Editors of Implantology: Dott. F. Mangini
(Assistant Dentistry Clinic University of Bari) Dott. N. Marini
(Treasurer ANIO) Dott. P. Mondani
(Lecturer at Dentistry Clinic, University of Modena)
"Un impianto alla volta: gli aghi di Mondani-
Extract from: Odontostomatologia & Implantoprotesi " 7/86

RUBRICA DI IMPLANTOLOGIA (spokesman for ANIO - Prof. P. Domenico Laforgia)
Prof. P. Domenico Laforgia - Dott. Francesco Mangini - Dott. Nazario Marini - Dott. Pierluigi Mondani
"Un impianto alla volta: gli aghi di Mondani"
editors: Dott. F. Mangini
(Assistant Dentistry Clinic University of Bari) Dott. N. Marini
(Treasurer ANIO) Dott. P. Mondani
(Lecturer at Dentistry Clinic, University of Modena)

Associazione Nazionale Implantoprotesi Orale (ANIO)

Under the scientific guidance of Prof. P; Domenico Laforgia - Director, Odontostomatology Clinic, University of Bari and President of ANIO.

Presentation

On this occasion we present another technique of implantology. The implant support does not use laminar retention or a cone-shaped trunk, as seen in earlier models, but instead absolutely vertical retention, together with a special three-dimensional layout that reflects the structure of the root anatomy.
Dr. Scialom's original method has been widely used by our colleague, Dr Mondani from Genoa, who should also be given the credit for having conceived and promoted the use of special equipment used for the intraoral welding of various metals and dental alloys.
Here is the presentation of this implant in the original description given by Dr. Piero Mondani.

Francesco Mangini

A brief compendium of "pin" or "post" implants

The validity and adaptability of pin implants has been widely acknowledged for the past thirty years. The inventor, a Frenchman Dr Scialom, first conceived the idea of inserting cylindrical tantalum rods of varying lengths measuring 1.2 mm in diameter, with a spear-shaped point at one end, using a rotary drill with a minimum speed of 50,100 revs/min into the jawbones. The points of these rods penetrated as far as the cortical bone, and having become solidified, they formed a geometric shape: the tripod. For the first time in endosseous implantology, following the introduction of these implants known as "pin" implants by the French, it was possible to implant the cortical bone as the elective site which today all implants attempt to reach.
Scialom joined them together using self-polymerising resin and creating a geometric figure, which was static at the time, but still gave excellent results. The prerogative of the pin implant lies in inserting the minimum quantity of metal into the bone, but obtaining the maximum extension.
The pin implant was widely used between 1968 and 1973 but was misinterpreted because it was thought of as being easy to achieve. In fact, and this is a point I would like to emphasise, it is the most complex and difficult implant. The technique cannot be learnt during the course of two or three days, as in the case of other implants. The procedure must be carried out by doctors who have considerable experience of implantology, anatomy, biology, biometallurgy and physics in order to understand its philosophy, its engineering and the rules dictated by building science. It requires specialists who are willing to spend considerable time learning how to use the implant that can be used where others cannot; that, owing to its variable morphology can be inserted into bone districts prohibited to other implants; the implant that can be removed without provoking any lesion in the event of failure. It is also the implant that enables patients to be fitted with dentures as soon as surgery has been finished, irrespect
In the first instance, given that modern implantology chooses the implant depending on the morphology of the jaw, I have changed "tantalum" to "titanium". Then, 14 years ago I invented the intraoral microwelder to solidify the various pins, pins with screws, pins with blades, depending on the method used. Lastly, the tripod is used for the front teeth and, on free-standing and total teeth it has been incorporated with other posts to form other geometric figures. The various pins remain in situ and, having been solidarised with the metal crossbars (personal method) they not only create a single block, but a mesial structure of enormous resistance.
Moldani's welder which is now used in a number of countries has the property of welding the various implants together in the oral cavity, without heating any metals or creating electrical discharges or lesions to mucosa or bone.
You will wonder why the pin implant needs to create a geometric figure to discharge the forces acquired during mastication in its polygon? Why are the pins rarely fixed vertically, but always at a slant in order to avoid divergences?
It is worth recalling a few fundamental principles relating to simple pressure, to the resolution of forces, the action of combined compressive and bending stress, before concluding with some important practical considerations affecting pin implants (taken from the Odontoimplantology Bulletin S.O.I.A. no. 8, 1969).
A solid body in a given section is subject to simple pressure when the resultant of all the forces affected by single band of the section is barycentric to the section and normal for it.
By way of example, if three pins have slopes compared to the resultant, in which direction the tooth is oriented, of 60°, 15°, 60°, always using P to indicate the action supported by a pin, the three pins together will support: 0.500 P + 0.966 P + 0.500P = 1.966 P. Given the slope angles in this case, the resistant action on the three pins is almost double than obtained with a single pin.
In the hypothesis that four pins are used to construct a post in a jawbone, the earlier comments are still valid because it is clear that the two pins P1 and P2 which contribute to R1, and the other two pins P3 and P4 which contribute in the same point as the former, determine another plane S in which the second resultant P2 is found (Fig.5). The first and second resultant also determine a new plane on which they can be composed, thus obtaining R3 the overall resultant for the four-pin system.
In some cases it might be advisable to insert a larger number of pins. In a five-pin implant, along the same lines as above, it might be possible to consider a fourth plane between R3 and the fifth pin and determine the overall results of the system in intensity and direction.
The problem of implementation is not that simple to resolve given that the pins form an irregular pyramid and only the experience gained through resolving numerous cases will throw light on the kind of solution to be used. The cautious use of pins will guarantee the distribution of the loads acting on each of them and, above all their axial nature, in order to prevent the onset of stress caused by flexion which might cause the pins to damage the bone tissue, similar to the results of combined compressive and bending stress. . The tails of the pins are then joined together as appropriate and welded with small crossbars of titanium in order to lock them in position; lastly, the superstructure is then fitted. The purpose of this note is clearly to outline briefly the theoretical solution of the problem, highlighting that, where possible, an increased number of pins enhances the load-bearing capacity of the result and also gives the system a transverse rigidity which is excellent in mastication during translation of the mandible.
The Vickers hardness of the titanium pins is approximately 170 at the tail and 260 in correspondence with the cutting edge, which does not provoke the emergence of bone tissue during deflection; this guarantees the perfect seal of the pin along its entire length in the cavity that it creates, preventing strains in the maxillary alveolus.

