Prevention of demineralization around orthodontic brackets in vitro

Influence of fluoride-containing acidic artificial saliva on the mechanical properties of Nickel-Titanium orthodontics wires

OBJECTIVE

This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva.

DESIGN

A prospective laboratory investigation.

SETTING

Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China.

MATERIALS AND METHODS

Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM).

RESULTS

A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion.

CONCLUSIONS

The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.

Effect of remineralizing agents on bond strength of orthodontic brackets: an in vitro study

Background

The purpose of this study is to evaluate the effect of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and CPP-ACP with fluoride (CPP-ACP-F) on the shear bond strength (SBS) of orthodontic brackets bonded with two different adhesive systems.

Methods

One hundred twenty-six human premolar teeth were selected. One hundred twenty teeth were used for SBS testing, and six teeth were used for scanning electron microscope (SEM) examination. One hundred twenty premolars were divided into mainly three groups: CPP-ACP (group A), CPP-ACP-F (group B), and control group (group C). Each group was sub-divided into two groups according to the bonding adhesive, light cure (groups A1, B1, and C1) and chemical cure (groups A2, B2, and C2). The teeth were pre-treated with the group-specified preventive agent 1 h/day for five consecutive days. Standard edgewise brackets were bonded with the respective adhesives. SBS evaluation was done with the universal testing machine. After debonding, all the teeth were scored for adhesive remaining on the buccal surface, in accordance to adhesive remnant index, under a stereomicroscope. The acid-etched enamel surfaces were observed under SEM after treatment with CPP-ACP, CPP-ACP-F, and artificial saliva.

Result

In light-cure adhesive group, CPP-ACP-F (B1) showed superior results compared to the control group (C1), whereas the CPP-ACP group (A1) showed lower mean SBS than the control group (C1). Both these differences were not statistically significant (p > 0.05). In chemical-cure adhesive group, control group C2 showed significantly superior results (p < 0.05) compared to group A2 and group B2. The results of two-way ANOVA showed highly significant difference due to adhesive types (p < 0.01), whereas enamel pre-treatment showed non-significant difference (p > 0.01).

Conclusion

The SBS of the orthodontic brackets was non-significantly affected when the brackets were cured with light-cure bonding system and treated with either CPP-ACP or CPP-ACP-F, whereas with chemical-cure adhesive, decreased bond strength was seen, which was within the clinically acceptable limits.

Effect of different preventive agents on bracket shear bond strength: in vitro study

Background

The effects of fluoride and CPP-ACP before bracket bonding on the shear bond strength of orthodontic brackets have been reported with contradicting results. The objective of this in vitro study was to evaluate the effect of different preventive agents namely; casein phosphopeptide-amorphous-calcium-phosphate (CPP-ACP), fluoride-containing-CPP-ACP (CPP-ACPF) and 5% sodium fluoride (5% NaF), on the enamel-bracket shear bond strength (SBS) and to compare their effects when applied before or after acid-etching.

Methods

Human premolar teeth were randomly divided into seven groups (16 teeth per group) as follows: the control group, where no preventive agent was applied on the enamel and 6 experimental groups. Teeth in groups 1a, 2a, and 3a were treated with CPP-ACP paste, CPP-ACPF paste, and 5% NaF, respectively before acid-etching. Teeth in groups 1b, 2b and 3b were treated using the same preventive agents after acid-etching. The brackets were then bonded and the teeth were thermocycled. The brackets' SBS was measured and the adhesive remnant was assessed using adhesive remnant index (ARI). Analysis of variance (ANOVA) and Tukey test were performed to compare the SBS among different groups. Chi-square test was used to evaluate differences in ARI scores between the groups.

Results

Enamel surface treatment with CPP-ACPF after acid-etching significantly increased SBS compared to the control and to its application before acid-etching (P < 0.05). Higher ARI index was recorded when the preventive agents were applied after acid-etching.

Conclusion

Brackets' SBS significantly increased when fluoride-containing-CPP-ACP was applied after acid-etching.

Evaluation of self-etching adhesive and Er:YAG laser conditioning on the shear bond strength of orthodontic brackets

The purpose of this study was to evaluate the shear bond strength, the adhesive remnant index scores, and etch surface of teeth prepared for orthodontic bracket bonding with self-etching primer and Er:YAG laser conditioning. One hundred and twenty bovine incisors were randomly divided into four groups. In Group I (Control), the teeth were conditioned with 35% phosphoric acid for 15 seconds. In Group II the teeth were conditioned with Transbond Plus SEP (5 sec); III and IV were irradiated with the Er:YAG 150 mJ (11.0 J/cm²), 150 mJ (19.1 J/cm²), respectively, at 7–12 Hz with water spray. After surface preparation, upper central incisor stainless steel brackets were bonded with Transbond Plus Color Change Adhesive. The teeth were stored in water at 37°C for 24 hours and shear bond strengths were measured, and adhesive remnant index (ARI) was determined. The conditioned surface was observed under a scanning electron microscope. One-way ANOVA and chi-square test were used. Group I showed the significantly highest values of bond strength with a mean value of 8.2 megapascals (MPa). The lesser amount of adhesive remnant was found in Group III. The results of this study suggest that Er:YAG laser irradiation could not be an option for enamel conditioning.

