NATIONAL BUREAU OF STANDARDS REPORT

10 611

Progress Report

on AMALGAM, CEMENTS AND ESTHETIC

RESTORATIVES: SOME NEW DEVELOPMENTS

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

311.05-11-3110189 September 14, 1971 10 611

Progress Report

on AMALGAM, CEMENTS AND ESTHETIC

RESTORATIVES: SOME NEW DEVELOPMENTS

by

N. W. Rupp, D.D.S*

* Research Associate from the American Dental

Association Research Unit, National Bureau of

Standards, Washington, D. C. 20234.

This investigation was supported in part by the

dental research program conducted by the National

Bureau of Standards, in cooperation with the

American Dental Association; the United States

Army Medical Research and Development Command;

the Dental Sciences Division of the School of

Aerospace Medicine, USAF; the National Institute

of Dental Research and the Veterans Administration.

IMPORTANT NOTICE NATIONAL BUREAU OF ST

for use within the Government,

and review. For this reason, th( whole or in part, is not author Bureau of Standards, Washingto

the Report has been specifically

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

ss accounting documents intended

subjected to additional evaluation

listing of this Report, either in

2 Office of the Director, National

ly the Government agency for which

opies for its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
.
AMALGAM, CEMENTS AND ESTHETIC RESTORATIVES:

SOME NEW DEVELOPMENTS

Nelson W. Rupp, D.D.S.

Over 80% of a general dentist's treatment procedures

involve the selection and manipulation of materials. As the

result of research new materials and techniques are continuously

being developed and these innovations stimulate quite convincing

claims by both dentists and manufacturers. Often this enthusiasm

for the new is well founded but on occasion the dentist who

adopts them learns to his dismay that the conclusions to use

the materials or technique were not based upon sound evidence.

An example was the almost universal acceptance followed by

nearly total rejection of unfilled resin as a replacement for

silicate cement. This loss of favor continues today even

though the resin manufacturers have improved the color

stability and modified the handling techniques which compensate

for the undesirable physical properties.

There are several sources of information available to

dentists regarding new materials. The American Dental

Association supports two laboratories. One is in the Chicago

office of the American Dental Association and the other is

in the National Bureau of Standards at Washington, D. C.
2 -

In addition, the ADA, as the need arises, requests an

individual or a laboratory to evaluate a material or technique. Two such instances where consultants prepared

reports occurred recently. Dr. Myers of the University

of Michigan prepared a literature review of zinc oxideeugenol cements for the Council on Dental Materials and

Devices.^ Professor Swartz at Indiana University prepared

for the Council on Dental Research a report which was titled

2 "Research in Dental Materials". Both reports were published

in the Journal of the American Dental Association. The

Council on Dental Materials and Devices of the ADA

occasionally prepares position statements for publication

in the JADA as new materials and techniques are introduced.

This is illustrated by a report in the past year on fissure

3 . . sealants. In addition to these current and timely articles

the Council on Dental Materials and Devices publishes

4 biannually a book "Guide to Dental Materials and Devices"

.

Each member of the ADA is supporting these services and has

access to the current information through the JADA.

The following discussion will include new developments

in restorative materials, dental amalgam, cements, esthetic

restorative materials and fissure sealants.
-3-

Dental Amalgam

Each year approximately 160 million amalgam restorations

5

are placed. This is approximately 80% of all single tooth

restorations. Consequently, it is easy to understand why

the manufacturers of composite resins are eager to replace

the conventional dental amalgam. Until the results of

rigorous clinical studies are more convincing, however,

dental amalgam, along with gold, will remain the choice for

load-bearing areas on posterior teeth. The amalgam restoration should be recognized as the dentist's best friend because

a well-condensed, contoured and polished amalgam will be

acceptable esthetically as well as functional for many years.

The results of a clinical study made by the author in

which the reasons for placing restorations were recorded

are shown in Table 1. This is unpublished data which was

observed in 1958. The study was prompted by a feeling that

a large percentage of time was spent in repeating prior

treatments. Two categories, new and replacements, were

selected to identify the reason for the restoration. Of

the 424 restorations, 119, or 28%, were replacements. This

study was completed prior to the plaque control era.

Consequently many replacements, both material failure or
4-

marginal breakdown, were attributed to faulty cavity preparation or improper handling of the material rather than the

lack of patient's education or motivation to prevent plaque

buildup. The record verified the feeling that considerably

more treatment could be done if the failures could be reduced.

Current research strongly indicates that corrosion and

its aftermath, pitting and marginal breakdown, are the

principal causes of amalgam failure.^ Along with this,

however, is the dynamic flow or creep and the resultant

7 extrusion of the amalgam from the cavity. These two factors

combined with inadequate bulk at the cavosurface margin are

believed to be directly involved in the majority of cases

involving marginal breakdown and secondary caries. A typical

example of such a failure is shown in Figure 1.

The following contributions to amalgam failure are within

the operator's control: (1) Inadequate amalgam bulk at the

cavosurface margin. (2) Failure to establish correct occlusal

contact. (3) Fracture of enamel at the cavosurface margin.

(4) Amalgam, either condensed into an acute cavosurface

angle or carved to a thin edge. (5) Condensation of amalgam

too long after trituration. (6) Improper compaction and

finish of the amalgam restoration.

The best way to tie all of the procedure together in one

package is to start with the preparation of the cavity and to

discuss each step separately.
-5-

Cavity preparation

Often there will be fractured enamel rods remaining

at the cavosurface margin following the use of ultraspeed

rotary instruments. These loosened rods are planed away with

hand instruments or more slowly revolving burs . The margin

is finished as nearly as possible to a 90° angle, being

certain to leave no unsupported enamel rods. This ensures

maximum bulk of amalgam and enamel at the margin and permits

a thorough condensation. There are, of course, many other

facets to cavity preparation; however, this paper will be

limited to the use of the material.

One of the complaints often made concerning amalgam

restorations is the darkening of adjacent tooth structure.

This can be minimized by coating the cavity walls with a

varnish prior to filling. Such a liner prevents leakage

during the first days after placement of the restoration

as well as blocking the migration of metallic ions into the

tooth tissues.

Alloy selection

Alloy selection and usage is based on the operator's technique and experience and the specific needs of the case.

Excellent amalgam restorations can be placed with conventional

lathe cut alloy, spherical alloy, or dispersion phase alloy.

The alloy should of course appear on the ADA Certified List
6 -

of dental amalgam alloys. The amalgam made from lathe cut

alloy requires heavy forces on relatively small condensers

to develop sufficient pressure for obtaining optimum proper0

ties. Figure 2. A condenser point 0.1 inch in diameter

requires approximately 8 pounds force to develop 1000 psi

or 0.8 pounds to yield 100 psi. For lathe cut 1000 psi is

required to develop adequate tensile strength while spherical

alloy can be successfully compacted with 100 psi (0.8 pounds

force) . The forces required for the lathe cut are difficult

to maintain throughout the day and in certain areas of the

preparation. In many Class V and buccal extension type

cavities it is difficult to apply matrices that can support

these forces. Also, children don't understand the discomfort

of heavy forces. Consequently, when using reduced forces there

is a definite advantage in using spherical alloy.

9 The dispersion phase alloy offers a different advantage in that the resultant amalgam is a two phase metallurgical system rather than the three phase amalgam made from

the conventional silver, tin, copper, zinc or non-zinc alloy.

The customary three phases in amalgam are: non-reacted alloy

(y phase) , silver-mercury ( Y-l phase) and tin-mercury (

Y

s phase) .
-7-

The is not found in the amalgam made using the dispersion

phase alloy, Dispersalloy . * This alloy has a silver copper

eutectic (82% silver, 28% copper) in spherical shape dispersed

within a conventional lathe cut alloy. Since the Y e (SnHg)

is the weakest as well as the phase most susceptible to

corrosion there is a distinct advantage to its being eliminated.

