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Biomedical subjects

A Konstantinidis

Publications and source records attributed to A Konstantinidis.

At least 37 records · Page 2Linked to original sources
PubMed2000

Removable prosthodontic treatment for the primary and mixed dentition.

Dental prosthetic treatment of children in the primary and mixed dentition years was planned with respect to the special conditions accompanying the absence of teeth. Besides the immediate functional and esthetic benefit of prosthetic therapy, the prosthetic appliance helps to maintain the oral functional status, which is considered necessary for undisturbed lower facial growth. Therefore, careful follow-up and thoughtful treatment decisions should be exercised, especially in cases where impairment of permanent dentition and supportive tissues complicate the prognosis.

Anodontia↗
PubMed1999

Severe muscle weakness due to hypokalemia as a manifestation of small-cell carcinoma.

We describe the case of a 56-year-old man with severe muscle weakness due to heavy hypokalemia (serum potassium 1.44 mmol/l) associated with inappropriate kaliuria and alkalemia. Subsequent investigation revealed the presence of ectopic ACTH hypersecretion due to a small-cell lung carcinoma. A significant clinical/laboratory improvement was achieved following chemotherapy-induced regression of the primary tumor. The profound hypokalemia was probably the result of cortisol hypersecretion, which in concert with the ACTH-induced decreased 11beta-hydroxysteroid dehydrogenase activity can exhibit an increased mineralocorticoid activity. In addition, other ACTH-dependent mineralocorticoids may play a contributory role in the development of severe hypokalemia.

ACTH Syndrome, Ectopic↗
PubMed1998

Artificial caries formation around fluoride-releasing restorations in roots.

Secondary caries is one of the most important factors leading to replacement of dental restorations. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in the buccal and lingual surfaces of 30 extracted premolars. The six materials used were: glass-ionomer cement (Fuji), glass-ionomer cement with silver particles added (Ketac-silver), fluoride-containing composite resin (Tetric), composite resin (Silux plus), fluoride-containing amalgam (Fluor-Alloy) and high-copper amalgam (Dispersalloy). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that repair with glass-ionomer materials of a carious lesion may be of great importance in the prevention of secondary caries around the restorations in roots.

Bicuspid↗
PubMed1998

In vitro evaluation of the cytotoxicity of a bleaching agent.

Cell cultures of L929 and BHK21/C13 cells were used to evaluate the toxicity of a newly introduced bleaching agent (Colgate Platinum) compared to hydrogen peroxide, an established bleaching agent. The cell reaction was determined by a quantitative technique at 24 h and 72 h. Both bleaching materials had a dose-dependent effect on cell viability. Concentrations of hydrogen peroxide causing a 50% decrease in cell number (50% inhibition dose-ID50) were calculated as 0.00034% after 24 h and 0.00001% after 72 h in L929 cells. The ID50 of hydrogen peroxide was found to be 0.00016% after 24 h and 0.00007% after 72 h in BHK21/C13 cells. The ID50 of Colgate Platinum was 0.00074% after 24 h and 0.00045% after 72 h in L929 cells and 0.00055% after 24 h and 0.00024% after 72 h in BHK21/C13 cells. The results showed that, in vitro, both bleaching agents were cytotoxic to fibroblasts and the new bleaching agent was less toxic than hydrogen peroxide.

Animals↗
PubMed1997

Gingival recession: a cross-sectional clinical investigation.

In this cross-sectional study, risk and potentially causative factors of gingival recession were examined and their relationship to apical migration of the gingival margin evaluated. Thirty eight patients (18-60 years), displaying one or more sites with gingival recession but without any significant periodontal disease participated. A total of 28 parameters were evaluated in both 'test' teeth (50 teeth with gingival recession) and 'control' teeth (50 contralateral teeth). The results revealed that gingival margin recession was associated with both high inflammatory and plaque scores, with decreased widths of keratinized and attached gingiva and with the subjects' toothbrush bristle hardness.

