Method and composition for priming and adhering to tooth structure

Description of equivalent WO 9623480 A1

METHOD AND COMPOSITION FOR PRIMING AND ADHERING TO TOOTH STRUCTURE

The invention relates to adhesion of restoratives

to teeth. The invention provides a method and

composition for adhering to dental tooth surface. One

or more portions of the composition are applied and

cured to form polymeric material on a cleaned tooth

surface to form a treated tooth surface. A restorative

material is applied to the tooth with a bond strength of

at least about 12 MPa. The polymeric material has a

yield strength of at least 50 MPa, an elastic modulus of

at least 1,000 MPa, a resilience of at least 0.4 MPa

when measured after storage in water at 37°C for 24

hours, and/or an initial marginal integrity between the

restorative material and etched dentin or etched enamel of at least 90 percent.

It is most desirable, when filling a tooth cavity

with a filling material, such as a polymerizable dental

restorative, to ensure good adhesion between the tooth

surrounding the cavity and the set (polymerized) filling

material since there is thereby obtained a good seal between the set filling material and the tooth which

prevents, or at least markedly inhibits, ingress of

mouth fluids and bacteria into the filled cavity and

thus prevents further decay or loss of the filling

material . In order to achieve good adhesion between the

filler material and the tooth enamel, it has been

recommended to provide a primer or adhesive bonding

layer intermediate the filling material and surfaces of

a prepared tooth.

The prior art does not disclose a method of

adhering polymerizable acrylate containing

restoratives to dentin by applying a priming adhesive

composition from only one container to provide

improved retention, acceptable marginal integrity and a bond strength of at least 12 MPa as is provided by

the present invention.

Bowen in U.S. Patent 3,785,832 discloses Dental

Primer varnish. Pluddemann in U.S Patent 3,884,886 discloses Cationic Unsaturated Amine-Functional Silane

Coupling Agents. Lee, Jr. et al in U.S. Patent

4,107,845 discloses Dental Adhesive Composites.

Yamauchi et al in U.S. Patent 4,182,035 discloses Adhesive Compositions for the Hard Tissues of the Human

Body. Omura et al. in U.S. Patent 4,499,251 discloses

Adhesive Compositions. Billington in U.S. Patent

4,514,342 discloses Polyethylenically Unsaturated

Monophosphates. Omura et al in U.S. Patent 4,515,930

discloses Highly Water-Resistant Adhesive. Martin in

U.S. Patent 4,525,256 discloses Photopoly erizable

Composition Including Catalyst Comprising Diketone Plus.

Omura et al. in U.S. Patent 4,537,940 discloses

Adhesive Compositions. Bunker in U.S. Patent 4,540,722

discloses Dentin and Enamel Adhesive. Bunker in U.S.

Patent 4,544,467 discloses Light-Curable Dentin ad

Enamel Adhesive. Aasen in U.S. Patent 4,553,941

discloses Acetal and Hemiacetal Dentin and Enamel

Adhesive Primers. U.S. Patent 4,589,756 relates to

similar aromatic based compositions employed in

dentistry. Asmussen et al. in U.S. Patent 4,593,054

disclose Adhesion Promoting Agent, Process for its

preparation and use thereof on Collageneous Material.

Janda in U.S. Janda in U.S. Patent 4,636,533 discloses

Photopolymerizable Adhesion Promoting Dental

Composition. Janda in U.S. Patent 4,640,936 discloses Photopolymerizable Phosphate-Containing Adhesive

Promoting Dental Composition. James in U.S. Patent

4,645,456 discloses Adhesive Composition for Tooth

Enamel. Bunker in U.S. Patent 4,669,983 discloses

Dentin and Enamel Adhesive. Bunker in U.S. Patent

4,670,576 discloses Polymerizable Phosphorus Esters.

Aasen in U.S. Patent 4,719,149 discloses Method for

Priming Hard Tissue. Blackwell et al in U.S. Patent

4,816,495 discloses Biologically Compatible Adhesive

Visible Light Curable Compositions. Bunker in U.S.

Patent 4,855,475 discloses (Meth)Acrylic Esters of

Phosphoric Acid Ester Dihalides. Montgomery in U.S.

Patent 4,863,993 discloses Surface Priming Composition

for Proteinaceous Substrates; Method of Making and Using

Same. Engelbrecht in U.S. Patent 4,872,936 teaches

dental cement mixtures containing polymerizable

unsaturated monomers and/or oligomers and/or prepolymers

containing acid groups and/or their reactive acid-

derivative groups. Aasen et al in U.S. Patent 4,880,660

discloses Method for Priming Hard Tissue. Montgomery in

U.S. Patent 4,913,939 discloses Method of Making and

Using Surface Priming Composition for Proteinaceous Substrates. Bunker in U.S. Patent 4,929,746 discloses

Dentin and Enamel Adhesive. Muggee et al in U.S. Patent

4,945,006 discloses Low Odor Adhesive Compositions and

Bonding Method Employing Same. Horn et al in U.S.

Patent 4,948,366 discloses Adhesive Bond Strength

Control for Orthodontic Brackets. Haas in U.S. Patent

4,948,367 discloses Orthodontic Accessories and Method

of Applying the Same. Huang et al in U.S. Patent

4,966,934 discloses Biological Compatible Adhesive

Containing a Phosphorous Adhesion Promoter and

Accelerator. Omura et al in U.S. Patent 5,064,495

discloses Method of Adhesion with a Mercapto Group

Containing Adhesive. Omura et al in U.S. Patent

5,085,726 discloses Method of Adhesion with a Sulfide

Group Containing Adhesive. Eppinger et al in U.S. Patent

5,089,051 discloses Adhesion-Promoting Dental

Composition. Omura in U.S. Patent 5,091,441 discloses Dental Composition. Orlowski in U.S. Patent 5,141,436

discloses Method of Bonding Article to Teeth Employing a

Light Curable Primer. Bunker in U.S. Patent 5,177,121

discloses Dentin and Enamel Adhesive. Kawashi a et al .

