Pieter Onclin

Implant-retained maxillary overdentures CHALLENGES AND TREATMENT MODALITIES Pieter Onclin Solaittary tachmen ts Atrophic te j aws mplate? Limepsslatnhtas?n four

Implant-retained maxillary overdentures CHALLENGES AND TREATMENT MODALITIES Pieter Onclin

Printing: Ridderprint, www.ridderprint.nl Layout and design: Hans Schaapherder, persoonlijkproefschrift.nl Artwork: Pieter Onclin The research presented in this thesis was performed and financed at the Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, The Netherlands. Additional support was obtained from an unrestricted grant of the Boering Stichting. Copyright 2023 © Pieter Onclin, The Netherlands. All rights reserved. No parts of this thesis may be reproduced, stored in a retrieval system or transmitted in any form or by any means without permission of the author.

CONTENTS Chapter 1 General introduction 9 Chapter 2 Maxillary implant overdentures retained with bars or solitary attachments: a 5-year randomised controlled trial 17 Chapter 3 Utilising the nasal aperture for template stabilisation for guided surgery in the atrophic maxilla 41 Chapter 4 Two or four implants to support a maxillary overdenture in fully edentulous patients: 1-year results of a randomized controlled trial 55 Chapter 5 The performance of two-implant overdentures in the atrophic maxilla: a case series with 1-year follow-up 75 Chapter 6 Incidence of peri-implant mucositis and peri-implantitis in patients with a maxillary overdenture: a sub-analysis of two prospective studies with a 10-year follow-up period 91 Chapter 7 Retreatment of multiple failing maxillary implants after full arch rehabilitation: a retrospective, observational cohort study 105 Chapter 8 General discussion and conclusions 121 Appendices Summary 134 Samenvatting 138 Dankwoord 142 Curriculum vitae 147 List of sponsors 148

Chapter 1 General introduction

10 Chapter 1 GENERAL INTRODUCTION Patients experiencing problems with their conventional maxillary denture can benefit from an implant-retained overdenture (IOD)1-3. For the maxilla, several retention systems for the connection of the overdenture to the implants are available which can be roughly divided into bar retained IODs, in which multiple implants are splinted and the overdenture is attached through retentive clips, and retention systems using non-splinted solitary attachments. Four implants with a bar-clip attachment is currently the favourable treatment option as implant survival rates are high, marginal bone level change is low, patient satisfaction is high, masticatory performance improves and ten years complication rates are low1-7. Therefore, this treatment may be considered the current gold standard. However, treating patients with a maxillary IOD can be challenging, especially in case of severe atrophy of the alveolar process, in which extensive reconstructive surgery using bone augmentation is needed. The implant survival after reconstructive surgery is reliable and predictable, but harvesting of bone grafts is expensive and invasive, can induce morbidity and, due to the extent of the reconstruction needed, it is often performed under general anaesthesia8. Because of these factors, this treatment may be undesirable for certain categories of patients. With an increasingly aging population and subsequent age-associated co-morbidities, the demand for less invasive elective surgical procedures, with a much lower burden, is increasing. Thus, when reconstructive surgery can be avoided, morbidity, treatment costs, invasiveness and treatment-time are also reduced. Furthermore, the procedure can then also be performed in an outpatient treatment setting. The need for a reconstructive procedure could be reduced using 3D virtual surgical planning (3D VSP). Using 3D VSP, a 3D reconstruction is made from the patient’s cone beam computed tomography (CBCT) images, including the patient’s conventional denture9. With this 3D reconstruction, the available maxillary bone volume, and surrounding structures such as the nasal cavity and maxillary sinuses can be inspected virtually. Subsequently, virtual implants can be planned in the prosthetically preferred position where sufficient bone volume is present. Next, the planned position of the implants can then be transferred to the patient using a mucosa supported surgical template. Using a mucosa supported template, the stability can be compromised in case of resilient underlying mucosa, a shallow palate, or alveolar bone resorption. These factors are often present in patients experiencing lacking stability and retention of their conventional denture. Therefore, an open flap approach may be more appropriate10,11. Using an open flap approach, the alveolar process offers a bony support which allows for less template displacement of the surgical template. However, in case of extreme atrophy of the alveolar process, template displacement may still occur12-14. To overcome template positioning problems and enable safe and precise implant placement in atrophied edentulous maxillae, a template with enhanced stabilisation is needed.

11 General introduction Besides the above-mentioned optimization of the surgical part of the treatment, there may also be room for optimization of the prosthetic part of the treatment. As an alternative to bar-clip retention, the overdenture could also be retained by using solitary attachments. Solitary attachments are easy to clean by the patient and repairs of the attachments can be often done chairside at the dental office15. Since these solitary attachments are generic, initial costs are lower than bar-retained overdentures. Another optimization might be using less than four implants to retain the overdenture, which also can reduce invasiveness and the costs of the surgical procedure. Both alternatives have been studied within a limited number of mostly short term, non-comparing, or retrospective studies. The results regarding marginal bone level change, implant survival and patient related outcomes are varying 7, 15-30 and need to be prospectively explored. Regardless of the treatment of choice, treatment of patients with implant-supported prosthetics always strives for a minimum of complications. Nevertheless, complications do occur. The technical complication rate in bar-retained four-implant maxillary IODs is known to be low1,2. On the other hand, the epidemiology of biological complications, i.e., peri-implant diseases is hardly reported. In general, peri-implant mucositis and peri-implantitis currently affects between 43-47% and 20-22% of patients treated with dental implants, respectively31,32. The incidence of peri-implant diseases in general and specifically for the edentulous patient has only been reported in a limited number of prospective studies33-40. If an implant is exposed to a longer infection period of peri-implantitis, this may lead to implant loss41. Furthermore, patients that have suffered from implant loss have a higher risk of losing additional implants41. While the loss of one implant may cause some retention loss in patients with maxillary IODs, the loss of multiple implants may also lead to prosthetic failure. If prosthetic failure occurs due to implant loss, a viable alternative without surgical treatment is not available42,43. Therefore, implant retreatment is often considered. Implant retreatment in general, however, is associated with lower implant survival rates because the patient is still subject to the factors that made the patient susceptible to implant failure44, e.g., a history of periodontitis, smoking, diabetes and genetic factors45. Specifically for the maxilla, additional factors are the lower bone density and quantity after implant failure, which further limit the implant survival rates46,47. Additionally, current knowledge is mostly based on retreatment cases that had previously failed to osseointegrate (i.e., early failure), rather than failure due to prolonged infection (i.e., late failure). The retreatment of late failures has been sparsely reported in case series46-49. 1

12 Chapter 1 GENERAL AIM AND OUTLINE OF THE THESIS The general aim of the PhD research described in this thesis was to assess the treatment outcomes of a number of maxillary implant overdenture treatment modalities for the atrophic edentulous maxilla in patients experiencing problems with their conventional denture. The specific aims were: 1. to assess the 5-year follow-up outcomes of bar or solitary retained maxillary overdentures supported by four implants in a randomised controlled trial; 2. to assess the clinical usability of a template and implant placement accuracy in patients with edentulous atrophic maxillae; 3. to assess the 1-year follow-up outcomes of bar-retained maxillary implant overdentures supported by two or four implants in a randomised controlled trial; 4. to assess the 1-year follow-up outcomes of solitary retained maxillary overdentures supported by two implants in compromised patients; 5. to assess the 10-year incidence of peri-implant mucositis and peri-implantitis in patients with implant-retained maxillary overdentures in a prospective study; 6. to assess outcomes of implant retreatment in a group of patients in whom all maxillary implants failed after full arch rehabilitation.

