Calvin D. Torneck

The Effect of Carbamide-Peroxide Gel on the Shear Bond Strength of a Microfil Resin to Bovine Enamel

Cylinders of a visible-light-cured microfil resin were formed on, and bonded to, the flattened labial enamel surfaces of young bovine incisor teeth which had previously been subjected to four different treatments: (1) immersion in 10% carbamide-peroxide gel, pH 4.7, for three h; (2) immersion in 10% carbamide-peroxide gel, pH 4.7, for six h; (3) immersion in 10% carbamide-peroxide gel, pH 7.2, for three h; and (4) immersion in 10% carbamide-peroxide gel, pH 7.2, for six h. For each experimental group, a control group of resin-bonded to saline-immersed teeth was prepared. In addition, two groups, prepared according to treatment 4, were leached in distilled water for one and seven d, respectively, prior to resin application. Specimens were stored in distilled water at 37°C for seven d prior to shear-bond-strength testing. A total of 90 teeth was tested. Statistical analysis of the results indicated that there was a highly significant reduction in the shear bond strength to carbamide-peroxide-treated enamel as compared with that to saline-treated enamel. The effects of duration of peroxide treatment and pH, as well as the interaction term, were not statistically significant. Leaching of the peroxide-treated enamel in water for either one or seven d prior to resin application restored the adhesiveness of the enamel. Scanning electron microscopic examination of randomly selected, fractured test specimens indicated that the peroxide-induced reduction in enamel adhesiveness was related to alterations in both attachment-surface area at the resin-enamel interface and resin quality.

Adhesion of a resin composite to bleached and unbleached human enamel

Cylinders of a visible light-cured microfil resin were formed on and bonded to the flattened enamel surface of 15 human hemisected premolar teeth which had previously been subjected to three different treatments: (a) immersion in 35% hydrogen peroxide (HP) for 60 min, (b) immersion in 35% HP for 60 min followed by storage in distilled water for 1 day prior to resin application, and (c) immersion in saline (S) for 60 min. Specimens were stored in distilled water at 37 degrees C for 7 days prior to shear bond strength testing. A total of 30 specimens were tested. Statistical analysis of the data indicated that there was a highly significant reduction in shear bond strength between HP- and saline-treated specimens. Water storage of HP-treated specimens for 1 day prior to resin application appeared to restore the adhesiveness but not to a point that was statistically significant. Scanning electron microscopic examination of randomly selected, fractured test specimens indicated that the reduction in bond strength may be related to alterations in the ability of the resin to attach itself to the HP-treated surface and to possible effects of the HP on the resin itself.

Revascularization: A Treatment for Permanent Teeth with Necrotic Pulp and Incomplete Root Development

INTRODUCTION Endodontic treatment of immature permanent teeth with necrotic pulp, with or without apical pathosis, poses several clinical challenges. There is a risk of inducing a dentin wall fracture or extending gutta-percha into the periapical tissue during compaction of the root canal filling. Although the use of calcium hydroxide apexification techniques or the placement of mineral trioxide aggregate as an apical stop has the potential to minimize apical extrusion of filling material, they do little in adding strength to the dentin walls. It is a well-established fact that in reimplanted avulsed immature teeth, revascularization of the pulp followed by continued root development can occur under ideal circumstances. At one time it was believed that revascularization was not possible in immature permanent teeth that were infected. METHODS An in-depth search of the literature was undertaken to review articles concerned with regenerative procedures and revascularization and to glean recommendations regarding the indications, preferred medications, and methods of treatment currently practiced. RESULTS Disinfection of the root canal and stimulation of residual stem cells can induce formation of new hard tissue on the existing dentin wall and continued root development. CONCLUSIONS Although the outcome of revascularization procedures remains somewhat unpredictable and the clinical management of these teeth is challenging, when successful, they are an improvement to treatment protocols that leave the roots short and the walls of the root canal thin and prone to fracture. They also leave the door open to other methods of treatment in addition to extraction, when they fail to achieve the desired result.

