Measurement of the mandibular canal and mandibular incisive canal using cone beam tomography in adults from South Brazil.

PURPOSE: To identify and measure the distance from the dental apices to the mandibular (MC) and mandibular incisive (MIC) canals, the diameter of the MC and the distances of the mental foramen (MF). METHODS: In this retrospective study, cone-beam computed tomography scans of 144 adult patients (males and females) from a dental school in South Brazil were evaluated. Cross-sections were selected on the MC and the MIC paths, perpendicular to the mandibular base, and measurements were taken from the dental apices to the mandibular cortices. The measurement and location of the mandibular and mental foramen on both sides were compared. Paired t-tests compared sides, while Student's t-tests compared sexes (P < 0.05). RESULTS: The distance from the dental apices to the upper wall of the MC was closest in the third molar and farthest in the central incisor region. In both sexes and sides, the path of the MC is in most cases lingually in the molar regions and moves to the buccal region from the second premolar. The MF emerges in the regions between the premolars or near the second premolar. CONCLUSION: The results of this study highlight the importance of evaluating specific individual characteristics of a given population.

Radiographic interpretation of changes in the tooth and adjacent bone tissue using the tools of the Moodle virtual environment / Interpretação radiográfica de alterações no órgãodentário e tecido ósseo adjacente utilizando as ferramentas do ambiente virtual Moodle

Virtual learning environments (VLEs) have numerous possibilities for the use of their tools and can assist in the processesof teaching and learning aboutthe radiographic image interpretation. This study aimed to evaluate the use of a virtual learning environment as a support material for students in the discipline of Dental Radiology.This radiographic interpretation was conducted to contribute to the knowledge and training of the changes in the tooth andadjacent bone tissue,visualized in periapical and interproximal radiographs. The scores of the virtual test (via the Moodle platform) and the interpretation test (in the classroom) were used to compare Group Number 1 (students thatperformed the virtual test before the classroom test) and Group Number 2 (students thatperformed the virtual test after the classroom test). It was observed that,in general, the mean score of the interpretation test was higher than the virtual.Also,66% of the students used the platform as the main resourceto follow the discipline, due to the possibility of reviewing the contents andactivities. The virtual learning environment can be considered an important complementary sourcefor teaching radiographic interpretation. The Moodle platform acts as a remarkable tool, with the potential capacity to support the teaching and learning process. For this, mutual collaboration among students, University,and educational institution isnecessarily required for the constant use, maintenance,and updating of the virtual environment (AU).

Os ambientes virtuais de aprendizagem (AVA) possuem inúmeras possibilidades de utilização de suas ferramentas e podem auxiliar nos processos de ensino e aprendizagem sobre a interpretação de imagens radiográficas. Este estudo teve como objetivo avaliar a utilização de um ambiente virtual de aprendizagem como material de apoio para alunos da disciplina de Radiologia Odontológica. Essa interpretação radiográfica foi realizada para contribuir com o conhecimento e treinamento das alterações no órgão dentário e tecido ósseo adjacente, visualizadas em radiografias periapicais e interproximais. As notas da prova virtual (via plataforma Moodle) e da prova de interpretação (em sala de aula) foram utilizadas para comparar o Grupo Número 1 (alunos que realizaram a prova virtual antes da prova presencial) e o Grupo Número 2 (alunos que realizaram a prova virtual, após o teste em sala de aula). Observou-se que, em geral, a média da prova de interpretação foi superior à da prova virtual. Além disso, 66% dos alunos utilizaram a plataforma como principal recurso para acompanhar a disciplina, devido à possibilidade de revisão dos conteúdos e atividades. O ambiente virtual de aprendizagem pode ser considerado uma importante fonte complementar para o ensino da interpretação radiográfica. A plataforma Moodle atua como uma ferramenta notável, com potencial capacidade de apoiar o processo de ensino e aprendizagem. Para isso, é necessária a colaboração mútua entre alunos, Universidade e instituição de ensino para a constante utilização, manutenção e atualização do ambiente virtual (AU).

