Tissue response to fixed partial denture pontics

Tissue

response

Edmund Cavazos, U. S. Army Dental

to fixed Jr.,

partial

denture

pontics

D.D.S.*

Unit, Fort Banning, Ga.

A

number of opinions have been expressed regarding the cause of unfavorable to detertissue response to fixed partial denture pontics. 1-5 This study was initiated mine the clinical and histologic effects of fixed partial denture pontics upon the underlying tissues. Specific factors of pontic design, materials employed, adaptation, and finish were considered in an attempt to demonstrate any tissue change that might develop. The subjects were patients ranging in age from 18 to 47 years, and they were in excellent health. Each appliance was temporarily seated for a period of 4 months, at which time each prosthesis was removed, and the tissue was photographed, biopsied, and analyzed. Where unfavorable tissue response resulted, the appliances were remade to conform to acceptable bioengineering standards. This study involved 67 subjects with 279 pontics on 102 fixed partial dentures. Forty of the fixed partial dentures were in the anterior part of the maxillary arch and these had 160 pontics. Sixty-two of the fixed partial dentures were in the posterior part of the mandibular arch, and these had 119 pontics. MATERIALS

AND

DESIGN

The pontics were designed so that different materials and forms would be used in the study. The maxillary anterior pontics included (1) long-pin facings, (2) porcelain interchangeable flatback facings, (3) acrylic resin facings, and (4) a combination of long-pin facings with porcelain interchangeable flatback facings in the same appliance, The mandibular posterior pontics included (1) long-pin ponticst (Pon-Tip facingst), (2) gold pontics with ovoid or saddled gingival ends, and (3) acrylic resin pontics with ovoid or saddled gingival ends. Presented as a table dontics in Chicago, Ill.

clinic

before

the American

*Lieutenant Colonel, Chief, Fixed Prosthodontics, TThese pontics are made of high-fusing porcelain highly glazed and pins for retention. $Harmony

Dental

Products,

South

Pasadena,

Academy

of Crown

Fort Benning, Ga. and have an ovoid

and

Bridge

gingival

Prostho-

end

that

is

Calif.

143

Several fixed partial dentures were Irladf, with pontics of diRerent desiqs. Itlaterials, adaptations, and finishc>s ill the santt’ restoratiorl so tllat the diffrrcnt pontics could hc conlpared under psac‘tly the san~t cxmditiona. METHODS

OF EVALUATION

Upon removal of thrb appliance: a clinical rxaulination of the soft tissucas ~vas made to determine such lnanifestations as discoloration, inflammation, proliferation. or ulceration. Fronn tllc.sc, arcas a 1. n11u. punch biopsy was p~~rformed for histologic evaluatiou. RESULTS

AND

Ma.xillary is contacting

DISCUSSION mfc~rior p0ntic.c. I,oqg-pin the gingiva. ‘I’hP gingival

facinlgs arca designed tissues were nornlal

so that only porcelain if these facin(ys wyyc

A

Fig. 1. Tissue reaction to long-pin facings. A, Ko change in the gingival gingival tissue in a biopsy from under a long-pin facing. (r.50.)

tissue. H, %~rmal

Tissue

yp~e; u

‘:I

Table

I. Tissue reaction to 48 long-pin facings Adaptation.

I

28

20

responseto denture

Finish

145

Effects

I

12

-

16 8

-

-

8 4

8

pontics

A

B

Fig . 2. Tissue Ireaction to porcelain interchangeable attributable to excessive scraping late :ral incisor) inflal nmation of the gingival tissue in B, Severe lr nm. (X22.)

(left flatback facings. A, Tissue reaction of the cast under the pon tic (1 n lm.). a biopsy where the cast had been scr aped

Table

II. Tissue reactiorl

Fig. 3. Tissue reaction cell infiltration, mild mad le under an acrylic

to 40 purcelairl

to acrylic resin pontics. pseudoepitheliomatous resin pontic.

interchangeable

A, Severe hyperplasia,

Nathack facings

reaction to the acl rylic resin. B, Koundulceration, and necrosis in a biopsy

ply,“,

‘20

Table

III. Tissue

”

Tissue reaction

to 32 acrylic

Finish contacting

(tissue

Excessive 1 mm. relief

Glazed

20

Unfinished

14

I

No

-

8

-

-

to long-pin

Adaptation

8 1

6 5

4

4 4

-

4

and porcelain

interchangeable

)

flatback

facings

I

’ Finish

fakngs

Tissue change

change

6

12

of ponf.

