Porcelain refinishing with two different polishing systems after orthodontic debonding

OBJECTIVE: To compare the effects of two polishing systems on the surface roughness of three types of porcelain after orthodontic debonding. MATERIALS AND METHODS: A total of 90 porcelain discs were fabricated from feldspathic (n = 30), leucite-based (n = 30) or lithia disilicate-based (n = 30) ceramics. Ten samples in each group served as the control and received no surface treatment. The remaining 60 samples in three of the porcelain groups were bonded with lower incisor brackets and debonded using a testing machine in shear mode at a rate of 1 mm/minute crosshead speed. After debonding, the remaining adhesive resin was removed with a tungsten carbide bur. Then, two experimental subgroups (10 each) in each porcelain group were treated as follows: in the first subgroup, porcelain polishing wheel and polishing paste were applied, whereas in the second, polishing was performed using a series of Sof-Lex discs. The average surface roughness (Ra) of the all samples was evaluated using SPM/AFM (surface probe microscope/atomic force microscope). Data were statistically analyzed by analysis of variance for each porcelain material and polishing method. RESULTS: The polishing techniques affected surface roughness significantly. There were significant differences between the groups; higher Ra values were obtained with the use of porcelain polishing wheel and polishing paste (P < .001). CONCLUSION: The application of Sof-Lex discs can produce smoother porcelain surfaces than porcelain polishing wheel and polishing paste.     

Shear bond strength and residual adhesive after orthodontic bracket debonding

OBJECTIVE: To compare the shear bond strength and determine the area of residual adhesive on teeth after the debonding of brackets bonded with two types of orthodontic adhesives. These were a resin-modified glass ionomer cement (RMGIC; Fuji ORTHO LC, GC Corporation, Tokyo, Japan) and a resin applied as a precoated bracket (APC bracket, 3M Unitek GmbH, Seefeld, Germany). MATERIALS AND METHODS: A total of 60 premolar teeth were randomly divided into two groups, and brackets were bonded according to the manufacturers' instructions. In group 1, the teeth were conditioned using 10% polyacrylic acid, and the brackets were bonded using Fuji Ortho LC in wet condition. In group 2, the teeth were etched using 37% phosphoric acid, and the APC brackets were bonded. Bond strength was measured using a testing instrument (2000S, Lloyds Instruments, Fareham, England) at a crosshead speed of 1 mm/min, and the residual adhesive was quantified using a three-dimensional laser scanning instrument. RESULTS: The Mann-Whitney test showed that the median bond strength of group 1 was significantly lower than that of group 2 (P < .001). A Pearson chi-square test of the Adhesive Remnant Index (ARI) revealed a significant difference among the groups tested. All the adhesives in group 1 failed at the enamel/adhesive interface (100%), whereas group 2 exhibited cohesive failure of the adhesive (90%). CONCLUSIONS: The bond strength values obtained with the RMGIC were above the minimum values suggested in the literature to achieve a clinically effective adhesion in orthodontics.     

An in vitro comparison of ultraviolet versus white light in the detection of adhesive remnants during orthodontic debonding

Objectives:To assess the effectiveness and efficiency of ultraviolet (UV) illumination compared to conventional white light in the detection of fluorescent-tagged adhesive remnants during orthodontic debonding.Materials and Methods:Orthodontic brackets were bonded to extracted human premolars using one of two bonding resins having fluorescent properties (Pad Lock, Reliance Orthodontics, Itasca, Ill; Opal Bond MV, Opal Orthodontics, South Jordan, Utah; n = 40 each). The brackets were then debonded and, in each adhesive group, half the teeth had the remaining adhesive resin removed under illumination using the operatory light and the other half using a UV (395 nm) light emitting diode (LED) flashlight (n = 20/group). Time for teeth cleanup was recorded. Follow-up images were obtained under a dissecting microscope using UV illumination, and the surface area of adhesive remnants was calculated. Effectiveness of adhesive removal was also assessed using scanning electron microscopy imaging. Analysis of variance and Kruskal-Wallis tests were used to analyze time and adhesive remnants, respectively.Results:Assessment using the dissecting microscope found groups using UV light during adhesive removal had statistically significantly lower amounts of adhesive remnants than groups using white light (P ≤ .01). Time for adhesive removal was significantly lower with Opal Bond MV adhesive using UV light when compared with the white light (P ≤ .01). Assessment by scanning electron microscopy showed that thin remnants of adhesive (<2 μm) remained undetected by UV illumination.Conclusions:UV light is more effective and tends to be more efficient than white light in the detection of fluorescent adhesive during orthodontic debonding. Although there are limitations, the use of UV LED lighting is a practical tool that aids in adhesive detection.     

