Biomedical subjects

William J Dunn

Publications and source records attributed to William J Dunn.

At least 19 recordsLinked to original sources

PubMed2006

Effective single-charge end point of cordless light-emitting diode light-curing units.

INTRODUCTION: The purpose of this study was to evaluate the battery lives of cordless light-emitting diodes (LEDs) and their effect on orthodontic bracket bond strength. METHODS: One hundred eighty-six metal orthodontic brackets were bonded to extracted molars. Two LED light-curing units (L. E. Demetron [SDS/Kerr, Orange, Calif] and Ortholux [3M Unitek, Monrovia, Calif]) were evaluated. Each light was used to bond 93 specimens. One bracket was bonded every 5 minutes until the battery ran out. The lights were activated for 20 seconds, then automatically turned off for 40 seconds every minute (33% duty cycle) without recharging. Bonded specimens were stored in water at 37 degrees C for 24 hours and then subjected to shear force with a universal testing machine until bracket failure. RESULTS: Repeated measures ANOVA detected significantly weaker mean shear bond strength and fewer consecutive cures with the Ortholux compared with the L. E. Demetron light-curing unit. However, when the first 5 time points were excluded, there were no differences between the 2 lights, demonstrating that the lights performed similarly after the first 20 minutes of operation Just before battery failure, both lights still provided the same power density as at the beginning. CONCLUSIONS: Both light-curing units provided adequate power density for up to 2 hours without recharging at a 33% duty cycle. There was no significant decrease in power in cordless LED light-curing units as the battery life approached its end point.

Analysis of Variance↗

PubMed2006

Comparison of torsional stability of 2 types of split crimpable surgical hooks with soldered brass surgical hooks.

INTRODUCTION: The purpose of this in-vitro study was to compare the torsional stability of split crimpable surgical hooks and soldered brass surgical hooks on a rectangular stabilizing archwire. METHODS: Coated split crimpable hooks (Never-Slip Grip, TP Orthodontics, LaPorte, Ind), ribbed crimpable hooks (TP Orthodontics), and .032-in brass soldered hooks/notched electrodes (Ormco/Sybron Dental Specialties, Orange, Calif) were attached to a 0.019 x 0.025-in stainless steel archwire. The archwire/hook attachment assembly was secured into a dual contact jig and statically mounted to the base of a universal testing machine. The hooks were engaged by a wire loop attached to the upper load cell of the machine, which pulled the wire until the hook was torsionally displaced from the archwire. RESULTS: The mean forces, measured in newtons (N), required to dislodge the hooks were as follows: soldered brass surgical hooks (51.3 +/- 5.2 N), coated split crimpable hooks (49.9 +/- 6.6 N), and ribbed split crimpable hooks (31.3 +/- 5.4 N). Data were analyzed with 1-way ANOVA and Tukey HSD post-hoc tests at alpha = .05. Ribbed split crimpable hooks provided significantly less resistance to torsional displacement than the other types of hooks (P <001). There was no difference between coated split crimpable hooks and soldered brass surgical hooks (P >05). CONCLUSIONS: Under the conditions of this study, the results suggest that soldered brass surgical hooks and coated split crimpable hook attachments provide more stability to torsional dislodgement from a rectangular stabilizing archwire than ribbed split crimpable hooks.

Analysis of Variance↗

PubMed2006

Comparison of in-vitro bond strengths between resin-modified glass ionomer, polyacid-modified composite resin, and giomer adhesive systems.

