Abstract: PURPOSE: To explore the clinical application effect of vacuum-formed compression film retainer (VFR) to improve the contact loss of implant restoration. METHODS: Fifty-eight patients with single crown restorations (all using Straumann implants) were selected from our hospital from June 2019 to October 2020. According to the clinical randomized case-control study, they were divided into 2 groups, each with 29 cases, with a total of 116 implanted single crown adjacent surfaces. The experimental group wore film retainer during the night, while the control group did not wear film retainer during day and night. The periodontal probing depth(PD), looseness (M), and gingival bleeding index (BI) of implants and natural teeth were checked immediately, 1, 3, 6 and 12 months after crown restoration. The surface contact tightness and the number of metal paper layers, and the mesial/distant/neighbor contact loss rate were calculated. The data was statistically analyzed by SPSS 19.0 software package. RESULTS: As time went by, the loss rate of the mesial and distant neighbors of the two groups of implanted single crowns gradually increased, and the loss rate of the mesial neighbors of the control group during the 12-month follow-up was 62.06%, which was significantly higher than that of the experimental group of 31.03% (P<0.05). The loss rates of single crown mesial contact loss in the experimental group at 1, 3 and 6 months of follow-up were 17.24%, 20.68% and 27.58%, respectively, while those in the control group were 20.68%, 37.93%, and 48.27% (P>0.05). There was no significant difference of the loss rate of single-crown distal neighbor contact between the two groups at 1, 3, 6 and 12 months of follow-up(P>0.05). At 12-month follow-up, the experimental group had 9 cases with loss of near neighbor contact, which was less than 18 cases of the control group(P<0.05). There was no significantly difference in the number of distant neighbor contact loss between the two groups(P>0.05). In the experimental group, the increase in metal paper wearing the film retainer was not more than 2 cases (an increase of 2 pieces was the standard), which was less than 19 cases in the control group (P<0.05). At 12-month follow-up, the tension value of the mesial adjacent surface was reduced. There was no contact loss on the mesial adjacent surface, but its tightness decreased. Time extension of the adjacent surface contact loss cannot be ruled out. There was no obvious change rule of tension value of the distance between the two groups of adjacent surfaces. During the entire follow-up period, the implants and natural teeth of the two groups had no obvious changes in PD, BI, and M. The experimental group had no significant food impaction complaints, but 8 cases had significant food impaction in the control group, however they could be cleaned by flossing. CONCLUSIONS: VFR can effectively reduce the contact loss rate of the near neighbors of the implanted single crown, it has no obvious impact on oral hygiene of implanted single crowns.

Key words: Vacuum-formed retainer, Implant restorations, Loss of adjacent contact