## 1 Introduction  
Inadequate alveolar bone poses great challenge when rehabilitation is planned with dental implants [1]. Bone resorbs progressively without loading in both horizontal and vertical dimensions. After tooth extraction, it might be prevented with alveolar preservation [2, 3]. The presence of bacteria and inflammation often compromises bone grafting at the time of tooth removal. Therefore, topical antibiotics can be applied to prevent infection and graft sequestration.  
The use of topical antibiotics is widespread both in orthopedics and oral surgery because it is difficult to reach a sufficient concentration of antibiotics in the bone due to its low metabolic rate. High local concentration and progressive elution might prevent the adhesion and proliferation of bacteria on the surface of grafts. Topical antibiotics have been used for preventing perioperative inflammation, treating chronic osteomyelitisitis or severe bone necrosis caused by compromised healing of patients with diabetes mellitus [4, 5, 6]. For topical application, gentamycinin, vancomycin, and tobramycin are the first-choice antibiotics due to their broad antibacterial spectrum and low percent existence of resistant bacteria species [4, 5, 7]. In vitro experiments proved the antibiotic-coated allograft could provide sustained release of antibiotics after emplacement [8, 9].The use of gentamycinin or other topical antibiotic is indeed indicated in limited cases, however, the practice is more widespread than it should be. The reasoning that oral surgery is contaminated and therefore prevention of infection is of importance is reasonable, and one choice is the use of local antibiotics where the first choice is typically gentamycin. One would hypothesize that adding an extra layer of prevention would not do any harm so even if this is not specifically indicated it may be used as a cautionary measure [10]. One of the key observations of the current study is that this reasoning is downright wrong, and not just because of the often cited issue of promoting antibiotic resistance, but also that gentamycin interferes with bone remodelling and thus hinders the very aim of the surgery [11]. However, its use is not supported by conclusive evidence and clear surgical protocol in the literature. Several type of antibiotics can be used in different dilution, which might be standardized with a factory made bone graft coated with antibiotics [10; 12; 13]. The current study aimed to use the best available bone filler that is known to support bone regeneration and test the hypothesis that it can be further enhanced by the use of an antibiotic.  
After third molar surgical removal, patients usually suffer from pain, swelling and trismus at the early postoperative healing time [14]. At the long-term follow-up gum recession or marginal bone level (MBL) loss at its distal site of second molar may cause tooth sensitivity and periodontal pocket formation [15; 16]. The risk of pocket formation is bigger when the third molar was is a mesioangular position and preoperative bone loss developed [17]. Flap design, suturing, preoperative periodontal status and postoperative plaque control care can also affect pocket formation. To avoid it alveolar preservation with bone grafts or guided tissue regeneration may be considered, although MBL loss is not always significant after third molar removal [18; 19]. Another study observed bone grafting has beneficial effect on MBL at the distal site of second molar, although MBL loss does not increase after six months when alveolar preservation was not applied [20]. It needs to be emphasized that periodontal pocket formation should be prevented when third molar removal is necessary. The secondary aim of this study was to examine when alveolar preservation is significantly beneficial to prevent MBL loss.