José Vinicius Bolognesi Maciel

Friction between different wire bracket combinations in artificial saliva: an in vitro evaluation

Objective The objective this work was to assess the friction coefficient between brackets and wires of different materials under conditions simulating the oral environment. Material and Methods Stainless steel (SS) and titanium-molybdenum alloy (TMA) wires of 0.019x0.025-in diameter (American Orthodontics) and polycarbonate bracket (American Orthodontics), ceramic bracket (American Orthodontics), and metal bracket (3M Unitek) with slots of 0.022x0.030-in were used. The friction coefficient was assessed by means of mechanical traction with the system immersed in artificial saliva. The mean roughness of both wire surface and bracket slots was evaluated by using a surface profilometer. Results The system using TMA wire and polycarbonate bracket had the highest roughness (p<0.05). SS wire with ceramic bracket had the highest friction coefficient, whereas the use of metallic bracket yielded the lowest (p<0.05). However, it was observed a statistically significant difference in the system using TMA wire and ceramic bracket compared to that using TMA wire and polycarbonate bracket (p=0.038). Conclusion Ceramic brackets in association with SS wire should be judiciously used, since this system showed a high friction coefficient.

Influence of anti-inflammatory administration in collagen maturation process during orthodontic tooth movement

Bone formation is essential to orthodontic tooth movement and bone is formed by collagen. To analyze the collagen maturation process on bone matrix neoformed under nonsteroidal and steroidal treatment during orthodontic tooth movement by polarized microscopy, male Wistar rats (n = 90) were randomly divided into three groups (n = 30): C (control), NSAID (potassium diclofenac) and SAID (disodic phosphate dexamethasone). The animals of the C group received 0.9% saline solution; NSAID group received 5 mg/kg potassium diclofenac (CATAFLAM®); and SAID group received 2 mg/kg phosphate dissodic dexamethasone (DEXANIL®). Animals were sacrificed 3, 7 or 14 days after the placement of orthodontic appliances and the upper first molars were processed histologically and stained with picrosirius. Bone formation was evaluated under polarized light microscopy and 4.5 Image Pro‐Plus® software calculated the percentage of immature/mature collagen present in the groups. On the third days after force application, SAID and NSAID groups showed greater proportion of immature collagen than C group. On the seventh and fourteenth days, there was a lower proportion of mature collagen only in the SAID group (P < 0.001). These data demonstrate that dexamethasone delays the collagen maturation process in established bone matrix. Microsc. Res. Tech., 2011.

New methodology for evaluating osteoclastic activity induced by orthodontic load

Orthodontic tooth movement (OTM) is a dynamic process of bone modeling involving osteoclast-driven resorption on the compression side. Consequently, to estimate the influence of various situations on tooth movement, experimental studies need to analyze this cell. Objectives The aim of this study was to test and validate a new method for evaluating osteoclastic activity stimulated by mechanical loading based on the fractal analysis of the periodontal ligament (PDL)-bone interface. Material and Methods The mandibular right first molars of 14 rabbits were tipped mesially by a coil spring exerting a constant force of 85 cN. To evaluate the actual influence of osteoclasts on fractal dimension of bone surface, alendronate (3 mg/Kg) was injected weekly in seven of those rabbits. After 21 days, the animals were killed and their jaws were processed for histological evaluation. Osteoclast counts and fractal analysis (by the box counting method) of the PDL-bone interface were performed in histological sections of the right and left sides of the mandible. Results An increase in the number of osteoclasts and in fractal dimension after OTM only happened when alendronate was not administered. Strong correlation was found between the number of osteoclasts and fractal dimension. Conclusions Our results suggest that osteoclastic activity leads to an increase in bone surface irregularity, which can be quantified by its fractal dimension. This makes fractal analysis by the box counting method a potential tool for the assessment of osteoclastic activity on bone surfaces in microscopic examination.

Effect of Growth Hormone in Experimental Tooth Movement

The aim of this study was to evaluate, by histological analysis, the effect of growth hormone (GH) on periodontal ligament and alveolar bone during experimental tooth movement in rats. Eighty male Wistar rats divided into control (C) and experimental (E) groups were examined after 3, 7, 14 and 21 days under controlled climate conditions. Orthodontic force (30 cN) was applied on the maxillary first molar by an orthodontic appliance. Group E received 0.1 IU/kg/day of GH and Group C received 0.5 mL/kg/day of saline. The samples were processed and evaluated under optical microscopy and polarized light microscopy. The Kruskal Wallis test was applied to compare the intergroup variables at 5% significance level. Group E presented a larger number of osteoclasts on the 3rd and 7th days and Howship lacunae on the 3 rd day, a smaller number of blood vessels and greater amount of mature collagen on the 3 rd and 7 th days than Group C (p<0.05). It was concluded that GH accelerated and intensified bone resorption and produced delay in immature collagen formation during experimental tooth movement.

Influence of Primekote® polymer in orthodontic bonding

Objetivo Avaliar a resistencia ao cisalhamento e o indice de remanescente adesivo (IRA) dos braquetes que tiveram o polimero Primekote® incorporado a suas bases. Material e metodo Foram confeccionados trinta corpos de prova com incisivos bovinos, divididos em dois grupos: o colado com braquete TP® Nu-Edge(n=15) e grupo controle com braquetes Morelli® (n=15) sem tratamento na base. O sistema adesivo TransbondTM XT foi utilizado nos dois grupos seguindo o mesmo protocolo de colagem e respeitando as instrucoes do fabricante. Os corpos de prova foram armazenados em agua destilada por 24 horas, e posteriormente submetidos ao teste de cisalhamento na maquina de ensaios universais (EMIC-DL2000). O IRA foi avaliado por dois examinadores calibrados utilizando lupa estereoscopica com aumento de 20 vezes. Resultado Na resistencia ao cisalhamento o teste T-independente mostrou nao haver diferenca estatisticamente significante entre os grupos (p>0,05), ambos tiveram desempenho semelhante. O teste Wilcoxon foi utilizado nos valores obtidos no IRA revelando diferenca estatistica, sendo que os braquetes TP® deixaram menos remanescente adesivo na superficie dental que os braquetes Morelli®. Conclusao Braquetes TP® apresentaram maior adesao ao sistema adesivo pois foi encontrado menor IRA nos mesmos, porem esta caracteristica nao reflete em melhora no desempenho clinico.

Forced eruption for all four maxillary incisors prior to implant rehabilitation

Periodontally compromised teeth are a common problem observed in adults, and the extraction is a viable solution in some of these situations. When prosthetic rehabilitation with implants take place after the extraction, orthodontic extrusion may convert the tooth indicated for extraction into a useful tooth. A 48-year-old womans chief complaint was the esthetics of her maxillary incisors with advanced periodontal disease. The incisors were orthodontically erupted to augment the bone topography for implant recipient sites and prosthetic rehabilitation. Three implants were selected and inserted in a single surgical procedure without any complications. A 10 months follow-up showed that the implants were stable with the prosthetic crowns preserving the surrounding soft tissues, and improving overall aesthetics and function.