13 General introduction REFERENCES 1. Slot W, Raghoebar GM, Cune MS, Vissink A, Meijer HJA. Maxillary overdentures supported by four or six implants in the anterior region: 10-year randomized controlled trial results. J Clin Periodontol. 2023;50:36-44. doi: 10.1111/ jcpe.13726. 2. Slot W, Raghoebar GM, Cune MS, Vissink A, Meijer HJA. Maxillary bar overdentures on four or six posterior implants: 10-year results from a randomized clinical trial. Clin Oral Implants Res. 2022;33:1147-56. doi: 10.1111/clr.13997. 3. Boven GC, Slot JWA, Raghoebar GM, Vissink A, Meijer HJA. Maxillary implant-supported overdentures opposed by (partial) natural dentitions: a 5-year prospective case series study. J Oral Rehabil. 2017;44:988-95. doi: 10.1111/ joor.12557. 4. Akca K, Cehreli MC, Uysal S. Marginal bone loss and prosthetic maintenance of bar-retained implant-supported overdentures: a prospective study. Int J Oral Maxillofac Implants. 2010;25:137-45. 5. Boven GC, Speksnijder CM, Meijer HJA, Vissink A, Raghoebar GM. Masticatory ability improves after maxillary implant overdenture treatment: A randomized controlled trial with 1-year follow-up. Clin Implant Dent Relat Res. 2019;21:369-76. doi: 10.1111/cid.12721. 6. Mangano C, Mangano F, Shibli JA, Ricci M, Sammons RL, Figliuzzi M. Morse taper connection implants supporting “planned” maxillary and mandibular bar-retained overdentures: a 5-year prospective multicenter study. Clin Oral Implants Res. 2011 ;22:1117-24. doi: 10.1111/j.1600-0501.2010.02079.x. 7. Ma S, Waddell JN, Atieh MA, Alsabeeha NH, Payne AG. Maxillary three-implant overdentures opposing mandibular two-implant overdentures: 10-Year Prosthodontic Outcomes. Int J Prosthodont. 2016;29:327-36. doi: 10.11607/ ijp.4631. 8. Putters TF, Wortmann DE, Schortinghuis J, van Minnen B, Boven GC, Vissink A, Raghoebar GM. Morbidity of anterior iliac crest and calvarial bone donor graft sites: a 1-year randomized controlled trial. Int J Oral Maxillofac Surg. 2018;47:1474-80. doi: 10.1016/j. ijom.2018.06.002. 9. Verstreken K, Van Cleynenbreugel J, Martens K, Marchal G, van Steenberghe D, Suetens P. An image-guided planning system for endosseous oral implants. IEEE Trans Med Imaging. 1998; 17: 842-52. 10. Block MS, Chandler C. Computed tomography-guided surgery: complications associated with scanning, processing, surgery, and prosthetics. J Oral Maxillofac Surg. 2009; 67: 13-22. doi: 10.1016/j.joms.2009.04.082. 11. Colombo M, Mangano C, Mijiritsky E, Krebs M, Hauschild U, Fortin T. Clinical applications and effectiveness of guided implant surgery: a critical review based on randomized controlled trials. BMC Oral Health. 2017; 17: 150. doi: 10.1186/ s12903-017-0441-y. 12. D’haese J, Van De Velde T, Elaut L, De Bruyn H. A prospective study on the accuracy of mucosally supported stereolithographic surgical guides in fully edentulous maxillae. Clin Implant Dent Relat Res. 2012; 14: 293-303. doi: 10.1111/j.17088208.2009.00255.x. 13. Di Giacomo GA, Cury PR, de Araujo NS, Sendyk WR, Sendyk CL. Clinical application of stereolithographic surgical guides for implant placement: preliminary results. J Periodontol. 2005; 76: 503-7. 14. Arisan V, Karabuda CZ, Ozdemir T. Implant surgery using bone- and mucosa-supported stereolithographic guides in totally edentulous jaws: surgical and post-operative outcomes of computer-aided vs. standard techniques. Clin Oral Implants Res. 2010; 21: 980-8. doi: 10.1111/j.1600-0501.2010.01957.x. 15. Cordaro L, di Torresanto VM, Petricevic N, Jornet PR, Torsello F. Single unit attachments improve peri-implant soft tissue conditions in mandibular overdentures supported by four implants. Clin Oral Implants Res. 2013;24:536-42. doi: 10.1111/j.1600-0501.2012.02426.x. 16. Al-Zubeidi MI, Alsabeeha NH, Thomson WM, Payne AG. Patient satisfaction with maxillary 3-implant overdentures using different attachment systems opposing mandibular 2-implant overdentures. Clin Implant Dent Relat Res. 2012;14 Suppl 1:e11-9. doi: 10.1111/j.17088208.2010.00332.x. 17. Bergendal T, Engquist B. Implant-supported overdentures: a longitudinal prospective study. Int J Oral Maxillofac Implants. 1998;13:253-62. 18. Boven GC, Meijer HJA, Vissink A, Raghoebar GM. Maxillary implant overdentures retained by use of bars or locator attachments: 1-year findings from a randomised controlled trial. J Prosthodont Res. 2020;64:26-33. doi: 10.1016/j. jpor.2019.04.013. 1

