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When obtaining 3-dimensional (3D) facial images for digital smile design (DSD) and dental implant planning, inaccuracies may frequently be introduced by distortion in the region between the lips' vermilion border and the teeth. The present clinical technique aimed to reduce such deformation during face scanning, thereby facilitating 3D DSD. This is also essential to plan bone reduction with precision for implant reconstructions. A custom-made silicone matrix acting as a blue screen provided reliable support for 3D visualization of facial images in a patient requiring a new maxillary screw-retained implant-supported fixed complete denture. Imperceptible volumetric changes were registered in the facial tissues when the silicone matrix was added. The usual deformation of the lip vermilion border originating in face scans was overcome by applying blue-screen technology with a silicone matrix. Reproducing the vermilion border of the lip contour accurately may offer improved communication and visualization for 3D DSD. The silicone matrix was a practical approach that acted as a blue screen to display the transition from lips to teeth with satisfactory precision. Implementing blue-screen technology in reconstructive dentistry might increase predictability by reducing errors when scanning objects with challenging-to-capture surfaces.

Objective: To evaluate the accuracy of digital models obtained from intraoral scanning of edentulous maxilla and mandible models with and without resin markers. Methods: A pair of standard edentulous models were scanned using a laboratory scanner and saved as reference models. The edentulous models were fixed onto a phantom head and scanned with an intraoral scanner (IOS) five times each. Six resin markers were attached on the maxilla model and two on the mandible model, and another five intraoral scans were taken of each model. The scanning time and number of images were recorded. The digital models obtained using the IOS were superimposed on the reference models using image processing software. The trueness and precision of the models made using the IOS were evaluated, and the scanning time and number of images were also compared. Results: The average trueness and precision of the IOS in the maxilla model with resin markers were 135.50 ± 36.28 μm and 254.55 ± 40.62 μm, respectively, while those in the mandible were 161.40 ± 55.45 μm and 368.75 ± 91.03 μm, respectively. Placing resin markers on the edentulous maxilla and mandible did not improve the trueness of the IOS, but placing resin markers on the edentulous maxilla improved the precision and scanning efficiency. However, placing resin markers on the buccal shelf of the edentulous mandible decreased the precision and increased the scanning time. Conclusion: Resin markers placed on the hard palate of edentulous maxillae could improve the precision of the IOS and improve scanning efficiency. However, they did not affect the trueness of the IOS for edentulous maxillae or mandibles.

To design and fabricate 3D-printed rigid constraint guides for the tooth preparation for laminate veneers and to evaluate the accuracy of guide-assisted preparation.Twenty maxillary right central incisor resin artificial teeth were randomly divided into two equal groups and prepared for laminate veneers. Tooth preparations were performed, assisted by guides in the test group and by depth gauge burs in the control group, and both were finished by freehand operation. The typodonts were 3D scanned before preparation, after initial preparation and after final preparation. The tooth preparation depths at each step, including initial preparation depth, final preparation depth and loss of tooth tissue during polishing, were measured by 3D deviation analysis. Statistical analyses were conducted to investigate differences.The initial preparation depth was 0.488 mm (median, quartile 0.013 mm) in the test group and 0.521 mm (median, quartile 0.013 mm) in the control group. A statistically significant difference was found between them (P0.05). The final preparation depth in the test group (0.547 ± 0.029 mm) was significantly less than that in the control group (0.599 ± 0.051 mm) (P0.05), and closer to the predesigned value (0.5 mm). There was no statistically significant difference in the loss of tooth tissue during polishing between the test group (0.072 ± 0.023 mm) and the control group (0.089 ± 0.038 mm) (P0.05).In maxillary central incisors, the tooth preparation for laminate veneers could be conducted using 3D-printed rigid constraint guides, the accuracy of which is better than that of depth gauge burs.

