Effect of bonding application time on the microleakage of Class V sandwich restorations.

BACKGROUND: The aim of this study was to assess the effect of bonding application time on the microleakage of Class V sandwich restorations. METHODS: Eighty non-carious third molars were randomly divided into 16 groups. Two Class V cavities were prepared on the buccal and lingual surfaces of teeth. Three groups were restored with Fuji II GIC and treated with a total-etch bonding system (Stea/SDI) immediately after insertion, at 7 minutes and 15 minutes after mixing the glass ionomer cements (GICs). Another three groups were restored with Riva Self Cure GIC and treated with the total-etch system identically. The other six groups were subjected to self-etching bonding (Frog/SDI) after GIC placement in an identical procedure. The remaining groups were made using light cure GICs (Fuji II or Riva Light Cure) in conjunction with the total-etch or self-etching systems. Cavities were then restored with composite (Valux plus, 3M/ESPE). Samples were subsequently immersed in 2% methylene blue solution for 48 hours and observed under a stereomicroscope after sectioning. Four-scale grading was used to assess microleakage in occlusal and gingival walls. Data were analysed using Kruskal-Wallis and Mann-Whitney tests. RESULTS: The self-etching bonding system exhibited more microleakage in occlusal margins regardless of time. Over time, microleakage significantly decreased in gingival margins in all self-cure groups except for Riva Self Cure treated with the total-etch system (p < 0.05). CONCLUSIONS: Bonding application time had no effect on the microleakage of occlusal margins. However, maturation of GICs induced a decreased microleakage in gingival margins.

Hygroscopic expansion of aesthetic restorative materials: one-year report.

OBJECTIVE: To measure the long-term linear hygroscopic expansion (LHE) of several materials using bulked and layered techniques. MATERIALS AND METHODS: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-Fil Aplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for each material using layered and bulked techniques (each group comprises five specimens). The specimens were stored in distilled water at 37°C. The length of each specimen was measured immediately after preparation, 24 hours, one week, one month, three months, six months, nine months and one year. This was used to calculate the percentage change in the length of materials. The mean LHE and standard deviation were calculated. Repeated measure analysis and paired sample t-test were used. RESULTS: The type of material and time had a significant effect on LHE. Fuji Cap II and Fuji II LC exhibited no significant changes after one-year and one month, respectively. However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansion until six month, whereas bulked specimens reached the constant length at three months. Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 at six month. Layered specimens of Vitremer showed no significant differences except between 24 hours and one year measurements. But in bulked specimens, the results at nine months and one year were significantly different from those obtained at three months and before. CONCLUSION: Fuji II showed no significant LHE and resin-modified glass ionomer cements (RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in comparison with RMGIC and composite resin.

A comparative study of dental pulp response to several pulpotomy agents.

AIM: To examine the in vivo response of dental pulps in dogs to three pulp-capping agents: calcium hydroxide (CH), mineral trioxide aggregate (MTA) and a new endodontic calcium enriched mixture (CEM) cement. METHODOLOGY: Thirty-six second and third premolar teeth in six beagle dogs were randomly assigned to three experimental groups; CH, MTA or CEM cement. Following isolation and exposure, pulp tissues were removed with a fissure bur and haemostasis achieved. The pulps were dressed with appropriate materials, and the access cavity restored with amalgam. Histological analysis was performed 8 weeks after treatment; the samples were assessed by an independent observer for calcified bridge formation, pulp vitality and pulp inflammation. The data were analysed by Kruskal-Wallis, Mann-Whitney and one-way anova tests. RESULTS: The number of root canals that showed calcified bridge formation, pulp vitality and lack of inflammation was significantly higher for teeth capped with either MTA or CEM cement in comparison with CH (P < 0.05). No significant difference was found between the CEM cement and MTA in terms of calcified bridge formation, pulp vitality and lack of inflammation (P > 0.05). CONCLUSIONS: Mineral trioxide aggregate and CEM cement were associated with a similar favourable biological response to pulpotomy treatment and demonstrated a more effective induction of dentinal bridge formation compared to CH.

Effects of ER,Cr:YSGG laser irradiation and fluoride treatment on acid resistance of the enamel.

