Three-year Follow-up of Immediately Loaded Implants in the Edentulous Atrophic Maxilla: A Study in Patients with Poor Bone Quantity and Quality Andreas Thor, DDS, PhD1/Karl Ekstrand, DDS, MS2/Russell A. Baer, DDS3/Joseph A. Toljanic, DDS4 Purpose: Immediate loading of implants in the edentulous maxilla has previously been successfully performed and reported. Severe resorption of the maxillary alveolar crest presents a more demanding situation for the restorative team. Thus, it would be valuable to assess outcomes for this immediate loading treatment protocol in subjects with marked maxillary alveolar crest atrophy. This study evaluated the 3-year results of dental implants that were immediately restored with provisional fixed prostheses in atrophic maxillae without previous augmentation. Materials and Methods: Two centers enrolled subjects with resorbed edentulous maxillae (Lekholm and Zarb quality 3 or 4 and quantity C, D, or E). Six implants were placed in each subject and restored with screw-retained fixed provisionals within 24 hours. Impressions were taken for definitive restorations, which were placed 20 to 24 weeks later. Radiographs were used to analyze marginal bone level changes throughout the study. Results: Fifty-one patients received 306 implants. Forty-five patients remained in the study at the 3-year follow-up visit and successfully used their definitive prostheses. Sixtytwo percent of the implants were placed in bone quantity C and quality 3 or 4, and 38% were placed in quantity D and quality 3 or 4 bone. Thirteen implants in six subjects were lost, resulting in a cumulative survival rate of 96% after 3 years. The mean marginal bone loss during the first year was –0.4 ± 0.8 mm (255 implants); at 3 years it was –0.6 ± 1.1 mm (253 implants). Conclusion: Data from the first 3 years of this study revealed good clinical outcomes. Careful selection of patients and planning by the restorative team can enable successful treatment outcomes for patients presenting with marked resorption of the edentulous maxilla. Int J Oral Maxillofac Implants 2014;29:642–649. doi: 10.11607/jomi.3163 Key words: atrophic maxilla, dental implants, edentulous maxilla, immediate loading
R
estoring the edentulous maxilla with immediately loaded implants can be an attractive treatment option for patients.1 For the clinician, it is important to consider the options for treatment and to evaluate them with regard to expected problems and known success rates. Esposito and coworkers included early loading protocols as one factor in the increased rate
1 Associate
Professor, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala University, Uppsala, Sweden. 2 Associate Professor and Director, Postgraduate Education, The University of Oslo, Institute for Clinical Dentistry, Oslo, Norway. 3 Private Practice, University Associates in Dentistry, Chicago, Illinois. 4 Associate Professor, Midwestern University College of Dental Medicine Illinois, Downers Grove, Illinois. Correspondence to: Dr Andreas Thor, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala University, SE-751 85 Uppsala, Sweden. Fax: +46-0-18-55-91. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
of complications in implant dentistry.2 Accelerated implant treatment in the maxilla has been less frequently explored and initially provided somewhat less favorable results compared to the same procedures in the mandible.3,4 The progressive resorption of maxillary bone after the loss of all teeth offers considerable challenges for the implant surgeon and restorative dentist. Vertical and horizontal losses of bone volume are accompanied by posterior sagittal movement of the maxilla, often making the actual positioning of the implants unfavorable with respect to the forces that will act upon them during mastication. Bone augmentation is often necessary to address this condition.5–8 Unfortunately, with autogenous bone grafting, the additional intervention involves pain, discomfort, and the risk of additional problems during and after the procedure.9 Reported success rates for edentulous patients with grafts and implants have also varied over the years but most often have been lower than those seen in nongrafted patients.10–12 However, encouraging results in other research groups have highlighted the possibility of immediately restoring implants placed in the edentulous maxilla, with a good
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Thor et al
long-term prognosis similar to the outcomes achieved with conventional protocols.1,12–15 Further scientific evaluation regarding the existing limits for different simplified and accelerated implant treatment protocols for patients appears to be warranted. Therefore, the current prospective long-term study examined the results over 3 years after implants were placed in the edentulous atrophic maxilla and restored with immediate fixed provisional restorations without the use of any additional augmentation procedures. The primary goal was to study the implant survival rate. In addition, marginal bone alterations were assessed by radiography, and soft tissue status was recorded by evaluation of plaque and bleeding. A total of 10 scheduled visits up to the occasion of the 3-year follow-up were carried out. In the study, subject satisfaction with the treatment was also recorded with the Oral Health Impact Profile-49 questionnaire,1 but these results will be reported elsewhere.
MATERIALS AND METHODS Fifty-one patients seeking routine care were recruited from two study centers (University of Chicago, Section of Dentistry, Chicago, Illinois; Uppsala University, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala, Sweden) for participation in this study. Study approval was obtained from the ethics committees representing the two centers, and informed written consent was obtained from all study subjects. Consecutive enrollment of subjects for the study was carried out if all inclusion and exclusion criteria were met. Criteria were discussed in a previous report from this study on the 1-year results and included the initial situation regarding dental status in the opposing arch, smoking habits, and oral hygiene.16 Only nonsmoking patients with atrophic totally edentulous maxillae (bone quality 3 or 4 and bone quantity C, D, or E according to Lekholm and Zarb17) were included in the study. The investigators determined eligibility for the study after clinical examination and assessment of panoramic radiographs without the use of other imaging tools. The preoperative radiologic examination included a panoramic view and intraoral dental films. A computed tomographic scan was obtained only if the investigator felt the need for a more extensive examination. Subjects were included if the bone volume of the recipient site in the maxilla was considered sufficient to allow the placement of the smallest available implant in the study (3.5 mm in diameter and 8 mm in length). No augmentation procedures were allowed in the study. Although patients with bone grafts older than 6 months were eligible for
Fig 1 Surgical guide made of an acrylic resin duplicate of the prosthesis.
inclusion, no such patients were included. Initial specific findings on oral status were presented earlier.16 To be included and eligible for dental implant treatment in the maxilla, patients needed to have 10 tooth units (second premolar to second premolar) in the mandible, represented either by a natural dentition or dental prosthesis. If needed, treatment was initiated and completed in the mandible prior to treatment in the maxilla.
Implants and Surgical Protocol
Six implants (OsseoSpeed, ASTRA TECH Implant System, Dentsply) were placed in each patient and loaded within 24 hours with a screw-retained fixed restoration. The implants used in this study have a modified titanium surface that has been blasted with titanium dioxide and then chemically modified with fluoride. The design of the implant includes self-tapping features and microthreads at its coronal end. Because no bone augmentation was allowed in this protocol, the available bone was limited in many cases, and a surgical guide in clear acrylic resin was used to indicate the planned implant sites (Fig 1). The guide was fabricated by duplicating the prosthesis worn by the patient prior to treatment. The surgical protocol is presented elsewhere in detail.16 The limited amount of bone and low bone density often required underpreparation of the implant osteotomies. With this technique and via the self-tapping features of the implant, adequate primary stability of the implant was sought. Three implants were placed on each side of the maxilla. The most posterior implant was often inclined distally, guided by the stent and indicators, and placed in close relationship to the anterior wall of the maxillary sinus. This resulted in maximum support for the planned fixed restoration (Figs 2 and 3). After all implants had been placed, straight or angulated transmucosal screw-retained abutments were placed (UniAbutment, 20- or 45-degree Angled Abutment, Dentsply The International Journal of Oral & Maxillofacial Implants 643
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Thor et al
Fig 2 A limited amount of bone characterized the maxillae in the study.
