Teaching debonding in dental hygiene programs.
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Adhesives↗
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[Elemental analytical and quantitative morphometric determination of the synthetic resin residues and enamel avulsion after the removal of metal brackets].
A number of clinical and experimental studies were performed to assess the quality of the enamel-adhesive-bracket bond. The aim was to present a combined method that enables the investigator both to examine the surface of metal brackets quantitative-morphometrically and to detect the presence of enamel particles. To this end, 38 metal brackets were examined in the scanning electron microscope. An EDAX-detecting unit was used to analyze morphologically conspicuous structures and identified them as enamel particles. The extent of adhesive remnants and enamel particles was quantified using the image analysis system IBAS. In 24 brackets (53%) bonding adhesive residue was found on the bracket base. In 18 brackets (47%) enamel particles were identified on the adhesive-bearing brackets. This method is easier to carry out and enables a more accurate quantification of enamel particles than the Adhesive Remnant Index. Since it can be applied universally to examine recommended improvements to adhesive technique, it facilitates their assessment.
Composite Resins↗
[Enamel damage depending on the method of bracket removal].
Two different methods of removing brackets, on the one side by torsion and on the other by bending, were compared for the purpose of analyzing the respective enamel lesions. Each test group consisted of 19 extracted human molars with metal brackets attached to the molars by means of the "concise etching technique". Bracket removal was standardized through the use of a Wolpert "Universalprüfmaschine TZZ 707" with modified torsion and bending mechanism. A scanning electron microscope was used to analyze the enamel surface. When using the torsion method, the mean extension of the enamel lesions was 48.3% of the adhesive free enamel surface. These lesions often reached into the deeper enamel layers and were mainly to be found on the broad side of the bonded area. On the other hand, when using the bending method, the enamel lesions were less frequent. They were mainly superficial and were confined almost exclusively to the pressure zones. The stress required to remove the brackets and the stress distribution were calculated on mechanical models and these results corresponded well with the enamel lesions observed on the molars. It can thus be concluded that the method of removing brackets is clinically relevant in relation to enamel lesions.
Dental Debonding↗
Use of luting agents with an implant system: Part I.
When removal of the provisionally cemented superstructure from a cemented abutment becomes necessary, the retentive strengths of the abutment/fixture and superstructure/abutment luting agents become important considerations. This study compared the retentive strengths of castings cemented to machined titanium implant abutments and to a human premolar with three provisional luting agents. Also tested were the retentive strengths of cast noble metal implant abutments cemented into titanium fixtures with three permanent luting agents both dry and after storage in 0.9% physiologic saline for 30 days at 37 degrees C. No significant differences (alpha < 0.05) were noted in retentive values between the cemented castings on the titanium abutments and the natural tooth. The Temp Bond zinc oxide-eugenol luting agent exhibited a lower mean retentive strength than the IRM reinforced zinc oxide-eugenol and Life calcium hydroxide luting agents. Ketac Cem glass-ionomer cemented abutments that were stored in saline exhibited a significantly higher mean retentive strength than abutments cemented with either Core Paste or Resiment resin luting agents. On the basis of results from this study, it may be concluded that superstructures provisionally cemented with Temp Bond, IRM, or Life luting agents may be removed from implant abutments without disturbing the abutment/fixture or implant bond.
Analysis of Variance↗
Use of luting agents with an implant system: Part II.
The purposes of this study were to determine the amount of die space necessary to reduce seating discrepancies of castings cemented onto implant abutments and to determine the effect that this space created for the luting-agent has on crown retention. Noble metal castings were made with 0.000 inch, 0.001 inch, 0.002 inch, and 0.003 inch spacing for premanufactured titanium implant abutments. The castings were cemented onto the abutments with three permanent luting agents. Seating discrepancies of each casting/abutment combination were measured, and the castings were pulled from the abutments by use of tensile force. The results of this study indicate that the use of die spacing decreased seating discrepancies and increased retentive values under the test conditions.
