Targeted endodontic microsurgery represents precise and advanced approach to resolving persisting chronic periapical periodontitis after non- surgical root canal treatment. This specialised procedure involves accessing the root tip of the tooth under high magnification using dental operating microscopes and employing microsurgical instruments to remove infected or inflamed tissue, as well as any pathological lesions present in the periapical region. Targeted Endodontic Microsurgery is useful for osteotomy and root- end resection when exacting control of depth, diameter, and angulation of osteotomy and root end resection is necessary. Using a CBCT(cone beam computed tomography) designed 3D - printed surgical guideis a more accurate method for access to the apical portion of the root during surgical endodontics compared with a "freehand" CBCT - approximated conventional method. These guided have the potential to increase accuracy and precision and to reduce intraoperative time as well as postoperative complications. Additionally, it provides a viable treatment option for patients who may not be candidates for traditional root canal therapy or retreatment due to anatomical complexities or previous treatment failures.

Conventional Endodontic microsurgery takes use of a preoperative scan and manual drilling of the osteotomy site with arbitrary measurements followed by retropreparation and forming the apical seal. One of the most critical disadvantages of conventional root-end resection include the damage to anatomically vital structures such as inferior dental nerve, mental nerve, adjacent root and maxillary sinus. In contrast, endodontic microsurgery using the guide template significantly reduces these damages. Pinsky et al confirmed in their in vitro study that the greater accuracyand consistency was achieved during endodontic surgery with surgical guidance without damaging vital structures. An error greater than 3 mm occurred over 22% of the time with freehand whereas none of errors occurred with surgical guidance.

Consequently, targeted endodontic microsurgery has garnered increasing attention as a viable alternative, offering a refined and precise approach to address such challenges.

Even the most skilled surgeons may find endodontic microsurgery difficult. Some medical professionals steer clear using freehand (FH) Endodontic microsurgery in regions where there is a chance of harming important anatomical features including the maxillary sinus, the mental foramen, and arteries. It is Perceived as complex sites include those with limited access, no direct sight, and areas where the apex is placed distant from the buccal cortical bone without any cortical plate fenestratio. Surgeons may be able to perform precise procedures in difficult-to-reach regions with guided Endodontic Microsurgery

Guided Endodontic Microsurgery is virtually planned on 3D software on the preoperative CBCT scan, and the surgeon executes the osteotomy and root-end resection (RER) under static or dynamic navigation.

Static navigation requires a customized 3D-printed surgical guide (3D-SG) to guide the drilling duringosteotomy and RER. Surgical guides contain a guide template that refers to the 3D location of the virtual Endodontic Microsurgery planned in the CBCT to drill accurately Prior research has demonstrated that 3D-SG can reduce the risk of intra-operative complications whileincreasing the precision and effectiveness of EMS. In comparison to free hand Endodontic Microsurgery, guided Endodontic Microsurgery with 3D-Surgical Guide shortens the surgical time, provides superior control over the resection level and bevel off the root, and enables a tailored osteotomy size.

Trephine burs have been used for the removal of failed implants and autogenous bone graft harvesting but have not previously been described in Endodontic Microsurgery .

Targeted Endodontic Microsurgery produces a single-step osteotomy; root-end resection; and biopsy with a defined perforation site, angulation, depth, and diameter. Previous reports have used 3D Surgical Guides to locate an ideal bone perforation site, but none have used trephine burs within a stent to define all parameters of osteotomy and root-end resection.

Also, no clinical study assessing the targeted approach of endodontic microsurgery with Oral health related quality of life has been done. Some of the RCT's are conducted assessing quality of life in patients after conventional periapical surgery, only two retrospective studies considering .Targeted Endodontic Microsurgery have been done and a lack of RCTs comparing targeted Endodontic Microsurgery with conventionalEMS warrants further research.

The aim of this study is to compare the effect of a static computer-aided surgical technique using a 3D- printed guide with a fully guided drill protocol on Oral Health Related Quality of Life against the conventional endodontic microsurgery in mandibular molars.

Inclusion Criteria:

• Patients in which non-surgical retreatment is unfeasible (post, anatomical complexity, iatrogenic errors) or previously failed treatment.
• Patients with persistent symptomatic apical periodontitis and periapical radiolucency.
• Tooth with a peri-radicular lesion of strictly endodontic origin (chronic apical periodontitis) and combined endodontic periodontic lesions with the size of lesion ≥5mm.

Patients between 18-55 years of age.

• No general medical contraindications for oral surgical procedures (ASA-1 and ASA-2 according to the classification of the American Society of Anesthesiologists)
• ASA 1- A normal healthy patient. Example: Fit, nonobese (BMI under 30), nonsmoking patient with good exercise tolerance.
• Tooth with adequate final restoration without clinical evidence of coronal leakage.
• No spontaneous pain or swelling.
• Good periodontal health condition at tooth level
• Able to completely understand and sign an informed consent form

Exclusion Criteria:

• Patients with systemic diseases (diabetes mellitus, uncontrolled hypertension grade III, hepatic/renal disease, or systemic bleeding disorders)
• Patients on anticoagulant/ antiplatelet drugs.
• Fractured/perforated teeth.
• Teeth with deep pockets (probing depth > 4 mm).
• Presence of vertical root fracture.
• Miller class III/IV mobility.
• Pregnancy.