Zeev Ormianer, DMD,1 Ady Palty, DMD,2 Arie Shifman, DMD3

1Private practice, 143 Bialik St., Ramat-Gan, Israel 52523

2Clinical Professor, College Of Dentistry, David B. Kriser Dental Center, New York University

3Senior Clinical Lecturer, Department of Prosthdontics, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel-Aviv University, Israel

Running Head: Survival

Corresponding Author:

Zeev Ormianer, DMD

143 Bialik St.

Ramat-Gan

Israel 52523

Phone: +972-3-6124224

Fax: +972-3-6124336

e-mail: drzeev@ormianer.com

web : http://www.ormianer.com/

SURVIVAL OF IMMEDIATELY LOADED DENTAL IMPLANTS IN DEFICIENT ALVEOLAR BONE SITES AUGMENTED WITH ß-TRICALCIUM PHOSPHATE

ABSTRACT

Purpose: Dental implant placement in atrophic alveolar ridges often necessitates grafting procedures, followed by immediate or delayed implant placement. This study assessed the survival of immediately loaded dental implants placed in deficient alveolar bone sites at the time of bone grafting.

Materials and Methods: From 1999 to May 2002, one operator (AP) inserted 1065 implants (607 in mandibles, 458 in maxillae) into 338 partially edentulous patients. Most implants were placed into compromised residual ridges or prepared tooth extraction sockets. Implants placed in augmented areas were splinted to implants in non-augmented sites for stability. In all cases, ß-tricalcium phosphate was mixed with blood from the surgical site to augment the ridge level or to fill spaces between the implant and the socket wall. When indicated, the same materials were used for sinus floor augmentation. All implants were tapered screws with roughened surfaces, primarily (75%) from one manufacturer. A total of 189 implants placed in 35 patients were prosthetically restored by one of the authors (ZO). In this group of patients, complete restorative data were available. All implants were monitored 12-48 months (mean = 19.2 months; median = 24 months).

Results: A total of 1039 implants survived and 26 implants failed (anterior mandible = 5 failures, maxillae = 21 failures). In the restorative group, 186 implants survived and 3 maxillary implants failed. All implant failures in this study occurred in augmented sites.

Conclusion: Within the limitations of this study, immediate loading of splinted implants in augmented sites is a predictable procedure.

KEY WORDS: immediate loading, augmentation, ß-tricalcium phosphate, implants

INTRODUCTION

The Branemark protocol has often been considered fundamental for the success of root- form dental implants.1 This protocol required that implants be made of a biocompatible material (commercially pure titanium) and that the surgical procedure be strictly sterile and atraumatic to avoid bone overheating. It also entailed that implants should be given a stress-free healing period by submerging them beneath the soft tissue for up to 6 months, followed by a second surgical procedure to expose the implants and attach a transmucosal extension component.1 The Branemark rationale for the extended healing period to achieve osseointegration was based on empirical observations during clinical trials in which the highest implant success rates were achieved by delaying prosthetic loading from 3 months in patients with atrophic mandibles.1

Various attempts at immediate implant loading have been made over the years in response to patients’ desires to shorten treatment time. The first protocol for the immediate loading of osseointegrated implants involved the placement of 3 to 4 implants in the anterior mandible to support an overdenture.2-5 Survival rates ranged from 91.2% to 98.1% with an average follow-up time of 18 months.2-5 A later protocol involved the placement of 6 to 10 implants evenly distributed in the mandible. Each alternate implant was used to immediately support a screw-retained provisional prosthesis, and the remaining implants were allowed a traditional submerged healing protocol.6-8 The underlying rationale was that the submerged implants could be used to support the definitive prosthesis in the event that any of the immediately loaded implants failed. Survival rates ranged from 80% to 85.7% for 10 years of follow-up.6-8 Utilizing a similar protocol, Salama9 and Tarnow10 reported an average 5- year survival rate of 97.1% to 100% for dental implants evenly placed in maxillae. Other attempts at the immediate loading of single-tooth implants in fresh extraction sites reported survival rates of 82.4% to100% after 12 months of clinical monitoring.11-13

The aim of this study was to evaluate the survival rates of dental implants immediately placed and loaded in augmented bone.

MATERIALS AND METHODS

Patients

Study candidates were selected from the general patient pools of the second author's (AP) private practices in Karlesruhaa, Germany and Tel-Aviv, Israel, and consisted of patients who needed dental implants in compromised bone sites. The exclusion criteria for the study group were confounding medical conditions, such as recent myocardial event, heavy smokers of more than 20 cigarettes daily and uncontrolled diabetes mellitus. Patients exhibiting temporomandibular disorders, severe dental wear or heavy bruxism were also excluded. A total of 338 partially edentulous patients (170 females 168 males) were enrolled in the study after providing written informed consent signed by each patient .

Surgical procedure

From 1999 to May 2002, one operator (AP) inserted 1065 immediate implants in 338 patients (Fig.1). Most implants were placed into compromised residual ridges and some implants were placed into carefully prepared tooth extraction sockets. Primary closure with keratinized gingival tissues surrounding the non-submerged implants was achieved by various surgical periodontal procedures, such as punch holes and rotational pedicle flaps. No barrier membranes were used.

In 311 patients, at least one implant site was treated with bone augmentation procedures to raise the ridge level or to fill spaces between the implant and the socket wall. Subantral augmentation procedures were performed in the remaining 27 patients (Fig.2). The augmentation material used for all cases consisted of ß-tricalcium phosphate (Cerasorb®, Curasan AG, Kleinostheim Germany) mixed with blood from the surgical site.

