摘要:

The formation of calcium (Ca) fluoride (CaF2) on bovine enamel blocks during clinically relevant treatment times using neutral fluoride (F) solutions (0.26mol/l F) with and without 0.1mol/l lactate was investigated. Uncoated and pellicle-coated blocks were evaluated for alkali-soluble (1 mol/l KOH, three consecutive 24-hour treatments) Ca, PO4, and F after treatment by the F solutions for 0, 5, 15, 30, and 60 min. There was an overall time-related increase in F recovery, while Ca tended to remain at baseline levels. Less F was recovered from the pellicle-coated blocks. The addition of lactate to the F treatment solution did not result in an overall increase in alkali-soluble F recovery, but did result in the formation of cuboidal shaped crystals which closely approached the morphology of pure CaF2. A 1:2 stoichiometric ratio Ca:2F (mohmol) was not established based on chemical analyses. The ultra-structural and elemental composition of surface deposits on the samples, as determined using scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy, established the presence of CaF2 after 24-hour F treatments; however, it was not possible to directly demonstrate the formation of CaF2 after clinically relevant treatment times.

ISSN:0008-6568    

DOI:10.1159/000261612

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

An in vitro oscillating system, employing human enamel and realistic time intervals and temperature (∼35°C) and measuring mineral loss/gain on a volume basis, was used to investigate the effects of both frequency and duration of exposure to low pH ( < 5) on the demineralization and remineralization behaviour of human enamel. Sections of human teeth were cycled through one of three different regimens: (1) 3 × 20-min acid challenges; (2) 6 × 10-min acid challenges and (3) 6 × 20 min acid challenges, over single 24-hour periods. The acid challenge periods of 3 × 20, 6 × 10 and 6 × 20 min produced no significant differences in net mineral lost, i.e., the volume of mineral lost per volume of enamel exposed was similar irrespective of frequency or duration of acid exposure (approximately 0.5% vol/vol). Increased frequency of acid exposure did, however, tend to alter the total demineralization/total remineralization amounts, resulting in significantly greater amounts of mineral loss and gain. The data suggest that the remineralization capacity of enamel is considerable and that factors such as inhibition of remineralization may be important in determination of net mineral loss from t

ISSN:0008-6568    

DOI:10.1159/000261613

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Root surfaces were exposed to demineralizing buffer in a continuous-flow system, with or without simultaneous perfusion of the pulp chamber with a supersaturated surrogate dentine fluid (SDF). Experimental lesions formed with perfusion of the pulp were significantly less deep than control lesions formed without perfusion, but the application of hydrostatic pressure to the SDF (15 or 30 cm water) did not produce significantly greater reductions. The lesion depth reduction was attributed to reduced undersaturation at the advancing lesion front through interdiffusion of the demineralizing buffer and the SDF. Translucent bands, resembling sclerotic dentine, were observed beneath 9 of 24 experimental lesions and 5 of 24 control lesions. Scanning electron microscopy showed that, in most of the bands beneath experimental lesions, dentinal tubules were either partly occluded by granular mineral deposits or were reduced in diameter. Thus, in vivo, dentine fluid may modify the rate of lesion progression and promote sclerosis in the underlying dentine.

ISSN:0008-6568    

DOI:10.1159/000261614

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Lesion formation in dentin involves demineralization followed by degradation of the exposed organic matrix. Proteinases from microorganisms present in the dentin are believed to play an important role in the breakdown of the dentinal collagen. In this study, the microflora colonizing decalcified dentin matrix, placed in situ, was identified. The gelatinolytic activity of the isolated strains was assessed and related to the degradation of the dentin matrix. The predominant species found were Streptococcus mitis, Peptostreptococcus productus, Lactobacillus casei, Propionibacterium species and Veillonella parvula. Marked interindividual variation in the composition of the microflora was observed. The microflora possessed gelatinolytic activity, although no correlation was found with the severity of dentin matrix degradation. The chemically determined loss of collagen varied between 0 and 67 wt% per participant and corresponded with the extent of collagen degradation observed by transmission electron microscopy.

