A New Carbide Finishing Bur for Bracket Debonding

Background: The removal of residual bonding resin with rotary instruments after bracket debonding may damage the enamel surface. Conventional carbide burs may scratch the enamel due to the shape and sharpness of their blades. Carbide Finishing Bur: A new carbide finishing bur with a slightly tapered shape, rounded tip and eight twisted blades has been developed. As a special feature the wedge angle of the blades has been enlarged to ca. 130-135° by means of an oblique ground chamfer (relief angle ca. 0-5°). The transition from head to shaft has been smoothed off with a safety chamfer. Overall, the cutting capacity has been reduced in the enamel, while the bur has remained sufficiently sharp within the adhesive resin. Prototype Testing: For prototype testing, incisor brackets were bonded in vitro to 70 human incisors according to the standard clinical technique and removed after 7 days. Residual bonding resin was removed with conventional carbide burs and with gradually modified prototypes of the new finishing instrument respectively. The resulting enamel surfaces were evaluated by scanning electron microscopy. The specimens were then treated with a polishing paste and evaluated again. Results: Conventional carbide burs remove not only residual bonding resin but also some enamel; scoring may occur. The newly developed finishing bur has been proven by morphological evaluation to be less aggressive in removing residual bonding resin after bracket debonding. Zusammenfassung Hintergrund: Die Entfernung von Kleberresten nach Bracketentfernung mit rotierenden Instrumenten ist nicht immer schmelzschonend. Konventionelle Hartmetallfinierer können aufgrund ihrer Gestalt und Schärfe der Schneiden Riefen im Schmelz hinterlassen. Hartmetallfinierer: Es wurde ein neuer Hartmetallfinierer entwickelt, der eine leicht konische Form mit abgerundeter Spitze und acht gedrallt verlaufende Schneidkanten aufweist. Als Besonderheit wurde der Keilwinkel der Schneidkanten durch einen schräg verlaufenden Fasenschliff (Freiwinkel ca. 0-5°) auf ca. 130-135° vergrößert. Der Übergang von Arbeitsteil zum Schaft wurde durch eine Sicherheitsfase entschärft. Insgesamt wurde die Schneidleistung im Zahnschmelz reduziert, im Kunststoff ist er aber ausreichend scharf. Testung der Prototypen: Zur Testung der Prototypen wurden auf 70 menschliche Schneidezähne Frontzahnbrackets nach klinisch üblicher Technik aufgeklebt (in vitro) und nach 7 Tagen entfernt. Die Kleberreste wurden mit konventionellen Hartmetallfinierern und mit nach und nach veränderten Prototypen der Neuentwicklung entfernt. Die Schmelzoberflächen wurden unter dem Rasterelektronenmikroskop untersucht. Zusätzlich wurden die Zähne mit Polierpaste bearbeitet und erneut untersucht. Ergebnisse: Konventionelle Hartmetallfinierer tragen außer den Kleberrest auch Zahnschmelz mit ab, Schmelzverletzungen (Riefen) können auftreten. Für den neu entwickelten Hartmetallfinierer wurde eine schmelzschonendere Beseitigung von Kleberresten nach Bracketentfernung morphologisch nachgewiesen.     

Surface roughness and wettability of enamel and dentine surfaces prepared with different dental burs

The aim of dental adhesive restorations is to produce a long lasting union between the restoration and the tooth structure. This bond depends on many variables including the geometry of the preparation and the type of bonding agent or luting cement. It is therefore suggested that the topography of the tooth surface may influence the wettability and the bonding quality of adhesive systems. This study measured the surface roughness and wettability of enamel and dentine after preparation with different dental burs. The mesial and distal surfaces of 15 extracted sound human premolar teeth were prepared with a tungsten carbide crown bur, a diamond bur and a tungsten carbide finishing bur and finished in enamel or dentin, respectively. The prepared surfaces were analysed with a surface profilometer and scanning electron microscopy (SEM). The contact angle of distilled water on each of the prepared surfaces was used as the measure of wettability. The differences in average surface roughness (Ra) were significant between the rotary instrument groups, as revealed by a two-way ANOVA test. No differences were detected between enamel and dentine surfaces prepared with the same type of dental bur. The smoothest surfaces were those completed with tungsten carbide finishing burs. The diamond bur preparations were intermediate in the roughness assessment and the tungsten carbide crown burs gave the roughest surfaces. There were no significant differences in the contact angle measurements for the various groups. It was concluded that the surface roughness of enamel and dentine prepared by different rotary instruments had no significant influence on the wettability of distilled water on these surfaces.     

