Computer-aided designed and computer-aided manufactured (CAD/CAM) implant surgical guides are long recommended to reliably transfer a virtual treatment plan to the surgical field. The 3d-printed guide stands a basic part of a process commonly referred to as guided implant surgery (GIS). The outcome of this process has been shown to be relatively accurate, even when the guide is in the hands of inexperienced surgeons.

The error in guided implant surgery, when defined as the difference between the planned and the actual position of the implant, is the cumulative result of flaws along the different stages of the procedure. Inaccuracies in the CBCT or CT acquisition process, the DICOM to STL conversion, the registration process of the different modes, the procedure followed for designing and manufacturing the surgical guide, the method used to stabilise the guide in the mouth (i.e. teeth, mucosa, bone), the way the guide is manipulated by the surgeon and finally the quality and quantity and morphology of the local bone.

All of the current research concerning the mechanical parts of a CAD/CAM surgical guide has so far investigated the accuracy of implant guides designed and manufactured professionally by companies specialising in the field of medicine and dentistry. These companies usually provide, in addition to the guide and software, their own correspondent surgical kit, especially designed to perform solely with their guide.

In-office 3d printing with low-cost fused deposition modelling (FDM) or desktop stereolithography apparatus (SLA) printers and freeware provides a cheaper alternative for manufacturing surgical guides with materials and components supplied from the free market. In-office 3d printing gives the opportunity to the implantologist to readily produce a CAD/CAM guide and place implants using the surgical kit at his current disposal. The production of such a 3d guide may pertain the same errors as a commercially constructed guide does, with the exception that now the implantologist is oblivious to the magnitude and, as a result, the clinical significances of these errors.

It is the aim of this paper to compute the maximum errors in the positioning of the implants with relation to the basic mechanical components of a 3d surgical guide/surgical kit combination taking into account the positional and dimensional properties of the guide’s metal part (sleeve) and the dimensional properties of any osteotomy bur used. The analytical equations for the bespoke computation of the errors for any conceivable combination of the relevant parameters will be provided. Reference tables will be reported facilitating the in-office production of any 3d surgical implant guide.