Palatal mucosa under dentures: A qualitative histologic and histochemical analysis

CHACONAS AND GONIDIS

REFERENCES

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4.

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6.

7.

8.

Broadbent BH: A new x-ray technique and its application to orthodontia. Angle Orthod 1:45, 1931. Hofrath H: Die bedeutung der roentgenfernund abstandsauf- nahme fur die diagnostik der kieteranomalien. Fortschr Orthod 1:232, 1931. Downs WB: Variations in facial relationships: Their significance in treatment and prognosis. Am J Orthod 34~812, 1948. Riedel RR: The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod 22142, 1952. Steiner CC: Cephalometrics for you and me. Am J Orthod 39:729, 1953.

Tweed CH: The Franfort mandibular incisor angle in orthodontic diagnosis, treatment planning, and prognosis. Angle Orthod 24121, 1954. Ricketts RM: A four-step method to distinguish orthodontic changes from normal growth. J Clin Orthod 9~208, 1975. Richetts RM: Role of cephalometrics in prosthetic diagnosis. J PROSTHET DENT 6~488, 1956.

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Nassif NJ: The relationship between the mandibular incisor and the lower lip. J PROSTHET DENT 24~483, 1970. L’Estrange PR, Vig PS: A comparative study of the occlusal plane in dentulous and edentulous subjects. J PROSTHET DENT 33:495,1975.

DiPietro GJ, Moergeli JR: Significance of the Frankfort mandibular plane angle to prosthodontics. J PROSTHET DENT 36:624, 1976.

Spyropoulos MN, Maragou-Papaioannou 0: Class II division 2 malocclusion. Odontostomatological Progress 38~173, 1984. Chaconas SJ: Orthodontics, ed 2. Boston, Bristol, London, 1982, Wright-PSG Inc.

Reprint requests to: DR. SPIRO J. CHACONAS UNIVERSITY OF CALIFORNIA SCHOOL OF DENTISTRY Los ANGELES, CA 90024

Palatal mucosa under dentures: A qualitative histologic and histochemical analysis

A. K. Sharma, B.D.S., M.D.S. (Born),* and F. D. Mirza, L.D.Sc., M.S.D. (Tufts)** Nair Hospital Dental College, Bombay, India

T o ensure the success of a prosthesis, the dentist has to capture and maintain the morphologic and histologic characteristics of the oral mucous membrane that is in close contact with the prosthesis. Prosthodontic literature about denture materials and occlusal problems is exten- sive but biologic research closely related to the oral mucous membrane is limited. The purpose of this study was to investigate histologically and histochemically the changes in the oral mucous membrane subjected to stress under complete dentures.

REVIEW OF LITERATURE

Since the work of Pendleton’ in 1951, it has been known that there is considerable regional variation in the oral mucosa of edentulous jaws. Therefore it is not surprising that when Ostlund2 examined palatal mucosa near the posterior border of maxillary dentures, he

*Former Registrar and Lecturer, Department of Prosthetics and Crown/Bridge.

**Professor and Head, Department of Prosthetics and Crown/ Bridge.

574

observed reduced thickness of keratinization and stratum corneum epidermidis whereas Kapur and Shklar3 examined mucosa of the alveolar crest and found increased keratinization and thick stratum corneum epidermidis.

Turck4 studied oral mucosa under partial dentures and observed few changes whereas Ostlund2 studied oral mucosa under complete dentures and reported significant changes.

Stansbury: Brinch,6 Mentz,’ Van &otter and Bouch- er,8 and Spreng and Haup19 obtained biopsy material from autopsies and reported conflicting results. Their findings could be the results of tissue changes occurring from rigor mortis or to disease that may have caused the death.

Ostlund,2 Langer,” Choudhary and Boucher,” Kydd and Mandley, l2 Philipsen and Fejejrskov,13 Picton and Wills,14 and Fleisch and Austinls made their studies on animals. The extent to which tissue changes in animals are representative of tissue changes in humans is subject to controversy. Moreover, different animals were used. The mucosa of a monkey is different from that of a dog

NOVEMBER 1986 VOLUME 56 NUMBER 5

ANALYSIS OF PALATAL MUCOSA UNDER DENTURES

Fig. 1. Schematic diagram of site of biopsy.

or a guinea pig. Therefore, these results could not give a true comparison of changes in the human oral mucosa.

