Implant therapy I

Effect of dental implant surface roughness in patients with a history of periodontal disease: a systematic review and meta-analysis

BACKGROUND

To review the literature on the effect of dental implant surface roughness in patients with a history of periodontal disease. The present review addresses the following focus question: Is there a difference for implant survival, mean marginal bone loss, and the incidence of bleeding on probing in periodontally compromised patients receiving a machined dental implant or rough surface dental implant?

METHODS

Electronic and manual literature searches were conducted on PubMed/MEDLINE and the Cochrane Library on studies published until May 2018 to collect information about the effect of machined, moderately rough, and rough dental implant surfaces in patients with a history of periodontal disease. The outcome variables implant survival, mean marginal bone level, and the incidence of peri-implantitis and bleeding on probing were evaluated. Meta-analysis was performed to obtain an accurate estimation of the overall, cumulative results.

RESULTS

Out of 2411 articles, six studies were included in this systematic review. The meta-analysis of the implant survival and implant mean marginal bone loss revealed a risk ratio of 2.92 (CI 95% 0.45, 18.86) for implant failure and a total mean difference of - 0.09 (CI 95% - 0.31, 0.14) for implant mean marginal bone loss measured in a total group of 215 implants, both not statistically significant.

CONCLUSIONS

Due to lack of long-term data (> 5 years), the heterogeneity and variability in study designs and lack of reporting on confounding factors, definitive conclusions on differences in implant survival, and mean marginal bone loss between machined and moderate rough implants in periodontally compromised patients cannot be drawn. Future well-designed long-term randomized controlled trials are necessary to reveal that machined surfaces are superior to moderately rough and rough surfaces in patients with a history of periodontal disease.

Bacteriological evaluation for one-and two-piece implant design supporting mandibular overdenture

Background:

This study evaluated and compared the bacteriological effect of two-piece implants and one-piece implants in complete overdenture cases on supporting structures.

Materials and Methods:

Ten male completely edentulous patients were selected and randomly divided into two equal groups according to the implant design and surgical technique for this study; Group 1: Patients were rehabilitated with complete mandibular overdenture supported by two-piece implants one on each side of the lower arch following two-stage surgical technique and Group 2: Patients were rehabilitated with complete mandibular overdenture supported by one-piece implants one on each side. Evaluation was made at the time of insertion, 6, 12, and 18 months after overdenture insertion, by measuring bacteriological changes around implants abutments.

Results:

Complete overdenture supported by one-piece implants showed better effect on the bacteriological changes as compared to that supported by two-piece implants.

Conclusion:

Complete overdenture supported by one-piece implants one on each side of the lower arch showed better effect on the bacteriological changes than using the same prosthesis supported by two-piece implants.

Survival of 352 titanium implants placed in 181 patients: a 4-year multicenter field study

PURPOSE

The aim of this retrospective chart review was to evaluate the four-year survival rate of a titanium implant system.

METHODS

A total of 352 sand-blasted, thermally acid-etched titanium implants were inserted into 181 partially or completely edentulous patients. Their cumulative survival rate was evaluated retrospectively. Associated factors, such as the implant distribution and treatment type were included in the evaluation.

RESULTS

The implants were equally distributed between the maxilla (52.3%) and the mandible (47.7%). 48 implants (13.6%) were placed in the anterior region and 304 implants (86.4%) in the posterior region. The majority of the implants were inserted into bone of type II and III quality (89.8%) and volume (quantity B and C, 87.2%). Most of the implants (70.7%) were restored as single crowns; 28.7% supported a bridge construction and 0.6% a full denture. Only one implant failed, resulting in a four-year cumulative survival rate of 99.7%.

CONCLUSIONS

The implant system showed an excellent four-year survival rate. It proved to be a safe and predictable means for restoration of the dentition in partially or completely edentulous patients.

Determination of inner implant's volumes: a pilot study for microleakage quantification by stereomicroscopy and spectrophotometry

AIM

Microleakage quantification of fluids and microorganisms through the connections of different implant parts seems to be sparse. Moreover, no data exist regarding the determination of the volumes of inner parts of dental implant systems. This study aims to determine the volumes of inner parts of three dental implant systems with the same interface and to evaluate the microleakage phenomenon.

MATERIALS AND METHODS

Three implant system sets (Euro-teknika(®), Astra Tech(®) and Implantium(®)) were used in this study. Implants were inoculated with safranin, brain heart infusion and distilled water. After inoculation and assembly of the different parts, different inner volumes (V1, V2, V3, V4, V5 and V6) were measured and, the surfaces of the micro gaps were observed through a stereomicroscope. Implants containing safranin were immersed in vials containing distilled water. Samples then were taken to determine optical density using a spectrophotometer.