Surface remineralization potential of casein phosphopeptide-amorphous calcium phosphate on enamel eroded by cola-drinks: An in-situ model study

AIM

The aim of this study was to investigate the remineralization potential of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on enamel eroded by cola drinks.

SUBJECTS AND METHODS

A total of 30 healthy subjects were selected from a random sample of 1200 children and divided into two groups of 15 each wherein calcium and phosphorus analyses and scanning electron microscope (SEM) analysis was carried out to investigate the remineralization of enamel surface. A total of 30 non-carious premolar teeth were selected from the human tooth bank (HTB) to prepare the in-situ appliance. Three enamel slabs were prepared from the same. One enamel slab was used to obtain baseline values and the other two were embedded into the upper palatal appliances prepared on the subjects' maxillary working model. The subjects wore the appliance after which 30 ml cola drink exposure was given. After 15 days, the slabs were removed and subjected to respective analysis.

STATISTICAL ANALYSIS USED

Means of all the readings of soluble calcium and phosphorous levels at baseline,post cola-drink exposure and post cpp-acp application were subjected to statistical analysis SPSS11.5 version. Comparison within groups and between groups was carried out using ANOVA and F-values at 1% level of significance.

RESULTS

Decrease in calcium solubility of enamel in the CPP-ACP application group as compared to post-cola drink exposure group (P < 0.05) was seen. Distinctive change in surface topography of enamel in the post-CPP-ACP application group as compared to post-cola drink exposure group was observed.

CONCLUSION

CPP-ACP significantly promoted remineralization of enamel eroded by cola drinks as revealed by significant morphological changes seen in SEM magnification and spectrophotometric analyses.

Influence of CO2 (10.6 μm) and Nd:YAG laser irradiation on the prevention of enamel caries around orthodontic brackets

One possible undesirable consequence of orthodontic therapy is the development of incipient caries lesions of enamel around brackets. The aim of this study was to compare the effects of CO2 (λ = 10.6 μm) and Nd:YAG (λ = 1,064 nm) lasers associated or not with topical fluoride application on the prevention of caries lesions around brackets. Brackets were bonded to the enamel of 65 premolars. The experimental groups (n = 13) were: G1--application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2--Nd:YAG laser irradiation (0.6 W, 84.9 J/cm(2), 10 Hz, 110 μs, contact mode); G3--Nd:YAG laser irradiation associated with AFP; G4--CO2 laser irradiation (0.5 W, 28.6 J/cm(2), 50 Hz, 5 μs, and 10 mm focal distance); and G5--CO2 laser irradiation associated with AFP. Quantitative light-induced fluorescence was used to assess enamel demineralization. The data were statistically compared (α = 5%). The highest demineralization occurred in the Nd:YAG laser group (G2, 26.15% ± 1.94). The demineralization of all other groups was similar to that of the control group. In conclusion, CO2 laser alone was able to control enamel demineralization around brackets at the same level as that obtained with topical fluoride application.

Shear bond strength of orthodontic resins after caries infiltrant preconditioning

OBJECTIVE

To investigate the influence of caries infiltrant preconditioning on the shear bond strength of orthodontic resin cements on sound and demineralized enamel.

MATERIALS AND METHODS

 Stainless-steel brackets were bonded to sound or artificially demineralized (14 d, acidic buffer, pH 5.0) bovine enamel specimens using a resin cement or a combination of caries infiltrant preconditioning (Icon, DMG) and the respective resin cement (light-curing composite: Heliosit Orthodontic, Transbond XT, using either Transbond XT Primer or Transbond Plus Self Etching Primer; light-curing resin-modified glass ionomer cement: Fuji Ortho; or self-curing composite: Concise Orthodontic Bonding System). Each group consisted of 15 specimens. Shear bond strength was evaluated after thermo-cycling (10,000×, 5°C to 55°C) at a crosshead speed of 1 mm/min, and data were statistically analyzed by analysis of variance, Mann-Whitney test, and Weibull statistics. Adhesive Remnant Index (ARI) scores and enamel fractures were determined at 25× magnification and were statistically analyzed by regression analyses (P < .05).

RESULTS

The caries infiltrant system significantly increased the shear bond strength of Transbond XT Primer, Transbond Plus Self Etching Primer, and Fuji Ortho in sound specimens, and of all resin cements except for the Concise Orthodontic Bonding System in demineralized enamel. Overall, caries infiltrant preconditioning decreased significantly the number of enamel fractures, but it did not affect ARI scores.

CONCLUSION

Preconditioning of sound and demineralized enamel with the caries infiltrant system did not impair but rather increased the shear bond strength of most orthodontic resin cements while decreasing the risk of enamel fracture at debonding.

