Maxillary Three-Implant Overdentures Opposing Mandibular Two-Implant Overdentures: 10-Year Surgical Outcomes of a Randomized Controlled Trial Sunyoung Ma, BDS, DClinDent;* Andrew Tawse-Smith, DDS, Cert Perio;† Rohana K. De Silva, BDS, FDSRCPS, FFDRCS, FDSRCS;‡ Momen A. Atieh, BDS, MSc, DClinDent, PhD;§ Nabeel H. M. Alsabeeha, DMD, MSc, MFDS RCPS, PhD;¶ Alan G. T. Payne, BDS, MDent, DDSc, FCD**
ABSTRACT Background: The surgical placement of four maxillary implants for overdentures may not be obligatory when opposing mandibular two-implant overdentures. Purpose: To determine 10-year surgical outcomes and implant success of three narrow diameter implants in edentulous maxillae with conventional loading. Materials and Methods: Forty participants with mandibular two-implant overdentures were randomly allocated for surgery for maxillary overdentures. Using osteotomes, three implants of similar systems were placed with a one-stage procedure and 12-week loading with splinted and unsplinted prosthodontic designs. Marginal bone and stability measurements were done at surgery, 12 weeks, 1-, 2-, 5-, 7-, 10 years. Results: One hundred seventeen implants were placed in 39 participants, with 35 being seen at 1 year; 29 at 2 years; 28 at 5 years; 26 at 7 years; and 23 (59%) at 10 years. Marginal bone loss was 1.35 mm between surgery and 12 weeks; 0.36 mm between 12 weeks and 1 year; 0.48 mm between 1 and 5 years; and 0.22 mm between 5 and 10 years. Implant stability quotients were 56.05, 57.54, 60.88, 58.80, 61.17 at surgery, 12 weeks, 1 year, 5 years, and 10 years. Four-field tables by implant showed success rates of 82% at 1 year; 69.2% at 2 years; 66.7% at 5 years; 61.5% at 7 years; 51.3% at 10 years. Data showed no differences between surgical technique, systems, or prosthodontic designs. Conclusions: Surgical placement with osteotomes of three narrow diameter implants for maxillary overdentures, opposing mandibular two-implant overdentures, is an acceptable approach, subject to strict patient selection. Implant success is independent of prosthodontic design. KEY WORDS: conventional loading, implant success, maxillary implant overdentures
INTRODUCTION *Senior Lecturer in Prosthodontics, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; †Senior Lecturer in Periodontics, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; ‡Associate Professor in Oral and Maxillofacial Surgery, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; §Periodontist, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; ¶Prosthodontist, Prosthetic Section, RAK Dental Centre, Ministry of Health, Ras Al-Khaimah, UAE; **Prosthodontist, Private Practice, Whangarei, New Zealand
Long-term research outcomes of implant treatment modalities on edentulous patients are essential for evidence-based clinical practice. The historical foundation of research on maxillary implant overdentures was to resolve the predicament of single maxillary dentures1 when opposing natural dentitions, extensive crowns/ bridgework, fixed implant bridges, or removable implant overdentures on multiple implants.2–7 Maxillary overdentures are most commonly recommended to
Corresponding Author: Dr. Alan G. T. Payne, Private Practice, 17 Rust Avenue, Town Centre, Whangarei, Northland 0110, New Zealand 0110. e-mail: [email protected]
© 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12325
527 1
Clinical Implant Dentistry Related Research, Volume 18, Number 3, 2016 2528 Clinical Implant Dentistry andand Related Research, Volume *, Number *, 2015
patients with hopeless maxillary dentitions, those with aesthetic demands having opposing natural teeth/fixed prostheses, or others without previous denture experience.8 Design concepts for maxillary overdentures dictated original surgical placement guidelines of as few as two, three, or four, or as many as six to eight machined implants2,4,9–11 which has been replaced by the current approach of advising four to six moderately rough surface implants.12–14 Literature reviews15–18 and systematic reviews with meta-analyses19–21 do reveal conflicting evidence on surgical recommendations for maxillary implant overdentures when evaluating the quality of clinical trials and opposing mandibular