Retrospective multicenter analysis of 3i endosseous dental implants placed over a five-year period

Immediate Occlusal Loading of Double Acid-Etched Surface Titanium Implants in 41 Consecutive Full-Arch Cases in the Mandible and Maxilla: 6- to 74-Month Results

BACKGROUND

The high success rate of dental implants has changed the quality of life for many patients. Immediate loading finds its application in some clinical cases and certainly adds another modality of treatment for the implant patient. Starting with a few implants immediately loaded with a bar overdenture in the mandible, the concept of immediate loading evolved to loading multiple implants in both the maxilla and mandible.

METHODS

In this investigation, 41 consecutive patients who needed full-arch restorations were treated with 343 double acid-etched surface implants between May 1998 and March 2004. The sample included smokers and bruxers. Twenty-three mandibular and 26 maxillary cases were treated, loading the implants within 48 hours, by using resin provisional prostheses, metal-reinforced provisional prostheses, or definitive prostheses (metal-acrylic or metal-ceramic). All implants were followed for 12 to 74 months. Follow-up consisted of clinical as well as radiographic examination. Furthermore, resonance frequency analysis was done in most of the implants during the last 2 years.

RESULTS

The success rate obtained was 99.42% (only two mandibular implants that are still surviving were considered failures). The bone level was measured every year. The average radiographic bone level change was 0.56 mm at 12, 0.76 mm at 24, 0.84 mm at 36, 0.82 mm at 48, 0.83 mm at 60, and 0.94 mm at 72 months.

CONCLUSION

A high success rate can be achieved when double acid-etched surface implants are immediately loaded with fixed full-arch restorations in the maxilla and mandible.

Peri-implant osteogenesis in health and osteoporosis

Long-term clinical success of endosseous dental implants is critically related to a wide bone-to-implant direct contact. This condition is called osseointegration and is achieved ensuring a mechanical primary stability to the implant immediately after implantation. Both primary stability and osseointegration are favoured by micro-rough implant surfaces which are obtained by different techniques from titanium implants or coating the titanium with different materials. Host bone drilled cavity is comparable to a common bone wound. In the early bone response to the implant, the first tissue which comes into contact with the implant surface is the blood clot, with particular attention to platelets and fibrin. Peri-implant tissue healing starts with an inflammatory response as the implant is inserted in the bone cavity, but an early afibrillar calcified layer comparable to the lamina limitans or incremental lines in bone is just observable at the implant surface both in vitro than in vivo conditions. Just within the first day from implantation, mesenchymal cells, pre-osteoblasts and osteoblasts adhere to the implant surface covered by the afibrillar calcified layer to produce collagen fibrils of osteoid tissue. Within few days from implantation a woven bone and then a reparative trabecular bone with bone trabeculae delimiting large marrow spaces rich in blood vessels and mesenchymal cells are present at the gap between the implant and the host bone. The peri-implant osteogenesis can proceed from the host bone to the implant surface (distant osteogenesis) and from the implant surface to the host bone (contact osteogenesis) in the so called de novo bone formation. This early bone response to the implant gradually develops into a biological fixation of the device and consists in an early deposition of a newly formed reparative bone just in direct contact with the implant surface. Nowadays, senile and post-menopausal osteoporosis are extremely diffuse in the population and have important consequences on the clinical success of endosseous dental implants. In particular the systemic methabolic and site morphological conditions are not favorable to primary stability, biological fixation and final osseointegration. An early good biological fixation may allow the shortening of time before loading the implant, favouring the clinical procedure of early or immediate implant loading. Trabecular bone in implant biological fixation is gradually substituted by a mature lamellar bone which characterizes the implant ossoeintegration. As a final consideration, the mature lamellar bone observed in osseointegrated implants is not always the same as a biological turnover occurs in the peri-implant bone up to 1mm from the implant surface, with both osteogenesis and bone reabsorption processes.

A 5-year prospective study on small diameter screw-shaped oral implants

Alveloar ridges of limited dimensions could preclude the placement of dental implants of the regular dimension. Smaller diameter implants - narrow platform (NP) implants were commercially available to address this issue. The aim of the study was to determine the 5-year clinical performance of 3.3 mm diameter NP implants. Twenty-three machined screw-shaped NP implants were placed in nine patients (six males; three females) between 18 and 70 years of age. Clinical and radiographic examinations were performed annually for 5 years. Recognized implant success criteria was used. The criteria were based on the mean marginal alveolar bone loss, the placement of prosthesis of satisfactory appearance, and the absence of implant mobility, peri-implant radiolucency, pain, discomfort or infection. One implant failed at abutment connection. The remaining 22 implants were restored and functioned successfully according to the criteria. The mean marginal alveolar bone loss during the first year was 0.41 +/- 0.17 mm. The mean marginal alveolar bone loss between the second and fifth year was 0.03 +/- 0.06 mm. The success rate of NP implants according to a well-established set of criteria was 96%.