PURPOSE: The purpose of this study was to evaluate the effect of the Er,Cr:YSGG loser on the enamel's acid resistance when irradiated alone, prior to or after acidulated phosphate fluoride (APF) treatment. METHODS: Eighty-five enamel surfaces were prepared from 17 extracted human premolars and randomly assigned to 5 groups: (1) untreated (control); (2) irradiated with a Er,Cr:YSGG loser; (3) exposed to a 1.23% APF gel; (4) loser-irradiated followed by APF treatment; and (5) APF-treated followed by loser irradiation. The specimens were individually demineralized in 0.2 M acetate buffer solution for 10 days, and the acid resistance was evaluated by determining the calcium ion using atomic absorption spectrometry. RESULTS: Significant differences were found between group 1 and groups 2 through 5 (P < 0.001). There were no signifIcant differences between groups 2 and 3 (P = 1.000). Compared to groups 2 and 3, a lower calcium content was detected in the demineralization solution for groups 4 and 5. The difference between groups 4 and 5, however, was not statistically significant (P = 0.289). CONCLUSIONS: Combining ocidulated phosphate fluoride with the Er,Cr:YSGG loser decreased the enamel demineralization more than either fluoride treatment or laser treatment alone.

Restorative treatment threshold reported by Iranian dentists.

OBJECTIVE: To study Iranian dentists' conceptions of the earliest stage to place a restoration on proximal caries lesions. BASIC RESEARCH DESIGN: A questionnaire survey was carried out among the participants of two annual dental meetings in Tehran, Iran, in December 2004 and July 2005. The questionnaire was filled in anonymously and returned during the meeting days. The questions covered two patient paper cases with schematic drawings of the radiolucency of proximal caries lesions according to bitewing radiographs from 20-year-old patients: one high-caries case and one low-caries case. Dentists' gender, age, working experience and place, and participation in continuing education served as background data. In total, 1,033 dentists completed the questionnaire, 63% were men. Statistical evaluation was by the Chi square test and logistic regression. MAIN OUTCOME MEASURES: Respondents were to select from four alternatives the earliest stage in the progression of a lesion at which they would intervene by restorative treatment. RESULTS: For the high-caries case, 77% of the respondents chose to restore a caries lesion confined to enamel; activity in continuing education was the strongest factor (OR = 1.4) to explain dentists' restoring a lesion no earlier than in dentine. For the low-caries case, 32% chose to restore a lesion in enamel. Restoring a lesion no earlier than in dentine was more likely (OR = 1.5) among female dentists. CONCLUSION: Iranian dentists seem to prefer early restorative intervention, which indicates a need to focus on the preventive aspects of caries treatment both in dental curricula and in continuing education.

Clinical performance of Class II restorations in which resin composite is laminated over resin-modified glass-ionomer.

This study evaluated the one-year functioning of resin-composite/resin-modified glass-ionomer open-laminate restorations when used for restoring Class II cavities. It also investigated the effect of the thickness of the resin composite layer on the performance of such restorations. The test restorations were made of Vitremer glass ionomer, Scotchbond Multipurpose Plus and Z100 resin composite, and the control restorations were made of Z100 with Scotchbond Multipurpose Plus. Forty pairs of restorations were placed in 40 patients aged 16 years and over. The thickness of the resin composite layer was measured both clinically and in the laboratory using a reflex microscope. The completed restorations were assessed in vivo and in vitro at baseline, six-month and one-year recalls using a modified Ryge system. The reflex microscope measurements showed that the majority of restorations had a resin composite layer of more than 1.5 mm in thickness, as intended. At one year, 37 pairs of restorations were examined. Apart from a few minor problems, all performed satisfactorily. Thus, it appears that the resin composite/resin modified glass ionomer open laminate is a suitable technique for restoring Class II cavities.

Fluoride release from tooth-colored restorative materials: a 12-month report.

BACKGROUND: This study measured the amount of fluoride released from three light-activated glass polyalkenoate (ionomer) cements, a conventional glass polyalkenoate, a compomer and a fluoridated composite over a period of 12 months. METHODS: Five discs (7 x 2 mm) of each material were sequentially immersed in 4 mL portions of deionized water at 37 degrees C and before each measurement, the test specimen was rinsed with 1 mL of deionised water. An Orion Model 901 microprocessor digital Ionalyzer was used for the measurements and the data obtained were converted into microgram/cm2. The amount of fluoride released was measured 86 times during the 12-month test period. RESULTS: It was found that the pattern of fluoride release from the light-activated glass polyalkenoates was similar to that of the conventional glass polyalkenoate. The light-activated glass polyalkenoates, however, released significantly more fluoride than the conventional material. The composite and the compomer released significantly less fluoride than any glass polyalkenoate tested and the difference between the composite and the compomer was not significant. CONCLUSION: It was concluded that the light-activated glass polyalkenoates tested released more fluoride than a conventional glass polyalkenoate, a compomer or a composite, and that with regard to fluoride release the compomer behaved more or less like the composite.