John W. Rapley

Morphologic changes following in vitro CO2 laser treatment of calculus-ladened root surfaces

The purpose of this study was to compare morphologic changes following CO2 laser or manual curette treatment of calculus‐ladened tooth root surfaces.

Comparing Suture Strengths for Clinical Applications: A Novel In Vitro Study

BACKGROUND The purpose of this study was to compare the tensile strengths of commonly used sutures over a 2-week period under simulated oral conditions. METHODS Three suture materials (chromic gut [CG], polyglactin [PG], and polyglactin-fast absorbing [PG-FA]) were used in 4-0 and 5-0 gauges. After pretensioning, 252 suture samples (42 of each material and gauge) were used. A biologic simulation was created in vitro by mixing 9 ml sterile human saliva and human serum in a 1:1 ratio in a petri dish maintained at a pH of 7.4 to 8.1 at 37 degrees C. All samples were tested preimmersion and 1 hour and 1, 3, 7, 10, and 14 days postimmersion. The tensile strength was assessed using a microtensile tester, and the maximum load required to cause suture breakage was determined. The point of breakage in the samples and the samples themselves were also assessed. RESULTS During the first 24 hours of immersion, all 4-0 and 5-0 samples of CG and PG maintained their initial level of tensile strength; PG-FA 5-0 decreased in strength, which was statistically significant (P = 0.001). Between days 1 and 3, the tensile strength of PG and PG-FA decreased significantly, with PG-FA 5-0 showing a greater and more precipitous decrease than PG-FA 4-0; the tensile strength of CG changed little during this time. After 7 days of immersion, PG 4-0 had significantly greater tensile strength than CG, and both were significantly greater than that of PG-FA. By day 10, CG and PG had statistically greater strength (P = 0.01) than PG-FA, and values were similar for the 4-0 and 5-0 gauge materials. All samples of PG-FA 5-0 and most samples of the PG-FA 4-0 exhibited 0.00 N strength (i.e., they had disintegrated) at the 10- and 14-day periods of evaluation. CONCLUSIONS 4-0 sutures are stronger and have greater tensile strength than 5-0 sutures. CG seems to sustain its strength better than PG and PG-FA after 2 weeks. PG-FA may not be a desirable suture if tensile strength is required after 10 days. Appropriately designed clinical studies are necessary to confirm this finding in an in vivo environment.

Treatment of root fracture by CO2 and Nd:YAG lasers: An in vitro study

The purpose of this in vitro study was to use scanning electron microscopy and polarized light microscopy to evaluate the feasibility of using either the CO2 laser or an Nd:YAG laser in combination with air/water surface cooling to effect fusion of fractured tooth roots. The experimental unit consisted of 81 single-rooted teeth, each with an induced root fracture. Fifty-six teeth that had been reapproximated in dental stone and 25 teeth that had been reapproximated with C-clamps were assigned to untreated control groups or groups for treatment using CO2 and Nd:YAG lasers. Laser treatment consisted of multiple passes along the line of fracture, which was inspected using a dissecting microscope after each pass until a visual indication of fusion or irreparable damage resulted. Scanning electron microscopy evaluation of the treated lines revealed heat-induced fissures and cracks, areas of cementum meltdown and resolidification, crater formation, and separation of cementum from underlying dentin. In no instance-regardless of reapproximation technique, laser type, energy, and other parameters-did the treatment effect fusion of the fractured root halves.