Abstract
The digital workflow and the application of Computer-Aided Manufacturing (CAM) to prosthodontics present the clinician with the possibility of adopting new materials that confer several advantages. Especially in the case of zirconia, these innovations have profoundly changed daily practice. This paper compares the satisfaction and perception of patients who received implant-supported single crowns (SC) and fixed partial dentures (FPD) made from zirconia, either monolithic or partially veneered, after 3 years of follow-up; the success and survival rate of these restorations were also measured. Forty patients, who had been previously treated with implant-supported SC or FPD, either monolithic or partially veneered, and submitted to a yearly maintenance program, were recalled 3 years after their treatment and requested to complete an 8-question questionnaire regarding their perceptions of the treatment. Any mechanical or biological complication that had occurred from the time of delivery was also recorded. Patients that experienced ≥1 complication were less likely to be prone to repeat the treatment. The 3-year success rate was 92.6% for monolithic restoration and 92.3% for partially veneered restoration, while the survival rate was 100% for both restorations. The 3-year follow-up found that monolithic and partially veneered zirconia restorations are both well-accepted treatment options, and patients preferred the veneered restorations (0.76, p < 0.05) from an aesthetic point of view. According to our results, monolithic and veneered zirconia restorations are both reliable treatment options and are both equally accepted by patients.
Highlights
Two of the most commonly used materials in fixed prosthodontics, zirconia (ZrO2) and lithium disilicate, are commonly utilized in digital workflows; while zirconia can only be used with this technology, several reports agree that pressed lithium disilicate produces better clinical performances [4, 5]
Twenty-seven patients received monolithic zirconia restorations, while 13 received partially veneered zirconia restorations; 26 patients received a fixed partial dentures (FPD), while the remaining 14 received a single crowns (SC). 27 patients were treated with a conventional workflow, while 13 with a digital workflow
Two restorations (5%) had a mechanical complication: one screw-retained monolithic single crown experienced a screw loosening, which was solved by retightening the screw at 35 N/cm, and one 4-unit, cement-retained, veneered FPD, occluding with a fixed partial denture, underwent a chipping of the veneering ceramic, possibly as a consequence of the parafunctional behavior of the subject; as the chipping was minor, this complication was resolved only by polishing the surface
Summary
The rapid evolution of CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing), and the advancements of its application to dentistry have heralded a series of innovations in all branches, especially in implantology and restorative dentistry, where its association with new materials presents the clinician a new treatment possibility that is both economically advantageous and clinically resilient [1,2,3].Two of the most commonly used materials in fixed prosthodontics, zirconia (ZrO2) and lithium disilicate, are commonly utilized in digital workflows; while zirconia can only be used with this technology, several reports agree that pressed lithium disilicate produces better clinical performances [4, 5].The adoption of CAD/CAM in implant dentistry can provide the clinician with abutments, both in zirconia or titanium, that are shaped appropriately to the position of the implant and the soft tissue characteristics.BioMed Research InternationalAmong these materials that can be milled with CAD/CAM technology, zirconia, the crystalline dioxide of zirconium, is by far the most adopted; thanks to its mechanical properties and aesthetic capabilities, it has been termed ceramic steel [6,7,8].Zirconia exists in monoclinic, tetragonal, and cubic phases; with the addition of stabilizing oxides such as MgO, CaO, or Y2O3, first- and second-generation zirconia are frozen in the tetragonal condition, preventing the so-called martensitic transformation [6]; instead, third-generation zirconia is metastable in the cubic phase [9].First-generation, or conventional, zirconia, developed almost 20 years ago, has a high light refraction index; it is an extremely opaque material. The adoption of CAD/CAM in implant dentistry can provide the clinician with abutments, both in zirconia or titanium, that are shaped appropriately to the position of the implant and the soft tissue characteristics. Among these materials that can be milled with CAD/CAM technology, zirconia, the crystalline dioxide of zirconium, is by far the most adopted; thanks to its mechanical properties and aesthetic capabilities, it has been termed ceramic steel [6,7,8]. As a consequence of these compromised aesthetic characteristics, conventional zirconia is used as a substitute for the cast metal core and veneered with glass-ceramic, providing higher translucency and overall better aesthetic [10]. The adhesion between the veneer and the core has improved since the introduction of this material; cohesive fracture, where a thin layer of ceramic remains on the framework, is still a common complication [11]
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