Markerlose Registrierung der Patientenlage

Assessment of the Accuracy of Two Different Dynamic Navigation System Registration Methods for Dental Implant Placement in the Posterior Area: An In Vitro Study

Purpose: To compare the U-tube and cusp dynamic navigation system registration methods in the use of dental implant placement, and to assess the influence of the location of missing teeth on these registrations. Methods: 32 resin mandible models and 64 implants were utilized, with implants being placed using one of the two registration methods selected at random. Accuracy was measured through the superimposition of the final and planned implant positions. Angular deviation, 3D entry deviation, and 3D apex deviation were analyzed. Results: The overall mean 3D deviation was 1.089 ± 0.515 mm at the entry point and 1.174 ± 0.531 mm at the apex point, and mean angular deviation was 1.970 ± 1.042 degrees. No significant difference (p > 0.05) was observed when comparing these two registration methods. However, the U-tube method showed significant difference when assessing the location of missing teeth (without distal-extension absence and distal-extension absence), whereas cusp registration was unaffected. Conclusions: Both the U-tube and cusp dynamic navigation system registration methods are accurate when implemented in vitro. Besides, the cusp registration technique can also overcome several of the limitations of the U-tube approach and the accuracy of it was not influenced by the location of the missing teeth, highlighting it as a method worthy of further clinical research.

Comparison of the accuracy of two different dynamic navigation system registration methods for dental implant placement: A retrospective study

BACKGROUND

Dynamic navigation approaches are widely employed in the context of implant placement surgery, with registration being integral to the accuracy of such navigation. Relatively few studies to date, however, have compared different registration approaches, and such a comparison has the potential to guide the development of more accurate and reliable clinical registration methodology.

PURPOSE

This study was developed to compare the accuracy of dynamic navigation-based dental implant placement conducted using either U-tube or cusp registration methods.

MATERIALS AND METHODS

Medical records from all patients that had undergone implant surgery between August 2019 and October 2020 in the First Clinical Division of the Peking University Hospital of Stomatology were retrospectively reviewed, with 64 patients and 99 implants ultimately meeting with study inclusion criteria. Implant placement accuracy was gauged via the superimposition of the planned implant position in preoperative cone-beam computed tomography (CBCT) images with the true postoperative implant position in postoperative CBCT images. Accuracy was measured based upon the angular deviation, entry deviation (3-dimensional [3D] deviation in the coronal aspect of the alveolar ridge), and apex deviation (3D deviation in the apical area of the implant) when comparing these two positions.

RESULTS

The angular deviation, entry deviation, and apex deviation of all analyzed implants were 3.29 ± 0.17°, 1.29 ± 0.07 mm, and 1.43 ± 0.08 mm, respectively, while in the cusp registration group these respective values were 3.25 ± 1.58°, 1.28 ± 0.60 mm, and 1.34 ± 0.63 mm as compared to 3.35 ± 1.78°, 1.30 ± 0.78 mm, 1.55 ± 0.9 mm in the U-tube group, respectively. No significant differences in accuracy were observed when comparing these two registration techniques.

CONCLUSION

Dynamic computer-assisted surgical systems can facilitate accurate implantation, and both the U-tube and cusp registration methods exhibit similar levels of accuracy. As the cusp registration technique can overcome some of the limitations of the U-tube strategy without the need for an additional registration device, it may be more convenient for clinical use and warrants further research.

Does Head Orientation Influence 3D Facial Imaging? A Study on Accuracy and Precision of Stereophotogrammetric Acquisition

This study investigates the reliability and precision of anthropometric measurements collected from 3D images and acquired under different conditions of head rotation. Various sources of error were examined, and the equivalence between craniofacial data generated from alternative head positions was assessed. 3D captures of a mannequin head were obtained with a stereophotogrammetric system (Face Shape 3D MaxiLine). Image acquisition was performed with no rotations and with various pitch, roll, and yaw angulations. On 3D images, 14 linear distances were measured. Various indices were used to quantify error magnitude, among them the acquisition error, the mean and the maximum intra- and inter-operator measurement error, repeatability and reproducibility error, the standard deviation, and the standard error of errors. Two one-sided tests (TOST) were performed to assess the equivalence between measurements recorded in different head angulations. The maximum intra-operator error was very low (0.336 mm), closely followed by the acquisition error (0.496 mm). The maximum inter-operator error was 0.532 mm, and the highest degree of error was found in reproducibility (0.890 mm). Anthropometric measurements from alternative acquisition conditions resulted in significantly equivalent TOST, with the exception of Zygion (l)–Tragion (l) and Cheek (l)–Tragion (l) distances measured with pitch angulation compared to no rotation position. Face Shape 3D Maxiline has sufficient accuracy for orthodontic and surgical use. Precision was not altered by head orientation, making the acquisition simpler and not constrained to a critical precision as in 2D photographs.

Validity of the 3D VECTRA photogrammetric surface imaging system for cranio-maxillofacial anthropometric measurements

PURPOSE

The use of three-dimensional (3D) photography for anthropometric measurements is of increasing interest, especially in the cranio-maxillofacial field. Before standard implementation, accurate determination of the precision and accuracy of each system is mandatory.

