Factors that Influence Direction Deviation in Freehand Implant Placement.

PURPOSE: This retrospective study investigates the accuracy of freehand implant placement and whether the factors of presence of an adjacent tooth, implant quadrant, number of missing teeth, and location of the implant site influence direction and angulation deviations. MATERIALS AND METHODS: According to specific inclusion and exclusion criteria, a total of 112 implants from 75 partially edentulous patients were recruited for this retrospective study. The implants were inserted using a freehand approach by one experienced clinician (right-handed). The full thickness flap was elevated to expose the alveolar bone in the implant surgery, and the implant crown consisted of an all-ceramic restoration retained by cement. The planned implant position was preoperatively determined using implant planning software. The postoperative implant position was determined by analyzing the alignment after optically scanning the dentition using a specifically designed registration model in Geomagic Studio software. The deviations between the planned and postoperative implant positions were then calculated. The outcomes included direction and angulation deviations between the planned and postoperative implant positions. All data were analyzed by ANOVA, Bonferroni correction, regression analysis, and one-sample t-tests conducted using SPSS. RESULTS: The 3D deviations between planned and postoperative implant positions were 1.22 +/- 0.63 mm at the entrance point, 1.91 +/- 1.17 mm at the apical point, and 7.93 +/- 5.56 degrees in angulation. The presence of adjacent teeth influenced deviations in the mesiodistal (F = 4.338, p = 0.006) and buccolingual directions (F = 3.017, p = 0.033) at the entrance point and mesiodistal angulation (F = 7.979, p < 0.001). The quadrant influenced deviation in the buccolingual direction at the apical point (F = 6.093, p = 0.001) and buccolingual angulation (F = 6.457, p < 0.001). The number of missing teeth had no effect on deviations of direction and angulation of implants. The location of the implant site affected the deviation in the buccolingual direction at the entrance point (F = 3.096, p = 0.049) and the mesiodistal direction at the apical point (F = 3.724, p = 0.027). CONCLUSION: The 3D accuracy of freehand-placed implants could be acceptable in clinical situations. The results showed that the presence of an adjacent tooth and the quadrant and the location of the implant site influenced the direction and angulation deviations of the implant position; however, the factor of number of missing teeth did not.