Fatigue survival and damage modes of lithium disilicate and resin nanoceramic crowns

Abstract

Polymer-based composite materials have been proposed as an alternative for single unit restorations, due to their resilient and shock absorbing behavior, in contrast to the brittleness of ceramic materials that could result in failure by fracture. Objective: To evaluate the fatigue strength and damage modes of monolithic posterior resin nanoceramic and lithium disilicate glass ceramic crowns. Methodology: Twenty-six resin nanoceramic (RNC) and lithium disilicate glass ceramic (LD) 2 mm monolithic crowns (n=13) were cemented on composite resin replicas of a prepared tooth and subjected to cyclic load with lithium disilicate indenters for 2 million cycles. Specimens and indenters were inspected every 500,000 cycles and suspended when presenting fractures or debonding. Surviving specimens were embedded in epoxy resin, polished and subsurface damage was analyzed. Specimens presenting fractures or severe subsurface damage were considered as failures. Survival data was subjected to Fisher's exact test; damage modes were subjected to Mann-Whitney test (p<0.05). Results: There were no debonding, cohesive or catastrophic failures. Considering subsurface damage, 53.8% of RNC and 46.2% of LD crowns survived the fatigue test, presenting no statistical difference. Chief damage modes were radial cracks for RNC and inner cone cracks for LD, presenting no statistical difference. Conclusions: The results suggest that if debonding issues can be resolved, resin nanoceramic figures can be an alternative to posterior crowns. Although distinct, damage modes revealed potential to cause bulk fracture in both glass ceramic and resin nanoceramic crowns.

Evaluation of mechanical properties of CAD/CAM ceramic systems: literature review

“…In a literature review, the flexural strength of feldspar ceramics presented the lowest values of strength in relation to the other types of ceramics mentioned. Lithium disilicate (LD) for injection (e.max® Press) had the lowest reduction in resistance after undergoing flexion test with 29.6%, whereas lithium disilicate for milling (e.max® CAD) showed a reduction of 53.4% [12]. André et al (2006) e Ferruzzi et al (2018) [12,13] investigated monolithic blocks of lithium disilicatereinforced ceramics after milling and crystallization at 840 °C, showing that lithium disilicate crystals grow in a controlled manner to 70% of the material volume, after which the color remains unchanged and the strength is about 360 MPa, according of flexural resistance (chart 4).…”

Features and use of glass-ceramics in fabrication of fixed prosthetic restorations

“…Ponad dwukrotnie większa odporność na kruche pękanie (2,9 MPa x m 1/2 ) w stosunku do ceramiki leucytowej oraz duża wytrzymałość na zginanie (400 MPa), trzykrotnie wyższa w porównaniu do ceramiki leucytowej i aż pięciokrotnie względem ceramiki skaleniowej, znacznie rozszerzyły zakres wskazań do stosowania. 2,4,9,[12][13][14] Ceramika dwukrzemowo-litowa wykazuje ścieralność zbliżoną do naturalnego szkliwa, nie powodując tym samym nadmiernego starcia zębów w łuku przeciwstawnym. 2,15 Z ceramiki szklanej wzmacnianej leucite crystals of smaller dimensions that are more densely packed in a glass matrix.…”

“…Znacznie upraszcza to procedurę range of indications for use. 2,4,9,[12][13][14] Lithium disilicate exhibits abrasion similar to natural enamel, thus not causing excessive tooth wear in the opposing arch. 2,15 Veneers of thickness of at least 0.3 mm are made from the ceramics reinforced with lithium silicate.…”

“…Dobra transparencja pozwala na wykonywanie wysoce estetycznych pełnokonturowych uzupełnień, które bardzo dobrze komponują się z naturalnym uzębieniem pacjenta. 4,10,12,14,15,20 Właściwości chemiczne determinowane są obecnością macierzy szklanej, dlatego analogicznie do ceramiki leucytowej, ceramika dwukrzemowo-litowa jest podatna na wytrawianie jedynie kwasem fluorowodorowym, zaś do osadzania uzupełnień dedykowane są cementy adhezyjne o właściwie dobranej barwie. Wytworzenie chemicznego połączenia pomiędzy uzupełnieniem, cementem oraz tkankami zęba zwiększa wytrzymałość mechaniczną konstrukcji a także eliminuje ryzyko odcementowania uzupełnienia z filaru o mało minimizes the risk of doctor's error during cementation.…”

“…Good transparency allows manufacturing highly aesthetic full-contour restorations that blend very well with the patient's natural dentition. 4,10,12,14,15,20 Chemical properties are determined by the presence of a glass matrix, which is why, like leucite ceramics, lithium disilicate ceramics are susceptible to etching only with hydrofluoric acid, while types of adhesive cements with a properly selected colour are dedicated to the placement of the restoration. Creating a chemical bond between the restoration, cement and tooth tissues increases the mechanical strength of the structure and also eliminates the risk of de-cementation of the restoration from an abutment tooth with low retentive geometry.…”