[Dissertations 25 years after date. 15. Remineralization of human enamel]. / Proefschriften 25 jaar na dato. 15. Remineralisatie van menselijk glazuur.

Remineralization of human enamel is an important issue in the prevention of caries. Fluoride has an important influence on the remineralization process. A great deal of research has been done into the role played by the method of application and by the concentration and type of fluoride. In the clinical study of this dissertation the process of remineralization of lesions in human enamel was longitudinally followed in vivo during a period of 3 months. Both the remineralization in the surface softened enamel lesion and the subsurface enamel lesion of human enamel were studied. In addition, attention was devoted especially to the influence of fluoride on this remineralization. The results indicated that the use of a 1,500 ppm fluoridated NaF toothpaste was more effective on the remineralization process than the use of a 50 pmm NaF mouthrinse. Important is the fluoride gradient in the enamel lesion, and in particular the fact that fluoride reaches the lesion front. This most likely accounts for the remineralization efficiency.

[The HA-Ti system]. / Het handgeschroefde titanium implantaat.

Some concepts and techniques are discussed while stressing the collaboration between specialists to design a new type of implant. Important aspects are: a simple implantation procedure, a wide field for indication and non-traumatic surgical placement.

[Magnetic retention in implantology]. / Toepassing van magnetische retentie bij implantaten.

The use of magnets in dentistry is not very common. The reason for this is, that the available room in the mouth allows only the use of very small magnets, and often the space between both magnets is too large. This leads to a poor retention. The development of new rare earth magnets offers now a retention comparable with the retention of precision attachments. Possibilities for the use of magnets in dental implantology are discribed.

The effect of fluoride containing toothpastes on sound human enamel in vivo during 3 weeks.

The F- uptake in vivo in sound human enamel from fluoridated toothpastes is described. Ten participants brushed for about 1 min twice a day, four enamel specimens in a dental appliance over three week periods. The enamel specimens were prepared so that only the right hand side of the enamel was positioned in the appliance; the left hand side being used as a control. The toothpastes all used hydrate silica as the abrasive and contained either 0.1 ppm F- as nicomethanolhydrofluoride, 1100 ppm F- as NaF or 1350 ppm F- as NaF/MFP. After three weeks brushing with the pastes in vivo the F- contents of three thin layers of enamel were determined in all specimens by means of acid etching. The results showed that 1) there were no statistically significant differences between the mean F- contents of the enamel (p less than 0.05), which were comparable, before and after three weeks brushing in vivo. This observation was independent of the toothpaste employed, 2) in the outer approximately 1.5 micron layer of human enamel there was an equilibrium F- level of about 1200 ppm. The microhardness data on polished enamel specimens showed that there was no statistically significant difference between the mean indentation lengths produced in control specimens and these made in specimens after the use of a placebo toothpaste (0.1 ppm F-) in vivo indentation lengths of all specimens brushed with any of the fluoridated toothpastes for three weeks showed, however, a statistically significant decrease of indentation length and thus an increased hardness.

In vivo remineralization of artificial subsurface lesions in human enamel. I.

In this paper in vivo remineralization of artificial subsurface lesions in human enamel, placed in partial prostheses of 30 patients during 3 months is presented. The patients were divided into 3 groups. Group A brushed daily with H2O: group B brushed with H2O and rinsed with a neutral 50 ppm F- solution and group C brushed with a neutral 1500 ppm F- toothpaste. Microhardness indentation measurements were carried out at the start of the experiment and after 2, 4, 16, 20, 44, 58 and 87 days. After 3 months, the indentation length reductions (in %) were for group A, B and C 16, 13 and 20%, respectively. These differences were all statistically significant at least at the p less than 0.05 level. In conclusion, subsurface lesions remineralize very slowly in vivo, much slower than in vitro situations. The remineralization rate is relatively fast in the first 2 weeks; for longer periods the remineralization rate of subsurface enamel lesions is very slow.

Microradiography of in vivo remineralized lesions in human enamel. II.

The purpose of this work was to investigate mineral deposition and redistribution in subsurface human artificial enamel lesions during in vivo remineralization period of 3 months. The enamel lesions were placed in lower prostheses of 30 patients, divided in 3 groups. Group A brushed daily with H2O; group B brushed with H2O and rinsed with a neutral 50 ppm F solution and group C brushed with a neutral 1500 ppm F toothpaste. The technique employed was microradiography. Initially the average vol % of mineral in the lesion body was 47%. After 3 months remineralization in vivo the vol % of mineral in the lesion body was for group A, B and C: 50.7, 48.7 and 53.1 vol %, respectively. The average lesion depth decreased for groups A, B and C 18, 13 and 25 microns respectively over 3 months. The original lesion depth was +/- 100 microns. The microradiographic data show conclusively that mineral is deposited "de novo" inside subsurface lesions. The remineralization percentages are for the control, rinse and brush group 20%, 15% and 31%, respectively.

Remineralization of softened human enamel in mucin- or CMC-containing artificial salivas.

The rehardening properties of four saliva substitutes on artificially softened human enamel have been investigated by microhardness measurements. The saliva substitutes were all based on the same formula, containing calcium, phosphate and fluoride as the main electrolytes, and mucin or carboxymethylcellulose as the main macromolecules. It has been shown that a rehardening potential exists in the saliva substitutes when calcium and phosphate are present. Omitting F- greatly reduces the rehardening potential. The rehardening is better in case of the CMC-containing saliva than in that containing mucin.