in U.S. Patent 5,186,783 discloses Method of Bonding with Adhesive Composition Containing a Thiocarboxylic

Acid Compound. Blackwell in U.S. Patent 5,218,070

discloses Dental/Medical Composition and Use. Imai et

al . in U.S. Patent 5,252,629 discloses Adhesives for

Dentin. Kawashima et al. in U.S. Patent 5,254,198

discloses Method of Bonding a Metal or Alloy Utilizing a

Polymerizable Thiocarboxylic Acid or a Derivative

Thereof. Oxman et al. in U.S. Patent 5,256,447

discloses Adhesive Composition and Method. Ikemura et

al. in U.S. Patent 5,264,513 discloses Primer

Composition. Wong in U.S. Patent 5,295,824 discloses Plastic Bracket with Adhesive Primer Layer and Methods

of Making. Betush in U.S. Patent 5,295,825 discloses

Control System for Dental Handpieces. Bunker in U.S.

Patent 5,304,585 discloses Dentin and Enamel Adhesive.

Dental primers and adhesives in accordance with the

invention have unexpectedly superior adhesion to dentin,

enamel, cavity liner, bonding materials and filling

materials.

It is an object of the invention to provide a

method of adhering a restorative material to a dental

tooth by applying to the tooth a liquid composition comprising including at least 50 percent by weight of a

volatile solvent, at least 15 percent by weight of one

or more polymerizable acrylate compounds and an

effective amount of a photoinitiator, at least a portion

of the polymerizable compounds being multifunctional

polymerizable compounds having at least three acrylate

moieties, to form a polymeric material which adheres to

dentin with a bond strength of at least 12 MPa. The

polymeric material has a yield strength of at least 50

MPa, an elastic modulus of at least 1,000 MPa, a

resilience of at least 0.4 MPa and/or a marginal

integrity of at least 90 percent with a restorative

material.

It is an object of the invention to provide a method

of adhering material to a tooth surface by sequentially

including applying portions of a liquid priming/adhesive

composition to a cleaned tooth surface and curing them to form the polymeric material having a yield strength

of at least 50 MPa, an elastic modulus of at least 1,000 MPa, a resilience of at least 0.4 MPa and/or a marginal

integrity of at least 90 percent with a restorative

material. Clinical retention of restorative material as used

herein refers to adhesive retention by bonding a

restorative material to a natural living tooth in a

patient's mouth effectively without undercutting the

tooth.

Acceptable marginal integrity as used herein

means marginal integrity which is at least 95

percent acceptable according to the Ryge criteria

after one year as being alpha or bravo in accordance

with Clinical Criteria by Gunnar Ryge, Inter. Dent.

J, 1980; 30(4) pages 347-358 particularly at pages

348 and 349; and Cvar et al Criteria for the

Clinical Evaluation of Dental Restorative Materials,

U.S. Department of Health, Education and Welfare,

U.S. Public Health Service Pub. No. 790-244, U.S.

Government Printing Office, 1971. Microleakage at

the margin is effectively eliminated by applying

restoratives with acceptable marginal integrity.

Unless otherwise stated herein elastic modulus,

yield strength and resilience modulus are measured

according to the method discussed herein under the

heading "Measurement of physical properties" . Volatile organic solvent (s) as used herein refers

to organic solvent (s) which are substantially more

volatile than water at 23°C.

Water miscible volatile solvent (s) as used herein

refers to solvent (s) which are miscible with water, and

when mixed with water effectively increase the vapor

pressure of the water bring about to a substantial

degree of increase in vaporization of water.

Acrylate as used herein refers to unsaturated polymerizable compounds within the general formula:

R₂

(R - C = C - C -)- . R_

I II

R₃ O

Wherein, k is an integer from 1 to 8,

R is hydrogen or methyl,

Rj_. is an alkyl having from 1 to 20 carbon atoms,

R₂ is an alkyl having from 1 to 8 carbon atoms, and R₃ is an alkyl having from 1 to 12 carbon atoms.

Polymerizable compound as used herein refers to monomers and/or oligomers. Acrylates are preferred

polymerizable compounds. Phosphates as used herein does not include

pyrophosphates.

Bond strength in units of MPa as used herein unless

otherwise indicated refers to bond strength is measured

as follows. Uncontaminated, caries free, extracted

human teeth without significant anatomical alterations,

defects or restorations were cleaned and disinfected by

soaking in 1% sodium hypo chlorite solution for 18 to 24

hours, rinsed with water and are then stored at from 1

to 8 C in 1% sodium chloride in water (saline solution)

until used within six months. The wet teeth are then

sanded flat by hand using wet 300 grit silicon carbide

paper to expose an area of dentine at a plane just below

the original interface between the enamel and the

dentin, and this area of dentine is polished by hand

with wet 600 grit silicon carbide paper. The teeth are

kept wet in water until used within from 1 to 12 hours.

Viscosity as referred to herein is determined

by a Brookfield Model LVT viscosity measuring

apparatus using a number 2 spindle at 12 RPM at 25°C.

Preferred viscosity at 23°C of liquid priming

adhesive compositions in accordance with the invention is less than 400 centipoise (cpi) , more

preferably less than 300 cpi and most preferably

less than 200 cpi.

The dentine surface is dried lightly with a paper

tissue, and the priming/adhesive solution of the

invention applied in a thin layer using a dental

operatory brush with bristles having a length of about 5

mm. The solution is allowed to stand on the dentine

surface for 10 seconds (unless otherwise noted) and the remaining solvent is evaporated by blowing the tooth

gently with a stream of dry oil free air. The layer of

primer/adhesive remaining is light cured by irradiating

it for ten seconds (unless otherwise noted) with light from a dental light curing unit having a minimum output

of 350 milliwatt/square centimeter in the 400 to 500 mm

wavelength range (Prismetics Lite, light curing unit,

L.D. Caulk is used) . A portion of plastic straw of 5mm internal diameter and about 4 mm long is placed end on

to the prepared surface and filled with a light curing

dental filling material (TPH, Dentsply Caulk, unless otherwise noted) . Finally the filling material is cured by irradiating with light from the dental light for

forty seconds.

