Even nowadays, complete edentulism is highly prevalent worldwide (Emami et al. 2013). Conventional complete dentures have been used for treating edentulous patients for more than a century. Although maxillary dentures are often effective in satisfying patient needs, some discomfort is common among mandibular denture wearers (Awad et al. 2000). During the last decade, clinical trials have emphasized the mandibular implant– retained overdenture as a cost-effective alternative for treating edentulism. Such an approach has shown better results than conventional dentures regarding oral health–related quality of life (OHRQoL) and patient satisfaction (Emami et al. 2009). International consensus recommends the 2-implant mandibular overdenture as the standard of care for edentulism due to favorable results and low costs, compared with most types of implant restorations (Feine et al. 2002; Thomason et al. 2009).

This article describes results from a 3–parallel group randomized trial with a follow-up period of 12 mo (ClinicalTrials.gov: NCT01411683). The protocol was approved by the institutional Ethics Committee. Participants were enrolled among patients of the School of Dentistry of Ribeirão Preto from January 2012 to January 2014. Participants had to be edentulous, older than 45 y, and presenting with a pair of clinically acceptable conventional complete dentures. Existing dentures had to be adequate in terms of base extension and fit, maxillomandibular relationships, tooth wear, and aesthetics. Mandibular ridges had to have space for the 3 planned interventions, and oral hygiene had to be satisfactory. Another requirement was the absence of systemic conditions that could avert minor oral surgery, such as severe cardiovascular diseases or uncontrolled type 2 diabetes mellitus. After an explanation of study procedures, participants needed to explicitly express their desire to convert their mandibular prostheses into implant-retained overdentures and sign an informed written consent form. Applicants were excluded if an examiner observed insufficient height in the anterior mandibular region (≤10 mm) or signs of severe oral parafunction. A history of radiotherapy in the orofacial region, alcoholism, or severe smoking (>10 cigarettes/day) also led to exclusion, as well as any suspicion of cognitive impairment. Patients unable to return to scheduled sessions were excluded. They should not have had any tooth extracted earlier than 6 mo or present mandibular ridges graded as I or II according to Cawood and Howell (1988).

Clinical parameters, including implant survival rate, were also recorded. Both 2 and 4 mini-implants led to better OHRQoL, compared with 2 standard implants. Treatment with 4 mini-implants was more satisfying than 2 standard implants, with 2 mini-implants presenting intermediate results. Implant survival rate was 89%, 82%, and 99% for 4 mini-implants, 2 mini-implants, or 2 standard implants, respectively. Overdentures retained by 4 or 2 mini-implants can achieve OHRQoL and satisfaction at least comparable with that of 2 standard implants. However, the survival rate of mini implants is not as high as that of standard implants.

In conclusion, mandibular mini-implant-retained overdentures can achieve results at least comparable with the standard of care for edentulism, according to the patient perspectives. The insertion of 4 mini-implants results in superior OHRQoL and patient satisfaction as compared with 2 mini- or standard implants. A major issue for using mini-implants, however, is their lower implant survival rate compared with standard fixtures.

References 

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