Embryotoxicity and teratogenesis of orthodontic acrylic resin in zebrafish.

Objectives: This study investigated the in vivo embryotoxicity, teratogenic potential, and additional effects of orthodontic acrylic resin as well as its components, utilizing zebrafish as a model organism. The research focused on morphological, cardiac, behavioral, and cognitive evaluations that were performed on embryos and larval-stage animals subjected to chronic exposure. Materials and methods: Embryo and larval-stage zebrafish were categorized into five experimental groups, which were further subdivided into five subgroups. These subgroups included three specific doses for each tested substance, a control with the vehicle (0.1 % dimethyl sulfoxide in water), and an absolute control (water). Assessments were performed on day 5 post-fertilization, which included morphological, cardiac, behavioral, and cognitive evaluations. All experiments had a sample size of ten animals and were performed in triplicate. Survival and hatching rates were analyzed using the Kaplan-Meier test, while other measurements were assessed using one-way analysis of variance (ANOVA), followed by the Tukey post hoc test. Results: Statistically significant differences were observed between the control and treatment groups across all the tested substances for heart rate, cognitive responsiveness, and cellular apoptosis. However, survival, hatching rate, and other parameters exhibited no significant variation, except for the highest dose in the dibutyl phthalate group, which demonstrated a notable difference in survival. Conclusions: Chronic exposure to acrylic resin and its components may be associated with decreased cognitive ability and cardiac rhythm, as well as an increase in the level of cellular apoptosis in zebrafish.

Dimensional and morphologic characteristics of unilateral impacted maxillary central incisors.

INTRODUCTION: This cross-sectional study aimed to investigate the crown and root characteristics of impacted central incisors compared with spontaneously erupted contralateral incisors and the influence of etiologic and local factors on their dimensions. METHODS: Forty-five patients (22 boys, 23 girls) who underwent orthodontic treatment for unilateral impaction of maxillary central incisors were referred for cone-beam imaging. Dimensions of the impacted and contralateral incisors were assessed using Dolphin 3D software (Dolphin Imaging & Management Solutions, Chatsworth, Calif). Paired t test and linear regression were used to compare the characteristics of the impacted and contralateral teeth. RESULTS: Contralateral and impacted central incisors showed statistically significant differences for root length (95% confidence interval [CI], 2.32-3.46; P <0.001), mesiodistal crown-root angulation (95% CI, 4.09-15.95; P = 0.001), and labiolingual crown-root angulation (95% CI, -18.69 to -4.70; P = 0.002). Etiologic factors did not alter the dimensions of incisors (95% CI, -1.17 to 0.76; P = 0.672). According to the multiple linear regression the independent variables associated with root length of contralateral and impacted incisors were sex (ß = -0.904; 95% CI, -1.62 to - 0.19; P = 0.014) and the presence of impaction (ß = -2.87; 95% CI, -3.67 to -2.07; P <0.001). CONCLUSIONS: Regardless of their etiology, the impacted incisors showed roots that were 2.89 mm shorter than the contralateral incisors and had greater angulation in the mesiodistal and labiolingual directions. Girls showed a reduction of 0.904 mm (7.6%) on the lengths of roots of both impacted and contralateral central incisors. The presence of impaction led to a reduction of 25% in incisor root lengths. Approximately 30% of the impacted teeth showed crown-root angulations >20° resulting in an increased distal and labial angulation of the root apical portion.

Disinfection of Orthodontic Elastomers and Its Effects on Tensile Strength.

OBJECTIVE: This study aimed to investigate the effect of different disinfection protocols on the mechanical properties of orthodontic elastomeric ligatures (EL), an important issue to biosafety improvement and infection control, and to avoid cross-contamination. METHODS: A total of 120 EL were randomly divided into 6 experimental groups (n = 20) according to the disinfection method employed: group 1, EL were not immersed in a disinfectant solution (control group); group 2, EL were immersed in 2% glutaraldehyde; group 3, EL were immersed in 70% alcohol solution; group 4, EL were cleaned in an ultrasound washing (UW) machine by immersion in 0.5% enzyme detergent solution; group 5, UW procedure was performed, followed by immersion in 2% glutaraldehyde; Group 6, UW procedure was performed, followed by immersion in 70% alcohol. After disinfection, EL were subjected to a tensile strength test where the maximum strength, maximum elongation, and work at failure were determined. Data were statistically evaluated using one-way ANOVA and Dunnett's t-test for multiple comparisons. RESULTS: Statistically significant different (P < .05) values were found between the disinfection methods, and 70% alcohol showed negative changes in all mechanical properties of orthodontic elastomers. By contrast, 2% glutaraldehyde did not show significant alteration in mechanical properties, whereas the UW procedure showed significant alteration in maximum strength and work at failure. CONCLUSION: Of the tested substances for disinfection, 2% glutaraldehyde was the only substance that did not cause significant changes in the mechanical properties of orthodontic elastics and is considered as an alternative for elastic disinfection before its use.

