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Biomedical subjects

Gottfried Schmalz

Publications and source records attributed to Gottfried Schmalz.

22 records · Page 2Linked to original sources
PubMed2002

Cytotoxicity of low pH dentin-bonding agents in a dentin barrier test in vitro.

The reaction of three-dimensional cultures of pulp-derived cells in a dentin barrier test was recorded after exposure to All-Bond 2, Prime & Bond NT, Syntac SC, Syntac Classic, and Prompt L-Pop. The materials were applied on bovine dentin disks in a perfusion chamber, and the experiments were performed with (0.3 ml/h, 2 ml/h) and without perfusion of the pulpal part of the chamber. The cell reaction was recorded (MTT assay) and related to noncytotoxic controls. Bonding agents with low pH did not show any cytotoxicity. Syntac Classic decreased the cell activities to 38% to 72%, depending on different experimental conditions, and was more cytotoxic than Syntac SC. Perfusion (2 ml/h) reduced the cytotoxicity for Syntac Classic and increased cell activities from 52% to 72%. Because low pH bonding agents did not show toxic reactions in this dentin barrier test, pulp damage caused by the tested substance is unlikely if a dentin layer protects the pulp.

Animals↗
PubMedDate not supplied

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.

Ceramics↗
PubMedDate not supplied

Partial ceramic crowns: influence of preparation design and luting material on internal adaptation.

The influence of three different cavity preparations on the marginal integrity of partial ceramic crowns (PCC) luted with four different luting systems was investigated in this in vitro study. PCC preparations were performed in 144 extracted human molars using one of the following preparation designs (n=48/preparation): A--Coverage of functional cusps/butt joint preparation; B--horizontal reduction of functional cusps and C--complete reduction of functional cusps/butt joint preparation. Non-functional cusps were not covered; mesial and distal proximal boxes were extended 1 mm below the cemento-enamel-junction. PCC were fabricated from Vita Mark II ceramic (Vita) with a Cerec 3 Unit (Sirona) and adhesively luted to the cavities using the following luting systems: (VL) Variolink II/Excite (Vivadent), (PA) Panavia F/ED Primer (Kuraray), (DY) Dyract/Prime & Bond NT (DeTrey/Dentsply) and (FU) Fuji Plus/GC Cavity Conditioner (GC). Samples were simultaneously exposed to thermocycling and mechanical loading (TC: 5000x8-55 degrees C, 30 seconds/cycle; ML: 500000x72.5N, 1.6Hz). Marginal adaptation was assessed by evaluating dye penetration on multiple sections by relating the actual penetration distance to the maximal length of the corresponding cavity wall (100%). Ceramic- and tooth-luting material interfaces were evaluated separately. The data were statistically analyzed with the Mann Whitney U-test and Wilcoxon Rank Sumtest. In general, no significant differences could be found between preparations A, B and C. The combination of preparation C and luting material PA showed a tendency for the lowest dye penetration values, especially within dentin (30%). Significant differences could be determined between luting materials: Composite luting materials PA (0%) and VL (1%) revealed less dye penetration than the compomer DY (6%) and resin-modified glass ionomer cement (RMGIC) FU (26%); use of RMGIC caused fractures of the restorations. The dentin/luting material interface showed the highest penetration values, ranging from 17% to 100%. In conclusion, with adhesively bonded partial ceramic crowns, the choice of luting material proved to be more relevant than preparation design under the limitations of this study. Margins below the cemento-enamel junction reveal significant loss of adhesion in spite of subsequent application of adhesive luting techniques. RMGIC cannot be recommended as a luting material for feldspathic PCC.

Acrylic Resins↗