Spectrophotometric analysis of dental bleaching after bonding and debonding of orthodontic brackets

IntroductionThe aim of this study was to evaluate the bleaching effect after aging simulation in teeth submitted to bonding and debonding of orthodontic brackets.Materials and methodsFor this study, 90 human premolars were selected, and randomly divided into 6 groups: control, bleaching, and other 4 groups submitted to bleaching after bonding and debonding brackets using different methods. Color measurement of sample through the CIE L*a*b* system was performed in three moments: T1 – after brackets debonding, T2 – after staining cycling, and T3 – after bleaching. For evaluation of results among the components L*, a* and b*, the two criteria analysis of variance and the multiple comparison Tukey test (p < 0.05) were used.ResultsStatistically significant difference was observed among the groups submitted to brackets bonding and debonding through self-conditioning adhesive system and tungsten drill, also the control and bleaching groups between the moments T1 e T2.ConclusionBonding and debonding brackets methods tested in this study showed influence on the sample color change, and after the tooth bleaching process, only the group without brackets previous bonding achieved the color value presented before the staining and aging of samples in the brackets absence.     

Laser-aided debonding of orthodontic ceramic brackets.

The removal of ceramic brackets from the enamel surface by means of laser heating was investigated with the use of CO2 and YAG lasers. The two bracket types investigated were polycrystalline alumina and monocrystalline alumina. The average torque force necessary to break the adhesive between the polycrystalline ceramic brackets and the tooth was lowered by a factor of 25 when the brackets were illuminated with a CO2 laser beam of 14 watts for 2 seconds. All polycrystalline brackets debonded with the CO2 laser resulted in a complete bracket detachment without bracket failure. The average torque force needed to debond monocrystalline brackets was lowered by a factor of 5.2 when illuminated with a laser setting of 7 watts. Monocrystalline brackets cracked along the bracket slot in 2 of 10 cases. Debracketing without laser heating resulted in a slightly higher incidence of bracket failure (12 of 50). Nevertheless, no visible damage to the enamel surface was observed. Advantages of the laser-aided bracket-removal techniques include the following: The heat produced is localized and controlled; the debracketing tool is essentially "cold"; and the method can be used for removal of various types of ceramic brackets, regardless of their design.     

紫外线照射对正畸粘接剂去除后牙面颜色影响的研究

目的 研究紫外线照射条件下,酸蚀时间及粘接剂的固化形式对正畸粘接剂去除后牙面颜色稳定性的影响.方法 筛选色度为A3.5的前磨牙30颗,随机均分为5组,设一对照组,其它4组中前二组用37%磷酸分别酸蚀15秒、30秒后用Unite~（Tm）粘接剂（3M）粘接托槽,另外三组用37%磷酸分别酸蚀15秒、30秒后用Transbond XT粘接剂（3M）粘接托槽.恒温水浴48小时后去除托槽及残留粘接剂,紫外线照射72小时,实验前后进行比色.结果 除对照组外,其它各组的色差均大于3.3;除酸蚀15秒光固化粘接刺组外,其它各组与对照组色差差异均有统计学意义（P＜0.05）;粘接剂的固化形式及酸蚀时间对色差的影响均有统计学意义（P＜0.05）.结论 在紫外线照射条件下,粘接剂的固化形式及酸蚀时间均会影响正畸粘接剂去除后牙面颜色的稳定性,使其发生临床可识别的颜色改变,其中酸蚀15秒使用光固化粘接剂进行粘接后的牙面颜色改变最小.     

