不同邻面抛光方法对牙釉质表面粗糙度及表面形貌的影响

目的：评价4种邻面抛光方法对邻面釉质表面粗糙度及显微形貌的影响,为邻面抛光方法的选择提供依据。方法：选择21颗离体牙前磨牙,沿颊舌面中线纵剖后获得邻面釉质试件42枚,再用自凝塑料包埋,暴露邻面釉质,用浮石粉抛光,并超声清洗。将42个试样均分为6组,分别作如下处理：A组空白对照,不做处理;B组：阴性对照,采用标准金刚砂车针切磨触点及其周围釉质,切磨后不抛光;其余4组为实验组,经标准金刚砂车针切磨后分别采用以下方法抛光：C组：极细粒度金刚砂车针抛光;D组：裂钻抛光;E组：矽粒子抛光;F组：彩虹抛光条抛光。之后用粗糙度仪测定釉面粗糙度,并进行扫描电镜观察。结果：标准金刚砂车针切磨后粗糙度大幅度增加（P〈0.05）,釉质表面发生明显条形凹陷性缺损;经4种方法抛光后,釉质表面粗糙度均有显著下降（P〈0.05）,显微形貌均较阴性组光滑,其中矽粒子抛光组可达到较空白对照组更为光滑的表面。结论：实验涉及的4种不同邻面抛光方法均有助于降低釉质切磨区域的表面粗糙度,但抛光效果存在差异;采用矽粒子抛光可完全抵消牙体预备时旋转器械对邻牙邻面的切磨作用,获得最为光滑的釉质表面。     

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.     

Effects of regional enamel and prism orientations on bovine enamel bond strength and cohesive strength

This study investigated the regional microtensile bond strength (MTBS) and cohesive strength of bovine enamel. The crowns of bovine incisors were sectioned, either horizontally along incisal and cervical thirds to produce horizontal and tangential segments, or longitudinally along the midline to produce longitudinal segments. Half of the horizontal and longitudinal segments were prepared using a 45° bevel. Then, the differently sectioned enamel surfaces were treated with one‐ or two‐step self‐etch adhesives (Clearfil SE Bond or Clearfil S3 Bond) and a composite resin (Clearfil Majesty) was placed. Resin‐bonded enamel samples were cut into beams for use in the MTBS tests. Labial horizontal and longitudinal segments of pure enamel beams were prepared for cohesive strength tests. Enamel microstructures were analyzed by scanning electron microscopy. Three‐way anova followed by Tukey's post‐hoc HSD multiple comparisons procedure showed that a 45° bevel cut did not statistically significantly improve enamel MTBS, which varied with the different regions. The longitudinally sectioned resin‐bonded enamel samples had the lowest MTBS, and the horizontal enamel cohesive strength was weaker than that of the longitudinal enamel. The scanning electron microscopy fractographs indicated that rows of parallel prisms were detached from the fractured surfaces. In conclusion, the regional enamel MTBS and the cohesive strength are strongly related to the enamel microstructures and prism orientations.     

Effect of surface preparation on microtensile bond strength of three adhesive systems to bovine enamel

PURPOSE: The purpose of this study was to compare the microtensile bond strength (microTBS) of three adhesives to bovine enamel prepared with 600-grit silicon carbide paper, diamond rotary instrument, or carbide bur. MATERIALS AND METHODS: Bovine teeth (n = 36) were randomly divided into three treatment groups and bonded using a total-etch adhesive (Single Bond, 3M ESPE), a self-etching primer system (Clearfil SE Bond, Kuraray), or a self-etching adhesive (One-Up Bond F, Tokuyama). A 4-mm composite crown was built on the bonded surfaces and specimens were stored in water for one day at 37 degrees C. Specimens were sectioned into 0.7-mm-thick slabs, trimmed to a cross-sectional area of 1 mm2, and loaded to failure at a crosshead speed of 1 mm/min using a tabletop tester (EZ-Test, Shimadzu). Microtensile bond strength data were analyzed using ANOVA and Fisher's PLSD test (alpha = 0.05). RESULTS: The bond strength of each self-etching system was lower when the enamel was prepared using a diamond or carbide bur, rather than with 600-grit silicon carbide paper. Differences in microTBS between carbide- and diamond-prepared surfaces were not significant. The surface preparation method did not affect the total-etch system. CONCLUSION: Different preparation instruments are unlikely to affect resin-enamel bond strengths.     

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.     

Effect of methods of tooth enamel preparation on the retentive strength of acid-etch composite resins.

The effect of three procedures of preparing enamel surface on the retentive strengths of Concise Enamel Bond. Adaptic acid etch, Restodent and Nurva-Seal/Nurva-Fil was investigated. Resins using an unfilled-filled resin combination(Concise Enamel Bond, Adaptic acid etch, and Nurva-Fil) had a significantly higher retentive strength when the enamel was prepared with a coarse diamond bur than when the surface was unprepared or prepared with a carbide bur. The different procedures of tooth preparation did not affect the retentive strength of the resin when only filled resin was used (Restodent).     