The prepared samples are stored for 24 hours in

water at 37°C before being thermocycled 500 times

(unless otherwise noted) between 5°C and 55°C with a

dwell time in each bath of 20 seconds. The thermocycled

samples are left in water at 37°C overnight before being

tested in shear using a Zwick universal testing machine

model 145501 with the load cell set for a maximum load

of 500 Newtons, and operating at a crosshead speed of 1

mm per minute using a 2 mm diameter cylindrical chisel .

The chisel has a tip point formed at the lower end by

grinding and polishing a planar surface across the end

of the cylinder at a 45 degree angle to the central axis

of the cylinder. The tip point is formed at the

intersection of a planar surface with the lower end of

the chisel. In test position the tip point of the

chisel is applied against the composite. Each tooth is

vertically mounted in plastic for the test. SUMMARY OF THE INVENTION

The invention is a composition and method for

adhering a restorative material to a dental tooth by

applying a liquid composition to at least a portion of

said tooth to form a treated surface. A first portion of

photopolymerizable liquid priming adhesive dental

composition is applied to a tooth surface. After

leaving the first portion of the liquid composition on

the tooth surface undisturbed for at least 15 seconds on

the tooth surface air is conveyed against the first

portion of the liquid. The light is impinged on the

first portion of the liquid composition whereby at least

a portion of the first portion of the liquid composition

polymerizes to form a first coating on the tooth. A

second portion of the liquid composition is applied to

the first coating, and air is substantially immediately

conveyed to the second portion of the liquid

composition. Light is then impinged on the first and

second portions of the liquid composition whereby at

least a portion of the second portion of the composition

polymerizes to form a treated tooth surface adapted to

retain a restorative material at a clinical retention rate of at least 98 percent with acceptable marginal

integrity. Composition of the invention includes at

least 50 percent by weight of a volatile organic

solvent, at least 15 percent by weight of one or more

polymerizable acrylate compounds and an effective amount

of a photoinitiator. At least a portion of the

polymerizable compounds are multifunctional

polymerizable compounds having at least three acrylate

moieties. The polymerizable compounds are substantially

soluble in the solvent. The composition is adapted to

form a polymeric material which adheres to dentin with a

bond strength of at least 12 MPa. The cured resin has a

yield strength of at least 50 MPa, an elastic modulus of

at least 1,000 MPa, a resilience of at least 0.4 MPa

when measured after storage in water at 37°C for 24

hours, and/or an initial marginal integrity between the

restorative material and etched dentin or etched enamel

of at least 90.

DETAILED DESCRIPTION OF THE INVENTION

A method of the invention comprises

conditioning a tooth surface, including applying a first portion of a liquid priming adhesive

composition to a cleaned tooth surface and curing

the first portion of liquid primer adhesive

composition to form a primed tooth surface.

Optionally a second portion of the liquid priming

adhesive composition is applied to the primed tooth

surface and cured. The polymeric material has a

yield strength of at least 50 MPa, an elastic

modulus of at least 1,000 MPa, a resilience of at

least 0.4 MPa and/or provides an initial marginal

integrity of at least 90 percent.

A polymerizable restorative composition is

bonded to the tooth with a bond strength of at least

about 12 MPa. Priming adhesive compositions useful

in accordance with the invention preferably include

in order of increasing preference at least 50, 60,

70 or 80 percent by weight of a volatile solvent and

at least 15 percent by weight of a polymerizable

compound. The present invention reduces

microleakage by infiltration at the interface of the

restorative and the tooth. A preferred embodiment of the invention

provides a method of treating a natural tooth by

applying a first portion of photopolymerizable

liquid primer/adhesive dental composition to tooth

surface to form a first coating. After leaving the

first portion of the liquid composition on the tooth

surface undisturbed for at least 15 seconds on the

surface, a second portion of the liquid composition

is applied to the first coating, and air is conveyed

to the second portion of the liquid composition.

Then light is impinged on the first and second

portions of the liquid composition so that at least

a portion of the second portion of said composition

polymerizes to form a treated tooth surface adapted

to retain a restorative material at a clinical

retention rate of at least 98 percent.

In accordance with a preferred embodiment of the

invention there is provided a method of adhering a

restorative material to a dental tooth by applying a

dental composition which includes at least 50 percent by

weight of a volatile solvent, at least 15 percent by

weight of one or more polymerizable acrylate compounds and an effective amount of a photoinitiator. At least a

portion of the polymerizable compounds are

multifunctional polymerizable compounds having at least

three acrylate moieties. The polymerizable compounds

are substantially soluble in the solvent. The

composition is adapted to form a polymeric material

which adheres to dentin with a bond strength of at least

12 MPa.

Preferably the composition includes in order of

increasing preference at least 2, 2.5, 3, 3.5, 4, 5, 6,

or 7 percent by weight of the multifunctional

polymerizable compounds. Preferably the solvent is

dimethyl ketone or methyl ethyl ketone and the bond

strength is at least 15 MPa. Preferably the

composition comprises at least 75 percent by weight of

said solvent. Preferably at least a portion of the

multifunctional polymerizable compounds are phosphate

esters.

Preferably at least a portion of the

multifunctional compounds have a chemical structure

within the scope of the general formula:

(R)_n-Z-(A)_m wherein each R independently is an acrylate containing

moiety, Z is an organic moiety, each A is independently

is a phosphate, n is an integer greater than 2, m is an

integer of 1 or more. Preferably at least a portion of

the polymerizable compounds are acids and the acids

comprise at least 2 percent by weight of the

composition. Preferably at least a portion of the

polymerizable compounds are acid esters.

