Oral Pathology

Histologie survey of the frena of the oral cavityRidley O. Ross* / Frederic H. Brown** / Glen D. Houston***

The literature shows an apparent lack of agreement concerning the histologie morphol-ogy of the frena of the oral cavity, particularly relating to the presence or absence ofskeletal or striated muscle. The purpose of this study was to do a histologie retrospec-tive analysis of 40 oral frenal biopsy specimens. The results of the study showed thatapproximately 37.5% of the frena investigated contained skeletal or striated muscle.(Quintessence Int 1990.21:233-237.)

Introduction

Clinicians have observed the apparent presence ofskeletal muscle during mucogingival surgery, espe-cially when frena are removed. But there appears tobe disagreement in the literature concerning the his-tologie morphology of frena, partieularly relating tothe presenee or absence of muscle.

Edwards and Boueher' found no muselé assoeiatedwith the maxillary or mandibular labtal frena. Theydescribed the maxillary and mandibular buccal frenaas folds of mucous membrane covering the caninus(levator anguh oris) and triangularis (depressor anguhoris) muscles, respectively. Likewise, they deseribed themandibular hngual frenum as a mucous membraneoverlying the genioglossus muselé.

* General Dentistij Resident, United States Air Force MedicaiCenter Keesler. Keesier Air t-arce Base, Mississippi.

** Chairman. Department of Periodontics, United States AirForce Medical Center Keesler.

" * Chairman, Department of Oral Pathology, United Stales AtrForce Medical Center Keesler.

Address all correspondence to Frederic H. Brown, Lt Col. USAF,DC, Chief of Periodontics, 3i3th Medical Group. Kadena Air Base,Japan, PSC # !, Box 21252, APO San Francisco 96230.

This article is a work of the United States government and may bereprinted without permission. The opinions or assertions containedherein are the private views of the authors and are not to be con-strued as ofïïcial or as reflecting the views of the Department of theAir Force or any other department or agency of the United Statesgovernment.

Sicher and du BruF deserihed the maxillary labialfrenum as "a persistence of the teetclabial frenum,"whieh connects the incisive papilla to the tubercle ofthe upper lip. The failure of the frenum to migrateapically during development has been imphcated as acausative faetor in the persistence of midline diaste-mata. Both the orthodontic and pedodontic literaturestate that most midline diastemata elose after theeruption of the maxillary lateral incisors and can-ines.̂ "" Frenectomies performed without prior ortho-dontic closure could result in the formation of searsbetween the central incisors. This could result in re-sistance to mesial movement by natural or orthodonticforces.'' Edwards' states, "there is also genera! agree-ment among practitioners that orthodontic closure ofdiastemas, which were presumably caused by abnor-mal frenal tissues, without the subsequent surgical ex-cision of the frenuins (sie) very often results in a re-lapse separation of the teeth after removal of the or-thodontic retaining applianees.'"

Frena become a problem when their attachment istoo close to the marginal gingiva. Pull by frena on ahealthy gingival margin, especially associated withminimal to no attached tissue, could lead to an ac-cumulation of irritants, inflammation, and eventualgingival recession. Also, pull through the frenum,transmitted by the retraction or stretching of the lipor cheek, may further aggravate the severity of a peri-odontal pocket by deflection of its wall. Posttreatmenthealing may also be delayed, or the pull may preventclose adaptation of the gingiva and lead to pocketformation. A large frenum may even interfere withproper toothbrushing."^'^

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Oral Pathoiogy

Frena attached near the crest of an edentulous ridgecan interfere with peripheral dentnre border extension,denture retention, and peripheral seal. Frena can he asource of chronic irritation causing a particular prob-lem with healing.'"*

