[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.

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.

[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.

Effect of skin tone on the accuracy of hybrid and passive stereophotogrammetry.

BACKGROUND: Three-dimensional (3D) surface images acquired from stereophotogrammetry are increasingly being used to plan or evaluate treatment by plastic surgeons. Stereophotogrammetry exists in active, passive, and hybrid forms. Active and hybrid stereophotogrammetry are believed to capture darker surfaces more accurately than passive stereophotogrammetry. The purpose of this study was to investigate whether skin tone has a clinically relevant effect on the accuracy of hybrid and passive stereophotogrammetry. MATERIALS AND METHODS: Seven subjects with different skin tones were recruited. 3D-printed face and breast were spray-painted in six different colors, ranging from white to black. The skin tones and paint colors were objectified by measuring their melanin index. 3D photos of the subjects and 3D prints were acquired with hybrid and passive stereophotogrammetry. These 3D photos were matched with specialized software, and their geometric differences were calculated. RESULTS: None of the 3D photos showed a clinically relevant mean inaccuracy. On the 3D prints, hybrid stereophotogrammetry resulted in a smaller standard deviation of the inaccuracies than passive stereophotogrammetry (0.20 ± 0.06 mm vs. 0.35 ± 0.07 mm, p < 0.001). Passive stereophotogrammetry yielded a correlation between the melanin index of the spray paint colors and the standard deviation of the inaccuracy (Pearson's R = 0.60, p = 0.04). On human subjects, no correlation or difference in standard deviation of the accuracy was found. CONCLUSION: Skin tone does not influence the accuracy of hybrid and passive 3D stereophotogrammetry in a clinically relevant way.

New software and breast boundary landmarks to calculate breast volumes from 3D surface images.

BACKGROUND: A method to accurately calculate breast volumes helps achieving a better breast surgery outcome. 3D surface imaging potentially allows these calculations in a harmless, quick, and practicable way. The calculated volume from a 3D surface image is dependent on the determined breast boundary and the method of chest wall simulation by software. Currently, there is no consensus on a robust set of breast boundary landmarks and validation studies on breast volume calculation software are scarce. The purposes of this study were to determine the robustness of newly introduced breast boundary landmarks and introduce and validate a new method to simulate a chest wall. METHODS: Sixteen subjects who underwent a unilateral simple mastectomy were included. In addition to the natural skin fold of the breast, the sternomanubrial joint, the transition of the pectoral muscle curve into the breast curvature, and the midaxillary line were used as landmarks to indicate the breast boundary. The intra- and interrater variability of these landmarks was tested. Furthermore, new chest wall simulation software was validated on the breastless chest side of the subjects. RESULTS: The intra- and interrater variability of the three breast boundary markers was small (mean 3.5-6.7 mm), and no significant difference was found between the intra- and interrater variability (p = 0.08, p = 0.06, and p = 0.10). The mean volume error of the most accurately simulated chest wall was 4.6 ± 37 ml. CONCLUSION: The newly introduced landmarks showed to be robust and our new chest wall simulation algorithm showed accurate results.Level of Evidence: Level IV, diagnostic study.

Accuracy and reproducibility of a newly developed tool for volume measurements of the arm using 3D stereophotogrammetry.

BACKGROUND: Lymph edema of the arm is a common complication after breast cancer treatment. To evaluate lymph edema volume and treatment outcome, an easy to use, objective quantification method of arm volume is necessary. Most often, water displacement is used to measure arm volume, as it is an easy and robust method that can be performed at any place with a simple equipment. However, when using water displacement, no exact localization of volume difference can be seen. To accurately measure hand and forearm volumes separately, an in-house-developed device was constructed for an accurate landmark placement. METHOD: An in-house developed measurement tool was used for placing artificial landmarks proximal to the wrist crease on ten healthy subjects. Three-dimensional (3D) images of the hand and forearm were acquired, and volume measurements of the hand and forearm were performed. Measurements were repeated to investigate the intra- and inter-rater variability caused by the landmark placement. RESULTS: Measuring volume of the hand and forearm while using artificially placed landmarks turned out to be a highly reproducible, quick, and easy procedure. Both intra- and inter-rater variability showed high reproducibility for hand (ICC = 0.96 and 0.98, respectively) and forearm (ICC = 0.99 and 0.99, respectively) volumes. CONCLUSION: Measuring volumes of the hand and forearm while using artificially placed landmarks was found to be a highly reproducible, quick, and easy procedure. The device enables to analyze the localization of lymph edema in greater details.

Intracavernous injection during diagnostic screening for erectile dysfunction; five-year experience with over 600 patients.

Psychophysiological diagnostic screening (PDS) was carried out on just over 1000 consecutive patients with erectile dysfunction (ED) during 1995 through 1999. Roughly one-third did not require an intracavernous injection (ICI) because of optimal penile response during visual and tactile penile sexual stimulation. The present article deals with those other patients (n = 609) who required an ICI and completed a 24-hour-postinvestigation questionnaire (PIQ). The two ICI preparations used, prostaglandin and papaverine + fentolamine, were virtually equally effective in the doses applied, with very low and similar percentages of unwanted side effects, for example, prolonged erection. Somatic ED patients displayed the lowest penile responses to ICI, whereas psychogenic ED patients had the highest penile responses. ED patients who also suffered from premature ejaculation (PE) ejaculated significantly more readily during PDS that those without PE. An ICI following an ejaculation/orgasm could lead to an erection presumably sufficient for intromission, which indicates ICI as a therapeutic option for rapid ejaculators. Our elaborate and lengthy PDS procedure, particularly the use of penile vibration as an addition to the visual sexual stimulation, obviates the diagnostic use of the PIQ.

Isolation technique for lymphocytes from bovine lymph glands.

A method is described for obtaining large quantities (grams) of lymphocytes from bovine retropharyngeal lymph glands, whereby contaminating erythrocytes are lysed and coagulation is prevented by the use of acetic acid (0.0143 mol 1(-1). On average 4.38 g (S. D. 1.83, n = 100) lymphocytes, including lymphoblasts, are obtained per lymph gland, with a purity level of about 99%.