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Resin composites: Sandwich restorations and curing techniques
Umeå University, Faculty of Medicine, Department of Odontology, Dental Hygiene.
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.
Series
Umeå University odontological dissertations, ISSN 0345-7532 ; 90
Keyword [en]
Medicine, Adaption, Clinical, Degree of conversion, Depth of cure, Flowable, Resin composite, Restorations, SEM
Keyword [sv]
Medicin
National Category
Dentistry
Identifiers
URN: urn:nbn:se:umu:diva-510ISBN: 91-7305-833-5 (print)OAI: oai:DiVA.org:umu-510DiVA: diva2:143655
Public defence
2005-05-27, 09:00 (English)
Available from: 2005-04-22 Created: 2005-04-22 Last updated: 2016-06-02Bibliographically approved
List of papers
1. Interfacial adaptation of a Class II polyacid-modified resin composite/resin composite laminate restoration in vivo.
Open this publication in new window or tab >>Interfacial adaptation of a Class II polyacid-modified resin composite/resin composite laminate restoration in vivo.
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.

Identifiers
urn:nbn:se:umu:diva-4516 (URN)10.1080/000163500429325 (DOI)10894429 (PubMedID)
Available from: 2005-04-22 Created: 2005-04-22Bibliographically approved
2. 3-year evaluation of a new open sandwich technique in Class II cavities.
Open this publication in new window or tab >>3-year evaluation of a new open sandwich technique in Class II cavities.
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.

Identifiers
urn:nbn:se:umu:diva-17662 (URN)12744410 (PubMedID)
Available from: 2007-11-15 Created: 2007-11-15 Last updated: 2009-10-06Bibliographically approved
3. Curing depths of a universal hybrid and a flowable resin composite cured with quartz tungsten halogen and light-emitting diode units.
Open this publication in new window or tab >>Curing depths of a universal hybrid and a flowable resin composite cured with quartz tungsten halogen and light-emitting diode units.
2004 (English)In: Acta Odontologica Scandinavica, ISSN 0001-6357, Vol. 62, no 2, 97-101 p.Article in journal (Refereed) Published
Abstract [en]

This in vitro study evaluated curing depths of a universal hybrid resin composite with two viscosities (Tetric Ceram and Tetric Flow) after curing with 6 different quartz tungsten halogen and light-emitting diode curing units. Irradiance (light intensity) of the curing units varied between 200 and 700 mW/cm2. The curing units were used for standard, soft-start, or pulse curing. Curing times were 20 and 40 s for standard curing, 3 + 10 s and 3 + 30 s for pulse curing, and 40 s for soft-start. Resin composite specimens, 5 in each group, with a diameter of 4 mm and a height of 6 mm, were made in brass molds and cured from one side at a distance of 6 mm. After 2 weeks, the specimens were ground longitudinally half through the specimen. Curing depth was then determined by measurement of Wallace hardness for each half millimeter starting at 0.5 mm from the top surface. For all curing units and for both resin composites an increased curing time led to statistically significantly higher depth of cure (P < 0.0005). Tetric Flow showed a statistically significantly higher depth of cure than Tetric Ceram (P < 0.0005). All curing units cured more than 2.0 mm of both composites from a distance of 6 mm at 20 s curing time. The value for 40 s was 3.0 mm. The composite closer to the surface than the depth of cure value was equally well cured with all curing units investigated. There was a significant linear correlation between the determined irradiance of the curing units and the depths of cure obtained (20s: r = 0.89, P < 0.025; 40 s: r = 0.91, P < 0.01).

Identifiers
urn:nbn:se:umu:diva-17144 (URN)10.1080/00016350410006905 (DOI)15198390 (PubMedID)
Available from: 2007-11-02 Created: 2007-11-02 Last updated: 2009-11-19Bibliographically approved
4. A Fourier transform Raman spectroscopy analysis of the degree of conversion of a universal hybrid resin composite cured with light-emitting diode curing units.
Open this publication in new window or tab >>A Fourier transform Raman spectroscopy analysis of the degree of conversion of a universal hybrid resin composite cured with light-emitting diode curing units.
2005 (English)In: Swedish Dental Journal, ISSN 0347-9994, Vol. 29, no 3, 105-112 p.Article in journal (Refereed) Published
Abstract [en]

The degree of conversion (DC), of a universal hybrid resin composite cured with LED curing units with low and high power densities and a 510 mW/cm2 quartz tungsten halogen unit, was investigated with Fourier Transform Raman spectroscopy. Three curing depths (0, 2, 4mm) and 0 and 7 mm light guide tip - resin composite (LT - RC) distances were tested. The DC of the LED units varied between 52.3% - 59.8% at the top surface and 46.4% - 57.0% at 4 mm depth. The DC of specimen cured with a 0 mm LT- RC distance at 4 mm depth varied between 50.8% - 57.0% and with 7 mm distance between 46.4% - 55.4%. The low power density LED unit showed a significantly lower DC for both distances at all depth levels compared to the other curing units (p < 0.05). Significant differences between the other curing units were only found at the 4 mm depth level cured from 7 mm distance (p < 0.05). The reduction in DC by increasing LT- RC distance was less than 10% for all curing units. It can be concluded that the improved LED curing units could cure the studied resin composite to the same DC as the control unit.

Identifiers
urn:nbn:se:umu:diva-17178 (URN)16255354 (PubMedID)
Available from: 2007-11-06 Created: 2007-11-06 Last updated: 2009-10-05Bibliographically approved
5. In vivo interfacial adaptation of class II resin composite restorations with and without a flowable resin composite liner.
Open this publication in new window or tab >>In vivo interfacial adaptation of class II resin composite restorations with and without a flowable resin composite liner.
2005 (English)In: Clinical Oral Investigations, ISSN 1432-6981, Vol. 9, no 2, 77-83 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to evaluate in vivo the interfacial adaptation of class II resin composite restorations with and without a flowable liner. In 24 premolars scheduled to be extracted after 1 month, 48 box-shaped, enamel-bordered class II cavities were prepared and restored with a flowable liner (FRC, Tetric Flow/Tetric Ceram/Syntac Single-Component) or without (TRC), cured with three different curing modes: soft start and 500- or 700-mW/cm2 continuous irradiation. Interfacial adaptation was evaluated by quantitative scanning electron microscopic analysis using replica method. Gap-free adaptation in the cervical enamel (CE) was observed for FRC and TRC in 96.2 and 90.2%, for the dentin (D) in 63.6 and 64.9%, and for occlusal enamel (OE) in 99.7 and 99.5%, respectively. The difference between the two restorations was not statistically significant (ns). Significant better adaptation was observed for OE than CE and D (p<0.01), and for CE than D (p<0.01). Gap-free adaptation with the soft-start and 500- and 700-mW/cm2 continuous-curing modes was observed for CE: 88.7%, 92.7%, 97.9% (ns); OE: 99.8%, 98.7%, 100% (ns); and D: 64.0%, 63.9%, and 64.6% (ns), respectively. It can be concluded that neither the use of flowable resin composite liner nor the curing mode used influenced the interfacial adaptation.

Identifiers
urn:nbn:se:umu:diva-17146 (URN)10.1007/s00784-005-0311-x (DOI)15815923 (PubMedID)
Available from: 2007-11-02 Created: 2007-11-02 Last updated: 2009-10-05Bibliographically approved

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