John F Laffoon

University of Iowa, Iowa City, Iowa, United States

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Publications (43)41.96 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective: The purpose of this study was to determine whether the curing protocol (light intensity and duration) affects the bond strength of single step self etch adhesive. Methods: Sixty human molars were cleaned, mounted, and randomly divided into three groups: 20 orthodontic brackets per group were bonded to teeth using Clearfil S3 following three protocols: group 1 following manufacturers instructions (20 sec before placing the bracket and 20 sec after placement), group 2: curing only after the placement of the precoated bracket for 20 seconds. and Group 3 : curing only after the placement of the precoated bracket for 10 seconds using a high intensity LED light. The teeth were debonded within 30 minutes after initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10X magnifications to determine the amount of residual adhesive remaining on the tooth. One Way Analysis of Variance was used to compare the shear bond strength (SBS) of the three groups, and the chi-square test was used to compare the Adhesive Remnant Index (ARI) scores for the three groups. Results: The mean SBS of the brackets bonded using protocol 1 was 6.0 3.6 MPa, for Protocol 2 was 5.3 3.1 MPa and the SBS for protocol 3 was 4.5 3.1 MPa. There was no statistically significant difference between the groups evaluated (P=.357).The comparisons of the ARI scores between the three groups (2 = 7.583) indicated that bracket failure mode was not significantly different (P = .475). Conclusions: There was no statistically significant difference in SBS and the ARI scores of the self-etch adhesive under different curing protocols. The clinical implications of the findings will be discussed.
    AADR Annual Meeting 2010; 03/2010
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    ABSTRACT: We have previously demonstrated enhanced aggregate formation and accelerated mineralization of human preosteoblastic cells when cultured in 3D-rotary wall vessel chambers. Objectives: To test the hypothesis that Bone Morphogenic Protein 2 (BMP2) and Vascular Endothelial Growth Factor (VEGF) are expressed in three-dimensional engineered aggregates. Methods: Human preosteoblastic cells (HEPM, ATCC 1486) were cultured in rotary wall vessels for 4 days. Vessels were treated with or without BMP2 polyclonal antibody to measure BMP2 involvement in aggregate calcification and morphology. Mineralization was initially detected using Alizarin Red stain; the aggregates were then acid hydrolyzed and calcium levels were measured with atomic absorption spectroscopy. Scanning electron microscopy was used for morphological comparison. Immunohistochemistry was used to detect BMP2. PCR was used to detect VEGF. Results: Level of calcium expression correlated to the presence or absence of BMP2 signal (P<0.05). SEM analysis showed the general morphology of those aggregates without BMP2 antibody to be more nodular than those exposed to the antibody. BMP2 was detected throughout the aggregate using immunohistochemistry techniques. PCR data showed that VEGF is consistently expressed over time in 3D environments. This demonstrates that inductive morphogenic signals are expressed in 3D-rotary wall vessel cultures. Conclusions: These results suggest that preosteoblastic cells cultured 3-dimensionally in rotary wall vessels do express BMP2 and VEGF. The absence of inductive signaling may result in phenotypical changes in aggregate formation, as well as reduced calcification, as was demonstrated with BMP2 antibody. The knowledge obtained in this study constitutes one step of many that are required in order to realize the advantages of 3-D culture systems clinically. NIH R21DE016677.
    AADR Annual Meeting 2010; 03/2010
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    ABSTRACT: Recently, a new type of debonding instrument designed to be used with ceramic brackets was introduced. The purpose of this study was to evaluate the debonding characteristics of the new instrument when removing ceramic and metal brackets and to compare these characteristics to those produced by conventional debonding pliers. Forty-five maxillary premolars were randomly assigned to 1 of 4 groups. In group 1, Clarity Collapsible Ceramic Brackets (3M Unitek, Monrovia, CA) were debonded using conventional Utility/Weingart pliers (3M Unitek, Monrovia, CA). In group 2, the ceramic brackets were debonded using the new Debonding Instrument (3M Unitek). In group 3, Metal brackets (Victory series 3M Unitek) were debonded using conventional pliers. In group 4, the metal brackets were debonded using the new debonding instrument. For all teeth, the same bracket bonding system was used. After debonding, all the teeth and brackets were examined under 10x magnifications. Adhesive remaining after debonding was assessed using the modified adhesive remnant index. The comparisons (χ2 = 8.73) of the adhesive remnant index scores indicated that the 2 pliers have significantly different (P = 0.013) bracket failure modes when debonding ceramic brackets. For both groups 1 and 2, most of the adhesive remained on the tooth; however, significantly less adhesive was observed on the teeth that were debonded with the new debonding pliers. There were no significant differences (χ2 = 0.10, P = 0.919) in the debonding mode of the metal brackets when using the 2 pliers. The results from this study suggest that the new Instrument may remove more of the adhesive during the debonding of ceramic brackets, which in turn may save the clinician chair time.