Reports of clinical studies verify the laboratory prediction of

increased resistance to corrosion and reduced flow at the

margins

.

Clinical evaluation and laboratory studies are in progress

on a recently developed alloy in which 10% of the silver has

been replaced with gold. Amalgam made using this alloy also

has no Y

§ phase and consequently it, too, is corrosionresistant. Whether this alloy will be produced commercially

is dependent on results of several clinical trials now being

conducted

.

* American Silver and Mercury Products, El Cajon, Calif.

Certain commercial materials and equipment are identified

in this paper in order to specify adequately the experimental

procedure. In no case does such identification imply recommendation or endorsement by the National Bureau of Standards

nor does it imply that the material or equipment identified

is necessarily the best available for this purpose.
- 8-

Mixing the amalgam

The manufacturers of the various alloys have made

extensive laboratory tests and clinical evaluations of amalgams

made from their products. As a result of these studies the

manufacturers have prescribed certain proportions of alloy

to mercury, mechanical mixing equipment and trituration

times. These procedures should be followed.

Basically, trituration accomplishes one goal; that is,

to wet each alloy particle with mercury. Filings require

more mercury and additional trituration time to cover each

particle than do spherical alloys. Regardless of the reason,

whether an oxide coating or the uneven surface, the filings

must be triturated adequately to obtain optimum physical

properties. More amalgams are probably defective due to

under-trituration than to over- trituration . Laboratory

and clinical studies have shown that the small shrinkage

resulting from over-trituration does not contribute to

failures, ^as long as there isn't excessive over-trituration.

Since each mechanical mixing device has its own characteristics of speed, force and path of travel, it is recommended

that trial mixes be made before an instrument is put into

clinical use. Usually proportioning devices are accurate and

will deliver mercury in consistent amounts. Pellets provide
-9-

convenience with accuracy consequently it is easy to standardize

to the manufacturer's directions. A prescribed capsule and

pestle, if recommended, should be used in making several mixes

at various trituration times. The correct mix should have

mercury covering each particle. Add a second or two to the

lowest trituration time that gives the proper mix.

Pre-proportioned sealed capsules provide an easy opportunity

to standardize the mix. With the proportioning devices now

available the dental assistant, however, can provide equally

consistent results. When pellets are used, a day's supply of

capsules can be prepared in advance by supporting the pellets

on top of the pestle to prevent contact with the mercury until

triturated

.

Condensation

Condensing the amalgam to a uniform mass is required

for all of the alloy types whether the minimal or excess

mercury technique is used. Lathe cut alloys require

1000 psi while 100 psi is needed for the compaction of spherical alloys. Using a number 2 Tarno condenser, approximately

0.1 inch in diameter, 8 pounds force is required to get the

1000 psi. The amalgam is compacted in small increments to

prevent layering or void formation and with sufficient force

and number of strokes to bring excess mercury to the surface.
-10

As excess mercury is removed, the Y* and Y2 matrix is reduced,

leaving the amalgam mass more corrosion-resistant. This

plashy amalgam is swept away for spherical as well as lathe

cut alloys leaving a mercury-rich layer to receive the next

increment. 11 As the cavity is filled and successively larger

condensers are used extra force is required to deliver the

necessary pressure. In order to develop at least 500 psi

with the number 3 Tarno nearly 7 pounds of force must be

used. The use of mechanical condensers, such as Hollenback

and McShirley, provide an opportunity to substitute many

relatively lighter strokes for the heavy manual condensation.

However, ultrasonic condensation should not be used due to

the potential mercury contamination from the shower of mercury12

rich particles generated as this instrument is used. It is

essential to remember that time has passed rapidly during

condensation and if three to four minutes have elapsed since

trituration was completed, that mix should be discarded for

it has lost its workability and its potential strength is

reduced. If a fresh mix is not made the amalgam at the

external surface, including the margins, will be of this overaged material. This hardening amalgam will have an excess of

residual mercury and a high number of voids due to reduced

plasticity so its compressive strength will be markedly

reduced. Thus, a fresh mix, thoroughly compacted and of
- 11 -

maximum bulk for the final filling and overfilling of the

cavity will contribute to less surface corrosion and decreased

marginal deterioration. The mercury-rich amalgam in the

excess is carved away with a sharp instrument. When the carving

is completed the surface is smoothed by wiping with a wet

cotton pellet. After the initial set, approximately 8 to 10

minutes following the trituration of the final mix, the surface is lightly burnished. This procedure, if done with light

pressure and slow strokes, will further smooth the surface and

reduce the porosity near the surface. Figure 3. If any heat

over 140 °F is generated, a mercury-rich, highly corrodible

surface will be formed.

Any polishing procedures can be used that further smooth

the surface but do not generate excessive heat. As the exposed

areas are cut to a more smooth surface the total surface area

will be reduced and composed principally of cut silver tin,

Y phase, particles which are the strongest and least corrodible.

Plaque control

A smooth surface cavity forms as a sequelae of plaque

retention. When the surface is repaired, plaque will again

form and be retained on the replacement material. The presence

of acid, oxygen and some anerobic areas on the metallic surface

permits the anodic and cathodic reactions which are part of the
- 12 -

13 . corrosion process. Therefore, the pitting observed at corrosion

sites is accelerated by plaque accumulation. Additionally as

the pitting increases, plaque is more difficult to remove and

the secondary caries sequel to the original caries develops

under the plaque covering the tooth adjacent to the new restoration. There may also be progression to periodontal involvement.

Therefore, the dentist's responsibility of motivating the

patient toward plaque control should continue even after

restoration of the tooth.

Summary

Excellent long-lasting and esthetically acceptable dental

amalgam restorations can be made using any alloy or mercury

on the ADA List of Certified Materials. The principal cause

of amalgam failure is corrosion with pitting or porosity and

subsequent margin breakdown. Condensing the amalgam to reduce

to a minimum the residual mercury content and porosity along

with careful subsequent polishing will increase the percentage

of corrosion-resistant phases on the surface. Additional

factors contributing to failure such as fractured enamel rods

at the margin, under trituration, amalgam fracture due to

occlusal contacts, faulty compaction techniques and lack of

plaque control by the patient are preventable by using the

procedures discussed.
-13-

CEMENTS

How we treat dentin is directly reflected in the

condition of the pulp. Dental caries and attrition gradually

expose dentin tubules inciting the natural defense mechanisms

of the tooth to form reparative and sclerotic dentin. This

is contrasted with the operative procedures and trauma which

immediately expose unaltered tubular contents to possible

destructive forces such as heat, dehydration and chemicals.

Generally, 2.0 mm of unaltered dentin between the floor of

the cavity and pulp provides an adequate insulating barrier

14 against irritating components of restorative materials.

In cases of pulpal exposure a calcium hydroxide-containing

cement, such as Dycal,* Hydrex, ** Hydroxyline,*** etc., is more

effective than any other class of cements in stimulating the

15 formation of a dentin bridge over the exposure. When there

is danger of material such as zinc phosphate or silicate

cements causing irritation of the cut tubules, protection

can be obtained with copal varnish or a protective base of

zinc oxide-eugenol , calcium hydroxide or polycarboxylate

cement

.

Dycal, L. D. Caulk Co., Milford, Delaware

Hydrex, Kerr Manufacturing Co., Detroit, Michigan

*** Hydroxyline, George Taub Products, Jersey City, New Jersey
-14-

In addition to chemical irritation of the pulp, a

chemical reaction of the base with the restorative materials

must be avoided. Nearly every material which hardens by free

radical polymerization should not contact eugenol-containing

bases because the eugenol inhibits the polymerization. This

is true for all acrylic resins, most composite filling

materials and rubber base impression material.

Cements for this discussion will be limited to intermediary base and cementation materials. Cements for esthetic

restorations will be covered later.

