Accuracy of computer-aided implant placement.

AIM: To assess the accuracy of static computer-guided implant placement. MATERIAL AND METHODS: Electronic and manual literature searches were conducted to collect information on the accuracy of static computer-guided implant placement and meta-regression analyses were performed to summarize and analyse the overall accuracy. The latter included a search for correlations between factors such as: support (teeth/mucosa/bone), number of templates, use of fixation pins, jaw, template production, guiding system, guided implant placement. RESULTS: Nineteen accuracy studies met the inclusion criteria. Meta analysis revealed a mean error of 0.99 mm (ranging from 0 to 6.5 mm) at the entry point and of 1.24 mm (ranging from 0 to 6.9 mm) at the apex. The mean angular deviation was 3.81° (ranging from 0 to 24.9°). Significant differences for all deviation parameters was found for implant-guided placement compared to placement without guidance. Number of templates used was significant, influencing the apical and angular deviation in favour for the single template. Study design and jaw location had no significant effect. Less deviation was found when more fixation pins were used (significant for entry). CONCLUSION: Computer-guided implant placement can be accurate, but significant deviations have to be taken into account. Randomized studies are needed to analyse the impact of individual parameters in order to allow optimization of this technique. Moreover, a clear overview on indications and benefits would help the clinicians to find the right candidates.

Extra short dental implants supporting an overdenture in the edentulous maxilla: a proof of concept.

OBJECTIVES: This study investigates the outcome of short implants additionally placed with longer implants to support a maxillary overdenture. MATERIALS AND METHODS: Twelve patients received six implants to support a maxillary overdenture. Only one patient still had two molars in the maxilla, while the others had no remaining teeth. The status of the opposing arch was diverse. The distal implant in each quadrant was 6 mm in height (S) and the middle implants ranged between 10 and 14 mm (L). All implants were placed following a one-stage procedure and early loaded (6 weeks). Clinical and radiological parameters were assessed 6, 12 and 24 months after loading. RESULTS: One short implant failed 2 weeks after surgery, probably due to early mobilization by the provisional prosthesis. The mean bone loss on the rough part of the implant was 0.7 mm (S) vs. 1.3 mm (L) during the first year and 0.3 mm (S) vs. 0.2 mm (L) during the second year after loading. The mean implant stability quotient values were 67 (S) vs. 70 (L) at placement and 75 (S) vs. 78 (L) after 1 year. At the 2-year follow- up, all prostheses were still stable and comfortable. CONCLUSION: An overdenture on six implants, of which two have a reduced length, might represent a successful treatment option. No significant difference could be found between both implant lengths at 2 years' follow-up. However, bone loss with short implants may increase the likelihood of failure.

Accuracy assessment of computer-assisted flapless implant placement in partial edentulism.

AIM: To assess the accuracy of implants placed flapless by a stereolithographic template in partially edentulous patients. MATERIAL AND METHODS: Eight patients, requiring two to four implants (maxilla or mandible), were consecutively recruited. Radiographical data were obtained by means of a cone beam or a multi-slice CT scan and imported in a software program. Implants (n=21) were planned in a virtual environment, leading to the manufacture of one stereolithographic template per patient to guide the implant placement in a one-stage flapless procedure. A postoperative cone beam CT was performed to calculate the difference between virtual implant (n=21) positions in the preoperative planning and postoperative situation. RESULTS: A mean angular deviation of 2.7 degrees (range 0.4-8, SD 1.9), with a mean deviation at the apex of 1.0 mm (range 0.2-3.0, SD 0.7), was observed. If one patient, a dropout because of non-conformity with the protocol, was excluded, the angular deviation was reduced to 2.2 degrees (range 0.6-3.9, SD 1.1), and the apical deviation to 0.9 mm (range 0.2-1.8). CONCLUSION: Based on this limited patient population, a flapless implant installation appears to be a useful procedure even when based on accurate and reliable 3D CT-based image data and a dedicated implant planning software.

Tolerance within a surgical guide.

