OBJECTIVETo study the influence of cervical settling method on marginal accuracy of wax patters.

METHODS24 wax patterns were made on the standard cast specimens and round capsules of which twelve patters were made with the method of cervical settling (experiment group), twelve patters were made with the method of wax dripping (control group). Marginal accuracy of patterns were measured before sublation, sublation half an hour and twenty-four hours.

RESULTSThe results revealed that marginal accuracy had significant difference between the cervical settling methods and wax dripping methods (P < 0.05). There was significant difference between the cervical settling methods measured after half an hour and twenty-four hours (P < 0.01). There was also significant difference between the wax dripping methods measured after half an hour and twenty-four hours (P < 0.01).

CONCLUSIONWax patterns with the method of cervical settling can improve marginal accuracy of patterns. The marginal accuracy of wax patters are influenced by the existing time.

Dental Casting Technique ; Dental Marginal Adaptation

PURPOSE: The anterior region is a challenge for most clinicians to achieve optimal esthetics with dental implants. The provisional crown is a key factor in the success of obtaining pink esthetics around restorations with single implants, by soft tissue and inter-proximal papilla shaping. Provisional abutments bring additional costs and make the treatment more expensive. Since one of the aims of the clinician is to reduce costs and find more economic ways to raise patient satisfaction, this paper describes a practical method for chair-side fabrication of non-occlusal loaded provisional crowns used by the authors for several years successfully. METHODS: Twenty two patients (9 males, 13 females; mean age, 36,72 years) with one missing anterior tooth were treated by using the presented method. Metal definitive abutments instead of provisional abutments were used and provisional crowns were fabricated on the definitive abutments for all of the patients. The marginal fit was finished on a laboratory analogue and temporarily cemented to the abutments. The marginal adaptation of the crowns was evaluated radiographically. RESULTS: The patients were all satisfied with the final appearance and no complications occurred until the implants were loaded with permanent restorations. CONCLUSIONS: The use of the definitive abutments for provisional crowns instead of provisional abutments reduces the costs and the same results can be obtained.
Crowns ; Dental Abutments ; Dental Implants ; Dental Marginal Adaptation ; Dental Prosthesis ; Esthetics ; Humans ; Male ; Patient Satisfaction ; Tooth

OBJECTIVETo investigate the effect of three different impression methods on the marginal fit of all-ceramic crowns. The three methods include scanning silicone rubber impression, cast models, and direct optical impression.

METHODSThe polymethyl methacrylate (PMMA) material of a mandibular first molar in standard model was prepared with 16 models duplicated. The all-ceramic crowns were prepared using three different impression methods. Accurate impressions were made using silicone rubber, and the cast models were obtained. The PMMA models, silicone rubber impressions, and cast models were scanned, and digital models of three groups were obtained to produce 48 zirconia all-ceramic crowns with computer aided design/computer aided manufacture. The marginal fit of these groups was measured by silicone rubber gap impression. Statistical analysis was performed with SPSS 17.0 software.

RESULTSThe marginal fit of direct optical impression groups, silicone rubber impression groups, cast model groups was (69.18±9.47), (81.04±10.88), (84.42±9.96) µm. A significant difference was observed in the marginal fit of the direct optical impression groups and the other groups (P<0.05). No statistically significant difference was observed in the marginal fit of the silicone rubber impression groups and the cast model groups (P>0.05).

CONCLUSIONAll marginal measurement sites are clinically acceptable by the three different impression scanning methods. The silicone rubber impression scanning method can be used for all-ceramic restorations.

Computer-Aided Design ; Crowns ; Dental Marginal Adaptation ; Dental Porcelain ; Dental Prosthesis Design ; Zirconium

OBJECTIVETo evaluate the accuracy of Cercon CAD/CAM system and the influence of different spacer thickness and spacer coverage area on the internal and marginal fit of the copings.

METHODSA stainless steel master model of first molar was replicated. After scanning, designs of copings were made with different spacer thickness and spacer coverage area. There were six groups: S10C70, S10C90, S30C70, S30C90, S60C70, S60C90. Measurements of the adaptation were performed with silicone impression material and an image analysis system.