This study’s aim was to develop and validate an approach to automatically extract and reconstruct three-dimensional (3D) digital root models from in vivo teeth based on the anatomical characteristics of the periodontal ligament using cone beam computed tomography (CBCT) data. Prior to undergoing dental extractions for orthodontic purposes, the CBCT data of each study participant were collected and imported into Mimics software to reconstruct 3D in vivo digital root models (test models). Twenty roots of 17 teeth extracted from the study’s participants were scanned using a dental scanner to obtain 3D in vitro digital root models (reference models). The 3D morphological deviation between the reference and test models was compared; the 3D size of the bucco-lingual, mesio-distal, and root length dimensions were calculated. This approach achieved an average 3D morphological deviation of 0.21 mm, and the average size error in the bucco-lingual, mesio-distal, and root length dimensions were −0.35 mm, −0.17 mm, and 0.47 mm, respectively. This new automatic extraction approach rapidly and accurately reconstructs 3D in vivo root models with detailed morphological information, and has the potential to improve diagnostic and treatment work flow in orthodontic clinics, as well as in other areas of dentistry.

Symmetry is a significant factor influencing the attractiveness of human faces. It is always a concern of patients as well as doctors, especially orthodontists and surgeons. The classic definition of facial symmetry refers to a state of equilibrium1: in which there is a correspondence in size, shape, and arrangement of facial landmarks on the opposite sides of the median sagittal plane. Hence, it is considerably important to determine the median-sagittal plane (MSP) for every patient prior surgery. Landmark-dependent methods have traditionally been the mainstream approach for the assessment of facial asymmetry.2,3 These methods, however, have been questioned because of unreliable identification of landmarks. The landmarks are often not exactly in the middle of the face, thus resulting in the unreliable MSP. Furthermore, landmark-dependent methods are also incapable of depicting asymmetries in regions where landmarks are few and far between.4,5 Most research on facial symmetry has been conducted using two-dimensional (2D) methods. Posterior–anterior radiographs1 and the panoramic6 are 2 traditional methods used for the analysis of hard-tissue asymmetry. Anthropometry7 and photography8 have been used to evaluate soft-tissue asymmetry. Clearly, the perception of three-dimensional structure at a two-dimensional level can lead to the loss of some data. With the rapid advent of three-dimensional scanning, holography and stereo photogrammetry, we can get a three-dimensional review of facial asymmetry. The interactive closest point algorithm (ICP)9 was already widely used to compute MSP for three-dimensional facial data, and Procrustes analysis (PA)10 was also reported for three-dimensional data. It is a morphometric approach to determine the MSP by using visually intact regions unaffected by the asymmetry as the reference. Both the ICP and the PA11 methods have already been reported for determining the MSP for normal subjects with no obvious facial asymmetry, but there were few articles for comparison between the 2 methods. The aim of this article is to compare the 2 digital methods for extracting MSP from three-dimensional facial data.

Purpose To evaluate the incidence and associated factors of pulmonary seed migration after parotid brachytherapy using a novel migrated seed detection technique. Methods and Materials Patients diagnosed with parotid cancer who underwent permanent parotid brachytherapy from January 2006 to December 2011 were reviewed retrospectively. Head and neck CT scans and chest X-rays were evaluated during routine follow-up. Mimics software and Geomagic Studio software were used for seed reconstruction and migrated seed detection from the original implanted region, respectively. Postimplant dosimetry analysis was performed after seeds migration if the seeds were still in their emitting count. Adverse clinical sequelae from seed embolization to the lung were documented. Results The radioactive seed implants were identified on chest X-rays in 6 patients. The incidence rate of seed migration in 321 parotid brachytherapy patients was 1.87% (6/321) and that of individual seed migration was 0.04% (6/15218 seeds). All migrated seeds were originally from the retromandibular region. No adverse dosimetric consequences were found in the target region. Pulmonary symptoms were not reported by any patient in this study. Conclusions In our patient set, migration of radioactive seeds with an initial radioactivity of 0.6–0.7 mCi to the chest following parotid brachytherapy was rare. Late migration of a single seed from the central target region did not affect the dosimetry significantly, and patients did not have severe short-term complications. This study proposed a novel technique to localize the anatomical origin of the migrated seeds during brachytherapy. Our evidence suggested that placement of seeds adjacent to blood vessels was associated with an increased likelihood of seed migration to the lungs.

