Ultrasonic Cavity Preparation with CVD Diamond Tips: A Scanning Electron Microscopy Study of Dentin Surface Morphology and Smear Layer Formation

Background: Minimally invasive dentistry has driven the development of alternative cavity preparation techniques aimed at preserving tooth structure and improving biological outcomes. Ultrasonic systems associated with chemical vapor deposition (CVD) diamond tips have emerged as a potential alternative to conventional rotary instruments; however, evidence regarding their effects on dentin surface morphology and smear layer characteristics under SEM remains limited. This study aimed to evaluate the morphological characteristics of dentin surfaces after cavity preparation using ultrasonic and conventional rotary techniques. Material and methods: Twenty extracted human teeth were sectioned longitudinally to obtain standardized specimens. Samples were assigned to ultrasonic preparation using CVD diamond tips or conventional rotary preparation using carbide burs at high and low speeds. After preparation, specimens were cleaned, stored in distilled water, sputter-coated, and analyzed by scanning electron microscopy (SEM). Surface morphology, smear layer presence, and dentinal tubule exposure were qualitatively assessed at different magnifications. Results: Ultrasonic preparation resulted in consistently cleaner dentin surfaces with minimal smear layer and open dentinal tubules, whereas conventional rotary instrumentation produced irregular surfaces covered by dense smear layer and debris. Conclusions: Ultrasonic cavity preparation using CVD diamond tips demonstrated superior surface characteristics compared with conventional rotary techniques, supporting its potential as a minimally invasive approach that may enhance adhesion and preserve dentin–pulp integrity.