An Investigation into the Use of a Single Component Self-etching Primer Adhesive System for Orthodontic Bonding: a randomized controlled clinical trial

Abstract

Objective: This study assessed the in vivo bond failure of the single component orthodontic self-etching primer system, Ideal 1 (GAC Orthodontic Products) and compared it with the conventional acid etching using a conventional 37% o-phosphoric acid, rinsing and drying regimen when bonding stainless steel orthodontic brackets to enamel.

Design: Prospective randomized, controlled clinical trial.

Setting: Orthodontic Department, Bristol Dental School.

Material and methods: Twenty consecutive patients undergoing upper and lower fixed orthodontic treatment entered this cross-mouth control study. Diagonally opposite quadrants were randomly allocated to either the self-etching primer group or the conventional etching group. A total of 339 teeth were bonded with Ideal 1 light-cured adhesive. Bond failures and locus of bond failure were then recorded at 1, 6 and 12 months.

Results: Significantly more bond failures occurred at each of the 3 time intervals, 1, 6 and 12 months, where the enamel was pretreated with the Ideal I self-etching primer, than when the enamel was treated with the conventional etchant, 37% o-phosphoric acid. With the latter the cumulative bond failure rates were 3.0, 5.3 and 14.8%, respectively. With the self-etching primer the cumulative failure rates were 29.4, 56.5 and 72.4%.

Conclusion: The study found that enamel pre-treatment with the Ideal 1 self-etching primer system prior to orthodontic bonding results in an unacceptably high bond failure rate when compared with conventional enamel acid etching.     

An in vivo investigation into bond failure rates with a new self-etching primer system.

Self-etching primers have recently been introduced to simplify the orthodontic bonding process. The aim of this study was to compare the effectiveness of such a product with conventional 2-stage etching and priming with 37% o-phosphoric acid and a conventional unfilled primer. Twenty consecutive patients having orthodontic bonds placed were selected to participate in this cross-mouth control study. Diagonally opposite quadrants were randomly allocated to either the self-etching primer group or the conventional etching and priming group. A total of 364 teeth were bonded with a light-cured diacrylate adhesive; bond failures were then monitored over 6 months. There were 20 bond failures (10.99%) in the self-etching primer group and 9 bond failures (4.95%) in the conventional etch and priming group over this period. The results were analyzed with the McNemar test and 95% confidence interval. The difference between the failure proportions was -0.06 with an associated 95% confidence interval of -0.121 to 0.001. This study produced weak evidence to suggest that bond failures with a self-etching primer will be higher than those with conventional etching and priming. This increased likelihood of bond failure must be weighed against the time advantage of the self-etching primer when used at the initial bonding appointment.     

An in-vitro investigation into the use of a single component self-etching primer adhesive system for orthodontic bonding: a pilot study

OBJECTIVE: This pilot study assessed force to debond (N); time, and site of bond failure of a single component self-etching primer (SEP) and adhesive system, Ideal 1 (GAC International Inc., USA) and compared it with the conventional acid etch and rinse regimen using 37% o-phosphoric acid solution and either Transbond XT (3M Unitek) or Ideal 1 adhesive. DESIGN: In vitro laboratory study. SETTING: Bristol Dental Hospital, UK. Sept 2003-Sept 2004. MATERIAL AND METHODS: Nine groups of 20 premolars were bonded using metal orthodontic brackets using three protocols: (1) 37% o-phosphoric acid etch and Transbond XT adhesive; (2) 37% o-phosphoric acid and Ideal 1 adhesive; (3) Ideal 1 SEP and Ideal 1 adhesive. Force to debond and locus of bond failure were determined at three time intervals. RESULTS: Enamel pre-treatment prior to bonding, namely SEP versus conventional etching had no significant effect on the median force to debond with the Ideal 1 adhesive. Similarly, when the enamel was conventionally etched, the adhesive type, namely Ideal 1 or Transbond XT, had no significant effect on the measured force to debond. However, there appeared to be differences in the locus of bond failure: failure predominated at the enamel/adhesive interface for the Transbond XT conventional etch group and at adhesive/bracket interface for the Ideal 1 SEP and adhesive group and the Ideal 1 adhesive conventional etch group. CONCLUSION: These results suggested that the complete Ideal 1 SEP and adhesive system might be successful in vivo leading therefore to a clinical trial. However, implications for clean up time are discussed and improvements to in vitro study designs are advised.     

Shear bond strength of orthodontic brackets bonded with a modified 1-step etchant-and-primer technique.

