Chipping behaviour of all-ceramic crowns with zirconia framework and CAD/CAM manufactured veneer

Objectives

The aim of this in vitro study was to assess the ultimate load to failure of zirconia based crowns veneered with CAD/CAM manufactured ceramic.

Methods

32 identical, anatoform zirconia (Sirona inCoris ZI, mono L F1) frameworks (thickness 0.6 mm) were constructed (Sirona inLab 3.80). Afterwards, 16 crowns were completed using a CAD/CAM manufactured lithium disilicate ceramic veneer (IPS e.max CAD, Ivoclar Vivadent). The remaining 16 frames were veneered using conventional manual layering technique. For the CAD/CAM manufactured veneers, the connection between framework and veneer was accomplished via a glass fusion ceramics. Before fracture tests, half of the specimens underwent thermocycling and chewing simulation (1.2 million chewing cycles, force magnitude F_max = 108 N). To further investigate the new technique, finite element computations were carried out on the basis of the original geometry.

Results

Nearly all (87.5%) conventionally veneered crowns failed already during chewing simulation, whereas crowns with CAD/CAM manufactured veneers were non-sensitive to artificial ageing. Crowns veneered with lithium disilicate ceramic displayed ultimate loads to failure of about 1600 N.

Conclusion

The CAD/CAM production of veneers for restorations with zirconia framework is a promising way to reduce failures originating from material fatigue.     

Correlation between accuracy of crowns fabricated using CAD/CAM and elastic deformation of CAD/CAM materials

Full crowns were fabricated from three different materials (titanium, ceramic, and resin composite) at different rest diameters using a dental CAD/CAM system, and then their marginal discrepancy measured. The deflection of cylindrical specimens at 500 gf was measured using the same materials and diameters as for the accuracy measurement. Marginal discrepancy decreased as rest diameter increased, and at the same rest diameter the titanium crown had lower marginal discrepancy than ceramic and composite crowns. A significant correlation was found between marginal discrepancy of the crowns and deflection of the materials. This correlation was aptly expressed in the regression equation, MG = 4.54DF+53.9, where MG represented marginal discrepancy and DF represented deflection. This equation can be used as a good measure for new materials which have different modulus of elasticity.     

In vitro failure of crowns produced by two CAD/CAM systems

Previous laboratory studies have demonstrated satisfactory fracture resistance of all-ceramic crowns placed using a resin-composite luting material and a dentine bonding system. This study investigated the fracture resistance of teeth restored using CAD/CAM technology, namely, Zirconia Based crowns and Cerec produced feldspathic porcelain crowns, both luted with a self adhesive resin luting material (RelyX Unicem Clicker 3M ESPE). Standardized preparations were carried out on two groups often sound, unrestored, maxillary premolar teeth. Ceramic crowns were constructed to have a thickness of 2mm at their midline fissure. Compressive fracture resistance was determined for each group using a Universal Testing Machine. The failure modes were also examined visually and interpreted according to a chosen scale. Mean Compressive fracture resistance of 746 (147)N and 1630 (175)N were recorded for the Cerec and Lava groups respectively; differences were statistically significant (p < 0.001). The fracture resistance of teeth restored with Lava crowns is significantly greater than a similar group of teeth restored with Cerec crowns.     

Implant-supported overdenture manufactured using CAD/CAM techniques to achieve horizontal path insertion between the primary and secondary structure: A clinical case report

This report describes the case of an edentulous patient with an atrophic maxilla and severe class III malocclusion. Prosthetic rehabilitation was performed using CAD/CAM techniques for manufacturing an implant-supported overdenture with horizontal insertion. A vestibulo-lingual insertion overdenture is a precision prosthesis with a fixation system affording a good fit between the primary and secondary structure. Both structures exhibit passive horizontal adjustment. This treatment option requires the same number of implants as implant-supported fixed dentures. The horizontal assembly system prevents the prosthesis from loosening or moving in response to axial and non-axial forces. The technique was used to rehabilitate a patient presenting an atrophic upper maxilla, with the insertion of 8 implants. No complications were reported at follow-up 3, 6 and 12 months after fitting of the prosthesis. This system offers solutions to the clinical and laboratory complications associated with hybrid prostheses, concealing emergence of the chimneys and improving implant-prosthesis hygiene.     