14 Chapter 1 19. Bouhy A, Rompen E, Lamy M, Legros C, Lecloux G, Lambert F. Maxillary implant overdenture retained by four unsplinted attachments and opposed by a natural or fixed dentition: Oneyear clinical outcomes. Clin Oral Implants Res. 2020;31:747-67. doi: 10.1111/clr.13623. 20. Di Francesco F, De Marco G, Sommella A, Lanza A. Splinting vs not splinting four implants supporting a maxillary overdenture: a systematic review. Int J Prosthodont. 2019;32:509-18. doi: 10.11607/ijp.6333. 21. Guédat C, Nagy U, Schimmel M, Müller F, Srinivasan M. Clinical performance of LOCATOR® attachments: A retrospective study with 1-8 years of follow-up. Clin Exp Dent Res. 2018;4:132-45. doi: 10.1002/cre2.122. 22. Mañes Ferrer JF, Fernández-Estevan L, Selva-Otaolaurruchi E, Labaig-Rueda C, Solá-Ruíz MF, Agustín-Panadero R. Maxillary implant-supported overdentures: mechanical behavior comparing individual axial and bar retention systems. A Cohort Study of Edentulous Patients. Medicina (Kaunas). 2020;56:139. doi: 10.3390/ medicina56030139. 23. Mo A, Hjortsjö C, Olsen-Bergem H, Jokstad A. Maxillary 3-implant removable prostheses without palatal coverage on Locator abutments - a case series. Clin Oral Implants Res. 2016;27:1193-9. doi: 10.1111/clr.12724. 24. Sanna A, Nuytens P, Naert I, Quirynen M. Successful outcome of splinted implants supporting a ‘planned’ maxillary overdenture: a retrospective evaluation and comparison with fixed full dental prostheses. Clin Oral Implants Res. 2009;20:406-13. doi: 10.1111/j.16000501.2008.01664.x. 25. Smeets EC, de Jong K J, Abraham-Inpijn L. Detecting themedically compromised patient in dentistry by means of the medical risk-related history. A survey of 29,424 dental patients in The Netherlands. Prev Med. 1998;27,530–5. 26. Raghoebar GM, Meijer HJ, Telleman G, Vissink A. Maxillary sinus floor augmentation surgery with autogenous bone grafts as ceiling: a pilot study and test of principle. Clin Implant Dent Relat Res 2013;15:550–7 27. Troeltzsch M, Troeltzsch V, Brodine AH, Frankenberger R, Messlinger K, Troeltzsch M. Clinical performance and peri-implant parameters of 132 implants supporting locator-retained overdentures: a case series of 33 patients. Int J Oral Maxillofac Implants. 2013;28:1132-9. doi: 10.11607/jomi.3009. 28. Wang F, Monje A, Huang W, Zhang Z, Wang G, Wu Y. Maxillary Four implant-retained overdentures via Locator® attachment: intermediate-term results from a retrospective study. Clin Implant Dent Relat Res. 2016;18:571-9. doi: 10.1111/ cid.12335. 29. Weng D, Richter EJ. Maxillary removable prostheses retained by telescopic crowns on two implants or two canines. Int J Periodontics Restorative Dent. 2007;27:35-41. 30. Zembic A, Tahmaseb A, Jung RE, Wismeijer D. One-year results of maxillary overdentures supported by 2 titanium-zirconium implants - implant survival rates and radiographic outcomes. Clin Oral Implants Res. 2017;28:e60-e67. doi: 10.1111/clr.12863. 31. Derks J, Tomasi C. Peri-implant health and disease. A systematic review of current epidemiology. J Clin Periodontol. 2015;42 Suppl 16:S158-S171. doi:10.1111/jcpe.12334 32. Lee CT, Huang YW, Zhu L, Weltman R. Prevalences of peri-implantitis and peri-implant mucositis: systematic review and meta-analysis. J Dent. 2017;62:1-12. doi:10.1016/j. jdent.2017.04.011 33. Donati M, Ekestubbe A, Lindhe J, Wennström JL. Implant-supported single-tooth restorations. A 12-year prospective study. Clin Oral Implants Res. 2016;27:1207-11. doi:10.1111/clr.12726 34. Krennmair S, Hunger S, Forstner T, Malek M, Krennmair G, Stimmelmayr M. Implant health and factors affecting peri-implant marginal bone alteration for implants placed in staged maxillary sinus augmentation: A 5-year prospective study. Clin Implant Dent Relat Res. 2019;21:32-41. doi:10.1111/cid.12684 35. Lopes A, Maló P, de Araújo Nobre M, Sanchez-Fernández E. The NobelGuide® All-on-4® Treatment Concept for Rehabilitation of Edentulous Jaws: A Prospective Report on Medium- and Long-Term Outcomes. Clin Implant Dent Relat Res. 2015;17 Suppl 2:e406-16. doi:10.1111/ cid.12260 36. Meijer HJ, Raghoebar GM, de Waal YC, Vissink A. Incidence of peri-implant mucositis and peri-implantitis in edentulous patients with an implant-retained mandibular overdenture during a 10-year follow-up period. J Clin Periodontol. 2014;41:1178-83. doi:10.1111/ jcpe.12311 37. Renvert S, Lindahl C, Rutger Persson G. The incidence of peri-implantitis for two different implant systems over a period of thirteen years. J Clin Periodontol. 2012;39:1191-7. doi:10.1111/ jcpe.12017

15 General introduction 38. Stoker G, van Waas R, Wismeijer D. Long-term outcomes of three types of implant-supported mandibular overdentures in smokers. Clin Oral Implants Res. 2012;23:925-9. doi:10.1111/j.16000501.2011.02237.x 39. van Velzen FJ, Ofec R, Schulten EA, Ten Bruggenkate CM. 10-year survival rate and the incidence of peri-implant disease of 374 titanium dental implants with a SLA surface: a prospective cohort study in 177 fully and partially edentulous patients. Clin Oral Implants Res. 2015;26:1121-8. doi:10.1111/clr.12499 40. Zetterqvist L, Feldman S, Rotter B, et al. A prospective, multicenter, randomized-controlled 5-year study of hybrid and fully etched implants for the incidence of peri-implantitis. J Periodontol. 2010;81:493-501. doi:10.1902/ jop.2009.090492 41. Manor Y, Oubaid S, Mardinger O, Chaushu G, Nissan J. Characteristics of early versus late implant failure: a retrospective study. J Oral Maxillofac Surg. 2009;67:2649-52. doi: 10.1016/j. joms.2009.07.050 42. Mardinger O, Ben Zvi Y, Chaushu G, Nissan J, Manor Y. A retrospective analysis of replacing dental implants in previously failed sites. Oral Surg Oral Med Oral Pathol Oral Radiol.2012;114:290-3. doi: 10.1016/j. tripleo.2011.07.010 43. Wang F, Zhang Z, Monje A, Huang W, Wu Y, Wang G. Intermediate long-term clinical performance of dental implants placed in sites with a previous early implant failure: a retrospective analysis. Clin Oral Implants Res. 2015;26:1443-9. doi: 10.1111/clr.12485 44. Grossmann Y, Levin L. Success and survival of single dental implants placed in sites of previously failed implants. J Periodontol. 2007:78;1670-4 45. Schwarz F, Derks J, Monje A, Wang HL. Peri-implantitis. J Clin Periodontol. 2018;45 Suppl 20:S246-66. doi: 10.1111/jcpe.12954. 46. Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Survival of dental implants placed in sites of previously failed implants. Clin Oral Implants Res. 2017;28:1348-53. doi: 10.1111/ clr.12992 47. Kim YK, Park JY, Kim SG, Lee HJ. Prognosis of the implants replaced after removal of failed dental implants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;110:281-6. doi: 10.1016/j.tripleo.2010.01.031 48. Machtei EE, Mahler D, Oettinger-Barak O, Zuabi O, Horwitz J. Dental implants placed in previously failed sites: survival rate and factors affecting the outcome. Clin Oral Implants Res. 2008;19:259-64. doi: 10.1111/j.16000501.2007.01466.x 49. Gomes GH, Misawa MYO, Fernandes C, Pannuti CM, Saraiva L, Huynh-Ba G, Villar CC. A systematic review and meta-analysis of the survival rate of implants placed in previously failed sites. Braz. oral res. 2018;32:e27. http:// www.scielo.br/scielo.php?script=sci_arttext&pid=S1806-83242018000100950&lng=en. [Accessibility verified July 9, 2019] 1