    Seminars in Orthodontics 01/2010; 16(1):76-82.
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    ABSTRACT: Objective: The purpose of this study was to determine whether self-adhesive universal cements, G-Cem (GC America, Alsip, IL 60803) and RelyX Unicem (3M ESPE, Seefeld, Germany), can be used successfully to bond orthodontic brackets to enamel. Methods: Sixty human molars were cleaned, mounted, and randomly divided into three groups: 20 orthodontic brackets per group were bonded to teeth using, G-Cem, RelyX Unicem, and Transbond XT (3M Unitek, Monrovia, Calif) adhesive system. The teeth were debonded within 30 minutes after initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10X magnifications to determine the amount of residual adhesive remaining on the tooth. One Way Analysis of Variance was used to compare the shear bond strength (SBS) of the three groups, and the chi-square test was used to compare the Adhesive Remnant Index (ARI) scores for the three adhesive systems. Results: The mean SBS of the brackets bonded using G-Cem was 5.0 2.4 MPa, for RelyX Unicem was 3.7 2.1 MPa and the SBS for the Transbond system was 5.9 4.2 MPa. There was no statistically significant difference between the groups (P=.085).The comparisons of the ARI scores between the three groups (χ2 = 32.229) indicated that bracket failure mode was significantly different (P Conclusions: There was no statistically significant difference in SBS of the self-adhesive universal cements and the control. However, there was a significant difference in the ARI scores. The clinical implications of the findings will be discussed.
    IADR General Session 2009; 04/2009
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    ABSTRACT: The acidic nature of carbonated beverages is hypothesized to facilitate bacterial growth and subsequently caries. Exposure of molars to carbonated beverages can erode enamel surfaces. However, the ability of eroded enamel surfaces to support bacterial growth following beverage exposure is unknown. Objective: The objectives were to determine if erosion of enamel surfaces by carbonated beverages increases microbial colonization and to determine if beverage sugar or acid composition increases colonization. Methods: Enamel windows, created on extracted molars (n=7/beverage) with varnish, were exposed to Coke, Diet Coke, Pepsi, Diet Pepsi, Mountain Dew, Diet Mountain Dew or water (negative control) for 10 hours or phosphoric acid (positive control) for 15 seconds. One molar/treatment was then examined by scanning electron microscopy. Remaining molars were sequentially incubated at 37oC in human saliva for 30 minutes; in 1 X108 CFU/ml S. mutans in trypticase soy broth with yeast extract, 1% glucose, and 2% sucrose (TSB-YE-GS) for 30 minutes; and in sterile TSB-YE-GS for 3 hours. Molars were then examined by confocal microscopy. Images were stacked using LSM image browser and analyzed with ImageJ. Two-sample t-test and one-way ANOVA with Tukey post-hoc test were conducted. Results: Molars, exposed to beverages or phosphoric acid, had various degrees of erosion. Significantly more (p<0.05) colonization was seen on enamel exposed to Coke (11356 pixels), Diet Coke (9034 pixels) or Pepsi (8629 pixels) than water (5122 pixels). More colonization (p > 0.05) was also seen on enamel exposed to Diet Pepsi, Mountain Dew or Diet Mountain Dew than water. Colonization did not differ between sugared and diet beverages, nor between beverages containing phosphoric acid, citric acid, or phosphoric and citric acids. Conclusion: Exposure to carbonated beverages erodes enamel surfaces and facilitates microbial colonization. However, colonization is not influenced by the beverage sugar or acid composition. Support: NIH/NIDCR R01 DE014390.
