A targeted review of study outcomes with short (< or = 7 mm) endosseous dental implants placed in partially edentulous patients.

BACKGROUND: Generally, threaded root-form endosseous dental implants are thought to perform poorly in short lengths (i.e., < 10 mm). However, whether modifications in implant surface geometry will improve performance of short threaded implants is less clear. METHODS: The relationship between dental implant failure rates and their surface geometry, length, and location (maxilla versus mandible) was explored in the published literature. Using a MEDLINE search (1985 through 2001), studies were sought with the following criteria: 1) data suitable to calculate failure rates of implant lengths < or = 7 mm versus > 7 mm; 2) data separable into maxillary versus mandibular results; 3) criteria for "failure" clearly defined; and 4) minimal functional period of 2 years. RESULTS: Twelve papers were identified as follows: eight with machined threaded implants, two with acid-treated threaded implants, and two with sintered porous-surfaced press-fit implants. The following results were found: 1) machined surface implants experienced greater failure rates than textured surface implants; 2) with the exception of sintered porous-surfaced implants, 7 mm long dental implants appear to have higher failure rates than those > 7 mm length; and 3) with textured surface implants, higher failure rates were more likely in the maxilla than in the mandible, but with machined surface implants there were no differences in failure rates between maxilla and mandible. CONCLUSIONS: Dental implant surface geometry is a major determinant in how well these implants perform in short lengths, defined here as lengths of < or = 7 mm. While threaded implants show higher failure rates in short versus longer lengths, sintered porous-surfaced implants perform well in the defined "short" lengths. More studies are needed to better assess the performance of short, acid-washed threaded implants.

The effect of sol-gel-formed calcium phosphate coatings on bone ingrowth and osteoconductivity of porous-surfaced Ti alloy implants.

Ti-6Al-4V implants formed with a sintered porous surface for implant fixation by bone ingrowth were prepared with or without the addition of a thin surface layer of calcium phosphate (Ca-P) formed using a sol-gel coating technique over the porous surface. The implants were placed transversely across the tibiae of 17 rabbits. Implanted sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment using backscattered scanning electron microscopy and quantitative image analysis. Bone formation along the porous-structured implant surface, was measured in relation to the medial and lateral cortices as an indication of implant surface osteoconductivity. The Absolute Contact Length measurements of endosteal bone growth along the porous-surfaced zone were greater with the Ca-P-coated implants compared to the non-Ca-P-coated implants. The Ca-P-coated implants also displayed a trend towards a significant increase in the area of bone ingrowth (Bone Ingrowth Fraction). Finally, there was significantly greater bone-to-implant contact within the sinter neck regions of the Ca-P-coated implants.

A possible "rescue" procedure for dental implants with a textured surface geometry: a case report.

Dental implants with textured surfaces are a valuable adjunct in restoring edentulous sites of poor bone quality and quantity, but on occasion may become denuded of bone and require "rescue." We report here the successful management of an intrabony crater affecting a single porous-surfaced dental implant using a combination of citric acid decontamination and grafting with freeze-dried, demineralized allograft covered with a barrier of calcium sulfate.

A prospective human clinical trial of Endopore dental implants in restoring the partially edentulous maxilla using fixed prostheses.

This is the first report of a group of 50 partially edentulous patients who received a total of 151 Endopore dental implants in the maxilla. A mean implant length of 8.7 mm was used, and 76.8% of implants were placed in the posterior maxilla. At re-entry, all implants appeared to be osseointegrated and were used to support fixed prostheses. Approximately half of the crowns (57%) in these prostheses were splinted to one another, while the remainder (43%) were not. At the time of this report, the mean functional time was 34.6 months and the cumulative survival rate was 97.3% (4 implants had failed). Analysis of carefully standardized sequential radiographs indicated no significant changes in mean crestal bone levels between baseline and any of the examination times (after 6 months, 1 year, and 2 years in function). There were no detectable correlations between crestal bone loss and the factors implant length (7, 9, or 12 mm); implant diameter (3.5, 4.1, or 5.0 mm); implant position anteriorly or posteriorly in the maxilla; or whether or not the implant-supported crowns were splinted.

Use of a tapered, porous-surfaced dental implant in combination with osteotomes to restore edentulism in the difficult maxilla.