Effect of fluoride on tooth erosion around orthodontic brackets

The aim of the present study was to evaluate the effect of fluoride in prevention of tooth erosion around orthodontic brackets under erosive challenge. Edgewise brackets were bonded with Transbond™ XT composite on vestibular surface of 40 bovine incisors. The teeth were assigned to 4 groups (n=10): G1: Remineralizing saliva; G2: Erosive challenge; G3: Experimental group submitted to topical application of neutral fluoride gel (2% NaF) before erosive challenge; G4: Experimental group submitted to three daily applications of fluoride dentifrice (PFM 1500 ppmF) during erosive challenge. After 14 days of erosive challenge, direct visual and tactile examination were performed by two calibrated and trained examiners (Kappa = 0.867). The following scores were used: 0 = Intact enamel, 1 = Demineralized enamel without cavity, 2 = Demineralized enamel with cavity, 3 = Remineralized enamel without cavity, 4 = Remineralized enamel with cavity. Kruskal-Wallis and Mann-Whitney tests were applied to determine erosion levels, establishing a confidence interval of 95% (p<0.05). G2 and G3 presented 100% of score 2, with large cavities, presenting rough and opaque surface. G4 showed 50% of score 3 and 50% of score 4. Considering the studied conditions, it was found a significant difference between G2 and G4 and between G3 and G4 (p<0.01). By contrast to single application of neutral fluoride gel, the high frequency of use of fluoride at low concentration had a great influence during the dynamics of erosion.

Influence of topical fluoride application on mechanical properties of orthodontic bonding materials under pH cycling

OBJECTIVE

To evaluate in vitro the influence of topical fluoride application on the mechanical properties of orthodontic cements containing fluoride under pH cycling conditions.

MATERIALS AND METHODS

Edgewise brackets for maxillary central incisors were bonded to 192 bovine incisors using Transbond XT (G1), Transbond Plus Color Change (G2), and Fuji Ortho LC (G3) (n  =  64 for each group). The specimens of each group were subdivided (n  =  16) into different subgroups. Subgroup A received no topical fluoride application during pH cycling, while the experimental subgroups received topical fluoride treatments as follows: B, application three times per day of fluoride dentifrice (1450 ppm F); C, application one time per day of fluoride mouth rinse (250 ppm F); and D, combination of fluoride dentifrice and fluoride mouth rinse. After 14 days of pH cycling, the shear bond strength and Adhesive Remnant Index were evaluated statistically.

RESULTS

Polarized light microscopy showed that pH cycling induced mineral loss in all specimens. The topical application of fluoride did not have an influence on shear bond strength, although the association of fluoride dentifrice and mouth rinse increased the shear bond strength of the resinous cement without fluoride (P < .01). Regarding the Adhesive Remnant Index, no statistical differences were found within the groups G1 (P  =  .23), G2 (P  =  .47), and G3 (P  =  .74).

CONCLUSION

Topical fluoride treatments improved the shear bond strength of resinous cement, regardless of the material's fluoride-releasing capacity, and reached the adhesive fractures.

Caries preventive effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP): a meta-analysis

OBJECTIVE

This systematic review with meta-analyses sought to answer the following question: "Does CPP-ACP [casein phosphopeptide-amorphous calcium phosphate], when introduced into the oral environment, provide any caries-preventive benefit superior to that of any other intervention or placebo?"

MATERIAL AND METHODS

Seven electronic databases were searched for trials relevant to the review question. Twelve articles were accepted after application of inclusion and exclusion criteria.

RESULTS

Of the accepted articles, five in situ randomized control trials (RCT) could be pooled for meta-analyses. During the short-term (7-21 days) in situ trials, participants wore appliances containing enamel slabs that were analyzed in the laboratory after exposure to CPP-ACP. The pooled in situ results showed a weighted mean difference (WMD) of the percentage remineralization scores in favor of chewing gum with 18.8 mg CPP-ACP as compared to chewing gum without CPP-ACP (WMD -8.01; 95% CI: -10.54 to -5.48; p = 0.00001), as well as compared to no intervention (WMD -13.56; 95% CI: -16.49 to -10.62; p = 0.00001). A significant higher remineralization effect was also observed after exposure to 10.0 mg CPP-ACP (-7.75; 95% CI: -9.84 to -5.66; p = 0.00001). One long-term in vivo RCT (24 months) with a large sample size (n = 2720) found that the odds of a tooth surface's progressing to caries was 18% less in subjects who chewed sugar-free gum containing 54 mg CPP-ACP than in control subjects who chewed gum without CPP-ACP (p = 0.03).

CONCLUSION

Within the limitations of this systematic review with meta-analysis, the results of the clinical in situ trials indicate a short-term remineralization effect of CPP-ACP. Additionally, the promising in vivo RCT results suggest a caries-preventing effect for long-term clinical CPP-ACP use. Further randomized control trials are needed in order to confirm these initial results in vivo.

