In general, the options to replace missing teeth are dentures, fixed bridges, implants AND DO NOTHING. Hence, the need to replace the second molar depends on a few considerations.
Firstly, we have to decide if the replacement is truly needed. Research from 1981 to present has strongly suggested that the modern human diet only requires 10 occluding pairs of teeth. This means that for rather reasonable esthetics and function, we only need 10 pairs of front and back teeth contacting well with each other. In this respect, if the MISSING second molar tooth does not affect function and certainly not esthetics, then replacement of the second molar may not be required.
Secondly, we have to consider the conditions of the surrounding tissues. If the LOWER second molar tooth was missing and the upper opposing second molar is present and was contacting the lower second molar previously, then there is a risk of the upper second molar migrating downwards - a phenomenon known as over-eruption or supra-eruption. In severe cases, the upper second molar may over-erupt so much that it may be biting on the lower gum, causing irritation to the gums. Conversely, if the UPPER second molar tooth was missing and the lower second molar was present, there is a lower chance of over-eruption of the lower second molar tooth in the upper direction. Often, there may still be contact of the neighbouring teeth with one another and that may be able to hold the remaining second molar to avoid over-eruption.
Thirdly, in close relation to the second point above, is the amount bone and gum tissue available to anchor a dental implant. There are anatomical boundaries that cannot be breached. In the upper jaw, the maxillary sinus is the main anatomical structure. If there is inadequate height of bone, a sinus bone augmentation procedure (adding bone into the sinus) to increase the height and width of bone is required PRIOR to placement of the dental implant. In the lower jaw, the inferior alveolar blood vessels and nerve (the inferior alveolar bundle) are vitally important. Invasion into the inferior alveolar bundle may lead to fatal bleeding and/or debilitating lifetime jaw and tongue numbness. Hence, again, if the conditions are not suitable for dental implant placement, there may be a need for costly adjunctive procedures prior to the actual implant placement procedure.
My sister, Dr Daylene Leong, an American Board certified periodontist, always says "Patients do not want implants; they want teeth!" With this philosophy in mind, it is crucial to realise that dental implant treatment must lead to a BETTER outcome, otherwise it may be prudent to choose another treatment option.