When bonding orthodontic brackets to enamel, most orthodontists use a conventional technique of etching tooth enamel with phosphoric acid, placing a hydrophilic primer on the etched, rinsed, and dried surface, then bonding the bracket with an adhesive resin composite. New systems simultaneously etch and prime the tooth surface in preparation for bonding. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to enamel with a conventional, multistep adhesive system and a self-etching primer adhesive system. In addition, a third group was included in which the air dispersion step in the self-etching primer system was omitted. Brackets were bonded to 108 extracted human molars according to 1 of 3 experimental protocols--group 1: conventional multistep adhesive (n = 36); group 2: self-etching primer system (n = 36); group 3: self-etching primer system without air dispersion (n = 36). Specimens were loaded to failure in a universal testing machine (Instron, Canton, Mass). Mean shear bond strengths in megapascals (standard deviation) were 11.3 (2.2), 11.9 (3.2), and 8.2 (2.8) for groups 1, 2, and 3, respectively. Data were subjected to 1-way analysis of variance at alpha =.05. The mean shear bond strength of the self-etching primer group in which the air dispersion step was omitted was significantly less than in the other 2 groups (P <.001). However, there was no difference in mean shear bond strength between the conventional, multistep adhesive system and the self-etching primer system when the primer was dispersed correctly (P =.34).     

Effect of using self-etching primer for bonding orthodontic brackets

Questions over the use of self-etching primers with composite resin adhesives in the bonding of orthodontic brackets remain unsolved. In addition, there are no previous reports on the efficacy of self-etching primers with resin-modified glass ionomer cements for bonding orthodontic brackets in orthodontic dentistry. The purpose of this study was to determine the shear bond strengths of orthodontic brackets bonded with one of four protocols: (1) a composite resin adhesive used with 40% phosphoric acid, (2) the same composite resin used with Megabond self-etching primer, (3) a resin-modified glass ionomer cement adhesive used with 10% polyacrylic acid enamel conditioner, and (4) the same resin-modified glass ionomer cement used with Megabond self-etching primer. The appearance of the tooth surfaces after acid etching or priming was observed with a field-emission scanning electron microscope (FE-SEM). When used with resin-modified glass ionomer cement, Megabond self-etching primer gave no significantly different shear bond strength compared with polyacrylic acid etching. But when used with composite resin adhesive, Megabond self-etching primer gave significantly lower shear bond strength than phosphoric acid etching. However, the shear bond strength of orthodontic brackets bonded with composite resin adhesive after Megabond priming was almost the same as that of brackets bonded with resin-modified glass ionomer cement after polyacrylic acid etching. FE-SEM observation revealed that Megabond self-etching primer produced less dissolution of enamel surface than did phosphoric acid and polyacrylic acid etching. Megabond self-etching primer may be a candidate for bonding orthodontic brackets using the resin-modified glass ionomer cement for minimizing the amount of enamel loss.     

Bonding durability of using self-etching primer with 4-META/ MMA-TBB resin cement to bond orthodontic brackets

This study determines the bonding durability when a self-etching primer is used with Superbond C&B (a 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane resin) to bond orthodontic brackets to enamel. Thermocycling test was used to assess bonding durability. Metal brackets were bonded to the phosphoric acid-etched or Megabond self-etching primer-treated enamel surface of human premolars using Superbond C&B. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours or after 2000 or 5000 cycles of thermocycling between 5 degrees C and 55 degrees C. Data were analyzed using 2-way analysis of variance and Fisher's protected least significant difference test for multiple comparisons. There was no significant difference in shear bond strength between phosphoric acid and Megabond self-etching primer treatment before the thermocycling test. After 2000 and 5000 thermal cycles, significant decreases in shear bond strength were observed with phosphoric acid etching. On the contrary, no significant differences in shear bond strength were observed after 2000 and 5000 thermal cycles with Megabond self-etching primer. The adhesive remnant indices were not significantly different between phosphoric acid etching and Megabond self-etching primer treatment either before or after thermal cycles. This study suggested that when used with Superbond C&B in bonding orthodontic brackets, Megabond self-etching primer is superior to phosphoric acid as an enamel preparation agent in providing durable bond strength.     

An evaluation and comparison of orthodontic bracket bond strengths achieved with self-etching primer.