Enamel surface roughness after debonding: Comparison of two different burs

Objective:To test the hypotheses that (1) there is no significant difference between the effects of two burs on the surface roughness of enamel after orthodontic debonding, and (2) there is no difference between resin removal times of the two burs.Materials and Methods:The crowns of 20 premolars were embedded in acrylic blocks, and the buccal surfaces were subjected to atomic force microscopy (AFM), with measurement of initial roughness values. The brackets were bonded with a light-cured adhesive and were debonded with a debonding plier. In half of samples, adhesive remnants were removed with a tungsten carbide bur, whereas a fiber-reinforced composite bur was used in the other half. The second AFM measurements were made after resin removal. Duration of removal procedures was also recorded. Results of roughness and duration measurements were analyzed with the use of repeated measurements analysis of variance and independent t-tests, respectively.Results:The two resin removal instruments had significantly different effects on enamel roughness; higher average roughness (Sa) (P < .001), root mean square roughness (Sq) (P  =  .046), and maximum roughness depth (Smax) (P < .001) values were obtained with use of the tungsten carbide bur. Time required for resin removal with the composite bur was significantly greater than time required with the carbide bur (P < .001).Conclusion:The hypothesis is rejected. The composite bur used for resin removal creates smoother surfaces after orthodontic bonding; however, the process takes longer than it does when the tungsten carbide bur is used.     

Optimization of a procedure for rebonding dislodged orthodontic brackets.

The purpose of this study was to compare shear bond strength (SBS) of bonded and rebonded orthodontic brackets following a variety of commonly used conditioning treatments and using both light-cured and self-cured composite resin systems. Brackets debonded during the initial determination of SBS were rebonded after the removal of residual resin from enamel surfaces using five different treatments: (1) Remove residual resin using a tungsten carbide bur, re-etch enamel surface, then bond a new bracket; (2) Remove resin from the base mesh with micro-etching then rebond the same bracket, (3) Remove residual resin from the enamel surface using resin-removing pliers, recondition the enamel with an air-powder polisher, then bond a new bracket; (4) Remove residual resin using a rubber cup and pumice, then bond a new bracket; (5) Remove residual resin using pliers alone, then bond a new bracket. The results revealed that the light-cured system produced higher shear bond strength in the initial bond than the self-cured system (p<0.005). Reconditioning the enamel surfaces using a tungsten carbide bur and acid-etching gave the highest SBS (difference 5.8 MPa; p<0.01) and clinically favorable fracture characteristics. The data suggest that the optimal procedure for rebonding dislodged orthodontic brackets is to resurface the enamel using a tungsten carbide bur, acid-etch the enamel, and use a new or re-use an old bracket after microetching.     

Enamel microabrasion followed by dental bleaching for patients after orthodontic treatment--case reports

This article reports clinical procedures used to remove residual bonded resin and enamel stains following bracket "debonding" at the conclusion of orthodontic treatment. A water-cooled fine-tapered diamond bur was used for resin removal, followed by enamel surface finishing using a commercially available microabrasion paste. It was noted that residual tooth coloration remained yellowish because of enamel translucency; the yellow dentin shade showed through. Additional tooth shade lightening was achieved using carbamide peroxide dental bleaching solution in custom-formed trays. This report describes a safe and effective technique that optimizes tooth appearance at the conclusion of orthodontic therapy. Mechanical resin removal, enamel microabrasion, and tooth bleaching are employed. CLINICAL SIGNIFICANCE: A combination of treatment methods are sometimes required for the best esthetic result. After orthodontic treatment, mechanical resin removal followed successively by enamel microabrasion and tooth bleaching can yield ideal long-lasting improvement.     

