Modification of Col Shape and Interproximal Area after Periodontal Surgery Associated with the Restorative Alveolar Interface (RAI) Technique. Histological Study in Dogs
Laura Bullamah STOLL1
Arthur Belém NOVAES2
Ruberval Armando LOPES3
1Department of Dental Materials and Prosthesis
2Department of Bucco-Maxillo-Facial Surgery and Traumatology and Periodontology
3Department of Morphology, Stomatology and Physiology
Faculty of Dentistry of Ribeirão Preto, University of São Paulo,
Ribeirão Preto, SP, Brazil
Correspondence: Dra. Laura Bullamah Stoll, Rua Álvares Cabral 1250, 14010-080 Ribeirão Preto, SP, Brasil. Tel: +55-16-625-2050 Fax: +55-16-636-6085. e-mail: lbstoll@ig.com.br
Braz Dent J (2001) 12(3): 147-153 ISSN 0103-6440
INTRODUCTION | MATERIAL AND METHODS | RESULTS | DISCUSSION | RESUMO | REFERENCES
The modification of the Col shape and position by the restorative alveolar
interface technique (RAI) was studied in the interproximal areas between
the mandibular first molars and fourth premolars of 10 dogs. Full thickness
flaps were raised to expose the interproximal root surface and alveolar bone
crest. The RAI procedure was performed only on the experimental sides and
the control areas were the opposite side of the same animal. The animals
were sacrificed at zero hour, 7, 14, 21 and 28 days for histological analyses.
Approximately 6.0-µm-thick sections were made in buccolingual and mesiodistal
directions and stained with hematoxylin-eosin and Mallory for light microscopy
analysis. A satisfactory healing process was observed up to the 14th and
21st days which showed a modified Col shape. At this time, an inflammatory
reaction developed affecting the evolution of the healing. The surgery had
probably created conditions for the installation of an inflammatory process
resulting from the modified anatomy of the interdental area.
Key Words: RAI, Col, periodontal surgery.
INTRODUCTION
A healthy coexistence between dental restorations and their surrounding periodontal
structures must be the objective of conscientious professionals. This ideal
inter-relation in the interproximal region is at times difficult to achieve.
When unfavorable situations exist, such as contact area between teeth, proximity
between roots, configuration of the interproximal gingiva, cleaning difficulties,
or location of restoration margins, this healthy coexistence is impossible
to be completely achieved. All treatments involving the interproximal region
must consider it as a whole and take into account the teeth and the gingival
tissue, as well as the inter-relation between them.
The subgingival location of restorations causes alterations in the deeper
periodontal tissues due to bacterial plaque retention in the setting area
(1-4). Margins of crowns should be placed in the most accessible position
for proper hygiene and as far as possible from the gingival sulcus base (5).
Restorative procedures should not be carried out in the presence of periodontal
disease nor should they cause irritation to the sub-sulcular anatomic structures
(2). The biological junction of the junctional epithelium to the teeth as
well as that of the supra-alveolar connective tissue must be preserved (6).
When teeth are too close, the interproximal areas present non-keratinous
epithelium and are more permeable to bacterial toxins. Whenever a restoration
is placed in such an area, all efforts must be made to make it more resistant
and healthier. Adequate preparation of the tooth must increase the interproximal
space, thus permitting the keratinization of the epithelium and creating
conditions for the effective control of bacterial plaque (7).
To make such procedures possible and meeting the previously cited requirements,
Ross and Garguilo (8) described the RAI (restorative alveolar interface)
technique for the modification of the interproximal area, which could create
the desired ideal conditions for the restoration of the tooth structure and
maintenance of periodontal health.
This technique is usually used for root separation in multiradicular teeth,
concavity reduction, correction of excessively close roots and in the idealization
of the tooth-alveolus relationship, thus improving the emergence profile
for future restoration (3,9,10).
The possible modifications of Col shape and position as well as those of
the interproximal tissues are analyzed after RAI surgery.
MATERIAL AND METHODS
Ten healthy adult male dogs of undefined breeds, weighing approximately 10
kg, with intact maxillary and mandibular teeth without malocclusion were
used.