Adolescent↗
PubMed1996

The use of ERCP in the study of patients with hepatic echinococcosis before and after surgical intervention.

BACKGROUND: Biliary tree involvement is the most common complication of hydatid liver disease, which is difficult to detect and manage. METHODS: During the last 7 years, we examined by ERCP 26 cases with echinococcal liver involvement. Indications in the preoperative group included cholangitis in 6 cases, right-sided hypochondralgia involving 4, preoperative assessment in 4, and icterus in 1 case. In the postoperative group, the indications for ERCP were cholangitis in 5 cases, external biliary fistulas in 5, and biliary colic in 1 case. RESULTS: ERCP findings in the preoperative group included external bile duct compression in 11 cases (73.3%), biliary fistula affecting 3 (20%), and echinococcal remnants within the common bile duct in 1 case (6.6%). With regard to the postoperative group, biliary fistula formation was detected in 6 cases (54.5%), echinococcal remnants within the common bile duct in 4 (36.3%), and external bile duct compression involving 1 case (9%). Endoscopic sphincterotomy was successfully performed in 13 patients in both groups. No serious complications were encountered. CONCLUSION: ERCP is a safe and helpful preoperative or postoperative tool that aids in the diagnosis and often the treatment of echinococcal liver disease with involvement of the bile ducts.

Aged↗
PubMed1996

Cystic angiomatosis of bone: a case report.

Diffuse skeletal cystic angiomatosis is an extremely rare disorder that has not previously been reported in detail in the dental literature. This case report deals with the oral manifestations in a 10-year-old boy. Clinical, radiographic, and computed tomographic examinations showed hyperplasia of the right side of the face. The computed tomographic imaging studies revealed the extent of the jawbone lesions and the adjacent hyperplastic soft tissues. The histologic appearance of the lesions, the course of the disease, and the differential diagnosis are discussed.

Angiomatosis↗
PubMed1994

Effect of a new pre-brushing rinse on dental plaque removal.

Non-prescription prebrushing rinses to facilitate dental plaque removal have been advertised in recent years. The purpose of the present study was to determine the plaque removal effectiveness of Plax (Colgate) prebrushing rinse by comparing it to a placebo solution. 19 dental students volunteered for this double blind study which consisted of 2 experimental periods. The following procedure was followed: 3 weeks after scaling and polishing, the participants abstained from oral hygiene for 3 days to allow dental plaque to accumulate. After plaque disclosing, the 4 mandibular incisors were photographed using a strictly defined technique, as described by Quirynen et al. Then the volunteers mouthrinsed for 30 s with 15 ml of a solution provided to them. Neither the volunteers nor the examiners knew which solution (test or control) was used. After mouthrinsing, the participants were allowed to brush their teeth and the remaining plaque was photographed again. During the 2nd experimental period, the same procedure was followed, and the 2nd solution was used for mouthrinsing. The effectiveness of the solutions was evaluated by comparing the proportion of dental plaque removed during the 2 experimental periods. The area of dental plaque was measured by an electronic high-precision device (planimeter). The proportion of plaque removed after rinsing with Plax was 0.40 +/- 0.23 and after rising with placebo 0.42 +/- 0.24, of the tooth surface (p = 0.962). Analysis of data by means of paired t-test between the 2 experimental periods revealed no beneficial effect regarding plaque removal when Plax was used.

Adult↗
PubMed1994

The role of the time of application of the promoter in two-stage chemically induced carcinogenesis in the oral mucosa: experimental study in the rat.

The purpose of this study is to determine the role of the time of application of the promoter (in this case, mechanical irritation) in two-stage chemically induced oral carcinogenesis. One hundred fifty-five male rats were divided into seven groups. Group 1, 2 and 3 each received two intraperitoneal injections of the carcinogen N-nitroso-N-methylurea (NMU): 50 mg/Kg BW. Mechanical irritation was applied on the left buccal mucosa, 7 days before the first injection of NMU (group 1), 16 days (group 2), and 80 days (group 3) after the carcinogenic administration. Animals of groups 4, 5, 6 and 7 served as controls. Only group 1 and 2 animals developed tumors in the irritated buccal mucosa. From the results of this study we conclude that the delay of the application of the promoter does not lead to tumor formation. This could be explained by the repair of the carcinogenic lesion at the cellular level.

