NATIONAL BUREAU OF STANDARDS REPORT

998 3

Progress Report

on A FILLED COLD-CURING

ACRYLIC RESIN AS A SPLINTING MATERIAL

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT MBS REPORT

3 11.05-1 1 -3 110 56 0 December 3 1, 1968 9983

Progress Report

on A FILLED COLD-CURING

ACRYLIC RESIN AS A SPLINTING MATERIAL

by

E. F. Huget,* G. M. Brauer,+ J. W. Kumpula+f and S. Civjan**

* Research Dental Officer, Division of Dental Materials,

U. S. Army Institute of Dental Research.

+ Research Chemist, Dental Research Section, National Bureau

of Standards, Washington, D. C. + + Mechanical Engineering Technician, Dental Research Section,

National Bureau of Standards, Washington, D. C.

** Chief, Division of Dental Materials, U . S. Army Institute

of Dental Research.

This investigation is part of the dental research program conducted by

the National Bureau of Standards, in cooperation with the Council on Dental Research of the American Dental Association; the National Institute

for Dental Research; the Dental Research Division of the U. S. Army

Medical Research and Development Command; the Dental Sciences Division

of the School of Aerospace Medicine, USAF; 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, Washingtc

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

;s accounting documents intended

subjected to additional evaluation

listing of this Report, either in

i Office of the Director, National

y the Government agency for which

opies for its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

A Filled Cold-Curing

Acrylic Resin as a Splinting Material

E. F. Huget, G. M. Brauer, J. W. Kumpula and S. Civjan

INTRODUCTION

The stabilization of alveolar fractures and avulsed,

subluxated and reimplanted teeth by acrylic splinting devices has been described by numerous authors . 1 ' 2 ' 3 ' 4 The

use of auto-polymerizable acrylics presents an intriguingly

simple and rapid means of achieving the. required degree of

stability for fixation purposes. The excessive heat evolved

during the polymerization of these substances and the accompanying patient discomfort and soft tissue damage have,

however, limited their use. The "rebound" tendency of

acrylics in dough form and intraoral manipulation problems

related to the use of more fluid mixes have also limited

the scope of acceptance of auto-polymerizable acrylic splints.

In this study, a number of acrylic formulations were

evaluated. A poly (methyl methacrylate) (PMMA) resin admixed

with the appropriate inert inorganic filler and mixed with

methyl methacrylate (MMA) monomer containing a low percentage

of amine accelerator yielded a material with desirable physical

- 2 -

and mechanical properties. This product also exhibited highly

desirable manipulation and setting characteristics that precluded the difficulties associated with materials currently

used for direct splinting procedures.

MATERIALS AND METHODS*

A series of commercially available methacrylate polymers

and copolymers were evaluated for potential use as direct

splinting materials (Table 1) 0 Inorganic fillers consisting

of A1 3 03 , dental stone , CaC03 or ZnO+ were added to

selected polymer powders. The A12 03 was passed through a

No. 325 sieve prior to use. All other inorganic fillers were

* Certain' commercial materials and equipment are identified

to adequately specify the experimental procedure. In no

case does such identification imply recommendation or endorsement by the National Bureau of Standards or the

Dept, of the Army, nor does it imply that the material

or equipment is necessarily the best for the purpose.

** T61 Tabular Alumina, Aluminum Co. of America, Bauxite, Ark.

*** Kerr Rapid Stone, Kerr Mfg. Co., Detroit, Michigan

**** precipitated calcium carbonate, 1— 10 p, particle size, NONFER-AL, USP, Diamond Alkali Co., Cleveland, Ohio.

+ Zinc oxide, USP, J. T. Baker Chemical Co., Phillipsburg, N. J.

-3-

used as supplied by the manufacturer. Polymer and filler

powders were mixed by tumbling weighed amounts of the constituents in glass jars. Some powders were blended with benzoyl peroxide ++ by suspending the polymer and filler in a

solution of the polymerization initiator in ethyl ether, followed by evaporation of the solvent.

