Clinical Survival of Reduced-Thickness Monolithic Lithium-Disilicate Crowns: A 3-Year Randomized Controlled Trial

The aim of this randomized controlled trial was to see if the minimally invasive approach (reduced restoration thickness) would result in good clinical success of monolithic ceramic crowns compared to conventional layered all-ceramic crowns, and thus be an alternative to conventional tooth preparation.

The ceramic that was investigated was IPS e.max lithium-disilicate ceramic produced using two different processing methods. A comparison was made between monolithic crowns with reduced thickness and standard layered crowns. Fifty-two patients, who had undergone endodontic treatment on either a premolar or molar, were randomly assigned into two groups. The teeth intended for layered crowns underwent to a 2 mm occlusal reduction with a 1 mm rounded shoulder, whereas the teeth intended for monolithic crowns underwent to a 1 mm reduction in the occlusal area with a 0.6 mm rounded shoulder. The clinical success was evaluated in eight categories using modified United States Public Health Service (USPHS) criteria. The observation period was 36 months, with control appointments every 6 months.

There was no significant difference in clinical success between monolithic and conventional layered crowns after 3 years. One monolithic crown fractured while all other crowns were intact and the survival rate was 96%. All layered crowns were intact and the survival rate was 100%.

The results of this study indicate that the minimally invasive approach can be a good alternative to conventional tooth preparation. IPS e.max lithium-disilicate ceramic demonstrated an exceptional three-year survival rate independently of the thickness of the material.