Accuracy and efficiency of dynamic navigated root-end resection in endodontic surgery: a pilot in vitro study.

BACKGROUND: The operation accuracy and efficiency of dynamic navigated endodontic surgery were evaluated through in vitro experiments. This study provides a reference for future clinical application of dynamic navigation systems in endodontic surgery. MATERIALS AND METHODS: 3D-printed maxillary anterior teeth were used in the preparation of models for endodontic surgery. Endodontic surgery was performed with and without dynamic navigation by an operator who was proficient in dynamic navigation technology but had no experience in endodontic surgery. Optical scanning data were applied to evaluate the length and angle deviations of root-end resection. And the operation time was recorded. T tests were used to analyze the effect of dynamic navigation technology on the accuracy and duration of endodontic surgery. RESULTS: With dynamic navigation, the root-end resection length deviation was 0.46 ± 0.06 mm, the angle deviation was 2.45 ± 0.96°, and the operation time was 187 ± 22.97 s. Without dynamic navigation, the root-end resection length deviation was 1.20 ± 0.92 mm, the angle deviation was 16.20 ± 9.59°, and the operation time was 247 ± 61.47 s. Less deviation was achieved and less operation time was spent with than without dynamic navigation (P < 0.01). CONCLUSION: The application of a dynamic navigation system in endodontic surgery can improve the accuracy and efficiency significantly for operators without surgical experience and reduce the operation time.

3D facial mask for facial asymmetry diagnosis.

Objectives: Facial asymmetry is a common problem seen in orthodontic clinics that may affect patient esthetics. In some instances, severe asymmetry that affects patient esthetics may cause psychological issues. An objective method is therefore required to help orthodontists identify asymmetry issues. Materials and methods: We used three-dimensional (3D) facial images and landmark-based anthropometric analysis to construct a 3D facial mask to evaluate asymmetry. The landmark coordinates were transformed using a symmetric 3D face model to evaluate the efficacy of this method. Patients with facial asymmetry were recruited to conduct mirror and overlap analysis to form color maps, which were used to verify the utility of the novel soft tissue landmark-based method. Results: The preliminary results demonstrated that the asymmetry evaluation method had a similar response rate compared to diagnosis using mirror and overlap 3D images, and could therefore identify 3D asymmetry problems. Conclusions: By using 3D facial scans and 3D anthropometric analysis, we developed a preliminary evaluation method that provides objective parameters to clinically evaluate patient facial asymmetry and aid in the diagnosis of asymmetric areas. Clinical relevance: This study presents a novel facial asymmetry diagnostic method that has the potential to aid clinical decisions during problem identification, treatment planning, and efficacy evaluation.

Slim the face or not: 3D change of facial soft and hard tissues after third molars extraction: a pilot study.

BACKGROUND: Whether slim the face or not after removed third molars is the concern of some orthodontic treatment candidates. The aim of this article is to explore the volume changes of facial soft and hard tissues after third molars extraction, as well as develop a reproducible clinical protocol to precisely assess facial soft tissue volume change. METHODS: A non-randomized, non-blind, self-controlled pilot study was conducted. 24 adults aged 18-30 had ipsilateral third molars extracted. The body weight change was controlled within 2 kg. Structured light scans were taken under a standardized procedure pre-extraction (T0), three (T1), and six (T2) months post-extraction; CBCTs were taken at T0 and T2. The projection method was proposed to measure the soft tissue volume (STV) and the soft tissue volume change (STVC) by the Geomagic software. The hard tissue volume change (HTVC) was measured in the Dragonfly software. RESULTS: The final sample size is 23, including 5 males (age 26.6 ± 2.5 years) and 18 females (age 27.3 ± 2.5 years). The HTVC was - 2.33 ± 0.46ml on the extraction side. On the extraction side, the STV decreased by 1.396 (95% CI: 0.323-2.470) ml (P < 0.05) at T1, and increased by 1.753 (95% CI: -0.01-3.507) ml (P = 0.05) at T2. T2 and T0 had no difference (P > 0.05). The inter and intra-raters ICC of the projection method was 0.959 and 0.974. There was no correlation between the STVC and HTVC (P > 0.05). CONCLUSIONS: After ipsilateral wisdom teeth extraction, the volume of hard tissue on the extraction side reduces, and the volume of facial soft tissue does not change evidently. However, further research with large sample size is still needed. The STV measurement has excellent repeatability. It can be extended to other interested areas, including forehead, nose, paranasal, upper lip, lower lip and chin, which is meaningful in the field of orthodontics and orthopedics. TRIAL REGISTRATION: ChiCTR, ChiCTR1800018305 (11/09/2018), http://www.chictr.org.cn/showproj.aspx?proj=28868 .