Cementation↗
Effect of adhesive metal primers on bonding a prosthetic composite resin to metals.
The effect of three adhesive metal primers on the shear bond strength of a light-cured prosthetic composite resin bonded to cobalt-chromium or silver-palladium-copper-gold casting alloy was evaluated. The adhesive metal primers used were New Metacolor opaque bonding liner, Cesead opaque primer, and 0.5% VBATDT in acetone. A newly prepared light-cured opaque resin was used to bond a light-cured veneering resin to dental alloys. The specimens were thermocycled in water for up to 20,000 cycles between 4 degrees C and 60 degrees C, and shear bond strengths were recorded. The light-cured composite resin bonded most strongly to Co-Cr alloy primed with Cesead primer and to Ag-Pd-Cu-Au alloy with the VBATDT primer. These adhesive metal primers may be clinically acceptable for bonding a light-cured prosthetic composite resin to base or precious metal.
Adhesives↗
Potassium nitrate-zinc oxide eugenol temporary cement for provisional crowns to diminish postpreparation tooth pain.
Pulpal injury commonly occurs with tooth preparation for complete fixed partial dentures. This can be documented by the substantial incidence of pain after tooth preparation. In this study, a 4% potassium nitrate-zinc oxide eugenol temporary cement was used to secure provisional crowns over recently prepared teeth and it significantly reduced the incidence and severity of pain after tooth preparation and impression taking.
Adult↗
Time required to remove totally bonded tooth-colored posterior restorations and related tooth substance loss.
OBJECTIVES: The study was conducted to measure the time required to remove large totally bonded tooth-colored posterior restorations and related tooth substance loss. This information was collected to determine if there were differences between bonded restorations and conventional restorations. METHODS: Molars were restored with the following materials: amalgam, composite, glass ionomer cement or glass ceramic cusp coverages. After submitting them to an in vitro aging process, they were attached to a lower jaw model in a phantom head. Six dentists removed the test restorations under standardized, quasi-clinical conditions. RESULTS: While the amalgam was completely removed, some glass ionomer cement vestiges were found. In the glass-ceramic group, the margins were covered with remnants of the composite luting agent in several places. The most restorative material was left in the composite group. The loss of tooth structure after removal of amalgam, glass ionomer cement, composite and glass ceramic was 17.6 mm3, 19.6 mm3, 39.9 mm3 and 41.8 mm3, respectively. When comparing the removal time, the glass ionomer group scored best with an average of 11.9 min followed by the amalgam group with an average of 15.2 min, followed by 24.9 min for the composite group and 30.4 min for the glass ceramic group. SIGNIFICANCE: The removal of totally bonded posterior restorations made of composite and ceramic is more technically demanding and more time-consuming than the removal of glass ionomer and amalgam restorations.
Acrylic Resins↗
Shear bond strength of resin bonded ceramic after different try-in procedures.
Final cementation of porcelain laminate veneers may require a previous colour match try-in. The purpose of this in vitro study was to evaluate the effect on shear bond strength of resin bonded to porcelain after the application of different try-in procedures. Forty porcelain specimens were fabricated, flattened with 600 grit SiC, etched with hydrofluoric acid and silane treated. After 24 h the specimens were divided into four groups at random and prior to bonding of a dual cure resin composite button were treated as follows: Group 1, no treatment (control); Group 2, non-activated resin applied for 5 min, cleaned in acetone for 3 min; Group 3, as for Group 2, with silane reapplied; Group 4, as for group 3, but re-etched for 30 s before reapplication of silane. After bonding the specimens were stored in water at room temperature for 7 days. Shear bond strength data were as follows: Group 1, 18.6 +/- 1.6; Group 2, 15.9 +/- 1.7; Group 3, 16.7 +/- 2.6; Group 4, 15.3 +/- 3.0 MPa. Fractured surfaces examined, under light microscopy and scanning electron microscopy (SEM), showed cohesive failure within the porcelain in all cases. The reduction in mean bond strength after application of a try-in resin was significant in Groups 2 and 4 compared with the control (ANOVA P < 0.05). No other significant differences were measured. In conclusion a single reapplication of silane maintained the bond strength of resin to porcelain when final cementation was preceded by a try-in procedure and cleaning.
