Abstract Objectives In this study, the authors attempted to develop a photoconductive method for measuring light transmission through a crown restoration to the root dentin; metal–ceramic crowns with ...four coping designs (metal collar, and metal framework ending 0, 1, and 2 mm coronal to the axiogingival line angle) and two all-ceramic crowns (Empress II and In-Ceram Alumina) were compared. Methods According to pre-registered templates, 36 crowns were fabricated for an extracted central incisor. A cadmium sulfide (CdS) photoconductive cell was secured onto the root of a tooth, which was fixed in a light box. The validity and reliability of the experimental design were verified, and the impedance of the cell was recorded when the crowns were placed on the prepared tooth with or without try-in pastes under a constant luminance. Results A significant correlation ( r = −0.99, p < 0.001) was found between the light intensity and impedance of the CdS cell, and a 1.15% coefficient of variation between repeated measurements was observed. In this study, Empress II crowns had the smallest impedance, indicating that they provided the best light transmission. Conventional metal–ceramic crowns had the least light transmission, which was significantly improved by reducing the metal collar ( p < 0.05). The framework of metal–ceramic crowns which ended 2 mm coronal to the axiogingival line angle showed as much light transmission as the In-Ceram crowns. The impedance increased when try-in pastes were employed in all test groups. Significance The photoconductive method was proven to be a reliable technique for measuring the light transmitted through restorations into the adjacent tissue.
코발트-크롬 합금으로 제작된 금속-도재관의 적합도 평가 김재홍; Jae Hong Kim; 김원수 ...
Han'guk Ch'iwisaeng Hakhoe chi,
04/2013, Letnik:
13, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Objectives: The purpose of this in vitro study was to evaluate the effect of firing cycles on the marginal and internal fit of metal ceramic crown. Methods: Ten same cases of stone models (abutment ...teeth 11) were manufactured. Ten cobalt-chrome cores were made per each models and the marginal and internal fit was evaluated through a silicone replica technique. The marginal and internal fit of specimens was measured twice. The first measurement was done after manufacturing cobalt-chrome alloy core and the second measurement was done after porcelain firing. T-test of paired sample for statistical analysis was executed with SPSS 12.0K for Windows (α=0.05). Results: Mean(SD) marginal and internal fit were 77.1(23.3) ㎛ for the cobalt-chrome alloy core group and 84.4(21.9) ㎛ for the metal-ceramic crown group. They were statistically significant differences between groups for marginal and internal fit (p<.05). Conclusions: All metal ceramic crowns showed marginal and internal fit ranged within the current clinical recommendations.
The objective of the present study was to evaluate the effect of five different metal framework designs on the fracture resistance of the metal-ceramic restorations.
For the purpose of this study, ...the central incisor tooth was prepared, and the metal analogue of it and a master die were fabricated. The counter die with the 0.5 mm clearance was used for fabricating the wax patterns for the metal copings. The metal copings with five different metal framework designs were designed from Group 1 to 5. Group 1 with the metal collar, Group 2, 3, 4 and 5 with 0 mm, 0.5 mm, 1 mm and 1.5 mm cervical metal reduction respectively were fabricated. Total of fifty metal ceramic crown samples were fabricated. The fracture resistance was evaluated with the Universal Testing Machine (Instron model No 1011, UK). The basic data was subjected to statistical analysis by ANOVA and Student's t-test.
Results revealed that the fracture resistance ranged from 651.2 to 993.6 N/m(2). Group 1 showed the maximum and Group 5 showed the least value.
The maximum load required to fracture the test specimens even in the groups without the metal collar was found to be exceeding the occlusal forces. Therefore, the metal frameworks with 0.5 mm and 1 mm short of the finish line are recommended for anterior metal ceramic restoration having adequate fracture resistance.
