Alvaro de Moraes Mendes

Relationship between dental size and normal occlusion in Brazilian patients

The present study was performed on dental casts and lateral cephalometric films of 30 Caucasian Brazilian individuals (15 males and 15 females) aged 18 to 27 years and 4 months, all presenting normal occlusion and satisfactory facial profile. The aims were to investigate the existence of dental discrepancies according to Boltons criteria, to obtain mean values for overbite, overjet, curve of Spee and interincisal angle, and to demonstrate any correlation among these parameters. A single calibrated operator measured each variable characteristics and the process was recorded twice with an accurate modified digital caliper. It was observed that the sample of normal occlusion did not present any dental discrepancy among the 12 teeth of opposite arches. The overall ratio (91.46) and anterior ratio (77.83) were in accordance with those proposed by Bolton. The mean values for normal occlusion in this Brazilian sample were defined as: 2.45 mm for overbite; 1.92 mm for overjet; 1.01 mm for curve of Spee and 129.57 degrees for interincisal angle. A statistically significant correlation was found between overjet and overbite.

Understanding the shape-memory alloys used in orthodontics.

Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA.

Force extension relaxation of medium force orthodontic latex elastics

OBJECTIVE To evaluate the force extension relaxation of different manufacturers and diameters of latex elastics subjected to static tensile testing under dry and wet conditions. MATERIALS AND METHODS Sample sizes of 15 elastics from American Orthodontics (AO) (Sheboygan, Wis), TP (La Porte, Ind), and Morelli Orthodontics (Sorocaba SP, Brazil) were used. Equivalent medium force products were tested--3/16, 1/4, and 5/16 inch lumen size from each manufacturer--making a total of 1080 specimens. An apparatus was designed to simulate oral environments during elastics stretching. Forces were read after 1, 3, 6, 12, and 24 hour periods using the Emic Testing Machine (Emic Co., Sao Paulo, Brazil) with 30 mm/min cross-head speed and load cell of 20 N (Emic Co). Kruskal-Wallis and Dunns tests were used to identify statistical significance. RESULTS Statistical differences between AO and the other brands were noted for all testing times. Significant variation in mechanical properties was observed in latex elastics from Morelli. Relationships among loads at the 0 hour time period were as follows: Morelli>AO>TP for 3/16 elastics (P = .0016), 1/4 elastics (P = .0016), and 5/16 elastics (P = .0087). CONCLUSION Significant differences in force extension relaxation were noted for elastics from these manufacturers. Force relaxation over the 24 hour time period was AO>Morelli>TP for 3/16 elastics, AO>TP>Morelli for 1/4 elastics, and TP>AO>Morelli for 5/16 elastics. The force decay pattern showed a notable drop-off of forces during 0 to 3 hours, a slight increase in force values from 3 to 6 hours, and a progressive force reduction over 6 to 24 hours.

Evaluation of esthetic brackets' resistance to torsional forces from the archwire.

INTRODUCTION The aim of this study was to evaluate the resistance to deformation or fracture of esthetic brackets produced by archwire torsion. METHODS Six types of maxillary right central incisor brackets were analyzed: traditional ceramic brackets (cer); ceramic brackets reinforced with a stainless steel slot (cer/ss); ceramic brackets reinforced with a gold slot (cer/gold); traditional polycarbonate brackets (poly); polycarbonate brackets reinforced with a stainless steel slot (poly/ss); and polycarbonate brackets reinforced with ceramic fillers and a stainless steel slot (poly/cer/ss). Stainless steel wire segments were used, and the testing instrument (Emic DL 10000, São José do Rio Preto, PR, Brazil) was moved at a rate of 1 inch per minute to generate the wire torsion. RESULTS The brackets showed deformation or fracture resistance values (gf x mm) in decreasing order as follows: cer/ss (3528.1 +/- 516.6), cer/gold (2858.7 +/- 611.6), cer (2424.0 +/- 352.1), poly/cer/ss (2279.5 +/- 174.5), poly/ss (2142.0 +/- 275.7), and poly (1463.6 +/- 193.3). The cer/ss ceramic brackets showed the greatest statistically significant (P <0.01) values of resistance to fracture, and the poly brackets had the lowest statistically significant (P <0.01) values of resistance to deformation. The cer brackets showed no significant differences (P >0.01) from the cer/gold, the poly/cer/ss, and the poly/ss brackets. CONCLUSIONS This suggested that the stainless steel slot might enhance resistance to deformation or fracture, although gold slots and ceramic fillers are ineffective for reinforcing esthetic brackets.

