**1. Introduction**

Many elderly patients with bone loss and tooth loss owed to periodontal disease visit the dentist in an aging society [1]. Sufficient alveolar bone regeneration is essential for successful periodontal treatment or dental implant treatment. However, compared to soft tissue, bone has a relatively low regeneration potential [2]. In guided bone regeneration (GBR) or guided tissue regeneration (GTR) treatment, factors such as barrier membranes, the skillful technique of dentists, healthy patients, and bone materials play an important role. Among them, the membrane used for GTR/GBR prevents invasion of the soft tissue into bone defects due to the fast growth rate of fibroblasts outwards and serves to maintain appropriate space inwards, thereby allowing sufficient time for bone regeneration [2,3]. Therefore, the membrane should have characteristics such as (1) biocompatibility to prevent soft tissue dehiscence and minimize tissue reactions, (2) space maintenance and structural integrity, (3) host tissue integration, and (4) an ease of handling during surgery with no memory [4].

The commercially available membranes that are currently used can be broadly divided into two types: non-resorbable membranes and resorbable membranes. Representative examples of non-resorbable membranes include expanded polytetrafluoroethylene (ePTFE)

**Citation:** Kim, J.-Y.; Park, J.-B. Various Coated Barrier Membranes for Better Guided Bone Regeneration: A Review. *Coatings* **2022**, *12*, 1059. https://doi.org/10.3390/ coatings12081059

Academic Editor: Gaetano Isola

Received: 29 June 2022 Accepted: 23 July 2022 Published: 26 July 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

and titanium (Ti) mesh. Their advantage is that they have the properties of good intensity and barrier effects. Especially, the Ti membrane could be deformed to suit various forms of bone defect and maintain the extensive space because of their high rigidity and plasticity [5]. However, the disadvantages include poor cellular adhesion, slower cellular growth, bone regeneration, and the need for secondary surgery, which may lead to secondary trauma to the gum [6,7]. Besides, the exposed non-resorbable membranes easily form a biofilm in the oral cavity and may experience failure of bone regeneration due to bacterial infection [8,9]. On the contrary, the resorbable membrane has a great advantage as it does not require secondary surgery for the removal after the regeneration of alveolar bone. In addition, it has advantages such as good biocompatibility, weak immunogenicity, higher cell adhesion, and tissue healing properties [10]. Representative resorbable membranes include collagen membranes made from a bovine or porcine source and biodegradable synthetic polymer membranes [11]. However, collagen membrane has disadvantages such as insufficient mechanical properties and a fast degradation speed that is short to maintain sufficient space for an appropriate time as a barrier [10]. Biodegradable polymer membranes, such as poly(L-lactide) (PLLA), has advanced mechanical properties but are associated with inherent shortcomings such as hydrophobicity, poor cellular affinity, and osteoconductive activity compared to collagen membrane [12].

Therefore, to compensate for these shortcomings and increase bone regeneration, research on the development of coating or the surface treatment of membranes have been conducted continuously. The technology of coating continues to develop, especially in membrane application. Coating of the membrane with various materials can be applied for GTR applications as bioactive and anti-bacterial purposes [13]. However, there exists only a few review papers focusing on the coating or surface treatment of barrier membranes. In this study, we have reviewed barrier membrane coating-related papers published in the last 5 years, investigated the research conducted to date, and seek the direction of development of coated membranes in the future.
