Purpose: To measure the long-term changes of clinical crown height in patients treated with single-implant crowns and compare them to those of an adult population with normal dentition. Materials and Methods: The test group comprised 23 patients, consecutively restored with a total of 48 single-implant crowns in the anterior maxilla. Mean age was 26.1 ± 11.4 years at inclusion. Original master casts were stored after treatment, and patients were recalled for new study casts an average of 15.8 ± 0.74 years later. The control group comprised 141 dental students with a mean age of 22.9 ± 1.20 years at inclusion. Study casts were made at inclusion and after 10 (n = 141) and 20 years (n = 60). Clinical crown height was measured for maxillary anterior teeth, and data were pooled and compared regarding clinical crown height and changes in height. Results: Implant clinical crowns were an average of 0.6 ± 1.04 mm longer than the contralateral teeth (P .05). Central and lateral incisors showed mucosal recession at an average of 0.4 ± 0.53 mm (P .05) and 0.6 ± 0.58 mm (P .01), respectively. In the control group, only minor insignificant changes (± 0.1 mm) in mean clinical crown height could be observed during the follow-up period. However, obvious individual variations of changes could be found in the control group, and were more pronounced for women. Altogether, 15% and 9% of measured teeth showed >= 1.0 mm increase or decrease of clinical crown height during 20 years, respectively. Initially, shorter teeth presented a trend (P .05 to .001) of more mucosal recession than longer teeth. Conclusion: Mean values of clinical crown height disguise significant individual variations of changes. To perform a risk evaluation for potential future mucosal recession, it could be suggested that greater changes in clinical crown height may occur in patients provided with implant-supported crowns than in untreated control subjects, possibly more for women than men, and more for initially shorter teeth than for longer adjacent teeth.