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Objective:To assess the impact of reducing the mesh density on the overall volume and trueness of single-crown restora-tions.Methods:15 single-crown restorations were included,and their mesh density in 3D software was simplified by 75%,50%,25%,10%and 5%respectively.The overal volume,file size and mesh edge length of the restorations with different reduction levels were compared.Deviation analysis was conducted by curving clipping the area of the shoulder,tissue surface(except for the shoulder)and occlusal surface of the restorations and compared with those of the corresponding regions in the non-simplified restorations.Trueness was assessed using the root mean square(RMS)values for the volume and trueness of different areas.Results:Reducing the mesh den-sity did not significantly affect the overal volume of the single-crown restorations(P>0.05),but it had a significant impact on the file size(P<0.001),mesh edge length(P<0.001)and the trueness of the shoulder(P<0.001),tissue surface(except for the shoulder)(P<0.001)and occlusal surface(P<0.001)areas.Conclusion:Reducing the mesh density had little impact on the overall volume of the restorations but significantly affected their trueness.
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Objective:To retrospectively evaluate the clinical outcomes of autonomous dental implant robot(ADIR)assisted implant surgery in 1-year follow-up.Methods:20 patients with tooth missing underwent implantation surgery by ADIR were incuded.The plat-form deviation,apex deviation and angular deviation of the implants were analyzed.The marginal bone height and peri-implant soft tis-sue health were measured and observed immediately,6 months and 12 months after the restoration.Results:The platform deviation,apex deviation and angular deviation of 20 implants at the 3 follow-up examinations were(0.34±0.11)mm,(0.34±0.15)mm and(0.82°±0.38°),respectively.There was no significant difference in the accuracy of different implant diameter and length(P>0.05).During the follow-up period,all implants had successful osseointegration,stable marginal bone height,and acceptable peri-implant soft tissue condition.Conclusion:The 1-year follow-up indicates that ADIR can achieve promising clinical performance.Long-term follow-up studies are still necessary for verification.
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Objective:To explore the differences of CBCT image gray value of commonly used dental materials.Methods:CBCT was used to scan 36 kinds of commonly dental material blocks,the tomographic image gray value was measured by Mimics software.Re-sults:CBCT image gray values of the materials were obtained.There were differences of the gray values of the materials not only among the different types,but also among the different varieties of the same materials.Conclusion:The discipline of CBCT image gray value differences of commonly used dental materials provided an objective basis for the establishment of 3D digital model including dental ma-terials.
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Objective:To evaluate the impression accuracy of different impression methods for flabby ridge.Methods:5 patients with flabby ridge were included.Conventional technique,perforation technique and window opening technique were performed to make im-pressions and then final models were prepared.The optical models of the flabby ridge area were obtained both in patients'mouths and on the master casts by intraoral optical scanner.Data handling and computations were made by using 3D inspection and metrology soft-ware,regarding SD,Mean +and Mean -,with subsequent analysis.Results:The 3D deviation of the models obtained by conventional technique was the biggest,that obtained by window opening technique was the least.Conclusion:Window opening technique can de-crease the deformation of flabby ridge impression.
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Objective:To explore the method of the establishment of edentulous mandible All-on-4 implant photoelastic model with various distally tilted implants by computer-aided design(CAD).Methods:The edentulous mandible specimen was scanned by CT. Three-dimensional models of the mandible consisting of implant location were reconstructed and edited with Mimics and Geomagic Stu-dio software.Each of the four models had four implant sockets in the interforaminal area.In the first model,the bilateral distal im-plants were placed vertically.In the other models,the posterior implants were respectively inclined by 1 5°,30°and 45°distally.The four models were manufactured by RP and then the All-on-4 photoelastic models were made by traditional ways.Results:The ob-tained ethoxyline resin models featured bright surface,homogeneous structure,faintly yellowish,high optical sensibility,precision im-plants location and with no natural stress.The model offered a good experimental basis for the stress measurement.Conclusion:The method of fabricating ethoxyline resin models by CAD is reproducible,which simplifies the operating process.
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Objective:To evaluate of the feasibility of low-dose CT(LDCT)in the reconstruction of three-dimensional(3D)model of maxillofacial hard and soft tissues.Methods:Lightspeed 16-slice spiral CT scanner was used to scan one adult cadaveric head specimens with conventional parameters(280 mA)and low dose parameters(200,150,100,50,35,25,15 and 5 mA)respectively;the 3D model of the hard and soft tissues were reconstructed with Mimics 10.01 software,and 3D comparison were carried on with Geomagic 11.0 software.A comparison of the surface morphology of the hard and soft tissues of the 3D models with different scanning parameters was made.Results:With the reduction of the tube current,the model surface became rough gradually.Compared with the 280 mA scan results,the model surface produced by 35 mA scanning was still fairing,when the dose fell to less than 25 mA,the model surface became rough and the exact shape of the model could not be recognized.The same results of model surface were pro-duced after registration.Conclusion:The low-dose (35 mA)CT can be used to reconstruct 3D model of the maxillofacial hard and soft tissues.
