Implant Rehabilitation of the Atrophic Edentulous Maxilla ... - EBSCOhost

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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 Joseph A. Toljanic, DDS1/Russell A. Baer, DDS2/Karl Ekstrand, DDS, MS, PhD, Odont Dr3/ Andreas Thor, DDS, PhD4 Purpose: The literature suggests that predictable integration can be achieved when dental implant placement is combined with immediate fixed provisional restoration in a variety of clinical situations. Fewer data are available, however, regarding outcomes for immediate provisional restoration of implants in the edentulous maxilla. This report presents 1-year data acquired from a long-term prospective clinical trial designed to assess outcomes following the immediate provisional fixed restoration of implants in the atrophic edentulous maxilla without the use of bone augmentation. Materials and Methods: Fifty-one subjects diagnosed with an atrophic edentulous maxilla received a total of 306 implants (six implants per subject) followed by fixed provisional restoration within 24 hours of implant placement. No subjects underwent grafting to enhance bone volume in preparation for implant treatment. Data acquired included bone quantity and quality, implant dimensions, implant locations, and implant placement stability. Subjects returned for 1-year follow-up examinations to assess implant integration and restoration function. Periapical radiographs were obtained and compared to baseline images to assess marginal bone height maintenance. Results: At the 3-month followup examination, 294 of 306 implants placed in 51 subjects were found to be integrated. This represents a cumulative implant survival rate of 96%. At the 1-year follow-up examination, mean marginal bone loss of 0.5 mm was noted, with no further loss of implants. Conclusions: These results support the contention that predictable long-term outcomes may be obtained for the atrophic edentulous maxilla when treated with an implant rehabilitation protocol that includes immediate fixed provisional restoration without the use of bone grafting. This strategy offers a promising treatment alternative for the patient with an atrophic edentulous maxilla. INT J ORAIL MAXILLOFAC IMPLANTS 2009;24:518–526 Key words: dental implants, edentulous maxilla, immediate restoration

large body of evidence has accumulated over the past 10 years in support of immediate fixed provisional restoration of dental implants.1–14 The combination of immediate fixed provisional restoration with implant placement appears to offer a predictable treatment option in a wide variety of clinical applications, with outcomes that rival those obtained using standard delayed implant restoration protocols.1–14 Less information is currently available describing outcomes for immediate fixed provisional restoration of implants in the edentulous maxilla. It is commonly anticipated that, following tooth extraction, the edentulous maxilla will exhibit marked progressive loss of alveolar bone volume and density. The loss of alveolar bone may reduce the number of adequate sites available for implant placement. Inadequate

A 1Former

Professor and Chief, Section of Dentistry, The University of Chicago, Illinois, and current Staff Prosthodontist, Jesse Brown VA Medical Center, Chicago, Illinois. 2Clinical Associate, Section of Dentistry, The University of Chicago, Illinois. 3Associate Professor and Director, Postgraduate Education, The University of Oslo, Norway. 4Assistant Professor, Oral and Maxillofacial Surgery, Department of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden. Correspondence to: Dr Joseph Toljanic, Jesse Brown VA Medical Center (160), 820 S. Damen Avenue, Chicago, IL 60612. Fax: +312-569-8089. Email: [email protected] Presented as a poster at the 16th annual meeting of the European Academy of Osseointegration, Barcelona, Spain, in 2007.

