Vincent D. Williams

Cast metal, resin-bonded prostheses: A 10-year retrospective study

A sample of 99 resin-bonded prostheses placed over a 10-year period were examined by four clinicians using a standardized criteria sheet. Areas examined included hard tissues, periodontium, retainer and pontic design, retention, the effect of occlusion on framework design and retention rate, and bonding media. The data from 7- and 10-year retrospective studies were compared for meaningful trends. Results showed (1) caries on retainer teeth was 3%, (2) gingival index of the retainer teeth was less than the gingival index of the rest of the mouth (0.7 +/- 0.5 versus 0.9 +/- 0.6), (3) the respective mean probing depths of retainer teeth of 34 patients in the 7- and 10-year studies were 2.2 +/- 0.4 mm and 1.9 +/- 0.7 mm, (4) the debond rate of all the prostheses from all causes was 31%, (5) the debond rate comparing etched metal and perforated retainers from all causes was 32% and 31% [corrected], respectively, and (6) 83% liked the prosthesis; 17% were noncommittal. The authors concluded that the resin-bonded prosthesis may be considered a permanent restoration and a valuable asset in the clinicians armamentarium.

The Masserann technique for the removal of fractured posts in endodontically treated teeth

In his 1923 text, Prothero’ mentions the “little Giant Post Puller,” a device designed by Dr. F. H. Skinner, which is the forerunner of “The Post Puller” advocated by Warren and Gutmann.* Both of these instruments have a clamp with strong beaks to grasp the dowel and a shoulder-post to rest on the root face. A screw is turned to remove the dowel occlusally. Ewing3 and Roberts4 suggest removal of cast post and cores by cutting a hole in the core, threading a brass wire through the hole to form a loop, attaching a crown puller to the loop, and tapping the post out in an incisal direction. The S. S. White Crown Repair Kit (S. S. White Dental Mfg. Co., Philadelphia, Pa.) uses trephines to gain access to the dowel. Threads are then cut on the dowel, and a jack screw is threaded to the dowel. Another screw on the tube removes the dowel incisally. Shelby5 and Tylman6 advocate troughing around the post with a small bur and then trying to vibrate the post out of the canal by grasping the post with either an endosilver point forceps or a hemostat. The forceps and hemostat can be used only on posts that are clinically exposed so that the instrument can be attached; they are of little value for posts broken. within the root canal. Tylman and Malone’ state that sometimes posts need to be drilled out of the root completely, with the

The effect of film thickness on the tensile bond strength of a prosthodontic adhesive

This study investigated the effect of cement film thickness on the tensile bond strength of a prosthodontic adhesive. Rexillium III alloy cylinders were bonded end-to-end with Panavia Opaque adhesive cement and film thicknesses of 20, 50, 80, 110, 140, and 200 microns were evaluated. The specimens were thermocycled for 24 hours (1080 cycles) between 5 degrees and 60 degrees C, stored for 30 days at 37 degrees C, and the mean bonds for tensile strength, including the mode of failures, were recorded. Statistical analysis revealed significant differences, but the strongest bond strengths were recorded for the 80 microns cement film thickness.

The effect of storage solutions and mounting media on the bond strenghts of a dentinal adhesive to dentin

Abstract The purpose of this study was to determine the effect of different storage solutions and mounting media on the in-vitro bond strength of a dentinal adhesive/composite to dentin. Thirty-six non-carious, unrestored human molars were randomly divided into 2 groups of 18: Group A were mounted in polymethyl methacrylate and Group C were mounted with improved dental stone in copper rings. The teeth were prepared to generate 4 planar surfaces which were oriented 90° to the mounting base to produce a total of 144 dentin bonding surfaces. Groups A and C were each subdivided into 3 groups of 6 teeth per group to be placed in 3 storage solutions: 0.9% aqueous NaCl (As, Cs); 0.05% saturated solution of thymol in distilled water (At, Ct); and distilled water (Aw, Cw). After 3 months in their respective storage solutions composite buttons 2.3 mm in diameter were attached using a dentinal adhesive. The bond strengths were tested in shear utilizing a cross-head speed of 0.5 cm/min and a 50 kg load cell. The results showed no significant differences at the 0.05 confidence level in mean bond strengths as related to the mounting media or the storage solutions tested.