Fig 3 With a surgical guide, the implants could be inclined for maximum spread over the available alveolar crest.
Implants). In this way the investigators could correct divergent angulations of placed implants, resulting in more favorable screw access holes in the restorations and better esthetic results. Titanium temporary abutments provided by the manufacturer were cut to a suitable length and screwed onto the abutments. The abutments were later used to support the provisional restoration. Surgery was completed with the suturing of flaps around the transmucosal abutments and restorative abutments.
Prosthetic Protocols
Fabrication of the screw-retained fixed provisionals differed between the two centers (see following). The Chicago team used a treatment protocol in which the fixed restoration was delivered within 3 hours of implant placement. They used the existing denture or a newly made denture that had been corrected for vertical dimension or other shortcomings. Holes were drilled in the prosthesis that corresponded well with the locations of the temporary abutments that had been screwed on to the implant abutments. Autopolymerizing acrylic resin was then applied around all temporary abutments to lute them to the prosthesis. After the resin had polymerized and all abutments were attached well to the prosthesis, the abutments were unscrewed and the prosthesis was removed from the mouth. The provisional fixed restoration was further revised by removal of acrylic resin from the prosthesis in the area of the palate and flanges. A glass fiber–reinforced material (EverStick C & B fiber reinforcement, Preat Corp) was used on the lingual surface, together with some autopolymerizing acrylic resin, to provide additional fracture resistance for the restoration. Upon delivery of the restoration, reduction of excessive occlusal contacts was carried out, along with esthetic changes, if needed. The team in Sweden used an indirect fabrication method for the provisionals. These restorations were delivered within 24 hours after implant surgery (Fig 4). Prior to implant surgery, initial steps were undertaken
Fig 4 Provisional fixed restoration delivered after 24 hours at the center in Sweden.
to fabricate a prosthesis to the level of the wax-up. This was duplicated to allow for fabrication of a resin surgical guide and a custom impression tray. A clear acrylic resin copy of the denture prosthesis wax-up was additionally fabricated. After the implants were placed, an abutment-level impression was made. The acrylic resin copy of the denture prosthesis wax-up was lined with silicone impression material (Provil, Heraeus-Kulzer) and placed into the mouth. Centric relation registration was performed at the same time, and the impression was then removed from the mouth. Next, the master cast was inserted into the silicone impression material contained within the clear denture prosthesis duplicate and mounted on an articulator. The screw-retained provisional was then fabricated on this mounted master cast. To increase the strength and increase fracture resistance of the prosthesis, a titanium mesh was laser-welded to the titanium copings and embedded into the restoration.
Postoperative Care
Oral antibiotics, analgesics, and a topical antimicrobial rinse were included in the postoperative protocol. Hygiene instructions prescribed a gentle brushing technique for the first week without flossing for the first 4 weeks. Thereafter, the study subjects were instructed to resume normal brushing and flossing. Subjects were instructed to eat a soft diet for 6 weeks.
Collection of Data and Follow-up Protocol
At the time of implant surgery and loading with the provisional, the implant characteristics (type, length, diameter, and position) were recorded. The implant surgeon documented bone quantity and quality by preoperative radiographic findings, visual inspection during surgery, and resistance in the bone and tactile sensation upon preparation of the implant sites. The final seating (last few millimeters of insertion) of the implants was performed with a calibrated torque wrench (Torque-Lock Wrench, Intra-Lock International) to measure primary stability and insertion torque value
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Thor et al
V1
V2
V3 +2 wk (±2 d)
2–3 wk
Screening Implant and placement inclusion
Fig 5 Clinical appearance of a subject at the 3-year follow-up visit. 30–
% of implants
18 15
15– 10–
14
7
5–
Postop
+20–24 wk
Impression
V7 +6 mo (±2 wk)
Definitive restoration
V8–V10 +1–3 y (±2 wk)
Follow-up
Follow-up
Second molars
First molars
Second premolars
First premolars
Canines
Lateral incisors
1 Central incisors
0–
Postop
+12 wk (±7 d)
V6
was delivered. This was reported earlier.16 Six months after implant surgery, function of the restoration was evaluated, and the prosthesis was removed for clinical evaluation of implant integration. The restorations were removed at the 1-, 2-, and 3-year visits, and the implants were manually assessed for stability. At these follow-up visits, clinical evaluation of the peri-implant mucosa was also performed. Plaque scores and bleeding on probing were registered on four surfaces (mesial, buccal, distal, and lingual) of each implant.
27
18
+4 wk (±2 d)
V5
Fig 6 Study flow chart. V = visit.
25– 20–
V4
Location Fig 7 Placement locations for 306 implants in the 51 subjects.
(ITVs). No minimum ITV was required for inclusion as long as clinical primary stability was deemed acceptable by the surgeon and prosthodontist. Subjects were followed for up to 3 years (Fig 5). Radiologic examinations were performed preoperatively at the time of screening and inclusion, at implant placement (baseline), when the definitive restoration was delivered, and annually to 3 years (Fig 6). A paralleling imaging technique was used with commercially available film holders to ensure reproducibility of the radiographs between examinations. An independent radiologist not affiliated with the two study centers interpreted all radiographs. The distance from the interproximal bone (mesial and distal) to the implant reference point (the junction of the roughened and machined beveled surfaces) was measured to the nearest 0.1 mm using ×7 magnification. The mean of these two measurements was used to represent the marginal bone height around each implant. The subjects were examined according to the study plan (Fig 6). At 12 weeks after implant placement, an impression for the definitive restoration was made, and after 20 to 24 weeks the definitive restoration
RESULTS All 51 included study subjects (mean age, 65.8 years; range, 47 to 83 years; 47% men and 53% women) received their fixed restorations, and 45 subjects have reached the 3-year follow-up. In all, 306 implants were placed (implant locations are shown in Fig 7), and 25 subjects received restorations that were fabricated chairside on the day of implant surgery. The other 26 restorations were fabricated using the indirect technique, but all 51 subjects had their implants loaded 24 hours after placement. At placement, ITVs were recorded, and the results are shown in Fig 8. The quantity and quality of bone in which the implants were placed are described in Table 1. During the first year of followup, one subject (six implants) was lost to follow-up, and 12 additional implants (in five subjects) were removed as a result of loss of integration. Three patients could no longer wear fixed restorations because of the implant losses and were therefore dropped from the study. Consequently, at 1 year, 47 patients and 280 implants were included. During the second year of follow-up, one subject died, resulting in a total of 274 available implants after 2 years. At 3 years, another patient had been lost to follow-up and another patient had lost one implant (45 patients and 267 implants). In summary, 13 implants were lost in six patients (Table 2). Twelve of these implants were lost before the definitive restoration was in place and were therefore considered early losses. Only one implant was lost between the 2- and 3-year follow-up examinations. Three The International Journal of Oral & Maxillofacial Implants 645
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Thor et al
Table 1 Characterization of Bone Quantity and Quality17 of the 306 Implants Placed
60– 49
Bone quality
36 35
32
30– 30
3 25
20 12
31–35
26–30
21–25
16–20
11–15
C
D
E
Total
116
58
1
175 (57%)
0
131 (43%)
74 190 (62%)
57 115 (38%)
1 (0%)
Unknown
13 10– 10 0–10
4 Total
>45
20– 20
0–0
Bone quantity
42
41–45
40– 40
42
36–40
No. of implants
50– 50
ITV (Ncm) Fig 8 ITVs of implants placed (n = 306).
