Fluoride uptake and distribution in enamel and dentin after application of different fluoride solutions.

The aim of this in vitro study was to examine the fluoride accumulation in enamel and dentin after short- and long-term application of four fluoride solutions, including a casein-based fluoride preparation. Cubical enamel and dentin specimens were cut out from extracted, caries-free, human third molars. The buccal surface of each specimen was moistened for 5 min or 24 h with 10 microl of the control or one of the four test solutions Olaflur, Oleaflur, sodium fluoride, or experimental fluoride containing hydrolyzed casein. The specimens were ground in 20- microm steps and the fluoride content was determined in each enamel and dentin layer. After application of the fluoride solutions, significantly more fluoride was associated with the superficial layer up to 20 microm. The values were 3-4 times higher in enamel and 4-8 times higher in dentin after 5-min application time and 10-24 times higher than the initial fluoride content in both hard tooth tissues after 24-h application time. Focusing on the experimental solution, the fluoride levels in enamel and dentin were somewhere in the order of the values of sodium and amine fluoride solutions. However, a tendency towards higher values could be observed after application of the experimental solution.

Curing efficiency of different polymerization methods through ceramic restorations.

The aim of this in vitro study was to examine the curing efficiency of three different polymerization methods through ceramic restorations by determination of the depth of cure and the universal hardness of a composite resin luting material. Therefore, 36 ceramic specimens [Empress 2 (Ivoclar), color 300, diameter 4 mm, height 2 mm] were prepared and inserted in steel molds (diameter 4 mm, height 6 mm) using a composite resin luting material [Variolink II (Vivadent)] with and without catalyst. The polymerization through six specimens of each group was done conventionally (40 s), by softstart polymerization (40 s), or by plasma arc curing (10 s). Depth of cure under the ceramic specimens was assessed according to ISO 4049. Additionally, universal hardness was determined at 0.5 and 1.0 mm from the ceramic using a universal testing machine (Zwick 14040). Curing without a catalyst, using conventional and softstart polymerization, resulted in greater hardness in both layers, compared to plasma arc curing. The use of a catalyst always produced a greater hardness and depth of cure with all polymerization methods. Depth of cure was always greater using conventional polymerization and softstart polymerization, compared to plasma arc curing. The curing efficiency of plasma arc curing through ceramic was lower compared to conventional and softstart-polymerization.

Marginal adaption of Class V restorations with and without "softstart-polymerization".

Polymerization shrinkage causing marginal gap formation is still a major problem in light curing restorations. The aim of the present study was to test the influence of "softstart polymerization" (prepolymerization at a low light intensity followed by a final cure at a high light intensity) on the marginal integrity of polyacid-modified resin and composite resin restorations in Class V cavities using a commercially available curing unit with two defined curing intensities. Sixty standardized Class V cavities were prepared. Twenty cavities at a time were filled either with a composite resin [Spectrum + Prime & Bond 2.1 (SP)], or with polyacid-modified resins [Dyract + Prime & Bond 2.1 (DY); Hytac + OSB Primer (HY)]. Ten fillings of each group were either conventionally cured (40 seconds, 800 mW/cm2), or they were cured with a lower starting intensity (10 seconds, 150 mW/cm2) and then with the full intensity (30 seconds, 800 mW/cm2). Margins were evaluated before and after thermomechanical loading (TCML) by quantitative margin analysis. Microleakage was assessed by dye penetration. The softstart polymerization showed no significant influence on gap formation for each material and interface before and after TCML. Quantitative margin analysis after TCML showed significantly fewer marginal gaps at the enamel/restoration interface for SP (0%) compared to DY (15.5%) and HY (44.5%) using softstart polymerization. At the dentin/restoration interface the corresponding results for gap formation were 29.6% for SP, 8.5% for DY, and 21.0% for HY. These results were not significantly different from each other. Dye penetration was significantly higher for SP at the dentin/restoration interface. SP showed significantly more marginal swelling at the dentin/restoration interface compared to DY. In conclusion, softstart polymerization using a very low starting intensity did not improve the marginal adaptation of polyacid-modified resins or composite resins in Class V cavity preparations. The best marginal adaptation in Class V cavities at the enamel/restoration interface was achieved with SP, using the acid-etch technique. In dentin, however, the polyacid-modified resins showed a superior marginal adaptation.

Marginal adaptation of heat-pressed glass-ceramic veneers to dentin in vitro.