Animals↗
PubMed1993

Large changes of transition-state structure during experimental evolution of an enzyme.

The question of whether, during the evolution of an enzyme, the transition state of the catalysed reaction is largely unchanged, or whether transition state and protein change together, was examined using the egb beta-galactosidases of Escherichia coli. Charge development at the first chemical state was assumed [Konstantinidis and Sinnott (1991) Biochem. J. 279, 587-593] to be proportional to delta delta G++, the ratio of second-order rate constants for the hydrolysis of beta-D-galactopyranosyl fluoride and 1-fluoro-D-galactopyranosyl fluoride, expressed as a free-energy difference. delta delta G++ (kJ.mol-1) falls from 10.4 for wild-type enzyme to 6.8 and 7.2 as a consequence of two different single amino-acid changes (which arise from single evolutionary events), to 6.3 as a consequence of the two amino-acid changes together, and then increases slightly to 7.3 as a consequence of a third single evolutionary change involving three further amino-acid changes.

Amino Acid Sequence↗
PubMed1992

Effect of non-surgical periodontal therapy in an undergraduate dental clinic. Results one year following treatment.

The aim of the present study was to evaluate the effectiveness of non-surgical treatment of moderately to severely advanced periodontitis in patients at the Department of Periodontology of the Aristotle University of Thessaloniki. The patients were treated by senior students of the Dental School under the supervision of specialized personnel. The conservative treatment consisted of oral hygiene instructions and repeated instrumentation (scaling and root planing) for a period of about 3 months. Seventeen patients with advanced periodontitis participated in the study. The following data were recorded: 1. Gingival index (Silness and Löe, 1963), 2. Plaque index (Löe and Silness 1964), 3. Bleeding on probing and 4. Pocket depth and probing attachment level. The measurements were taken by the same examiner four times, that is at baseline, immediately after completion of the conservative therapy, 6 months and 12 months after treatment. Measurements from single and multi-rooted teeth were divided into three groups with respect to the initial pocket depth (less than or equal to 3 mm, 4-6 mm, greater than or equal to 7 mm). The findings of the present study demonstrated that non-surgical therapy can achieved a marked reduction in bleeding on probing scores and pocket depth 12 months after treatment. A gain in probing attachment levels was found for sites with initially deep (greater than or equal to 7 mm) and moderate (4-6 mm) pockets, while in sites with initially shallow pockets (less than or equal to 3.0 mm), a loss of attachment level was established.

Adult↗
PubMed1991

The interaction of 1-fluoro-D-glucopyranosyl fluoride with glucosidases.

1. 1-Fluoro-D-glucopyranosyl fluoride undergoes pH-independent loss of F- ion at a rate of 1 x 10(-8) s-1 at 50.0 degrees C, some 10(3)-fold slower than alpha-D-glucopyranosyl fluoride and 4 x 10(4)-fold slower than beta-D-glucopyranosyl fluoride. 2. The (inverting) amyloglucosidase II of Aspergillus niger hydrolyses the difluoride according to Michaelis-Menten kinetics (Km 34 mM and kcat. 0.27 s-1), by apparently the same (simple) mechanism by which it hydrolyses alpha-D-glucopyranosyl fluoride (Km 38 mM and kcat. 730 s-1), rather than by the Hehre resynthesis-hydrolysis mechanism used to transform beta-D-glucopyranosyl fluoride. 3. The difluoride is also a substrate for the (inverting) trehalase of pig kidney [Km 17.3 mM and Vmax. 6.2 x 10(-4) relative to alpha-D-glucopyranosyl fluoride (Km 38 mM]). 4. The quantitatively similar effect of fluorine substitution on the one-step enzymic reactions and on the non-enzymic reactions suggests that they go through similar (oxocarbonium-ion-like) transition states. 5. The difluoride is a substrate for the (retaining) beta-glucosidases from Aspergillus wentii (A3 enzyme) and sweet-almond meal (B isoenzyme) and for the retaining alpha-glucosidase from rice: comparison with the appropriate monofluoride reveals a variable rate-retarding effect of the second fluorine atom on kcat./Km that correlates with other measures of oxocarbonium ion character in the transition state. 6. The difluoride is a substrate for the (retaining) alpha-glucosidase from yeast, but also gives an insidious mimicry of active-site-directed irreversible inhibition, which we tentatively attribute either to formation of the non-covalent complex or to the fluoroglucosyl-enzyme increasing the well-known tendency of this enzyme to come out of solution by adsorption on the walls of the vessel.

