From the Research
According to Meijer 2018, single tooth non-splinted implants with a 2:1 crown to implant ratio demonstrated similar technical complications compared to those with a 1:1 ratio. This finding suggests that implants with higher crown-to-implant ratios can perform adequately from a technical standpoint despite the potentially increased biomechanical stress 1. Clinicians can consider using single implants in situations where anatomical limitations result in higher crown-to-implant ratios without necessarily expecting more technical problems such as screw loosening, fractures, or other hardware complications. This is particularly relevant in areas with vertical bone loss or in the posterior regions where crown height may be greater. However, proper case selection, occlusal adjustment, and regular maintenance remain important factors for long-term success regardless of the crown-to-implant ratio. The biomechanical principle behind this finding may relate to the ability of modern implant systems and connections to effectively distribute occlusal forces even when the crown portion is significantly longer than the implant itself.
Some key points to consider:
- The study by Meijer 2018 found that high crown-to-implant ratios may lead to complications due to unfavorable occlusal forces, but the data reviewed did not demonstrate a high occurrence of biological or technical complications 1.
- A systematic review and meta-analysis published in 2021 found that the crown-to-implant ratio did not significantly influence implant survival rate, but the qualitative data suggested that marginal bone loss increased as the crown-to-implant ratio increased 2.
- Another study published in 2020 found that short implants supporting fixed prostheses in the posterior region achieved predictable clinical outcomes over a 3 to 7 year period, and the higher the crown-to-implant ratio, the less the peri-implant marginal bone loss 3.
- The effect of abutment screw design and crown/implant ratio on preload maintenance of single-crown screw-retained implant-supported prostheses was investigated in a study published in 2019, which found that the conical head screw set presented a higher maintenance of applied preload than the flat head screw set 4.
Overall, the available evidence suggests that single tooth non-splinted implants with a 2:1 crown to implant ratio can be a viable option for patients, but careful consideration of the individual patient's needs and anatomical limitations is necessary to ensure long-term success.