title: Effect of mouth-motion fatigue and thermal cycling on the marginal accuracy of partial coverage restorations made of various dental materials.
abstract: OBJECTIVE
  To investigate the influence of mouth-motion fatigue on marginal-accuracy of partial-coverage-restorations-(PCRs) of various dental materials.
  
  
  METHODS
  Eighty molars were prepared equally and divided into five groups (n=16). PCRs were fabricated of following dental materials: Group-GO=Gold-Pontor-MPF(double dagger), Group-TA=Targis*, Group-EX=IPS-e.max-Press*, Group-EM=IPS-Empress*, Group-PC=ProCAD*/Cerec 3(dagger) ((double dagger)Metalor/*Ivoclar-Vivadent/(dagger)Sirona-Dental-System). Gold-PCRs were cemented conventionally. Residual 64 PCRs were adhesively luted and subjected to masticatory loading (1.2million-cycles, 1.6Hz, 49N) and thermal cycling (5 degrees C/55 degrees C, 60s, dwell-time, 5500cycles). Discrepancies in marginal-accuracy were examined on epoxy replicas (200 x magnification). Statistical analysis was performed by unpaired and paired t-tests (alpha=0.05).
  
  
  RESULTS
  After cementing, marginal-accuracy (geometrical mean)[95% confidence limits] was recorded: GO-47[43-51]microm, TA-42[38-45]microm, EX-60[52-67]microm, EM-52[45-60]microm and PC-75[59-94]microm. No significant differences were found between groups GO, TA and EM. Values of Group-EX were significantly higher compared to Group-TA (p=0.04). Group-PC demonstrated significantly decreased marginal-accuracy towards groups GO (p=0.03) and TA (p=0.02). Except for Group-GO (p=0.01), no significant changes in marginal-accuracy were observed after mouth-motion fatigue and thermal cycling (GO-42[38-45]microm, TA-42[38-47]microm, EX-56[49-65]microm, EM-54[46-64]microm and PC-71[59-84]microm). However, Group-GO and Group-EM showed significant deviations in marginal-accuracy after aging (p=0.04). Marginal discrepancies of groups EX and EM were similar (p=1.0). Values of Group-PC were significantly higher when compared to groups GO (p=0.01) and TA (p=0.02). Buccal-lingual marginal discrepancies were significantly higher than mesial-distal in all groups and stages.
  
  
  CONCLUSIONS
  Cast-gold-PCRs demonstrated superior marginal-accuracy, followed by indirect ceromer PCRs. All-ceramic PCRs showed in vitro clinical acceptable marginal widths, even though CAD/CAM fabrication slightly compromised marginal-accuracy. Since preparation margins were not exposed to occlusal loading directly, increased marginal discrepancies due to marginal chipping during mouth-motion fatigue were not experienced.
authors.affiliation: Department of Prosthodontics, Albert-Ludwigs-University, Faculty of Dentistry, Freiburg, Germany. christian.stappert@nyu.edu
authors.forename: Christian F J
authors.initials: CF
authors.lastname: Stappert
authors.forename: Somsak
authors.initials: S
authors.lastname: Chitmongkolsuk
authors.forename: Nelson R F A
authors.initials: NR
authors.lastname: Silva
authors.forename: Wael
authors.initials: W
authors.lastname: Att
authors.forename: Joerg R
authors.initials: JR
authors.lastname: Strub
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D001732:Bite Force; D002484:Cementation / Q000379:methods; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D017076:Computer-Aided Design; D003722:Dental Alloys / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000145:classification; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D005899:Glass Ionomer Cements / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007284:Inlays; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D012823:Silicate Cement / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D003722:Dental Alloys; D003764:Dental Materials; D005899:Glass Ionomer Cements; D006047:Gold Alloys; C508050:IPS e.max Press; C075815:IPS-Empress ceramic; C454801:ProCAD Ceramic; D019279:Resin Cements; C111841:ceromer; C111282:dental polyglass; D003776:Dental Porcelain; D012823:Silicate Cement