prostheses/dentitions. Sadowsky15 suggested four implants with good bone quality, but six implants in compromised bone. Klemetti,16 reviewing only four prospective studies, concluded that irrespective of prosthodontic design, four implants were necessary. Systematic reviews with metaanalyses19,21 do recommend differentiation in implant surgery for splinted and unsplinted prosthodontic designs. Higher survival rates of 98.2% and 96.3% are reported when six and four implants are used with bar attachments. This is in comparison with lower survival rate of 95.2%, when four implants are used with ball attachments. However, Dudley17 concluded that evidence for maxillary overdentures was still inconsistent, poorly standardized, and could not be cumulatively analyzed. Recommendations were for standardized research to provide more robust guidelines for maxillary implant overdenture management. More implants may not produce superior results and there could be economic and surgical benefits for patients with a reduced number of implants to obtain predictable outcomes.17 Reducing the number of implants for maxillary overdentures has recently been reaffirmed as a disadvantage, preferring an approach of using four to six implants.18 Raghoebar and colleagues,21 when comprehensively categorizing 24 studies on maxillary implant overdentures, identified a single randomized controlled trial22 and one historic prospective study10 with limited elements of randomization, where less than four implants were used for maxillary overdentures. Payne and colleagues22 used three implants with splinted and unsplinted designs in participants with opposing mandibular two-implant overdentures. Bergendal and Engquist10 used two to five implants, also with splinted and unsplinted designs, but the prosthetic status of the opposing mandibles was unclear.
Definitions and statements of standard of care should reflect ever-changing therapeutic approaches, recognize multiple approaches to deal with clinical situations, and be easily understood by the average practitioner.23 Guidelines of the McGill consensus24 can be seen to fall short of acceptable criteria for standard of care and fail to recognize multiple approaches for clinical situations.23,25 The McGill consensus statement can also be seen to fail to acknowledge adverse longitudinal changes in opposing maxillae from the two anterior mandibular implants,23 reminiscent of the so-called “combination syndrome.”26 Patients enjoying the benefits of mandibular two-implant overdentures may request surgical placement of implants to wear maxillary implant overdentures to resolve their entire edentulous state.27 Potential patients have to be informed of the future problems of advanced maxillary ridge resorption, together with the need for extensive surgical interventions. A cost-effective, minimal intervention at an earlier stage with fewer implants may be more appealing to these patients. Currently, there is no strong evidence to support the argument that patients wearing mandibular two-implant overdentures must always have four or more implants to assist an opposing maxillary overdenture. In fact, currently there is even a notion that as few as two moderately rough implants could be adequate for a maxillary overdenture.28 Narrow diameter implants are today supported by clinical29 and biomaterials research.30 In 2001, our research group became interested in reevaluating surgical treatment planning for patients requesting placement of maxillary implants for overdentures to oppose their existing mandibular two-implant overdentures. We have to date reported early surgical outcomes22 and patient outcomes31 of a surgical approach using three narrow diameter implants with osteotome techniques.32–34 The evidence for surgical recommendations on the minimum number of implants required and the type of prosthodontic design for maxillary overdentures, when opposing mandibular two-implant overdentures, remains weak. The purpose of this randomized controlled trial was to determine surgical outcomes and implant success of three narrow diameter implants in edentulous maxillae for overdentures over 10 years, in participants with opposing mandibular two-implant overdentures.