Comparison of the effect of three cements on prevention of enamel demineralization adjacent to orthodontic bands

Background and aims

This in vitro study was designed to compare enamel demineralization depths adjacent to bands cemented with zinc polycarboxylate, glass ionomer (GI) and resin-modified glass ionomer (RMGI), in order to achieve minimal enamel demineralization during orthodontic treatment.

Materials and methods

Sixty fully developed extracted third molars were randomly divided into three testgroups each containing 20 samples, used to cement orthodontic bands with zinc polycarboxylate, GI and RMGI. All samples were demineralized using White method using hydroxyapatite, latic acid and Carbapol for in vitro caries simulation, and then, immersed in 10% solution of methylene blue. The mean depth of dye penetration was assessed up to 0.1 millimeter, reflect-ing the depth of enamel demineralization. One way ANOVA and LSD statistical tests were employed to evaluate significant differences among groups.

Results

The highest dye penetration depth was seen in zinc polycarboxylate group, followed by GI, and RMGI groups, respectively, with significant differences among each two groups (P < 0.05).

Conclusion

The use of RMGI cement seems to present significantly better prevention of enamel demineralization adja-cent to orthodontics bands.

Glass ionomer cement as an orthodontic bonding agent

AIM

To find an alternative to popular orthodontic bonding agent composite resin and elimination of acid etching. To assess GC Fuji Ortho as an orthodontic bonding agent under different enamel conditions and evaluate the shear bond strength. Enamel surfaces intentionally contaminated with saliva, conditioned enamel using Fuji dentin conditioner and conventional 37% phosphoric acid/60 seconds. To evaluate and compare shear bond strength to a 'gold standard' composite bonding agent--Rely-a-Bond.

MATERIALS AND METHODS

The sample consisted of 50 human premolar teeth collected and stored in formalin. Out of 50 samples, 38 were upper premolars and 12 were lower second premolars. The total sample divide into 10 each. Stainless steel contour bracket with bondable mesh measured about 3.42 mm in length and 3.31 mm in width. Each tooth sample was embedded in a cylindrical acrylic block of polymethyl methacrylate (PMMN). The buccal surfaces of all the samples were polished with fluoride-free pumice and rinsed thoroughly. Group 1 bonded with GC Fuji Ortho after getting etched with 37% phosphoric acid/60 seconds. Group 2 was contaminated with saliva. Group 3 was conditioned with Fuji dentin condition. Group 4 unetched, uncontaminated, and Group 5 was treated with rely bond composite resin after getting etched with 37% phosphoric acid. The shear bond strength was tested using Instron universal testing machine. The force at which bond failed was recorded on XY recorder as shear/peel bond strength of the material used for bonding. The reading obtained were statistically analyzed.

RESULT

Rely bond showed highest bond strength of 64.70 N (Newtons). The next highest value was that of Group 1. The lowest bond strength in the Group 4.

CONCLUSION

GC Fuji Ortho can be used as a bonding agent on etched enamel. Unetched, uncontaminated enamel surfaces were inadequate for bracket bonding.

CLINICAL SIGNIFICANCE

Potential benefits of glass ionomer cements can be utilized in orthodontic bonding.

Preventing and treating white-spot lesions associated with orthodontic treatment: a survey of general dentists and orthodontists

BACKGROUND

The authors investigated the prevention and treatment of white-spot lesions (WSLs) during and after orthodontic therapy from the perspective of general dentists and orthodontists.

METHODS

The authors administered a cross-sectional survey to general dentists (n = 191) and orthodontists (n = 305) in Virginia, Maryland and North Carolina.

RESULTS

Sixty-nine percent of general dentists and 76 percent of orthodontists recommended in-office fluoride treatment for patients with severe WSLs immediately after orthodontic treatment. Sixty-nine percent of general dentists reported that they had treated WSLs during the previous year, and 37 percent of orthodontists reported that they had removed braces because of patients' poor oral hygiene. Sixty percent of orthodontists referred patients with WSLs to general dentists for treatment. Eighty-five percent of orthodontists responded that they encouraged patients to use a fluoride rinse as a preventive measure. More than one-third of general dentists indicated that severe WSLs after orthodontic treatment could have a negative effect on their perception of the treating orthodontist.

CONCLUSIONS

WSLs are a common complication of orthodontic treatment and their presence can result in a negative perception of the treating orthodontist by the patient's general dentist. Clinical implications. General dentists and orthodontists should work together to prevent the development of WSLs in their patients. Treatment with fluoride supplements and motivating and training patients to practice good oral hygiene will help achieve this goal. Treatment after debonding should include the topical application of low concentrations of fluoride.

In vitro caries-preventive effect of fluoridated orthodontic resins against cariogenic challenge stimulation

AIM

The aim of the present study was to evaluate the in vitro caries preventive effect of fluoridated orthodontic resins under pH cycling with two types of acid demineralizing saliva.

