ABSTRACT
OBJECTIVE: The objective of this work, commissioned by the Academy of Dental Materials, was to review and critically appraise test methods to characterize properties related to critical issues for dental resin composites, including technique sensitivity and handling, polymerization, and dimensional stability, in order to provide specific guidance to investigators planning studies of these properties. METHODS: The properties that relate to each of the main clinical issues identified were ranked in terms of their priority for testing, and the specific test methods within each property were ranked. An attempt was made to focus on the tests and methods likely to be the most useful, applicable, and supported by the literature, and where possible, those showing a correlation with clinical outcomes. Certain methods are only briefly mentioned to be all-inclusive. When a standard test method exists, whether from dentistry or another field, this test has been identified. Specific examples from the literature are included for each test method. RESULTS: The properties for evaluating resin composites were ranked in the priority of measurement as follows: (1) porosity, radiopacity, sensitivity to ambient light, degree of conversion, polymerization kinetics, depth of cure, polymerization shrinkage and rate, polymerization stress, and hygroscopic expansion; (2) stickiness, slump resistance, and viscosity; and (3) thermal expansion. SIGNIFICANCE: The following guidance is meant to aid the researcher in choosing the most appropriate test methods when planning studies designed to assess certain key properties and characteristics of dental resin composites, specifically technique sensitivity and handling during placement, polymerization, and dimensional stability.
Subject(s)
Acrylic Resins/chemistry , Composite Resins/chemistry , Polyurethanes/chemistry , Elastic Modulus , Hardness , Materials Testing , Polymerization , Surface PropertiesABSTRACT
OBJECTIVE: The objective of this project, which was initiated from the Academy of Dental Materials, was to review and critically appraise methods to determine fracture, deformation and wear resistance of dental resin composites, in an attempt to provide guidance for investigators endeavoring to study these properties for these materials. METHODS: Test methods have been ranked in the priority of the specific property being tested, as well as of the specific test methods for evaluating that property. Focus was placed on the tests that are considered to be of the highest priority in terms of being the most useful, applicable, supported by the literature, and which show a correlation with clinical findings. Others are mentioned briefly for the purpose of being inclusive. When a standard test method exists, including those used in other fields, these have been identified in the beginning of each section. Also, some examples from the resin composite literature are included for each test method. RESULTS: The properties for evaluating resin composites were ranked in the priority of measurement as following: (1) Strength, Elastic Modulus, Fracture toughness, Fatigue, Indentation Hardness, Wear-abrasion (third body) and Wear-attrition (contact/two body), (2) Toughness, Edge strength (chipping) and (3) Wear determined by toothbrush. SIGNIFICANCE: The following guidance is meant to aid the researcher in choosing the proper method to assess key properties of dental resin composites with regard to their fracture, deformation and wear resistance.
Subject(s)
Composite Resins , Dental Materials , Elastic Modulus , Hardness , Humans , Materials Testing , Surface PropertiesABSTRACT
OBJECTIVE: Bioactive glass (BAG) is known to possess antimicrobial and remineralizing properties; however, the use of BAG as a filler for resin based composite restorations to slow recurrent caries has not been studied. Accordingly, the objective of this study was to investigate the effect of adding 15wt% BAG to a resin composite on bacterial biofilms penetrating into marginal gaps of simulated tooth fillings in vitro during cyclic mechanical loading. METHODS: Human molars were machined into approximately 3mm thick disks of dentin and 1.5-2mm deep composite restorations were placed. A narrow 15-20 micrometer wide dentin-composite gap was allowed to form along half of the margin by not applying dental adhesive to that region. Two different 72wt% filled composites were used, one with 15wt% BAG filler (15BAG) and the balance silanated strontium glass and one filled with aerosol silica and silanated strontium glass without BAG (0BAG-control). Samples of both groups had Streptococcus mutans biofilms grown on the surface and were tested inside a bioreactor for two weeks while subjected to periods of cyclic mechanical loading. After post-test biofilm viability was confirmed, each specimen was fixed in glutaraldehyde, gram positive stained, mounted in resin and cross-sectioned to reveal the gap profile. Depth of biofilm penetration for 0BAG and 15BAG was quantified as the fraction of gap depth. The data were compared using a Student's t-test. RESULTS: The average depth of bacterial penetration into the marginal gap for the 15BAG samples was significantly smaller (â¼61%) in comparison to 0BAG, where 100% penetration was observed for all samples with the biofilm penetrating underneath of the restoration in some cases. SIGNIFICANCE: BAG containing resin dental composites reduce biofilm penetration into marginal gaps of simulated tooth restorations. This suggests BAG containing composites may have the potential to slow the development and propagation of secondary tooth decay at restoration margins.
