Using part of the initial analgesic dose as the epidural test dose did not delay the onset of labor analgesia: a randomized controlled clinical trial.

BACKGROUND: Epidural test dose for labor analgesia is controversial and varies widely in clinical practice. It is currently unclear whether using a portion of the initial dose for analgesia as the test dose delays the onset time of analgesia, compared to the traditional test dose. METHODS: One hundred and twenty-six parturients who chose epidural analgesia during labor were randomly assigned to two groups. The first dose in group L was 3 ml 1.5% lidocaine, and in the RF group was 10 ml 0.1% ropivacaine combined with 2 µg/ml fentanyl. After 3 min of observation, both groups received 8 ml 0.1% ropivacaine combined with 2 µg/ml fentanyl. The onset time of analgesia, motor and sensory blockade level, numerical pain rating scale, patient satisfaction score, and side effects were recorded. RESULTS: The onset time of analgesia in group RF was similar to that in group L (group RF vs group L, 7.0 [5.0-9.0] minutes vs 8.0 [5.0-11.0] minutes, p = 0.197). The incidence of foot numbness (group RF vs group L, 34.9% vs 57.1%, p = 0.020) and foot warming (group RF vs group L, 15.9% vs 47.6%, p < 0.001) in group RF was significantly lower than that in group L. There was no difference between the two groups on other outcomes. CONCLUSIONS: Compared with 1.5% lidocaine 3 ml, 0.1% ropivacaine 10 ml combined with 2 µg/ml fentanyl as an epidural test dose did not delay the onset of labor analgesia, and the side effects were slightly reduced. CLINICAL TRIAL REGISTRATION: http://www.chictr.org.cn (ChiCTR2100043071).

The anesthesia induction effect of dexmedetomidine in patients undergoing laryngeal mask intubation: a systematic review and meta-analysis of 7 RCTs.

BACKGROUND: During laryngeal mask airway (LMA) insertion, patients need to enter a sufficient depth of sedation to prevent limb movement, coughing, laryngospasm, and other adverse reactions. This study conducted a meta-analysis to investigate the effect of dexmedetomidine on anesthesia induction in patients undergoing laryngeal mask intubation (LMI). METHODS: The Embase, PubMed, Cochrane, and Web of Science databases were searched using the keywords [Dexmedetomidine] AND [Laryngeal mask/Laryngeal mask intubation/LMI] OR [Anesthesia induction] to retrieve articles on randomized controlled trials (RCTs) in which dexmedetomidine sedation had been used in the LMI surgery. After screening the articles, the Jadad scale was used to assess the bias of the studies, and Stata16.0 software was used for the analysis to determine the anesthetic-induction effects of dexmedetomidine, fentanyl, morphine, and midazolam as sedatives. RESULTS: In total, 352 articles were initially retrieved, and 7 articles with a total of 410 patients were ultimately included in the meta-analysis. The effective rate of LMI induced by dexmedetomidine-assisted sedation was better than that of the control group [odds ratio (OR) =1.10, 95% confidence interval (CI): 0.78, 1.53], but the difference between the 2 groups was not significant (Z=0.533, P=0.594). The respiratory rate of the dexmedetomidine group at 5 minutes after dexmedetomidine catheterization was higher than that of the control group [standardized mean difference (SMD) =3.17, 95% CI: 1.38, 4.96; Z=3.476, P=0.001]. The heart rate of the dexmedetomidine group at 1 minute after dexmedetomidine catheterization was significantly lower than that of the control group (SMD =-1.31, 95% CI: -1.91, -0.71; Z=-4.255, P=0.000). The mean arterial pressure (MAP) of the dexmedetomidine group at 1 minute after dexmedetomidine catheterization was lower than that of the control group (SMD =-0.24, 95% CI: -0.94, 0.45), but the difference was not statistically significant (Z=-0.684, P=0.494). The coughing count rate of the dexmedetomidine group was lower than that of the control group (OR =0.36, 95% CI: 0.15, 0.86; Z=-2.286, P=0.022). DISCUSSION: The application of dexmedetomidine in the anesthesia induction with LMI has a good sedative effect, improves the success rate of LMI, reduces adverse reactions.

[Osteogenesis of human adipose-derived mesenchymal stem cells-biomaterial mixture in vivo after 3D bio-printing].

