K. F. Chow BDS., FDSRCS October 23rd, 2009

Narrow diameter dental implants are being increasingly used not only to stabilize dentures but also for long term applications like crowns and bridges. I agree with Carl in that there is no such thing as an absolute contraindication in medicine. Even botox which will kill you if injected into your bloodstream is used ingeniously and judiciously to extend the youthful looks of people. The key word is “judiciously”. Know your medicine well and know what you want to do with it and then you can apply it safely and usefully.

It is significant that one of the doyens of implant dentistry has recognized that narrow diameters have their uses especially in narrow ridges and in suitable bone. I started out with conventionals and with the advent of minis, incorporated them into my treatment planning and in many complex cases have successfully integrated them both into my treatment planning taking into consideration the patient’s expectations and budget,the materials available and their limitations and my own experience, knowledge and skill.

However, with the greatest of respect, having read the classic Contemporary Implant Dentistry, I wish to highlight some misconceptions and give my opinion.

As pointed out earlier, many narrow diameters or minis used for fixed applications are 2.4mm to 2.9mm in diameter and are made of solid titanium alloy grade 5. They are certainly stronger than say a 4mm diameter fixture that has a hole in the middle to receive an abutment. Say the abutment is 2mm in diameter. That leaves the surrounding rim with a thickness of only 1mm! That is weaker definitely than a solid 2.5mm diameter mini. Furthermore, many of the conventional fixtures are made of titanium grade 3 or 4 which is 99.9% pure titanium and is softer and therefore weaker than the alloy.

One piece minis heal very well if they are placed in with a torque of at least 35 to 50ncm.Reason being that the healing challenge is much less than conventionals and also the transmucosal wound is very small, so that chances of infection in a normal patient is minimal.

As for the misconception that the surface area is insufficient, Paresh Patel has given an eloquent correction to that. Minis are usually placed longer than conventionals and in multiples. So as Patel has pointed out, two 2.5 by 10mm minis give a total surface area of 157sq mm. This has a greater surface area than a conventional of 4 by 10mm which gives only 125sq mm. 2.5 by 13mm gives 100sq mm. 2.5 by 16mm gives 125sq mm. All these are commonly used such that the argument of insufficient surface area for osseointegration holds no water.

The initial or primary stability of minis, I find often surpasses that of conventionals. In fact, I surmise that because of the minimal trauma and small entrance, the surrounding bone and soft tissue has overwhelming healing advantage when compared to conventionals that invokes a much greater healing challenge to the surrounding tissues. The overwhelming healing advantage in the context of minis may mean that the classical necrotic margin phase of osseointegration may be bypassed and osseointegration in the case of minis may be taking place almost immediately. Anyone wants to do a PhD on this?

Narrow diameter users must concede however that the charges of inadequate prosthodontic solutions to solve the problems of non-parallellism, insufficient prosthetic components, and poor emergence profile may have some credence. These problems I believe are being sorted out. As it is, narrow diameters or minis are here to stay and will be increasingly integrated into treatment plans to cater to all sorts of situations that it can solve much better than conventionals. I look forward to minis making great strides to make the benefits of implant dentistry affordable to everyone who needs them, and not just to the well-off only. I forsee that they will play an increasingly greater part in the development of implant dentistry and am preparing a book…”Minimized Dental Implants” and hope to outline and deliver elegant prosthodontic solutions to minis that will address the current shortcomings as pointed out.