Subject(s)
Acrylic Resins/chemistry , Biofilms , Bioreactors , Composite Resins/chemistry , Dental Caries/microbiology , Dental Marginal Adaptation , Dental Restoration, Permanent/methods , Glass/chemistry , Polyurethanes/chemistry , Dental Caries/prevention & control , Dental Cavity Preparation , Dental Leakage , Humans , In Vitro Techniques , Microscopy, Electron, Scanning , MolarABSTRACT
OBJECTIVES: Secondary caries is the most common reason for composite restoration replacement and usually forms between dentin and the filling. The objective of this study was to investigate the combined effect of cyclic loading and bacterial exposure on bacterial penetration into gaps at the interface between dentin and resin composite restorative material using a novel bioreactor system and test specimen design. METHODS: Human molars were machined into 3mm thick disks with 2mm deep × 5 mm diameter cavity preparations into which composite restorations were placed. A â¼ 15-30 µm (small) or â¼ 300 µm wide (large) marginal gap was introduced along half of the interface between the dentin and restoration. Streptococcus mutans UA 159 biofilms were grown on each sample prior to testing each in a bioreactor both with and without cyclic loading. Both groups of samples were tested for 2 weeks and post-test biofilm viability was confirmed with a live-dead assay. Samples were fixed, mounted and cross-sectioned to reveal the gaps and observe the depth of bacterial penetration. RESULTS: It was shown that for large gap samples the bacteria easily penetrated to the full depth of the gap independent of loading or non-loading conditions. The results for all cyclically loaded small gap samples show a consistently deep bacterial penetration down 100% of the gap while the average penetration depth was only 67% for the non-loaded samples with only two of six samples reaching 100%. SIGNIFICANCE: A new bioreactor was developed that allows combining cyclic mechanical loading and bacterial exposure of restored teeth for bacterial biofilm and demineralization studies. Cyclic loading was shown to aid bacterial penetration into narrow marginal gaps, which could ultimately promote secondary caries formation.
Subject(s)
Biofilms , Bioreactors , Dental Caries/microbiology , Dental Leakage , Dental Marginal Adaptation , Dental Restoration, Permanent/methods , Composite Resins/chemistry , Dental Cavity Preparation , Dental Stress Analysis , Equipment Design , Humans , In Vitro Techniques , Molar , Sterilization , Streptococcus mutansABSTRACT
OBJECTIVES: Bioactive glass (BAG) is known to possess antimicrobial properties and release ions needed for remineralization of tooth tissue, and therefore may be a strategic additive for dental restorative materials. The objective of this study was to develop BAG containing dental restorative composites with adequate mechanical properties comparable to successful commercially available composites, and to confirm the stability of these materials when exposed to a biologically challenging environment. METHODS: Composites with 72 wt% total filler content were prepared while substituting 0-15% of the filler with ground BAG. Flexural strength, fracture toughness, and fatigue crack growth tests were performed after several different soaking treatments: 24h in DI water (all experiments), two months in brain-heart infusion (BHI) media+Streptococcus mutans bacteria (all experiments) and two months in BHI media (only for flexural strength). Mechanical properties of new BAG composites were compared along with the commercial composite Heliomolar by two-way ANOVA and Tukey's multiple comparison test (p≤0.05). RESULTS: Flexural strength, fracture toughness, and fatigue crack growth resistance for the BAG containing composites were unaffected by increasing BAG content up to 15% and were superior to Heliomolar after all post cure treatments. The flexural strength of the BAG composites was unaffected by two months exposure to aqueous media and a bacterial challenge, while some decreases in fracture toughness and fatigue resistance were observed. The favorable mechanical properties compared to Heliomolar were attributed to higher filler content and a microstructure morphology that better promoted the toughening mechanisms of crack deflection and bridging. SIGNIFICANCE: Overall, the BAG containing composites developed in this study demonstrated adequate and stable mechanical properties relative to three successful commercial composites.
