Special Issue on Current Techniques and Materials in Dentistry

1. Introduction

In the field of dentistry, the use of regenerative therapy, as well as biocompatible and biomimetic materials, is well-established. Biocompatible and biomimetic materials have advanced, as have methods for maximizing the effectiveness of their applications and the associated technology. The application of polymer compounds, such as composite resins and dentin adhesives, in crown restoration is an extremely interesting topic, along with techniques for implanting jawbones and digital dentistry. Advances therein over time have led to innovations.

2. Innovations in Dental Materials and Technology

Composite resins, which are among the most innovative dental materials, are composed of organic polymers, inorganic fillers, and silane coupling agents [1,2]. Composite resins imitate the tooth structure and require a lot of attention; they form cured products via the polymerization of monomers, and the polymerization reaction affects their properties.

For photo-polymerized resins under ambient temperatures, the double bond conversion is rapid [3]. As the resin turns glassy and vitrifies, mobility is reduced, monomer conversion is hindered, and the reaction rate slows [4,5]. Mobility is reduced to the extent that photo-polymerization always leads to incomplete conversion. For photo-polymerized composites, there are guiding principles to maximize conversion, where insufficient conversion can lead to color instability and material degradation [6,7,8,9,10]. It has been suggested that heat polymerization, as used in polymer-infiltrated ceramic network (PICN) materials, may provide a more consistent source of energy for the reaction, leading to a higher degree of conversion.

The bond between the resin composite and tooth surface has also been subject to many innovations. Functional monomers with hydrophilic groups, which form chemical bonds with the tooth surface, have been used in various resin-based materials, such as self-adhesive resin cements, universal adhesives, self-adhesive flowable restorative materials, and orthodontic adhesive pastes. These adherent materials can simply be applied to the tooth substance. However, they have weaker etching capabilities than previous adhesive systems, leading to concerns about their low elastic modulus and marginal gap formation when used on enamel without any pre-treatment [11,12]. The effect of the application method on adhesiveness is also of concern.

Dental implants are one of the most interesting types of dental materials. For dental implant materials, inorganic materials such as titanium, titanium alloys, alumina oxide-based ceramics, hydroxyapatite and zirconia have been presented along with various applications. PEEK (polyetheretherketone) has recently been reported as a further innovation in polymer implant materials [13], although it has not yet met biomechanical requirements. In orthodontics, mini-implants are crucial to the success of treatment and are used in various clinical situations. Mini-implants, composed of titanium, titanium alloys, or other materials, are implanted into the bone, and the implant success rate is an important clinical endpoint. Microcracks caused by over-torquing in thick and hard bone [14], and the consequent heat production, may lower the success rate.

Digital technology is also revolutionizing the field of dentistry. Computer-aided design/computer-aided manufacturing (CAD/CAM) techniques are becoming increasingly popular. In the field of prosthodontics, 30 years after the first report on digital removable prostheses, many systems now exist to reduce the number of patient appointments and laboratory time [15,16,17,18]. The process of manufacturing complete dentures using computer-assisted technology involves the acquisition of clinical information and designing the prostheses using computer software. Complete dentures can be produced using an additive (3D printing) or subtractive (milling) process. Thus, CAD/CAM techniques for denture fabrication have many clinical and laboratory advantages [19,20,21,22].

Treatment planning and diagnosis are also expected to improve greatly with innovations in materials and technology. Although this Special Issue is now closed, innovative and detailed research on dental material technology is expected in the future. We encourage the integration and upgrading of clinical practice applications.