[Innovative methods and developments in oral care. 3D planning in oral and maxillofacial surgery]. / Serie: Innovatieve technieken en ontwikkelingen in de mondzorg. 3D-planning in de mka-chirurgie.

With the use of cone beam computed tomography, intraoral scanning and 3D stereophotogrammetry, a virtual 3D head model of a patient can be reconstructed with image fusion. In this way, the malposition, deficiency and other anomalies at the level of bone, dentition and soft tissue can be quantified objectively. The desired position of the dentition, occlusion and soft tissue in the facial profile can be virtually drawn in and used as a guideline for treatment planning. Based on the principle of backward planning, it is possible to determine what repositioning of the jaw is required, where there is a need for bone augmentation and how many dental implants are necessary to obtain the desired treatment outcome. From this perspective, 3D treatment planning has become a treatment standard for the 4 clinical pillars supporting oral and maxillofacial surgery, specifically orthognathic surgery, implantology, craniofacial surgery and head & neck oncology. 3D planning has influenced today's workflow, planning of complex surgery and contributed to useful further innovations and efficient healthcare.

[The 3D-printed surgical guides used during genioplasty]. / De 3D-geprinte zaag- en repositiemal voor een kinplastiek.

Genioplasty is a seemingly simple procedure performed to correct the bony chin. The results of the procedure are, however, strongly correlated with the experience of the surgeon. 3D-printed surgical guides could act as a transfer modality to translate the preoperative planning directly into the achieved result. Prospective studies evaluating the usefulness of the 3D-printed surgical guides have not yet been carried out and consensus regarding the best design is lacking. In order to become more familiar with working with surgical guides, a genioplasty using 3D-printed surgical guides was performed. The postoperative analysis of the achieved result showed minor differences compared to preoperative planning. Surgical guides have the potential to improve the accuracy and predictability of genioplasty. The design should be further refined and the added value of the guides should be confirmed by means of prospective research.

Soft tissue-based registration of intraoral scan with cone beam computed tomography scan.

The aim of this study was to evaluate a novel soft tissue-based method to register an intraoral scan (IOS) with a cone beam computed tomography (CBCT) scan. IOS and CBCT data were obtained from eight dentate patients (mean age 21±2 years; three male, five female) and 14 fully edentulous patients (mean age 56±9 years; eight male, six female). An algorithm was developed to create a soft tissue model of the CBCT scan, which allowed a soft tissue-based registration to be performed with the IOS. First, validation was performed on dentate jaws with registration of the palatal mucosal surface and accuracy evaluation at the level of the teeth. Second, fully edentulous jaws were registered using both the palatal and alveolar crest mucosal surfaces. Distance maps were created to measure the method accuracy. The mean registration error was 0.49±0.26mm for the dentate jaws. Registration of the fully edentulous jaws had a mean error of 0.16±0.08mm at the palate and 0.16±0.05mm at the alveolar crest. In conclusion, the high accuracy of this registration method may allow the digital workflow to be optimized when no teeth are available to perform a regular registration procedure.

Surgical accuracy in 3D planned bimaxillary osteotomies: intraoral scans and plaster casts as digital dentition models.

The aim of this study was to assess whether the use of intraoral scans (IOS) is an eligible alternative to conventional plaster casts in terms of surgical accuracy of three-dimensionally planned bimaxillary osteotomies. This retrospective cohort study included patients who underwent bimaxillary surgery between 2016 and 2020 in the Department of Oral and Maxillofacial Surgery at Radboud University Medical Center, Nijmegen. Three-dimensional virtual planning was performed with the use of plaster casts in one group and IOS in the other group. Cone beam computed tomography scans were acquired preoperatively and at 1 week following surgery. By using voxel-based matching, the maxillary movements were quantified in six degrees of freedom. The primary outcome variable, surgical accuracy, was defined as the difference between the planned maxillary movements and those achieved. Of 152 patients, 113 were documented with plaster casts and 39 with IOS. The surgical accuracy was comparable in terms of maxillary vertical, sagittal, and transverse translations, as well as roll and yaw. Maxillary pitch (difference 0.55 ± 0.26°; P = 0.001) was in favour of the IOS group. This study demonstrated that IOS can be used as an alternative to conventional plaster casts in the three-dimensional planning of bimaxillary osteotomies.

Registration-free workflow for electromagnetic and optical navigation in orbital and craniofacial surgery.