5种不同去牙面正畸残余粘接剂方法比较

目的 通过比较5种方法去除牙面残余正畸粘接剂对牙面的影响及操作所用时间,为筛选最佳去牙面粘接树脂方法提供参考。方法 选用正畸治疗需要拔除的健康前磨牙40颗,按不同的去牙面粘接剂方法随机分为5组,每组8颗。在常规粘接托接槽并去粘接后,分别用碳化钨钻（A组）、碳化钨钻+矽粒子（B组）、金刚砂钻（C组）、金刚砂钻+矽粒子（D组）、矽粒子（E组）做牙面处理,记录各组操作时间(T),并在扫描电镜(SEM)下观察、照相,记录釉质损伤指数（enamel damage index）。采用SPSS20.0软件包对操作时间T及EDI分别进行单因素方差分析及非参数秩变换分析。结果 各组EDI排序为C组>D组>A组>B组>E组,差异具有统计学意义（P<0.05）。各组操作时间排序为E组>D组>B组>A组>C组,差异具有统计学意义（P<0.05）。结论 用高速碳化钨钻加矽粒子去除残余粘接剂对釉质损伤较小且操作时间合理,值得临床推荐。     

Effect of surface roughness of cavity preparations on the microleakage of Class V resin composite restorations

This study determined whether surface roughness of the internal walls of a Class V resin composite preparation, using a carbide bur, a medium-grit diamond bur and a fine-grit diamond bur, affected the degree of microleakage of the restoration. The facial and lingual surfaces of 45 non-carious extracted human molars provided 90 samples for evaluation. The specimen surfaces were assigned randomly in equal numbers to one of three groups (n = 30). Conservative Class V composite preparations were made using one of three different burs: a 330-carbide bur, a 330 fine-grit diamond bur or a 330 medium-grit diamond bur (Brasseler USA). After acid etching, PQ1 (Ultradent Products Inc) primer/bonding resin and Vitalescence (Ultradent Products Inc) were applied and cured following the manufacturers' instructions. After minor finishing, the apices of all root surfaces were sealed with Vitrebond (3M), and the unprepared external surfaces were sealed with nail polish to within 1 mm of the restoration margins. The specimens were stored in distilled water at room temperature for 24 hours, then subjected to 1,200 thermocycles at 5 degrees C and 55 degrees C with a 30-second dwell time. After cycling, the teeth were immersed in a 5% solution of methylene blue dye for 12 hours. The molars were invested in clear acrylic casting resin, labeled, then sectioned once vertically approximately midway through the facial and lingual surfaces using a diamond coated saw blade. Microleakage was evaluated using a 10x microscope for the enamel and cementum surfaces and blindly scored by two independent examiners. In all cases, regardless of the examiner, at both the enamel and the dentin margins, the analysis revealed no statistically significant differences in microleakage across bur types. Further results show that dentin margins leaked significantly more than enamel margins for all bur types.     

Iatrogenic tooth abrasion comparisons among composite materials and finishing techniques

STATEMENT OF PROBLEM: Many different rotary instruments are available for shaping composite restorations. Whether use of these instruments causes undesirable iatrogenic abrasion of either the tooth surface or the composite restorative material is unknown. Assuming that damage occurs, which technique is least damaging is unknown. PURPOSE: This in vitro study quantified the loss of surface enamel and dentin surrounding Class V preparations during composite shaping and finishing procedures. The susceptibility of 2 types of composites to tooth abrasion was also examined. MATERIALS AND METHODS: Standardized Class V cavities were prepared at the amelodentinal junction of 36 human molar teeth. The teeth were randomly assigned to 6 groups of 6 teeth each. They were restored with either a low- or high-viscosity composite (Revolution or Prodigy Condensable, respectively) and finished with aluminum oxide disks, tungsten carbide burs, or ultrafine finishing diamond burs. The preparations were profiled before and after restoration. After each finishing procedure, morphological measurements of surface changes in the dentin and enamel were made and reported as volume (in cubic millimeters); maximum depth, mean maximum depth, and mean depth (in micrometers); and surface area (in square millimeters). The results were subjected to a 2-way analysis of variance for restorative material and finishing technique (P<.05). RESULTS: Aluminum oxide disks removed significantly less enamel than tungsten carbide burs or ultrafine finishing diamond burs, as measured by volume, maximum depth, mean maximum depth, mean depth, and surface area (P<.05). Conversely, aluminum oxide disks removed significantly greater dentin than either tungsten carbide burs or ultrafine finishing burs as measured by loss of volume, mean depth, and surface area (P<.05). There was no significant difference in the loss of surrounding tooth substance based on resin type (low or high viscosity). CONCLUSION: Within the limitations of this study, the 3 finishing systems tested resulted in varying degrees of iatrogenic abrasion of enamel and dentin. The composite material used had no significant effect on abrasion of the surrounding enamel or dentin.     