Bracket bonding with 15- or 60-second etching and adhesive remaining on enamel after debonding

The purposes of this study were to (1) evaluate the shear bond strength of brackets fixed to enamel that has been etched for 15 or 60 seconds, (2) correlate etch time with amount of resin remaining on the enamel after debonding; and (3) evaluate enamel morphology after acid etching. Sixty recently extracted human premolars were randomly divided into two groups. Group 1 was etched for 15 seconds, and group 2 for 60 seconds. A 37% phosphoric acid solution was used for etching. The brackets were Mini-Taurus, and the bonding system was Mono-Lok2. After bonding, the teeth were held at 37 degrees C and 100% humidity for at least 48 hours. To debond, a blade was placed at the ligature groove of the bracket. The force in Newtons required to dislodge the bracket was measured, employing a crosshead speed of 1 mm/min. Bond strength was calculated on the basis of bracket area. Immediately after removal of the bracket, the teeth were rinsed and dried using an air-water syringe, and the adhesive remnant index (ARI) was assessed. Enamel surfaces were analyzed using a scanning electron microscope (SEM). The results showed that shear bond strength was greater (p=0.016) when the enamel was etched for 60 seconds, and the amount of adhesive remaining on the teeth was also greater (p=0.001). There was no significant correlation between shear bond strength and the ARI calculated in the total sample (n=60, r=0.017; p>0.05). SEM evaluation revealed that the shorter etching time created a less retentive enamel surface. Absolute enamel loss also decreased.     

A comparison of traditional orthodontic polishing systems with composite polishing systems following orthodontic debonding

IntroductionAt the completion of treatment, the orthodontic practitioner’s goal is to effectively remove all traces of adhesive and return enamel to its initial state. With the advent of new polishing systems being released each year, there may be one product that is superior to others.AimThe purpose of this study is to determine the efficacy of new polishing systems (in the last 5–10 years) used in general dentistry on enamel surface roughness following debond utilizing profilometery and scanning electron microscopy and compare them to established orthodontic polishing systems results.MethodsFifty-two mandibular incisors were randomly assigned to one of five test groups (N = 10) and two incisors (untreated enamel) were used for profilometer and scanning electron microscopy analysis at the end of testing. After bracket removal, the teeth were polished using traditional polishing products (Komet H48L bur, Reliance ‘Renew’ point) and newer polishing products (Coltene Spiral Composite Plus Polisher, Ultradent Jiffy Composite Polishing Spiral or 3M Sof-Lex™ Diamond Polishing System). The results were evaluated using a profilometer and scanning electron microscopy images.ResultsThe results of a one-way analysis of variance (ANOVA) determined that the mean change in enamel surface roughness was not statistically different both in the traditional and novel groups. Tukey’s Honestly Significant Difference (HSD) test found that there was no statistically significant difference in the change in enamel surface roughness between instrument groups.ConclusionsThere was no statistically significant difference in enamel surface roughness after polishing between traditional orthodontic polishing systems and the selected novel polishing systems. SEM analysis revealed similar findings. This supports previous research suggesting that a wide variety of polishing systems or none at all, may be used to restore enamel smoothness after removal of orthodontic appliances.     

Nd: YAG laser for debonding ceramic orthodontic brackets.

INTRODUCTION: The purpose of this study was to develop an effective method for debonding ceramic orthodontic brackets with a high-peak power Nd:YAG laser. METHODS: Two types of ceramic brackets (single crystal and polycrystalline) were bonded to mandibular bovine teeth with 2 types of bonding resins (4-META/MMA and Bis-GMA). The laser was applied to 2 points on each bracket, each with a 1-pulse-per-second shot. Bond strength and thermal effects of the laser on the dentin surface were assessed at 3 laser energy levels: 1.0, 2.0, and 3.0 joules (J). Shear tests were performed on the irradiated test group and on a nonirradiated control group. ANOVA was used to determine significant differences. RESULTS: The shear test (P < .05) showed that every specimen in the 2.0-J and 3.0-J groups underwent a significant decrease in bonding strength compared with the nonirradiated group. However, the 1.0-J group did not exhibit any such difference. In the 2 former groups, laser irradiation alone was sufficient to debond some specimens. No significant difference was found between bonding resins. The maximum temperature rise measured on the pulpal walls at the lasing points was 5.1 degrees C. CONCLUSIONS: The application of a high-peak power Nd:YAG laser at 2.0 J or more is effective for debonding ceramic brackets.     

