Objective: We constructed a trial model of the gum surrounding the abutment tooth using viscoelastic acrylic resin and investigated whether gingival retraction was possible. Methods: The trial model was produced as follows. A section of the gum (5mm in width, 3mm in depth) was removed around the left central incisor and the left first molar of an epoxy model of the upper jaw, and the excised section of gum was replaced with heat-cured viscoelastic acrylic resin. A gingival retraction cord was then applied to the abutment tooth for 5 min. On removal of the retraction cord, an impression was taken using silicon rubber impression material and 3 plaster molds were made. The abutment tooth for the central incisor (I) was prepared for a facing crown (IF) and a jacket crown (IJ), and the abutment tooth for the first molar (M) was prepared for a full cast crown (MC). The effectiveness of the gingival retraction was measured the gap between the gingival margin and the tooth using a profile projection of the plaster molds at the labial (La) and lingual (Li) sides taken before (B) and after (A) retraction. Results: Before-and-after examination of the plaster molds confirmed the enlargement of the gingival pocket in all cases of gingival retraction (Student' t-test, p<0.01). I-La-B:0.133±0.059, I-La-A:0.552±0.054, I-Li-B:0.270±0.063, I-Li-A:0.483±0.058, IF-La-B:1.116±0.103, IF-La-A: 1.483±0.023, IF-Li-B: 0.540±0.040, IF-Li-A:0.874±0.095, IJ-La-B:10163±0.033, IJ-La-A:1.620±0.062, IJ-Li-B:1.363±0.083, IJ-Li-A:1.666±0.081, M-La-B:0.148±0.041, M-La-A:0.326±0.107, M-Li-B:0.273±0.047, M-Li-A:0.527±0.009, MC-La-B:0.836±0.115, MC-La-A:1.051±0.038, MC-Li-B:0.900±0.065, MC-Li-A:1.088±0.029 (Mean±SD, mm) Conclusion: From the results of the present study, we conclude that effective gingival retraction is possible on the trial model with gums made from heat-cured viscoelastic acrylic resin.

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