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J M Fonseca

Publications and source records attributed to J M Fonseca.

5 recordsLinked to original sources
PubMed1995

The use of debonding pliers in the removal of ceramic brackets: force levels and enamel cracks.

The purpose of this study was to determine the magnitude of the applied forces when using pliers as a debonding method for removing three types of ceramic brackets. The following variables were evaluated: debonding strengths, the Adhesive Remnant Index, and enamel damage with transillumination. All the brackets in this investigation was debonded with a direct bond remover plier. An Instron Model Universal testing machine was used to measure debonding strengths. From the results of this study, the following conclusions can be drawn: (1) The diamteral compression mean bond strengths for the three bracket types tested ranged from a low of 67.8 Kg/cm2 to a high of 102.9 Kg/cm2 and are in the clinically acceptable range for orthodontic force application. (2) There was no significant difference in the mean bond strengths of the three ceramic brackets tested. (3) The ARI scores were found to range between 2 and 4 indicating a cohesive type of bond failure. (4) Transillumination was used to evaluate minute enamel damage, and the results indicated that most of the teeth (82.02%) experienced no increase in enamel cracks after debonding. The teeth that showed an increase in the number of cracks after debonding had a significantly higher mean bond strength (113.0 Kg/cm2) than those with no increase in the number of cracks (72.9 Kg/cm2).

Adhesives↗
PubMed1987

Colony-stimulating factors regulate the development of multinucleated osteoclasts from recently replicated cells in vitro.

Osteoclasts mediate the process of bone resorption. However, little is known about the mechanisms that regulate the formation of either osteoclasts or osteoclast precursors. In contrast, colony-stimulating factors (CSFs) are well-known to regulate the formation of myeloid cells and their precursors. Because osteoclasts and myeloid cells may originate from a common stem cell, we examined the effects of two CSFs, granulocyte-macrophage CSF (GM-CSF) and interleukin 3 (IL-3), on bone resorption, osteoclast formation, and the incorporation of recently replicated nuclei into the osteoclasts of mouse bone cultures. CSFs had little effect on the formation rate of osteoclasts or their resorptive activity but significantly decreased the percentage of recently replicated osteoclast progenitor cell nuclei present in the osteoclasts of bones treated with parathyroid hormone. GM-CSF also increased the number of myeloid cells in the marrow space of the cultures and the percentage of these cells derived from recently replicated progenitors. These results demonstrate that GM-CSF and IL-3 can regulate the development of osteoclasts from recently replicated precursor cells in cultured fetal mouse long bones. However, the mechanisms by which CSFs influence osteoclast formation are difficult to determine from these studies because markers for the osteoclast progenitor and precursor do not exist. These data also provide evidence that the differentiation of osteoclast progenitors is regulated by different factors at different points in their ontogeny.

Animals↗