Abstract: In this retrospective clinical study, 32 oral implants were placed subcrestally in 30 patients who were followed from 1 to 3 years to identify the effect of platform bone switch implants on cervical bone preservation and associated soft-tissue profile. Peri-implant bone, including subpapillary bone and marginal gingival bone, as measured from the implant-abutment junction, was evaluated quantitatively. Preliminary findings indicate that the platform bone switch implants used in this study, compared to conventional straight-wall implants, appear to preserve additional bone at or above the implant-abutment junction to help support papillae and marginal gingiva and maintain coverage of the implant body, with most bone levels shown to be above the implant-abutment junction.
Cervical bone is the most critical bone to preserve around a dental implant, as it determines peri-implant gingival esthetics, peri-implant health, and, therefore, potentially, implant longevity.1-4 For natural teeth, a specialized connective tissue attachment functions as the first line of protection. However, for oral-penetrating titanium implants, which are absent this protective attachment, the cervical bone itself serves as a "defensive wall" from bacterial aggression. Although the importance of cervical bone around a dental implant is intuitively understood to be crucial, few scientific publications have addressed quantity of cervical bone as a critical factor with regard to the placement and maintenance of implants.
The Critical "Ring of Bone"
The first 2 mm of circumferential bone around an implant has been described as a "ring of bone," the idea being that continuity and integrity of this bone ring is clinically important. From the time of implant placement forward, the ring of bone "stands guard" over osseointegration, the cervical bone being where osseous lesions initially occur.5-7 Also, from this relatively small but critical bone fragment comes marginal gingival stability, subpapillary support for papillary height, and bone barrier protection between an implant and a tooth or between implants.8,9
A threshold of ring of bone thickness exists where greater risk for breakdown and consequent exposure of implant surface occurs. For the facial marginal gingiva this has been reported to be less than
2 mm of bone thickness.10 Loss of this marginal bone integrity leads to lengthening of the visible crown due to lack of bone support and subsequent gingival recession.11,12 This resulting dehiscence is caused by loss of continuity of the cervical ring of bone.13
Loss of thickness of the ring of bone at interdental sites risks the loss of papilla height. Placing an implant body too close to a tooth risks the loss of papillary form partly because of diminished bone support. Similarly, when implants are placed too close together, the peri-gingival architecture may flatten due to reduced bone support. These issues are generally most importantly considered for anterior maxillary restorations.14-16
Platform Bone Switch
Titanium dental implants are foreign-body elements from which the human body is shielded by chronic inflammation termed "foreign-body osseointegration."17 Dental implants are also confronted by oropharyngeal-sourced bacterial biofilm that requires the implementation of consistent oral hygiene measures.18 Both of these inflammatory settings can provoke osteoclastic bone loss due to chronic inflammatory response.19,20 While surgical, prosthetic, and hygiene efforts may help mitigate these challenges, it is the body's immune response that keeps the dental implant in a state of osseo-immunologic balance, as Albrektsson and colleagues described.21 For this reason, cervical bone volume is considered to be an early line of immunological defense, and, therefore, attention should be given to the ring of bone mass at every stage of implant treatment and follow-up care.
Danza et al described the narrowing of the top 1.8 mm of the neck of an implant as a favorable design feature (Figure 1) that can help preserve more cervical bone and possibly decrease the risk of bone loss (eg, for a 4.2-mm diameter implant, 5.56 mm3 of bone is preserved by narrowing the implant at the crest).6 This has been called "platform bone switch," where bone is switched in place of titanium around the critical cervical margin of the implant (Figure 2 through Figure 4).22
Despite being in use for two decades, very little study and reporting has elucidated the advantage of platform bone switching. In the present study, the authors retrospectively reviewed the results of 32 platform bone switch implants (Ultimate™ Implant, Ditron Dental, ditrondental.com) placed by three different practitioners in three separate clinics and followed from 1 to 3 years to observe peri-implant findings related to the use of platform bone switch. The aim of the study was to follow three areas of clinical interest at the peri-implant margin: marginal gingiva, papilla, and bone presence above or below the implant-abutment junction. The intent was to evaluate stability or disturbance of the cervical ring of bone and its effect on these clinical variables in the presence of platform bone switch.
Methods
Thirty-two implants were placed from 0.5 mm to 1 mm below bone level in 30 patients and retrospectively studied from 1 to 3 years. Following implant restoration, papillae and marginal gingivae were comparatively assessed in relation to adjacent soft-tissue height findings, including increase or decrease in papillary and marginal gingival height. Pocket depths were measured at the papillae and the midfacial marginal gingiva.
Peri-implant bone presence above or below the implant-abutment junction was observed on periapical x-rays. The implant used in this study (Ultimate Implant) does not leak at the abutment junction, essentially functioning as a one-piece implant; therefore, bone measure is not confounded by bone loss due to implant-abutment junction bacterial leakage.
