Indiana University-Purdue University Indianapolis (IUPUI) / Clinical evidence suggests that the use of liners in posterior composite
restorations may increase the frequency of restoration fractures. Materials that have
been used as liner materials for resin composite (RC) restoration include conventional
glass ionomers, resin-modified glass ionomers (RMGI), and flowable composites.
The aim of this study was to compare the flexural strength of a monolayer of resin
composite with that of a bilayer of resin composite and liner. Four types of RC beams
were tested: a monolayer control that is an un-lined RC (Tetric EvoCeram, Ivoclar
Vivadent) and three “bilayer” specimens that consisted of this same RC lined with
one of three liners. The three liners used included two RMGI cements (Vitrebond LC
liner; 3M ESPE and, GC Fuji Lining LC; GC America) and a flowable resin
composite (Tetric EvoFlow, Ivoclar Vivadent). Each group was tested after water
storage for 24 h and 30 d. Altogether, eight, 12-specimen groups were fabricated and
tested.
Methods: A 25 x 2 x 2 mm mold was completely filled with the RC to form
the control beams. To form the bilayer beams, this mold was filled with 0.5 mm of
the liner and then with 1.5 mm of the RC. Specimens were stored in 37oC distilled
for either 24 h or 30 d. Immediately prior to testing, the 30-day groups were also
thermocycled 2500 times, between water baths at 7 oC and 48oC with a 30-s dwell
time and a 10-s transit time.
Flexural strength was determined using a three-point–bending device. A twoway
analysis of variance (ANOVA) with interactions was used to investigate how
liner group (or no liner) and storage time affected strength.
Results: The interaction between liner type and storage time was significant (p
= 0.0128). The un-lined RC (the monolayer beam) was significantly stronger after 24
h than after 30 d in water (p = 0.0098). Water storage between 24 h and 30 d did not
change the flexural strength of any of the bilayer (lined) beams (p > 0.05). After
storage for 24 h and also for storage for 30 d, both un-lined RC and RC lined with the
flowable RC exhibited significantly higher flexural strength (p = 0.0001) than the
bilayer beams lined with either RMGI liners.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/2077 |
| Date | January 2009 |
| Creators | Azzam, Mai |
| Contributors | Platt, Jeffrey A., Levon, John, Taskonak, Burak, Brown, David, Andres, Carl, Legan, Joseph |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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