Surgical Procedures
The animals were kept em jejum for 12 h prior to surgery. They were sedated
with iv thionembutal (2.5% solution; Abbott, São Paulo, SP) through
the cephalic vein. The animals were kept on spontaneous respiration and intubated
with an endotracheal tube.
The proximal region between the mandibular first molars and the fourth premolars,
whose contact areas were crowded and therefore appropriate for the RAI technique,
were used. In the experimental areas (right side), mucoperiosteal flaps were
made to expose the interproximal areas and root scaling and planning, osteotomy-osteoplasty
and the RAI technique were performed. The osteotomy and osteoplasty procedures
were carried out with chisels to reduce the interproximal bone crest by approximately
1.0 mm.
The RAI procedure was performed on each of the experimental sites with long
conic diamond high-speed drills with abundant irrigation, as recommended
by Ross and Garguilo (8). The movement in the root buccolingual proximal
direction and parallel to the long axis of the teeth created a straight emergence
profile in relation to the bone tissue. Root divergence was eliminated in
the cervical-occlusal direction, thus increasing the interproximal embrasure.
A sulcus was made with a #½ spherical drill on the interproximal surfaces
of the roots to establish a reference for histological analysis. The flap
was sutured back to its original position (4.0 silk thread, Ethicon Johnson
& Johnson, São José dos Campos, SP). The same surgical
procedures were performed in the control areas (left side) of the same animals.
The height of the interproximal bone septum was reduced and its shape was
modified, thus marking the root. RAI procedure was not carried out.
The animals received 1200 IU penicillin and 500 mg streptomycin (Laboratório
Fort Dodge, Campinas, SP) for 8 days. The healing process was evaluated weekly
and the sutures were removed after 7 days. The teeth were sprayed 3 times
a week with 0.12% chlorhexidine until the day the animals were sacrificed.
Histological Technique
The animals were sacrificed at zero hour, 7, 14, 21 and 28 days and separated
into two groups. Five of them were used for buccal-lingual sections and the
other five for mesiodistal sections. Their mandibles were dissected, immediately
fixed and decalcified. The blocks containing the samples were dehydrated,
embedded in paraffin and 6.0-µm thick sections were obtained, which
provided an integral view of the interproximal areas. The slides were stained
with hematoxylin/eosin and Mallory’s trichrome stain and examined with light
microscopy.
Morphometric Technique - Karyometry
The nuclear measurements of the basal, squamous and granular cells in the
epithelium of the interproximal gingival papilla (control), as well as those
of the epithelium in healing regions (14th and 21st days), were calculated
according to Sala et al. (11). The longest (D) and the shortest axis (d)
were measured in the drawing of each nucleus in order to estimate the following
nuclear parameters: mean geometric diameter, ratio D/d, volume (V), area
(A), ratio V/A, perimeter, shape factor, contour index and eccentricity.
Comparision of the results for the experimental and the control groups was
made by the nonparametric Mann-Whitney test (12).
RESULTS
Zero Hour - Control and Experimental Groups
The control and experimental areas had similar aspects at zero hour. The
surgical procedure that affected periodontal tissues was distinguished only
by the larger wearing of the tooth surface on the experimental side, which
resulted from the RAI technique. The general aspect of the injury showed
two gingival margins, buccal and lingual, with whole oral epithelium and
connective tissue. In the incision area, cut fibers and open blood vessels
were observed. In the mesial-distal plane there was a clot which thoroughly
covered the exposed bone surface and filled the notches and the space between
the gingival margins. This is typical of periodontal surgery with a total
flap.
Seven Days - Control
Suture removal and handling of the part during histological processing caused
the separation of the flap margins. The marginal gingiva epithelium was normal
and showed migration in order to cover the exposed connective tissue. It
was slightly concave in the interproximal area. There was a large clot in
the inner central area alternating with regions of granulation tissue that
covered the bone tissue in its initial healing phase (Figure
1A).
Seven Days - Experimental
The interproximal tissues were more organized than those in the control area.
The division between the original tissue of the buccal and lingual flaps
and the young tissue in the central area was more evident. The typical oral
mucosa epithelium was more advanced with differentiated migration towards
the central Col in order to keep its lining and superficial protection function
(Figure 1B). The Col region did not yet have lining epithelium either in
the control or in the experimental area. The connective tissue was exposed,
showing new organization (granulation tissue), dilated and congested vessels
and many inflammatory cells. The entire region was edematous.
