Thermal Changes following Er,Cr:YSGG Laser Irradiation through a Translucent Zirconia

Yttria-stablilized zirconia (YSZ) is increasing in popularity among dentists due to its ability to be used as a monolithic restoration [1]. Monolithic zirconia restorations have combined better esthetics and strength than other tooth-colored restorations, making them an attractive and convenient choice by dentists and patients [2, 3]. Single- and multiple-unit restorations such as abutments, implant supported prosthesis, and orthodontic brackets are examples of zirconia's use in clinical practice [1]. Material complications for monolithic YSZ restorations are minimal; [4, 5] however, biological and technical complications such as recurrent decay, cementation errors, iatrogenic causes, endodontic access, esthetic failure, and occlusal issues, to name a few, occur more often [2]. Any of those circumstances required the removal or replacement of the restoration. Typically, coarse tapered or cylindrical diamond burs on a high-speed handpiece are used to remove failed ceramic restorations [2, 6] that are still in place. In single crowns, the process starts by sectioning the buccal and lingual surfaces to break into two pieces the cemented restoration that can later be removed using a crown separator [2]. This multi-step instrumentation represents a risk for damage to the soft and hard tissues, e.g., the harm of the gingiva, removal of unnecessary tooth structure, high heat causing pulpal necrosis, tooth fracture, or even damage to an adjacent tooth [2]. To prevent these undesirable damages, removing fixed restorations using dental lasers is becoming an area of interest.