CAD/CAM to fabricate ceramic implant abutments and crowns: a preliminary in vitro study

Background:  This study evaluated the feasibility of fabricating implant abutments and crowns from pre-sintered feldspathic porcelain blocks using the chair-side CAD/CAM, CEREC3D^® system.
Methods:  Thirty-two implant analogues were divided into two groups. In the control group, prefabricated machined anatomical titanium (Ti) abutments were screw-retained to the analogues. In the test group, machined feldspathic porcelain abutments were cemented on prefabricated machined Ti links and screw-retained to the implant analogues. These feldspathic porcelain abutments were fabricated out of pre-sintered feldspathic porcelain blocks as duplicates of the abutments in the control group using the CAD/CAM, CEREC3D^® system. Thirty-two feldspathic porcelain crowns, also fabricated out of pre-sintered ceramic blocks, were then cemented with resin cement on all the abutments in both groups. All samples were subsequently subjected to fracture strength testing under static load. An unpaired t-test was used to compare fracture load values between the two groups.
Results:  The test group using feldspathic porcelain abutments and crowns showed statistically significant higher mean fracture strength than the control group with the Ti abutments and feldspathic porcelain crowns.
Conclusions:  This preliminary study showed that the chair-side CAD/CAM technology can be utilized to fabricate customized ceramic abutments with their associated ceramic crowns using pre-sintered feldspathic porcelain blocks.     

CAD/CAM锆瓷冠在后牙种植修复中的临床应用

目的：探讨CAD/CAM锆瓷冠在后牙种植体修复的临床应用。方法：选取ITI种植术后病例30例,采用CAD/CAM全瓷冠修复,3年后复查,对修复效果进行评价。结果：经6-36个月随访观察发现1例饰瓷脱落外,其余修复体均正常：全冠的形状、颜色与邻牙相协调,全冠修复体未见有明显磨耗,冠颈缘与基台密合度良好,近远中邻接面接触关系正常,龈周组织正常,未见有破损与脱落,修复成功率为97%,效果满意。结论：CAD/CAM锆瓷冠在后牙种植修复中的临床应用效果良好,值得推广。     

In vitro study on marginal and internal fit of CAD/CAM all-ceramic crowns

The purpose of this study was to evaluate the marginal and internal fit of all-ceramic crowns fabricated using the Decsy CAD/CAM system. A master die of maxillary first premolar was measured, and experimental crowns were fabricated. Four conditions were established by combining two convergence angles (4 degrees and 12 degrees) of the abutment with two different luting space settings (15 microm and 55 microm). The results showed that the experimental crowns had a marginal gap of 42 to 56 microm. When the luting space setting was 15 microm, the internal gap was 85-88 microm; when the setting was 55 microm, the internal gap was 126-138 microm. The marginal gap for each experimental crown met the clinically acceptable criterion.     

Chairside CAD/CAM: an overview of restorative material options

A number of categories of materials are available for chairside CAD/CAM restorations that have demonstrated predictability and longevity. These materials include esthetic and high-strength ceramics, composite resins for both final and temporary restorations, and newer nanoceramics that offer ease of handling and a glossy surface finish. Each category of materials has unique features designed for specific clinical applications. This article will examine currently available materials designed for chairside CAD/CAM restorations and the various outcomes that are possible with this technologically advanced process.     

CAD/CAM氧化锆及Empress全瓷冠修复三年临床效果比较

目的:比较CAD/CAM氧化锆及Empress全瓷冠修复3年的临床效果。方法:选择350例患者共838个全冠修复体(其中CAD/CAM氧化锆全冠428颗、Empress铸瓷全冠410颗),平均观察期36.2±5月,随访检查基牙和修复体情况,分别对两组全瓷冠的存留率和修复成功率进行统计学分析。结果:观察期内共有41颗全瓷冠(19颗为氧化锆,22颗为Empress铸瓷)完全失败,需重新制作。氧化锆全瓷冠和Empress铸瓷全冠的存留率分别为95.1%和95.8%,成功率分别为90.7%和91.2%,其差异均无统计学意义。结论:CAD/CAM氧化锆和Empres铸瓷全冠均能满足临床需要,有较好的修复效果。     

Retention and surface changes of zirconia primary crowns with secondary crowns of different materials

Objectives

To evaluate zirconia as a substitute for gold alloy in primary crowns facing secondary crowns manufactured with different materials, in terms of long-term retention force changes, wear, and phase transformation was aimed.

