Use of an ultrahigh-speed laser scanner for constructing three-dimensional shapes of dentition and occlusion

STATEMENT OF PROBLEM: Acquisition of the 3-dimensional shape of dental casts is useful for quantitative evaluation of the diagnosis and treatment of occlusion. PURPOSE: This study demonstrated the acquisition of data through the use of an ultrahigh-speed laser scanner and an originally developed goniometer, the use of these tools to measure the entire 3-dimensional shape of the dental cast from multiple directions, and the connection of the data measurements to reconstruct the cast's occlusion with the use of a computer. MATERIAL AND METHODS: A commercially available apparatus that emits a line laser and completes 1 scan in only 0.6 seconds was used. To compensate for the unmeasured region, the cast was measured from 4 directions on the original goniometer, and the connection of data to obtain the entire image was carried out. Further, the reconstruction of the occlusion between the upper and lower casts was attempted by transferring the upper cast data to the lower cast. RESULTS: By the data connection, the entire shape of the upper and lower casts was constructed, and the characteristic structure was reproduced. The data connections were satisfactory for the flat surfaces but less accurate for the inclined surfaces. Reconstruction of the occlusion between the upper and lower casts was accomplished. It was then possible to visualize the occlusion from arbitrary directions and sections with computer graphics. CONCLUSION: The construction of the entire 3-dimensional shape of a dental cast and the reconstruction of the occlusion were accomplished using an ultrahigh-speed measurement system and original goniometer. These results will be useful for clinical applications such as computerized diagnoses and treatment of occlusion, and for the replacement of the stone casts in the dental office by computerized data.     

牙颌模型三维激光扫描系统可靠性研究及与手工测量的比较

目的 对牙颌模型三维激光扫描系统的可靠性进行研究,并为其临床应用提供科学依据。方法 利用Ｄ．０１－Ｌ－３Ｄ ＳＣＡＮＮＥＲ系统扫描和测量了３０例基本正常石膏模型。采用三种方法检验了牙颌模型三维激光扫描系统的可靠性,并与手工测量进行了比较。结果 可靠性一个方法的结果显示无显著性差异;与手工测量的比较无显著性差异,但牙颌模型三维激光扫描系统具有一些手工测量所无法达到的功能。结论 牙颌模型三维激光扫描系     

Validation of a low-cost laser scanner device for the assessment of three-dimensional facial anatomy in living subjects

The present study compared the reliability of a low-cost laser scanner device to an already-validated stereophotogrammetric instrument. Fifty volunteers underwent duplicate facial scans through laser scanner and stereophotogrammetry. Intra- and inter-instrument reproducibility of linear distances, angles, facial surface area and volume was verified through the Bland–Altman test and calculation of absolute (TEM) and relative (rTEM) technical errors of measurement; rTEM was then classified as follows: <1% excellent; 1–3.9% very good; 4–6.9% good; 7–9.9% moderate; >10% poor. The scans performed through different devices were registered and superimposed to calculate the root mean square (RMS) (point-to-point) distance between the two surfaces. The same protocol was applied to a mannequin head. In inter-instruments comparison, 12/26 measurements showed a “good” rTEM; 5 were “very good”. In intra-instrument comparison, most performances worsened, with only 10 of 26 measurements classified as “good” and “very good”. All the measurements made on mannequin scans were at least “good”, and 14/26 were “very good”. Surface area was “very good” only in intra-instrument comparison; conversely, volumes were poorly repeatable for all the comparisons. On average, RMS point-to-point distances were 0.65 mm (inter-devices comparison), 0.56 mm (mannequin scans), 0.42 mm (intra-device comparison). In conclusion, the low-cost laser scan device can be reliably applied to inanimate objects, but does not meet the standards for three-dimensional facial acquisition on living persons.     

一种新型三维牙颌模型激光扫描仪可靠性对比研究

目的：检验新型三维牙颌模型激光扫描仪的可靠性。方法：分次利用不同方法，扫描和测量8副牙列石膏模型上的解剖标志点，对测量结果进行统计分析。结果：同一激光扫描两次定点的线距和角度的测量结果之间差异没有显著性；两次激光扫描分别定点测量的线距和角度结果之间差异也没有显著性；激光扫描定点测定和三维测量仪分别测得的线距和角度结果之间差异也没有统计学意义。结论：D.0.2-L-3D SCANNER激光扫描仪具有较高的精度，较好的可靠性，扫描速度快，扫描盲区少，该系统可以用于以后修复体CAD/CAM系统光学印模的制取。     

A digital approach to dynamic jaw tracking using a target tracking system and a structured-light three-dimensional scanner

Purpose

This technical procedure describes a method for tracking mandibular movement using a three-dimensional (3D) optical scanner and target tracking system to digitally portray the motion of the mandible and temporomandibular joints by merging cone beam computed tomography (CBCT) data.