Maxillary Three-Implant Overdentures Maxillary Three-Implant Overdentures 5293
MATERIALS AND METHODS Participant Sample and Trial Design Forty edentulous participants (21 women; 19 men; mean age 64 years; range 55–76 years) wearing conventional maxillary dentures opposing mandibular two-implant overdentures were enrolled at the Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Inclusion criteria were edentulous maxillae, adequate intermaxillary space, and wearing an opposing mandibular two-implant overdentures for 3 years. Exclusion criteria were preoperative radiographically determined Lekholm and Zarb35 classification Type E or Cawood and Howell36 Type VI maxillae, any history of smoking, any systemic disease compromising implant surgery or previously bone-grafted maxillae. Preoperative spiral tomography (Scanora®, Soridex, Orion Corporation, Helsinki, Finland) using each participant’s duplicated denture as a radiographic stent facilitated selection in terms of residual maxillary bone.37 Ethical approval/renewals were obtained from the Lower South Ethics Committee, New Zealand (LRS/06/05/020). Registration was with the Australian New Zealand Clinical Trials Registry (ACTRN12605000653662). Participants were allocated firstly to two-implant system groups with moderately rough surfaces
(Brånemark System, Nobel Biocare AB, Göteborg, Sweden; Southern Implants, Irene, South Africa) using a table of random numbers, sequentially numbered opaque sealed envelopes, and maximum concealment by a senior dental surgery assistant. Regardless of implant system, participants were to have either a ridge expansion with osteotome-only procedure32 or a combined ridge-split-and-osteotome procedure33 depending on bucco-palatal width of the residual maxillary ridge and the degree of ridge resorption. Secondly, participants of each group were further subdivided and randomly allocated to equal groups of either splinted or unsplinted prosthodontic design. For the splinted designs, multiunit abutments (Brånemark) or standard abutments (Southern) were used, with corresponding gold cylinders, standardized micro-U-shaped gold bars, and gold matrices (Figure 1). For the unsplinted designs, ball abutments (ø 2.25 mm) were used with respective gold matrices (Figures 2 and 3). Maxillary overdentures were to have full palatal coverage for 1 year, which was reduced with removal of the central palate thereafter. Surgical and Prosthodontic Procedures Mid-crestal incisions connecting premolar regions and vertical buccal relieving incisions distally were made on all participants’ edentulous maxillae.22 Full thickness muco-periosteal flaps were raised, residual ridges leveled
A
B
C
D
Figure 1 Splinted design for both Brånemark and Southern groups. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
Clinical Implant Dentistry Related Research, Volume 18, Number 3, 2016 4530 Clinical Implant Dentistry andand Related Research, Volume *, Number *, 2015
A
B
C
D
Figure 2 Unsplinted design for Brånemark group. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
to a width of 3 mm, and anterior implant sites (either area 11 or 21) selected on either side of the incisive foramen and posterior sites (both 14 and 24 areas) which were anterior to the maxillary sinuses. Distal pilot drill points were 20 mm either side from the midline along the anterior border of the maxillary sinus for either a straight or
a distally angled implant site depending on antrum anatomy.38 Bucco-palatal angulation of up to 30 degrees for the implants was allowed using a duplicated denture stent. In each participant, three narrow diameter titanium implants (Brånemark ø 3.3 mm; Southern ø 3.25 mm) were inserted using either a ridge expansion
A
B
C
D
Figure 3 Unsplinted design for Southern group. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
Maxillary Three-Implant Overdentures Maxillary Three-Implant Overdentures 5315