Osseointegrated Dental Implants in Private Practice: A Long-Term Case Series Study

BACKGROUND

Osseointegrated dental implants have become a routinely recommended procedure in the clinical practice of dentistry and periodontics. Due to their predictability, they have changed the way many cases are treatment planned. The purpose of this paper is to report the results of a prospective study of factors affecting the successes and failures of a large group of dental implants and compare them to published literature.

METHODS

A total of 1,003 consecutively placed pure titanium dental implants placed from August 1987 to January 2002 and followed to October 2003 are reported. All implants were placed in one private practice by the same surgeon.

RESULTS

Success rates statistically were influenced only by the age of the implant, although when the raw data are examined, some trends are seen. Success was unaffected by patient age, gender, surface roughness of implant, site of placement, smoking, bone type, arch, screw versus press-fit, diameter, length, manufacturer, reason for tooth loss, site bony augmentation and timing, placement timing, one-versus two-stage placement, or torque testing of implants; 75% of failures occurred before restoration.

CONCLUSIONS

Osseointegrated dental implants are a highly predictable procedure with proper case selection. Failure rates vary for a number of factors reviewed, although only the age of the implant was statistically important in predicting failure. Male smokers, maxillary first molars, and type 4 bone had increased failure rates. Threaded, surface-roughened implants had the highest success rates.

Loaded custom-made zirconia and titanium implants show similar osseointegration: an animal experiment

BACKGROUND

Zirconia might be an alternative material to titanium for dental implant fabrication. The aim of the present study was to investigate the histological behavior (osseointegration) of loaded zirconia implants in an animal model and to compare it with the behavior of titanium implants.

METHODS

Five months after extraction of the upper anterior teeth, 12 custom-made titanium implants (control group) and 12 custom-made zirconia implants (test group) were inserted in the extraction sites in six monkeys. Before insertion, the titanium implant surfaces were sandblasted with Al2O3 and subsequently acid-etched. The zirconia implants were only sandblasted. Six months following implant insertion, impressions were taken for the fabrication of single crowns. A further 3 months later, nonprecious metal crowns were inserted. Five months after insertion of the crowns, the implants with the surrounding hard and soft tissues were harvested, histologically prepared, and evaluated under the light microscope regarding the peri-implant soft tissue dimensions and mineralized bone-to-implant contact.

RESULTS

No implant was lost during the investigational period. The mean height of the soft peri-implant tissue cuff was 5 mm around the titanium implants and 4.5 mm around the zirconia implants. No statistically significant differences were found in the extent of the different soft tissue compartments. The mean mineralized bone-to-implant contact after 9 months of healing and 5 months of loading amounted to 72.9% (SD: 14%) for the titanium implants and to 67.4% (SD: 17%) for the zirconia implants. There was no statistically significant difference between the different implant materials.

CONCLUSION

Within the limits of this animal experiment, it can be concluded that the custom-made zirconia implants osseointegrated to the same extent as custom-made titanium control implants and show the same peri-implant soft tissue dimensions.

Predicting osseointegration by means of implant primary stability

The purpose of the present clinical study was (1) to evaluate the Osstell as a diagnostic tool capable of differentiating between stable and mobile ITI implants, (2) to evaluate a cut-off threshold implant stability quotient (ISQ) value obtained at implant placement (ISQitv) that might be predictive of osseointegration, (3) to compare the predictive ISQitv of immediately loaded (IL) implants and implants loaded after 3 months (DL). Two patient groups were enrolled, 18 patients received 63 IL implants and 18 patients were treated with 43 DL implants. The ISQ was recorded at implant placement, after 1, 2, 4, 6, 8, 10 and 12 weeks. All implants passed the 1-year loading control. Two implants failed, one DL implant with ISQ at placement (ISQi) of 48 and one IL implant with ISQi of 53. The resonance-frequency analysis (RFA) method was not a reliable diagnostic tool to identify mobile implants. However, implant stability could be reliably determined for implants displaying an ISQ> or =47. After 1 year of loading, all DL implants with an ISQi> or =49 and all IL implants with an ISQi> or =54 achieved and maintained osseointegration. By the end of 3 months, implants with ISQi<60 had an increase of stability. Implants with ISQi 60-69 had their stability decrease during 8 weeks before returning to their initial values. Implants with ISQ>69 had their stability decrease during the first 4 weeks before remaining stable. Although preliminary, these data might orient the practitioner to choose among various loading protocols and to selectively monitor implants during the healing phase.