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bone volume and density may further limit the ability to achieve primary implant stability, permitting postoperative implant micromotion to occur beyond currently accepted physiologic thresholds for successful integration.15,16 In spite of these inherent challenges, reports have appeared in the literature describing favorable outcomes for the edentulous maxilla. Tarnow and coworkers, in evaluating the efficacy of provisional restorations in both the mandible and maxilla, immediately loaded 34 implants in four subjects with edentulous maxillae. 17 They reported no loss of implants over a follow-up period from 1 to 3 years. Horiuchi and coworkers reported similarly promising outcomes in five subjects following immediate loading of 44 implants; they obtained a 95.4% survival rate over a 1- to 2-year follow-up interval.18 Recent reports in the literature continue to describe good outcomes. Balshi and coworkers, in a prospective study of 55 subjects who received 522 implants immediately loaded with fixed provisional restorations, reported an implant survival rate of 99% over a mean follow-up interval of 2.78 years.19 Van Steenberghe and coworkers reviewed outcomes of 164 implants placed in 24 subjects using a computerized tomographic (CT) scan–derived customized surgical guide stent and a flapless surgical procedure followed by immediate fixed provisional restoration. They reported a 100% implant survival rate at 1 year.20 Ibanez and coworkers treated subjects with one or both arches edentulous. They reported a 100% survival rate for 217 implants placed into 26 edentulous maxillae and restored with fixed provisional restorations within a 48-hour period over a follow-up interval of 1 to 6 years.21 Ostman and coworkers placed 123 implants in 20 subjects followed by provisional fixed restoration within 12 hours.22 They then retrospectively compared these outcomes to a reference group of 20 patients previously treated with 120 implants but who received no provisional restoration. The authors reported a 1-year implant survival rate greater than 99% in the study population, as compared to an implant survival rate of 100% in the reference group. Malo and coworkers reported on 1-year outcomes for 32 patients who had undergone implant rehabilitation in the edentulous maxilla followed by immediate provisional fixed restoration. The authors employed a CT scan–derived surgical guide stent for implant placement combined with a protocol that, most interestingly, limited the number of implants placed to four per patient.23 They reported a cumulative implant survival rate of 97.6%. Most recently, Capelli and coworkers evaluated the outcomes of 246 implants placed in 41 subjects, who received fixed provisional restorations within 48 hours

of implant placement. They reported an implant survival rate of 97.6% over an interval up to 3 years.24 While this initial work is clearly encouraging, additional research appears warranted to better assess the predictability of this protocol over time. The purpose of the present article is to report on outcomes obtained to date from a prospective long-term clinical trial designed to further assess the efficacy of a treatment protocol that includes immediate fixed provisional restoration of implants placed in the atrophic edentulous maxilla without the use of bone augmentation procedures.

MATERIALS AND METHODS Fifty-one subjects recruited from a population of patients under routine care at two participating centers (the University of Chicago, Section of Dentistry, and Uppsala University Hospital, Sweden) were enrolled in the study. The mean age of this population was 65.8 years (range, 47 to 83 years), with a gender distribution of 47% men and 53% women. Informed written consent was obtained from all subjects following approved institutional review board guidelines for clinical research. Individuals identified as having an atrophic edentulous maxilla based on clinical and radiographic examination were considered for study enrollment. A diagnosis of maxillary atrophy was made using a classification system designed to score alveolar bone quantity on a scale from A (minimal alveolar bone resorption) to E (extreme bone resorption) and bone quality on a scale from 1 (mostly compact bone present) to 4 (mostly trabecular bone present).25 All scoring was made based on the clinical judgment of the investigators after examination of each maxilla and visual assessment of panoramic radiographs without the use of other imaging tools (eg, grayscale measurements in Hounsfield units). Subjects were considered eligible for enrollment if they received bone quantity scores of C, D, or E and bone quality scores of 3 or 4. Because no bone augmentation was permitted within 6 months of study enrollment, subjects were therefore required to have sufficient native bone volume to accept placement of the smallest implant available to the investigators (3.5 mm in diameter and 8 mm in length). Subject enrollment occurred consecutively for candidates identified as having atrophic edentulous maxillae and who met all other study inclusion/exclusion criteria (Table 1). Strict adherence to these criteria would have permitted enrollment of an individual with a history of alveolar bone augmentation more than 6 months prior to implant placement, but none of the participants had any history of bone grafting. The International Journal of Oral & Maxillofacial Implants 519