Intermediary base

The intermediary base materials are used to replace

a portion of the lost dentin to prevent thermal and chemical

irritation of the pulp tissue. They also may be used to modify

the contour of the internal walls of cavity preparations.

Since these materials line the pulpal and axial walls of the

cavity, they require adequate strength to resist forces used

16 17 in compacting amalgam and direct golds ' as well as the

hydrostatic forces built up during cementation of precisionfit castings. The highest compressive stress is usually

exerted during compaction of the dental amalgam or gold

restoration and is within the first three to eight minutes

1

8

after the cement is prepared. Table 2 lists the early and
- 15 -

ultimate compressive strengths of some of these materials.

Adequate thickness of the intermediary base to disseminate

the compressive forces is also important. It has been shown

that 1 mm thick bases made of material exceeding 200 psi in

strength will not crumble or be displaced by the usual condensing forces.'1' 9

Modifying internal cavity walls

Another function of a base material, modifying internal

walls of cavity preparations, is required for indirect

restorations, i.e., those completed outside the mouth to be

cemented in place. Proper selection and use of materials for

this function reduces the amount of tooth structure needing

removal and thereby assists in retention of the restorations

since parallelism can be achieved without removing excessive

amounts of tooth structure. Selection of a material for this

base need not be limited to the usual cements but can include

dental amalgam and gold. The recently introduced adhesive

polycarboxylate cement offers an additional choice, and will

be discussed later.

Radiopacity

Since they are completely covered by permanent restorations, intermediary bases cannot be identified by visual

examination. To facilitate subsequent interpretation of

radiographs in the diagnosis of recurrent caries, the
-16-

intermediary base should be radiopaque. The relative radiopacity of various materials is shown in Figure 4. Unfortunately/ cements of calcium hydroxide and resins do not have

this feature.

Mixing

The ingredients are carefully formulated and packaged

by the manufacturer after exhaustive experimentation and

testing. Carefully worded and illustrated instructions for

each product are generally included in the package to insure

obtaining optimum physical properties. Consequently, detailed

mixing instructions will be omitted in this discussion.

Zinc phosphate cement

Zinc phosphate cement continues to be the standard

used for the evaluation of physical properties for all new

dental base and cementation materials. Table 2 shows the

high early compressive strength and the severe pulpal inflammation resulting when this material is used on the floor

of a cavity which is close to the pulp.

The powder for this cement contains approximately nine

parts calcined zinc oxide to one part magnesium oxide and

when mixed with the liquid containing phosphoric acid

buffered with salts of aluminum or zinc, the compounds

formed are phosphates of zinc, magnesium and aluminum. The
-17-

liquid reacts with the surface of the particles to form a

phosphate matrix that surrounds the core of unreacted powder.

As the ratio of particle content to matrix increases better

physical property values are obtained. This is true for all

core matrix systems used in dentistry. Therefore, the

operator should always try to obtain high powder-liquid ratios

for these materials.

In the past few years a zinc phosphate cement has been

introduced using water as the liquid which replaces the relatively unstable phosphoric acid. The resultant cements, when

compared to the acid liquid zinc phosphate, have greater film

thickness, less strength, higher solubility and are equally

20 irritating to the pulp tissues. Consequently, their use

is contraindicated.

Zinc oxide eugenol cements

In the 1960's considerable research and development was

focused on zinc oxide eugenol cements. The favorable response

of the pulp to this material has always stimulated interest in

improving physical properties such as compressive strength,

21 22 solubility and film thickness. ' Table 3 lists representative ZOE and modified ZOE products as they progressed from the

addition of zinc acetate to hasten the set to the most recent

additive, polycarbonate, which contributes strength and

abrasion resistance. The products containing Al2 O3 and polymethylmethacrylate) (PMMA) develop early compressive strengths
-18-

that are in excess of the minimum 200 psi required to resist

. 17

the forces used in compacting amalgam. Table 4. Virmani

reports that two modified ZOE cements, B & T* and Temrex

Extra,** along with the zinc phosphate material Tenacin, * have sufficient early strength to resist forces necessary to

place direct gold restorations.

Pulpal response to ZOE with additives (EBA, hydrogenated

rosin, Al2 03 or PMMA) is similar to that of the unaltered

ZOE.

23-24

These cements are radiopaque. Figure 4, and can be used

safely in deep cavities without endangering the pulp. When

actual pulp exposures occur the formation of secondary dentin

has not been as consistent with coverage by ZOE as with Ca(0H) 2 . Therefore, when the operator senses he is close to the pulp

tissue and there might be an undetected pulp exposure, use of

these cements is not the treatment of choice. In these cir2 5-2 9 cumstances Ca(0H) 2 is indicated.

Calcium hydroxide cements

Calcium hydroxide is an effective agent for the treatment

of exposed pulp tissue. Unfortunately, it has very little.

B & T and Tenacin, L. D. Caulk Co., Milford, Delaware

Temrex, Interstate Dental Company, New York, N. Y.
-19

if any, strength and is moderately difficult to manipulate

even when mixed with distilled water. There are several

commerical cements containing Ca(0H) 2 , e.g., Dycal and

Hydrex which, when hardened, have sufficient early compressive

strength to withstand compaction forces required for placing

17 amalgam but not for direct gold. Table 2. They also

permit resolution of mild pulpal inflammation and stimulate

the formation of reparative dentin. These materials are used

mainly in deep cavities for their therapeutic effect on the

pulp and for bases under resin restorations. When they are

placed on dry dentin, they flow freely onto the dentin surface ensuring complete adaptation. Moisture accelerates

hardening and interferes with coverage of the dentin wall.

Calcium hydroxide is not radiopaque, therefore some of the

commercial products have added varying amounts of radiopaque

material. Figure 4.

30 Thanik reported that with less than 0.1 mm of dentin,

Ca(0H)2 is the least irritating base material, with ZOE next

and zinc phosphate cements the most irritating. To

avoid pulp displacement and resulting injury in deep cavities,

Ca (OH) 2 should be carefully placed over the dentin in the

pulpal or axial walls because there may be an undetected

pulp exposure. Sufficient bulk must be provided so the

combined dentin and intermediary base will withstand compaction forces.
- 20 - The Ca(0H)2 bases are the material of choice under

some composite and resin restorations so that there is

usually no eugenol to interfere with polymerization hardening.

2 8 Berk demonstrated that these materials protect the pulp

against irritation by silicate and zinc phosphate cements.

They are equally effective in protecting the pulp under

composite restorative materials.

Polycarboxylate cements

Polycarboxylate cements are a mixture of a modified

31 zinc oxide powder and aqueous polyacrylic acid solution.

t $ Duralon*, Poly-C**, Zopak , and PCA are among the representative

products currently on the market. The results of several

31-33 studies show adhesion of Duralon to enamel and to a lesser

extent to dentin. This adhesion to tooth structure is of

interest in the potential use of the material as an intermediary base to modify the contour of tooth preparations. It

can be painted on undercut areas and, upon hardening, the

crown or inlay preparation can then be completed. Its early

33 strength is not knovn . However, the 24 hour strength , Table 4, should be adequate to protect a thin dentin wall

against displacement by hydrostatic forces that occur during

cementation of castings. It is radiopaque. Figure 4, and

* Duralon, Premier Products, Philadelphia, Penna.

** Poly-C, Claudius Ash, Inc., Niagara Falls, New York.

Zopak, The Lorvic Corp. St. Louis, Missouri

t PCA, S.S. White Mfg. Co, Philadelphia, Penna.
- 21 -

is less irritating to pulp tissue than zinc phosphate

3 1 r> o cement. ' These properties indicate that this may be a

useful material. The extremely critical method for handling

polycarboxylates to obtain maximum adhesion is discussed

later in the Cementation section.