    IADR General Session 2009; 04/2009
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    ABSTRACT: To test the null hypothesis that no difference in bracket failure characteristics is noted when use of a new ceramic bracket debonding instrument is compared with the use of conventional pliers. Thirty maxillary premolars were randomly assigned to one of two groups. In group 1, Clarity collapsible ceramic brackets (3M Unitek, Monrovia, Calif) were debonded with the use of conventional Utility/Weingart (3M Unitek, Monrovia, Calif) pliers. In group 2, Clarity brackets were debonded with a new Debonding Instrument (3M Unitek). For all teeth, the same bracket bonding system was used. Following debonding, teeth and brackets were examined under 10x magnification for assessment of bracket failure (fracture) and of residual adhesive on the enamel surface. Enamel surfaces were visualized with transillumination prior to bonding and after removal of the residual adhesive, so the effect of the debonding forces could be determined. The results of Adhesive Remnant Index comparisons indicated that a statistically significant difference (chi2 = 8.73; P = .013) in bond failure patterns was apparent when the two groups were compared. Brackets debonded with the new instrument showed a greater tendency for the adhesive to be removed from the tooth during debonding. The hypothesis is rejected. Although the incidence of enamel damage following debonding was similar in the two groups, the use of the new Debonding Instrument decreased the incidence of bracket fracture.
    The Angle Orthodontist 12/2008; 78(6):1078-83. · 1.18 Impact Factor
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    ABSTRACT: To determine if a new premixed self-etch adhesive can be used to successfully bond orthodontic brackets to enamel. Forty human molars were cleaned, mounted, and randomly divided into two groups. In group 1, 20 teeth were conditioned using the self-etching primer Transbond Plus (3M Unitek, Monrovia, Calif). In group 2, 20 teeth were conditioned using a new premixed self-etching adhesive, AdheSE One (Ivoclar Vivadent Inc, Amherst, NY). Both groups were bonded using brackets precoated with a composite adhesive. The teeth were debonded within half an hour following initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10x magnifications to determine the amount of residual adhesive remaining on the tooth. A Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the Chi-square test was used to compare the adhesive remnant index (ARI) scores for the two adhesive systems. The mean SBS of the brackets bonded to the teeth using AdhesSE One was 3.6 +/- 1.3 MPa and was significantly lower (t = 2.80, P = .01) than the SBS of the brackets bonded using Transbond Plus (x = 5.9 +/- 3.2 MPa). The comparisons of the ARI scores between the two groups (chi2 = 19.26) indicated that bracket failure mode was also significantly different (P < .001), with more adhesive remaining on the teeth bonded using Transbond Plus. The SBS of the new premixed self-etching adhesive needs to be increased for it to be successfully used for bonding orthodontic brackets.
    The Angle Orthodontist 11/2008; 78(6):1101-4. · 1.18 Impact Factor
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    ABSTRACT: Self-etching primers (SEPs) have been used successfully during bonding to reduce technique sensitivity while minimizing the etching of enamel. Although serving the same purpose, SEPs differ in acidity and aggressiveness. Thus, the purpose of this study was to determine whether the pH of SEPs affects the shear bond strength of orthodontic brackets. Forty-five molars were cleaned, mounted, and randomly divided into 3 groups with different SEPs: in group 1 (control), 15 orthodontic brackets were bonded to the teeth with Transbond Plus (3M Unitek, Monrovia, Calif) with a pH of about 1.0; in group 2, 15 brackets were bonded with Adper Prompt L-Pop (3M ESPE, St Paul, Minn) with a pH of 0.9 to 1.0; in group 3, 15 brackets were bonded with Clearfil S3 Bond (Kuraray America, New York, NY), with a pH of 2.7. All teeth were bonded with Transbond XT paste (3M Unitek). The teeth were debonded within half an hour after initial bonding by using a universal testing machine. The residual adhesive on each tooth was evaluated. ANOVA was used to compare the shear bond strength (SBS) of the 3 groups, and the chi-square test was used to compare the adhesive remnant index (ARI) scores for the 3 groups. ANOVA indicated significant differences between the groups. The Duncan multiple range test indicated that Clearfil S3 Bond produced a significantly stronger mean SBS (6.5 +/- 1.9 MPa) than the Transbond Plus system (mean, 4.2 +/- 1.9 MPa). No significant differences were seen between the SBS of the brackets bonded with Adper (mean, 5.9 +/- 3.4 MPa) and the other 2 groups. The comparisons of the ARI scores between the 3 groups indicated that bracket failure mode was not significantly different. The SEP with the highest pH (least acidic), Clearfil S3 Bond, bonded brackets successfully and with the strongest SBS; this suggests that the pH of the SEP is not the primary determinant of the SBS. The clinician should be aware that some SEPs can leave the enamel surface healthier after debonding.
