Short implants vs vertical GBR: the 8-year model favors the simpler choice

Choosing between a short implant (6–8.5 mm) placed without bone augmentation and a regular-length implant (>10 mm) placed after vertical guided bone regeneration (GBR) is a common decision point when rehabilitating the posterior atrophic mandible. Both approaches are clinically viable, but they differ substantially in cost, morbidity, and treatment time — a tradeoff seldom quantified with formal economic modeling. This study built a discrete-time state-transition microsimulation model to compare the two strategies over an 8-year horizon from a private-payer perspective, using clinical inputs drawn from a recent meta-analysis of randomized trials and unit costs from Chilean fee schedules (converted to 2025 USD via purchasing power parity).

Outcomes were expressed as implant-years (IY) and the stricter complication-free implant-years (CFIY), with incremental cost-effectiveness ratios (ICERs) calculated between strategies. Over the 8-year horizon, short implants without GBR were both cheaper and modestly more effective: mean cost of USD 3,662 versus USD 6,030 for regular-length implants with GBR, and 6.77 versus 6.49 implant-years (6.71 versus 6.27 complication-free implant-years). This translates into incremental savings of USD 2,367 alongside incremental gains of 0.28 IY and 0.44 CFIY for the short-implant strategy — meaning short implants dominated the comparison rather than merely being "non-inferior at lower cost."

One-way deterministic sensitivity analysis identified initial implant cost as the most influential parameter, and probabilistic sensitivity analysis across 2,000 Monte Carlo iterations confirmed the finding was robust: the large majority of simulated scenarios fell in the cost-saving, more-effective quadrant of the cost-effectiveness plane.

For clinicians and practice managers weighing treatment planning against patient cost and chairside time, this is one of the more rigorous economic arguments yet published for defaulting to short implants in posterior atrophic mandible cases rather than routinely reaching for vertical GBR — provided the clinical scenario (Seibert type II defects) and bone quantity support a short implant in the first place. The authors caution that absolute cost figures are specific to the Chilean private-payer setting, but the underlying clinical/effectiveness relationship is likely to generalize.