Retention of restorations placed in noncarious cervical lesions after centric and eccentric occlusal loading in a chewing simulator--A pilot study.
OBJECTIVE
To evaluate in a pilot study whether (1) loading of restored teeth in a chewing simulator is an adequate method to reproduce clinical data about the retention rate of restorations placed in noncarious cervical lesions by means of the one-step self-etching adhesive system Prompt-L-Pop, and (2) whether eccentric loading contributes to the loss of Class V fillings.


METHODS
In 12 extracted mandibular premolars with noncarious buccal cervical lesions of similar dimensions, restorations were placed without preparation using Prompt-L-Pop and Tetric Ceram. The adhesive was applied in one layer and cured at 650 mW/cm2 for 10 s, while the composite was placed in two increments and cured at 1200 mW/cm2 for 10 s. After storage in water at 37 degrees C for 7 days, the teeth were mounted in a chewing simulator that uses pneumatic cylinders as force actuators and subjected to a centric load of 50 N and 1,200,000 load cycles at a frequency of 1.6 Hz and simultaneously to 3125 thermocycles (5 degrees C/55 degrees C). The antagonists were standardized and made of Empress ceramic material. Every 100,000 load cycles, the fillings were evaluated with regard to retention. In the second phase, the same teeth were loaded on the lingual cusps with new antagonists for another 1,200,000 cycles.


RESULTS
Neither during centric nor eccentric loading was any restoration loss observed.


CONCLUSIONS
The short-term loading of extracted teeth with Class V fillings in a chewing simulator was inadequate to reproduce the data of clinical studies on the retention rate of a self-etching adhesive system. Obviously, long-term degradation mechanisms (eg, hydrolysis) acting on the composite/dentin interface play a more crucial role when it comes to the loss of retention of Class V restorations. Eccentric loading alone did not contribute to the loss of fillings, so that the theory--which maintains that this type of occlusal stress is a major cause for abfractions or the retention loss of restorations placed in abfraction lesions--may be questioned.
Heintze
Siegward D
SD
Ivoclar Vivadent, Research and Development, Bendererstrasse 2, FL-9494 Schaan, Liechtenstein. siegward.heintze@ivoclarvivadent.com
Cavalleri
Andrea
A
D000538:Aluminum Silicates / Q000737:chemistry; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry; D003793:Dental Restoration, Permanent / Q000145:classification; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D008409:Mastication / Q000502:physiology*; D008422:Materials Testing; D010865:Pilot Projects; D019279:Resin Cements / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D019237:Tooth Cervix / Q000473:pathology*; D014076:Tooth Diseases / Q000628:therapy*; D014867:Water / Q000737:chemistry
D000538:Aluminum Silicates; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C075815:IPS-Empress ceramic; C408584:Prompt L-Pop; D019279:Resin Cements; C121818:Tetric ceram; D014867:Water; D003776:Dental Porcelain