Effect of Intraoral Aging on Debris Accumulation and Friction of First Molar Tubes.

AIM: The aim of this article was to evaluate the impact of intraoral aging and site specificity on debris accumulation and friction in molar tubes after intraoral use. MATERIALS AND METHODS: A total of 80 intraorally used first molar convertible tubes were provided by 20 orthodontic adolescent patients after 6 months of treatment. The specimens were divided into eight groups (n = 10) according to the mouth quadrant and the type of examination [four groups of ten tubes for scanning electron microscope (SEM) and four groups of ten tubes for friction test]. Scanning electron microscope examination was performed after opening the convertible caps and friction test was executed using a 0.019'' × 0.025'' stainless steel wire, which was inserted in the tubes belonging to each group. The Mann-Whitney test, analysis of variance (ANOVA), and Bonferroni tests were performed for statistical analysis at 0.01 level of significance. RESULTS: There was a significant increase in the amount of debris and frictional force after 6 months of intraoral exposure (p < 0.0001). Debris scores were higher (10% increase) on the upper tubes when compared with the lower ones, with no statistical difference. Mean frictional force ranged from 0.22 to 0.26 N according to the mouth quadrant, but the difference between groups was also not significant. CONCLUSION: After 6 months of intraoral exposure, there was a significant increase in the amount of debris in the first molar tube slots, leading to significantly higher frictional forces during sliding mechanics. The influence of site specificity on the amount of debris and on frictional forces of the first molar tubes could not be demonstrated. CLINICAL SIGNIFICANCE: Molar tubes should be cleaned, before and during sliding mechanics, in order to minimize friction.

The 2D lingual appliance system.

The two-dimensional (2D) lingual bracket system represents a valuable treatment option for adult patients seeking a completely invisible orthodontic appliance. The ease of direct or simplified indirect bonding of 2D lingual brackets in combination with low friction mechanics makes it possible to achieve a good functional and aesthetic occlusion, even in the presence of a severe malocclusion. The use of a self-ligating bracket significantly reduces chair-side time for the orthodontist, and the low-profile bracket design greatly improves patient comfort.

Shear bond strength of deciduous and permanent bovine enamel.

PURPOSE: The use of bovine teeth as a substitute for human enamel has been proposed for dental studies. The aim of this study was to determine the shear bond strength and Adhesive Remnant Index (ARI) of deciduous and permanent bovine teeth. MATERIALS AND METHODS: Twenty deciduous and 20 permanent extracted bovine teeth were embedded in resin blocks. Stainless steel conventional orthodontic brackets were bonded to the teeth using an orthodontic adhesive. All samples were tested in shear mode on a testing machine. ARI scores were then recorded. Statistical analysis was performed to determine significant differences in bond strength and ARI scores. RESULTS: The bond strength of permanent bovine teeth was significantly higher (p = 0.0010) than that of the deciduous teeth. ARI scores showed no significant differences (p = 0.74). CONCLUSION: Deciduous teeth show lower shear bond strength than permanent teeth.

Shear bond strength of fibre-reinforced composite nets using two different adhesive systems.

The purpose of this study was to evaluate the effect of two different adhesive systems (Tetric Flow and Transbond XT) in combination with fibre-reinforced composites (FRC) net (Ever Stick) on the shear bond strength (SBS) of orthodontic brackets. Eighty bovine permanent mandibular incisors were randomly divided into four equal groups. Stainless steel maxillary central incisor brackets with a 0.018 inch slot (DB Leone) were bonded to the teeth using the two different adhesive systems. Fifty per cent of the brackets were bonded without and 50 per cent with a FRC net under the bracket base. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for SBS. Analysis of variance indicated significant differences among the various groups. Brackets bonded with FRC nets under the base showed a significantly lower SBS than those bonded without nets (P < 0.05). Moreover, teeth bonded with Transbond XT showed a significantly higher SBS than the other groups. Additionally, significant differences in debond locations [adhesive remnant index (ARI) score] were found among the various groups. Transbond XT can successfully be used for direct bonding of FRC nets, thus improving their SBS values.

In vitro bond strength evaluation of four orthodontic cements.