Wright,“” Pendleton,’ Nyquist,16 Ostlund,2 Lytle,“, ‘* Jani and Bhargava, l9 Watson,” and Kydd et a1.2’ studied the oral mucosa under dentures in human subjects.

Wrightis” reported thickening of the stratum corneum epidcrmidis of oral mucosa under stress; the change was directly proportional to the stress applied.

Pendleton’ reported changes in mucosa as a form of injury. He observed that cornification and changes were found more in the deeper layers, with bone presenting evidence of resorption and repair.

Nyquist16 observed inflammatory change with marked edema in cell layers of epithelium under ill-fitting dentures.

Ostlund2 observed an increase in the overall thickness of the epithelium with reduction in thickness of the granulosum and corneum layers. Reduced mitotic activity in cells of epithelial layers, indicating more advanced injury, was observed.

Lytle “3 ‘a, 22 observed osteoclastic activity in the underlying bone when overlying mucosa was subjected to stress under ill-fitting dentures. Radiologic study showed evidence of osteoclasis, which disappeared after the dentures were discontinued for 6 months.

Jani and 13hargava19 observed increased keratinization and thickness of epithelium, both in the rete peg and interrete peg region.

Kydd et al.” observed that the oral mucosa behaves like the skin under similar conditions of stress.

METHOD AND MATERIAL

A total of 25 patients was selected for the study. The criteria for selection were as follows: (1) all

patients were edentulous, (2) ages ranged from 40 to 70

THE JOURNAL OF PROSTHETIC DENTISTRY

years, (3) no significance was attributed to the sex of the patient, (4) all patients were in good general health, (5) there was absence of pathology in the oral cavity, (6) the oral mucosa of all patients was clinically normal, and (7) all patients were willing to partake in the study.

The selected patients were then divided into two groups:

Group 1. The experimental group, with minimum denture experience of 6 months to a maximum of 10 years

Group ZZ. The control group, which had no denture experience but had been edentulous for a period ranging from 3 months to 6 years

A biopsy made with a biopsy punch 3 mm in diameter was obtained, from all patients, from the palate in the vicinity of the right first molar and second premolar, between the crest of the edentulous alveolar ridge and the midpalatine raphe (Fig. 1). The entire procedure was performed with the patient under local infiltration anesthesia with lidocaine (Xylocaine) 2% and adrenalin 1:80,000.

The biopsies were immediately placed in small auto- claved bottles containing 10% formalin as a fixer. After 24 hours they were embedded in paraffin and sections 5 p in thickness were obtained by routine laboratory procedures. The sections were then stained with (1) hematoxylin and eosin stain,23 (2) resorcinol fuchsin- Weighert method,23 and (3) one set was counterstained with Van Geison stain.23

The stained slides were then subjected to microscopic study for all groups.

OBSERVATION AND DIBCDSMMJ

Figs. 2 to 4 are of the control group. The slides of the experimental group showed marked changes, both in the