Ceramic bracket bonding: a comparison of bond strength with polyacrylic acid and phosphoric acid enamel conditioning

The purpose of this study was to compare in vitro shear bond strength with three different enamel surface preparations: (1) 37% phosphoric acid etch, (2) sulfated polyacrylic acid etch with removal of crystals by vigorous rinsing and (3) polyacrylic acid etch with crystal growth. Forty extracted human premolar teeth were divided into four groups of ten. Ceramic brackets were bonded to teeth in each of three groups. The fourth group used was bonded with metal brackets and a phosphoric acid enamel preparation. The same lightly filled resin cement was used for all groups. A shearing force was applied to the teeth. The results demonstrated that the shear force needed to debond with ceramic brackets was 21% greater than the shear force with metal brackets. The polyacrylic acid crystal growth group had shear bond strength values approximately one half as great as the phosphoric acid etch group when ceramic brackets were used. Bond failures in the phosphoric acid etch group were at the bracket/resin interface with the bulk of the resin remaining on the tooth compared with the polyacrylic acid crystal growth group in which the bond failure was at the enamel resin interface. Enamel fractures were not found when healthy nonrestored teeth were subjected to the shearing force. In a preliminary test using phosphoric acid etch and teeth with compromised enamel (large restorations involving three or more surfaces), half of the teeth fractured during debonding. The study demonstrated that a polyacrylic acid conditioning of the enamel surface produces different retentive surfaces, depending on the presence or absence of crystal growth.(ABSTRACT TRUNCATED AT 250 WORDS)     

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

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

Shear strengths of a gallium alloy bonded to human enamel following nine different surface treatments.

OBJECTIVE: Gallium and indium-containing alloys have demonstrated an ability to wet and bond to many types of materials including enamel. The purpose of this study was to evaluate and compare the bond strengths of a gallium-and-indium-containing alloy and a dental amalgam to human enamel surfaces. METHOD: A flat enamel bonding surface was created by slicing recently extracted human molars with a 180-grit diamond wheel. Cylinders of amalgam or a gallium-indium alloy were bonded to the as-cut surfaces or to as-cut surfaces that had been pumiced, air-abraded or acid-etched for various times. Before testing, samples were stored under different conditions (100% humidity, immersed in water, thermocycled). The shear-bond strength was determined using a crosshead speed of 0.1 mm x min(-1). Sample size was 10. Data was subjected to ANOVA and a post-hoc Tukey's test. RESULTS: The bond strength of amalgam to enamel was zero. The bond strength of the gallium-indium alloy ranged between 6.5 MPa (10s etch with 10% phosphoric acid) and 4.2 MPa (pumiced enamel). Acid-etching significantly increased the bond strength (P>0.0001) The bond strength was not significantly affected by the type of mechanical surface preparation, storage conditions, thermocycling, etching times or acid concentrations. SIGNIFICANCE: Bonding, particularly chemical bonding, suggests a greater potential for better wetting and therefore better sealing of a cavity. Since microleakage of restorations is one of the principal causes of restoration failure, materials that can bond may in turn posses enhanced resistance to microleakage and ultimately, resistance to restoration failure. The gallium-indium alloy evaluated in this study may be such an alloy.     

Topographical characteristics and shear bond strength of tooth surfaces cut with a laser-powered hydrokinetic system.

STATEMENT OF PROBLEM: Erbium lasers, specifically Er;YAG and Er, Cr;YSGG that emit in the near red wavelengths, cut both enamel and dentine. Bonding to these cut surfaces with composites has not been assessed for all laser systems. PURPOSE: This investigation assessed the shear bond strength of composite bonded to tooth structure treated with an Er,Cr;YSGG-powered hydrokinetic system (HKS, Millennium system) and then was compared with surfaces treated with a carbide bur. MATERIAL AND METHODS: Extracted human molars were cut into enamel and dentin with both systems. Nonetched and acid-etched subgroups were evaluated. Shear bond strength was measured with an Instron test machine with a knife-edge loading head. In addition, SEMs were evaluated. RESULTS: There were no significant differences in shear bond strength between etched bur cut (23.3 +/- 2.5 MPa), etched laser-cut enamel (23.7 +/- 4.5 MPa), and nonetched laser-cut enamel (20.5 +/- 2.8 MPa). For nonetched enamel, bond strength values for laser-cut surfaces were significantly higher than the bur-cut surfaces (8.7 +/- 4.3 MPa). Bond strength differences for dentin between bur (14.3 +/- 1.7 MPa) and laser cuts (11.5 +/- 4.3 MPa) were not significant (P =.03). SEM revealed that laser cutting of enamel did not cause formation of a smear layer. CONCLUSION: There were no significant differences in shear bond strength between etched bur-cut, etched laser-cut, and nonetched laser-cut enamel. With nonetched enamel, bond strength values for nonetched laser-cut surfaces were significantly higher than for the bur-cut surfaces. No bond strength differences between bur and laser cutting existed for dentin. Similar topography was observed for bur and laser prepared surfaces of etched enamel and nonetched dentin.     

