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 ¡À 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 ¡À 0.74 years later. The control group comprised 141 dental students with a mean age of 22.9 ¡À 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 ¡À 1.04 mm longer than the contralateral teeth (P < .05). Central and lateral incisors showed mucosal recession at an average of 0.4 ¡À 0.53 mm (P < .05) and 0.6 ¡À 0.58 mm (P < .01), respectively. In the control group, only minor insignificant changes (¡À 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 ¡Ý 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. Int J Prosthodont 2006;19:455¨C461