Enamel Surface Roughness of Preferred Debonding and Polishing Protocols

Objective:: This study investigated the surface roughness of enamel after debonding and instrumentation with commonly used methods.

Methods:: Part I: a survey was sent to active members of the American Association of Orthodontists to determine popular bonding, debonding, and polishing protocols. Part II: brackets were bonded to the buccal surface of 30 extracted human premolar teeth. After debonding, residual adhesive was removed with 12-, 16-, and 20-fluted titanium carbide burs as based upon the survey results. The teeth were scanned with a surface profilometer for surface roughness. Part III: the teeth were further polished using a Reliance Renew polishing point or a prophy cup with pumice and rescanned for surface roughness.

Results:: Part I: the majority of respondents used a generic bracket-removing plier to remove fixed appliances (53%) and a high-speed handpiece for adhesive removal (85%). The most popular bur was a 12-fluted carbide bur without water spray. The majority of respondents used pumice paste and/or Reliance Renew points after adhesive removal. Part II: there was a significant difference in enamel surface roughness when 12-, 16-, and 20-fluted carbide burs were compared via surface profilometry. Part III: further polishing with a Reliance Renew point or a prophy cup and pumice did not provide a significantly smoother surface.

Conclusions:: The results show large variation in debonding and polishing techniques. Creating a smooth enamel surface is equally possible with 12- or 20-fluted carbide burs. Further polishing with pumice and prophy cup or Renew point does not provide an enamel smoother surface.     

Enamel loss associated with orthodontic adhesive removal on teeth with white spot lesions: an in vitro study.

Teeth with white spot lesions (WSL) might be more prone to enamel loss during bracket debonding. This in vitro study compared enamel loss from teeth with (n = 14) and without (n = 14) WSL after polishing with low-speed finishing burs or disks (Sof-Lex, 3M ESPE, St Paul, Minn). Debonded surfaces were analyzed with a contact stylus profilometer, and digitized data were compared with baseline readings by using AnSur NT software (Regents, University of Minnesota, Minneapolis, Minn). Specimen surfaces were also examined with a scanning electron microscope. Two-way analysis of variance was performed to analyze the data. In teeth without WSL, the volume losses were 0.16 mm(3) for the bur group and 0.10 mm(3) for the disk group; the mean maximum depths were 47.7 microm for the bur group and 54.3 microm for the disk group. In teeth with WSL, the volume losses were 0.06 and 0.17 mm(3), and the mean maximum depths were 35.1 and 48.7 microm for the bur and disk groups, respectively. There were no significant differences in enamel loss between the 2 groups of teeth without WSL (P =.12). However, in teeth with WSL, the burs removed less enamel than the disks (P = 0.006). Scanning electron microscope examination showed that any damage on the enamel surface was usually located in the cervical third of the teeth. On most specimens, even though tooth surfaces appeared resin-free to the naked eye, there were remnants of it. The differences between groups were so small that they might be clinically insignificant.     

Enamel surface roughness following debonding using two resin grinding methods

The purpose of this study was to assess quantitatively the roughness of the enamel surface following debonding using two resin removal methods. The enamel surface of 30 premolar crowns was covered with black tape with a 3 mm window on the middle buccal third to standardize the area of analysis. The initial enamel surfaces were subjected to profilometry, registering four roughness parameters (Ra, Rq, Rt and Rz). The brackets were bonded to the plaster-embedded enamel surfaces with a chemically cured, no-mix adhesive, and debonded after 1 week. Resin removal in half of the specimens was performed with an eight-bladed carbide bur, and in the other half with an ultra-fine diamond bur, both attached to a high speed hand piece; a second profilometric measurement was made after resin removal. Finishing of all surfaces was achieved with Soflex discs and a third registration of roughness followed. The duration of each resin removal protocol was also recorded. The results were analysed with two-way ANOVA and the Newman-Keuls test with the two resin grinding modes and the three intervals serving as discriminating variables (n = 15). For the duration results, a one-way ANOVA was used. Significant differences (P < 0.05) were observed with respect to enamel roughness parameters between the two resin grinding methods used, while there was no consistent roughness-reducing effect of finishing with Soflex discs. Resin removal with a diamond bur was achieved in approximately half the time compared with the eight-bladed bur. The increase in most roughness variables induced by the debonding procedures was not reversed at the end of the finishing stage, regardless of the resin removal protocol used, suggesting an irreversible effect on enamel texture.     