Fourteen Days - Control
Healing developed satisfactorily and the epithelium of the Col area was recovered
with less extense stratification and concavity. The connective tissue had
a slight inflammatory reaction that is consistent with the interproximal
Col under normal conditions. It was integrated to the buccal and lingual
flaps, which demonstrates that the transition from granulation tissue to
connective tissue was complete. The bone septum medullary spaces were recovered.
The normality patterns were present in the mesiodistal plane. In the papilla
central areas, the epithelial tissue was not very thick, uniform, with few
circumvolutions, rectilinear in its basal portion and covered young connective
tissue that was not very dense and had slightly increased vascularization (Figure
1C).
Fourteen days - experimental
Despite some similarity to the control side, the quality of the epithelial
and connective tissues suggests that healing was slightly more advanced.
The sub-epithelial connective tissue was denser and more fibrous. The Col
central portion was less accentuated and had simple epithelium. A difference
between the quality of the connective tissue and that of the epithelium in
the flap area was still observed and identified the young tissues formed
during this period. This connective tissue was fibrous in the gingival papillae
and organization fibers could already be observed in the healing region.
There were inflammatory cells and edematous regions (Figure
1D). The surface
of the bone crest was more uniform, with less communication with the medullary
spaces. A periosteum and supra-alveolar transeptal fibers were being formed.
Twenty-one days - control
The central epithelial tissue was thin and continuous. The connective tissue
was more fibrous in deeper areas as well as in those close to the bone septum,
whose surface was relatively plane and showed recovery activity in normal
development. The most superficial cellular epithelial layers showed slight
scaling mixed with slight exudate, suggesting that the epithelium was undergoing
the beginning of a degeneration process due to inflammation (Figure
2A).
Twenty-one days - experimental
The tissue characteristics of the experimental side were similar to the control
side. The Col epithelial tissue was discontinuous and was thinner in some
areas and more stratified in others. The underlying connective tissue was
more cellular and more vascularized than in deeper areas. The external surface
of the epithelium was frayed in some sections where only the cell membranes
were visible. The healing connective tissue in the central area was less
edematous; however, the number of inflammatory cells was increasing. On the
whole, this region appeared to be more degenerated than the control side
and the epithelium was formed by looser cells. In these areas, the surface
of the epithelial tissue remained continuous; however, superficial cellular
scaling was accentuated (Figure 2B).
Twenty-eight days - control
The epithelium of the buccal and lingual papillae was normal with stratified
squamous keratotic epithelium characteristics. Towards the Col, epithelial
destruction and connective disorganization were generalized. The gingiva
had an intense inflammatory process. The Col epithelium, which was previously
recovered, was almost entirely eliminated, and was discontinuous and exposed
a connective tissue layer in which an inflammatory process predominated.
The absence of lining epithelial tissue led to the assumption that ulceration
or necrotizing gingivitis was taking place because of the characteristic
fibrinous pseudomembrane (Figure 2C).
Twenty-eight days - experimental
The general aspect was similar to the control side. There was destruction
of the connective tissue by an intense inflammatory process. The oral and
lingual epithelia were normal, thick and had the characteristic epithelial
projections of inflamed areas. Epithelium, however, was absent in the Col
area (Figure 2D). The main characteristics of the inflammatory process and
the destruction of the Col epithelium suggest that although the inflammatory
reaction was more restrained, it was intense enough to revert the healing
recovery process that had satisfactorily developed until the second week.
The general aspect of the healing region was that of an exposed injury with
degenerated and loose tissue, whose epithelium had recently been extracted,
probably by food mastication, since there had not been enough time for the
formation of the fibrinous pseudomembrane.
Morphometric Results
The morphometric results are reported in Table 1.
DISCUSSION
The reduction of dental tissues during crown preparation must be compatible
with the necessary thickness of the restorative material in use, thus leading
to a correct emergence profile between the restoration and the root portion
that emerges from the alveolus. The space created must be large enough to
accommodate the gingival tissues at the same time that it allows interdental
hygiene.
