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Biomedical subjects

L Holmen

Publications and source records attributed to L Holmen.

16 recordsLinked to original sources
PubMed2001

Occupational exposure to airborne proteolytic enzymes and lifestyle risk factors for dental erosion--a cross-sectional study.

This study examined the hypothesis that occupational exposure to airborne proteolytic enzymes is associated with dental erosions on the facial surfaces of exposed teeth. Individuals (n = 425) working at a pharmaceutical and biotechnological enterprise (Novozymes A/S) were examined; their mean age was 35 years (range = 18-67 years) and 143 (34%) were women. Two hundred and two of these individuals were newly employed by the company. Occupational exposure was assessed from questionnaire and workplace information. For practical analytical purposes, individuals were categorized as either previously exposed to proteolytic enzymes or not. Information on relevant lifestyle factors and medical history was obtained from a questionnaire. The main effect measure was facial erosion, but lingual erosion indices and the presence of Class V restorations were also considered. The validity of these measures was shown to be very high. Adjusted for potential confounders, there was no association between history of occupational exposure to proteolytic enzymes and prevalent facial or lingual erosion. With respect to prevalence of Class V restorations, the association was significant. The present study did not support directly our primary hypothesis that occupational exposure to airborne proteolytic enzymes is associated with dental erosions on the facial surfaces of exposed teeth. However, the results indicate that exposure to proteolytic enzymes may lead to pronounced tooth substance loss, demanding treatment.

Adolescent↗
PubMed1999

A polarized light and scanning electron microscopic study of human fissure and lingual enamel of unerupted mandibular third molars.

Using histological and ultrastructural techniques the aims of this study were to investigate whether the mineralization pattern and surface microanatomy of the caries-susceptible fissure enamel were different from those on the caries-inactive lingual surface. The material consisted of 31 unerupted third mandibular molars. The specimens were initially grouped into four categories: (1) without, (2) with initial, (3) with almost completed and (4) with completed root formation. One ground section with fissure-like morphology was selected from each tooth. Using water as a medium the observed birefringence was negative along the lingual and fissure transverses in specimens with almost completed and with completed root formation, while the observed birefringence was positive at different distances in the enamel in sections representing less maturation stages. Qualitative imbibition studies revealed hypomineralized enamel in the lower part of the fissures in specimens representing almost and completed root formation. Imbibed in quinoline, parts of the hypomineralized enamel behaved like a molecular sieve due to the presence of micropores, indicating that the structural arrangement is different from that in the enamel adjacent to this areas. After division of the sections into a lingual and a buccal part, SEM features were described from lower and upper parts of the buccal fissure wall and on lingual enamel in the area corresponding to the bottom part of the fissure. The surface microanatomy varied greatly. Negative developmental irregularities such as fissures and holes were associated with the immature enamel, while matured enamel - particularly fissures - housed many positive developmental irregularities such as enamel caps and protrusions. The crystal size in the mature specimens appeared smaller and more uniform than the crystals from the immature specimens. Apart from the occurrence of hypomineralized enamel in fissures and numerous positive developmental irregularities on the fissure surface, no major differences between fissure and lingual enamel were noticed, neither with respect to mineralization pattern during final stages of tooth development nor to the degree of surface porosity prior to tooth emergence.

Crystallography↗
PubMed1995

Scanning electron microscopy, a useful tool in forensic dental work.

In selected cases there is a need for microscopic information found on the surface of tooth specimens. Scanning electron microscopy is the method of choice. Based on the knowledge of the structural organization of the mineralized dental tissues differential diagnoses of physical and chemical changes can be made. It is suggested that the forensic dental profession cooperates in establishing a collection of reference material illustrating different traumas to enamel and dentin, deposits on teeth and the structure of restorative dental materials as they will appear after some years in position on a tooth. Four different cases are presented.

Animals↗
PubMed1994

In vivo caries models--mechanisms for caries initiation and arrestment.

