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Biomedical subjects

H H Messer

Publications and source records attributed to H H Messer.

At least 55 records · Page 3Linked to original sources
PubMed1997

Endodontic management of a rare combination (intrusion and avulsion) of dental trauma.

Combined trauma involving intrusive luxation of one tooth and avulsion of another is rare. A case is presented involving the endodontic management of two traumatised maxillary central incisors, one of which was intrusively luxated and the other avulsed. Spontaneous re-eruption of the intruded tooth occurred, thereby avoiding the need to further traumatise the periodontal ligament with either orthodontic or surgical repositioning, and allowing endodontic therapy to be carried out uneventfully. Endodontic therapy of the avulsed tooth was completed and its prognosis is considered good.

Child↗
PubMed1997

Variability in cytotoxicity and fluoride release of resin-modified glass-ionomer cements.

New-generation glass-ionomer cements contain resin to improve their restorative properties. These resin-modified glass-ionomer cements vary considerably in their chemistry, which could result in corresponding variability in their physical and biological properties. This study investigated the cytotoxicity and the fluoride release of two resin-modified glass ionomers, a conventional glass-ionomer cement, and a resin composite. Samples were prepared and extracted in distilled water for 1, 4, and 7 days; eluates were filtered and tested by means of 3T3 mouse fibroblasts. Cytotoxicity (MTT assay) values were low for all materials and extraction times, indicating minimal cytotoxicity of all materials (less than 30% inhibition). Cytotoxicity of one resin-modified glass ionomer was significantly higher than for the other materials (p < 0.001). One resin-modified glass ionomer and the conventional glass-ionomer cement released significantly more fluoride at each time interval (p < 0.001) than the other resin-modified glass-ionomer cement and the resin composite. Fluoride release and cytotoxicity were correlated (r2 = 0.60; p < 0.001), although the fluoride release does not account for the cytotoxicity observed. Cytotoxicity and fluoride release suggest that one hybrid behaved more like a conventional glass ionomer, and the other like a resin composite. These differences may have implications for material selection in specific clinical situations.

3T3 Cells↗
PubMed1996

The identification of proteoglycan-associated mRNAs in human dental pulp cells.

Characterization of the dental pulp proteoglycans has been largely confined to the glycosaminoglycan component of the proteoglycan molecule, while the protein core has received little attention. This study was conducted to identify mRNAs of previously well-characterized proteoglycans-biglycan, decorin and versican-and link protein in dental pulp cells. Dermal fibroblasts were used as a positive control. Oligonucleotide probes were constructed based on published sequences for the four proteins from human tissues. Total RNA was isolated from cultured human pulp and dermal cells, separated according to size by formaldehyde gel electrophoresis and subsequently transferred to a nylon filter. Northern hybridizations using the oligonucleotide probes revealed the expression of biglycan, decorin, versican and link protein mRNAs. Biglycan and decorin are small proteoglycans that have a regulatory effect on collagen fibrillogenesis. Assuming expression of link protein and versican in vivo, the larger proteoglycans in the dental pulp are capable of forming large proteoglycan aggregates.

Biglycan↗
PubMed1995

Root strains associated with different obturation techniques.

The influence of different obturation techniques (lateral condensation, Obtura, and Thermafil) on root strains was assessed in 27 upper central incisors using strain gauges mounted on the coronal and apical one-thirds of the root surface. The vertical load applied with each obturation technique was also measured. Comparison of the strains was conducted with two-way analysis of covariance (with condensation load as covariate). The technique of obturation significantly influenced the root strains, with the Obtura generating the highest strains. The Thermafil group showed significantly less strain than the Obtura or lateral condensation groups. Thermal expansion of dentin was an unexpected finding. A large proportion of strain in the Obtura and Thermafil groups was found to be thermal strain. The mean load required to cause vertical root fracture was five to six times higher than the load used in obturation.

Analysis of Variance↗
PubMed1995

Cuspal deflection in molars in relation to endodontic and restorative procedures.

The extent of cuspal flexure following endodontic and restorative procedures has important consequences for potential fracture. This study was undertaken to determine the extent to which cusps of molars are weakened by progressively larger restorative preparations and endodontic access. Cuspal flexure of 13 extracted, intact human mandibular molars was measured under controlled occlusal loading. A ramped load of 100 N was applied to the mesial cusps via a steel sphere, using a closed-loop servohydraulic testing machine. Lateral cuspal displacement was recorded by linear measuring devices (direct current differential transformers) accurate to 1 micron. Increasingly extensive MO or MOD cavity preparations followed by endodontic access were cut in each tooth. Cuspal deflection increased with increasing cavity size and was greatest following endodontic access. Cuspal deflections of more than 10 microns were observed. These findings reinforce the importance of cuspal coverage to minimize the danger of marginal leakage and cuspal fracture in endodontically treated teeth.

Analysis of Variance↗
PubMed1995

A complex treatment of dens invaginatus.

