• 대한치과교정학회지
• /
• 제36권3호
• /
• pp.207-217
• /
• 2006

사회 문화적 발달과 함께 심미적 요구가 증가되면서 교정 환자 수의 증가와 함께 교정 치료 중의 심미성에 대한 요구도 늘어나고 있다. 치료 중 심미성을 증진시키기 위한 목적으로 세라믹 브라켓이 개발되어 널리 사용되고 있으나 세라믹 자체의 취성(brittleness), 대합치의 마모뿐만 아니라, 임상적으로 높은 마찰 저항이 그 문제점으로 지적되고 있다. 본 연구는 세라믹 브라켓의 마찰 저항을 알아보고 그 개선방안을 찾는데 지침이 되고자 하는 목적으로 시행하였다. 연구 재료로는 마찰 저항을 줄이기 위해 금속 슬롯이 삽입된 다결정 세라믹 브라켓과 금속 슬롯이 삽우되지 않은 단결정 세라믹 브라켓과 금속 브라켓을 이용하였으며, $.019{\times}.025$ 스테인리스 와이어를 브라켓 슬롯에 대해 $0^{\circ},\;10^{\circ}$의 각도를 부여하여 만능시험기상에서 이동시켜 그때의 정적, 동적 마찰력을 측정하였다. 연구 결과, 전체적인 평균 마찰력은 금속 브라켓, 금속 슬롯이 삽입된 다결정 세라믹 브라켓, 단결정 세라믹 브라켓 순으로 증가하였다. 브라켓 슬롯과 와이어 사이의 각도가 $0^{\circ}$일 때가 $10^{\circ}$일 때에 비해서 낮은 마찰 저항을 보였으며, 브라켓 슬롯과 와이어 사이의 각도가 $10^{\circ}$일 때 단결정 세라믹 브라켓의 동적, 정적 마찰 저항은 금속 브라켓이나 금속 슬롯이 삽입된 다결정 세라믹 브라켓에 비해 유의성 있게 크게 나타났다 (p<0.05). 본 연구를 통해서 금속 브라켓에 비해 세라믹 브라켓, 특히 금속 슬롯이 삽입되지 않은 단결정 세라믹 브라켓의 마찰 저항이 높은 것을 확인할 수 있었으며, 브라켓 슬롯과 와이어간의 각도가 증가하면 마찰 저항도 커지는 것을 확인할 수 있었다. 따라서 마찰력을 줄이기 위한 세라믹 브라켓의 개발과 함께 교정 치료 시 과도한 치관 경사를 막음으로써 마찰 저항을 줄이고 심미성을 유지하면서 치료의 효율을 높이도록 해야할 것이다.

• 대한치과보철학회지
• /
• 제32권2호
• /
• pp.195-211
• /
• 1994

The purpose of this study was to evaluate the fracture resistance of the four kinds of dental porcelains for the all-ceramic crown(Vita In-Ceram, Vita Hi-Ceram, IPS-Empress, Vitadur-N) and one kind for the metal-ceramic non(Vita VMK 68) was used as the control group. In order to determine the fracture resistance, the hi-axial flexure strength was measured at a crosshead speed of 0.5mm/min, and the Vickers hadrness was measured at an indentation load of 1kg for 20 seconds. The results obtained were summarized as follows ; 1. The maximum Weibull modulus of 24.61 for Vitadur-N and the minimum one of 852 for IPS-Empress were observed ; the maximum characteristic strength of 353.26MPa for Vita In-Ceram and the minimum that of 63.20MPa for Vitadur-N were also observed. 2. The maximum mean bi-axial flexure strength of 339.12MPa for Vita In-Ceram and thd minimum one of 61.99MPa for Vitadur-N were calculated. Results of the Scheffe test indicated that the statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vitadur-N. 3. The maximum mean hardness of $980.55kg/mm^2$ for Vita VMK 68 appeared. Results of the Scheffe test indicated that statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vita VMK 68.

• The Journal of Advanced Prosthodontics
• /
• 제5권2호
• /
• pp.92-97
• /
• 2013

PURPOSE. All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS. Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS. The mean fracture strengths were as follows: $54.9{\pm}15.6$ N for the Lava CAD/CAM zirconia crowns and $87.0{\pm}16.0$ N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION. The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.

