**1. Introduction**

The success of dental implant in the oral cavity depends on direct bone-implant surface contact as well as the soft tissue attachment surrounding the implant abutment (and dental im‐ plant), which the latter acts as biological seal against external oral environment. Much of the attentions in the early dental implant studies were given to the bone-to-titanium interface.

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These studies range from clinical [1, 2] to molecular levels [3], and from animal model [4, 5] to human biopsies [6, 7]. In all studies, the bone appears to be in direct contact with implant without the presence of any connective tissue or fibrous tissue encapsulating the implant.

The extensive and well-established researches on bone-implant interface have led to the wide acceptance of the concept of osseointegration. Presently, more focuses are placed on under‐ standing and improving the implant-soft tissue interface. The biological seal of the soft tissueimplant interface is created by epithelium and connective tissue. The presence of keratinized mucosa surrounding an implant is thought to be one of the important factors in maintaining peri-implant soft tissue health. Moreover, materials and surface topography of implant abutment materials may also influence the biological seal formed at the implant-soft tissue interface. The available data from animal studies and emerging information from human investigations suggest that different material with different surface energy and enhanced surface topography is associated with increased soft tissue-to-implant contact [8, 9]. The nature of soft tissue-implant against normal periodontium is compared in the subsequent paragraph. By understanding the tissue around transmucosal region, the factors influencing this biological seal will be better appreciated.
