Preparation and characterization of NaF/Chitosan supramolecular complex and their effects on prevention of enamel demineralization.

Fluoridated mouthrinse is indicated for individuals with high risk of caries. Chitosan (Chit) exhibits antibacterial properties, but little is known about its effects on enamel when combined with sodium fluoride (NaF) to form NaF/Chit supramolecular complexes. In our study, NaF/Chit supramolecular complexes structured as microparticles were synthetized and characterized, and their effects on human enamel were evaluated after cariogenic challenge simulating the daily mouthrinse use. Initially, NaF/Chit complex formation was investigated based on several titrations by measuring the zeta potential, electrical conductivity (κ), hydrodynamic diameter (Dh), viscosity (η) and heat flow (by isothermal titration calorimetry) against the molar ratio [NaF]/[Chitmonomer], which allowed us to identify the interactions between Chit-NaF with a stoichiometry of approximately 0.68. Spontaneous microparticle formation was observed. Samples of enamel blocks were prepared and divided into eight groups (n = 10/group): (i) 0.2% Chit; (ii) 0.2% NaF; (iii) 0.2% NaF/Chit suspension; (iv) 0.2% acetic acid; (v) 0.05% Chit; (vi) 0.05% NaF; (vii) 0.05% NaF/Chit suspension; and (viii) 0.05% acetic acid. Cariogenic challenge was performed in each sample by cycling in demineralization and remineralization solutions for 7 days. Before each demineralization cycle, the corresponding substances were passively applied daily for 90 s, even in groups with 0.02% concentration. After 7 days, samples were examined for Knoop hardness (KHN) measurements. The data were analyzed by repeated-measures ANOVA and Tukey tests (α = 0.05). The 0.2% NaF and 0.2% NaF/Chit groups showed higher KHNpost-challenge values than the other groups. The 0.2% NaF/Chit microparticle suspension reduced the enamel hardness loss after cariogenic challenge as effectively as the 0.2% NaF solution and demonstrated potential for use in a formulation with anti-caries effects.

Possible Relationship Between the Oral and Gut Microbiome, Caries Development, and Obesity in Children During the COVID-19 Pandemic.

The COVID-19 pandemic has brought health damage and socioeconomic disruptions, together with lifestyle disorders around the world. Children are one of the most commonly affected, mainly due to social isolation and changes in eating habits and physical activities. This way, the risk of weight gain and obesity is possibly enhanced, as well as poor oral hygiene conditions and early childhood caries (ECC) development during the lockdown. In children under 6 years of age, ECC is defined as carious lesions in one or more primary teeth, with or without cavitation. Importantly, alterations in the oral microbiome caused by changes in children lifestyles have much more than a local impact on oral tissues, interplaying with the gut microbiome and influencing systemic environments. Recent studies have been exploring the oral health conditions, eating habits, and weight gain in the childhood population during the COVID-19 pandemic; however, there is a lack of information concerning the association among oral and gut microbiome, dental caries, and obesity in the COVID-19 era. In this context, this review aimed at analyzing a possible relationship between the oral and gut microbiome, caries, and obesity in children during the COVID-19 pandemic.

Synthesis and characterization of TPP/chitosan nanoparticles: Colloidal mechanism of reaction and antifungal effect on C. albicans biofilm formation.