    American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 09/2008; 134(2):203-8. · 1.33 Impact Factor
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    ABSTRACT: To determine the shear bond strength of a new resin glass ionomer adhesive with higher fluoride release properties when bonding orthodontic brackets. Sixty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into three groups according to the enamel conditioner/etchant and adhesive used. Group I: 20 teeth conditioned with 10% polyacrylic acid and brackets bonded with the new glass ionomer adhesive. Group II: 20 teeth conditioned with 37% phosphoric acid and brackets bonded with the new glass ionomer adhesive. Group III (control): 20 teeth etched with 37% phosphoric acid and brackets bonded with a composite adhesive. The results of the analysis of variance comparing the three experimental groups (F = 10.294) indicated the presence of significant differences between the three groups (P = .0001). The shear bond strengths were significantly lower in the two groups bonded with the new glass ionomer adhesive whether conditioned with polyacrylic acid ( x = 3.2 +/- 1.8 MPa) or phosphoric acid (x = 2.3 +/- 1.1 MPa), while the mean shear bond strength of the composite adhesive was 5.2 +/- 2.9 MPa. Although the increased fluoride release from the new glass ionomer has the potential of decreasing decalcification around orthodontic brackets, the shear bond strength of the material is relatively low.
    The Angle Orthodontist 02/2008; 78(1):125-8. · 1.18 Impact Factor
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    ABSTRACT: To determine the influence of self-etching primer (SEP) application time on the shear bond strength of orthodontic brackets. Forty human molars were cleaned, mounted, and randomly divided into two groups. The same SEP, adhesive, and brackets were used in both groups. Twenty teeth were conditioned following the manufacturers' recommendations by rubbing the SEP on the enamel surface for 3 to 5 seconds. The remaining 20 teeth were conditioned using the same SEP, but the application time was increased to 15 seconds. The teeth were debonded within half an hour following initial bonding using a universal testing machine. After debonding, the amount of residual adhesive remaining on the tooth was determined. Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the chi2 test was used to compare the Adhesive Remnant Index (ARI) scores for the two adhesive systems. The mean SBS of the brackets bonded to the teeth subjected to the SEP for 3 to 5 seconds was 8.0+/-4.6 MPa and was not significantly different (t=-0.69, P=.494) from the SBS of the brackets bonded using a 15-second SEP application time (x=8.9+/-3.4 MPa). The comparisons of the ARI scores between the two groups (chi2=2.16) indicated that bracket failure mode was not significantly different (P=.340) for both groups, and most failures were at the bracket-adhesive interface. The present findings indicate that increasing the SEP application from 3 to 5 seconds to 15 seconds does not result in a significant increase in SBS.
    The Angle Orthodontist 10/2007; 77(5):885-9. · 1.18 Impact Factor
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    ABSTRACT: To evaluate a new self-etch conditioner used with resin-modified glass ionomers (RMGIs) in bonding orthodontic brackets. Sixty human molars were cleaned, mounted, and randomly divided into three groups. In group 1 (control), 20 orthodontic brackets were bonded to teeth using Transbond Plus Self-etching Primer; in group 2, 20 brackets were bonded using an RMGI with a 10% polyacrylic acid conditioner. In group 3, 20 brackets were bonded using Fuji Ortho LC with a new no-rinse self-conditioner for RMGIs. The same bracket type was used on all groups. The teeth were debonded in shear mode using a universal testing machine, and the amount of residual adhesive remaining on each tooth was evaluated. Analysis of variance was used to compare the shear bond strength (SBS), and the chi(2) test was used to compare the Adhesive Remnant Index (ARI) scores. There were no significant differences in the SBS (P = .556) between the groups. The mean SBS for Transbond Plus was 8.6 +/- 2.6 MPa, for Fuji Ortho LC using 10% polyacrylic acid 9.1 +/- 4.6 MPa, and for Fuji Ortho LC using GC Self-conditioner 9.9 +/- 4.1 MPa. The comparisons of the ARI scores between the three groups (chi(2) = 35.5) indicated that bracket failure mode was significantly different (P < .001), with more adhesive remaining on the teeth bonded using Transbond. Conclusions: The new self-etch conditioner can be used with an RMGI to successfully bond brackets. In addition, brackets bonded with Fuji Ortho LC resulted in less residual adhesive remaining on the teeth.