PURPOSE: To determine the shear bond strength and adhesive remnant index of orthodontic molar bands cemented with four different adhesives. MATERIALS AND METHODS: Eighty extracted human third molars were embedded in resin blocks and randomly assigned to one of four groups. Four different band cements were investigated: Ormco OptiBand, Dentaurum GlasTec, GC Fuji Ortho Band Paste Pak, and Unitek Multi-Cure Glass lonomer Orthodontic Band Cement. Bands were cemented on the molar crowns, and tensile loads were applied to measure the retentive strength. One-way ANOVA was performed for the retentive strength, and the Scheff multiple comparison test was applied as a post-hoc test. The Fisher exact test was used to determine significant differences in the ARI scores. RESULTS: The mean tensile bond strength of GC Fuji Ortho Paste Pak was significantly higher than those of all the other groups tested. No statistically significant differences were found among the other three groups. CONCLUSION: Among the adhesives investigated in the present study, Fuji Ortho Paste Pak resin-modified glass-ionomer cement provided the highest tensile bond strength values.

Nickel release from new conventional stainless steel, recycled, and nickel-free orthodontic brackets: An in vitro study.

INTRODUCTION: The aim of this study was to compare the nickel released from 3 kinds of orthodontic brackets: new conventional stainless steel, recycled stainless steel, and nickel-free brackets. METHODS: This in-vitro study was performed by using a classic batch procedure. Samples were immersed in artificial saliva at various acidities (pH 4.2, 6.5, 7.6) over an extended time interval (0.25, 1, 24, 48, and 120 hours). The amount of nickel released was determined by using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber White robust standard errors to account for intrabracket correlation of data. For post-hoc comparisons, the Bonferroni correction was applied. RESULTS: The recycled brackets released the most nickel (74.02 +/- 170.29 microg per gram); the new stainless steel brackets released 7.14 +/- 20.83 microg per gram. The nickel-free brackets released the least nickel (0.03 +/- 0.06 microg per gram). All the differences among the groups were statistically significant (P = 0.000). CONCLUSIONS: Reconditioned brackets released the most nickel. Moreover, the highest nickel release was recorded in the 2 experiments performed at pH 4.2; it was lower at pH 6.5 and 7.6. Conversely, no relevant differences were observed overall between the maxillary and mandibular arches.

Chromium release from new stainless steel, recycled and nickel-free orthodontic brackets.

OBJECTIVE: To test the hypothesis that there is no difference in the amounts of chromium released from new stainless steel brackets, recycled stainless steel brackets, and nickel-free (Ni-free) orthodontic brackets. MATERIALS AND METHODS: This in vitro study was performed using a classic batch procedure by immersion of the samples in artificial saliva at various acidities (pH 4.2, 6.5, and 7.6) over an extended time interval (t(1) = 0.25 h, t(2) = 1 h, t(3) = 24 h, t(4) = 48 h, t(5) = 120 h). The amount of chromium release was determined using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber-White robust standard errors to account for intrabracket correlation of data. For post hoc comparisons the Bonferroni correction was applied. RESULTS: The greatest amount of chromium was released from new stainless steel brackets (0.52 +/- 1.083 microg/g), whereas the recycled brackets released 0.27 +/- 0.38 microg/g. The smallest release was measured with Ni-free brackets (0.21 +/- 0.51 microg/g). The difference between recycled brackets and Ni-free brackets was not statistically significant (P = .13). For all brackets, the greatest release (P = .000) was measured at pH 4.2, and a significant increase was reported between all time intervals (P < .002). CONCLUSION: The hypothesis is rejected, but the amount of chromium released in all test solutions was well below the daily dietary intake level.

Force levels of fiber-reinforced composites and orthodontic stainless steel wires: a 3-point bending test.

INTRODUCTION: The purpose of this study was to evaluate the force levels of 2 sizes (diameters, 0.6 and 1.2 mm) of fiber-reinforced composites (FRCs) (Ever Stick; Stick Teck Ltd, Turku, Finland) compared with orthodontic stainless steel wires (sections, 0.016, 0.018, 0.017 x 0.025, and 0.019 x 0.026 in) under the same testing conditions. METHODS: The samples were divided into 12 groups, each consisting of 10 specimens. Each sample was evaluated with a 3-point bending test on a universal testing machine. The FRC groups were light-cured by hand with a halogen curing unit (Optilux 501; SDS Kerr, Danbury, Conn) for 40 seconds. Groups 1 through 6 were tested at 1-mm deflection, and groups 7 through 12 at 2-mm deflection. RESULTS: The results of ANOVA indicated significant differences among the various groups (P = .000). The post-hoc test showed that the 2-mm deflection groups had significantly higher load values than the 1-mm deflection groups (P = .000). The highest force levels were recorded with the 1.2-mm FRCs, followed by the 0.019 x 0.026-in stainless steel wires. No significant differences were found between the 0.6-mm FRCs and the 0.017 x 0.025-in wires. The lowest load values were reported with the 0.016-in stainless steel wires. CONCLUSIONS: The 1.2-mm FRCs showed higher load values than the other stainless steel wires and the FRCs, whereas no significant difference was found between the 0.6-mm FRCs and the 0.017 x 0.025-in stainless steel wires. Thus, FRCs can be considered a viable esthetic alternative to full-size stainless steel wires to rigidly join dental segments to form anchorage units or units for active tooth movement.