Evaluation of a Fluorescence-aided Identification Technique (FIT) to assist clean-up after orthodontic bracket debonding

Objectives:To compare a fluorescence-aided identification technique (FIT) with a conventional light source (CLS) for removing composite during debonding of brackets with respect to time needed, composite remnants, and tooth substance loss.Materials and Methods:Twelve maxillary models with 10 bovine teeth each were digitally surface-scanned and metal brackets were bonded on each tooth with Opal Seal and Opal Bond. Two operators: an experienced orthodontist (A) and an undergraduate student (B) received six models each and were asked to remove the composite remnants with a tungsten carbide bur and Sof-Lex discs by both a conventional light source (CLS group, n = 3), and fluorescent inducing light (FIT group, n = 3). The time taken was recorded, and a postoperative scan was digitally superimposed on the preoperative scan to quantify number of teeth with composite remnants and volume and thickness of enamel loss and composite remnants. Chi-square test and independent t-tests were performed to compare methods with a significance level of 5%.Results:Compared to CLS, both operators needed significantly less time when using the FIT method and degree of enamel loss, height, and volume of composite remnants and total remaining composite remnants were significantly reduced. By FIT, the volume of enamel loss was significantly reduced for operator A only. Operator B removed the same enamel volume with either method.Conclusions:Cleanup after orthodontic debonding with the FIT was superior regarding time needed and removal of composite remnants. Total enamel loss reduction was operator-dependent.     

Distortion of edgewise orthodontic brackets associated with different methods of debonding

The effects of three different methods of bracket removal on the dimensions of the arch wire slot of edgewise brackets were examined. Gross distortion (visible to the naked eye) and microscopic distortion were found for all three methods. Gross bracket distortion was found infrequently with one method. At a microscopic level, all methods produced approximately equal levels of distortion, principally an increase in vertical slot dimensions. The implications of these findings for recycling brackets are discussed.     

Bracket bond strength with transillumination of a light-activated orthodontic adhesive

The literature describes transillumination as a means of curing orthodontic light-cured composite adhesive. The literature also recommends a 2 to 3 times increase in light exposure time when light curing using transillumination. The purpose of this study was to determine the transmittance of the curing light through human enamel and the effect of transillumination on the bond strength of orthodontic brackets. One hundred extracted human maxillary incisors were used in this study. Brackets with orthodontic composite adhesive were placed on the labial surface of the incisors and light cured from either the labial or the lingual (transillumination). The control sample was cured from the labial for a total of 40 seconds of light exposure. Experimental samples were cured from the lingual (transillumination) for 20, 30, 40, or 50 seconds. The shear-peel bond strengths were tested at 30 minutes and 24 hours after light application. The results of this study demonstrated no statistically significant difference between 40 seconds of labial curing and most of the lingually cured groups. The only experimental group that differed statistically from the control group was the 40-second lingual cure group tested at 30 minutes after light application. Actual bond strengths, however, were lower for all experimental samples. The samples tested at 24 hours that received 50 seconds of transillumination were nearly the same as the control values. This study demonstrated that transillumination of maxillary incisors is an acceptable method of curing orthodontic adhesive, particularly if the exposure time is increased from 40 to 50 seconds.     

Fracture incidence on debonding of orthodontic brackets from porcelain veneer laminates.

The bonding force and the incidence of porcelain fracture for two porcelain systems, on removal of orthodontic brackets bonded to porcelain veneer laminates after thermocycling, were determined. A factorial design with a total sample size of 256 was used. The factors tested were (1) porcelain type (feldspathic [porcelain CE] or high alumina [porcelain VI]), (2) surface treatment (glazed or roughened), (3) priming agent (silane or alcohol), (4) bonding resin (macrofilled or microfilled), and (5) debonding time (30 minutes or 24 hours). An analysis of variance revealed that surface treatment, primer, resin type, and debonding time each contributed significantly to the debonding force. The probability of porcelain fracture was dependent on the porcelain type and the debonding force, with porcelain VI exhibiting a significantly higher probability of fracture than porcelain CE at the same debonding force. The etched surface of porcelain CE exhibited a more retentive microstructure than porcelain VI. The success of using bonded orthodontic brackets on porcelain veneer laminates depends on both the bond of resin to porcelain and the resistance of porcelain to fracture during debonding. For a given porcelain veneer, factors that provide a higher debonding force result in a higher probability of porcelain veneer fracture.