Clinical performance of Experimental Glass-Ceramic Posterior Crowns: 3D Measurement of Clinical Wear

The clinical behavior of the newly developed all-ceramic systems in the posterior region of the mouth is relatively unknown. Objectives: This study reports the results of clinical evaluations of three ceramic systems {experimental hot-pressed ceramic (EC)¹, Procera-AllCeram (PA)² and metal ceramic (PFM)³}. Methods: A total of 90 posterior crowns were randomised into three groups equally in 48 patients. They were assessed at baseline following USPHS criteria and impressions were taken. Clinical images were taken after using a fluorescent dye to stain the surface changes in the crowns. Recalls were made at six-monthly intervals. The impressions were digitized using a UBM Microfocus Measurement System⁴. The digitized images were modelled as superimposable 3D colored surface images using 3D Scan-Surf software⁵. The amount of wear in the occlusal contact areas was quantitatively measured at 6, 12 and 18 months and statistically analysed using Univariate analysis of variance (Scheffe) test. Results: USPHS evaluation showed only visible wear in material PA at the region of occlusal contact with opposing teeth after 18 months, whereas EC and PFM did not alter clinically. Scheffe test showed a significant difference in the amount of enamel worn by all types of restoration over 18 months. The mean depth of enamel wear was 150mm (EC), 199mm (PA) and 124mm(PFM). There was no significant difference in the mean depth of wear of EC and PFM crowns. There was a significant difference between PA and the other two crown systems. The mean depth of wear in the restorations was 129.91mm (EC), 265.12mm(PA), and 129.89mm(PFM). Conclusions:The non-layered hot-pressed glass ceramic (EC) showed a comparable clinical performance with Procera-AllCeram (PA) crowns according to USPHS criteria, but significantly improved wear resistance. Enamel opposing EC showed less wear compared to PA.

1: Ivoclar-Vivadent, 2: NobelBiocare/Ducera, 3: Panadent/Ivoclar, 4: UBM Messtechnik, 5: 3DD Corp, USA.