In the present study chitosan (Chit) nanoparticles were synthetized by the ionic gelation process, using tripolyphosphate (TPP) as crosslinking agent. The TPP/Chit nanoparticle formation was evaluated by titrations, measuring electrical conductivity (k), zeta potential (ZP), hydrodynamic diameter (Dh), viscosity (η) and heat by isothermal calorimetry (ITC). The antifungal effects were evaluated by C. albicans time-kill assays, inhibition of C. albicans initial adhesion and biofilm formation in comparison with nystatin and chitosan. Conductometric titration exhibited a typical precipitation profile, with an inflection at molar ratio of [TPP]/[Chitmon] ≈ 0.3, suggesting a 1:3.3 stoichiometry. The highest Dh, ZP and η values were shown at the beginning of titrations, due to the intramolecular repulsion between Chit-Chit. With addition of TPP, the values showed gradual reduction, with an intermediary transition at [TPP]/[Chitmon] ≈ 0.16, which was attributed to the partial breakdown of interchain crosslinking and formation of discrete charged aggregates. After this point, reaction should occur by neutralization of these assemblies, causing new reduction in values of Dh, ZP and η until [TPP]/[Chitmon] ≈ 0.3, when they reached their lowest values. ITC experiment also showed the occurrence of two bindings (K1 = 3.6 × 103 and K2 = 7.7 × 104), which were entropy driven. Biological results showed lower C. albicans viability for TPP/Chit over 24 h compared with chitosan and nystatin at MIC and 2 MIC. Moreover, TPP/Chit showed 25-50% inhibition of C. albicans adhesion and biofilm formation. The results showed that TPP/Chit nanoparticles reduced the initial adhesion and biofilm formation of C. albicans and demonstrated potential for use in a formulation for the treatment of oral candidiasis.

In vitro Effect of Erosive Challenge on Surface Microhardness of Orthodontic Composites

Objective: To evaluate in vitro the effect of erosive challenge and continuous immersion in cola drink on surface microhardness of orthodontic composites. Material and Methods: Forty samples of three composites (Transbond XT, Quick Cure and Ortho Cem) were prepared (4 x 2 mm) and distributed into 4 groups (n=10): erosive challenge, artificial saliva immersion (control 1), continuous cola immersion and artificial saliva immersion (control 2). Erosive challenge was performed 4 times per day (5 min) in cola drink for 2 h in artificial saliva for 7 days. Samples of continuous cola immersion group were soaked in cola drink for 5 weeks and the beverage was renewed every two days. Control samples were immersed in artificial saliva for 7 days (control 1) and 5 weeks (control 2). Vickers microhardness (VHN) measurements were performed before and after erosive challenge and continuous immersion. Data were evaluated by paired Student's T-test, ANOVA one-way and Tukey tests (α = 0.05). Results: After 7 days of erosive challenge, there was no statistical difference between VHN values before and after erosive challenge and artificial saliva immersion. However, after 5 weeks of cola drink and artificial saliva immersion, significant reduction in VHN values was observed for all composites when compared to baseline values, and specimens immersed in cola drink showed lower VHN compared to those immersed in saliva, regardless of composite composition. Conclusion: After 7 days of erosive challenge, there was no alteration in superficial VHN of orthodontic composites. However, after 5 weeks of immersion in cola drink, significant reduction of VHN values was observed for all composites.

Impact of malocclusion on affective/romantic relationships among young adults.

OBJECTIVE: To evaluate the extent to which different types of malocclusion influence the development of affective/romantic relationships among young adults of both sexes. MATERIALS AND METHODS: A cross-sectional study was conducted with 360 men and women ranging in age from 18 years to 25 years. Criteria for exclusion from the sample were the following: participants could not be married, visually impaired, or students of a higher education course in the area of health. In this study, images of young adult men and women in the same age range as that of the evaluators were used. These images were manipulated to create different types of malocclusion: diastema, open bite, crowding, gingival (or gummy) smile, little exposure of teeth. Six groups of images containing six images each were formed and consisted of two experimental images (digitally manipulated) and four control images. These images were provided to the participants, who evaluated them by means of a questionnaire and a visual analog scale. The Kruskal-Wallis, Mann-Whitney, chi-square, and Fisher exact tests were used for data analysis. RESULTS: All malocclusions had a negative impact on acceptance by the evaluators for the purposes of affective/romantic relationships, with crowding being the type of malocclusion that led to the highest level of rejection (P < .01). CONCLUSION: Malocclusions have a negative influence on the development of affective/romantic relationships among young adults. Individuals with good occlusion are seen in a more positive light, from the perspective of affective life.

Assessment of the effectiveness of mouthwashes in reducing cariogenic biofilm in orthodontic patients: a systematic review.

