OAR@UM Collection:https://www.um.edu.mt/library/oar/handle/123456789/299452024-03-29T10:40:09Z2024-03-29T10:40:09ZAn investigation of the giant cell fibromahttps://www.um.edu.mt/library/oar/handle/123456789/325802018-11-13T13:52:30Z2006-01-01T00:00:00ZTitle: An investigation of the giant cell fibroma
Abstract: The giant cell fibroma is a reactive fibrous overgrowth of the oral mucosa
characterised by the presence of bizarre large stellate mononuclear and
multinuclear cells in the lamina propria. Since this lesion had never been reported
in Malta, the pathology archives at St Luke's Hospital were searched for possible
cases of giant cell fibroma and data on the incidence of this lesion were tabulated
and compared with those reported in the literature.
Immunohistochemistry was carried out on material retrieved from the pathology
archives and identified as cases of giant cell fibroma in order to ascertain the
phenotype of the cells which characterize this lesion. The phenotype of these
cells was compared to that of histologically similar cells found in the cervix, in
fibrous papules of the nose (face) and in one case of allergic nasal polyps. It was
concluded that the characteristic cells of the giant cell fibroma and histologically
similar cells in fibrous papules of the nose (face) and frequently in the cervix are
fibroblasts whilst a subset of similar cells in the cervix and in allergic nasal
polyps are myofibroblasts.
The expression of the cell proliferation markers Ki67 and proliferating cell
nuclear antigen was also investigated in order to test the hypothesis that
mutinucleation of the stellate cells is being caused by cell division in the absence
of kinesis. Since two reports by previous authors mention that in several lesions
and anatomical sites mast cells were noted to be in contact with the large stellate
cells, the presence and location of mast cells in giant cell fibromas, cervix,
fibrous papules of the nose (face) and in the case of allergic nasal polyps were
investigated. It was concluded that the cells under study in all sites and lesions
studied are not cycling and that therefore multinucleation is probably achieved by
the fusion of mononuclear cells. Furthermore, very few stellate cells were seen to
be in contact with or in the immediate vicinity of a mast cell, and so it is unlikely
that mast cells are inducing multinucleation in the stellate cells.
The final part of this study consisted of the comparison of the distribution of
various components of the extracellular matrix of giant cell fibromas, fibrous
polyps and epulides of the oral mucosa and denture related fibrous overgrowths
in order to ascertain whether any differences exist between giant cell fibromas
and other reactive fibrous overgrowths of the oral mucosa. It was concluded that
no significant differences between these lesions exist and that these lesions
probably form part of the same disease process. Because of this and because of
the fact that the atypical stellate cells which characterize the giant cell fibroma
are not unique to this lesion but are in fact widely-distributed in many lesions and
even in normal mucosa in various anatomical sites, it is proposed that the giant
cell fibroma should not he separated out as a discrete disease entity hut should he
described as a reactive fibrous polyp or epulis containing large stellate
fibroblasts.
Description: M.PHIL.2006-01-01T00:00:00ZThe use of Portland cement and its modified forms as a dental core build-up materialhttps://www.um.edu.mt/library/oar/handle/123456789/318302020-11-23T06:07:19Z2006-01-01T00:00:00ZTitle: The use of Portland cement and its modified forms as a dental core build-up material
Abstract: The use of mineral trioxide aggregate (MTA) for various applications in dentistry is
difficult due to its long setting time and poor compressive strength. The aim of this
research project was to study the properties of MT A, and modify the material in an
attempt to make it suitable as a core build-up material.
Materials and Methods
The chemical constituents of MT A (Dentsply, Tulsa Dental Products, Tulsa UK,
USA), Portland cement (CEM 1 45,5N; Italcementi spa, Bergamo, Italy) and other
cement prototypes wos determined hy performing both phase and elemental analysis
on both un-reacted powders and hydrated cements. The cement properties were
improved by addition of calcium aluminate cement to Portland cement, by exclusion
of gypsum from the end stage of the manufacturing process and also by using calcium
fluoroaluminate (CF A) cement. Fast setting proprietary brands (3) were also tested. In
addition, various fillers (3), and micro-silica were added in conjunction with the use
of a superplasticizing admixture. DSP (densified with small particles) mortars and
composite materials were thus produced. Compressive strength testing was performed
using two methods of testing cements namely using cylinders 6 mm in diameter and
12 mm high and cubes of side 70.7 mm. Both methods of testing were compared. The
method of testing compressive strength was also modified and flexural strength of the
composite materials was also measured.
Biocompatibility was assessed using a cell culture technique and cell growth and
proliferation was evaluated under the scanning electron microscope. The method of
testing biocompatibility was also improved upon and assessment of cell activity by a
vital dye that measures mitotic dehydrogenase activity was also used. The assessment
of cell activity using a vital dye was preferred to scanning electron microscopic
assessment of cell proliferation as it avoided material contamination during
processing. The cements were tested by placing the cells directly on the cement and
cells were also grown on an elution. Other tests performed included pH evaluation,
marginal adaptation tested using a fluorescent dye and a confocal microscope and
field emission scanning electron microscope, and acid resistance tests performed to
check resistance of material to acid attack evaluated using the polarized light
microscope, the scanning electron microscope and the confocal microscope. The
different testing methods were compared.