Immunohistochemical analysis of soft tissues in implants with healthy and peri-implantitis condition, and aggressive periodontitis

Today, implant-supported prostheses are widely accepted as a reliable treatment modality, but failures in longitudinal studies have been shown. In some cases, peri-implantitis with a progressive periodontal bone loss takes place, and mechanical or load factors and biological or plaque-induced lesions have been claimed as main etiologic factors. We compared five cases of peri-implantitis, with five cases of healthy peri-implant tissues and five cases of aggressive periodontitis in order to give new findings on the osseointegration loss process. Biopsy specimens from the peri-implant tissues including oral (O), sulcular, and junctional epithelium and the underlying and supracrestal connective tissue, were taken in all cases for histological and immunohistochemical analysis. T lymphocytes were the most prominent cell in the peri-implantitis (PG) and aggressive periodontitis (AG) groups, but not in the peri-implant healthy group (HG). CD1a-positive cells (Langerhans and immature dendritic cells) were observed more frequently in the O than in the sulcular-junctional (S-J) epithelium: they were located in the basal and parabasal layers, without any differences between the three groups. Vascular proliferation analysed by immunoreactivity for CD34, Factor VIII, and vascular endothelial growth factor was more prominent in the PG comparing with HG and AG in the S-J area. Apoptosis, analysed by bcl2 and p53 immunoreactivity, was similar in the three groups. In conclusion, we suggest that the osseointegration loss process is due to an inflammatory process similar to that observed in aggressive periodontitis according to the number of T lymphocytes, but not to the vascular proliferation.

Implant stability measurement of delayed and immediately loaded implants during healing.. A clinical resonance-frequency analysis study with sandblasted-and-etched ITI implants

The purpose of the present study was (1) to measure the primary stability of ITI implants placed in both jaws and determine the factors that affect the implant stability quotient (ISQ) determined by the resonance frequency method and (2) to monitor implant stability during the first 3 months of healing and evaluate any difference between immediately loaded (IL) implants and standard delayed loaded (DL) implants. The IL and DL groups consisted of 18 patients/63 implants and 18 patients/43 implants. IL implants were loaded after 2 days; DL implants were left to heal according to the one-stage procedure. The ISQ was recorded with an Osstell apparatus (Integration Diagnostics AB, Gothenburg, Sweden) at implant placement, after 1, 2, 4, 6, 8, 10 and 12 weeks. Primary stability was affected by the jaw and the bone type. The ISQ was higher in the mandible (59.8+/-6.7) than the maxilla (55.0+/-6.8). The ISQ was significantly higher in type I bone (62.8+/-7.2) than in type III bone (56.0+/-7.8). The implant position, implant length, implant diameter and implant deepening (esthetic plus implants) did not affect primary stability. After 3 months, the gain in stability was higher in the mandible than in the maxilla. The influence of bone type was leveled off and bone quality did not affect implant stability. The resonance-frequency analysis method did not reveal any difference in implant stability between the IL and DL implants over the healing period. Implant stability remained constant or increased slightly during the first 4-6 weeks and then increased more markedly. One DL and IL implant failed; both were 8 mm long placed in type III bone. At the 1-year control, the survival rate of the IL and the DL implants was 98.4% and 97.7%, respectively. This study showed no difference in implant stability between the IL and DL procedures over the first 3 months. IL short-span bridges placed in the posterior region and full arch rehabilitation of the maxilla with ITI sandblasted-and-etched implants were highly predictable.

Screw Loosening for Standard and Wide Diameter Implants in Partially Edentulous Cases: 3- to 7-Year Longitudinal Data

Screw loosening is considered to be a common problem with both screw-retained and cemented implant restorations. A wider abutment platform, as well as using a torque driver to tighten specifically designed screws may help prevent this loosening. However, there has been no clinical study evaluating either of these. To longitudinally compare the frequency of screw loosening in standard diameter, (3.75 and 4.0 mm) implant supported prostheses to that of wide diameter, (5.0 and 6.0 mm) implant supported prostheses that were hand tightened, and to evaluate whether using a torque driver would minimize or prevent this problem, if screw loosening occurred. A total of 213 dental implants in 106 patients were included in this prospective longitudinal study. Of the implants 68 were wide diameter and 145 were standard diameter implants. Wide diameter implants showed 5.8% screw loosening, while standard diameter implants showed 14.5% screw loosening after insertion with only hand torquing. When these loose screws were tightened with a torque driver, there was no more loosening of screws. Within the limitations of this study, the wide diameter implants tested showed less screw loosening than the standard diameter implants when hand torqued. Additionally, within the scope of our study, using a torque driver to tighten the screws with the recommended force prevented this loosening from reoccurring in all cases.

Biological properties of acid etched titanium implants: effect of sandblasting on bone anchorage

The SLA (sandblasted with large grit and acid etched) surface is a textured surface that has been documented to lead to a rapid and strong implant fixation. The purpose of the present study was to determine the contribution of sandblasting in addition to etching to implant anchorage. It was also aimed to determine if the pits carved during etching alone have a bone-interlocking capacity that leads to microanchorage between the implant and bone. SLA implants and machined-and-acid-etched (MA) implants were placed in the maxilla of Land Race pigs. After 10 weeks of healing, they were reverse torqued. The reverse torque of the SLA and MA implants was 157.29 +/- 38.04 N cm and 105.33 +/- 25.12 N cm, respectively. Sandblasting increased bone anchorage by 49.3%; the difference was statistically significant (p =.028). Bone was found attached to both surfaces; bone ingrowth was found in the pits of both surfaces. It is suggested that the two surfaces are able to generate bone interlocking and mechanical coupling at the interface. When finite-element modeling is performed with these surfaces, it is suggested that the bound mode be used instead of the slip mode.