METHODS

A mannequin head was labelled with 52 landmarks, and 28 three-dimensional images were taken using a commercially available five-pod 3D photosystem (3D VECTRA; Canfield, Fairfield, NJ) in different head positions. Distances between the landmarks were measured manually using a conventional calliper and compared with the digitally calculated distances acquired from labelling by two independent observers. The experimental set-up accounted for clinical circumstances by varying the positioning (vertical, horizontal, sagittal) of the phantom.

RESULTS

In the entire calliper measurement data set (n = 410), a significant difference (p = 0.02) between the directly measured and corresponding virtually calculated distances was found. The mean aberration between both modalities covering all data was 7.96 mm. No differences (p = 0.94) between the two groups were found using a cut-off of 10 % (leaving n = 369 distances) due to considerable errors in direct measurements and the necessary manual data translation. The mean diversity of both measurement modalities after cut-off was 1.33 mm (maximum, 6.70 mm). Inter-observer analysis of all 1,326 distances showed no difference (p = 0.99; maximal difference, 0.58 mm) in the digital measurements.

CONCLUSION

The precision and accuracy of this five-pod 3D photosystem suggests its suitability for clinical applications, particularly anthropometric studies. Three-hundred-and-sixty degree surface-contour mapping of the craniofacial region within milliseconds is particularly useful in paediatric patients. Proper patient positioning is essential for high-quality imaging.

The influence of various registration procedures upon surgical accuracy during navigated controlled petrous bone surgery

OBJECTIVE

The goal of this study was to investigate the dependence of surgical accuracy with a navigated controlled (NC) drill on selected registration procedures.

STUDY DESIGN

The target registration error of the instrument and the maximum proximity to a typical high-risk structure (facial nerve) were determined within an artificial petrous bone.

SETTING

The studies took place in two groups: group 1, navigation bow with six integrated markers and attachment at the upper jaw, and group 2, landmark registration with four titanium microscrews. Measurement of the target registration error took place at three targets (3 titanium screws) with 20 repeated registration procedures via evaluation of the deviation between a target and the indicated position in the navigation data.

SUBJECTS AND METHODS

For measurement of the conversion accuracy of the planned cavity, 20 petrous bone models were milled by inexperienced test subjects. The evaluation of 20 cavities was conducted via a microscope by five jurors.

RESULTS

Registration accuracy showed a maximum deviation between the actual position achieved and the computed position in the navigation system of 1.73 mm in group 1 and 0.93 mm in group 2. In group 1, the nerve in five of 20 cases was damaged, and a maximum penetration into the nerve of 1.5 mm (0.25 mm SD; milled beyond) was measured. In group 2, the facial nerve was not damaged at all, and a maximum deviation of 0.5 mm (0.63 mm SD; stopped before) was measured.

CONCLUSION

The results for registration and conversion accuracy are significantly better for the landmark-based registration than with the registration of the patient model with registration bow on the upper jaw.

[New developments in computer-assisted surgery (CAS). From intraoperative imaging to ultrasound-based navigation]

Ever faster processor capacity is having an impact on computer-assisted or computer-aided surgery (CAS). The fusion of different imaging modalities enables functional data such as PET-CT, for example, to be available in image-guided surgery. Referencing of image data is the key to precise navigation. Intraoperative data acquisition is a new approach to improving accuracy. Thus, intraoperative CT conducted under navigational support enables automatic referencing of up-to-date image data. Alternatively, intraoperative magnetic resonance imaging or intraoperative sonography can be performed. Ultrasound systems have already been successfully integrated in existing navigational systems to compensate for intraoperative tissue shifting. Ultrasound systems may play a role in the future as a single modality in image-guided surgery in soft tissue of the neck and skull bone.

Comparison of different registration methods for surgical navigation in cranio-maxillofacial surgery

BACKGROUND

Surgical navigation requires registration of the pre-operative image dataset with the patient in the operation theatre. Various marker and marker-free registration techniques are available, each bearing an individual level of precision and clinical practicability. In this study the precision of four different registration methods in a maxillofacial surgical setting is analyzed.

MATERIALS AND METHODS

A synthetic full size human skull model was registered with its computer tomography-dataset using (a) a dentally mounted occlusal splint, (b) the laser surface scanning, (c) five facial bone implants and (d) a combination of dental splint and two orbital bone implants. The target registration error was computed for 170 landmarks spread over the entire viscero- and neurocranium in 10 repeats using the VectorVision2 (BrainLAB AG, Heimstetten, Germany) navigation system. Statistical and graphical analyses were performed by anatomical region.

RESULTS

An average precision of 1mm was found for the periorbital region irrespective of registration method (range 0.6-1.1mm). Beyond the mid-face, precision linearly decreases with the distance from the reference markers. The combination of splint with two orbital bone markers significantly improved precision from 1.3 to 0.8mm (p<0.001) on the viscerocranium and 2.3-1.2mm (p<0.001) on the neurocranium.

CONCLUSIONS

An occlusal splint alone yields poor precision for navigation beyond the mid-face. The precision can be increased by combining an occlusal splint with just two bone implants inserted percutaneously on the lateral orbital rim of each side.