Comparison of 6‐mm and 11‐mm dental implants in the posterior region supporting fixed dental prostheses: 5‐year results of an open multicenter randomized controlled trial

OBJECTIVE: The aim of this multicenter, randomized controlled trial was to compare the clinical and radiographic outcomes of 6‐mm or 11‐mm implants, placed in the posterior maxilla and mandible, during a 5‐year follow‐up period. MATERIALS AND METHODS: Ninety‐five patients with adequate bone height for 11‐mm implants, were randomly allocated to a 6‐mm group (test group with short implants) or an 11‐mm group (control group with standard‐length implants). Two or three implants of the same length were placed in each patient and after 6 weeks loaded with a splinted provisional restoration. This was followed by definitive splinted restoration 6 months after implant placement. Clinical and radiographic parameters, including the occurrence of complications were recorded. RESULTS: A total of 49 patients were enrolled to receive 6‐mm implants (n = 108) and 46 patients to receive 11‐mm implants (n = 101). Three implants (two of 6 mm and one of 11 mm in length) were lost before loading and one 6‐mm implant after 15 months of function, and one 11‐mm implant was lost during the first year of function. The 5‐year survival rates were 96.0% and 98.9% in the 6‐mm and 11‐mm group, respectively. The mean marginal bone level changes 5 years post‐loading were 0.01 ± 0.45 mm (bone gain) in the 6‐mm group and −0.12 ± 0.93 mm (bone loss) in the 11‐mm group (p = .7670). Clinical parameters, including plaque, bleeding on probing and pocket probing depth were not significantly different between the groups, and also technical complications were low. CONCLUSION: The clinical and radiographic outcomes of 6‐mm short and 11‐mm standard‐length implants were not different during a 5‐year evaluation period.