Three particular advantages are achieved in this way:

-obtaining a real perforating point at the scalpel end of the pin, thus creating a housing that is precisely the same diameter as the point and the pin;
- having sections that are increasingly strong from the tail to the top of the pin;
- having a pliable tail so that it can be bent as required ensuring, when several pins are used, that the corresponding ends are close together before they are welded and the prosthesis is fitted.

The above comments highlight a number of important practical considerations:
- it is important to ensure that the attachments at the tip and head of the pins are extremely firm, avoiding the possibility of slight transverse deflections when the pins are subject to heavy crushing;
- the diameter of each hole must be as close as possible to that of the pin to be fitted in order to prevent any slight bending of the pin during crushing which would disturb bone tissue;
- the pins inserted at a slope to the action of mastication, which is only considered vertical in theory, reduce the force in relation to the angle of slope;
- wherever possible, it is advisable to divide the stress on two or more slanted pins to benefit from the breakdown of acting forces. In this event, the microwelder must be used to weld the tails of the pins in order to guarantee the distribution and axial transmission of the loads;
- it is important to carry out a careful prior examination of the two jawbones to calculate which are the most healthy and solid positions in which to insert pins, bearing in mind that their points will always lodge in cortical bone without interfering with the various anatomical structures;
- lastly, it is important to determine where possible the point of intersection between the resultant and the maxillary arch because this will be the most solid point on which to anchor the prosthesis, eliminating the transversal component of stress that is always detrimental to the stability of the system.

Pierluigi Mondani

Personal contribution

Provided that the pins are lodged in the cortical bone, osteointegration is not a necessary premise for the stability of the implant and it can be immediately be loaded with the prosthesis. Compact bone will quickly form around the titanium oxides of the thin pins and after just a few months it will be mechanically load-bearing even if thinner than the screws: this is precisely why thickened bone is integral in elastic terms with the pins, following their movements (which are restricted).
This system could be compared in longitudinal terms (i.e. along the dental arch) to a rigid beam on elastic supports (e.g. the Winkler beam supported on the ground).

DIAGRAM OF THE WINKLER BEAM