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The preparation of an access cavity is the first part of endodontic treatment and is a key stage in the healing of both periapical and pulpal infections. It should allow endodontists to remove obstructions in the pulp chamber, locate all canal orifices and clean the entire root canal system with minimum coronal tooth structure removed. This has been done traditionally through establishing straight line access. The development of minimally invasive endodontics aimed to preserve as much of the natural tooth structure as possible, particularly dentine, while undertaking root canal treatment, resulting in the development of other access cavity preparations. This includes conservative, ultra conservative (ninja), truss, guided access, caries-orientated and restorative access cavities. These access cavity preparations also gained popularity due to increased magnification and enhanced lighting, allowing practitioners to visualise the pulpal space in greater detail throughout treatment.Our current recommendation is to conduct access cavities traditionally rather than conservatively. Ideally, conservative access cavities need magnification, which might not be available for all clinicians. With traditional access cavity, the procedure takes less time and it is more predictable to locate the canal orifices, deliver irrigation effectively, avoid iatrogenic damage with biomechanical preparation and achieve better obturation., (© 2023. The Author(s), under exclusive licence to the British Dental Association.)

Background: Analysis of the survival of root‐filled posterior teeth and the associated prognostic tooth‐related factors will enable clinicians to predict the outcome of root canal treatment. Objectives: To investigate (i) the survival of root‐filled posterior teeth and (ii) the tooth‐related factors that may affect their survival. Methods: Randomized controlled trials, comparative studies and observational studies assessing survival rates of root‐filled posterior teeth with a minimum 4‐year follow‐up period were identified through an electronic search of the following databases up to January 2023: The Cochrane Central Register of Controlled Trials, Medline via PubMed, the Cochrane Database of Systematic Reviews, Embase, Web of Science and NIHR centre for reviews and dissemination. Two reviewers (SP and ML) independently selected the final studies based on pre‐defined inclusion criteria. The Newcastle Ottawa Scale and the Cochrane Risk of Bias Tool for Randomized Trials were used to assess the risk of bias. Pooled weighted survival rates were analysed using a random effects meta‐analysis model using DerSimonean and Laird methods. Descriptive analysis of studies describing any prognostic tooth‐related factors was conducted. Results: Of the 72 studies identified, data from 20 studies were included in the survival meta‐analysis, and data from 13 of these studies were included in the descriptive analysis of tooth‐related factors; 12 studies were retrospective, 7 were prospective, and one was a randomized control trial. The pooled survival rates at 4–7 years and 8–20 years of root‐filled posterior teeth regardless of tooth type was 91% (95% CI, 0.85; 0.95) and 87% (95% CI, 0.77; 0.93), respectively. The prognostic tooth‐related factors mentioned in the included studies were (i) remaining coronal tooth structure, (ii) ferrule, (iii) crown‐to‐root ratio (iv) tooth type and location (v) periodontal disease (vi) proximal contacts and (vii) cracks. Conclusions: The meta‐analysis suggests that root canal treatment has a high medium to long term survival outcome. The narrative summary identified 7 factors that affect tooth survival. However, there is a paucity of evidence, and more research is needed in this area. Registration: PROSPERO Registration: CRD42021227213. [ABSTRACT FROM AUTHOR]