Subject(s)
Dental Materials , Dental Restoration, Permanent , Glass , Materials TestingABSTRACT
This practice-based, randomized clinical trial evaluated and compared the success of direct pulp capping in permanent teeth with MTA (mineral trioxide aggregate) or CaOH (calcium hydroxide). Thirty-five practices in Northwest PRECEDENT were randomized to perform direct pulp caps with either CaOH (16 practices) or MTA (19 practices). Three hundred seventy-six individuals received a direct pulp cap with CaOH (n = 181) or MTA (n = 195). They were followed for up to 2 yrs at regular recall appointments, or as dictated by tooth symptoms. The primary outcomes were the need for extraction or root canal therapy. Teeth were also evaluated for pulp vitality, and radiographs were taken at the dentist's discretion. The probability of failure at 24 mos was 31.5% for CaOH vs. 19.7% for MTA (permutation log-rank test, p = .046). This large randomized clinical trial provided confirmatory evidence for a superior performance with MTA as a direct pulp-capping agent as compared with CaOH when evaluated in a practice-based research network for up to 2 yrs.
Subject(s)
Aluminum Compounds/therapeutic use , Calcium Compounds/therapeutic use , Calcium Hydroxide/therapeutic use , Dental Pulp Capping/methods , Oxides/therapeutic use , Pulp Capping and Pulpectomy Agents/therapeutic use , Silicates/therapeutic use , Adolescent , Adult , Aged , Aged, 80 and over , Child , Community-Based Participatory Research , Dental Pulp/physiology , Dental Pulp Exposure/therapy , Dentin-Bonding Agents/chemistry , Drug Combinations , Female , Follow-Up Studies , Glass Ionomer Cements/chemistry , Humans , Male , Middle Aged , Pulpotomy/methods , Radiography, Bitewing , Resin Cements/chemistry , Root Canal Therapy , Tooth Extraction , Treatment Outcome , Young AdultABSTRACT
The introduction of many new packable composites suggests that these products are rapidly gaining popularity. The purpose of this study was to evaluate the in vitro properties of a variety of packable composites and to determine if significant enhancements in physical and mechanical properties have been achieved for these materials compared with two popular nonpackable posterior composites. For the five packable and two regular composites tested (ALERT, Pyramid-Dentin, Pyramid-Enamel, Solitaire, SureFil, Heliomolar, and Z100), the values for fracture toughness, flexure strength, flexure modulus, hardness, and volumetric polymerization shrinkage were determined. In general, although the packable composites were of heavier consistency, they had mechanical properties that were intermediate to (ALERT, Pyramid, and SureFil) or lower than (Solitaire) those of the nonpackable materials. These results could have been predicted based on the similar methacrylate resin chemistry and filler volumes of the various composites. No composite had adequate depth-of-cure when tested in increments greater than 2 mm thick. Polymerization contraction of the packable composites was similar to or higher than that of the nonpackable composites. In addition, the radiopacity of at least one material, Solitaire, was not considered to be adequate (less than 2 mm of aluminum). The results of this study suggest that these packable composites are unlikely to offer improved clinical performance over well-placed nonpackable composites.
Subject(s)
Composite Resins/chemistry , Dental Restoration, Permanent/methods , Acrylic Resins , Analysis of Variance , Contrast Media , Elasticity , Hardness , Materials Testing , Methacrylates , Pliability , Polymers/chemistry , Polyurethanes , Silicon Dioxide , Viscosity , ZirconiumABSTRACT
The purpose of this study was to determine the accuracy of four commercially available radiometers when curing tips of different diameters were used. A visible-light curing unit (Optilux 500) with a new 80-watt quartz-halogen bulb (OptiBulb) was used as the light source for all measurements. The unit's irradiance value was measured using three hand-held radiometers (Demetron model #100, Cure-Rite model #644726, and Coltolux Light Meter) and a built-in visible-light curing unit radiometer (Optilux 500). Measurements were made with four curing tips of diameters 4 mm, 7.5 mm, 10.5 mm, and 12 mm. For each tip, trials were made with five radiometers of each model. Student's t-tests at the 0.05 level of significance were used to compare the mean irradiance measured by each model of radiometer, to the irradiance value measured by a laboratory-grade power meter. A one-way analysis of variance at the 0.05 level of significance was used to compare the irradiance values among the five samples of each commercially available radiometer model. Except for the Optilux 500 built-in radiometer with the 10.5-mm tip, all the commercially available radiometers exhibited irradiance values significantly different from those of the laboratory-grade power meter. There were no statistically significant differences among the five samples of each commercially available radiometer model.