The Wittig bioconjugation of maleimide derived, water soluble phosphonium ylides to aldehyde-tagged proteins.

Herein we disclose the transformation of maleimides into water-soluble tris(2-carboxyethyl)phosphonium ylides and their subsequent application in the bioconjugation of protein- and peptide-linked aldehydes. The new entry into Wittig bioconjugate chemistry proceeds under mild conditions and relies on highly water soluble reagents, which are likely already part of most biochemists' inventory.

Intranasal drug delivery for treatment of Alzheimer's disease.

The Alzheimer's disease is a neurodegenerative condition with severe consequences interfering with patient quality of life. It is characterized as a progressive and irreversible brain disorder hampering memory and thinking, affecting the capacity to perform daily tasks leading to physical and cognitive incapacitation. The conventional treatment occurs by the oral route, but it presents relevant drawbacks such as low bioavailability, fast metabolism, limited brain exposure, and undesirable side effects. The intranasal route has been proposed as a promising alternative to deliver drugs and improve the Alzheimer's disease treatment. Still, there is not a clear alternative delivery system available in the market with advantageous bioavailability and safety. The aim of this review is to perform an overview on the strategies for drug intranasal delivery for Alzheimer's disease treatment. The advantages and disadvantages of this delivery route and the delivery systems developed so far are discussed. A special focus is given on the use of permeation enhancers, the types of intranasal drug delivery devices, as well as possible toxicity concerns.

Rational Design of Azastatin as a Potential ADC Payload with Reduced Bystander Killing.

Auristatins are a class of ultrapotent microtubule inhibitors, whose growing clinical popularity in oncology is based upon their use as payloads in antibody-drug conjugates (ADCs). The most widely utilized auristatin, MMAE, has however been shown to cause apoptosis in non-pathological cells proximal to the tumour ("bystander killing"). Herein, we introduce azastatins, a new class of auristatin derivatives encompassing a side chain amine for antibody conjugation. The synthesis of Cbz-azastatin methyl ester, which included the C2-elongation and diastereoselective reduction of two proteinogenic amino acids as key transformations, was accomplished in 22 steps and 0.76 % overall yield. While Cbz-protected azastatin methyl ester (0.13-3.0 nM) inhibited proliferation more potently than MMAE (0.47-6.5 nM), removal of the Cbz-group yielded dramatically increased IC50 -values (9.8-170 nM). We attribute the reduced apparent cytotoxicity of the deprotected azastatin methyl esters to a lack of membrane permeability. These results clearly establish the azastatins as a novel class of cytotoxic payloads ideally suited for use in next-generation ADC development.

Investigating the Impact of Sample Preparation on Mass Spectrometry-Based Drug-To-Antibody Ratio Determination for Cysteine- and Lysine-Linked Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) are heterogeneous biotherapeutics and differ vastly in their physicochemical properties depending on their design. The number of small drug molecules covalently attached to each antibody molecule is commonly referred to as the drug-to-antibody ratio (DAR). Established analytical protocols for mass spectrometry (MS)-investigation of antibodies and ADCs often require sample treatment such as desalting or interchain disulfide bond reduction prior to analysis. Herein, the impact of the desalting and reduction steps-as well as the sample concentration and elapsed time between synthesis and analysis of DAR-values (as acquired by reversed phase liquid chromatography MS (RPLC-MS))-was investigated. It was found that the apparent DAR-values could fluctuate by up to 0.6 DAR units due to changes in the sample preparation workflow. For methods involving disulfide reduction by means of dithiothreitol (DTT), an acidic quench is recommended in order to increase DAR reliability. Furthermore, the addition of a desalting step was shown to benefit the ionization efficiencies in RPLC-MS. Finally, in the case of delayed analyses, samples can be stored at four degrees Celsius for up to one week but are better stored at -20 °C for longer periods of time. In conclusion, the results demonstrate that commonly used sample preparation procedures and storage conditions themselves may impact MS-derived DAR-values, which should be taken into account when evaluating analytical procedures.

