THE HISTOLOGICAL STUDY OF MONKEY
(1985)
STUDIO HISTOLOGICO EN MANDIBULAS DE MONOS DEL NUEVO MUNDO

CON IMPLANTES ENDOOSEOS TORNILLOS TITANIO DE GARBACCIO

( 31 meses )

AUTORES: Oscar Sarnachiaro - Oscar Bonal - Eleodoro Grato Bur - Angel Vaamonde

 
 
 
INTRODUCTION

With the purpose of establish the potential utility of the new method of dental implant, we are studying and analysing the reactions and changes of the peripheral tissue and reconstruction process of the bone structures. We have needed more than 10 years researching to describe the physiological condition of the implant retention by meanings of the experimental phase. The object of this study is to show the results of the Garbaccio's screw method, offering in its future evolution through the morphological results obtained after 31 months of activity.

MATERIALS AND METHODS

The surgical procedures developed in this experience are made according to the standard application in humans, it means under the same methodology and using the Cebus Apella  (monkey of the New World ). Then we insert a bicortical self-cutting screw  (with 3 threads and the diameter of 3,5 mm.) of Garbaccio; after going through the occlusal cortical, it goes also through the medullar to insert itself in the opposite distal cortical. The bicorticality allows to the maximum biomechanical stabilization. According to what was exposed by Garbaccio, the other basic principle of the screw is the protection of the healing process, considered of being the great importance for the retention of the implant. The implant is splinted to the canine of the lower jaw in the right side, with previous endodontics therapy, by meanings of one fixed bridgework. Garbaccio's implant is studied in the scanning electronic microscopy.

RESULTS

Macroscopically discoveries

At the end of the experience, clinically and radiologically, the implant is a success according to the following evaluation criteria:

a) in spite of the tartar deposits, the marginal gingiva does not present any sign of edema or inflammation remainding normally its appearance.

b) absence of mobility and consequently of pain.

c) sulcus test going around the implant with a distance of 1.5 mm. approximately.

d) the X-rays give a normal view with a cortically formed after 90 days.

MICROSCOPICALLY DISCOVERIES

The histological test of the piece is done dividing the specimen in two parts:

a) Upper or adjacent to the oral membrane in which is studied the oral membrane behavior in relation to the implant in transversal cuts of the bone.

b) Lower in which the bone is investigated in the longitudinal cuts of the bone.

EPITHELIUM

Normal characteristics showing deep invaginations in the external slope of the gingiva. In order to build the implantary wall, we invaginate abruptly. This wall is called "neogingiva" because the components were rebuilt as soon as the implant was inserted. This implantary wall determines a neosulcus between it and the implant with a depth of 1,5 millimeters approximately, according to clinical and histometric determinations. Here the peri-implant epithelium gets thinner until a thickness formed by 5 or 6 lines of cells; in the surface are pavementous and "paracheratinizzate" in contrast with the man in which frequently we find pavementous cells not "cheratinizzate" in the normal relation tooth-gingiva. The limit in the corium is generally presented without epithelium crest even that in this case there is a deep crest oblique to apical of the implant. We have checked that the presence of one thin joining pseudo-epithelium with 3 or 4 pavementous with no thickness "cheratinizzazione" and leaving from the depth of the gingival is projected over the corium, making a stop in the deepest faces of it. Since this an implant with 31 month evolution it is interpreted that the pseudo-epithelium has made its maximal apical slipping and that its relation with the implant is of hermetically continuity closing all connection with the environment. This joining pseudo-epithelium originated in the permanent relation with a corium exposed by the surgical trauma has already been described in other researches. We call it joint pseudo-epithelium because of its histotopographic situation, since there are many difference with the normal joining epithelium in relation to the dental surface to which it is joined through hemidesmosomas.

