## 1 Introduction  
Materials for dental applications can be essentially divided into two main groups: materials for restorative dentistry and materials for dental implantology [1; 2]. These two types of materials differ in their application environment, preferred properties, and end use. The main requirement that the materials belonging to the first class should fulfil is the compatibility with the oral environment, as dental restorations pursue the aim to substitute the natural tooth enamel. The tooth is mainly constituted of two elements: (i) the outer enamel (2-3 mm in thickness at the tip of each tooth), subjected to the chemical environment within the mouth and to the loads due to chewing and biting; and (ii) the dentine, which lies underneath the enamel [3]. If the enamel is breached due to tooth fracture, cracking, or wear, the dentine is directly exposed to the mouth environment [4]. The key attributes of enamel are the excellent wear resistance and the ability to support a wide range of loads due to mastication. In addition, the outer surface of tooth undergoes severe working conditions, e.g., reciprocating movements, impacts, thermal shocks, and acid attacks [5]. Therefore, tooth enamel is characterized by unique tribological properties that can only partly be reproduced by artificial restorative materials. Bioceramics are very promising materials for dental restoration due to their chemical stability, proper aesthetics, and durability. Organic/inorganic composites, made of glass, glass-ceramic,or ceramic particles embedded in a polymeric matrix, have been widely used in dentistry for three decades [6; 7; 8]. In addition, bioceramics have also been used alone as fillers for small cavities occurring on tooth enamel. Specifically, glass-ceramics with controlled chemical, mechanical, and aesthetic properties have been proposed as materials for dental restoration. The first compositions, developed in the early 1970s, belonged to the Li\({}_{2}\)O-ZnO-SiO\({}_{2}\) system; other systems based on leucite or mica phases have been more recently investigated [9; 10; 11]. The situation is different as regards the materials used for implantological applications, as they have to exhibit bioactive properties, i.e., the ability to (i) bond to the alveolar bone; (ii) promote the growth of new bone tissue; and (iii) create a stable interface between the implant and the host bone [12]. Optical or aesthetic properties, such as a good degree of whiteness, are not fundamental for these applications. Depending on the particular clinical case, the implant may be load-bearing or not and, therefore, it may be expected to fulfil some specific mechanical requirements in terms of bending stress, toughness, and Young's modulus. The toughness of bioceramics is usually much lower than that of tooth structures: this is the major reason why metals are often used to replace the root of the tooth instead of ceramics. Due to their favourable mechanical strength, biocompatibility, and light weight, pure titanium and its alloys (e.g., the well-known Ti-6 Al-4V) have extensively been studied and proposed for dental implantology [13]. In order to promote osteointegration, hydroxyapatite (HA)-coated metal implants have been developed [14]. In fact, HA-coated implants combine the mechanical advantages of metal alloys with the bioactivity of HA due to its chemical and crystallographic similarity to the carbonated bio-apatite in human teeth and bone [15]. Ceramic or polymer/ceramic composite restorative crowns can be mounted on dental implants that aim to treat edentulism (toothlessness) by serving as anchors for partial, single-tooth, or full-arch dental prostheses [16; 17; 18]. Other advanced applications of bioceramics and bioactive glasses in modern dentistry, including their use for sealing the root canal, regenerating the alveolar bone, and treating dental hypersensitivity, have been comprehensively reviewed by other authors [19; 20; 21; 22; 23; 24].