The accuracy of intra-operative navigation is largely dependent on the intra-operative registration procedure. Next to accuracy, important factors to consider for the registration procedure are invasiveness, time consumption, logistical demands, user-dependency, compatibility and radiation exposure. In this study, a workflow is presented that eliminates the need for a registration procedure altogether: registration-free navigation. In the workflow, the maxillary dental model is fused to the pre-operative imaging data using commercially available virtual planning software. A virtual Dynamic Reference Frame on a splint is designed on the patient's fused maxillary dentition: during surgery, the splint containing the reference frame is positioned on the patient's dentition. This alleviates the need for any registration procedure, since the position of the reference frame is known from the design. The accuracy of the workflow was evaluated in a cadaver set-up, and compared to bone-anchored fiducial, virtual splint and surface-based registration. The results showed that accuracy of the workflow was greatly dependent on tracking technique used: the workflow was the most accurate with electromagnetic tracking, but the least accurate with optical tracking. Although this method offers a time-efficient, non-invasive, radiation-free automatic alternative for registration, clinical implementation is hampered by the unexplained differences in accuracy between tracking techniques.

Virtual splint registration for electromagnetic and optical navigation in orbital and craniofacial surgery.

In intra-operative navigation, a registration procedure is performed to register the patient's position to the pre-operative imaging data. The registration process is the main factor that determines accuracy of the navigation feedback. In this study, a novel registration protocol for craniofacial surgery is presented, that utilizes a virtual splint with marker points. The accuracy of the proposed method was evaluated by two observers in five human cadaver heads, for optical and electromagnetic navigation, and compared to maxillary bone-anchored fiducial registration (optical and electromagnetic) and surface-based registration (electromagnetic). The results showed minimal differences in accuracy compared to bone-anchored fiducials at the level of the infra-orbital rim. Both point-based techniques had lower error estimates at the infraorbital rim than surface-based registration, but surface-based registration had the lowest loss of accuracy over target distance. An advantage over existing point-based registration methods (bone-anchored fiducials, existing splint techniques) is that radiological imaging does not need to be repeated, since the need for physical fiducials to be present in the image volume is eradicated. Other advantages include reduction of invasiveness compared to bone-achnored fiducials and a possible reduction of human error in the registration process.

Fusion of intra-oral scans in cone-beam computed tomography scans.

PURPOSE: The purpose of this study was to evaluate the clinical accuracy of the fusion of intra-oral scans in cone-beam computed tomography (CBCT) scans using two commercially available software packages. MATERIALS AND METHODS: Ten dry human skulls were subjected to structured light scanning, CBCT scanning, and intra-oral scanning. Two commercially available software packages were used to perform fusion of the intra-oral scans in the CBCT scan to create an accurate virtual head model: IPS CaseDesigner® and OrthoAnalyzer™. The structured light scanner was used as a gold standard and was superimposed on the virtual head models, created by IPS CaseDesigner® and OrthoAnalyzer™, using an Iterative Closest Point algorithm. Differences between the positions of the intra-oral scans obtained with the software packages were recorded and expressed in six degrees of freedom as well as the inter- and intra-observer intra-class correlation coefficient. RESULTS: The tested software packages, IPS CaseDesigner® and OrthoAnalyzer™, showed a high level of accuracy compared to the gold standard. The accuracy was calculated for all six degrees of freedom. It was noticeable that the accuracy in the cranial/caudal direction was the lowest for IPS CaseDesigner® and OrthoAnalyzer™ in both the maxilla and mandible. The inter- and intra-observer intra-class correlation coefficient showed a high level of agreement between the observers. CLINICAL RELEVANCE: IPS CaseDesigner® and OrthoAnalyzer™ are reliable software packages providing an accurate fusion of the intra-oral scan in the CBCT. Both software packages can be used as an accurate fusion tool of the intra-oral scan in the CBCT which provides an accurate basis for 3D virtual planning.

Virtual occlusion in orthognathic surgery.

The aim of this retrospective study was to determine whether a virtually created occlusion is as accurate as a conventionally created occlusion. Seventeen orthognathic patients were included in the study, which was conducted in a university clinic. Plaster cast models were obtained and digitized. Two experienced observers created the conventional (gold standard) and virtual occlusion to assess inter-observer variability. One observer created the conventional and virtual occlusion a second time to assess the intra-observer variability. The criterion for accepting the virtual occlusion was that the difference between the gold standard and the virtual occlusion was not larger than the intra-observer variability for the gold standard. A non-parametric Kruskal-Wallis H test was performed to detect statistically significant differences between the intra- and inter-observer groups for both the conventional and virtual occlusion. No statistically significant differences were found between the different groups. The difference between the conventional and virtual occlusion group was 0.20mm larger than the intra-observer variability of the gold standard. The virtual occlusion tool presented here can be utilized in daily clinical practice and makes the use of physical dental models redundant.

Digital surface scanning in flap perfusion.