MATERIALS AND METHODS

Brackets were bonded to 120 extracted human premolars, using Rely-a-bond (n = 40), Tru- Bond (n = 40) and Ortho-one (n = 40) orthodontic bonding agents. Each group of resin was divided into 2 subgroups (n = 20): immersion in remineralizing artificial saliva for 14 days and acid saliva with pH 4.3. After 14 days of pH cycling the caries preventive effect on the development of white spot lesion was evaluated considering the presence of inhibition zones to white spot lesions using two scores: 0 = absence and 1 = presence. Kruskal-Wallis ANOVA and Mann-Whitney U tests were used.

RESULTS

Formation of white spot lesions was observed only under pH cycling using acid saliva with pH 4.3; with Rely-a-bond and Tru-Bond being significantly more effective in preventing the appearance of white spot lesions effect than Ortho-one.

CONCLUSION

The acidity of the demineralizing solution influenced the formation of white spot lesions around orthodontic brackets under highly cariogenic conditions. Rely-a-bond and Tru-bond presented higher caries-preventive effect than Orthoone.

CLINICAL SIGNIFICANCE

The development of fluoride-containing materials cannot be regarded as a permanent means to control dental caries lesions, but a complement along with other preventive methods.

Effects of procedures of remineralization around orthodontics bracket bonded by self-etching primer on its shear bond strength

AIM

To evaluate the effect of the application of either fluoride varnish (FV) or amorphous calcium phosphate (ACP) as preventive method on shear bond strength (SBS) at the same time of their bonding in vitro using self-etching primer (SEP) as an agent for enamel pre-treatment FV.

MATERIALS AND METHODS

SIXTY HUMAN BICUSPIDS WERE RANDOMLY DIVIDED INTO FIVE GROUPS: G1 was rubbed by SEP for 5 s, G2 for 5 s by SEP and ACP, G3 for 10 s by SEP and ACP, G4 for 5 s by SEP and FV, and G5 for 10 s by SEP and FV. Stainless steel metal brackets were bonded. A Zwick/Roell Z020 Universal Testing Machine (Zwick GmbH and Co, Germany) with a 500 N load cell was used to test SBS. SBS values were analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc tests (P≤0.05). Differences in adhesive remnant index (ARI) values between groups were calculated.

RESULTS

The mean SBS values were 10.00±4.48 MPa, 5.71±4.3 MPa, 7.47±4.44 MPa, 4.4±2.39 MPa, and 3.98±0.83 MPa for groups 1-5, respectively. Significant differences in SBS values between all groups were found. The mean SBS values of groups 2, 4, and 5 were significantly lower than that of the G1. No significant difference was found between G3 and G1. Significant difference in ARI between the groups was found (P<0.001) and G1 had a significantly higher ARI.

CONCLUSION

The results suggested that the application of ACP at the same time of using SEP for 10 s has no effect on SBS.

In vitro evaluation of the effects of a fluoride-releasing composite on enamel demineralization around brackets

OBJECTIVES

The aim of this in vitro study was to evaluate the effectiveness of a fluoride-releasing bonding agent in inhibiting enamel demineralization around orthodontic brackets after the exposure to a demineralizing solution.

MATERIALS AND METHODS

Twenty-six extracted upper molars were bonded with two different composites: Transbond XT (TXT) and Transbond Plus (TPlus), fluoride-releasing (both 3M Unitek, Monrovia, CA, USA). The samples were exposed to an acid lactic solution for three days and then subjected to Metallographic Optical Microscope (MOM) and Scanning Electron Microscope/Energy Dispersive X-Ray (SEM/EDX) analyses. Enamel surface was examined in different areas: un-treated, etched and primer-painted, un-treated area with no acid exposure, central area with bracket bonded. The maximum demineralization depths and the fluoride content at 100, 200 and 300 μm depth were evaluated.

RESULTS

MOM analysis showed statistically significant (p<0.001) differences in demineralization depth for TPlus group compared to TXT group with lower values for the first one. EDX analysis confirmed the presence of fluoride in TPlus group.

CONCLUSIONS

The fluoride content of TPlus appeared able to weakly reduce the enamel demineralization.

Effects of bonding materials on the mechanical properties of enamel around orthodontic brackets

OBJECTIVE

To determine if the enamel around orthodontic brackets is significantly altered after demineralization followed by application of adhesives with and without fluoride-releasing ability.

MATERIALS AND METHODS

One hundred eight noncarious human premolars were divided into six groups of 18 each and exposed to a demineralization solution. Stainless steel brackets were bonded using two conventional composite resin etch-and-rinse systems, three self-etching primer (SEP) composite resin systems, and one resin-modified glass ionomer cement (RMGIC) system. One conventional and one SEP composite resin adhesive did not have fluoride-releasing ability, which was claimed for the other four adhesives. The elastic modulus and hardness of the enamel were determined with a nanoindenter at 10 equidistant depths ranging from 1-46 µm and at four regions: control (not exposed) enamel surface, under the adhesive, and at 50 µm and 100 µm from the bracket edges. Using the Kruskal-Wallis and Mann-Whitney U-tests (P < .0125 for statistical significance), these properties were compared at different regions.