Enhanced Lip-Contour During Facial Scan for 3D DSD and Implant Planning: A Blue Screen Approach.

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.

Morphologic reproducibility in 6 regions of the 3-dimensional facial models acquired by a standardized procedure: An in vivo study.

INTRODUCTION: A standardized procedure was proposed to control involuntary motion and other factors during the capture of structural light scanning that could influence the morphology of 3-dimensional facial models; interoperator reproducibility was evaluated. METHODS: Twenty subjects volunteered for facial scanning. Three researchers scanned each volunteer 3 times on the same day using the FaceScan structural light scanning system (Isravision, Darmstadt, Germany) and after the proposed procedure. Captures were done at 5-minute intervals. The 3 facial scans acquired by the same researcher were compared by reverse engineering software (Geomagic; 3D Systems, Rock Hill, SC). Six facial regions, including forehead, nose, paranasal, upper lip, lower lip and chin, and cheek, were divided. With the first scan as a reference, the other 2 scans were registered, and surface-to-surface distance maps were acquired to calculate the mean, standard deviation, and root mean squares (RMS) between 2 surfaces. The reproducibility between 3 researchers was then evaluated by a 1-way analysis of variance. RESULTS: The mean of 6 facial regions was close to 0. The RMS of lip regions were largest (0.48-0.53 mm), the forehead was smallest (0.21 mm), and the others ranged 0.37 mm to 0.42 mm. The standard deviation was slightly smaller than RMS and had the same trend of change. There was no significant difference in RMS among the 3 researchers (P >0.05). CONCLUSIONS: With the constraint of the standardized procedure, the morphologic reproducibility of facial models in 6 regions was satisfying.

3D Evaluation of Accuracy of Tooth Preparation for Laminate Veneers Assisted by Rigid Constraint Guides Printed by Selective Laser Melting.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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 (P < 0.05). 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) (P < 0.05), 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) (P > 0.05). CONCLUSION: 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.

Accuracy of Intraoral Scanning of Edentulous Jaws with and without Resin Markers.

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.

Radioactive seed migration following parotid gland interstitial brachytherapy.

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.

Three-Dimensional Accuracy of Facial Scan for Facial Deformities in Clinics: A New Evaluation Method for Facial Scanner Accuracy.

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.

[A cone-beam computed tomography study on crown-root morphology of maxillary anterior teeth in Class II, division 2 malocclusion].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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°. CONCLUSION: 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.

[Constructing 3-dimensional colorized digital dental model assisted by digital photography].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Three-dimensional verification of ¹²5I seed stability after permanent implantation in the parotid gland and periparotid region.

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 (125)I 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: (125)I 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.

Molecular cloning and characterization of presenilin gene in Bombyx mori.

