Clarice Nishio

Disruption of periodontal integrity induces expression of apin by epithelial cell rests of Malassez

BACKGROUND AND OBJECTIVE It has been suggested that epithelial cell rests of Malassez (ERM) may express enamel matrix proteins and play an important role in periodontal regeneration. Two novel proteins, apin (APIN) and amelotin (AMTN), produced by maturation-stage ameloblasts and junctional epithelium, have recently been identified. The objective of this study was to evaluate whether the ERM express APIN and AMTN under normal conditions and after periodontal challenge. MATERIAL AND METHODS Gingivectomy and orthodontic tooth movement were carried out on the left side of the maxillae of rats. The control group included the untreated contralateral side of these animals and the maxillae of normal, untreated rats. Animals were sacrificed by intracardiac perfusion on days 3 and 5 after the experimental procedures and maxillary molars were decalcified and processed for paraffin embedding. Immunohistochemistry was used to evaluate the expression of various ameloblast products, including APIN, AMTN, ameloblastin (AMBN) and amelogenin (AMEL). RESULTS At 3 and 5 days after periodontal challenge, ERM were more evident in the periodontal ligament along the root surface and in the root furcations. Immunodetection of APIN, but not of the other three proteins, was observed in the ERM following the disruption of periodontal integrity. No immunolabeling for APIN, AMTN, AMBN and AMEL was detected in the ERM under normal conditions. CONCLUSION The expression of APIN at an early time-point following disruption of periodontal integrity suggests that this protein may be part of the cascade of events leading to the activation of ERM during periodontal healing and regeneration.

Expression of odontogenic ameloblast-associated and amelotin proteins in the junctional epithelium

Two novel proteins - odontogenic ameloblast-associated protein and amelotin - have recently been identified in maturation-stage ameloblasts and in the junctional epithelium. This article reviews the structure and function of the junctional epithelium, the pattern of expression of odontogenic ameloblast-associated and amelotin proteins and the potential involvement of these proteins in the formation and regeneration of the junctional epithelium.

Stress analysis in the mandibular condyle during prolonged clenching: a theoretical approach with the finite element method

Abstract Parafunctional habits, such as bruxism and prolonged clenching, have been associated with functional overloading in the temporomandibular joint (TMJ), which may result in internal derangement and osteoarthrosis of the TMJ. In this study, the distributions of stress on the mandibular condylar surface during prolonged clenching were examined with TMJ mathematical models. Finite element models were developed on the basis of magnetic resonance images from two subjects with or without anterior disc displacement of the TMJ. Masticatory muscle forces were used as a loading condition for stress analysis during a 10 min clenching. In the asymptomatic model, the stress values in the anterior area (0.100 MPa) and lateral area (0.074 MPa) were relatively high among the five areas at 10 min. In the middle and posterior areas, stress relaxation occurred during the first 2 min. In contrast, the stress value in the lateral area was markedly lower (0.020 MPa) than in other areas in the symptomatic model at 10 min. The largest stress (0.050 MPa) was located in the posterior area. All except the anterior area revealed an increase in stress during the first 2 min. The present result indicates that the displacement of the disc could affect the stress distribution on the condylar articular surface during prolonged clenching, especially in the posterior area, probably leading to the cartilage breakdown on the condylar articular surface.

Gene expression profiling and histomorphometric analyses of the early bone healing response around nanotextured implants

UNLABELLED While in vitro studies have shown that nanoscale surface modifications influence cell fate and activity, there is little information on how they modulate healing at the bone-implant interface. AIM This study aims to investigate the effect of nanotopography at early time intervals when critical events for implant integration occur. MATERIALS & METHODS Untreated and sulfuric acid/hydrogen peroxide-treated machined-surface titanium alloy implants were placed in rat tibiae. Samples were processed for DNA microarray analysis and histomorphometry. RESULTS At both 3 and 5 days, the gene expression profile of the healing tissue around nanotextured implants differed from that around machined-surface implants or control empty holes, and were accompanied by an increase in bone-implant contact on day 5. While some standard pathways such as the immune response predominated, a number of unclassified genes were also implicated. CONCLUSION Nanotexture elicits an initial gene response that is more complex than suspected so far and favors healing at the bone-implant interface.

Skeletal Anchorage for Orthodontic Correction of Severe Maxillary Protrusion after Previous Orthodontic Treatment

The correction of a severe maxillary protrusion in an adult by distal movement of the maxillary molars has been one of the most difficult biomechanical problems in orthodontics. This article reports on the treatment of an adult case of severe maxillary protrusion and a large overjet treated with a skeletal anchorage system. A female patient, age 22 years and 3 months, complained of the difficulty of lip closure due to severe maxillary protrusion with a gummy smile. Overjet and overbite were +7.6 mm and -0.9 mm, respectively. She had a history of orthodontic treatment in which her maxillary first premolars were extracted. In order to conduct distal movement of the maxillary molars, anchor plates were placed in the zygomatic process. After achieving a Class I molar relationship, retraction and intrusion of the maxillary incisors were performed. After a 2-year treatment, an acceptable occlusion was achieved with a Class I molar relationship. Her convex facial profile with upper lip protrusion was considerably improved, and the lips showed less tension in lip closure. After a 2-year retention period, an acceptable occlusion was maintained without recurrence of maxillary protrusion, indicating a stability of the occlusion. The result of this treatment indicated that skeletal anchorage is of great importance as a remedy for achieving intrusion and retraction of the maxillary incisors in cases of severe maxillary protrusion with a patient who had previous orthodontic treatment.

