Clinical trials in zirconia: a systematic review.
TL;DR: Based on the limited number of short-term in vivo studies, zirconia appears to be suitable for the fabrication of single crowns, and fixed partial dentures and implant abutments providing strict protocols during the manufacturing and delivery process are adhered to.
Abstract: Zirconia is unique in its polymorphic crystalline makeup, reported to be sensitive to manufacturing and handling processes, and there is debate about which processing method is least harmful to the final product. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. Chipping of the veneering porcelain is reported as a common problem and has been labelled as its main clinical setback. The objective of this systematic review is to report on the clinical success of zirconia-based restorations fabricated by both milling processes, in regard to framework fractures and veneering porcelain chipping. A comprehensive review of the literature was completed for in vivo trials on zirconia restorations in MEDLINE and PubMed between 1950 and 2009. A manual hand search of relevant dental journals was also completed. Seventeen clinical trials involving zirconia-based restorations were found, 13 were conducted on fixed partial dentures, two on single crowns and two on zirconia implant abutments, of which 11 were based on soft-milled zirconia and six on hard-milled zirconia. Chipping of the veneering porcelain was a common occurrence, and framework fracture was only observed in soft-milled zirconia. Based on the limited number of short-term in vivo studies, zirconia appears to be suitable for the fabrication of single crowns, and fixed partial dentures and implant abutments providing strict protocols during the manufacturing and delivery process are adhered to. Further long-term prospective studies are necessary to establish the best manufacturing process for zirconia-based restorations.
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TL;DR: The outcomes of the meta-analysis demonstrated high implant survival rates for both the single tooth implants and the respective single crowns after 5 and 10 years, however, technical, biological, and aesthetic complications were frequent.
Abstract: Objective
To assess the 5-year survival of implant-supported single crowns (SCs) and to describe the incidence of biological, technical, and aesthetic complications. The focused question was: What is the survival rate of implants supporting single crowns and implant-supported crowns with a mean follow-up of 5 years and to which extent do biological, technical, and aesthetic complications occur?
Methods
A Medline search (2006–2011) was performed for clinical studies focusing on implant-supported SCs with a mean follow-up of at least 5 years. The search was complemented by an additional hand search and the inclusion of 24 studies from a previous systematic review (Jung et al. 2008a). Survival and complication rates were analyzed using random-effects Poisson's regression models to obtain summary estimates of 5- and 10-year proportions.
Results
Forty-six studies derived from an initial search count of 1083 titles and the complementary publications from the previous systematic review (Jung et al. 2008a) were selected and the data were extracted. Based on the meta-analysis, survival of implants supporting SCs at 5 years amounted to 97.2% (95% CI: 96.3–97.9%), and at 10 years amounted to 95.2% (95% CI: 91.8–97.2%). The survival of implant-supported SCs was 96.3% (95% CI: 94.2–97.6%) after 5 years and 89.4% (95% CI: 82.8–93.6%) after 10 years. For biological complications, a 5-year cumulative soft tissue complication rate of 7.1% (95% CI: 4.4–11.3%) and a cumulative complication rate for implants with bone loss >2 mm of 5.2% (95% CI: 3.1–8.6%) were calculated. Technical complications reached a cumulative incidence of 8.8% (95% CI: 5.1–15.0%) for screw-loosening, 4.1% (95% CI: 2.2–7.5%) for loss of retention, and 3.5% (95% CI: 2.4–5.2%) for fracture of the veneering material after 5 years. The cumulative 5-year aesthetic complication rate amounted to 7.1% (95% CI: 3.6–13.6%).
Conclusions
The outcomes of the meta-analysis demonstrated high implant survival rates for both the single tooth implants and the respective single crowns after 5 and 10 years. However, technical, biological, and aesthetic complications were frequent.
762 citations
TL;DR: It is demonstrated that highly polished zirconia yielded lower antagonist wear compared with porcelains, and combined application of silica coating and/or silane coupler, and 10-methacryloyloxydecyl dihydrogen phosphate is currently one of the most reliable bonding systems for zirConia.
529 citations
Cites background from "Clinical trials in zirconia: a syst..."
...Zirconia-based ceramics, especially Y-TZP, are clinically available as an alternative to metal frameworks for FDPs [16,17]....
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TL;DR: The use of zirconia frameworks for long-span fixed partial dentures or for implant-supported restorations is currently under evaluation and further in vivo, long-term clinical studies will be needed to provide scientific evidence for drawing solid guidelines as discussed by the authors.
403 citations
Cites background or methods from "Clinical trials in zirconia: a syst..."
...Loss of retention has been reported to be another possible echnical complication with all kinds of luting agents, particlarly in FPDs; anyway, in the zirconia clinical trials, all of the ebonded restorations were eventually recemented successully [96]....
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...None of the cited clinical trials took bruxism into account, more often such a parafunction figuring among the exclusion criteria: consequently, since they were not considered in any clinical investigation, parafunctional activities should be regarded as a potential limitation for zirconia-based restorations [96]....
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...In the hard machining technique, on the other hand, the 3Y-TZP blocks are previously densely sintered through a process called “hot isostatic pressing”: at high temperatures (1400–1500 ◦C) and high pressure in inert gas environment, very hard, dense and homogeneous blocks of fully sintered zirconia are produced [96], out of which the frameworks are shaped to the proper, desired form and to the right, final dimension by using powerful and resistant milling machines with diamond abrasives....
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...[96] Al-Amleh B, Lyons K, Swain M....
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TL;DR: An overview of the current knowledge of monolithic and bilayer dental all-ceramic systems, addressing composition and processing mechanisms, laboratory and clinical performance, and possible future trends for all-cersamic materials is explored.
255 citations
TL;DR: Although the translucency improvement by La2O3 doping was less effective than for introducing a substantial amount of cubic zirconia, this strategy was able to maintain the mechanical properties of typical 3Y-TZP ceramics.
245 citations
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TL;DR: This review introduces concepts and background from the ceramics engineering literature regarding metastable zirconia ceramic to establish a context for understanding current and emerging zIRconia-based dental ceramic technology.
925 citations