Dental implants: How many implants do I need?

It is not always easy to answer this question: according to the rules, every single tooth should be replaced by an individual implant, however when this is not possible due to anatomical or economical purposes, it becomes imperative to fall back on a compromise. It is possible to execute anchoring like that of natural teeth without implants, but in order to obtain this result it is necessary that to take into consideration the total natural root area encapsulated in the bone and compare it to the implant area.

The posterior teeth have two or three roots and the provide a total bone anchoring area of 450-533  mm², a typical implant of 3.75 mm diameter is made up of only one root with a variable area between 72 and 256  mm², in function of the length. This means that the tooth is able to dissipate all of the masticatory forces, that may reach many hundreds of kilos in value, in a very efficient way, certainly more efficient than an implant. More so, the crown of a molar tooth has an area of about 100 mm², while the transversal area of a 3.75 mm diameter implant has an area of only 10.95  mm². When exerted at an angle correlated to the implant area, mastication forces provoke an excessive amount of stress of the torsion and inclination vectors. These considerations explain the reason why today implant manufacturers provide elements with greater diameter, up to 5 or 6 mm, which greatly improve the discrepancies; these implants  are selected in relation to the roots which they replace. Therefore, even if generally the rule “one tooth- one implant” is followed, the regulation can be modified in function of the individual situation and the kind of treatment desired. For example: a patient without teeth (total edentulia) does not intend to sacrifice his lower dentures but only wishes to increase their stability. In this case only two implants are necessary in order to obtain the desired results, even if often normally the number of implants inserted increases prosthesis stability and consequently, the long term prognosis of the entire implant.

last update: 21 January 2008