with osteotome-only procedure32 or a combined ridgesplit-and-osteotome procedure33 depending on the ridge anatomy. Exposed implant threads in the intra-osseous groove of the ridge-split cases were filled with corticocancellous autogenous bone which had been collected. Muco-periosteal flaps were trimmed and sutured around 4 mm healing abutments (4-0 Vicryl, Ethicon, Johnson & Johnson, Brussels, Belgium) completing a one-stage surgical procedure. Immediately after surgery, participants’ maxillary complete dentures were relieved and had a generous layer of tissue conditioner placed (Viscogel, Dentsply De Trey GmbH, Konstanz, Germany). After 12 weeks of healing, permanent abutments were placed, and using participants’ existing complete maxillary dentures, reline procedures facilitated inclusion of matrices into the intaglio surfaces of their maxillary dentures. Data Collection Standardized intraoral radiographs for marginal bone levels were taken at implant level using adapted radiographs holders at surgery, 12 weeks, 1-, 2-, 5-, 7-year and 10-year recalls. Rinn holders (XCP Instrument, Dentsply Rinn Corporation, Elgin, IL, USA) incorporating an implant-level impression coping were used.39 An extended-cone Phillips Secondent machine of 60 kV with an exposure time of 0.8 second and the same films were used (Size 0, Kodak DF 54 Dental Film Ultraspeed Eastman Kodak Company, Rochester, NY, USA). Implant stability was recorded at implant level using the same third-generation electronic resonance frequency analysis (RFA) machine throughout the trial (Osstell, Integration Diagnostics AB, Göteborg, Sweden).40 For the splinted design, bars including the multiunit (Brånemark) or standard (Southern) abutments were removed to facilitate placement of the radiograph holders and wired transducers perpendicular to the alveolar crest.41 The same approach was followed with the participants of the unsplinted designs, where the ball abutments (Brånemark or Southern) were removed. Panoramic and lateral cephalometric radiographs were taken using spiral tomography (Figure 4). To assess marginal bone loss, mesial and distal bone levels were measured on the shielded radiographs with a 7× peak loupe and the average value was used. Three calibrated blinded examiners (S.M., A.T-S., and A.G.T.P.) repeated the measurements for intra- and interobserver variabilities. The marginal bone measurements were taken from the implant-abutment junction
as a reference point of each implant to the most coronal position of bone-to-implant contact. Data Analysis Independent samples t-tests were used to determine the differences between marginal bone level changes and implant stability measurements at different time points (SPSS 17.0, SPSS Inc., Chicago, IL, USA). The paired t-test was used for within-group comparison over time to compare marginal bone level changes and implant stability between the time of implant placement and subsequent measurements at the different time points. The mean marginal bone levels at each of the time points of surgery, 12 weeks, 1, 2, 5, 7, and 10 years were determined at the 95% CI. Implant success by participant was determined and tabulated with four-field tables.42,43 Implant success by implant via cumulative marginal bone loss was evaluated with a criteria of
ABSTRACT Background: The surgical placement of four maxillary implants for overdentures may not be obligatory when opposing mandibular two-implant overdentures. Purpose: To determine 10-year surgical outcomes and implant success of three narrow diameter implants in edentulous maxillae with conventional loading. Materials and Methods: Forty participants with mandibular two-implant overdentures were randomly allocated for surgery for maxillary overdentures. Using osteotomes, three implants of similar systems were placed with a one-stage procedure and 12-week loading with splinted and unsplinted prosthodontic designs. Marginal bone and stability measurements were done at surgery, 12 weeks, 1-, 2-, 5-, 7-, 10 years. Results: One hundred seventeen implants were placed in 39 participants, with 35 being seen at 1 year; 29 at 2 years; 28 at 5 years; 26 at 7 years; and 23 (59%) at 10 years. Marginal bone loss was 1.35 mm between surgery and 12 weeks; 0.36 mm between 12 weeks and 1 year; 0.48 mm between 1 and 5 years; and 0.22 mm between 5 and 10 years. Implant stability quotients were 56.05, 57.54, 60.88, 58.80, 61.17 at surgery, 12 weeks, 1 year, 5 years, and 10 years. Four-field tables by implant showed success rates of 82% at 1 year; 69.2% at 2 years; 66.7% at 5 years; 61.5% at 7 years; 51.3% at 10 years. Data showed no differences between surgical technique, systems, or prosthodontic designs. Conclusions: Surgical placement with osteotomes of three narrow diameter implants for maxillary overdentures, opposing mandibular two-implant overdentures, is an acceptable approach, subject to strict patient selection. Implant success is independent of prosthodontic design. KEY WORDS: conventional loading, implant success, maxillary implant overdentures
