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Interfacial adaptation of a Class II polyacid-modified resin composite/resin composite laminate restoration in vivo.
Umeå University, Faculty of Medicine, Odontology.
2000 (English)In: Acta Odontologica Scandinavica, ISSN 0001-6357, Vol. 58, no 2, 77-84 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this in vivo study was to evaluate the interfacial adaptation of Class II resin composite open sandwich restorations with a polyacid-modified resin composite as a stress-absorbing layer (PMRC/RC). Twenty Class II box-shaped, enamel-bordered cavities were prepared in 10 premolars scheduled to be extracted for orthodontic reasons. An open PMRC/RC sandwich restoration was placed in 1 of the cavities of each tooth. The first layer, PMRC, in the proximal box extended to the periphery in the cervical part of the cavity. The following RC layers were placed with a horizontally incremental technique. The PMRC was excluded from the control cavity. The teeth were extracted after 1 month and the interfacial adaptation of the restorations was studied with quantitative scanning electron microscope analysis using a replicate technique. Gap-free interfacial adaptation was observed for the PMRC/RC and RC restorations in cervical enamel in 97% and 73%, respectively (P = 0.006). The gap-free scores for dentin were 87% and 64%, respectively (P = 0.022). Excellent interfacial adaptation was observed in both groups for the occlusal enamel 99% and 100%, respectively. The adaptation to occlusal enamel for the direct resin composite restorations was significantly better than to dentin or cervical enamel. A higher frequency of enamel fractures was observed parallel to the cervical margins compared to the occlusal. No dentin fractures were observed in the experimental groups. The PMRC/RC sandwich technique showed a statistically significant improved interfacial adaptation to dentin and cervical enamel in Class II enamel-bordered cavities. The clinical significance of the differences has to be evaluated.

Place, publisher, year, edition, pages
2000. Vol. 58, no 2, 77-84 p.
URN: urn:nbn:se:umu:diva-4516DOI: 10.1080/000163500429325PubMedID: 10894429OAI: diva2:143650
Available from: 2005-04-22 Created: 2005-04-22Bibliographically approved
In thesis
1. Resin composites: Sandwich restorations and curing techniques
Open this publication in new window or tab >>Resin composites: Sandwich restorations and curing techniques
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since the mid-1990s resin composite has been used for Class II restorations in stress-bearing areas as an alternative to amalgam. Reasons for this were the patients’ fear of mercury in dental amalgam and a growing demand for aesthetic restorations. During the last decades, the use of new resin composites with more optimized filler loading have resulted in reduced clinical wear. Improved and simplified amphiphilic bonding systems have been introduced. However, one of the main problems with resin composites, its polymerization shrinkage, has not been solved yet. During the polymerization of the resin composites, they shrink as a result of the conversion of the monomers into rigid polymers by a radical addition reaction. The resulting shrinkage stresses in the bonded resin composite restorations may cause adhesive failures at the resin composite/tooth structure interface and/or cohesive failures within the tooth or the resin composite. The interfacial failures may result in post-operative sensitivity, recurrent caries or pulpal injury. This thesis evaluates different restorative and light-curing techniques that are proposed to reduce the polymerization shrinkage and also the effect of new lightcuring units, light-emitting diodes (LED) and high-power quartz tungsten halogen (QTH) light on curing depth and degree of conversion of resin composites. Two restorative techniques using a polyacid-modified resin composite or a flowable resin composite in combination with conventional resin composite in sandwich restorations were evaluated in an intraindividual comparison with a conventional resin composite restoration. The durability of the polyacid-modified resin composite sandwich technique was investigated in a three year clinical follow-up study. A scanning electron microscope replica method was used for evaluation of the interfacial adaptation in vivo of both sandwich combinations. The depth of cure of the flowable resin composite was evaluated with the use of Wallace hardness testing. Degree of conversion for resin composite cured with the new LED units was evaluated with Fourier Transform Raman spectroscopy.

Major results and conclusions from the studies are:

• Neither the sandwich restoration with polyacid-modified resin composite nor the flowable resin composite improved the interfacial adaptation of the restorations.

• No difference in durability was found between the sandwich restorations with polyacidmodified resin composite or the resin composite restorations. A low failure rate was observed for both types of restorations after a clinical observation time of three years.

• The depth of cure of the flowable resin composite was higher than the depth of cure of the resin composite. It was found that the curing time of the resin composite studied could be reduced or the increment layer thickness increased compared to earlier recommendations.

• LED curing units of the latest generation were able to cure resin composites to a higher degree of conversion than the control QTH unit

• The use of soft-start curing did not improve the interfacial adaptation of neither of resin composite restorations tested.

Place, publisher, year, edition, pages
Umeå: Odontologi, 2005. 65 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 90
Medicine, Adaption, Clinical, Degree of conversion, Depth of cure, Flowable, Resin composite, Restorations, SEM, Medicin
National Category
urn:nbn:se:umu:diva-510 (URN)91-7305-833-5 (ISBN)
Public defence
2005-05-27, 09:00 (English)
Available from: 2005-04-22 Created: 2005-04-22 Last updated: 2016-06-02Bibliographically approved

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