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3-year evaluation of a new open sandwich technique in Class II cavities.
Umeå University, Faculty of Medicine, Odontology, Dental Hygiene.
Umeå University, Faculty of Medicine, Odontology, Dental Hygiene.
2003 (English)In: American Journal of Dentistry, ISSN 0894-8275, Vol. 16, no 1, 33-36 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE: To evaluate the durability of a new open sandwich restoration with, as shown in a previous scanning electron microscope study, improved interfacial adaptation. A polyacid-modified resin-based composite (PMRC; compomer) was placed as an intermediate layer and covered with resin composite (RC). A direct RC restoration was used as control. MATERIALS AND METHODS: Of 57 patients, each received at least one pair of Class II restorations, one PMRC/RC open sandwich and one RC control. In total, 75 pairs of Class II restorations, 68 premolars and 82 molars, all in occlusion, were placed by two dentists. Most of the cavities were surrounded by enamel. The restorations were evaluated at baseline, 6, 12, 24 and 36 months by a slightly modified USPHS criteria. RESULTS: Five of 148 restorations evaluated during 3 years were rated as unacceptable. Two, one in each group, because of endodontic treatment and one RC restoration was replaced because of tooth fracture. Secondary caries was observed contiguous to one restoration in each group at the 36-month recall. Except for the two patients with pulpitis, none of the others reported postoperative sensitivity. No significant differences were seen between the restoration techniques. For marginal adaptation a significant change occurred between baseline and 6 months in both groups. For marginal discoloration, a significant change was observed at 6 months in the sandwich group and at 36 months in the RC group. Color match of the resin composite material changed significantly in both groups at 36 months. It was concluded that both techniques showed good durability during the 3-year follow up.

Place, publisher, year, edition, pages
2003. Vol. 16, no 1, 33-36 p.
URN: urn:nbn:se:umu:diva-17662PubMedID: 12744410OAI: diva2:157335
Available from: 2007-11-15 Created: 2007-11-15 Last updated: 2009-10-06Bibliographically 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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