As stated earlier, disagreement exists concerning thepresence or absence of skeletal tnuscle tissue withinfrena of the oral cavity. Most literature has concen-trated on the maxillary labial frenum. Knox andYoung'̂ reported muscle fibers along with collagenand elasttc fibers and that the muscle originated fromthe orbicularis oris. Archer"' described the anatotnyof broad, heavy maxillary labial frena as being com-posed of hypertrophied depressor septi muscle fusedwith dense collagenous tissue whose origin is the in-terproximal space between the central incisors andwhose fibers fan out and become interwoven with theorbicularis oris muscle. Other authors have substan-tiated the presence of muscle fibers in the maxillarylabial frenum'""'^'' as well as other oral frena.'"-'" Incontradiction, several other researchers and authorsconcluded that no muscle is present either in the max-illary labial frenum-''"" or any other frena of the oralcavity.-'''' Henry et al-" studied only the maxillary labialfrenum and found no muscle tissue present. Theyfound no microscopic differences between an abnor-mal or aberrant frenum and a frenum of a more "nor-mal" configuration. They believed "the destructivecapacity of the displaced frenum is apparently dueentirely to its elastic and collagenous components andnot a result of direct muscle tension."" Sadeghi et al-'studied 15 hyperplastic maxillary anterior frena. Theirspecimens were divided into a gingival side and a ves-tibular side for examination. Striated muscle fiberswere found in the vestibular section of only one spec-imen. None of the specimens revealed muscle fibers inthe gingival side. Their study did reveal calcificationand ossification associated with high levels of inflam-matory infiltrates and reactive connective tissue. Thesefindings, they believed, confirmed "the fact that hy-perpiastic freni (sic) are constantly irritated by factorssuch as microbial populations and muscular activityof the lip and are traumatized by personal oral hygieneprocedures and incising of food." They advocated theremoval of these hyperplastic frena, regardless of thepresence or absence of muscle tissue, to improveplaque control.

The purpose of this retrospective study was to ex-amine the histologie features of frena and to investi-gate the presence or absence of skeletal (striated) mus-cle.

Method and materials

Forty biopsy specimens were studied from a group offrena on file at the Oral Pathology Service, Keesler,Air Force Base, Mississippi. These biopsies were fromtissue submitted for histologie ex;iminations as partof routine mucogingival surgery.

All specimens had been placed in 10% buffered for-malin before preparation. They were embedded in par-afin, and sectioned at a thickness of approximately7 |im. Three levels or step-cuts were taken from prox-imal to distal ends. Fach section was further dividedinto three serial seetions with representative cuts madeon each outer end and central area. Specimens werestained with hematoxylin and eosin, and selected slideswere stained with Masson's trichrome.

The slides were inspected critically by three inves-tigators using a multiviewing position microscope atx40, X 100, and x200power. Observation of thedataresulted in a consensus of the three investigators con-cerning the histology of the specimens.

Results

The forty specimens were obtained from nine differentpractitioners, who removed frena in association withvarious surgical procedures. They were submittedfrom all anatomic locations of the oral cavity exceptthe mandibular lingual area. Epithelium, nerve, andconnective tissue were all found to be components ofthe frena; skeletal (striated) muscle was evident in apercentage of the specimens.

Epithelium

Both orthokeratinized and parakeratinized stratifiedsquamous cpithelia were observed. Extensions of theepithelial rete pegs or rete ridges into the underlyingconnective tissue were evident in several specimens.Melanin granules were noted in the basal cell layer.

Connective tissue

The lamina propria showed varying degrees of bothloose and dense connective tissue components. Col-lagenous fibers and fibrocytes were the predominantcomponents observed.

Adipose tissue, with its distinctive histologie ap-pearance (sometimes described as "chicken wire")could be seen in several specimens.

Blood vessels containing red blood cells were prev-

234 Quintessence International Volume 21, Number 3/1990

Oral Pathology

aient throughout the connective tissue, and smoothmnscle cells were associated with many of these struc-tures.

Several specimens revealed minor salivary glandstrnctures showing predominantly mucous-produeingacini.

Peripheral nerve cells were usually associated with theneurovascular bundles found within the connective tis-sne proper.

Table I Distribution of muscle

Area

Mandibular labialMandibular bucealMaxillary labialMaxillary buceal

Total

No.

133

213

4Ü

Muscle

4281

15

%

30.866,738.133,3

37.5

Muscle

Skeletal (striated) muscle fibers were found in ap-proximately one third of all specimens studied. Table 1summarizes the data on the various percentages ofstriated mnscle found, according to anatomic loca-tion.

Discussion

The results of this study did not disagree with theepithelium, nerve fiber distribution, or connective tis-sue components reported by previous authors.'""-'Also, no specific calcified material could be demon-strated, in agreement witb the findings of Sadeghi etal,-' A lack of agreement does exist concerning thepresence of skeletal (striated) muscle.