Summary

The care with which the operator treats the dentin is

directly reflected in the condition of the pulp. There are

a wide range of materials available for use as intermediary

bases, to aid dentists in maintaining health in the pulp

tissues. The choice should be determined by the role the

operator wants the material to fulfill, i.e., strength (zinc

phosphate cement) , non-irritation (ZOE, modified ZOE) , dentin

formation (Ca(OH)s), adhesion (polycarboxylate) , and

radiopacity (all the zinc containing cements and others with

radiopacity added) . Frequently, a combination of materials

is desirable such as calcium hydroxide to permit formation

of a dentin bridge followed by either a ZOE or zinc phosphate

cement. Some commercial preparations of Ca(0H) 3 , such as

Dycal and Hydrex, have sufficient strength to be used alone

under dental amalgams. EBA or ZOE with alumina and hydrogenated

rosin have improved the early strength so that these cements

can be placed on freshly cut dentin with confidence that
- 22 -

there will be no pulpal irritation and that the cement

will withstand compaction forces. Studies concerning the

response of the pulpal tissue to all the modified ZOE cements

indicate that they retain the " kind-to-the-pulp" characteristics

of unmodified ZOE. However, before new formulations and

modifications of old ones are brought on the market, they

should be evaluated for pulp tissue response. This is true

for any product even though it may be only slightly varied in

34 formulation from products that have been accepted clinically

Cementation

Results of recent laboratory studies indicate that

polycarboxyl ate cements may add adhesion to the list of

factors responsible for retention of castings.

Included in the physical properties responsible for

prolonged mechanical retention are: (1) high compressive

strength; (2) good ability to wet the surfaces of the tooth

and restoration; (3) high resistance to solubility

and disintegration in the oral environment; and (4) low

film thickness. Among many additional factors affecting

retention are: (1) total area of the walls of the preparation;

(2) degree of parallelism of opposing walls; (3) accuracy

of fit of the restoration; and (4) direction of forces of

occlusion in relation to the path of insertion of the

restoration or appliance.
-23-

The criteria for selecting a cementing medium are

based on the need for these physical properties and the

biological response of the pulp tissue to the cement. The

ease of handling also has a bearing on selection since this

is extremely important for the clinician.

35 Jorgensen presented a comprehensive analysis of

various operator-controlled factors which affect film

thickness. He states that the more viscous the cement

the more difficult it is to seat the restoration completely.

Viscosity may be dependent on inherent characteristics of

the cement, powder-liquid ratio, duration of mixing time

and temperature. Once the cement is mixed and placed on

the materials to be cemented, the viscosity will have been

established, and will increase with time as the setting reaction proceeds. The amount and method of applying the positioning forces then becomes the principal factor controlling

residual film thickness at the tooth-restoration interface.

35 The operator should apply a steady force of approximately

10 pounds until the cement has hardened. A small dab of wet

cement on the adjacent tooth provides a good test sample.

An additional element contributing to low film thickness

is venting of the casting. In this way the hydraulic pressure

is released as the cement escapes. An accurately fitting

casting seated with a minimum of film thickness takes full

advantage of the frictional resistance, compressive strength

and adhesion.
-24-

Film thickness is a part of the American Dental

Association Specification No. 8 for dental zinc phosphate

4 . _ cement. Two types of cement based on powder particle size

are specified as Type I or II. Maximum film thickness permitted for Type I is 25 pm (0.001 inch) . Type II may have

a film thickness up to 40 Mm (0.0016 inch) . Type I is

designed to permit seating of precision castings. Type II

is suitable for all other uses. The manufacturer should

specify on the package the type of cement. Manufacturers

should state in their directions the appropriate powder -liquid

ratio required to obtain the specified film thickness. The

physical properties are also used as a standard for comparison

of the other classes of cementing materials as listed in Table 4

Zinc phosphate cement

Zinc phosphate cement. Type I, (Tenacin, Fleck's* and

S. S. White Zinc Improved**) continues to be the standard for

comparison of retention of new materials being developed for

luting precision castings. Although zinc phosphate is irritating to the pulp tissue, varnish (two thin layers) or a base

of either Ca(0H) 2 or ZOE covering unaltered dentin effectively

protects the pulp. A thin layer of varnish does not reduce

Fleck's, Mizzy, Inc., Clifton Forge, Virginia

* * S. S. White Mfg . Co., Philadelphia, Penna
-25a

the retentive strength of the zinc phosphate cement. 36

Eugenol as an additive to the liquid is not

effective in reducing pulpal irritation. If the sedative

effect of zinc oxide-eugenol is desired, temporary cementation with a ZOE cement is recommended. Permanent cementation

with zinc phosphate cement can be delayed until pulpal health

has returned.

Water settable zinc phosphate cements are inferior to

the conventional zinc phosphate and should not be used,

20,37 Table 4.

Polycarboxylate cement

The polycarboxylate cements, such as Duralon, Poly-C,

Zopak and PCA, were first introduced for cementation of stain31 less steel to enamel. Smith claims that the carboxyl bonds

are available immediately after mixing and that they form a bond with the calcium ions in the tooth. Etching or other

pretreatment of the enamel surface so far has not changed

38 the bond strength. Thermal cycling apparently has no effect

32

on strength. Water uptake and solubility are quite high in

laboratory testing and indicates that long-term clinical testing is required before routine use can be recommended.

Strict observance of the mixing instructions is necessary

31 to obtain the maximum properties of the polycarboxylate cements.
-2 5bThe powder-liquid proportion for cementation should be

between 1-1/2 to 2-1/2 parts of powder to one part liquid

by weight, depending on the manufacturer's instructions.

The desired consistency should be developed through trial

and error. Once the proportions are determined mixing can be
-26-

completed by bringing all the powder into the liquid and

spatulating quickly. Unfortunately, present methods of

powder and liquid dispensing are inadequate to allow this

technique to be followed with accurate results. The mixing

should be completed in less than 30 seconds and the mix

placed on the restoration and tooth immediately. Correct

powder to liquid ratio and usage well before the gloss disappears from the mix will develop the strongest adhesive and

31 the most desirable physical properties . Operators who

have used this cement are enthusiastic over the lack of

discomfort experienced by the patient during and subsequent

to cementation.

Although polycarboylate cements were specifically

formulated for cementation of stainless steel orthodontic

appliances to enamel, tests have been made on retention of

39 gold cast crowns with teeth prepared with a 10° taper

Results have also been reported on laboratory tests of

gold castings in Class I cavities prepared in recently ex33 tracted teeth . A comparable force was required in both

experiments to remove crowns cemented with zinc phosphate

and polycarboxylate cements. ZOE with polymer had about

one half the retentive strength of polycarboxylates . These

laboratory tests do not indicate a superiority over zinc

phosphate cement for cementing gold crowns.
-27-

Modified zinc oxide-eugenol and EBA cements

The modified zinc oxide-eugenol and EBA cements discussed in the intermediary base section are sometimes

used as luting agents for castings. Some have certain

2140 physical properties as indicated in Table 4 ' which are

comparable to zinc phosphate cement. Viscosity and wetting

ability are superior to zinc phosphate cement.

In light of the favorable qualitites, these cements are

growing in popularity as luting agents. The EBA cements

with A1 a 0 3 have compressive strength and retention values

similar to zinc phosphate cement, Table 4, but are higher

2

in their solubility values . Solubility and disintegration

data based on the ADA Specification No. 8 test yield lower

4 values for EBA cements . Another aspect of disintegration

related to solubility but not determined by the 24 hour

41 residue is the loss of eugenol as shown by Wilson and Batchelor

These investigators claim that aqueous leaching of eugenol

from the ZOE cement (unmodified) is continuous as the cement

matrix hydrolyzes to eugenol and zinc hydroxide. Thus, the

cement in 20 weeks time lost mechanical strength and disintegrated. This long-term process is not evident in the 24 hour

specification test.