subjects were lost to follow-up and three were withdrawn from the study because of implant losses. In patient 104, the left distalmost implant was shown to have inaccurate seating of an angled titanium cylinder at visit 2. At the 3-year follow-up visit, severe bone loss was noted around this implant, which was removed at this time. To date, this is the only late removal in the study. Subjects 107 and 114 also had distal implants removed; in the latter case, this was tentatively explained by heavy occlusion. Framework fracture of the provisional resulted in the loss of three implants in patient 205. The subject with the highest number of implant losses (patient 214) was a male ex-smoker, 76 years of age, with bone quantity C and quality 3. In this subject, the ITVs of the lost implants were between 10 and 35 Ncm. Finally, one subject with mobile implants (patient 225) had a history of bruxism but also better ITVs during placement of the implants. Three implants were lost and removed after 78 days. Implant survival rates, expressed using KaplanMeier analysis, displayed a stable cumulative survival rate of 96% from the 1-year to the 3-year examinations (Table 3). At this time, the condition of the peri-implant mucosa showed bleeding when probing in 20% of the implant surfaces, and plaque was present on 32% of the surfaces (Table 4). The marginal bone levels around the implants were stable after placement of the fixed restorations up to the 3-year control (Table 5). Twenty-six percent of the implants showed no evidence of marginal bone loss at the 3-year follow-up. Marginal bone level changes are illustrated in Fig 9. Other complications, including with the prostheses, that occurred during the first 3 years of follow-up are listed in Table 6. The most common complaint was fractured denture teeth.
DISCUSSION In this study, subjects were followed for 3 years after implant rehabilitation in atrophic edentulous maxillae. Forty-five subjects reached the 3-year follow-up appointment, and 13 implants were lost in six patients. Of the 306 implants initially placed in 51 subjects, 267 implants remained in the study, for an implant survival rate of 95.7%. Mean marginal bone loss was 0.57 (± 1.12) mm at 3 years. The results of this study must be interpreted with the knowledge that conventional loading of implantsupported fixed prostheses in the edentulous maxilla with rough-surfaced dental implants has shown good results, with implant survival rates ranging from 95% to 98%.18–21 Previous studies reporting on immediate loading in edentulous maxillae have not used the demanding inclusion criteria of this study regarding bone quantity (Lekholm and Zarb C, D, and E).14,15,22,23 During the recruitment process in this study, subjects were excluded if they had type A or B bone. Given this fact, the results presented here are consistent with previous findings from other research groups regarding implant survival and marginal bone level changes. Few studies are available in the literature with longer follow-up following immediate loading in the edentulous maxilla. One study with a similar design to the present study was performed by Capelli et al.24 They reported on the 3-year results of a multicenter study from four centers on 246 Osseotite NT implants (Biomet/3i). These implants were placed in the maxilla, and the distalmost implants were tilted 25 to 35 degrees. Patients were included if they displayed severe resorption of the maxilla, but no data were presented on bone volume classification (eg, Lekholm and Zarb index) or
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Thor et al
Table 2 Summary of Implant Losses Subject no. Position* Sex Age (y)
Smoking history
Bone quantity/quality17
Implant length (mm)
Time to loss (d)
104
25
M
74
Nonsmoker
C/3
13
1,057
107
16
M
75
Ex-smoker
C/4
11
98
114
16
M
53
Ex-smoker
C/4
11
78
205
15
F
67
Nonsmoker
C/4
11
65
205
13
F
67
Nonsmoker
C/4
15
1
205
25
F
67
Nonsmoker
C/4
9
65
214
15
M
76
Ex-smoker
C/3
13
189
214
13
M
76
Ex-smoker
C/3
15
77
214
12
M
76
Ex-smoker
C/3
13
77
214
21
M
76
Ex-smoker
C/3
13
77
225
15
F
72
Nonsmoker
C/3
13
78
225
13
F
72
Nonsmoker
C/3
13
78
225
11
F
72
Nonsmoker
C/3
11
78
Total losses
13
*FDI tooth numbers.
Table 3 Kaplan-Meier Implant Survival Analysis over 3 Years No. at risk
Failures
Censored*
Interval survival probability
IP (visit 2)
Interval
306
0
0
1.0000
Survival proportion
IP to visit 3 (+2 wk)
306
1
0
0.9967
0.9967
Visit 3 to 4 (+4 wk)
305
0
0
1.0000
0.9967
Visit 4 to 5 (+12 wk)
305
11
14
0.9639
0.9608
1.000
Visit 5 to 7 (+26 wk)
280
0
0
1.0000
0.9608
Visit 7 to 8 (+1 y)
280
0
0
1.0000
0.9608
Visit 8 to 9 (+2 y)
280
0
6
1.0000
0.9608
Visit 9 to 10 (+3 y)
274
1
6
0.9964
0.9573
13
26
0.9573
IP = implant placement. *Lost to follow-up.
Table 4 Presence of Bleeding and Plaque (No. of Implant Surfaces) IP + 12 wk (n = 1,120)
IP + 22 wk (n = 1,119)
IP + 26 wk (n = 1,120)
IP + 1 y (n = 1,116)
IP + 2 y (n = 1,096)
IP + 3 y (n = 1,068)
Presence of bleeding Yes No
27% 73%
19% 81%
24% 76%
24% 76%
23% 77%
20% 80%
Presence of plaque Yes No
33% 67%
25% 75%
32% 68%
40% 60%
36% 64%
32% 68%
IP = implant placement.
Table 5 Marginal Bone Level Changes (mm) from Implant Placement to 3 Years
Table 6 Prosthodontic Complications Complication
No.
Time
Fracture denture tooth
15
20–24 wk 1y
n
Mean
SD
262
–0.45
0.73
Max 2.1
Min –4.3
Median –0.4
Attachment screw loose
3 3
0.79
2.6
–3.8
–0.4
Crestal bone loss
–0.37
0.82
2.6
–4.6
–0.3
Inaccurate seating of angled titanium cylinder
2
–0.57
1.12
2.3
–7.9
–0.4
Food impaction
2
Framework fracture
2
Other*
9
255
–0.44
2y
258
3y
253
Negative values represent bone loss and positive values represent bone gain. Reduced numbers are primarily a result of insufficient radiographic quality for evaluation.
