Karina Santos Mundstock

PAX9 and MSX1 transcription factor genes in non-syndromic dental agenesis

OBJECTIVE The molecular variation of paired domain box gene 9 (PAX9) was previously investigated by our research group and a high degree of evolutionary conservation in coding and non-coding regions was observed except in exon 3. PAX9 is a transcription factor important in tooth development, and we wanted to verify its role in dental agenesis in detail. Since dental development is a complex trait we also decided to examine the influence of another transcription factor, muscle segment homeodomain-homeobox 1 (MSX1) on it. DESIGN A total of 360 consecutively ascertained patients seeking orthodontic treatment were screened for tooth agenesis and 33% of them were found to have it. Thirty-five of those with agenesis and 15 controls had their DNA studied for PAX9 exons 2, 3, 4 and adjacent regions (total of 1476 base pairs, bp) as well as MSX1 exon 2 (698bp). A trio (a proband and her parents) was also studied. RESULTS Six polymorphic sites were found, three in PAX9 exon 3 and three in MSX1 exon2. MSX1 rs1095 derived allele occurred in individuals with agenesis only, and two other mutations in this gene had been earlier associated with tooth agenesis. Homozygosity for the PAX9 Ala240Pro mutation was studied in a family (proband and her parents), suggesting recessive inheritance with variable expressivity for the dental agenesis found. CONCLUSION Common variants located out of the DNA binding domain of the two PAX9 and MSX1 genes can also be related to tooth agenesis.

Association among pain, masticatory performance, and proinflammatory cytokines in crevicular fluid during orthodontic treatment

INTRODUCTION Orthodontic patients usually complain about masticatory limitations associated with the activation of fixed appliances. The aim of this investigation was to evaluate whether orthodontic pain reflects differences in the objective evaluation of mastication and in the levels of proinflammatory cytokines in the crevicular fluid of patients undergoing orthodontic treatment. METHODS Twenty patients with malocclusions requiring orthodontic treatment were included in this prospective study. Their pain experience, masticatory performance, and levels of interleukin 1-beta and prostaglandin E2 in crevicular fluid were evaluated at 3 times: before bracket placement, 24 hours after archwire placement, and 30 days after the initial appointment. All variables were compared with those of a control group of 25 subjects with normal occlusion. RESULTS The masticatory performance of the patients was significantly reduced at 24 hours after bracket placement, the period in which they reported higher values of pain and had higher levels of interleukin 1-beta. The levels of prostaglandin E2 did not change in the periods evaluated, and there were no correlations between the levels of cytokines and the functional limitations observed. The only significant correlation was between pain and decreased masticatory performance. CONCLUSIONS The masticatory performance of orthodontic patients is significantly reduced only during the period of greatest pain. However, these alterations did not correlate with any measurement of interleukin 1-beta or prostaglandin E2 in the crevicular fluid, suggesting that these solitary measurements are inadequate to predict the temporary pain and masticatory limitations experienced by patients undergoing orthodontic treatment.

MSX1 and PAX9 Investigation in Monozygotic Twins With Variable Expression of Tooth Agenesis

Non-syndromic agenesis of permanent teeth is one of the most common anomalies in human development, a multifactorial characteristic caused by genetic and environmental factors. We describe a pair of monozygotic twins who showed second premolar and third molar agenesis, albeit with different expressions. We studied the DNA of two genes, paired domain box gene 9 (PAX9) and muscle segment homeodomain-homeobox1 (MSX1), encoding transcription factors that earlier studies found were involved in the manifestation of this condition. No specific causative mutation was found. However, we detected a C→T change in MSX1 exon 2 in both twins, suggesting that this polymorphism might be involved in the traits expression.

Pain, masticatory performance and swallowing threshold in orthodontic patients

OBJECTIVE The aim of this study was to assess pain, masticatory performance and swallowing threshold of patients undergoing orthodontic treatment. METHODS Ten patients of both genders (mean age of 17.25 ± 5.21 years), with complete permanent dentition, who underwent orthodontic treatment with fixed appliances were evaluated. The masticatory performance and the swallowing threshold were assessed by patients individual capacity of fragmenting an artificial test food (Optocal) which was chewed and had the resulting particles processed by a standardized sieving method, presenting the median particle size (MPS) of crushed units. The intensity of pain / discomfort during chewing was evaluated by means of a visual analog scale. All tests were performed at the following times: T0 - before activating the orthodontic appliance; T1 - 24 hours after activation, and T2 - 30 days after activation. RESULTS The results showed a significant increase in pain at T1 (T0 = 0.60 ± 0.70 mm; T1 = 66.2 ± 34.5 mm), returning to baseline values at T2 (3.20 ± 3.82 mm). Masticatory performance was also reduced in T1 (MPS = 10.15 ± 1.1 mm2) in comparison to T0 (MPS 7.01 ± 2.9 mm2) and T2 (MPS 6.76 ± 1.3 mm2). However, particle size was not affected in the swallowing threshold test (T0 = 5.47 ± 2.37 mm2; T1 = 6.19 ± 2.05 mm2; T2 = 5.94 ± 2.36 mm2). CONCLUSIONS The orthodontic appliances did not interfere in the size of the particles that would be swallowed, even in the presence of pain.

In vitro analysis of shear bond strength and adhesive remnant index of different metal brackets

ABSTRACT Introduction: There is a great variety of orthodontic brackets in the Brazilian market, and constantly evaluating them is critical for professionals to know their properties, so as to be able to choose which product best suits their clinical practice. Objectives: To evaluate the bond strength and the adhesive remnant index (ARI) of different brands of metal brackets. Material and Methods: A total of 105 bovine incisors were used, and brackets of different brands were bonded to teeth. Seven different bracket brands were tested (MorelliTM, American OrthodonticsTM, TP OrthodonticsTM, Abzil-3MTM, OrthometricTM, TecnidentTM and UNIDENTM). Twenty-four hours after bonding, shear bond strength test was performed; and after debonding, the ARI was determined by using an optical microscope at a 10-fold increase. Results: Mean shear bond strength values ranged from 3.845 ± 3.997 (MorelliTM) to 9.871 ± 5.106 MPa (TecnidentTM). The majority of the ARI index scores was 0 and 1. Conclusion: Among the evaluated brackets, the one with the lowest mean shear bond strength values was MorelliTM. General evaluation of groups indicated that a greater number of bond failure occurred at the enamel/adhesive interface.

In vitro force delivery of nickel-titanium superelastic archwires in vertical displacement

OBJECTIVE: The purpose of this study was to evaluate the force delivered by different superlastic nickel-titanium wires during vertical displacement, in order to determine whether their stress release meets the criteria for constant and light forces that are usually accredited to these archwires. METHOD: Ten samples of 6 brands of 0.016-in archwires (Ormco, GAC, Morelli, TP, American Orthodontics e Rocky Mountain) were tested in a complete metal model using Dynalock brackets (3M Unitek™). In the canine position, there was a sliding bracket connected to a pole. This set was related to a load cell of 0.5 kg attached to a universal testing machine (Autograph AG-199kNG, Shimadzu). The crosshead speed was 0.5 mm/min and the maximum displacement was 1.0 mm. The model was submerged in temperature-controlled water. The results were analyzed by ANOVA (p < 0.05), using the software SAS System 8.02, Cry, NC, USA. RESULTS: The TP archwire had the lowest force throughout the test, although the final force was high (277.91 g). The Rocky Mountain archwire had the highest force release (455.41 g). CONCLUSION: The different brands of wires tested in this study failed in delivering low and constant forces as expected from superlastic nickel-titanium wires. The forces were extremely heavy for a vertical tooth movement.