Soft tissue changes after orthodontic surgical correction of jaws asymmetry evaluated by three-dimensional surface laser scanner

ABSTRACT: Aesthetic improvement is an essential goal of treatment of facial asymmetry, and it is often difficult to achieve. Reliable three-dimensional measurements are required to support outcome studies.In this study, 15 white adult subjects, 9 females and 6 males, with maxillomandibular asymmetry and malocclusion were studied. The patients were treated with orthodontics and different surgical procedures in single or multiple steps. All patients received double-jaw surgery, except 1 patient who underwent only maxillary osteotomy. Nine of the 15 patients received additional procedures (genioplasty and rhinoplasty) to achieve better symmetry. Posterior-anterior and lateral cephalometry and three-dimensional facial surface data were obtained before (T0) and 1 year (T1) after surgery. Scan data at T0 and T1 were pooled by electronic surface averaging to obtain the mean pretreatment and posttreatment facial model. A symmetric model was constructed by averaging the actual T0 scans and their mirrored models to obtain the virtual optimal symmetric face. Different linear and angular measurements were then calculated for comparison of the mean T0 and T1 models. The normalization of facial proportion and a high increase in symmetry were evident. Residual defects were documented in the postoperative symmetry of the chin. Treatment of facial asymmetry, combined with dental occlusion problems, is still a challenge for maxillofacial surgeons. Orthognathic surgery provides an important improvement of symmetry, but further refinements of technique are still required. Three-dimensional evaluation results in an effective method to support outcome studies on the surgical correction of complex facial deformities.     

Reliability and validity of measurements of facial swelling with a stereophotogrammetry optical three-dimensional scanner

Volume changes in facial morphology can be assessed using the 3dMD DSP400® stereo-optical 3-dimensional scanner, which uses visible light and has a short scanning time. Its reliability and validity have not to our knowledge been investigated for the assessment of facial swelling. Our aim therefore was to assess them for measuring changes in facial contour, in vivo and in vitro. Twenty-four healthy volunteers with and without an artificial swelling of the cheek were scanned, twice in the morning and twice in the afternoon (in vivo measurements). A mannequin head was scanned 4 times with and without various externally applied artificial swellings (in vitro measurements). The changes in facial contour caused by the artificial swelling were measured as the change in volume of the cheek (with and without artificial swelling in place) using 3dMD Vultus® software. In vivo and in vitro reliability expressed in intraclass correlations were 0.89 and 0.99, respectively. In vivo and in vitro repeatability coefficients were 5.9 and 1.3 ml, respectively. The scanner underestimated the volume by 1.2 ml (95% CI -0.9 to 3.4) in vivo and 0.2 ml (95% CI 0.02 to 0.4) in vitro.     

Crown angulation measured by laser scanner

The aim of this study was to measure the crown angulation of Japanese subjects with normal occlusion using a laser scanner to minimize human error. Twenty study models with normal occlusion were scanned by laser scanner. Crown angulations of each tooth in scanned 3D dental images were measured according to Andrews’ procedure. In Andrews’ procedure, a plane was established along the mesiodistal contact points of each tooth. The crown angulations of each tooth were measured by projecting the facial axis of the clinical crown (FACC) and a vertical line from the occlusal plane, and the mean and standard deviation were calculated. In maxillary teeth, the canine crown angulation was highest at about 7°, thus indicating a mesial tip, which was seen in all teeth except the second molar. In mandibular teeth, the second molar crown angulation was highest at about 7°, thus indicating a mesial tip, and only the lateral incisor exhibited slight distal tip, while all the remaining teeth exhibited mesial tip. Standard deviations for the maxillary and mandibular teeth ranged from 2.5° to 8°. The standard deviation of the maxillary and mandibular second molars was particularly large.     