All histologie features were examined and recordedfrom the middle group of trisected specimens. Becausethe biopsies were not tagged to identify the proximaland distal ends, no attempt was made to identify thegingival side or vestibular side, as had been done ina previous study.-'

Henry et aF" concluded that the presence of striatedmuscle reported by other investigators might be dueto generously excised specimens, Sadeghi et al-' foundmuscle in one specimen and thought that the musclefibers were deeply located and related to the musclesof the upper lip. The muscle found in the present studywas within 2 to 3 mm of the outer surface of the ep-ithelium, u.sually immediately below the lamina pro-pria. The studies by Henry et aP" and Sadeghi et a!''focused on the maxillary labial frenum (11 and 15specimens, respectively). Although the present studyreviewed 40 specimens, 21 were from the maxillarylabial area. Table 1 shows eight positive findings ofskeletal (striated) muscle. This positive Unding of38,1% corresponds closely with the overall positive

finding of 37,5% of all frena reviewed, Al,w. the frenain this study were removed by nine different practi-tioners, not for the specific purpose of identifying skel-etal muscle, but to satisfy a particular surgical pro-cedure. Five of the nine dentists showed a positivefinding of striated muscle in their submitted samples.

Histologie evidence of skeletal (striated) muscle canbe seen in Figs 1 to 3. which show different amountsof muscle found within representative specimens takenfrom the maxillary labial and buccal areas and thetnandibular labial frenum. Skeletal muscle was foundbetween 2 and 3 mm of tbe outer surface of the epi-thelium. Fig 2a shows that Masson's trichrome is ableto discern the presence of skeletal (striated) muscleeasily.

The results of this study showed 37,5% of all frenaexamined to have a positive finding of skeletal (striat-ed) muscle. This contradicts other reports on allfrena,"" and especially the maxillary labial fren-um,•*•"*•-"•-' that state that no muscle is present.

If approximately one third of all frena contain skel-etal (striated) muscle, this eould explain several of theproblems associated with frena; that is, the possibledestructive nature of tbe frenum is not necessarily aresult of its clastic and coUagenous components, asstated by Henry et al.-" Several of tbese problems, sucbas persistence of midline diastetnata, pull on minimalattached gingiva leading to gingival recession, aggra-vation of periodontal pockets, and interference withtoothbrushing and prostheses, have been discussedpreviously, A possible follow-up study could be to tryto correlate these problems with the histologie evi-dence of the presence of skeletal (striated) muscle.

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Oral Pathology

Fig 1 Maxiliary iabiai frenum showing rete ridges (R),dense connective tissue proper (ct). blood vessels (V), andskeletal (striatedl muscie (M). Note peripheral nuclei ofmuscular bundles. (Original magnification x 100.)

Fig 2a Maxillary buceal frenum showing orthokeratinizedstratified squamous epitheiium (E), melanin granules (g),adipose tissue fa), minor salivary giand (s), and skeietal(striated) muscle fíM/ stained with Masson's trichrome.(Original magnitication x40.¡

Fig2t) Same buceai trenum as in Fig 2a, stained withhemotoxylin and eosin. Note nuclei (arrows) on peripheryot muscie bundles (M) and minor salivary gland (s). (Orig-inal magnilieation x200.)

Fig 3 Mandibular labial frenum showing evidence of skel-etal (striated) muscle (M). (Original magnification x 100.)

Summary

Histologie examination was performed on 40 frenalbiopsy specimens that were on file at the Oral Pa-thology Service at Keesler Air Force Base, in Missis-sippi. This retrospective study centered around thepresence or absence of skeletal (striated) muscle. Thefrena showed epithelium, connective tissue proper,

nerve tissue, and varying degrees of striated muscle.Of the 40 specimens studied, 15 (37.5%) showed evi-dence of skeletal (striated) muscle.

Acknowledgment

The authors thank Colonel Kenneth Stoffers for his constructivecriticism of this manuscript

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Oral Pathology

References

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17 Bisnoff HL: The frenum labium. Dem Outlook 1944;31:146-147.18. Shirazy E: The frenum labii superions, J Am Dent As.mc

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