OBJECTIVES: The use of fixed orthodontic appliances makes it difficult to clean the teeth and accessories associated with it. For this reason, orthodontic patients have used oral antiseptics as coadjuvent means to reduce cariogenic plaque. The aim of this systematic review was to evaluate the effectiveness of oral antiseptics on the reduction of cariogenic plaque on orthodontic patients. DATA: This review has been registered at PROSPERO--international prospective register of systematic reviews under the number CRD42013006857. SOURCES: A systematic review of the literature was conducted in the following electronic databases: Scopus, PubMed, Web of Science, Medline, Embase and Cochrane, Grey literature and Clinical Trials, without limitations on the year of publication or language. Clinical studies in patients with fixed orthodontic appliances, who were making use of oral mouthwashes in order to reduce cariogenic plaque, were included. Articles with patients using systemic drugs, syndromic patients, those using mouthwashes for other purposes and/or using different cleaning techniques, and clinical cases were excluded. After selection by title and abstract, potentially eligible articles were read in full. The methodological quality and risk of biases of articles included were evaluated according to the characteristics of the study, measurements and statistical analyses of the study. The methodological quality was classified as high, moderate or low. STUDY SELECTION: The search identified 2716 articles, of which 15 met the inclusion criteria. Of these, 8 analyzed chlorhexidine-based mouthwashes, while in 1 article Cetylpyridinium was used; 1 analyzed the mouthwash containing sanguinaria; 1 the use of NaF; 2 articles the use of AmF/SnF2; 2 the use of Listerine(®), 1 also analyzed the association between mouthwashes with octenidine and with PVP-I. Of the articles analyzed, 11 were classified as having high and 4 as having moderate methodological quality. CONCLUSION: There is evidence of effectiveness of the use of oral mouthwashes in the control of cariogenic plaque in patients with fixed orthodontic appliances. The orthodontists may suggest the use of oral antiseptics in the oral hygiene of their patients as coadjuvent means to reduce cariogenic plaque. CLINICAL SIGNIFICANCE: Given current evidence, orthodontists may prescribe mouthwash as an auxiliary method in the control of cariogenic biofilm in orthodontic patients.

In vitro cytotoxicity of self-curing acrylic resins of different colors.

OBJECTIVE: The aim of this study was to assess the in vitro cytotoxicity of acrylic resins of different colors over time. METHODS: Specimens were divided into 4 groups (n = 6) according to the color of the acrylic resin (Orto Class, Clássico, Campinas, São Paulo, Brazil): Group 1, clear acrylic resin; Group 2, pink acrylic resin; Group 3, blue acrylic resin; and Group 4, green acrylic resin. All specimens were fabricated according to the mass manipulation technique and submitted to mechanical polishing protocol. The control was performed with an amalgam specimen (C+), a glass specimen (C-) and cell control (CC). Specimens were immersed in Minimum Eagle's Medium (MEM) and incubated for 24 h at 37ºC. The extracts from the experimental material were filtered and mixed with L929 fibroblast. Cytotoxicity was evaluated at four different times, 24, 48, 72 and 168 h. After contact, cells were incubated for 24 h and added to 100 µ of 0.01% neutral red dye. The cells were incubated for 3 h for pigment incorporation and fixed. Cells viability was determined by a spectroscopic (BioTek, Winooski, Vermont, USA) with a 492-nm wavelength λ=492 nm). RESULTS: There were no statistical differences between the experimental groups and the CC and C- groups. CONCLUSION: Clear, pink, blue and green self-curing acrylic resins fabricated by means of the mass manipulation technique and mechanically polished are not cytotoxic. Neither the pigment added to the self-curing acrylic resin nor the factor of time influenced the cytotoxicity of the material.

Anteroposterior and vertical changes in skeletal class II patients treated with modified Thurow appliance.