RESULTS

The same behavior was observed for values of elastic modulus and hardness. Significant differences were found within approximately 21 µm of the enamel surface for etching with 35% phosphoric acid or priming with SEP, but only minimal changes occurred for the SEP adhesive. Increases in near-surface elastic modulus and hardness of enamel were found with the SEP adhesive and RMGIC with fluoride-releasing ability.

CONCLUSIONS

Clinical use of the fluoride-releasing adhesives investigated may prevent demineralization of enamel around brackets during orthodontic treatment.

Evaluation of the effects of the bonding agent on acid-etched human enamel demineralization: in situ study

This in situ study evaluated the influence of the bonding agent on demineralization of acid-etched human enamel. Enamel blocks obtained from 20 human molars (four blocks per tooth) were divided into five groups. For the control groups, healthy control (HC, no treatment) and acid-etched control (EC, etching with 35 per cent phosphoric acid for 20 seconds), the specimens were obtained by sectioning in half, one block from each tooth. For the experimental groups, experimental etched group (EE), experimental Concise™ group (CE), and experimental Transbond™ group (TE), all specimens were etched with 35 per cent phosphoric acid for 20 seconds (EE) and treated with Concise™ enamel bond (CE) and Transbond™ XT primer (TE). Specimens from the experimental groups were fixed at intra-oral appliances wore by 10 volunteers and exposed to oral environment. After 28 days, the specimens were sectioned in the mesial-distal direction and the enamel cross-sectional Knoop hardness number (KHN, 50 g, 15 seconds) was measured at the cervical and occlusal regions at 25, 50, and 75 μm from the enamel surfaces. Data were analysed by analysis of variance (ANOVA) and Tukey honestly significantly different test for multiple comparisons (α = 0.05). Enamel KHN (P < 0.05) was recovered only in the Concise-treated group (CE; P < 0.05). When considering depth measurements, KHN results were 25 > 50 > 75 μm (P < 0.05). None of the groups exposed to the intra-oral environment for 28 days have recovered completely the enamel microhardness, but the order of improvement was better in the CE group than the TE group, the latter being only slightly better than the EE group.

Bracket bond strength and cariostatic potential of an experimental resin adhesive system containing Portland cement

OBJECTIVE

To determine if a new experimental resin-based material containing Portland cement (PC) can help prevent enamel caries while providing adequate shear bond strength (SBS).

MATERIALS AND METHODS

Brackets were bonded to human premolars with experimental resin-based adhesive pastes composed of three weight rations of resin and PC powder (PC 30, 7:3; PC 50, 5:5; PC 70, 3:7; n  =  7). Self-etching primer (SEP) adhesive (Transbond Plus) and resin-modified glass ionomer cement (RMGIC) adhesive (Fuji Ortho FC Automix) were used for comparison. All of the bonded teeth were subjected to alternating immersion in demineralizing (pH 4.55) and remineralizing (pH 6.8) solutions for 14 days. The SBS for each sample was examined, and the Adhesive Remnant Index (ARI) score was calculated. The hardness and elastic modulus of the enamel were determined by a nanoindenter at 20 equidistant depths from the external surface at 100 µm from the bracket edge. Data were compared by one-way analysis of variance and a chi-square test.

RESULTS

PC 50 and PC 70 showed significantly greater SBS than Fuji Ortho FC Automix, although Transbond Plus showed significantly greater SBS than other bonding systems. No significant difference in the ARI category was observed among the five groups. For specimens bonded with PC 50 and PC 70, the hardness and elastic modulus values in most locations were equivalent to those of Fuji Ortho FC Automix.

CONCLUSIONS

Experimental resin-based bonding material containing PC provides adequate SBS and a caries-preventive effect equivalent to that of the RMGIC adhesive system.

In vivo remineralising effect of GC tooth mousse on early dental enamel lesions: SEM analysis

OBJECTIVE

Casein phosphopeptide-amorphous calcium phosphate nanocomplexes (CPP-ACP) exhibit anticariogenic potential in laboratory, animal and human experiments. The remineralising potential of synthetic CPPs on early enamel caries was investigated.

DESIGN

In vivo study.

SETTING

University of Naples 'Federico II', School of Dentistry, Department of Paediatric Dentistry, 2010, Italy.

PARTICIPANTS

40 volunteers (age range 10-16 years) were recruited and divided in two groups of 20 (Group A and B).

INTERVENTIONS

In Group A subjects two demineralised enamel specimens were placed on the buccal surfaces of the first molars and subjects were instructed to apply a commercial product containing CPPs (GC Tooth Mousse) only on the right-sided specimen and a placebo mousse on the left, for 1 month. In Group B subjects two enamel specimens were similarly placed into the mouth and used as controls.

RESULTS

SEM analysis revealed a diffuse and homogeneous mineral coating, reducing the surface alterations only in the demineralised specimens treated with synthetic CPPs into the mouth.

CONCLUSIONS

Results demonstrate that CPPs are able to promote remineralisation of early enamel lesions.