The effects of intra-oral mechanical forces on caries initiation, progression, and arrestment are evaluated by examination of different in vivo caries models. The models are grouped in four categories: (1) a population study, (2) short-term clinical trials, (3) clinical experiments, and (4) controlled clinical observations. Taken together, these in vivo studies convincingly demonstrate that partial or total elimination of the intra-oral mechanical forces operating during mastication or toothbrushing leads to evolution of cariogenic plaque, resulting in localized carious enamel dissolution. In addition, they show that re-exposure to the partly or totally eliminated mechanical forces not only arrests further lesion progression, but also results in partial lesion regression. The data from in vivo caries studies also show that the clinical and structural changes associated with lesion arrestment or partial regression are not related to any salivary repair mechanism, but are solely the result of mechanical removal of the cariogenic biomass which is physically interrelated with the eroded surface of the active, dull-whitish enamel lesion. No indications of superficial mineral deposition or "blocking" of the external intercrystalline spaces are seen in the surface layer of lesions arrested in vivo. For this reason, the conventional usage of the terminology 'remineralization' is considered absolutely misleading when used to describe the mechanisms responsible for the arrest of lesion progression in vivo.

Clinical Trials as Topic↗
PubMed1993

Exaggerated abrasion/erosion of human dental enamel surfaces: a case report.

An atypical, rapidly proceeding abrasion/erosion of the labial enamel surfaces of the maxillary and mandibular incisors and canines in a 27-yr-old man is reported. Ultrastructural examination of a replica of the teeth showed a practically structureless enamel surface both at the initial examination and after 12 months. However, at the end of the period, minor areas of dentin tubules became visible, indicating that a substantial loss of the tooth substance had taken place. The patient's occupation involved daily environmental contact with proteolytic enzymes. In vitro study of enamel exposed to one of the actual proteolytic enzymes showed dissolution of enamel substance, and it cannot be excluded that enzymatic decomposition of the organic enamel matrix is a contributing cause of the observed exaggerated loss of tooth substance.

Adult↗
PubMed1990

A light and scanning electron microscopic study of enamel decalcification in children living in a water-fluoridated area.

Eleven children, each having one or two pairs of premolars to be extracted for orthodontic purposes, participated in the study. The model involved placement of a special orthodontic band that allowed the accumulation of plaque in a defined area between the band and the buccal enamel. Examination of enamel changes was carried out in experimental teeth that had been exposed to local plaque accumulation for one, two, four, eight or 14 days. The specimens were examined under the light (LM) and the scanning electron microscope (SEM). All teeth had signs of very mild dental fluorosis. No indications of demineralization were noted after one day. SEM examination showed signs of crystal dissolution in some of the two-day specimens. Six of eight four-day specimens exhibited surface dissolution. All eight- and 14-day specimens showed signs of surface demineralization in the LM as well as in the SEM. These observations documented that undisturbed bacterial deposits are capable of initiating enamel demineralization within short time periods, even in children living in a water-fluoridated area.

Adolescent↗
PubMed1989

The microflora associated with the development of initial enamel decalcification below orthodontic bands in vivo in children living in a fluoridated-water area.

Thirty-four caries-free teeth destined for orthodontic extraction were banded to provide a protected area for the accumulation of plaque. The teeth were extracted at one, two, four, eight, and 14 days after being banded, and samples of the flora below the band were analyzed for the presence of Streptococcus sanguis, Streptococcus 'mitior', 'mutans streptococci', Actinomyces viscosus, Actinomyces naeslundii, Actinomyces odontolyticus, Lactobacillus species, and Veillonella. After plaque sampling, the teeth were sent to the Royal Dental College (Copenhagen) for histological analysis. The results showed that S. mutans could colonize the area below the band after one day, but that colonization was only 100% at 14 days. Lactobacillus was only isolated from 2/8 samples at four days and from 4/8 samples at 14 days. S. sanguis and 'S. mitior' were regularly isolated at all banding times, and Veillonella was isolated from all samples. A. viscosus was the most commonly isolated Actinomyces. The numbers of Streptococcus and Veillonella were significantly higher at day 1 than at day 14 (p less than 0.05). S. mutans and A. viscosus were isolated more frequently at day 14 than at day 1 (p less than 0.01). Histological examination revealed that dissolution of the enamel below a band could occur after two days, but that even after 14 days dissolution could be questionable. Dissolution was detected in areas where S. mutans was not isolated (8/34), but S. mutans was also present in samples showing dissolution (12/34). There was no relationship between dissolution and the numbers of S. mutans; however, the isolation frequency of S. mutans was associated with dissolution (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1988

The effect of regular professional plaque removal on dental caries in vivo. A polarized light and scanning electron microscope study.