Magnetic Beads for Desalting of Monoclonal Antibodies and Antibody-Drug Conjugates.

Characterization of antibody-drug conjugates (ADCs) using mass spectrometry (MS) is important in drug discovery and formulation development and as part of the quality control processes. To facilitate electrospray ionization (ESI) and produce high-quality mass spectra, common components of storage solutions for monoclonal antibodies (mAbs) and ADCs, such as nonvolatile phosphate-buffered saline (PBS), should be replaced before analysis. Centrifugal spin-type kits are extensively used for the desalting or buffer-exchange of mAbs and ADCs samples. The commercially available kits commonly require at least 100 µL of a sample at 1 mg/mL for optimal recovery. However, most ESI-MS based analyses require no more than 25 µg of protein for triplicate injection. In this study, we present a novel method for desalting of ADCs and mAbs building on the SP3 approach with nonfunctionalized carboxylate coated magnetic beads without affinity ligands. The analytes bind to the hydrophilic beads upon the addition of organic solvent, and various solutions of volatile salts or acids can be used in the elution step. The optimized protocol allowed for 88% recovery of ADC at a 25 µL sample volume and 90% recovery at 100 µL. More than 90% of the salts were removed using a process of 20 min. The intra- and interday precision showed little variation with an RSD of 1% and 2%, respectively. The compatibility of this new workflow with low sample volumes is highly valuable since a smaller fraction of the sample is wasted for analysis of the expensive analytes, without compromising recovery.

Application of triple quadrupole mass spectrometry for the characterization of antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are an inherently heterogeneous class of biotherapeutics, the development of which requires extensive characterization throughout. During the earliest phases of preclinical development, when synthetic routes towards the desired conjugate are being assessed, the main interest lies in the determination of the average drug-to-antibody ratio (DAR) of a given batch as well as information about different conjugation species. There has been a trend in mass spectrometry (MS)-based characterization of ADCs towards the use of high-resolving mass spectrometry for many of these analyses. Considering the high cost for such an instrument, the evaluation of cheaper and more accessible alternatives is highly motivated. We have therefore tested the applicability of a quadrupole mass analyzer for the aforementioned characterizations. Eight ADCs consisting of trastuzumab and varying stoichiometries of Mc-Val-Cit-PABC-monomethyl auristatin E conjugated to native cysteines were synthesized and served as test analytes. The average DAR value and molecular weights (Mw) of all detected chains from the quadrupole mass analyzer showed surprisingly high agreement with results obtained from a time-of-flight (TOF) mass analyzer and hydrophobic interaction chromatography (HIC)-derived values for all investigated ADC batches. Acquired Mw were within 80 ppm of TOF-derived values, and DAR was on average within 0.32 DAR units of HIC-derived values. Quadrupole mass spectrometers therefore represent a viable alternative for the characterization of ADC in early-stage development. Graphical abstract.

Correction to: Influence of foraminal enlargement on the healing of periapical lesions in rat molars.

Figures 2 and 3 in the published version of this article contained a mistake. CCP and DCP should have been FEG and NFEG. Correct figures are presented here.

Antimicrobial efficacy of 0.5% peracetic acid and EDTA with passive ultrasonic or manual agitation in an Enterococcus faecalis biofilm model.

We compared the antimicrobial efficacy of EDTA and 0.5% peracetic acid (PAA), with manual agitation (MA) or passive ultrasonic irrigation (PUI) in an Enterococcus faecalis biofilm model. Fifty-five single-rooted human premolar teeth were chemo-mechanically prepared and inoculated with E. faecalis for biofilm formation. These were divided into five groups (n = 11): saline solution, PAA+MA, PAA+PUI, EDTA+MA and EDTA+PUI. Root canal sampling and scanning electron microscopy of the canal lumen and dentinal tubule areas at the different root thirds were performed. The images were ranked based on contamination level. Only the PAA groups presented with no bacterial growth, with the remaining groups not presenting significant differences among them. PAA+PUI presented with the highest median position rankings in every third and location, whereas EDTA+MA performed similarly to the saline control. No differences were found when comparing MA and PUI within the same solution, however, PUI was associated with lower contamination levels mean rankings.