Results
The chemical constituents of MTA (Dentsply, Tulsa Dental Products, Tulsa OK,
USA) showed the material to be similar to Portland cement except for the bismuth
oxide which is present in MTA. Both MTA and Portland cement were composed of
1ri ami rli cakilll11 ~iliootc, which on hydration prodl](~cd eakilll11 silicate hydr11te Klnd
calcium hydroxide. The materials were susceptible to contamination by inorganic
compounds and other chemicals routinely used to evaluate cell viability under the
scanning electron microscope. Calcium hydroxide was not always produced during
hydration. Emaco Ultra-rapid, and both calcium sulpho-aluminate (CSA) and calcium
fluoro-aluminate (CF A) did not show any release of soluble calcium ions.
Combinations of Portland cement (OPC) and high alumina cement (HAC), various
proprietary brands of cement, the use of cement clinker interground without the
gypsum during the manufacturing process and the use of CSA and CF A cement
resulted in a reduced setting time. The setting time was less than 9 minutes for all the
cement prototypes tested. Compressive strength testing showed that one fast setting
proprietary brand (Emaco Ultra-rapid), and both CSA and CF A had compressive
strength values comparable to that reported for glass ionomer cement. The CSA
cement was stronger than the CFA cement both in compression and in flexure at all
curing times (p < 0.001) except for flexural strength at 1 day where no difference
between the two cements was demonstrated (p > 0.05). Addition of granite to the
CSA cement resulted in an increase in flexural strength at 28 and 56 days but a
reduction in the compressive strength at all ages (p < 0.001). Addition of granite to
CF A increased the flexural strength up to 28 days (p < 0.01) but the flexural strengths
of the cement and the cement composite were the same at 56 days (p > 0.05). The
mixtures of OPCIHAC and the other proprietary brands showed very low strengths.
The cement clinker had low initial strengths. Addition of bismuth oxide affected the
material adversely with marked reduction in compressive strengths. The fast-setting
DSP mortars had a lower compressive strength at 1 day (p < 0.005), but there was no
difference between the cements and DSP mortars at later curing times. Vacuum
mixing did not improve the compressive strength of the prototype cements at any age.
Wet curing improved the compressive strength of Portland cement at all ages (p <
0.05) in comparison to the prototype cement where compressive strength at 1 day
(35.98 Nmm-2
, p = 0.011) and 7 days (44.08 Nmm-2
, p = 0.025) was reduced by
immersion in water. The filler replaced cement prototypes were more stable and less
susscebtable to changes in less compressive strength by varifying the curing method (p >0.05).
The compressive strength of Portland cement was different between the two methods
namely the testing of cubes and that of cylinders (p < 0.001). All the fast-setting
cements tested showed no difference in compressive strength regardless of the
method of testing at 1 and 7 days (p > 0.05), but the cylinders showed a lower
compressive strength at 28 days (p < 0.05). Thus, specimen size and shape seemed to
affect the compressive strength testing results.
The pH was alkaline for all the cements tested. Storage solutions also demonstrated a
high pH. Prototype materials took up more water than glass ionomer cement. Curing
at 100% humidity resulted in a net loss of weight for all the materials tested. Glass
ionomer cement restorations showed marginal leakage along their walls and along the
restoration floor. The changes caused by acid contact were different for the CSA and
CF A cements compared with glass ionomer cement. These cements exhibited
changes in their internal chemistry with no changes in surface characteristics while
the glass ionomer cement showed erosion of the cement matrix early after acid
contact. No changes were observed in the cement composite based on calcium
sulpho-aluminate.
Biocompatibility testing of the cements showed that cell proliferation was enhanced
only in cements which produced soluble calcium ions as a by-product of cement
hydration (MTA, cement clinker and Portland cement). Indirect studies of the eluants
showed an increase in cell activity after 24 hours compared with the control in culture
medium (p < 0.05). Direct cell contact with the cements resulted in a fall in cell
viability for all time points studied (p < 0.001). Emaco Ultra-rapid, and both CSA and
CF A cements did not encourage cell growth similar to glass ionomer cement. The
addition of bismuth oxide did not interfere with the biocompatibility of the cements.
Conclusions
MTA (Dentsply, Tulsa Dental Products, Tulsa OK, USA) and Portland cement (CEM
1 45,5N; Italcementi spa, Bergamo, Italy) were composed primarily of tricalcium
silicate and calcium hydroxide was produced as a reaction by-product on hydration.
The setting time of MTA could be reduced by addition of calcium aluminate cement.
In excess of gypsum the cement produced showed both a reduction in setting time and
good compressive strengths. Similar results were obtained for CF A and a brand of
fast setting cement. Exclusion of gypsum from the cement at the end of the
manufacturing process reduced the setting time but initial strengths were low. The
compressive strength of these prototype materials was enhanced by the use of a
superplasticizing admixture that allowed the reduction of the water/cement r(ltio at the
same rheology. Addition of an inert material to the cement increased the flexural
strength.
Most standard testing procedures used to test dental cements did not seem suitable for
testing cements based on Portland cement. Processing for scanning electron
microscopy reacted with the cement hydration by-products; the cements were even
susceptible to changes in size of specimen when tested in compression and use of
acidic dyes which are used routinely for evaluation of marginal adaptation of
materials affected the cement. Materials which had calcium hydroxide produced
during hydration encouraged cell proliferation. In fact cells grew preferentially on the
material elution rather than directly on the cement surface.
Description: PH.D.DENTAL SURGERY2006-01-01T00:00:00Z