This paper demonstrates the successful application of a novel approach to the computer aided design (CAD) of removable partial denture (RPD) framework. Firstly, we get the data of the partially edentulous cast, a mandibular Kennedy Class II, through a 3D-optical grating measuring system after corresponding pretreatment. Then, the reverse engineering software and 3D CAD software was used to design basis, big conjunction, clasp, small conjunction of the RPD framework. Finally 3D surface model of the RPD framework was created in preparation for direct manufacture using rapid prototyping (RP) methods and foundry. The result indicated that the RPD framework was fabricated successfully and the resulting frameworks provided a satisfactory fit.
Computer-Aided Design ; Dental Alloys ; Dental Casting Technique ; Dental Prosthesis Design ; methods ; Denture Design ; methods ; Denture, Partial, Removable ; Humans

OBJECTIVETo introduce a method applied in computer aided design and computer aided manufacture (CAD-CAM) of removable partial denture framework for rehabilitating edentulous arch of Kennedy Class II and found a basis for this project.

METHODSPoint cloud data of dental stone model was obtained by laser scanning. The following processes were made: drawing framework outline on the reconstructed triangle mesh model, picking up and processing its inner side data as the data of tissue surface, shelling it for 3-D model of framework, and transferring the data to rapid prototyping equipment for manufacture.

RESULTS3-D model of the removable partial denture framework was preliminarily accomplished. The resin framework used as a sacrificial pattern was manufactured with the rapid prototyping equipment. The fit between resin framework and plaster model was good.

CONCLUSIONSThis method, as an integrated procedure including data acquisition, 3-D computer modeling and fabrication by rapid prototyping, is feasible to implement CAD-CAM of removable partial denture framework.

Computer-Aided Design ; Dental Casting Technique ; Dental Prosthesis Design ; methods ; Denture, Partial, Removable ; Imaging, Three-Dimensional

OBJECTIVETo analyze the stress distribution on cast retentive clasp arms in dislodging denture, and to discuss the deepest undercuts of the second mandibular premolar (abutment) for cobalt-chromium alloy cast clasps with different widths.

METHODSThree-dimensional finite element models of the abutment with different depths of undercuts and retentive arms with different widths were set up. Dynamic displacement load (3 mm/s) was exerted on the middle of the retentive arms to analyze the stress in retentive arms while they were being removed from the abutment.

RESULTSThe peak stress in retentive arms was positively correlated to the undercuts displaced by clasp tips, and those were not obviously related to the undercuts displaced by the middle of retentive arms. When width/thickness of retentive arms was 3, the increase of peak stress of retentive arms with similar locations of clasp tips was significantly related to the increase of the arm width. The deepest undercuts of the second mandibular premolar for cobalt-chromium alloy cast retentive arms with different widths of 1.8 mm, 1.6 mm, and 1.4 mm were 0.25 mm, 0.30 mm, and 0.35 mm respectively.

CONCLUSIONSWhen width/thickness of the retentive clasp arm is fixed, the wider the arm is, the smaller depth it should be placed on the undercut of abutment. Retentive clasp arms with different widths should be placed on different depths of undercuts in order to prevent their permanent deformation.

Chromium Alloys ; Dental Casting Technique ; Dental Clasps ; Dental Prosthesis Design ; Dental Stress Analysis ; Denture Retention ; Finite Element Analysis ; Humans

OBJECTIVETo evaluate the accuracy of 3 impression materials in reproductions of simian dental arches using a 3-dimensional optical digitizer.

METHODSTwo simian dental arches were prepared as the master models. Impressions were made for stone casts using three impression materials, including alginate impression materials, C-silicone materials and Impregum-Penta polyether rubber. Five plaster replication models for each master model, as well as for each impression materials were made. The master models and the casts were digitized using a 3-dimensional optical scanner and digitizer. The images of each plaster cast and its original master model were superimposed to obtain the setting cross-section volume of the dental crown. The ratios of the plaster cast volume change and discrepancy distribution patterns were analyzed.