147

Effects

-

No.

jontics

area)

Polished

t-

Table IV. Tissue reaction in the same appliance

to denture

resin pontics

Adaptation Normal 0.25 mm. relief

response

/ facings

(

relief

I

20

1

relief

/ Glared

12

8 14

i

( Polished

-8

-4

4

-

-

Effects I Unfin1 ished -

I-

82

-2

4

3 2

1 2

6

6 3

2 3

20

overglazed with a high-fusing porcelain, if there was minimal tissue contact commensurate with acceptable esthetic standards, and if the cast was not scraped more than 0.25 mm. (Fig. 1, A and B) . On the other hand, if a low-fusing overglaze was used, if polishing was attempted to restore the glaze, or if the cast was relieved more than 0.25 mm., then there was an unfavorable tissue change (Table I). In 28 per cent of the cases, there was an unfavorable tissue change under the porcelain interchangeable flatback facings (Table II). This can be attributed only to the material, which consisted of approximately r/s porcelain and 2/s gold, contacting the tissue. Unfavorable tissue changes increased proportionately when the cast was relieved more than 0.25 mm. and/or when the porcelain was not adequately glazed (Fig. 2, A and B) . An unfavorable tissue change was evident under 43 per cent of the properly adapted acrylic resin pontics (Table III). Upon removal of these appliances, a fetid odor emerged. If the cast was scraped 1 mm. deep or if the acrylic resin pontics were improperly polished, the number and the severity of the tissue changes were increased (Fig. 3, A and B) .

148

.I. bus. Dent. Auqust, 1968

Cava;o.r

A

B

As a control, a combination of long-pin and porcelain interchangeable Aatback facings were used in the same appliance under exactly the same conditions (Fig. 4,. A and B) . The results obtained from this group were the same as those obtained in the group in which the pontics were used individually. Therefore, the findings from each category arc characteristic and typical and not the results of individual variations (Table IV).

Volume Number

20 2

Tissue

response

to denture

pontics

149

A

B

Fig. 5. Tissue reaction to Pon-Tip facings. properly “relieved.” B, Normal tissue. (x50.)

Table

A, No

change

in the gingival

tissue

when

cast

was

V. Tissue reaction to 26 Pon-Tip facings Adaptation

Normal 0.25 mm. relief

Excessive I mm. relief

Design

! Ovoid -

14

12

1-

1

Eflects

-

Saddled -

No

change

chance

14 -

--

8

-

-

( Tissue

-

4

150

Cavazos

Table

VI. ‘Tissue

reaction

to 32 gold

pontics --

_-----

Adaptation Normal 0.25 mm. relief

Fig.

6. A

Fig.

6, B

1 Excessive 1 I mm. relief

Desqn i

Ovoid

i

Saddled

/

No

chan.ge”~~issue

chan,ge

Fig. 6. Tissue reaction to gold pontics. A , Accumulation of materia alba when pontics were “saddled.” B, Biopsy shows moderate inflammation and dissolution of basal layer. (x50.) Fig. 7. Tissue reaction to acrylic resin pontics. A, Tissue reaction to an acrylic resin pontic whose cast was scraped 1 mm. B, Biopsy illustrating severe inflammation with the dissolution of the basal layer. (x50.)