Crown inclination measured by laser scanner

We developed the computer measurement procedure to measure crown inclination of three-dimensional (3D) dental images scanned by laser scanner to reduce human error.20 study models with normal occlusion were scanned by laser scanner. Crown inclinations of each tooth of scanned 3D dental images were measured according to Andrews’ method. Results: The mean value measured by our method and that measured by manual procedure in the same sample did not detect significant differences. In the variances of the measurements, the results of measurement by our method were larger than that by manual procedure for almost all teeth.Compared to other data, the results of our procedure tended to show large variances than that of other report with manual method. On the other hand, compared to non-manual procedure, the data and that of variances tended similar.Our procedure could objectively measure inclinations with less prejudice and or human error of examiner. This procedure would be useful in research and in the clinic.     

三维点激光扫描仪的扫描可靠性研究

目的全面评价Roland LPX-1200三维点激光扫描仪的扫描可靠性，为临床研究提供参考。方法规则加工的仿牙齿样模具，使用Roland LPX 1200点激光扫描仪获得其数字化模型，通过比较不同起始位置的扫描结果，评价扫描仪的扫描可重复性；选择长，宽，高三维方向上65项测量项目，比较数字化模型测量与实物测量之间的差异，评价其扫描准确性。结果连续扫描以及改变扫描初始位置引起的扫描随机误差在0．02mm以内；数字化模型测量与实物测量之间的差值均数为0．0012±0．05mm，P〈0．05。结论扫描仪具有良好的可靠性，能满足正畸临床对模型测量精度的要求。     

A novel three-dimensional analysis of standardized bone defects by means of confocal scanner and micro-computed tomography

Objectives

The aim of the study was to introduce a novel three-dimensional (3D) method to quantify the relative amount of different tissue components in bone substitute-treated defects by means of integration of confocal laser imaging into micro-computed tomography (μCT) analysis.

Materials and methods

One standardized semisaddle intraosseous defect was prepared in the mandibles of six minipigs and scanned by an optical scanner to capture the surface of the fresh defect in a 3D manner. Subsequently, all the defects were filled with a biphasic calcium phosphate material. The animals were divided into two groups of three animals each, which were allowed to heal for 3 and 8 weeks, respectively. μCT analysis followed the two healing periods and was performed on all defect locations. The data from optical scanning and μCT were used for three-dimensional evaluation of bone formation, nonmineralized tissue ratio, and graft degradation. The integration of confocal laser scanning into μCT analysis through a superimposition imaging procedure was conducted using the software Amira (Mercury Computer Systems, Chelmsford, MA, USA).

Results

The feasibility of combining the confocal imaging into μCT data with regard to obtaining accurate 3D quantification was demonstrated. The amount of tissue components was identified and quantified in all the investigated samples. Quantitative analysis demonstrated that a significant increase in the amount of bone filling the defect was observed in vivo (p?<?0.02) while a significant decrease in the amount of nonmineralized tissue occurred (p?<?0.04). No difference in the amount of residual grafting material was detected between 3 and 8 weeks in vivo (p?>?0.38).

Conclusions

The combination of confocal imaging and micro-computed tomography techniques allows for analysis of different tissue types over time in vivo. This method has revealed to be a feasible alternative to current bone regeneration quantification methods.

Clinical relevance

Assessment of bone formation in a large animal model is a key step in assessing the performance of new bone substitute materials. Reliable and accurate methods are needed for the analysis of the regenerative potential of new materials.     

Three-dimensional facial anatomy evaluation: Reliability of laser scanner consecutive scans procedure in comparison with stereophotogrammetry

Laser scanner devices are acquiring a growing importance in facial anatomy. Most studies have analysed facial scans obtained through two simultaneous captures, whereas the same result can be obtained by consecutive three-dimensional (3D) scans. However, this latter procedure has not yet been validated.Fourteen volunteers underwent face image capture through stereophotogrammetry (VECTRA M3) and three consecutive facial scans through a laser scanner (Konica Minolta Vi910). The concordance between 14 linear distances, 12 angles, facial surface area and volume measurements was verified by the Bland–Altman test and calculation of absolute and relative technical errors of measurement (TEM/rTEM). The two facial images obtained by the different devices were then registered to calculate point-to-point distance.Most of linear distances and angles showed a high agreement, with “very good” or “good” rTEMs, ranging between 1.1% and 6.4%. Surface area measurements agreed well between the devices (rTEM: 6.3%), while volumes were poorly comparable (rTEM: 25.8%); the root mean square point-to-point distance was 0.80 mm (SD: 0.41).This study first tested the concordance of measurements on facial images obtained by stereophotogrammetry and consecutive laser scans. Results highlight the reliability of linear distances, angles and surface areas measurements, but discourage volume assessment and registration of surfaces acquired through different devices.     