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Table 1 Inclusion and Exclusion Criteria for Subject Enrollment Inclusion criteria 1. Adults (defined as individuals 20 years of age or older) 2. History of a fully edentulous maxilla for a minimum of 3 months 3. Clinical and radiographic findings indicating bone quantity types C, D, or E at sites of proposed implant placement (Lekholm and Zarb classification25) 4. Clinical and radiographic findings indicating bone quality scores of 3 or 4 at sites of proposed implant placement (Lekholm and Zarb classification25) 5. Presence of natural healthy and/or restored mandibular teeth to level of second premolars 6. Ability to provide informed written consent. 7. Ability to return for all study visits as outlined in investigational plan Exclusion criteria 1. Inability to comply with all study procedures as outlined in investigational plan 2. Presence of uncontrolled systemic disease 3. Presence of uncontrolled dental disease 4. History of chemotherapy or head and neck radiotherapy 5. History of alveolar bone augmentation surgery within 6 months of study treatment 6. History of tobacco product use within 6 months of study treatment 7. Subject pregnancy

Each subject underwent surgery following an investigational protocol that included the placement of 6 implants into the maxilla. A threaded selftapping implant with microthreads in the collar area was chosen for use in this study (OsseoSpeed, Astra Tech, Sweden). This implant has a microroughened titanium surface that is chemically modified with fluoride. It was theorized by the investigators that an implant with these design features and surface modifications might maximize the ability to obtain primary implant stability while enhancing the potential for osseointegration. Screw-retained fixed provisional restorations were fabricated and delivered to each subject within 24 hours of implant placement.

Surgical Protocol Implant surgery was performed under infiltrative local anesthesia using standard accepted soft tissue flap designs. The flap was first raised on one side of the maxilla, extending from a point just posterior to the nasopalatine papilla distally to the site of anticipated placement of the distal implant. Osteotomies were initiated by introducing a pilot drill to the site. A clear acrylic resin surgical stent, fabricated by duplicating the denture prosthesis previously worn by the subject, was used to guide osteotomy locations. Care was taken during the osteotomy site enlargement sequence to take into account the lack of bone density that was commonly encountered. This led to frequent underpreparation of the osteotomy site relative to the planned implant diameter, with reliance on the self-tapping design of the implant to laterally compress the bony walls to maximize primary stability (Fig 1). Crestal bone fenestrations were commonly encountered, which at times resulted in exposure of several implant threads on the buccal side of the

osteotomy. Typically no action was taken to surgically correct these areas of thread exposure. Where limited bone was available in the posterior maxilla, the distal osteotomy preparation was further modified to place the implant with a distal angulation (Fig 2). This permitted the use of longer implants to maximally engage native bone while at the same time positioning the implant platform posteriorly to enhance the distribution of support for the restoration. This angulated placement commonly resulted in the implant being positioned adjacent to the anterior wall of the maxillary sinus (Fig 3). Following the placement of three implants on one side, attention was turned to the opposite side of the maxilla, where the surgical procedures were repeated. Transmucosal abutments were screwed into place on the implants (Fig 4). Straight or angled transmucosal abutments were chosen by the investigators to correct for divergent implant placement angulations and to enhance screw access hole positions for maximum esthetic outcomes. Six stock copings available from the implant manufacturer were then cut to the desired size and screwed into place onto the transmucosal abutments for later use in retaining the fixed provisional restoration. Finally, the soft tissue flaps were sutured around the transmucosal abutments/retentive copings (Fig 5).

Provisional Restoration Protocols Provisional screw-retained fixed restorations were fabricated using both direct and indirect methods in this study. To initiate direct fabrication, complete maxillary denture prostheses worn by the subjects at the time of study enrollment were commonly used. If the prosthesis was ill-fitting and/or possessed inadequate


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Fig 1 The 2.5-mm twist drill used for final osteotomy preparation next to the 4.5-mmdiameter implant inserted into the prepared site. Note the differences in diameters between the implant and the twist drill.

Fig 2 Panoramic image demonstrating implants in place on the day of surgery. Note the angulation of posterior implants following the anterior wall of maxillary sinus.