Results
Table 1 presents "plus/minus" data indicating bone above (+) or below (-) the implant-abutment junction as well as soft-tissue levels above or below adjacent teeth (ambient).
Patient Treatments
Three sample patient treatments are described. The first patient (implant case 4, Table 1) was a 74-year-old woman who presented with a fractured tooth No. 6 (Figure 5). The tooth was removed, and immediate placement of a platform bone switch implant was performed with associated bone grafting. A digital record was made 5 months later using digital scanning (Figure 6). The final crown was delivered, providing good esthetics and functionality (Figure 7). At the 1-year follow-up a periapical x-ray revealed a stable soft-tissue profile with cervical bone above the implant junction (Figure 8).
A second patient (implant case 17, Table 1) was a 35-year-old woman who was missing tooth No. 13 for the previous few years (Figure 9). Placement of a platform bone switch implant (4.2 mm x 8 mm with a 3.75-mm diameter at the neck) was performed (Figure 10). The final crown was placed 4 months later (Figure 11). Papillary soft-tissue maturation became evident over time (Figure 12).
A third patient treatment example (implant case 11, Table 1) was a 62-year-old male patient who presented with a failing maxillary left second molar next to a long-standing edentulous site at the first molar (Figure 13). The patient had a history of well-controlled hypertension. The failing tooth, No. 15, was removed, and the socket was curetted and grafted with graft material (Figure 14). Three months later, two platform bone switch implants (6 mm x 10 mm) were placed side by side with sinus floor intrusion (Figure 15). The implants were left to heal for 2 additional months and then restored with single crowns. At the 2-year follow-up, full papillary form, shallow pocketing, well-positioned marginal gingiva, and bone above the implant-abutment junctions were evident (Figure 16).
With the use of this type of implant, the lack of bacterial effluence from the implant-abutment junction eliminates a significant source of bacteria that can cause inflammatory zone bone loss. A tight seal helps provide a favorable environment for bone maintenance above the junction, as shown in Figure 17 through Figure 19 (implant case 16, Table 1), acting similar to a one-piece implant.
Overall, for the 32 implant treatments, results demonstrated bone for support of papillae and marginal gingivae as well as cervical bone persistence above the implant-abutment junction in 86 of 96 sites during the study period (Table 1).
Discussion
This study showed satisfactory soft- and hard-tissue findings. Typically, implant junctions leak bacteria and express an inflammatory zone that subtracts bone at the abutment connection, a confounding variable when measuring bone loss (or gain).23 In this study, no inflammatory bone loss at the implant-abutment junction was observed.
At 59 of the 64 implant-adjacent papillary sites, bone presence above the junction and associated papillary form was assessed as satisfactory, meaning within acceptable papillary height. However, it was not possible to assess bone support contribution to final papilla height.
In all 32 implants placed, facial gingival stability was present with no observable facial marginal bone loss. In five patients, however, the marginal gingiva was slightly less high than observed on adjacent teeth.
Bone persistence above the implant-abutment junction of 0.5 mm or more was observed in 28 of the 32 implants. One patient had 1 mm bone loss of the implant. No implants had significant inflammation, including no bleeding on probing or pocket depths above 4 mm. No evidence of peri-implant disease was observed.
Conclusion
In implant dentistry, the approach known as platform bone switch could play a role in bone maintenance, gingival architectural stability, and peri-implant health. Platform bone switch was studied retrospectively in 32 implant restorations in place from 1 to 3 years. Subcrestally placed implants were found to demonstrate marginal gingival stability, esthetic papillary form, and negligible bone loss as measured from the implant-abutment junction. Platform bone switch is a promising bone-sparing modification that preserves additional cervical bone when compared to straight-wall implants, leading to improved soft-tissue support for marginal gingiva and papillae as well as, potentially, persistence of greater peri-implant bone volume. Further quantitative study is needed to verify these preliminary findings.
Acknowledgment
Figure 1 and Figure 4 are courtesy of Ditron Dental, published with permission. Figure 2 and Figure 3 appeared in Jensen OT, Romanos G, Glick P. Front Oral Maxillofac Med.2023;5:73-83, and are published with permission from AME Publishing Company.
Disclosure
Dr. Jensen is chairman of Ditron Dental.