As with the zinc phosphate, mixing for intermediary

base and cementation differ only in the proportion of powder

added to a given amount of liquid.
-28-

Well controlled, long-term clinical studies of cementation with modified ZOE or EBA have not been reported. Two

42 43

progress reports ' have indicated favorable results over

a short period of time. However, other operators are observing failures after one year, especially in those cases involving bridge abutments or short crown teeth. Consequently,

until long-term (three years or more) well controlled studies

are reported, these modified ZOE cements are not recommended

for general use in permanent cementation of restorations.

Silico phosphate cement

Silico phosphate cements, such as Kryptex, * Lucent, ** and Fluorothin* may be termed hybrid cements for the powder

is a mechanical mixture of about nine parts silicate and one

44 part zinc phosphate cement. Since the liquid is similar

to that used for the zinc phosphate cements the same handling

precautions are necessary.

The compressive strength of these products is superior

45 46 to zinc phosphate while solubility is inferior, ' Table 4.

Kryptex and Fluorothin, S. S. White Mfg . Co., Philadelphia,

Penna

.

** Lucent, L. D. Caulk Co., Milford, Delaware
- 29-

Fluoride (a basic ingredient of the silicate portion) is

gradually leached out and may increase the resistance of the

47 adjacent enamel to caries. In addition, the retention of

crowns and castings is almost as great as that obtained with

36 zinc phosphate cement. The manipulative characteristics,

viscosity and film thickness, however, make it difficult

to seat closely fitting castings. Several brands have

recently been introduced which meet the film thickness specification of 25 Mm for Type I zinc phosphate cement.

This type of cement, because of its silicate-like

translucency , is used principally for its esthetic value

in cementing materials such as porcelain and resins.

Acrylic resin cements

The physical properties, esthetic qualities and

manipulative characteristics of acrylic cements are similar

to the direct filling acrylic resins. Solubility, which is

near zero, and surface wettability, are two properties which

are superior to zinc phosphate cement. This surface wettability,

or adaptation, makes it seem as though a bonding reaction has

occurred. The apparent bonding is lost, however, as the

cement absorbs water and the cement -tooth interface becomes

48 wet. They should not be used.

Recently, a cementing medium has been introduced which

is based on the resin present in most of the composite resin
- 30 -

materials. This cement, Epoxylite Crown and Bridge Adhesive,*

though it is insoluble, has excessive film thickness for

precision casting and is dependent upon an etched surface

for mechanical retention. Until this material can be prepared with sufficiently thin film thickness to completely

seat precision castings or its clinical behavior has been

assessed in long term studies it cannot be recommended for

general use.

Polyurethane

In recent years polyurethanes have attracted much

attention as potential adhesive liners and tissue sealants.

These materials are still in the experimental stage but

appear promising.

Summary

For many years cementation of precision-fit castings

has been dependent on a material which combines resistance

to breakage with mechanical or frictional locking of the

casting to the tooth. With the introduction of polycarboxylate cements adhesion to enamel surfaces may be obtained.

This material, with its apparent adhesion countering the

* Lee Pharmaceutical, South El Monte, Calif.
- 31 -

lower compressive strength, resists removal of castings

similar to zinc phosphate and silico phosphate cements.

Careful handling of all the materials is essential.

Optimum physical properties result when the maximum percentage of powder is mixed within the range of the manufacturer's

instructions. To get the maximum retention, the cement must

be applied to the tooth and the restoration as soon as

possible after the mix is completed.

ESTHETIC RESTORATIVE MATERIALS

The materials available for use as direct filling

esthetic restorations range from the silicate cements and

the unfilled resins to the more recent composite resins.

Each will be discussed along with clinical techniques.

Silicate cement

The silicate cements have one overriding desirable

property. The continuous leaching of fluoride from the

silicate acts to decrease the susceptibility of the adjacent

enamel to caries. Other desirable attributes are the low

setting shrinkage and the close similarity of its coefficient

of thermal expansion to that of dental hard tissues. Undesirable characteristics include the severe inflammation in pulps

not protected during placement of the silicate and its high

solubility in most mouths. Silicate restorations, however.
-32-

sometimes will last for many years if placed: (1) in a tooth isolated by a rubber dam; (2) using the correct powderliquid ratio; and (3) protected with a silicone grease or

wax for the first six hours after placing. The low pH

associated with plaque is primarily responsible for the

disintegration of silicate restorations. Even so, many

operators continue to favor silicates for individuals with

a high caries incidence because of the caries resistance

brought about by the presence of the fluoride. Other than

for this purpose, its usage is probably not recommended.

Unfilled resins

Unfilled resins such as Bonfil* and Sevriton Simplified**

have had a bad reputation that is principally due to misuse

of earlier similar products through lack of sufficient knowledge and techniques. Adequate esthetic restorations can be

placed by using techniques which compensate for the principal

weakness of the unfilled resin, i.e., shrinkage during curing.

Other weaknesses include a coefficient of thermal expansion

at great variance from dental hard tissues and a low resist-

* Bonfil, L. D. Caulk Co., Milford, Delaware

** Sevriton Simplified, Claudius Ash, Inc., Niagara Falls, N.Y.
- 33 - 49

ance to abrasion. Etching the enamel at the resin-tooth

interface and using the Nealon Bead, or brush, technique

to place the resin enhanced the marginal seal and the

retention of the restoration. These improvements result

from each increment wetting and covering completely the

tooth surface or previous portion of resin. In this way,

each addition tends to fill the space formed by the curing

shrinkage of each prior portion. With this technique these

materials can be used to restore Class V cavities, fractures

of incisal angles when less than one half the mesial distal

tooth width is involved, and defective areas such as hypoplastic pits on the labial surface of anterior teeth.

Retention is enhanced when pins are used as a supplement

to the etching technique

These direct filling resins have a low resistance to

abrasion and lack color stability in the mouth. Restorations

showing wear and color change can be renovated by removing

some of the labial or esthetic surface and then brushing on

new material

Some manufacturers have added fluoride to their resin

to imitate the anticariogenic effect of the fluoride in

silicates. The lack of favorable results from this additive

may be because the resin is insoluble and the fluoride is

not gradually leached out as in silicates.
-34-

Composites

Composite resins are replacing the silicate cements

and the unfilled resins for direct filling, esthetic

restorations in non-load-bearing areas. These resins

have a matrix material based in general on a formula

developed by Bowen. 50 The resin... matrix and silane treated

fillers (glass beads, glass rods, quartz, lithium aluminum

silicate, silica, fused silica, or borosilicates) form

unique composite materials in that the particles are chemically bonded to the resin matrix. Figure 6. Some of the

fillers contain glasses that are radiopaque. The treated

filler makes up about 70-80% by weight of the composite

material. As a result the coefficient of thermal expansion

and susceptibility to abrasion are greatly reduced as compared to the unfilled resins. Data on various composite

materials, silicate and unfilled resins, are given in Table 5.

The physical properties of composites are superior to the

unfilled resins in the following: abrasion resistance,

curing shrinkage, coefficient of thermal expansion, modulus

of elasticity and compressive strength. The toughness and

the low solubility of the composites give them a decided

advantage over silicate cements. The low curing shrinkage
- 35 -

of the composites enables the operator to bulk pack these

materials. One of the greatest disadvantages of the

composites (and silicates) is the difficulty in obtaining

a good final polish.

The biological response in the pulp tissue to composites

is similar to that for silicate cements. A pulp protecting

base of calcium hydroxide is used since the eugenol in zinc

oxide-eugenol materials usually interferes with the polymerization of the resin matrix.

The setting reaction on the surface of composites is

somewhat inhibited by air. Therefore, care should be taken

to ensure that the materials are covered by a grease or matrix

strip during set.

One of the difficulties encountered during placement is

the presence of voids at the tooth-composite interface.

The use of an injection tube technique may reduce these

voids by making it possible to flow the material onto the

base of the cavity and filling from the inside out.

One of the brands, Blendant*, has been made radiopaque.