Fig 3 Periapical radiograph showing angulation of the distal implant in close proximity to the anterior wall of the maxillary sinus.

Fig 4 Intraoperative placement of transmucosal implant abutment cylinders.

vertical dimension or occlusal contacts, a new denture prosthesis was fabricated. On the day of treatment, holes were drilled into the prosthesis corresponding to the locations of the six copings screwed onto the implant abutments (Fig 6). An autopolymerizing acrylic resin was then painted around each of the retentive copings to lute them to the prosthesis. Following polymerization of the acrylic resin, the retentive copings were unscrewed and the prosthesis was removed from the mouth. The palate and flanges of the prosthesis were then removed and glass-fiber reinforcement material was luted into the lingual surface with additional autopolymerizing acrylic resin (EverStick C & B fiber reinforcement, Preat Corp, Santa Ynez, CA) (Fig 7). After the provisional restoration was delivered, centric occlusal contacts were assessed

Fig 5 Sutures were used to close the wound around the transmucosal abutments and retentive copings immediately prior to provisional restoration fabrication.

and excessive focal contacts were reduced. Esthetics were assessed and revised as needed (Fig 8). The use of this treatment protocol resulted in the delivery of the fixed provisional restorations within 3 hours of implant placement. For indirect fabrication, fixed provisional restorations were created as follows. Prior to treatment, maxillary denture prosthesis fabrication was performed up to the wax-up stage. The wax-up was duplicated to permit fabrication of an acrylic resin surgical guide stent and a custom impression tray. A clear acrylic resin copy of the denture prosthesis wax-up was also fabricated. Immediately after implant placement surgery, an abutment-level impression was made. The clear acrylic resin copy of the denture prosthesis waxup was then lined with a silicone impression material The International Journal of Oral & Maxillofacial Implants 521

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Fig 6 Prosthesis held in place in the mouth. Note the easy visualization of the six retentive coping cylinders through previously prepared holes.

Fig 7 Fixed provisional restoration finished with removal of flanges/palate and with incorporation of glass fiber reinforcement material into the lingual aspect of the prosthesis.

Fig 8 Anterior view of fixed provisional restoration demonstrating the esthetic outcome.

Fig 9 A clear acrylic resin denture prosthesis duplicate was used to mount the master cast onto an articulator. Fig 10 Occlusal view of treatment site at 12 week follow-up interval.

(Provil, Heraeus-Kulzer, South Bend, IN) and placed into the mouth. While it was in place, a registration of centric relation was obtained. After removal from the mouth, the master cast was inserted into the silicone impression material contained within the clear denture prosthesis duplicate and mounted on an articulator (Fig 9). The screw-retained provisional restoration was then fabricated on this mounted master cast. A titanium mesh, laser-welded to the titanium copings, was embedded into this restoration to increase fracture resistance. These restorations were delivered within 24 hours of implant placement surgery. Postoperative medications included appropriate oral antibiotics and a topical antimicrobial rinse as well as oral analgesics. Hygiene instructions included gentle brushing for the first week without flossing for the first 4 weeks. After this time, subjects were instructed to resume normal brushing and flossing. Subjects were dismissed with instructions to maintain a soft diet for 6 weeks.

Data Acquisition and Subject Follow-up Data recorded at the time of implant placement/provisional restoration included the length and diameter of each implant placed, along with implant locations. Bone quantity and quality at each implant placement site were scored based on visual inspection, radiographic findings, and the tactile sense gained by the

surgical investigators during osteotomy preparation. Primary stability measurements were made for each implant using a calibrated torque wrench (TorqueLock Wrench, Intra-Lock International Inc, Boca Raton, FL) that measured the amount of torque (in Ncm) required to fully seat the implant. Baseline periapical radiographs of all implants were obtained at implant placement surgery using commercially available film holders and a paralleling imaging technique. Marginal bone height was determined on these images by measuring the distance from a reference point, defined as the junction of the roughened and machined beveled surface, to the most coronal point of bone-to-implant contact on both the mesial and distal sides of the implant. A single value for marginal bone height was then calculated by obtaining the mean of these two measurements for each implant. All measurements were obtained to the nearest 0.1 mm under 7⫻ magnification by an independent radiologist not affiliated with the two study treatment centers. Subjects returned at posttreatment weeks 2 and 4 for follow-up examination. Assessment of healing at the surgical sites and function of the fixed provisional restorations were performed at these visits without removing the fixed provisional restorations. Subjects then returned at posttreatment week 12, at which time the provisional restorations were removed and implant integration clinically assessed