*One each: fractured resin provisional fixed partial denture, fracture resin + framework, phonetic problems, irregularities, abutment fracture, construction too bulky, excessive occlusal contacts, implant mobility, postoperative swelling.
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Thor et al
100 90 % of implants
80 70 60 50 40 30 20 10 0 –8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 MBL change (mm) Fig 9 Marginal bone level changes from implant placement to 3 years. Implants with no bone loss (gain) appear to the right of the vertical line (one square represents one implant).
ITVs. However, no bone augmentation was allowed. A provisional full-arch restoration was delivered within 48 hours of surgery, and after 3 months of healing, the definitive restoration was seated. After a mean followup of 22.5 (up to 40) months, five implants had been lost, all before 18 months of loading, and the cumulative implant survival rate was 97.59%. The authors further reported on the mean marginal bone loss after 1 year and found no significant difference between upright and tilted implants in the maxilla (0.95 mm, standard deviation [SD] 0.44 mm, n = 84, and 0.88 mm, SD 0.59 mm, n = 42, respectively). Using another implant system, Bergkvist et al studied the 32-month outcome of immediate loading in edentulous maxillae (mainly quantity B and C) of 28 patients and 168 Straumann Tissue-Level implants.13 The cumulative survival rate was 98.2% at the end of the observation period. Eight months after baseline, the mean marginal bone loss was 1.6 mm (SD 1.16), and after 20 months an additional loss of 0.41 mm (SD 0.63) was reported. At the last observation period, from 12 months up to 32 months at the end of the study, the bone loss had leveled out at only 0.08 mm. The current data on marginal bone level changes indicate that 25% of the subjects had gained bone around the implants. This is surprising and may perhaps be attributable to the marginal design of the implant system used. The implant used in this study displays minute threads (Micro Thread) on the cervical portion and an internal conical seal design of the implant/abutment connection that may be favorable
to the maintenance of crestal bone levels.25,26 Collaert and De Bruyn successfully treated 25 patients with 195 Astra Tech implants with a follow-up of 3 years, without any failures.26 Mean marginal bone loss after 3 years was 0.72 mm (SD 0.63). Eighty-six percent of the implants displayed < 1.5 mm of bone loss after 3 years and were considered successful; in the present study, this number was 89.6% after 3 years, which holds up well in comparison. There have been suggestions in the literature that the design of the implants plays an important role in the maintenance of marginal bone levels over time, in favor of conical implant-abutment connection systems.27 Plaque was found on about one-third of the total investigated implant surfaces, and bleeding was noted on about one-fifth of the surfaces. One can only speculate on whether an even stricter level of oral hygiene would have influenced the marginal bone loss in this study sample. Additionally, based on the selection criteria, the bone quantity was often sparse and the alveolar crests thin. Implants were placed palatal to the thin crest in many instances, which, from the perspective of the wide range (but low mean) of marginal bone loss, could be explained by the fact that these particular implants initially lose bone around the marginal part. This aspect will be further evaluated in the future 5-year report. A technical and surgical method to overcome the problem of a thin alveolar crest in the anterior arch would be to place the implants in the canine buttress and more posterior, as was done by the preference of a surgeon in the Chicago study center in the present study. Regarding the positions of the implants, 25% were placed in incisor areas, 27% in the canine area, 33% in premolar areas, and 15% in molar regions. Implant losses were seen in all positions of the maxilla, and there seemed to be no clear pattern. The restorations were deliberately kept to no more than one cantilever unit, and the opposing occlusion always consisted of a minimum of 10 units (second premolar to second premolar) of teeth or other prosthetic restorations to ensure optimal balance of the occlusion. The ITVs for the included implants varied, as seen in Fig 8. Of the 256 implants placed, 175 implants had a recorded ITV of ≤ 30 Ncm. Other studies excluded implants with ITVs below 30 or 40 Ncm.15,23 This may therefore be considered a strength of this study. The authors decided to report ITVs in an attempt to clinically monitor the stability of the implants in the various bone situations and resulting site preparations at the two centers, as the Lekholm and Zarb index is based on both radiologic assessment and clinical evaluation of implant sites during preparation.17 Other measurements to describe implant stability over time, eg, Periotest or resonance frequency analysis,28,29 are of course possible but were not used in this study.
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CONCLUSION The data from the first 3 years of this long-term study revealed good clinical outcomes (cumulative survival rate of 96%). Careful patient selection and planning by the restorative team enabled successful treatment outcomes for patients presenting with marked resorption of the edentulous maxilla.
ACKNOWLEDGMENTs This study was supported by DENTSPLY Implants (former Astra Tech AB). The authors reported no conflicts of interest related to this study.
References 1. Erkapers M, Ekstrand K, Baer RA, Toljanic JA, Thor A. Patient satisfaction following dental implant treatment with immediate loading in the edentulous atrophic maxilla. Int J Oral Maxillofac Implants 2011;26:356–364. 2. Esposito M, Hirsch JM, Lekholm U, Thomsen P. Biological factors contributing to failures of osseointegrated oral implants. (II). Etiopathogenesis. Eur J Oral Sci 1998;106:721–764. 3. Weber HP, Morton D, Gallucci GO, Roccuzzo M, Cordaro L, Grutter L. Consensus statements and recommended clinical procedures regarding loading protocols. Int J Oral Maxillofac Implants 2009;24(suppl):180–183. 4. Grunder U. Immediate functional loading of immediate implants in edentulous arches: Two-year results. Int J Periodontics Restorative Dent 2001;21:545–551. 5. Sailer HF. A new method of inserting endosseous implants in totally atrophic maxillae. J Craniomaxillofac Surg 1989;17:299–305. 6. Nystrom E, Kahnberg KE, Gunne J. Bone grafts and Brånemark implants in the treatment of the severely resorbed maxilla: A 2-year longitudinal study. Int J Oral Maxillofac Implants 1993;8:45–53. 7. Astrand P, Nord PG, Brånemark PI. Titanium implants and onlay bone graft to the atrophic edentulous maxilla: A 3-year longitudinal study. Int J Oral Maxillofac Surg 1996;25:25–29. 8. Nystrom E, Nilson H, Gunne J, Lundgren S. A 9-14 year follow-up of onlay bone grafting in the atrophic maxilla. Int J Oral Maxillofac Surg 2009;38:111–116. 9. Lundgren S, Nystrom E, Nilson H, Gunne J, Lindhagen O. Bone grafting to the maxillary sinuses, nasal floor and anterior maxilla in the atrophic edentulous maxilla. A two-stage technique. Int J Oral Maxillofac Surg 1997;26:428–434. 10. Schliephake H, Neukam FW, Wichmann M. Survival analysis of endosseous implants in bone grafts used for the treatment of severe alveolar ridge atrophy. J Oral Maxillofac Surg 1997;55:1227–1233. 11. Widmark G, Andersson B, Andrup B, Carlsson GE, Ivanoff CJ, Lindvall AM. Rehabilitation of patients with severely resorbed maxillae by means of implants with or without bone grafts. A 1-year follow-up study. Int J Oral Maxillofac Implants 1998;13:474–482. 12. Strietzel FP, Karmon B, Lorean A, Fischer PP. Implant-prosthetic rehabilitation of the edentulous maxilla and mandible with immediately loaded implants: Preliminary data from a retrospective study, considering time of implantation. Int J Oral Maxillofac Implants 2011;26:139–147. 13. Bergkvist G, Nilner K, Sahlholm S, Karlsson U, Lindh C. Immediate loading of implants in the edentulous maxilla: Use of an interim fixed prosthesis followed by a permanent fixed prosthesis: A 32-month prospective radiological and clinical study. Clin Implant Dent Relat Res 2009;11:1–10.