A 7-year life table analysis from a prospective study on ITI implants with special emphasis on the use of short implants

This paper reports on a 7-year life table analysis on ITI titanium plasma-sprayed (TPS) and sandblasted and etched (SLA) implants placed in a private practice and loaded for at least 1 year. In 236 patients, 528 (264 TPS and 264 SLA) implants were placed, 351 (66.5%) implants rehabilitated the posterior region and 71.1% implants were < or =11 mm. In the posterior mandible and maxilla, the mean implant length was 9.90 and 9.74 mm respectively. Implant length was determined through standard radiographs only. Increase of the number of implants or reduction of the width or length of the rehabilitations was no specifically sought for the shorter implants. One hundred and twenty-two SLA implants were loaded within 63 days. All early loaded SLA implants resisted the applied 35 N cm without rotation or pain. Three implants failed, one early and two late failures, all were SLA implants placed in the mandible. Shorter implants did not fail more than longer ones. The cumulative success rate was 99.40%. The predictable use of short implants supporting single crowns and small fixed partial dentures of 2-4 units supported by two to three implants permitted (1) restricting the need for sophisticated and expensive presurgical procedures aimed to determine precisely the available bone height by computerized radiographic methods, (2) the placement of prosthetically driven restoration instead os surgically driven ones, (3) reducing the indications span for complex invasive procedures like sinus lift and bon grafting procedures, (4) facilitating the surgery, without attempting to place the longest implant and (5) avoiding the occurrence of sensation disturbance. The safe use of short implants in a private practice should make implant therapy simpler and accessible to a higher number of patients and practitioners.

Reimplantation and Immediate Loading of an Accidentally Avulsed Beaded Implant: Case Report

We present a case of reimplantation of an accidentally avulsed beaded Endopore (Innova Corp., Toronto, Canada) implant. The technique of immediate splinting and pharmacotherapy is described together with the clinical and radiologic evaluation for reosseointegration. This single case of reimplantation with immediate functional loading would suggest that, contrary to the manufacturer's recommendation, the Endopore implants can be successfully loaded immediately, functionally or nonfunctionally.

Success and Failure Rates of 9 mm or Shorter Implants in the Replacement of Missing Maxillary Molars When Restored with Individual Crowns: Preliminary Results 0 to 84 Months in Function. A Retrospective Study

BACKGROUND

The ability to utilize shorter implants in the reconstruction of the posterior maxilla would, theoretically, simplify therapy by lessening the need for augmentation surgery. The purpose of this retrospective study was to assess the success and failure rates of < or = 9 mm or shorter implants in the maxillary posterior regions restored with individual crowns.

METHODS

A total of 979 implants were placed in maxillary molar positions and restored with individual crowns. The implants were followed in function for up to 84 months. The results are discussed in terms of clinical applicability and indications for use.

RESULTS

The cumulative success rates in function were 94.5% for implants in the maxillary first molar positions and 98.7% for implants in the maxillary second molar positions, yielding an overall cumulative success rate of 95.1%, in function for up to 84 months.

CONCLUSION

These findings suggest that non-countersunk implants of 7 to 9 mm in length may be successfully restored with single crowns in the maxillary molar region.

Etched implants: A comparative surface analysis of four implant systems

Surface texturing by acid etching has recently become popular among dental implant manufacturers. The aim of this study was to compare the surface topography of four implant systems and to check the reproducibility of the industrial process of each implant system. Three implants per system have been selected from three distinct batches. They were observed under a scanning electron microscope (SEM), and roughness was determined with a contact profilometer by measuring five height-descriptive parameters (Ra, Rq, Rz(ISO), Rt, and Rsk, a texture parameter Sm, and a hybrid parameter RDeltaq. The analysis showed that each implant system displayed a distinct surface topography that could not be mistaken. When sandblasting was performed prior to etching, surface topography was a combination of macro- and microroughness. The roughness and the amount of remaining sand varied among the batches, showing that the industrial process is not fully developed. Deviation from the released technical information was found for two out of four implant manufacturers. Based on the available biological and clinical data on textured surfaces, it is suggested that it is bone interlocking at the interface that maintains the biological properties of textured surfaces, rather than a strong implant fixation per se.

The anchorage of Brånemark and ITI implants of different lengths. I. An experimental study in the canine mandible

The anchorage of machined Brånemark and ITI TPS-coated implants of various lengths was investigated in an animal model. Brånemark fixtures 7 and 10 mm long and ITI implants 6 and 10 mm long were inserted in the mandible of dogs and were reverse-torqued after 3 months of healing. The failing mode was different for the two implant systems. For the ITI implants, loosening coincided with the peak reverse-torque values. For the Brånemark fixtures, two reverse-torque values were identified and recorded, a 'start to rotate' and a peak value. The 'start to rotate' values for the 7 and 10 mm Brånemark fixtures were 36.67 and 38.57 Ncm, respectively, the peak values were 61.88 and 69.13 Ncm. The increase in implant length from 7 to 10 mm did not significantly improve the anchorage. The mean reverse-torque values for the 6- and 10-mm ITI implants were 104.66 and 192.25 Ncm, respectively; the difference was statistically significant. The mean removal torque of the 6-mm ITI implant was higher than the 7- and 10-mm Brånemark implants. It is suggested that the distinct anchorage magnitude and the distinct loosening patterns registered for both implant systems might be related to the various surface states. The latter might account for the different failure tendencies mentioned in the literature for short Brånemark and ITI implants.