The purpose of the present study was to examine the marginal adaptation of ceramic veneers to dentin at the cervical margins and to enamel at the palatoincisal margins using four dual-curing composite resin cements of different viscosity with their corresponding dentin bonding systems. Thirty-six caries-free human maxillary incisors were prepared for facial ceramic veneers with cervical cavity margins located in dentin. Heat-pressed glass-ceramic veneers (IPS Empress) were inserted adhesively using one of the following luting systems: Sono-Cem (SC) with EBS; Variolink Ultra (VU), Variolink High Viscosity (VHV), and Variolink Low Viscosity (VLV) with Syntac. Both the cervical and the palatoincisal margins of the veneers (tooth/composite resin cement interface and ceramic/composite resin cement interface) were evaluated before and after thermocycling and mechanical loading (TCML) by quantitative margin analysis under a scanning electron microscope (SEM) using an image analysis system. Microleakage was assessed by dye penetration after TCML. Before TCML, SC and VU showed statistically significantly fewer marginal gaps than VHV and VLV. After TCML, SC, VU, and VHV revealed significantly fewer marginal gaps than VLV. TCML had a statistically significant influence on marginal gap formation at both the dentin and enamel margins. After TCML, the percentage of marginal gaps was not significantly different at the cervical dentin than at the palatoincisal enamel margins. Cervical dye penetration after TCML showed no statistically significant differences in microleakage among the four luting systems. In conclusion, this in vitro study showed that similarly favorable marginal adaptations of ceramic veneers to dentin and enamel can be achieved using Sono-Cem, Variolink Ultra, or Variolink High Viscosity with their corresponding dentin bonding systems.

Marginal adaptation of heat-pressed glass-ceramic veneers to Class 3 composite restorations in vitro.

The aim of the present in vitro study was to compare the marginal adaptation and integrity of heat-pressed glass-ceramic veneers to adjacent class 3 composite restorations and to enamel using four dual-curing composite resin cements of different viscosity with their corresponding dentin bonding agents. Thirty-six caries-free human maxillary incisors were first restored with mesial and distal class 3 composite restorations and then prepared for facial ceramic veneers. The cavity margins of the veneers were located either in the class 3 composite restorations or in the residual enamel. Heat-pressed glass-ceramic veneers (IPS Empress) were inserted adhesively using one of the following four luting systems in nine teeth: SonoCem (SC) with EBS; Variolink Ultra (VU), Variolink High-Viscosity (VHV), and Variolink Low-Viscosity (VLV) with Syntac. The veneer margins in the region of the composite restoration and in the region apical to the composite restoration (ceramic/composite resin cement interfaces, composite resin cement/composite restoration interface, and composite resin cement/enamel interface) were evaluated before and after thermo-cycling and mechanical loading (TCML) by quantitative margin analysis under a scanning electron microscope (SEM) using an image analysis system. Furthermore, microleakage was assessed in each tooth by dye penetration after TCML. For all luting systems, SEM analysis revealed excellent marginal adaptation of the ceramic veneers to the composite restorations as well as to enamel. The median percentages of marginal gap formation were 1.1% and less before TCML and 5.1% and less after TCML. The error-rates method revealed no statistical influence of the interface or of the viscosity of the luting material. Maximal values of dye penetration showed a significantly higher microleakage at veneers cemented with VU (median: 86.4%) compared to SC (median: 13.3%). In conclusion, the present data demonstrated that existing clinically acceptable class 3 composite restorations have no negative influence on the marginal adaptation of ceramic veneers. This was valid independent of the viscosity of the dual-curing composite resin cement when SC, VHV, or VLV was used.

Clinical performance of polyacid-modified resin restorations using "softstart-polymerization".

This study investigated the influence of "softstart-polymerization" on the clinical performance and marginal integrity of polyacid-modified resin restorations (PMR) in class V cavities. Eighty PMR restorations were placed in 20 patients [40 Dyract (DY); 40 Hytac (HY)] with (npat = 10) and without preparation (npat = 10). Restorations were light cured for 40 s either conventionally (CP) or with a lower light intensity for the first 10 s (SSP). Each patient received four restorations (DY-CP, DY-SSP, HY-CP, HY-SSP), which were examined clinically according to modified USPHS criteria, and by quantitative SEM-analysis after 7 days (baseline), 6 months and 1 year. Statistical analysis was performed using the Mann-Whitney-U test (P < or = 0.05) and error rates method. Clinically, no restoration showed recurrent caries or crevices. After 1 year, margins of 24-47% of the HY- and 36-53% of the DY-restorations were rated "Bravo". Marginal discoloration occurred in 20-37% in HY- and in 18-21% in DY-restorations. The error rates method revealed no significant differences between materials or between polymerization modes with and without preparation. Pairwise testing showed that without preparation, the marginal adaptation to dentin was significantly worse compared to enamel for HY with both polymerization modes, for DY with SSP. With preparation, no significant differences were found. Cavity preparation may have an influence on differences in marginal quality between enamel and dentin.