Cone-beam computed tomography evaluation of bone plate and root length after maxillary expansion using tooth-borne and tooth-tissue-borne banded expanders.

INTRODUCTION: The objective of this research was to evaluate the buccal bone plate and root length of maxillary permanent first molars using cone-beam computed tomography after maxillary expansion with different activation protocols. METHODS: Cone-beam computed tomography images of growing patients were obtained from the orthodontic department of Pontifical Catholic University of Rio Grande do Sul in Brazil. The groups were Haas-type 2/4 turns, Haas-type 4/4 turns, hyrax-type 2/4 turns, and hyrax-type with alternate rapid maxillary expansions and constrictions (alt-RAMEC) 4/4 turns a day. Tooth length, periodontal insertion, alveolar bone thickness, and intermolar distances were evaluated. The data at the start of treatment and 6 months later were compared using generalized linear models. The intergroup differences were determined by univariate analysis of variance with the Bonferroni adjustment. RESULTS: Tooth length was significantly shortened after expansion in all groups (-0.28 to -0.51 mm), except for the alt-RAMEC group. Bone level variables (bone level and bone level at the tooth tip) changed statistically in all groups, except for the Haas 4/4 turns group. There was significant periodontal attachment loss after rapid maxillary expansion with the hyrax/alt-RAMEC (5.09 mm). The hyrax/alt-RAMEC and hyrax groups had more dehiscences, fenestrations, and exposures of the root. CONCLUSIONS: The consequence of rapid maxillary expansion using the hyrax was alveolar bone resorption, especially in the hyrax/alt-RAMEC group, whereas the Haas expander caused mild root resorption.

Conventional surgical-orthodontic approach with double-jaw surgery for a patient with a skeletal Class III malocclusion: Stability of results 10 years posttreatment.

This case report presents the treatment of a young man with a skeletal Class III malocclusion. He was treated with a conventional surgical-orthodontic approach in which 2 jaw surgeries were performed. The esthetic facial profile, pleasant smile, appropriate occlusion, and overall good treatment outcome remained stable 10 years after active orthodontic treatment.

Cytotoxic outcomes of orthodontic bands with and without silver solder in different cell lineages.

INTRODUCTION: The safety of orthodontic materials is a matter of high interest. In this study, we aimed to assess the in-vitro cytotoxicity of orthodontic band extracts, with and without silver solder, by comparing the viability outcomes of the HaCat keratinocytes, the fibroblastic cell lineages HGF and MRC-5, and the kidney epithelial Vero cells. METHODS: Sterilized orthodontic bands with and without silver solder joints were added to culture media (6 cm2/mL) and incubated for 24 hours at 37°C under continuous agitation. Subsequently, the cell cultures were exposed to the obtained extracts for 24 hours, and an assay was performed to evaluate the cell viability. Copper strip extracts were used as positive control devices. RESULTS: The extracts from orthodontic bands with silver solder joints significantly reduced the viability of the HaCat, MRC-5, and Vero cell lines, whereas the viability of HGF was not altered by this material. Conversely, the extracts of orthodontic bands without silver solder did not significantly modify the viability index of all evaluated cell lines. CONCLUSIONS: Except for HGF fibroblasts, all tested cell lines showed decreased viability percentages after exposure to extracts of orthodontic bands containing silver solder joints. These data show the relevance of testing the toxicity of orthodontic devices in different cell lines.

Juvenile idiopatic arthritis in orthodontics: Case report with a 6-year follow-up.

Juvenile idiopathic arthritis is a childhood disease that causes joint swelling and pain, and limitation in the range of joint movements. It is characterized by progressive destruction of the joints. Juvenile idiopathic arthritis is the most frequent systemic inflammatory disease of the temporomandibular joint. When the temporomandibular joint is involved, orthodontic treatment becomes more challenging. This case report shows the treatment of a young patient with a Class II subdivision malocclusion and juvenile idiopathic arthritis. Excellent results were achieved and maintained at the 6-year follow-up, when neither clinical symptoms nor radiographic changes in the temporomandibular joint were seen.

Nickel, chromium and iron levels in the saliva of patients with simulated fixed orthodontic appliances.

