Connective tissue papillae of the gingiva

In the free gingiva, connective tissue
papillae were slender and pointed (type I) (Figs.
4a, d and g). They were 20 to 60 µm wide and100 to 200 µm high. They were distributed at adensity of 200 to 300/mm2. Their height wasreduced the farther they were from the free gin-

gival margin, and the tips tended to exhibit
bifurcation and twisting. In the molar region,
the papillae were arranged in an parallel array
along the gingival margin (Fig. 4g).
In the attached gingiva, the papillae wereshort and branched, showing a bud-like appear-adgbehcfiFig. 4. Connective tissue papillae of the gingiva of the lower jaw prepared by the NaOH maceration method.
a–c: incisor region, d–f: canine region, g–i: molar region. c, f, i: alveolar mucosa, b, e, h: attached gingiva, a,d, g: free gingiva. a–i: × 60.

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T. Yura et al.

specimen preparation methods have beendeveloped, by which an epithelial layer ismechanically peeled off (Klein-Szanto andSchroeder, 1977; Ooya and Tooya, 1981). Other
preparation methods using chemical digestion
have offered good results in cleaving the interface (Scaletta and Maccallum, 1974; TakahashiIwanaga and Fujita, 1986; Kobayashi, 1990;
Ushiki and Murakumo, 1991; Inoué and Gabella,1992). At first, we applied the 6 N NaOH digestion method (Inoué and Gabella, 1992) to thegingiva, but the ultrastructural preservation ofthe connective tissue papillae was unsatisfactory as shown in Fig. 1. In contrast, the 2N NaOH
maceration technique (Ohtani et al., 1988) offered good results in the preservation of connective tissue papillae (Figs. 2 to 4).
The three-dimensional architecture of theconnective tissue papillae of the human gingiva
has also been examined by the reconstructionof paraffin sections using light microscopy(Karring and Löe, 1970; Löe and Karring, 1971).
Karring and Löe (1970) have classified the connective tissue papillae into two types: “papillae” and “ridges”. They are identical to types I
and III in this study, respectively. But since thewax remodeling technique was insufficient inreconstructing ultrastructures, the short type II
papillae would not have been recognizable.
In the human epidermis, essential changes
occur at an advanced age: a thinning of the epidermis and a reduction in the height and numberof epidermal ridges (Hill and Montgomery,1940). However, in the gingiva, the height ofepithelial ridges increases with age (Wentz etal., 1952). According to Löe and Karring (1971),
distinct differences exist in the morphology ofthe epithelium-connective tissue interface ofthe gingiva between young and old individuals.
They described that the essential age change ofthe epithelium-connective tissue interface is theconversion of the connective tissue “ridges” to“papillae”. According to the present SEM
study, the connective tissue papillae were slender and pointed at the tip in the free gingiva(type I). They were gradually reduced in height
towards the attached gingiva and the tip becamerounded (type II). In the alveolar mucosa, theconnective papillae became flattened (type III).

ance (type II) except for those in the molar
region (Figs. 4b, e and h). They measured 30 to100 µm wide and 50 to 120 µm high and were
distributed at the density of 80 to 120/mm2. In
the incisor region, type II papillae tended to bearranged in rows perpendicular to the gingival
margin (Fig. 4b). In the canine region, type I
papillae were mixed with type II papillae (Fig.
4e). In the molar region, neither type I nor typeII papillae were visible, but fork-shaped type III
papillae were observed (Fig. 4h).
In the alveolar mucosa, type III connective
tissue papillae were scattered on a relatively
smooth epithelium-connective tissue interface(Figs. 4c, f and i). The papillae showed a platelike appearance whose tips were forked into
several tips, showing a fork-appearance as awhole. The type III papillae tended to be arranged in rows. The basal portion of the papillae measured 10 × 120 µm. The height of thepapillae ranged from 50 to 250 µm. The densityof the papillae was almost the same among theincisor, canine and molar regions (40–60/mm2).
Small openings were often visible among
the connective tissue papillae in the free gingiva(Figs. 4a, d and g) and attached gingiva in theincisor (Fig. 4b) and canine regions. They measured 10 to 30 µm in diameter. They were mostfrequently observed in the attached gingiva of
the canine region (60 to 70/mm2). In the otherregions, the density of the opening was 30 to 40/mm2. Larger openings, surrounded by the elevation of the papillae, were observed in the freegingiva of the canine region, showing flowerlike configurations (Fig. 4d). They measured
110 to 130 µm in diameter.

Discussion
The interface between the epithelium and lamina propria, lined by a sheet of the basal lamina,
is an important place from the viewpoint ofmaterial exchange and invasion of cancer cells(Barsky et al., 1983; Ishikura, 1995). Since thebasal lamina firmly connects the basal epithelial
surface with the superficial surface of the lamina propria, it is generally difficult to observe theepithelium-connective tissue interface. Several
44

Connective tissue papillae of the gingiva

Considering the findings of Löe and Karring(1971), it is reasonable to assume that all partsof the connective tissue papillae in the free gingiva show type I, because the materials used inthis study were obtained from old individuals.
Klein-Szanto and Schroeder (1977) examined the connective tissue papillae of thealveolar mucosa and attached gingiva in themolar region by SEM. Their findings including
their morphometric data are almost identical tothose obtained in this study. They also studied
various part of the oral mucosa, and found thatthe number of papillae in the oral floor was thelowest in the oral cavity. They considered thatthe development of the papillae was closely
related to the contact with food. The interaction
between the gingiva and food is more intimate
in the free gingiva than the attached gingiva andalveolar mucosa. The high density of the pointed papillae (type I) in the free gingiva may beconcerned with such interaction. Anotherfactor influencing the number and height of thepapillae is dental plaque and dental calculus.
When this plaque and calculus exist around theteeth, inflammation may occur in the free gingiva. Since papillae contain lots of capillaries,
it is reasonable to assume that the elongated papillae of type I are intensively distributed in thefree gingiva.
The present SEM study clearly demonstrated the presence of small openings in the upperand lower incisor and canine regions. Suchopenings have not been reported in previous
SEM studies to the best of our knowledge. Although they appeared as openings in the glandular ducts (Moss-Salentijn and Applebaunm;1972), the diameters of the ducts must havebeen much larger (over 50 µm) than those observed in this study (10–30 µm). Another possibility for the pores is that they are structuresassociated with small depressions referred to as
stipplings. The stipplings occurred in young
adults and were restricted to the attachedgingiva (Orban, 1948; Rosenberg and Massler,1967), ranging from 100 to 400 µm in width and
30 to 500 µm in depth (Rosenberg and Massler,1967), and are limited to only the epitheliallayer (Orban, 1948). Judging from the size andlocation, it is obvious that the openings observ-

ed in this study are not directly related to thestipplings. Although the functional significance of the openings remains unknown at present, it would be interesting in a further study to
see whether the openings occur in young individuals or not. If not, they may be concernedwith the retrogressive change of the gingiva.
Further studies including transmission electron
microscopic studies are expected.

Acknowledgments: We express our sincere thanks toProf. K. Ryoke, Dept. of Oral and Maxillofacial
Surgery, Faculty of Medicine, Tottori University for
his useful advice and support for this study. We arealso grateful to Prof. M. Mihara, Dept. of Dermatology, Faculty of Medicine, Tottori University forreading this manuscript.

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(Received December 21, 1999, Accepted January 6, 2000)

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