Accuracy of a custom two-piece surgical guide for all-on-four dental implant placement: An in vitro study

Although fully guided dental implant surgery has been reported to provide a high degree of accuracy, it has disadvantages including the lack of external irrigation during osteotomy formation and the need for special drills and equipment. Whether a custom 2-piece surgical guide has sufficient accuracy is unclear.

The purpose of this in vitro study was to design and fabricate a new surgical guide concept that fully guides the placement of implants to the desired position and angulation without affecting the external irrigation during osteotomy preparation, to eliminate the need for a special armamentarium, and to determine the accuracy of the guide.

A 2-piece surgical guide was 3-dimensionally designed and fabricated. Implants were placed according to the all-on-4 concepts in laboratory casts using the newly fabricated surgical guide. Placement accuracy was determined from a postoperative cone beam computed tomography scan that was superimposed over the preplanned implant positions to calculate the degree of angular deviation and position of placement. Adopting 5% alpha error and 80% study power in estimating sample size, a total of 88 implants were placed according to the all-on-4 concept in 22 mandibular laboratory casts. These were divided into 2 groups: with the newly fabricated surgical guide and with a traditional fully guided protocol. Deviations at the point of entry, at the apex horizontally, the vertical apical depth, and angular deviations from the proposed plan were measured from the superimposed scans. Differences in apical depth, horizontal deviation at the apex, and horizontal deviation in the hexagon measurements were compared with the independent t test, while differences in angular deviation were assessed with the Mann-Whitney U test (α=.05).

No statistically significant difference was found in the apical depth deviation (P>.05), but significant differences were found in the apex (P=.002), hexagon (P<.001), and angular deviation (P<.001) between the new guide and the traditional guide.

The new surgical guide showed potential for higher accuracy in implant placement when compared with the fully guided sleeveless surgical guide. In addition, it provided an undisturbed flow of irrigation around the drill throughout the drilling procedure, with the advantage of eliminating the special armamentarium usually required.