# Endodontic Management of Endo-Period Lesions
## 3 Discussion  
This article presents three clinical cases representing combined apical and marginal pathology cases that were resolved successfully with endodontic and periodontal treatment. The comprehensive multidisciplinary approach described here is of utmost importance in the diagnosis and management of endodontic-periodontal lesions in order to maximize the chance of achieving an optimal outcome. Correct endodontic diagnosis based on dental history, and clinical and radiographic evaluation play important roles in prognosis of the endodontic-periodontal lesions and in the preparation of an optimized treatment plan. Figure 3: Clinical case 3. (**a**) CBCT (coronal section) with a periapical radiolucent lesion and mucosal thickening of the right maxillary sinus membrane. (**b**) CBCT (lateral section) with a periapical radiolucent lesion and mucosal thickening of the right maxillary sinus membrane. (**c**) CBCT (axial section) with a radiolucent area visible on the first right maxillary molar. (**d,e**) Tooth appearance after instrumentation of the root canals. (**f**) Final periapical radiographic after the retreatment. (**g–i**) CBCT follow-up after 11 months (coronary section). (**j**) CBCT follow-up after 11 months (lateral section). (**k,l**) CBCT follow-up after 11 months (axial section). GuttaFlow Bioseal, a bioactive root canal filling material, was used in all of the cases. GuttaFlow Bioseal is composed of gutta percha, polydimethylsiloxane, platinum catalyzer, zirconium dioxide, and bioglass [10]. The biological activity of bioglass is provided by the high content of Na\({}_{2}\)O and CaO, and a relatively high level of CaO/P\({}_{2}\)O\({}_{5}\) Hench [2]. The key element is silicon, and the activity is due to the formation of a chemical bond between the surface of the bioglass particles and the surrounding tissue [11]. Hydrolysis of the bioglass in the interstitial fluid leads to the formation of a thin jelly-like layer (gel) of silicic acid--SiO\({}_{2}\)xH\({}_{2}\)O. Negatively charged hydroxyl groups on the surface of the silicic acid layer attract Ca\({}^{2+}\) ions from the surrounding interstitial fluid solution; then, once the surface charge becomes positive, phosphate ions are deposited on the surface and amorphous calcium phosphate deposits are formed. This leads to the crystallization of hydroxyapatite and the formation of a layer of apatite. As the next stage, biologically active molecules from the extracellular matrix are adsorbed on this apatite layer, and these promote the migration of macrophages and stem cells to the damaged area. Thus, the differentiation of stem cells, and the formation and crystallization of bone matrix occur on the surface of bioactive glass [12]. In dentistry, bioceramics based on calcium phosphates are used to restore bone defects and based on calcium silicates and bio-aggregates (mineral trioxide aggregate, MTA) to ensure the process of apexification and filling of endodontic perforations [11; 13; 14]. HyFlex EDM NiTi files was used for the instrumentation. Preservation of the original anatomy of the root canal during its preparation is extremely important [12; 15]. HyFlex EDM NiTi files are manufactured using the electric discharge machine method. They have a controlled shape memory and, at the same time, possess a unique combination of high flexibility and resistance to breakage [16]. This is because the thermal action of pulsed electrical discharges, excited between the electrode tool and the work piece, means that the entire surface of the file is active and not just the edges, as in tools made by the classical milling method [17]. Another important property is that the phase composition of HyFlex EDM files allows them to change form by reorientating the component martensite, which increases their resistance to torsion loads compared with other files, including those made using wire technology [18].