摘要:

The histopathology of arrested root caries lesions was examined in extracted human teeth. The main structural characteristics of arrested lesions were the completely mineralized surface area and the formation of a distinct sclerosis of the dentinal tubules. Intertubular dentin was, with the exception of the dentinal tubules, fully mineralized up to the surface. Dentinal tubules near the surface were either filled with ghosts of microorganisms or with crystals of different shapes. Sclerosis of the dentinal tubules was characterized by the presence of three different patterns of intratubular mineralization that occur in distinct regions of the zone of tubular sclerosis. The patterns were distinguishable by the type of crystals and their association with organic structures such as collagenous fibrils or odontoblast processes. It is suggested that arrested lesions are based on (1) the formation of an inner barrier that interrupts the diffusion of substrata from the pulp to invaded bacteria, (2) the formation of an outer barrier by a compact, highly mineralized surface region which blocks the diffusion of products of bacterial metabolism into dentin, and (3) an area of mineralization which extends from the outer barrier toward the root canal within demineralized dentin. The present study demonstrates the considerable potential of caries lesions in dentin to become arrested, and subsequently partially remineralized. These phenomena seem to depend on the severity of an active lesion and its location on the root surface. This should be taken into account when diagnosing root caries lesions. The potential of root caries lesions to become arrested indicates that the treatment concept of active root caries lesions should be reconsidered.

ISSN:0008-6568    

DOI:10.1159/000261436

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Temperature changes in enamel tissue and the pulp chamber under the influence of a CO2 laser were measured by direct methods in vitro. X-ray diffraction analysis revealed α-Ca3(PO4), the high-temperature modification of enamel hydroxyapatite, thus indicating that the enamel melting temperature was above 1,000 °C in the interaction area of laser (continuous wave, 15 s exposure time, 1 mm spot size) and tissue. Powers of 0.5 and 1 W (continuous wave), 1.5 mm spot size, and 10 s exposure time vaporize and carbonize dentin tissue at the cavity bottom of class I preparation molars. The observed temperature rise of 4 °C indicates that thermal injury to the pulp tissue does not occ

ISSN:0008-6568    

DOI:10.1159/000261437

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The crowns of 60 permanent human molars were sectioned transversally. The exposed dentin surface was divided into different parts: a first part was kept as control, a second part was immediately varnished, and a third part was irradiated with a CO2 laser using the same irradiation conditions as those applied for caries removal (10 impulses of the same energy; 0.2 s/impulse; energy density/ impulse 280-715 J/cm2. After irradiation, a small portion of this area was varnished. The teeth were immersed for 4 weeks in a cariogenic gel (pH = 4.5) at 36 °C. Twenty teeth were studied by scanning electron microscopy, and longitudinal sections of the other teeth were prepared for microradiography and microdensitometry measurements. The lased dentin surface appeared smooth for energy densities lower than 425 J/cm2. Longitudinally fractured samples revealed a layer of dentin devoid of tubular structure (20-70 μm thick, depending on the energy density used), whereas below the sealed layer, the dentinal tubules retained their normal aspect. Although the sealed layer showed no demineralization when exposed to acid, demineralization of the underlying dentin occurred, but to a much lesser extent than in the unlased denti

ISSN:0008-6568    

DOI:10.1159/000261438

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The objectives of this study were to determine how salivary flow rate and pH vary with time during use of chewing-gums and lozenges. Twenty-four young adults collected unstimulated saliva and then, on different occasions, chewed one of six flavoured gums, or gum base, or sucked on one of two lozenges, for 20 min, during which time eight separate saliva samples were collected. Flow rate peaked during the 1st minute of stimulation with all nine products. With the lozenges, flow rate fell towards he unstimulated rate when the lozenges had dissolved. There were no significant differences in the flow rates elicited by cinnamon- or peppermint-flavoured gums or between sugar-containing or sugar-free gums. With the flavoured gums, the mean flow rate followed a power curve (r = -0.992) with time and within about 10 min was not significantly different from that when gum base was the stimulus. The initial stimulated flow rate with flavoured gums was about 10-12 times greater than the unstimulated rate (0.47 ml/min). After 20 min of chewing, it was still about 2.7 times that rate and about the same as the flow rate elicited by chewing-gum base alone. The pH of unstimulated saliva was about 6.95. With one gum containing about 1.5% organic acids, the salivary pH fell to a minimum of 6.18 in the 1st minute of stimulation, but then rose rapidly to a level above that in unstimulated saliva. With a sucrose-containing and a sucrose-free gum, the pH rose immediately on stimulation and then fell slightly with time to levels which were significantly above the pH of unstimulated saliva.

