Improved Dental Abutment Geometries for Cement-Retained Crowns


    According to the American Academy of Implant Dentistry, over 500,000 dental implants are performed per year in the United States. Despite being such a common procedure, peri-implant disease has been found to affect as much as 48% of implants according to the American Academy of Periodontology. Inefficiencies of commercial dental implant systems have become increasingly apparent as the link between residual cement and peri-implant disease has been made, with excess cement being associated with signs of peri-implant disease in approximately 80% of cases. Despite residual cement being a known problem, little has been done to reduce its extrusion into the subgingival space around implants. In fact, most current commercial dental abutments are based on decades-old natural tooth form preparations for crown augmentations and were never reconfigured, until now.

    The unpredictability of dental cement flow in current implant systems and the lack of cement application technique standards has led surgeons to utilize the technique of their own particular preference. These problems were addressed by developing abutment geometries to improve dental cement flow characteristics and maintain mechanical stability under functional loads. The resulting NOVO abutment design allows for predictable cement flow through the dental implant system, reducing excess cement in the oral environment and thereby enabling the standardization of cementation techniques for clinicians. While current abutment systems utilize Teflon tape to maintain retrievability of the screw, this design incorporates a novel screw insert that not only allows access to the screw, but also improves cement flow throughout the abutment body and reduces void formation (air pockets). Since the long-term success of dental implants is partially attributed to how well dental crowns are attached to their associated implants, one of the key design considerations was to minimize such air pocket formation. The NOVO abutment reduces the “dead space” where cement cannot flow, increasing overall stability of the crown compared with existing abutment designs.

Figure 1. Results of fluid flow evaluation experiment. Cement was able to flow throughout the entire geometry and each of the 16 vents was completely filled, demonstrating completely uniform fluid flow throughout the entire system.

Figure 2: Computational fluid dynamics analysis of amended abutment geometry to reduce cement flow “dead space” within the system. (A) Represents the line drawing of the abutment cut through the sagittal plane, (B) represents the vector image of the vent flow through the abutment, and (C) represents the filled flow pattern of a 45° insert to enable laminar flow through the abutment with no “dead space”.

Technical Summary:

      Key abutment design features were identified to improve dental cement flow characteristics while retaining mechanical stability of the abutment under functional loads. These features have the potential to direct future abutment designs in an effort to improve flow of dental cements and reduce the risk of residual cement extrusion by allowing for a standardization of cement loading volumes prior to seating. To this end, the NOVO abutment design has been optimized to:

  1. Provide flow channels for dental cement within the crown-abutment system
  2. Increase volume within the abutment to decrease the risk of residual cement extrusion
  3. Increase surface area in contact with cement thereby increasing retentive strength of the crown
  4. Add a screw insert to guide cement flow and protect the screw head

    All device characterization has been performed with regard to the Food and Drug Administration’s (FDA) Special Controls Guidance Document for Root-form Endosseous Dental Implants and Endosseous Dental Abutments. The mechanical performance of the NOVO abutment system was demonstrated in vitro: static compression, fatigue, and tensile retention strength values were all within or exceeded the range of similarly tested commercially-available designs. From a clinical utility perspective, the mechanical characteristics demonstrated by the NOVO abutment were above the minimum range necessary for intraoral implantation. The device is ready to enter the FDA approval process for class II medical devices as soon as a manufacturer is identified.