    The Angle Orthodontist 07/2007; 77(4):711-5. · 1.18 Impact Factor
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    ABSTRACT: To compare the shear bond strength (SBS) of orthodontic brackets when the self-etching primer (SEP) and the bracket adhesive are light cured either separately or simultaneously. Seventy-five human molars were randomly divided into five equal groups. Brackets precoated with Transbond XT composite adhesive were used. The five protocols were: Group 1 (control), the SEP Transbond Plus was applied, brackets placed, and adhesive light cured for 20 seconds; Group 2, SEP Adper Prompt L-Pop was applied, light cured, brackets placed, and light cured; Group 3, the same SEP as in Group 2 was used, however, the SEP and bracket adhesive were light cured together; Group 4, SEP Clearfil S3 Bond was applied, light cured, brackets placed, and light cured; and Group 5, the same SEP as in group 4 was used, however, the SEP and the adhesive were light cured together. The teeth were debonded using a universal testing machine, and the enamel was examined for residual adhesive. Analysis of variance was used to compare the SBS. The SBS of Clearfil S3 Bond after one light cure and two light cures were significantly greater than the bonds of brackets using Transbond Plus. Brackets bonded using Adper Prompt L-Pop after one light cure and two light cures were not significantly different from the other groups. The groups did not differ significantly in their bracket failure modes. Only one light curing application is needed to successfully bond brackets when using SEPs and adhesives. This approach can potentially reduce technique sensitivity as well as chair time.
    The Angle Orthodontist 06/2007; 77(3):504-8. · 1.18 Impact Factor
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    ABSTRACT: To compare the effects of a standardized thermocycling protocol on the shear bond strength (SBS) of two adhesive systems: a resin-modified glass ionomer and a composite resin used with a new self-etching primer. Forty human molars were cleaned, mounted, and randomly divided into two groups. In group 1, brackets were bonded to the teeth using Fuji Ortho LC adhesive, and in group 2, the Transbond Plus system was used. The teeth were stored in water at 37 degrees C for 24 hours, thermocycled between 5 and 55 degrees C, and debonded using a universal testing machine. The enamel surface was examined under 10x magnification to determine the amount of residual adhesive remaining on the tooth. Student's t-test was used to compare the SBS and the chi-square test was used to compare the adhesive remnant index (ARI) scores. The mean SBS for the brackets bonded using the Fuji Ortho LC was 6.4 +/- 4.5 MPa, and the mean SBS for the Transbond Plus system was 6.1 +/- 3.2 MPa. The result of the t-test comparisons (t = 0.207) indicated that there was no significant difference (P = .837) between the two groups. The comparisons of the ARI scores (chi(2) = 0.195) indicated that bracket failure mode was not significantly different (P = .907) between the two adhesives. Although SBS and ARI scores were not significantly different for the two adhesives, clinicians need to take into consideration the other properties of the adhesives before using them.
    The Angle Orthodontist 04/2007; 77(2):337-41. · 1.18 Impact Factor
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    ABSTRACT: To compare the shear bond strength of a nano-hybrid restorative material, Grandio (Voco, Cuxhaven, Germany), to that of a traditional adhesive material (Transbond XT; 3M Unitek, Monrovia, CA, USA) when bonding orthodontic brackets. Forty teeth were randomly divided into 2 groups: 20 teeth were bonded with the Transbond adhesive system and the other 20 teeth with the Grandio restorative system, following manufacturer's instructions. Student t test was used to compare the shear bond strength of the 2 systems. Significance was predetermined at P 5 .05. The t test comparisons (t = 0.55) of the shear bond strength between the 2 adhesives indicated the absence of a significant (P = .585) difference. The mean shear bond strength for Grandio was 4.1 +/- 2.6 MPa and that for Transbond XT was 4.6 +/- 3.2 MPa. During debonding, 3 of 20 brackets (15%) bonded with Grandio failed without registering any force on the Zwick recording. None of the brackets bonded with Transbond XT had a similar failure mode. The newly introduced nano-filled composite materials can potentially be used to bond orthodontic brackets to teeth if its consistency can be more flowable to readily adhere to the bracket base.
