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The increase with age of the width of attached gingiva


J.Ainamo and A.Talari


Department of Periodontology. Institute of Dentistry,
University of Helsinki, Heldinki, Finland


The purpose of the study was to determine the variation with age of the width of attached gingiva and the location of the mucogingival junction.


The material comprised orthopantomograms of 20 female dental students aged 20-30 years and 20 male and 20 female adults aged 39-51 years.


All the subjects had practically full dentitions and no supraerupted teeth.


The mucogingival junctions were revealed with Schiller's iodine solution and marked with short pieces of metal wire,
attached to the teeth and gingivae with Squibb's Orahesive Denral Bandage in the midline of the facial surface of each tooth.


The orthopantomograms were taken with the X-ray beam passing the horizontally positioned occlusal level at a -5°angle.


From the radiographs the distance from the cemento-enamel to the mucogingival junction was measured to the nearest millimeter separately for each tooth.


In the mandible also the distance from the mucogingival junction to the lower border of the jaw was assessed accordingly.


The results showed that the measured anatomical width of attached gingiva does not differ between sexes but also that it increases significantly with age.


The distance between the mucogingival junction and the lower border of the mandible did not increase with age.


It was concluded that the mucogingival junction remains at a probably enetically predetermined location white the teeth move in an occlusal direction through adalt life.


In the absence of concurrent retraction of the gingival margin this results in an increase of the width of attached ginigiva with advancing age.


( Received for publication Aug. 8, 1975, accepted Jan. 24, 1976 )


Introduction


In a healthy and intact periodontium the attaced gingiva extends from the level of the bottom of the gingival crevice coronally to the mucogingival junction apically (Bowers 1963, Ainamo & Loe 1966).


The width of the attached gingiva ranges between 1 and 9 mm and varies widely between different teeth and jaws (Ainamo & Loe 1966).


According to Lang & Loe (1972) a minimum of a 1 mm wide zone of attached gingiva is needed to preserve a healthy gingival margin.


Ainamo & Low (1966) found that the width of attached gingiva was the same in young adults with the gingival margin on enamel as in older patients whose gingival margin after retraction was located on the cementum.


This finding was at that time suggested to be a result of an apical migration with age of the mucogingival junction.


As there is no possibility to clinically determine the location and possible movements of the mucogingival junction in relation to fixed skeletal reference points within the jaws,
this suggestion has been shown that the location of the mucogingival junction is resistant to alterations by means od mucogingival surgery (Karring,Cumming & Loe 1973).


According to another hypothesis (Pietrokowski & Masslerb1967) ,
the mucogingival junction forms the border line between the genetically determined basal bone of the jaws and the alveolar processes,the growth of which is induced by the developing teeth (Ten Cate & Mills 1974).


Due to difficulties of measurement, this theory also remains unverified.


If it were true,
i.e. if the mucogingival junction would stay at a fixed location,
changes in the width of the attached gingiva might be the result of a shift of its coronal rather that its apical border.



In their clinical measurements both Bowers (1963) and Ainamo & Loe (1966)used the horizontal projection of the bottom of the gingival crevice or pocket as the coronal border of the attached gingiva.


Which means that the more there is of retraction of the gingival margin,
caused either by chronic periodontal disease or by trauma from toothbrushing,
the less is the width of the band of attached gingiva thus measured.


With no retraction, the attached gingiva of the older patients in the study by Ainamo & Loe (1966) would probably have been broader than that of the young adults.


Though relevant from a clinical point of view,
there seems to be no acientific justification for the use the bottom of the retracted gingival crevice as the coronal border of the anatomical attached gingiva (Ainamo & Talari 1975).


There is no biological evidence in favour of the theory of passive eruption as presented by Gottlieb & Orban (1938).


On the coutrary, the bottom of a healthy gingival pocket seems in human type of teeth to stay at the cementoenamel junction both at old age (Waerhang 1952, Loe & Listgarten 1973),
and during supraeruption of a tooth without antagonists (Anneroth & Ericsson 1967).


In the present study the width of the attached gingiva was measured from the cementoenamel to the mucogingival junction.


For determination also of the exact location of the mucogingival junction in relation to skeletal structures,
an orthopantomographc method (Talari, Kilpinen & Ainamo 1975,talari & Ainamo 1976) was used.


The principal objectives of the study were;


1. to study the variation with age of the anatomical width of the attached gingiza and


2. to determine whether the possible increase in its width is caused by an apical shift of the mucogingival or a coronal shift of the cementoenamel junction.
Material and Methods


The participants of the study were 20 male dental students aged 21_26 years (mean age 23,4±1,3 years),
20 female dental students aged 20_30 years (mean age 23,9±2,1 years) ,
20 adult males aged 39_48 years (mean age 43,6±3,8 years) and 20 adultbfemales aged 39_51 years (mean age 43,6±3,8 years).


All the participants had practically full dentitions,
a normal occlusion and no teeth supraerupted beyond the occlusal plane.


In each subject,
the mucogingival junction was revealed with Schiller's iodine solution and maeked,
separately at each tooth,
with a short piece of metal wire,
attached to the tooth and gingiva with a rectangular strip of Squibb's Orahesive Dental Bandage (Talari & Ainamo 1976).