不同粘接剂去除方式对釉质微观结构及托槽抗剪切粘接强度的影响

目的 对比研究5种不同牙面残留粘接剂去除方式对釉质及托槽抗剪切粘接强度(shear bond strength, SBS)的影响。方法 选取66颗离体前磨牙,随机分为6组。A组：空白组,牙面不做任何处理;B组：金刚砂车针处理组;C组：绿砂石处理组;D组：慢速钨钢钻处理组;E组：慢速钨钢钻+抛光杯处理组;F组：慢速钨钢钻+硅粒子处理组,用上述处理方法对各组等量粘接剂样本进行磨除,记录操作时间,分别用扫描电镜和表面粗糙度仪对釉质表面进行定性和定量评价。各组处理样本粘接金属托槽后,应用万能力学测试仪检测各组托槽SBS,分析牙面粘接剂残留指数(adhesive residual index, ARI)。结果 B、C组去除效率较高,E组效率最低;扫描电镜显示F组处理后的釉质形态最接近正常牙釉质;F组表面粗糙度最低((0.48±0.13)μm),与A组无统计学差异(P>0.05);D组托槽再粘接强度最高((16.61±1.99)MPa),明显高于A组(P<0.05);各组托槽去除后的ARI指数无显著性差异(P>0.05)。结论 金刚砂车针及绿砂石去除效率较高,但对釉质损伤较大;慢...     

An in vitro investigation of the effectiveness of bioactive glass air-abrasion in the 'selective' removal of orthodontic resin adhesive

The process of clinically debonding orthodontic brackets causes histomorphological damage to enamel that needs to be quantified and minimized. This study compared three methods for removing residual resin adhesive following bracket debonding. The surface finish following removal of residual adhesive using a slow-speed eight-bladed tungsten carbide bur (group 1), alumina air-abrasion (group 2), and bioactive-glass air-abrasion (group 3) and following polishing, was examined using scanning electron microscopy imaging of resin replicas. Contact profilometry was used to image surfaces before and after debonding for quantifiable volumetric analysis of enamel damage. Surface scarring was seen on scanning electron micrographs from group 1, a sharp pitted surface was identified in group 2, while group 3 exhibited similar, but subjectively smoother, pits. The surface finish following polishing was similar for groups 2 and 3 but did not completely remove the scarring evident from group 1. Quantifiable enamel lost was as follows: group 1, 0.285 mm(3); group 2, 0.386 mm(3); and group 3, 0.135 mm(3); statistical differences were observed between groups 2 and 3. From these results, bioactive-glass air-abrasion more consistently caused less physical damage to enamel and achieved a clinically smooth surface finish following polishing and is therefore to be recommended for clinical use.     

Effect of various grit burs on marginal integrity of resin composite restorations

The purpose of this study was to evaluate the generation of enamel cracks and gaps at the cavosurface margin of resin composite restorations using various burs. Saucer-shaped cavities with a bevel were prepared on mid-coronal buccal or lingual surfaces of extracted human molars using a regular-grit round diamond bur, a fine-grit diamond bur, a superfine-grit diamond bur or a six-bladed tungsten carbide bur with an air turbine handpiece. The enamel margin of the cavity in each group was observed by a light microscope. Cavities were restored with a self-etching adhesive and a light-cured composite resin. After thermocycling, enamel cracks and gaps at the cavosurface margins were observed and scored. Specimens were sectioned longitudinally in two halves, and the resin-cavity interface was observed by means of a light microscope. In cavity preparation, the regular-grid diamond bur and the tungsten carbide bur caused more cracks in the marginal enamel than other groups. From the surface and sectioned surface observation of restored teeth, the superfine-grit diamond bur generated fewer cracks and gaps than the other burs.     