Chapter 2 Maxillary implant overdentures retained with bars or solitary attachments: a 5-year randomised controlled trial Onclin P Boven GC Vissink A Meijer HJ Raghoebar GM This chapter is an edited version of the manuscript: Maxillary implant overdentures retained with bars or solitary attachments: a 5-year randomised controlled trial. J Prosthodont Res. 2022. doi: 10.2186/jpr.JPR_D_22_00076. Epub ahead of print.

18 Chapter 2 ABSTRACT Introduction There are several retention systems available for maxillary implant overdentures (IODs), which can be roughly divided into bar-retained IODs, in which multiple implants are splinted and the overdenture is attached through retentive clips, and into retention systems using non-splinted solitary attachments. While splinted retention can be considered the gold standard, prospective research on the non-splinted alternatives is currently lacking. The aim of this study was to compare the 5-year follow-up outcomes of maxillary overdentures retained by bars or solitary attachments. Materials and methods Fifty consecutively selected fully edentulous patients experiencing problems with their conventional denture received four implants and were randomly allocated to receive a maxillary overdenture with either bar- or solitary attachment retention. Marginal bone level change (primary outcome), implant- and overdenture survival rate, clinical- and patient related outcome measures were recorded at baseline, and after 1 and 5 years. Biological and technical complications were recorded throughout the entire follow-up period. Results After 5 years, the mean marginal bone level change was higher in the solitary attachment group (-1.41±1.38mm, p=0.024) than in the bar group (-0.99±0.96mm). Also, fewer implants survived in the solitary attachment group (89.5%, p=0.027) than in the bar group (96.3%). The overdenture survival rate was 95.0% and 91.3% in the bar and solitary attachment group, respectively. Although the clinical and patient related outcomes were favourable and did not differ significantly between the groups, the peri-implantitis incidence was 25.8% in the solitary attachment group and 5.1% in the bar group. Any technical complications were minor. Conclusion In maxillary 4-implant overdenture therapy, the marginal bone level, implant survival rate, and the number of complications are better with bar attachments than with solitary attachments. Both groups’ clinical and patient related outcome measure scores were equal throughout the entire follow-up period.

19 Maxillary implant overdentures: bars or solitary attachments 2.1 INTRODUCTION Patients experiencing problems with their conventional maxillary denture can benefit from implant-retained overdentures (IODs)1-3. Several retention systems are available which can be roughly divided into bar-retained IODs, in which multiple implants are splinted and the overdenture is attached through retentive clips, and into retention systems using non-splinted solitary attachments. Bar-retained IODs on four implants provide good retention, require little maintenance, but are more expensive than solitary attachments. The medium term results of IODs on four implants (4-IOD) with bar retention are promising, with high implant and overdenture survival rate and a low incidence of complications, and may be considered the gold standard1-6. Solitary attachments, an alternative to bars, are more economical and easy to clean by the patient7, but wear more easily, which can cause lack of retention8. However, replacing these attachments can often be done chair side. A recent review reported that, when a maxillary IOD is supported by four implants, both types show equal implant survival rate, overdenture survival rate and patient satisfaction9. However, these conclusions are based on a limited number of randomised controlled trials. Moreover, most studies on solitary attachments were mostly short term, non-comparing or retrospective, and therefore inconclusive. This underlines the need for studies comparing different attachment systems with a longer follow-up. We conducted a randomised controlled trial to compared the treatment outcomes of fully edentulous patients with maxillary IODs, supported by four implants, retained by either bars or solitary attachments. Marginal bone level change, implant and overdenture survival rate, technical and biological complications, clinical characteristics and patient related outcome measures were assessed during a 5-year follow-up. 2.2 MATERIALS AND METHODS Patients Between January 2013 and January 2016, all eligible fully edentulous patients experiencing problems with their maxillary conventional denture that were referred to the Department of Oral and Maxillofacial Surgery (University Medical Center Groningen, the Netherlands) were asked to participate in a randomised controlled trial. The patients were considered eligible to participate if they had been fully edentulous for at least one year and had sufficient bone volume to place four implants in the anterior maxilla. The patients were allowed to have mandibular IODs. The bone volume was assessed using cone beam computed tomography (CBCT). The exclusion criteria were an American Society of Anaesthesiologists score (ASA score10) of ≥III, smoking, former radiotherapy in the head and neck region, pre-prosthetic surgery or previous loss of implants in the maxilla. All the participants received oral and written information about the trial. Signed informed consent was obtained from each participant. The initial 1-year trial was approved by the Medical Ethical Committee of the UMCG and the study was registered in the Dutch Trial Register (NL3813). In the present 5-year follow-up study, no new interventions were carried out and was therefore not considered research performed on test-subjects as meant in the Medical Research Involving Human Subjects Act (WMO) (MEC-reference M20.259187). The 2

20 Chapter 2 study was registered in the trial register as NL9031. The study was conducted in accordance with the 2008 revised requirements of the Helsinki Declaration of 1975 and the CONSORT Guidelines. Using sealed envelope randomisation, the participants were randomly assigned to receive either the maxillary 4-IOD with solitary attachments (n = 25), or the maxillary 4-IOD with bar attachments (n = 25) (Fig. 2.1). The treatment procedures will be described in brief; a full description of all the procedures can be found in the previously reported 1-year results8. Figure 2.1 | CONSORT flow diagram.