In this study, the practical accuracy (PA) of optical facial scanners for facial deformity patients in oral clinic was evaluated. Ten patients with a variety of facial deformities from oral clinical were included in the study. For each patient, a three-dimensional (3D) face model was acquired, via a high-accuracy industrial "line-laser" scanner (Faro), as the reference model and two test models were obtained, via a "stereophotography" (3dMD) and a "structured light" facial scanner (FaceScan) separately. Registration based on the iterative closest point (ICP) algorithm was executed to overlap the test models to reference models, and "3D error" as a new measurement indicator calculated by reverse engineering software (Geomagic Studio) was used to evaluate the 3D global and partial (upper, middle, and lower parts of face) PA of each facial scanner. The respective 3D accuracy of stereophotography and structured light facial scanners obtained for facial deformities was 0.58±0.11 mm and 0.57±0.07 mm. The 3D accuracy of different facial partitions was inconsistent; the middle face had the best performance. Although the PA of two facial scanners was lower than their nominal accuracy (NA), they all met the requirement for oral clinic use.

To explore a method of constructing universal 3-dimensional (3D) colorized digital dental model which can be displayed and edited in common 3D software (such as Geomagic series), in order to improve the visual effect of digital dental model in 3D software.The morphological data of teeth and gingivae were obtained by intra-oral scanning system (3Shape TRIOS), constructing 3D digital dental models. The 3D digital dental models were exported as STL files. Meanwhile, referring to the accredited photography guide of American Academy of Cosmetic Dentistry (AACD), five selected digital photographs of patients'teeth and gingivae were taken by digital single lens reflex camera (DSLR) with the same exposure parameters (except occlusal views) to capture the color data. In Geomagic Studio 2013, after STL file of 3D digital dental model being imported, digital photographs were projected on 3D digital dental model with corresponding position and angle. The junctions of different photos were carefully trimmed to get continuous and natural color transitions. Then the 3D colorized digital dental model was constructed, which was exported as OBJ file or WRP file which was a special file for software of Geomagic series. For the purpose of evaluating the visual effect of the 3D colorized digital model, a rating scale on color simulation effect in views of patients'evaluation was used. Sixteen patients were recruited and their scores on colored and non-colored digital dental models were recorded. The data were analyzed using McNemar-Bowker test in SPSS 20.Universal 3D colorized digital dental model with better color simulation was constructed based on intra-oral scanning and digital photography. For clinical application, the 3D colorized digital dental models, combined with 3D face images, were introduced into 3D smile design of aesthetic rehabilitation, which could improve the patients' cognition for the esthetic digital design and virtual prosthetic effect.Universal 3D colorized digital dental model with better color simulation can be constructed assisted by 3D dental scanning system and digital photography. In clinical practice, the communication between dentist and patients could be improved assisted by the better visual perception since the colorized 3D digital dental models with better color simulation effect.

To study crown-root morphology of maxillary anterior teeth in Class II, division 2 malocclusion using cone-beam CT (CBCT) combined with computer aided measurement technology to provide guidance for clinical treatment.The samples which consisted of 36 cases radiographed with CBCT techniques were selected and divided into two groups (18 each ) based on the type of malocclusion presented: Class II, division 2 group (group II 2) and Class I group (group I). The measurements of crown-root morphology including crown-root angle and surface-shaft angle were got by Multiple Planer Reconstruction of CBCT data uploaded into InvivoDental software 5.0. The data were processed with SPSS 20.0 software package and t test was employed for comparison of angular measurements.In group I, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 179.08° ± 3.31°, 176.55° ± 2.77° and 184.20° ± 2.51° respectively, surface-shaft angles were 21.00° ± 2.63°, 19.63° ±2 .35° and 19.36° ± 2.30° respectively. While in group II 2, crown-root angles of maxillary central incisor, maxillary lateral incisor and maxillary canines were 176.80° ± 2.62°, 174.13° ± 3.28° and 181.79° ± 2.88° respectively, surface-shaft angles were 23.20° ± 2.95°, 22.29° ± 2.19° and 20.61° ± 2.34° respectively. Compared with group I, significant statistical differences were observed with the exception of surface-shaft angle of maxillary incisor. There was significant difference in crown-root angle between group II 2 and 180°.The maxillary anterior teeth in Class II, division 2 malocclusion exhibited significant crown-root morphology which would influence the torque after orthodontic treatment. Special attention should be paid to the position of maxillary anterior teeth roots during orthodontic treatment for Class II, division 2 malocclusion. The ideal position of tooth movement should be decided by the root rather than the location of the crowns.

