evaluated the following parameters using the software’s linear- and angular-measurement device: the angle between the appropriate direction of ramal bone screw placement and the line tangential to the buccal surfaces of the first and second permanent molars; and the proximity of the bone screw to the neurovascular bundle. Results: The angle between the constructed line of insertion and the occlusal line, as evaluated from our study, was 19.04 (SD ± 6.89) degrees. The proximity of the neurovascular bundle from the screw is 7.1773 (SD ± 1.73988) mm. Conclusion: We can conclude that ramal bone screws can be placed with a comfortable margin of safety.

Quantitative assessment of ramal bone width and the proximity of the inferior canal for the predictable insertion of ramal implants: Cone-beam computed tomography study

“…[5,[54][55][56] e use of a long-collared implant of 2 mm diameter and 14 mm length implant helps mitigate some of these challenges. [5,43] According to Chang et al, [5] a minimum of 14 mm implant length is recommended because the implant must clear the soft tissue by at least 5 mm for oral hygiene considerations, 5 mm length is required to penetrate the thick soft tissue, leaving only 3-4 mm of the implant to penetrate the bone.…”

“…e distance to the IAC was measured from the selected point of insertion at all the above-mentioned six levels and this measurement was recorded parallel to the occlusal line. [43] To avoid any variations between the right and left sides, e measurements were performed for both the right and left sides in all subjects [Figure 1]. Since a dental landmark could have variation due to malocclusions causing alterations in the occlusal plane, a skeletal reference point was also used as a comparative landmark to remove any disparity.…”

“…[57] Some authors have recommended that angulating the implant 13-25° laterally from the occlusal line offers a greater clearance up to 7 mm from IAC thus reducing the odds of injury to the IAC. [43] However, further investigations are required to validate such observations. e lingula was also utilized in this study as a stable anatomical reference [49][50][51][52] to compare and evaluate the use of the occlusal plane as a clinical reference and only the cases where there was no significant difference between the measurements of the skeletal and dental landmarks were used in this study.…”

“…[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Although ramal implants have been successfully inserted in a variety of clinical situations, there has always been concern about their safety due to variations concerning the position of the neurovascular structures, the anatomy of the ramus of the mandible and the optimum height from the occlusal plane from which the implant is inserted. [5,[43][44][45][46][47] erefore, this study was conducted to identify the optimum level for the placement of ramal extra-alveolar implants by considering the transverse bone width of the Ramus and the proximity of the inferior alveolar canal (IAC) to the site of insertion using 3-dimensional (3D) perspective.…”