RESULTSCompared with the volume of the master models, the discrepancies of the plaster casts volume were -5.84%, -3.21%, and -0.63% for alginate impression materials, silicone materials and Impregum-Penta polyether rubber, respectively. The discrepancy between the master models and casts from alginate material was statistically significant (P<0.05), but not for silicone materials or Impregum-Penta polyether rubber. Maximal deviation of image fitting was located in the cervix and the gingival areas.

CONCLUSIONThe volumes of all the plaster casts from the 3 impression material are smaller than that of the master model. Impregum-Penta polyether rubber allows the most precise and silicone material the relatively accurate reproduction of the denture model, while alginate can not. The major error areas are in the dental cervix and gingival region.

Dental Casting Technique ; Dental Impression Materials ; chemistry ; Dental Impression Technique ; Dental Models ; Humans ; Imaging, Three-Dimensional ; methods

The presence of a large palatal or maxillary defect after partial or total maxillectomy for tumor, trauma or congenital deformation poses a challenge to prosthodontists, particularly when the use of an implant cannot be considered. This case report described the use of an air valve in a hollow silicone obturator to manufacture an inflatable obturator that could be extended further into undercut area to retain itself. The inflatable obturator exhibited adequate retention, stability and border sealing, thereby improving the masticatory,pronunciation and swallowing functions of patients. It may be a suitable alternative treatment option to an implant-retained obturator.
Dental Impression Technique ; Dental Prosthesis Design ; Dental Prosthesis Retention ; Denture Retention ; Denture, Complete, Upper ; Fibrous Dysplasia of Bone ; rehabilitation ; surgery ; Humans ; Male ; Maxilla ; surgery ; Orthognathic Surgical Procedures ; instrumentation ; methods ; rehabilitation ; Palatal Obturators ; Silicones ; Treatment Outcome ; Young Adult

OBJECTIVETo probe the feasibility of fabricating Ni-Cr alloy coping with laser rapid forming (LRF).

METHODSThe digitalized model of coping was designed using the technology of reverse engineering and computer aided design (CAD) based on the abutment. The Ni-Cr alloy coping was fabricated with LRF. The gaps between the internal surface of coping and the external surface of abutment were measured respectively at the locations of occlusal surface edge, midpoint of axial wall and shoulder edge. The results were compared with the reference of 120 microm which was accepted generally to analyze the adaptation by statistical means.

RESULTSWith statistical analysis of the t-test, the mean of gap width of each group, (82.60 +/- 13.58) microm for group A, (45.80 +/- 16.12) microm for group B, and (57.90 +/- 9.04) microm for group C, was less than 120 pm and the differences were statistically significant (t(A) = 8.71, t(B) = 14.56, t(C) =21.72, P <0.05).

CONCLUSIONSThe Ni-Cr alloy coping with a thickness of 0.8 mm can be fabricated with LRF successfully and the adaptation can meet the reference of 120 microm.

Chromium Alloys ; Computer-Aided Design ; Crowns ; Dental Alloys ; Dental Prosthesis Design ; Lasers ; Technology, Dental ; methods

Computer-Aided Design ; Dental Prosthesis Design ; methods ; Humans ; Oral Medicine ; methods ; Research Design ; Technology, Dental ; methods

OBJECTIVETo compare color parameters and transmittance of Y2O3 stabilized tetragonal zirconia polycrystals (Y-TZP) all-ceramic restorations using different veneering technologies.

METHODSFifteen disc specimens with 10 mm in diameter and (0.50 +/- 0.01) mm in thickness were fabricated of IPS e. max ZirCAD core material, and ZL1 IPS e. max ZirLiner was layered in 0.10 mm thickness. The specimens were divided into three groups randomly (n=5 per group). Group ZP was veneered 0.60 mm by heat-pressing; group ZC was veneered 0.60 mm by layering; group ZPC was veneered 0.30 mm by heat-pressing and then 0.30 mm by layering. Color parameters L*, a*, b* and transmittance of zirconia specimens were measured before and after veneering with ShadeEye NCC dental chromameter and spectrophotometer. Color saturation C* ab and color difference deltaE were calculated in the following formulae: C* ab = [(a*)2 + (b*)2](1/2), deltaE = [(deltaL*)2 + (deltaa*)2 + (deltab*)2](1/2) One-way analysis of variance and Turkey's multiple comparison test were used to analyze data (alpha = 0.05) by SPSS 10.0 statistic software. Color parameters of A2 shade tabs were measured, and color differences between each group and tab were calculated.

