Do Rough Surfaced Implants Really Have An Advantage Over Smooth Surfaced Ones?

The smooth surfaced classic implant is as good as extinct. In its place we are faced with a number of 'rough surfaces'. Each manufacturer seems have some sort of unique surface and claims magical properties for their own surface.
How much of a difference the newer rough surfaces make to the ultimate success of the implant compared to the older smooth machined surface has been an area of much controversy.
A retrospective analysis of thousands of implants placed over the past many years at the world renowned Mayo Clinic in Minnesota published in the latest issue of The International Journal of Oral and Maxillofacial Implants claims interestingly enough that "....there was no significant difference in the survival rates of smooth and rough-surface implants...."
It is worth looking into this study in some detail, because, beyond the assertion that forms the title of the paper are many other significant findings that are quite interesting.
The study compares two groups of patients.
The first group of 593 patients (322 women and 271 men) received 2,182 smooth -surface implants , while 905 patients ( 539 women and 366 men) received 2,425 rough surfaced implants (Nobel Biocare, TiUnite).
At 5 years after implant placement, survival rates were 94.0% and 94.5%, respectively for smooth and rough surface implants.
As we can see the differences were not significant.
The only criteria of success were that the implant be symptom free and present in the mouth at the time of evaluation.
The Albrektsson criteria were not used.
There were no significant differences between the survival rates of smooth- and rough-surface implants.
However there are some more interesting observations that tilt the balance in favour of rough surface implants

1. Anatomic location was associated with failure of smooth-surface implants only.
2. Anatomic location was not associated with failure of rough surface
3. Smooth-surface implants performed better in the mandible than rough-surface implants.
4. Rough surface implants performed better in the maxilla
5. Survival of smooth-surface implants was highest in the anterior mandible compared to any other area.
6. Implant length of less than or equal to 10mm was associated with failure in smooth surface implants
   
7. Implant length of less than or equal to 10mm was not associated with failure of rough surface implants
8. Although this study used one system (Nobel Biocare) for comparison of the survival of the two surfaces, the surface roughness value of both implant systems are similar to those of other implant systems.
9. The population of this study included smokers and nonsmokers. Smoking was found to be a risk factor for smooth surface implants only.

Although this study is remarable for its large sample size of over 2000 implants in each group it has the limitations inherent in a retrospective analysis.
Nevertheless this study offers an affirmation of many previous observations made in earlier studies with smaller sample sizes and much shorter observation times.
It seems on reading this study that there is little justification for using smooth surface implants anymore and that rough surface implants offer significant advantages by limiting anatomic location risk and the risk associated with shorter implant lengths.
It would be worthwhile if you could read the paper in it's entirety.