Impact of a Bone Leveler on Prosthetic Abutment Fit in Guided Sub-Crestal Implant Placement: An In-Vitro Study

PURPOSE: Guided sub-crestal implant placement is limited by the lack of visual confirmation, making abutment connection dependent on tactile feedback, which may be compromised by residual bone at the implant crest. A bone leveler can remove excess bone above the implant platform, but no clinical guidelines exist for its use in guided sub-crestal surgery. This in-vitro study evaluated the effect of a bone leveler on prosthetic abutment fit. MATERIALS AND METHODS: Ten 3D-printed artificial bone models with irregular cortical morphology were prepared using CAD-CAM technologies from a micro-CT scan obtained from the NIH 3D Print Exchange. Sleeveless surgical guides were digitally designed and additively manufactured, and a 3-mm polyvinyl siloxane layer simulated soft tissue. Guided osteotomies for four implants per model (N = 40) were performed using two protocols: conventional drilling (Control) and conventional drilling plus a bone leveler (Test). Abutments were hand-tightened and assessed for seating by two blinded clinicians through tactile and radiographic evaluation. Inter-rater agreement was quantified via Cohen's Kappa, and Chi-square tests evaluated the effect of the bone leveler on seating outcomes. RESULTS: All abutments were deemed fully seated by tactile assessment of Clinician 1. Independent blinded tactile assessment by Clinician 2 confirmed 80% of abutments in Controls and 85% in Tests as fully seated. Radiographic evaluation revealed 80% fully seated abutments in Test versus only 15% in Controls. The difference was statistically significant (χ² = 7.27, p = 0.007). Inter-rater agreement between tactile and radiographic assessments was poor (C1 vs C2: Kappa = 0; C2 vs R: Kappa = -0.10), highlighting that tactile assessment alone is unreliable. Implants placed in osteotomies prepared with a bone leveler consistently achieved complete abutment seating, whereas those placed without a bone leveler frequently exhibited gaps and were often misclassified as properly fitted. CONCLUSIONS: Within the limitations of this in vitro study, incorporating a bone leveler in guided sub-crestal implant placement significantly improves prosthetic abutment fit. Its use should be considered a prerequisite in clinical protocols to enhance prosthetic abutment seating accuracy and improve predictability in guided implant therapy.