The aim of this study was to evaluate the post-treatment anteroposterior and vertical alterations in skeletal Class II malocclusion with different maxillary patterns in patients treated with modified Thurow appliance. Forty-five patients (22 girls and 23 boys) with skeletal Class II and angle SN.GoGn ≤ 35 and different maxillary patterns (n = 15), as follows: retrusive (SNA<80°), normal (SNA = 80°- 84°) or protrusive (SNA>84°) maxilla; mean age 9 years at pre-treatment (T1) and 9 years and 10 months at post-treatment (T2), were treated with modified Thurow cervical traction appliance, with expander screw and extraoral face bow with 10° to 20° fold in relation to the intraoral arch. Force of 500 gf was applied and use for 12 to 14 h/day, with fortnightly adjustments. Analysis of variance ANOVA followed by post-hoc Tukey and Kruskal-Wallis test, followed by Mann-Whitney were used (α = 5%). In changes obtained from stage T1 to T2, no statistically significant differences were found among the groups Protrusive, normal and retrusive maxilla for the variables SNB, SN.GoGn, 1.NA, overjet, overbite and Class II discrepancy (right and left) (p>0.05). Angular measurements SNA and ANB in the protrusive maxilla group were significantly greater than in the normal and retrusive maxilla groups (p<0.01). However, in the normal maxilla group these values did not differ significantly from those of the retrusive maxilla group (p>0.05). Within the limits of this study, it may be concluded that the modified Thurow cervical traction appliance was efficient for the correction of skeletal Class II irrespective of the maxillary pattern. The mandible had no significant rotation during treatment.

Influence of degree of conversion on the biocompatibility of different composites in vivo.

PURPOSE: To evaluate the relationship between biocompatibility and degree of monomer conversion of composites used to bond brackets to enamel, porcelain, resin, or metal surfaces at different time intervals. MATERIALS AND METHODS: Twenty-four male Wistar rats were used, divided into 4 groups (n = 6) as follows: group C (control, polyethylene), group TCC (Transbond Color Change), group QC (Quick-Cure), and group EB (Eagle Bond). These substances were inserted into subcutaneous tissue. The events of inflammatory infiltrate, edema, necrosis, granulation tissue, multinuclear giant cells, young fibroblasts, and collagen formation were analyzed. The degree of conversion was evaluated by the Fourier method using infrared spectroscopy. Biocompatibility and degree of conversion were statistically analyzed using the Kruskal-Wallis and Dunn tests, and ANOVA and Tukey's test, respectively (p < 0.05). RESULTS: The composites caused a small amount of inflammatory infiltrate, edema, and granulation tissue at all experimental time intervals, showing a gradual reduction over time (p > 0.05). Group TCC showed the highest amount of fibroblasts and EB the smallest at the time interval of 15 days (p = 0.035). Group TCC showed the highest amount of collagen fibers and EB the smallest throughout the experiment; there was a significant difference in terms of collagen fibers between groups QC and EB, which differed from the control at 7 days (p = 0.006), and between groups EB and TCC (p = 0.018) at 30 days. Monomer conversion ranged from 64.1% in group EB at 7 days to 85.3% in group TCC at 30 days. CONCLUSION: Transbond Color Change composite showed a higher degree of conversion and a better healing process compared to Eagle Bond composite at 15 and 30 days. Quick-cure composite demonstrated a better degree of conversion and healing process than that of Eagle Bond, but this was not statistically significantly different.

In vitro effect of S. mutans biofilm on fluoride/MDPB-containing adhesive system bonded to caries-affected primary dentin.

PURPOSE: To evaluate the effect of storage in S. mutans culture or water on the durability of fluoride and MDPB-containing adhesive system on artificial caries-affected primary dentin. METHODS: Dentin flat surfaces of primary molars were submitted to artificial caries development using S. mutans biofilm. CAPD cavities were restored with Adper Scotchbond Multi-Purpose (SBM) or Clearfil Protect Bond (CPB) and they were serially sectioned into sticks (1 mm2 cross-sectional area) and stored in S. mutans biofilm for 3 days, in deionized water for 3 months and afterwards subjected to microtensile bond strength (µTBS) test. A control group was submitted to immediate TBS testing. Two-way ANOVA and Tukey's tests were used. Failure sites were observed by SEM and classified as cohesive (dentin or resin) and adhesive failures. RESULTS: The control group showed the highest µTBS values (MPa) for both SBM (25.2 ± 8.5) and CPB (15.6 ± 6.1) adhesive systems. A significant decrease in µTBS values after S. mutans biofilm and water storage was observed for SBM (18.7 ± 5.7 and 17.4 ± 4.1, respectively) and CPB (13.9 ± 5.2 and 13.7 ± 4.8, respectively), but no difference was found between them. The highest percentage of adhesive failure was observed for all groups. However, cohesive failure in dentin was observed in a higher percentage for SBM than CP.