21 Maxillary implant overdentures: bars or solitary attachments a) b) c) Figure 2.2 | Intra-oral view (a) and corresponding overdenture (b/c) of a participant with solitary retention after five years. 2

22 Chapter 2 Surgical procedure All the participants received four maxillary implants (Nobel Active Narrow Platform ⌀ 3.5 mm, Nobel Biocare AB, Gothenburg, Sweden), guided by a surgical stent at crestal bone level in predefined positions (anterior implants in the central/lateral incisor region, posterior implants in the cuspid/first bicuspid region) via a two-stage surgical protocol. Incidental bone dehiscence was covered with a mixture of maxillary tuberosity bone and organic bovine bone (Bio-Oss, Geistlich Pharma AG, Wolhusen, Switzerland) and a resorbable membrane (Bio-Gide, Geistlich Pharma AG). In case of partial extension into the anterior region of the sinus, sinus floor elevation surgery was performed using the lateral window technique11 with bone harvested from the tuberosity and mixed with organic bovine bone. The lateral window was covered by a resorbable collagen membrane. If not already present, the participants simultaneously received two mandibular implants (Nobel Replace Select TC, Nobel Biocare AB). All the participants received antibiotic prophylaxis before the surgery (Amoxicillin, 3000mg, one hour preoperatively), and then continued afterwards with antibiotics (amoxicillin, 500mg, three times daily, seven days) and an additional 0.2% chlorhexidine mouth rinse (Corsodyl, GlaxoSmithKline). The participants were instructed not to wear their conventional prosthesis for two weeks. Thereafter, the prosthesis was adjusted with a resilient lining material (Soft liner; GC Corp., Tokyo, Japan). After a 3-month osseointegration period, second stage surgery was performed by placing healing abutments and a standard prosthetic procedure was initiated. Prosthodontic procedure The solitary attachment group’s final superstructure consisted of an overdenture with a built-in cobalt chromium reinforcement structure with Locator® denture caps and nylon Locator® males which were connected to four Locator® attachments (DIT-USA, Scottsdale, Arizona, USA; Fig. 2.2). The study’s participants were initially provided with pink inserts (13.4 N; medium force), providing possibilities to strengthen or loosen the retention force. Regarding the bar group, the final superstructure consisted of an overdenture with gold retentive clips (Cendres+Metaux, Biel/Bienne, Switzerland) that were point-lasered to a virtually designed, 3D-printed cobalt chromium reinforcement (Proscan, Zonhoven, Belgium), attached to a virtually designed, milled ovoid titanium bar with distal extensions (Proscan, Zonhoven, Belgium) which were screw-retained to multi-unit abutments (Nobel Biocare AB) (Fig. 2.3). The overdenture was attached to the two bars with three retentive clips per bar. Both groups’ overdentures were designed without palatal coverage of the maxilla. Most participants simultaneously received a mandibular IOD. In case the participant’s current IOD was adequate, no new IOD was made. The participants were instructed in hygiene procedures associated with the overdentures and superstructures, and routine maintenance appointments were scheduled.

23 Maxillary implant overdentures: bars or solitary attachments a) b) c) Figure 2.3 | Intra-oral view (a) and corresponding overdenture (b/c) of a participant with bar retention after five years. 2

24 Chapter 2 Outcome measures The primary outcome measure was marginal bone level change (MBLC). Implant survival rate, overdenture survival rate, clinical characteristics, biological complications, technical complications and patient related outcome measures (PROMs) were the secondary outcome measures. Clinical and radiographic evaluations took place at one month (T1), 12 months (T12) and 60 months (T60) after the prosthetic loading. The PROMs were evaluated before treatment (T0), at T12 and T60. Marginal bone level change The radiographs were taken with an Extension Cone Paralleling Photostimulable Phosphor holder (RINN, Dentsply, Elgin, IL, USA). Linear measurements were performed by one blinded experienced observer (HJAM) with measurement software (Biomedical Engineering, University Medical Center Groningen, the Netherlands). Prior to analysis, the superstructures were cropped from the digital radiographs to facilitate blinded measurements. The neck of the implant was used as a reference line for all the measurements. The images were calibrated using the implant’s dimensions. Measurements were done at the mesial and distal side of each implant. MBLC was defined as the difference in bone height between the radiograph taken at T1 (baseline) and T12 or T60. The side having the largest MBLC (mesial or distal) of each individual implant was used for analysis. Implant and overdenture survival rate Implant survival rate was defined as the percentage of implants still present and not mobile at the follow-up evaluation. Percussion testing was done to assess implant mobility. The bar group’s assessment occurred after the bar was removed. Maxillary overdenture survival rate was defined as the percentage of the initially placed overdentures still present at the follow-up. Clinical parameters For each implant, the following clinical characteristics were assessed: • The presence of plaque using the index described by Loë and Silness12 (score 0: no detection of plaque; score 1: plaque can be detected by running a probe across the smooth marginal surface of the abutment and implant; score 2: plaque can be seen by the naked eye; score 3: an abundance of plaque). For each participant, the implant with the highest score was used for analysis. • The presence of calculus with a score of 0 or 1 (the absence or presence of calculus, respectively). For each participant, the implant with the highest score was used for analysis. • Peri-implant mucosa health using the modified Löe and Silness index12(score 0: normal peri-implant mucosa; score 1: mild inflammation, slight change in colour, slight oedema; score 2: moderate inflammation, redness, oedema and glazing; score 3: severe inflammation, marked redness and oedema, ulceration). For each participant, the implant with the highest score was used for analysis.

25 Maxillary implant overdentures: bars or solitary attachments • Bleeding on probing using the Mombelli et al. index13 (score 0: no bleeding when using a periodontal probe; score 1: isolated bleeding spots visible; score 2: a confluent red line of blood along the mucosa margin; score 3: heavy or profuse bleeding). For each participant, the implant with the highest score was used for analysis. • The peri-implant probing depth was measured at four sites of each implant (mesial, vestibular, distal and oral) with a manual periodontal probe; the distance between the marginal border of the mucosa and the tip of the periodontal probe was noted as probing depth. Probing depth change (PDC) was defined as the difference in probing depth between the T1 (baseline) and T12 or T60. The largest PDC of each participant was used for analysis. Biological and technical complications Biological complications, i.e. peri-implantitis and peri-implant mucositis, were calculated at the end of the follow-up period. A case of peri-implantitis was defined as a site showing bleeding and/or suppuration on probing and a MBLC ≥-2 mm, whereas peri-implant mucositis was defined as a site showing bleeding and/or suppuration on probing with a radiographic MBLC <-2mm, following the consensus reached at the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions14. Implants that failed due to severe bone loss (e.g. were untreatable for peri-implantitis) were removed and were scored as lost implants. Any implants that were treated or lost because of peri-implant diseases were added to the 5-year follow-up data. Technical complications were scored at any time after overdenture placement and included loosening of denture teeth, replacement or tightening of nylon caps or gold clips due to retention loss, and adaptation of the denture edges because of pressure ulcers. Patient related outcome measures The PROMs were assessed from three validated questionnaires focusing on chewing ability15, denture satisfaction16 and oral health quality of life17. PROMs were compared within and between groups. Sample-size estimation A sample size estimation was carried out with a statistical power analysis software18. A 0.4±0.5 mm marginal bone level change was estimated as a clinically relevant difference between groups, partly based on a previous systematic review on IODs19. An alpha of 0.05 and a power of 0.85 meant the calculated sample size for between group comparison had to be n = 46. A sample size of 50 took into account any possible loss to follow-up. Data analysis Continuous data (MBLC, PDC, PROMs) were tested for normality with the Shapiro-Wilk test and additional histogram observation. If normality was assumed, these data were analysed using a student T-test. If normality was not assumed, these data were analysed with the Wilcoxon signed rank test (for within-group differences) and Mann-Whitney U-test (for between-group differences). 2