The maxilla is the more difficult arch to restore with endosseous dental implants because of hurdles such as low bone density, narrow buccopalatal width, minimal bone height, and proximity to the maxillary sinus. In this article, a technique to resolve all of these problems using a short, tapered, porous-surfaced implant and a placement protocol using hand osteotomes rather than surgical burs is presented.

The Endopore implant-enhanced osseointegration with a sintered porous-surfaced design.

The Endopore implant provides a novel method for reliable fixation of endosseous dental implants within the bone. Through the use of a porous-surfaced zone formed by sintering Ti alloy particles of the appropriate size and under appropriate processing conditions to a sold Ti alloy core of desired shape (tapered truncated cone), an implant is now available that can be placed using a relatively simple surgical procedure using either surgical burs or hand osteotomes. Of even greater value is the suitability of this implant design for treatment of cases that because of minimal bone height cannot be treated routinely using other currently-available implants. The high success rates experienced with significantly shorter implant lengths compared with other designs indicate the appropriateness of this system for difficult-to-treat cases. The Endopore system represents the next generation of endosseous dental implants characterized by uncomplicated and reliable treatment for a wider range of dentally-compromised patients. Its history is founded on extensive and fully-documented research at the human preclinical stage as well as human use experiences. The results during the past nine years have confirmed the high expectations that those early studies suggested.

Use of the Endopore dental implant to restore single teeth in the maxilla: protocol and early results.

This report outlines the experimental, surgical, and prosthodontic protocols for a prospective clinical trial using the Endopore dental implant to replace single maxillary teeth. Twenty patients (10 male, 10 female) ranging in age from 30 to 60 years each received one implant (mean length 10.1 mm), which, after an initial healing period of 4 months, was restored with a single crown. Records collected included radiographs, Periotest mobility measurements, supragingival Plaque Index, and an assessment of peri-implant soft tissue health using pocket probing depths, sulcular bleeding following probing, and probing attachment levels. Radiographs were exposed at predetermined intervals following crown placement (1 and 6 months, and then yearly) in a standardized procedure using a specialized filmholder that attaches to each implant after removal of the crown. At the time of this preliminary report, all of the 20 implants placed had been uncovered and were in function; 16 of the implants had been in function for 6 months or more, 14 had passed 1 year of function, and 3 had passed the 2-year function point. There have been no failures to date.

A comparison of radiographic bone height and probing attachment level measurements adjacent to porous-coated dental implants in humans.

The changes in crestal bone height observed in standardized radiographs of porous-coated dental implants after 3 to 4 years of function in the support of mandibular overdentures is reported for a group of 48 completely edentulous patients. Possible correlations between bone height and each of probing attachment level, Plaque Index, and Sulcular Bleeding Index were investigated. Mean bone loss values were determined to be 0.43 mm in year 1, decreasing to 0.17 mm and 0.13 mm in years 2 and 3, respectively. During year 4, there was an apparent mean gain of 0.05 mm. While the mean mucosal tissue thickness (1.3 mm) was similar to that reported by other investigators, it was not possible to show a correlation between bone height and probing attachment level. Likewise, correlations between bone height and Plaque Index or between bone height and Sulcular Bleeding Index could not be demonstrated.

Simplifying the treatment of edentulism: a new type of implant.

In this article, the authors describe the application of a new and unique root-form dental implant in a simplified approach to treating the completely edentulous mandible using an overdenture. The technique is supported by the results of a prospective clinical trial involving 52 patients that showed a three- to four-year success rate of 95 percent.

Periodontal parameters around porous-coated dental implants after 3 to 4 years supporting overdentures.

In this study, an assessment using modified periodontal indices was done on a group of 48 fully edentulous patients who had each been treated with 3 porous-coated (EndoPore) dental implants and a mandibular overdenture. Parameters assessed included plaque index (PI), sulcular bleeding index (SBI), pocket probing depth (PD), probing attachment level (PAL) and mobility (M) using a Periotest device. At the time of the assessment, all of the patients had passed 3 years of continuous function while 26 had passed 4 years. Approximately 50% of implant surfaces were plaque-free while 79% of surfaces showed no bleeding upon probing. There was no correlation between PI and SBI. The mean PD was 3.1 mm with 64% of sites < or = 3.5 mm. Mobility measurements taken with the Periotest device gave a mean PTV of (-4.35) with 96% of measurements (-0.5). No significant correlations were found between mobility and either PAL or implant length.

Initial healing in the dog of submerged versus non-submerged porous-coated endosseous dental implants.