575

SHARMA AND MIRZA

Table I. Changes in epithelium

Slide number Stain Degree

Keratinization

Extent Type Thickness Constituent cell layers

Ortho 4-6 Layers Throughout covering the surface epithelium

Throughout Patchy

Para Para

Throughout Ortho + para

- Absent Absent

2-3 Layers 2-3 Layers

l-2 Layers

Absent

Absent Absent Absent

6 Patchy Para

Absent Absent

2-3 Layers

Absent

8 Absent

9 +t Throughout

10 + Throughout

11 + Throughout

Absent

Para

Para

Absent

Para

3-4 Layers

3-4 Layers

l-2 Layers



Patchy Para

Patchy Para

3-4 Layers

2-3 Layers

No change observed in any of the cell layers

10 Control slides H&E Consistantly present in all slides ++

Experimental 1 2

3

4

No change Change in corneum

and basale mitotic Crowding of germinal

and basal cells Single process of

downgrowth; marked basal cell proliferation

Marked basal cell proliferation; mitotic activity

Prominence of keratohyalin granules

Single process of epithelial downgrowth mitotic activity

Granular keratohyalin layer

Spinous cell layer more prominent

No change but marked mitotic activity

Spinous cell layer and corneum more prominent

Granular keratohyalin layer

Change in corneum and basale, marked mitotic activity

Marked basal cell proliferation

Change in corneum and basale; marked mitotic activity

+ +

-I-

5

7

12

13

14 +

15 +

H&E = Hematoxylin and eosin.

epithelium and connective tissue (Tables I and II). The changes were consistent (Figs. 5 to 7).

Keratinization was definitely of a parakeratinized variety. The corneum and basale layers showed high mitotic activity. Rete pegs were thin and elongated, exhibiting a “sawtooth” appearance (Fig. 5).

In regard to epithelial changes, the present study is in close agreement with Pendleton,l Ostlund,2 Spreng and Haupl: Lytle,‘7~‘*~22 Kydd and Mandley,12 Kydd et al.2’ and Watson.20

The findings are strikingly different from those of

Van Thei1,24 Kapur and Shklar,’ and Jani and Bhar- gava, l9 all of whom observed increased keratinization with denture wear. The findings are in sharp contrast with those of Kapur and Shklar’ who observed construc- tive tissue response to wearing dentures. The present study showed a detrimental tissue response.

The connective tissue of the experimental group on hematoxylin and eosin stain showed thin long papillae and marked chronic inflammatory exudate. The foci were mainly concentrated under the stressed epithelium or around blood vessels (Fig. 5). The collagen was

576 NOVEMBER 1986 VOLUME 56 NUMBER 5


Epithelial pearls Epithelial rete pegs Basement membrane Epithelial thickness

(qualitative)

Not present Short and truncated. Some areas flattened out

Not present I,

Short and blunt Short but thinned out

I Short but thinned out

n Shows down growth into connective tissue

Thinned out sawtooth appearance

Slightly visible

Thinned out Not seen

Shows downgrowth into connective tissue

Thinned out sawtooth appearance

Short and blunt

Short and blunt

Short but thinned out

Thinned out, sawtooth appearance

Thinned out, sawtooth appearance

I Thinned out long pegs

Short

arranged in an irregular nonspecific pattern, with a definite reduction in fiber content (Figs. 6 and 7).

The findings of the present study agree with those of Pendleton,’ Spreng and Haupl: Van Theil,24 Turck,4 and Kydd et al.21 regarding the presence of chronic inflammatory cells. However, we observed definite thin- ning out of the papillae, in contrast to their findings. Failure to bring out the basement membrane conspicu- ously may indicate decreased activity and hence low glycogen content. This could be the reason for decreased keratinization and that of the parakeratinized variety. Increase in epithelial thickness may be due to increased cellular activity in the corneum and basale layers.

Not markedly thickened, hence not visible

Not seen Not seen

Slightly visible

Discontinuous in area of downgrowth

Discontinuous in area of downgrowth

Not seen

Not seen

Not seen

Not seen

Not seen

Slightly visible

Slightly visible

Slightly visible

Normal Normal

Increased in parts

Increased in region of downgrowth

Increased

Reduced, but not uniform

Increased in region of downgrowth

Increased in parts

Increased in parts

Increased in parts

Increased in one area, reduced in another

Increased in parts

Increased

Increased

Increased

--.-

The histochemical findings of the present study are revealing. On staining with resorcinol and fuchsin, darkly staining fibers were evident in increased number, especially at sites where there was marked irregularity and decrease of ‘collagen. Inasmuch as resorcinol fuchsin stains only elastic or oxytalan fibers, these fibers were thought to be oxytalan fibers (Figs. 6 and 7).