OBJECTIVE: To assess the in vivo release of nickel, chromium, and iron ions into saliva by different metallic brackets. MATERIALS AND METHODS: Thirty volunteers wore removable appliances with bonded brackets and were divided according to the brand of brackets: group A, 3M/Unitek (AISI 303); group B, American Orthodontics (AISI 316L); and group C, Dentaurum (AISI 316L). The appliances were worn for 60 days, and saliva samples were collected at the following time points: T1, before placement of the appliance; T2, after 10 minutes; T3, 24 hours; T4, 7 days; T5, 30 days; and T6, 60 days after insertion of the removable appliance. Saliva samples were analyzed for nickel, chromium, and iron by atomic absorption spectrophotometry. Statistical analysis was performed by nonparametric tests (Friedman, Mann-Whitney, Kruskal-Wallis). RESULTS: Saliva evaluation revealed a large variation in concentration of these ions between individuals. The results also appeared to indicate an increase in nickel and chromium ions immediately after placement of the appliance (T2), but this was statistically significant only for groups B and C. There was no increase in iron levels. A tendency for increases in nickel and chromium concentrations was verified immediately after placement of the appliance, but these values are probably reduced because of biofilm formation regardless of the bracket used. CONCLUSION: Nickel and chromium ion concentrations increased immediately after placement of the appliance in the mouth for all study groups. There were no significant differences in the nickel, chromium, and iron levels released by the three groups of appliances at all study periods.

Cytotoxicity of two autopolymerized acrylic resins used in orthodontics.

OBJECTIVE: To test in vitro the null hypothesis that the toxic effect of different acrylic resins used in orthodontics cannot be reduced when a prior elution is performed. MATERIALS AND METHODS: Three established cell lines were used (HeLa, NIH3T3, and Hep2) and cultured under standard conditions. Resin segments were immersed in a culture medium and left to elute for 24 and 48 hours. Cells were exposed to medium containing eluates for 24 or 48 hours. The 3-(4,5 dimethyl-2-thiazolyl)-2.5-diphenyl-2H-tetrazolium bromide (MTT) assay was used as the cytotoxicity test. Control cells contained standard medium with no eluate. Analysis of variance and Tukey test were used for statistical analysis. RESULTS: Fibroblastic viability was not affected when the elution time was 24 hours, but treatments showed higher cell viability than controls when the elution time was 48 hours. When left to elute for 24 hours, both resins had a cytotoxic effect on epithelial cells, but this effect was not observed when the elution time was 48 hours. CONCLUSIONS: The hypothesis was rejected as both tested materials showed lower cytotoxic effect when treated with 48-hour elutes compared with 24-hour elutes, which indicates that a longer elution time reduces resin toxicity.

Molar changes with cervical headgear alone or in combination with rapid maxillary expansion.

OBJECTIVE: To test the hypothesis that there is no difference in the distal movement of the maxillary first permanent molars when cervical headgear is used alone or in combination with rapid maxillary expansion. MATERIALS AND METHODS: The sample was composed of 36 subjects (aged 9 to 13 years), treated in the Faculty of Dentistry, Pontifícia Universidade Cat;aaolica, Rio Grande do Sul, Brazil. The individuals were in good health and in their pubertal growth period. All had Class II division 1 malocclusion. The patients were divided into two groups: group 1 (22 subjects), Class II, with a normal transverse maxilla treated with cervical traction headgear (HG) 400 g 12 h/d, and group 2 (14 subjects), Class II maxillary transverse deficiency treated with rapid maxillary expansion plus cervical traction headgear (RME + HG). An additional group 3 (17 subjects) served as a control group and included individuals with the same characteristics. All subjects had two lateral cephalograms: initial (T1) and progress (T2), taken 6 months later. Differences between T1 and T2 were compared with the Student's t-test, and three groups were compared by the analysis of variance and Tukey multiple comparison test. RESULTS: Results showed greater distal tipping and greater distal movement of the first permanent molars in group 1 (HG) than in group 2 (RME + HG), P < .05. No extrusion of first permanent molar occurred in either group (P > .05). CONCLUSION: The hypothesis was rejected. Cervical traction headgear alone produced greater distal movement effects in maxillary first permanent molars when compared with rapid maxillary expansion associated with cervical headgear.

Surface roughness of auto polymerized acrylic resin according to different manipulation and polishing methods: an in situ evaluation.

OBJECTIVE: To test the hypothesis that no differences exists in the in situ level of surface roughness of an auto polymerized acrylic resin irrespective of the method of manipulation and polishing. MATERIALS AND METHODS: Forty volunteers received the test specimens. Surface roughness was evaluated using a rugosimeter. Samples of auto polymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing--mechanical and chemical. Four test groups were designated according to manipulation and polishing techniques: mass-mechanical, mass-chemical, addition-mechanical, and addition-chemical. Five measures of surface roughness were taken from each sample and average surface roughness (Ra) was determined before and 20 days after the samples were worn by the volunteers. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance. RESULTS: Significant differences in Ra were found between mechanical and chemical polishing. Surface roughness was not influenced by manipulation techniques. Mechanical polishing presented the lowest values of Ra. There was a significant increase in surface roughness after volunteers wore the specimens for 20 days. CONCLUSIONS: The hypothesis is rejected. There were differences on the surface roughness according to the different methods of manipulation and polishing used, but high values of surface roughness were found for all groups. Mechanical polishing showed the lowest values of surface roughness and thus should be preferred.