Pulp histology after Er:YAG laser cavity preparation in subhuman primates--a pilot study.

UNLABELLED: The aim of the study was to make a direct comparison of the pulpal effects of laser and turbine preparations in subhuman primates. One female baboon (Papio Ursinus ursinus), weighing 15 kg, was used. General anaesthesia was administered (ketamine 100 mg/ml/kg body weight) and maintained with acepromazine (10 mg/ml/kg body weight). Class V cavities were prepared buccally in a total of 28 teeth (7 in each quadrant). Teeth in the upper right and lower left quadrants were prepared using a conventional 330 carbide bur in a high-speed fibre-optic handpiece with copious water spray. Teeth in the upper left and lower right quadrants were prepared using an Er:YAG laser drill (Fotona Twinlight, Llubljana, Slovenia) delivering 500 mJ at a pulse rate of 10 Hz and a wavelength of 2940 nm. The animal was sacrificed after 25 days. After general anaesthesia as described before, perfusion fixation of the head was accomplished with 10% neutral buffered formalin, pumped through a catheter inserted into the left carotid artery. The jaws were removed and, using a 330 carbide bur in a high speed handpiece, a continuous groove was cut through the bone and the roots at the level of the middle third of all the roots to promote thorough fixation of pulpal tissue. Decalcification and grading of the severity of the pulpal responses were conducted according to standard procedures. RESULTS: Owing to procedural errors seven teeth, FDI numbers 23, 24, 31, 34, 35, 44 and 45, had to be eliminated. The turbine-prepared teeth (N = 11) had a mean remaining dentine thickness (RDT) of 0.77 mm (SD = 0.42) and the laser-prepared teeth (N = 10) had a mean RDT of 0.81 mm (SD = 0.60). All pulps appeared normal except in one turbine-prepared tooth (12 with RDT = 0.20) and one laser-prepared tooth (27 with RDT = 0.30, where irreversible damage was caused. The only other deviations from normal were seen in the laser-treated 41 (RDT = 0.69) and the turbine-treated 36 (RDT = 0.77) where moderate hyperaemia was seen. Within the limitations of this study it can be concluded that there is no significant difference between dental pulp of teeth where Class V cavities were prepared with an Er:YAG laser drill compared with those prepared with a standard turbine drill.

Pulp capping with a modified bioglass formula (#A68-modified).

PURPOSE: To evaluate a modified Bioglass (Formula #68 (MBF68) when used as a pulp capping agent. MATERIALS AND METHODS: After exposure, the pulps were contaminated with saliva for 60s, rinsed, dried and treated with Consepsis, acting as a hemostatic and bactericidal agent. After drying the Consepsis, the MFB68, having been pre-mixed in sterile saline, was carefully deposited over the pulp exposure, covered with polycarboxylate cement and restored with the ProBond bonding resin system. A calcium hydroxide group was used as control. RESULTS: There was no evidence of mummification, the incidence of properly positioned dentin bridge formation was higher and the incidence of extruded dentin bridge formation was reduced.

Adherence of "stuck" restorations to demineralized dentin following use of experimental primers.

PURPOSE: This in vivo study histopathologically evaluated the biocompatibility of four self-conditioning dentinal primer formulas in four bonding systems and evaluated the pulpal responses of the self-conditioning dentinal bonding systems for Class V tooth preparations in primates. MATERIAL AND METHODS: The basic formula consisted of proprietary carboxylic diacid monomer, dipentaerythritol pentaacrylate phosphoric acid ester, acetone, and ethanol that was used alone or mixed with other commercial priming agents. After application of primers, Prisma Universal Bond 3 was selected to restore the cavity preparations. RESULTS: All systems were judged histopathologically biocompatible. "Stuck" restorations that were resistant to acid demineralization necessary for processing of histologic slides, occurred more frequently with intact smear layers and increasing use of dehydrating agents. CONCLUSIONS: Tests should be performed to determine whether "stuck" restorations in in vivo studies that maintain dentin-pulpal relationships can support in vitro shear bond strength tests.

Significance of pulpal pressure during clinical bonding procedures.

PURPOSE: To determine whether pulpal pressure in vital teeth plays a significant role in dentin bonding procedures. MATERIALS AND METHODS: Half the teeth in three baboons received root canal treatment thus eliminating pulpal pressure. All teeth were then prepared on the buccal surface with a diamond wheel to create flat surfaces into dentin, measuring at least 4 mm in diameter. Dentin bonding systems from two manufacturers were applied. Using a Bencor tensile nozzle freehand, 3.5 mm diameter composite buttons were bonded to the prepared surfaces. The animals were sacrificed 24 hours later, the teeth removed and mounted in specimen rings, using the same Bencor tensile nozzle for proper axial alignment. The composite buttons were tested for shear bond strength in a tensometer. RESULTS: The results showed no statistically significant difference between the two materials tested, furthermore there was no difference in SBS between materials bonded to vital or non-vital teeth. After completion of the tests, 20 teeth (10 for each dentin bonding system) were prepared according to standard laboratory procedures for a dentin bond strength test using the Bencor Multi-T system. The values obtained were higher, but again there was no statistically significant difference between the two systems.

Repairing fractured porcelain: how surface preparation affects shear force resistance.

This article reports on a study of the shear bond strength of porcelain repaired with any of several currently available dentin bonding systems and composite resin. The authors describe the benefits of the use of silane and the decrease in shear bond strength values after thermocycling. The results should be helpful to any practitioner confronted with a restoration that is a candidate for intraoral repair of fractured porcelain.

Replacing amalgam fillings with composite inlays--a case report.

The latest revival of the old amalgam controversy is causing dentists to be inundated with requests from patients to replace their amalgam fillings with more "acceptable" filling materials. A patient with chronic lymphocytic leukaemia has been monitored since 1981. All his amalgam fillings were replaced by baked composite inlays. The amount of mercury in his urine was determined before and after treatment. Although there was a slight decrease of the mercury in urine after treatment (6 mu gm/l compared to 10 mu gm/l before treatment) his blood picture remained unchanged. Replacement of sound amalgam fillings is not recommended.

Comparative study of the retentive strengths of dowels of three different diameters in combination with one or two different-sized threaded pins.

Vented parallel-sided, serrated posts cemented into matching precision channels provide excellent retentive strength; however, they do not offer significant resistance to rotational forces. This article explores the effectiveness of using supplementary pins to compensate for this deficiency. A standardized method was used to place combinations of parallel-sided posts and screw-type pins in prepared root canals of extracted human teeth. Standardized composite resin cores were made for the posts. Results indicate that the dentist must take note of the amount of dentin available for pin placement and, with reference to the provided graphs, determine the ideal size and number of pin(s) to be inserted.