Different techniques of residual composite removal following debonding--time taken and surface enamel appearance.

Four different methods of in vitro residual composite removal following debonding performed by two different operators (an orthodontist and a hygienist) were assessed for enamel surface damage (using scanning electron microscopy) and the time involved. There was no difference in the quality of enamel surface appearance between the two operators, regardless of the method used for composite removal. There was a statistically significant difference (P less than 0.05) for the time taken for composite removal between the two operators using a tungsten carbide bur method only. It is suggested that an expanded duties auxiliary with the practical skills of the hygienist would be able to remove residual composite debris and produce a satisfactory polished enamel surface using tungsten carbide burs and aluminium oxide polishing discs, thus becoming a safe and cost-effective member of the orthodontic team.     

Effects of different orthodontic adhesives and resin removal techniques on enamel color alteration

Objective: To investigate the color alterations in enamel following the use of different orthodontic bonding resins and adhesive residue–removal burs.Materials and Methods:Metal brackets were bonded to extracted human premolars (n  =  175) by using an etch-and-rinse adhesive system, a self-etch adhesive system (SEP), or a resin-modified glass ionomer cement (RMGIC). After 24 hours of photoaging, the brackets were removed and the adhesive residue on the tooth surfaces was cleaned with either a tungsten carbide bur or a Stainbuster bur. Tooth colors were measured with a spectrophotometer at baseline, after adhesive removal, and after additional photoaging. Color evaluation was made, and color differences induced by photoaging were calculated. Statistical evaluation was made using the Kruskal-Wallis test and the Mann-Whitney U-test, with Bonferroni correction.Results:All specimens showed discoloration at varying levels. The highest color change was observed in the etch-and-rinse adhesive/tungsten carbide bur group. When the etch-and-rinse and self-etch adhesives were used, adhesive-remnant removal with Stainbuster burs resulted in significantly lower discoloration. The type of bur did not affect the extent of enamel discoloration in the RMGIC group.Conclusions:Orthodontic treatment alters the original color of enamel, and both the adhesive system and the resin-removal methods are responsible for this change. When brackets are bonded with the etch-and-rinse system or the SEP, cleaning the adhesive residuals with Stainbuster burs is recommended for minimal change. RMGIC can be safely cleaned with tungsten carbide burs.     

Enamel gloss changes induced by orthodontic bonding

ABSTRACT

Objective: The purpose of this study was to assess enamel gloss changes induced by orthodontic bracket bonding with a light-cured composite or a light-cured resin-reinforced glass ionomer cement.

Setting: The Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Greece.

Design: Laboratory study.

Methods: A total of twenty extracted upper human first premolars were included in this study and each tooth served as a control for itself. Their buccal surfaces were subjected to 60^o-angle gloss measurement (G%60) with a standardized and secure repeated analysis of the same site. After baseline evaluation, a bracket was bonded on the buccal surface of each tooth. Half of the specimens were bonded with acid-etching and a light-cured composite whereas the other half with a light-cured resin-reinforced glass ionomer cement without prior enamel conditioning. Gloss measurements were repeated after bracket debonding and removal of the composite/glass ionomer cement with an 18-fluted carbide bur. Gloss differences between the two measurement conditions (baseline and post-debonding) were analyzed through linear regression with standard errors derived using the bootstrap method. Level of significance was set at a?<?0.05.

Results: A statistically significant difference was detected between the tested groups for the outcome of interest. Teeth bonded with light-cured composite exhibited larger enamel gloss changes as compared to resin-reinforced glass ionomer cement (β?=?0.74; 95% CIs: 0.10, 1.38; p?=?0.02).

Conclusions: Bracket bonding with two common bonding protocols (acid-etching with a light-cured composite vs. no etching with resin reinforced glass-ionomer cement) and subsequently debonding and adhesive removal with an 18-fluted carbide bur induced enamel gloss changes.     

