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(2) Measurement of Fluorine Ions: 

2 Grams of the adhesive composition, 100 g of water and 10 g of diethyl ether were vigorously mixed together, left to stand still, the aqueous phase thereof was filtered through the syringe filter, and the obtained filtrate was measured by using an ion chromatography to measure the concentration of fluo› rine ions (mmols/g) contained in 100 parts by mass of the polymerizable monomer. The concentration of the fluorine ions was calculated by using a calibration curve found from the standard samples of fluorine ions (10 ppm, 25 ppm, 50 ppm). 

(3) Evaluating the Adhesion to the Tooth. 

( a) Preparation of an Adhesion Test Piece: 

Within 24 hours after the slaughter, a bovine foretooth was pulled out, and the enamel surface and the dentin surface were ground by using a #600 emery paper while pouring water so as to be in parallel with the labial face to thereby prepare a tooth for testing the strength. 

Next, the compressed air was blown onto the above surface of the tooth for testing the strength for about 10 seconds to dry 20 the surface and, thereafter, a double-sided adhesive tape hav› ing a hole of3 mm in diameter perforated therein was fixed to either the enamel surface or the dentin surface. Next, a par› affin wax of a thickness of 0.5 mm having a hole of 8 mm in diameter perforated therein was fixed onto the above hole in 25 concentric therewith to form a mimic cavity. 

A sample adhesive composition was applied into the mimic cavity, left to stand for 20 seconds and, thereafter, the com› pressed air was blown thereto for about 10 seconds to dry the composition followed by the irradiation with light from a dental visible ray irradiator (Tokuso Powerlight, manufac› tured by Tokuyama Co.) for 10 seconds. Further, a dental composite resin (Estelite ~, manufactured by Tokuyama Den- tal Co.) was applied thereon, and was irradiated with light from the visible ray irradiator for 30 seconds to prepare an adhesion test piece. 

(b) Method of Testing the Adhesion. 

The above adhesion test piece was dipped in water of37° C. for 24 hours and was, thereafter, pulled by using a tension tester (Autograph manufactured by Shimazu Seisakusho Co.) 40 at a crosshead speed of 2 mm/min. to measure the tensile adhering strength between the dentin and the composite resin. Four test pieces were measured for their adhering strength per a test relying upon the above method, and an average value thereof was regarded as an adhering strength to the enamel or 45 to the dentin to evaluate the adhesion to the tooth. 

( 4) Testing the Storage Stability. 

(a) Evaluating the Salt Precipitation. 

After the adhesive composition was prepared, 1 0 g of the adhesive composition was introduced into a 20-ml glass bottle and was stored in an incubator maintained at 37° C. Precipitation of a white solid matter from the adhesive com› position was observed by the eye with the passage of time, and the timings of the salt precipitation were evaluated on the basis of the following three steps. 

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@: No salt prec1p1tation was observed even after two months have passed. 

0: Slightly precipitated (precipitated on the bottom of the glass bottle). Number of days until precipitated was recorded. 

X: White solid matter precipitated in large amounts within 3 days (the liquid was cloudy). 

(b) Evaluating the Gelling Property. 

10 Grams of the sample adhesive composition was intro› duced into the 20-ml glass bottle and was stored in the incu- bator maintained at 37° C. Gellation of the adhesive compo› sition was observed by the eye with the passage of time, and the gellation timings were evaluated on the basis of the fol› lowing three steps. 

@: The solution was not gelled even after two months have passed. 

0: The solution was not gelled for more than one month. The number of days until gelled was recorded. 

X: The liquid gelled within 3 days. 

The components were weight out according to the follow› ing recipe, and were stirred and mixed together at room tem› perature (23° C.) for 24 hours to prepare a dental adhesive. 

Grams of PM2/hydrogenphosphoric diester monomer (A-1), 

2 Grams of Al(O-1-pr)/polyvalent metal ion source (B’), 

0.4 Gram ofFNa/fluoride ion source (E’), 

34 Grams ofIPA/water-soluble organic solvent (D), 

7.6 Grams of water, and 

0.4 Grams ofCQ and 0.4 g ofDMBE/photopolymerization initiator (G). 

The adhesive was measured for its amount of polyvalent metal ions and amount of fluorine ions. Thereafter, the adhe› sive was tested for its adhesion and was evaluated for its adhesion to the enamel and to the dentin. The adhesive was, further, tested for its storage stability and was evaluated for its salt precipitation and gelling property. The composition of the adhesive was as shown in Table 1 and the measured results were as shown in Tables 2 and 3. 

Dental adhesives of compositions shown in Table 1 were prepared according to the method of Example 1. 

The obtained adhesives were measured for their amounts of polyvalent metal ions and amounts of fluorine ions, and were tested for their adhesion and storage stability in the same manner as in Example 1 to obtain results as shown in Tables 2 and 3. 

Adhesives of compositions shown in Table 4 were prepared according to the method of Example 1. 

The obtained adhesives were measured for their amounts of polyvalent metal ions and amounts of fluorine ions, and were tested for their adhesion and storage stability in the same manner as in Example 1 to obtain results as shown in Tables 5 and 6. 

## Comparative Examples 1 to 12 

## Example 1 

## Examples 2 to 22 

