Analysis of the safe zone for palatal mini-implant insertion between the maxillary second premolar and first molar in adult patients

CHEN Lingyun; ZHAN Huayong; WU Zhiyuan; LIN Yi; LIN Youlai

Abstract：Objective The goal of this work was to investigate the palatal interradicular distances and the midpoints,palatal bone tissue thickness,palatal mucosal thickness and mesiodistal width of neighboring roots by using cone beam computed to-mography(CBCT)in the region of maxillary palatal interradicular space between the second premolar(P2)and the first molar(M1).We analyzed and compared the difference of the measurements for better determining the optimal implantation site and insertion angle of mini-implants.Methods 40 adult patients who underwent CBCT scanning were selected as the research ob-ject for this study,and the jaw bone was reconstructed by scanning.The maxillary palatal interradicular distance between P2 and M1(DPM)was measured at 3.00,6.00 and 9.00 mm from the alveolar crest,in all,the midpoint of DPM(MDM)was marked.The palatal mucosal thickness,palatal bone tissue thickness and mesiodistal width of neighboring roots where mini-implants were touched the mesiobuccal root's palatal side were measured when mini-implants were implanted in MDM with 30°,45°,60°and 90° angle.The data were analyzed statistically by using software of SPSS 21.0.Results The farther away from the alveolar crest,the wider the palatal interradicular distance between P2 and M1 palatal roots.Moreover,the lower away from the alveolar crest,the higher probability of touching the adjacent root.All midpoints between the P2 and M1 palatal roots were located distal in the proximity surface of the crown.The higher the implantation position,the greater the mucosal thickness,and the results showed a significant difference(P<0.001).When implanted at angle of 30°,45°,60°,the higher the implantation position,the smaller the bone tissue thickness;when implanted at 90°,the higher the height,the greater the bone tissue thickness,the difference was significant(P<0.001);the farther the implantation position from the alveolar crest,the greater the mesiodistal distance of neighboring roots,and the difference was statistically significant(P<0.05).Conclu-sion In the region of maxillary palatal between the second premolar and first molar,it seems better to place mini-implants 1.42 to 2.48 mm distally to the proximity junction.It is not recommended to implant mini-implants with 90° angle at 3 mm and 6.00 mm from the alveolar crest when implanting with 60° angle at 6.00 mm from the alveolar crest.In addition,it is recom-mended to choose a mini-implant with a diameter of no more than 1.60 mm.There are more types of mini-implants when it is im-planted with 45° angle.It is more secure and stable to implant at 9.00 mm from the alveolar crestwith 60°angle.