Mini implants for definitive prosthodontic treatment: a systematic review

Statement of problem: Mini implants are commonly used in orthodontics and for interim prosthodontic treatment, but evidence for their use in definitive prosthodontic treatment is not clear.

Purpose: This systematic review evaluated the mini-implant literature to analyze short-term (1 to 5 years), medium-term (5 to 10 years), and long-term (beyond 10 years) survival rates when used for definitive prosthodontic treatment.

Material and methods: An electronic search of the English language literature for articles published between January 1974 and May 2012 was performed by using PubMed and Cochrane databases with predetermined inclusion criteria. Key terms included in the search were mini dental implants, narrow diameter implants, reduced diameter implants, small diameter implants, transitional implants, interim implants, and provisional implants. After a systematic filtering process, the selected articles were subjected to a detailed review, and the data collected were used to calculate the 1-year interval survival rate (ISR) and the cumulative survival rate (CSR).

Results: The electronic database search yielded 1807 titles. By scrutinizing the titles and abstracts with inclusion and exclusion criteria, the researchers identified 9 studies of mini implants for definitive prosthodontic treatment. Of the studies identified, 1 was a randomized controlled trial, 2 were prospective studies, and 6 were retrospective studies. The majority of mini implants were placed by using a flapless surgical technique in the mandibular anterior region to support an overdenture. The 1st year ISR was 94.7% and the CSR over a 9-year period, primarily attributed to data from 1 study, was 92.2%. Most implants were immediately loaded and almost all implant failures occurred during the first year after implant placement.

Conclusions: For short-term survival, the first year ISR of 94.7% of mini dental implants appears encouraging, but the true 1-year survival rate is unknown, as the minimum follow-up period reported for several implants was less than a year. Insufficient information about failures after the first year makes it difficult to draw conclusions about the medium-term survival of these implants. Currently, there is no evidence for the long-term survival of mini implants.