To evaluate and compare the measurement accuracy of three facial scanners, based on different scanning principles: line laser, structured light and stereophotography.Three-dimensional (3D) digital face models of the same plaster head model were obtained by three facial scanners separately. The measurement values of the length of 10 feature lines and the angle of 5 feature angles were measured on these 3D models in the software respectively. The standard values of these characteristics were measured by a coordinate measure machine (CMM) with high accuracy. Statistical and surveying analyses were made between the measurement values and standard values. Facial morphology theory measurement accuracy of these three facial scanners was obtained finally.There was no statistical significant difference between the measurement values from the three facial scanners and the standard value from CMM. The 3dMD and Faro scanners were better in length measurements and the length measurement accuracy was about 0.2 mm. The Faro scanner was also better in angle measurements and the angle measurement accuracy was about 0.5°.The three facial scanners all have good reliability in facial measurements, and their actual measurement accuracy for patients needs further research.

To explore a new method of patient-involved digital design, esthetic outcome prediction and fabrication for the esthetic rehabilitation of anterior teeth, and to provide an alternative choice for the restoration of anterior teeth.In this study, 32 patients with esthetic problems in their anterior teeth were included and divided into two groups randomly: the experimental group (16 patients) and control group (16 patients). In the experimental group, the dentition and facial images were obtained by intra-oral scanning and Three-dimensional (3D) facial scanning and then calibrated. The design of the rehabilitation and the esthetic outcome prediction were created by computer-aided design (CAD) software. After morphologic modification according to the patients' opinions, prostheses were fabricated according to the final design by computer-aided manufacturing (CAM) equipment. As for the control group, the regular design method was applied to restore their anterior teeth. The time consuming in the first insertion of each restoration in both groups was recorded. The quality of the prostheses was assessed by another prosthedontist. The satisfaction to prostheses and the facial appearance were evaluated by the patients.The process of the patient-involved digital design and outcome anticipation was successfully established. The patients were satisfied with the esthetic effects of the anterior restoration made by the digital technique. The acceptance rate of the patients on the digital rehabilitation in the experimental group was 100%. There was no significant difference of the quality of the prostheses between the two groups. The satisfaction rate of the patients on prostheses and facial appearance was significantly higher in the experimental group than in the control group (P0.05). In addition, the time consuming in the first insertion of the experimental group was much shorter than that in the control group (P0.01).The new method of the patient-involved digital design, esthetic outcome prediction and fabrication for the esthetic rehabilitation of anterior teeth is a practical technique. This method is useful in shortening the time consuming of the restoration of anterior teeth and improving the patient satisfaction with the esthetic outcome.

To evaluate the design and manufacture accuracy of a domestic computer aided design (CAD) and computer aided manufacture (CAM) system, and to compare it with similar foreign products.Thirty models of posterior-teeth-single-crown preparations were collected, and STL data of these preparations was collected by Denmark 3Shape scanner. Three copings were made for each preparation, the one designed and manufactured using commercial CAD/CAM system (3Shape CAD software and Wieland T1 CAM equipment) was assigned into control group T0, the one designed and manufactured using domestic CAD software (developed by Peking University School and Hospital of Stomatology and Nanjing University of Aeronautics and Astronautics) and Wieland T1 CAM equipment was assigned into experimental group TCAD for design accuracy evaluation, and the one designed and manufactured using 3Shape CAD software and domestic CAM equipment (developed by Peking University School and Hospital of Stomatology, Tsinghua University and ShanDong XinHua Incorporated Company of medical apparatus and instruments) was assigned into experimental group TCAM for manufacture accuracy evaluation. Finally, the marginal fitness were compared and evaluated by using 3DProfile measurement microscope laser.The marginal fitness of TCAD was 27.98 (19.10, 46.57) µm in buccal, 32.67 (20.65, 50.82) µm in lingual, 27.38 (22.53, 52.61) µm in mesial, 29.50 (22.68, 53.65) µm in distal; of TCAM was 21.69 (15.87, 30.21) µm in buccal, 18.51 (13.50, 22.51) µm in lingual, 19.15 (15.42, 26.89) µm in mesial, 22.77 (18.58, 32.15) µm in distal; and there were no statistical differences compared with T0 [20.16 (17.16, 48.00) µm in buccal, 21.51 (17.05, 28.31) µm in lingual, 23.54 (17.89, 30.04) µm in mesial and 23.94 (17.93, 28.19) µm in distal] except lingual data of TCAD.The design and machining precision of this domestic CAD/CAM system is at the same level of those comparable foreign products.