Volume Number

20 2

Table

VII. Tissue reaction

Tissue

Adaptation Normal 0.25 mm. relief

to 28 acrylic

Ovoid 9

Porcelain

Gold

Acrylic

-

to a combination

Tissue

of porcelain,

change

3 1

6 6

1

6 5

-

5

gold, and acrylic

resin

Normal 0.25 mm. Adaptat~relief 3

II 5

i-

I8 12

change

7

-

9 12

No

-

7

12

employed

151

Effects Saddled

-

reaction

pontics

I .Design

Excessive 1 mm. relief

Table VIII. Tissue pontics

to denture

resin pontics

I

16

Pontic

response

-

-4 2 4

-

9 2

- 1

-2

21

1

1 2

2

4 2

_

i 6 -

2

-

2

-

-

1

i

Mandibular posterior pontics. When Pon-Tip facings were used and the cast was not scraped more than 0.25 mm., the tissue was normal (Fig. 5, A and B) . When the cast was relieved 1 mm., a tissue change was evident under 33 per cent of the facings (Table V) . These Pon-Tip facings are ovoid in shape and, by virtue of their design, have minimal contact with the gingival tissues. The gingival contacting ends of the pontics require no grinding; therefore, the vitrified surface of the porcelain remains intact. When properly adapted gold pontics of an ovoid shape were used, a tissue change was produced under 20 per cent of the pontics. Seventy-five per cent of the gold pontics that were shaped to “saddle” the ridges had evidently unfavorable tissue changes. The tissue changes were proportionately increased as the amount of cast scraping was increased (Table VI and Fig. 6, A and B) . When acrylic resin pontics were used, even though they were ovoid in design and highly polished, and the casts were scraped 0.0 to 0.15 mm., a tissue change was produced under 66 per cent of the pontics (Table VII). Acrylic resin pontics

152

Cacaro \

n

rrsirt ponticx which Fig. 8. Tissue wactitm to a combination t~f porcelain. gold, and .ic.rylir had normal “relirf” of vast and WY-P propuly finished and ovoid in design. A. Clinical observation shows ulceration tx,ne:~ th rhr second 1)icuspid acrylic rrsin prmtic:. mild inflammation beneath the first molar gold pontic. and no tisjw rraction hvnwth thr swolld molar porcelain pontic. R, The biopsy of thr sr~ond hicuspitl wgion shows mild inflammation, ulceration, and a central area of necrosis. ( -.?I). i

of “saddled” design produced changes under 85 per cent of the pontics. The severity of the tissue change increased proportionately as the amount of scraping of the cast was increased (Fig. 7. A and Bii The combination of porcelain, gold, and acrylic resin facings in the same appliance was used as a control. The tissue changes found in this combination were the same as those found in pontics used individually (Table VIII and Fig, 8, A and B) .

Tissue

response

to denture

pontics

153

SUMMARY AND CONCLUSIONS This study demonstrates that the adaptation of a pontic to the ridge or the amount of “relief” (scraping of the cast) provided in the cast is highly significant and directly proportionate to the amount of unfavorable tissue change. Absolute minimal contact (0.0 to 0.25 mm. of cast scraping) produced no tissue change. When the cast scraping was increased to 1 mm., tissue changes were produced varying from mild inflammation to acute ulceration. Tissues respond dramatically to acrylic resin and, in a lesser degree, to gold alloy, which makes both these undesirable as tissue contacting materials. In order to maintain a completely healthy and hygienic condition for fixed partia1 dentures, the pontics must be constructed of highly glazed, high-fusing porcelain of an ovoid design with minimal adaptation to the tissue and properly reinforced with a gold alloy casting. I wish to express my appreciation to Colonel Carlos B. Harmon, D.D.S., for his guidance during the clinical part of this study and to Lieutenant Colonel Harvey Graham, M.D., for his aid in preparing and evaluating the histologic sections.

References 1. Allison, J. R., and Bhatia, H. L.: Tissue Changes Under Acrylic and Porcelain Pontics, J. D. Res. 37: 66-67, 1958 (abstr.). 2. Henry, P. J.: Investigation Into the Changes Occurring in the Oral Mucosa Beneath Fixed Bridge Pontics, thesis, Indiana University Library, 1963. 3. Podshadley, A. G., and Harrison, J. D.: Rat Connective Tissue Response to Pontic Materials, J. PROS. DENT. 16: 110-118, 1966. 4. Podshadley, A. G.: Gingival Response to Pontics, J. PROS. DENT. 19: 51-57, 1968. 5. Stein, R. S.: Pontic-Residual Ridge Relationship: A Research Report, J, PROS. DENT. 16: 251-285,

1966.

DENTAL UNIT FORT BENNING,

GA.

31905