INTRODUCTION: The purpose of this in-vitro study was to compare the shear bond strength of orthodontic brackets bonded to tooth enamel with 4 adhesives: a commercially available giomer material, a polyacid-modified composite resin (PMCR), a resin-modified glass ionomer (RMGI), and a standard resin-based composite (RBC) adhesive. MATERIALS: Eighty extracted human molars were collected and divided into 4 groups (n = 20). Two stainless steel premolar brackets were bonded to each tooth with 1 of the 4 adhesives, according to each manufacturers' instructions. One bracket was tested for shear bond strength at 1 hour and the other at 7 days. A shear force was applied to the bracket/tooth interface with a chisel-shaped rod attached to a universal testing machine at a crosshead speed of 0.5-mm per minute until bracket failure. The force in newtons was recorded. Debonded enamel surfaces were examined under a stereomicroscope to assess the amount of residual adhesive. RESULTS: A 2-factor analysis of variance detected significant differences among adhesive types and time of load test. The Tukey HSD test determined that the RBC and the RMGI adhesives had significantly higher shear bond strength than the giomer and the PMCR materials at both 1 hour and 7 days. The chi-square test detected a significant difference in adhesive remnant index scores. The bracket/resin interface was the most common site of failure for all groups except the RMGI group. CONCLUSIONS: RMGI orthodontic cement provides acceptable bond strength in vitro. Further clinical research is needed to validate this laboratory finding.

Acrylic Resins↗

PubMed2005

Synthesis and monoamine transporter affinity of 3-aryl substituted trop-2-enes.

A series of new 3-aryl-tropanes have been synthesized, and their affinities and selectivities were evaluated for monoamine transporters. (1RS)-3-(Fluoren-2-yl)-8-methyl-8-azabicyclo[3.2.1]oct-2-ene exhibited the highest affinity for the human serotonin transporter (IC(50)=14.5nM). It is also 52-fold and 230-fold selective over human dopamine and norepinephrine transporters, respectively.

Dopamine Plasma Membrane Transport Proteins↗

PubMed2005

Identification and treatment of scurvy: a case report.

Scurvy is a nondiscriminatory disease process resulting from a nutritional deficiency of ascorbic acid (vitamin C). The severe vitamin deficiency produces a breakdown in the cellular structure of the body. This case report describes a middle-age woman with a history of edema, bruising of the lower extremities, anemia, and severe periodontal disease. Her presentation and medical history are classic for the signs of scurvy. Scurvy is now only uncommonly seen in developed countries, but there are still vulnerable populations whose nutritional status can lead to scurvy. The aim of this report is to help the clinician identify and treat scurvy, a disease that was once feared for its high mortality but is now easily treatable, even in cases that have progressed to multiple organ dysfunction and failure.

Adult↗

PubMed2005

Effect of shorter polymerization times when using the latest generation of light-emitting diodes.

INTRODUCTION: Recent studies have suggested that a 10-second cure time with a high-energy quartz-tungsten-halogen (QTH) or a light-emitting diode (LED) light might be adequate when bonding orthodontic brackets to tooth enamel. The purpose of this study was to evaluate the ability of the latest generation of QTH and LED light-curing units (LCUs) to bond orthodontic brackets to teeth at decreased polymerization times. METHODS: Two LED LCUs (Ortholux LED, 3M Unitek, Monrovia, Calif; UltraLume LED 5, Ultradent Products, South Jordan, Utah) and a QTH LCU (Optilux 501, Demetron, Danbury, Conn) were evaluated. One hundred eighty metal orthodontic brackets were bonded to extracted human molars. The specimens were divided into 9 groups (3 lights and 3 curing times) of 20 teeth each. Each group was cured with 1 of the 3 lights for 20, 10, or 6 seconds. Thirty minutes after polymerization, the specimens were subjected to shear force on a universal testing machine until bracket failure. RESULTS: Two-way ANOVA detected significant differences among the main effects of light type and cure time. Tukey post-hoc tests determined that brackets bonded by all light types had lower bond strengths with the 6-second cure than the 20-second cure (P < .001). The highest bond strengths were obtained with the Optilux 501 QTH LCU and the UltraLume LED 5 LCU at the longest cure time of 20 seconds. CONCLUSIONS: It is recommended that orthodontic brackets be photopolymerized for at least 20 seconds with the QTH or the LED LCU before the archwires are engaged.

