Dental Tribune Middle East & Africa Edition

osseo-integration accept crestal bone remodeling and resorption of up to 1.5 – 2mm during the first year following fixture placement and prosthetic insertion 51 . The concept of “biological width” outlines the minimum soft tissue dimension that is phys- iologically necessary to protect and separate the osseous crest from a healthy gingival margin surrounding teeth and the peri- implant environment. A bacteria-proof seal, the lack of micro-movement associated with a friction grip interface and a minimally invasive second- stage surgery (where indicated) without any major trauma to the periosteal tissues, are also impor- tant factors in preventing cervical bone loss. The literature suggests that the stability of the implant/ abutment interface may have an important early role to play in de- termining crestal bone levels 52 . Tarnow’s seminal study on crestal bone height support for the interdental papilla clearly showed the influence of the bony crest on the presence or absence of papillae between implants and adjacent teeth 53 . Twenty years lat- er, logic dictates that anticipated early crestal bone loss and dimin- ished, albeit continual loss, dur- ing successive years of function, should have been engineered out of the substitution algorithm for peri-implant tissues 54 . Platform switching: By de- fault or by design ‘There is no logical way to the dis- covery of elemental laws. There is only the way of intuition, which is helped by a feeling for the order lying behind the appearance,’ Al- bert Einstein. Platform switching theorises that by using an abutment diame- ter of a lesser dimension than the periphery of the implant fixture, horizontal relocation of the im- plant-abutment connection will reduce remodeling and resorp- tion of crestal bone after insertion and loading. The concept implies that peri- implant hard tissue stability will engender soft tissue and papilla preservation. Maeda et al report- ed that stress levels in the cervical bone area peripheral to a fixture were reduced when a narrow di- ameter abutment was connected in comparison to a size commen- surate with the fixture diameter 55 . The authors concluded that the biomechanical advantage of shifting stress concentrations away from the cervical area will diminish their impact on the bio- logic dimension of hard and soft tissue extending apically from the FAI (Fig 11a, 11b and 11c). The inherent disadvantage is that it shifts stress to the abutment screw with the potential for loos- ening or fracture. Ericsson et al 56 detected neu- trophilic infiltrate in the connec- tive tissue zone contacting the implant-abutment interface. The facility by which platform switch- ing/shifting reduces bone loss around implants has been inves- tigated by Lazzara et al 57 . The authors hypothesised, that if the abutment diameter matches that of the implant, the inflammatory cell infiltrate is formed in the con- nective tissue contacting the mi- crogap created at the FAI. If an abutment of narrower diameter is connected to wider neck implant, the FAI is shifted away from the outer edge of the implant, thus distancing inflam- matory cell infiltrate away from bone. Hypothetically, less crestal bone loss is expected and an in- creased implant/abutent disparity allows more stable peri-implant soft tissue integration. Baggi et al conducted a finite element analysis experiment to define stress distribution and magnitude in the crestal area around three commercially avail- able implants – ITI Straumann® (Institut Straumann AG, Basel CH), Nobel Biocare (Nobel Bio- care AB, Goteborg SE) and Anky- los C/X (Dentsply-Friadent, Man- heim, DE) 58 . Numerical models of maxillary and mandibular mo- lar bone segments were gener- ated from computed tomography images and local stress vectorsimages and local stress vectors or thewere introduced to allow for the d risk.assessment of bone overload risk. Different crestal bone geometries were also modeled. Type II bone quality was ap- proximated and complete os- seous integration was assumed. It was concluded that the Ankylos C/X implant based on its platform Fig 10b Fig 11a Fig 11b trition and communication for the body and be the gate- keeper on guard and in func- tion throughout our lifetime. As such, our role is to ensure that however we reengineer nature, we must adhere to its rules, its logic and fundamentals. The best evidence This is not an easy task, as fil- tering out the best range of evidence from a wide range of sources, presenting clear, comprehensive analyses and incorporating patient experi- ence is a Herculean task. In many ways, this is analogous to Alice’s Adventures in Wonder- land as so much of what we do grows ‘curiouser and curi- ouser’ as each new innovation demands that we go through the looking glass and determine what Alice found there. ‘There’s no use trying,’ said Alice. ‘One can’t believe impossible things.’ ‘I daresay you haven’t had much practice,’ said the Queen. ‘When I was your age, I always did it for half an hour a day. Why, some- times I’ve believed as many as six impossible things before breakfast?’ Lewis Carroll.’ DT Fig 11c Fig 12a About the author Kenneth S Serota, DDS, MMSc gradu- ated from the University of Toronto, Faculty of Dentistry in 1973 and was awarded the George W Switzer Me- morial Key for excellence in Prostho- dontics. He received his Certificate in Endodontics and Master of Medical Sciences Degree from the Harvard- Forsyth Dental Center in Boston, MA. The founder of ROOTS – an online educational forum for dentists from around the world who wish to learn cutting edge endodontic therapy, he recently launched IMPLANTS (www. rximplants.com) and www.tdsonline. org in order to provide a clear under- standing of the endodontic/implant al- gorithm in foundational dentistry. be enhanced by osseous genera- tion over the collar of the fixture (Figs 12a and 12b)59,60 . The endodontic implant al- gorithm parallels the question, which came first, the chicken or the egg as an example of circular cause and consequence. It could be reformulated as follows: ‘Which came first, X that can’t come without Y, or Y that can’t come without X?’ An equivalent situation arises in engineering and science known as circular reference, in which a param- eter is required to calculate that parameter itself. This is the es- sence of foundational dentistry. Nature wisely created a structure that could harmoni- ously interpolate hard and soft tissue, act as the portal of nu- Fig 12bFig 12b A preconfigured platform switched design has a signifi- cant impact on the implant treat- ment in esthetic areas as not only is the tissue biotype pre- served, but it has been shown to DENTALTRIBUNE Middle East & Africa Edition Media CME 7