It has previously been reported that porous-coated root form endosseous dental implants, became well integrated when used in the traditional 2-stage surgical approach. In this study, the placement of the implant in a 1-stage (non-submerged) technique was to be explored. Implants were placed in the mandibles of dogs, and 2 designs were used differing only in that one (experimental) had a 3-mm transgingival extension, permitting it to be exposed to the oral cavity from the outset. 12 (3 per animal) non-submerged implants were placed on 1 side of 4 beagle dogs and 12 control (submerged) implants were placed contralaterally. All implants were allowed to heal for 6 weeks, after which histological preparations were made. 2 of 12 non-submerged implants were lost due to post-operative complications; otherwise, all implants healed uneventfully. Histomorphometric analysis revealed bone-implant contact, as assessed by absolute bone contact (ABC) and contact length fraction (CLF), to be greater for the submerged design, suggesting that bone healing may be delayed with the non-submerged approach. As well, at this early stage of healing, for both implant designs, ABC and CLF were significantly greater on proximal than on buccal and lingual aspects.

A prospective clinical study in humans of an endosseous dental implant partially covered with a powder-sintered porous coating: 3- to 4-year results.

A dental implant covered partially with a porous coating (EndoPore) developed at the University of Toronto was tested. This new implant is a tapered, truncated-cone endosseous root-form implant fabricated from Ti-6Al-4V. It utilizes a powder-sintered porous surface geometry over most of its length to promote three-dimensional bone ingrowth and implant stabilization. In this trial, three implants were placed in the anterior mandibles of 52 patients and were used subsequently as free-standing units to support an overdenture. Much shorter implants, shorter initial healing periods, and simpler surgical techniques than are customary with other implant designs were used. At the time of this report, all patients with implants had passed 3 years of function, and the cumulative implant success rate was 94.8%. Analysis of carefully standardized radiographs revealed a pattern of crestal bone loss similar to earlier published dog data. On a yearly basis, the mean bone loss was 0.43 mm in year 1, 0.17 mm in year 2, and 0.13 mm in year 3.

Predictable crestal bone remodelling around two porous-coated titanium alloy dental implant designs. A radiographic study in dogs.

We have previously suggested that altering the height of the porous-coat segment of a partially porous-coated TiAl6V4 endosseous dental implant would affect the degree of crestal bone loss occurring during implant function by changing the patterns of stress transfer. This conclusion arose from the analysis of data from several different experiments and lacked a direct intra-animal comparison. In the present study we have compared two implant designs varying only in the extent to which they were porous-coated. With one design (type A) the coronal 1.8 mm of the implant root had a machined surface while the remainder of its length was porous-coated with TiAl6V4 beads. The other design (type B) had all but the coronal-most 0.75 mm porous-coated. Two implants of each type were placed in each of 4 dogs and the sites allowed to heal for 4 weeks before re-entry and prosthesis attachment. Monthly the implant-supported bridges were removed and radiographs exposed of each implant using a special film holder connected separately to each implant. These radiographs were analyzed for crestal bone loss using both direct visual and computer-assisted techniques. The results showed that bone remodelled to the machined surface-to-porous coat junction for type B implants and achieved a steady state by 12 weeks of function, whereas a longer time was required to achieve this state with type A implants. Significantly more bone loss occurred with the type A design, and this difference was detectable as early as after the first month of function.

The effect of partial coating with hydroxyapatite on bone remodeling in relation to porous-coated titanium-alloy dental implants in the dog.

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant designs became securely fixed by bone ingrowth into the porous-coated apical region of the implants. The plasma-sprayed HA coating resulted in significantly greater bone height formation and maintenance next to the coronal portion of the implant compared with non-HA-coated implants of similar design. In addition, significant resorption of the 20-to-50-microns-thick plasma-sprayed HA coating occurred over the 18-month period of function.

Dental implant design--effect on bone remodeling.

Bone remodeling around three different endosseous dental implant designs placed in dog mandibles was studied using radiography during lengthy periods of function and by histology after animal sacrifice. The three designs investigated were (a) threaded (c.p. titanium), (b) fully porous-coated (titanium alloy), and (c) partially porous-coated (titanium alloy). The implants were kept in function for either 32 weeks (fully porous-coated) or 73 to 77 weeks (partially porous-coated and threaded). The studies indicated that some crestal bone loss occurred for both the threaded and partially porous-coated implants while no significant bone loss was seen with fully porous-coated implants in the absence of plaque-associated infection. It is suggested that these observed differences are a result of the different stress states that develop in bone surrounding the three designs underlying the importance of implant design on bone remodeling.