OBJECTIVE: To construct human adipose-derived mesenchymal stem cells (hASCs)-biomaterial mixture 3D bio-printing body and detect its osteogenesis in vivo, and to establish a guideline of osteogenesis in vivo by use of 3D bio-printing technology preliminarily. METHODS: P4 hASCs were used as seed cells, whose osteogenic potential in vitro was tested by alkaline phosphatase (ALP) staining and alizarin red staining after 14 d of osteogenic induction. The cells were added into 20 g/L sodium alginate and 80 g/L gelatin mixture (cell density was 1 × 10(6)/mL), and the cell-sodium alginate-gelatin mixture was printed by Bioplotter 3D bio-printer (Envision company, Germany), in which the cells'survival rate was detected by live- dead cell double fluorescence staining. Next, the printing body was osteogenically induced for 1 week to gain the experimental group; and the sodium alginate-gelatin mixture without cells was also printed to gain the control group. Both the experimental group and the control group were implanted into the back of the nude mice. After 6 weeks of implantation, the samples were collected, HE staining, Masson staining, immunohistochemical staining and Inveon Micro CT test were preformed to analyze their osteogenic capability. RESULTS: The cells'survival rate was 89%± 2% after printing. Six weeks after implantation, the samples of the control group were mostly degraded, whose shape was irregular and gel-like; the samples of the experimental group kept their original size and their texture was tough. HE staining and Masson staining showed that the bone-like tissue and vessel in-growth could be observed in the experimental group 6 weeks after implantation, immunohistochemical staining showed that the result of osteocalcin was positive, and Micro CT results showed that samples of the experimental group had a higher density and the new bone volume was 18% ± 1%. CONCLUSION: hASCs -biomaterial mixture 3D bio-printing body has capability of ectopic bone formation in nude mice, and it is feasible to apply cells-biomaterial mixture 3D bio-printing technology in the area of bone formation in vivo.

[Short-term effect of CaCl2on human adipose-derived mesenchymal stem cells proliferation and osteogenic differentiation].

OBJECTIVE: To examine the effect of CaCl2, a sodium alginate crosslinker, to stimulate cells for a short time period on human adipose-derived mesenchymal stem cells (hASCs) proliferation and osteogenic differentiation ability, and to determine the appropriate concentration of CaCl2for post three-dimensional biological experiments. METHODS: hASCs stimulated with or without CaCl2at various concentrations were seeded and cultured in control medium and osteogenic medium, respectively. The cell counting kit-8 (CCK8) was used to estimate the cell proliferation level of each group. After 7 days of osteogenic induction, alkaline phosphatase (ALP) staining and activity assays were performed using an ALP kit. After 14 days of osteogenic induction, alizarin red staining and quantitative detection were used to determine the calcium mineral density. The results were analyzed using analysis of variance (ANOVA) and Student-Newman-Keuls (SNK) tests for pairwise comparisons implemented in the SPSS 17.0 software. RESULTS: The CCK-8 assays showed that the differences between the control groups and experimental groups were not statistically significant, so different concentrations of CaCl2had no significant effect on hASCs proliferation. The ALP staining and activity assays showed that ALP activity first increased and then decreased as the CaCl2concentration increased. Furthermore, the differences between all the groups were statistically significant (P<0.05), except the difference between the 50 mmol/L CaCl2group and the 100 mmol/L CaCl2group, and between the osteogenetic medium(OM) group and the 200 mmol/L CaCl2group. Alizarin red staining and quantitative detection showed that the differences between all pairwise combinations of the groups were statistically significant (P<0.05). As the CaCl2 concentration increased, the calcium deposition increased, initially in the form of a scattered sheet and eventually a laminated sheet. CONCLUSION: Stimulation by a high concentration of CaCl2over a short time period can enhance hASCs osteogenic differentiation ability, but has no effect on hASCs proliferation.

Quantitative Evaluation of Tissue Surface Adaption of CAD-Designed and 3D Printed Wax Pattern of Maxillary Complete Denture.

OBJECTIVE: To quantitatively evaluate the tissue surface adaption of a maxillary complete denture wax pattern produced by CAD and 3DP. METHODS: A standard edentulous maxilla plaster cast model was used, for which a wax pattern of complete denture was designed using CAD software developed in our previous study and printed using a 3D wax printer, while another wax pattern was manufactured by the traditional manual method. The cast model and the two wax patterns were scanned in the 3D scanner as "DataModel," "DataWaxRP," and "DataWaxManual." After setting each wax pattern on the plaster cast, the whole model was scanned for registration. After registration, the deviations of tissue surface between "DataModel" and "DataWaxRP" and between "DataModel" and "DataWaxManual" were measured. The data was analyzed by paired t-test. RESULTS: For both wax patterns produced by the CAD&RP method and the manual method, scanning data of tissue surface and cast surface showed a good fit in the majority. No statistically significant (P > 0.05) difference was observed between the CAD&RP method and the manual method. CONCLUSIONS: Wax pattern of maxillary complete denture produced by the CAD&3DP method is comparable with traditional manual method in the adaption to the edentulous cast model.