BACKGROUND: Recently, guided surgery has been introduced and several papers verified its accuracy. AIM: While those studies reported on the accuracy of the entire procedure, this experiment wanted to make clinicians aware of the amount of the deviation that can already occur during the drilling procedure alone, due to the tolerance of the drill in the drill key. MATERIAL AND METHODS: Drilling was executed in plexi-glass with a maximal inclination of the drills within the drill keys. RESULTS: A mean deviation in angulation of 4.7 degrees occurred with a mean horizontal deviation at the implant shoulder of 0.8 mm and 1.8 mm at the apex of 13 mm implant. The deviation was further dependent of the implant length, the distance of the sleeve above the bone and the respective guiding system. DISCUSSION: Increasing the height of the drill key will minimize the inaccuracy. CONCLUSIONS: The results from this experiment showed the importance of keeping the drill parallel to the guide in a centric position.

The use of CT scan based planning for oral rehabilitation by means of implants and its transfer to the surgical field: a critical review on accuracy.

The purpose of the present paper is to review the literature on the use of CT scan based planning for oral rehabilitation and its transfer to the surgical field by means of a surgical guide. The first part will deal with surgical guides based on tomographies or CT scan data often using dedicated software, but manually fabricated. In the second part, CT-derived drill guides are discussed, which are fabricated by means of CAD/CAM technology or other computer-controlled technology. The deviations between the position of the implants at the planning stage and after the surgery are of utmost importance, especially when flapless procedures are applied. The maximal deviations are often not stated in the literature. This should be taken into account when a system is applied clinically.

Comparative localized linear accuracy of small-field cone-beam CT and multislice CT for alveolar bone measurements.

OBJECTIVES: To compare the accuracy of cone-beam computerized tomography (CBCT) and multislice CT (MSCT) for linear jaw bone measurements. STUDY DESIGN: An ex vivo formalin-fixed human maxilla was imaged with both CBCT (Accuitomo 3D; Morita, Kyoto, Japan) and MSCT (4-slice Somatom VolumeZoom and 16-slice Somatom Sensation 16; Siemens, Erlangen, Germany). The MSCT images were reconstructed using different reconstruction filters to optimize bone visualization (U70u and U90u for VolumeZoom, H30s and H60s for Sensation 16). Before scanning, triplets of small gutta-percha markers were glued onto the soft tissues overlying the maxillary bone on the top and on both sides of the alveolar ridge to define a set of reproducible linear measurements in 11 planes. Image measurements were performed by 2 observers. The gold standard was determined by means of physical measurements with a caliper by 3 observers. RESULTS: The accuracy of the linear measurements was 0.35 +/- 1.31 mm (U70u) and 0.06 +/- 1.23 mm (U90u) for the Somatom VolumeZoom, 0.24 +/- 1.20 mm (H60s) and 0.54 +/- 1.14 mm (H30s) for the Sensation 16, and -0.09 +/- 1.64 mm for the Accuitomo 3D. Statistical analysis with 2-way analysis of variance showed no significant inter- or intraobserver disagreement for the physical or the radiologic measurements. There was also no significant difference for the measurements on the different reconstruction filters. CONCLUSION: Both CBCT and MSCT yield submillimeter accuracy for linear measurements on an ex vivo specimen.

Accuracy of implant placement based on pre-surgical planning of three-dimensional cone-beam images: a pilot study.

AIM: To evaluate the precision of transfer of a computer-based three-dimensional (3D) planning, using re-formatted cone-beam images, for oral implant placement in partially edentulous jaws. MATERIAL AND METHODS: Four formalin-fixed cadaver jaws were imaged in a 3D Accuitomo FPD cone-beam computed tomography (CT). Data were used to produce an accurate implant planning with a transfer to surgery by means of stereolithographic drill guides. Pre-operative cone-beam CT images were subsequently matched with post-operative ones to calculate the deviation between planned and installed implants. RESULTS: Placed implants (length: 10-15 mm) showed an average angular deviation of 2 degrees (SD: 0.8, range: 0.7-4.0 degrees ) as compared with the planning, while the mean linear deviation was 1.1 mm (SD: 0.7 mm, range 0.3-2.3 mm) at the hex and 2.0 mm (SD: 0.7 mm, range 0.7-2.4 mm) at the tip. CONCLUSIONS: Cone-beam images could be used for implant planning, taking into account a maximal 4 degrees angular and 2.4 mm linear deviation at the apical tip.