In accordance with a preferred embodiment of the

invention there is provided a method of adhering a

restorative material to a dental tooth by applying a

liquid composition to at least a portion of the tooth to form a treated surface. The composition includes at

least 50 percent by weight of a volatile solvent, at

least 15 percent by weight of one or more polymerizable

acrylate compounds and an effective amount of a

photoinitiator. At least a portion of the polymerizable

compounds are multifunctional polymerizable compounds

having at least three acrylate moieties. The

polymerizable compounds are substantially soluble in the

solvent. The composition is adapted to form a polymeric

material which is adapted to adhere to dentin with a bond strength of at least 12 MPa. Restorative material

is then affixed to at least a portion of the treated

surface with a bond strength of at least about 12 MPa.

Acid-etching of enamel may be done but is not

necessary. To fill deep tooth cavities it is preferred

to cover the dentine closest to the pulp of the tooth

with a hard-setting calcium hydroxide liner (such as

DYCAL, sold by Dentsply International Inc.) leaving the

rest of the cavity floor and walls free for chemical bonding with a dental restorative such as Dyract, sold

by Dentsply International Inc.

Preferred volatile solvents include, ethanol,

methanol, isopropanol, dimethyl ketone, ethylmethyl

ketone, and mixture of these.

Preferred monomers for use in primer adhesive compositions in accordance with the inventor have a

solubility in water of less than about 5%, and more

preferably have a solubility in water of less than 1%. Exemplary monomers include triethylene glycol

dimethacrylate, tetraethyleneglycol dimethacrylate, glycerol-1,2-dimethacrylate, glycerol-1,3-

dimethacrylate, the reaction product of butanediol diglycidyl ester and ethacrylic acid,

tetrahydrofurfural methacrylate, methacryloxyethyl

maleic ester, methacryloxyethyl succinate, urethane

dimethacrylate, Bis-GMA, Ethoxylated bisphenol-A

dimethacrylate, bisphenol-A dimethacrylate, and mixtures

thereof. Monomers having a solubility in water higher

than 5% are less preferred. Monomer having a solubility

in water less than about 1% are more preferred. Highly

water soluble monomers such as hydroxyethyl methacrylate

and hydroxypropyl methacrylate tend to provide lower

adhesion and are less suitable for use in compositions

of the invention.

A volatile solvent is removed after application of

the primer of the dentine surface. The monomer is

preferably less volatile than the solvent .

In use, compositions of the invention are applied

to a clean dry dentine surface, and the solvent is

evaporated, for example, by application of a gentle

stream of air. The layer of resin remaining is

preferably cured by exposing it to light from a dental

curing lamp. The composite filler formation is then applied by exposing it to light from a dental curing

lamp and cured.

Prior art dentine adhesive systems giving adhesion

higher than 12 MPa have required separate applications

of a primer composition and an adhesive composition.

The combined primer/adhesive composition of the present

invention achieves high bond strength adhesion levels

with application of one liquid.

As the free radical-polymerizable monomer or

prepolymer to be employed in this invention, use may be

made of any monomer, dimer, trimer, or other oligomer of

the type that is usable in dental applications. Thus,

the polymerizable monomer portion of the present

adhesive composition generally comprises one or more

monofunctional or polyfunctional ethylenically

unsaturated monomers or prepolymers, e.g., dimers,

trimers, and other oligomers, or mixtures or copolymers

thereof, based on acrylic or methacrylic or itaconic

acid, or derivatives thereof, including their esters

which can be polymerized by free radical initiation.

These materials include, but are not limited to acrylic

and methacrylic acid, itaconic acid and the like, acrylic or methacrylic or itaconic acid esters of

monohydric or polyhydric alkanols or polyhydric alcohols

containing at least one phenyl group. Examples of such

compound include monovinylmethacrylates, e.g.,

methylmethacrylate, ethyl acrylate, propyl methacrylate,

hydroxyethylmethyacrylate, hydroxypropylmethacrylate,

diethylene glycol acrylate, triethylene glycol acrylate,

the monoester of trimellitic acid with hydroxyethyl

methacrylate, hydroxypropyl itaconate and the like,

esters of aliphatic polyhydric alcohols, such as for

example, the di- and polyacrylates, the di- and

polymethacrylates, and the di- and polyitaconates of

alkylene glycols, alkoxylene glycols, alicyclic glycols

and higher polyols, such as ethylene glycol, triethylene

glycol, tetraethylene glycol, tetramethylene glycol,

trimethylolethane, trimethylolpropane, pentaerythritol,

dipentaerythritol, tripentaerythritol, and the like, or

mixtures of these with each other or with their

partially esterified analogs, and their prepolymers,

such compound or mixture optionally having free hydroxyl

content. Typical compounds of this type, include but are

not limited to, trimethylolpropane triacrylate, trimethylolethane triacrylate, trimethylolpropane

trimethacrylate, trimethylolethane trimethacrylate,

tetramethylene glycol dimethacrylate, ethylene glycol

dimethacrylate, triethylene glycol dimethacrylate,

tetraethylene glycol diacrylate, tetraethylene glycol

dimethacrylate, pentaerythritol diacrylate,

pentaerythritol triacrylate, pentaerythritol

tetraacrylate, dipentaerythritol diacrylate,

dipentaerythritol triacrylate, dipentaerythritol

tetraacrylate, dipentaerythritol pentaacrylate,

dipentaerythritol hexacrylate, tripentaerythritol

octaacrylate, pentaerythritol dimethacrylate,

pentaerythritol trimethacrylate, dipentaerythritol

dimethacrylate, glycerin trimethacrylate, ethylene

glycol dimethacrylate, butanediol dimethacrylate,

trimethylolpropane trimethacrylate, tetramethylolmethane

tetramethacrylate,bisphenol-A

dimethacrylate, bisphenol-A diglycidyl methacrylate,

2,2, ' -bis- (4-methacryloxyethoxyphenyl) propane and so

on.