Subject(s)
Dental Equipment , Radiometry/instrumentation , Technology, Dental/instrumentation , Analysis of Variance , Dental Instruments , Equipment Design , Evaluation Studies as Topic , Light , Polymers/chemistry , Reproducibility of ResultsABSTRACT
PURPOSE: To determine if alteration of any of the following factors could reduce microleakage following placement of Class II resin-based composites (RBC) at intraoral temperature: cavity preparation (vertical wall bevels), finishing technique (delayed vs. immediate), or postoperative re-bonding (marginal sealing). An additional purpose was to determine if a decalcification/clearing protocol was a valid technique for assessing three-dimensional microleakage. MATERIALS AND METHODS: Twenty recently extracted human molars had standardized Class II slot cavities prepared on the mesial and distal surfaces with the gingival floor located on dentin. The teeth were imbedded in a stone template, warmed to 37 degrees C and restored immediately upon removal from the oven with visible light-cured (VLC) adhesive (All-Bond 2) and three horizontal increments of VLC RBC (Bisfil P) using a metal matrix. Teeth were placed into one of four groups: (1) Control; (2) The preparation was modified to include 0.5-1.0 mm enamel bevels on the vertical walls (facial and lingual); (3) Finishing of the RBC was delayed 24 hours; (4) Following immediate finishing, all margins of the RBC restorations were sealed by dentin bonding agent application. Teeth were stored at 37 degrees C for 2 weeks, thermocycled 1000x at 5/55 degrees C, stained with silver nitrate, underwent a decalcification and clearing protocol, and evaluated for three-dimensional dye penetration. RESULTS: Axial-occlusal enamel margins exhibited minimal leakage and no differences among the groups. Vertical walls without bevels exhibited pronounced microleakage. Beveled vertical proximal walls exhibited significantly less facial and lingual wall microleakage compared to all other groups, and less gingival marginal leakage compared to the control group.
Subject(s)
Composite Resins , Dental Bonding , Dental Cavity Preparation/methods , Dental Leakage/prevention & control , Dental Restoration, Permanent/methods , Acid Etching, Dental , Body Temperature , Decalcification Technique , Dental Leakage/diagnosis , Dental Polishing , Dentin-Bonding Agents , Humans , MolarABSTRACT
The effectiveness of different methods for cleaning and preparing occlusal fissures before placing sealants was evaluated. Extracted mandibular molars received such treatments as brushing, pumicing, bur preparing, and air abrasion before application of fissure sealants. FluroShield fissure sealant was then applied to the occlusal fissures. Specimens were subjected to thermo-cycling and then immersed in a 10% solution of methylene blue, and finally sectioned. The sections were examined and photographed in a stereomicroscope, and the dye penetration was recorded using a scoring system. The results indicated that only the control (brushing with a dry brush) and the pumicing groups demonstrated dye penetration to the base of the sealant. Teeth prepared with the #1/4 round bur and air abrasion demonstrated a better seal in evaluated fissures. For this study, those three groups (occlusal fissures prepared with the #1/4 round bur and two air abrasion methods), demonstrated significantly better sealing (P < 0.01) than the control group and the other groups tested.