The polymer or polymer-filler blend was mixed with methyl

methacrylate monomer +++ containing 0 . 2-0 . 5%' amine accelerator,

N,N-dimethyl-£-toluidine. ++++ At ambient temperature the

monomer-polymer slurries reached the dough stage of polymerization in less than one minute after mixing. The dough

was removed from the jar and held in the palm of the hand

until peak polymerization temperatures were reached. Cylindrical segments of dough (approximately 20 mm in length and 4 mm

in diameter) derived from formulations evolving quantities of

Fisher Reagent, Fisher Scientific Co., Pittsburgh, Pa.

+++ Methyl methacrylate, inhibited with 35 ppm butylated

hydroxytoluene , Rohm and Haas Co., Philadelphia, Pa Q

+ + + + Eastman Organic Chemicals, Rochester, N. Y.

-4-

heat well tolerated by the skin of the palm of the hand

were then placed in the muco-buccal folds of volunteer

patients for more definitive evaluation of heat tolerance.

Ratios of 1.5-1 0 7 gm. of polymer or blended polymer powder

to 1.0 ml liquid provided practical amounts of material

for evaluation of dough stage manipulative characteristics,

hardening time and heat evolution.

The polymer powder used in the most promising formulation

was analyzed microscopically for further characterization.

Sorption, solubility and color stability, were determined

according to American Dental Association Specification No.

12 for denture base polymer6

; transverse deflection by

American Dental Association Specification No. 13 for denture

cold curing repair resin6

; hardening time and temperature

rise by American Dental Association Specification No. 17 for

denture base temporary relining resin7

. Ultimate compressive

strength was determined as prescribed by American Dental

Association Specification No. 9 for dental silicate cement8

.

Tensile strength was measured by the diametral method using

disc shaped specimens 1/4 inch in diameter and 1/16 inch

in thickness without platen modification as recommended by

Civ j an and de Simon9

. Shear strength was determined by the

-5-

"punch" method described by Taylor and Margetis1

0

using disc

shaped specimens 1/2 inch in diameter and 1/16 inch in

thickness. All strength determinations were performed using

with an electric strain' gauge load cell

a universal testing machine /operated at a crosshead

speed of 0.02 in/min’.

RESULTS . Polymerization characteristics of the 14 formulations

evaluated are presented in Table 1. Three monomer-polymer

slurries (No. 1, 2 , 3) did not polymerize. Hardening time

the

(from the time/dough stage had been reached) of three mixtures (No. 4, 12, 13) exceeded 10 minutes. Most mixtures

that hardened in 10 minutes or less at room temperature evolved

excessive amounts of heat (formulations No. 7-9, 14) . One mixture that evolved a tolerable amount of heat yielded an

elastic dough that was not readily adaptable to the labial

and buccal surfaces of the teeth (formulation No. 6) . Formulation 5 containing 2% of accelerator gave a slightly yellow

product. Two formulations (No. 10 and 11) exhibited desirable

gross polymerization characteristics. The doughs resulting

- 6 -

from these mixtures were readily formed into ropes and

easily adapted to the labial and buccal surfaces of the teeth

of volunteer patients. Hardening of cylindrical segments of

dough (formulation No. 11) approximately 20 mm in length and

20 mm in diameter _(vol. —63 mm3

) occurred in 6-8 minutes.

Substitution of aluminum oxide, dental stone or zinc

oxide for the calcium carbonate filler in the most promising

formulations resulted in inferior products that were usually

chalky and friable.

Microstructure analysis of the polymer constituent of the

most promising formulation revealed spherical particles ranging

from l|j,n^to 150 ^min diameter with the largest portion of the

h particles having diameters of 25[imto 75n,m.

The physical and mechanical properties of the most

desirable filled acrylic mixture used in all further evaluation procedures are given in Tables 2 and 3.

-7-

DISCUSSION

Physical Properties of Filled Splinting Resin

The physical and chemical characteristics of the polymer

powder as well as the type and amount of inorganic filler affected the molding quality of the resultant dough. Poly (ethyl

methacrylate) and copolymers of methyl methacrylate and

ethyl acrylate yielded rubbery reaction products when

reacted with methyl methacrylate monomer. Two methyl methacrV'

late polymers also produced very elastic doughs when, reacted

with' methyl methacrylate monomer. A slurry of high molecular

weight poly (methyl methacrylate) homopolymer powder with

monomer did not harden (formulation 11) . A small particle

size powder appeared to be beneficial as a splinting material.

