ObjectivesTo compare the success, survival and costs of selective versus stepwise carious tissue removal (SE/SW) in permanent teeth with deep (>2/3 dentine depth) carious lesions.DesignRandomised controlled, unicentre, clustered two-arm superiority trial.SettingOutpatient clinic of a private university in Cairo, Egypt.ParticipantsOne hundred and fifteen participants (n=132 teeth), aged 18–47 years, from Cairo, Egypt, were enrolled. Premolars/molars with occlusal/occlusal-proximal deep lesions (radiographically >2/3 dentine), sensible pulps, without spontaneous pain, were included.InterventionsPeripheral carious tissue removal to hard dentine was performed. Pulpo-proximally, soft dentine was left. A glass ionomer (GI) restoration was placed. After 3–4 months, teeth were randomly allocated to SE (n=66), with reduction of the GI into a base and no further tissue removal, followed by a composite resin restoration, or SW (n=66), with full removal of the GI, additional excavation until firm dentine pulpo-proximally, followed by a GI-based composite restoration. Mean follow-up was 1 year.Primary and secondary outcome measuresPrimary outcome was success (absence of endodontic/restorative complications). Secondary outcomes were tooth survival and initial and total treatment costs.ResultsZero/five pulp exposures occurred during SE/SW, and seven/five SE/SW teeth required endodontic therapy. Success after 12 months was 89.4% for SE and 84.9% for SW. The estimated mean time free of complications was 23 and 18 months for SE and SW, respectively, without significant differences between SE and SW (p>0.05/Cox). Initial treatment costs were significantly higher for SW (mean (SD): 507.5 (123.4) Egyptian pounds (EGP)) than SE (mean (SD): 456.6 (98.3) EGP), while total costs showed no significant difference (p>0.05).ConclusionWithin the limitations of this interim analysis, and considering the depth of these lesions (>2/3 dentine), SE and SW showed similar risk of failure and overall costs after 1 year.Trial registration numberPACTR201603001396248.