Histological evaluation of the Serf EVL evolution implant: a pilot study in a dog model

PURPOSE

The purpose of this study was to compare bone-to-implant contact (BIC) of the one-stage sandblasted surface EVL implant (SERF, Decines, France) with that of the two-stage turned (machined) Branemark Nobel BioCare implant in a dog model system.

MATERIALS AND METHODS

Three 1-year old female beagle dogs (canine) were acquired, examined, and quarantined. In dog no. 1, three test implants were placed on one side of the jaw, and four control implants were placed on the other side. In dog no. 2, two test implants were placed in alternation with two control implants on the left and right sides (total 4 tests, 4 controls). In dog no. 3, three test implants were placed on one side and three control implants on the other. After a 3-month period of healing, the dogs were killed and the jaws sectioned for histological preparation. Eleven implants, six tests, and five controls were available for histological evaluation.

RESULTS

The percent of BIC for the test implants varied from 24.9% to 61.6%, with an average of 42.7%. The percent of BIC for the control implants varied from 22.1% to 42.6%, with an average of 27.4%.

CONCLUSION

The degree of BIC of the EVL implants was on average greater than that of the turned surface of the Branemark implant. However, because of the limited number of implants placed in this pilot study, the results should be interpreted with caution.

Clinical complications with implants and implant prostheses

The purpose of this article is to identify the types of complications that have been reported in conjunction with endosseous root form implants and associated implant prostheses. A Medline and an extensive hand search were performed on English-language publications beginning in 1981. The searches focused on publications that contained clinical data regarding success/failure/complications. The complications were divided into the following 6 categories: surgical, implant loss, bone loss, peri-implant soft tissue, mechanical, and esthetic/phonetic. The raw data were combined from multiple studies and means calculated to identify trends noted in the incidences of complications. The most common implant complications (those with a greater than a 15% incidence) were loosening of the overdenture retentive mechanism (33%), implant loss in irradiated maxillae (25%), hemorrhage-related complications (24%), resin veneer fracture with fixed partial dentures (22%), implant loss with maxillary overdentures (21%), overdentures needing to be relined (19%), implant loss in type IV bone (16%), and overdenture clip/attachment fracture (16%). It was not possible to calculate an overall complications incidence for implant prostheses because there were not multiple clinical studies that simultaneously evaluated all or most of the categories of complications. Although the implant data had to be obtained from different studies, they do indicate a trend toward a greater incidence of complications with implant prostheses than single crowns, fixed partial dentures, all-ceramic crowns, resin-bonded prostheses, and posts and cores.

Immediate loading of osseotite implants: two-year results

The high success rate of dental implants has changed the quality of life for many patients. Immediate loading finds its application in some clinical cases and certainly adds another modality of treatment for the implant patient. Starting with a couple of implants placed in the mandible and immediately loaded within 72 hours after surgical placement with an overdenture, this concept evolved to immediately loading multiple implants in both the maxilla and the mandible. In this investigation, 11 consecutive patients were treated with 87 screw-shaped endosteal acid-etched, Osseotite implants (3i, Implant Innovations, Inc., Palm Beach Gardens, FL) between June 1998 and June 1999. Two mandibular and two maxillary cases received screw-retained provisional prostheses the day of surgery. Three mandibular and four maxillary cases were loaded 48 hours after surgery with the final screw-retained, porcelain-fused-to-metal prostheses. All implants were followed for 2 to 3 years. Follow-up consisted of clinical as well as radiographic examination. All implants were successful. There was no implant mobility or periimplant radiolucency. The bone level was measured at the 12th and 24th months. The average radiographic bone level from the implant platform to the first bone-to-implant contact was 0.654 mm at the 12th month and 0.946 mm at the 24th month. We conclude that a high success rate can be achieved when implants with a hybrid surface, machined/acid-etched, are immediately loaded within 48 hours after surgical placement in the maxilla and the mandible.

Risk factors for dental implant failure: a strategy for the analysis of clustered failure-time observations

This study's objective was to identify, in a statistically valid and efficient manner, the risk factors associated with dental implant failure. We hypothesize that factors exist which can be modified by clinicians to enhance outcome. A retrospective cohort study design was used. Cohort members had >or= one implant placed. Risk factors were classified as demographic, health status, implant-, anatomic-, or prosthetic-specific, and reconstructive variables. The outcome variable was implant failure. The cohort was composed of 677 patients who had 2349 implants placed. Based on the adjusted multivariate model, factors associated with implant failure were tobacco use, implant length, staging, well size, and immediate implants (p <or= 0.05). In the setting of correlated survival observations, we recommend adjusting for the correlation of the observations to provide statistically valid and efficient results. Three of the identified factors--tobacco use, immediate implants, and implant staging--potentially may be modified to enhance implant survival.