Increasing the benzoyl peroxide initiator or. dimethyl-ptoluidine accelerator concentration shortened the hardening

time.

Enough residual peroxide is apparently present in the

polymer powder normally used in dental applications to act

as a polymerization initiator. Addition of 0 . 2% peroxide,

however, yielded mixtures that hardened more rapidly.

\

-8 -

The presence of 50% CaCO^ filler prevented the temperature rise from exceeding clinically tolerable limits, thus

rendering these materials suitable for splint fabrication.

Only two of the fifteen formulations evaluated in this

study demonstrated potential for use as a direct splinting

material (Noa 10 and 11) . The powder component of formulation

11 included a 49.8% finely ground poly (methyl methacrylate)

polymer powder with 0.2% benzoyl peroxide and 50.0% CaC0,(

filler. The monomer portion was methyl 'methacrylate with 0.2%

N/N-dimethyl-o-toluidine. The mixing of 1.5 gm of the filledpolymer powder with 1.0 ml of monomer produced a non-sticky

easily qaanaged dough within less than one minute. The hardening of relatively large cylindrical segments approximately 90

mm in length and 6 mm in diameter (vol. "2500 mm ) occurred in

the mouth within 6 minutes without any appreciable rise in

temperature. If a slower hardening material is desired,

formulation 10 should be used which has the same composition

as formulation 11, but does not contain any added peroxide -;

The CaCO^ filler not only serves as an efficient attenuant

for the heat evolved during the polymerization of a mixture

of acrylic polymer (SR-120) and methyl methacrylate monomer,

but also imparts a "dead-fall" characteristic to the dough

-9-

stage. The dough does not rebound from the affected portion

of the dentition after initial adaptation.

The relatively low exothermic heat of polymerization

allows border molding and smoothing of the material after

adaptation by direct contact and movement of the mucosa of

the lips and cheeks over the intact segment of material.

Physical and mechanical properties of .the CaCO^ filled

acrylic were determined to more completely characterize the

material. The hardening time of 12 minutes (Table 2) reflects

the influence of the geometry of the polymerizing mass (required in the specification test) on polymerization characteristics. Disc shaped specimens 60 mm in diameter and 2 mm in

thickness required twice as much time for polymerization as

cylindrical specimens approximately 90 mm in length and 6 mm

in diameter. Rupture of transverse deflection specimens at

loads of 2500-2600 gm was the result of the high percentage

of inorganic filler. For clinical use, the CaCO^ filled

acrylic has demonstrated adequate rigidity and strength for

splint fabrication. With the exception of the fracture of

the material in the transverse deflection test, this material

possesses properties similar to those associated with denture

cold-curing repair resins.

- 10 -

Clinical Application

The advantages of the preferred material over previously

suggested products are its low heat of polymerization, as well

as its ease of manipulation. This material should therefore

be the material of choice for the stabilization of alveolar

fractures and avulsed, subluxated and fractured teeth Q It

can also be used for the stabilization of ^implants and reimplants. Initial clinical results of these applications have

been most encouraging.

a The filled acrylic could also be used with preformed, noncorrosive metallic pins (Fig. 1 and Fig. 2) for the maxillomandibular fixation and stabilization of mandibular fractures

(Fig. 3) . The acrylic material prevents lingual displacement

of the metallic pins that serve as anchor points for interarch

elastics

.

The characteristics and properties of the filled acrylic

suggest its usefulness in nondental as well as dental procedures.

Nondental applications may possibly include:

(1) the fabrication of orthopedic appliances, (2) the

stabilization of surgica'l implants, and (3) a replacement for

portions of the calvarium following craniotomy procedures.

- 11-

SUMMARY

The reaction products of a series of filled and unfilled

acrylic polymer-monomer mixtures were evaluated for use as

splinting materials 0

Polymer powder particle size, type and amount of inorganic

filler and amine concentration in the monomer influenced the

polymerization characteristics of the mixtures and the properties of the resultant products.