Corium

It is moderately fibrous in the neo-gingiva with the large corium papillae in the free slope and almost without them in the implantary slope of the neo-cervice. Its collagenous faces are ring-shaped bundles in relation to the implant neck and make remind the normal gingival dispositive of the men and monkeys. We have not verified a great presence of inflammatory cells of chronic type which indicates the installation of a defensive wall in relation to the bucal environment, generally septic in these animals, because of the dental plate without adequate hygiene. It is possible to see some monocites normal phenomenon. There is also an increase of gauge in the corium vessels, fact that was also verified in studies about other kinds of implants. The deep corium is more fibrous and the collagenous faces are perpendicular to the implant axis but we must take note that its relation with the implant is direct, it means without any kind of joining pseudo-epithelium cover but, on the other hand, the have been seen another kind of implants like the spiral pins.

Pre-Implant Bone

This is a compact bone in the internal and external side and in the basel portion, in this area it is particularly dense and the tip of the implant is inserted. This bone is getting spongy in the implantary locus showing thick trabeculas whit small areolas are occupied by adiposa osseous medullar well irrigated and without any inflammatory.

Post-Implant Bone

This it the bone which is in immediate contact with the implant and without any doubt neo-formed. The panoramical or topographical aspect, shows a smooth peri-implantary surface which does not present inter-face tissue of immediate contact, at least, with optical microscopy in maximal increases, except in very limited areas.

The histological study of this post-implant bone let us see the following characters:

a) it is solidly fusionated with the pre-implant or pre-existent bone, even thought is evident one particularly noticeable cement line, which identifies them in transversal cuttings and in the PAS staining. The separation between both kinds of bone is not uniform along all the periphery, it has some interruptions in small intervals.

b) structurally, this is an amorphous bone, with small and scarce lamellas with irregular run in small areas. Histometrically we can admit a promedium thickness of 30 millimicron for this neo-formation bone. The hematoxilina-eosina staining shows that this special kind of bone is more basophilic than the pre-existent one and therefore less mature than this one.

c) the series study of the transversal and longitudinal cuttings, let us be sure that in some areas of the internal surface which are covered by connective tissue and even blood vessels that seemed to break the osseous surface continuity, are really covering the bone in neo-formation.

d) one aspect of particular interest is the osseous bed of the extreme (the tip) which as it is described above is compact bone. By recovering this bone, we can also obtain the neo-formation peri-implantary bone with the same characters as the ones in the areas related to the spirals, it means more basophilic, amorphous with scarce osteocites and lamellas and surface with no conjuntiv inter-face shown by optical microscopy.

PHOTOMICROGRAPHIES

Fig. 1 - Neo-gingiva in implant hematoxilina eosina staining. Increase 400x. Number 1: External slope of the neogingiva. Epithelium pavemented stratificated paracheratinizzato. Number 2: Implantary slope of the neo-gingiva with epithelium pavemente stratificated with an epithelial crest in direction to apical. Corium papillae are not observed. Number 3: Joining pseudo-epithelium emigrated toward the gingival corium. Number 4: Implantary locus. Number 5 : Collagenous fibers of the superficial corium in transversal cutting. Number 6: Stop of the joining pseudo-epithelium in the depth corium.

Fig. 2 - Depth corium of the neo-gingiva in implant hematosilina eosina staining. Increase 400 x. Number 1: Collagenous fibers in the longitudinal and perpendicular to the implant area. Number 2: Implantary locus.

Fig. 3 - Peri-implant bone in fusionated transversal cut with the pre-existent one. PAS staining.Increase 250 x. Number 1: Peri-Implant bone or neo-bone. Number 2: Pre-implant bone or pre-existent bone. Number 3: Implantary locus.

Fig. 4 - Above mentioned item. PAS staining. Increase 400 x. Number 1: Peri-implant bone or neo-bone. Number 2: Pre-implant bone or pre-existent bone. Number 3: Implantary locus.

Fig. 5 - Transversal and panoramic section of the implantary locus and osseous tissue pre and post-implant. PAS staining. Plain increasing. Number 1: Implantary locus. Number 2: Peri-implant bone. Number 3: Pre-implant bone.