14. Ostman PO, Hellman M, Sennerby L. Direct implant loading in the edentulous maxilla using a bone density-adapted surgical protocol and primary implant stability criteria for inclusion. Clin Implant Dent Relat Res 2005;7(suppl 1):S60–69. 15. Gallucci GO, Bernard JP, Bertosa M, Belser UC. Immediate loading with fixed screw-retained provisional restorations in edentulous jaws: The pickup technique. Int J Oral Maxillofac Implants 2004;19:524–533. 16. Toljanic JA, Baer RA, Ekstrand K, Thor A. Implant rehabilitation of the atrophic edentulous maxilla including immediate fixed provisional restoration without the use of bone grafting: A review of 1-year outcome data from a long-term prospective clinical trial. Int J Oral Maxillofac Implants 2009;24:518–526. 17. Lekholm U, Zarb GA. Patient selection and preparation. In: Brånemark PI, Zarb GA, Albrektsson T (eds). Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago: Quintessence, 1987:199–209. 18. Bergkvist G, Sahlholm S, Nilner K, Lindh C. Implant-supported fixed prostheses in the edentulous maxilla. A 2-year clinical and radiological follow-up of treatment with non-submerged ITI implants. Clin Oral Implants Res 2004;15:351–359. 19. Ferrigno N, Laureti M, Fanali S, Grippaudo G. A long-term follow-up study of non-submerged ITI implants in the treatment of totally edentulous jaws. Part I: Ten-year life table analysis of a prospective multicenter study with 1286 implants. Clin Oral Implants Res 2002;13:260–273. 20. Rasmusson L, Roos J, Bystedt H. A 10-year follow-up study of titanium dioxide-blasted implants. Clin Implant Dent Relat Res 2005;7:36–42. 21. Fischer K, Stenberg T, Hedin M, Sennerby L. Five-year results from a randomized, controlled trial on early and delayed loading of implants supporting full-arch prosthesis in the edentulous maxilla. Clin Oral Implants Res 2008;19:433–441. 22. van Steenberghe D, Glauser R, Blomback U, et al. A computed tomographic scan-derived customized surgical template and fixed prosthesis for flapless surgery and immediate loading of implants in fully edentulous maxillae: A prospective multicenter study. Clin Implant Dent Relat Res 2005;7(suppl 1):S111–120. 23. Malo P, Rangert B, Nobre M. All-on-4 immediate-function concept with Brånemark System implants for completely edentulous maxillae: A 1-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S88–94. 24. Capelli M, Zuffetti F, Del Fabbro M, Testori T. Immediate rehabilitation of the completely edentulous jaw with fixed prostheses supported by either upright or tilted implants: A multicenter clinical study. Int J Oral Maxillofac Implants 2007;22:639–644. 25. Kim JS, Sohn JY, Park JC, et al. Cumulative survival rate of Astra Tech implants: A retrospective analysis. J Periodontal Implant Sci 2011;41:86–91. 26. Collaert B, De Bruyn H. Immediate functional loading of TiOblast dental implants in full-arch edentulous maxillae: A 3-year prospective study. Clin Oral Implants Res 2008;19:1254–1260. 27. Schmitt CM, Nogueira-Filho G, Tenenbaum HC, et al. Performance of conical abutment (Morse Taper) connection implants: A systematic review. J Biomed Mater Res Part A 2014 Feb;102(2):552–574. Epub 2013 May 9. 28. Salonen MA, Raustia AM, Kainulainen V, Oikarinen KS. Factors related to Periotest values in endosseal implants: A 9-year follow-up. J Clin Periodontol 1997;24:272–277. 29. Friberg B, Sennerby L, Meredith N, Lekholm U. A comparison between cutting torque and resonance frequency measurements of maxillary implants. A 20-month clinical study. Int J Oral Maxillofac Surg 1999;28:297–303.
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R
estoring the edentulous maxilla with immediately loaded implants can be an attractive treatment option for patients.1 For the clinician, it is important to consider the options for treatment and to evaluate them with regard to expected problems and known success rates. Esposito and coworkers included early loading protocols as one factor in the increased rate
1 Associate
Professor, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala University, Uppsala, Sweden. 2 Associate Professor and Director, Postgraduate Education, The University of Oslo, Institute for Clinical Dentistry, Oslo, Norway. 3 Private Practice, University Associates in Dentistry, Chicago, Illinois. 4 Associate Professor, Midwestern University College of Dental Medicine Illinois, Downers Grove, Illinois. Correspondence to: Dr Andreas Thor, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala University, SE-751 85 Uppsala, Sweden. Fax: +46-0-18-55-91. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
of complications in implant dentistry.2 Accelerated implant treatment in the maxilla has been less frequently explored and initially provided somewhat less favorable results compared to the same procedures in the mandible.3,4 The progressive resorption of maxillary bone after the loss of all teeth offers considerable challenges for the implant surgeon and restorative dentist. Vertical and horizontal losses of bone volume are accompanied by posterior sagittal movement of the maxilla, often making the actual positioning of the implants unfavorable with respect to the forces that will act upon them during mastication. Bone augmentation is often necessary to address this condition.5–8 Unfortunately, with autogenous bone grafting, the additional intervention involves pain, discomfort, and the risk of additional problems during and after the procedure.9 Reported success rates for edentulous patients with grafts and implants have also varied over the years but most often have been lower than those seen in nongrafted patients.10–12 However, encouraging results in other research groups have highlighted the possibility of immediately restoring implants placed in the edentulous maxilla, with a good
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Thor et al
long-term prognosis similar to the outcomes achieved with conventional protocols.1,12–15 Further scientific evaluation regarding the existing limits for different simplified and accelerated implant treatment protocols for patients appears to be warranted. Therefore, the current prospective long-term study examined the results over 3 years after implants were placed in the edentulous atrophic maxilla and restored with immediate fixed provisional restorations without the use of any additional augmentation procedures. The primary goal was to study the implant survival rate. In addition, marginal bone alterations were assessed by radiography, and soft tissue status was recorded by evaluation of plaque and bleeding. A total of 10 scheduled visits up to the occasion of the 3-year follow-up were carried out. In the study, subject satisfaction with the treatment was also recorded with the Oral Health Impact Profile-49 questionnaire,1 but these results will be reported elsewhere.