This study aims to describe the histological and ultrastructural enamel reactions to regular disturbance/removal of dental plaque, using an in vivo caries model. Fourteen young volunteers undergoing orthodontic treatment participated in the study. To create local protected areas, orthodontic bands with a buccal space were placed in homologous pairs of premolars. One tooth in each pair served as control and had the band cemented for the entire test period of 5 weeks. The other band was removed weekly and the buccal surface cleaned, either by careful pumicing with a nonfluoride toothpaste, or by simple cleaning with a cotton pellet. Results indicated that 5 weeks with completely undisturbed plaque accumulation resulted in visible enamel demineralization in all 14 individuals, whilst a weekly performed professional plaque removal was able to prevent lesion progress independent of the cleaning procedure. It is therefore concluded that regular mechanical disturbance of dental plaque is able to suppress bacterial activity and hence caries development.

Bicuspid↗
PubMed1987

Surface changes during the arrest of active enamel carious lesions in vivo. A scanning electron microscope study.

The present study examines early enamel surface alterations taking place when active carious lesions enter an arrested stage. Orthodontic bands with a standardized space for plaque accumulation were used to produce incipient carious lesions on the buccal surface of all four first premolars of four young adolescents. The premolars were to be extracted for orthodontic reasons. After 4 weeks of local cariogenic challenge, all teeth were debanded. In each patient one tooth was extracted at the time of debanding. The remaining premolars were extracted 1, 2, and 3 weeks after re-exposure to the oral environment. No fluoride was added during the entire test period, and the patients were told to maintain usual oral hygiene. Scanning electron microscope examination of the experimental surface areas disclosed a gradual wearing away of the outermost crystals during the 3 weeks of observation. This was associated with a leveling off of surface irregularities and the development of a multitude of scratches. The observed attrition of the porous surface in the lesion area indicates that functional wear and toothbrushing were responsible for the arrestment by disturbance and removal of bacterial deposits.

Bacteria↗
PubMed1987

A scanning electron microscopy study of approximal premolar surfaces from fifteen year old children living in a fluoridated community.

The aim of the present study was to examine approximal enamel surfaces in the scanning electron microscope (SEM). Thirty premolars developed and erupted in an 'optimally' fluoridated (1 ppm) community had clinical indications of dental fluorosis and early signs of dental caries corresponding to the approximal contact area. The SEM-examination disclosed a spectrum of posteruptive changes ranging from isolated surface fractures to carious dissolution, abrasion and calcified microbial deposits. Conclusively, we found that teeth developed and erupted in areas with fluoridated water undergo similar posteruptive alterations due to prevailing environmental conditions as reported in teeth from low fluoride areas.

Adolescent↗
PubMed1986

A polarized light and scanning electron microscope study of the effect of Duraphat treatment on in vivo caries.

The present study was carried out to examine the effect of application of a fluoride varnish (Duraphat) on experimentally produced caries in vivo. After a 4-wk period of cariogenic challenge on homologous pairs of premolars, Duraphat was applied on one of the teeth while the other was extracted and saved as a control. The Duraphat treated teeth remained in a cariogenic environment for a new period of 2 wk prior to extraction. All the control teeth displayed the classical characteristics of active incipient subsurface carious lesions. The Duraphat treated lesions showed an increase in surface porosity relative to their controls while the subsurface porosity was dramatically reduced. When examined in the SEM, the corresponding surface appeared smooth with a leveling out of the original surface irregularities. High power microscopy disclosed, however, a distinct network of intercrystalline spaces. Application of Duraphat prior to reestablishment of cariogenic challenge apparently gives rise to a marked redistribution of minerals in active initial carious lesions.

Adolescent↗