Background: Cervical end preparation design is an important procedure in fixed partial denture. If the cervical end preparation design is inadequate, dental plaque will easily be formed and this may ...indicate the beginning of periodontal disease. Purpose: This study was aimed to analyze the effect of cervical end preparation design on collarless metal ceramic crown towards the decrease of bacterium colony number. Methods: This study was quasi-experimental study applying pre and post test on a control group involving 48 subjects with shoulder, bevel shoulder, and deep chamfer cervical end preparation. The bacterium colonies were examined on the 1st, 7th, and 21st days after the insertion of collarless metal ceramic crown. Results: The study showed that bacterium colony increased significantly in deep chamfer and bevel shoulder preparation design between the treatment group and the control group (p<0.05). In shoulder preparation there was not significant different between the treatment group and the control group (p>0.05). Conclusion: Compared to the bevel shoulder and deep chamfer, shoulder design is the best design for collarless metal ceramic crown restoration.Latar belakang: Desain preparasi tepi servikal merupakan suatu tahap yang sangat menentukan dalam pembuatan gigi tiruan cekat. Apabila desain preparasi tepi servikal tidak adekuat dapat menyebabkan pembentukan plak gigi pada daerah tersebut. Keadaan ini merupakan tahap awal terjadinya penyakit periodontal. Tujuan: Untuk menganalisis pengaruh desain preparasi tepi servikal yang dibuat pada mahkota collarless metal ceramic untuk mengurangi jumlah bakterium koloni. Metode: Penelitian ini adalah penelitian eksperimental semu dengan metode pre and post test dan kelompok kontrol terhadap 48 subyek penelitian. Dilakukan preparasi gigi dan pembuatan akhiran preparasi tepi servikal shoulder, bevel shoulder, dan deep chamfer pada subyek penelitian. Pemeriksaan koloni bakteri dilakukan pada hari ke-1, 7, dan 21 setelah pemasangan mahkota collarless metal ceramic. Hasil: Menunjukkan bahwa terjadi, peningkatan jumlah koloni bakteri yang bermakna antara kelompok perlakuan dengan kelompok kontrol (p<0,05) pada desain preparasi deep chamfer dan bevel shoulder. Sedangkan pada desain preparasi tepi servikal shoulder tidak ada perbedaan yang bermakna antara kelompok perlakuan dengan kelompok kontrol (p>0,05). Kesimpulan: Desain shoulder adalah desain tepi preparasi yang terbaik bagi mahkota collarless metal ceramic dibandingkan bevel shoulder dan deep chamfer.
A male patient presented for maxillary and mandibular complete-arch prostheses. A total of eight all-ceramic restorations, eight metal-ceramic crowns, and four metal-ceramic fixed partial dentures ...were placed. The restorations were examined for marginal integrity, anatomic form, surface, and color for a period of 12 months. All restorations were in function at the end of the evaluation period. There was no adverse event. No substantial difference between the all-ceramic onlays and the metal-ceramic crowns was apparent. The all-ceramic restorations exhibited the least plaque growth. Bleeding on probing was minimal at both restoration types. The marginal integrity of the all-ceramic restorations was considered to be nearly as precise as that of the metal-ceramic crowns.
Purpose The purpose of this investigation was to determine the mean marginal discrepancy of metal‐ceramic crowns fabricated with gold cylinders and cemented on implant abutments. These discrepancies ...were then compared with those measured previously for implant‐supported ceramic crowns.
Materials and Methods Fifteen Nobel BioCare CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. Marginal discrepancies were determined for gold cylinders, gold cylinders plus ceramic alloy (metal frameworks), completed metal‐ceramic crowns, and cemented metal‐ceramic crowns using a stereomicroscope equipped with a video camera linked to a computer. A Hotelling's T2 test (p .05) was used to evaluate potential differences in mean marginal discrepancies among groups.
Results The mean marginal discrepancies were: 1) gold cylinders, 7.56 ± 2.73 μm; 2) metal frameworks, 6.21 ± 1.34 μm; 3) metal‐ceramic crowns, 11.06 ± 3.21 μm; and 4) zinc‐phosphate cemented crowns, 31.47 ± 6.65 μm. No significant difference between gold cylinders and metal frameworks was found. Mean marginal discrepancies for metal‐ceramic crowns were significantly greater than discrepancies for cast gold cylinders. Cemented‐crown mean marginal discrepancy was significantly greater than all other means.
Conclusions Cemented metal‐ceramic crowns fabricated using proprietary gold cylinders exhibited well‐fitting margins (31.47 μm).
This study has revealed the effects of collarless metal-ceramic crowns on the dog gingival tissues at one and three months after setting, and compared the effects with those of metal-ceramic crowns ...by means of light-and scanning electron microscopy. In addition, the morphology of the marginal surface of these two types of crowns was also examined before setting. The results obtained were summarized as follows : 1. It seemed to be necessary to use the correct powder of margin (C.P.M.) for getting a good adapted margin of collarless metal-ceramic crowns made by the non-matrix method. 2. The average thickness of cement layers was 66.2μm in metal-ceramic crowns and 73.2μm in collarless metal-ceramic crowns. 3. Similar inflammatory changes in gingival tissues were observed in both cases of these two crown types by light- and scanning electron microscopy, even when the brushing treatment was performed during experimental periods. 4. Plaque observed in the area of the crown margin had a tendency to accumulate in the boundary between metal collar and porcelain in metal-ceramic crowns, and in the rounded marginal surface in collarless metal-ceramic crowns. 5. When margins of these two types of crowns were observed scanning electron microscopically before setting, a number of pits were found on the surface closely associated with metal collar in case of metal-ceramic crowns. In collarless metal-ceramic crowns, on the other hand, the surface of C.P.M. showed rough appearances. 6. Roughness of C.P.M. surface could be reformed smoothly by reglazing after scraping its superficial layer with sandpaper- or white points.
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