26 Chapter 2 All the other clinical variables (ordinal data) were analysed via Wilcoxon signed rank tests (for within-group differences) and a Mann-Whitney U test (for between-group differences). Implant and overdenture survival rate differences between the groups were calculated using a Log Rank test. A p-value of less than 0.05 was considered statistically significant. Pairwise deletion was used for missing data and between-group comparisons. List-wise deletion was used for missing data and within-group comparisons. All the analyses were performed with the SPSS 23.0 software (SPSS, Inc., Chicago, IL, USA). 2.3 RESULTS Patient Characteristics The solitary attachment group’s mean age was 60.1 years (+- 8.6, range 37.5-75.0) and the bar group’s was 63.8 years (+- 5.4, range 53.0 – 72.6). Gender distribution was equal in both groups (13 male, 12 female). During the follow-up period, four participants deceased (one in the solitary attachment group, three in the bar group), two participants moved without leaving an address (one in each group) and one participant (bar group) was too ill to attend the 5-year follow-up. Consequently, 23 solitary attachment group participants and 20 bar group participants were available for the 5-year evaluation (Fig. 2.1). Table 2.1 | Mean values and standard deviations (SD) of the marginal bone level change in mm for the solitary attachment and bar attachment groups, and the frequency distribution of the marginal bone level change 1 and 5 years after overdenture placement. 1 year after prosthesis placement 5 years after prosthesis placement Solitary attachment (n = 23) Bar attachment (n = 24) p-value Solitary attachment (n = 23) Bar attachment (n = 20) p-value Mean mm (SD) -0.58 (0.71) -0.31 (0.47) p = 0.002a -1.41 (1.38) -0.99 (0.96) p = 0.024a 0 to -0.5 mm 55.9% 71.4% 29.5% 42.7% >0.5 to -1.0 mm 17.2% 18.4% 18.2% 15.9% >-1.0 to -1.5 mm 17.2% 6.1% 18.2% 17.1% >-1.5 to -2.0 mm 6.5% 3.1% 11.4% 6.1% > -2.0 to -2.5 mm 1.1% 1.0% 1.1% 8.5% > -2.5 to -3.0 mm 1.1% 0.0% 5.7% 4.9% > -3 mm 1.1% 0.0% 15.9% 4.9% a Differences between the study groups were tested with the independent Student’s t-test.

27 Maxillary implant overdentures: bars or solitary attachments Normality testing Regarding MBLC and PDC, normality of data was assumed since the Shapiro-Wilk test did not result in a significant difference between the groups and the histograms had a bell-shaped curve. The PROMs did show a significant difference between the groups, thus normality of data was not assumed. Marginal bone level change The mean MBLC after 5 years was -1.41±1.38mm for the solitary attachment group and -0.99±0.96mm for the bar group, which was statistically significant (p=0.024, Table 2.1). Implant survival rate Five implants in five participants were lost during osseointegration (three in the solitary attachment group, two in the bar group); they were not replaced since an overdenture could still be fabricated using the remaining three implants. No additional implants were lost in the first year but, after five years, four other participants had lost seven implants, all in the solitary attachment group. This resulted in a 5-year survival rate of 89.5% in the solitary attachment group and 96.3% in the bar group. The difference in implant survival between the groups was statistically significant (p = 0.027, Log Rank test, Fig. 2.4). Figure 2.4 | Kaplan Meier curve of implant survival. 2

28 Chapter 2 Overdenture survival rate A decision was made not to replace two of the participants’ implants because they did not experience any loss of retention. The two and three implants that were lost by two other participants were replaced, as were their overdentures. One additional participant’s (bar group) overdenture was replaced due to wear, resulting in an overdenture survival rate of 95.0% for the bar group and 91.3% for the solitary attachment group, which means the difference between the groups was not statistically significant (p = 0.591, Log-Rank test, Fig. 2.5). Figure 2.5 | Kaplan Meier curve of overdenture survival. Probing depth change and clinical indices The mean PDC at the 5-year follow-up was +0.6±1.1mm for the solitary attachment group and +0.7±0.9mm for the bar group. The median plaque, calculus, gingival condition and bleeding indices scores are depicted in Table 2.2; there were no significant differences between the groups. Biological and technical complications Peri-implant mucositis occurred in 47.8% and 15.0% of the solitary attachment and bar groups’ participants, respectively. Peri-implantitis occurred in 25.8% and 5.1% of the solitary attachment and bar groups’ participants, respectively (Table 2.3). The calculated incidence rates include the treated and lost implants. Technical complications consisted of the replacement of attachment matrices (n=4), retightening of an abutment screw (n=1, solitary attachment group), tooth fracture repair (n=2, solitary attachment group) and prosthesis base fracture repair (n=1, bar group).

29 Maxillary implant overdentures: bars or solitary attachments Table 2.2 | Median change and interquartile range of the highest score per participant, from baseline to the 1 and 5 year follow-ups, for plaque-index, bleeding-index, gingival-index and presence of calculus. Mean change and standard deviations of the largest probing depth change per participant from baseline to the 1 and 5 year follow-ups. Change from baseline After 1 year After 5 years Solitary attachment (n=23) Bar attachment (n=24) p-value Solitary attachment (n=23) Bar attachment (n=20) p-value Plaque-index [IQR] (range 0-3) 0 [-1;1] 0 [-1;1] 0.870a 0 [-1;0] 0 [-1.5;0] 0.541a Bleeding-index [IQR] (range 0-3) 0 [-1;0] 0 [0;0.75] 0.135a 0 [0;1] 0 [0;0.5] 0.719a Gingival-index [IQR] (range 0-3) 0 [-1;0] 0 [-0.75;0] 0.239a 0 [-1;0] 0 [0;0.5] 0.490a Calculus-presence [IQR] (range 0-1) 0 [0;0] 0 [0;0] 1.000a 0 [0;0] 0 [0;0] 0.114a Probing depth change in mm (SD) 0.4 (1.0) 0.3 (0.9) 0.541b 0.6 (1.1) 0.7 (0.9) 0.697b Differences between the study groups were tested with the aMann–Whitney U test or bthe independent Student’s t-test. IQR: interquartile range; SD: standard deviation. Table 2.3 | Incidence rates of peri-implant mucositis and peri-implantitis (including lost implants). 5 years after prosthesis placement Solitary attachment Bar attachment Total Implants at risk (n) 89 79 168 Peri-implant mucositis 69.6% 45.0% 58.1% Peri-implantitis 44.9% 22.8% 34.5% Patients at risk (n) 23 20 43 Peri-implant mucositis 47.8% 15.0% 32.6% Peri-implantitis 25.8% 5.1% 16.1% Patient related outcome measures: within group comparison The within groups PROMS comparison is listed in Table 2.4. All the OHIP-NL and subscale items had improved significantly at the 5 year follow-up. The functional complaints questionnaire items regarding ‘functional complaints upper denture’, ‘general functional complaints’, ‘facial aesthetics’ and ‘general satisfaction score upper denture’ had also improved significantly in both groups. The same applied to chewing of all types of foods according to the 5 year follow-up questionnaire. 2

