Advances in Implant Design
With implant restorations, a successful outcome begins in the surgical treatment phase. An ideal outcome can be achieved only through harmony of the tissue and the restoration.
Where it is not possible to idealize the tissue framework due to preoperative anatomic limitations, the restorative dentist and technician are under greater pressure to compensate for these deficiencies. This emphasizes the importance of comprehensive treatment planning by the surgical–restorative team and underscores the fact that surgical decisions made by the periodontist as well as the skill, methodology, and materials used will create the foundation for prosthetic success or failure.
Surgical decisions regarding implant size (ie, length/width) and bone density–based site preparation protocols (ie, press-fit or undersizing the osteotomy) are important for the goal of optimizing initial implant stability; however, implant design also influences the short- and long-term successes of implants.1 Although no one optimal implant design exists, macrogeometry features that allow for superior initial stability open opportunities for implant placement at the time of extraction into less favorable bone quality and early or immediate restoration protocols. Implant design can influence initial or primary stability; tapered implant designs significantly improve initial or primary stability as assessed by insertion torque over traditional parallel-walled implants, by mechanically enhancing implant stability through a wedging effect. Also, thread design, pitch, angle, depth, and width, as well as the crestal module (microthreads), can influence the stability of an implant by affecting the distribution of stress forces around it.
Due to efforts to improve integration or bone-to-implant contacts, newer surface treatments have been developed. The introduction of moderately rough implant surfaces, generally random patterns, increase the implant surface area, thus increasing the potential for enhanced bone-to-implant contacts.2,3 Most of these surfaces are generated through some type of acid-etching or various blast treatments, whereas others are created using additive processes and historically with rougher surfaces (eg, titanium spheres, titanium plasma-sprayed, hydroxylapatite). Moderately rough surfaces are particularly important in sites with inferior bone quality (type III to type IV), when placed in previously grafted sites, and when placing short implants (reduced surface or contact area). The osseointegration rate might be influenced by surface chemistry (addition of specific ions) or activity (hydrophilicity).
Important for long-term and predictable esthetic outcomes, features to enhance crestal bone stability and gingival tissue architecture have been incorporated into implant collar designs, including the addition of bone-retentive collar microgrooves. These have resulted in reduced crestal bone remodeling compared with implants that have standard threads. Microgrooves may mitigate the formation of the biologic width by increasing the surface area at the implant collar. This is particularly important in situations where adjacent implant placement is necessary and the advantages of teeth in supporting supracrestal soft tissues are lost.
Unique and challenging clinical situations such as poor bone quality, reduced ridge height, and grafted areas demand the use of new surfaces and implant shapes that improve both initial and secondary stability. Although many abutment materials are available, ranging from titanium, gold-anodized coatings to zirconia and lithium disilicate, their design and handling can significantly contribute to a healthy and stable soft tissue response. It remains important to emphasize that implants and abutments are merely the tools, and that the clinician’s treatment planning prowess and level of skill will have the most impact on the treatment outcome.
1. Elias CN, Rocha FA, Nascimento AL, Coelho PG. Influence of implant shape, surface morphology, surgical technique and bone quality on the primary stability of dental implants. J Mech Behav Biomed Mater. 2012;16:169-180.
2. Valencia S, Gretzer C, Cooper LF. Surface nanofeature effects on titanium-adherent human mesenchymal stem cells. Int J Oral Maxillofac Implants. 2009;24(1):38-46.
3. Wennerberg A, Albrektsson T. Effects of titanium surface topography on bone integration: a systematic review. Clin Oral Implants Res. 2009;20(suppl 4):172-184.
ABOUT THE AUTHOR
Sonia S. Leziy, DDS, Dipl Perio, FCDS(BC), FRCD(C)
Private Practice, Imperio Group Dental Health Specialists
North Vancouver, British Columbia, Canada
Clinical Associate Professor
University of British Columbia
Vancouver, British Columbia, Canada