Scanning electron microscopy observations on the penetration and structure of resin tags in bleached and unbleached bovine enamel

The purpose of this study was to determine the effect of hydrogen peroxide on the ability of composite resin to penetrate bovine enamel etched with phosphoric acid. In a previous investigation, the flattened enamel surfaces of extracted bovine incisors were immersed in either saline (control) or 35% hydrogen peroxide (experimental) for 5 or 30 min before or after acid etching with 37% phosphoric acid gel for 60 s. A standard-sized light-cured resin cylinder was then bonded to the enamel surface. The specimens were stored in a water bath at 37 degrees C for 1 day or 7 days, after which the enamel-resin bond was tensile tested to failure. Sixteen of the failed specimens (eight control and eight experimental) were randomly selected for the present scanning electron microscopic study to evaluate the appearance of the resin tags at the resin-enamel interface. In the control specimens, the tags were well defined and contiguous with resin which was uniformly adherent to the enamel surface. In the experimental specimens, large areas of the enamel surface were free of resin. When tags were present, they were fragmented, poorly defined, and penetrated to a lesser depth than in the saline controls. The changes observed suggest that there may be interaction between resin and residual peroxide at or near the enamel surface.

The influence of time of hydrogen peroxide exposure on the adhesion of composite resin to bleached bovine enamel

Standard sized cylinders of a small particle light-cured resin were bonded to the flattened labial surface of young bovine incisor teeth which had been previously subjected to four different treatments: (a) immersion in 35% hydrogen peroxide and etched with 37% phosphoric acid gel for 60 s, (b) immersion in saline and etched for 60 s, (c) etched for 60 s and immersion in hydrogen peroxide, and (d) etched for 60 s and immersion in saline. Two hydrogen peroxide and saline immersion periods were used, 5 and 30 min. Specimens were stored in water at 37 degrees C for 1 and 7 days before tensile and shear testing. A total of 256 teeth were used, 8 for each treatment group, each immersion period, and each water storage period for each test. Statistical analysis of the results indicated that there was a highly significant reduction in the adhesive bond strength of the resin when the enamel was exposed to hydrogen peroxide and that the reduction was, within the limits of this study, time dependent. The bond strength was unaffected by the etching order and the period of water storage. Scanning electron microscopic examination of randomly selected fractured peroxide-treated specimens indicated that the failure occurred primarily at the bonding resin-enamel interface and that it was associated with areas of resin nonattachment and an alteration in resin quality. It is suspected that these changes were caused by the presence of residual peroxide or peroxide-related substances at or near the enamel surface.

Adhesion of Composite Resin to Bleached and Unbleached Bovine Enamel

Cylinders of microfil and small-particle light-cured composite resin were bonded to the flattened labial enamel surface of young bovine incisor teeth which had previously been subjected to four different treatments: (1) teeth immersed in 35% hydrogen peroxide (HP) for 60 min and etched (E) with 37% phosphoric acid gel for 60 sec; (2) teeth immersed in saline (S) for 60 min and E for 60 sec; (3) teeth E for 60 sec and immersed in HP for 60 min; and (4) teeth E for 60 sec, immersed in S for 60 min. Specimens were stored in water at 37°C for one and seven days prior to tension- and shear-testing. A total of 256 teeth was tested— eight teeth in each group for each day, for each resin, and for each test. Statistical analysis of the results indicated that there was a highly significant reduction in adhesive bond strength of the resins when the enamel was exposed to HP as compared with S. SEM examination of randomly selected fractured test specimens indicated that this reduction in adhesive bond strength occurred primarily at the bonding resin-enamel interface. Less significant differences in bond strength were noted in the control specimens, with regard to resin type, time of storage, and the etching order.