Dens invaginatus is a developmental malformation of teeth. A case is presented of successful treatment of a peg lateral incisor with a severe dens invaginatus extending to the root apex. Both conventional endodontic therapy and periapical surgery were ineffective in resolving a persistent, long-standing sinus tract. Removal of the tooth in the present case would have created a difficult prosthetic problem. Intentional replantation, with improved access to the apical part of the canal was attempted as a last resort. A 10-month recall radiograph is presented showing successful healing of the periapical lesion. Pre-treatment and post-treatment photographs are presented to show successful esthetic treatment, using bonded composite resin.

Adult↗
PubMed1995

The effects of neuropeptides (calcitonin gene-related peptide and substance P) on cultured human pulp cells.

The sensory neuropeptides substance P and calcitonin gene-related peptide have been implicated in the mediation of pulpal inflammation. A possible role in healing following injury has also been suggested (Byers et al., 1990). This possibility has been investigated by an examination of a direct effect of substance P and calcitonin gene-related peptide in vitro on fibroblast-like cells derived from human dental pulp. Cells were cultured for 48 hr in Dulbecco's modified Eagle medium plus 20% fetal calf serum and antibiotics. Substance P and calcitonin gene-related peptide were added in the range from 10(-12) to 10(-4) mol/L. Fibroblast growth factor was used as a positive control. Effects on cell proliferation were assessed by cell counts (daily for 6 days) and [3H]-thymidine uptake (24 hr after the addition of peptides). An effect on cellular functional activity was measured by [35S]-sulfate incorporation into glycosaminoglycans, in confluent cell cultures. Both substance P and calcitonin gene-related peptide showed concentration-dependent stimulation of cell proliferation. The maximum stimulation of approximately 40% was achieved at substance P and calcitonin gene-related peptide concentrations of 10(-6) mol/L, comparable with stimulation by fibroblast growth factor. By contrast, little increase in glycosaminoglycan synthesis by confluent cells could be detected. The direct effect on pulp cells is consistent with a role of the neuropeptides in pulp healing. This is exerted at the level of cell proliferation, rather than functional activity.

Adolescent↗
PubMed1994

Effect of restorative procedures on the strength of endodontically treated molars.

Endodontically treated molar teeth are considered susceptible to fracture because of loss of tooth bulk. This study evaluated the significance of retaining intact marginal ridges and selective cusp coverage in preserving tooth stiffness during restoration. Strain gauges were bonded to four cusps of 36 intact extracted human lower molars. Teeth were loaded mesially and distally in a closed-loop servohydraulic system to measure stiffness. Endodontic access was followed by mesio-occlusal or mesio-occluso-distal preparation. Teeth were restored with either amalgam (no overlay), amalgam overlay, or gold overlay with partial or complete cusp coverage. Relative stiffness was calculated for all test conditions. Preserving a marginal ridge in molars did not fully conserve the strength of adjacent cusps; selective cusp coverage reinforced only the capped cusps; full occlusal coverage with gold or amalgam strengthened all cusps, but gold did so more consistently. It is more important to cover cusps than to preserve tooth structure (including a marginal ridge) in endodontically treated molar teeth.

Analysis of Variance↗
PubMed1994

Moisture content of vital vs endodontically treated teeth.

The moisture content of vital and endodontically treated teeth was compared in matched pairs of contralateral human teeth extracted for prosthodontic reasons. Samples from each tooth were weighed then placed in an oven to remove the unbound water from the dentin. Weighing was carried out daily until a constant weight was achieved for three days. The moisture content was then calculated and expressed as a percentage of the initial sample weight. It was found that vital dentin had a moisture content of 12.35% whilst dentin from endodontically treated teeth had a moisture content of 12.10%. These results indicated that there was no significant difference in the moisture content between endodontically treated teeth and vital teeth.

Adult↗
PubMed1994

Cytotoxicity of gallium and indium ions compared with mercuric ion.

The use of mercury in dental amalgam restorations has become the subject of political controversy despite its long history of safe clinical use, and alternative materials based on gallium and indium rather than mercury have been developed. The biological safety of these metals must be evaluated, as part of their assessment as mercury substitutes. The cytotoxicities of mercury (II) nitrate, gallium (III) nitrate, and indium (III) nitrate were assessed at concentrations between 0.001 mmol/L and 1.0 mmol/L, using L929 mouse fibroblasts and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and scanning electron microscopy. The mitochondrial dehydrogenase activity at each metal ion concentration as a percentage of the control was calculated from the absorbance values. The 50% inhibition concentration of mercury (II) nitrate was 0.35 mmol/L for cells in the rapid-growth phase and at confluence; gallium (III) nitrate and indium (III) nitrate did not significantly inhibit dehydrogenase activity in either the growing or confluent phase. Gallium and indium ions were not significantly toxic under the conditions of this assay.

Animals↗
PubMed1993

pH changes in root dentin over a 4-week period following root canal dressing with calcium hydroxide.