    World journal of orthodontics 02/2007; 8(1):8-12.
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    ABSTRACT: The purpose of this study was to determine whether a self-adhesive universal cement, RelyX Unicem (3M ESPE, Seefeld, Germany), can be used successfully to bond orthodontic brackets to enamel. Forty human molars were cleaned, mounted, and randomly divided into two groups: 20 orthodontic brackets were bonded to teeth using RelyX Unicem, and 20 brackets were bonded using the Transbond XT (3M Unitex, Monrovia, Calif) adhesive system. The teeth were debonded within 30 minutes after initial bonding using a universal testing machine. After debonding, the enamel surface was examined under 10x magnification to determine the amount of residual adhesive remaining on the tooth. Student's t-test was used to compare the shear bond strength (SBS) of the two groups, and the chi-square test was used to compare the Adhesive Remnant Index (ARI) scores for the two adhesive systems. The mean SBS of the brackets bonded using the RelyX Unicem was 3.7 +/- 2.1 MPa and was significantly lower (t = 2.07, P = .048) than the SBS of the brackets bonded with the Transbond system (x = 5.97 +/- 4.2 MPa). The comparisons of the ARI scores between the two groups (chi(2) = 17.4) indicated that bracket failure mode was significantly different (P = .002) with more adhesive remaining on the teeth bonded with Transbond XT. The SBS of the self-adhesive universal cement needs to be increased for it to be successfully used for bonding orthodontic brackets.
    The Angle Orthodontist 08/2006; 76(4):689-93. · 1.18 Impact Factor
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    ABSTRACT: Orthodontic brackets adhesive systems use three different agents, an enamel conditioner, a primer solution, and an adhesive resin. A unique characteristic of some new bonding systems is that they combine the conditioning, priming, and adhesive agents into a single application. The purpose of this study was to assess and compare the effects of using one-step and two-step self-etch primer/adhesive systems on the shear bond strength of orthodontic brackets. The brackets were bonded to extracted human molars according to one of two protocols. Group I (control): a two-step self-etch acidic primer/adhesive system was used, Transbond Plus was applied to the enamel surface as suggested by the manufacturer. The brackets were bonded with Transbond XT and light cured for 20 seconds. Group II: a one-step self-etch, self-adhesive resin cement system, Maxcem, was applied directly to the bracket. The self-etch primer/adhesive is made of two components that mix automatically during application. The brackets were then light cured for 20 seconds. The mean shear bond strength of the two-step acid-etch primer/adhesive was 5.9 +/- 2.7 Mpa and the mean for the one-step system was 3.1 +/- 1.7 MPa. The in vitro findings of this study indicated that the shear bond strengths (t = 3.79) of the two adhesive systems were significantly different (P = .001). One-step adhesive systems could potentially be advantageous for orthodontic purposes if their bond strength can be improved.
    The Angle Orthodontist 02/2006; 76(1):123-6. · 1.18 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the effect of enamel bleaching on the shear bond strength of orthodontic brackets bonded with a composite adhesive. Two protocols were used on 60 human molars. In the at-home bleaching group (n = 30), Opalescence bleaching agent (Ultradent, South Jordan, Utah), which contains 10% carbamide peroxide, was brushed onto the teeth daily for 14 days and left for 6 hours each day. Teeth in the in-office group (n = 30) were treated with Zoom! (Discus Dental, Culver City, Calif), which contains 25% hydrogen peroxide gel, and then exposed to a light source for 20 minutes; these teeth were treated twice. After bleaching, the specimens were randomly divided into equal subgroups and stored in artificial saliva at 37 degrees C for 7 or 14 days before bonding. Shear bond strength testing was performed on all teeth. The Kruskal-Wallis test for nonparametric means was used to determine whether significant differences existed between the various subgroups and an unbleached control group. The mean shear bond strength for the control group was 5.6 +/- 1.8 MPa. Means for the at-home groups were 5.2 +/- 3.6 MPa and 7.2 +/- 3.2 MPa for the 7- and 14-day waiting periods, respectively. Means for the in-office groups were 5.1 +/- 5.3 MPa and 6.6 +/- 2.6 MPa for the 7- and 14-day waiting periods, respectively. The Kruskal-Wallis test (X(2) = 8.089) indicated no significant differences between the 5 subgroups (P = .088). The results showed that in-office and at-home bleaching did not affect the shear bond strength of orthodontic brackets to enamel.
