Effect of fixed partial dentures on surrounding tissues

Effect of fixed Sven G. Ericsson, Karl-Erik Markh,

partial

dentures

L.D.S., Dr. Odont.,* L.D.S., Dr. Odont.**

on surrounding

tissues

and

Karolinska Institutet, School of Dentistry, Stockholm, Sweden

F

ixed partial dentures are often thought to have favorable effects upon the marginal periodontium.l However, the follow-up that is required to approach this contention scientifically presents many difficulties. 2-6 If examination of a group of patients could be given an experimental aspect, it might be possible to obtain meaningful data. The examination might be made by means of the investigating technique of Welander,? who recorded pairs of homologous teeth. However, even with this technique, a follow-up study must be carried on over a considerable period of time. This investigation was carried out to determine the effects of fixed partial dentures on the surrounding tissues by comparing homologous teeth. A further aim was to answer questions relating to planning of fixed partial dentures through certain comparisons with Ericsson’s2 material from a study conducted in 1953. In addition, studies were included to ascertain the effects of fixed partial dentures on the degree of attrition on opposing teeth. MATERIAL Fixed partial dentures were constructed for 98 of Mark&n’s private patients over a period of 17 years. Of these, 7 1 patients (40 women and 3 1 men) were available for study. The distribution of the patients in regard to sex and availability for examination is seen in Table I. The distribution according to age of the 71 patients at the time of the examination is shown in Table II. Eighty-seven fixed partial dentures were constructed for the 71 patients (Table III). The time lapses, measured to the nearest number of whole years elapsing since the cementing of the fixed partial dentures, are shown in Table IV. *Associate **Associate

Professor Professor,

and

Chairman,

Department

Department of Prosthetic

of Stomatognathic

Physiology.

Dentistry.

517

518

Eric-ssou

and

Table I. IXstributiorr examination

Mark&

of patients

I\-ith reference

--

for

.~

Aoailable

to sex and availability

Women

for examination

/

-

40

available for .c.uarnimtion Dcrcased Ill for protracted period Moved to other district :\ddress mknown Pmmted by work l:ixrBd partial drnturc: mtractvd

Men

Totals

:41

71

2

,Tof

Totals *Of

these.

6 wmnen

and 2 men had 5 women

of patients

settled who

were

7 6t 0 I

5 0 3 1)

12” 0 :4 I

4X1

98

30-34 35-39 40-4-l 45-49 50-5-t 55-59 60-64.

not rnarrird

at tht? time

at the time of examination No.

of construction

Tyith reference

of patients I

Men

Totals

4 8 9 5 :i I1 I

10 22 19 9 6 1 ',

0 I

1 0

I I

40

31

71.

TO--74

of the

to age

6 14 10 I :i I 1

65-69 Totals

?I

abroad.

/ -... ~__...... -~~~~-~~. .-.... women

Age

I

i)

58

+This number includes fixed partial denturr.

Table II. Distribution

I

:4

DISCUSSION OF THE MATERI.AL The material is homogeneous in t\\o respects: ( 1 ) all patients were treated by the same dentist and (2) the laboratory procedures for all 87 fixed partial dentures were performed by the sane dental laboratory technician. Of the 98 patients, 71 returned for examination. In only one instance (fixed partial

denture

extracted)

could

lack

of participation

in

the

project

be related

to the

problem posed in the investigation (Table I) . Although 71 patients and 87 fixed partial dentures do not constitute a small sample, the material can be used only to a limited extent. The patients constitute a selected group as they are part of the private practice of one dentist. Furthermore, it might be desirable to use the age distribution of the patients at the time the prostheses were made and at the time of investigation, the age distribution of the fixed partial dentures on the occasion of the investigation, and the sex distribution. However, the unsuitability of this emerges from the information contained in Tables

Volume

Number

20

Eflect

6

Table Ill. Number No.

of fixed

of patients

with one, two, or three fixed partial No.

partial

dentures

27 4 0

58 20 9

40

31

87

of the fixed partial No.

No.

of yrs.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Totals

patients Mf3Z

since cementing

Women 2 9 7 3 3 8 2 2 2 2 2 5 3 0 0 2 52

519

dentures

31 6 3 Totals

elapsed

of

on tissues

Women

1 2 3

Table IV. Time

of dentures

of fixed

partial Men 1 10 1 1 5 1 3 1 5 0 4 1 0 2 0 0 35

Total

fixed

partials

dentures dentures Totals 3 19 8 4 8 9 5 3 7 2 6 6 3 2 0 2 ii

II and IV. It would be necessary to work with small groups. NyquisP processed data from small groups, but this procedure was not deemed necessary in this investigation.

