Influence of Bruxism on Wear of Ceramic Single Crowns

Objectives: The aim of this study was to quantify and compare clinical wear of ceramic single crowns in patients with and without bruxism to better assess the risk factor of bruxism and derive clinical consequences.
Methods: For this study, patients with and without bruxism, bruxers (Br) and non-bruxers (nBr), who had been restored with zirconia (Zr) or lithium disilicate (Li) single crowns as part of a clinical study were prospectively followed-up. They were classified as affected or unaffected by Bruxism based on questionnaires, clinical signs and overnight portable electromyography (Bruxoff). Conventional dual-phase polyvinylsiloxane impressions (Flexitime Putty/ Correct Flow, Kulzer) of the intraoral situation were taken one week after crown cementation (baseline) as well as at follow-ups 6 and 12 months after baseline. The resulting plaster models were digitized (D2000, 3Shape) and the crown geometries recorded at the follow-ups superimposed with the baseline situation using a commercial CAD software (Geomagic Design X, 3D Systems). An automated recognition of the individual wear areas (regions of interest, ROIs) was performed by intersecting aligned follow-up scans with a baseline geometry shifted inwards by 30 µm. For each ROI, the wear depth evaluation was performed perpendicular to the associated best fitting plane of the follow-up after 12 months and mean as well as maximum wear were determined.
For samples showing no wear in our evaluation a mean and maximum wear of 15µm was assumed.
Results: After 12 months bruxers demonstrated maximum vertical wear between 15µm and 178µm for Zr and 15µm to 163µm for Li crowns.
The maximum vertical wear for non-Bruxers ranged from 15µm to 115µm for Zr and from 15µm to 91µm.
Conclusions: With clinically acceptable maximum vertical wear, ceramic single crowns made of Zr or Li seem to be an alternative material for Bruxers.