Subject(s)
Dental Cavity Preparation/instrumentation , Dental Cavity Preparation/methods , Dental Fissures/therapy , Air Abrasion, Dental , Humans , Mandible , Molar , Pit and Fissure Sealants , Silicates , ToothbrushingABSTRACT
OBJECTIVES: The purposes of this study were to evaluate the use of 0.12% chlorhexidine gluconate as a prophylactic therapy for the prevention of alveolar osteitis and to further examine subject-based risk factors associated with alveolar osteitis. STUDY DESIGN: The trial was a randomized, double-blind, placebo-controlled, parallel-group study conducted among 279 subjects, each of whom required oral surgery for the removal of a minimum of one impacted mandibular third molar. Subjects were instructed to rinse twice daily with 15 ml of chlorhexidine or placebo mouthrinse for 30 seconds for 1 week before and 1 week after the surgical extractions. This regimen included a supervised presurgical rinse. Alveolar osteitis diagnosis was based on the subjective finding of increasing postoperative pain at the surgical site that was not relieved with mild analgesics, supported by clinical evidence of one or more of the following: loss of blood clot, necrosis of blood clot, and exposed alveolar bone. RESULTS: In comparison with use of the placebo mouthrinse, prophylactic use of the chlorhexidine mouthrinse resulted in statistically significant (p < 0.05) reductions in the incidence of alveolar osteitis. With chlorhexidine therapy, the subject- and extraction-based incidences of alveolar osteitis in the evaluable subset (271 subjects) were reduced, relative to placebo, by 38% and 44%, respectively. The corresponding odds ratios that describe the increased odds of experiencing alveolar osteitis in the placebo group were 1.87 and 2.05 for subject- and extraction-based analyses, respectively. In comparison with nonuse of oral contraceptives, the use of oral contraceptives in female subjects was related to a statistically significant increase in the incidence of alveolar osteitis (odds ratio = 1.92, p = 0.035). Relative to male subjects, the observed incidence of alveolar osteitis for female subjects not using oral contraceptives was not statistically significant (odds ratio = 1.18, p = 0.64). Smoking did not increase the incidence of alveolar osteitis relative to not smoking (odds ratio = 1.20, p = 0.33). CONCLUSIONS: These data confirm that the prophylactic use of 0.12% chlorhexidine gluconate mouthrinse results in a significant reduction in the incidence of alveolar osteitis after the extraction of impacted mandibular third molars. In addition, oral contraceptive use in females was confirmed to be a risk factor for the development of alveolar osteitis.
Subject(s)
Anti-Infective Agents/therapeutic use , Chlorhexidine/analogs & derivatives , Dry Socket/prevention & control , Mouthwashes/therapeutic use , Premedication , Adolescent , Adult , Alveolar Process/pathology , Anti-Infective Agents/administration & dosage , Blood Coagulation , Chemoprevention , Chlorhexidine/administration & dosage , Chlorhexidine/therapeutic use , Contraceptives, Oral/adverse effects , Double-Blind Method , Dry Socket/diagnosis , Female , Humans , Incidence , Male , Mandible/surgery , Middle Aged , Molar, Third/surgery , Necrosis , Odds Ratio , Pain, Postoperative/diagnosis , Placebos , Risk Factors , Smoking/adverse effects , Tooth, Impacted/surgeryABSTRACT
Twenty recently extracted human molars had standardized Class II slot cavities prepared on the mesial and distal surfaces with the gingival floor located on dentin. The teeth were embedded in a stone template, warmed to 37 degrees C, and restored immediately using one of two incremental placement techniques with visible light-cured composite (VLC), or one of two directed shrinkage placement techniques using an autocure/VLC composite combination. Teeth were stored at 37 degrees C for 2 weeks, thermocycled, stained, sectioned in the middle of the preparation, and evaluated for dye penetration. Reevaluation of the microleakage following removal of the resin composite from the preparation revealed greater microleakage at the gingival margin than did the initial sectioning technique. There were no differences among any of the groups. Enamel margins exhibited minimal leakage and no differences among the groups.
Subject(s)
Dental Leakage/prevention & control , Dental Marginal Adaptation , Dental Restoration, Permanent/methods , Composite Resins , Dental Alloys , Dental Restoration Failure , Humans , Polymers/chemistry , Statistics, NonparametricABSTRACT
The purpose of this study was to measure the effect rebonding, with and without etching restoration margins, had on the microleakage of class 5 composite restorations. Eighty-two class 5 composite restorations were placed in extracted human molars with one margin on etched enamel and one below the cementoenamel junction. After finishing with disks, the teeth were divided into seven margin treatment groups: 1) restorations with no rebonding (control), 2) restoration margins rebonded with Universal Bond 3 primer, 3) restoration margins etched with 37% phosphoric acid and rebonded with Universal Bond 3 primer, 4) restoration margins rebonded with Universal Bond 3 adhesive, 5) restoration margins etched and rebonded with Universal Bond 3 adhesive, 6) restoration margins rebonded with Fortify, and 7) restoration margins etched and rebonded with Fortify. After storage in a chlorine-based disinfectant for 1 week, the restorations were thermocycled and then soaked in dye. After sectioning, microleakage was assessed by measuring the extent of dye penetration along the restoration-tooth interface. At the enamel margins there was no statistical difference in microleakage rebonded with or without etching. On the gingival margins there was a statistically significant reduction in microleakage for the nonetched Universal Bond 3 adhesive rebonded group compared to the nonrebonded control.
