Biomedical subjects

M M Khamis

Publications and source records attributed to M M Khamis.

5 recordsLinked to original sources

PubMed1998

A comparison of the effect of different occlusal forms in mandibular implant overdentures.

STATEMENT OF PROBLEM: Posterior tooth form selection for implant overdentures is made according to personal preference and experience using the concepts of conventional complete denture prosthodontics. PURPOSE: This study (1) compared the masticatory efficiency of three occlusal forms, 0 degrees, 30 degrees, and lingual contact (lingualized occlusion), in subjects with mandibular implant overdentures, and (2) determined their effects on the implant supporting tissues. MATERIAL AND METHODS: Eight patients who had four root form implants in the mandibular symphysis area connected with a Hader bar were selected. Maxillary and mandibular dentures were constructed for each patient with interchangeable posterior segments and the three occlusal forms were tested. The masticatory efficiency for each posterior tooth form was assessed with objective food tests and a subjective patient preference questionnaire. Periodic evaluation of implant-supporting tissues also was performed. RESULTS: Reliability analysis showed that all R1 coefficients were > or =0.80 (<0.001), indicating high subject consistency between multiple chewing efficiency trials. MANOVA analysis indicated a significant difference in chewing efficiency among the three occlusal forms (p < 0.001). The 0 degree occlusal form was associated with a significantly higher number of chewing strokes compared with 30 degrees or lingualized occlusal forms. The different occlusal forms were not found to have a clinically detrimental effect on the peri-implant soft or hard tissues. CONCLUSION: Chewing efficiency tests and patient preference ratings showed that 30 degree teeth and lingual contact provided better chewing efficiency than 0 degree teeth. None of the tested occlusal forms showed any clinical or radiographic detrimental effect on the implant-supporting tissues.

Aged↗

PubMed1997

A procedure for constructing dentures with interchangeable teeth.

Studies that compare different types of complete denture teeth have repeatedly emphasized the importance of standardizing all denture factors, except the type of teeth. Within-subject comparisons have also been recommended to avoid personal differences between patients. For optimum results, one denture should be constructed for each patient with interchangeable teeth. This article describes a simple and accurate procedure for constructing dentures with interchangeable posterior teeth.

Acrylic Resins↗

PubMed1988

Effects of anions on the fluorescence emission of the 1-anilino-8-naphthalenesulfonate-phosphoglycerate kinase complex.

When 1-anilino-8-naphthalenesulfonate (ANS) interacts with phosphoglycerate kinase (ATP:3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) its fluorescence is enhanced and a blue shift occurs. There is evidence that ANS binds to the site of the nucleotide substrate. The work described herein shows that when various anion inhibitors are added to the ANS-enzyme solution, de-enhancement of the fluorescence occurs. Extrapolation to infinite anion concentration shows that pyruvate ions are the most effective quenchers (ca. 90%) and nitrate ions the least effective, sulfate and phosphate ions being intermediate. The results are consistent with earlier enzymes kinetic findings suggesting that pyruvate ions and ANS, both competing with the nucleotide substrate, are able to bind to the enzyme simultaneously and that sulfate, phosphate and nitrate ions can, to various extents, affect the properties at the active centre of phosphoglycerate kinase via conformational changes without sharing ligands with the nucleotide substrate.

Anilino Naphthalenesulfonates↗

PubMed1987

Anion effects on the kinetics of yeast phosphoglycerate kinase.

(A) The effects of phosphate, chloride, nitrate, pyruvate, malate, succinate and glutamate ions on the kinetics of yeast phosphoglycerate kinase (ATP: 3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) were studied with MgATP2- and 3-P-glycerate as variable substrates. Three types of patterns were obtained: (1) Nitrate, succinate, malate and glutamate ions, strictly noncompetitive versus both the substrates. (2) Phosphate and chloride ions, noncompetitive versus MgATP2- and mixed versus 3-P-glycerate. (3) Pyruvate ions, being very weak inhibitors, competitive with MgATP2- and noncompetitive with 3-P-glycerate. (B) Based on experiments with simultaneous inhibition by various combinations of two anions the following suggestions were made: The type 1 anions presumably bind to a site outside the active centre. These ions appear to bind to the enzyme independently of type 2. The latter also appears to include sulfate ions, which are competitive versus both the substrates as well as versus the phosphate and chloride ions. Sulfate and phosphate ions are electronically similar, but show different inhibition patterns, presumably due to various effects on the protein conformation. Type 3 inhibition exerted by pyruvate ions was shown earlier for 1-anilino-8-naphthalenesulfonate and salicylate ions, but as these two anions are supposed to bind to the adenine binding pocket of the catalytic centre, the results indicate that pyruvate ions might preferably compete with the nucleotide substrate for the polyphosphate binding site.

Anions↗

PubMed1981

Activation and inhibition of phosphoglycerate kinase by sulphate ion.

A kinetic study of the effects of SO4(2-) in the activity of phosphoglycerate kinase (ATP: 3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) is presented. SO4(2-) behaves both as an activator and inhibitor of the reaction. Activation does not appear to affect binding of one or the other of the two substrates to the catalytic centre. As an inhibitor SO4(2-) competes with both the substrates. Thus, each substrate can constrict SO4(2-) from the inhibitor binding site, probably the catalytic centre. Under these conditions activation becomes more and more evident. There appear to exist at least two SO4(2-) binding sites, one which earlier has been defined as an anion binding site, and a second, being the catalytic centre. The former seems to have a higher affinity for SO4(2-) than the latter.

Anions↗