Karl-Heinz Friedl

Polymerization efficiency of different photocuring units through ceramic discs

This study compared the ability of a variety of light sources and exposure modes to polymerize a dual-cured resin composite through ceramic discs of different thicknesses by depth of cure and Vickers microhardness (VHN). Ceramic specimens (360) (Empress 2 [Ivoclar Vivadent], color 300, diameter 4 mm, height 1 or 2 mm) were prepared and inserted into steel molds according to ISO 4049, after which a dual-cured composite resin luting material (Variolink II [Ivoclar Vivadent]) with and without self-curing catalyst was placed. The light curing units used were either a conventional halogen curing unit (Elipar TriLight [3M/ESPE] for 40 seconds), a high-power halogen curing unit (Astralis 10 [Ivoclar Vivadent] for 20 seconds), a plasma arc curing unit (Aurys [Degré K] for 10 seconds or 20 seconds) or different light emitting diode (LED) curing units (Elipar FreeLight I [3M/ESPE] for 40 seconds, Elipar FreeLight II [3M/ESPE] for 20 seconds, LuxOmax [Akeda] for 40 seconds, e-Light [GC] for 12 seconds or 40 seconds). Depth of cure under the ceramic discs was assessed according to ISO 4049, and VHN at 0.5 and 1.0 mm distance from the ceramic disc bottom was determined (ISO 6507-1). Medians and the 25th and 75th percentiles were determined for each group (n=10), and statistical analysis was performed using the Mann-Whitney-U-test (p < or = 0.05). The results showed that increasing ceramic disc thickness had a negative effect on the curing depth and hardness of all light curing units, with hardness decreasing dramatically under the 2-mm thick discs using LuxOmax, e-Light (12 seconds) or Aurys (10 seconds or 20 seconds). The use of a self-curing catalyst is recommended over the light-curable portion only, because it produced an equivalent or greater hardness and depth of cure with all light polymerization modes.

Clinical performance of a new glass ionomer based restoration system: A retrospective cohort study

OBJECTIVES This retrospective clinical study evaluated the suitability of a glass ionomer system as a permanent restoration material in posterior cavities. METHODS 26 Class I (1-surface (S1)) and 125 Class II (84 2-surface (S2), 41 3- and 4-surface (S3+)) restorations were placed in permanent molars (n=94) and premolars (n=57) in 43 patients in 6 dental practices. Restorations were evaluated at 4.5× magnification using modified USPHS criteria. Statistical analysis was performed using the Pearsons Chi-square-test (p ≤ 0.05). RESULTS The median age of the restorations was 24 months. No failures were observed. The original volume of the restoration was retained in 88.5% of the S1, in 64.2% of the S2 and in 53.7% of the S3+ restorations. A distinct volume loss in S1 restorations was evident in 3.8%. A visible and perceptible roughness was shown in 11.5% of the S1, in 14.3% of the S2 and in 24.4% of the S3+ restorations. Marginal disintegrities occurred in none of the S1, in 1.2% of the S2 and in 7.3% of the S3+ restorations. A distinct marginal discoloration was found less than 1%. CONCLUSIONS Within the limitations of this study it can be concluded that EQUIA can be used as a permanent restoration material for any sized Class I and in smaller Class II cavities. However, results of ongoing prospective studies shall provide a more exact indication definition in Class II situations. SIGNIFICANCE Modern glass ionomer systems may not only serve as long-term temporaries, but also as permanent restorations in posterior teeth.

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.

Clinical performance of polyacid-modified resin restorations using ”softstart-polymerization”

Abstract 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≤ 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.

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

Abstract 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.