This is an advantage in radiographic diagnosis.

* Blendant, Kerr Mfg. Co., Detroit, Michigan
-36-

Polishing the composites to a high lustre is currently

impossible. The extreme contrast in hardness between the

matrix and filler and the presence of innumerable voids

prevent polishing with available techniques. It is hoped

that a successful technique can be developed. One suggestion

by Chandler"'* is the use of diamond particles in the size

range of 1 to 5 dm on a flexible disk or strip.

The best surface finish is that which cures next to

the matrix strip. However, some cutting for contour and

margin perfection is always necessary. This can be done with

a 12-bladed carbide bur using ultra speeds to lightly brush

the excess away, being careful not to injure the adjacent

tooth structure. Following this shaping with the bur

successively finer lubricated cuttlefish disks and strips

will develop the best finish currently available. Figure 6.

Several manufacturers claim that composites can successfully replace amalgam in load-bearing areas of posterior teeth.

52 The only long-term clinical study to be reported (three

years) indicated a significant loss of anatomical contour.

53 . A current study is m its second year and the results of

these observations are required before routine use in posterior

teeth can be recommended. Figure 8 shows the loss of a composite material after 18 months as observed in our program

at the National Bureau of Standards.
- 37 -

Future developments will probably include a coupling

agent for bonding the restorative material to enamel. This

would give true adhesion to the enamel. Until such a system

is perfected further refinement will probably be made in

cavity surface pretreatment such as etching. Additional

improvements are needed in color matching, color stability

and polishing to make the composite materials more permanent

and esthetic.

Summary

Composite resins are becoming increasingly popular as

direct filling esthetic restorations. They are designed

for use on non-load-bearing areas such as the interproximals

of anterior teeth and gingival areas of all teeth. As the

polishing procedure is improved, these materials will probably

replace silicate cements.

Enamel pretreatment by etching is effective in improving

the marginal seal and retention of unfilled resins. This

type of restoration is for slight, less than one half tooth

width, enamel fracture on anterior teeth.

FISSURE SEALANTS

Fissure sealant materials are primarily intended to

seal or fill anatomical defects. There are essentially two
”38

types of material, one is inert and can be regarded as being

in the restorative material category. The other, containing

a fluoride additive, is considered a carrier for an active

ingredient having a potential therapeutic effect. Only the

inert material will be discussed here.

Considerable clinical evaluation should be completed

before accepting pit and fissure sealants for general use.

54 Clinical studies concerning an inert resin have been reported

and appear promising. The formulations of one sealant resin,

. . 50 Nuva Seal,* is similar to that proposed by Bowen for use

as the matrix material in the composite resins. An ultraviolet activator replaces the chemical activation usually

used, and there is no filler. Another sealant, Epoxylite

Fissure Sealer 905** (which is chemically activated) has been

more recently introduced and has the same potential effectiveness as Nuva Seal but here, too, reports of long-term studies

are needed. The claim for adhesion by these materials to

enamel is questionable since both depend on acid etch pretreatment for retention. However, this mechanical retention by

penetration of the material into the etched surface is reported

to be effective in retaining the material for at least six

months

.

Nuva Seal, L. D, Caulk Co., Milford, Delaware

Lee Pharmaceutical, South El Monte, Calif.
- 39-

The lack of adhesion is a cause for some concern.

The rapid progression of decay under a loose orthodontic

band or a gold inlay raises the question as to what will

happen if a sealant loosens but is retained because it is

wedged in place. Another question concerns the progress

of existing but undiscovered caries in a pit when a sealant

is applied. It is most difficult to diagnose this type of

caries early in its progress even by an experienced examiner.

This could be a problem if the treatment is being applied

by a relatively inexperienced individual on a mass treatment

scale

Fissure sealants are being subjected to extensive

clinical study. If the current promising results hold up

over long periods of observation, they may become an

excellent adjunct in the preventive caries program.
-40-

R'S f arences

1. Myers, G« E. Status report on zinc cxide-eugenol and

modified cements • JADA 76s 1053 May 1968.

2. Swartz, M. L. Research in dental materials. JADA 79:

901, Oct 1969 (197 ref*)

3. Council on Dental Materials and Dei^ices report. JADA 82:

305 Feb 1971.

4. Guide to Dental Materials and Devices, 6th Edition,

1972-73, Amer. Dent. Assoc., Chicago, 111*

5. Moen, B. D. and Poetsch, W. E. More preventive care

and less tooth repair. JADA 81:25 July 1970.

6. Jorgensen, K.D. The mechanism of marginal fracture of

amalgam fillings. Acta Odont. Scandinav. Vol 23, #4,

347, 1965.

7. Mahler, D. B. and Van Eysden, J. Dynamic creep of dental

amalgam. J. Dent. Res. 48:501, July-Aug 1969.

8. Eden, G. T. and Waterstrat, R. M. Effects of packing

pressure on the properties of spherical alloy amalgams,

JADA 74:1024, Apr 1967.

9. Innis, D. B. K. , and Youdelis, W. V. Dispersion

strengthened amalgam. J. Can. Dent. Assoc. 29:587,

1963.

10. McDonald, R. E,, Phillips, R a W. Clinical observations

on contracting amalgam alloy. J. D. Res. 29:482, Aug 1950

11. Wing, G. Clinical Use of Spherical Amalgams. Aust. Dent.

Jour. 185, June 1970.

12. Chandler, H. H. , Rupp, N. W. and Paffenbarger , G. C.

Poor mercury hygiene from ultrasonic amalgam condensation

JADA 82:553 Mar 1971.

Fraunhofer, J. A. and Staheli, P. J. Corrosion of

amalgam restorations. Brit. Dent. J. 130:522, 1971.

13 .
-41-

14. Stanley, H. R. Design for a Human Pulp Study. Oral Surg .

,

Oral Med., and Oral Path. 25:633, April; 25:756, May 1968.

15. Stanley, H. R. Pulp Response to Dental Techniques and

Materials. Dental Clinics of North America 15, #1, 115,

Jan 1971.

16. Phillips, R. W. , Swartz, M. L. , Norman, R. D. Materials

for the Practicing Dentist . C. V. Mosby, St. Louis, Mo.

1969.

17. Virmani, R., Phillips, R. W. , Swartz, M. L. Displacement

of cement bases by condensation of direct gold. J. of Am.

Acad, of Gold Foil Operators, Vol . 13, No. 1, p.39, Apr

1970.

18. Lyall, J. S. Base forming materials for restorations of

silver amalgam. Aust. Dent. J. 5:132, 1962.

19. Chong, W. F., Swartz, M. L. , Phillips, R. W. Displacement of cement bases by amalgam condensation. JADA 74:

97, Jan 1967.

20. Simmons, F. F., D' Anton, E. W. , Hudson, D. C. Property

studies of a hydrophosphate cement. JADA 76:337, Feb 1968.

21. Civjan, S., Brauer, G. M. Physical properties of cements,

based on zinc oxide, hydrogenated rosin, o-ethoxybenzoic

acid and eugenol . J. Dent. Res. 42:281, Mar-Apr 1964.

22. Brauer, G. M. , McLaughlin, R. P. , Huget, E. F. Aluminum

oxide as a reinforcing agent for zinc oxide-eugenol-EBA

cements. J. Dent. Res. 47:622 July-Aug 1968.

23. Bhaskar, S. N. , Cutright, D. E., Beasley, J. D. , Boyers,

R. C. Pulpal response to four restorative materials.

Oral Surg., Oral Med., and Oral Path. 28:126, July 1969.

24. Coleman, J. M. and Kirk, E. E. An assessment of a modified

zinc oxide-eugenol cement. Brit. Dent. J. 118:482, 1965.

25. Glass, R. L. , Zander, H. A. Pulp healing. J. Dent. Res.

28:97, Apr 1949.
-42-

26. Sayegh, F. S., Reed, A. J. Correlated clinical and

histological evaluation of Hydrex in pulp therapy.

