PHYSIOLOGICAL AND HISTOLOGICAL ASPECTS

Mechanical quiescence is a fundamental premise for the development of osteointegration around any type of implant embedded in an osseous structure. Although until recently this fact was regarded as being dogmatic and of absolute importance, it is now the subject of critical revision. More recently, operators in this field have acknowledged the importance of this “new” implantology on which the structure can be loaded in a short time.
These two opposite viewpoints both contain risks and benefits that are far from negligible.
It is worth recalling that the forces inside the oral cavity are of considerable intensity, exposing the supporting bone structure to a positive and negative risk of transformation according to the laws of Roux and Wolf.

Roux: The increase in compressive forces leads to the formation of new bone tissue, whereas the diminution and lack of compressive stimuli leads to the formation of osteoid tissue.

Wolf: Each functional stimulus leads to a modification in bone and consequently every alteration in the intensity and direction of forces leads to a change in the solidification of the implants using electrowelding by syncrystallisation.

The connection of the tooth to bone is provided by cells in the junctional epithelium and by the complex of collagen fibres that form a component part of the structure of all periodontal tissues. These can be identified as:
- Gingival dental bands that connect the cementum on one side and gingival tissue on the other, or more precisely the gingival margin in an occlusal direction and the adherent gingiva in a horizontal and apical direction.
- Circular or Kolliker’s bands that surround the tooth like a ring and help to maintain the gingiva closely adherent to the tooth surface.
- Transeptal bands that connect the neck of contiguous teeth by running above the alveolar crests.
- Dental periosteal bands that connect the cementum to the alveolus (Sharpey’s fibres). In topographical terms, these bands are subdivided into the alveolar crest group, the horizontal group, the oblique group, the apical group.
In addition, all these structures fulfil a defensive function against irritants and physiological and non-physiological masticatory loads.
The passive defence is provided by the action of the ligamentous apparatus defined by collagen fibres containing glycoprotein substances. Its function can be compared to a hydraulic shock absorber.
When loaded there is an interchange of proteoglycans between the ligamentous and osseous space using a real pump mechanism that produces a return movement in both directions.

The coronal circular bands seal the space off from the outside.
If we take for granted the occurrence of osteointegration during the load phase which has not yet been accomplished, we must ask ourselves whether this state is destined to last when masticatory forces come into play.
At this point we are obliged to recall all the studies carried out in the past by expert researchers like
Pasqualini, Tramonte, Pierazzini, Muratori, Zerosi, Russo, Camera, Emanuelli, Lo Bello, etc. etc.
It would be impossible to give a complete list of all those researchers to whom we should pay tribute for their enormous scientific contribution.
The work by James at the University of Loma Linden in California is particularly interest and is mentioned by Pierazzini in his treatise to which readers wishing to make a more detailed study should refer.

James carried out electron microscope studies not only on the implant but also on necks where he highlighted the presence of a lamina made up of macromolecules of proteoglycans in which it was possible to identify hemidesmosomes originating from epithelial cells. This intimate connection of the epithelial hemidesmosomes using the lamina of proteoglycans as an interface might confirm the hypothesis of the presence of a seal not identical to that of the natural tooth, and therefore with a different function.

He also analyses the structure of the perimplant using radiological methods and it can be summarised into different concentric layers.

1 -The layer of proteoglycans adherent to the titanium of the implant
2 - The layer of collagen fibrils lying in a circular pattern, which also contains oblique fibres that penetrate the proteoglycan layer.
3 - The intermediate vascular layer of vessels and fibres creating a more fluid structure in a bath of proteoglycans
4 - The peripheral layer of dense bands with a circular and radial pattern acting as the anchorage for the newly formed bony lamina.

This leads to the observation that the biointegration of the implant differs depending on the anatomical districts. The bone-titanium contact is not univocal but may appear in different forms along its length. One feature, even in the zone of intimate contact (above all the paracortical bones) is the constant presence of proteoglycans.
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Personal observation

In 1980, Zerosi gave a paper at the 10th International Meeting on Implants and Dental Transplants in Bologna on the histology of tissues around implant stumps: it is worth recalling that at this time questions were often focused on whether the implant constituted a point of entry for infective foci.

In the conclusion that absolved the method from this accusation, Zerosi described a degenerative type alteration in the most superficial cells of the epithelium which he termed “pallonitis”.
This histological picture offers confirmation for the observations made by various researchers.
Cytoplasmatic infarction is the proof of a functional mechanism that differs from the perimplant neo-periodontium.
The proteoglycan pumping mechanism is clearly not only bidirectional in terms of the lamina dura.
The different architectural structure of the pattern of the collagen fibres cannot withstand the circulation of fluids at deep levels.
According to Laplace’s theorem, the less fragmented septation of the new periodontium produces higher specific pressures in the interspace.
The loads therefore create a piston effect that, unable to discharge itself physiologically on the walls, leads to the emergence of the proteoglycan layer.
(It is worth remembering the reduced cervical seal due to the lack of physiological circular bands, sustained by newly formed but not equally effective bands).
The purposeful nature of every organism prompts the cervical cells to exercise a barrier function leading to the recovery of fluids deriving from a deeper level.
This leads to the cytoplasmatic infarction which is a sign of the profound physiology.
Cytoplasmatic degeneration is a phenomenon that can be seen in all types of non-solidified implants, using both embedded and transmucosal techniques.


The first histological findings regarding the emergence of electrowelded elements show the total absence of the phenomenon or a presence in a very mitigated form.

A study is now being carried out to evaluate the deep behaviour of welded structures.

As shown by the biomechanical studies which have been completed, these show a 15-20% drop in cortical tensions. This fact leads to the non-formation of the reabsorption cone and instead to an intimate contact in which the glycoprotein quota is minimal and contained within the site.