Monitoring vascular perfusion of transferred tissue is essential in reconstructive surgery to recognize early flap failure. The aim of this study was to evaluate the ability of a digital surface scanner to detect vascular perfusion disorders through the monitoring of skin colour changes. A total of 160 surface scans of the forearm skin were performed with a TRIOS 3D scanner. Vascular compromise was simulated at different time-points by intermittent occlusion of the blood supply to the forearm skin (first the arterial blood supply and then the venous blood supply). Skin colour changes were examined according to the hue, saturation, and value colour scale. Colour differences were analysed with a paired t-test. Significant differences were observed between the colour of the normal skin and that of the vascular compromised skin (P<0.01). The surface scanner could distinguish between arterial occlusion and venous congestion (P<0.01). A digital surface scan is an objective, non-invasive tool to detect early vascular perfusion disorders of the skin.

Symmetry of palatal shape during the first year of life in healthy infants.

OBJECTIVES: The purpose of this study was to quantify the symmetry of the alveolar process of the maxilla and palate during the first year of life in healthy infants with the help of a semiautomatic segmentation technique. MATERIALS AND METHODS: Maxillary plaster models of seventy healthy babies at 0, 3, 6, 9, and 12 months were collected and digitized. A semiautomatic segmentation tool was used to extract the alveolus and palate. The resulting model was aligned within a reference frame and mirrored on its medial plane. Distance maps were created and analyzed to compare and quantify the differences between the two hemispheres. Additional hemispherical width and area measurements were performed. An ANOVA test with additional post hoc tests was performed to check if the symmetry changed during development. Finally, the results were tested on intra- and interobserver variability. RESULTS: The absolute mean inter-surface distance between the original and mirrored models in each age group ranged between 0.23 and 0.30 mm. Width and area analysis showed a small but significant larger left palatal hemisphere. ANOVA and post hoc tests showed no significant difference in symmetry between groups. Reliability analysis showed no significant differences between observers. CONCLUSIONS: This study showed that in this infant population, only a small degree of palatal asymmetry was present, which can be considered as normal and clinically irrelevant. CLINICAL RELEVANCE: The data from this study can be used in future comparative studies as reference data. Furthermore, modeling of these data can help in predicting the growth pattern, which may lead to improved treatment protocols for children with craniofacial anomalies.

[Innovations in dentistry. The influence of build angle on the fit of a 3D printed occlusal splint]. / Serie: Innovaties in de tandheelkunde. Het effect van printoriëntatie op de pasvorm van een 3D-geprinte occlusale wafer.

3D virtual planning optimises the predictability of orthognathic surgery. The planning is based on a cone beam computed tomography-scan of the patient as well as a plaster model, and is transferred to the patient by a 3D printed occlusal splint. In 3D printing the build angle influences, among other things, the accuracy (in earlier research, proven in dental crowns), manufacturing time and capacity. In this research, using 10 plaster models, 3 different build angles (0°, 30° and 90°) are compared. The fit of the splints was tested by 2 physicians using plaster models. According to this small sample, the fit does not depend on the build angle. When considering the manufacturing time and capacity, there is a preference for the 90º oriëntation, because it increases the manufacturing capacity and decreases the manufacturing time per splint.

Splintless surgery using patient-specific osteosynthesis in Le Fort I osteotomies: a randomized controlled multi-centre trial.

The accuracy of orthognathic surgery has improved with three-dimensional virtual planning. The translation of the planning to the surgical result is reported to vary by >2mm. The aim of this randomized controlled multi-centre trial was to determine whether the use of splintless patient-specific osteosynthesis can improve the accuracy of maxillary translation. Patients requiring a Le Fort I osteotomy were included in the trial. The intervention group was treated using patient-specific osteosynthesis and the control group with conventional osteosynthesis and splint-based positioning. Fifty-eight patients completed the study protocol, 27 in the patient-specific osteosynthesis group and 31 in the control group. The per protocol median anteroposterior deviation was found to be 1.05mm (interquartile range (IQR) 0.45-2.72mm) in the patient-specific osteosynthesis group and 1.74mm (IQR 1.02-3.02mm) in the control group. The cranial-caudal deviation was 0.87mm (IQR 0.49-1.44mm) and 0.98mm (IQR 0.28-2.10mm), respectively, whereas the left-right translation deviation was 0.46mm (IQR 0.19-0.96mm) in the patient-specific osteosynthesis group and 1.07mm (IQR 0.62-1.55mm) in the control group. The splintless patient-specific osteosynthesis method improves the accuracy of maxillary translations in orthognathic surgery and is clinically relevant for planned anteroposterior translations of more than 3.70mm.

Virtual setup in orthodontics: planning and evaluation.