Implants

Of the 1065 implants placed, 605 (57%) were placed in mandibles and 458 (43%) were placed in maxillae. All implants featured roughened surfaces from two manufacturers (75%, n = 799, Centerpulse Dental Inc., Carlsbad CA; 25%, n = 266, Dentsply Friadent, Lakewood, CO).



Follow-up protocol

During the first year, each patient was recalled every 3 months for clinical monitoring. The restoration was removed and the stability of each implant was evaluated by applying manual percussion and torque with hand instruments. Panoramic radiographs were made and compared every 12 months to assess alveolar bone levels relative to the implant/abutment connection. Implants with any degree of mobility and/or those that elicited pain during manual testing were considered failures and removed. All implants were monitored from 12 to 48 months (mean = 19.2 months; median = 24 months) (Fig. 3).

Prosthetic Treatment



After the surgical phase was completed, all patients were returned to their referring dentists for prosthetic treatment. A total of 35 patients with 189 implants were rehabilitated by one of the authors (ZO). In this group of patients, complete restorative data was available (group A). The remaining 303 patients were referred to 14 dentists who did not compile complete restorative data (group B).

RESULTS

The distribution of implant types placed was similar for both groups A (Fig. 4) and B. Each patient had at least 1 implant placed in augmented bone, and all implants placed in residual bone were splinted to implants in augmented bone.

Of the 189 implants comprising group A, 116 implants were placed in maxillae (augmented bone = 88 implants; residual bone = 28 implants) and 73 implants were placed in mandibles (augmented bone = 42 implants; residual bone = 31 implants) (Fig. 5). A total of 164 implants (mandibles = 65 implants; maxillae = 99 implants) were immediately loaded using a progressive loading protocol14 with a provisional acrylic-resin restoration (Fig. 6). The time from implant insertion to delivery of the final restoration ranged from 2.8 to 6.7 months (mean = 4.8 months) (Fig. 7). In mandibles, 9 restorations were fixed and 7 were removable, whereas 22 restorations were fixed and 1 was removable in maxillae (Fig. 8). Abutments for cemented (fixed) copings were connected to the implants and splinted with porcelain-fused-to-metal restorations. Whenever feasible, maximal intercuspation was formed and group function pattern was made for lateral mandibular excursions. In opposing jaws, 11 (31.4%) patients had implant-supported restorations and 22 (62.35%) patients were dentate (Fig. 9).

After up to 4 years of clinical follow-up, 1039 (97%) implants survived and 26 (2.4%) implants failed in groups A and B combined (Fig. 10). In group A, 186 implants survived and only 3 failed, all in the maxilla (Fig.11). Radiographically, no marginal bone loss beyond the first thread was detected around the cervical parts of the surviving implants. In group B, there were 23 failures (mandibles = 5 implants; maxillae = 18 implants). All implant failures occurred in augmented sites.

DISCUSSION

One of the main objectives in the immediate loading of dental implants is to achieve primary implant stabilization during the surgical phase. In the present study, all implants achieved primary stabilization at the time of placement, regardless of the amount of alveolar bone. Additional supporting bone for the implants was attained by augmentation with a pure-phase ?-tricalcium phosphate material, a material designed to resorbed simultaneously with the formation of new bone. Remodelling of the new bone is reportedly not precluded by changes in physical stress patterns caused by immediate loading.15 Filling bone defects with ß-tricalcium phosphate and immediate loading was performed in the present study with the goal of improving implant survival.

The cumulative survival rate for immediately loaded implants was 97% (1039 implants). In group A, 98.4% of the implants survived and only 3 maxillary implants failed. In group B, implant survival was 97%, with a 23 failures occurring in the anterior mandible (n = 5 implants) and maxillae (n = 18 implants). The number of cumulative implant failures for groups A and B was 26 (2.4%), with 21 maxillary implant failures (group A = 3 implants, group B = 18 implants) and 5 mandibular implant failures (group B). Failed implants were associated with augmented sites, abutments for fixed restorations and opposing natural teeth (Fig.11).

Other studies of immediately loaded implants have shown survival rates of 97% to 100%.8-13 Although bone augmentation was used in the present study, a similar high success rate was found. Higher failure rates have been previously reported for implants placed in the maxilla compared to the mandible and for implant-supported fixed cantilever prostheses opposing natural teeth.16 In the present study, the higher failure rate of non-cantilevered, implant-supported restorations occluding natural teeth was an unexpected finding, since natural teeth have been reported to better control occlusal forces through neurophysiological feedback mechanisms compared to implant-supported occlusion in the opposing arches.17 More studies are needed to elucidate this phenomenon.

Premature loading was previously considered a leading cause of dental implant failure.1 In this study, as well as many others,2-13 a higher implant success rates were gained, despite the immediate loading of the implants. It has been previously theorized that early loading of implants may induce implant micromovements of more than 150 µm, which may cause destruction on the regenerating bony matrix and result in formation of fibrous connective tissue around the implants.18-19 It is conceivable that, in the present study, micromotion of immediately-loaded implants was controlled by splinting of the abutments.

The main strength of this study is the large group of patients treated by the same surgeon (AP) utilizing the same surgical protocols in two different centers. In addition, a controlled prosthodontic treatment and 4-year clinical follow-up protocol was used by one prosthodontist in one center (group A). Implant failures could attributed to prosthodontic parameters, such as the condition of the opposing arch.

The limitation of this study, however, is uneven number of patients in group A (n = 35) in comparison to group B (n = 338). Patients in group B were treated by more than 10 dentists utilizing a variety of implant designs from two manufacturers (Fig 5).

CONCLUSIONS

Within the limitations of this study, immediate loading of splinted implants in augmented sites is a predictable procedure.



REFERENCES

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9.Salama H, R