[Chemical constituents of Sapium sebiferum leaves].

Chemical constituents of ethyl acetate extract of Sapium sebiferum leaves were isolated and purified by various chromatographic methods, including column chromatographies over silica gel, macroporous adsorption resin, and Sephadex LH-20, as well as preparative TLC and semi preparative HPLC. As a results, 15 compounds were separated from Sapium sebiferum leaves and their structures were examined by spectral analysis including NMR and MS data and identified as( + )-(7R,7'R,7"S,7'"S,8S,8'S,8"S,8'"S)-4", 4"'-dihydroxy-3,3',3",3',5,5'-hexamethoxy-7,9';7',9-diepoxy-4,8";4',8'"-bisoxy-8,8'-dineo-lignan-7",7"',9",9"'-tetraol(1) ,1-(4'- hydroxy-3'-methoxyphenyl)-2-[4"-(3-hydroxypropyl) -2", 6"-dimethoxyphenoxy] propane-1, 3-diol (2), Thero-2, 3-bis-(4-hydroxy-3- methoxypheyl)-3-methoxy-propanol(3) , threo-5-hydroxy-3,7-dimethoxyphenyl propane-8,9-diol (4), boropinol B (5), threo-8S-7-methoxysyringylglycerol(6), 5-hydroxymethylfurfural(7), 5-( methoxy-methyl)-1H-pyrrole-2-carbaldehyde (8), quercetin (9) , kaempferol (10), ethyl gallate(11), coniferaldehyde(12), vanillin(13), 7-hydroxy-6-methoxy-2H-1-henzopyran-2-one(14),and 1-heptacosanol (15). All compounds except for compounds 9-11,14 were separated from this plant for the first time.

Evaluation of the quantitative accuracy of 3D reconstruction of edentulous jaw models with jaw relation based on reference point system alignment.

OBJECTIVES: To apply contact measurement and reference point system (RPS) alignment techniques to establish a method for 3D reconstruction of the edentulous jaw models with centric relation and to quantitatively evaluate its accuracy. METHODS: Upper and lower edentulous jaw models were clinically prepared, 10 pairs of resin cylinders with same size were adhered to axial surfaces of upper and lower models. The occlusal bases and the upper and lower jaw models were installed in the centric relation position. Faro Edge 1.8m was used to directly obtain center points of the base surface of the cylinders (contact method). Activity 880 dental scanner was used to obtain 3D data of the cylinders and the center points were fitted (fitting method). 3 pairs of center points were used to align the virtual model to centric relation. An observation coordinate system was interactively established. The straight-line distances in the X (horizontal left/right), Y (horizontal anterior/posterior), and Z (vertical) between the remaining 7 pairs of center points derived from contact method and fitting method were measured respectively and analyzed using a paired t-test. RESULTS: The differences of the straight-line distances of the remaining 7 pairs of center points between the two methods were X: 0.074 ± 0.107 mm, Y: 0.168 ± 0.176 mm, and Z: -0.003± 0.155 mm. The results of paired t-test were X and Z: p >0.05, Y: p <0.05. CONCLUSION: By using contact measurement and the reference point system alignment technique, highly accurate reconstruction of the vertical distance and centric relation of a digital edentulous jaw model can be achieved, which meets the design and manufacturing requirements of the complete dentures. The error of horizontal anterior/posterior jaw relation was relatively large.

Controlling dental enamel-cavity ablation depth with optimized stepping parameters along the focal plane normal using a three axis, numerically controlled picosecond laser.

