Single implant crowns: neighbouring teeth show more complications over time

A single implant is often presented as the conservative choice: it replaces the missing tooth without touching its neighbours. This retrospective longitudinal study from the University of Michigan (Wang HL and colleagues) looked at what happens to those neighbours over time, asking whether single implant-supported crowns affect the health of the adjacent natural teeth.

The authors analysed clinical and radiographic records of 456 patients with a single implant. Complications of the adjacent teeth — new caries, new restorations and tooth loss — were compared with three intra-patient control groups made of teeth in the other quadrants, using crown delivery as baseline. Multivariable models estimated risk over a short-term window (1–5 years; mean follow-up 3.9 years, n = 456) and a long-term window (5–15 years; mean 8.9 years, n = 180).

Teeth next to the implant fared worse in both windows. In the short term, the overall complication rate was 8.0% versus 2.2–2.7% in the control quadrants (odds ratios 2.92–3.65); in the long term, 15.0% versus 6.4–7.8% (odds ratios 2.16–2.57). The pattern depended on position: mesial neighbours showed higher short-term caries susceptibility, while distal neighbours accounted for the short-term risk of tooth loss. The need for new restorations stayed elevated throughout. Bone-level implants, narrow-diameter implants and prior orthodontic alignment were associated with fewer complications; bruxism and male sex were associated with more.

For clinicians, the finding reframes the single implant as a site whose follow-up extends beyond the implant itself: at recall, the neighbouring teeth deserve the same attention as the peri-implant probing. The design, however, limits causal reading. It is retrospective and from a single university setting, the long-term cohort shrinks to 180 patients, and some odds ratios are large enough to suggest imprecise estimates. The study describes an association worth checking at every recall, not a reason to avoid single implants.