Does the time-point of orthodontic space closure initiation after tooth extraction affect the incidence of gingival cleft development? A randomized controlled clinical trial.

Background Gingival clefts (GCs) develop frequently during orthodontic space closure and may compromise the treatment outcome. This study assessed whether the time-point of orthodontic space closure initiation, after permanent tooth extraction, affects the incidence of GC. Methods In 25 patients requiring bilateral premolar extraction because of orthodontic reasons, one premolar, chosen at random, was extracted 8 weeks before space closure initiation ("delayed movement," DM), whereas the contralateral premolar was extracted 1 week before ("early movement," EM) ("treatment group"). Presence or absence of GC after 3 and 6 months ("time-point") was recorded and any association with various parameters (i.e., treatment group, time-point, gender, jaw, craniofacial growth, gingival biotype, buccal bone dehiscence after extraction, space closure) was statistically assessed. Results Twenty-one patients contributing with 26 jaws were finally included in the analysis. Overall, GCs were frequent after 3 (DM: 53.9%; EM: 69.2%) and 6 months (DM: 76.9%; EM: 88.5%). EM (P = 0.014) and larger space closure within the study period (P = 0.001) resulted in a significantly higher incidence of GC. Further, there was a tendency for GC development in the presence of buccal bone dehiscence (P = 0.052) and thin gingival biotype (P = 0.054). "Fast movers" (herein cases with a tooth movement >= 1 mm per month) developed a GC in >90% of the cases already after 3 months. "Slow movers" developed a GC in 25% and 70% after 3 months and final evaluation, respectively. Conclusions GC development is a frequent finding during orthodontic space closure and seems to occur more frequently with early tooth movement initiation and in "fast movers."