To evaluate clinical effects of computer aided design and computer aided manufacturing (CAD/CAM) milled zirconia crown in three aspects: aesthetic, contact wear and fracture.Sixty patients were divided into two groups.In one group, 35 full contour CAD/CAM zirconia crown were made on molars of 30 patients. The manufacturing process of zirconia crown was as follow. First, the three dimensional(3-D) data of working models, antagonist impression and check records were acquired by 3-D laser scanning Dental wings S50. Then full contour zirconia crowns, which had functional occlusal contacts with antagonistic teeth, and appropriate contact with adjacent teeth were designed with Zeno-CAD(V4.2.5.5.12919) software. ZENOSTAR Zr pure zirconia material was milled in digital controlled machine WIELAND 4030 M1.In the end, the zirconia crown were completed with the method of second sintering and polishing. After clinical try-in, the crown was cemented.In the control group, thirty gold alloy full crown were made and cemented on molars of 30 patients. According to the modified U S Public Health Service Criteria(USPHS) evaluation standard, all crowns were evaluated on the same day, at three months, half a year, one year and two years following delivery. There were three aspects we were focusing on in the evaluation: aesthetic, contact wear(restoration and antagonist), and fracture.In all the prosthesis we evaluated during the 24 months, no fracture was found. Contact wear of crowns varies according to different antagonist teeth.The zirconia crowns show privilege in aesthesis, toughness and anti-wearing.However, there is contact wear on antagonistic natural teeth. Thus it is a good choice when full zirconia crowns are indicated on two antagonistic teeth in both jaws.

To evaluate the accuracy of four dominant methods of three-dimensional multisource data registration.Laser-scanned dental model and maxillofacial cone-bean CT rebuilt model were collected for one orthodontic patient before treatment. Registration process was done based on locating spheres' center, anatomic landmarks, partial characteristic region and global data separately. The registration errors were detected by the function of Geomagic Studio 12.0 software. A comparison of the registration accuracy among these four methods was done by analyzing mean error and standard deviation.The mean errors and standard deviations of methods of locating spheres' center, anatomic landmarks, partial characteristic region and global data were -(0.082 ± 0.221), -(0.104 ± 0.218), -(0.047 ± 0.138) and -(0.025 ± 0.129) mm respectively.ICP registration methods had better reliability than landmark methods. The global registration was more accurate than partial characteristic region registration and the locating spheres' center method was better than anatomic landmarks method.

To establish a method to evaluate dental model three-dimensional scanner quantitatively, and to evaluate the accuracy which is a core indicator of 3Shape D700 scanner.A standard geometric model similar to the dental arch was designed by three-dimensional reverse software and processed by high precision CNC (computer numerical control) processing technology. Core indicators of dental model three-dimensional scanner including single scanning accuracy, space consistency and rescan accuracy were evaluated.The result of single scanning accuracy of 3Shape D700 scanner was (15.00±10.84) μm, and there was no statistics difference between the accuracy given by manufacturer's instructions which is 20 μm (P=0.053), and same as the results of space consistency (compare the accuracy in vertical direction and horizontal direction, P=0.524) and rescan accuracy (compare the rescan accuracy in vertical direction, P=0.633, and in horizontal direction P=0.221).It is feasible to evaluate accuracy of dental model three-dimensional scanner by this method, which can avoid observer error caused by selecting points manually.