Acetone↗
Scanning electron microscope (SEM) evaluation of clinical failures of single crystal ceramic brackets.
The objective of this work was to perform failure analysis on Starfire brackets that failed in clinical use. The failed brackets were examined with a scanning electron microscope (SEM) to obtain micrographs at magnifications of 20, 50, 100, and other magnifications, whenever necessary. With the aid of the micrographs, the fracture origin and the probable defect that initiated the fracture were identified. The percentages of failure origins for each area of the bracket were arch wire slot 36.0%, tie wing slot 22.0%, undetermined 11.0%, saddle 9.0%, impact 9.0%, during removal 7.5%, and parting area 5.5%. By observing the micrographs pertaining to each field failure, the primary causes of failure were internal defects 47.5%, machining interference 42.5%, and undetermined 10.0%.
Aluminum Oxide↗
Shear/peel bond strength of orthodontic attachments to moist and dry enamel.
INTRODUCTION: The purpose of this study was to evaluate the in-vitro shear-peel bond strength of orthodontic attachments bonded to moist and dry enamel surfaces with orthodontic resin. METHODS: Two stainless-steel mesh-based buttons were bonded to pumiced and etched enamel of each of 60 human molars mounted in cylindrical molds with Transbond XT (3M/Unitek, St Paul, Minn) (control), Smartbond (Gestenco International, Goteborg, Sweden), or Assure (Reliance Orthodontic Products, Itasca, Ill) according to each manufacturer's instructions. Half of the teeth were bonded under dry conditions, and half were given a thick layer of whole, unstimulated, fresh human saliva just before bonding. The teeth were stored in distilled deionized water at 37 degrees C. The shear-peel bond strength of 1 button on each tooth was evaluated in a testing device (Zwick, Ulm, Germany) at 24 hours; the remaining button on each tooth was evaluated at 6 months. RESULTS: Statistically significant differences (P < .05) were evident in button adhesion to the tooth surface between moisture variations for Transbond XT, but not for Assure and Smartbond. Superior bond strengths were obtained for Transbond XT on dry enamel; the bond strength of Assure to saliva-contaminated enamel was better than that of the other materials. CONCLUSIONS: Bonding to moist and dry enamel appears to be material-specific. Adequate in-vitro bonding to moist, saliva-contaminated enamel is possible with certain bonding materials.
Compomers↗
Bond strength evaluation of ceramic and stainless steel bracket bases subjected to cyclic tensile loading.
INTRODUCTION: The aim of this study was to evaluate the effects of loading, static and cyclic, on 1 stainless steel and 3 ceramic bracket bonding bases. METHODS: The brackets were chosen because of the different characteristics of their bonding bases. The brackets in each group were bonded to bovine teeth by using the same adhesive and subjected to both static and cyclic tensile loading; the results were analyzed (ANOVA and Scheffé) for statistical differences among the groups. RESULTS: The analysis showed that ceramic brackets have unique characteristics compared with stainless steel; the most significant is higher bond strengths. The effects of cyclic loading were shown to be significant, in that fatigue testing caused a decrease in mean tensile bond strength for most groups. An additional factor on the bond strength might be the composition and design of the bracket base. CONCLUSIONS: Simulations of occlusal forces (a combination of tensile, shear, and compressive forces) to orthodontic materials during in-vitro studies in accordance with clinical use might adequately describe actual clinical performance.
Analysis of Variance↗
Complications associated with fixed partial dentures with a loose retainer.