30 Chapter 2 Table 2.4 | Within-group comparison of the patient related outcome measures, specifically the OHIP-49NL, denture complaints questionnaire and chewing ability before treatment and 1 and 5 years after treatment. Solitary attachment group Bar attachment group Pre-­ treatment After 1 year Comparison Pre-­ treatment – After 1 year After 5 years Comparison Pre-­ treatment – After 5 years Pre-­ treatment After 1-year Comparison Pre-­ treatment – After 1 year After 5-year Comparison Pre-­ treatment – After 5 years Functional limitation [IQR] (max. 36) 17 [12.5-23] 9 [3-17] p = 0.002** 7.5 [5-12.75] p <0.001*** 19 [11.5-23.25] 6 [2-8.5] p <0.001*** 4 [0.75-11.25] p <0.001*** Physical pain [IQR] (max. 36) 17 [10-23] 3.5 [0.25-10.5] p <0.001*** 4 [1-11] p <0.001*** 19 [10.75-23] 2 [0-6.75] p <0.001*** 1 [0-10] p <0.001*** Psychological discomfort [IQR] (max. 20) 10 [8-16] 4 [0-9] p = 0.001** 1 [0-8] p <0.001*** 8.5 [2-14] 1 [0-6.5] p = 0.002** 0 [0.3.25] p <0.001*** Physical disability [IQR] (max. 36) 17 [9-26.5] 4.5 [1-10] p <0.001*** 3.5 [0.25-8.5] p = 0.001** 16 [9-21.5] 1 [0-6] p <0.001*** 1.5 [0-6.75] p <0.001*** Psychological disability [IQR] (max. 24) 6 [3-15] 1.5 [0-4] p = 0.002** 1 [0-5.5] p = 0.016* 7 [0.75-13] 0 [0-2] p <0.001*** 0 [0-2.5] p = 0.001** Social disability [IQR] (max. 20) 6 [1.5-13.5] 0 [0-2.75] p = 0.006** 0 [0-1.75] p = 0.002** 4 [0.75-8.25] 0 [0-0.5] p = 0.001** 0 [0-0.25] p = 0.004** Handicap [IQR] (max. 24) 8 [3-11] 1 [0-3.75] p = 0.001** 0 [0-2.75] p <0.001*** 3.5 [1.75-9] 0 [0-0] p <0.001*** 0 [0-2] p = 0.002** Total OHIP-NL49 score [IQR] (max. 196) 77 [59.5-120.5] 26.0 [9.0-61.0] p <0.001*** 21.0 [8.0-46.0] p <0.001*** 84 [52-105.5] 12.5 [3-36.5] p <0.001*** 8 [2-43.5] p <0.001*** Functional complaints upper denture [IQR] (max. 27) 13 [8.75-23] 2 [0-4] p <0.001*** 2 [1-4] p <0.001*** 15.5 [8.75-19.25] 1.06 [1-2] p <0.001*** 1[0-4] p <0.001*** [continued on next page]

31 Maxillary implant overdentures: bars or solitary attachments Table 2.4 | [continued] Solitary attachment group Bar attachment group Pre-­ treatment After 1 year Comparison Pre-­ treatment – After 1 year After 5 years Comparison Pre-­ treatment – After 5 years Pre-­ treatment After 1-year Comparison Pre-­ treatment – After 1 year After 5-year Comparison Pre-­ treatment – After 5 years Functional complaints in general [IQR] (max. 54) 23 [16.25-31.25] 3 [1-6.25] p <0.001*** 2.5 [0-5.75] p <0.001*** 15 [7.25-27.50] 1 [0-4.75] p <0.001*** 2[0-7.25] p <0.001*** Facial aesthetics [IQR] (max. 9) 4.5 [1-6.5] 0 [0-3] p =0.006** 1 [0-2.75] p <0.001*** 2 [0-5.25] 0 [0-0] p =0.003** 0[0-3] p = 0.045* “Neutral Space” [IQR] (max. 9) 1 [0-3] 0.5 [0-2.25] ns 0 [0-2] ns 0.5 [0-2] 0 [0-1] ns 0[0-2] Ns Aesthetics [IQR] (max. 36) 1 [0-5.5] 0 [0-1.25] ns 1 [0-3] ns 0 [0-1.25] 0 [0-1] ns 0[0-2.25] ns General satisfaction score upper denture [IQR] 4 [1-6] 8 [7-9] p <0.001*** 8 [8-9] p <0.001*** 4 [2-6] 9 [8-10] p <0.001*** 8 [8-9] p <0.001*** Total food chewing score [IQR] (max. 18) 11 [6-15] 4 [2-7] p <0.001*** 3 [1-6] p <0.001*** 11 [9-12] 0 [0-3] p <0.001*** 2 [2-5] p <0.001*** Soft foods score [IQR] (max. 6) 1 [1-3] 0 [0-0] p =0.007** 0 [0-0] p =0.007 ** 2 [1-3] 0 [0-0] p <0.001*** 0 [0-0] p <0.001*** Tough foods score [IQR] (max. 6) 3 [2-5] 0 [0-2] p <0.001*** 1 [0-2] p <0.001*** 4 [3-4] 0 [0-0] p <0.001*** 0 [0-0] p <0.001*** Hard foods score [IQR] (max. 6) 6 [4-6] 3 [2-6] p =0.007** 2 [1-4] p <0.001*** 6 [5-6] 0 [0-2] p <0.001*** 2 [0-4] p <0.001*** Differences were tested with the Wilcoxon Matched Pairs Signed Ranks test. IQR: interquartile range; ns: no significant differences. *: p < 0.05, ** p<0.01, *** p<0.001. 2