ISSN:0008-6568    

DOI:10.1159/000261615

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The purpose of this in vitro study was to assess the effect of graded concentrations of calcium in artificial saliva on the output of fluoride from HEMA/ MMA controlled-release devices. After the initial release rates were determined in deionized water, the devices were assigned to five groups. The devices of one group remained in deionized water throughout the 19-day study while those of the other groups were placed in artificial saliva containing 0,4.5, 8.0, or 12.0 mg% calcium on days 4–13. Ten devices of each group were placed in deionized water again on days 14–17 and then in 0.1 mol/l HCl on days 18–19. The five devices of each group that were not placed in deoinized water on day 14 were inspected for surface crystals and then placed in 1 mol/l KOH for 2 days. The fluoride release rates in artificial saliva were reduced by 71–90% and in proportion to the calcium concentration. The release rates in deionized water (days 14–17) approached the baseline values; they exceeded baseline rates by 13–49% while in HCl. The fluoride release rates did not differ among the groups while in KOH, but calcium output was directly related to the calcium concentration of the artificial saliva. The results indicate that fluoride release from HEMA/MMA devices is markedly reduced in artificial saliva and that the reduction is proportional to the concentration

ISSN:0008-6568    

DOI:10.1159/000261616

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000261617

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The development of an in vitro model simulating the oral cavity has allowed the antiplaque activity of a toothpaste containing 0.004% chlorhexidine to be tested. The model is based on the continuous irrigation of bovine tooth samples with artificial saliva. Scanning electron microscopy showed homogeneous colonization of monobacterial plaque by Streptococcus mutans on dental surfaces under these model conditions. The enamel was colonized with regular cell clusters showing a globular appearance. The globules coalesced with increasing plaque thickness. Treatment with toothpaste containing 0.004% chlorhexidine showed a more marked inhibition of bacterial colonization on enamel surfaces than placebo paste lacking this antimicrobial agent. These results indicate that the toothpaste formulation is compatible with chlorhexidine. It is concluded that the in vitro model developed in this study is suitable for the testing of the antiplaque activity of antimicrobial agents, particularly when in a semisolid form such as in a toothpaste.

ISSN:0008-6568    

DOI:10.1159/000261618

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Previous work showed that oral fluoride levels increased with increasing applied F dose for both mouthwashes and dentifrices. This study aimed to determine whether the above dependence was related to applied fluoride concentration or applied fluoride amount. Ten adults mouthrinsed with aqueous NaF solutions of 1–10 ml each of which contained 2.5 mg F, i. e. in the concentration range 250–2,500 ppm F. Subjects rinsed for 1 min and then spat out. Samples of mixed saliva were collected for 3 h afterwards, which were analysed for fluoride. Salivary fluoride clearance curves were obtained which could be fitted to a pharmacokinetic model involving processes ascribed to loss of fluoride from saliva by swallowing and to exchange of fluoride between saliva and an oral reservoir. Mean salivary fluoride concentrations increased significantly with increasing applied F concentration both within the first 3 h after single use and up to at least 18 h after regular daily use. These findings suggest that applied F concentration is a more important factor than applied F amount per se in determining the elevation of oral fluoride levels following topical fluoride use. This implies that application of a given F dose, in a smaller volume at higher concentration than the current norm, may increase efficacy without increasing the risk of adverse effe

ISSN:0008-6568    

DOI:10.1159/000261619

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Seventeen subjects with more than 3 × 105 mutans streptococci per millilitre of saliva completed this randomised, cross-over study. Four different chewing-gums, containing: (1) 70% xylitol, (2) 35% xylitol+ 35% sorbitol, (3) 17.5% xylitol+ 52.5% sorbitol, and (4) 70% sorbitol, were tested. The participants used 12 pieces of each gum per day for 25 days. During the four experimental periods, they wore a removable palatinal plate containing two demineralised enamel samples, and brushed their teeth with a non-fluoridated toothpaste. The results showed that an increased concentration of xylitol in the gum resulted in a lower number of mutans streptococci in both saliva and dental plaque, although the decreases were only significant in the saliva samples (p < 0.01). The pH drop in plaque, measured in vivo after a 1-min mouthrinse with a 10% sorbitol solution, was least pronounced after the 70% xylitol gum and most pronounced after the 70% sorbitol gum period (p < 0.01). No significant differences were found after a mouthrinse with a 10% sucrose solution. All demineralised enamel samples lost mineral during the experimental periods. However, the lesion depth as well as the mineral loss values, assessed microra-diographically, did not differ significantly between the four chewing-gums

ISSN:0008-6568    

DOI:10.1159/000261620

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Approximal surfaces of 13 extracted molar and premolar teeth were classified directly and radiographically as sound or decayed. Eleven faculty dentists examined bitewing radiographs of the teeth and responded on a 5-point certainty scale, whether caries was present. Ten other faculty dentists used a computer-based program to examine the radiographs. For sensitivity, area under the receiver operating characteristic curve, and interexaminer agreement (Kappa), the computer-assisted faculty was significantly (p < 0.05) superior or equal to the unassisted faculty group.

ISSN:0008-6568    

DOI:10.1159/000261621

出版商:S. Karger AG    

年代:1994

数据来源: Karger