Intraoral repair of fiber-reinforced composite fixed partial dentures.

STATEMENT OF THE PROBLEM: Fractured composite facings may result in replacement of a fixed partial denture unless a reliable intraoral repair method can be provided. PURPOSE: This in vitro study tested the quality of an intraoral repair method for fractured facings of fixed partial dentures made of a fiber-reinforced composite system. MATERIAL AND METHODS: Shear bond strengths of a light-curing composite to a fiber-reinforced composite material were determined after different mechanical surface treatments. Aluminum oxide air abrading provided the most reliable bond strength values and therefore was used as a pretreatment for the facing repair of three-unit posterior fixed partial dentures. Facing repair was performed with the tested light-curing hybrid composite. Facing fracture strengths of repaired and original fixed partial dentures were determined after thermocycling and mechanical loading. RESULTS: Median facing fracture strength of the original fixed partial dentures was 1450 N after a simulated clinical service of 5 years. Facing fracture strengths of the repaired fixed partial dentures were significantly lower compared with the control group after an additional simulated 2-year interval. However, the median fracture force was still 1000 N. CONCLUSIONS: The facing repair of a fiber-reinforced fixed partial denture with a hybrid composite in combination with aluminum oxide air-abrading pretreatment and silanization provided sufficient fracture strength. Therefore the replacement of the complete restoration may be avoided.

Resin-modified glass ionomer cements: fluoride release and influence on Streptococcus mutans growth.

The aims of the present study were to measure the fluoride release of 1 glass ionomer cement, 1 cermet, 3 resin-modified glass ionomer cements and 1 compomer, and to determine the influence of each material on bacterial growth. Test specimens were eluted in saline for 180 days. Every 2 days, the specimens were transferred into fresh saline and the fluoride content of the solution was measured. Furthermore, 48-h, 14-d, 90-d, and 180-d eluates were inoculated with Streptococcus mutans and bacterial growth was recorded nephelometrically. Fluoride release dropped significantly over time for each material with values between 6.2 (Ketac-Silver) and 29.3 (Photac-Fil) ppm after 48 h to values between 0.6 (Ketac-Silver) and 1.7 (Ketac-Fil, Vitremer) ppm after 180 days. Each material reduced bacterial growth at each time of examination, but the effect decreased significantly over time with a maximum growth of 71.7% (Ketac-Fil) to 85.6% (Ketac-Silver) after 48 h and 94.7 (Vitremer) to 99.0% (Ketac-Silver) after 180 days (growth control = 100%). Both Ketac-Silver and Dyract showed a significantly lower inhibiting effect on bacterial growth than the other materials. The tested materials showed a good correlation between fluoride release and influence on bacterial growth. However, both effects dropped dramatically over the 180-days period.

Marginal adaptation of composite restorations versus hybrid ionomer/composite sandwich restorations.

The aim of this in vitro study was to compare the approximal marginal quality of composite fillings using a dentin bonding system to the marginal quality of hybrid ionomer/composite sandwich restorations. Forty-eight standardized class 2 cavity preparations were prepared in caries-free, human third molars. Twelve preparations at a time were filled either with a composite using the matching dentin bonding system, SZ (Scotchbond MP/Z100) or PP (PROBOND/Prisma TPH) or with hybrid ionomer/composite sandwich fillings VZ (Vitremer/Z100) or DP (Dyract/Prisma TPH). Margins were evaluated before and after thermomechanical loading (TCML) (5000 cycles [+5 degrees C/+55 degrees C], 72.5 N [1,7 Hz]) by quantitative scanning electron microscope analysis using an image analyzing system. Furthermore, microleakage was assessed by dye penetration before and after TCML. Statistical analysis was performed using the Mann-Whitney test at the 0.05 level of significance. SEM analysis after TCML showed significantly fewer marginal gaps at the material/dentin interface with VZ (2.2%), DP (7.3%), and PP (6.0%) compared to SZ (29.6%). After TCML, SZ showed significantly more marginal gaps at the material/dentin interface, whereas VZ, DP, and PP were not susceptible to TCML. PP showed the highest percentage in marginal swelling before (18.2%) and after TCML (15.9%), while VZ showed no marginal swelling at all. VZ showed significantly fewer marginal gaps at the composite/hybrid ionomer interface than DP. After TCML there was no significant difference in marginal gaps between the hybrid ionomer/enamel and the hybrid ionomer/dentin interface for both Vitremer and Dyract. Using the sandwich technique the Z100/enamel interface had significantly more marginal gaps than all other composite/enamel interfaces after TCML. There was no significant difference in microleakage between the test groups at the material/dentin interface. SEM analysis and dye penetration showed that hybrid ionomer/composite sandwich restorations have good marginal qualities and may be an alternative to composite restorations using a dentin bonding system.