INTRODUCTION *Senior Lecturer in Prosthodontics, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; †Senior Lecturer in Periodontics, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; ‡Associate Professor in Oral and Maxillofacial Surgery, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; §Periodontist, Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; ¶Prosthodontist, Prosthetic Section, RAK Dental Centre, Ministry of Health, Ras Al-Khaimah, UAE; **Prosthodontist, Private Practice, Whangarei, New Zealand
Long-term research outcomes of implant treatment modalities on edentulous patients are essential for evidence-based clinical practice. The historical foundation of research on maxillary implant overdentures was to resolve the predicament of single maxillary dentures1 when opposing natural dentitions, extensive crowns/ bridgework, fixed implant bridges, or removable implant overdentures on multiple implants.2–7 Maxillary overdentures are most commonly recommended to
Corresponding Author: Dr. Alan G. T. Payne, Private Practice, 17 Rust Avenue, Town Centre, Whangarei, Northland 0110, New Zealand 0110. e-mail: [email protected]
© 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12325
527 1
Clinical Implant Dentistry Related Research, Volume 18, Number 3, 2016 2528 Clinical Implant Dentistry andand Related Research, Volume *, Number *, 2015
patients with hopeless maxillary dentitions, those with aesthetic demands having opposing natural teeth/fixed prostheses, or others without previous denture experience.8 Design concepts for maxillary overdentures dictated original surgical placement guidelines of as few as two, three, or four, or as many as six to eight machined implants2,4,9–11 which has been replaced by the current approach of advising four to six moderately rough surface implants.12–14 Literature reviews15–18 and systematic reviews with meta-analyses19–21 do reveal conflicting evidence on surgical recommendations for maxillary implant overdentures when evaluating the quality of clinical trials and opposing mandibular prostheses/dentitions. Sadowsky15 suggested four implants with good bone quality, but six implants in compromised bone. Klemetti,16 reviewing only four prospective studies, concluded that irrespective of prosthodontic design, four implants were necessary. Systematic reviews with metaanalyses19,21 do recommend differentiation in implant surgery for splinted and unsplinted prosthodontic designs. Higher survival rates of 98.2% and 96.3% are reported when six and four implants are used with bar attachments. This is in comparison with lower survival rate of 95.2%, when four implants are used with ball attachments. However, Dudley17 concluded that evidence for maxillary overdentures was still inconsistent, poorly standardized, and could not be cumulatively analyzed. Recommendations were for standardized research to provide more robust guidelines for maxillary implant overdenture management. More implants may not produce superior results and there could be economic and surgical benefits for patients with a reduced number of implants to obtain predictable outcomes.17 Reducing the number of implants for maxillary overdentures has recently been reaffirmed as a disadvantage, preferring an approach of using four to six implants.18 Raghoebar and colleagues,21 when comprehensively categorizing 24 studies on maxillary implant overdentures, identified a single randomized controlled trial22 and one historic prospective study10 with limited elements of randomization, where less than four implants were used for maxillary overdentures. Payne and colleagues22 used three implants with splinted and unsplinted designs in participants with opposing mandibular two-implant overdentures. Bergendal and Engquist10 used two to five implants, also with splinted and unsplinted designs, but the prosthetic status of the opposing mandibles was unclear.