In-vitro fluoride release rates from 9 orthodontic bonding adhesives.

INTRODUCTION: The purpose of this study was to compare the in-vitro fluoride release rates from 9 orthodontic adhesives in distilled water. METHODS: Of the adhesives tested, 4 were bracket bonding agents (Fuji Ortho LC [GC, Leuven, Belgium], Enlight LV [Ormco, Glendora, Calif], ConTec LC [Dentaurum, Ispringen, Germany], and Transbond XT [3M Unitek, Monrovia, Calif]); the remaining 5 were molar banding cements: Fuji Ortho Band Paste Pak (GC), OptiBand (Ormco), GlasTec (Dentaurum), Multi-Cure (3M Unitek), and Transbond Plus (3M Unitek). Ten samples of each adhesive were stored in containers holding 5 mL of deionized distilled water at 37 degrees C. Fluoride release was measured with an ion-specific electrode (model 96-09BN, Orion Research, Beverly, Mass). Readings were taken periodically for a total time period of 3 months. Descriptive statistics were calculated for the fluoride release rates of each material group. The data were subjected to a general linear regression model to detect differences in fluoride ion concentration by material and time. Post-hoc test with the Bonferroni adjustment was used to further delineate group differences. RESULTS: Among the bracket bonding adhesives, statistically significant differences were found in fluoride release rates (P = .000), with Fuji Ortho LC releasing the most fluoride. Enlight LV, ConTec LC, and Transbond XT released negligible amounts of fluoride. Fuji Ortho Band Paste Pak released more fluoride (P = .000) than all remaining molar banding adhesives. Multi-Cure released more fluoride than GlasTec, Transbond Plus, and Optiband. The latter released negligible amounts of fluoride. CONCLUSIONS: Fuji Ortho Band Paste Pak released more fluoride than the other adhesives. Fuji Ortho Band Paste Pak and Fuji Ortho LC might have sufficient fluoride-release rates to reduce white spot formation, and they are recommended as suitable fluoride-releasing orthodontic adhesives.

Flexural strengths of fiber-reinforced composites polymerized with conventional light-curing and additional postcuring.

INTRODUCTION: The purpose of this study was to evaluate the effect of hand light-curing (Optilux 501; SDS Kerr, Danbury, Conn) and secondary oven polymerization (Liculite; Dentsply, Dreieich, Germany) on the mechanical properties of 2 sizes (diameters, 0.6 and 1.2 mm) of fiber-reinforced composites (FRCs) (Ever Stick; Stick Tech, Turku, Finland). METHODS: The FRC samples were divided into 8 groups. Each group consisted of 10 specimens. Each FRC sample was evaluated with a 3-point bending test with a universal testing machine. Groups 1, 3, 5, and 7 were hand light-cured with a halogen curing unit for 40 seconds. Groups 2, 4, 6, and 8 were light-cured with the same curing unit for 40 seconds, followed by polymerization for 15 minutes in a light-curing oven. Groups 1 through 4 were tested at 1-mm deflection, and groups 5 through 8 at 2-mm deflection. RESULTS: The results of ANOVA indicated significant differences among the various groups (P = .000). The post-hoc test showed that the 2-mm deflection groups had significantly higher flexural strengths than the 1-mm deflection groups (P = .000). Moreover, the 1.2-mm FRCs showed significantly higher flexural strength than the 0.6-mm FRCs (P = .000). No significant differences (P >.05) were found between the hand light-cured and the oven-polymerized groups. CONCLUSIONS: This investigation demonstrated that oven postcuring does not increase the flexural strength values of 0.6- and 1.2-mm FRCs compared with conventional hand light-curing. Thus, hand light-curing of FRCs is recommended directly in the mouth for orthodontic purposes.