Effects of incorporation of nano-fluorapatite or nano-fluorohydroxyapatite on a resin-modified glass ionomer cement

This study aimed to investigate the fluoride release properties and the effect on bond strength of two experimental adhesive cements. Synthesized particles of nano-fluorapatite (nano-FA) or nano-fluorohydroxyapatite (nano-FHA) were incorporated into a resin-modified glass ionomer cement (Fuji Ortho LC) and characterized using X-ray diffraction and scanning electron microscopy. Blocks with six different concentrations of nano-FA or nano-FHA were manufactured and their fluoride release properties evaluated by ultraviolet spectrophotometry. The unaltered glass ionomer cement Fuji Ortho LC (GC, control) and the two experimental cements with the highest fluoride release capacities (nano-FA+Fuji Ortho LC (GFA) and nano-FHA+Fuji Ortho LC (GFHA)) were used to bond composite blocks and orthodontic brackets to human enamel. After 24 h water storage all specimens were debonded, measuring the micro-tensile bond strength (μTBS) and the shear bond strength (SBS), respectively. The optimal concentration of added nano-FA and nano-FHA for maximum fluoride release was 25 wt.%, which nearly tripled fluoride release after 70 days compared with the control group. GC exhibited a significantly higher SBS than GFHA/GFA, with GFHA and GFA not differing significantly (P>0.05). The μTBS of GC and GFA were significantly higher than that of GFHA (P≤0.05). The results seem to indicate that the fluoride release properties of Fuji Ortho LC are improved by incorporating nano-FA or nano-FHA, simultaneously maintaining a clinically sufficient bond strength when nano-FA was added.

Force and amount of resin composite paste used in direct and indirect bonding

OBJECTIVE

To investigate the relationship between the forces applied by the operator and the amount of adhesive used in the direct and indirect bonding methods.

MATERIALS AND METHODS

A system for measuring the force applied by operator was used to test specimens prepared by 12 orthodontic specialists. To determine the proper amount of adhesive, metal brackets were bonded to transparent resin teeth using composite resin paste and different forces (100, 200, and 300 g); the area of the composite resin paste was then measured using image-analysis software. The mean forces applied in direct and indirect bonding were compared by Student's t-test.

RESULTS

Various values for force were obtained for the direct bonding (53-940 g) and indirect bonding (150-870 g) techniques. Although in all cases the area of composite resin paste after the application of constant force was greater than the area of the metal brackets, an insufficient amount of composite resin paste on the bracket base was observed with forces of 100 and 200 g.

CONCLUSIONS

A force of greater than 200 g might be preferable for obtaining a thin composite resin layer and for achieving sufficient spreading of the composite resin paste.

Treatment of post-orthodontic white spot lesions with casein phosphopeptide-stabilised amorphous calcium phosphate

This study aims to investigate the effect of topical applications of 10% casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on white spot lesions (WSL) detected after treatment with fixed orthodontic appliances. Sixty healthy adolescents with ≥1 clinically visible WSL at debonding were recruited and randomly allocated to a randomised controlled trial with two parallel groups. The intervention group was instructed to topically apply a CPP-ACP -containing agent (Tooth Mousse, GC Europe) once daily and the subjects of the control group brushed their teeth with standard fluoride toothpaste. The intervention period was 4 weeks and the endpoints were quantitative light-induced fluorescence (QLF) on buccal surfaces of the upper incisors, cuspids and first premolars and visual scoring from digital photos. The attrition rate was 15%, mostly due to technical errors, and 327 lesions were included in the final evaluation. A statistically significant (p < 0.05) regression of the WSL was disclosed in both study groups compared to baseline, but there was no difference between the groups. The mean area of the lesions decreased by 58% in the CPP-ACP group and 26% in the fluoride group (p = 0.06). The QLF findings were largely reflected by the clinical scores. No side effects were reported. Topical treatment of white spot lesions after debonding of orthodontic appliances with a casein phosphopeptide-stabilised amorphous calcium phosphate agent resulted in significantly reduced fluorescence and a reduced area of the lesions after 4 weeks as assessed by QLF. The improvement was however not superior to the "natural" regression following daily use of fluoride toothpaste.

Preventive effect of fluoridated orthodontic resins subjected to high cariogenic challenges

The aim of the present study was to evaluate the in vitro caries preventive effect of fluoridated orthodontic resins under pH cycling with two types of acid demineralizing saliva. Brackets were bonded to 60 bovine incisors, using either Transbond Plus Color Change (n=30) or Orthodontic Fill Magic (n=30) orthodontic resins. Each group of resin was divided into 3 subgroups (n=10): immersion in remineralizing artificial saliva for 14 days, pH cycling with high cariogenic challenge in acid saliva with pH 5.5, and acid saliva with pH 4.5. After 14 days of pH cycling, the caries preventive effect on the development of white spot lesion was evaluated considering the presence of inhibition zones to white spot lesions using two scores: 0= absence and 1= presence. Kruskal Wallis and Mann-Whitney tests (a=0.05) were used. Formation of white spot lesions was observed only under pH cycling using acid saliva with pH 4.5; with Transbond Plus Color Change being significantly more effective (p<0.05) in preventing the appearance of white spot lesions effect than Orthodontic Fill Magic. The acidity of the demineralizing solution influenced the formation of white spot lesions around orthodontic brackets under highly cariogenic conditions. Transbond Plus Color Change resin presented higher caries preventive effect than Orthodontic Fill Magic.