Dentists' knowledge of dental trauma based on the International Association of Dental Traumatology guidelines: A survey in South Brazil.

BACKGROUND/AIM: Dental trauma is a public health issue with a high prevalence in children. The aim of this study was to evaluate the level of knowledge of dentists in Rio Grande do Sul, Brazil, of the management of traumatic dental injuries, using the International Association of Dental Traumatology (IADT) Guidelines as a reference. MATERIALS AND METHODS: An electronic questionnaire investigating personal and professional characteristics and 12 questions about dento-alveolar trauma, was sent to all registered dentists of the Regional Council of Dentistry of Rio Grande do Sul (n=14 753). The respondents were grouped according to the sociodemographic and professional profiles and the data were evaluated by the Student-T test or one-way ANOVA, with Tukey's post-hoc, with α = 5%. RESULTS: A total of 1414 dentists responded to the survey (9.59% response rate). The overall mean self-reported knowledge of dental trauma was 5.87 ± 1.57, of a maximum possible score of 12. Some factors associated with a higher knowledge of the IADT guidelines were: female gender, previous clinical experience, years from qualification, self-reported knowledge, and academic postgraduate degree. Dentists who are specialized in endodontics (6.58 ± 1.63) and pediatric dentistry (6.05 ± 1.44) achieved higher levels of knowledge on dental trauma. Analysis of the characteristics (gender, location, and proportion of specialists) of the respondents confirmed that they were representative of the target population. CONCLUSION: The overall level of knowledge of dentists from Rio Grande do Sul of the IADT guidelines is moderate. These results highlight the need for continuing education on dento-alveolar trauma in this population.

Influence of foraminal enlargement on the healing of periapical lesions in rat molars.

OBJECTIVES: The aim of this study was to evaluate the influence of foraminal enlargement on the healing of induced apical periodontitis in a rat model. MATERIAL AND METHODS: Periapical lesions were bilaterally induced in mandibular first molars of 24 Wistar rats, through root canals exposure to the oral environment during 3 weeks. Endodontic treatment was performed in the mesial canal of right molars, which were separated into two experimental groups (n = 12/group). The foraminal enlargement group (FEG) received instrumentation in the entire root canal length, including the cemental canal, while in the non-foraminal enlargement group (NFEG), instrumentation was carried out 1 mm short of the apical foramen. Root canals were filled with gutta-percha and AH Plus sealer, in the same visit, 1 mm short of the apical foramen in both experimental groups. Left molars were not treated and served as a baseline control group. The animals were killed after 4 weeks, and their hemi-mandibles were prepared for radiographic and histological analysis. Data were analyzed by Student's t test and ANOVA. RESULTS: Only FEG presented lower areas of periapical radiolucency compared to the control (p < .05). Both FEG and NFEG allowed decreased inflammation intensity (p < .0001 and p < .01) and higher scores of cementum neoformation when compared to non-treated samples (p < .0001). FEG was more effective than NFEG in promoting biological seal, i.e., apical closure with cementum (p < .01). FEG, but not NFEG, showed lower scores of root resorption than the control. CONCLUSIONS: Foraminal enlargement during root canal preparation improved periapical healing in rat molars. CLINICAL SIGNIFICANCE: Foraminal enlargement has been suggested to improve disinfection at the apical portion of root canals. This procedure may favor the healing of chronic periapical lesions.

Apical transportation in simulated root canals prepared using HyFlex CM, WaveOne Gold and manual technique / Avaliação do transporte apical em canais simulados preparados com instrumentação manual e com movimentos rotatório contínuo e reciprocante

Objective: To assess the apical transportation in simulated root canals with different curvature angles prepared using manual instrumentation and rotary and reciprocating motions. Methods: Sixty simulated root canals were prepared using manual instrumentation (Flexofile K-file) (MT), continuous rotation (HyFlex CM) (HF), and reciprocating motion (WaveOne Gold) (WG). A trained operator prepared the canals, and the apical enlargement was standardized up to a #25 file in all systems tested. Two different curvature angles of the simulated root canals were tested: 70° and 50°. Overlapping photographs of the simulated root canals, before and after root canal preparation, were used to measure the apical transportation (mm), using the ImageJ software. Descriptive statistics (mean and standard deviation) were analyzed and the groups were compared with two-way ANOVA followed by Tukey's post-hoc, with α=5%. Results: There was a statistically significant interaction between the effects of group and angle in the apical transportation (F = 3.740; p = 0.031). Simple main effects analysis showed that HyFlex CM produced a significantly lower apical transportation when compared to WaveOne Gold (p = 0.02) and the manual technique (p < 0.01), regardless of the angle. However, there were no differences between WaveOne Gold and manual technique in canals with the 70° angle (p>0.05). The group with the highest mean apical transportation was the MT, with 0.0917 mm, followed by WG and HF, with 0.0633 and 0.0325, respectively. Conclusion: Simulated root canals prepared with rotary motion (HyFlex CM) showed the lowest apical transportation, followed by the reciprocating motion (WaveOne Gold). The manual technique showed the most unfavorable results, with the highest apical transportation.(AU)

Objetivo: avaliar o transporte apical em canais radiculares simulados com diferentes ângulos de curvatura preparados por meio de instrumentação manual e dos movimentos rotativo e reciprocante. Métodos: sessenta canais simulados foram preparados usando instrumentação manual (Flexofile K- -file) (MT), rotação contínua (HyFlex CM) (HF) e movimento reciprocante (WaveOne Gold) (WG). O preparo do canal radicular foi realizado por um operador treinado, e o alargamento apical foi padronizado até o instrumento #25 em todos os sistemas testados. Dois diferentes ângulos de curvatura dos canais simulados foram testados: 70° e 50°. Fotografias sobrepostas dos canais simulados, antes e após o preparo do canal radicular, foram utilizadas para medir o transporte apical (mm), utilizando o software ImageJ. Estatísticas descritivas (média e desvio padrão) foram analisadas e as comparações entre os grupos foram realizadas através de ANOVA de duas vias, seguido por post-hoc de Tukey, com α=5%. Resultados: houve interação estatisticamente significativa entre os efeitos do grupo e do ângulo no transporte apical (F = 3,740; p = 0,031). A análise simples dos efeitos principais mostrou que o sistema Hy- Flex CM produziu um transporte apical significativamente menor quando comparado ao sistema WaveOne Gold (p = 0,02) e à Técnica Manual (p <0,01), independentemente do ângulo. No entanto, não houve diferenças entre o WaveOne Gold e a Técnica Manual em canais com ângulo de 70 ° (p> 0,05). O grupo que apresentou maior transporte apical médio foi o MT, com 0,0917 mm, seguido pelo WG e pela HF, com 0,0633 e 0,0325, respectivamente. Conclusão: canais radiculares simulados preparados com movimento rotatório (HyFlex CM) mostraram o menor transporte apical, seguido de movimento reciprocante (WaveOne Gold). A técnica manual revelou os resultados mais desfavoráveis, com maior transporte apical.(AU)

Qualitative analysis of antibody-drug conjugates (ADCs): an experimental comparison of analytical techniques of cysteine-linked ADCs.

Antibody-drug conjugates (ADCs) are an emerging type of biotherapeutics that utilize multiple tissue-specific antibodies combined with a range of linker designs to enable the transportation and selective release of cytotoxic drugs in close proximity to tumours. Consisting of antibodies conjugated to small drug molecules through a variety of linkers, ADCs are chemically complex analytes. Here we present a unique experimental comparison of four techniques for ADC analysis: hydrophobic interaction chromatography (HIC-UV/Vis), reversed phase liquid chromatography mass spectrometry (RPLC-MS), using either a QToF or an Orbitrap analyser, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Four different ADCs consisting of Trastuzumab, monomethyl auristatin E (MMAE) and a peptidic linker moiety differing in their respective stoichiometric ratios in regard to drug-to-antibody ratio (DAR) were used for the comparison. We found that the determined DAR from all techniques was comparable, while the accuracy of the molecular weights for the conjugated light and heavy chain differed more extensively. This indicates that the choice of a mass analyser is more crucial for determining the accurate weights of the light and heavy chains than to evaluate the DAR of a given batch. However, ambiguous DAR assignment in HIC-UV/Vis or bias for either the light or heavy chain fragments in the mass spectrometry-based techniques can influence the obtained average DAR value and the use of complementary techniques is advisable. Out of the four techniques evaluated, HIC-UV/Vis and MALDI required less time to obtain an average DAR value and would therefore be good for initial screenings in the early stages of the discovery phase of new ADCs.

Dendritic cells and their relation to apical peridontitis.

The purpose of this manuscript was to re-discuss apical periodontitis, apical biofilm, and its possible relationship with dendritic cells (DC). DCs are potent regulators of the immune system and their function is divided into three categories that involve the presentation of antigens: the presentation of antigens and activation of T cells; a not well established category suggested that DCs induce and maintain immunological tolerance; and the maintenance of the immune memory in conjunction with B cells. DCs in periapical inflammatory lesions are composed of at least two subpopulations that can be distinguished on the basis of ultrastructure and phenotype. These populations might differ in lineage, state of maturation, differentiation, activation, and/or function. The authors hereby analyzed the root apexes of teeth under SEM, after performing apicoectomy due to the failure of conventional endodontic treatment. Microbial biofilm with multispecies and areas of resorption with the presence of Howship lacunae, and images suggestive of denditric cells could be observed. The presence of DCs in periapical lesion could be an indication of the severity of the lesion, with a constant presence of antigen in the periradicular region.

Root canal preparation in 3-rooted maxillary premolars through hand, rotary, and reciprocating techniques: a microcomputed tomography evaluation.

Endodontic management of 3-rooted maxillary premolars is a challenge due to their complex anatomy and narrow root canal walls. This study aimed to evaluate, by microcomputed tomography (µCT), the apical enlargement and centering ability promoted by hand, rotary, and reciprocating instrumentation in 3-rooted maxillary premolars. Eighteen teeth were divided into 3 groups (n = 6) according to the preparation technique: crown-down hand, rotary, and reciprocating instrumentation. Instruments with similar apical diameters were used (25 and 40 mm for buccal and palatal canals, respectively). Centering ability and canal enlargement were evaluated through the comparison of µCT images obtained before and after instrumentation. Distances of 0, 2, 4, and 6 mm from the apical stop were considered. Differences between canal areas before and after instrumentation were calculated. In addition, distances between the original canal center and the prepared canal center at the apical stop were measured in both the mesiodistal and buccopalatal directions. Significant differences in enlargement areas and centering ability among the techniques were determined using 2-way analysis of variance and Tukey post hoc test (P > 0.05). Root canal enlargement was similar for all techniques. Excessive enlargement was observed in only a few specimens, and root perforation did not occur. Some specimens presented untreated canal areas. In mesiobuccal and distobuccal roots, reciprocating instrumentation promoted more centered preparations than hand instrumentation when measured in the mesiodistal direction (P > 0.05). There were no other statistically significant differences. The results established that hand, rotary, and reciprocating techniques presented similar safety margins for instrumentation of the apical third of 3-rooted maxillary premolars. Reciprocating instrumentation presented some advantages over hand preparation regarding centering ability.

