Root length in transplanted premolars.

The objectives of the present prospective longitudinal study were to establish the survival and success rates for premolars with partly developed roots transplanted according to a set protocol, and to analyze the effect of varying pre-surgery root development on final root length. Standardized periapical radiographs of 132 consecutively transplanted premolars were obtained at predetermined intervals over a 4-year follow-up period. Survival and success rates were calculated on the basis of presence of teeth and recording of defined radiological variables, respectively. Final root length was compared to normative metric data for root morphology. From the total sample, 54 patients with 68 transplanted premolars suitable for analysis of root growth relative to initial root length were identified, and divided into subsamples according to root length pre-transplantation. Survival rates were 100% after 1, 2, and 3 years, and 98.6% 4 years post-transplantation. The success rates were 92.9%, 92.8%, 89%, and 90.5% in subsamples collected 1, 2, 3, and 4 years after transplantation, respectively. The transplants obtained on average 78% of normative root length, and by dichotomizing the transplanted teeth in subsamples with 'short' and 'long' roots pre-surgery, similar final root lengths were observed even if 'short' roots had the greatest increase. Very early transplantation (roots < 7 mm), however, tended to result in short final root length. It is concluded that the success and survival rates were comparable to results obtained in similar studies. Initial root length was a significant predictor of root length increase. Transplanting teeth with short roots is to risk short final root length.