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Table 2 Marginal Bone Height at Implant Placement, Placement of Definitive Restoration (20 to 24 Weeks), and at 1 Year Time

Marginal bone height

No. of implants

Mean ± SD

262 264 262

0.4 ± 0.5 0.9 ± 0.7 0.9 ± 0.8

Implant placement 20–24 wk 1y

Median Minimum Maximum 0.3 0.9 0.8

0.0 0.0 0.0

2.8 4.3 4.1

Table 3 Distribution of Implants with Respect to Bone Quantity and Quantity at Implant Placement24 Bone quantity Bone quality

A

B

C

D

E

%

No. of implants

3 4 % No. of implants

0 0 0 0

0 0 0 0

116 74 62 190

58 57 38 115

1 0 0 1

57 43

175 131 306

Table 4 Distribution of Implant Dimensions Length (mm) Diameter (mm)

8

9

11

13

15

17

%

No. of implants

3.5 4.0 4.5 5.0 % No. of implants

2 0 0 0 1 2

3 5 1 0 3 9

30 21 11 1 21 63

77 80 41 11 68 209

13 4 2 1 6 20

2 1 0 0 1 3

42 36 18 4

127 111 55 13

in preparation for fabrication of the definitive fixed screw-retained restorations (Fig 10). Fabrication of the definitive restoration proceeded using standard accepted restorative procedures for a metal/acrylic resin framework (titanium) prosthesis, with delivery occurring 20 to 24 weeks after implant surgery. Follow-up periapical radiographs were obtained at the time of restoration delivery. Subjects returned 6 months after implant surgery, at which time the function of the definitive restoration was assessed. This restoration was then removed, and implant integration was clinically evaluated. Subjects then returned 1 year after implant surgery, at which time all restorations were again removed and inspected. Implants were assessed clinically for integration maintenance. Periapical radiographs were obtained and marginal bone height measurements repeated to permit comparisons with baseline data.

RESULTS Following the investigational protocol, 306 implants were placed into the study population, retaining 51 fixed provisional restorations. Twenty-five of these restorations were fabricated directly on the day of

306

implant surgery, and the remaining 26 restorations were fabricated using the indirect technique. One subject was subsequently lost to follow-up 4 weeks after implant placement for reasons unrelated to study participation. During the 12-week follow-up interval following implant placement/provisional restoration, 12 implants in five subjects were identified as integration failures requiring removal.Three of these subjects were no longer able to wear a fixed restoration and subsequently were withdrawn from study participation. One additional subject who remains under follow-up has not reached the scheduled 1-year follow-up visit at this time. Of the 46 subjects reaching the 1-year follow-up interval, no additional implant integration failures have occurred, resulting in a cumulative survival rate of 96%. Mean marginal bone loss from implant surgery (baseline) to placement of the definitive fixed restoration was found to be 0.5 mm (SD 0.7), with no additional marginal bone loss encountered at the 1-year followup interval (0.5 mm, SD 0.8) (Table 2). In assessing the distribution pattern of implant placement in relationship to bone quantity and quality, the majority of implants were noted to have been placed in osseous tissue clinically rated as type C bone quantity, although 38% of all implants were placed in sites clinically rated as type D bone quantity (Table 3).