Two formulations demonstrated potential for use in splinting- procedures . The powder component of the preferred formulation contained 49.8% finely ground poly (methyl methacrylate)',

50.0% CaCO^, and 0.2% benzoyl peroxide. If a slower cure is

desired, the peroxide can be omitted. The monomer portion was

methyl methacrylate with 0 o 2% N,N-dimethyl-jo-toluidine. The

dough produced by this reaction mixture polymerized in the

mouth within 6 minutes without the evolution of excessive

amounts of heat 0 The physical and mechanical properties of

the polymerized product render this material suitable for the

fabrication of short span intraoral splints.

The material, because of its low exothermic heat of polymerization, may also be useful for the fabrication of small

-12

orthopedic splints, the stabilization of surgical implants,

and as a replacement for portions of the calvarium following

craniotomy procedures.

C

USCOMM-NBS-DC

-13-

REFERENCES

1. Freedman, G. L. , and Hooley, J. R. Immobilization of anterior alveolar

injuries with cold-curing acrylic resins. JADA 76:785 Apr 1968.

2. Law, D. B. Prevention and treatment of traumatized permanent anterior

teeth. Dent Clin N America Nov 1961, p. 615.

3. Lewis, T. M. , and Dow, P. R. Replantation of an avulsed permanent

central incisor - case report. J Dent Child 31:103 2nd quart 1964.

4. Johnson, W. N. , and Groat, J. E. A new fixed temporary dental splint.

Periodontal abstract 14:153 Dec 1966.

C

5. American Dental Association. Guide to dental materials, ed. 3.

Chicago, American Dental Association, 1966, p. 143.

6. American Dental Association. Guide to dental materials, ed. 3.

Chicago, American Dental Association, 1966, p. 149,

7. American Dental Association. Guide to dental materials, ed. 3.

\ Chicago, American Dental Association, 1966, p. 158.

8.

' .American Dental Association. Guide to dental materials, ed. 3.

Chicago, American Dental Association, 1966, p. 133.

9. Civjan, S., and de Simon, L. B. Evaluation of the diametral compressiontest. IADR 45th general meeting-program and abstracts, 1967, p. 126.

10.

Taylor, D. F. , and Margetis, ?. M. Unpublished data. Dental Research Section

Polymer

and

Copolymer

Mixtures

Evaluated

for

Use

as

Direct

Splinting

Materials

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TABLE 2

PHYSICAL PROPERTIES OF A CaCO FILLED RESIN*

3

Sorption Solubility Color Stability

Peak

Temperature

Hardening

Time

2

mg/cm mg/cm °C min

0.4 0.02 no perceptible

change

50.5 12

* Powder: 49.8% PMMA copolymer (SR-120) with 0.2% benzoyl

peroxide and 50.0% CaCO

3

Liquid: MMA containing 0.2% N, N-dimethyl-_o-toluidine

Powder-liquid ratio 1.5 gm/1.0 ml

Values are averages obtained from 2 specimens

TABLE 3

MECHANICAL PROPERTIES OF A CaC0

3

FILLED RESIN*

Transverse

Deflection

** Shear

Strength SD

Tensile

Strength SD

Compressive

Strength * SD

mm deflection

1500 to 2500

_ * * * gm load

psi psi psi psi psi psi

C1.1 5700 160 2450 200 8850 350

Composition: Same as reported in Table 2; values are

averages obtained from 5 or more specimens.

** Determined after 24 hours.

*** Determined after one week. Specimens broke

before 4000 gm load was reached.

SYNOPSIS

A polymeric material suitable for the rapid fabrication

of splint-type appliances has been developed. The dough-like

product formed on mixing a powder and liquid can be readily

adapted to the cervical third of the intact teeth. Autopolymerization occurs in the mouth within 6 minutes at peak

temperatures not exceeding 50 °C. The polymerized product

exhibits sufficient strength, rigidity and dimensional stability

to function as a splint.

This material may also find application for the fabricaO tion of orthopedic splints and other medical uses.

Fig.

1.

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interproximal

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2.

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pin

provide

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for

interarch

elastics

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