Mechanical evaluation of quad-helix appliance made of low-nickel stainless steel wire.

OBJECTIVE: The objective of this study was to test the hypothesis that there is no difference between stainless steel and low-nickel stainless steel wires as regards mechanical behavior. Force, resilience, and elastic modulus produced by Quad-helix appliances made of 0.032-inch and 0.036-inch wires were evaluated. METHODS: Sixty Quad-helix appliances were made, thirty for each type of alloy, being fifteen for each wire thickness, 0.032-in and 0.036-in. All the archwires were submitted to mechanical compression test using an EMIC DL-10000 machine simulating activations of 4, 6, 9, and 12 mm. Analysis of variance (ANOVA) with multiple comparisons and Tukey's test were used (p < 0.05) to assess force, resilience, and elastic modulus. RESULTS: Statistically significant difference in the forces generated, resilience and elastic modulus were found between the 0.032-in and 0.036-in thicknesses (p < 0.05). CONCLUSIONS: Appliances made of low-nickel stainless steel alloy had force, resilience, and elastic modulus similar to those made of stainless steel alloy.

Maxillary incisor retraction: evaluation of different mechanisms.

OBJECTIVE: To mechanically evaluate different systems used for incisors retraction. METHODS: Three different methods for incisors retraction using 0.019 x 0.025-in stainless steel wire were evaluated. The samples were divided into three groups: Group A (retraction arch with 7-mm high vertical hooks); Group G3 (elastic chain attached to the mini-implant and to the 3-mm stainless steel hook welded to the retraction arch); Group G6 (elastic chain attached to the mini-implant and to the 6-mm stainless steel hook welded to the retraction arch). A dental mannequin was used for evaluation in order to simulate the desired movements when the device was exposed to a heat source. The analysis of variance (ANOVA) and the Tukey test were used (p < 0.05). RESULTS: The results demonstrated that Groups G3 and G6 exhibited less extrusion and less incisor inclination during the retraction phase (p < 0.05). With regard to incisor extrusion, statistically significant differences were observed between Groups A and G3, and between Groups A and G6 (p < 0.05). Regarding incisor inclination, statistically significant differences were observed between the three evaluated systems (p < 0.05). CONCLUSIONS: Arches with 6-mm vertical hooks allow the force to be applied on the center of resistance of the incisors, thus improving mechanical control, when compared with the other two systems.

Miniscrew-supported coil spring for molar uprighting: description.

INTRODUCTION: Since the beginning of miniscrews as orthodontic anchorage, many applications have been described in the literature. Among these, one is the uprighting of mesially inclined molars. In regard to the mechanical aspects, however, there is little information about the application of orthodontic forces using such devices. OBJECTIVE: The objective of this study was to describe a miniscrew supported spring for uprighting of mesially inclined molars. With this device, one can achieve the correct use of orthodontic biomechanics, thus favoring more predictable tooth movements and preventing unwanted movements from occurring.

Cross sectional: perception of children from public and private schools regarding the esthetic impact of different types of face masks.

PURPOSE: The purpose was to evaluate the esthetic perception among children from public and private schools regarding the use of different types of face masks. METHODS: Six different types of orthopedic face masks made from images of the same patient were evaluated. Initially, the images were standardized with the help of Adobe Photoshop software. The variable considered was type of mask: (A) Delaire with facebow; (B) Petit; (C) Delaire; (D)Turley; (E) Hickham; and (F) Sky Hook. The images were printed on photographic paper and incorporated into a specific personalized questionnaire that was distributed to 7- to 10-year-olds attending public and private schools (n=120). The data obtained were compared via chi-square, Fisher's exact tests, Mann-Whitney and Spearman's tests. RESULTS: The proportion of participants who chose image A as the best was significantly higher (P<.05) compared to the other masks. Images B and F were chosen as the worst, without a significant difference between them (P>.05). The mean scores between groups were not significantly correlated between private vs public schoolchildren (r=0.32) and between boys and girls (r=0.41). CONCLUSIONS: Delaire face mask with facebow was chosen as the most attractive, and the Petit and Sky Hook face masks were voted the least attractive.