Effect of water and saliva contamination on the shear bond strength of a new light-cured cyanoacrylate adhesive.

AIM: The purpose of the study was to assess the effect of water and saliva contamination on the shear bond strength and site of bond failure of two different orthodontic adhesives (Transbond XT and cyanoacrylate Smartbond LC). MATERIALS AND METHODS: 120 bovine permanent mandibular incisors were randomly divided into 6 groups, and each group consisted of 20 specimens. Each adhesive was tested under three different enamel surface conditions: 1) dry, 2) water contamination, 3) saliva contamination. 120 stainless steel brackets (0.018-inch slot DB, Leone) were bonded in each test group with the respective adhesive. After bonding, all samples were stored in distilled water for 24 hours and subsequently tested in a shear mode on an Instron Universal Testing Machine. Shear bond strength and site of bond failure were evaluated. Kruskal-Wallis and Fisher's exact tests were applied to determine significant differences in terms of bond strength among the 6 groups. The chi-square test was used to determine significant differences in the Adhesive Remnant Index (ARI) scores. RESULTS: Transbond XT showed the highest bond strength values when it was applied onto dry enamel (P < 0.0002). No significant differences were reported when Transbond was used either on water- or saliva- contaminated enamel (P = 0.5), however the bond strength values were significantly low. For Smartbond LC no significant differences were found between dry and moist with water conditions (P = 0.3). Significantly higher bond strength values were reported when Smartbond LC was used on saliva contaminated enamel (P = 0.002). Significant differences in debond locations were found among the different groups. CONCLUSIONS: The use of a cyanoacrylate adhesive is indicated under moist conditions (particularly saliva), and when a short setting time is required. This can be considered advantageous in clinical orthodontic bonding compared to conventional composites.

Effect of various adhesive systems on the shear bond strength of fiber-reinforced composite.

INTRODUCTION: The purpose of this study was to evaluate the effect of 3 adhesive systems on the shear bond strength of a fiber-reinforced composite (FRC). METHODS: Sixty bovine permanent mandibular incisors were randomly divided into 3 groups of 20. The FRCs (Ortho, Stick Teck Ltd, Turku, Finland) were bonded to the teeth with 3 adhesive systems (Tetric Flow [Ivoclar-Vivadent, Schaan, Liechtenstein], Transbond XT [Unitek/3M, Monrovia, Calif], and Fuji Ortho LC [GC Europe, Leuven, Belgium]). After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. Analysis of variance and the Sheffé post-hoc tests were used at a significance level of P < .05. RESULTS: ANOVA indicated significant differences among the various groups. Fibers bonded with Transbond XT showed significantly higher shear bond strengths than the other 2 groups. No significant differences in shear bond strength values were reported between Tetric Flow and Fuji Ortho LC. No significant differences in debond locations (ARI scores) were found among the various groups. CONCLUSIONS: For maximum bond strength, use Transbond XT for direct bonding of FRC.

Three-dimensional digital modeling and setup.

Obtaining accurate images of the craniofacial region is critical when developing an orthodontic diagnosis and treatment plan. The purpose of this article is to describe a new imaging method that provides complete 3-dimensional views of the maxilla and the mandible, and the model setup with individual anatomic roots. The method uses computed tomography technology and laser scanning; it offers high-resolution images with relatively low radiation exposure. Technical aspects of the new procedure and its possible uses for orthodontic diagnosis and treatment planning are discussed.

The effect of bleaching on shear bond strength of brackets bonded with a resin-modified glass ionomer.

INTRODUCTION: This study assessed the effect of a 35% hydrogen peroxide bleaching gel on the shear bond strength and bond failure site of a resin-modified glass ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium). METHODS: Forty-five bovine mandibular permanent incisors were randomly divided into 3 groups; each group contained 15 teeth. Bleaching treatment was performed at 2 different times before the bonding procedure. Forty-five stainless steel brackets were bonded with the resin-modified glass ionomer. After bonding, all samples were stored in distilled water for 24 hours and then tested in shear mode on a testing machine. RESULTS: Group 1 (no bleaching) showed significantly higher shear bond strength values than groups 2 (bleaching immediately before bonding) and 3 (bleaching 1 week before bonding). No significant differences were found between groups 2 and 3. Moreover, no significant differences in debond locations were found among the 3 groups. CONCLUSIONS: Bleaching treatment before bonding significantly lowered the bond strength values of Fuji Ortho LC.

