| Many researchers focus on the esthetic effect of implant-supported single crown. All-ceramic materials have been increasingly used in clinic due to its unique esthetical properties. Numeral studies have proved that optimal esthetic effect can be achieved by restoring all-ceramic crown on all-ceramic abutment. However, fracture of all-ceramic abutment or crown because of its brittleness was seen during follow-up period. So, observing the stress distribution of implant-supported all-ceramic single crown will help to analyze the cause of fracture of all-ceramic abutment and crown and prevent the failure of implant.The purpose of present study was to observe the stress distribution of implant-supported all-ceramic single crown by computing the three dimensional finite element model of the mandibular first premolar, analyze possible factors that could influence the stress distribution of all-ceramic crown, ceramic abutment, screw, fixture and bone. There are four parts in this study.Part 1: The stress distribution of implant-supported ail-ceramic crown with different abutmentObjective: To observe the stress distribution of implant-supported all-ceramic crown with alumina, zirconia and titanium abutment.Materials and methods : The three dimensional finite element model of implant-supported mandibular first premolar was computed by COSMOS/M 2.85 software. Vertical 600N and horizontal 225N loading was applied on the occlusal surface. Alumina, zirconia and titanium were used as abutment materials respectively. The stresses of crown, abutment, screw, fixture and bone with different abutment were compared with those of metal-ceramic crown with titanium abutment.Results: The stress distribution with ceramic abutment was similar to titaniumabutment, the maximal tensile stress and Von mises stress was higher under horizontal loading while compressive stress was higher under vertical loading. The maximal tensile stress, compressive stress and Von mises stress has no significant difference between all-ceramic crown and metal-ceramic crown; the maximal stress of titanium abutment was lower than that of ceramic abutment while the displacement of titanium abutment was higher than that of ceramic abutment; the Von mises stresses of screw, fixture and bone with titanium abutment was a little higher than those of ceramic abutment.Conclusions: The stresses of all-ceramic crown have no difference with that of metal-ceramic crown; the displacement of abutment and stresses of fixture and bone are lower when ceramic abutments are used; the stress distribution of prostheses with alumina abutment and zirconia abutment shows no significant difference.Part 2: The influence of cement on the stress distribution of implant-supported all-ceramic single crownObjectives: To observe the influence of cement types and thickness on the stress distribution of implant-supported all-ceramic single crown.Materials and methods: Three dimensional finite element model of implant-supported mandibular first premolar was computed with In-Ceram alumina crown and zirconia abutment. The cements included zinc oxide eugenol, resjjkraedrffgcTglass ionomer and two kinds of resin with different Young's modulus. The thickness of cement was 50jum and 100/un. The stresses of all-ceramic crown, abutment, screw, cement, fixture and bone were analyzed when different cement types and thickness were used under vertical and horizontal loading.Results: The maximal tensile stress, compressive stress and Von mises stress were higher under horizontal loading except that the compressive stress of all-ceramic crown was higher under vertical loading. The stresses of all-ceramic crown were almost the same with different cement types and thickness; the stresses of abutment with different cement types had no difference while the stresses of 50|um were lower than those of lOQum; the stresses of different cement types were different, the values were higher when the thickness was 50/um; the tensile stress of zinc oxide eugenol was higher than its bond strength; the stresses of screw, fixture and bone showed no difference with different cement types and were lower when thethickness was 5Qam.Conclusions: The type of cement and thickness have no significant influence on the stress distribution of all-ceramic crown, screw, fixture and bone; the stresses of abutment is lower when the thickness of cement is thinner; the stresses of different types of cement are different and lower when the thickness is thinner; zinc oxide eugenol is not good for permanent cementing the implant-supported all-ceramic crown.Part 3: The stress distribution of implant-supported all-ceramic single crown restored with different all-ceramic materialsObjectives: To observe the stress distribution of implant-supported all-ceramic single crown restored with different all-ceramic materials.Materials and methods: The three dimensional finite element model of implant-supported mandibular first premolar was computed using COSMOS/M 2.85 software. The all-ceramic crown was restored with different all-ceramic materials. The stresses were compared under vertical and horizontal loading.Results: The maximal tensile stress of all-ceramic crown was lowest when restored with IPS Empress 2 (15.79MPa) and highest when restored with In-Ceram; the maximal compressive stress was highest when restored with In-Ceram Spinel (26.5 IMPa) and lowest when restored with IPS Empress 2 (18.08MPa). the stresses of abutment, screw, fixture and bone were almost the same when restored with different all-ceramic materials.Conclusions: The stress distribution of implant-supported all-ceramic crown shows no significant difference when restored with different all-ceramic materials.Part 4: The influence of cusp inclination on the implant-supported all-ceramic single crownObjectives: To observe the influence of different cusp inclination on the stress distribution of implant-supported all-ceramic single crown.Materials and methods: 5 three dimensional finite element models were computed using COSMOS/M 2.85 software. The crown was restored with In-Ceram alumina, the abutment was zirconia. The cusp inclination of buccal cusp was 20°, 25°, 30°, 35° and 40°respectively. The stresses of different cusp inclination were analyzed under vertical and horizontal loading.Results: The stress distribution of implant-supported all-ceramic crown was similar with different cusp inclination. Under vertical loading, the maximal tensile stress of all-ceramic crown increased as the cusp inclination increased, the stresses of abutment, screw, fixture and bone had no different with different cusp inclination. Under horizontal loading, the maximal tensile stress of all-ceramic crown decreased as the cusp inclination increased, the stresses of abutment, screw, fixture and bone increased as cusp inclination increased.Conclusions: The maximal tensile stress of all-ceramic crown decreases as the cusp inclination increases, the stresses of abutment, screw, fixture and bone increases as the cusp inclination increases.
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