Fig. 6 - Longitudinal section of the implantary locus and closer bone tissue. Tricromica de Masson staining. Plain increasing. Number 1: Implantary locus. Number 2: Pre-existent spongy osseous tissue. Number 3: Adiposeous bone narrow not close to the implant. Number 4: Bone tissue neo-formation peri-implant. Number 5: Spiral's extremes. Number 6: Inter-spirals spaces. Number 7: Fibrous osseous narrow close to the implant.

Fig. 7 - Insertion of the implant extreme in the basal cortical of the jaw bone. Tricromica de Masson staining. Plain increasing. Number 1: Extreme of the implant. Number 2: Pre-existent bone. Number 3: Peri-implant compact bone or neo-formation bone

Fig. 8 - Spirals and spaces in implant. Tricromica de Masson staining. Plain increasing. Number 1: Compact bone of the lingual cortical. Number 2: Pre-implant spongious bone of the maxilla diploe. Number 3: Peri-implant compact bone or neo-formation bone. Number 4: Extreme of the spira. Number 5: Implantary locus.

Fig. 9 - Space and spiral of the implant. Tricromica de Masson staining. Increase 400 x. Number 1: Peri-implant bone of inter-spiral space. Number 2: Extreme of the spiral. Number 3: Peri-implant bone in front of spiral extreme. Number 4: Pre-implant bone. Number 5: Fibrous osseous narrow close to the implant.

DISCUSSION

Epithelium and peri-implant corium

The insertion of this kind of implant, after 31 months, shows a neo-gingiva with normal characters compared to the periodonto of normal pre-protection, standing out specially, the presence of the joining pseudo-epithelium which has gotten deeper by slipping over the corium's collagenous.

There has not been found any kind of chronic inflammatory cells in great amount in the epithelium and in the connective tissue which represent a defensive wall to all kind of aggressions in the bucal environment research, is not present despite the presence of the inevitable plaque because of the lack of hygiene.

Perhaps the lack of defensive reaction, can be attributed to a fibrous transformation of the peri-implant corium with functional organization of the collagenous fibers since it is admitted that the dense connectors have relatively few blood vessels and do not present typical or chronicle cases, l like in the displace ability connector whose structure allows the vasodilatation and diapedesis as well as the installation of real inflammatory granulomas.

Peri-Implant Bone

It does not have any specific structural characteristics for the implant since its structure is amorphous, a little bit lamillar it has been observed in other kind of implants, attributing it to the mineralization of a peri-implant collagenous tissue produced because of the fibrous-blastic invasion of the blood clot,  as a consequence of the insertion of the element. We have no doubts about the induceable phenomenon of the mineralization of the Titanium metal, probably of the Titanium oxide, since according to some studies made in other kind of implants with less evolution period, the first tissue to be formed around itself is always the collagenous and its mineralization is centrifugal it means in the direction of the pre-existent bone has been confirmed but for us they have different structure and origin. To confirm what is mentioned above, the area of insertion of the implant extreme, has also its peri-implant bone with the special characteristics which is in close connection with the pre-existent bone event that it was penetrated and is located in the compact osseous tissue of the basel cortical of lower jaw. This also means that the spongous bone of the diploe as well as the compact bone of the basel supply with the fibroblasts which will originate the post-surgery clot.

CONCLUSIONS

1. The epithelium and peri-implant corium do not show any special histologic characteristics, they present deep corium expanded papillae and also a join pseudo-epithelium covering the gingival corium.

2. The peri-implant bone is amorphous, with no many cells a little bit lamillar but with a firm and solid fusion of the pre-existent bone.

3. The study of the neo-formation peri-implant bone, let us say that its mineralization its centrifugal to fix closely to the pre-existent bone.

4. We have not found collagenous peri-implant tissue in the amount and distribution enough to consider the presence of an interface of soft tissue or peri-implantary ligament.