Subject(s)
Acid Etching, Dental , Composite Resins , Dental Bonding/methods , Dental Leakage , Dental Restoration, Permanent/methods , Analysis of Variance , Dentin-Bonding Agents , Evaluation Studies as Topic , Humans , Methacrylates , Resin Cements , Statistics, NonparametricABSTRACT
Traditional dental education has recommended the generous use of bases and liners under amalgam restorations, primarily to prevent postoperative sensitivity. However, new developments in bases and liners, as well as a better understanding of pulp biology, have changed the indications for the use of these materials. Understanding the properties of currently available materials and how they interact with pulpal tissues can help the practitioner decide when to use bases and liners and which products to choose.
Subject(s)
Dental Cavity Lining , Dental Pulp Capping , Dental Restoration, Permanent/methods , Calcium Hydroxide , Dental Amalgam/adverse effects , Dental Cavity Lining/methods , Dental Pulp/drug effects , Dentin Sensitivity/prevention & control , Dentin-Bonding Agents , Glass Ionomer Cements , Humans , Patient Care PlanningABSTRACT
PURPOSE: To compare the effect of thermocycling on the microleakage of conventional and resin modified glass ionomer restorative materials. MATERIALS AND METHODS: Class V preparations, centered on the CEJ, were prepared on the lingual and facial surfaces of 30 extracted human third molar teeth. Preparations were conditioned and restored randomly on one surface with Ketac-Fil and on the other surface with Photac-Fil. Restorations were protected during curing, finishing, and storage with Ketac-Glaze. Specimens were aged in room temperature distilled water for 7 days. Half of the specimens were thermocycled for 2,500 cycles in 5 degrees-55 degrees water baths with 5-second dwell times. All specimen apices were sealed with red compound, occlusal fissures sealed with pit/fissure sealant, and surfaces painted to within 1.5 mm of restoration margins with red nail polish. Specimens were stained with 5% methylene blue, invested in orthodontic resin, and sectioned faciolingually. The percentage of dye penetration along the tooth restoration interface was measured with a digital imaging system. RESULTS: Statistical analysis showed that neither thermocycling or type of material had a significant effect on dye penetration (P > 0.5).
Subject(s)
Dental Leakage , Glass Ionomer Cements , Resin Cements , Analysis of Variance , Dental Marginal Adaptation , Dental Research/methods , Glass Ionomer Cements/chemistry , Hot Temperature , Humans , Maleates , Materials Testing/methods , Resins, Synthetic , Specimen Handling , Water/chemistryABSTRACT
The purpose of this study was to determine if air thinning three dentin adhesives would affect bond strength to dentin. Ninety human molars were mounted in acrylic and the occlusal surfaces ground to expose a flat dentin surface. Thirty teeth were randomly assigned to one of the following dentin bonding agent/composite combinations: A) Universal Bond 3/TPH (Caulk), B) All-Bond 2/Bis-Fil-P (Bisco), and C) Scotchbond Multi-Purpose/Z-100 (3m). The primers were applied following the manufacturers' instructions. The adhesives were applied by two methods. A thin layer of adhesive was applied with a brush to 15 specimens in each group and light cured. Adhesive was brushed on to the remaining 15 teeth in the group, air thinned for 3 seconds, and then polymerized. The appropriate composite was applied in 2 mm increments and light cured utilizing a 5 mm-in-diameter split Teflon mold. Following 3 months of water storage, all groups were shear tested to failure on an Instron Universal Testing Machine. Bond strength was significantly higher in all groups when the dentin bonding agent was painted on without being air thinned. Scotchbond Multi-Purpose had significantly higher bond strength than All-Bond 2, which had significantly higher bond strength than Universal Bond 3.
