The space-closure alternative for missing maxillary lateral incisors: an update.

maxillary lateral incisors traditionally includes either space closure1,2 or space reopening and insertion of implants.2,3 Some common objections to orthodontic space closure are that the treatment outcome may not look “natural”, that the functional occlusion is compromised, and that retention of the treatment result is difficult. Although it may appear preferable esthetically and functionally to create space for replacement of the missing lateral incisor with a single-tooth implant4,5 or resin-bonded bridge,6 and while high survival rates for implant-supported porcelain crowns can be expected, long-term biological complications are frequent7-19 (Table 1). At present, it is not possible to predict when such unesthetic changes will appear. Progressive infraocclusion may occur due to the continuous eruption of adjacent teeth (Fig. 1), even when an implant is placed in a mature adult.8,9,13-15 Obviously, an osseointegrated implant crown will not undergo the normal uprighting of upper and lower incisors that occurs from adolescence to adulthood,16,17 which means the implant crown will become more infraoccluded and protrusive in appearance over time.13 Furthermore, blue coloring of the labial gingiva has been reported above more than 50% of single-implant crowns at four-year follow-ups.12 Such darkening is caused by the resorption of endosteally derived bone, which is more porous and more prone to resorption than periosteal bone. Abutment exposure due to retraction of the labial gingiva is another complication,13 possibly caused by toothbrushing damage and other factors. The frequent lack of complete gingival papillary fill around implant crowns12,18 may also have esthetic