OBJECTIVES: The purpose of this study was to evaluate the clinical accuracy of virtual orthodontic setups by using a new CBCT-based approach. MATERIALS AND METHODS: Ten patients who underwent pre-surgical orthodontics were included in this study. Pre-treatment and pre-surgical cone-beam CT (CBCT) scans and digital dental models were available. The pre-treatment digital dental model was used to create an orthodontic virtual setup. The digital dental models were fused with the corresponding CBCT scans, and the two CBCT scans were aligned using voxel-based matching. Moving each individual tooth from the virtual setup to the final outcome allows the calculation of the accuracy of the virtual setup by using an iterative closest point algorithm. Differences between virtual setup and final outcome were recorded as well as the ICC between two observers. RESULTS: The inter-observer variability showed a high level of agreement between the observers. The largest mean difference between observers was found in the cranial/caudal direction (0.36 ± 0.30 mm) and the roll rotation (1.54 ± 0.98°). Differences between the virtual setup and final outcome were small in the translational direction (0.45 ± 0.48 mm). Rotational mean differences were larger with the pitch of the incisors (0.00 ± 7.97°) and molars (0.01 ± 10.26°) as largest difference. Excessive extrusion of all upper teeth and more anterior movement than planned were seen for both upper and lower arch. Lower molars showed less extrusion. CLINICAL RELEVANCE: The data of this study can be used to obtain more insight in the accuracy and achievability of orthodontic virtual setup. Tooth movement can now be studied in more details which can lead to new insights.

Splintless orthognathic surgery in edentulous patients-a pilot study.

The aim of this pilot study was to evaluate the accuracy and predictability of a splintless treatment protocol for edentulous patients undergoing orthognathic surgery in four consecutive cases. All operations were virtually planned, followed by computer-aided design of individual osteotomy guides and patient-specific fixation implants, which were three-dimensionally printed in titanium. In order to evaluate the discrepancy between the planned and the achieved postoperative result, the postoperative outcome was compared to the virtual treatment plan. Rotational and translational movement and discrepancies with the planned movements were quantified for the maxilla; the advancement was quantified for the mandible. For the maxilla, there was a mean translation discrepancy of 0.6mm. With regard to rotation, there was a mean discrepancy of 1.9°, 0.1°, and 0.4° for pitch, yaw, and roll, respectively. The mean discrepancy in translation of the mandible was 0.4mm. The results of this pilot study indicate that the splintless treatment protocol for orthognathic surgery in edentulous patients presented here is accurate and predictable.

Three dimensional maxillary growth modeling in newborns.

OBJECTIVES: The aim of this study was to develop an accurate and intuitive semi-automatic segmentation technique to calculate an average maxillary arch and palatal growth profile for healthy newborns in their first year of life. MATERIALS AND METHODS: Seventy babies born between 1985 and 1988 were included in this study. Each child had five impressions made in the first year after birth that were digitalized. A semi-automatic segmentation tool was developed and used to assess the maxillary dimensions. Finally, random effect models were built to describe the growth and build a simulation population of 10,000 newborns. The segmentation was tested for inter- and intra-observer variability. RESULTS: The Pearson correlation coefficient for each of the variables was between 0.94 and 1.00, indicating high inter-observer agreement. The paired sample t test showed that, except for the tuberosity distance, there were small, but significant differences in the landmark placements between observers. Intra-observer repeatability was high, with Pearson correlation coefficients ranging from 0.87 to 1.00 for all measurements, and the mean differences were not significant. A third or second degree growth curve could be successfully made for each parameter. CONCLUSIONS: These findings indicated this method could be used for objective clinical evaluation of maxillary growth. CLINICAL RELEVANCE: The resulting growth models can be used for growth studies in healthy newborns and for growth and treatment outcome studies in children with cleft lip and palate or other craniofacial anomalies.

Added value of pharmacogenetic testing in predicting statin response: results from the REGRESS trial.

It was investigated whether pharmacogenetic factors, both as single polymorphism and as gene-gene interactions, have an added value over non-genetic factors in predicting statin response. Five common polymorphisms were selected in apolipoprotein E, angiotensin-converting enzyme, hepatic lipase and toll-like receptor 4. Linear regression models were built and compared on R(2) to estimate the added value of single polymorphisms and gene-gene interactions. The selected polymorphisms and the gene-gene interactions had a small added value in predicting change in low-density lipoprotein cholesterol levels (LDL-c) as response to statins over the non-genetic predictors (P=0.104), and also in predicting LDL-c in non-treated patients (P=0.016). Moreover, four gene-gene interactions with statin therapy were identified. The added value of genetic factors over non-genetic variables is for the greater part produced by gene-gene interactions. This underlines the importance to examine gene-gene interactions in future (pharmaco)genetic research.