Biomedical subjects

C Penning

Publications and source records attributed to C Penning.

16 recordsLinked to original sources

PubMed1992

An in vitro assessment of the extent of caries under small occlusal cavities.

Many clinicians take for granted that occlusal caries which is just visible as a cavity is extended (deep) into the dentine. This study was aimed at quantifying this opinion. The study was carried out with 60 molars containing small but visible occlusal cavities. After taking bite-wing radiographs the crowns were separated from the roots and embedded. 700-microns sections were cut and glued on plastic sheets. X-ray pictures were taken of the sections which were scored by independent examiners. The bite-wings provided inaccurate estimates of the extent of caries. Radiographs of the sections revealed that about 25% of the molars had caries which reached just to the dentino-enamel junction, while the remaining 75% showed caries extending far into the dentine.

Dental Caries↗

PubMed1992

Validity of probing for fissure caries diagnosis.

One hundred extracted molar teeth with discoloured fissures but without any visible carious cavitation were selected from a large supply, using standardized criteria. The teeth were mounted, placed on a mechanical balance, and probed with a force of 500 g in every fissure, at as many places as possible. Every time the probe was found to stick, the spot was marked. After probing colour slides were made of the occlusal faces. Subsequently, the crowns were embedded in epoxy resin. 700 microns thick sections were cut in a facial-lingual direction with a diamond wheel. From the sections X-rays were taken which were scored as follows: a measuring grid was placed on the X-ray image of a section, and the caries score (0-4) for every millimetre was determined. By scoring every section of a tooth in this way, an overview was obtained of the location of all caries lesions in the occlusal surface. By comparing this overview with the colour slide of the tooth, the relationship between the sticky spots and the lesions was visualized. The results indicate that only 24% of the caries lesions were discovered by probing for stickiness (low sensitivity), but that the probe seldom stuck in a sound fissure (high specificity, > 99%). Probing proved to be unreliable for the diagnosis of fissure caries.

Dental Enamel↗

PubMed1990

Expression and site-directed mutagenesis of the catalytic domain of human poly(ADP-ribose)polymerase in Escherichia coli. Lysine 893 is critical for activity.

Bacterially expressed fusion proteins containing the COOH-terminal domain of the human poly(ADP-ribose)polymerase were analyzed by means of a novel assay, the "activity blot," which allows the detection of transferred polypeptides involved in poly(ADP-ribose) synthesis. Deletion analysis demonstrated that the 40-kDa COOH-terminal region of the enzyme is an autonomous catalytic domain exhibiting both the polymerizing and branching activities in the absence of DNA. Site-directed mutagenesis demonstrated that lysine 893 is essential for these catalytic processes. In addition, sequence similarities obtained with the NAD(P)+ amino acid dehydrogenases suggest that (i) lysine 893 may interact with the substrates of poly(ADP-ribose)polymerase and (ii) the COOH-terminal part of the 40-kDa fragment may also contain a Rossman fold structure.

Amino Acid Sequence↗

PubMed1990

Temperature changes during the finishing of amalgam restorations.

The finishing and polishing of amalgam restorations may be harmful to the pulp because of the heat generated during these procedures. In this study, changes in temperature of the pulp in extracted teeth were determined in vitro. During the polishing procedure, a variety of instruments were used under a variety of circumstances: with or without a water coolant, intermittent or continuous operation, high or low rotation speed, and high or low pressure. Finishing or polishing without a water coolant always increased the temperature of the pulp. When the pressure was high, during continuous polishing, or during a higher velocity of rotation, pulpal temperatures increased more than 20 degrees C within 30 seconds. However, when a water coolant was used, a decrease in the temperature was always observed. Procedures carried out with low pressure showed a decrease in the pulpal temperature of approximately 9 degrees C. High pressure decreased the temperature of the pulp by only 4 degrees C. Therefore a water coolant is always advised when amalgam restorations are being finished and polished.

Body Temperature↗

PubMed1990

Microleakage of extended and nonextended Class I composite resin and sealant restorations.

Favorable results of composite resin sealant restorations in narrow occlusal cavities raise the question of whether extended cavity preparation is justified. Larger restorations are subject to increased polymerization shrinkage. Microleakage of extended and nonextended composite resin sealant restorations was tested in this study. Forty extracted caries-free third molars were allocated to four experimental groups. Occlusal cavity preparations were prepared, varying from narrow cavities restricted to the central fossa to preparations eradicating all fissures. Composite resin restorations were inserted with or without a base and with or without a sealant. Control restorations were inserted in nonetched preparations. Microleakage occurred when cavities were not etched and occassionally when a sealant was not applied. Conclusions indicate that a class I composite resin restoration extended beyond the central fossa can be free of microleakage if covered with a fissure sealant.

Acid Etching, Dental↗

PubMed1990

[Microleakage and pulp protection].

Clinically undetectable leakage around amalgam and composite restoration, normally referred to as microleakage, will cause a bacterial invasion of the dentinal tubules. Such an invasion demands precautions. Although without a protective base many patients do not have complaints, this does not imply that the pulp is not affected. Therefore, dentin which is exposed during dental treatment should always be sealed hermetically. Of the lining materials, calcium-hydroxide and glass-ionomer are strongly favourable among the general practitioners. Disadvantages of these popular materials justify, however, the conclusion that other linings are to be preferred.

Calcium Hydroxide↗

PubMed1989

Cloning of rodent cDNA coding the poly(ADP-ribose) polymerase catalytic domain and analysis of mRNA levels during the cell cycle.

We have isolated a partial 2.0 kb cDNA (pRATC) encoding the entire 489 amino acids of the NAD binding domain located at the C terminus of the rat poly(ADP-ribose) polymerase. pRATC sequences were analysed and compared with the human mRNA. Our analysis reveals a remarkable homology between the rat and human nucleotide and amino acid sequences. Although a few minor amino acid changes were detected, we have found that the total number of possible phosphorylation sites remained constant in the NAD binding domain of both enzymes. We have also found that a 102 amino acid sequence, containing the putative nucleotide binding site Gly-Lys-Gly (position 378), is perfectly conserved between the rat and human sequences. Strong homology was also detected between pRATC and genomic DNA isolated from various vertebrates. In addition, we have analysed the levels of poly(ADP-ribose) polymerase mRNA throughout the cell cycle. Our results show that the levels of mRNA culminate in the G1 phase. We have also found that the increase in enzymatic activity observed in rats following treatment with phenobarbital did not correspond to an increase in the mRNA levels.

Amino Acid Sequence↗

PubMed1988