Effects of CPP-ACP paste on the shear bond strength of orthodontic brackets

OBJECTIVE

To evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on shear bond strength and debonding failure modes of orthodontic brackets.

MATERIALS AND METHODS

Freshly extracted premolars were randomly divided into four groups (n =18) as follows: in groups 1 and 3, the enamel was treated with a solution of CPP-ACP dissolved in artificial saliva; groups 2 and 4 served as controls, and the enamel was treated with artificial saliva. After conventional acid etching, in groups 1 and 2, brackets were bonded using a light-cured bonding system (Blugloo); while in groups 3 and 4, brackets were bonded using a conventional bonding system (Unite Bonding Adhesive). Bonded specimens were subjected to thermal cycling for 1000 cycles before debonding procedures. After debonding, teeth and brackets were examined under a stereomicroscope at 10x magnification to determine whether any adhesive remained, in accordance with the adhesive remnant index. The acid-etched enamel surfaces were also observed using scanning electron microscopy after treatment with and without CPP-ACP paste.

RESULTS

The shear bond strengths of group 1 were significantly higher than those seen in group 2 (P < .01). There was no significant difference in the shear bond strengths of groups 3 and 4 (P > .05). Scanning electron microscopic observation showed that the pretreated enamel surface was rougher than that of the control surface after acid etching.

CONCLUSION

The use of CPP-ACP can be considered as an alternative prophylactic application in orthodontic practice since it did not compromise bracket bond strength.

In vitro evaluation of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) effect on stripped enamel surfaces. A SEM investigation

OBJECTIVES

Interproximal enamel reduction (orthodontic stripping) leaves surface-roughness that encourages plaque adherence. Sealants and fluoride products have been recommended to avoid possible detrimental effects. The objective of this study was to qualitatively evaluate, by means of scanning electron microscopy (SEM), the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on stripped enamel morphology after exposure to an acid solution.

METHODS

15 extracted lower incisors underwent stripping with metal strips (Horico, 80 microm) by 1 operator. Mesial and distal surfaces were sectioned into 30 samples (22 stripped; 8 unstripped) and assigned to 2 groups: Group A (2 stripped; 2 unstripped) served as control; in Group B (20 stripped; 6 unstripped) tooth mousse containing CPP-ACP was tested. For 8 days, teeth were placed in acid lactic solution for 2h three times a day (from 9a.m. to 9p.m.) with 2h water preservation in between. After each demineralizing bath, samples of group B were coated with CPP-ACP for 5 min before immersion into water.

RESULTS

In Group A, stripped samples exhibited greater demineralization compared to unstripped. In Group B, CPP-ACP reduced enamel dissolution on both intact and abraded samples compared to Group A.

CONCLUSIONS

Injuries to enamel morphology caused by stripping might predispose to greater demineralization in the event of exposure to acid environment. Topical applications of CPP-ACP could be effective in promoting enamel remineralization after interdental stripping.

Bond Strength of Amorphous Calcium Phosphate–Containing Orthodontic Composite Used as a Lingual Retainer Adhesive

Objective: To evaluate the shear bond strength and fracture mode difference between amorphous calcium phosphate (ACP)–containing adhesive and conventional resin-based composite material used as an orthodontic lingual retainer adhesive.

Materials and Methods: Forty crowns of extracted lower human incisors were mounted in acrylic resin, leaving the buccal surface of the crowns parallel to the base of the molds. The teeth were randomly divided into two groups: experimental and control, containing 20 teeth each. Conventional lingual retainer composite (Transbond-LR, 3M-Unitek) and ACP-containing orthodontic adhesive (Aegis-Ortho) were applied to the teeth surface by packing the material into the cylindrical plastic matrices with a 2.34-mm internal diameter and a 3-mm height (Ultradent) to simulate the lingual retainer bonding. For shear bond testing, the specimens were mounted in a universal testing machine, and an apparatus (Ultradent) attached to a compression load cell was applied to each specimen until failure occurred. The shear bond data were analyzed using Student's t-test. Fracture modes were analyzed by χ2 test.

Results: The statistical test showed that the bond strengths of group 1 (control Transbond-LR, mean: 24.77 ± 9.25 MPa) and group 2 (ACP-containing adhesive, mean: 8.49 ± 2.53 MPa) were significantly different from each other. In general, a greater percentage of the fractures were adhesive at the tooth-composite interface (60% in group 1 and 55% in group 2), and no statistically significant difference was found between groups.

Conclusion: The ACP-containing Aegis-Ortho adhesive resulted in a significant decrease in bond strength to the etched enamel surface.