Analysis of Variance↗

PubMed2005

Shear bond strength and SEM evaluation of composite bonded to Er:YAG laser-prepared dentin and enamel.

OBJECTIVES: The purpose of this study was to evaluate dentin and enamel bond strength to resin composite following high-speed rotary or Er:YAG laser preparation using a total etch adhesive system. The microstructure of resin-tooth interfaces was also investigated. METHODS: Human dentin and enamel specimens were prepared with a high-speed handpiece (KaVo) or Er:YAG laser (DELight) at manufacturer's recommended settings and etched with either 37% H(3)PO(4), laser etched, or not etched. Composite rods (Z-250, 3M/ESPE) were bonded to specimens with an adhesive (Adper Scotchbond Multi-Purpose, 3M/ESPE). After thermocycling, specimens were tested in shear to failure. RESULTS: Two-factor ANOVA detected significant differences in the main effects of preparation and etch type, and interaction (p<0.001). Post hoc analyses showed that in both dentin and enamel, only the acid-etched specimens had significantly higher mean bond strengths, with rotary-prepared specimens having significantly higher mean bond strengths versus laser prepared specimens. Within each preparation type, in both dentin and enamel, acid etch was better than laser etch, and laser etch was better than no etch. Scanning electron microscopy of laser-ablated specimens demonstrated significant surface scaling and subsurface fissuring beyond normal resin penetration depth. SIGNIFICANCE: Adhesion to laser-ablated or laser-etched dentin and enamel was inferior to that of conventional rotary preparation and acid etching.

Analysis of Variance↗

PubMed2005

Effect of light dispersion of LED curing lights on resin composite polymerization.

PURPOSE: This study evaluated the effect of light dispersion of halogen and LED curing lights on resin composite polymerization. MATERIALS AND METHODS: One halogen (Optilux 501, SDS/Kerr, Orange, CA, USA) and five light-emitting diode (LED) curing lights (SmartLite iQ, Dentsply Caulk, Milford, DE, USA; LEDemetron 1, SDS/Kerr; FLASHlite 1001, Discus Dental, Culver City, CA, USA; UltraLume LED 5, Ultradent Products, South Jordan, UT, USA; Allegro, Den-Mat, Santa Maria, CA, USA) were used in this study. Specimens (8 mm diameter by 2 mm thick) were made in polytetrafluoroethylene molds using hybrid (Z100, 3M ESPE, St. Paul, MN, USA) and microfill (A110, 3M ESPE) composite resins. The top surface was polymerized for 5 seconds with the curing light guide tip positioned at a distance of 1 and 5 mm. Degree of conversion (DC) of the composite specimens was analyzed on the bottom surface using micro-Fourier Transform Infrared (FTIR) spectroscopy (Perkin-Elmer FTIR Spectrometer, Wellesley, PA, USA) 10 minutes after light activation. DC at the bottom of the 2 mm specimen was expressed as a percentage of the mean maximum DC. Five specimens were created per curing light and composite type (n=5). Percent mean DC ratios and SDs were calculated for each light under each testing condition. Data were analyzed by analysis of variance (ANOVA)/Tukey's test (alpha = .05). A beam analyzer (LBA-700, Spiricon, Logan, UT, USA) was used to record the emitted light from the curing lights at 0 and 5 mm distances (n=5). A Top Hat factor was used to compare the quality of the emitted beam profile (LBA/PC, Spiricon). The divergence angle from vertical was also determined in the x- and y-axes (LBA/PC). Mean values and SDs were calculated for each light under each testing condition (0 and 5 mm, x- and y-axes) and analyzed by a two-way ANOVA/Tukey's test (alpha = .05). RESULTS: For DC ratios, significant differences were found based on curing light and curing distance (p < .05). At 1 mm, Optilux 501 and FLASHlite 1001 produced significantly higher DC ratios with the hybrid resin composite. No differences were found among lights with the microfill at 1 mm. At 5 mm, SmartLite iQ, FLASHlite 1001, LEDemetron 1, and UltraLume LED 5 produced significantly higher DC ratios with the hybrid resin composite, whereas LEDemetron 1 and SmartLite iQ produced significantly higher DC ratios with the microfill resin composite. The UltraLume LED 5, Allegro, and Optilux 501 had significant reductions in mean DC ratios at curing distances of 1 and 5 mm with both resin composite types. For dispersion of light, significant differences were found in Top Hat factor and divergence angle (p < .001). SmartLite iQ had overall the highest Top Hat factor and lowest divergence angle of tested lights. A linear regression analysis relating pooled DC with pooled Top Hat factors and divergence angles found a very good correlation (r2 = .86) between dispersion of light over distance and the ability to polymerize resin composite. CLINICAL SIGNIFICANCE: The latest generation of LED curing lights provides DC ratios similar to or better than the halogen curing light at a curing distance of 5 mm. Dispersion of light plays a significant role in the DC of resin composite. To maximize curing effectiveness, light guides should be maintained in close proximity to the surface of the light-activated restorative material.