Preliminary Surface Analysis of Etched, Bleached, and Normal Bovine Enamel

X-ray photoelectron spectroscopic (XPS) and secondary ion-mass spectroscopic (SIMS) analyses were performed on unground un-pumiced, unground pumiced, and ground labial enamel surfaces of young bovine incisors exposed to four different treatments: (1) immersion in 35% H2O2 for 60 min; (2) immersion in 37% H 3PO4 for 60 s; (3) immersion in 35% H2O2 for 60 min, in distilled water for two min, and in 37% H3PO 4 for 60 s; (4) immersion in 37% H3PO4 for 60 s, in distilled water for two min, and in 35% H2O2 for 60 min. Untreated unground un-pumiced, unground pumiced, and ground enamel surfaces, as well as synthetic hydroxyapatite surfaces, served as controls for intra-tooth evaluations of the effects of different treatments. The analyses indicated that exposure to 35% H2O2 alone, besides increasing the nitrogen content, produced no other significant change in the elemental composition of any of the enamel surfaces investigated. Exposure to 37% H3PO4, however, produced a marked decrease in calcium (Ca) and phosphorus (P) concentrations and an increase in carbon (C) and nitrogen (N) concentrations in unground un-pumiced specimens only, and a decrease in C concentration in ground specimens. These results suggest that the reported decrease in the adhesive bond strength of resin to 35% H 2O2-treated enamel is not caused by a change in the elemental composition of treated enamel surfaces. They also suggest that an organic-rich layer, unaffected by acid-etching, may be present on the unground un-pumiced surface of young bovine incisors. This layer can be removed by thorough pumicing or by grinding. An awareness of its presence is important when young bovine teeth are used in a model system for evaluation of resin adhesiveness.

The Effect of Concentrated Hydrogen Peroxide Solutions on the Surface Morphology of Human Tooth Enamel

Sections of human tooth enamel were exposed to concentrated hydrogen peroxide solution for periods of time ranging from 1 to 60 min. Some sections were posttreated with 37% phosphoric acid for 60 s and others were pretreated (etched) with 37% phosphoric acid for 60 s. Each of the sections used in the study was compared with a control specimen from the same tooth area which was exposed only to saline before and after treatment with 37% phosphoric acid for 60 s. A comparison of control and experimental sections indicated that exposure to concentrated hydrogen peroxide solution produced a precipitate on the enamel surface. The amount of precipitate appeared to be related to the length of the hydrogen peroxide exposure. The combination of hydrogen peroxide and acid etching resulted in an enamel surface that displayed more precipitate and appeared to be more porous than enamel surfaces used as controls. The significance of these findings relative to the adhesion of dental materials to bleached enamel surface is discussed.

Biologic effects of endodontic procedures on developing incisor teeth

Abstract A series of pulp injuries was induced on fourteen developing incisor teeth of four young primates. Following this injury the pulp canals of the teeth were allowed to remain open and exposed to the oral environment for a period of 7 to 95 days. Microscopic examination of the teeth and periodontal tissues revealed a progression in the intensity and severity of the periapical inflammation during the early stages of the observation period. Later stages displayed irregular and limited attempts at continued root formation and apical closure by dental hard tissue and bone. The genesis of this tissue was apparently related to residual odontogenic cells of the pulp and to the growth of cells into the pulp space from the periapical tissues. Continued root growth and foraminal closure was often seen despite the presence of pronounced inflammatory changes in both the residual pulp and the periapical tissues.

Effect of water leaching on the adhesion of composite resin to bleached and unbleached bovine enamel

Standardized cylinders of light-cured composite resin were bonded to the ground labial enamel surface of bovine incisor teeth that had been immersed in double-distilled water for 7 days after having been (a) immersed in hydrogen peroxide for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (b) immersed in saline for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (c) etched with 37% phosphoric acid for 60 s, then immersed in hydrogen peroxide for 5, 30, or 60 min; or (d) etched with 37% phosphoric acid for 60 s, then immersed in saline for 5, 30, or 60 min. The enamel surface was washed with water for 1 min and dried with compressed air for 30 s prior to applying the resin. The tooth and applied resin were stored in water at 37 degrees C for 1 day prior to shear and tensile testing. A total of 192 specimens was used, 8 for each enamel preparation mode, for each time period, and for each test. Test values were tabulated and statistically analyzed. Analysis of variance revealed significantly higher bond strength values (p less than 0.005) for hydrogen peroxide-treated as compared with saline-treated specimens. A significant interaction was also noted between test solution and etching order. Scanning electron microscopic examination of failed shear- and tensile-tested specimens revealed no significant solution-related differences in the fracture pattern or the resin quality.(ABSTRACT TRUNCATED AT 250 WORDS)