The nature of the oxytalan fiber systems is not well understood. Fullme95*zs discovered and termed them as immature elastic fibers. Seivig29 believed them to be degenerating collagen. Goggim? interpreted them as neutral structures.

Edwards” postulated that an increase in oxytalan may

THE JOURNAL OF PROSTHETIC DENTISTRY 577

SHARMA AND MIRZA

Table II. Changes in connective tissue

Collagen fiber network

Slide number Stain Papillae

Inflammatory cells

Increased/ decreased Vascularity

Chronic inflam. cells around blood vessels, lymphocytes, macrophages, tissue histocytes

No increase or decrease seen; regular wavy arrangement

No proliferation; hence no increase

IO Control slides Short, with or without blood vessels, extending % thickness into epithelium

Experimental 1 Chronic inflam. cells

present No change No change

No change No change

Decreased; condensed more compactly

Condensed; decreased

Condensed; decreased Loss of wavy pattern

Condensed; decreased Irregular arrangement

Condensed; decreased Irregular arrangement

Condensed; decreased irregular arrangement

Edematous, esp. in superficial

part Dense;

condensed into coarse bundles

Dense; condensed into coarse bundles

Dense; condensed into coarse bundles

Condensed and reduced



Increased

H&E; resorcinol fuschin/Van Geison

I

Lengthened more than normal, extending into epithelium

Thinned out, extending H its thickness into epithelium

Thinned out, extending I% its thickness into epithelium

Short, blunt

2 Chronic inflam. cells beneath epithelium

3 ” Chronic inflam. cells beneath epithelium

4

5

Increased

Increased

Fairly increased around papillae

Fairly increased around papillae

Thin, long; shows intense vascularity

Thin, long Chronic cells beneath epith.

Slightly

Thin, long Marked increase around rete pegs

No change

K Elongated, shows Polymorphs and intense eosinophils also vascularity seen

” Elongated; shows intense vascularity

darked increase

,, Elongated; shows intense vascularity

Marked increase

Thin, elongated Chronic beneath epithelium

Increased

9 Increased

10

11

12

Increased

Slightly increased

Slightly increased

” Elongated; shows intense vascularity

Chronic beneath epithelium

13 I Short, blunt Marked increase Increased

Increased

Increased

14 ” Thin, elongated

15 v Thin, elongated

Marked increase

Marked increase

H&E = Hematoxylin and eosin.



--- .----. - -...---_____-_.

Oxytalan fiber system

Presence Increase

Few darkly staining -

fibers seen

Decrease

-

Relation of oxytalan to collagen

Mucous salivary glands

No change evident

Marked increase in dark staining fibers















++

++

++

+++

+++

++

+++

+t

tt

tt

tt

ttt

No relation observed No change

No relation observed

Decrease in collagen; increase in oxytalan



Decrease in collagen; increase i:n oxytalan



Decrease in collagen; increase in oxytaian




Chronic sialadenitis

No change

No change

No change

No change

No change

No change

No change

No change

No change

No change

ttt

ttt

t+t




No change

No change

No change


SHARMA AND MIRZA

indicate an “anchoring” effect that may prevent over- stretching of the tissues, preventing tearing and injury to the underlying sensitive connective tissue. Boese32 was of the same opinion. Hurst3” thought that the fibers were responsible for the initial healing process. Sims34*35 suggested that oxytalan fibers are responsible for regu- lating vascular flow.

contrast to what is expected. This abnormal behavior of the connective tissue is probably a reaction to the changes in epithelium. As a result of reduction in keratinization, a highly resistant and protective layer, the connective tissue exhibits altered metabolism and function.

The present study agreed with the findings of Fullm- er 25-28 Edwards,” Hurst,33 Sims,34x 35 and Boese32 regard- , ing the relationship of oxytalan to stress. Oxytalan fibers were found to increase in regions where there was increased stress with irregular arrangement of collagen.

We hypothesize that connective tissue takes up a more dominant role of protection and absorption of stress, a role hitherto fulfilled by the epithelium. Thus stresses exerted by dentures on connective tissues are prevented from reaching the bone where they could cause resorption.