METHODS In this study, the fixed partial dentures had been in the mouth at the time of examination for periods ranging from 1 to 16 years. Complete mouth roentgenograms were made on each patient, and these were examined for apical osteitis, fractured abutments, or undermining caries lesions affecting the stability of the restoration. No findings of this nature were observed. Alginate (irreversible hydrocolloid) impressions were made of both jaws, and diagnostic casts were poured. The following recordings were then made by one of the authors (Ericsson) . The load conditions were recorded in a manner similar to the one used by

520

Erimou

and iMal-/i61/

J. 150s. Decembrr,

Dent. 1968

Ericsson’ in 1Wi, although thty casts LL’YI‘Ctlot mounted on thta articulator. A clii~it~ai inspection leas made to dctrrlljinc thcl 1mWnce of dcflccti\,t~ occlus;~l contacts in tht: region of the fiscd 1)artial dt~nturc, thy presence of attrition facets in the gold, and whether there was irlcrt-ased mobility during clenching of thtL teeth or during lateral mandibular movemrsnts. In this \~a);: the fixtd partial dentures WNYZ divided rough11 into groups showing the xani~ load and sho\virlg 3 greater load than thcl rest of thr teeth. The depth of pingival pockets \~as ~ueasurt~l around (
Effect Table

V. The number

No. of units fier partial denture

No.

of retainers of fixed

Total

35 21 11 7 3 1 0 3 1 1 1 2 1 Totals

VI. Comparison

No. of units

No. of abutments

105 84 55 42 21 8 0 30 11 12 13 28 15

i?

of pocket depths around of pairs

abutments

of homologous

17 (22.7%) 9 (20.9%)

30 23

(40.0%) (53.5%)

28 (37.3%) 11 (25.6%)

26

53

(44.9%)

39

abutments;

in 53 pairs

teeth

teeth

Same load Greater load

Same pocket depth

Ise

and homologous

Lesser pocket depth around abutment

(22.0%)

35 24 20 16 10 4 0 14 6 6 6 14 9

iii57

Load conditions of fixed partials in relation to rest of teeth

Totals

521

No. of pontics

70 60 35 26 11 4 0 16 5 6 7 14 6

424-

No.

on tissues

and pontics

dentures

3 4 5 6 7 8 9 10 11 12 13 14 15

Table

partial

of dentures

Greater pocket depth around abutment

(33.1%)

Totals 75 43

(100.0%) (100.0%)

118

(100.0%)

(44.9 per cent), the pocket depths were the same; and in 39 the pocket depths were greater around the abutments. These differences were not significant (PzO.10). Somewhat unexpectedly, the abutments showed relatively better results when they occurred in fixed partial dentures with a greater load as determined by occlusal contacts, The pocket depths were compared around those pairs of homologous teeth where one tooth opposed a fixed partial denture while the other did not. It was possible to make comparisons with 122 pairs of teeth (Table VII). In all, the pocket with the least depth was recorded around the tooth which opposed a fixed restoration in 27 instances (22.1 per cent), equal pocket depth was recorded in 58 instances (47.5 per cent), and greater pocket depth was recorded in 37 instances (30.3 per cent). These differences were not significant. Again, a more favorable result was found for teeth opposing restorations with a greater load than that found for the rest of the occlusion. Retraction of the gingiva at the margin of the preparation. The margin was

pairs (33.1 per cent),

Erics~otl

522

I,oad conditiun~ fixed partials relation

atlo!

MarkCtr

~

of in

to rest

of

@ck& on ~an2~

\ide us fixed

teeth

Totals

i21.0%)

I (J

( 24.4.‘%

‘7

pocket

drpth

nn %atnP

~

)

39 l!)

148.1% 146.3%)

I\‘-“‘2.1’,:‘1 ,

58

(47.5%)

~

,irla nr fixed

depth

Ii

(:rr/c/rr

)

7’otals

partials

25 : 30.9% ) I ‘2 ( 29.3 5,5’‘) :ii

81 41 1’2

:30.3%)

(100.0% (100.0%)

Comparison between abutments with the same load and those with load with reference to retraction of the gingiva

Load conditions of fined partials in relation to rest of occlusion

/ /-

Gingivn

~.._

I

Retraction

Same load

53

Greater load

31 (42.0%)

Totals

IX.