MATERIALS AND METHODS Fifty-one patients seeking routine care were recruited from two study centers (University of Chicago, Section of Dentistry, Chicago, Illinois; Uppsala University, Department of Surgical Sciences, Oral and Maxillofacial Surgery, Uppsala, Sweden) for participation in this study. Study approval was obtained from the ethics committees representing the two centers, and informed written consent was obtained from all study subjects. Consecutive enrollment of subjects for the study was carried out if all inclusion and exclusion criteria were met. Criteria were discussed in a previous report from this study on the 1-year results and included the initial situation regarding dental status in the opposing arch, smoking habits, and oral hygiene.16 Only nonsmoking patients with atrophic totally edentulous maxillae (bone quality 3 or 4 and bone quantity C, D, or E according to Lekholm and Zarb17) were included in the study. The investigators determined eligibility for the study after clinical examination and assessment of panoramic radiographs without the use of other imaging tools. The preoperative radiologic examination included a panoramic view and intraoral dental films. A computed tomographic scan was obtained only if the investigator felt the need for a more extensive examination. Subjects were included if the bone volume of the recipient site in the maxilla was considered sufficient to allow the placement of the smallest available implant in the study (3.5 mm in diameter and 8 mm in length). No augmentation procedures were allowed in the study. Although patients with bone grafts older than 6 months were eligible for
Fig 1 Surgical guide made of an acrylic resin duplicate of the prosthesis.
inclusion, no such patients were included. Initial specific findings on oral status were presented earlier.16 To be included and eligible for dental implant treatment in the maxilla, patients needed to have 10 tooth units (second premolar to second premolar) in the mandible, represented either by a natural dentition or dental prosthesis. If needed, treatment was initiated and completed in the mandible prior to treatment in the maxilla.
Implants and Surgical Protocol
Six implants (OsseoSpeed, ASTRA TECH Implant System, Dentsply) were placed in each patient and loaded within 24 hours with a screw-retained fixed restoration. The implants used in this study have a modified titanium surface that has been blasted with titanium dioxide and then chemically modified with fluoride. The design of the implant includes self-tapping features and microthreads at its coronal end. Because no bone augmentation was allowed in this protocol, the available bone was limited in many cases, and a surgical guide in clear acrylic resin was used to indicate the planned implant sites (Fig 1). The guide was fabricated by duplicating the prosthesis worn by the patient prior to treatment. The surgical protocol is presented elsewhere in detail.16 The limited amount of bone and low bone density often required underpreparation of the implant osteotomies. With this technique and via the self-tapping features of the implant, adequate primary stability of the implant was sought. Three implants were placed on each side of the maxilla. The most posterior implant was often inclined distally, guided by the stent and indicators, and placed in close relationship to the anterior wall of the maxillary sinus. This resulted in maximum support for the planned fixed restoration (Figs 2 and 3). After all implants had been placed, straight or angulated transmucosal screw-retained abutments were placed (UniAbutment, 20- or 45-degree Angled Abutment, Dentsply The International Journal of Oral & Maxillofacial Implants 643
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Thor et al
Fig 2 A limited amount of bone characterized the maxillae in the study.
Fig 3 With a surgical guide, the implants could be inclined for maximum spread over the available alveolar crest.
Implants). In this way the investigators could correct divergent angulations of placed implants, resulting in more favorable screw access holes in the restorations and better esthetic results. Titanium temporary abutments provided by the manufacturer were cut to a suitable length and screwed onto the abutments. The abutments were later used to support the provisional restoration. Surgery was completed with the suturing of flaps around the transmucosal abutments and restorative abutments.
Prosthetic Protocols
Fabrication of the screw-retained fixed provisionals differed between the two centers (see following). The Chicago team used a treatment protocol in which the fixed restoration was delivered within 3 hours of implant placement. They used the existing denture or a newly made denture that had been corrected for vertical dimension or other shortcomings. Holes were drilled in the prosthesis that corresponded well with the locations of the temporary abutments that had been screwed on to the implant abutments. Autopolymerizing acrylic resin was then applied around all temporary abutments to lute them to the prosthesis. After the resin had polymerized and all abutments were attached well to the prosthesis, the abutments were unscrewed and the prosthesis was removed from the mouth. The provisional fixed restoration was further revised by removal of acrylic resin from the prosthesis in the area of the palate and flanges. A glass fiber–reinforced material (EverStick C & B fiber reinforcement, Preat Corp) was used on the lingual surface, together with some autopolymerizing acrylic resin, to provide additional fracture resistance for the restoration. Upon delivery of the restoration, reduction of excessive occlusal contacts was carried out, along with esthetic changes, if needed. The team in Sweden used an indirect fabrication method for the provisionals. These restorations were delivered within 24 hours after implant surgery (Fig 4). Prior to implant surgery, initial steps were undertaken
Fig 4 Provisional fixed restoration delivered after 24 hours at the center in Sweden.
to fabricate a prosthesis to the level of the wax-up. This was duplicated to allow for fabrication of a resin surgical guide and a custom impression tray. A clear acrylic resin copy of the denture prosthesis wax-up was additionally fabricated. After the implants were placed, an abutment-level impression was made. The acrylic resin copy of the denture prosthesis wax-up was lined with silicone impression material (Provil, Heraeus-Kulzer) and placed into the mouth. Centric relation registration was performed at the same time, and the impression was then removed from the mouth. Next, the master cast was inserted into the silicone impression material contained within the clear denture prosthesis duplicate and mounted on an articulator. The screw-retained provisional was then fabricated on this mounted master cast. To increase the strength and increase fracture resistance of the prosthesis, a titanium mesh was laser-welded to the titanium copings and embedded into the restoration.
Postoperative Care
Oral antibiotics, analgesics, and a topical antimicrobial rinse were included in the postoperative protocol. Hygiene instructions prescribed a gentle brushing technique for the first week without flossing for the first 4 weeks. Thereafter, the study subjects were instructed to resume normal brushing and flossing. Subjects were instructed to eat a soft diet for 6 weeks.
Collection of Data and Follow-up Protocol
At the time of implant surgery and loading with the provisional, the implant characteristics (type, length, diameter, and position) were recorded. The implant surgeon documented bone quantity and quality by preoperative radiographic findings, visual inspection during surgery, and resistance in the bone and tactile sensation upon preparation of the implant sites. The final seating (last few millimeters of insertion) of the implants was performed with a calibrated torque wrench (Torque-Lock Wrench, Intra-Lock International) to measure primary stability and insertion torque value
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Thor et al
V1
V2
V3 +2 wk (±2 d)
2–3 wk
Screening Implant and placement inclusion
Fig 5 Clinical appearance of a subject at the 3-year follow-up visit. 30–
% of implants
18 15
15– 10–
14
7
5–
Postop
+20–24 wk
Impression
V7 +6 mo (±2 wk)
Definitive restoration
V8–V10 +1–3 y (±2 wk)
Follow-up
Follow-up
Second molars
First molars
Second premolars
First premolars
Canines
Lateral incisors
1 Central incisors
0–
Postop
+12 wk (±7 d)
V6
was delivered. This was reported earlier.16 Six months after implant surgery, function of the restoration was evaluated, and the prosthesis was removed for clinical evaluation of implant integration. The restorations were removed at the 1-, 2-, and 3-year visits, and the implants were manually assessed for stability. At these follow-up visits, clinical evaluation of the peri-implant mucosa was also performed. Plaque scores and bleeding on probing were registered on four surfaces (mesial, buccal, distal, and lingual) of each implant.
