Timo Kero

Accuracy of CAD/CAM-guided surgical template implant surgery on human cadavers: Part I

STATEMENT OF PROBLEM An optimal method for approaching the clinical surgical situation, when using preoperatively, virtually planned implant positioning, is to transfer data to a CAD/CAM-guided surgical template with the definitive position of the implant placed after surgery. The accuracy of CAD/CAM-guided surgeries must be determined to provide safe treatment. PURPOSE The purpose of this study was to compare the deviation between the position of virtually planned implants and the position of implants placed with a CAD/CAM-guided surgical template in the mandible and the maxilla in human cadavers. MATERIAL AND METHODS Ten maxillae and 7 mandibles, from completely edentulous cadavers, were scanned with CT, and 145 implants (Brånemark RP Groovy) were planned with software and placed with the aid of a CAD/CAM-guided surgical template. The preoperative CT scan was matched with the postoperative CT scan using voxel-based registration. The positions of the virtually planned implants were compared with the actual positions of the implants. Data were analyzed with a t test (alpha=.05). RESULTS The mean measurement differences between the computer-planned implants and implants placed after surgery for all implants placed were 1.25 mm (95% CI: 1.13-1.36) for the apex, 1.06 mm (95% CI: 0.97-1.16) for the hex, 0.28 mm (95% CI: 0.18-0.38) for the depth deviation, 2.64 degrees (95% CI: 2.41-2.87) for the angular deviation, and 0.71 mm (95% CI: 0.61-0.81 mm) for the translation deviation. CONCLUSIONS The results demonstrated a statistically significant difference between mandibles and maxillae for the hex, apex, and depth measurements in the variation between the virtually planned implant positions and the positions of the implants placed after surgery with a CAD/CAM-guided surgical template.

Accuracy of Virtually Planned and CAD/CAM-guided Implant Surgery on Plastic Models

STATEMENT OF PROBLEM Studies of guided implant surgery have identified various methods that could influence accuracy. The present investigation was designed to limit the factors contributing to accuracy and to compare the results for 5 different surgeons. PURPOSE The purpose of this study was to evaluate any deviation between virtually planned and actually placed implants by 5 surgeons performing computer-aided design/computer-aided manufacturing (CAD/CAM)-guided implant surgery on duplicate plastic models. MATERIAL AND METHODS Five surgeons participated in the study, and each received 5 plastic maxillary jaw models. Thus, 25 models were used for implant placement with CAD/CAM-fabricated surgical templates. Each model contained 6 implants; therefore, a total of 150 implants were placed. The virtually planned and actually placed implant positions were compared for the apex, hexagon, depth, and angle with 2 computed tomography scans that were matched with voxel-based registration software. In addition, any differences in the 4 parameters among the surgeons were statistically tested. The data were analyzed with the t test, ANOVA, and Scheffé test (α=.05). RESULTS A statistically significant difference between the virtually planned and actually placed implant positions was observed for 3 of the 4 outcome variables (the apex, hexagon, and depth; P<.05). A statistically significant difference was also noted among all surgeons regarding the positions of the apex, depth, and angle. CONCLUSIONS The results of this study provide a better understanding of the differences in accuracy between surgeons when using a CAD/CAM surgical technique. There was a significant difference between the virtually planned and actually placed implant positions and between the surgeons for some of the variable parameters analyzed. The null hypothesis was thus rejected.

Virtual variation simulation of CAD/CAM template-guided surgeries performed on human cadavers: Part II.

STATEMENT OF PROBLEM CAD/CAM template-guided surgery has gained attention as a method of improving the predictability of dental implant placement. However, due to possible variations during the manufacturing process and in the robustness of the template design, a virtual prediction of the potential positioning of the implants is needed. PURPOSE The purpose of this study was to perform virtual variation simulations on virtually planned implant placements and to compare them with corresponding results from actual surgeries performed on human cadavers in a previous study. MATERIAL AND METHODS Seventeen computer-aided plans were used for virtual variation simulation of surgeries conducted on 17 human cadavers and 145 implants placed in the cadavers. For each surgery, 10,000 virtual surgeries were performed, resulting in 1,450,000 implant placements. The results from the virtual variation simulations were statistically compared with the results from the actual surgeries. The Mann-Whitney U test was used to compare the implant distributions (alpha=.05). RESULTS In the maxillae, the difference between the simulated average mean of the mean and the compared surgical average of the median was 0.22 mm (apex) and -0.35 mm (hex), and for the mandible, the corresponding values were -0.19 mm (apex) and -0.69 mm (hex). The simulated average mean of the range compared to the mean range of the maximum deviation results from the surgeries of the maxillae was 2.96 mm (apex) and 0.44 mm (hex), and 2.3 mm (apex) and 0.26 mm (hex) for the mandible. The implant distributions between the simulations and the surgeries were significantly different at both the hex (P<.001) and apex (P<.001). CONCLUSIONS The implant distributions were neither static nor normally distributed. Thus, within the limitations of this study, the definitive geometrical variations of the implants were not static, as they depend on the individual anatomy of the jaws and the ability to place the CAD/CAM-guided surgical template in the proper position.

Appearance FMEA: A Method for Appearance Quality Evaluation of Early Design Concepts

For consumer products, early design stages are often concerned with the product’s industrial design, with primary focus on the consumer’s product experience. At this stage, aspects such as manufacturability and robustness are often not thoroughly taken into account. Industrial design concepts not properly suited for manufacture, assembly and process variability can result in final products in which the appearance intent is not satisfactorily realized. This can have a negative impact on the customer’s product quality perception. If such problems are discovered late in the product development process, late design changes and increased project costs may follow. The main difficulty in evaluating perceived quality aspects during industrial design is that the product is still under development. It is not mature enough to enable prediction of the prerequisites for achieving high manufacturing quality. In this paper, we suggest that concepts instead could be evaluated as far as the intrinsic tendency of the product appearance to support manufacturing variation and other noise factors. This is addressed through the concept of visual robustness: the ability of a product’s visual appearance to stimulate the same product experience despite variety in its visual design properties. Here, a method is suggested based on the Failure Modes and Effects Analysis (FMEA). The method follows a structured procedure for addressing appearance issues.Copyright

Introducing digital pulse as a deviation management methodology for dental product development and production

Pulse methodology is a lean deviation management methodology that helps to visualise the deviations using visualisation artefacts (e.g., white boards and TVs) and frequent meetings for internal synchronisations within a company. The purpose of this study is to fill the gap within the lean literature about teaching and introducing pulse methodology. It presents a case study where digital pulse methodology was introduced to a customer-order-driven product development and production company within the dental device industry to help the company efficiently manage the deviations arising from daily operations so that it becomes more lean by visualising important data and capturing and reusing knowledge. The presented case study and the conclusions will be useful for researchers, companies, and consultants who want to try out pulse methodology or understand the implementation process.