Attrition

87

of opposing

Load conditions of j fixed partials in relation to that on rest of occlusion 1

Same load Greater load Totals

nt the

a

abutment ~~

I

No

(32.3%i (35.5%')

teeth as compared of fixed

partials on other

Greater

/

Same

Totals

retractzon

111 47 _--.-158

Attrition

j

( 99.0%)

VIII.

greater

Table

nS’m~r~ locket

partialr

/

Same load Greater load

Table

l.risut

~ dc,bth

(67.7%) (58.0%; (64.5%

with

in relation side I

.!

attrition

164 81

(100.0%) (100.0%)

245

( 100.0%

)

of rest of the teeth

I

to that

:

I.&.,,17

iI

Total.\

8

7

fi

4

i

I

21 15

-17

1.1

IU

36

prepared for the restorations in a location somewhat below the free gingival margin. Of the 260 abutments, 245 were examined. The gingiva rnore frequently showed retraction around the abutment when the occlusal load was greater on the fixed partial denture than when the occlusion was harmonious (Table VIII). However, the difference was not significant. Attrition on opposing teeth. The attrition of the teeth opposing the fixed partial dentures was compared with the attrition of the rest of the teeth. One requirement for this comparison was that the opposing jaw have no edentulous spaces or have the same space on both sides. Furthermore, there could be no crown restorations located on the other side of the same jaw from the fixed partial denture nor could there be fixed partial dentures present in both halves of the jaw. Consequently, only

Effect

of dentures

on tissues 523

36 patients were examined in this phase (Table IX). Findings indicate no difference in the tendency to attrition in the 1967 study. In the 1953 study, a tendency was found to increase attrition of the opposing teeth on the same side as the fixed partial denture.? DISCUSSION Free-end cantilever pontics occurred relatively often in the 1967 study but never in the 1953 study.’ There are probably two main reasons for the use of free-end pontics; either a longer restoration is desired where molars are missing, or it is undesirable to use an undamaged canine or incisor as an anterior abutment. The latter alternative applied in 21 of the 23 instances where free-end pontics were used. The dentist may have allowed esthetic considerations to encroach on mechanical requirements and, thus, reduced the stability of the fixed partial denture. The comparisons which were made of homologous teeth imply an experimental aspect. One tooth was treated in a certain way while the other tooth did not receive similar treatment. The roentgenographic status of each patient was known, but comparisons of these were not suitable. The projections were not identical, and marked, dramatic changes in the periodontal status were extremely rare in this material. An attempt to assess minor changes in the structure or in the level of the alveolar bone under the existing conditions was pointless. The depth of the gingival pocket was shown to be greater around an abutment or around a tooth opposing a fixed partial denture than around the respective homologous control tooth. Although the difference observed may have arisen by chance, it is in the direction expected if one considers the stresses to which the periodontium of an abutment is exposed during preparation in the cervical region, during impression procedures, during temporary restorations, and during the functioning of the finished fixed partial denture. Koivumaa and Wennstriim” histologically demonstrated gingival changes in experiments in which full crowns were excessively contoured in the cervical portion and control teeth were shaped with optimal anatomy in relation to the gingival tissue. The contradictory results obtained with respect to the pocket depth around abutments or around teeth opposin, 0‘ the fixed partial denture could be ascribed to chance, as the material was distributed between two subgroups. The absence of differences in regard to attrition must be regarded as expected. A tendency for more attrition on the same side as the fixed partial denture was observed in the study in 1953, but the masticating surfaces on the pontics were constructed of a steel alloy (Vitallium) .? In the 1967 study, the material was gold, which is a softer material than the steel alloy. Attrition studies are complicated inasmuch as the grinding is often performed on the opposing teeth. Therefore, an attrition study is without validity when diagnostic casts are not made at the time of completion of the fixed partial denture. Even then, it is difficult to satisfy validity requirements. A further consideration is that severe attrition has become rare, unless a completely unsuitable material is used. Nonsignificant results were obtained in regard to “depths of gingival pockets” in two comparisons and to “retraction of the gingiva . . . .” Certain tendencies were found, however, in all comparisons. Supposing these tendencies were true, a comple-

524

Ericsron

J. PIOS. Dent. December, 1968

and Markr’tl

mentary material 50 per crnt greater j 180 units irrstead 01’ 118) \voultl have been necessary to contir~n significance at the 5 per cent level and more than 200 per cent greater (370 units instead of 1 18 j at the one per cent Ic~~c~l. Such comprehensive materials would be difficult IO c.ollcct. ‘l‘his may serve as an example of the difhculties involved in follo\v-up examinations of fixed partial tlciltures as these invcstigations are usually- l>t~rforrrrcYl. PROPER