Effect of chlorhexidine application on shear bond strength of brackets bonded with a resin-modified glass ionomer.

INTRODUCTION: The purpose of study was to assess the effect of chlorhexidine application on the shear bond strength and bond failure site of a resin-modified glass ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium). METHODS: Forty-five bovine permanent mandibular incisors were randomly divided into 3 groups of 15. Group 1 had no chlorhexidine treatment and served as the control; groups 2 and 3 had chlorhexidine application immediately before and 1 week before bonding, respectively. Stainless steel brackets (DB, Leone, Sesto Fiorentino, Italy) were bonded with the resin-modified glass ionomer. After bonding, all samples were stored in distilled water for 24 hours and subsequently tested in a shear mode on a testing machine. Analysis of variance (ANOVA) and the Scheffé test were applied to determine significant differences in the shear bond strength values, and the chi-square test was used to determine significant differences in the adhesive remnant index scores among the groups. Significance for all statistical tests was predetermined at P < .05. RESULTS: Group 1 (no chlorhexidine application) showed significantly higher shear bond strength values than group 2 (chlorhexidine applied immediately before bonding). No significant differences were found between groups 1 and 3 (chlorhexidine applied 1 week before bonding). Moreover, significant differences in debond locations were found among the 3 groups. CONCLUSIONS: Chlorhexidine application immediately before bonding significantly lowered the bond strength values of Fuji Ortho LC but did not affect its bond strength when applied 1 week before bonding.

Effect of light-tip distance on the shear bond strengths of resin-modified glass ionomer cured with high-intensity halogen, light-emitting diode, and plasma arc lights.

INTRODUCTION: The purpose of this study was to assess the effect of light-tip distance on the shear bond strength and the failure site of brackets cured with 3 light-curing units (high-intensity halogen, light-emitting diode, and plasma arc). METHODS: One hundred thirty-five bovine mandibular permanent incisors were randomly allocated to 9 groups of 15 specimens each. Stainless steel brackets (Victory Series, Unitek/3M, Monrovia, Calif) were bonded with a resin-modified glass-ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium) to the teeth, and each curing light was tested at 3 distances from the bracket: 0, 3, and 6 mm. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. RESULTS: When the 3 light-curing units were compared at a light-tip distance of 0mm, they showed no significantly different shear bond strengths. At a light-tip distance of 3 mm, no significant differences were found between the halogen and plasma arc lights, but both lights showed significantly higher shear bond strengths than the light-emitting diode light. At a light-tip distance of 6 mm, no significant differences were found between the halogen and light-emitting diode lights, but both showed significantly lower bond strengths than the plasma arc light. When the effect of the light-tip distance on each light-curing unit was evaluated, the halogen and light-emitting diode lights showed no significant differences among the 3 distances. However, the plasma arc light produced significantly higher shear bond strengths at a greater light-tip distance. No significant differences were found among the adhesive remnant index scores of the various groups, except with the LED light at a distance of 3 mm. CONCLUSIONS: In hard-to-reach areas, the plasma arc curing light is suggested for optimal curing efficiency.

Effect of light-tip distance on the shear bond strengths of composite resin.

The purpose of this study was to assess the effect of light-tip distance on the shear bond strength and failure site of brackets cured with three different light curing units: a high-intensity halogen (Astralis 10, 10-second curing), a light-emitting diode (LED, e-Light, six-second curing), and a plasma arc (PAC System, four-second curing). One hundred and thirty-five bovine permanent mandibular incisors were randomly allocated to nine groups of 15 specimens each. Stainless steel brackets were bonded with a composite resin to the teeth, and each curing light was tested at zero, three, and six mm from the bracket. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. When the three light curing units were compared at a light-tip distance of zero mm, the three lights showed no significantly different shear bond strengths. At light-tip distances of three and six mm, no significant differences were found between the halogen and plasma arc lights, but both lights showed significantly higher shear bond strengths than the LED light. When evaluating the effect of the light-tip distance on each light curing unit, the halogen light showed no significant differences between the three distances. However, the LED light produced significantly lower shear bond strengths at a greater light-tip distance, and the plasma arc lamp showed significantly higher shear bond strengths at a greater light-tip distance. In hard-to-reach areas, the use of PAC system is suggested, whereas the LED evaluated in this study is not recommended.