Achieving bone health using Ditron implants Platform Switching and Platform Bone Switching— Osseointegration, restoration of function, and aesthetics are all the achievable goals of implant treatment. But to achieve these goals, clinicians must make all possible efforts to prevent bone loss and avoid microgaps that can harbor bacteria. Platform switching and platform bone switching are integral to implant longevity — minimizing both bone loss and bacterial growth. This white paper defines the basics of platform switching and platform bone switching and their involvement in the health of successfully placed dental implants. Dr. Ole T. Jensen, DDS MS What is platform switching? In 2006, the concept of platform switching was introduced by Drs. Richard J. Lazzara and Stephan S. Porter. 1 lt is a “hardware” phenomenon. This is gained by inward displacement of the abutment from the implant platform which is in continuity with the alveolar bone crest. Radiographic studies have shown a smaller than expected vertical crestal bone loss around platform- switching implants than around implants that were restored conventionally with prosthetic components of matching diameters. This may be due to a greater distance between implant abutment junction and alveolar crestal bone. A study by Drs. Yoshinobu Maeda, Jiro Miura, Ikuro Taki, and Motofumi Sogo suggests that a platform-switching configuration has the biomechanical advantage of shifting the stress concentration area away from the cervical bone-implant interface. Another beneficial result is more protection from microflora. 1 What is bone platform switching? The concept of bone platform switching arose from the concept of hardware platform switching. Bone platform switching involves the cervical two millimeters of bone around an implant as a kind of separate conceptual entity though it is in continuity with the alveolar bone. This conceptualization of Drs. Francesco Carinci, Giorgio Brunelli, and Matteo Danza was studied as the most critical supporting bone around an dental implant. Platform bone switching can be achieved by using a dental fixture with a reverse conical neck and therefore enhance this critical bone volume. Dr. Carinici and colleagues noted that an implant with a conical neck offers several advantages: 10 • Reduced mechanical stress in the crestal alveolar bone area • Repositioning of gingival papillae on the bone ring • A more robust vascular supply to hard and bone tissue, also in cases of reduced inter-implant space. What is the Ring of Bone Concept? The ring of bone concept describes the critical crestal bone at the neck of an implant for which platform-bone switch and platform-abutment switch help to define the quantity of supporting cervical bone volume. When comparing a straight wall implant platform to a reverse conical neck platform, there is a significant difference at the crestal 2mm of bone support in terms of bone volume preserved. Danza and Paracchini calculated the cubic volume of bone saved per implant using the reverse conical neck implant to be 5.6mm. This is substantial bone volume and is comprised of: • The narrowing of the implant neck to 3.75mm from 4.2mm • The curved concavity of the neck itself • The 11 cervical grooves which additionally purpose a small increase in bone volume. Together, these increase viable crestal bone and help to keep cervical bone ring thickness above the threshold where resorption becomes a greater risk to expose the titanium surface to bacterial contamination. The implication is that greater bone volume may hinder implant surface exposure. Also problems associated with early implant surface exposure have been correlated with late development of peri-implantitis. , Horizontal Thickness of the Cervical Ring In the best possible scenario, the thickness of peri-implant bone around an implant should be greater than 1.7mm, with 2mm or greater bone thickness being the most ideal. However, in the anterior maxilla that would suggest an 8mm to 9mm diameter site be required to place a 4.2mm diameter implant which is often not available. To overcome this deficit bone grafting is commonly done facially to increase bone thickness up to 2mm to 3mm to prevent implant surface exposure and help establish gingival form. Bone volume support for papilla near implants Cervical bone volume between implants that are 3mm apart does not greatly support a papilla. The use of platform switch in side-by-side implants is not a factor for the hard tissue unless the implants are placed sub-crestally. With only minimal papilla support, if bone is lost to a sub-platform position, any papilla could potentially become “punched out” severely compromising esthetics and the ability to self-cleanse. Side by side reverse conical neck implants placed level to the crest would lead to an addition of about .45mm between the implants or 3.45mm of space—a 15% improvement in bone preservation. If implants were placed slightly sub-crestally, the 0.5mm platform switch would be additive for a 3.95mm spacing, a 32% increase in cervical bone. Abutment-implant junction Cervical bone preservation is supported by accurate fitting abutments. Precision fit at the abutment implant interface is very important . Junction movement from a poor fit can completely undermine any switching bone preservation strategy. Zone of Inflammation Abutment misfit or large gap width from a loose abutment screw leads to abutment movement, percolation of bacterial contaminates, and titanium metallic debris leading to the 1mm to 1.4mm zone of inflammation. Bacterial composition in the implant-abutment connection is also affected by the precision fit and can contribute to marginal bone loss magnitude. Efforts to reduce gap size to less than .5 microns to eliminate bacterial ingress are now achievable by using aerospace engineering technology. One implant system, Ditron Dental USA, the implant abutment gap was measured at less than 0.5 microns which is smaller than typical bacterial constituents of oral microflora. , , Prevention of Peri-Implant Disease The cervical ring of bone is the first line of defense in the prevention of gingival recession and exposure of titanium potentially leading to peri-implant disease.8 When cervical bone volume is thin (as little as 1.7mm as found in one