An orthopantomogram was then taken with a _5 degree angulation of the X-ray beam towards the horizontally positioned occlusal plane (Talari et al. 1975).


A Biangulix Rapid (Siemens) X-ray tube,
an 0.3*0.3 mm focus,
a 70_75 kV anode a 15 sec. exposure time were applied.


The film used was an Agfa Gewaert Curix RP1 sized 15*30 cm and it was automatically debeloped in a Picker Pixamatic using Agfa Gevarct's Adefo developer and G 344 fixative.


From the orthopantomograms the distance between the mucogingival and the cementoenamel junctions was covered by deep approximal fillings or crowns,
were discarded.


Third molars were not included.


A total of 2122 readings were recorded,
i.e. a mean of 26 measurements per subject.


In a separate series of measurements the distance from the mandibular mucogingival janction to the lower border of the mandible was determined in the same manner to the nearest millimeter.


Similar measurements were attempted in the maxilla but discontinued for the present time due to the lack of a stable reference level comparable to that of the lower border od the mandible.


The recordings were processed at the Helsinki University Institute of Nuclear Physics on a Burrough 6700 computer.


As no differences were observed between the right and left sides of the jaws,
the data were bilaterally pooled for final analysis.


Results.


Comparisons were made between the two age groups (23 and 43 years)
and between sexs in both the younger and the older group.


As to the orthopantomographic width of attached gingiva there was no difference between sexes in either age group.


However, the older age group presented a wider zoon of attached gingiva than the group of students (Fig. 1).


This difference was statisically highly significant (P<0.001) separately for each one of the fourteen teeth examined and occurred both among males and females.


White the distance from the mandibular mucogingival junction to the lower border of the mandible did not vary with age (Fig.2),
this particular distance was found to be greater in males than females in both age groups (Fig.3).


Also this diference was statistically highly significant separately for each tooth measured (P<0.001).


Discussion


When interpreting the present results,
it must be born in mind taht orthopantomographic measurements are not identical with clinical assessments.



The enlargement of a vertical distance within the sharp image layer is about 32 % when the object is positioned perpendicular to tha X-ray beam (Tammisalo 1964).



In gingival measurements this enlargement decreases the more the gingival surface diviates from the vertical plane (Talari et al. 1975).


Due to the standard positioning of both the radiation source,
the object and the film,
the orthopantomographic method seems,
however, to offer a reproducibility which makes posible a comparison of there relative measures in suffuciently large materials (Talari & Ainamo 1976).




The results obtained with the between the mandibular mucogingival junction and the lower border of the manaible does not change with age (Fig. 2) seems to outrule the possibility that the mucogingival junction would shift apically (Aimano & Loe 1966),
and supports the view of Pietrokowski & Massler (1967) of a predetermined borferline between basal and alveolar bone.


The fact that the same distance is greater in males than infemales (Fig.3) could explain the more robust look of the male than female face.


The finding of no difference between sexes in the width of attached gingiva conforms to the report by Bowers (1963).


However, the orthopantomographic distance between the mucogingival and cementoenamel junctions was in the present study found to increase significantly with age (Fig. 1).



In case the location of the mucoigingival junction is atable,
the increase in the anatomical width of the attaachied gingiva (Fig.1) must be the result of a continuous shift through abult life of the cementoenamel junction.



It thus seems that the teech of adult humans,
like the teeth of most other mammals,
are subjected to a continuous eruption (Ainamo & Talari 1975).



That it really is the cementoenamel junction which shifts coronally and not the mucogingival junction and lower border of the mandible shifting apically,
has been demonstrated in a later study on supraerupted teeth (Talati, in preparation).



According to Murphy (1959) an eruption of the teeth during adult human life is necessary to comprensate for the progressive wear of the occlusal surfaces and incisal edges.


In Australian aborigines,
whose teeth are rapidly worn,
the height of the lower face does thus not essentially decrease with advancing age (Murphy 1959) .


In case the eruption of the teeth at adult age is not only a functional but also a genetically predetermined compensation for the wear of the teeth,
the same theory would imply that in the absence of wear the height of the lower face would increase with age.




Also this has been shown to be true.


The lower facial height,
as measured from the anterior nasal apine to the menton in prophile skull X-rays of adult western men,
shows a yearly increase of 0.37 mm (Thompson & Kendrick 1964 ).


Continuous eruption of the teeth is typical to several species of mammals.


The molar teeth of the guinea pig both grow,
erupt and wear continuously (Ainamo 1971) while the bovine molars continue to erupt out of their sockets after the growth period has ended,
and finally exfoliate at old age (Ainamo 1970).


Only in teeth of the human type the healthy gingiva and the alveolar bone follow the erupting tooth (Anneroth & Ericsson 1967, Loe & Listgarten 1973).


The genetically predetermined compensatory eruption of the teeth of adult humans thus
_ in the absence of concurrent retraction of the periodontal attachment _
seems to result in an increased width of attached gingiva with advancing age.




The clinical implications of this theory are presently subjected to experimental studies.
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