基于激光扫描的面部软组织三维模型准确性评估

目的 评估基于激光扫描所建立的面部软组织三维模型和软组织测量标志点的准确性.方法 在一受试者的面部进行标志点标记,直接测量各标记点间的距离,之后使用Minolta Vivid 9i三维激光扫描仪进行面部扫描合成三维图像后,应用软件测量标记点间距离,对比两种方法的差异.另选择10名成年女性,在激光扫描前预先标记左右耳屏中点为固定标志点,再选取面部其余测量标志点22个.直接测量耳屏点与测量标志点间的距离,之后测量三维成像后耳屏点与测量标志点间距离,对比两者的差异.所有数据进行配对t检验.结果 基于激光扫描所建立的面部软组织三维模型的准确度为（0.72±0.51）mm.其中水平向、垂直向和前后向的准确度分别为（0.70±0.41）mm、（0.73±0.47）mm和（0.72±0.54）mm.59％的软组织测量标志点具有较高的准确性.结论 基于激光扫描的面部软组织三维模型具有较好的准确性.     

Reliability of a 3D surface laser scanner for orthodontic applications.

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.     

Measurement accuracy of alveolar soft tissue contour using a laboratory laser scanner

Steric analysis of morphological changes is important for evaluation of surgical techniques. This study was performed to assess the measurement accuracy of alveolar soft tissue contour with a laboratory laser scanner. The width of the maxillary alveolar soft tissue contour was evaluated in 20 volunteers. Measurement sites were established in the alveolar soft tissue contour of the maxillary incisor and canine areas. Each site was evaluated by direct measurement with a microcaliper for each subject (DMM) and image measurement using a laboratory laser scanner (IMS). The accuracy of measurement methods was evaluated. Additionally, two plaster models obtained from the same subjects were scanned and superimposed, and the nonoverlapping areas were measured. Each measurement method exhibited a strong correlation (r = 0.89). The interclass correlation coefficient (single measure) between examiners was also high for each measurement method (PMM 0.978; IMS 0.997). In the superimposed images of the two plaster models, the distance of the nonoverlapping region was only 0.06 ± 0.08 mm in the labial aspect and 0.07 ± 0.09 mm in the palatal aspect. The image measurement of the scanning data shows high accuracy in evaluation of the alveolar soft tissue contour. This technique is useful for evaluation of chronological changes in the alveolar contour after soft and hard tissue augmentation.     

CAD-CAM generated ear cast by means of a laser scanner and rapid prototyping machine

Sculpting a wax ear cast for use when making a definitive prosthesis for a patient who has had auricle ablative surgery, is challenging. It requires a skilled anaplastologist along with complex instrumentation able to perform facial laser scans and reproduce anatomic details. The aim of this article is to present a technique to create a cast by laser scanning a stone cast of the existing ear. A 3D laser scanner develops an integrated 3D digital image of the unaffected ear, which is copied and then mirrored. A rapid prototyping machine collects the necessary data to manufacture the definitive resin ear. This procedure is time and cost effective only if the technology is free of charge.     

Integration of 3-D shapes of dentition and facial morphology using a high-speed laser scanner

PURPOSE: The purpose of this study was to develop a method to integrate three-dimensional data of dentition and facial morphology measured by a high-speed laser scanner, and visualize them by computer graphics. The accuracy of integration was also examined. MATERIALS AND METHODS: The 3-D shapes of upper and lower dental casts and the face of a subject were measured by a high-speed laser scanner with zoom lens facility. As an interface to integrate the coordinates between dentition and face, an extraoral marker plate attached to the occlusal record plate was devised. It was applied between the upper and lower dental casts, and with the subject, and measured. Integration was attempted by coinciding the data of the interface. The accuracy of integration was examined using the conditions of the marker plate such as surface shape and attachment angle. RESULTS: Integration of the data of dentition and face was accomplished. The 3-D relationship between them could be visualized in any direction or section by computer graphics. For optimal accuracy of integration, the marker plate with a mixed shape of flat and sinusoidal wave attached at 45 degrees to the occlusal record plate showed the most appropriate results. CONCLUSION: An original method to integrate the 3-D data of dentition and face measured by 3-D laser scanner was developed and shown to have acceptable accuracy.