Definitions and statements of standard of care should reflect ever-changing therapeutic approaches, recognize multiple approaches to deal with clinical situations, and be easily understood by the average practitioner.23 Guidelines of the McGill consensus24 can be seen to fall short of acceptable criteria for standard of care and fail to recognize multiple approaches for clinical situations.23,25 The McGill consensus statement can also be seen to fail to acknowledge adverse longitudinal changes in opposing maxillae from the two anterior mandibular implants,23 reminiscent of the so-called “combination syndrome.”26 Patients enjoying the benefits of mandibular two-implant overdentures may request surgical placement of implants to wear maxillary implant overdentures to resolve their entire edentulous state.27 Potential patients have to be informed of the future problems of advanced maxillary ridge resorption, together with the need for extensive surgical interventions. A cost-effective, minimal intervention at an earlier stage with fewer implants may be more appealing to these patients. Currently, there is no strong evidence to support the argument that patients wearing mandibular two-implant overdentures must always have four or more implants to assist an opposing maxillary overdenture. In fact, currently there is even a notion that as few as two moderately rough implants could be adequate for a maxillary overdenture.28 Narrow diameter implants are today supported by clinical29 and biomaterials research.30 In 2001, our research group became interested in reevaluating surgical treatment planning for patients requesting placement of maxillary implants for overdentures to oppose their existing mandibular two-implant overdentures. We have to date reported early surgical outcomes22 and patient outcomes31 of a surgical approach using three narrow diameter implants with osteotome techniques.32–34 The evidence for surgical recommendations on the minimum number of implants required and the type of prosthodontic design for maxillary overdentures, when opposing mandibular two-implant overdentures, remains weak. The purpose of this randomized controlled trial was to determine surgical outcomes and implant success of three narrow diameter implants in edentulous maxillae for overdentures over 10 years, in participants with opposing mandibular two-implant overdentures.
Maxillary Three-Implant Overdentures Maxillary Three-Implant Overdentures 5293
MATERIALS AND METHODS Participant Sample and Trial Design Forty edentulous participants (21 women; 19 men; mean age 64 years; range 55–76 years) wearing conventional maxillary dentures opposing mandibular two-implant overdentures were enrolled at the Oral Implantology Research Group, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Inclusion criteria were edentulous maxillae, adequate intermaxillary space, and wearing an opposing mandibular two-implant overdentures for 3 years. Exclusion criteria were preoperative radiographically determined Lekholm and Zarb35 classification Type E or Cawood and Howell36 Type VI maxillae, any history of smoking, any systemic disease compromising implant surgery or previously bone-grafted maxillae. Preoperative spiral tomography (Scanora®, Soridex, Orion Corporation, Helsinki, Finland) using each participant’s duplicated denture as a radiographic stent facilitated selection in terms of residual maxillary bone.37 Ethical approval/renewals were obtained from the Lower South Ethics Committee, New Zealand (LRS/06/05/020). Registration was with the Australian New Zealand Clinical Trials Registry (ACTRN12605000653662). Participants were allocated firstly to two-implant system groups with moderately rough surfaces
(Brånemark System, Nobel Biocare AB, Göteborg, Sweden; Southern Implants, Irene, South Africa) using a table of random numbers, sequentially numbered opaque sealed envelopes, and maximum concealment by a senior dental surgery assistant. Regardless of implant system, participants were to have either a ridge expansion with osteotome-only procedure32 or a combined ridge-split-and-osteotome procedure33 depending on bucco-palatal width of the residual maxillary ridge and the degree of ridge resorption. Secondly, participants of each group were further subdivided and randomly allocated to equal groups of either splinted or unsplinted prosthodontic design. For the splinted designs, multiunit abutments (Brånemark) or standard abutments (Southern) were used, with corresponding gold cylinders, standardized micro-U-shaped gold bars, and gold matrices (Figure 1). For the unsplinted designs, ball abutments (ø 2.25 mm) were used with respective gold matrices (Figures 2 and 3). Maxillary overdentures were to have full palatal coverage for 1 year, which was reduced with removal of the central palate thereafter. Surgical and Prosthodontic Procedures Mid-crestal incisions connecting premolar regions and vertical buccal relieving incisions distally were made on all participants’ edentulous maxillae.22 Full thickness muco-periosteal flaps were raised, residual ridges leveled
A
B
C
D
Figure 1 Splinted design for both Brånemark and Southern groups. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
Clinical Implant Dentistry Related Research, Volume 18, Number 3, 2016 4530 Clinical Implant Dentistry andand Related Research, Volume *, Number *, 2015
A
B
C
D
Figure 2 Unsplinted design for Brånemark group. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
to a width of 3 mm, and anterior implant sites (either area 11 or 21) selected on either side of the incisive foramen and posterior sites (both 14 and 24 areas) which were anterior to the maxillary sinuses. Distal pilot drill points were 20 mm either side from the midline along the anterior border of the maxillary sinus for either a straight or
a distally angled implant site depending on antrum anatomy.38 Bucco-palatal angulation of up to 30 degrees for the implants was allowed using a duplicated denture stent. In each participant, three narrow diameter titanium implants (Brånemark ø 3.3 mm; Southern ø 3.25 mm) were inserted using either a ridge expansion
A
B
C
D
Figure 3 Unsplinted design for Southern group. A, 12 weeks. B, Year 1. C, Year 5. D, Year 10.
