The Effect of Curing Light Intensity on Free Volume Size in Some Dental Composites.

BACKGROUND: Dental composite resins - reinforced polymers - are types of synthetic resins that are used in dentistry as restorative material or adhesives. The effect of curing-light intensity on free volume sizes of 4 commercial dental composites has been studied by means of the well-known positron annihilation lifetime spectroscopy technique. OBJECTIVES: The aim of the study was to compare the photosensitivity of 4 commercial dimethacrylate-based dental composites. MATERIAL AND METHODS: Positron lifetime spectra were collected using a slow-fast coincidence lifetime spectrometer with a time resolution of 365 ps. The positron source was a ~20 µCi 22Na beta emitter between two 7 µm thick stainless steel foils. The positron source was sandwiched between two identical samples under investigation. The 1st group of samples was polymerized by a 20-second photo-exposure, and the 2nd group of samples was irradiated by the blue curing light for 40 s. The positron annihilation lifetime spectrums were separated into components using the PAScual Positron Annihilation Spectroscopy data analysis program. RESULTS: The results showed that the lifetime component associated with free volumes differed in the different composites and depended on the irradiation time. The results indicated that the Coltene composite has higher photosensitivity than the other samples; the Denfil composite exhibited the lowest photosensitivity of the 4. CONCLUSIONS: The appropriate light-curing intensity depends on the thickness of the composite, which in turn is proportional to the depth of the hole in the tooth undergoing repair.

How Trustworthy Are Clinical Examinations and Plain Radiographs for Diagnosis of Scaphoid Fractures?

BACKGROUND: Sometimes patients with a scaphoid fracture, especially in an acute phase of injury, can have normal radiographs and, therefore, initial diagnosis of the scaphoid fracture may be neglected. In this study, we determined the value in of clinical examination and a radiograph in the diagnosis of scaphoid fracture based on the results of a two-week follow-up magnetic resonance imaging (MRI). OBJECTIVES: In this study, sought to assess the value of using both a clinical examination (tenderness of scaphoid tubercle, tenderness of anatomical snuffbox, and compression test) and radiographic imaging in the diagnosis of scaphoid fractures based on the results after a two-week follow-up MRI. PATIENTS AND METHODS: From December 2012 to February 2013, we enrolled 48 patients with suspected scaphoid fractures who had been referred to the emergency department of Baqiyatallah hospital, Tehran, Iran. Patients with negative results for clinical and radiographic examinations were excluded from the study. Cast immobilization was done for patients who had at least one positive finding during a physical examination test and who had normal radiographs. Patients who had a normal physical examination, but abnormal radiographs were referred to the orthopedic clinic after cast or split treatment. These patients also had a follow-up MRI two weeks after wrist trauma; the MRI was used to determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the clinical and radiographic examinations. RESULTS: Scaphoid tubercle tenderness had a sensitivity of 95.23% and a specificity of 74.07% in the diagnosis of scaphoid fracture. This test did not show a statistically difference with MRI results (P = 0.05). The results of the tenderness of the anatomical snuff box (sensitivity = 85.71%, specificity = 29.62%) was statistically different from the MRI results (P = 0.000). The results for the sensitivity (42.85%) and specificity (29.62%) for a compression test were not statistically different from the MRI results (P = 0.05). All of the radiographic tests that we applied in our project had 100% specificity for the diagnosis of a scaphoid fracture. However, the results were significantly different from the MRI results (P = 0.000). CONCLUSIONS: A clinical examination combined with a plain radiograph should be considered to improve the diagnostic precision for patients presenting with scaphoid fractures in an emergency department. In this way, both overtreatment and undertreatment of patients can be avoided.