Presenilin (PS), the catalytic core of the γ-secretase complex, is considered to be a causative protein of the early­onset familial form of Alzheimer's disease. Aging is a risk factor for Alzheimer's disease and a number of genetic studies have utilized Bombyx mori (B. mori) as a model, making it possible to use B. mori to investigate Alzheimer's disease. However, the homologous gene of human PS in B. mori has remained to be elucidated. In the present study, the PS homologue gene in B. mori was identified and characterized, and six B. mori presenilin (BmPS) mRNA transcripts were generated by selecting multiple transcription start sites and/or alternative splice sites. The longest mRNA of BmPS (termed BmPS1) contains a 153 nt 5' untranslated region (UTR), a 1,440 nt open reading frame and a 1,063 nt 3' UTR. The predicted protein of BmPS1 consists of 479 amino acid residues and has two highly­conserved aspartate residues, which form the catalytic core of aspartic proteases. It exhibits a sequence identity of ~44 and 51% with homologues in Homo sapiens and Drosophila melanogaster, respectively. However, the amino acid sequence of the BmPS loop region does not completely match between the two B. mori strains R13Q and Dazao. Genomic analysis revealed that B. mori had a single copy of the BmPS gene, which was composed of 14 exons. A total of four isoforms of BmPS (BmPS­A, ­B, ­C and ­D) owing to multiple transcriptional start sites and alternative splice sites were identified. The alternative splicing events occurring in the loop region improved the diversity of the BmPS protein and were detectable in all tissues, as determined using reverse transcription quantitative polymerase chain reaction (RT­qPCR). Furthermore, the expression levels of BmPS in the brain at different developmental stages were detected using RT­qPCR, and significantly higher expression levels of BmPS were found in the adult stage compared with those in the larval and pupal stages. The present study on BmPS provided insight into the pathogenesis of Alzheimer's disease and mechanisms of silkworm developmental regulation.

[Preliminary evaluation on 3-demension changes of facial soft tissue with structure light scanning technique before and after orthognathic surgery of Class III deformities].

OBJECTIVE: To evaluate facial soft tissue 3-deminsion changes of skeletal Class III malocclusion patients after orthognathic surgery using structure light scanning technique. METHODS: Eight patients [3 males and 5 females, aged (27.08 ± 4.42) years] with Class III dentoskeletal relationship who underwent a bimaxillary orthognathic surgical procedure involving advancement of the maxilla by Le Fort I osteotomy and mandibular setback by bilateral sagittal split ramus osteotomy (BSSO) and genioplasty to correct deformity were included. 3D facial images were obtained by structure light scanner for all the patients 2 weeks preoperatively and 6 months postoperatively. The facial soft tissue changes were evaluated in 3-dimension. The linear distances and angulation changes for facial soft tissue landmarks were analyzed. The soft tissue volumetric changes were assessed too. RESULTS: There were significant differences in the sagittal and vertical changes of soft tissue landmarks. The greatest amount of soft tissue change was close to lips. There were more volumetric changes in the chin than in the maxilla, and fewer in the forehead. CONCLUSION: After biomaxillary surgery, there were significant facial soft tissue differences mainly in the sagittal and vertical dimension for skeletal Class III patients. The structure light 3D scanning technique can be accurately used to estimate the soft tissue changes in patients who undergo orthognathic surgery.

[Evaluation of measurement accuracy of three facial scanners based on different scanning principles].

OBJECTIVE: To evaluate and compare the measurement accuracy of three facial scanners, based on different scanning principles: line laser, structured light and stereophotography. METHODS: 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. RESULTS: 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°. CONCLUSION: The three facial scanners all have good reliability in facial measurements, and their actual measurement accuracy for patients needs further research.

[Application of patient-participated digital design in esthetic rehabilitation of anterior teeth].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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 (P < 0.05). In addition, the time consuming in the first insertion of the experimental group was much shorter than that in the control group (P < 0.01). CONCLUSION: 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.

[Initial evolution research for design and process accuracy of one type of domestic computer aided design soft and computer aided manufacture].

OBJECTIVE: 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. METHODS: 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 3D & Profile measurement microscope laser. RESULTS: 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. CONCLUSIONS: The design and machining precision of this domestic CAD/CAM system is at the same level of those comparable foreign products.

[Preliminary evaluation of clinical effect of computer aided design and computer aided manufacture zirconia crown].

OBJECTIVE: 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. METHODS: 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. RESULTS: In all the prosthesis we evaluated during the 24 months, no fracture was found. Contact wear of crowns varies according to different antagonist teeth. CONCLUSIONS: 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.

[Accuracy of different registration methods for laser-scanned dental cast data and maxillofacial cone-bean CT data].

OBJECTIVE: To evaluate the accuracy of four dominant methods of three-dimensional multisource data registration. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Quantitative evaluation for the accuracy of dental model three-dimensional scanner].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.