27
18
+4 wk (±2 d)
V5
Fig 6 Study flow chart. V = visit.
25– 20–
V4
Location Fig 7 Placement locations for 306 implants in the 51 subjects.
(ITVs). No minimum ITV was required for inclusion as long as clinical primary stability was deemed acceptable by the surgeon and prosthodontist. Subjects were followed for up to 3 years (Fig 5). Radiologic examinations were performed preoperatively at the time of screening and inclusion, at implant placement (baseline), when the definitive restoration was delivered, and annually to 3 years (Fig 6). A paralleling imaging technique was used with commercially available film holders to ensure reproducibility of the radiographs between examinations. An independent radiologist not affiliated with the two study centers interpreted all radiographs. The distance from the interproximal bone (mesial and distal) to the implant reference point (the junction of the roughened and machined beveled surfaces) was measured to the nearest 0.1 mm using ×7 magnification. The mean of these two measurements was used to represent the marginal bone height around each implant. The subjects were examined according to the study plan (Fig 6). At 12 weeks after implant placement, an impression for the definitive restoration was made, and after 20 to 24 weeks the definitive restoration
RESULTS All 51 included study subjects (mean age, 65.8 years; range, 47 to 83 years; 47% men and 53% women) received their fixed restorations, and 45 subjects have reached the 3-year follow-up. In all, 306 implants were placed (implant locations are shown in Fig 7), and 25 subjects received restorations that were fabricated chairside on the day of implant surgery. The other 26 restorations were fabricated using the indirect technique, but all 51 subjects had their implants loaded 24 hours after placement. At placement, ITVs were recorded, and the results are shown in Fig 8. The quantity and quality of bone in which the implants were placed are described in Table 1. During the first year of followup, one subject (six implants) was lost to follow-up, and 12 additional implants (in five subjects) were removed as a result of loss of integration. Three patients could no longer wear fixed restorations because of the implant losses and were therefore dropped from the study. Consequently, at 1 year, 47 patients and 280 implants were included. During the second year of follow-up, one subject died, resulting in a total of 274 available implants after 2 years. At 3 years, another patient had been lost to follow-up and another patient had lost one implant (45 patients and 267 implants). In summary, 13 implants were lost in six patients (Table 2). Twelve of these implants were lost before the definitive restoration was in place and were therefore considered early losses. Only one implant was lost between the 2- and 3-year follow-up examinations. Three The International Journal of Oral & Maxillofacial Implants 645
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Thor et al
Table 1 Characterization of Bone Quantity and Quality17 of the 306 Implants Placed
60– 49
Bone quality
36 35
32
30– 30
3 25
20 12
31–35
26–30
21–25
16–20
11–15
C
D
E
Total
116
58
1
175 (57%)
0
131 (43%)
74 190 (62%)
57 115 (38%)
1 (0%)
Unknown
13 10– 10 0–10
4 Total
>45
20– 20
0–0
Bone quantity
42
41–45
40– 40
42
36–40
No. of implants
50– 50
ITV (Ncm) Fig 8 ITVs of implants placed (n = 306).
subjects were lost to follow-up and three were withdrawn from the study because of implant losses. In patient 104, the left distalmost implant was shown to have inaccurate seating of an angled titanium cylinder at visit 2. At the 3-year follow-up visit, severe bone loss was noted around this implant, which was removed at this time. To date, this is the only late removal in the study. Subjects 107 and 114 also had distal implants removed; in the latter case, this was tentatively explained by heavy occlusion. Framework fracture of the provisional resulted in the loss of three implants in patient 205. The subject with the highest number of implant losses (patient 214) was a male ex-smoker, 76 years of age, with bone quantity C and quality 3. In this subject, the ITVs of the lost implants were between 10 and 35 Ncm. Finally, one subject with mobile implants (patient 225) had a history of bruxism but also better ITVs during placement of the implants. Three implants were lost and removed after 78 days. Implant survival rates, expressed using KaplanMeier analysis, displayed a stable cumulative survival rate of 96% from the 1-year to the 3-year examinations (Table 3). At this time, the condition of the peri-implant mucosa showed bleeding when probing in 20% of the implant surfaces, and plaque was present on 32% of the surfaces (Table 4). The marginal bone levels around the implants were stable after placement of the fixed restorations up to the 3-year control (Table 5). Twenty-six percent of the implants showed no evidence of marginal bone loss at the 3-year follow-up. Marginal bone level changes are illustrated in Fig 9. Other complications, including with the prostheses, that occurred during the first 3 years of follow-up are listed in Table 6. The most common complaint was fractured denture teeth.
DISCUSSION In this study, subjects were followed for 3 years after implant rehabilitation in atrophic edentulous maxillae. Forty-five subjects reached the 3-year follow-up appointment, and 13 implants were lost in six patients. Of the 306 implants initially placed in 51 subjects, 267 implants remained in the study, for an implant survival rate of 95.7%. Mean marginal bone loss was 0.57 (± 1.12) mm at 3 years. The results of this study must be interpreted with the knowledge that conventional loading of implantsupported fixed prostheses in the edentulous maxilla with rough-surfaced dental implants has shown good results, with implant survival rates ranging from 95% to 98%.18–21 Previous studies reporting on immediate loading in edentulous maxillae have not used the demanding inclusion criteria of this study regarding bone quantity (Lekholm and Zarb C, D, and E).14,15,22,23 During the recruitment process in this study, subjects were excluded if they had type A or B bone. Given this fact, the results presented here are consistent with previous findings from other research groups regarding implant survival and marginal bone level changes. Few studies are available in the literature with longer follow-up following immediate loading in the edentulous maxilla. One study with a similar design to the present study was performed by Capelli et al.24 They reported on the 3-year results of a multicenter study from four centers on 246 Osseotite NT implants (Biomet/3i). These implants were placed in the maxilla, and the distalmost implants were tilted 25 to 35 degrees. Patients were included if they displayed severe resorption of the maxilla, but no data were presented on bone volume classification (eg, Lekholm and Zarb index) or
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Thor et al
Table 2 Summary of Implant Losses Subject no. Position* Sex Age (y)
Smoking history
Bone quantity/quality17
Implant length (mm)
Time to loss (d)
104
25
M
74
Nonsmoker
C/3
13
1,057
107
16
M
75
Ex-smoker
C/4
11
98
114
16
M
53
Ex-smoker
C/4
11
78
205
15
F
67
Nonsmoker
C/4
11
65
205
13
F
67
Nonsmoker
C/4
15
1
205
25
F
67
Nonsmoker
C/4
9
65
214
15
M
76
Ex-smoker
C/3
13
189
214
13
M
76
Ex-smoker
C/3
15
77
214
12
M
76
Ex-smoker
C/3
13
77
214
21
M
76
Ex-smoker
C/3
13
77
225
15
F
72
Nonsmoker
C/3
13
78
225
13
F
72
Nonsmoker
C/3
13
78
225
11
F
72
Nonsmoker
C/3
11
78
Total losses
13
*FDI tooth numbers.