Ovariectomy hinders the early stage of bone-implant integration: histomorphometric, biomechanical, and molecular analyses

Postmenopausal osteoporosis is a contributing factor to alveolar bone atrophy associated with tooth loss in the elderly. The use of dental titanium implants has been increasingly adapted to treat these edentulous patients. This study examines whether female gonadal hormone deficiency interferes with the critical integration process between bone and implants. Two types of experimental titanium implants with acid-treated surfaces were placed in the femurs of ovariectomized (ovx) and sham-operated control rats: T-cell implants with a hollow chamber for histomorphometric and steady-state mRNA expression assays, and unthreaded cylindrical implants for biomechanical push-in tests. At week 2, less bone area was found in the ovx-implant group (p = 0.0495) than in the sham-implant group. The implant push-in test showed that the ovx-implant group had approximately half of the withstanding value of the sham-implant group (p = 0.009). However, these differences between the ovx and sham groups became diminished at week 4. Total RNA samples were examined by a reverse transcriptase-polymerase chain reaction assay for col1a1, col3a1, bone sialoprotein (bSP) II, osteonectin, osteopontin, osteocalcin, integrin beta1 and integrin beta3. In untreated bones and in created bone defects without implant placement, ovx did not affect the steady-state levels of the mRNAs tested. When implants were placed, significant upregulation of these genes was observed in the sham-implant group; however, only osteocalcin and integrins were upregulated in the ovx-implant group. The results suggest a biphasic effect of female gonadal hormone deficiency that may temporarily interfere with the early implant-tissue integration process, and which may be associated with a failure to upregulate a selected set of bone extracellular matrix genes. Once established, however, functional bone-implant integration can be achieved even in ovx rats.

A meta-analytic, quantitative assessment of osseointegration establishment and evolution of submerged and non-submerged endosseous titanium oral implants

Two implant placement methods are used in oral implantology: submerged (S, two-stage surgical procedure) and non-submerged (NS, one-stage surgery). However, a quantitative assessment of their influence on implant osseointegration, summarising the whole present experience, is not directly possible, owing to the lack of normalisation of the published results. To overcome this difficulty, selection criteria have been applied to the latter in a process of a meta-analysis of specialised literature, in order to authorise a pooled treatment with an adequate statistical method. Survival life tables are established (up to 15 and 10 years respectively for S and NS implants placed in normal situations) for extended samples (13049 S and 5515 NS implants). Early (before loading) failure rates and 95% confidence level ranges of cumulative implant survival rates are shown. For both categories, the quality of the placement stage remains critical to ensure optimal osseointegration behaviour. Both categories match current survival requirements, but with a quite different behaviour over time. NS implants, while osseointegrating better initially, are subject to causes of osseointegration loss, which persist over a longer period of time. Implant design characteristics (including the type of surface) seem to be more relevant than the placement procedure for the implant's behaviour. This is in agreement with recent histological and preliminary clinical results, and should be confirmed by further studies.

Kaplan-Meier analysis of dental implant survival: a strategy for estimating survival with clustered observations

The study's purposes were to estimate dental implant survival in a statistically valid manner and to compare three models for estimating survival. We estimated survival using three different statistical models: (1) randomly selecting one implant per patient; (2) utilizing all implants, assuming independence among implants from the same subject; and (3) utilizing all implants, assuming dependence among implants from the same subject. The cohort was composed of 660 patients who had 2286 implants placed. Due to the high success rates of implants, the five-year survival point and standard error estimates varied little among the three models. Patients at high risk for implant failure (smokers) manifested greater variation in the standard error estimates among the three models, 8.2%, 4.0%, and 5.6%, respectively. To obtain statistically valid survival confidence intervals when performing Kaplan-Meier survival analyses, we recommend adjusting for dependence when there are multiple observations within the same subject.

Osseotite implant: 3-year prospective multicenter evaluation

PURPOSE

This prospective multicenter study evaluates the cumulative success rate of the Osseotite implant after 3 years of prosthetic loading.

MATERIALS AND METHODS

A total of 413 Osseotite implants (Implant Innovations) were placed in 142 patients (completely or partially edentulous) in five dental offices exclusively devoted to implants. The average age of the patients was 58.3 years. Of the 413 implants, 191 were placed in the maxilla and 222 in the mandible; 271 (65.6%) were posterior implants and 142 (34.4%) were anterior implants. Clinical and radiographic evaluations were made after completion of the prosthetic restoration, after 6 months of loading, at 1 year, and at 3 years.

