Assessment of Simulated Biofilm Removal Across Different Crown Width-to-Implant Diameter Ratios Using Interproximal Oral Hygiene Aids: An In Vitro Study.

Abstract

Peri-implant diseases, including peri-implant mucositis and peri-implantitis, are common complications following dental implant placement, affecting up to 47% and 22% of patients, respectively, within 5–10 years.[1] Effective peri-implant hygiene is critical for implant longevity; however, anatomical differences between natural teeth and implants pose challenges for interproximal cleaning, particularly in relation to the crown width-to-implant diameter (CW/ID) ratio, a parameter rarely investigated for its influence on oral hygiene performance and interproximal cleaning efficacy. To date, no prior studies have comprehensively assessed this gap under controlled, participant-driven in vitro conditions. This study is the first controlled in vitro study to systematically test two CW/ID ratios using participant-based protocols and machine-learning quantification of cleaning ratio, aimed to investigate the impact of the CW/ID ratio on implant cleanability and to determine the most effective interproximal oral hygiene aid for effective biofilm removal. This in vitro study utilized 3D-printed maxillary arch models with missing anterior and posterior teeth, restored with implants of varying diameters (BioHorizons Internal 4.5 mm and 3.0 mm implant analogs) and screw-retained zirconia crowns. A simulated gingival mask was applied to replicate peri-implant soft tissue. Fifteen participants, including dentists, dental hygienists, and laypersons, were trained to use four different interproximal oral hygiene tools: a manual toothbrush, dental floss, an interdental brush, and a water flosser. An artificial biofilm was simulated using green occlusal spray, and post-cleaning assessments were conducted via standardized photography of the mesial, distal, and basal surfaces of each crown. A total of 720 in vitro cleaning trials were performed to assess the effectiveness of four oral hygiene tools across two crown width to implant diameter ratios (Model 1 and Model 2), two implant positions (Anterior and posterior), crown surfaces (Mesial, Distal, Basal), and participant types (Dentists, Hygienists, laypersons). No statistically significant differences were observed between Model 1 and Model 2 across any tool, participant group, position, or surface (all p > 0.1), indicating that the crown 2 width-to-implant diameter ratio did not independently influence cleaning performance. In contrast, oral hygiene tool type had a significant effect on efficacy (p < 0.0001), with the water flosser achieving the highest mean cleaning ratio, followed by dental floss, toothbrush, and interdental brush. Participant group also influenced performance significantly (p = 0.0003), with dental hygienists outperforming both dentists and laypersons. Cleaning performance did not differ significantly by tooth position (p = 0.099). However, surface type had a strong effect (p < 0.0001), with basal surfaces significantly more difficult to clean than mesial or distal surfaces. Clinically, the results suggest that maintaining peri- implant tissue health depends more on proper selection of oral hygiene tools and user technique than on prosthetic dimensions, although certain prosthetic features may still impede effective cleaning. The demonstrated superiority of water flossers underscores their value as a first-line adjunctive tool for peri-implant care and supports the integration of targeted hygiene training into clinical practice. In conclusion, the crown width-to-implant diameter ratio appears to have minimal impact on cleanability, whereas operator skill and the choice of oral hygiene aid are more influential.