Clinical and quantitative marginal analysis of feldspathic ceramic inlays at 4 years.

The aim of this clinical study was to evaluate feldspathic ceramic inlays both by clinical criteria and quantitative margin analysis in continuation of an earlier, identically conducted 2-year study. Fifty feldspathic ceramic inlays were adhesively luted in Class II preparations with all margins located in enamel. The inlays were evaluated clinically according to modified USPHS criteria after 3 and 4 years. Quantitative margin analysis was performed with a scanning electron microscope (SEM). Clinically, the inlays showed no recurrent caries and no changes in colour, but superficial marginal discolouration (6%) was apparent after 4 years. Margins were perceptible clinically in 64% of the cases after 4 years. Quantitative margin analysis showed significantly more marginal gaps at the composite/ceramic interface than at the enamel/composite interface, There was neither a significant decrease in perfect margins nor a significant increase in marginal gaps and marginal imperfections at both interfaces between the third and fourth year. Clinically, the inlays performed very well up to 4 years. Clinical evaluation using an explorer only detected substance loss in the cementation gap. The SEM evaluation showed significantly higher changes in marginal qualities during the first 2-year interval of clinical service compared to the second 2-year interval following an exponential mathematical regularity. Quantitative margin analysis should be included in clinical long-term trials to detect early marginal deficiencies at the luting interfaces.

Bond strength of composites to hybrid ionomers.

Tensile bond strengths among three different hybrid ionomers and two different hybrid composites were evaluated. With one exception, bond strength to a high-modulus composite (Z-100) was higher than that to a low-modulus composite (Charisma). Thermocycling lowered the bond strength of Charisma, whereas storage for 3 months increased the bond strength of Z-100 compared to storage for 24 hours. Etching the hybrid ionomers with phosphoric acid had no effect on bond strength.

In-vivo evaluation of a feldspathic ceramic system: 2-year results.

OBJECTIVES: The aim of this clinical study was to evaluate feldspathic ceramic inlays by clinical criteria and quantitative margin analysis, and to compare clinical performance with the quantitative margin analysis results. METHODS: Fifty fibre-reinforced feldspathic ceramic inlays were placed in box-shaped, Class II preparations with all margins located in enamel. A low-viscosity type dual-curing resin luting material was used for luting. The inlays were evaluated clinically according to modified US Public Health Service criteria after 2 days, 1 year, and 2 years. In addition, quantitative margin analysis was performed under a scanning electron microscope using an image analysing system. RESULTS: Clinically the inlays performed very well after 2 years, showing no changes in colour, no recurrent caries and no marginal discolouration. Because of the wear of the composite resin luting material, margins were perceptible with an explorer in 54% of the cases after 2 years. Quantitative margin analysis showed significantly (P < or = 0.05) more marginal gaps at the composite/ceramic interface compared with the enamel/composite interface at each evaluation. There was a significant increase in marginal gaps at both interfaces during the first year, whereas marginal gaps at the composite/ceramic interface did not increase significantly during the second year. Quantitative margin analysis showed that both time and interface had a significant influence on marginal gaps. CONCLUSION: Quantitative margin analysis should be included in clinical long-term trials on this type of restoration to recognize possible deficiencies in ceramic, composite resin luting material, and the luting interfaces.

Color stability of light-cured and post-cured composites.

PURPOSE: To determine the color stability of five composites after light-curing and recommended post-curing using reflection spectrophotometry. MATERIALS AND METHODS: Samples of the composites were prepared as disks 10 mm in diameter and 1 mm thick. The pre-cured samples were prepared with a clear plastic sheet on the top and bottom of disk, pressed between two glass slabs to the thickness of the mold, and then removed from between the glass slabs. The color of the samples was measured with the clear plastic sheets in place. The color of the composites before curing served as the control. RESULTS: Light-curing caused barely perceptible to perceptible color changes for all of the composites from the pre-cured shade. Clearfil and TrueVitality changed color significantly more than Charisma, Conquest C&B and Herculite XRV. Once the composites were light-cured, post-curing caused no further perceptible changes in shade.