RESULTS

A cumulative success rate of 95.3% was obtained after 3 years of prosthetic loading. The success rate was similar in both arches: 95.1% in the maxilla and 96.8% in the mandible. Early failures (before prosthetic loading) were greater (n = 12) than late failures (n = 2). After 3 years of prosthetic loading, the marginal bone level of 385 (93.2%) implants were evaluated radiographically. Bone level was at the first thread for 91.4% of the implants. A slightly increased loss was observed around 26 implants (6.7%). Including survival implants, the cumulative implant success rate after 3 years was 96%. A success rate of 98.4% was obtained with 187 short implants (8, 5 and 10 mm) reported in this multicenter evaluation.

CONCLUSION

This multicenter evaluation demonstrates excellent predictability for Osseotite implants.

Small-diameter implants: indications and contraindications

The choice of implant diameter depends on the type of edentulousness, the volume of the residual bone, the amount of space available for the prosthetic reconstruction, the emergence profile, and the type of occlusion. Small-diameter implants are indicated in specific clinical situations, for example, where there is reduced interradicular bone or a thin alveolar crest, and for the replacement of teeth with small cervical diameter. Before using a small-diameter implant, the biomechanical risk factors must be carefully analyzed. Preliminary reports of this type of implant show good short- and medium-term results.

Tooth loss and implant replacement

Osseointegrated dental implants are increasingly used to replace missing teeth in a variety of situations ranging from the missing single tooth to complete edentulism. The implant possibility must be carefully considered because treatment involves extended time frames, considerable expense and is not without risk. Accordingly, treatment-planning decisions should have an evidence-based strategy with appropriate risk assessment. Implant systems need to be adequately tested before they are released for general use and success rates should be assessed from peer review scientific publication data and not commercial promotional literature. It is the responsibility of the dentist to ensure the patient is educated so an informed decision can be made on difficult treatment alternatives. The clinical decision making process must respect the issues to assure quality of care and reduction of liability for negligent care. Today, the three-unit fixed bridge can no longer be considered as the standard of care for restoration of a single missing tooth. The evidence has accumulated that the single tooth implant supported replacement is more conservative, more cost-effective and more predictable with respect to long-term outcome in uncomplicated cases.

A comparison of endosseous dental implant surfaces

Endosseous dental implants are available with various surface characteristics ranging from relatively smooth machined surfaces to more roughened surfaces created by coatings, blasting by various substances, by acid treatments, or by combinations of the treatments. Studies characterizing these implants and surfaces include in vitro experimentation, animal studies, and human clinical trials. Both descriptive and functional testing of the bone-implant interface includes histomorphometrics and biomechanical testing such as torque removal values and push out/pull out strength. Using these assays to evaluate and compare different surfaces, the data demonstrate that rough implant surfaces have increased bone-to-implant contact and require greater forces to break the bone-implant interface compared to more smooth surfaces. The objective of this report was to evaluate publications of human clinical experiences evaluating implant use in patients and to determine if differences existed in success rates of implants with relatively smooth surfaces compared to implants having roughened implant surfaces. Human trials were reviewed to determine the clinical efficacy of implants under various clinical indications. Synopsis tables were constructed and the experiences segregated by implant surface characteristics. Meta-analyses were performed on all implants in all locations, on implants placed only in the maxilla or the mandible, and, finally, on implants placed in the maxilla compared to implants placed in the mandible. Evaluation of the data revealed that predictably high success rates can be achieved for implants with both rough and smooth titanium surfaces and for hydroxyapatite-coated implants. When studies were clustered by specific indications or patient populations, rough surfaced implants had significantly higher success rates compared to implants with more smooth surfaces except in the case of single tooth replacements where the success rates were comparable. In general, implants placed in the mandible had significantly higher success rates than implants placed in the maxilla. However, in the partially edentulous patient group, titanium implants with a rough surface had significantly higher success rates in the maxilla compared to the mandible and, in cases of single tooth replacement, success rates were similar in the maxilla and in the mandible as was the case for hydroxyapatite-coated implants. The documented advantage of implants with a roughened surface in animal and in vitro experiments has been demonstrated in clinical cases when studies were compared in which specific indications or patients were treated. Additionally, implants placed in the mandible have, in general, higher success rates than implants placed in the maxilla, with only a few exceptions noted. These data from human clinical experiences support the documented advantage of implants with a roughened surface in animal and in vitro experimentation and indicate that the magnitude of the advantage is significant for patient care.

Using two surgical protocols to restore the edentulous patient with implant-supported overdentures

Long-term success rates are reported for dental implant systems using both the two-stage and one-stage surgical protocols. Although the one-stage offers several advantages, prudent diagnosis is a key factor for selecting the appropriate surgical protocol. This article will review the relevant literature for both protocols and will illustrate their use in patient treatment.

