Dynamic fatigue and fracture resistance of non-retentive all-ceramic full-coverage molar restorations. Influence of ceramic material and preparation design.
OBJECTIVE
The purpose of the study was to evaluate the influence of preparation design, and ceramic material, masticatory fatigue and fracture resistance of non-retentive all-ceramic full-coverage restorations luted on human mandibular molars.


METHODS
Full-coverage occlusal restorations were laboratory fabricated from leucite reinforced glass-ceramic (IPS Empress Esthetic) or lithium disilicate glass-ceramic (IPS e.max Press). For each ceramic material four groups with eight specimens each were randomly assigned. Groups had either a non-retentive, occlusal preparation with chamfer finishing line or straight-beveled finishing line and the preparation was either completely within enamel or within dentin with a finishing line in enamel. Restorations were adhesively luted to the teeth using composite resin. After storage in water for 1 week specimens were cyclic loaded 600,000 times with a weight of 10kg and additionally, thermocycled 3500 times (5/55 degrees C) in a masticatory simulator. Surviving specimens were loaded until, fracture in a universal testing machine. Statistical analysis was done using three-way ANOVA.


RESULTS
All specimens survived the masticatory fatigue. Mean fracture resistance ranged from 2895 to 4173N. Influence of ceramic material on fracture resistance was significant (p=0.0001). Lithium disilicate glass-ceramic restorations had higher fracture resistances than leucite reinforced glass-ceramic restorations. Different preparation designs showed no significant influence on fracture resistance (p=0.0969). The design of the finishing line did not influence the fracture resistance (p=0.9461).


CONCLUSIONS
The fracture resistance of adhesively luted non-retentive full-coverage molar restorations, made of lithium disilicate or leucite reinforced glass-ceramic is promising and seems to permit clinical application.
Clausen
Jan-Ole
JO
Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Strasse 16, Kiel, Germany.
Abou Tara
Milia
M
Kern
Matthias
M
D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D001732:Bite Force; D002484:Cementation / Q000379:methods; D003188:Composite Resins / Q000737:chemistry; D003743:Dental Enamel / Q000033:anatomy & histology; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000033:anatomy & histology; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D019246:Tooth Preparation / Q000379:methods*; D014867:Water / Q000737:chemistry
D000538:Aluminum Silicates; D003188:Composite Resins; C508050:IPS e.max Press; C075815:IPS-Empress ceramic; C469607:OptiBond FL; D019279:Resin Cements; C493120:lithia disilicate; D014867:Water; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink