There is a lack of data regarding the shapes and distribution of the mineralized tissue that composes the cementoenamel junction. A sample of 198 permanent human teeth was analyzed by optical microscopy and scanning electron microscopy. Scanning electron microscopy showed three types of tissue interrelations: enamel overlapped by cementum; enamel and cementum edge-to-edge; and a gap, revealing a strip of exposed dentin. Using optical microscopy, a fourth type of cementoenamel junction was observed: cementum overlapped by enamel. The distribution of the hard tissues found at the cementoenamel junction is unpredictable and irregular both for any tooth type (e.g. on cuspids) and on any one individual tooth. Based on these results and on analysis of the mechanisms involved in cervical root resorption, it is possible to consider the cervical region as prone to external resorption.

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.

Depois de 20 anos da publicação da pesquisa que mudou o conhecimento sobre a junção amelocementária e passou a ser um dos artigos mais citados mundialmente sobre o assunto clareamento dentário e reabsorção cervical externa, será aqui relatada a contribuição desse trabalho na compreensão de algumas situações clínicas que envolvem a região cervical dos dentes, como: a reab- sorção cervical externa, a hipersensibilidade dentinária pós-clareamento, a abfração e outras, especialmente as relacionadas à clínica ortodôntica.