DESIGN

OF THE STUDY

(Zertain proceclr~r~er should be follov\eti to properly design an experiment for studying the cflect of fixed partial dentures on the supporting periodontium. In relation to trratrrial. OIW sho~~lcl choose patients in whom the fixed partial denture is indicated \vithin one quadrant d the occlusion. Recordings of each pocket depth must be rr~~cle in connection with construction of the restoration and after adequate periodontal therapy. The side of the occlusion containing the fixed partial denture \vould be t11e t~speriniental side, while the other side would be the control side. The follow-up study should be based on comparisons of homologous teeth in the manner described. The study of the periodontal changes in opposing teeth should be carried out analogously. Great attention sho~dd be paid to the problenr of the observer. Certainly, a change of observers should not be made durin,g the recording period. However, it is doubtful lvhether a single observer is sufficient for a protracted follow-up study. The observation lrvrl has been shown by Mark&r I1 to change from time to time. For this reason and to obtain a better approximation of the true facts. simultaneous examination and recording should he conducted by at least two observers. It is also desirable that at least one of the observers be a specialist in periodontology, and that the observers undergo a period of intensive cotraining.” The risk of nonappearance of srihjects indicates the need for a relatively large number of patients. ‘Ihe c;mses of nonappearance should be controlled particularly to prevent extraction of abutments. of the authors If the procedures outlined above are follotved, it is the opinion that follohv-up investigations of fixed partial dentures may give reliable results even when the nunrber of patients constituting the experimental material is kept relatively lol\-. SUMMARY A study of the effect of fixed partial dentures upon the marginal periodontium on 98 patients was described. Comparisons WYI‘C)inade Lvith a study conducted several years earlier. Suggestions for the planning and carrying out of a more thorough investigation of a similar kind were presented. Primary recording of the variables relevant to the investigation leas considered essential. The observer strategy was discussed, and simultaneous techniques of investigation arc recommended. The Uppsala

statistical Uni\w-sity,

analyses Uppsala,

have been Sweden.

performed

by

Docent

G. Eklund,

Statistical

Institution,

Effect

of dentures

on tissues 525

References 1.

Hildebrand, G. Y.: Studies in Dental Prosthetics, Svensk tandl. tidskr. 30: l-2 (Suppl.), 1937. 2. Ericsson, S. G.: Broprotesens inverkan pa de marginala parodontala fiirhallandena i bettet (The Influence of the Bridge on the Marginal Periodontal Conditions of the Dentition), Svensk tandl. tidskr. 46: 171-182, 1953. 3. Backlund, N., and Akesson, N. A.: Efterundersokning av kronoch broarbeten, Odont. Revy 8: 121-133, 1957. 4. Karlstrijm, S.: Pontostruktormetodiken: Dess principer samt dess vid broframstlllning tillampade teknik belyst av behandlade fall, Svensk tandl. tidskr. 40: 613-704, 1947. 5. Karlstrom, S.: Pontostruktormetodiken sedd i kasuistikens belysning (A Follow-Up Examination of Fixed Bridges Produced by the Pontostructor Method), Svensk tandl. tidskr. 45: 439-465, 1952. 6. KarlstrGm, S.: Efterkontroll av brofall framstallda enligt den s. k. pontostruktormetodiken (Follow-Up Examination of Bridges Prepared by the Pontostructor Method), Svensk tandl. tidskr. 53: 957-972, 1960. 7. Welander, E.: The Occurrence of Dental Caries in the Permanent Dentition, Uppsala, Sweden, 1955, Almqvist & Wiksell, pp. 7-122. 8. Nyquist, G.: A Study of Denture Sore Mouth, Acta odont. scandinav. 10: 9, 11-154 (Suppl.), 1952. 9. Forsberg, A.: A Clinical Study of the Periodontal Tissues of the Upper Incisors in TWO Groups, Acta odont. scandinav. 9: 8, 7-105 (Suppl.), 1951. 10. Koivumaa, K. K., and WennstrGm, A.: A Histological Investigation of the Changes in Gingival Margins Adjacent to Gold Crowns, Odont. tidskr. 66: 373-385, 1960. 11. Mark&n, K.-E.: Studies of Deviations Between Observers in Clinico-Odontological Recording, Tr. Roy. Schools Dent., Stockholm and Umeg, Sweden, Almqvist & Wiksell, pp. 9-186, 1962. 12. Westin, G., and Wold, H.: 1942 brs tandmijnstring av inskrivningsskyldiga, Odont. tidskr. 51: 487-615, 1943. KAROLINSKA INSTITUTET SCHOOL OF DENTISTRY

Box

3207

STOCKHOLM

3, SWEDEN