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.     

Relationship between enamel etch characteristics and resin-enamel bond strength

OBJECTIVES: The aim of the study was to investigate the relationship between etch patterns produced on surface enamel by phosphoric acid and the corresponding bond strengths achieved. MATERIALS AND METHODS: Twenty-eight patients had the buccal surface of their teeth etched and replicated for examination under the scanning electron microscope, at the commencement of orthodontic treatment. Histometry was employed to assess the nature and quality of etch patterns using a four-point scale. Twenty of each tooth type (total of 240), were collected and A Company pre-adjusted orthodontic brackets, bonded using Transbond light-cured orthodontic adhesive according to the manufacturer's instructions and 24-hour bond strength testing was undertaken. The Adhesive Remnant Index (ARI) was recorded for the tooth and bracket surface for all specimens. RESULTS: The type of etch was not significantly affected by the side (left or right) of the mouth assessed (p = 0.532). Overall, there was no significant difference between etch types for upper and lower teeth (p = 0.218); however, there were significant differences between specific teeth in the upper and lower arch. The greatest amount of Type A etch (well-defined etched enamel prisms) was found on the lower incisors, yet in all cases this 'ideal' etch was found to occupy less than 5% of the etched buccal surface enamel. The greatest area of etched enamel surface was occupied by Type C (etched but enamel prisms not evident). The mean bond strength values varied significantly between different tooth types, with the lowest bond strength found on the upper first molar(6.5MPa) and the highest on the lower first molar (13.1 MPa). CONCLUSIONS: An ideal etch pattern is not essential in order to produce a strong bond.     

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.     

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.     

Retention of composite resin restorations in class IV preparations

Clinicians often utilized composite resin restorations in combination with different types of preparation to restore class IV fractures on anterior incisors. A new preparation technique called (stair-step chamfer technique) is investigated in this study to detect bond strength to tooth structure. Eighty-eight bovine teeth were divided into 4 groups. Group I had twenty-three samples with a 45 degree bevel that extended 2 millimeters beyond the fracture line. Group II had twenty-three samples with a circumferential chamfer, which extended 2 mm beyond the fracture line and half the enamel thickness in depth. Group III had twenty-three samples with a facial stair-step chamfer, which followed the anatomical contour and extended 2 mm beyond the fracture line with a lingual plain chamfer. Group IV had eighteen samples as controls, which were untreated teeth. The first three groups were prepared and restored with hybrid composite resin in conjunction with a single step bonding agent and as surface penetrating sealer, then tested for shear-bond strength on the Instron machine. The results were that there was no significant difference found between the treated teeth when tested for shear-bond strength. However, according to the site of the fracture, the stair-step chamfer technique gave significantly better results. It can be concluded that, the stir-step chamfer technique provides the clinician better environment to place a composite resin restoration resulting in good shear-bond strength and better esthetics.     

Bond strength of simplified-step adhesives to enamel prepared with two different diamond burs

BACKGROUND: Self-etching primers are reported to produce considerable etching on flat enamel surfaces. However, little is known about the influence of different enamel surface textures. In this study the influence of grinding enamel on bond strength of two all-in-one and one two-step adhesives was investigated. METHODS: Resin composite was bonded to the ground enamel of extracted human third molars that was reduced 0.5 mm from the buccal or lingual surfaces using either regular- or superfine-grit diamond burs with each of the three adhesives. After 24 hours in 37 degrees C water, the specimens were sectioned into slabs of 0.7 mm thickness, trimmed to an hourglass configuration, and subjected to microtensile bond strength (MTBS) testing. RESULTS: For all adhesive systems, MTBS to enamel ground with a regular-grit diamond bur was not significantly different from that with a superfine-grit diamond bur. The etching patterns of these adhesives were partly varied according to the aggressiveness of the adhesives. CONCLUSION: The use of two different burs does not affect the tensile bond strength of the adhesives to enamel.     