To analyze the changes in facial feature region during posed smile three dimensionally.The three-dimensional facial images during posed smiles and resting position in 44 volunteers (18 men, 26 women, 26.7 ± 2.6 years old) were acquired by using FaceScan optical three-dimensional sensor. These scanned three-dimensional images were processed and superimposed with commercially-available reverse modeling software. Quantitative and qualitative three dimensional analyses of changes in facial feature region during posed smile were done by using color maps.The changing area accounted for (29.65 ± 8.40)% during posed smile, and the difference of the left and right half face was 6.69% (2.07%, 13.11%). Displacements in cheilion, zygomatic area, lower lip were detected in every subject during posed smile. Women [(4.49 ± 1.51) mm] gained more changes than men [(3.25 ± 1.75) mm] did in nasolabial fold.Posed smile was asymmetric. Displacement variation and ratio are different at facial feature regions.Women shows greater changes around lips during posed smile.

To explore the effect of gingival retraction time on the gingival sulcus width in different gingival areas, using three-dimensional (3D) model analysis.Forty-six premolars from 10 volunteers were included, gingival retraction cords were applied on the buccal sulcus for three times, and the retraction time was 5, 10 and 15 minutes respectively. The least interval between two retraction procedures was 2 weeks. Impressions and stone models were made before and after gingival retraction. 3D data of the models were acquired by a 3D line laser scanner. Models were superimposed and tooth coordinate was set up with special software. Sulcus widths from different retraction time and different gingival areas were measured and compared.Sulcus widths between retraction of 5 and 10 minutes were significantly different at midbuccal and transitional line angle (TLA) gingival areas. At TLA areas, sulcus widths between retraction of 10 and 15 minutes were also statistically different, but the difference was not significant when compared with that of 5 and 10 minutes. Sulcus widths at midbuccal areas were significantly greater than that at TLA areas for all three retraction time.Before making impressions, gingival retraction time of single-cord mechanical technique should be at least 10 minutes. For different gingival areas, the enlargement of gingival sulcus from gingival retraction and the optimal retraction time were different. 3D model analysis could be used as a new objective method to evaluate gingival retraction effect from different retraction time.

To establish the computer aided design (CAD) software platform of individualized abutment for the maxilla central incisor.Three-dimentional data of the incisor was collected by scanning and geometric transformation. Data mainly included the occlusal part of the healing abutment, the location carinae of the bedpiece, the occlusal 1/3 part of the artificial gingiva's inner surface, and so on. The all-ceramic crown designed in advanced was "virtual cutback" to get the original data of the abutment's supragingival part. The abutment's in-gum part was designed to simulate the individual natural tooth root. The functions such as "data offset", "bi-rail sweep surface" and "loft surface" were used in the process of CAD.The CAD route of the individualized all-ceramic abutment was set up. The functions and application methods were decided and the complete CAD process was realized.The software platform was basically set up according to the requests of the dental clinic.

To study the method of automatic tooth selection for computer-aided design in complete denture, evaluate the results by comparison with traditional denture tooth selection.3D data of occlusal rim made by the dentist were obtained with a 3D laser scanner and specific points on the occlusal rim were measured on Imageware11 platform. Based on Matlab 7.1 software platform, an automatic tooth selection software was programmed with adequate consideration of complete denture tooth selection factors, for example: face form of the patient, mesiodistal diameter of the artificial anterior teeth and posterior teeth, etc. Oclusal rim and edentulous models were selected from 20 patients. The artifical teeth were selected by both technician and software. The result of automatic tooth selection was evaluated by comparison with traditional method.In 20 cases the concordant rate of automatic and traditional method is 70%.The method of automatic tooth selection for computer-aided design in complete denture was realized in accordance with traditional method of denture tooth selection, the relationship between the curve of artificial teeth arranged on the occlusal rim and cuspid line--which was calculated accurately; automatic denture tooth selection; the denture tooth selected by software can be directly used in CAD complete denture tooth arrangement.