STATEMENT OF PROBLEM: When 1 retainer of a definitive fixed partial denture (FPD) becomes loose, the clinician has the option of either sectioning and removing the FPD or attempting removal of the intact cemented retainer. Excessive force during attempted FPD removal may irreversibly damage dentition. PURPOSE: This study evaluated the type and frequency of complications that may accompany the removal of definitive cemented FPDs with a single loose retainer. MATERIAL AND METHODS: Participants included 22 patients with a definitive cemented FPD with complete cast crown coverage castings in which 1 retainer became loose and the other retainer remained cemented. Cemented FPD retainers were removed using 1 of 2 attachments supplied with a crown removal system (Dentco). The patient and FPD characteristics, type of attachment, number of attempts before removal, condition of removed FPD, and condition of the abutment teeth were recorded. Descriptive statistics were used to analyze the data. RESULTS: Clinical findings recorded prior to FPD removal showed that 41% of patients were unaware they had a loose FPD retainer and 82% reported no discomfort associated with the loose retainer. Caries were noted on 50% of the teeth with a loose retainer. Damage resulting from attempted removal of the cemented retainer included minor porcelain fracture (9%), minor core chipping (14%), minor incisal edge chipping of tooth preparations (27%), and major damage to the abutment tooth (4%). CONCLUSION: Retrieval of an intact FPD and recementation was possible 64% of the time.
Adult↗
Multiple prosthodontic uses for permanent crown remover forceps.
Practitioners will find multiple uses for Perm Gripper forceps. These crown remover forceps are likely to become an indispensable adjunct in the busy prosthodontic practice.
Crowns↗
Effects of dental laboratory processing variables and in vitro testing medium on the porcelain adherence of high-palladium casting alloys.
PURPOSE: This study assessed the effects of dental laboratory processing variables and testing medium on porcelain adherence of representative high-palladium alloys. MATERIAL AND METHODS: The processing variables were recasting two and three times, porcelain stripping with hydrofluoric acid and rebuilding, and changing the recommended oxidation procedures. The testing medium was air for these four groups and the nontreatment group. In the last group, the specimens were stored and tested in artificial saliva. The metal ceramic specimens were fractured with biaxial flexure in constant strain. The area fraction of adherent porcelain (%) was calculated with a standardized spectrometric technique. A gold-palladium alloy served as the control. RESULTS: Recasting without adding new alloy negatively affected some high-palladium alloys. Porcelain stripping did not cause a decrease in adherence of the tested alloys. The alternate oxidation treatment reduced significantly the porcelain adherence of the Au-Pd and one Pd-Cu-Ga alloy. Storage and testing in artificial saliva did not significantly affect the porcelain adherence of the alloys. The Au-Pd alloy exhibited the highest porcelain adherence.
Adhesiveness↗
A simple method for maintaining retrievability of occlusal screws when the access channel is shallow.
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Dental Debonding↗
Bonding porcelain laminate veneer provisional restorations: An experimental study.
STATEMENT OF PROBLEM: Minimal tooth preparation is required for porcelain laminate veneers, but an interim restoration is anticipated by patients to protect their teeth against thermal insult, chemical irritation, and to provide esthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and the fit and final bonding of the porcelain laminate veneer. PURPOSE: This in vitro study inspected the tooth surface for remaining debris from cement after removal of a provisional restoration. MATERIAL AND METHODS: Seventy-two extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with 3 bonding methods: temporary eugenol-free cement, spot etching combined with dual-curing luting cement, and polyurethane adhesive combined with dual-curing luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with an SEM. RESULTS: Traces of cement debris were found on provisionally prepared teeth for all 3 material methods. CONCLUSION: The use of polyurethane adhesive combined with the dual-curing cement revealed significantly less teeth with debris than the other methods. This difference was less distinct when the smear layer was removed.
Acid Etching, Dental↗
A safe technique for removal of provisionally cemented crowns.
A technique is presented for removing full-cast crowns and porcelain crowns that have been temporarily or provisionally cemented. A rubber dam retainer clamp with rubber dam attached is placed on the crown and clamped near its margins. Steiglitz forceps are used to apply pressure and leverage. The assembled unit is removed with the Steiglitz and safely removes the loosened crown from the mouth.
Crowns↗