Also included among the polymerizable monomers which

may be used are the vinyl urethane or urethane-acrylate prepolymers which are well known in the art. These

prepolymers are polymerizable by free radical initiation

and may be prepared, for example, by reacting an organic

diisocyanate or an isocyanate-terminated urethane

prepolymer with an ethylenically unsaturated monomer

which is reactive with the diisocyanate or urethane

prepolymer. These polymers also may be prepared by

reacting a hydroxyl-containing material, such as a

polyol or a hydroxyl-terminated urethane prepolymer with

an ethylenically unsaturated monomer which is reactive

with the polyol or hydroxyl-terminated urethane. The

urethane prepolymers, which may be linear or branched,

carry isocyanate end groups and generally are prepared

by reacting a compound having hydroxyl functionality

with a molar excess of diisocyanate.

Any of a wide variety of diisocyanates may be used to

prepare the isocyanate-terminated urethane prepolymer

including aliphatic, cycloaliphatic, heterocyclic, and

aromatic diisocyanates, and combinations of these.

Examples include, but are not limited to, 2,4-tolylene

diisocyanate, 2,6-tolylene diisocyanate, 1,4-phenylene

diisocyanate, 2, 2,4-trimethyl hexamethylene diisocyanate, hexamethylene diisocyanate,

1,4-naphthalene diisocyanate, 1,5-naphthalene

diisocyanate, 4,4, ' -diphenylmethane diisocyanate,

p,p, ' -diphenyl diisocyanate, butylene-1,4-diisocyanate,

ethylene diisocyanate, trimethylene diisocyanate, tetramethylene-1,4-diisocyanate,

butylene-2,3-diisocyanate,

cyclohexylene-1,2-diisocyanate,

methylene-bis- (4-phenyl-isocyanate) ,

dipheny1-3,3, ' -dimethyl-4, , '-diisocyanate, xylylene

diisocyanate, cyclohexane-1,4-diisocyanate,

1-methoxyphenyl-2,4-diisocyanate and the like, and

mixtures thereof.

A wide variety of compounds having hydroxyl

functionality may be used to form the isocyanate-terminated urethane prepolymers. For example,

diols of the structure

HO (CH-CH-O) _aAr (O-CH-CH) _bOH I I I I

I I I I <img file="EP0806931A1_D0001.tif" /> may be used, where RI and R2 are hydrogen atoms or alkyl

groups, e.g., methyl, and Ar is a divalent aromatic

group in which each free valency is on an aromatic carbon atom, and where a and b, independently, may be

zero or an integer. Other suitable hydroxyl containing

compounds include diols and polyols such as ethylene

glycol, propylene glycol, triethylene glycol,

tetramethylene glycol, trimethylolpropane,

pentaerythritol, dipentaerythritol, and the like, or

esters of acrylic acid, methacrylic acid or itaconic

acid or the like with aliphatic polyhydric alcohols.

Among the more preferred hydroxyl containing compounds

are the esters of acrylic or methacrylic acid and a

hydroxyalkanol of at least two carbon atoms such as

hydroxyethyl acrylate, hydroxyethyl methacrylate,

hydroxypropyl acrylate, hydroxypropyl methacrylate,

hydroxyisopropyl methacrylate, and the like.

Formation of the isocyanate terminated urethane

prepolymers may be assisted by the use of a catalyst

known in the art to assist polyurethane formation, for

example, tertiary amines and metal salts, e.g., tin

salts, titanium salts and

the like.

To form the vinyl urethane or urethane-acrylate

prepolymer starting materials, an isocyanate-terminated urethane prepolymer or a diisocyanate is reacted with an

ethylenically unsaturated compound having hydroxyl

functionality. These compounds include for example,

esters of acrylic acid, methacrylic acid or itaconic

acid with aliphatic polyhydric alcohols, such as

hydroxyethyl acrylate, hydroxypropyl methacrylate or the

like. The resulting vinyl urethanes are well known in

the art and are described for example, in U.S. Pat. No.

3,629,187 to Waller, U.S. Pat. No. 3,759,809 to Carlick

et al, U.S. Pat. No. 3,709,866 to Waller and U.S. Pat.

No. 4,459,193 to Ratcliffe et al, and all of these

patents are incorporated herein by reference.

Formation of the vinyl urethane prepolymers may be

assisted by the use of the same catalysts noted above,

namely, tertiary amines and metal salts.

The foregoing list of polymerizable ethylenically

unsaturated monomers and prepolymers is intended to be

exemplary only, and other known polymerizable materials

can be used in compositions of this invention.

In accordance with a preferred embodiment of the

invention two or more ethylenically unsaturated

compounds are included in dental treatment compositions. In a preferred embodiment of the invention the

polymerizable monomer is liquid at temperatures from

about 20° C to about 25° C.

Preferred monomers are TEGDMA, glyceryl

dimethacrylate, polyethylene glycol dimethacrylate,

trimethylolpropane, trimethacrylate, UDMA, R5-62-1,

EBPDMA, and ethylene glycol dimethacrylate.

Preferred solvents are ethanol, 2-propanol, and

dimethyl ketone.

A preferred bonding composition in accordance with

a preferred embodiment of the invention includes about 5

percent by weight of PENTA; about 13.2 percent by weight

of urethane diacrylate; 0.59 percent by weight of

Bisphenol-4-dimethacrylate; 0.2 percent by weight of

camphorquinone (CQ) ; 0.6 percent by weight of EDAB; 0.1

percent by weight of BHT; from 0 to 0.4 percent of an

organic fluoride salt, and 78 to about 81 percent by

weight of dimethyl ketone.

A preferred etchant includes 36 percent by weight

of H₃P0₄ and 64 percent by weight of water.

Exemplary acrylic monomers for use in compositions

of the invention include: 1, 4-butanediol dimethacrylate (BDEM) ; glyceryl dimethacrylate (GlyDM) ; hydroxyethyl

methacrylate (HEMA) ; triethyleneglycol dimethacrylate

(TGD) ; tetrahydrofuran dimethacrylate (THFMA) .

