Biomedical subjects
M A Cochran
Publications and source records attributed to M A Cochran.
Technique on restoring cervical lesions.
This paper describes a technique of placing a semi-rigid cervical matrix slightly past the cervical border of a lesion that extends below (apical to) the gingival crest and inserting the glass ionomer cement through an opening cut in the matrix above the soft tissue level.
Comparison of glass-ionomer cements used to repair cast restorations.
Based on SEM analysis, this study evaluates the usefulness of three glass-ionomer cements to repair margins of cast restorations. These findings are compared to those previously obtained for amalgam, resin, and direct gold used as repair materials. This information can assist the clinician in choosing the most appropriate repair material in selected cases.
An in-vivo comparison of microleakage of composite resins placed with and without dentin bonding material.
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Direct restorative resins--an update for the clinician.
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High Copper amalgam--a review.
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One appointment amalgam core preparation.
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Class 5 composite resin restorations: margin configurations and the distance from the CEJ.
An in vitro study of 60 teeth examined the cervical microleakage of class 5 composite resin restorations in regard to preparation design and location from the cementoenamel junction (CEJ). Four groups of 15 teeth each were prepared for a class 5 composite resin restoration with the cervical margins finished as follows: a butt joint margin placed less than 1 mm from the CEJ, a beveled margin placed less than 1 mm from the CEJ, a butt joint placed greater than 1.5 mm from the CEJ, and a beveled margin placed greater than 1.5 mm from the CEJ. The teeth were acid etched, treated with an enamel bonding agent, and restored with a microfilled composite resin, and then sectioned for further analysis. The sectioned specimens were evaluated for cervical microleakage by Ca45 autoradiography. The butt joint margins placed less than 1 mm from the CEJ had significantly more microleakage than the other groups, indicating that all enamel margins of a class 5 composite resin restoration should be beveled to decrease microleakage regardless of their location relative to the cementoenamel junction.
The glass-ionomer-lined cervical composite restoration: an in vitro investigation.
The marginal adaptation and microleakage of the glass-ionomer-lined composite resin restoration in simulated erosion and conventional class 5 preparations were evaluated. The most common site of leakage for all restorations was the gingival margin. In erosion lesion restorations, the etched thick liners were superior to the etched thin liners with respect to marginal leakage. Acid-etched and unetched liners in both the erosion lesion and the conventional class 5 restorations were comparable. Under the SEM a gap was often found in the liner rather than at the liner-resin interface in restorations with etched liners.
Improving casting contours by regaining horizontal space.
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An in vitro shear bond strength study of enamel/dentin bonding systems on enamel.
The purpose of this study was to compare the enamel shear bond strengths achieved with four acid conditioners employed by current enamel/dentin bonding systems (maleic acid, citric acid, nitric acid, oxalic acid) with a 37% phosphoric acid etching technique. The study also compared enamel shear bond strengths between the manufacturers' enamel/dentin conditioner used with an unfilled enamel bonding resin. The facial surfaces of 135 bovine incisors were ground flat and divided into nine test groups of n=15. Conditioning and bonding procedures were carried out following manufacturers' instructions. The phosphoric acid groups were etched for 15 seconds, rinsed for 30 seconds, and dried for 20 seconds with compressed air. All bonding was accomplished at a constant temperature of 21 degrees C and a relative humidity of 60%. A single composite restorative resin (Z-100) was used with all specimens to eliminate variables between composite materials. All specimens were thermocycled 2500 times (5 to 45 degrees C) and had a total storage time of 21 days prior to shear testing on an Instron at a crosshead speed of 1.0 mm/minute. Shear strengths were calculated by dividing load at failure by specimen area. A light microscope was used to determine failure mode. The data were subjected to Bartlett's test for homogeneity of variance and were found not to be homogeneous. The Welch Test was applied and indicated that the treatments used had influence on bond strength at P<0.05. There was no significant difference in bond strength values between traditional phosphoric acid/enamel bonding resin and Mirage Bond Dentin and Enamel Adhesive, Clearfil Liner Bond System, and Scotchbond Multi-Purpose Dental Adhesive System.