Agreement Evaluation of a Newly Proposed System for Malocclusion Classification

The current malocclusion classification systems, routinely used in orthodontic practice, still yield different disagreement values among examiners who evaluate one and the same clinical case. Objectives: The purpose of this study was to evaluate the agreement effectiveness of a Newly Proposed System for malocclusion classification - in the anteroposterior orientation -, conceived by the present authors.Thirty-four examiners evaluated 15 malocclusion cases using Angles, Katzs and the Newly Proposed System classifications to determine which system shows the highest degree of agreement and accuracy when results were communicated among examiners. A comparison of the classifications attributed to each indivi- dual case and the mean figures found for the total data in each classification showed that the methods advanced by the Newly Proposed System yielded a higher degree of agreement (73.33%) than Angles (26.66%) and Katzs (26.66%). The Newly Proposed System proved to be an outstanding malocclusion classification system with a high degree of agreement among examiners. On the other hand, however, further studies involving a wider sample of malocclusions and a greater number of examiners are strongly recommended if more conclusive results are to be achieved.

Formação do esmalte dentário, novas descobertas, novos horizontes

A formação do esmalte dentário é um processo biológico complexo, porém bem coordenado e que envolve duas fases: secreção e maturação9. O desenvolvimento do esmalte é regulado por células epiteliais, ameloblastos, que expressam um importante conjunto de genes que codificam a produção de proteínas essenciais para a formação desse tecido dentário6. Sabe-se até o presente momento que, durante o estágio de secreção, os ameloblastos sintetizam e secretam proteínas da matriz do esmalte, tais como amelogenina, ameloblastina e enamelina; e da enzima enamelisina, também chamada MMP-206,9. A deficiência de uma dessas proteínas e/ou enzimas pode levar à má formação dentária, tal como uma hipoplasia do esmalte (amelogênese imperfeita) de diversas magnitudes de severidade. Porém, o mecanismo de como cada uma dessas proteínas exerce a sua função e influencia o processo de mineralização do esmalte dentário ainda permanece obscuro. Recentemente, foram identificadas duas novas proteínas, chamadas amelotina3,7 e apina5,6 (em Inglês, amelotin e apin), que também são sintetizadas pelos ameloblastos. Diferentemente das outras proteínas, a amelotina e a apina são produzidas durante a amelogênese no estágio de maturação; fase importante para o desenvolvimento final da dureza do esmalte. Essas duas novas substâncias são codificadas por dois diferentes genes que, de acordo com a sua localização genômica e estrutural, fazem parte de um mesmo grupo de proteínas que secreta e estabiliza íons de Ca e PO4 no corpo e/ou guia a deposição de CaPO4 em matrizes extracelulares receptoras. A similaridade dessas proteínas, encontradas tanto em seres humanos como em suínos, ratos e camundongos, sugere que são proteínas que se perpetuam nas espécies mamíferas6. Estudos com imunolocalizadores3,7 demonstraram que a amelotina está presente tanto na lâmina basal, na interface com a superfície do esmalte, como no epitélio juncional. Uma vez que o epitélio juncional é uma estrutura que está firmemente aderida à superfície dentária, especula-se que a amelotina tenha alguma participação no processo de adesão celular7. O epitélio juncional é uma estrutura especializada que veda a superfície do dente na cavidade bucal. A perda da sua integridade é um dos primeiros processos que ocorre durante o desenvolvimento da doença periodontal, podendo levar à perda óssea e dentária2. Em relação à nova proteína apina, pouco se sabe sobre o seu mecanismo de função e atividade. No entanto, tem-se sugerido que a apina exerce um papel fundamental nas fases finais de formação dentária, pois sua atividade foi localizada apenas na fase transitória de pós-secreção da amelogênese, estendendo-se até a fase de maturação do esmalte dentário. Assim como a amelotina, a apina foi identificada tanto na lâmina basal como no epitélio juncional e, por isso, especula-se que ela também tenha alguma participação no mecanismo de adesão celular6. Estudos prévios, utilizando diferentes materiais e métodos, já encontraram apina em fragmentos de DNAc de vários tecidos, tais como da glândula lacrimal8, da glândula salivar, da traquéia4, do naso6, da língua12, do dente5,6,7,9, entre outros. Além dis-