Estudo comparativo entre as diferentes cores de ligaduras elásticas

AIM: the purpose of this study was to evaluate the different colors of molded elastomerics ligatures from Morelli trademark. METHODS: the ligatures were stretched over stainless dowels with a circumference approximating that of upper central incisor bracket. They were immersed in a synthetic saliva bath at 37oC and had force levels measured at initial (0h) and after 24 hours of immersion. The results were obtained from a computer connected to a traction machine and were submitted to statistical analysis (ANOVA e Tuckey) with p<0.05. RESULTS AND CONCLUSION: the medium values were md=0.3792KgF for 0h and md=0.1286KgF for 24h and the percentage of force decay were 66.07% ± 2.31%. The results revealed statically differences between forces delivered in 0h and 24h. At 0h, there were differences statistically significance between some colors of ligatures before the action of the time and the immersion in artificial saliva bath, with higher values for the pearl (md=0.4024KgF) and minors values for the slight green (md=0.3511KgF). At 24h, it was also find differences statistically significances between some colors, but the distribution was different than the observed at 0h. The slight green, red, yellow and white colors had the minor percentage of force decay, in which slight green showed the best behavior (62.60%). However, the pearl, silver and gray had the highest percentage of force decay, with pearl showing the worst behavior (69.23%).

A clinical photogrammetric method to measure dental arch dimensions and mesio-distal tooth size

The aim of this research was to evaluate the reliability and validity of measurements obtained from clinical standardized occlusal photographs compared with dental cast measurements. This study comprised a consecutive sample of 16 patients (eight males and eight females, aged 15-24 years) in the permanent dentition without agenesis and/or tooth loss. A paired t-test and intraclass correlation coefficient (ICC) were used to examine validity and reliability. Both statistics were applied for intra- and inter-methods error analysis, at P < 0.05. Random error for the photogrammetric method (less than 0.48 mm) was similar to that for the dental cast measurements (less than 0.43 mm). ICC revealed excellent reliability for both methods (P < 0.01) and no significant difference for any variables, with the exception of upper inter-canine width obtained on the dental casts (P = 0.0038) and photogrammetry (P = 0.01). However, differences were less than 1 per cent of the mean inter-canine width. Inter-method analysis showed a significant correlation for all variables (P < 0.001), with good to excellent reliability (r = 0.66-0.93). A significant mean inter-method difference was consistently observed for the upper first molars (0.33 mm, P < 0.01). For the remaining teeth (left to right second premolars), the largest mean difference was approximately equal to the resolution of the human eye (0.2 mm or less). Minor differences (around 2 per cent of the mean) and an excellent ICC (0.75-0.93, P < 0.01) were observed for arch dimensions. Except for the mesio-distal width of the upper first molars, the recently developed photogrammetric method showed accuracy, validity, and reliability acceptable for clinical and scientific purposes.

Bleaching effects on shear bond strengths of orthodontic brackets

OBJECTIVES The purpose of this research was to investigate the influence of 35% hydrogen peroxide on orthodontic bracket adhesion at zero hour, 24 hours, 7, 21 and 56 days after dental bleaching. MATERIALS AND METHODS Ninety bovine incisors were prepared for adhesion test and adhesive remnant index (ARI) determination. The 35% hydrogen peroxide was used as a bleaching agent and the Transbond XT as a bonding agent. RESULTS Statiscally significant differences were observed between all the groups (p<0.001) and were observed in the comparison of zero hour and control group (p<0.001) and in the comparison of zero hour and 24 hours (p<0.001). ARI scores (0, 1, 2 e 3) also showed statiscally differences between all the groups (p=0.011) and at the comparison of all the test groups with the control: zero hour (p=0.001), 24 hours (p=0.009), 7 days (p=0.018), 21 days (p<0.001) e 56 days (p=0.004). CONCLUSIONS The shear bond strength values became significantly lower when the bracket was bonded immediately after bleaching and quickly returned to control level in 24 hours. In seven days, there was a slight increase that was not significant and recovered to normal values in the next weeks. Different patterns of fractures were observed in bleached enamel when ARI scores were analyzed. The control group showed a high frequency of 3 score and none of zero score, the opposite behavior was observed in the test groups.