• 대한치과보철학회지
• /
• 제42권5호
• /
• pp.514-523
• /
• 2004

Statement of problem: All-ceramic restorations have been advocated for superior esthetics. Various post and core systems have been used to improve the strength of damaged teeth, but it is unclear whether they affect the final shade of finished all-ceramic restorations. Purpose: The influence of different types of post and core systems on light transmission through all-ceramic crowns was assessed by spectrophotometric analysis. Also the masking effect of different thickness of ceramic ingot was evaluated. Material and Methods : Forty-five sample disks (15mm in diameter) at several thickness(1.0, 1.5, 2.0mm) and value(shade 100, 200, 300) were made in heat pressed ceramic(IPS-Empress). Background specimens simulating gold-alloy cast posts(Type III casting gold alloy), metal posts(Ni-Cr casting alloy) and ceramic posts(CosmoPost) were fabrica-ted. Resin composite(Z250, A3 shade) was used as a tooth substrate reference. For each combination, the change in color was measured with a spectrophotometer. Readings were performed for 2 conditions (1) ability of ceramic to mask the core in relation to its thickness(1.0, 1.5, or 2.0mm) ; (2) influence of post and core types on the final color of the ceramic. Data were recorded according to the CIE $L^*a^*b^*$ systems and color difference($\Delta$E) was calculated. Results: 100 shade ingot: when ceramic thickness was 1.0mm, $\Delta$E value for ceramic post larger than 1 but $\Delta$E value for metal and gold post was larger than 2. For ceramic thickness of 1.5mm, only $\Delta$E value for metal was larger than 2, and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 2. 200 shade ingot: when ceramic thickness was 1.0mm, $\Delta$E value for ceramic post was smaller than 1 but $\Delta$E value for metal and gold post was larger than 2. For ceramic thickness of 1.5 mm, only the $\Delta$E value for metal was larger than 2, and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 1. 300 shade ingot: when ceramic thickness was 1.0mm, only $\Delta$E value for metal was larger than 2 and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 1.5mm, $\Delta$E values for all specimens was smaller than 1. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 1. Conclusion: The final esthetic result of the IPS-Empress glass-ceramic restoration was not affected by the presence of different core materials when the thickness was more than 2.0 mm. When ceramic thickness decreases to 1.5mm, it is advised to take the substrate aspects into consideration. If the ceramic thickness is less than 1.0mm, using the tooth color matched substrate is strongly recommended.

• The Journal of Advanced Prosthodontics
• /
• 제8권2호
• /
• pp.131-136
• /
• 2016

PURPOSE. The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS. Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant ($3.7mm{\times}10mm$) with a straight abutment, and the other model was designed as a 30-degree inclined implant ($3.7mm{\times}10mm$) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS. The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION. The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS. These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

• 대한치과보철학회지
• /
• 제20권1호
• /
• pp.7-17
• /
• 1982

In order to investigate the internal adaptability and cytotoxicity for porcelain fused to metal Ni-Cr alloy, two commercial alloys (Generic Gold-R alloy, Aalba Dent- Valloy)were employed and compared with new developed beryllium free Ni-Cr alloy (KIST-K alloy). After cementation of each crown to abutment die before and after ceramic bonding respectively, dies were mounted to epoxy resin and the internal space was measured between crown and die of each point on sagittal section. The results were as follows: 1) The results show that the space between the crown and the die was largest at the incisal edge, followed by the shoulder or the bevel and chamfer. The least was to be in the axial surface. 2) There were no significant difference in the adaptability of the compared alloys. 3) On day 2 of the experiment the cell multiplication was slightly inhibited by R and K alloys. However, observations taken at day 4 and 7 showed normal cell multiplication process compared to control group. 4) Alloy V exhibited the most severe cell toxicity among the alloys tested on day 2. By day 4 and 7 it showed a decrease level in toxicity, however it did not exhibit normal cell growth as compared to control group.

• 대한심미치과학회지
• /
• 제7권1호
• /
• pp.28-31
• /
• 1998

It is difficult to make an artificial central incisor similar to natural tooth. All ceramic porcelain of this patient is not esthetic, and there is gingival recession due to ill-fitted margin. She has class II division 1 occlusion, so upper central incisors is labioversed. Upper light central incisor is well-characterized but the yellowish brown color of dentin is appeared on the incisal third portion of the central incisor. At 1st trial, the shape and characterization of restoration is good but shade is little dark. At 2nd trial, the shape is better but patient complained on black triangle of mid interdental space, so mesiocervical portion of restoration is overcontoured to compromise the black triangle. Completed metal ceramic crown is in harmony with the adjacent central incisor in aspect of shape, shade, and characterization.