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Objective:To provide anatomic image data for ossointegrated implant for patients with nasal defect. Methods: 100 cases of (50 males, 50 females) 3D spiral CT images of normal bone of skull were measured with mimics 10.01 software. Results: The minimum distance between the root tips of central incisor and the anterior nasal floor was 13.03 in males and 11.06 in females. The minimum distance between the root tips of lateral incisor and the anterior nasal floor was 15.95 mm in males and 13.04 mm in females, the minimum thickness of palatine process 6mm inferior to piriform aperture was 9.96 mm, the minimum thickness of alveolus 6mm inferior to piriform aperture was 11.57 mm in males and 10.61 mm in females, the thickness of glabella adjoin to frontal sinus was 3.57mm. Conclusion: The lateral incisor region is an optimal one for nasal implants 4-8 mm in length. The inclined direction can either be forward or backward. When the vertical bone depth is not enough, horizontal placement of the implants in the inferior region of piriform should be considered. 4-8 mm implants is suitable in this region. The glabella region is not optimal but an alternative option for nasal implants.
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Both with the advantages of fixed and removable dentures,the attachment prostheses is an important component of prosthodontics.At present,the resin base for the removable part of attachment denture was majorly made with traditional methods such as cartoning,resin-filling,heat treatment.But the produced fixed part of attachment denture was easy to be deformed or broken off during such processes.Here a method were introduced to produce resin base with injection moulding,which could avoid the occurrence of the mistakes of traditional methods and simplify the process.
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Objective: To develop titanium posted keeper removable magnetic attachment and to decrease its influence on magnetic resonance imaging(MRI). Methods: Pre fabricated soft magnetic alloy pin cap keeper(PSAPK), casting non precious alloycoping keeper(CNPAK), casting precious alloy coping keeper(CPACK), titanium post keeper(TPK) and titanium post(TP) were prepared and applied on the maxilla of a volunteer, MRI was taken and measured. Results: ①The attachments producing artifacts in MRI from the biggest to the smallest were listed in following rank: PSAPK, CNPAK, CPACK, TPK and TP. ②After removing the keeper from titanium post keeper, the post had no artifact on MRI. ③The artifact was the smallest taken with SE sequence. Conclusion: Titanium post keeper is an effective way to solve the artifact problem and will bring benefits to the patients who need MRI examination of head.
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Objective:To investigate the three-dimensional accuracy of four impression materials for fixed denture:silicone(OX),hydrocolloid(HT) and two kinds of alginate impression(FC and ZS).Methods:Ten plaster replication models for each impression materials were made on the same metal master cast respectively, vertical and horizontal dimensions between landmarks on the masters and plaster casts were measured with an optical microscope. ANOVA was used to compare the measurements among the materials.Results:The difference between the masters and casts in horizontal distances measured on ZS produced models was bigger than that on other impression material produced ones (P<0.01) and beyond clinical requirment.The difference between the masters and casts in all measured dimensions on OX produced models was the smallest.Conclusion:Alginate paste is not accurate enough for denture model,while silicone is.The hydrocolloid material is relatively accurate.
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Objective:To study the stress distribution of Magsoft (cushion type) and Magnedisk magnetic attachment. Methods: 2 overdentures were prepared on each of 5 edentulous jaw models. The overdentures were pared and retained with Magnedisk and Magsoft magnetic attachments respectively.Photoelastic analysis was used to study the stress distribution for the implanted complete overdentures. Results: Under the same load, around the implants, the stress under the overdentures retained with Magsoft was lower than that with Magnedisk. Compared with Magnedisk, the stress around the abutments under the overdenture retained with Magsoft were distributed in a more even manner. Conclusion: Magsoft magnetic attachment has better biomechanical characteristic than Magnedisk and can distribute stress more evenly throughout the whole supporting structure for its special cushioned design.
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Objective:To investigate the stress distribution of the edentulous maxilla with unilateral maxillary defect after implant rehabilitation under occlusal loads.Methods:Three dimensional finite element model of the edentulous maxilla with unilateral maxillary defect was build.The stress distribution of the edentulous maxilla under occlusal loads with computer simulated implant rehabilitation was investigated.Results:Regardless of load manner,the stress of the bone around 1 were high when just healthy side implanted,but the stress reduced after implantantion in health side combined with the implantation in zygoma in defect side.Conclusion:Implantation in health side combined with that in zygoma in defect side can reduce the stress of the bone around the implant.