study), especially in the maxillary anterior, or if the ring of bone is thin or interrupted, as is sometimes found with angled implant placement, the body of the implant is more easily accessible to oral biofilm. However, as long as bone is present up to platform level, particularly if there is healthy and adequate quantity of bone, the “gateway” to peri-implant disease is closed. Ericsson et al. described histological inflammation around two-piece implants which must be considered in any bone preservation strategy. The authors found peri-implant inflammation to be of two types. • Sulcular plaque-associated inflammation • Inflammation at the implant abutment junction Radiographic evaluation demonstrates the zone of inflammation that develops over time at the abutment junction is 1mm to 1.4mm of potential bone loss. Hardware platform switch displaces the abutment junction slightly away from bone to reduce the effect of inflammation on surrounding bone, the so-called distance-effect. The purpose of the platform bone switch is a bone volume-effect. This method also reduces the chance for peri-implant disease by increasing peri-implant bone volume which may inhibit or retard inflammatory bone resorption, delaying exposure of implant surface into the oral cavity. 7,8,9 How Does This Relate to Implants? The need for a narrow neck but a wider apical portion of an implant satisfies the dual need for biomechanical retention and preservation of crestal bone. This is particularly important with extraction and immediate implant placement such as in the anterior maxilla. A reverse conical neck minimizes encroachment on thin facial bone while at the same time maintains implant diameter apically to increase primary stability for immediate temporization. The design feature of the reverse conical neck has become particularly beneficial in partially edentulous areas with narrow spaces for implants and in segmental edentulous situations where there is limited space for side-by-side implants. Instead of using narrow diameter implants to solve proximity problems, a standard diameter implant can be used without adding substantial risk to marginal bone and papillary support while still maintaining needed biomechanical advantage.5, Ditron Dental Implants Several implant manufacturers have recognized the benefit of narrowing the neck of the implant, but the vast majority of implants are straight-walled and often tapering outward, getting wider at the alveolar crest than the implant body, impacting cervical bone dimension and potentially compromising ring of bone continuity. Ditron Dental Implants achieve the goal of platform bone switching in several ways. • The particular morphology of the collar, the Reverse Conical Neck, increases implant contact surface area with bone and preserves a greater proportion of bone and periosteum. • The taper and concavity of the collar reduces stress on the crestal cortical bone. • By inserting an Ultimate™implant, 5.6 mm3 of bone (based on a 4.2mm diameter implant) will be preserved as compared to a straight wall implant. • The Reverse Conical (and Concave) Neck provides greater implant stability and better distribution of the stress at the bone implant interface. Summary A tapered straight-wall implant and a reverse conical neck implant were compared at the cervical margin in terms of bone volume of the cervical ring of bone. The reverse conical neck implant showed a substantial difference in ring of bone volume with an increase of 5.6mm.3 These findings suggest a greater chance for maintaining adequate bone at the margin of the implant which if otherwise lost could lead to peri-implantitis. A precision fit abutment-implant junction, a sub-crestal platform switch, the platform bone switch of the reverse concave neck and cervical micro-grooves all serve to increase and help maintain cervical bone volume to preserve critical marginal and subpapillary bone. 1 Lazzara RJ, Porter SS. Platform switching: a new concept in implant dentistry for controlling postrestorative crestal bone levels. Int J Periodontics Restorative Dent. 2006;26(1):9-17.. 2 Maeda Y, Miura J, Taki I, Sogo M. Biomechanical analysis on platform switching: is there any biomechanical rationale? Clin Oral Implants Res. 2007;18(5):581-584. 3 Danza M, Zollino I, Avantaggiato A, Lucchese A, Carinci F. Distance between implants has a potential impact on crestal bone resorption. Saudi Dent J. 2011; 23(3):129-133. 4 Galindo‐Moreno P, León‐Cano A, Ortega‐Oller I, Monje A, O′ Valle F, Catena A. Marginal bone loss as success criterion in implant dentistry: beyond 2 mm. Clin Oral Implants Res. 2015;26(4):e28-e34. 5 Danza M, Aollino I, Paracchini L, et al. Bone platform switching in 3D Finite element analysis comparing standard and reverse conical neck implants. EDI Journal 2008, 2-20110. 72. 6 Widmark G, Andersson C, Ivanoff CJ. Mandibular bone graft in the anterior maxilla for single tooth implants: presentation of a surgical method. Int J Oral Maxillofac Surg. 1997;26(2):106-109. 7 Ericsson I, Persson LG, Berglundh T, Marinello CP, Lindhe J, Klinge B. Different types of inflammatory reactions in peri-implant soft tissues. J Clin Periodontol. 1995;22(3):255-261. doi: 10.1111/j.1600-051x.1995.tb00143.x. 8 Carinci F, Brunelli G, Danza M. Platform switching and bone platform switching. J Oral implantol. 2009;35(5):245-250. doi: 10.1563/AAID-JOI-D-09-00022.1. 9 Taheri M, Akbari S, Shamshiri AR, Shayesteh YS. Marginal bone loss around bone-level and tissue level implants: a systematic review and meta-analysis. Ann Anat. 2020 Sept;231:151525. Doi:10.1016.aanat 2020.151525. Epub 2020May4. PMID; 3280195. 10 Spray JR, Black CG, Morris HF, Ochi S. The influence of bone thickness on facial marginal bone response: stage 1 placement through stage 2 uncovering. Ann Periodontol. 2000;5(1):119-128. doi: 10.1902/annals.2000.5.1.119. 11 Atieh MA, Ibrahim HM, Atieh AH. Platform switching for marginal bone preservation around dental implants: a systematic review and meta-analysis. J Periodontol. 2010;81(10):1350-1366. doi: 10.1902/jop.2010.100232. 12 Danza M, Palmieri A, Farinella F, Brunelli G, Carinci F, Girardi A, Spinelli G. Three-dimensional finite element analysis to detect stress distribution in spiral implants and surrounding bone. Dent Res J. 2009;6(2):59–64.