An In Vitro Investigation of a Comparison of Bond Strengths of Composite to Etched and Air-Abraded Human Enamel Surfaces

PURPOSE: The purposes of the study were to measure the tensile bond strength of composite resin to human enamel specimens that had been either etched or air-abraded, and to compare the quality of the marginal seal, through the assessment of microleakage, of composite resin to human enamel specimens that had been either etched or air-abraded. MATERIALS AND METHODS: Thirty mandibular molar teeth were decoronated and sectioned mesio-distally to produce six groups, each containing ten specimens that were embedded in acrylic resin using a jig. In each of the four treatment groups, the specimen surfaces were treated by either abrasion with 27 or 50 microm alumina at 4 mm or 20 mm distance, and a composite resin was bonded to the treated surfaces in a standardized manner. In the two control groups the specimens were treated with 15 seconds exposure to 36% phosphoric acid gel and then similarly treated before being stored in sterile water for 1 week. All specimens were then subjected to tensile bond strength testing at either 1 or 5 mm/min crosshead speed. For the microleakage study, the degree of dye penetration was measured 32 times for each treatment group, using a neutral methylene blue dye at the interface between composite and either 27 or 50 microm air-abraded tooth structure or etched enamel surfaces. RESULTS: The mean bond strength values recorded for Group 1 (phosphoric acid etch, 5 mm/min crosshead speed) was 25.4 MPa; Group 2 (phosphoric acid etch, 1 mm/min), 22.2 MPa; Group 3 (27 microm alumina at 4 mm distance), 16.8 MPa; Group 4 (50 microm alumina at 4 mm distance), 16.9 MPa; Group 5 (27 microm alumina at 20 mm distance), 4.2 MPa; and for Group 6 (50 microm alumina at 20 mm distance) 3.4 MPa. An analysis of variance (ANOVA) demonstrated significant differences among the groups, and a multiple comparison test (Tukey) demonstrated that conventionally etched specimens had a greater bond strength than air-abraded specimen groups. No significant difference in dye penetration could be demonstrated among the groups (p= 0.58). CONCLUSIONS: Composite resin applied to enamel surfaces prepared using an acid etch procedure exhibited higher bond strengths than those prepared with air abrasion technology. The abrasion particle size did not affect the bond strength produced, but the latter was adversely affected by the distance of the air abrasion nozzle from the enamel surface. The crosshead speed of the bond testing apparatus had no effect on the bond strengths recorded. The marginal seal of composite to prepared enamel was unaffected by the method of enamel preparation.     

Acid-etch patterns on the buccal surface of human permanent teeth

Since the introduction of acid etching to aid adhesion to enamel, there has been much research into dental materials to improve bond strength, but little into the surface topography of etched enamel, particularly regarding possible variations between tooth types. This study was a systematic investigation into the quality and quantity of etch patterns found on the buccal surfaces of different human permanent teeth. Twenty-nine orthodontic patients had high-resolution silicone impressions taken of the buccal surface of incisor, canine, premolar and molar, upper and lower teeth, following etching for 30s with 37% phosphoric acid. Impressions (n=266) were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A modification of the classification of Galil and Wright was used, with histometric techniques, to quantify the quality of etch patterns on enamel surfaces where orthodontic brackets are typically bonded. There was no difference between right and left or between upper and lower teeth of the same type (P>0.05). There was a general trend toward the increasing occurrence of no etch (type D) from anterior to posterior teeth, and a trend toward fewer good-quality etches (types A and B) in the same direction. Etch types A and B were found to occupy the smallest area on the etched buccal surface enamel. The greatest amount of type A etch 'ideal' was found on the lower incisors, yet it occupied less than 5% of the etched buccal surface enamel. The greatest area of etched enamel surface was occupied by type C (etched, but enamel prisms not evident). It was concluded that there is a significant difference in the acid-etch patterns achieved on different tooth types, which suggests that bond-strength studies should be performed with a single tooth type or that an equal number of different tooth types be included.     

Rebond strength of bonded lingual wire retainers

There is no consensus in the literature concerning the rebonding procedure for orthodontic retainers. The aim of this in vitro study was to evaluate the bond and rebond strength of retainers bonded to enamel surfaces with and without composite remnants. The retainers were bonded with Excite and Tetric Flow on three different surfaces: clean enamel, enamel where the composite had been removed by a tungsten carbide bur, and with cured composite remnants roughened by a tungsten carbide bur. The bond strength was determined by means of a cantilever-tensile bond strength test using a repeated crossover design. Each tooth was rebonded twice and tested three times (N = 114). The surface was examined by scanning electron microscopy (SEM), electron backscatter diffraction and micro X-ray fluorescence (EDAX), and scored using the adhesive remnant index (ARI). Two-way analysis of variance of the mean bond strengths did not show significant differences between the three different enamel surface treatments. However, the specimens with cured composite remnants showed a higher standard deviation. This was confirmed by Weibull analyses. The ARI score showed that 96.5 per cent of bond fractures occurred at the retainer-resin interface. In contrast to the ARI score obtained in this study, the clinical ARI scores also showed failures at the resin-enamel interface. Based on these results, it is recommended that for rebonding the bond site is controlled, and the enamel surfaces are free of old composites remnants.