To evaluate the availability of the estimation method of the single-root surface area on periapical radiographs, and to compare with the measured method by 3-dimension laser scanning and reconstructed images.Ninety single-root teeth with severe periodontitis were selected, periapcal radiographs were taken before teeth extracted. Root lengths and crown lengths were measured on periapical radiographs. The ratio of crown to root of each tooth was calculated. Then the root surface areas were also estimated according to mathematics limit principle on the periapical radiographs. The image of the roots were reconstructed by using a 3D laser scanning, the root surface areas were measured with a CAD/CAM software.No significant difference was found between the measured values of the ratio of crown to root by 3D laser scanning and the estimated values on periapical radiographs (t=0.58, P0.05). For the lower incisors, no significant difference was found between the measured root surface areas with the 3D laser scanning and the estimated ones on periapical radiographs(t=0.46, P0.05). The surface area of the root in each tooth was divided into three parts: the coronal 1/3, the middle 1/3 and the apical 1/3. Each part of root surface area was measured and estimated. And then the percentage of each part in total root surface area was calculated. The measured percentage was similar to the estimated one except the middle 1/3 part of the upper premolars(t=0.77, P0.05).No significant difference was found between the measured ratio of crown to root with 3D laser scanning and the estimated one on periapical radiographs. The evaluated method on periapical radiographs to estimate root surface areas was relatively reliable for the lower incisor.

The study was to investigate the occlusal contacts with a set of dental casts based on their three-dimensional models in the intercuspal position.3D point-clouds of the dental casts in the intercuspal position were acquired by D.02-L-3D scanner with a special casts-locating device, and reconstructed . The areas of occlusal contacts were calculated, and were further compared with the results from the methods of articulating paper and photocclusion technique.There was no significant difference in the result of occlusal contacts analysis between the 3D reconstructive measurement and articulating paper or photocclusion technique. The virtual articulating paper was also preliminarily carried out in this research.The study verified the reliability of the measurement for occlusal contacts by the 3D digital model, and may lead to a new way for occlusal contacts research.

A method for 3D-data acquisition of partially edentulous cast was introduced to lay the foundation for reconstructing 3D digital model of a partially edentulous cast and studying computer aided design (CAD) to a removable partial denture framework.Using projection system controlled by a computer, four frames of sinusoidal fringe pattern at pi/2 intervals were projected onto the surface of partially edentulous cast consecutively within 0.4 second. Deformed fringe patterns modulated by the surface height of the cast were recorded by a digital camera. The phase value with the height information was demodulated with phase-shifting method. The transition from the unwrapped phase to the height of the points on the cast was performed with triangulation method. The multiview 3D data was integrated automatically to obtain the complete 3D profile data and the 3D digital model of the partially edentulous cast was reconstructed.Dense and complete points-cloud data was achieved without scanning blind zone basically. The anatomic structure of reconstructed 3D digital model was sharp and clear.As an alternative for acquiring 3D data of partially edentulous cast, this method presented here with high precision and high speed meets the need for the subsequent 3D design to removable partial denture framework.

To acquire the 3D point-cloud of the dental casts of intercuspal position and rebuild it in computer.A special scanning method was used to acquire the point-cloud of dental cast by using the D.02-L-3D SCANNER and rebuild the model by computer.The method could acquire a 3D model with high resolving power and clear-cut dental anatomic configuration for the dental casts of intercuspal position.This is a viable method of scanning with many advantages, such as precision, simplicity, high efficiency. It could satisfy the requirements of clinical practice, teaching and scientific research.

Objective To evaluate seed stability after permanent implantation in the parotid gland and periparotid region via a three-dimensional reconstruction of CT data. Material and methods Fifteen patients treated from June 2008 to June 2012 at Peking University School and Hospital of Stomatology for parotid gland tumors with postoperative adjunctive 125I interstitial brachytherapy were retrospectively reviewed in this study. Serial CT data were obtained during follow-up. Mimics and Geomagic Studio software were used for seed reconstruction and stability analysis, respectively. Results Seed loss and/or migration outside of the treated area were absent in all patients during follow-up (23–71 months). Total seed cluster volume was maximized on day 1 post-implantation due to edema and decreased significantly by an average of 13.5 % (SD = 9.80 %; 95 % CI, 6.82–17.68 %) during the first two months and an average of 4.5 % (SD = 3.60 %; 95 % CI, 2.29–6.29 %) during the next four months. Volume stabilized over the subsequent six months. Conclusions 125I seed number and location were stable with a general volumetric shrinkage tendency in the parotid gland and periparotid region. Three-dimensional seed reconstruction of CT images is feasible for visualization and verification of implanted seeds in parotid brachytherapy.