One of the most important age changes of palatal mucosa is a tendency to become more fibrous and less cellular, along with marked reduction in the elastic fibrin network of connective tissue. However, the slides of the experimental group, when stained by resorcinol fuchsin and counterstained by Van Geison stain, showed an increase in the elastic oxytalan fiber network (Figs. 6 and 7). This finding is in sharp contrast to what is expected in aging connective tissue. Hence it is hypothe- sized that this abnormal behavior of the connective tissue under dentures could be a reaction to changes in epithelium.

We therefore feel that denture wear not only results in change within the epithelium, but in an equally significant reaction of the connective tissue. This reaction results in the appearance of a highly resistant and elastic oxytalan fiber system, which assists the connective tissue to react successfully to the stresses exerted on it.

We acknowledge the assistance of Dr. U. M. Wagholikar, Professor and Head, Department of Pathology, Grant Medical College, Bom- bay, and Mr. M. M. Saste, Department of Pathology, Nair Hospital Dental College.

REFERENCES

1. Pendleton EG: Changes in denture supporting tissue. J Am Dent Assoc 421, 1951.

2.

Because of reduction in the keratinized layer, which is highly protective, the connective tissue exhibits altered metabolism and function and thus takes up the more dominant role of protection and absorbing stresses exerted by dentures. Thus, stresses that would lead to bone resorption are prevented from being exerted on the underlying bone.

Ostlund SG: Effects of complete dentures on gum tissue. A histological/histopathological investigation. Acta Odontol Stand l&l, 1958.

3. Kapur K, Shklar G: Effects of a power device for oral physio- therapy on mucosa of endentulous ridges. J PROSTHET DENT

12762, 1962. 4.

5.

We therefore submit that denture wear not only results in reduced keratinization and marked cellular activity, but an equally significant reaction of the connective tissue. This results in the production of elastic oxytalan fibers, which assists the connective tissue to deal with the stresses exerted on it.

Turck D: A histologic comparison of edentulous denture and nondenture bearing areas. J PROSTHET DENT 15419, 1965.

Stansbury C J: Tissue changes under dentures. J Am Dent Assoc 15:349, 1928.

6. 7.

8.

9.

SUMMARY AND CONCLUSIONS 10.

These histologic observations of the epithelium and connective tissue are in close agreement with a host of earlier workers. The striking feature is an increase in thickness of epithelium due to an increase in constituent cell layers, but a decrease in keratinization, with keratin mainly of the parakeratinized variety. There is a definite reduction of collagen fiber network in regions of stress where the fibers present an ‘irregular arrangement in contrast to the normal wavy pattern. Marked chronic inflammatory exudate is also seen.

11.

Brinch 0: Acta Odontol Stand 16:1, 1958. Menta E: In Sharry, JJ: Complete Denture Prosthodontics, ed 3. New York, 1974, McGraw-Hill Book Co, p 21. Van Scatter DE, Boucher LJ: Effect of denture base materials on stratum corneum. J PROSTHET DENT 15:45, 1965.

Spreng M, Haupl K: Histological observations of soft tissues under dentures. J PROSTHET DENT 1:720, 1951.

Langer H: The unfavourable effect of acrylic dentures on oral mucous membrane. Dent Abstr 6:201, 1961. Choudhary SC, Boucher LJ: Histological response of stratum corneum to denture base materials. J Am Dent Assoc 36:3, 1964.

12.

13.

14.

15.

Histochemical investigation of the connective tissue under dentures revealed the presence of a highly elastic and resistant oxytalan fiber network, especially in regions that showed a reduction in collagen fibers. Thus the connective tissue response under dentures is in sharp

15a

16.

Kydd WL, Mandley J: The stiffness of palatal mucoperiosteum. J PROSTHET DENT l&116, 1967. Philipsen HP, Fejejrskov 0: Normal histology and the effect of acute mechanical stress on the esophagus epithelium of guinea pigs. Acta Odontol Stand 31:201, 1973. Picton DCA, Wills WIR: Viscoelastic properties of periodontal ligament and mucous membrane. J PROSTHET DENT 40:263,1978.