32 Chapter 2 Table 2.5 | Between-group comparisons of patient related outcome m8ujjjeasures, specifically the OHIP-49NL, Denture Complaints questionnaire and chewing ability before treatment and 1 and 5 years after treatment. Pre-treatment After 1 year After 5 years Solitary attachment group (n=25) Bar attachment group (n=25) p-value Solitary attachment group (n=23) Bar attachment group (n=24) p-value Solitary attachment group (n=23) Bar attachment group (n=20) p-value Functional limitation [IQR] (max. 36) 17 [12.5-23] 19 [11.5-23.25] ns 9 [3-17] 6 [2-8.5] ns 7.5 [5-12.75] 4 [0.75-11.25] ns Physical pain [IQR] (max. 36) 17 [10-23] 19 [10.75-23] ns 3.5 [0.25-10.5] 2 [0-6.75] ns 4 [1-11] 1 [0-10] ns Psychological discomfort [IQR] (max. 20) 10 [8-16] 8.5 [2-14] ns 4 [0-9] 1 [0-6.5] ns 1 [0-8] 0 [0.3.25] ns Physical disability [IQR] (max. 36) 17 [9-26.5] 16 [9-21.5] ns 4.5 [1-10] 1 [0-6] ns 3.5 [0.25-8.5] 1.5 [0-6.75] ns Psychological disability [IQR] (max. 24) 6 [3-15] 7 [0.75-13] ns 1.5 [0-4] 0 [0-2] ns 1 [0-5.5] 0 [0-2.5] ns Social disability [IQR] (max. 20) 6 [1.5-13.5] 4 [0.75-8.25] ns 0 [0-2.75] 0 [0-0.5] ns 0 [0-1.75] 0 [0-0.25] ns Handicap [IQR] (max. 24) 8 [3-11] 3.5 [1.75-9] ns 1 [0-3.75] 0 [0-0] ns 0 [0-2.75] 0 [0-2] ns Total OHIP-NL49 score [IQR] (max. 196) 77 [59.5-120.5] 84 [52-105.5] ns 26.0 [9.0-61.0] 12.5 [3-36.5] ns 21.0 [8.0-46.0] 8 [2-43.5] ns Functional complaints upper denture [IQR] (max. 27) 13 [8.75-23] 15.5 [8.75-19.25] ns 2 [0-4] 1.06 [1-2] ns 2 [1-4] 1 [0-4] ns [continued on next page]

33 Maxillary implant overdentures: bars or solitary attachments Table 2.5 | [continued] Pre-treatment After 1 year After 5 years Solitary attachment group (n=25) Bar attachment group (n=25) p-value Solitary attachment group (n=23) Bar attachment group (n=24) p-value Solitary attachment group (n=23) Bar attachment group (n=20) p-value Functional complaints in general [IQR] (max. 54) 23 [16.25-31.25] 15 [7.25-27.50] p=0.033* 3 [1-6.25] 1 [0-4.75] ns 2.5 [0-5.75] 2 [0-7.25] ns Facial aesthetics [IQR] (max. 9) 4.5 [1-6.5] 2 [0-5.25] ns 0 [0-3] 0 [0-0] ns 1 [0-2.75] 0 [0-3] ns “Neutral Space” [IQR] (max. 9) 1 [0-3] 0.5 [0-2] ns 0.5 [0-2.25] 0[0-1] ns 0 [0-2] 0 [0-2] ns Aesthetics [IQR] (max. 36) 1 [0-5.5] 0 [0-1.25] p=0.046* 0 [0-1.25] 0 [0-1] ns 1 [0-3] 0 [0-2.25] ns General satisfaction score upper denture [IQR] 4 [1-6] 4 [2-6] ns 8 [7-9] 9 [8-10] p = 0.041* 8 [8-9] 8 [8-9] ns Total food chewing score [IQR] (max. 18) 11 [6-15] 11 [9-12] ns 4 [2-7] 0 [0-3] 0.001 3 [1-6] 2 [2-5] ns Soft foods score [IQR] (max. 6) 1 [1-3] 2 [1-3] ns 0 [0-0] 0 [0-0] ns 0 [0-0] 0 [0-0] ns Tough foods score [IQR] (max. 6) 3 [2-5] 4 [3-4] ns 0 [0-2] 0 [0-0] 0.034 1 [0-2] 0 [0-0] ns Hard foods score [IQR] (max. 6) 6 [4-6] 6 [5-6] ns 3 [2-6] 0 [0-2] <0.001 2 [1-4] 2 [0-4] ns Differences between the study groups were tested with the Mann–Whitney U test. IQR: interquartile range; ns: no significant differences. *: p < 0.05, ** p<0.01. 2

34 Chapter 2 Patient related outcome measures: between group comparison The between groups PROMs comparison is listed in Table 2.5 and did not result in significant differences between the groups for any individual questionnaire items or the Total OHIP-NL49 score. Considering the functional complaints questionnaire, both groups were equally satisfied with their maxillary overdenture. Despite chewing in general, as well as chewing tough and hard foods favouring the bar group at the 1 year follow-up, these differences had balanced out by the five year follow-up. 2.4 DISCUSSION Based on the results of the present study’s 5-year follow-up period, a maxillary 4-IOD with a bar attachment system is the more favourable therapy for fully edentulous patients compared to a 4-IOD with a solitary attachment system, considering the significantly lower amount of marginal bone level change and significantly higher implant survival rate. Other studies Current maxillary 4-IOD research is mainly focused on retention with bars. Several prospective studies with a 5-year follow-up period reported high survival rates, ranging from 97.7% - 100%, combined with a low MBLC ranging from -0.2mm to -1.2mm after five years1-5, which are in line with the present study’s findings. The studies focusing on solitary attachments were mostly retrospective. Compared to bars, these studies showed a predominantly higher MBLC ranging from -0.4 to -1.7 mm, lower survival rates ranging from 92% to 98.9%, but a shorter mean follow-up period ranging from 32.9 – 58 months20-23. The only RCT on 4-IODs retained by solitary attachments, performed by Bouhy et al.24 reported a mean MBLC of -1.01 mm after one year, with a relatively low survival rate of 86.2%. There are two prospective studies available with a follow-up longer than 5 years. The first study compared 3-IOD with ball- or bar-attachments over a follow-up period of 10 years and reported a mean MBLC of -0.84 mm and a 87% survival rate, with no differences between the groups6. The low survival rate was mostly due to failed osseointegration (12 out of 16 implants). The second study reported 4-IODs with bars and solitary in a prospective cohort study with a mean follow-up of 11.4 years25. They reported a cumulative failure rate of 23.8%. Though more implants were lost by the solitary attachment group, the difference was not significant. Interestingly, most of the bar group’s implants failed in the first year after loading, while the solitary attachment group’s implant failure was more wide-spread, with 5 failures in the first year, 4 in the fourth year and 2 in the eleventh year. A similar failure pattern was observed in the present study. The effect of clinical parameters In the present study, the median plaque, bleeding, gingival and calculus scores and mean probing pocket depth change remained low throughout the entire follow-up period, which is in line with the findings of other studies1-3, and so we do not think it contributed to the differences in MBLC and implant loss found between the groups. Therefore, the idea that solitary attachments aid in easier oral hygiene could not be supported either. In fact, while the peri-­

Made with FlippingBook

RkJQdWJsaXNoZXIy MTk4NDMw