A histological comparison in the dog of porous-coated vs. threaded dental implants.

The histological findings of an 18-month trial, in the dog of a partially porous-coated endosseous dental implant made of Ti-6Al-4V, with a truncated conical shape, are described and compared with those for a cylindrical, threaded, endosseous implant made of commercially pure Ti. Six beagle dogs each received two porous-coated implants on one side of the mandible and two threaded implants on the contralateral side. Each set of two implants supported a two-unit fixed bridge for an 18-month functional period. Methylmethacrylate sections of both the buccolingual and mesiodistal aspects of each implant were examined qualitatively and by computer-assisted morphometry. The morphometric measurements were used for determination of the length of implant surface in direct contact with bone on each aspect of each implant. The data were expressed both as an absolute length and as a fraction of the maximum length available for contact (contact length fraction or CLF). On the buccal and lingual aspects of the implants, both the absolute lengths and CLF were significantly smaller for the porous-coated design. For the mesial and distal aspects, the absolute lengths and CLF were less for the porous-coated design, but the differences were not significant. However, when the absolute contact length was related to the corresponding vertical bone height, significant differences were observed, the absolute contact length being greater for any given bone height for the porous-coated design. Taken together, the data suggest that shorter implants may be used with the porous-coated design.

Preprosthetic alveolar ridge correction using glutaraldehyde cross-linked, lyophilized scleral allografts.

Following the loss of a maxillary anterior tooth, there is often a change in the topography of the residual alveolar ridge, resulting in a ridge defect that requires surgical correction by the dentist before the placement of a fixed prosthesis. The present study utilized glutaraldehyde cross-linked, lyophilized human sclera as an allograft material to correct such ridge defects. The cases treated with this allograft were followed postoperatively for 3 months and were objectively assessed by digitization of sectioned sequential stone casts. The results showed statistically significant improvement at the grafted sites with no shrinkage at 3 months and verified that glutaraldehyde cross-linked, freeze-dried human sclera is useful in localized ridge augmentation procedures.

A histological evaluation of a functional endosseous, porous-surfaced, titanium alloy dental implant system in the dog.

We have previously reported the clinical and radiographic findings of a trial in dogs of a new dental implant system after a functional period of eight months. The present report consists of the corresponding qualitative and quantitative histological data. The implant system was fabricated from Ti-6A1-4V and employed a porous-surfaced configuration to achieve implant fixation by bone ingrowth. A similar porous surface was used on the apical 1/3 of the transgingival collar in an attempt to gain ingrowth and attachment of gingival connective tissue. The qualitative histological data confirmed that while such attachment to the collar did occur for some implants, in the majority of implants (22 of 32) the porous region of the collar became contaminated with bacterial plaque, resulting in implant failure (four implants) or suggesting future implant failure (18 implants). Statistical analyses of the quantitative histological data indicated that there were no significant differences in surface contact of bone with the middle third of the porous implant surface (CLF) when initial healing interval (four or eight weeks), implant location, or aspect of implant (buccal vs. lingual vs. mesial vs. distal) were compared. However, comparison of the current group of functional implants with an earlier group of similarly implanted non-functional implants indicated that function produced a highly significant increase in CLF.

Reconstituted bovine skin collagen enhances healing of bone wounds in the rat calvaria.

The value of reconstituted fibrillar collagen (Zyderm Collagen Implant I, a concentrated solution of pepsin-solubilized, bovin skin collagen) as a bone graft material was tested in 4 mm diameter surgically created defects of rat calvaria. All wounds were allowed to heal for 4 weeks, and were assessed both qualitatively and by computer-assisted morphometry. The fibrillar collagen was found to produce significantly more new bone than no graft or than heat-denatured fibrillar collagen. The fibrillar collagen was generally well tolerated, appeared to act as a hospitable osteoconductor, and became incorporated into the newly formed bone. The effect of collagen concentration was also tested by comparing the fibrillar collagen at 3.5% (Zyderm Collagen Implant I) with 6.5% suspension of collagen (Zyderm Collagen Implant II). There were no significant differences observed, but a definite trend was evident for Zyderm II to encourage more bone formation than Zyderm I. It is concluded that reconstituted fibrillar collagen is a hospitable, osteoconductive substance that enhances bone healing of calvarial defects in the rat.