Materials and Methods

A total of 12 groups, each containing six samples, consisting of gold alloy primary crown-electroformed gold secondary crowns (AA), zirconia primary crown-electroformed gold secondary crowns (ZA) and zirconia primary crown-casted non-precious alloy secondary crowns (ZC) with conus angles of 0°, 2°, 4°, and 6° were evaluated. Samples were subjected to 10,000 insertion–separation cycles in artificial saliva and retention force was measured. X-ray diffraction and scanning electron microscope analysis were performed on the sample surfaces.

Results

The highest retention forces were obtained from ZC-0° group (72.09–71.26 N) and the lowest were obtained from ZA-4° (12.73–19.44 N) and ZA-6° (5.36–19.73 N) groups in the beginning and after 10,000 cycles, respectively. Retention force increased as the conus angle decreased. The monoclinic phase ratio of the zirconia primary crowns decreased after the experiments. No wear was observed in zirconia primary crowns except for the ZC-0° and ZC-2° groups. The use of zirconia primary crowns resulted in a less excursive retention force.

Conclusions

A more predictable and less excursive retention force can be obtained using a hard and rigid primary crown material like zirconia.

Clinical Relevance

Despite a lack of knowledge about the aging of zirconia without a veneer layer in the oral environment, zirconia primary crowns are more advantageous in terms of retention force development and wear.     

The aesthetics of all-ceramic veneered and monolithic CAD/CAM crowns

The aim of this study was to examine whether crowns fabricated from machinable blocks would achieve acceptable aesthetics and whether these could compete with the aesthetics of restorations obtained by individual layering technique. Fourteen patients, who were to receive single anterior crown restorations, participated in this study. For each person two kinds of crowns were provided: one crown was made with the Cergogold system. The second one was produced in a Cerec machine and was additionally stained. Three independent examiners assessed the aesthetic appearance of crowns fabricated to match each subject's anterior shade. A scale of 1-6 was used to assess the aesthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 marking the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analysed with the Wilcoxon signed rank test (P相似文献   

Machining accuracy of crowns by CAD/CAM system using TCP/IP: influence of restorative material and scanning condition

The purpose of this study was to determine the optimal condition for fabricating accurate crowns efficiently using an internet-based CAD/CAM system. The influences of three different CAD/CAM restorative materials (titanium, porcelain, and composite resin) and three different step-over scanning distances (0.01 mm, 0.11 mm, and 0.21 mm) were evaluated, and their interactive effects were carefully examined. Several points on the inner and outer surfaces of machined crowns - as well as height - were measured. These measurements were then compared with the original models, from which machining accuracy was obtained. At all measuring points, the inner surface of all crowns was machined larger than the die model, whereas the cervical area of porcelain crown was machined smaller than the crown model. Results of this study revealed that a step-over distance of 0.11 mm was an optimal scanning condition, taking into consideration the interactive effects of scanning time required, data volume, and machining accuracy.     

Retention of veneered stainless steel crowns on replicated typodont primary incisors: an in vitro study

PURPOSE: The purpose of this in vitro study was to determine the effect of crimping and cementation on retention of veneered stainless steel crowns. METHODS: One hundred twenty crowns, 90 from 3 commercially available brands of veneered stainless steel crowns (Dura Crown, Kinder Krown, and NuSmile Primary Crown) and 30 (plain) Unitek stainless steel crowns were assessed for retention. An orthodontic wire was soldered perpendicular to the incisal edge of the crowns; the crowns were fitted to acrylic replicas of ideal crown preparations and were divided equally into 3 test groups: group 1--crowns were crimped only (no cement used); group 2--crowns were cemented only; and group 3--crowns were crimped and cemented to the acrylic replicas. An Instron machine recorded the amount of force necessary to dislodge the crowns and the results were statistically analyzed using 2-way ANOVA and Tukey honestly significant difference (HSD) test. RESULTS: Group 3 was statistically more retentive than groups 1 and 2. Group 2 was statistically more retentive than group 1 (P < .001). In group 1, Unitek crowns were statistically more retentive than the veneered crowns (P < .05). In group 2, NuSmile crowns showed statistically less retention values than all other crowns (P < .05). In group 3,Kinder Krown crowns showed statistically better retention rates than all other brands (P < .05). CONCLUSIONS: Significantly higher retention values were obtained for all brands tested when crimping and cement were combined. The crowns with veneer facings were significantly more retentive than the nonveneered ones when cement and crimping were combined.     