• 대한치과기공학회지
• /
• 제29권2호
• /
• pp.119-128
• /
• 2007

Although there are many different ways that restorations can be made, it can be said that the biocompatibility of abutment and crown is very important in this experiment. When placed in the actual oral cavity, the differences were obvious. Compared to In-ceram Aluminium, the structure that is obtained after firing reveals a particularly homogeneous distribution of the crystal and glass phase. The In-ceram aluminium system had many problems, such as having weak tensile strength, and having low bonding strength due to the shrinking that occurs after firing. Because of the opaque finish of the metal frame, the two may look similar from the outside, but it is evident that there are differences between using a metal frame and In-ceram. VITA VM9 has been designed as a special ceramic featuring a fine structure or stabilized Zro2 substructures, and so the VITA VM9 excels in its light refraction and reflection behavior, which is similar to natural teeth. It also has outstanding chemical balance, which presents advantages such as considerably reduced accumulation of plaque on the ceramic surface.? This ultimately results in easier care and cleaning for the patient.

• 대한치과보철학회지
• /
• 제38권5호
• /
• pp.606-617
• /
• 2000

The purpose of this study was to measure the marginal fidelities and the fracture strength of IPS Empress $2^{(R)}\;and\;In-Ceram^{(R)}$ ceramic crowns. After constructed of 12 experimental dies for each group, ceramic crowns were fabricated on the metal master dies prepared on the maxillary right premolar Marginal gaps were measured on the specimen between the margin of each crown and finish-ing line of the metal master die by using stereo-microscope($SZ-ST^{(R)}$ Olympus, Japan) and all specimens were cemented on the metal master die with Bistite $II^{(R)}$ (Tokuyama soda Co, LTD., Japan) resin cement. Finally marginal gaps were measured again. To measure of the fracture strength, buccal incline on the functional cusp of specimens were loaded until the catastrophic failure occurred by using the AGS-1000 $D^{(R)}$(Shimadzu, Japan). The result of marginal fidelities and fracture strength were statistically analyzed with the SPSS version 8.0 programs. The results of this study were as follows : 1. No significant difference was found in the mean marginal fidelities and fracture strength between the IPS Empress $2^{(R)}\;and\;In-Ceram^{(R)}$. 2. In comparison of marginal fidelities between before and after cementation, there was significant difference(P<0.05). The IPS Empress 2 system was shown in this study that had good marginal fidelities and fracture strength compared to In-Ceram ceramics. Although this system was acceptable to clinical applications, the system still has to be considered long-term researches about marginal fidelities and fracture strength due to the lack of data about the clinical researches.

• The Journal of Advanced Prosthodontics
• /
• 제11권1호
• /
• pp.48-54
• /
• 2019

PURPOSE. The aim of the present randomized controlled study was to compare prefabricated all-ceramic, anatomically shaped healing abutments followed by all-ceramic abutments and all-ceramic crowns and prefabricated standard-shaped (round-diameter) titanium healing abutments followed by final titanium abutments restored with porcelain-fused-to-metal (PFM) implant crowns in the premolar and molar regions. MATERIALS AND METHODS. Forty-two patients received single implants restored either by all-ceramic restorations (test group, healing abutment, final abutment, and crown all made of zirconia) or conventional titanium-based restorations. Immediately after prosthetic incorporation and after 12 months of loading, implant survival, technical complications, bone loss, sulcus fluid flow rate (SFFR) as well as plaque index (PI) and implant stability (Periotest) were analyzed clinically and radiologically. RESULTS. After 12 months of loading, an implant and prosthetic survival rate of 100% was observed. Minor prosthetic complications such as chipping of ceramic veneering occurred in both groups. No statistical significant differences were observed between both groups with only a minimum of bone loss, SFFR, and PI. CONCLUSION. All-ceramic implant prostheses including a prefabricated anatomically shaped healing abutment achieved comparable results to titanium-based restorations in the posterior region. However, observational results indicate a benefit as shaping the peri-implant soft-tissue with successive provisional devices and subsequent compression of the soft tissue can be avoided.