The bonding of orthodontic brackets to enamel is a multistep process. To simplify bonding and decrease chair time, Transbond Plus Self-Etching Primer (3M Unitek, Monrovia, Calif) has been introduced; the primer combines the etching, rinsing, and priming steps. This in vitro study evaluated the shear bond strengths and interoperator variability of self-etching primer, as compared with conventional phosphoric acid etching with 2 common orthodontic resins. A total of 214 teeth were bonded, according to the following protocols: group A: self-etching primer plus Transbond XT light-cured resin (3M Unitek); group B: 35% phosphoric acid (15 seconds) plus Transbond XT resin; and group C: 37% phosphoric acid (15 seconds) plus Enlight bonding resin (Ormco, Glendora, Calif). Significantly higher bond strengths were seen in group B than in group A (P =.004) and group C (P =.002). The mean shear bond strengths of group A were not significantly different from those of group C (P =.99). When 3 orthodontists bonded a total of 60 premolars using the protocols of groups A and B, significant differences in shear bond strengths and strength ranking were found. The mean values they obtained using the self-etching primer were not significantly different, but significant differences in mean values were found between operators when the phosphoric acid-etching technique was used.     

Efficacy of using self-etching primer with a 4-META/MMA-TBB resin cement in bonding orthodontic brackets to human enamel and effect of saliva contamination on shear bond strength

The objective of this study was (1) to evaluate the effectiveness of Megabond when used with Superbond C&B, a 4-methacryloloxyethyl trimellitate anhydride (4-META)/methyl methacrylate (MMA)-tri-n-butyl borane (TBB) resin, to bond orthodontic metal brackets to human enamel and (2) to examine the influence of saliva contamination on shear bond strength. Metal brackets were bonded to phosphoric acid-etched or Megabond-treated human premolars using Superbond C&B resin cement. The effects of saliva contamination after acid etching or self-etch priming, and the effect of re-etching or self-etch priming after saliva contamination on shear bond strength were also assessed. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Data were analyzed using two-way analysis of variance and Fisher's protected least significant difference test for multiple comparisons. There were no significant differences in shear bond strength between phosphoric acid etching and self-etch priming for no contamination, saliva contamination, and repeat treatment (etching or priming) after saliva contamination. With phosphoric acid etching, saliva contamination significantly decreased the shear bond strength. Repeat phosphoric acid etching after saliva contamination did not significantly improve the bond strengths. With self-etching primer treatment, however, saliva contamination did not cause any decrease of bond strength. Phosphoric acid etching produced more enamel fracture than self-etching primer treatment. Field-emission scanning microscopy revealed less dissolution of enamel surface resulted from self-etching primer compared with phosphoric acid. These results suggest that Megabond when used with Superbond C&B resin cement may be a good candidate for bonding orthodontic brackets to human enamel.     

Assessing the performance of a methyl methacrylate-based resin cement with self-etching primer for bonding orthodontic brackets

Questions over the usefulness of a self-etching primer with resin adhesive in the bonding of orthodontic brackets remain unsolved. The purpose of this study was to determine the effects of using Multibond, a new methyl methacrylate (MMA)-based resin cement with self-etching primer, on the shear bond strength of orthodontic brackets compared with Superbond C&B, which is a well-known MMA-based resin cement containing phosphoric acid etching. Metal or plastic brackets were bonded to etched or self-etching primed bovine teeth using Superbond C&B or Multibond. The shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours. Data were analyzed by two-way analysis of variance and Scheffe's test. The surface appearances of the teeth after phosphoric acid etching or self-etching priming were observed by field-emission scanning electron microscopy (FE-SEM). Metal brackets bonded with Multibond had a significantly lower shear bond strength than metal brackets bonded with Superbond C&B. No significant differences in shear bond strength were observed between Multibond and Superbond C&B when plastic brackets were bonded to the enamel. The shear bond strength of metal brackets bonded with Multibond was comparable with that of plastic brackets bonded with Superbond C&B. Adhesive remnant index score showed a tendency of more residual resin cement remaining on the teeth when metal brackets were bonded with Multibond. FE-SEM observation revealed less dissolution of the enamel surface resulting from treatment with Multibond self-etching primer as compared with phosphoric acid. Thus, the Multibond system may be a candidate for bonding orthodontic brackets with the advantage of minimizing enamel loss.     

An in-vitro investigation into the use of a single component self-etching primer adhesive system for orthodontic bonding: a pilot study

Abstract

Objective: This pilot study assessed force to debond (N); time, and site of bond failure of a single component self-etching primer (SEP) and adhesive system, Ideal 1 (GAC International Inc., USA) and compared it with the conventional acid etch and rinse regimen using 37% o-phosphoric acid solution and either Transbond^TM XT (3M Unitek) or Ideal 1 adhesive.

