# Decision Support for Removing Fractured Endodontic Instruments: A Patient-Specific Approach
###### Abstract  
The instrumental fracture is a common endodontic complication that is treated by surgical or non-surgical removal approaches. However, no tool exists to help the clinician to choose between available strategies, and decision-making is mostly based on clinical judgment. Digital solutions, such as Finite Element Analysis (FEA) and Virtual Treatment Planning (VTP), were recently proposed in maxillofacial surgery. The aim of the current study is to present a digital tool to help decide between non-surgical and surgical strategies in a clinical situation of a fractured instrument. Five models have been created: the initial state of the patient, two non-surgical removal strategies using a low or high root canal enlargement, and two surgical removal strategies using a 3- or 6-mm apicoectomy. Results of the VTP found a risk of perforation for the non-surgical strategies and sinus proximity for surgical ones. FEA showed the lowest mechanical risk for the apicoectomy strategy. A 3-mm apicoectomy approach was finally chosen and performed. In conclusion, this digital approach could offer a promising decision support for instrument removal by planning the treatment and predicting the mechanical impact of each strategy, but further investigations are required to confirm its relevance in endodontic practice.  
finite element analysis; virtual treatment planning; endodontics; apicoectomy; Instrument removal; decision-making +
Footnote †: journal: Medicalperforming an apicoectomy [7], but it induces a reduction of the crown-to-root ratio [8; 9]. Both strategies thus impact mechanically the tooth and the success of the endodontic retreatment [10; 11]. No tool exists, at the time of writing, to guide the clinician in choosing between these strategies, and decision-making is mostly based on clinical judgment instead of scientific evidence [3]. Furthermore, numerous different tools are available to deal with retained instruments, including mini forceps, broach and cotton, hypodermic surgical needles, wire loops, Masseran instruments, extractors, and ultrasonic tips [1; 4]. In the face of the multitude of possible therapeutical choices, instrument removal is still considered highly technical and time-consuming because dental practitioners have difficulties planning the removal and its impact on tooth resistance.  
Digital approaches have been used for many years; for instance, virtual treatment planning (VTP) has been used to improve the reconstruction accuracy and outcome in the maxill facial field [12; 13], and patient-specific finite element analysis (FEA) has been used to provide better predictions on bone fracture than experienced clinicians in orthopedic practice [14]. In endodontics, FEA has been used to evaluate the influence of the instrument position and the resection length on the root stress distribution [15; 16; 17]. However, these studies use standard anatomic dimensions to create finite element (FE) models, and the success rate mainly depends on patient-specific parameters such as bone loss and canal anatomy [6; 9; 18]. A recent study proposed combining VTP and FEA for computer-aided decision-making, with the aim to predict the mechanical behavior of different maxillofacial surgeries and choose the most adapted solution for the patient [19]. Herein, we report a case of an endodontic instrument fracture and the application of a digital approach combining VTP and FEA to help decide between surgical and non-surgical strategies for its removal.