ObjectivesTo compare pulpal survival and treatment needs following selective and total caries removal in mature permanent teeth. MethodsThe design was a parallel double blind, randomized clinical trial. Mature teeth with caries radiographically extending ≥ 2/3 of dentine and without spontaneous pulpitis were included. Teeth were allocated to either selective (SCR) or total caries removal (TCR) using block randomization technique. In the SCR group, caries removal to firm dentine was followed by placement of Biodentine and composite restoration. In TCR group caries removal was to hard dentine; with immediate management by vital pulp therapy (VPT) using Biodentine in case of pulp exposure. Preoperative pain levels were recorded. Teeth were followed up after 6 and 12 months. Data were analyzed using Chi square test and regression analysis. Results124 teeth with a diagnosis of reversible pulpitis were treated (63 in SCR, 61 in TCR). 17/ 61 teeth (28%) in the TCR had pulp exposure, managed by VPT and were successful at recall. Pulp survival was significantly higher in TCR compared to SCR at 6 months (100 % vs 93.65%, p =0.04 respectively) and at 12 months (98.4% vs 82.5, P= 0.003 respectively). Multivariate analysis revealed the type of procedure (SCR vs TCR) and the preoperative pain levels (above or below 5/10) as significant prognostic factors. The odds of failure increased significantly for teeth treated with SCR (OR 27.6, 3.6–212.4, p=0.001) and if preoperative pain levels were ≥5/10 (OR 0.2, 0.04-0.8, P=0.024). ConclusionSelective caries removal for deep carious lesions in mature teeth failed to reveal overt pulp exposures in more than one quarter of cases and led to significantly lower pulp survival over one year, when compared with complete caries removal and immediate VPT. Clinical significanceIn deep carious lesions of mature permeant teeth with revrsible pulpitis, total caries removal to hard dentine is recommended for a predictable pulp survival. Clinical trial registrationThis trial was registered at CliniclTrials.gov (NCT05144711).