RESULTSUnivariate ANOVA showed that variation in the internal fit of copings was related to measuring location, spacer thickness and spacer coverage area. There was significant difference between different spacer coverage area groups, and significant difference between spacer thickness 10 microm and 30 microm groups, 10 microm and 60 microm groups, no significant difference between spacer thickness 30 microm and 60 microm groups. Mean marginal fit was (27.7+/-7.6) microm. There was statistically significant difference between both mesial, distal marginal gaps and both buccal, lingual marginal gaps. No difference between mesial and distal marginal gaps, and between buccal and lingual marginal gaps.

CONCLUSIONThe accuracy by Cercon CAD/CAM system for the marginal and internal fit of zirconium dioxide copings is well within the range of clinical acceptability. Spacer thickness and spacer coverage area have statistically significant influence on the internal fit.

Computer-Aided Design ; Crowns ; Dental Marginal Adaptation ; Dental Prosthesis Design ; Humans ; Molar ; Zirconium

PURPOSE: The purpose of this study is to see what impact the heat and press-on-metal technique has on the marginal fit of metal ceramic crown. MATERIALS AND METHODS: Prior to the experiment, 4 metal master models were prepared. Each model has margin of chamfer, margin of heavy chamfer, margin of shoulder with bevel and margin of shoulder (collarless). Additionally, 10 crowns were made for each margin, total of 40 crowns. Marginal discrepancy between the master model and crown was observed at x100 microscopic magnification in two states; in coping state and upon completion of making metal ceramic crown. Data analysis was performed using paired t-test along with one-way ANOVA and Duncan multiple comparison test. RESULTS: After analyzing mean and standard deviation of marginal discrepancy, it was confirmed that marginal discrepancies were within the clinical permitted range for all states; in coping state and upon completion of making metal ceramic crown. For the chamfer group, a significant increase in marginal discrepancy upon completion of making metal ceramic crown was observed compared to the heavy chamfer group. Also, a marginal discrepancy of porcelain margin in shoulder group was significantly less than the marginal discrepancy of metal margin in chamfer and shoulder group. CONCLUSION: From the test result, one can conclude that marginal fit of metal ceramic crown built with heat and press-on-metal technique is not significantly different from marginal fit of metal ceramic crown built with traditional technique. And along with efficiency of this system, heat and press-on-metal technique is considered in clinic.
Ceramics ; Crowns* ; Dental Marginal Adaptation ; Dental Porcelain ; Hot Temperature* ; Shoulder ; Statistics as Topic

OBJECTIVETo investigate the marginal adaptation of crowns fabricated by selective laser melting (SLM) and wax-lost-casting method, so as to provide an experimental basis for clinic.

METHODSCo-Cr alloy full crown were fabricated by SLM and wax-lost-casting for 24 samples in each group. All crowns were cemented with zinc phosphate cement and cut along longitudinal axis by line cutting machine. The gap between crown tissue surface and die was measured by 6-point measuring method with scanning electron microscope (SEM). The marginal adaptation of crowns fabricated by SLM and wax-lost-casting were compared statistically.

RESULTSThe gap between SLM crowns were (36.51 ± 2.94), (49.36 ± 3.31), (56.48 ± 3.35), (42.20 ± 3.60) µm, and wax-lost-casting crowns were (68.86 ± 5.41), (58.86 ± 6.10), (70.62 ± 5.79), (69.90 ± 6.00) µm. There were significant difference between two groups (P < 0.05).

CONCLUSIONSCo-Cr alloy full crown fabricated by wax-lost-casting method and SLM method provide acceptable marginal adaptation in clinic, and the marginal adaptation of SLM is better than that of wax-lost-casting method.

Chromium Alloys ; Computer-Aided Design ; Crowns ; Dental Casting Technique ; Dental Marginal Adaptation ; Dental Prosthesis Design ; Freezing ; Lasers

OBJECTIVEThe purpose of this study was to compare the clinical application and effect of two temporary restorations materials: composite and self-cured acrylic resin.