Analysis of Variance↗

PubMed2004

Structure-activity relationships for substrate recognition by the human dopamine transporter.

Information is available on the structure-activity relationships for dopamine as a substrate for uptake by the dopamine transporter. However, dopamine transport is a complex process involving substrate binding, translocation, release as well as transporter reorientation. The present study examines only the substrate recognition step by assessment of the potency of various dopamine-related compounds in inhibiting the binding of the cocaine analog [3H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane ([3H]WIN 35,428) to human dopamine transporters expressed in HEK-293 cells. alpha-Methylation of the side chain, the presence of the amine, and the 2-carbon-length of the side chain were found to be important for binding affinity, whereas beta-hydroxylation of the side chain and methoxylation at the phenyl ring generated weaker compounds. In addition, the presence of both m- and p-OH at the phenyl ring bestowed an increase in potency but the presence of p-OH alone a decrease. N-alkylation (propylation or methylation) had little or an even slightly beneficial effect on affinity, whereas alpha-carbonylation and alpha-methanoylation reduced affinity. Amino naphthalene compounds with a fused benzenoid ring system retained some potency consonant with the extended (i.e. beta-rotameric) trans (=anti) form of the side chain in dopamine when interacting with the transporter. In a second series of experiments, the interaction between dopamine and structural variants was assessed by monitoring the capability of a compound to shift the dopamine inhibition curve to the right as expected for a competitive inhibitor acting at the same site. Appreciable deviation from competitive interaction was observed by removal of the amine from the side chain, by alpha-carbonylation, and by alpha-methanoylation. Two blocker-type compounds, semi-rigid variants of cocaine, also displayed significant deviation. A substrate-based compound, inhibiting cocaine analog binding without interfering with dopamine recognition, could be a cocaine antagonist allowing conformational changes to occur during dopamine uptake.

Binding, Competitive↗

PubMed2004

Effect of fluoride varnish on the in vitro bond strength of orthodontic brackets using a self-etching primer system.

To reduce the number of steps involved with bonding procedures, manufacturers have simplified adhesive systems by combining the hydrophilic primer and the adhesive, or by combining the etchant, the primer, and the adhesive into 1 bottle and application. The purpose of this study was to investigate the relationship between the shear bond strength of orthodontic brackets to enamel, with or without fluoride varnish, by using either conventional or self-etching primer systems. Forty-eight extracted teeth were divided into 4 groups of 12 teeth each: group 1, fluoride varnish, conventional adhesive; group 2, fluoride varnish, self-etching primer system; group 3, no fluoride varnish, conventional adhesive; and group 4, no fluoride varnish, self-etching primer system. The bonding procedure followed the manufacturers' recommendations for the materials. Precoated adhesive orthodontic brackets were light-cured to the facial surfaces of the teeth and stored in whole human saliva at 37 degrees C for 24 hours. The specimens were subjected to a shear force in a testing machine until failure. The adhesive remnant index was used to score the teeth. Data were analyzed with a 2-way analysis of variance to test for differences in shear bond strength with respect to fluoride varnish and type of adhesive system used. The results showed no difference in bond strength among any of the experimental groups. Similarly, chi-square analysis determined that adhesive remnant index scores were not statistically different. The application of fluoride varnish does not affect the bond strength of orthodontic brackets to enamel with conventional or self-etching primer systems.