Subject(s)
Dental Bonding/methods , Dentin-Bonding Agents , Resin Cements , Air , Analysis of Variance , Composite Resins , Dentin/ultrastructure , Dentin-Bonding Agents/chemistry , Humans , Materials Testing , Methacrylates , Microscopy, Electron, Scanning , Oxygen/chemistry , Silicon Dioxide , Surface Properties , ZirconiumABSTRACT
PURPOSE: To compare the shear fracture resistance of complex amalgam restorations retained by four regular TMS pins, four amalgapins, Amalgambond, or four amalgapins in conjunction with Amalgambond. MATERIALS AND METHODS: Sixty maxillary molars free of caries were mounted in acrylic resin and the occlusal surfaces were ground flat to within 2 mm of the CEJ. The specimens were randomly divided into four groups of 15 teeth. Each group provided one of the four different methods of resistance. Dispersalloy was condensed into the prepared specimens. The specimens were adjusted to provide 4 mm height of amalgam. After 1000 thermocycles, the specimens were loaded at a 45 degree angle to the occlusal surface at a crosshead speed of 1 mm/second. RESULTS: Statistical analysis revealed that Amalgambond, four amalgapins and four amalgapins in conjunction with Amalgambond provided more resistance to shear force than four regular TMS pins.
Subject(s)
Dental Amalgam , Dental Bonding , Dental Pins , Dental Restoration, Permanent/methods , Dentin-Bonding Agents , Methacrylates , Analysis of Variance , Dental Alloys , Dental Stress Analysis , Humans , Materials TestingABSTRACT
UNLABELLED: This study compared the compressive force required to fracture amalgam over nine base materials: a calcium hydroxide product (Dycal); two autocured glass ionomers (GlasIonomer Base Cement and Ketac-Bond); three light-cured glass ionomers (Photac-Bond, Variglass VLC, and Vitrebond); two light-cured resins (Timeline and VLC Dycal); and a zinc phosphate cement (Fleck's Zinc Cement). For the control group, 10 aluminum dies (25 mm x 12 mm x 10 mm) were milled with 3.0 mm x 3.0 mm slots, which were filled with hand-condensed Tytin amalgam with no underlying base. For experimental groups, 10 aluminum dies of equal dimension were milled with 3.5 mm x 3.0 mm slots. Following manufacturer's instructions, the nine base materials were successively placed in these 10 dies using a depth-limiting device made of light-transmitting clear acrylic to ensure a 0.5 mm thickness, and Tytin amalgam was again condensed over each base such that the depth of the amalgam equalled that in the control. All test specimens were stored in 100% humidity for 48 hours then fractured in compression on an Instron machine. Mean force, in Newtons (S D in parentheses), required to fracture the specimens was: CONTROL: 1934(210), Zinc Cement: 1874(147), GlasIonomer Base Cement: 1839(174), Ketac-Bond: 1723(225), Vitrebond: 1485(155), Photac-Bond: 1422(294), Advanced Formula II Dycal: 1296(237), VLC Dycal: 1035(116), Variglass: 909(294) and Timeline: 906(275). ANOVA and Student-Newman-Keuls statistical analysis (alpha = 0.05) indicated that the autocuring glass ionomers, GlasIonomer Base Cement and Ketac-Bond, and a zinc phosphate cement, Zinc Cement, provided significantly more fracture resistance for amalgam than the other bases tested and were not statistically different from a no-base control.
Subject(s)
Dental Amalgam/chemistry , Dental Cavity Lining , Acrylic Resins , Analysis of Variance , Calcium Hydroxide , Composite Resins , Compressive Strength , Dental Alloys/chemistry , Glass Ionomer Cements , Materials Testing , Minerals , Sodium Fluoride , Urethane/analogs & derivatives , Zinc Phosphate CementABSTRACT
This study was conducted to determine the average dimensions of the six maxillary anterior teeth in a targeted population and to evaluate the relationships between intertooth and intratooth dimensions. Casts were obtained from 54 patients ranging in age from 18 to 35. Measurements of length and width were made on the casts using a digital caliper. Using these measurements, ratios were calculated: length to width, width to width, and length to length. Although the tooth dimensions varied somewhat by race and gender, the ratios were quite consistent. In addition, the golden proportion was not found to correlate with any of the calculated ratios.