METHODS153 composite temporary crowns (and bridges) placed in 44 patients and 144 self-cured acrylic resin temporary crowns (and bridges) placed in 49 patients were evaluated according to the California Dental Association's (CDA) criteria and questionnaire.

RESULTSIt showed that composite temporary crowns (and bridges) had better surface smoothness, marginal integrity and anatomic form than self-cured acrylic resin temporary crowns (and bridges). In the 49 patients with self-cured acrylic resin temporary crowns (and bridges), 67% and 88% of them complained of food impaction and mouth odor, while only 2% and 30% in the 44 patients with composite temporary crowns (and bridges) had the same complaint.

CONCLUSIONBetween the two temporary restoration materials, composite is better than self-cured acrylic resin.

Acrylic Resins ; Composite Resins ; Crowns ; Dental Bonding ; Dental Marginal Adaptation ; Dental Restoration, Temporary ; methods ; Humans ; Surveys and Questionnaires

OBJECTIVETo evaluate the adaptation of different lithium disilicate glass-ceramic crown and whether different fabrication processes affect the adaptation of crowns.

METHODSThirty epoxy dies crowns were divided into 3 groups. They were cemented to domestic lithium disilicate glass-ceramic crowns in Group A, to IPS e.max CAD crowns in Group B and to IPS e.max Press crowns in Group C respectively. All crowns were cut by cutting machine. A confocal laser scanning microscope was used to measure the gap between crown tissue surface and die.

RESULTSThere were significant differences in the three groups of measurement points(P<0.05). Within the groups, specimens in group A showed in the lowest marginal fit([46.8±9.1] μm). Those in group B showed the lowest shoulder suitability([59.3±7.9] μm), axial plane([50.5±3.6] μm) and occlusal surface([87.6±11.6 μm]. Those in group C demonstrated the lowest axial plane angle[(84.4±10.1) μm]. In addition to the axial plane angle, the CAD/CAM system exhibited good accuracy of fit.

CONCLUSIONSThe three groups of lithium disilicate glass-ceramic crowns appeared to have clinically acceptable fit.

Ceramics ; Computer-Aided Design ; Crowns ; Dental Marginal Adaptation ; Dental Porcelain ; Dental Prosthesis Design ; methods ; Humans ; Microscopy, Confocal ; Surface Properties

OBJECTIVETo investigate the effect of camera control devices of Cerec 2 on the fit of CAD/CAM all-ceramic copyings of posterior tooth.

METHODS24 all-ceramic copyings were made by Cerec 2 with camera control devices and that without camera control devices. Copyings were embed and sectioned, then SEM and image analyzer was used to measure the space between the copyings and dies at the marginal opening, the axial wall, and the occlusal adaptation at the measurement locations.

RESULTSThe marginal fit at buccal space of copyings with camera control devices group was smaller than that without camera control devices group (P < 0.05). The internal fit of of copyings had statistically significant difference at mesio-axial, disto-axial, bucco-axial, bucco-occlusal, linguo-occlusal and disto-occlusal space between camera control device group and without camera control devices group (P < 0.05). There was no statistical difference on the marginal fit and internal fit of copyings between Vita MK II and porous alumina oxide (P < 0.05).

CONCLUSIONThe Cerec 2 with camera control devices reduced effectively the inaccuracy of inner space of copyings which contributed from the technical errors of the operator, and provided well-proportioned space for adhesive. Both the fit of copyings made of Vita MK II and porous alumina oxide satisfied the clinical demand.

Aluminum Oxide ; Ceramics ; Computer-Aided Design ; Dental Marginal Adaptation ; Dental Porcelain ; Dental Prosthesis Design ; Humans ; Molar ; Tooth Preparation, Prosthodontic

OBJECTIVETo 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.

METHODSThirty 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.

RESULTSThe 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.

CONCLUSIONSThe design and machining precision of this domestic CAD/CAM system is at the same level of those comparable foreign products.

China ; Computer-Aided Design ; Crowns ; standards ; Dental Marginal Adaptation ; Humans ; Software