Colonization of Streptococcus mutans on esthetic brackets: self-ligating vs conventional.

INTRODUCTION: Self-ligating orthodontic brackets rely on clips, rather than ligatures, to hold the archwire in place. It is unknown whether replacing ligatures with clips affects the adherence of Streptococcus mutans. The aim of this research was to evaluate whether self-ligating brackets have an advantage over conventional brackets as determined by the adherence of S mutans. METHODS: The sample consisted of 50 esthetic brackets, divided into 3 experimental groups and 2 control groups of 10 brackets each. Two experimental groups were active self-ligating brackets (QuicKlear; Forestadent, Pforzheim, Germany; and In-Ovation C; Dentsply GAC, Bohemia, NY); the other was a passive self-ligating bracket (Damon 3; Ormco, Glendora, Calif). The 2 control groups were conventional brackets (Mystique; Dentsply GAC; and Clarity; 3M Unitek, Monrovia, Calif). The brackets were randomly bonded to the canines, first and second premolars, and first and second molars in the mandibular left hemiarch of 10 male participants. Biofilm was collected from the tooth surfaces before bonding and from the brackets on day 21 and placed in Petri dishes containing Mitis salivarius agar. The brackets were removed on day 28 and examined by using scanning electron microscopy. Statistical analysis, analysis of variance, and the Tukey correction with a P value of 0.05 were used. RESULTS: The greatest numbers of colonies were found in an active self-ligating bracket group (In-Ovation C), and the fewest colonies were in a conventional bracket group (Clarity). The largest colonies formed on active self-ligating brackets. In the slot, the greatest formation was in a control group (Mystique). CONCLUSIONS: Self-ligating esthetic brackets do not promote greater or lesser S mutans colonization when compared with conventional brackets. Differences were found to be related to the material composition of the bracket.

Influence of low-intensity laser therapy on the stability of orthodontic mini-implants: a study in rabbits.

OBJECTIVE: The objective of this study was to assess stability of different orthodontic mini-implants in the tibia of rabbits after low-intensity laser therapy. MATERIAL AND METHODS: Thirty-two mini-implants were assessed, 16 were self-threading (Titanium Fix) and 16 self-perforating (INP). These were inserted into the tibia of rabbits and immediately loaded with a horizontal force of 200g uniting 2 mini-implants in each tibia. Then they were submitted to low-intensity laser therapy for 21 days. Sixteen male New Zealand breed rabbits were used, and divided into 2 groups of 8 animals each as follows: Groups INP and TF. In both groups, mini-implants were submitted to low-intensity laser therapy (right tibia) and their respective controls (left tibia) did not undergo laser therapy. After the animals were killed, blocks of bone tissue containing the mini-implants were removed so as to perform mechanical pull-out tests. RESULTS: There was a statistically significant difference only between Group TF submitted to laser and all the other groups (P < .05). CONCLUSIONS: Low-intensity laser was capable of increasing stability of self-threading orthodontic mini-implants.

Evaluation of the cytotoxicity of elastomeric ligatures after sterilisation with 0.25% peracetic acid.