Operative dentistry education: the pendulum ... and the pit.
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Influence of bonded amalgam restorations on the fracture strength of teeth.
This study evaluated the effect of bonded amalgam on the fracture strength of teeth using five adhesive systems: Panavia 21, Amalgambond Plus, Imperva Dual Bond, All-Bond 2 Primer/Bonding Resin, and All-Bond 2 Primer/Liner F. Intact teeth and amalgam lined with Copalite were used as control groups. Large MOD preparations were made in 20 extracted maxillary premolars for each group. The teeth were restored with Tytin. All groups were stored in water at 37 degrees C for 15 days and thermocycled 2500 times, over 8-48 degrees C. The specimens were preloaded five times in compression to 10 kg using a 5 mm-in-diameter, cylindrical steel indenter that contacted the teeth only on the cuspal inclines. Then the teeth were loaded to failure at 5.0 mm/min. The failure mode was recorded (amalgam failure, cusp fracture, or failure at the tooth/amalgam interface). The mean fracture strengths were analyzed using ANOVA and Newman-Keuls multiple comparisons. The Imperva Dual Bond group showed the highest mean forces followed by All-Bond 2 Primer/Bonding Resin. The All-Bond 2 Primer/Liner F and Amalgambond Plus groups demonstrated lower means and were not significantly different from the Copalite group. The Panavia 21 group was in between these two groups and was not statistically different from either group. The mean strength of intact teeth was the highest, but its very large coefficient of variation (60%) prevented effective use of these data for statistical comparison. Analysis of the mode of fracture showed that Panavia 21, All-Bond 2 Primer/Bonding Resin, and Amalgambond Plus failed cohesively in the amalgam in 35%, 25%, and 15% of the specimens respectively. This fracture type is a good indication of effective bonding between tooth and amalgam. The most common type of fracture for all the restored groups was the one that occurred at the tooth/restoration interface. This would suggest that current bonding procedures could be improved.
The effects of varied etching time and etching solution viscosity on bond strength and enamel morphology.
The effects of varied etching time and etching solution viscosity on bond strength were evaluated by measuring the tensile bond strength of a composite resin to bovine enamel. Also, six enamel surfaces were examined to evaluate the effect of acid treatment on the morphology of etched enamel using scanning electron microscopy. There was no significant difference in tensile bond strength between three etchants of differing viscosity or between etch times. Light microscopy revealed that most bond failures were cohesive in nature. When the three etchants of differing viscosity were compared under the scanning electron microscope, the liquid and the thin gel produced a more even etch pattern than the thick gel. In addition, the thin gel appeared to produce the most well-defined pattern of the three conditioners.
The effect of air abrasion on shear bond strength to dentin with dental adhesives.
This study compared the effects of different dentin surface treatments on the shear bond strengths of three adhesive systems. The adhesive systems included a resin-modified glass ionomer, Fuji II LC, and two dentin bonding systems, One Step and Scotchbond Multi-Purpose Plus. The surface treatments compared for each adhesive system were as follows: 1) the controls, which were conditioned, 2) air abrasion at 120 psi without conditioning, 3) air abrasion at 160 psi without conditioning, 4) air abrasion at 120 psi with conditioning, and 5) air abrasion at 160 psi with conditioning. The KCP 1000 Whisperjet was used for all air-abrasive specimens. Controls for each adhesive material (Fuji II LC, One Step, Scotchbond Multi-Purpose Plus) were bonded using manufacturers' recommendations. Results showed that air abrasion significantly lowered bond strength of the resin-modified glass ionomer, conditioned or nonconditioned (P < 0.01). Air abrasion alone significantly lowered bond strengths of the dentin bonding agent systems (P < 0.01). However, air abrasion plus conditioning of the dentin surface resulted in bond strengths that were similar to the conditioned-only specimens (P < 0.01).