Design: In vitro laboratory study

Setting: Bristol Dental Hospital, UK. Sept 2003-Sept 2004

Material and Methods: Nine groups of 20 premolars were bonded using metal orthodontic brackets using three protocols: (1) 37% o-phosphoric acid etch and Transbond^TM XT adhesive; (2) 37% o-phosphoric acid and Ideal 1 adhesive; (3) Ideal 1 SEP and Ideal 1 adhesive. Force to debond and locus of bond failure were determined at three time intervals.

Results: Enamel pre-treatment prior to bonding, namely SEP versus conventional etching had no significant effect on the median force to debond with the Ideal 1 adhesive. Similarly, when the enamel was conventionally etched, the adhesive type, namely Ideal 1 or Transbond^TM XT, had no significant effect on the measured force to debond. However, there appeared to be differences in the locus of bond failure: failure predominated at the enamel/adhesive interface for the Transbond^TM XT conventional etch group and at adhesive/bracket interface for the Ideal 1 SEP and adhesive group and the Ideal 1 adhesive conventional etch group.

Conclusion: These results suggested that the complete Ideal 1 SEP and adhesive system might be successful in vivo leading therefore to a clinical trial. However, implications for clean up time are discussed and improvements to in vitro study designs are advised.     

An investigation into the use of an anaerobic adhesive with two commercially available orthodontic brackets.

OBJECTIVES: The two objectives of this experiment were to determine the surface temperature of enamel following acid etching, rinsing and drying, and to see whether two commercially available orthodontic brackets could be bonded to enamel using an anaerobic adhesive. METHODS: Enamel surface temperature was determined in vivo using a surface temperature probe on a total of 60 patients. Stainless steel orthodontic brackets were bonded to human enamel using an anaerobic adhesive and a control orthodontic adhesive. The enamel was etched prior to bonding either with a solution of 37% o-phosphoric acid or, in the case of the anaerobic adhesive specimens, with a solution of 37% o-phosphoric acid containing copper (II) chloride. After bench curing the specimens were shear bond tested to failure and the load at debond recorded in each case. RESULTS: The bond test results were analyzed using median force to debond (N) and 95% confidence intervals, Kaplan-Meier survival probabilities and log-rank tests. CONCLUSIONS: After etching rinsing and drying the enamel surface temperature ranged from 21.54 to 24.19 degrees C, which is within the range suitable for anaerobic adhesive use. Bond testing to failure demonstrated that bracket base design affected the measured force to debond with both the anaerobic adhesive under test and the control adhesive. In addition, the anaerobic adhesive was affected by the material composition of the bracket base and curing time. After 1h of curing and using the Miniature Twin bracket, the measured force to debond exceeded the 10 min force to debond results of the control adhesive. SIGNIFICANCE: It is possible to bond commercially available orthodontic brackets to teeth using an anaerobic adhesive.     

Effect of fluoride varnish on the in vitro bond strength of orthodontic brackets using a self-etching primer system.

To reduce the number of steps involved with bonding procedures, manufacturers have simplified adhesive systems by combining the hydrophilic primer and the adhesive, or by combining the etchant, the primer, and the adhesive into 1 bottle and application. The purpose of this study was to investigate the relationship between the shear bond strength of orthodontic brackets to enamel, with or without fluoride varnish, by using either conventional or self-etching primer systems. Forty-eight extracted teeth were divided into 4 groups of 12 teeth each: group 1, fluoride varnish, conventional adhesive; group 2, fluoride varnish, self-etching primer system; group 3, no fluoride varnish, conventional adhesive; and group 4, no fluoride varnish, self-etching primer system. The bonding procedure followed the manufacturers' recommendations for the materials. Precoated adhesive orthodontic brackets were light-cured to the facial surfaces of the teeth and stored in whole human saliva at 37 degrees C for 24 hours. The specimens were subjected to a shear force in a testing machine until failure. The adhesive remnant index was used to score the teeth. Data were analyzed with a 2-way analysis of variance to test for differences in shear bond strength with respect to fluoride varnish and type of adhesive system used. The results showed no difference in bond strength among any of the experimental groups. Similarly, chi-square analysis determined that adhesive remnant index scores were not statistically different. The application of fluoride varnish does not affect the bond strength of orthodontic brackets to enamel with conventional or self-etching primer systems.     

