Coronal reinforcement with cross-splinted pin-amalgam restorations

SMALES

REFERENCES 1.

Osborne clinical

2.

Phillips

comparison

RW,

Gale

EN,

of three amalgam

appraisal of the evaluation 93:784, 1976. Letzel H, .2ardening CJhlW,

Binon

3:8X, 1978 Smales R,J,

Creaven

PJ:

assessing the surface DEST 42:45, 1979.

alloy

method Fick

types emphasizing

used. JM,

J Am

Dent

van Leusen

an

Evaluation

roughness

of clinical

of restorations.

methods

for

Vrijhoef marginal

Res 58(Special

issue A):

hIhL2, fracture

J PKOSTHET

1979 (Abstr

DENT 49:67,

No. H:

issue

1081. Icinfclder Proceedings

B):lOO,

1075,

Restorative University

Materials.

of Nijmegen,

12.

evaluating cial issue

posterior composite /\):328. 1979 (Abstr

IA,

restora-

RD:

clinical research. on .4malgam and

A new

E: Clinical

materials. U.S. San Francisco,

standards. .4bou-Rass

6:391,

1979.

evaluation

of resin

of dental

amal-

1980. JW, Morganstein

SI: An

evaluation

in scoring

of amalgam

restora-

evaluation

of dental

Public Health Service 1971, U.S. Government

Pub1 No. Printing

The

Nether-

method

for

J Am Dent Assoc M: Observational Washington,

DC,

89:842, 1974. Measurement 1975,

U.S.

S, Levine Development

of Clinical

Department

Perfor-

22

amalgam restorations. J Dent Res 52:823, 1973. Sabott DC, Cooley RW, Greener EH: A clinical evaluation high copper

admixed

amalgam

alloy. J Dent

23

A):l83, Forsten

197.5 (Abstr No. 551). L, KalIio ML: Marginal

24

Stand J Dent Res 84:430, 1976. Leinfelder KF, Sockwell CL, Sluder silver

evaluation.

amalgams Oper

Dent

with

fracture

added

3:42,

TB, copper:

fracture

Res 54(Special of dental Taylor

R, of

of Health.

Education and Welfare, Vol 6, pp 117-149. LIahler DB, Terkla LG, van Eysden J.: Marginal

01 of a issue

amalgams. DF:

A two-year

Expericlinical

1978.

/iqwrn I recp3 1\ lo: DR. ROGER J. SII.U.ES DEP.\RI‘M~.~I

Res 58(Spe-

M, Grass0 J, Holzman P. Quality of dental care:

21.

mental

J Dent

for

on the marginal

Dent J 30~359, 1980. RL: Clinical assessments

Bailir H, Koslowsky Valluzzo P, Atwood

514).

Haq MS: A comparison of plaque and gingivitis.

restorations. No. 945).

methods

Int Dent J 30:327, Leon AR. Ribbons

Haugen

restorative 790-244.

LJNIV~RSITY

1977. Norman

Rehabil

Oflice.

hierrill SIP. Leinfelder KF, Oldenburg TR, Taylor DF: Methods of evaluating pit and lissure sealants. J Dent Child 42:123,

J C:an L)eni ~2ssoc 43:576, Snntucci EXS, Racz WB,

clinical

of time

18.

pp 87-104.

Johnson RH, Rozanis J. Schofield IDF, of clinical and photographic assessment

Indirect

effect J Oral

bl,jor

20

Ni,jmegen,

The

tions. Srand J Dent Res 84:333, 1976. Cvar JF, Ryge G: Criteria for the clinical

for assessing

aspects of Symposium

RL:

of amalgam.

17.

mance.

No.

Marantz

CREAVEN

assessment of the inter- and intra-examiner agreement gingivitis clinically. J Periodont Res 6:146. 1971.

19

1975. I I.

16.

gam restorations. Alexander ,\C,

1983.

1976 (Abstr

KF~lethodological of the International

Tooth-Coloured lands,

IS.

filling materials. Int Mahler DB. Marantz

348).

Xljtrr IA. Ryge G: Comparison of techniques for the evaluation of marginal adaptation of amalgam restorations. Int Dent J 31:1,

0.