Fracture load of composite resin and feldspathic all-ceramic CAD/CAM crowns

STATEMENT OF PROBLEM: Various machinable materials are currently used with computer-aided design/computer-assisted manufacturing (CAD/CAM) technologies for the chairside fabrication of restorations. However, properties of these new machinable materials, such as fracture load, wear, marginal deterioration, and color stability, should be investigated in vitro under replicated clinical conditions prior to time-consuming clinical studies. PURPOSE: This study investigated the effect of cyclic loading fatigue and different luting agents under wet conditions on the fracture load of CAD/CAM machined composite resin and all-ceramic crowns. MATERIALS AND METHODS: Ninety-six intact human maxillary premolars were prepared for composite resin and all-ceramic crowns with the following preparation criteria: 6-degree axial taper, 1.5-mm shoulder finish line placed 0.5 mm occlusal to the cemento-enamel junction, 1.5-mm axial reduction, 2-mm occlusal reduction, and 5-mm occluso-gingival height. Sixteen unprepared premolars served as controls. Forty-eight all-ceramic crowns (Vita Mark II) and 48 millable composite resin crowns (MZ100 Block) were fabricated using a CAD/CAM system (Cerec 3). Three luting agents-RelyX ARC (RX), GC Fuji CEM (FC), and zinc phosphate cement (ZP)-were used for cementation (n = 16). After 1-week storage in water, half of the specimens (n=8) in each subgroup were cyclically loaded and thermal cycled under wet conditions for 600,000 masticatory cycles and 3500 thermal cycles (58 degrees C/4 degrees C; dwell time, 60 seconds) in a masticatory simulator; the other half (n = 8) were fractured without cyclic loading. All specimens were loaded in a universal testing machine with a compressive load (N) applied along the long axis of the specimen at a crosshead speed of 1 mm/min until fracture. Fracture loads (N) were recorded for each specimen. Three-way analysis of variance was used to detect the effects of the experimental factors (crown material, luting agent, and loading conditions) on the fracture load. The comparison with the unprepared natural teeth as controls was done by means of t tests (alpha=.05). RESULTS: Analysis of variance revealed a statistically significant influence of the luting agent and the cyclic loading (P < .001), whereas the crown material had no significant influence. Cyclic loading fatigue significantly decreased the mean fracture load of test groups independent of the 3 luting agents used: MZ100/ZP, 827.1 to 552.5 N; MZ100/FC, 914.7 to 706.2 N; MZ100/RX, 955.9 to 724.4 N; Vita/ZP, 772.3 to 571.5 N; Vita/FC, 923.6 to 721.1 N; and Vita/RX, 929.1 to 752.7 N. However, there was no significant difference in the mean fracture load of control specimens before and after cyclic loading (1140.1 N and 1066.2 N, respectively). Adhesive luting agents RelyX ARC and GC Fuji CEM increased fracture load significantly compared to zinc phosphate cement. CONCLUSIONS: Cyclic loading fatigue significantly reduced the fracture loads of composite resin and all-ceramic crowns, whereas adhesive cementation significantly increased the fracture loads.     

