Purpose: The purpose of this study was to compare the differences in surface characteristics and roughness of teeth finished for porcelain veneer laminates using different instrumentation and to assess their influence on microleakage. Materials and Methods: Fifty-six extracted human maxillary central incisors were divided randomly into two groups: Group HsR teeth were finished with a high-speed handpiece with diamond burs; group SO teeth were finished with a sonic oscillating diamond instrument. Porcelain veneers were bonded to 24 teeth in each group. Microleakage was measured in the cervical area. Four remaining teeth in each group were examined using confocal laser-scanning microscopy and scanning electron microscopy. Results: Oscillating instruments produced a rougher dentinal surface (Ra values; P = .029) than those finished with high-speed rotary technology. Conclusions: There is less microleakage when bonded restoration edges are situated over dentin that has been finished with sonic oscillating instrumentation (P = .006).