HM:

Retrieval bias of J Dent Res 58(Spe-

Eick ,JD. ,Jendresen hll), R yge G: Comparison of three clinical evalu.ttion systems used with amalgam restorations. J Dent Res 55(Special

IO.

180,

Lourens FL, Letzel of amalgam restorations.

cial issue ‘1): 181, 1979 (Abstr No. 350). Smalcs RJ, Evaluation of clinical methods

8.

Eriksen

PROSTHEY

J

5.

7.

14.

J, Vri,jhoef

Spangberg E, Goldberg J, Sanchez L, Lambert K, Munster E: (:linical e\.rluation of high copper amalgam restorations. J Dent

tions.

behaviour

Assor

4.

6

DB,

PP: Three-year

Mhl;\: T,unish. corrosion, marginal fracture, and creep of amalgam restorations: .4 two-year clinical study. Oper Dent 3.

Mahler fracture

13. JW,

AND

G.P.O. Ancl..\ll)F.,

Bos

oc RESTORATIVE

DENTISTKY

OF AL)EI,AIIIF.

498 SoLlIt

AUS?‘R.~I.I.~, so01

Coronal reinforcement with cross-splinted pin-amalgam restorations R. L. Lambert, University

D.M.D.,

M.S.,* F. B. Robinson,

D.D.S.,**

T

wenty-five years ago Markley’ suggested that a weak tooth could be strengthened against-possible frac-

*Associate tistry. **Assistant ***Captain, 346

Professor

and J. S. Lindemuth,

D.D.S.***

Health SciencesCenter, Schoolof Dentistry, Denver, Colo.

of Colorado

and

Chairman,

Professor, Division USAF (DC)

Division

of Operative

of

Dentistry.

Operative

Den-

ture by use of stainless steel pins cemented into dentin and splinted together with an amalgam restoration. In later publications he provided further details of the technique and described how cross-splinted amalgam restorations can be used to reinforce endodontically treated teeth and to unite a weak cusp with the amalgam restoration.‘, 3 Research related to the pin amalgam restoration has SEPTEMBER

1985

VOLUME

54

NUMBER

3

A

Fig. 1. Clinical example of cross-splinted pin amalgam restoration. A, Overextended preparation with weak remaining cusps. B, Four pins (TMS Minikin) placed into remaining facial and lingual dentin. C, Cross-splinting completed with amalgam restoration.

established that the pins do not reinforce the dental amalgam.4, 5 However, the concept of reinforcing the remaining tooth structure continues to be a clinically successful procedure.6-8 The horizontal placement of pins into the compromised facial and lingual tooth structure and condensation of amalgam to unite the pins and reinforce the weakened cusps is termed cross-splinting (Fig. 1). The technique is described and well illustrated in a recent text.8 A quantitative measure of the effect that crosssplinting has on fracture resistance of teeth under occlusal loading has not been reported in the literature. The purpose of this in vitro investigation was to determine the resistance to fracture of teeth restored with cross-splinted amalgam restorations.

MATERIAL

AND

METHODS

Forty extracted premolars were categorized as large, medium, and small according to the mesiodistal and buccolingual dimensions. The teeth were divided into four test groups with an equal distribution of sizes in each group. The teeth were embedded in acrylic resin THE

JOURNAL

OF PROSTHETIC

DENTISTRY

tray material to form a base. The apical end of the base was ground flat until the root tip was exposed. The teeth were then stored in water until testing was completed. The first group of 10 teeth was composed of intact premolars with no preparation and served as the control. The remaining three groups were prepared with an oversized cavity preparation. Group No. 2 did not receive a restoration while group No. 3 was restored with dental amalgam. Group No. 4 was cross-splinted with four Minikin (0.45 ‘mm) TMS (Thread Mate System, Whaledent International, New York, N.Y.) pins embedded within an amalgam restoration (Fig. 2). A mesial-occlusal-distal (MOD) amalgam cavity preparation was designed that would stimulate an oversized preparation such as is frequently encountered in a clinical situation. The teeth in group Nos. 2, 3, and 4 were prepared to prescribed dimensions with a No. 556 crosscut fissure bur in a high-speed air turbine handpiece using an air-water spray coolant. The occlusal isthmus was cut to half the intercuspal distance. The pulpal floor was established at a depth of 4 mm and the 347

A

Fig. 2. Experimental teeth mounted in acrylic resin base. Left: Tooth preparation; middle: four pins placed into remaining dentin; right: completed restoration.