Color stability of hybrid ionomers after accelerated aging.

PURPOSE: The color stability and surface roughness of three commercial hybrid ionomers were determined in vitro after accelerated aging. Three shades of each hybrid ionomer prepared in light-cured and dark-cured conditions were tested. MATERIALS AND METHODS: Samples were aged in an artificial aging chamber by subjecting them to total ultraviolet light irradiation of 150 kJ/m2 over a period of 77 hours. Color (CIE LAB system) was measured before and after aging on a reflection spectrophotometer. Surface roughness was measured with a profilometer. RESULTS: After accelerated aging, all samples became lighter. Photac-Fil Aplicap (ESPE-Premier, Norristown, PA) and Fuji II LC (GC America, Chicago, IL) also became less chromatic (less red and less yellow). Among the light-cured samples, Fuji II LC had the greatest change in color followed by Photac-Fil Aplicap and Vitremer (3M Dental Products, St Paul, MN). For the dark-cured samples, Fuji II LC had the greatest change in color followed by Vitremer and Photac-Fil Aplicap. There were no differences in delta E* between the two lightest shades, but the darker shades of each product showed the greatest changes in color. All samples became significantly rougher after aging. CONCLUSIONS: Hybrid ionomers changed color significantly and perceptibly after in vitro accelerated aging. Surfaces became significantly rougher and showed evidence of cracking and degradation.

Influence of different factors on bond strength of hybrid ionomers.

A new generation of filling materials, the hybrid-ionomer cements, has been introduced recently. In many clinical situations these hybrid ionomers may be an alternative to conventional glass-ionomer cements and resins bonded with dentin bonding agents. During the past years research has focused on factors influencing bond strength of dentin bonding systems, but there is not much knowledge about the bond strength of hybrid- and glass-ionomer filling materials under different conditions. Bond strengths of four hybrid ionomers, one conventional glass-ionomer cement, and one cermet cement were determined in superficial and deep, dry and moist dentin using a simplified pulp chamber model. All materials showed significantly higher bond strength to superficial compared to deep dentin. Moisture showed no significant influence on any material neither in deep nor in superficial dentin. Bond strengths of Fuji II LC, Variglass, and Vitremer were distinctly higher than those of the conventional glass-ionomer cement (Ketac-Fil) and the cermet cement (Ketac-Silver), while that of Photac-Fil was not significantly different. Ionomer samples failed cohesively in superficial dentin in over 60% of the samples. The bonding interfaces between Fuji II LC and Variglass and the treated dentin surface showed tags but no distinct hybrid layer. Bond strength is not only dependent on the pretreatment of the dentin, but also on the glass-ionomer resin composition of the material.

Placement and replacement of composite restorations in Germany.

From 15 September to 15 October 1991, 102 dentists practicing in a rural area of Germany provided information on 3375 composite resin fillings. The purpose of this cross-sectional study was to record the reasons for placement and replacement of composite resin restorations, including any change of material when replacing a filling, and to register the age of any failed restoration. First placements because of primary caries were made in 50.6% of all cases; 49.4% were replacements of failed restorations. Composite resins were used as a material for the first placement of a restoration in 19.2% of primary teeth and in 47.8% of permanent teeth. More amalgams were replaced by composites than vice versa. Secondary caries was the most frequent reason for replacement in permanent teeth and in restorations with less than four surfaces, whereas fracture caused most failures in primary teeth and in fillings with four surfaces. The median age of the replaced restorations was 43.5 months. Failed restorations with four surfaces had the lowest median age.

Placement and replacement of amalgam restorations in Germany.

From 15 September to 15 October 1991, 102 dentists practicing in a rural area of Germany provided information on 5240 amalgam restorations. The aim of the present cross-sectional study was to investigate the reasons for placement and replacement of amalgam fillings and to register the age of the failed restorations. First placements because of primary caries were made in 47.1% of all cases; 52.9% were replacements of failed restorations. The most frequently recorded reason for replacement was secondary caries, irrespective of size of the filling, dentition, and age group. The second most frequently recorded reasons for replacement depended on the size of the filling, the age and the dentition of the patient: Bulk fractures were predominant in primary teeth and in fillings with three or four surfaces, primary caries in permanent teeth of patients 16 years old or younger and marginal gaps in adults and in fillings with one or two surfaces. The median age of replaced amalgam restorations in adults was 60 months.