J. Dent, for Children. 34:471, 1967.

27. Accepted Dental Therapeutics , 33rd Edition, 1969-1970.

American Dental Associatioh, Chicago, 111.

28. Berk. H. Preservation of the dental pulp in deep seated

cavities. JADA 54:226, Feb 1957.

29. Massler. M. Indirect pulp capping and vital pulpotomy

for potential and actual pulp exposure. J. Tennessee

Dent. Assoc. 35:393, 1955.

30. Thanik, K. D., Boyd, D. A., van Huysen, G. Cavity base

materials and the exposed pulp marginal blood vessels.

J. Pros. Dent. 12:165, 1962.

31. Smith, D. C. A new dental cement. Brit. Dent. J. 125:

381, Nov. 5, 1968.

32. Mortimer, K. V., Tranter, T. C. A preliminary laboratory

evaluation of polycarboxylate cements. Brit. Dent. J.

8:365, Oct. 21, 1969.

33. Phillips, R. W. , Swartz, M. L. , Rhodes, B. An evaluation

of a carboxylate adhesive cement. JADA 81:1353, Dec 1970.

34. Stanley, H. R. , Swerdlow, H., Stanwick, L., Suarez, C.

A comparison of biological effects of filling materials

with recommendations for pulp protection. J. Am. Acad,

of Gold Foil Operators, 12:56, Sept 1969.

35. Jorgensen, K. D. Factors affecting the film thickness

of zinc phosphate cements. Acta Odont. Scandinav. 18:

479, 1960.

36. Oldham, D. F., Swartz, M. L. , Phillips, R. W. Retention

properties of dental cements. J. Pros. Dent. 14:760,

1964.

37. Higashi, S., Morimoto, K., Satomura, A. et al . Studies

on the water settable cement. Part 10. J. Nihon Univ.

School of Dent. Vol. 11, 105, Sept 1969.

Mizrahi, E. and Smith, D. C. The bond strength of a zinc

polyacrylate cement: Investigation in the behavior under

varying conditions. Brit. Dent. J. 127:410, Nov. 4, 1969.

38 .
-43-

39. Grieve, A. R. A study of dental cements. Brit. Dent. J.

127:405, Nov. 4, 1969.

40. Brauer, G. M. , Huget, E. F., Termini, D. J. Plastic reinforced EBA cements as temporary restorative cement.

J. Dent. Res. 49:1487, Nov-Dec 1970.

41. Wilson, A. D., Batchelor, R. F. Zinc oxide-eugenol cements:

II. Study of erosion and disintegration. J. Dent. Res. 49:

593, May-June 1970.

42. Gilson, T. D. , Myers, G. E. Clinical studies of dental

cements: IV. A preliminary study of a zinc oxide-eugenol

cement for final cementation. J. Dent. Res. 49:75, JanFeb 1970.

43. Horn, H. R. The cementation of crowns and fixed partial

dentures. Dental Clinics of North America . Mar. 1965.

W. B. Saunders Co., Philadelphia, Penna. p.76.

44. Souder, W., Paffenbarger , G. C. Physical properties of

dental materials. National Bureau of Standards Circular

C433, Feb. 6, 1942.

45. Griffith, J. R. , Ware, A. L. An evaluation of dental

cements. Aust. Dent. J. Vol . 5, No. 5:285, Oct 1960.

46. Anderson, J. N. , Paffenbarger , G. C. Properties of silicophosphate cement. Dental Progress, Vol. 2, No. 2, Jan 1962.

47. Norman, R. D. , Phillips, R. W. and Swartz, M. L. Fluoride

uptake by enamel from certain dental materials. J. Dent.

Res. 39:11, Jan-Feb 1960.

48. Schoube, P. J. , Paffenbarger, G. C., Sweeney, W. T. Resin

cements and posterior-type direct filling resins. JADA 52:

584, May 1956.

49. Laswell, H. R. , Welk, D. A., Reginos, J. W. Attachment of

resin restorations to acid pretreated enamel. JADA 82:558,

Mar 1971.

Bowen, R. L. Direct filling material comprising vinyl silane

treated fused silica and a binder consisting of the reaction

product of bisphenol and glycidyl acrylate. U. S. Patent

No. 3,066,112, Nov 1962.

50 .
-44-

51. Chandler, H. H. , Bowen, R. L. , Paffenbarger , G. C.

Method for finishing composite restorative materials.

JADA 83:344, Aug 1971.

52. McCune, R. J. , Cvar, J. F., Ryge, G. Clinical comparison

of anterior and posterior restorative materials. Presented

at Annual Meeting, IADR, March 1969, Abstract No. 482.

53. Phillips, R. W. , Avery, D. R., Mehra, R„, Swartz, M. L.,

McCune, R. J. One-year observations on a composite resin

for Class II restorations. J. Pros. Dent. Vol . 26, No. 1,

p.68, July 1971.

54. McCune, R. J. and Cvar, J. F. Pit and Fissure Sealants:

Preliminary Results. J. Dent. Res. Program and Abstracts

of Papers, Abst. #745, March 1971.
-45 -

Table 1

REASONS FOR PLACING RESTORATIONS

New caries

Smooth surface

Anatomical defect

Replacements

Cavity preparation

(self cleansing,

undermined enamel)

Material

(handling, selection)

silicate, amalgam, resin

TOTAL

199

106

305

52

67

119

424

28%
-46-

Table 2

Intermediary Base

Material

Compressive

Strength

k -k Pulp

Response Early

7 min

Ultimate

24 hr

Zinc

phosphate

Acid

MN/ms psi

I (16)*

7.5 1 1100

MN/m2 psi

i (16)

108 1 16900

(30)

++++

Water

settable

not

available

1 (20)

66.1 | 9550

(20)

Zinc

oxideeugenol

Zinc

acetate

| (16)

3.9 ; 600

1

| (16)

8.6 1 1250

(25,29,

++

30 >

EBA &

Alg O3

1 (21)

39. 3i ,f2°°- 1

1 (10 mm)

1 (21)

88.4 , l 3000

. . (one week)

(23/ 24)

++

PMMA 5.8 | 900 (16) 13.7 | 2000 (16) ++ (23)

Cavetec 2.9 1 400 <16 *' 5.2 | 750 (16 ^ ++ (16)

Calcium

hydroxide

Hs 0 0 | 0 0 I 0 (25,29/

30)

Dycal 7.5 | 1100 (16) 7.5 | 1100 (16) (16)

Hydrex

; cw

3.4 I 500 9.8 | 1400 (16 ^ (26)

Polycarboxylate

not

available

(33)

34.4 | 5000

(33)

H—

b

Figures in parentheses represent reference

Pulp response

a. Exposure

Dentin bridge

b. Dentin unbroken

Mild inflammation ++

Moderate inflammation +++

Severe inflammation +-H-+
-47-

Table 3

ZINC OXIDE-EUGENOL CEMENTS

Composition Commercial Products

Powder Liquid

Intermediary bases

Temporary restorations

Periodontal packs

Root canal sealers

ZnO

Hydrogenated rosin

Zn acetate

Eug

ZnO

Hydrogenated rosin

EBA

Eug

Opotow EBA

ProCem

Ultim EBA

EBAC

Temrex Extra

ZnO

AI2 O3

Hydrogenated rosin

Eug

EBA

Opotow EBA with alumina

ProCem with alumina

ZnO

PMMA

Eug

Acetic

acid

Fynal

IRM

B & T

Opotow temporary

ZnO

Polystyrene

Eug .+ ? Kalzinol

ZnO

Polycarbonate

Eug .+ ? Decigenol

ZnO

Polymerized resin

Carnaba wax

Zn acetate

Eug.