Preferably a restorative composition is applied

to a tooth surface treated in accordance with the

invention, and photocured to form a restorative

filling having a clinical retention rate after one

year of at least 98 percent. Preferably prior to

applying liquid primer/adhesive to a tooth surface

the surface of smear layer of the tooth is removed,

for example by acid etching by applying dilute or

concentrated acid(s) , or at neutral pH by applying

EDTA. Thus, the photopolymerizable dental

restorative composition is applied to the treated

tooth surface, light is then impinged on the

restorative composition whereby at least a portion

of the restorative composition polymerizes to form a

cured restorative material adhered with a high bond

strength to the treated tooth surface.

This bond strength is greater than a

comparative bond strength of a bond between the

restorative material and a tooth formed essentially by applying a first portion of the liquid

composition to the treated tooth surface. Then

impinging light on the first portion of the liquid

composition. A photopolymerizable dental

restorative composition is then applied to the

treated tooth surface. Light is then impinged on

the restorative composition whereby at least a

portion of the restorative composition polymerizes

to form a cured restorative material adhered with a

comparative bond strength to the treated tooth

surface.

In accordance with a preferred embodiment of

the invention is provided a method for clinical

retention of restorative material by a natural tooth

by applying a portion of photopolymerizable liquid

priming adhesive dental composition to tooth

surface. After leaving the first portion of the

liquid composition on the tooth surface

undisturbed for at least 15 seconds on the surface,

air is conveyed (forced or directed) against the

first portion of the liquid on the surface. Light

is then impinged on the first portion of the liquid composition whereby a portion of the first portion

of the liquid composition polymerizes to form a first coating on the tooth. A second portion of

the liquid composition is applied to the first

coating. Substantially immediately thereafter air

is conveyed to the second portion of the liquid

composition. Light is then impinged (irradiated) to

the first and second portions of the liquid

composition whereby at least a portion of the second portion of the composition polymerizes to form a

treated tooth surface adapted to retain a

restorative material at a clinical retention rate of

at least 98 percent.

Preferably the first portion of the liquid

composition is left on the surface undisturbed for

at least 15 seconds. Preferably the solvent is

miscible with water and when mixed with water substantially lowers the effective vapor pressure of

the water bringing about a substantial degree of

increased vaporization of the water in-situ at the

treated surface. Preferably the liquid dental

composition has a viscosity of less than 400 centipoise. Preferably the liquid dental

composition includes oligomer having a weight

average molecular weight greater than 600.

Preferably before applying the first of the

liquid composition at least a portion of the tooth

is treated by steps of :

(1) applying a dilute acid to the tooth

surface to form an etched tooth

surface,

(2) rinsing the dilute acid from the

etched tooth surface to form a rinsed

etched surface, and

(3) partially drying the rinsed etched

surface to form a wetted etched

surface .

Preferably the first portion of the liquid

composition remains undisturbed on the surface for

at least 20 seconds, and has a viscosity of less

than 300 centipoise and includes at least 70% of a

water miscible volatile solvent. Preferably the

liquid composition includes at least 2% of an oligomer having a weight average molecular weight

greater than 650.

In accordance with a preferred embodiment of

the invention is provided a method of adhering a

restorative material to a natural tooth by applying

a first portion of photopolymerizable liquid

primer/adhesive dental composition to tooth

surface. After leaving the first portion of the

liquid composition on the tooth surface undisturbed

for at least 15 seconds on the surface, air is

conveyed against the first portion of the liquid on

the surface. Light is then impinged on the first

portion of the liquid composition whereby a portion

of the first portion of the liquid composition

polymerizes to form a first coating on the tooth. A

second portion of the liquid composition is applied

to the first coating, and substantially immediately conveying air to the second portion of the liquid

composition. Light is impinged on to the first and

second portions of the liquid composition whereby at

least a portion of the second portion of the

composition polymerizes to form a treated tooth surface adapted to retain a restorative material at

a clinical retention rate of at least 98 percent.

Preferably liquid composition remains on the surface

substantial undisturbed for at least 20 seconds, has

a viscosity of less than 300 centipoise, includes at

least 70% of a water miscible volatile solvent, and

at least 2% of an oligomer having a weight average

molecular weight greater than 650.

In the wet dentin techniques dentin surface is

exposed and ground flat with 600 grit paper. Dentin

is rinsed with clean water prior to bonding. Primer

or primer/adhesive is then applied. A cotton pellet

is used to remove any excess moisture on the dentin

surface leaving a small amount of residual moisture

on the immediate surface of the dentin.

Total Etching refers to preparation of the

tooth surfaces by applying ten percent phosphoric

acid for 10 to 15 seconds, then rinsing the acid off

thoroughly for 10 to 15 seconds.

Shear dentin bond strengths of dentin through

the Primer/Adhesive composition of the invention to

Dyract Restorative Material are in excess of 18 MPa and have at least 98 percent retention of

restorative.

Shear dentin bond strengths achieved with

primer/adhesive of the invention with TPH

restorative on wet unetched dentin is 19 MPa. The

shear bond strength for TPH restorative are

approximately 37% higher for primer/adhesive of the

invention than with ProBond of the prior art.

In accordance with a preferred embodiment of the

invention is provided a method of adhering a

restorative material to a dental tooth by applying a

dental composition which includes at least 50

percent by weight of a volatile solvent, at least 15

percent by weight of one or more polymerizable acrylate compounds and an effective amount of a

photoinitiator. At least a portion of the

polymerizable compounds are multifunctional polymerizable compounds having at least three acrylate moieties. The polymerizable compounds are substantially soluble in the solvent. The

composition is adapted to form a polymeric material which adheres to dentin with a bond strength of at

least 12 MPa.

Having generally described the invention, a more

complete understanding can be obtained with reference to

certain specific examples, which are included for

purposes of illustration only. It should be understood

that the invention is not limited to the specific

details of the Examples.