两种含氟粘接系统对托槽粘接性能的临床研究

目的：研究含氟自酸蚀粘接系统和牙面酸蚀后涂氟粘接系统粘接正畸托槽的临床效果。方法：随机选取39名正畸患者,均分为三组,以自酸蚀粘接系统、牙面酸蚀后涂氟粘接系统和京津釉质粘接系统两两组合分别于患者双侧牙面粘接托槽,随访12个月,记录3种粘接系统的托槽脱落率。结果：3种粘接体系粘接托槽的脱落率无统计学差异。结论：自酸蚀粘接系统和牙面酸蚀后涂氟粘接系统对托槽的粘接效果与京津釉质粘接剂无显著性差异。     

Evaluation of a new self-etching primer on bracket bond strength in vitro

The purpose of this in vitro study was to evaluate the influence of a new self-etching primer (Adper Prompt L-pop; 3M ESPE, St Paul, Minn) on shear bond strength of orthodontic brackets. Forty extracted human premolars were obtained and randomly divided into two groups of 20 each: group 1 (control), phosphoric acid + Transbond XT primer (3M Unitek, Monróvia, Calif) and group 2, Adper Prompt L-pop. Transbond XT adhesive paste (3M Unitek) was used in both groups for bracket bonding. All products were used according to the manufacturer's instructions. Instron Universal Testing Machine was used to apply an occlusal shear force directly onto the enamel-bracket interface at a speed of 0.5 mm/min. The groups were compared using Student's t-test. Mean results and standard deviation for the groups were: group 1 = 16.23 MPa (4.77), group 2 = 13.56 MPa (4.31). No significant difference was observed in the bond strengths of the two groups evaluated (P = .069). However, the adhesive remnant index was significantly less when conditioning the enamel with Adper Prompt L-pop compared with phosphoric acid (P = .0003). The results suggest no difference in bond strength whether a conventional etching and primer or Adper Prompt L-pop is used. The amount of adhesive on the enamel after debonding was significantly less when using Adper Prompt than when using phosphoric acid. These results indicated that Adper Prompt is potentially adequate for orthodontic bonding needs.     

Effects of a self-etching primer and 37% phosphoric Acid etching on enamel: a scanning electron microscopic study

Objective: The purpose of this study was to compare the etching effects of a self-etching primer with 37% phosphoric acid on enamel by using a scanning electron microscope. Bond strength and the site of bond failure were also determined for brackets bonded using SEP and 37% phosphoric acid. Materials and methods: A total of 60 maxillary premolar teeth were used for this study and they were divided into four groups. First two groups were used for studying the different types of etch patterns obtained and the next two groups were used to test the bond strength with the help of Universal testing machine. After debonding, the amount of residual adhesive was assessed according to adhesive remnant index using a stereomicroscope. Results: The majority of etch patterns obtained in the 37% phosphoric acid group were type II, whereas in the SEP group, type IV pattern was more common. There was no statistically significant difference between mean bond strengths obtained with the SEP group and the phosphoric acid group. Use of SEP results in less amount of residual adhesive on tooth surface after debonding. Conclusion: SEP produces more conservative etch pattern compared to 37% phosphoric acid. Use of SEP for bonding provides similar and clinically acceptable bond strength compared to use of 37% phosphoric acid etching technique and requires less clean-up procedures hence, reduces enamel loss. Clinical significance: Use of 37% phosphoric acid for orthodontic bonding yields high bond strength but, causes enamel loss during both etching and debonding. SEPs not only provide adequate bond strength with a more conservative etch pattern but also enable easy debonding, thereby reducing the enamel damage. Keywords: Etch pattern, Enamel, SEM, Self-etching primer. How to cite this article: Nanjannawar LG, Nanjannawar GS. Effects of A Self-Etching Primer and 37% Phosphoric Acid Etching on Enamel: A Scanning Electron Microscopic Study. J Contemp Dent Pract 2012;13(3):280-284. Source of support: Nil Conflict of interest: None declared.     