Maxillary Three-Implant Overdentures Maxillary Three-Implant Overdentures 5315
with osteotome-only procedure32 or a combined ridgesplit-and-osteotome procedure33 depending on the ridge anatomy. Exposed implant threads in the intra-osseous groove of the ridge-split cases were filled with corticocancellous autogenous bone which had been collected. Muco-periosteal flaps were trimmed and sutured around 4 mm healing abutments (4-0 Vicryl, Ethicon, Johnson & Johnson, Brussels, Belgium) completing a one-stage surgical procedure. Immediately after surgery, participants’ maxillary complete dentures were relieved and had a generous layer of tissue conditioner placed (Viscogel, Dentsply De Trey GmbH, Konstanz, Germany). After 12 weeks of healing, permanent abutments were placed, and using participants’ existing complete maxillary dentures, reline procedures facilitated inclusion of matrices into the intaglio surfaces of their maxillary dentures. Data Collection Standardized intraoral radiographs for marginal bone levels were taken at implant level using adapted radiographs holders at surgery, 12 weeks, 1-, 2-, 5-, 7-year and 10-year recalls. Rinn holders (XCP Instrument, Dentsply Rinn Corporation, Elgin, IL, USA) incorporating an implant-level impression coping were used.39 An extended-cone Phillips Secondent machine of 60 kV with an exposure time of 0.8 second and the same films were used (Size 0, Kodak DF 54 Dental Film Ultraspeed Eastman Kodak Company, Rochester, NY, USA). Implant stability was recorded at implant level using the same third-generation electronic resonance frequency analysis (RFA) machine throughout the trial (Osstell, Integration Diagnostics AB, Göteborg, Sweden).40 For the splinted design, bars including the multiunit (Brånemark) or standard (Southern) abutments were removed to facilitate placement of the radiograph holders and wired transducers perpendicular to the alveolar crest.41 The same approach was followed with the participants of the unsplinted designs, where the ball abutments (Brånemark or Southern) were removed. Panoramic and lateral cephalometric radiographs were taken using spiral tomography (Figure 4). To assess marginal bone loss, mesial and distal bone levels were measured on the shielded radiographs with a 7× peak loupe and the average value was used. Three calibrated blinded examiners (S.M., A.T-S., and A.G.T.P.) repeated the measurements for intra- and interobserver variabilities. The marginal bone measurements were taken from the implant-abutment junction
as a reference point of each implant to the most coronal position of bone-to-implant contact. Data Analysis Independent samples t-tests were used to determine the differences between marginal bone level changes and implant stability measurements at different time points (SPSS 17.0, SPSS Inc., Chicago, IL, USA). The paired t-test was used for within-group comparison over time to compare marginal bone level changes and implant stability between the time of implant placement and subsequent measurements at the different time points. The mean marginal bone levels at each of the time points of surgery, 12 weeks, 1, 2, 5, 7, and 10 years were determined at the 95% CI. Implant success by participant was determined and tabulated with four-field tables.42,43 Implant success by implant via cumulative marginal bone loss was evaluated with a criteria of