Enamel loss during bonding, debonding, and cleanup with use of a self-etching primer

Self-etching primers have recently been introduced to simplify the orthodontic bonding process. The aim of this investigation was to compare the enamel loss at each stage of the bonding and debonding process with the use of such a product compared with the conventional two-stage etching and priming process with 37% o -phosphoric acid. In the laboratory, a planer surfometer was used to measure enamel surface height before any enamel treatment, after pumicing, after etching, and once the brackets had been debonded, after enamel clean-up with one of 4 clean-up methods. The latter included a high-speed tungsten carbide bur, a slow-speed tungsten carbide bur, debanding pliers, and an ultrasonic scaler. A change in enamel surface height was seen at each stage of the bonding and debonding process. After pumicing and conventional etching, the cumulative median enamel loss was -2.76 microm; however, the range was from -1.11 to -4.57 microm. This observed loss was much less than in previous reports on enamel loss after acid etching. With the self-etching primer, the median enamel loss was significantly lower, at -0.27 microm (range, -0.03 to -0.74 microm). At debond, there was also a significant difference in the adhesive remnant index scores between the 2 groups, with more adhesive remaining on the enamel surface in the conventional-etch group. It was during enamel clean-up that most surface loss occurred. In both the conventional and self-etch groups, most enamel loss occurred after the use of the high-speed tungsten carbide bur or the ultrasonic scaler and least with the slow-speed tungsten carbide bur or the debanding pliers.     

Resin bond strength and micromorphology of human teeth prepared with an Erbium:YAG laser

PURPOSE: To evaluate the in vitro effect of the Er:YAG laser and high-speed rotary instrumentation on the bond strength of resin composite to human enamel and dentin, and determine which conditioner, either phosphoric acid or a self-etching primer, resulted in higher bond strengths with either of the surface treatments. METHODS: 48 third molars were used. Dentin and enamel specimens were sectioned and polished with 600-grit SiC paper and treated either with carbide bur or an Erbium:YAG laser and treated with one of three different conditions, acid-etch/bonding agent (Scotchbond Multi-Purpose Plus), no etching and same bonding agent, and an experimental self-etching primer (EXL 547). After storage for 48 hours at 37 degrees C and 100% humidity, specimens were prepared in an hourglass shape for microtensile bond test (ca. 1 mm2) and debonded in tension. Areas were measured and bond strengths were calculated for each specimen. Failure modes, micromorphology of surface treatments and bonding interfaces of representative specimens from acid-etched and self-etched groups were analyzed with scanning electron microscopy. Means were compared using three-way analysis of variance, and Scheffé post-hoc test (P < 0.05) was used to determine differences among surface treatments, tooth substrate and conditioners. RESULTS: Dentin prepared with the carbide bur and treated with phosphoric acid followed by the application of Scotchbond Multi-Purpose had the highest bond strengths (35.7 MPa). Enamel and dentin prepared with the Er:YAG laser had the highest bond strengths when the surfaces were acid-etched followed by Scotchbond Multi-Purpose (25.8-21.1 MPa). Carbide bur exhibited higher bond strengths than laser with the use of the experimental self-etching primer but laser showed higher bond strengths than the bur with the use of Scotchbond Multi-Purpose and no etching. The predominant failure mode of most of the treatment conditions was partially adhesive between the bonding resin and enamel or dentin, and partially cohesive within the bonding resin. SEM analysis revealed the absence of a smear layer on laser-treated teeth when compared to untreated control and bur-cut teeth.     

Evaluation of a self-limiting concept in dentinal caries removal

The mechanical removal of dentinal caries traditionally involves the use of tactile sensation and/or caries-indicating dyes. This study tested the hypothesis that self-limiting polymer burs are as effective as conventional carbide burs in creating substrates for dentin bonding. Carious dentin from extracted human molars was removed with carbide or polymer burs, with dental explorer hardness as the end-point for caries removal. Dentin substrates were bonded with etch-and-rinse or self-etch adhesives and prepared for microtensile bond testing and transmission electron microscopy. For each bur type, there was no difference in bond strength between adhesives. However, the polymer bur surface exhibited significantly lower bond strengths than the carbide bur, and both were lower than flat, non-carious dentin controls. TEM revealed areas of incompletely removed, denatured caries-infected dentin in the polymer bur specimens. These first-generation polymer burs might best be utilized for deep caries removal where pulpal exposure is a concern.