INTRODUCTION: Sterilisation using peracetic acid (PAA) has been advocated for orthodontic elastic bands. However, cane-loaded elastomeric ligatures can also become contaminated during processing, packaging, and manipulation before placement in the oral cavity and are therefore susceptible, and possible causes, of cross-contamination. AIM: To test the hypothesis that 0.25% peracetic acid (PAA), following the sterilisation of elastomers, influences the cytotoxicity of elastomeric ligatures on L929 cell lines. MATERIALS AND METHODS: Four hundred and eighty silver elastomeric ligatures were divided into 4 groups of 120 ligatures to produce, Group TP (latex natural, bulk pack, TP Orthodontics), Group M1 (Polyurethane, bulk pack, Morelli), Group M2 (Polyurethane, cane-loaded, Morelli) and Group U (Polyurethane, cane-loaded, Uniden). Of the 120 ligatures in each group, 100 were sterilised in 0.25% PAA at time intervals (N = 20) of 1 hour, 2 hours, 3 hours, 4 hours and 5 hours. The 20 remaining elastomeric ligatures in each group were not sterilised and served as controls. Cytotoxicity was assessed using L929 cell lines and a dye-uptake method. Analysis of variance (ANOVA), followed by the Tukey post hoc test (p < 0.05) determined statistical relevance. RESULTS: There was a significant difference between TP, Morelli and Uniden elastomerics (p < 0.05), but no difference between the two types of Morelli elastomerics at the 1 hour time interval. In addition, there was a significant difference between Group CC and the other groups assessed, except between Groups CC and TP at the 1 hour time interval. The non-sterilised elastomeric ligatures showed similar cell viability to that observed after 1 hour of standard sterilisation. CONCLUSION: PAA did not significantly influence the cytotoxicity of elastomeric ligatures after a sterilisation time of 1 hour and is therefore recommended for clinical use.

Mechanical and biological properties of acrylic resins manipulated and polished by different methods.

This study evaluated the influence of the manipulation technique and polishing method on the flexural strength and cytotoxicity of acrylic resins. Two manipulation techniques and three polishing methods were used in the fabrication of acrylic plates that were divided into 6 groups (n=10). Groups MM, MC and MW: mass technique with mechanical polishing, chemical polishing and without polishing, respectively; and Groups SM, SC and SW: Saturation technique with mechanical polishing, chemical polishing and without polishing, respectively). Flexural strength was tested in a universal testing machine and the cytotoxicity assay used cell cultures (L-929) for periods of 24 h to 168 h. Flexural strength and cytotoxicity data were assessed using two-way and three-way ANOVA, respectively (α=0.05), followed by post hoc Bonferroni test for multiple comparisons. The effect of combinations of manipulation techniques and polishing methods on flexural strength showed significant differences only between Group SC and Groups MW, MM and MC (p<0.01). Cell viability ranged from 51% (3.9%) to 87,6% (3.2) in the 24-h time interval, and from 87.8% (5.0) to 95.7% (3.1%) in the 168-h time interval. With the increase of cell viability, from the third day (72 h), there was no significant difference among the groups, except between MM and SC (p<0.01) at 72 h. In conclusion, the manipulation technique and polishing method had more influence on the cytotoxicity than on flexural strength.

Effect of 10% papain gel on enamel deproteinization before bonding procedure.

OBJECTIVE: To test the null hypothesis that enamel deproteinization with 10% papain gel does not increase the shear bond strength of orthodontic brackets bonded with resin-modified glass ionomer cement (RMGIC). MATERIALS AND METHODS: One hundred and twenty bovine incisors were used and divided into eight groups: 1) Transbond XT according to the manufacturer's recommendations, 2) Transbond XT deproteinized with 10% papain gel, 3) RMGIC without enamel deproteinization and without etching, 4) RMGIC without enamel etching and with deproteinization with 10% papain gel, 5) RMGIC deproteinized with 10% papain gel and etched with polyacrylic acid, 6) RMGIC deproteinized with 10% papain gel and etched with phosphoric acid, 7) RMGIC deproteinized with 2.5% sodium hypochlorite, and 8) RMGIC etched with polyacrylic acid. After bonding, the mechanical tests were performed in a Universal mechanical test machine. The values obtained were submitted to an analysis of variance and afterward to the Tukey test (P < .05). RESULTS: It was demonstrated that group 2 presented the highest shear bond strength value, and this differed statistically from the others; group 3 presented the lowest value and showed no differences from groups 4, 5, 7, and 8. Regarding the Adhesive Remnant Index, groups 2 and 6 presented the best results and groups 3 and 8 the worst. It could be concluded that enamel deproteinization with 10% papain gel increases the shear bond strength, irrespective of the etching agent. CONCLUSIONS: The hypothesis is rejected. Papain gel was shown to be a new ally in the orthodontic clinic.