FIRST COMPARATIVE EXAMPLE

A commercially available primer composition is made

by stirring 6 percent by weight of PENTA, 30 percent by

weight of HEMA, 63.9 percent by weight of 95% ethanol;

and 0.1 percent by weight of BHT. The primer

composition is applied to a cleaned tooth surface,

solvent is blown away, and then Dyract, a polymerizable

acrylate containing restorative is applied which forms a

bond strength of 6.3 MPa.

SECOND COMPARATIVE EXAMPLE

The procedure of the First Comparative Example is

followed except that after removal of solvent, a

commercially available adhesive composition is applied and cured. The adhesive composition is made by stirring 24.90 percent by weight of triethylene glycol

dimethacrylate, 9.24 percent by weight of bisphenol-A-

dimethacrylate, 0.03 percent by weight of butylated

hydroxy toluene, 2.0 percent by weight of morpholino

ethyl methacrylate, 0.12 percent by weight of lithium P-

toluenesulfinate, 0.24 percent by weight of

camphorquinone, 53.32 percent by weight of urethane

diacrylate, 4.55 percent by weight of DPEPAP, and 5.6

percent by weight of HEMA. The restorative forms a bond

having bond strength of 10 Mpa.

EXAMPLE 1A

A) Priming Adhesive Composition

A priming and adhesive polymerizable composition in

accordance with the invention is formed by stirring 3.13 grams of 7,7,9,63,65 hexamethyl-4,13,60,69-tetra-oxo-

3, 14,19,24,29,34,39,44,49,54,59,70-dodecanaoxa-

5, 12,61, 68-tetra-azadoheptacontane-l,72 diyl- dimethacrylate, (also known as urethane dimethacrylate

resin); 5.00 grams of 2,2,6-6 tetra acryloxyloxymethyl-

4, 8 dioxa-9-oxo-ll-undecyl phosphoric acid, also known as dipentaerythritol pentacrylate phosphoric acid ester

(PENTA) ; 11.07 grams of 2,7,7,9, 15-pentamethyl-4, 13-

dioxo-3, 14-dioma-5, 12-diaza hexadecane 1,1 diyl

dimethacrylate; also known as urethane dimethacrylate

(UDMA) ; 0.1 grams of phenol-2, 6-bis- (1, l-dimethethyl-4-

methyl) , also known as butylated hydroxytoluene (BHT) ;

0.2 grams of bicyclo [2.2.1] heptane-2, 3-dione-l, 7, 7-

trimethyl, also known as camphorquinone; 0.60 grams of

4-Ethyl dimethyl aminobenzoate (DMABE) , 0.59 grams of

isopropylidenbis-4-phenoxymethacrylate also known as

bis-phenol-A-dimethacrylate (BPADMA) and 79.31 grams of

dimethyl ketone.

B) Priming a tooth surface

Extracted human teeth are treated in 1% sodium

hypochlorite for 18 to 24 hours, washed with water, and

stored in distilled water in a refrigerator at about 4°C

until needed. The teeth are mechanically wet sanded

successively with 320/600 grit carborundum paper until

the dentin is exposed. Each tooth sample is then etched

with 36% phosphoric acid for 20 seconds, rinsed with water for 15 seconds, and then air dried to remove surface water. The priming adhesive composition (made as described in Example 1A section A) is then applied

with a brush and left to stand for 30 seconds, dried

with oil-free air for five seconds, and cured for 10

seconds with a Prismetics Lite light curing unit.

Prisma®TPH restorative is placed in a cylindrical

plastic matrix with a 5.0 mm inside diameter, set on the

treated dentin and cured by irradiating with the curing

unit for 40 seconds. The specimens are stored in

distilled water for approximately 24 hours at 37°C.

Each specimen is mounted vertically in a plastic

cylinder with self cure polymethyl methacrylate so that

the dentin surface is parallel to the Instron needle;

and then debonded on a Zwick Universal Testing Machine

with a crosshead speed of 1 mm/minute. The priming

adhesive has an elastic modulus of 1641 MPa, a yield

strength of 60.7 MPa and a resilience modulus of 1.1

MPa. The restorative bonds to the treated tooth surface

with a bond strength of 13.9 MPa, and marginal integrity as shown in Tables 1 and 1A. THIRD COMPARATIVE EXAMPLE

A) Priming Adhesive Composition

Dyract PSA (TM) priming and adhesive sold by

Dentsply G.m.b.H. polymerizable composition in a single

bottle is used in this example.

B) Priming a tooth surface

Extracted human teeth are treated in 1% sodium

hypochlorite for 18 to 24 hours, washed with water, and

stored in distilled water in a refrigerator at about 4°C

until needed. The teeth are mechanically wet sanded

successively with 320/600 grit carborundum paper until

the dentin is exposed. Each tooth sample is then etched with 36% phosphoric acid for 20 seconds, rinsed with

water for 15 seconds, and then air dried to remove

surface water. The priming adhesive composition (Dyract

PSA priming adhesive) is then applied with a brush and left to stand for 30 seconds, dried with oil-free air

for five seconds, and cured for 10 seconds with a

Prismetics Lite light curing unit. Prisma®TPH

restorative is placed in a cylindrical plastic matrix

with a 5.0 mm inside diameter, set on the treated dentin and cured by irradiating with the curing unit for 40

seconds. The specimens are stored in distilled water

for approximately 24 hours at 37°C. Each specimen is

mounted vertically in a plastic cylinder with self cure

polymethyl methacrylate so that the dentin surface is

parallel to the Instron needle; and then debonded on a

Zwick Universal Testing Machine with a crosshead speed

of 1 mm/minute. The priming adhesive has an elastic

modulus of 612 MPa, a yield strength of 16.8 MPa and a

resilience modulus of 0.23 MPa. The restorative bonds

to the treated tooth surface with a bond strength of 12.0 MPa, and marginal integrity as shown in Tables 1

and 1A.