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Table 5 Distribution of Implant Locations

No. %

Central incisors

Lateral incisors

Canines

First premolars

Second premolars

First molars

Second molars

Third molars

Total

56 18

21 7

82 27

46 15

55 18

43 14

3 1

0 0

306 100

Table 6 Primary Implant Stability as Assessed by Seating Torque Values Seating torque values (Ncm)

No. %

0–10

11–15

16–20

21–25

26–30

31–35

36–40

41–45

> 45

Unknown

Total

36 12

35 11

42 14

42 14

20 7

32 11

13 4

12 4

49 16

25 8

306 100

A more equal distribution for implant placement was noted in types 3 and 4 bone quality (Table 3). Marked variability was noted in the implant sizes selected for placement, although implants of 11 mm and 13 mm in length and 3.5 mm, 4.0 mm, and 4.5 mm in diameter were most commonly used ( Table 4). Marked variability was noted in implant placement locations, although canine sites were most commonly selected, followed by second premolar and central incisor sites (Table 5). A large variability in primary implant stability achieved for each implant, as assessed via seating torque values, was also noted, although 38% of all implants placed required a torquing force of 20 Ncm or less to fully seat the implant (Table 6).

DISCUSSION Recent reports have provided support for a hypothesis that good outcomes may be achieved in the edentulous maxilla with the use of an implant rehabilitation protocol that includes immediate fixed provisional restoration. Implant survival rates ranging from 97.6% to 100% have been described over a follow-up interval of 1 year or longer for most subjects.19–24 Mean periimplant marginal bone loss of 0.76 to 1.15 mm has been reported. 20–24 The findings from the current study are consistent with these reported outcomes, where the 1-year implant survival rate was found to be 96%, with mean marginal bone loss of 0.5 mm. The results of this study were obtained in subjects with atrophic maxillae. The favorable outcomes seen in this more challenging population might be viewed as added support for this treatment protocol. Future reports describing outcomes with longer follow-up will certainly provide further insight regarding the efficacy of this treatment approach. It may be equally important to better understand the individual factors that may affect long-term outcomes. It appears to be generally accepted that achieving primary

implant stability is essential for success when immediate fixed provisional restoration is included in implant rehabilitation. Based on a recent in-depth review of the literature on immediate provisional restoration of implants, one set of authors found strong support for the conclusion that primary implant stability is a requisite for obtaining predictable outcomes.26 Following a literature review that focused on published reports of outcomes for immediate loading in completely edentulous patients, another author found a similar consensus of opinions regarding the importance of primary implant stability.27 Factors that might favorably impact on achieving primary implant stability in the edentulous maxilla may include the use of implants with specific surface modifications, underpreparation of osteotomy sites, and cross-arch splinting of implants.21,22 The technique of distally tilting implants has also been recommended for use in the posterior maxilla. This configuration, designed to avoid the placement of implants in bone of poorer quality and quantity in the area of the maxillary sinus, could enhance primary implant stability by engaging more bone with longer implants.24 Such a placement strategy may offer an effective alternative to sinus-lifting augmentation techniques for the atrophic maxilla.24 In two recent studies that included an assessment of angulated implant placement in the edentulous maxilla, the authors reported good integration outcomes for distally tilted implants.24,28 Atrophy is a common clinical condition among patients with edentulous maxillae. Such a condition can create a more challenging environment for obtaining primary stability. Because the investigational plan in the current study was specifically designed to select subjects with atrophic maxillae, the investigators incorporated the strategies described here, including the use of implants with favorable surface qualities, underpreparation of osteotomy sites, and angulated implant placement in the area of the maxillary sinus with the intent of