About the Authors
Ole T. Jensen, DDS, MS
Adjunct Professor, University of Utah School of Dentistry, Department of Oral and Maxillofacial Surgery, Salt Lake City, Utah
Robert J. Miller, DDS
Private Practice, Delray Beach, Florida; Fellow, American College of Dentists
Iham Gammas, DMD
Private Practice, Boston, Massachusetts; Diplomate, American Board of Oral Implantology/Implant Dentistry
Álvaro Gracia, DDS, DMD
Private Practice, Norton, Massachusetts; Diplomate, American Board of Oral Implantology/Implant Dentistry; Diplomate, Fellow, International Congress of Oral Implantologists
References
1. Danza M, Fromovich O, Guidi R, Carinci F. The clinical outcomes of 234 spiral family implants. J Contemp Dent Pract. 2009;10(5):E049-E056.
2. Danza M, Riccardo G, Carinci F. Bone platform switching: a retrospective study on the slope of the reverse conical neck. Quintessence Int. 2010;41(1):35-40.
3. Ting M, Tenaglia MS, Jones GH, Suzuki JB. Surgical and patient factors affecting marginal bone levels around dental implants: a comprehensive overview of systematic reviews. Implant Dent. 2017;26(2):303-315.
4. Insua A, Monje A, Wany HL, Miron RJ. Basis of bone metabolism around dental implants during osseointegration and peri implant bone loss. J Biomed Mater Res A. 2017;105(7):2075-2089.
5. Chapple ILC, Mealey BL, Van Dyke TE, et al. Periodontal health and gingival diseases and conditions on an intact and a reduce periodontium: consensus report of workgroup of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions. J Periodontol. 2018;89 suppl 1;S74-S84.
6. Carinci F, Brunelli G, Danza M. Platform switching and bone platform switching. J Oral Implantol. 2009;35(5):245-250.
7. Shah B, Dukka H, Alhachache S, et al. Analysis of risk factors for early crestal bone loss in osseointegrated, submerged implants prior to restoration. J Periodontol. 2023;94(12):1405-1413.
8. Roccuzzo M, Roccuzzo A, Ramanuskaite A. Papilla height in relation to the distance between bone crest and interproximal contact point at single-tooth implants: a systematic review. Clin Oral Implants Res.2018;29 suppl 15:50-61.
9. Danza M, Zollino I, Avantaggiato A, et al. Distance between implants has a potential impact on crestal bone resorption. Saudi Dent J.2011;23(3):129-133.
10. Cicciu M, Pratella U, Fiorillo L, et al. Influence of buccal and palatal bone thickness on post-surgical marginal bone changes around implants placed in posterior maxilla: a multi-center prospective study. BMC Oral Health. 2023;23(1):309.
11. Dagher M, Mokbel N, Aboukhalil R, et al. Marginal bone level and bone thickness reduction in delayed and immediate implant placement protocol 6 months post-loading: an observational clinical prospective study. J Maxillofac Oral Surg.2022;21(2):571-579.
12. Romandini M, Pedrinaci I, Lima C, et al. Prevalence and risk/protective indicators of buccal soft tissue dehiscence around dental implants. J Clin Peridontol. 2021;48(3):455-463.
13. Jung RE, Herzog M, Wolleb K, et al. A randomized controlled clinical trial comparing small buccal dehiscence defects around dental implants treated with guided bone regeneration or left for spontaneous healing. Clin Oral Implant Res. 2017;28(3):348-354.
14. Chow YC, Wang HL. Factors and techniques influencing peri implant papillae. Implant Dent. 2010;19(3):208-219.
15. Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-implant bone crest. J Periodontol. 2000;71(4):546-549.
16. Romanos GE. Tissue preservation strategies for fostering long-term soft and hard tissue stability. Int J Periodontics Restorative Dent.2015;35(3):363-371.
17. Jensen OT, Albrektsson T, Jemt T. Foreign body osseointegration. Int J Oral Maxillofac Implants.2023;38(5)838-840.
18. Albrektsson T, Chrcanovic B, Östman PO, Sennerby L. Initial and long-term crestal bone response to modern dental implants. Periodontol 2000. 2017;73(1):41-50.
19. Jensen OT, Weiss E, Grainger DW. The job to be done with biofilm and titanium implants. Front Oral Maxillofac Med.2021;3:21.
20. Trindade R, Albrektsson T, Tengvall P, Wennerberg A. Foreign body reaction to biomaterials: on mechanisms for buildup and breakdown of osseointegration. Clin Implant Dent Relat Res. 2016;18(1):192-203.
21. Albrektsson T, Tengvall P, Amengual L, et al. Osteoimmune regulation underlies oral implant osseointegration and its perturbation. Front Immunol.2023;13:1056914.
22. Jensen OT, Romanos G, Glick P. Platform bone switch to increase cervical ring of bone mass. Front Oral Maxillofac Med.2023;5:73-83.
23. Sasada Y, Cochran DL. Implant-abutment connections: a review of biologic consequences and peri-implantitis implications. Int J Oral Maxillofac Implants. 2017;32(6):1296-1307.