Marginal leakage in class V cavities

Method;

Cylindrical class V cavities in human teeth are filled with the priming adhesive of Example 1A, or the Third

Comparative Example or a reference adhesive plus TPH. Syntac and ProBond are used as reference materials.

Both the enamel and total etch technique are carried out

and the results are shown below in Tables 1 and 1A. The etched specimens are etched for 30 seconds using 36%

phosphoric acid. Each specimen is thermocycled (1500

times) and thereafter analyzed for marginal breakdown.

Table 1;

Enamel efrπh technique

Adhesive system percent perfect margin after thermocycling in enamel in dentine

Example 1A 96.2 (3.5) 72.0(7.7)

Syntac 94.1 (4.9) 54.2(29.2)

ProBond 83.8 (12.8) 48.9(25.0)

Dyract PSA 87.7(7.4) 66.2(18.6)

(Third Comparative Example)

Table 1A:

Total etch technique

Adhesive system percent perfect margin after thermocycling in enamel in dentine

Example 1A 96.1(3.0) 91.8(5.4)

Dyract PSA 92.2(6.3) 72.8(16.8)

(Third Comparative Example)

Marginal leakage in class II cavities (MOD)

MOD cavities are prepared and subsequently etched

(enamel and dentine) with 36% phosphoric acid for 15

seconds. In each case, one of the approximal boxes ended in the enamel region while the other was extended

into the dentine area. The cavity walls are covered

with either of the adhesive systems (the composition of

Example 1A, Dyract PSA or ProBond) and then filled with

TPH composite filling material. During placement of the

restoration and the stress test the specimens are

subjected to pressure simulating the dentinal liquid.

The entire cavity is filled with two increments of

composite and cured from the occlusal direction. The

stress is applied to the restored teeth by 1.2 million

chewing cycles and thermocycling 3000 times.

Thereafter the specimens are investigated for marginal

integrity by means of SEM technique.

Table 2:

Total Etch Technique

Adhesive system percent perfect after stress margin initially application

Example 1A 91.2 (3.8) 63.2(4.8)

Dyract PSA 81.5 (9.4) 53.0(12.1) (Third Comparative Example)

ProBond 85.3 (4.3) 59.4(8.0) ProBond is sold by Dentsply International. Scotch

Bond Multi-Purpose (TM) system is sold by 3M. ProBond

and Scotch Bond are both sold with separate bottles of

primer and adhesive solutions. In use, the primer is

first applied and blown dry, but not cured. A separate

adhesive is next applied and cured, followed by the

composite material .

Syntac (TM) system is sold by Vivadent as two

solutions which are applied sequentially with

intermediate drying, but neither layer is cured.

Finally an adhesive resin is applied before application

of the composite material.

Kerr's OptiBond (TM) system has a primer which is

applied and light cured, followed by application from a

second bottle of a layer of adhesive and light curing

before application of the composite material.

Clearfil Liner Bond II (TM) sold by Kuraray

includes three separate bottles. Solutions from two of

the bottles are mixed, and the mixture applied to a tooth surface and blown dry but not cured. A third

solution is then applied to the tooth surface and cured

before application of composite material. Denthesive II (TM) is sold by Kulzer, two separate

solutions which are mixed, applied to the tooth surface

and blown dry, but not light cured. A third solution is applied to the tooth surface and then cured before

application of composite material.

Gluma (TM) is sold by Bayer. The dentine is first

cleaned with a specially provided solution, washed with

water and blown dry. A primer is then applied and blown

dried, and finally a solution called a "sealer" is

applied, the composite material is placed on top, and

the sealer and composite are cured together.

Table 3

Physical properties of the adhesive resin part of various adhesive systems

Material After storage one After storage one Percent Number of day in water at month in water at decrease in separate 37°C 37°C property solutions

E Y R E Y R E Y R (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa)

Example 1A 1641 60.7 1.1 1187 39.3 0.7 28 35 36 1

Dyract PSA 612 16.8 0.23 187 5.1 0.1 70 70 57 1 (Third Comparative Example)

ProBond 573 18.5 0.29 267 7.4 0.1 53 60 65 2 σs

Scotchbond 2180 84.3 1.63 1862 61.9 1.03 15 27 37 2 Multi¬ purpose

Gluma 1793 69.1 1.33 1905 69.1 1.26 15 0 5 3

Syntac/ 1992 76.1 1.46 1920 69.3 1.26 4 9 14 3 Heliobond

OptiBond 1714 60.2 1.06 1722 60 1.05 0 0 1 2

Liner Bond 2042 79.0 1.53 1306 39.7 0.61 36 50 60 3 II

Denthesive 1384 51.2 0.95 1533 53.2 0.92 -11 -4 3 3 II

<img file="EP0806931A1_D0002.tif" />

Measurement of physical properties

Test specimens for each material are prepared by

filling the uncured resin (after removal of solvent if

necessary) into cylindrical molds 4mm diameter and 6mm long, and curing the resin for 40 seconds from each end by

irradiation with light from a dental curing lamp. The

hardened specimens are then removed from the molds and

stored under water at 37°C for the required length of time. The specimens are then tested in compression along the axis

of the cylinder using a Zwick Universal Testing Machine set

to a crosshead speed of 1mm per minute.

Throughout this disclosure elastic modulus E is derived from

the following equation.

E = _______ = F X 1 stress e X A where F is the applied force, e is the change in length, 1

is the original length, A is the cross sectional area of the material under stress. Throughout this disclosure yield strength is derived from the equation

Y = E A

Where P is the force at the proportional limit, and A is the

cross sectional are of the specimen under test.

Throughout this disclosure resilience modulus R is

calculated from the equation

R = ² 2E where E an Y are the elastic modulus and yield strength as defined above.

While present embodiments of the invention and methods

of practicing the same have been illustrated and described, it will be recognized by those skilled in the art that this

invention may be otherwise variously embodied and practiced within the scope of the following claims.