Mineral

oil

Cavitec (ingredients

blended in two tubes)
PHYSICAL

PROPERTIES

OF

VARIOUS

MATERIALS

MIXED

TO

CEMENTING

CONSISTENCY -48 -

Relative

retention

ZP=

100

No specification (

36)

100

not

available

CDCO oo1—1 (

36)

55 (

36)

80

Not available (

33)

100

Diametral tensile strength 24

hr

MN/m 2pSi

No

specification (

16)

12300 0

-P rHrQ (

40)

700

1000

Not

available Not available Oo

00 o

00 0 0

rH G -P0>0

00• rii (

40)

6.8

(32

5.4 ^—v

/•

—^

>i i CO CM

-P G G CM o CM o LO of CO •H *P 0 _ £ CM CM CM of Of 

— i—1 0 -H 4J — "

LO ^00

— of -P *P -P o ^ 6 CM of o o Of • cD

rQ Q 0 % ^ • -P • • • • • o • g p O X O O o o o 1 O

tH T3 Cn rd o 0 a CD £ • W 0 -P o , x ,—_ „ . ,—, 0 CD o CM cD CD CO co 0 CO CM CM rH of of CO

a> g v ' V > ’—<" £ c 3 o i ^ £ ld £ 00 LO CD CM CM CD rH •H U 3- CM -P T—\ r- CM CO of 1 CM

fa -P X o

rG rd rH

-P £ O o O o K

CD o o O o LOO * O o 0 •H LO o o O o ofO O O > rG 0 CTi LO o> Of '-to LO CD •H -P P a cn pH rH o O Of 0 tr> rt CM 0 g , ^ ,—

rV / 0 0 CM r- CM o CO * CO p p of CM ro CM ’ of , * of * co fa -p cm oi CD • " —. cD 1—1

of O' of £ W o £\ 00

COO

rHcD CO CO

P'- CM LO rH o S CD rH <T> of CD CO s

in CM o LO 00 ro c CM of Of of ro

a) -p c • • !

— " '—

— g m -p •P G X LO LO LO o

•P 0 -P £ -P 0 • • • r—1

Of o LO

Eh 0 £ £ LO 00 l 1 rH • CO CD i O' LO <T> CO of

of 0 n

rH O

rQ R 0 0 P 0 rH g -p -p TO 0 -P < P § 0 0

00 •H -P -P 0 fa rG p rH r—1 — u 0 0 0 fa G b

rti C7> 0 £ 0 G rP 0 0 X • g -P rH 0 £ 0 p o H -P CQ £ 0 rG 0 rQ 0 0 -P fa 3 a fa 0 P

-P a 0 g rH 0 0

rd co a, 0 1 0 + 0 + 0 G U s >i £ o 0 -P •H tH

<; E* 0 c 0 0 W T3

w rH 0 rH Q U •p t ^ O G o •H 0 0 a - tS3 fa fa N 0 N CO fa fa

**
-49-

Table 5

PHYSICAL PROPERTIES

•Compressive

Strength

Coefficient

of thermal

expansion

Shrinkage

on cure

Tooth Enamel

psi

14-56,000

ppm/ °C

8-11

%

Dentin 30,50,000 4-8

Silicate 24-31,000 8 0.03-0.25

Unfilled resin 14,000 80 2-3

Composite 27-40,000 22-35 0.22-0.6
Fig.

1.

Amalgam

fillings

in

place

as

least

one

year.

(Wann,

W.

L.

,

J.

Am.

Dent.

Assoc.

73:1321,

Dec.

1966).
(ISdOOOl) H19N3dlS 31ISN31

Fig.

2.

Packing

pressure

vs.

tensile

strength.

(Average

particle

size

given

for

the

spherical

alloy)
•^ftr - Tik. ';?<^~'-PV~*5r7fi|

0

0

-P 13

(DU 03

rd m rC iH P 4-> r-4 0 *P ro

cn £ -U0 •- -P g 13 13 0

ro 0 C 0 i-H tn > 0 ,£ ^4 H M 4h M (D

rd fO 4-1 -H a BO £

rd 4-1 p C

Pi 2 O

44 H (1) ,Q -P O g 4-1 0 >i O

0 ' p h u

d) 4-1 4-1 4-1

5-i fi in & -P

pi

4-1 U 4-> •H Pi ft -Ho

pi ft 0

•H *H £

rd m

rd ,£

ftP

_ rd . , . 0 ftPP > -p ft ft 0 -H O rd (D £

U rd u

0 -P rd i3 O to pi P O

P P 44 P ft U -H -H pi -H H 4-4 £ m £

^ -P 13 0 13

rd (D pp C

> -P rd w P

ft 0 X 4J

Pi U -H Pi •H g 0

4P — B

0) tN P d

H 0

ftp • - 0 -P

Pi *H 44 1

I •P 4-4 Pi

Pi 0 >4-1 Pi in g o

0 pi p! U O P p

W-H P p _ P 0 0 pd

0 pi -P 0

• > -h 0

00 0

.ftp

. 0 p 0 pjp tn-P 0 4J -P H M-4 .Cl 4-4 -H

Pm 0 in 0 £
u £

fd i o oo

1—

d 4J •H O 0

e N d £

•H O O — 1

1

1 ro co CD

<4-4 O U

0 .v « £

X H Q

m 0 <

i—

£ i *

fd T3 < CD •H -P U ffi w fd

<u 1 1 i—

-p ffi H >i

fd o o X

£ fd N 0

u X

in u

d ^ in fd 0 CM 0

•H IV p m r—

rd i—i - 0

> fd M d

u u

<4-1 >i 0) 0 Q H n*

l d

ffi • *» dO -

fd fd # u u o o3 tn d

0 — £ PO H r-\ N

• • fd Pd • ^ g w

w • - d

• <u u 1 £ 0) H

4J o

t U <D N

tn •H >

•h fd ,—

,

d -P U <vD

-Adaptic
Figure 5

SILICEOUS FILLER —O-f-Si—

0

—[—CHg —C—CH§

0

I , R O—C—C —CH3

SILANE COUPLING AGENT

POLYMERIC BINDER

Fig. 5. Simplified schematic diagram of the means

of bonding between resin and filler.
ft0 Ti -p g to

CD 0 g

u i •rH fd (3 fd ft -H p ft P Q cu fd g g

to ^•H -p rH ft 0)

<U to rC >i

-P • rH to

to u <

ft CD >

0 P •h g to ro

to ^ to 0 u (D P u U P

3 0 U g

-P P g rd U ftW u

•H H

a ft.

fi CN rQ <D-H

ft,g

O to x

U-H W

CO fi -H O-H T3 p ft u

-H O

e 3

p

0) -p

-p p g

0) &

ft

fd fd g

O

P

-P- u

(D

ft

fi g

•H o

£o

i

1

—I £

(PH 1

O

ftft ld gH g O

C-H -P g to

fd d) i—

up —

U)

a) to -P (D

• -H i—

veto o

O *H

• ft-P

ft£ P

•h O fd ft u ft

ft O

u

cuttlefish

disks

glass

surface.
w

-PC

O

I

I £

£ O

o u

u

£ M-l (D O

00 Xi

i-H 4-1 Cfl m

d> o o U-PH

rti <D > O CPS •H rtf U

p 03 d)

rtf ft P

H-tf tf O -H +> £ P u

•H

•P H ftPtf

4-> w fl h o

ip ftptf g

P +J

a) rtf P C

•H -H

po o -p s -P co e O TS •p £ P

-P rtf O O

U -H -P £ Ttf P

03 0 ftptf

>4-1 U 44

rtf w cn

fi H H

•H ftP

£ 03 o

Q

ft O ,£ £ -P X £

I—i rtf -H *h H g I/!

co p rtf B tfitf -H

rtf £ O p

i—I t-I -P 0) U 44 £ 44

rtf O rtf £ U g

• -H

r- X d> 03 O 44 44

• P t4 *H

Cn ft cn w H ft O O

ft ft ft