Viability of Bovine Teeth as a Substrate in Bond Strength Tests: A Systematic Review and Meta-analysis.

PURPOSE: To assess whether bovine teeth can be used as viable alternatives for human teeth in tensile and shear bond strength testing. MATERIALS AND METHODS: Articles were selected from Web of Science, PubMed, Scopus, LILACS-Bireme, and BBO electronic databases using keywords obtained from Medical Subject Headings (MeSH). Of 1540 potentially eligible studies, 157 were selected for full text analysis. Five independent reviewers (Kappa = 0.89) selected the studies, abstracted information, and assessed quality based on standardized scales. After the analysis, 78 studies comparing bovine teeth to human teeth were found. Only 18 studies comparing bovine and human substrates in bond strength tests were included in the systematic review and 13 in the meta-analysis. Two authors independently selected the studies, extracted the data and assessed the risk of bias. Mean differences were obtained by comparing tensile and shear bond strengths between human and bovine teeth (permanent and deciduous) and considering enamel and dentin separately (subgroup analysis). Statistical analysis was performed using RevMan5.1, with a random-effect model, at a 5% significance level. RESULTS: No significant difference was found between human and bovine teeth in tensile tests (p = 0.41) for dentin (p = 0.86), but there was a difference for enamel (p = 0.01). Regarding shear bond strength, no significant difference was found between human and bovine teeth (p = 0.16) either for enamel (p = 0.07) or dentin (p = 0.68). Regarding shear bond strength on deciduous teeth, no significant difference was found between human and bovine substrates (p = 0.54), either for enamel (p = 0.42) or dentin (p = 0.05). Most studies were at high (low or unclear) risk of bias. CONCLUSIONS: In shear bond strength testing, bovine teeth can be a suitable alternative for permanent and deciduous human teeth, for both enamel and dentin substrates. However, they may not be suitable for enamel tensile bond strength testing. The findings are based on low quality studies (considerable heterogeneity) and should be interpreted with caution.

Epigenetic regulation of matrix metalloproteinase expression in ameloblastoma.

BACKGROUND: An ameloblastoma is a benign odontogenic neoplasm with aggressive behaviour and high recurrence rates. The increased expression of matrix metalloproteinases (MMPs) has been reported in ameloblastomas. In the present study, we hypothesised that epigenetic alterations may regulate MMP expression in ameloblastomas. METHODS: We investigated the methylation status of the genes MMP-2 and MMP-9 in addition to mRNA transcription and protein expression in ameloblastomas. Methylation analysis was performed by both methylation-specific polymerase chain reaction (MSP-PCR) and restriction enzyme digestion to evaluate the methylation profile of MMP-2 and MMP-9 in 12 ameloblastoma samples and 12 healthy gingiva fragments, which were included as controls. Furthermore, we investigated the transcription levels of the genes by quantitative reverse-transcription PCR (qRT-PCR). Zymography was performed to verify protein expression in ameloblastomas. RESULTS: The ameloblastomas showed a high frequency of unmethylated MMP-2 and MMP-9, whereas the healthy gingival samples presented a sharp prevalence of methylated MMPs. Higher expression levels of MMP-9 were found in ameloblastomas compared to healthy gingiva. However, no significant differences in the MMP-2 mRNA expression between groups was found. All ameloblastomas showed positive expression of MMP-2 and MMP-9 proteins. CONCLUSIONS: Our findings suggest that expression of MMP-9 is increased in ameloblastomas and is possibly modulated by unmethylation of the gene.

Overdentures implantorretidas em carga imediata: experiência de um projeto de extensão / Implant-retained overdenture withimmediate loading: the experience of an extension program project

O objetivo desse estudo é relatar a experiência e os resultados de um projeto de extensão universitária que se propõe a reabilitar pacientes de baixa renda, com dentição seriamente comprometida, utilizando-se próteses totais imediatas (PTI) para a arcada superior e overdentures retidas por dois implantes em carga imediata, para a arcada inferior. Métodos: quarenta e dois pacientes foram selecionados para o estudo. Em três casos, não se alcançou travamento primário compatível com o procedimento de carga imediata sobre implantes. Nesses pacientes, as próteses foram capturadas de forma convencional, após o período de osseointegração. Trinta e nove pacientes receberam overdentures em carga imediata. Três deles sofreram perda precoce de um dos implantes, todos ainda no primeiro mês após o procedimento. Os implantes perdidos foram, posteriormente, substituídos e recapturados após três meses. Trinta e seis pacientes completaram o período de osseointegração sem apresentar perdas. Os pacientes passaram, então, a ser avaliados periodicamente, sendo que os casos mais antigos chegaram a 36 meses de acompanhamento e, os mais recentes, incluídos nesse estudo, a 6 meses de controle. Resultados: até o momento das últimas avaliações, não foi observada nenhuma perda adicional de implantes. A taxa de sobrevivência observada foi de 96,15%, isso é, 3 implantes perdidos em 78 imediatamente carregados. Conclusão: o projeto tem alcançado resultados estéticos e funcionais altamente satisfatórios, proporcionando uma melhora acentuada na qualidade de vida da população assistida...

The aim of this study is to report the experience and results of a university extension program project which proposes to rehabilitate low-income patients with severely compromised dentition, using immediate complete dentures (ICD) for the upper arch and overdenture supported by two immediatly loaded implants on the lower jaw. Methods: Forty-two patients were selected for the study. In three cases,primary locking was not consistent with the procedure of implant immediate loading. In these patients, theprostheses were captured in a conventional manner after osseointegration. A total of 39 patients received overdenture with immediate loading. Three of them suffered early loss of one of the implants, all in thefirst month after the procedure. Implants that had been lost were recaptured and replaced three monthslater. A total of 36 patients completed the period of osseointegration without any implant loss. Patientswere periodically evaluated. The oldest cases reached 36 months of follow-up, whereas the newest one was6 months under control. Results: By the time of the latest reviews, no further loss of implants was observed.The survival rate was 96.15%, i.e., only 3 out of 78 implants were lost after immediate loading. Conclusion:The project is highly satisfactory in terms of esthetic and functional results. Additionally, it provides significantimprovements in quality of life of the assisted population...