Study tests polymeric resins for primary tooth restorations

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When faced with the need to restore primary teeth, the development of CAD/CAM systems and materials offers new treatment possibilities. But do these materials suffer excessive tooth wear that would make them inappropriate to use? A new study investigated.

Researchers put five CAD/CAM polymeric resin blocks through their paces in a test that simulated tooth wear. While the test resulted in loss of volume and weight for each of the five materials, the wear patterns differed.

"Since the wear patterns of antagonists and materials differed, it is evident that appropriate restorative materials selection should be based on considerations of specific clinical situations," the authors wrote.

The study was published December 9, 2017, in the journal Materials. The lead author was Jae-Won Choi from the department of prosthodontics in the School of Dentistry at Pusan National University in Yangsan, South Korea.

5 blocks tested

With patients seeking more esthetic restorations, practitioners are increasingly using dental CAD/CAM systems in combination with machinable CAD/CAM materials to produce restorations with excellent physical properties.

However, little is known about the use of various CAD/CAM materials based on evaluations of tooth wear. The researchers sought to fill this gap to suggest an innovative treatment method for these teeth.

Previous studies have shown that fixed dental prostheses made from CAD/CAM polymeric resins have better fracture resistance than those produced from manually polymerized resins. These resins are also less affected by aging than polymerized resins and glass ceramics, along with having color stabilities and mechanical properties (such as flexural strength) similar to those of glass ceramics, according to the authors. These resins are regarded as being suitable for long-term restorations and as alternatives to glass ceramics for some patients.

In this study, the following five CAD/CAM polymeric resin blocks were tested:

  • Mazic Duro (Vericom, South Korea), a ceramic-polymer composite material
  • Pekkton (Cendres+Metaux, Switzerland), a high-performance polymer
  • Vita Enamic (Vita Zahnfabrik, Germany), a ceramic-polymer composite material
  • Vipi Block Monocolor (Vipi, Brazil), a CAD/CAM material based on polymethyl methacrylate (PMMA)
  • Yamahachi PMMA (Yamahachi Dental, Japan), a PMMA-based CAD/CAM material

All of the specimens were tested in a thermomechanical loading machine with the primary canine as the antagonist.

In terms of loss of volume for each material, there was no significant difference between any of the materials (p > 0.05), the authors reported.

However, when considering antagonist tooth wear, Vipi Block Monocolor and Vita Enamic showed significantly higher values than Pekkton (p < 0.05). There was no significant difference observed among the others (p > 0.05).

Tooth-wear test of 5 CAD/CAM polymeric resins
Test Mazic Pekkton Vita Enamic Vipi Block Yamahachi PMMA
Antagonist tooth wear 0.7260 ± 0.5786 mm3 0.2621 ± 0.2707 mm3 1.3983 ± 0.9264 mm3 1.4261 ± 1.6156 mm3 1.2833 ± 1.9111 mm3
Material volume loss 0.7432 ± 0.6296 mm3 1.7617 ± 1.4097 mm3 0.7197 ± 0.4958 mm3 1.0306 ± 0.8135 mm3 0.8857 ± 0.5807 mm3
Total wear 1.4692 ± 0.6006 mm3 2.0238 ± 1.4974 mm3 2.1180 ± 1.2189 mm3 2.0238 ± 1.4974 mm3 2.1690 ± 1.7496 mm3

In terms of material weight loss, Pekkton lost significantly more material than the Vita Enamic group (p < 0.05). However, no significant difference was observed between Vipi Block Monocolor, Yamahachi PMMA, Mazic Duro, and Vita Enamic (p > 0.05).

Mixed results

The authors noted two main limitations of the study:

  • Primary tooth wear was not investigated.
  • Severe, dynamic conditions in the oral cavity, such as temperature variations, pH fluctuations, and microbiota, were not investigated.
“The volumetric and weight losses of materials exhibited similar patterns.”
— Jae-Won Choi and colleagues

"Certainly, clinical studies provide the best means of establishing tooth wear, but they are costly and time-consuming, and are disadvantaged by a lack of control over important variables such as chewing forces and environmental factors," the authors wrote.

They also noted that because the material specimens were not polished after CAM processing, it is unreasonable to directly compare the results with the clinical situation.

The oral cavity is a dynamic environment, and practitioners have to make decisions based on their patient's specific needs and environment, the authors wrote. They added that no one material was clearly superior.

"Within the limits of this study, the volumetric and weight losses of materials exhibited similar patterns," they wrote. "Pekkton caused the least antagonist wear, but the greatest material wear. Vipi Block Monocolor and Vita Enamic caused significantly more antagonist wear than Pekkton, and Vita Enamic showed significantly less material weight loss than Pekkton."

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