    American Journal of Orthodontics and Dentofacial Orthopedics 01/2006; 128(6):755-60. · 1.46 Impact Factor
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    ABSTRACT: The purpose of this study was to determine whether the use of an iodine compound for disinfecting the waterlines in dental units has an effect on the shear bond strength of orthodontic brackets bonded to enamel. Forty molar teeth were divided randomly into two groups- group 1 control: twenty teeth were etched for 15 seconds with 35% phosphoric acid, washed with a distilled water spray for 10 seconds, stored in distilled water for 5 minutes, dried to a chalky white appearance, and the sealant applied to the etched surface; group 2 experimental: twenty teeth were etched for 15 seconds with 35% phosphoric acid and washed for 10 seconds with water containing iodine. The teeth were stored for five minutes in the iodinated water, dried to a chalky white appearance, and the sealant applied to the etched surface as in the control group. Precoated brackets were placed on all the teeth and light cured for 20 seconds. All teeth were debonded within 30 minutes from the initial time of bonding. The t-test results (t = 1.74) indicated that there were no significant (P = .09) differences in the shear bond strengths of the teeth that were washed and immersed in the iodine solution and the control group in which distilled water was used. The mean shear bond strengths for the two groups were 6.5 +/- 3.5 MPa and 4.7 +/- 3.1 MPa, respectively.
    The Angle Orthodontist 12/2005; 75(6):1032-5. · 1.18 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the effects of a new self-etching primer/ adhesive used to enhance the shear strength of orthodontic brackets bonded to porcelain surfaces. Forty-five porcelain maxillary central incisor teeth were used in the study. The teeth were divided randomly into three groups: group I (control), the porcelain teeth were etched with 37% phosphoric acid followed by a sealant and the brackets were bonded with a composite adhesive; group II, the porcelain teeth were microetched and hydrofluoric acid and silane applied and metal brackets were then bonded with the composite adhesive; and group III, the porcelain teeth were etched with phosphoric acid and a self-etching primer/adhesive applied before bonding. Brackets precoated with the adhesive were used on all three groups of teeth. All teeth were stored for 24 hours at 37 degrees C before debonding. The results of the analysis of variance (F = 10.7) indicated that there was a significant difference (P = .001) between the three groups. The mean shear bond strengths of conventional bonding using a 37% phosphoric acid and sealant was 4.4 +/- 2.7 MPa, whereas that of microetching followed by the application of hydrofluoric acid and silane was 11.2 +/- 4.7 MPa, and for the new self-etching primer/adhesive it was 10.3 +/- 5.3 MPa. The last two groups had the highest bond strength values and were not significantly different from each other.
    The Angle Orthodontist 10/2005; 75(5):858-64. · 1.18 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the effect of changing the crosshead speed of the testing machine on the shear bond strength of orthodontic brackets to enamel while standardizing all the other variables. Forty freshly extracted human molars were bonded using the Transbond XT adhesive system (3M Unitek, Monrovia, Calif). The teeth were randomly divided into two groups. In group I, the shear bond strength was measured at a crosshead speed of 5.0 mm/min, and in group II the shear bond strength was measured at a crosshead speed of 0.5 mm/ min. Within half an hour from the initial bonding of each tooth, an occlusogingival load was applied to the bracket, producing a shear force at the bracket-tooth interface. This was accomplished by using the flattened end of a steel rod attached to the crosshead of a Universal Test Machine (Zwick GmbH & Co, Ulm, Germany). The t-test results (t = 2.71) indicated that there was a significant difference (P = .014) in the shear bond strengths between the group tested at a crosshead speed of 5.0 mm/min and the group tested at a crosshead speed of 0.5 mm/min. The mean shear bond strengths for the two groups were 7.0 +/- 4.6 MPa and 12.2 +/- 4.0 MPa, respectively. These findings indicated that it is important to identify the parameters included in shear bond testing in order to enable meaningful comparisons of the performance of different materials.
    The Angle Orthodontist 10/2005; 75(5):832-5. · 1.18 Impact Factor