Root canals in extracted human teeth were cleaned and shaped and subsequently dressed with a calcium hydroxide root canal dressing. pH Changes in the root dentin were measured over a 4-wk period with microelectrodes in small cavities at apical and cervical levels in inner and outer dentin. The pH increased within hours in the inner dentin, peaking at pH 10.8 cervically and 9.7 apically. However, 1 to 7 days elapsed before the pH began to rise in the outer root dentin, reaching peak levels of pH 9.3 cervically and 9.0 apically after 2 to 3 wk. The results show that hydroxyl ions derived from a calcium hydroxide dressing do diffuse through root dentin. They diffuse faster and reach higher levels cervically than apically. Surface pH measurements showed that hydroxyl ions do not diffuse in more than a minor way through the intact root surface.

Adult↗
PubMed1993

Influence of gastric acidity on fluoride absorption in rats.

The rate of F absorption from the stomach is pH-dependent, with greater absorption at low pH. Since the rate of absorption is also strongly influenced by the rapidity of gastric emptying, we have compared the relative importance of gastric acidity and gastric emptying in overall F absorption. Male rats (350 g, n = 85) were pre-treated with cimetidine (to inhibit gastric acid secretion) or pentagastrin (to stimulate gastric acid secretion) or were untreated controls, and given 50 micrograms F by stomach intubation. The pH of the F-containing solution was varied in the cimetidine-pre-treated group (pH 1.5, 5.5, 8.5), and was 5.5 for the control and pentagastrin-pre-treated groups. Gastric emptying was measured by addition of 14C polyethylene glycol to the F solution as an unabsorbed marker of fluid movement. F absorption was measured after 10, 20, and 40 min. The rate of gastric emptying was unaffected by pre-treatment or pH of the intubating solution. Initially, F absorption was greatest at low pH. After 40 min, absorption was comparable in all groups, averaging approximately 70% of the initial dose. The extent of absorption from the stomach was inversely related to pH, but increased absorption from the small intestine compensated for the low gastric absorption at high pH.

Absorption↗
PubMed1993

Efficacy of tunnel restorations in the removal of caries.

Tunnel restorations have been advocated as a conservative treatment modality for early carious lesions. However, the question arises as to quantity of dentin that remains within the marginal ridge above the tunnel path. In this experiment, extracted maxillary premolars with early carious lesions were sectioned and photographed. Measurements taken from tracings of the projected slides revealed that no dentin remained within the marginal ridge, irrespective of the direction of the tunnel path. These measurements indicate that the tunnel restoration is not a satisfactory treatment for proximal caries. The position of caries precludes the cutting of a tunnel preparation that leaves sufficient dentin under the marginal ridge, unless the bulk of enamel caries is left untouched.

Bicuspid↗
PubMed1993

Tunnel restorations versus class II restorations for small proximal lesions: a comparison of tooth strengths.

An increased emphasis on the preservation of tooth structure has led to alternative cavity designs for early proximal caries. The tunnel restoration (which preserves the marginal ridge) and a conservative Class II composite resin restoration were compared in vitro for effects on tooth strength with nondestructive and destructive tests. The tunnel restoration, which is generally thought to be the more conservative of the two techniques, was actually more damaging, as shown by the stiffness, load at fracture, and proximity to the pulp.

Analysis of Variance↗
PubMed1992

Are endodontically treated teeth more brittle?

This study compared biomechanical properties (punch shear strength, toughness, hardness, and load to fracture) of 23 endodontically treated teeth (mean time since endodontic treatment: 10.1 yr) and their contralateral vital pairs. Analyses using paired t tests revealed no significant differences in punch shear strength, toughness, and load to fracture between the two groups. Vital dentin was 3.5% harder than dentin from contralateral endodontically treated teeth (p = 0.002). The similarity between the biomechanical properties of endodontically treated teeth and their contralateral vital pairs indicates that teeth do not become more brittle following endodontic treatment. Other factors may be more critical to failure of endodontically treated teeth.

Adult↗
PubMed1991

Effect of delayed gastric emptying on fluoride absorption in the rat.

The rate and site of fluoride (F) absorption were compared in fasted 350 g male rats given 50 micrograms F (as NaF) in either water or a 7.5% pectin solution. Absorption was measured at intervals up to 2 h following gastric intubation. Gastric emptying was measured by inclusion of 14C-PEG in the F solution. The extent of gastric F absorption was derived from rates of gastric emptying (14C-PEG loss) and F loss. Pectin markedly slowed gastric emptying, but by 2 h, more than 90% of the solution had passed into the small intestine in both groups, and F absorption exceeded 90% in both groups. The rate of F absorption was initially much slower in the pectin group than in the group given F in water, and plasma F concentration increased more slowly and reached a lower maximum value. Absorption from the stomach was greater in the pectin group, but still accounted for only approx 25% of total gastrointestinal absorption. The reduced rate of F absorption and slower rise in plasma F concentration accompanying delayed gastric emptying indicate that passage of F into the small intestine is the major factor in rapid F absorption.

Animals↗