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Thermocycling has been shown to cause surface degradation of many dental materials, but its effect on the fracture toughness and hardness of direct core buildup materials is unknown.This study was designed to determine the effect of thermocycling on the fracture toughness and hardness of 5 core buildup materials.Fifteen specimens were prepared from each of the following materials: Fluorocore, VariGlass VLC, Valiant PhD, Vitremer, and Chelon-Silver. American Standard for Testing Materials guidelines for single-edge notch, bar-shaped specimens were used. Ten specimens of each material were thermocycled for 2000 cycles; the other 5 specimens were not thermocycled. All specimens were subjected to 3-point bending in a universal testing machine. The load at fracture was recorded, and the fracture toughness (K(IC)) was calculated. Barcol hardness values were also determined. Data were analyzed with 1-way analysis of variance and compared with the Tukey multiple range test (P.05). Pearson's correlation coefficient was also calculated to measure the association between fracture toughness and hardness.Fluorocore had the highest thermocycled mean K(IC) and Valiant PhD the highest non-thermocycled K(IC). Chelon-Silver demonstrated the lowest mean K(IC) both before and after thermocycling. One-way analysis of variance demonstrated significant differences between conditions, and the Tukey test showed significant differences (P.05) between materials for both conditions. Most specimens also showed significant hardness differences between conditions. Pearson's correlation coefficient indicated only a mild-to-moderate correlation between hardness and fracture toughness.Within the limitations of this study, the thermocycling process negatively affected the fracture toughness and hardness of the core buildup materials tested.

Purpose This study determined the fracture toughness of four core buildup materials. Materials and Methods Single-edge notch, bar-shaped specimens conforming to the American Society for Testing Materials standard E-399 were fabricated for a high copper amalgam alloy, two composite resins, and a glass ionomer buildup material. The specimens were stored in air for 1 week and then tested in three-point bending mode with an Instron Universal Testing Machine (Instron Corporation, Canton, MA). Results Fracture toughness values obtained were as follows: Fluorocore (composite resin; Caulk, Milford, DE), 1.54 MN · m−1.5; Ti-Core (composite resin and titanium; Essential Dental Systems, New York, NY), 1.34 MN · m−1.5; Valiant Ph.D. (amalgam; Caulk), 1.29 MN · m−1.5; and Coreshade Glass lonomer Base Cement (Shofu Inc, Kyota, Japan), 0.55 MN · m−1.5. Conclusions Glass ionomer materials are probably unsuitable as core buildup materials because of their relatively low fracture toughness. Fluorocore, Ti-Core, and amalgam all had fracture toughness values significantly greater than the glass ionomer (P < .01).

Gastroesophageal reflux disease (GERD) is a condition where stomach acids are chronically regurgitated into the esophagus and oral cavity, resulting in pathology, such as esophagitis, varices or ulcers. Continual exposure of the teeth to these acids can also cause severe dental erosion. This condition frequently is asymptomatic, and the only evident sign may be the irreversible erosion of tooth structure. The dentist often is the first health care professional to identify the affected dentition. Knowledge of this cause and effect relationship between GERD and dental erosion will better prepare the practitioner to refer patients for appropriate diagnosis and treatment of the underlying medical condition and provide treatment for the affected teeth. This article presents a case report where dental erosion was present due to GERD. After management of the disease with medication, dental treatment of the eroded dentition is described, including diagnosis, treatment planning and restorative reconstruction.