Clinical experiences with dental implants

The clinical utilization of dental implants has accelerated in recent years, and new applications continue to emerge. Concomitantly, alternative implant systems have introduced conceptually different approaches to treatment using altered protocols. The purpose of this paper is to address some of the background issues pertinent to the long-term success, survival, safety, and effectiveness of these devices. The requirements for clinical acceptance of implants are controlled initially by regulatory bodies; however, the dentist eventually must make a decision on which type of implant should be used in clinical practice. This clinical decision-making process should involve the strategy of using an evidence-based approach to ensure quality of care and reduction of liability for negligent care. This is particularly the case when treatment is undertaken in identified high-risk categories. While short- to medium-term data have been accumulated on the success rates of several implant systems, it is apparent that long-term data comparing and contrasting the various advantages and disadvantages of different systems do not exist, and adequate criteria applicable to the collective clinical experience need to be defined. Expanding areas of application are dependent on continuous improvements in implant hardware, surgical protocol development, and rationalized osteopromotive and site installation augmentation technology. Many treatment endeavors are still largely at the pilot study level of development, and long-term prospective clinical trials on large numbers of patients are required to document results adequately and to elucidate the most likely productive areas for future investigation.

Two-stage implant systems

Since the advent of osseointegration approximately 20 years ago, there has been a great deal of scientific data developed on two-stage integrated implant systems. Although these implants were originally designed primarily for fixed prostheses in the mandibular arch, they have been used in partially dentate patients, in patients needing overdentures, and in single-tooth restorations. In addition, this implant system has been placed in extraction sites, in bone-grafted areas, and in maxillary sinus elevations. Often, the documentation of these procedures has lagged. In addition, most of the reports use survival criteria to describe results, often providing overly optimistic data. It can be said that the literature describes a true adhesion of the epithelium to the implant similar to adhesion to teeth, that two-stage implants appear to have direct contact somewhere between 50% and 70% of the implant surface, that the microbial flora of the two-stage implant system closely resembles that of the natural tooth, and that the microbiology of periodontitis appears to be closely related to peri-implantitis. In evaluations of the data from implant placement in all of the above-noted situations by means of meta-analysis, it appears that there is a strong case that two-stage dental implants are successful, usually showing a confidence interval of over 90%. It also appears that the mandibular implants are more successful than maxillary implants. Studies also show that overdenture therapy is valid, and that single-tooth implants and implants placed in partially dentate mouths have a success rate that is quite good, although not quite as high as in the fully edentulous dentition. It would also appear that the potential causes of failure in the two-stage dental implant systems are peri-implantitis, placement of implants in poor-quality bone, and improper loading of implants. There are now data addressing modifications of the implant surface to alter the percentage of osseointegration. New types of reinforcements for dental implants and the use of growth factors to augment bone regeneration so that implants can be placed more easily are now being actively investigated.

Clinical complications of osseointegrated implants

STATEMENT OF PROBLEM

There is no comprehensive review of the literature that identifies the complications reported in clinical dental implant studies.

PURPOSE

This article attempted to determine the types of complications that have been reported and to provide data regarding their frequency.

METHODS

All available clinical studies from 1981 to 1997, published in English or with English abstract, that presented success/failure data regarding implant treatment were evaluated to determine the types of reported complications and to quantify implant loss as it relates to type of prosthesis, arch, time, implant length, and bone quality.

RESULTS

Greater implant loss occurred with overdentures than with other types of prostheses. There was greater loss in the maxilla than mandible with fixed complete dentures and overdentures, whereas little arch difference was noted with fixed partial dentures. Implant loss increased with short implants and poor bone quality. The time of implant loss (preprosthetic vs postprosthetic) varied with type of prosthesis. Surgical complications included neurosensory disturbance, hematoma, mandibular fracture, hemorrhage, and tooth devitalization. Initial and long-term marginal bone changes were identified. Peri-implant soft tissue complications included dehiscence, fistulas, and gingival inflammation/proliferation. Mechanical complications were screw loosening/fracture, implant fractures, framework, resin base and veneering material fractures, opposing prosthesis fractures, and overdenture mechanical retention problems. Some studies also presented phonetic and esthetic complications.

CONCLUSIONS

Although the literature presents considerable information on implant complications, variations in study design and reporting procedures limited the available data and therefore precluded proper analysis of certain complications.

Future therapeutic directions for management of the edentulous predicament

The 1982 Toronto Conference on Tissue-Integrated Prostheses introduced the technique of osseointegration to the academic dental community. Subsequently, prosthodontists have played a leading role in the educational and clinical development of implant-supported fixed and removable prostheses for the treatment of the edentulous jaw. The success rates of treatment in the mandible have been replicated in many parts of the world and results are rewarding when compared with conventional complete denture therapy. Unfortunately, treatment results in the maxilla do not parallel those in the mandible and the shortfall requires the development of alternative strategies in diagnosis, treatment planning, surgery, and prosthetic management. As these treatment concepts become an everyday practice reality, osseointegrated implants have predictably found their way into the curriculum of all dental specialties. However, in many localities, the role of the prosthodontist in continuing education and research and development has become diluted as other areas of dentistry realize the enormous potential for treatment with osseointegrated implants. Accordingly, prosthodontists need to reevaluate their clinical mind-set if the specialty is to provide a lead role in future therapeutic endeavors.