Marginal and internal fit of Cerec 3 CAD/CAM all-ceramic crowns

PURPOSE: The purpose of this study was to examine the effects of the occlusal convergence angle of the abutment and the computer's luting space setting on the marginal and internal fit of Cerec 3 computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns. MATERIALS AND METHODS: Mandibular second premolar all-ceramic crowns were fabricated for nine different conditions using Cerec 3: all combinations of abutments with three different total occlusal convergence angles (4, 8, and 12 degrees) with three different luting space settings (10, 30, and 50 microm). The completed crowns were seated on the abutments, and the marginal gaps were measured. The internal gaps between the crowns and abutments were also measured, using test-fit silicone paste. RESULTS: When the luting space was set to 10 microm, the marginal gaps of the crowns were greater than when it was set to 30 or 50 microm. When the luting space was set to 30 or 50 microm, the marginal gaps ranged from 53 to 67 microm and were not affected by the occlusal convergence angle of the abutment. The internal gaps were within a range of 116 to 162 microm and tended to decrease as the occlusal convergence angle of the abutment decreased. CONCLUSION: When the luting space was set to 30 microm, crowns with a good fit could be fabricated on the Cerec 3 system, regardless of the occlusal convergence angle of the abutment.     

Fatigue resistance and microleakage of CAD/CAM ceramic and composite molar crowns

Purpose: The aim of this study was to determine effect of compressive cyclic loading on fatigue resistance and microleakage of monolithic CAD/CAM molar ceramic and composite crowns. Materials and Methods: Thirty‐two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using a special paralleling device (Parallel‐A‐Prep). Sixteen feldspathic ceramic crowns (VITABLOCS Mark II) (VMII) and 16 resin‐composite crowns (Paradigm‐MZ100 blocks) (PMZ) were milled using a CEREC‐3D machine. Eight crowns of each group were cemented to their respective teeth using self‐etching resin cement (Panavia‐F‐2.0) (PAN), and eight were cemented using self‐adhesive resin cement (RelyX‐Unicem‐Clicker) (RXU). Following storage for 1 week in water, specimens were subjected to uniaxial compressive cyclic loading in an Instron testing machine at 12 Hz for 1,000,000 cycles. Load was applied at the central fossa, and the cycle range was 60–600 N. Specimens were then subjected to microleakage testing. Data were statistically analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests. Results: All composite crowns survived compressive cyclic loading without fracture, while three ceramic crowns from the subgroup cemented with RXU developed surface cracks at the center of occlusal surfaces, extending laterally. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other three subgroups (p < 0.05). Conclusions: After 1,000,000 cycles of compressive cyclic loading, PMZ composite molar crowns were more fatigue‐resistant than VMII ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05).     

Fatigue behavior and crack initiation of CAD/CAM resin composite molar crowns

Objective

The aim of this study was to evaluate long-term fatigue behavior using an in vitro step-stress accelerated life test (SSALT), and to determine the crack initiation point using in silico finite element analysis for computer-aided designed and manufactured (CAD/CAM) molar crowns fabricated from three commercial CAD/CAM resin composite blocks: Cerasmart (CS; GC, Tokyo, Japan), Katana Avencia Block (KA; Kuraray Noritake Dental, Niigata, Japan), and Shofu Block HC (HC; Shofu, Kyoto, Japan).

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

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 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 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.     

CAD/CAM氧化锆全瓷冠联合玻璃纤维桩的临床应用研究

目的探讨CAD/CAM氧化锆全瓷冠修复体的临床应用及其美学性、稳定性和生物相容性。方法应用计算机辅助设计和计算机辅助制作技术,对25例患者的40颗牙齿采用氧化锆全瓷联合纤维桩修复,采用金铂烤瓷冠修复为对照组,随访患者12个月,对两组修复体色彩的口内适应性、冠体有无破损和脱落及修复前、后牙周指标、局部龈沟液水平和龈沟液中碱性磷酸酶水平进行监测。结果氧化锆全瓷修复体的色彩更接近口内自然环境,无破损及脱落,患者满意率达到100%,而对照组满意率仅为40%。两组修复体治疗后一年内牙周情况比较,差异具有统计学意义(P<0.05)。氧化锆全瓷组修复后同修复前龈沟液量及龈沟液中碱性磷酸酶水平相比差别均无统计学意义(P>0.05),而金铂烤瓷冠组同等情况比较差异具有统计学意义(P<0.01)。结论通过CAD/CAM技术完成的氧化锆全瓷冠联合纤维桩修复增加了冠修复的美学效果,其稳定性及生物相容性均佳,值得在临床上推广。