Animals↗
PubMed1990

[Treatment of sialolithiasis and its complications with intraglandular injection of biotherapeutic solution].

The creation of sialoliths in the ductal system of major salivary glands causes characteristic symptoms due to the obstruction of the flow of produced saliva. If sialolithiasis is not treated early obstructive sialadenitis will develop and its repeated relapses may lead to fibrosis and degeneration of glandular parenchyma. In this study we present the method of intraglandular injection of biotherapeutic solution (1.000.000 I.U. penicillin G in 5 cc normal saline) to achieve treatment of obstructive sialadenitis and rejection of the sialolith. Our results as shown in tables I and II and in figures 1-9 are very encouraging. From the conclusions drawn it looks like this method can be recommended as an optional solution to surgery (lithectomy-adenectomy) under the conditions mentioned in the discussion.

Humans↗
PubMed1983

Age-dependent odontogenic lesions in rats after a single i.p. injection of N-nitroso-N-methylurea.

The development of a variety of odontogenic lesions was elicited by a single i.p. injection of N-nitroso-N-methylurea (NMU) at a dose of 150 mg/kg body weight. A total of 190 male Wistar/Furth rats were used in this study. The odontogenic lesions appeared macroscopically, mainly as supernumerary lower incisors, 88 +/- 3.48 (SE) days after administration of the carcinogen. Tumors were classified as compound and complex odontomas, odontoameloblastomas and ameloblastomas. 72% of rats (31 out of 43) 6 weeks old at the time of inoculation developed microscopic alterations in the odontogenic organs of the incisors; only 4% (2 of 49) of rats injected at 8 weeks of age developed similar alterations. These findings suggest the presence of an ontogenic mechanism susceptible to damage by chemical carcinogens.

Animals↗
PubMed1982

Tumorigenesis at a predetermined oral site after one intraperitoneal injection of N-nitroso-N-methylurea.

Tumors in the soft tissues of the oral cavity of rats developed at predetermined sites as a result of a combination of an intraperitoneal injection of a direct-acting carcinogen. N-nitro-N-methylurea, and a continuous irritation of the buccal mucosa by a stainless steel wire. The incidence of histologically malignant tumors was significantly higher in the irritated area than in any other area of the body. These results constitute evidence for a carcinogenic mechanism whereby the cells that develop into tumors may require the promotional effect of a nonspecific, nonmutagenic stimulus.

Animals↗
PubMedDate not supplied

[Tissue response under hyperpressure from convex pontics].

The aim of the present study was the evaluation of tissue response under ceramometal pontics that had smooth convex tissue surfaces and were pressing against the soft tissues of the residual ridge while the subjects were applying excellent plaque control. Fixed patial dentures were fabricated full filling the above criteria. Clinical and histologic evaluation followed. The results led to the conclusion that pressure from convex and smooth pontics under the condition of excellent plaque control do not create inflammation, while the pressure is neutralized as the time goes by through modification of the morphology of the soft tissues adjacent to the pontics.

Alveolar Process↗