The Application of Short Dental Implants in Modern Dentistry

Treatment of the atrophic maxilla and mandible can pose significant anatomical challenges when dental implant prostheses are desired. Guided bone regeneration procedures may be attempted to increase native ridge dimensions and overcome sinus pneumatization for future implant placement. However, variations in dental implant size and shape can minimize the need for traditional site development surgeries that may prove costly and unpredictable, as well as high risk for medically compromised patients.

The actual definition of short implants remains controversial in the literature. Based on known studies, this review will define short dental implants as ≤ 8 mm in length, and extra short will be considered ≤ 6 mm long. While both implant designs represent viable alternatives, they are not immune to biologic and prosthetic complications.^1,2 The ability to readily identify situations in which short implants are appropriate will set realistic clinical expectations and improve long-term surgical and prosthetic outcomes.

The design and application of short implants cannot be fully understood without first tracing their origin. The concept of replacing missing teeth goes back millennia and was revolutionized by implant dentistry. While the transition from subperiosteal to endosseous implants dramatically improved their survival rate, it was not until the introduction of titanium that surgeons could truly appreciate osseointegration. Titanium is bioinert and offers high corrosion resistance, lending to optimal bone apposition, chemical stability, and a low elastic modulus. The protective titanium oxide layer that forms around the implant surface is still vulnerable to pathogenic bacteria, micromotion and fretting. To counteract these factors, titanium has modifiable surface properties, which have become central to its evolution in recent years.³

Commercially pure titanium implants placed and documented by Brånemark were originally used in the edentulous patient. Multiple parallel implants were placed interforaminally in the mandible and between the anterior walls of the maxillary sinuses. These implants had a machined surface with an external hex connection that were splinted by a metal framework in the definitive restoration because they lacked anti-rotational features.⁴ The mean vertical bone loss in the first year after installation was 1.2 mm, with 0.2 mm bone loss every year thereafter.⁵

References

1. Lee SA, Lee CT, Fu MM, Elmisalati W, Chuang SK. Systematic review and meta-analysis of randomized controlled trials for the management of limited vertical height in the posterior region: short implants (5 to 8 mm) vs longer implants (> 8 mm) in vertically augmented sites. Int J Oral Maxillofac Implants. 2014;29:1085–1097.
2. Ravidà A, Barootchi S, Askar H, Suárez-López del Amo F, Tavelli L, Wang HL. Long-term effectiveness of extra-short (≤ 6 mm) dental implants: a systematic review. Int J Oral Maxillofac Implants. 2019;34:68–84.
3. Linkow LI, Rinaldi AW, Weiss W Jr, Smith GH. Factors influencing long-term implant success. J Prosthet Dent. 1990;63:64–73.
4. Adell R, Lekholm U, Rocker B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg. 1981;10:387–416.
5. Albrektsson T, Zarb G, Worthington P, Eriksson AR. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986;1:11–25.

This information originally appeared in Botto AA, Saltz AE. Clinical utility of short dental implants. Decisions in Dentistry. 2021;7(6)36-39.