Fleisch L, Austin JC: A histological study of response of masticatory and lining mucosa to mechanical loading in ververt monkeys. J PROSTHET DENT 39:211, 1978.

Wright HH: Morphological changes in oral mucous membranes covering edentulous areas of alveolar process in humans. J Dent Res 13~159, 1933. Nyquist G: A study of denture sore mouth. Acta Odontol Stand lo:l, 1952.



Fig. 2. Flattened epithelial connective tissue junction. Minimal mitotic activity, wavy collagen arrangement, minimal inflammatory exudate. (Hematoxylin and eosin stair; magnification x 250.) Fig. 3. Connective tissue with scant darkly staining oxytalan fibers. (Resorcinol fuchsin stain; magnification X 250.) Fig. 4. Collagen-stained light brown, wavy pattern; darkly staining oxytalan fibers not seen. (Resorcinol fuchsin stain, Van Geison counterstain; ma:gnification X 250.) Fig. 5. Marked basal cell activity, including mitotic activity, inflammatory exudate, irregular collagen arrangement with decrease. (Hematoxylin and eosin stain; magnification X 250.) Fig. 6. Connective tissue shows darkly staining oxytalan fibers in irregular arrangement. (Resorcinol fuchsin stain; magnification X 250.) Fig. 7. Reduced irregular collagen. Light brown, darkly staining oxytalan fibers increased. (Resorcinol fuchsin stain, Van Geison counterstain; magnification X 400.)


SHARMA AND MIRZA

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

Lytle RB: Management of abused oral tissues under complete dentures. J PROSTHET DENT 7~27, 1957. Lytle RB: Complete denture construction based on study of deformation of underlying soft tissues. J PROSTHET DENT 9:539, 1959. Jani RM, Bhargava K: A histologic comparison of palatal mucosa before and after wearing complete dentures. J PROSTHET DENT 51:1183, 1972. Watson IB: The effect of complete dentures on oral mucosa. J Dent 6~171, 1978. Kydd WL, Daly CH, Wheeler JB: Thickness measurements of masticatory mucosa. Int Dent J 21:430, 1971. Lytle RB: Soft tissue displacement beneath removable partial and complete dentures. J PROSTHET DENT 1234, 1962. McManus, Mowry RW: Staining Technique and Staining Methods. New York, 1960, Paul B. Hocber Inc. Van Theil H: Alterations in tissues underlying complete dentures. Int Dent J 10~518, 1960. Fullmer HM: The oxytalan fibre-A previously undescribed fibre. J Histochem/Cytochem 6~425, 1958. Fullmer HM: Observations on development of oxytalan libres in periodontal ligament of man. J Dent Res 38~510, 1959. Fullmer HM: Comparative histochemical study of oxytalan, elastic and pre-elastic connective tissue libres. J Histochem/ Cytochem 8:290, 1960.


28.

29.

30.

31.

32.

33.

34.

35.

Fullmer HM: Observations on development of oxytalan fibres in dental granulomas and radicular cysts. Arch Pathol 70~59, 1960. Selving: Non-banded fibrils of collagenous nature in periodon- tium of man. JPR 3:169, 1968. Goggins HF: The distribution of oxytalan tibres in the periodontal ligament of deciduous teeth. Periodontics 4~182, 1966. Edwards JG: Study of periodontal ligament during orthodontic rotation of teeth. Am J Orthod 54:441, 1968. Boese LR: Increased stability of orthodontically rotated teeth following gingivectomy. AJO 56:273, 1969. Hurst RV: Regeneration of connective tissue fibres after auto- grafts in Rhesus monkeys-A qualitative approach. J Dent Res 51:1183, 1972. Sims MR: Oxytalan fibre system in molars of mouse mandibles. J Dent Res 52797, 1972. Sims MR: Oxytalan vascular relationship of periodontal ligament of man and mouse. Arch Biol 20~713, 1975.

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Palatal mucosa under dentures: A qualitative histologic and histochemical analysis

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