Clinically relevant dimensions of 3-rooted maxillary premolars obtained via high-resolution computed tomography.

INTRODUCTION: This study aimed to characterize the dimensions of a selection of 3-rooted maxillary premolars through high-resolution computed tomographic analysis considering measures of clinical interest for root canal treatment, such as root wall thickness, canal diameters, and distances between 2 canals in fused roots and between the root apex and foramen. METHODS: Fifteen 3-rooted human maxillary premolars extracted for therapeutic reasons were individually scanned using a high-resolution desktop high-resolution computed tomographic system. Starting from the apical foramen, the selected cross-sectional images corresponding to each millimeter of the roots were evaluated. Measures of clinical interest were determined using Image J software (version 1.41; National Institutes of Health, Bethesda, MD). RESULTS: Root wall thickness as thin as 0.4 and 0.6 mm was detected in the apical portion of buccal and palatal roots, respectively. In the cervical portion, buccal roots had narrower root walls (0.817-1.670 mm) compared with palatal roots (1.361-2.720 mm). In all thirds, the palatal canal was wider compared with the mesiobuccal and distobuccal canals. In the buccopalatal direction, all roots had thicker root walls toward the furcation, whereas in the mesiodistal direction the mesiobuccal and distobuccal roots had the thinnest walls along their distal and mesial aspects, respectively. Both buccal canals revealed dentin apposition 2 mm from the canal orifice, resulting in cervical constriction. Generally, the distance between the root apex and the foramen was greater in distobuccal roots in comparison with the others with a tendency for foramina to be eccentric. CONCLUSIONS: Three-rooted premolars are a clinical challenge not just because of their low frequency and difficulties regarding diagnosis and root canals access but also because of their fragile roots. These phenomena are critical in terms of the amount of dentin removed during the preparation of root canals and during post space preparation.

Transfixação da placa de crescimento com fios metalicos lisos e rosqueados: estudo experimental em coelhos / Growth plate transfixation with smooth and threaded pins: an experimental study

Realizou-se estudo experimental na placa epifis ria de crescimento distal do femur de 50 coelhos com cinco semanas de vida. A placa epifisaria foi transfixada com pinos metalicos lisos e rosqueados, introduzidos perpendicular ou obliquamente ao seu eixo longitudinal. Os animais foram divididos em cinco grupos, de acordo com a técnica de transfixação e implante metalico empregado. Os cinco grupos foram subdivididos em 10 subgrupos de cinco animais cada, de acordo com a época em que foram mortos. As alterações no crescimento longitudinal, na angulação dos candilos femorais e na microestrutura da placa de crescimento foram analisadas por meio de mensuração do comprimento longitudinal do femur, por radiografias de controle e estudo histol¢gico, apos oito e 12 semanas. A placa epifis ria distal do femur de coelhos com cinco semanas de vida foi transfixada por um pino metalico liso de 1,5mm de diametro que atravessou a placa epifisaria perpendicularmente e foi retirado em seguida no mesmo ato cir£rgico. Esse procedimento não alterou o crescimento longitudinal do osso e tampouco modificou a estrutura morfologica da placa de crescimento. Entretanto, quando o pino foi deixado no local, provocou lesõe definitiva na rea lesada. Os pinos metalicos lisos cruzados em relação à placa epifisaria produzem lesão definitiva na placa de crescimento, com substituição do tecido cartilaginoso por tecido osseo no local da lesão. A maior incidencia de retardo de crescimento e alterações fisarias ocorreram apos 12 semanas, no grupo em que a placa epifisaria foi transfixada com pinos intramedulares ou pino rosqueado. Esses achados experimentais sugerem que se deve ter cuidados quando os pinos que transfixam a placa epifisaria são utilizados no tratamento de fraturas, pois podem produzir lesão permanente da placa epifisaria