Studies Demonstrate Flexural Loading and Fracture Toughness Qualities of New Provisional Material

Posted on October 9, 2013

SOUTH BEND, INDIANA, August 12, 2013 — Heraeus Kulzer, LLC’s new Venus Temp 2 provisional was shown by two studies to demonstrate superior flexural strength and resistance to fracturing when compared to three other leading products. The findings were presented at the American Association for Dental Research (AADR) Annual Meeting in Seattle, Washington in March 2013 and published as abstracts in Special Issue A of the Journal of Dental Research.

For both studies, the principal investigator was Ronald Perry, DMD, MS, Director, Gavel Center for Restorative Research, and the co-investigator was Masly Harsono, DDS, MS, DMD. The two are Clinical Professor and Assistant Professor, respectively, at Tufts University School of Dental Medicine.1 Both studies were funded by Heraeus Kulzer, LLC.

The methodologies and results of the two studies are summarized below.

Study #1: “Evaluating the Flexural Loading Conditions of Three Restorative Materials”

The objective of this study was to compare in vitro the flexural strength of four provisionals: ProTemp™ Plus (3M ESPE), Luxatemp® Solar (DMG America), Integrity® (Dentsply Caulk), and Heraeus Kulzer’s new Venus Temp 2.

Methodology

Teeth Nos. 19 and 21 were prepared as abutment teeth for the 3-unit bridge on a Typodont. The amount of reduction was approximately 2 mm of occlusal; 2-2.5 mm of buccal, lingual, and proximal walls; 1-1.5 mm full deep chamfer margin; and 15-20 degrees of total occlusal convergence. All line angles were rounded and no undercuts were present on the prepared teeth. A metal cast duplicate was made from the Typodont as a template in preparation for the provisional bridge restorations. Ten provisional bridges were made for each of the four provisionals.

Silicone putty was used as a template for the provisional bridge. The putty was also placed on the metal to mimic oral soft tissues. The metal and soft tissue-like putty were coated with petroleum jelly to more easily dislodge the temporary after it set. The pontic design for the missing tooth No. 20 was a modified ridge lap. The samples’ margins were trimmed using acrylic burs. All samples were then polished with pumice and cemented.

The 3-point bending test was carried out on a Universal Testing Machine with 1 mm/min crosshead speed. The initial crack was recorded and the test was stopped upon catastrophic failure of the bridges. The initial crack happened on different parts of the temporary, mostly between the abutment and prepped tooth, or in the middle of the abutment. There was no trend to any of the catastrophic failures. In addition, digital high magnification video camera with macro lens attached to the Instron machine recorded the mode of failure. One-way ANOVA with Tukey-Kramer analysis for pairwise comparison was done to determine if there is a significant difference among groups.

Results

The flexural load readings were as follows:

1. Venus Temp 2 883.99

2. Luxatemp Solar 770.80

3. Protemp Plus 720.08

4. Integrity 378.98

From a statistical standpoint (p<0.001), Integrity was significantly weaker than Venus Temp 2, Luxatemp Solar, and Protemp Plus in resisting fracture. No statistical difference was evident between Venus Temp 2, Luxatemp Solar, and Protemp Plus.

Study #2: Comparison of Fracture Toughness of Provisional Materials

Methodology

For each of the four provisionals tested, ten samples were made using a stainless steel mold 2 mm in height, 4.95 mm in width, and 25 mm in length. The provisional materials were poured into a mold on top of the glass plate and polyester (Mylar) film strip. The second mylar film was placed on top of the mold followed by the glass plate. Load was applied on top of the glass and thus displacing excess material. After 24 hours of polymerization, a notch (2.6 ± .05 mm) was inserted into the middle of each sample using a separating disc (thickness 320 μm) attached to an immobilized low-speed handpiece. Microscope examination was used to observe any defects in all the samples.

The three-point bending test was performed using a universal testing machine at a cross-head speed of 1mm/min (load cell 500 N). The notch was positioned centrally beneath the contact and the distance between the two supports was 20 mm. The radius of each support was 1 mm.

The fracture toughness (K1C) was calculated according to ISO 13586. The Kolmogorov-Smirnov test was used to determine normal distribution and the homogeneity of the samples was checked using the Levene test. A one-way ANOVA was used to test the mean fracture toughness between groups. Statistical significance was predetermined at level p < 0.005.

Results

Mean Fracture Toughness (MPa · m0.5)

1. Venus Temp 2 1.38 +/- 0.19

2. Protemp Plus 1.33 +/- 0.13

3. Integrity 1.02 +/- 0.068

4. Luxatemp Solar 0.98 +/- 0.04

Statistically speaking, Venus Temp 2’s fracture toughness was significantly higher than both Integrity and Luxatemp Solar. No statistical difference was evident between Venus Temp 2 and Protemp Plus.

 

1Tufts University does not endorse any particular brand or product.

Source: Heraeus Kulzer North America

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