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improving the primary stability of each implant. Overall implant stabilization was enhanced by providing cross-arch stabilization through the use of immediate fixed provisional restoration. The favorable outcomes as experienced in this study might be interpreted as resulting from these combined surgical and restorative strategies. However, it should be noted that more than one third of the implants placed in the study were seated with a torque of 20 Ncm or less. While primary implant stability likely plays a role in achieving successful outcomes, perhaps other factors may be acting separately or synergistically with implant stability to obtain the degree of success currently being reported in the literature. Efforts to better understand all factors involved and their interrelationships would help clinicians to predictably provide implant rehabilitation to patients with an edentulous maxilla. While some strategies may present as intuitively appealing methods for enhancing primary stability, outcomes as published in the literature make their actual value less clear. Increased implant length would seem to offer an opportunity to further augment primary implant stability. Ibanez and coworkers, however, in describing outcomes when immediately loading implants in both the edentulous maxilla and mandible, reported no failures with short implants (≤ 10 mm).21 In the current study, 74 of the 300 implants placed were ≤ 11 mm, with only four of these shorter implants experiencing integration failures. Perhaps other factors limit the impact of implant length on outcomes. Similarly, bone type as defined using currently accepted indices of quantity and quality25 may not be as clearly linked to successful integration outcomes as previously thought. It might be anticipated that poor quantity and quality bone should be viewed as providing an inadequate bed for establishing primary implant stability. Good integration outcomes in the edentulous maxilla have been reported, however, for implants placed in types C and D bone quantity20,22 as well as in types 3 and 4 bone quality.20–22 In the current study, all implants were placed in atrophic maxillae with types C and D bone quantity and types 3 and 4 bone quality. The high rate of integration experienced here seems to suggest that as long as there is sufficient bone to encase the implants of the dimensions proposed for use, then bone quality and quantity may play a lesser role in outcomes than other factors in the edentulous maxilla. Questions remain regarding the number of implants needed to achieve predictable outcomes in the edentulous maxilla. Recommended numbers range from six to 10 implants per subject.19–22 In the current study, six implants were used for each subject,

resulting in good outcomes. Of note, Malo and coworkers reported good outcomes for a protocol that included the use of four implants in the edentulous maxilla followed by immediate provisional restoration. 23 Such outcomes provide strong evidence for the efficacy of immediate provisional restoration while showing promise for a new approach that would have important implications for routine clinical practice, where patient acceptance of treatment is frequently a matter of cost. Perhaps cross-arch stabilization creates a group primary implant stability that supersedes the value of individual implant stability in enhancing outcomes. A study design that prospectively introduces suboptimal implant primary stability combined with cross-arch stabilization may prove to be a fruitful path of inquiry for future research to assess the relative merits of individual implant stability. In a related side note, it has been suggested that immediate loading of implants in the edentulous maxilla might provide a positive stimulatory effect on osseous tissues and enhance osseointegration outcomes.22 Finally, the impact of the forces of occlusion generated by an opposing dentition on implant rehabilitation outcomes for the atrophic edentulous maxilla remains to be clarified. Questions linger regarding the impact of the forces generated by a fully dentate mandible when compared to that seen with a partially edentulous mandible with or without a removable partial denture restoration. Because the status of the mandibular dentition has been recorded in the present ongoing study, this issue might be clarified as more outcome data are acquired over the planned 5-year follow-up interval. The outcomes described for the current study have been drawn from an ongoing long-term clinical trial with an investigational plan that includes 5-year subject follow-up. All 47 subjects are scheduled to remain under annual observation over this 5-year interval, with the intent to continue reporting on outcomes over time and so further contribute to the body of knowledge currently available with regard to immediate loading of implants in the edentulous maxilla.

CONCLUSION The outcomes from this ongoing study reported at the 1-year follow-up interval suggest that predictable implant integration outcomes can be achieved when implant placement is combined with immediate fixed provisional restoration in the atrophic edentulous maxilla. These outcomes are comparable to those reported elsewhere. Stable marginal bone levels were

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maintained. The use of such an implant rehabilitation strategy may offer a valuable alternative to patients who wish treatment to be provided more rapidly and comfortably when compared to protocols that do not include immediate fixed provisional restoration.

13.

ACKNOWLEDGMENTS

15.

The authors wish to acknowledge Mr Sten Berglind of Silverline Dental Laboratories and Mr Bruce Wallace of University of Chicago Dental Laboratories for their dedicated efforts to help make this study a success. This research is supported by a grant from Astra Tech.

16.

14.

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