Force Relaxation Characteristics of Medium Force Orthodontic Latex Elastics: A Pilot Study

To evaluate force extension relaxation of different brands and diameters of latex elastics subjected to static tensile testing under an apparatus designed to simulate oral environments, sample sizes of 5 elastics from American Orthodontics (AO), Tp, and Morelli Orthodontics (Mo) of equivalent medium force, (3/16, 1/4, and 5/16 inch size) were tested. The forces were read after 1-, 3-, 6-, 12- and 24-hour periods in Emic testing machine with 30 mm/min cross-head speed and load cell of 20 N. Two-way ANOVA and Bonferroni tests were used to identify statistical significance. There were statistically differences among different manufacturers at all observation intervals (P < 0.0001). The relationships among loads at 24-hour time period were as follows: Morelli>AO>Tp for 3/16, 1/4, and 5/16 elastics. The force decay pattern showed a notable drop-off of forces until 3 hours, a slight increase in some groups from 3–6 hours and a more homogeneous force pattern over 6–24 hours.

Craniofacial characteristics of patients with heart disease.

INTRODUCTION Children with congenital heart disease commonly experience delayed growth. Studies comparing growth and development of these children generally found that they have decreased height and weight, but with no information on craniofacial growth. The aim of this study was to evaluate the craniofacial characteristics of patients with heart disease. METHODS We used lateral head cephalograms of 131 patients, aged 8 to 12, attending the Department of Pediatrics of the Hospital of the State University of Rio de Janeiro in Brazil on a routine basis. The study group comprised 50 boys and 38 girls with congenital heart disease. The control group included 20 boys and 23 girls with no heart disease. The skeletal, dental, growth, esthetic, and vertical patterns were analyzed with several cephalometric measurements. The chi-square test was applied to verify a possible association between sex and heart disease, and the Student t test was used to verify differences between the groups of patients with and without heart disease. RESULTS Heart disease is not sex-related (chi-square = 0.267). But some measurements had sex differences in the groups with and without heart diseases. The Student t test showed significant differences between the groups in the SNA angle measurement in male patients (P = 0.032), and in ANB angle (P = 0.002) and the relationship of the lower lip to the Steiner line (P = 0.034) in the girls. CONCLUSIONS Skeletal patterns were characterized by maxillary protrusion in the boys with heart disease and by increased ANB angles in the girls without heart disease. The esthetic pattern showed a more pronounced lower lip in the girls without heart disease. However, from a clinical point of view, these were slight and irrelevant alterations. The results suggest that patients suffering from heart disease have similar craniofacial characteristics to those without this condition.

Percentual de degradação das forças liberadas por ligaduras elásticas

OBJETIVO: avaliar ligaduras elasticas da marca Morelli, dos tipos modular e bengala, nas cores cinza e cristal para determinacao do percentual de degradacao das forcas geradas pelas mesmas. METODOLOGIA: as ligaduras elasticas foram estiradas em estiletes de aco inoxidavel com diâmetro de 4mm, imersas em solucao de saliva artificial a 37oC, sendo a intensidade das forcas liberadas medidas nos tempos de zero hora, 24 horas, 1 semana, 2 semanas, 3 semanas e 4 semanas, em maquina de ensaios de tracao. RESULTADOS E CONCLUSOES: as ligaduras do tipo bengala liberaram, em media e no periodo de 4 semanas, maior intensidade de forca que as do tipo modular. O percentual de degradacao das forcas liberadas por todas as ligaduras aumentou de forma acentuada entre zero e 24 horas e de forma gradativa apos este periodo, com excecao do 28o dia quando, provavelmente, houve perda das propriedades elasticas das ligaduras. Nao foi observado um comportamento constante das ligaduras bengala e modular em relacao as cores cinza e cristal.