| Objective To measure and analyze the position and shape of implant-related anatomical structure such as mandibular lingual foramen,mental foramen,mental canal,the anterior ring of mental nerve and the submandibular fossa in the adult mandible based on CBCT images,and analyze the anatomice buccalingual angulation of the alveolar bone at implant site in order to help determine the implant angulation and depth at the implant treatment-planning phase.Methods A total of 181 patients who met the inclusion criteria for CBCT examination from January 2016 to December 2021 were screened from the radiology image database of Affiliated Stomatological Hospital of Anhui Medical University,including 109 patients with dentition defects,59 males and 50 females;72 patients(36 males and 36 females)with non-dentition defects were treated with 3D reconstruction using DCTViewer software,and the horizontal plane axis and sagittal plane axis were adjusted to obtain the coronal image of the alveolar bone in the measurement plane.The anatomic markers of the mandible were measured and analyzed in the coronal plane passing through the center of the alveolar bone or the center of the tooth at the implant site.Results 1.The buccal and lingual inclination angles of the alveolar bone in the mandibular anterior teeth area:the average physiological inclination angles of the left mandibular central incisor,lateral incisor and canine alveolar bone in the dentition defect group were(23.61±2.96)°,(23.73±4.23)°,(24.99±5.14)°,and the right side were(23.56±7.26)°,(24.66±4.48)°,(23.46±5.81)°;The mean left side of the group of nondentition defects were(24.92±6.29)°,(25.44±6.25)°,(21.60±6.81)°,and the right side were(24.78±7.24)°,(24.90±6.87)°,(21.48±7.45)°.The alveolar bone in the mandibular anterior tooth area was inclined to the buccal side,and there was no significant difference between the two groups(P>0.05).2.The buccal and lingual inclination angles of the alveolar bone in the mandibular posterior tooth area:the buccal and lingual inclination angles of the alveolar bone in the left and right side of the mental foramen area of the dentition defect group were(5.27±3.98)° and(4.82±3.48)°,and(4.56±3.72)° on the left and(4.28±2.73)° on the right in the non-dentition defect group;the buccal lingual inclination angles of the alveolar bone at the mandibular first molar were(8.57±5.03)°on the left and(9.54±5.19)° on the right in the group of dentition defect,and(9.17±4.83)° on the left and(7.89±4.67)° on the right in the non-dentition defect group;The angles of the alveolar bone at the mandibular second molar were(15.48±5.23)° on the left and(14.21±6.67)° on the right in the group of dentition defect,and(20.56±5.01)°on the left and(19.77±5.35)° on the right in the non-dentition defect group;There were statistical differences in gender and left and right sides of the mental foramen region(P<0.05),with females being larger than males and left larger than right,and the nondentition defect group at the second molars was larger than the group of dentition defects(P<0.05).3.Data of the mental foramen area:the inclination angles of the left and right mental canal in the dentition defect group were(41.81±10.07)° and(44.77±8.96)°,and the non-dentition defect group were(41.05±10.24)° and(43.17±9.22)° respectively.The distance from the upper edge of the mental foramen to the top of the alveolar ridge was(12.35±2.38)mm,the distance from the upper edge of the mental canal to the top of the alveolar ridge was(14.14±2.46)mm,and the distance from the upper edge of the mental canal to the apex of the alveolar crest at 1.5 mm on the medial side of the buccal cortex at the upper edge of the mental foramen was greater than the distance from the upper edge of the chin foramen to the apex of the buccal side(P<0.05),and the difference was(1.99±0.77)mm.4.The depth of the submandibular fossa at the first and second molars was(0.80±0.56)mm and(1.00±0.50)mm,the non-dentition defect group was greater than the group of dentition defects,and the second molar was greater than the first molar(P<0.05).The distances from the concave point of the submandibular fossa to the top of the alveolar ridge at the first and second molars were(14.15±5.95)mm and(14.52±3.55)mm,the distances from the convex point of the crown to the top of the alveolar ridge were(10.71±4.72)mm and(9.25±2.81)mm,the distances from the upper edge of the mandibular canal to the top of the alveolar ridge were(15.52±3.48)mm and(13.83±2.76)mm,and the distance from the most concave point of the submandibular fossa to the alveolar crest at the left first molars and the distance from the upper edge of the mandibular canal to the alveolar crest in the non-dentition defect group were larger than those in the group of dentition defects(P<0.05),and there was no significant difference between the other groups(P>0.05).Conclusion 1.There are lingual foramen and lingual canals in the alveolar bone of the mandibular anterior dental area,which gradually decrease from the proximal middle to the far middle,and there are sublingual arteries and lingual nerves in the mandibular lingual canal,therefore,the initial and long-term stability of the implant should be improved under the premise of ensuring safety.The mandibular alveolar bone inclines from buccal to lingual from the anterior tooth area to the molar area,and the lingual inclination of the alveolar bone in the second molar area is the most obvious.2.The implant tip can be stopped at the level of the upper edge of the mental foramen to obtain better initial stability.3.The existence of submandibular fossa limits the depth and direction of implant implantation to a certain extent.It is necessary to use CBCT to accurately measure and analyze this part before operation to avoid complications such as mandibular lingual perforation and improve the success rate of implant repair. |
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