ISSN:0008-6568    

DOI:10.1159/000261439

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

This study aimed to investigate the prevalence of selected components of the oral microflora in breast-fed children who developed rampant caries (resembling nursing caries) under hitherto unexplained circumstances. Dental plaque and saliva samples were collected from breast-fed children, aged between 1 and 2.5 years, with and without rampant caries. Mutans streptococci and lactobacilli were isolated from dental plaque of all children with rampant caries and from most caries-free children. None of the colonies of mutans streptococci resembled those of Streptococcus sobrinus. The mean counts of the mutans streptococci and lactobacilli were 100-fold higher in plaque samples from children with rampant caries as compared with caries-free children. No difference could be found between the numbers of mutans streptococci in plaque overlaying cavities and that from adjacent sound enamel. In contrast, the counts of lactobacilli in plaque were approximately 100-fold higher from cavities than from sound surfaces. The levels of mutans streptococci in saliva were directly related to the presence of rampant caries. The results show that caries-free and caries-active breast-fed children, aged 1 to 2.5 years, harbour mutans streptococci and lactobacilli on their teeth. Rampant caries in these children can occur in the absence of nursing bottles or any other feeding abuse during weaning and in the presence of an aciduric plaque microflora, as has been reported for children with nursing bottle caries.

ISSN:0008-6568    

DOI:10.1159/000261440

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

This study was to evaluate the accuracy of visual inspection, conventional radiography, and digital radiographic methods for the detection of occlusal carious lesions in third molars from a present-day adolescent population. Seventy-eight third molars, considered clinically to be without occlusal cavities, were extracted from young soldiers. Before extraction, an intra-oral radiograph was obtained. After extraction, the teeth were examined visually as per the criteria: 0 = no caries, 1 = chalky/stained fissure indicative of enamel caries, 2 = chalky and dark-stained fissure considered indicative of a dentinal lesion, and 3 = as per criterion 2, but with small surface defects (microcavities). The radiographs were digitised, and image enhancement with contrast stretch and a filtering procedure was performed, respectively. The three types of radiographic image were assessed as per the criteria: 1 = no caries/caries confined to enamel, 2 = caries involving the outermost dentine, and 3 = deep dentinal caries extending half-way or more to the pulp. Ground sections (500-600 μm in thickness) served as validation for lesion depth. The digital radiographic method with contrast stretch performed overall best of the four methods ( > 70% detection rate) while visual inspection (53% detection rate) performed better than conventional radiography (48% detection rate). When results from visual inspection and conventional radiography were combined, an increase in the detection rate of 11% was obtained with a 7% increase in false-positive scorings. When digitally contrast-manipulated radiographs were combined with visual inspection, a gain of 33% was obtained with an 11 % increase in false positives. The presence of microcavities was a good indicator of deep dentinal caries, whilst staining of fissures was of limited value

ISSN:0008-6568    

DOI:10.1159/000261441

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Data were taken from six randomised controlled trials of caries prophylactic agents in order to investigate the capacity of bite-wing radiographs of posterior approximal tooth surfaces to enhance discrimination between test and control group measurements. The findings showed that, where an active control agent was employed, the addition of radiographic to clinical examination data failed to improve discriminatory power in comparisons between 3-year caries increments.

ISSN:0008-6568    

DOI:10.1159/000261442

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

In a comparable epidemiological study of kindergarten children, 455 4- and 5-year-olds in Salzgitter (FRG) and 171 4- and 5-year-olds in Oslo (Norway) were examined. Caries was scored at the cavitation level according to WHO criteria. The percentage of caries-free children was higher and the dmfs scores were lower in Oslo than in Salzgitter. It is postulated that this was the result of different levels of fluoride exposure, nutritional habits and dental treatment provision.

ISSN:0008-6568    

DOI:10.1159/000261443

出版商:S. Karger AG    

年代:1992

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000261444

出版商:S. Karger AG    

年代:1992

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000261445

出版商:S. Karger AG    

年代:1992

数据来源: Karger