The RAI technique described by Ross and Garguilo (8) aims at modifying the
interproximal embrasure through root recontour by making it larger and thus
altering the root emergence profile in relation to the alveolus. It prevents
the onset of interproximal periodontal disease in the presence of prosthetic
restorations.
We observed the development of constant healing until the 14th day when interdental
tissue with thick connective tissue, normal vascularization and stratified
epithelium undergoing keratinization were formed. This evolution, marked
by slight alterations, continued until the 21st day. Col shape was modified,
became slightly concave and showed a smaller distance between its margins.
After this period, there was a complete inversion in the conditions with
the onset of an intense inflammatory process and the resulting destruction
of the histological aspect that had been previously observed, probably due
to the interference of external factors (bacterial plaque and food impaction).
The inflammatory process was typical of gingivitis and the increased interdental
space in the experimental area, where the RAI technique had been performed,
may have permitted a larger accumulation of food and bacterial plaque as
well as trauma due to food impaction, which caused a more accentuated inflammatory
response.
After 28 days, the inflammatory process compromised the healing of the soft
interproximal tissues in both the control and experimental sides. The epithelial
tissue was disorganized and interrupted, which left the subjacent connective
tissue exposed to the external environment.
Because there are no other studies similar to ours, it is not possible to
compare results in order to confirm or contradict them. We must admit that
in experimental studies in animals the interproximal region is more subject
to food retention, and needs intense hygienic care. Since the animals cannot
carry out cleaning, the total absence of hygiene causes consequences as those
observed in this study. The healing process of the interdental bone tissue
did not suffer alterations as had occurred with the epithelium and the suprajacent
connective tissue, thus with satisfactory development with increasingly more
accentuated organization in the medullary spaces.
Unpredicted factors resulting from the anatomic characteristics, such as:
experimental study in an interproximal area, interdental space opened by
the RAI technique and the embrasure vertically increased by osteotomy, would
have caused the formation of bacterial plaque, food retention and trauma
due to food impaction, thus fraying the upper layers of the epithelium and
partially or totally shattering it in the last two periods observed (21 and
28 days).
We suggest that in order to clinically achieve the Col transformation into
a saddle with keratinization of the interproximal epithelium, the space between
the teeth during application of the RAI technique should be increased even
more. A more aggressive osteotomy would be necessary to reach a region where
the roots might be more divergent, permitting an apical replacement of the
flaps with larger margin approximation and the resulting reduction of the
distance to be occupied by the interproximal gingival tissue.
The Col morphology found after 14 and 21 days indicates that the objective
of modifying it can be achieved through surgical techniques. The projection
of a healing development without interference suggests that in longer periods
with greater tissue maturation the ideal shape would certainly be achieved.
RESUMO
Stoll LB, Novaes AB, Lopes RA. Modificação da forma do col
e da área interproximal após cirurgia periodontal associada
à técnica de iar – interface alvéolo restauração.
Estudo histológico em cães. Braz Dent J 2001;12(3):147-153.
Foi avaliada a modificação da forma e posição
do Col das áreas interproximais entre os primeiros molares e quartos
pré-molares inferiores de 10 cães, utilizando-se a técnica
de IAR – Interface Alvéolo Restauração. Realizou-se
retalhos de espessura total para exposição da superfície
radicular interproximal e da crista óssea alveolar. Os procedimentos
de IAR foram realizados apenas nos lados experimentais e as áreas
controle foram os lados opostos dos mesmos animais. Os animais foram sacrificados
a zero hora, 7, 14, 21 e 28 dias para análises histológicas.
Secções de aproximadamente 6.0 µm de espessura foram
obtidas no sentido buco-lingual e mésio-distal, coradas com hematoxilina-eosina
e Mallory para análise em microscopia óptica. Uma cicatrização
satisfatória foi observada entre o 14o e 21o dia, evidenciando uma
modificação na forma do Col. A partir desse período,
desenvolveu-se uma reação inflamatória afetando a evolução
da cicatrização. A cirurgia provavelmente criou condições
para a instalação de um processo inflamatório, resultante
da modificação da anatomia da área interdental.
Unitermos: IAR (interface alvéolo restauração), col,
cirurgia periodontal.
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Accepted November 17, 1999