OBJECTIVE: The purpose of this study was to establish a depth-control method in enamel-cavity ablation by optimizing the timing of the focal-plane-normal stepping and the single-step size of a three axis, numerically controlled picosecond laser. BACKGROUND DATA: Although it has been proposed that picosecond lasers may be used to ablate dental hard tissue, the viability of such a depth-control method in enamel-cavity ablation remains uncertain. METHODS: Forty-two enamel slices with approximately level surfaces were prepared and subjected to two-dimensional ablation by a picosecond laser. The additive-pulse layer, n, was set to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70. A three-dimensional microscope was then used to measure the ablation depth, d, to obtain a quantitative function relating n and d. Six enamel slices were then subjected to three dimensional ablation to produce 10 cavities, respectively, with additive-pulse layer and single-step size set to corresponding values. The difference between the theoretical and measured values was calculated for both the cavity depth and the ablation depth of a single step. These were used to determine minimum-difference values for both the additive-pulse layer (n) and single-step size (d). RESULTS: When the additive-pulse layer and the single-step size were set 5 and 45, respectively, the depth error had a minimum of 2.25 µm, and 450 µm deep enamel cavities were produced. CONCLUSIONS: When performing three-dimensional ablating of enamel with a picosecond laser, adjusting the timing of the focal-plane-normal stepping and the single-step size allows for the control of ablation-depth error to the order of micrometers.

Method to control depth error when ablating human dentin with numerically controlled picosecond laser: a preliminary study.

A three-axis numerically controlled picosecond laser was used to ablate dentin to investigate the quantitative relationships among the number of additive pulse layers in two-dimensional scans starting from the focal plane, step size along the normal of the focal plane (focal plane normal), and ablation depth error. A method to control the ablation depth error, suitable to control stepping along the focal plane normal, was preliminarily established. Twenty-four freshly removed mandibular first molars were cut transversely along the long axis of the crown and prepared as 48 tooth sample slices with approximately flat surfaces. Forty-two slices were used in the first section. The picosecond laser was 1,064 nm in wavelength, 3 W in power, and 10 kHz in repetition frequency. For a varying number (n = 5-70) of focal plane additive pulse layers (14 groups, three repetitions each), two-dimensional scanning and ablation were performed on the dentin regions of the tooth sample slices, which were fixed on the focal plane. The ablation depth, d, was measured, and the quantitative function between n and d was established. Six slices were used in the second section. The function was used to calculate and set the timing of stepwise increments, and the single-step size along the focal plane normal was d micrometer after ablation of n layers (n = 5-50; 10 groups, six repetitions each). Each sample underwent three-dimensional scanning and ablation to produce 2 × 2-mm square cavities. The difference, e, between the measured cavity depth and theoretical value was calculated, along with the difference, e 1, between the measured average ablation depth of a single-step along the focal plane normal and theoretical value. Values of n and d corresponding to the minimum values of e and e 1, respectively, were obtained. In two-dimensional ablation, d was largest (720.61 µm) when n = 65 and smallest when n = 5 (45.00 µm). Linear regression yielded the quantitative relationship: d = 10.547 × n - 7.5465 (R (2) = 0.9796). During three-dimensional ablation, e 1 was the smallest (0.02 µm) when n = 5 and d = 45.00 µm. The depth error was 1.91 µm when 450.00-µm depth cavities were produced. When ablating dentin with a three-axis picosecond laser scan-ablation device (450 µm, 3 W, 10 kHz), the number of focal plane additive pulse layers and step size along the focal plane normal was positively correlated with the single-layer and total ablation depth errors. By adjusting the timing of stepwise increments along the focal plane normal and single-step size when ablating dentin by using the numerically controlled picosecond laser, the single-step ablation depth error could be controlled at the micrometer level.

An automatic robotic system for three-dimensional tooth crown preparation using a picosecond laser.

BACKGROUND: Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for tooth crown preparation have several drawbacks which affect the long-term success of the dental treatment. OBJECTIVE: To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) tooth ablation, and thus to realize automatic tooth crown preparation in clinical operations. METHOD: We present an automatic laser ablation system for tooth crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy crown preparation. The system consists of an end-effector, a real-time monitor and a tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth. RESULTS: The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin. CONCLUSIONS: The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for tooth crown preparation. Also, the errors of tooth shape and preparation angle are able to satisfy the requirements of clinical crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D tooth crown preparation, many research issues still need to be studied before the system can be applied to clinical operations.

Computer-aided design of tooth preparations for automated development of fixed prosthodontics.

BACKGROUND: This paper introduces a method to digitally design a virtual model of a tooth preparation of the mandibular first molar, by using the commercial three-dimensional (3D) computer-aided design software packages Geomagic and Imageware, and using the model as an input to automatic tooth preparing system. METHODS: The procedure included acquisition of 3D data from dentate casts and digital modeling of the shape of the tooth preparation components, such as the margin, occlusal surface, and axial surface. The completed model data were stored as stereolithography (STL) files, which were used in a tooth preparation system to help to plan the trajectory. Meanwhile, the required mathematical models in the design process were introduced. RESULTS: The method was used to make an individualized tooth preparation of the mandibular first molar. The entire process took 15min. DISCUSSION: Using the method presented, a straightforward 3D shape of a full crown can be obtained to meet clinical needs prior to tooth preparation.

