Objective: A powder jet deposition (PJD) process can be used to create a thick hydroxyapatite (HA) layer on the human tooth surface. The purpose of this exploratory trial was to evaluate the safety and efficacy of the hydroxyapatite layer formed by a new dental treatment system for cases of caries, dentin hypersensitivity, or discolored teeth. Methods: A single facility, non-blinded study comparing before and after treatment interventions, without a comparative control, was conducted. A rubber dam was attached to the teeth followed by the application of Vaseline to the gingival margins. Extra-and intra-oral vacuums and a saliva discharge tube were used to spray HA powder over the target site with the PJD equipment. Results: The formation of an HA layer tended to reduce pain on exposure to cold water and air in the cases with caries, and increase brightness and satisfaction in the cases with tooth discoloration. The pain on exposure to air was significantly reduced in the cases with dentin hypersensitivity. PJD was not observed to cause any inflammation of the surrounding gingiva or pulpal symptoms. Conclusions: HA is anticipated to reduce the need for repeat treatment by offering superior compatibility with the tooth substance when compared with other dental materials.