Village, Ill.) matrix band and retainers were used in the restoration of the teeth in group Nos. 3 and 4. Dispersalloy (Johnson & Johnson Dental Products Co., F,ahi Windsor, N. J.) dental amalgam was condensed vertically and horizontally with a 1 mm diameter hand condens er to fill the preparation. The occlusai anatomy was established to harmonize with the cusp slopes. The teeth were crushed with an Instron universal testing machine (Model TT-C. Instron Corp., Canton. Mass.). The load was applied centrally to the occlusa! surface of the tooth by a ?/lo-inch (4.76 mm) steel ball that descended at 0.02 inch/min (0.508 mm/min).

RESULTS

Fig.

3.

The loads required to fracture the test specimens are listed in Table I. The unprepared premolars fractured under a mean load of 243 pounds (110.3 kg). The teeth with a large MOD preparation and without a restoration fractured under a load of 47.3 pounds (21.4 kg), while teeth with a large preparation and restored with an amalgam required a load of 70.1 pounds (31.8 kg). The teeth that were cross-splinted fractured under a load of 169.7 pounds (77.0 kg). A t test determined that the difference between teeth restored ‘with the conventional amalgam restoration and those that received the cross-splinting amalgam restoration was highly significant (p < .Ol).

Standard oversized cavity preparation.

DISCUSSION Table I. Load required

to fracture

teeth

Load Mean Group Intact tooth MOD preparation only MOD amalgam restoratidn MOD cross-splinted restoration

Pounds

SD kg;

Pounds

kg;

No.

243.0 47.3

110.3 21.4

30.1 17.4

13.7 7.9

7 10

70.1

31.8

20.9

9.5

10

169.7

77.0

54.6

24.8

9

gingival floor of the proximal box was prepared 1 mm apical to the pulpal floor. The axial wall was placed at a depth of 1.5 mm and the proximal walls were extended to the approximate line angles of the tooth. Retention grooves were not placed (Fig. 3). In addition to the standardized MOD cavity preparation, the teeth in group No. 4 received four TMS Minikin pins to provide cross-splinting. The pins were placed 0,5 mm inside the dentinoenamel junction in the occlusoproximal corners of the teeth. The pins were angled as close to horizontal as the convenience f$rm would allow. Tofflemire (Teledyne Dental Products, Elk Grove 348

The overcut cavity preparation with a wide isthmus and deep pulpal floor is a frequent dinical problem and is a good indication for a restoration that will unite the cusps to reinforce the remaining tooth structure. The standard procedure is to overlay the cusps with a cast gold restoration. An alternative to the cast gold restoration is the cross-splinted amalgam restoration first advocated by Markley’.’ and recently by Gilmore et al.” The results of our study support the contention of these authors that cross-splinting the cusps with retention pins and amalgam will significantly improve the resistance to fracture. The inherent variability in extracted teeth resulted in several problems during the in vitro testing. Some samples were discarded due to failure of the mounting technique prior to tooth fracture. The discrepancies between cusp heights and inclines of the cusp quite possibly contributed to the large standard deviations reported for each group. In this investigation the force required t.o fracture the intact premolars was similar to that found by Mondelli et al.” and Blaser et al.“’ However, the teeth with MOD cavity preparations demonstrated an 81% reduction in strength and were considerably weaker than those of the previous studies. The difference was expected and was probably related to the greater depth of the pulpal floor.“’ SEPTEMBER

1985

VOLUME

54

NUMBER

3

CORONAL

REINFORCEMENT

REFERENCES

A slight improvement in strength was observed when the prepared teeth were restored with the conventional amalgam technique. However, there was still an overall 71% reduction in strength, which would render these restored teeth weaker than desired to withstand occlusal forces. The difference in resistance to fracture of the prepared and conventionally restored teeth is apparently the result of the amalgam of some of the restorations coming into contact with the steel ball during the crushing tests. The average maximum biting force that can be applied to a molar is about 100 pounds and the force applied to a premolar considerably less. The amount of force applied to the teeth during normal function is about one-third of the maximum.” In this study, restoring the teeth with the cross-splinting technique resulted in a reduction in strength of 30% from that of intact teeth. Although the cross-splinted teeth were weaker than the intact teeth, the forces required to fracture the teeth in this experimental situation were higher than maximum biting forces.