RESULTSAs to ZP,ZPC,ZC groups, the value of a* increased (-1.35 +/- 0.07, -0.64 +/- 0.06, -0.36 +/- 0.05) (P < 0.05), the value of b* decreased (27.01 +/- 0.07, 25.48 +/- 0.11, 23.28 +/- 0.25) (P < 0.05), and the value of C* ab decreased (27.04 +/- 0.08, 25.49 +/- 0.11, 23.28 +/- 0.25) (P < 0.05). L* and transmittance were maximum in ZP group (87.53 +/- 0.48, 1.64 +/- 0.03) and minimum in ZPC group (82.14 +/- 0.18, 1.47 +/- 0.01) (P < 0.05). Compared with standard A2 shade tab, the color difference of ZC group was minimum (delta = 1.04), and the color difference of ZP group was maximum (deltaE = 4.86).

CONCLUSIONSY-TZP all-ceramic restoration veneered by heat-pressing was the most transparent and lightest; while veneered by both heat-pressing and layering, the restoration was worst in translucency and the least light. The color of zirconia all-ceramic restoration veneered by layering was the most similar to standard shade tab, and the color difference was minimum.

Dental Porcelain ; chemistry ; Dental Prosthesis Design ; Hot Temperature ; Materials Testing ; Prosthesis Coloring ; Technology, Dental ; methods ; Zirconium ; chemistry

Current biomechanical research of dental implants focuses on the mechanical damage and enhancement mechanism of the implant-abutment interface as well as how to obtain better mechanical strength and longer fatigue life of dental implants. The mechanical properties of implants can be comprehensively evaluated by strain gauge analysis, photo elastic stress analysis, digital image correlation, finite element analysis, implant bone bonding strength test, and measurement of mechanical properties. Finite element analysis is the most common method for evaluating stress distribution in dental implants, and static pressure and fatigue tests are commonly used in mechanical strength test. This article reviews biomechanical research methods and evaluation indices of dental implants. Results provide methodology guidelines in the field of biomechanics by introducing principles, ranges of application, advantages, and limitations, thereby benefitting researchers in selecting suitable methods. The influencing factors of the experimental results are presented and discussed to provide implant design ideas for researchers.
Biomechanical Phenomena ; Computer Simulation ; Consensus ; Dental Abutments ; Dental Implant-Abutment Design ; Dental Implants ; Dental Prosthesis Design ; Dental Stress Analysis ; Finite Element Analysis ; Stress, Mechanical

The objective of this study was to investigate the mechanical characteristics of implant-abutment interface design in a dental , using nonlinear finite element analysis (FEA) method. This finite element simulation study was applied on three commonly used commercial dental implant systems: model I, the reduced-diameter 3i implant system (West Palm Beach, FL, USA) with a hex and a 12-point double internal hexagonal connection; model II, the Semados implant system (Bego, Bremen, Germany) with combination of a conical (450 taper) and internal hexagonal connection; and model III, the Brinemark implant system (Nobel Biocare, Gothenburg,Sweden) with external hexagonal connection. In simulation, a force of 170 N with 45" oblique to the longitudinal axis of the implant was loaded to the top surface of the abutment. It has been found from the strength and stiffness analysis that the 3i implant system has the lowest maximum von Mises stress, principal stress and displacement while the Br Bnemark implant system has the highest. It was concluded from our preliminary study using nonlinear FEA that the reduced-diameter 3i implant system with a hex and a 12-point double internal hexagonal connection had a better stress distribution, and produced a smaller displacement than the other two implant systems.
Computer Simulation ; Computer-Aided Design ; Dental Implant-Abutment Design ; statistics & numerical data ; Dental Prosthesis Design ; Dental Stress Analysis ; methods ; Finite Element Analysis ; Humans ; Stress, Mechanical