Table 3 Kaplan-Meier Implant Survival Analysis over 3 Years No. at risk
Failures
Censored*
Interval survival probability
IP (visit 2)
Interval
306
0
0
1.0000
Survival proportion
IP to visit 3 (+2 wk)
306
1
0
0.9967
0.9967
Visit 3 to 4 (+4 wk)
305
0
0
1.0000
0.9967
Visit 4 to 5 (+12 wk)
305
11
14
0.9639
0.9608
1.000
Visit 5 to 7 (+26 wk)
280
0
0
1.0000
0.9608
Visit 7 to 8 (+1 y)
280
0
0
1.0000
0.9608
Visit 8 to 9 (+2 y)
280
0
6
1.0000
0.9608
Visit 9 to 10 (+3 y)
274
1
6
0.9964
0.9573
13
26
0.9573
IP = implant placement. *Lost to follow-up.
Table 4 Presence of Bleeding and Plaque (No. of Implant Surfaces) IP + 12 wk (n = 1,120)
IP + 22 wk (n = 1,119)
IP + 26 wk (n = 1,120)
IP + 1 y (n = 1,116)
IP + 2 y (n = 1,096)
IP + 3 y (n = 1,068)
Presence of bleeding Yes No
27% 73%
19% 81%
24% 76%
24% 76%
23% 77%
20% 80%
Presence of plaque Yes No
33% 67%
25% 75%
32% 68%
40% 60%
36% 64%
32% 68%
IP = implant placement.
Table 5 Marginal Bone Level Changes (mm) from Implant Placement to 3 Years
Table 6 Prosthodontic Complications Complication
No.
Time
Fracture denture tooth
15
20–24 wk 1y
n
Mean
SD
262
–0.45
0.73
Max 2.1
Min –4.3
Median –0.4
Attachment screw loose
3 3
0.79
2.6
–3.8
–0.4
Crestal bone loss
–0.37
0.82
2.6
–4.6
–0.3
Inaccurate seating of angled titanium cylinder
2
–0.57
1.12
2.3
–7.9
–0.4
Food impaction
2
Framework fracture
2
Other*
9
255
–0.44
2y
258
3y
253
Negative values represent bone loss and positive values represent bone gain. Reduced numbers are primarily a result of insufficient radiographic quality for evaluation.
*One each: fractured resin provisional fixed partial denture, fracture resin + framework, phonetic problems, irregularities, abutment fracture, construction too bulky, excessive occlusal contacts, implant mobility, postoperative swelling.
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Thor et al
100 90 % of implants
80 70 60 50 40 30 20 10 0 –8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 MBL change (mm) Fig 9 Marginal bone level changes from implant placement to 3 years. Implants with no bone loss (gain) appear to the right of the vertical line (one square represents one implant).
ITVs. However, no bone augmentation was allowed. A provisional full-arch restoration was delivered within 48 hours of surgery, and after 3 months of healing, the definitive restoration was seated. After a mean followup of 22.5 (up to 40) months, five implants had been lost, all before 18 months of loading, and the cumulative implant survival rate was 97.59%. The authors further reported on the mean marginal bone loss after 1 year and found no significant difference between upright and tilted implants in the maxilla (0.95 mm, standard deviation [SD] 0.44 mm, n = 84, and 0.88 mm, SD 0.59 mm, n = 42, respectively). Using another implant system, Bergkvist et al studied the 32-month outcome of immediate loading in edentulous maxillae (mainly quantity B and C) of 28 patients and 168 Straumann Tissue-Level implants.13 The cumulative survival rate was 98.2% at the end of the observation period. Eight months after baseline, the mean marginal bone loss was 1.6 mm (SD 1.16), and after 20 months an additional loss of 0.41 mm (SD 0.63) was reported. At the last observation period, from 12 months up to 32 months at the end of the study, the bone loss had leveled out at only 0.08 mm. The current data on marginal bone level changes indicate that 25% of the subjects had gained bone around the implants. This is surprising and may perhaps be attributable to the marginal design of the implant system used. The implant used in this study displays minute threads (Micro Thread) on the cervical portion and an internal conical seal design of the implant/abutment connection that may be favorable
to the maintenance of crestal bone levels.25,26 Collaert and De Bruyn successfully treated 25 patients with 195 Astra Tech implants with a follow-up of 3 years, without any failures.26 Mean marginal bone loss after 3 years was 0.72 mm (SD 0.63). Eighty-six percent of the implants displayed < 1.5 mm of bone loss after 3 years and were considered successful; in the present study, this number was 89.6% after 3 years, which holds up well in comparison. There have been suggestions in the literature that the design of the implants plays an important role in the maintenance of marginal bone levels over time, in favor of conical implant-abutment connection systems.27 Plaque was found on about one-third of the total investigated implant surfaces, and bleeding was noted on about one-fifth of the surfaces. One can only speculate on whether an even stricter level of oral hygiene would have influenced the marginal bone loss in this study sample. Additionally, based on the selection criteria, the bone quantity was often sparse and the alveolar crests thin. Implants were placed palatal to the thin crest in many instances, which, from the perspective of the wide range (but low mean) of marginal bone loss, could be explained by the fact that these particular implants initially lose bone around the marginal part. This aspect will be further evaluated in the future 5-year report. A technical and surgical method to overcome the problem of a thin alveolar crest in the anterior arch would be to place the implants in the canine buttress and more posterior, as was done by the preference of a surgeon in the Chicago study center in the present study. Regarding the positions of the implants, 25% were placed in incisor areas, 27% in the canine area, 33% in premolar areas, and 15% in molar regions. Implant losses were seen in all positions of the maxilla, and there seemed to be no clear pattern. The restorations were deliberately kept to no more than one cantilever unit, and the opposing occlusion always consisted of a minimum of 10 units (second premolar to second premolar) of teeth or other prosthetic restorations to ensure optimal balance of the occlusion. The ITVs for the included implants varied, as seen in Fig 8. Of the 256 implants placed, 175 implants had a recorded ITV of ≤ 30 Ncm. Other studies excluded implants with ITVs below 30 or 40 Ncm.15,23 This may therefore be considered a strength of this study. The authors decided to report ITVs in an attempt to clinically monitor the stability of the implants in the various bone situations and resulting site preparations at the two centers, as the Lekholm and Zarb index is based on both radiologic assessment and clinical evaluation of implant sites during preparation.17 Other measurements to describe implant stability over time, eg, Periotest or resonance frequency analysis,28,29 are of course possible but were not used in this study.
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Thor et al
CONCLUSION The data from the first 3 years of this long-term study revealed good clinical outcomes (cumulative survival rate of 96%). Careful patient selection and planning by the restorative team enabled successful treatment outcomes for patients presenting with marked resorption of the edentulous maxilla.
ACKNOWLEDGMENTs This study was supported by DENTSPLY Implants (former Astra Tech AB). The authors reported no conflicts of interest related to this study.
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