Analysis of Variance↗

PubMed2004

Shear bond strength of orthodontic brackets bonded with light-emitting diode curing units at various polymerization times.

Light emitting diode (LED) light-curing units have recently been used to polymerize resin-based orthodontic adhesives, and preliminary studies indicate their use has been successful. The purpose of this study was to evaluate the relationship between the shear bond strength of orthodontic brackets bonded to enamel and the duration of photopolymerization with LEDs and conventional quartz-tungsten-halogen light-curing units. Three LED light-curing units (GC e-light, GC America, Alsip, Ill; Elipar FreeLight, 3M ESPE Dental Products, St Paul, Minn; and UltraLume LED 2, Ultradent Products, South Jordan, Utah) and 1 halogen-based light-curing unit (Ortholux XT, 3M Unitek, Monrovia, Calif) were evaluated. Two hundred forty metal orthodontic brackets were bonded to extracted molars. Specimens were divided into 12 groups of 20 teeth each. Each group was cured with a different light-curing unit for 40, 20, or 10 seconds. The specimens were stored in water at 37 degrees C for 24 hours and then subjected to a shear force with a universal testing machine until bracket failure. Two-way ANOVA detected significantly weaker mean shear bond strength with the GC e-light at 10 and 40 seconds (P<.001) and higher mean shear bond strength for the UltraLume LED 2 at 40 seconds (P<.001). All experimental groups had laboratory mean shear bond strengths greater than 8 MPa, even with a 10-second cure.

Analysis of Variance↗

PubMed2004

The effect of saliva contamination on enamel and dentin using a self-etching adhesive.

BACKGROUND: The authors conducted a study to evaluate the effect of saliva contamination on enamel and dentin before or after application of a self-etching adhesive. METHODS: The authors divided 120 extracted molars into enamel and dentin groups of 60 specimens each, and then further divided each group into three groups of 20 specimens each. Resin-based composite cylinders were bonded to tooth specimens that were uncontaminated (control) or were contaminated with saliva either before or after application of the adhesive and then loaded to the failure point. The authors calculated the mean shear bond strength for each group and subjected data to a one-way analysis of variance, or ANOVA, to test for differences among groups. RESULTS: Mean shear bond strength was 16.7 megapascals (+/- 3.0 standard deviation, or SD) for the dentin control group, 14.8 MPa (+/- 2.3 SD) for dentin contaminated with saliva before adhesive application, 15.9 MPa (+/- 3.8 SD) for dentin contaminated with saliva after adhesive application, 19.1 MPa (+/- 4.8 SD) for the enamel control group, 12.3 MPa (+/- 4.4 SD) for enamel contaminated with saliva before adhesive application, and 13.1 MPa (+/- 5.5 SD) for enamel contaminated with saliva after adhesive application. One-way ANOVA detected no difference in the dentin groups, but the authors found a significant difference among enamel groups. Uncontaminated enamel had higher bond strengths than either of the contaminated enamel groups. CONCLUSIONS: Saliva contamination did not affect the dentin shear bond strength of the self-etching adhesive. Saliva did have a detrimental effect on enamel bond strength. CLINICAL IMPLICATIONS: Newer generations of adhesives appear to be more tolerant of saliva contamination, but proper isolation still should be accomplished until further research proves otherwise.

Acid Etching, Dental↗

PubMed2004

Dental satisfaction survey at an expeditionary dental clinic in support of Operations Enduring Freedom and Iraqi Freedom.