MR:

foundations

Pin

reinforcement

and restorations. MR:

Pin-retained

retention

Dent

3.

Dent Assoc 73:1295, 1966. Markley MR: Pin-retained

and

reinforced

foundations.

Am,

hlarch

Dent

Clin

and pin-reinforced

North

of

amalgam

Assoc 56675,

Markley

1958.

amalgam.

,J Am

restorations

and

1967, p 229.

Going RE, Moffa JP, Nestrant GW, Johnson BE: The strength of dental amalgam as influenced by pins. J Am Dent Assoc 77:1331,

5.

1968.

Cecconi BT, Asgar K: Pins in amalgam: ment. J PROSTHET DENT 26~159. 1971.

6.

Collard

EW,

retained 1970.

amalgam

Dawson 1970.

PE: Pin-retained

8.

Gilmore

HW,

9.

Dentistry, Mondelli

7.

Caputo

AA,

Standlee

restorations.

Lund

amalgam. MR,

Bales

10.

Blaser

P, Lund

MR,

Cochran

Jenkins GN: The Physiology 4. Oxford, 1978, Blackwell

liqmrll

Dent DJ,

North

Clin

7wpet1i

MA,

cavity

Rosario

on resistance

for Am

North

Vernetti

teeth with

of reinforce-

Rationale

Clin

ed 4. St. Louis, 1982, The CV Mosby J, Steagall L, Ishikiriama A. Navarro

designs of class II preparations Oper Dent 8:6, 1983. 11.

A study JP:

Dent

FB: Fracture strength of human PRMTHET DENT 43:419,1980.

This study has demonstrated that teeth weakened by overextended preparations can be significantly strengthened by the cross-splinted pin-amalgam technique. Even though the cross-splinted teeth were weaker than intact teeth, their resistance to fracture should be sufficient to withstand occlusal forces in most patients.

and

J Am

2.

4.

CONCLUSIONS

Influence amalgam

Markley

1.

JP:

pin14~43,

Am 14:63, Operative

Co, p 152. MFL, Soares preparations.

J

HP:

of

Ell’ects

of teeth to fracture.

and Biochemistry of the hlouth, ed Scientilic Publications. pp 518-523.

111.

DR. RALPH L. LAMBEKT UNIVERSTY OF COKIKADO

HEALTH

SCXFACES CEKTEX

Scmm. OF DENTISTRY DENVER, CO 80262

of variations in preparation of dental on dimensional stability and porosities

Jan Ekstrand, D.D.S., Odont.Dr,,* Randi B. Jdrgensen, Roy I. Holland, D.D.S., M.Sc., Dr.Odont.***

B.S.,** and

NIOM, Scandinavian Institute of Dental Materials, Oslo, Norway

T

he physical properties of most dental amalgams have high standards. However, less than half of the amalgam restorations serve more than 10 years, and the most frequent reason for replacement (55% to 60%) is recurrent caries,‘.’ which is not clearly linked to any particular physical property of amalgam. Some physical prop*Visiting Scientist, NIOM; Karolinska Department of Cariology, Huddinge, **Research Engineer. PhvsicallChemical ***Senior Scientist, Physical/Chemical

THE

JOURNAL

OF PROSTHETIC

Institute, School Sweden. Division. Division.

DENTISTRY

of Dentistry,

\

ertie$ of amalgam may, however, be associated with recurrent caries with greater probability than others. Two such properties are dimensional stability during setting, and porosities, both of which are known to vary with different brands of amalgam.4s5 There are less frequent reasons for replacement, such as fracture or faulty. marginal adaptation.3 These are more easily relatkd to strength and creep. The physical properties of amalgam are usually tested under controlled conditions with optimally prepared specimens. However, little information is available about 349