Preliminary study on a miniature laser manipulation robotic device for tooth crown preparation.

BACKGROUND: The existing methods in dental clinical operations for hard tissue removal have several drawbacks which affect the long-term success of the dental treatment. METHODS: In this paper, we introduce a miniature robotic device called LaserBot, which can manipulate a femtosecond laser beam to drill/burr a decayed tooth to realize clinical tooth crown preparation. In order to control the 3D motion of the laser focal point on the surface of a tooth, three miniature voice-coil motors with optical grating rulers are utilized to drive the 2D pitch/yaw rotation of a vibration mirror and 1D translation of a protruding optical lens. This method can provide high-resolution control of the laser beam. In order to maintain the small size of the robot, a parallel five linkage mechanism combined with a slider-rocker mechanism is developed to realize 2D pitch/yaw rotation of the vibration mirror. RESULTS: Experiment results show that the movement range and resolution of the laser beam point can meet the requirement of typical dental operations. The size of the working end of the device that enters the mouth is 25 × 22 × 57 mm (height × width × length), which is small enough to be mounted on any tooth. The average repeatability error of the laser focal point is about 40 µm. Ablation experiments on wax-resin material and on tooth validate that a femtosecond laser can be used for tooth ablation. CONCLUSIONS: The developed robotic device achieved precise 3D motion control of a laser focal point and is small enough to be used in the narrow workspace of the oral cavity. Limitations of the prototype have been identified, and quantified specifications are identified for designing the next generation prototype.

Evaluation of the accuracy of a common regional registration method for three-dimensional reconstruction of edentulous jaw relation by a 7-axis three-dimensional measuring system.

This study was to design a method to quantitatively evaluate three-dimensional (3D) reconstruction accuracy of spatial relationship of dental models based on a 7-axis contact 3D measuring system, and to evaluate the accuracy of a common regional registration method for edentulous jaw relation reconstruction. 3D surface data of edentulous dental casts with 10 positioning cylinders and wax occlusion rims of five patients were obtained using a dental scanner. The jaw relation was reconstructed using the common regional registration in the Geomagic software. Measurements were obtained for line length, vertical distance and horizontal distance between centric points from two sources with upper jaw model base plane as a reference plane. The statistical description of measurement data was done. x ± s of line length, vertical distance and horizontal distance between the center points of each data set were 0.107 ± 0.354, 0.076 ± 0.576 and 0.108 ± 0.530 mm, respectively. Data was analyzed using the paired samples t-test and one-way analysis of variance. Paired t-test results of each patient and one-way analysis of variance for the five patients showed no significant differences (P>0.05). Using the Faro Edge system and standardized positioning cylinders, quantitative evaluation of the 3D reconstruction accuracy of edentulous jaw relation was workable. And results of common regional registration method met clinical requirements.

[Quantitative assessment on artifacts of dental restorative materials in cone beam computed tomography].

OBJECTIVE: To quantitatively evaluate the artifacts appearance of eight kinds of common dental restorative materials, such as zirconia. METHODS: For the full-crown tooth preparation of mandibular first molar, eight kinds of full-crowns, such as zirconia all-ceramic crown, glass ceramic crown, ceramage crown, Au-Pt based porcelain-fused-metal (PFM) crown, Pure Titanium PFM crown, Co-Cr PFM crown, Ni-Cr PFM crown, and Au-Pd metal crown were fabricated. And natural teeth in vitro were used as controls. These full-crown and natural teeth in vitro were mounted an ultraviolet-curable resin fixed plate. High resolution cone beam computed tomography (CBCT) was used to scan all of the crowns and natural teeth in vitro, and their DICOM data were imported into software MIMICS 10.0. Then, the number of stripes and the maximum diameters of artifacts around the full-crowns were evaluated quantitatively in two-dimensional tomography images. RESULTS: In the two-dimensional tomography images,the artifacts did not appear around the natural teeth in vitro, glass ceramic crown, and ceramage crown. But thr artifacts appeared around the zirconia all-ceramic and metal crown. The number of stripes of artifacts was five to nine per one crown. The maximum diameters of the artifacts were 2.4 to 2.6 cm and 2.2 to 2.7 cm. CONCLUSION: In the two-dimensional tomography images of CBCT, stripe-like and radical artifacts were caused around the zirconia all-ceramic crown and metal based porcelain-fused-metal crowns. These artifacts could lower the imaging quality of the full crown shape greatly. The artifact was not caused around the natural teeth in vitro, glass ceramic crown, and ceramage crown.