This study used a survey to gather information about soldiers' perceptions of the quality of dental treatment delivered at a deployed clinic. An ordinal scale of 1 through 5 scored access, dental facility and equipment, pain control, technical skill, and interpersonal skills of the provider. Four additional items identified whether the respondent was new to military or deployment dentistry, was in pain before arriving at the clinic, or had any concerns about being treated at a deployed dental clinic. Percentages for each type of response were recorded. Data were further analyzed by the Mann-Whitney U test to investigate the relationship between respondent variables and how they rated the attributes of quality. Deployed service members reported a high degree of satisfaction with the quality of care they received. Ninety-seven percent of respondents believed that the care they received was as good as the care they would have received at their regular stateside military dental facility.

Data Collection↗

PubMed2004

Dental emergency rates at two expeditionary medical support facilities supporting operations enduring and Iraqi Freedom.

This study reports dental emergency rates and distribution of causes of dental emergencies at two expeditionary medical support facilities supporting operations Enduring Freedom/ Iraqi Freedom. A retrospective cohort analysis of 9948 soldiers deployed to Prince Sultan Air Base, Kingdom of Saudi Arabia, and 1467 soldiers at Baghdad International Airport, Iraq, was accomplished from a phased deployment from January 2003 to September 2003. Procedures were divided into 11 categories: endodontic, extraction of teeth other than third molars, extraction of third molar teeth, restoration of teeth (caries), restoration of broken teeth (not caries), orthodontic bracket/wire problem, sensitive teeth, temperomandibular pain, periodontal, oral pathology, and prosthodontic. The dental emergency rates for Prince Sultan Air Base and Baghdad International Airport were 153 and 145 dental emergencies per 1000 soldiers per year, respectively. Most of the emergencies were because of dental caries. Pain from third molars was the second most common reason for visiting the dental clinic.

Dental Service, Hospital↗

PubMed2003

In vitro wear of various orthotic device materials.

STATEMENT OF PROBLEM: Orthotic devices are advocated to decrease occlusal attrition caused by bruxism but tend to wear with time. PURPOSE: This study investigated the wear rate of various materials used to fabricate orthotic devices. MATERIAL AND METHODS: Five experimental groups (n=8) were studied: Splint Biocryl autopolymerized (SBA), Splint Biocryl autopolymerized plus additional heat and pressure (SBHP), Forestacryl autopolymerized (FA), Forestacryl autopolymerized plus additional heat and pressure (FHP), and Quick Splint 15-minute (QS), light-polymerized composite. Specimens were mounted to the base of a universal testing machine. A wear device using steatite balls and a load of 9.1 kg was positioned against the specimens, submerged in a 37 degrees C water bath and subjected to 2500 reciprocal cycles. Wear, in micrometers, was calculated as the maximum peak to valley measurement (Ry) using profilometry. Data were subjected to analysis of variance (ANOVA) and Tukey's HSD (alpha=.05). RESULTS: Mean acrylic wear in micrometers was as follows: FA 6.8 +/-3.0; FHP 7.1 +/- 1.8; SBA 20.4 +/- 5.6; SBHP 23.7 +/- 7.8; and QS 23.8 +/- 6.9. One-way ANOVA detected significant differences between groups (P<.001); the Tukey honestly significant difference test determined that FA and FHP specimens were significantly more resistant to wear than all other specimens (P=.007). CONCLUSION: Differences in in vitro wear resistance among various orthotic device materials exist. The in vitro wear resistance among other autopolymerizing materials appears to be related to proprietary differences.

Acrylic Resins↗

PubMed2003

Shear bond strength of orthodontic brackets bonded with a modified 1-step etchant-and-primer technique.

