Biomedical subjects

Lawrence H Mair

Publications and source records attributed to Lawrence H Mair.

3 recordsLinked to original sources

PubMed2006

Bonding of composite to water aged composite with surface treatments.

OBJECTIVE: The purpose of this study was to determine the shear bond strength of new composite to water aged composite with and without interfacial surface treatment. METHODS: Two hundred and eighty cylindrical samples were prepared for each of three resin composites (Spectrum, Dentsply; Durafill, Kulzer; Herculite, Kerr). Seventy samples of each material were bonded immediately and the remaining were stored in water. After 1, 4 and 12 weeks 70 samples were removed and the surface treated prior to bonding a second fresh increment. The treatments were: (1) no treatment, (2) abrasion with pumice, (3) a layer of Prime and Bond (Dentsply), (4) abrasion+Prime and Bond, (5) a layer of Optibond Solo Plus (Kerr), (6) abrasion+Optibond and (7) a layer of bis-GMA/TEGDMA. The specimens were loaded to failure in shear mode with a crosshead speed of 50 mm/min until fracture. The fracture surface of a number of specimens were examined in a scanning electron microscope. RESULTS: At all time intervals the treatment that resulted in the highest bond strengths (>20 MPa) was treatment with the dentine bonding agents (DBS) Prime and Bond or Optibond Solobond Plus. No treatment or abrasion alone resulted in very low bond strengths even after 1 week in water. When used in conjunction with DBS's abrasion did not increase the bond strength over the use of the DBS alone. The bis-GMA/TEGDMA was not as effective as the DBS's. SIGNIFICANCE: When bonding new composite to composite that has been underwater it is essential to treat the original composite surface. The results of this study indicated that the application of a dentine bonding agent significantly enhanced the bond. Abrasion alone did not produce an adequate bond.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2005

Thermal conductivity through various restorative lining materials.

OBJECTIVES: Traditional teaching has advocated the placement of insulating materials under restorations to protect against 'thermal shock'. Often this involves placement of a thick zinc-oxide eugenol cement lining. The purpose of this in vitro study was to assess the heat transfer through four lining materials and dentine and to relate these findings to the temperature exposures that may be experienced in the oral environment. METHODS: Two 'traditional' linings, zinc oxide eugenol cement (ZNOE) and calcium hydroxide paste (CAOH), and two more contemporary materials, a resin modified glass polyalkenoate (RMGP) and dentine bonding system (DBS) were studied in addition to dentine itself. Seven samples of each material were tested by utilising a Lees' Disc apparatus. Incorporation of thermocouples allowed heat transfer through the sample to be recorded. Thermal conductivity (J/m/s/ degrees C) was calculated for individual samples and a mean value obtained for each material. One way ANOVA and post hoc Tukey's tests were applied to the data obtained. RESULTS: In ascending order of thermal conductivity, DBS<CAOH<RMGP<DENTINE<ZNOE. Statistical analysis revealed that the thermal conductivity of DBS was significantly less than RMGP, DENTINE and ZNOE (p<0.05); CAOH was significantly less than DENTINE and ZNOE (p<0.05); RMGP was significantly higher than DBS and significantly less than DENTINE and ZNOE (p<0.05). CONCLUSIONS: Thermal insulation is not a major consideration in cavity lining and therefore other criteria for selection of a lining material should be applied.

Analysis of Variance↗

PubMed2003

The recharge of esthetic dental restorative materials with fluoride in vitro-two years' results.

OBJECTIVES: A range of esthetic restorative dental materials are now available to dental clinicians. The aim of this study was to evaluate the relative fluoride recharge potential of a number of these materials in vitro over two years. METHODS: Disc samples (12 mm x 2 mm) of each of the materials were placed into artificial saliva at neutral pH. The materials tested were: two glass ionomers (Chemfil; Ketac-Fil), two resin-modified glass ionomers (Photac-Fil Aplicap; Vitremer), two compomers (Dyract; Compoglass) and two composites (Heliomolar; Concise). At 13 intervals over a two years period the discs were subjected to a 2 min fluoride recharge by exposure to sodium fluoride (500 ppm F). The pre- and post-recharge fluoride release values were determined using an ion sensitive electrode. RESULTS: At all time intervals the post-recharge fluoride release of the materials was significantly different (MANOVA p<0.0001). The mean values for post-recharge fluoride release after two years were: Chemfil 10.3, Ketac 3.0, Vitremer 9.0, Photac-Fil Aplicap 12.1, Compoglass 5.0, Dyract 3.6, Concise 0.3, Heliomolar 0.2 (units = microgF/cm(2)/h). SIGNIFICANCE: Esthetic fillings vary significantly in their capacity to absorb and re-release fluoride. The glass ionomer-based materials displayed a far greater potential for fluoride recharge than the composites, in which the recharge was virtually negligible. Whilst it cannot be assumed that fluoride release is directly proportional to cariostatic potential, these results suggest that, where possible, glass ionomer-based materials should be used in patients who have a high caries rate.

Analysis of Variance↗