[Three dimensional bioprinting technology of human dental pulp cells mixtures].

OBJECTIVE: To explore the three dimensional(3D)bioprinting technology, using human dental pulp cells (hDPCs) mixture as bioink and to lay initial foundations for the application of the 3D bioprinting technology in tooth regeneration. METHODS: Imageware 11.0 computer software was used to aid the design of the 3D biological printing blueprint. Sodium alginate-gelatin hydrosol was prepared and mixed with in vitro isolated hDPCs. The mixture contained 20 g/L sodium alginate and 80 g/L gelatin with cell density of 1×10(6)/mL. The bioprinting of hDPCs mixture was carried out according to certain parameters; the 3D constructs obtained by printing were examined; the viability of hDPCs after printing by staining the constructs with calcein-AM and propidium iodide dye and scanning of laser scanning confocal microscope was evaluated. The in vitro constructs obtained by the bioprinting were cultured, and the proliferation of hDPCs in the constructs detected. RESULTS: By using Imageware 11.0 software, the 3D constructs with the grid structure composed of the accumulation of staggered cylindrical microfilament layers were obtained. According to certain parameters, the hDPCs-sodium alginate-gelatin blends were printed by the 3D bioprinting technology. The self-defined shape and dimension of 3D constructs with the cell survival rate of 87%± 2% were constructed. The hDPCs could proliferate in 3D constructs after printing. CONCLUSION: In this study, the 3D bioprinting of hDPCs mixtures was realized, thus laying initial foundations for the application of the 3D bioprinting technology in tooth regeneration.

[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.

Coordinated control and experimentation of the dental arch generator of the tooth-arrangement robot.

BACKGROUND: The traditional way of acquiring the dental arch curve form is based on manual operation, which will randomly bring numerous errors caused by human factors. The purpose of this paper is to automatically acquire the dental arch curve and implement the coordinated control of the dental arch generator of the multi-manipulator tooth-arrangement robot, which can be used in full denture manufacturing. METHODS: Based on the arc length constant theory, kinematics on dental arch generator is analyzed. The control pulse realization methods of high-resolution timing and CPU time-stamp timing are studied, and testing and comparative analysis of the control precision and stability of the two methods is carried out. Control experimentation of the dental arch generator and preliminary tooth-arrangement experimentation are performed using the multi-manipulator tooth-arrangement robot system. RESULTS: The dental arch generator can automatically generate a dental arch curve that fits a patient according to the patient's jaw arch parameters. Repeated positioning accuracy is 0.12 mm for the slipways which drive the dental arch generator. The maximum value of single point error is 1.64 mm when the arc width direction (x-axis) is 37.25 mm. The experimental results indicate that the method of control pulse realized by high-resolution timing to achieve high precision coordinated motion control of dental arch generator of tooth-arrangement robot is feasible. The error analysis results indicate that the control strategy and technical route can fulfill the requirements for motion speed and location precision. CONCLUSION: A novel system to generate the tooth arch curve has been developed. The traditional method of manually determining the dental arch may soon become obsolete in favour of the use of a robot to assist in generating a more standard tooth arch curve. The system can be used to manufacture a full denture. It will lay an important theoretical foundation for quantitative research of oral restoration, and also provide a way to standardize the manufacturing process of full denture.

[Methodology of computer-aided design of automatic artificial tooth selection for complete denture].

OBJECTIVE: 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. METHODS: 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. RESULTS: In 20 cases the concordant rate of automatic and traditional method is 70%. CONCLUSION: 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.

[Computer-aided design for occlusal rest of the removable partial denture].

OBJECTIVE: To explore the route of automatic computer-aided design for occlusal rest of the removable partial denture. METHODS: A new module for the design of occlusal rest was developed. The three-dimensional data of a partially dentate dental cast was obtained and imported into the new module. The contour of the occlusal's tissue surface was identified. Then, the tissue surface and polished surface were constructed respectively and connected to each other to form an integrated entity. RESULTS: The surface of the occlusal rest was smooth and the curvature matched that of the surrounding area of the abutment tooth. The accuracy was satisfying. CONCLUSION: Design of occlusal rest was much more convenient and time-saving using the newly developed module. The future development of special software package for the design of removable partial denture will benefit from it.

[Measurement and estimation of the root surface of single-root teeth].

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