## 1 Introduction  
Fural perforations are serious complications of iatrogenic errors throughout endodontic access opening or pathological processes that can adversely affect tooth prognosis. The perforation size, location, and time before repair are all noteworthy factors determining the prognosis of perforated teeth [1]. When perforation is not managed promptly, periodontal destruction will occur around the perforation site, resulting in the surrounding bone resorption [2]. Different materials have been used to seal such perforations, with mineral trioxide aggregate (MTA) showing superiority in terms of sealing ability and biocompatibility; therefore, it has become the gold standard [3,4]--yet MTA has a delayed setting time and poor handling characteristics [5]. Moreover, MTA is difficult to control and can extrude into the periodontium, especially in large fural perforations which act as a \"bottomless pit\" [6] causing mechanical and chemical irritation, triggering tissue inflammation, interfering with the periodontal reattachment, and impairing treatment prognosis [7,8]. Accordingly, internal matrices have been introduced to restrict MTA overextension [9], and this approach presented favorable outcomes of perforation repair when compared to matrix-free treatment [10].  
Chitosan (CS), a natural biocompatible and biodegradable material has generated great interest in medicine and has been used in tissue engineering (TE) and wound healing due to its hemostatic, anti-inflammatory, and antimicrobial properties. In addition, it can enhance cell adhesion, proliferation, and differentiation [11]. CS's advantageous physical properties such as the adequate pore size, its ability to be modified, and its ability to be combined with other polymers allowed the development of a wide range of scaffolds that have been used in bone, neural and vascular tissues, cartilage, and skin regeneration [12]. A porous CS scaffold was fabricated and was able to promote the regenerative potential of dental pulp cells and osteoblastic differentiation [13]. Furthermore, a recent study presented CS to be a viable therapeutic option to hinder root resorption while enhancing healing outcomes in cases of severe inflammatory root resorption [14]. Simvastatin (SIM), a widely used statin and a well-established cholesterol-lowering drug [15], has increased the expression of bone morphogenic protein 2 (BMP-2) in osteoblasts and encouraged bone formation [16]. Its ease of purchase and affordable price make its selection more convenient than laboratory bone-driven costly stimulators. In addition, obesity and metabolic syndrome are characterized by lipid metabolism disorders holding the risk of increasing developing periodontal disease [17; 18], which is known as the most common chronic infection in the world [19]. In periodontitis, SIM has been reported to stimulate the proliferation and osteoblastic differentiation of human periodontal ligament cells (PDL) [20] and to offer aid to mechanical periodontal therapy (MPT) in improving periodontal parameters compared with MPT alone or in association with placebo [21].  
To our knowledge, no study has investigated the effect of CS scaffold, alone or with SIM impregnation, in repairing fural perforations in vivo. This study aimed to histologically evaluate the inflammatory reactions and tissue responses to the experimental CS scaffold, with and without SIM, when used to repair fural perforation and compare it to the absorbable collagen wound dressing most commonly used in endodontic wound healing, CollaCote (CL). CollaCote is a soft, white, pliable, nonfriable sponge used in dental surgery due to its coherent structure, bleeding control, and protecting properties of the wound bed while accelerating the healing process [22]. The null hypothesis was that there is no difference between CS scaffold and CL in repairing fural perforations and bone healing with and without SIM impregnation.