When bonding orthodontic brackets to enamel, most orthodontists use a conventional technique of etching tooth enamel with phosphoric acid, placing a hydrophilic primer on the etched, rinsed, and dried surface, then bonding the bracket with an adhesive resin composite. New systems simultaneously etch and prime the tooth surface in preparation for bonding. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to enamel with a conventional, multistep adhesive system and a self-etching primer adhesive system. In addition, a third group was included in which the air dispersion step in the self-etching primer system was omitted. Brackets were bonded to 108 extracted human molars according to 1 of 3 experimental protocols--group 1: conventional multistep adhesive (n = 36); group 2: self-etching primer system (n = 36); group 3: self-etching primer system without air dispersion (n = 36). Specimens were loaded to failure in a universal testing machine (Instron, Canton, Mass). Mean shear bond strengths in megapascals (standard deviation) were 11.3 (2.2), 11.9 (3.2), and 8.2 (2.8) for groups 1, 2, and 3, respectively. Data were subjected to 1-way analysis of variance at alpha =.05. The mean shear bond strength of the self-etching primer group in which the air dispersion step was omitted was significantly less than in the other 2 groups (P <.001). However, there was no difference in mean shear bond strength between the conventional, multistep adhesive system and the self-etching primer system when the primer was dispersed correctly (P =.34).

Acid Etching, Dental↗

PubMed2003

Wear comparison of thermoplastic materials used for orthodontic retainers.

Clear thermoplastic retainers are an alternative to fixed lingual retainers and removable Hawley appliances. However, thermoplastic retainers have demonstrated poor wear resistance and durability after only a few months of use. In this study, a simulated wear device was used to compare the wear of different thermoplastic materials used for orthodontic retainers. Three thermoplastic products were evaluated: C+ (Raintree Essix, New Orleans, La),.040-in Invisacryl C (Great Lakes Orthodontics, Towanda, NY), and.040-in TR sheet material (Bay Dental Direct, Bay City, Mich). Twenty specimens were fabricated for each group. The specimens were vacuum thermoformed according to the manufacturers' recommendations and subjected to wear for 1000 cycles in a wear apparatus with steatite ceramic abraders. Depth of wear was determined by surface profilometry. The maximum peak-to-valley measurement was recorded for each specimen. Mean wear (SD) in microns was as follows: C+, 5.9 (2.4); Invisacryl C, 6.1 (2.6); and TR, 1.6 (0.9). One-way analysis of variance detected a significant difference between groups (P <.001). TR material, a hard polyethylene terephthalate glycol copolymer (PETG), demonstrated greater resistance to wear than did the other 2 materials, which were softer, polypropylene-based thermoplastics. There was no evidence to suggest a difference in mean wear between the 2 polypropylene-based materials (P >.05).

Analysis of Variance↗

PubMed2003

Shear bond strength comparison between direct and indirect bonded orthodontic brackets.

The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to teeth with either an indirect bonding technique and a new adhesive resin or a direct bonding technique and a light-activated adhesive. Fifty-four extracted premolars were mounted in acrylic blocks and randomly divided into 2 groups (n = 27). In one group, orthodontic brackets were bonded to premolars with an indirect bonding adhesive system; in the other, brackets were bonded with the direct method. Seventy-two hours later, the brackets were placed in a testing machine and subjected to a shear force with a crosshead speed of 1 mm/minute. The mean shear bond strengths for the indirect and direct groups were 11.2 and 10.9 MPa, respectively, both exceeding the minimum shear bond strength range of 5.9 to 7.8 MPa often cited in the literature for clinical success. Data were analyzed with Student t tests. No significant difference in shear bond strength between the 2 groups was detected (P =.76). Resin remnants on orthodontic bracket pads were observed with a dissecting microscope at 30x magnification and scored with a modified adhesive remnant index. There was no significant difference between groups (P >.05). There was also no correlation between shear bond strength and the percentage of adhesive resin remnants left on the orthodontic bracket. Under the conditions of this study, no evidence suggests a difference in shear bond strength of orthodontic brackets bonded to tooth enamel, whether they are bonded with the direct or indirect technique.

Dental Bonding↗