Bond strength and surface characterization of a Ni-Cr-Be alloy

OBJECTIVES Since resin composite cements adhere directly to base metal surfaces, the composition and integrity of the surface oxide layer is considered critical for adequate bonding. The aims of this study were to determine the tensile bond strength, and assess predominant surface oxides and oxide layer depth on the surface of a Ni-Cr-Be alloy after subjecting the alloy to various surface treatments. METHODS Cylinders of Ni-Cr-Be (Rexillium III, Jeneric/Pentron) were cast and the following test groups were investigated: Group 0: no furnace oxidation, no air abrasion; Group 1: air fired, starting temperature 650 degrees C, ending temperature 1000 degrees C (1 min hold); Group 2: same firing sequence under vacuum; Group 3: same air firing sequence followed by air abrasion with 50 micrometers Al2O3; Group 4: vacuum fired, air abraded with 50 micrometers Al2O3; Group 5: air fired, air abraded with 280 micrometers Al2O3; Group 6: vacuum fired, air abraded with 280 micrometers Al2O3; Group 7: no furnace oxidation, air abraded with 50 micrometers Al2O3; and Group 8: no furnace oxidation, air abraded with 280 micrometers Al2O3. The oxide composition of three cylinders per group was analyzed with x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Twenty cylinders from each group were bonded together with Panavia 21 (Kuraray), stored in water for 30 d, and tensile tested. Data were analyzed using one-way ANOVA and Duncans Multiple-Range test (p=0.05). RESULTS Furnace oxidation brought Be to the surface and increased the oxide thickness. Air abrasion removed the oxide layer and resulted in surfaces containing significant amounts of Al2O3. Bond strengths for Group 0 were significantly lower than bond strengths for Groups 1, 3, 4, 5, 6, 8, but not significantly different from bond strengths for Groups 2 and 7 (p<0.05). SIGNIFICANCE Results of this study suggest differences in oxide composition and thickness due to various surface treatments. Furnace oxidation did not significantly affect bond strength and may not be required as a separate step for metal preparation if a resin adhesive is used.

The retentive capacity of rebonded retainers to enamel

Twenty-one whole, extracted canines and castings that had been bonded and tested to failure in a previous study were used as samples for this study.’ The designs that were retested had been previously illustrated.’ The teeth had been mounted in improved dental stone (Velmix, Kerr Manufacturing Co., Romulus, Mich.) in copper tubing 1% inches in diameter and 11% inches high. Linden2 reported’that fluid diffuses from the pulp through the dentin and enamel in vitro. To provide for similar hydration of the sample teeth, each root apex was removed and a hole through the mounting stone allowed storage water to penetrate the pulp chamber. The samples were stored in distilled water containing thymol, as suggested by Silverstone.’ After 1 year of storage, the residual composite resin was removed from the lingual surface of the tooth with a 12-bladed carbide finishing bur. The surface was then polished with oil-free pumice and examined visually to determine if all the composite resin had been removed. The castings (Fig. 1) were cleaned with a hand chisel, a high-speed composite resin finishing bur, and an air brush (Paasche Air Brush Co., Chicago, Ill.). The teeth were returned to the distilled water/thymol solution for an additional 6 months. For rebonding, the teeth were cleaped with oil-free pumice, rinsed in tap water, and dried with a commercial hair dryer (Sears, Roebuck & Co., Chicago, Ill.). The lingual surface was etched for 1 minute with 35% phosphoric acid (Adaptic, Johnson and Johnson, East Windsor, N. J.), as recommended by the manufacturer,

Bond versus rebond strengths of three luting agents for resin-bonded fixed partial dentures

Recently, new luting materials have been claimed to have adhesion to metal and tooth structure. This study determined if rebonding the specimens affected their tensile bond strength. Ten samples each of Rexillium III metal cylinders (12 x 6.3 mm) were bonded and rebonded with Comspan Panavia and Super-bond materials. The film thickness was controlled with a micrometer device at 20 microns. The samples were stored for 24 hours in deionized water at 37 degrees C and were then thermocycled for 24 hours and tested for tensile failure on an Instron testing machine. A stereomicroscope was used to determine adhesive/cohesive failure. The results showed a significant difference at p greater than 0.01 in tensile bond strengths (bond versus rebond strength) for all three luting agents. Most of the failures were adhesive in nature.