自酸蚀和酸蚀剂正畸牙面处理效果的临床与扫描电镜研究

目的 比较自酸蚀偶联剂和磷酸凝胶酸蚀剂作为正畸牙面处理剂的粘结效果和釉质脱矿情况.方法 选取临床26例病人,左侧采用37%磷酸凝胶酸蚀剂,右侧使用自酸蚀偶联剂处理牙面,观察3个月内托槽脱落情况,比较临床脱落率.采用扫描电镜分别观察对照组、酸蚀组、自酸蚀组样本树脂突和粘结剂边缘牙釉质的脱矿情况.结果 酸蚀组的托槽脱落率2.44%,自酸蚀组为2.02%,经χ2检验无显著性差异.扫描电镜下自酸蚀较酸蚀组树脂突数量多、粗短且较规则,釉质表面脱矿程度较弱.结论 两种牙面处理剂的临床粘结效果差异不大,自酸蚀偶联剂对釉质脱矿作用更小.     

Artificial saliva contamination effects on bond strength of self-etching primers

OBJECTIVE: To test the hypothesis that there is no difference in the bond strength with or without contamination with artificial saliva when using two different self-etching primers (Transbond Plus and iBond) in comparison with a conventional acid-etching method (37% phosphoric acid and Transbond XT) for bonding of orthodontic brackets. MATERIALS AND METHODS: One hundred fifty extracted human premolars were randomly allocated to six different groups, with 25 teeth in each group. Orthodontic metal brackets (APC II, Victory Twin 22 UNIV) were used. For contamination, a saliva replacement (Ptyalin) was applied. After contamination the surface was air-dried for 5 seconds and the bonding procedure continued. The bonded teeth were stored in deionized water at 37 degrees C for 30 days and then thermocycled for 24 hours before debonding with a universal testing machine. The load was recorded at bond failure. The location of adhesive failure was determined under magnification using the adhesive remnant index (ARI). RESULTS: Clinically acceptable bond strengths were found for all primers used in this study. The contamination by saliva significantly decreased the bond strength when using the conventional acid-etching method (t = 0.0001). Self-etching primers were less influenced by saliva contamination. There was no significant difference in the ARI score among the groups (P > .05). CONCLUSIONS: Saliva contamination significantly decreased the bond strength when the conventional acid-etching method was used. The self-etching primers were influenced the least. The bond strengths achieved for the self-etching primers and the conventional etching method after saliva contamination were not significantly different.     

Bond strength comparison and scanning electron microscopic evaluation of three orthodontic bonding systems

This study sought to assess the efficacy of two self-etching primer systems (Transbond Plus and Beauty Ortho Bond) on orthodontic brackets. Therefore, shear bond strengths and bracket-adhesive failure modes (ARI scores) were determined and compared against an etch-and-rinse adhesive system (Transbond XT) under two experimental conditions (dry and saliva application). Shear bond strength test was performed at a crosshead speed of 0.5 mm/min, while enamel surfaces and enamel-adhesive interfaces were examined with SEM. There were no significant differences between Transbond XT (9.15 MPa) and Transbond Plus (9.74 MPa) under the dry condition, whereas that of Beauty Ortho Bond (6.47 MPa) was significantly lower than these two systems. Under SEM examination, both self-etching primers showed a milder etching effect and decreased depth of resin penetration into intact enamel than Transbond XT. In conclusion, results of this study showed that both self-etching systems seemed to offer more merits than conventional acid etching because of fewer irreversible changes to enamel.     

Micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel

PURPOSE: The aim of this study was to evaluate micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel. MATERIALS AND METHODS: Extracted human molars were classified according to the severity of fluorosis using Thylstrup and Fejerskov index into four groups (TFI: 0, normal; 1-3, mild fluorosis; 3-6, moderate fluorosis; 6-7, severe fluorosis) and divided into following two sub-groups. For the first sub-group, a self-etching primer adhesive system was applied to the ground enamel surfaces and the other sub-group was conditioned with 37% phosphoric acid for 30s prior to application of the same adhesive system. Teeth were then restored with a resin composite, stored for 24h in water and micro-shear bond strengths were measured. After shear testing, the fracture modes were observed under a laser scanning microscope. Morphological study of etching patterns and adhesive interface was done under a scanning electron microscope (SEM). The data were analyzed using two-way ANOVA and Sheffe test (p=0.05). RESULTS: No statistically significant difference was there between the different degrees of fluorosis in each sub-group. However, significant difference in the bond strengths between phosphoric acid etching and self-etching was found in moderate and severe groups. The SEM observations showed at the resin-enamel interface, thick resin tag like extensions penetrated around 3.5 microm into the enamel etched with phosphoric acid, while self-etching primer created, 1 microm lamina like penetration. CONCLUSION: Severity of fluorosis affects the micro-shear bond strength of a self-etching bonding system to fluorosed enamel.     

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.