An oral cleaning unit, e.g. a head for an oral cleaning and/or treatment device, includes electrodes for generating an RF field for providing an oral cleaning and/or treatment function. The unit includes at least a first and second protruding structure, which protrude in a same general direction away from a base or support structure. Each comprises one or more electrodes. The protruding structures are arranged facing one another and separated by a space or gap which is configured so as to be able to receive a tooth pushed or inserted therein between the first and second protruding structures, and with the protruding structures extending on either side of the tooth, i.e. straddling the tooth. This allows the RF electrodes comprised by the protruding structures to reach to a location at least part way down side faces of the tooth, closer to interproximal spaces, enabling interproximal spaces to be better cleaned, and optionally also to be sensed using RF energy/fields interacting with dental features, when the electrodes are suitably driven by an RF signal.