RESULTS

Regardless the used substance, volumes of the 3-implant systems are different. Although volumes V1, V 2, V 3 and V5 appeared to be constant within the same system regardless the used substance, volumes V4 and V6 were not.

CONCLUSION

The determination of the volumes and the evaluation of leaked substance using stereomicroscopic and spectrophotometric methods showed the accuracy of these methods and the importance of their use in the study of microleakage.

CLINICAL SIGNIFICANCE

Leakage is an important factor for chronic inflammatory infiltration and marginal bone resorption. Studies have shown fluid and bacterial leakage into abutment- implant (A-I) assemblies of certain implants with 'closely locked' abutments and the creation of a constant bacterial reservoir in the empty space found between the implant and the abutment.

Evaluating the clinical and esthetic outcome of apically positioned flap technique in augmentation of keratinized gingiva around dental implants

PURPOSE

Dental implants though a successful treatment modality there exists controversies regarding the relationship between the adequacy of the keratinized gingiva (KG) and peri-implant health. The presence of an adequate amount of peri-implant KG reduces gingival inflammation and hence soft-tissue augmentation should be frequently considered. Among the various periodontal plastic surgical procedures, the apically displaced flap increases the width of keratinized tissue with reduced patient morbidity. The current study aims at evaluating the esthetic improvement in KG around dental implants applying apically positioned flap (APF) technique.

MATERIALS AND METHODS

A total of 10 endosseous dental implants were placed in eight systemically healthy patients. APF surgery was performed at the implant site on the buccal aspect either at the time of implant placement (one stage surgical protocol) or during the implant recovery stage (two stage surgical protocols) for increasing the width of KG and reviewed until 12 weeks post-operatively. The width of KG was evaluated at baseline and at the end of 12 weeks after surgery. Paired t-test was performed to evaluate the changes in the width of KG at baseline and at 12 weeks post-operatively. In addition, soft-tissue esthetic outcome was assessed by using visual analog scale (VAS).

RESULTS

The mean width of KG at baseline was 1.47 mm and 12 weeks post-operatively was 5.42 mm. The gain in KG from baseline was 3.95 mm with the P value of 0.000, which was highly statistically significant. The assessment of esthetic outcome using VAS gave an average score of 7.1 indicating good esthetics.

CONCLUSION

The technique of APF yielded a significant improvement in keratinized tissue, which is both functionally and esthetically acceptable.

Evaluating the clinical and esthetic outcome of apically positioned flap technique in augmentation of keratinized gingiva around dental implants

Purpose:

Dental implants though a successful treatment modality there exists controversies regarding the relationship between the adequacy of the keratinized gingiva (KG) and peri-implant health. The presence of an adequate amount of peri-implant KG reduces gingival inflammation and hence soft-tissue augmentation should be frequently considered. Among the various periodontal plastic surgical procedures, the apically displaced flap increases the width of keratinized tissue with reduced patient morbidity. The current study aims at evaluating the esthetic improvement in KG around dental implants applying apically positioned flap (APF) technique.

Materials and Methods:

A total of 10 endosseous dental implants were placed in eight systemically healthy patients. APF surgery was performed at the implant site on the buccal aspect either at the time of implant placement (one stage surgical protocol) or during the implant recovery stage (two stage surgical protocols) for increasing the width of KG and reviewed until 12 weeks post-operatively. The width of KG was evaluated at baseline and at the end of 12 weeks after surgery. Paired t-test was performed to evaluate the changes in the width of KG at baseline and at 12 weeks post-operatively. In addition, soft-tissue esthetic outcome was assessed by using visual analog scale (VAS).

Results:

The mean width of KG at baseline was 1.47 mm and 12 weeks post-operatively was 5.42 mm. The gain in KG from baseline was 3.95 mm with the P value of 0.000, which was highly statistically significant. The assessment of esthetic outcome using VAS gave an average score of 7.1 indicating good esthetics.

Conclusion:

The technique of APF yielded a significant improvement in keratinized tissue, which is both functionally and esthetically acceptable.

Sandblasted-acid-etched titanium surface influences in vitro the biological behavior of SaOS-2 human osteoblast-like cells

Osseointegrated dental implants have been successfully used over the past several years, allowing functional replacement of missing teeth. Surface properties of titanium dental implants influence bone cell response. Implant topography appears to modulate cell growth and differentiation of osteoblasts thus affecting the bone healing process. Optimal roughness and superficial morphology are still controversial and need to be clearly defined. In the present study we evaluated in vitro the biological behavior of SaOS-2 cells, a human osteoblast-like cell line, cultured on two different titanium surfaces, smooth and sandblasted-acid-etched, by investigating cell morphology, adhesion, proliferation, expression of some bone differentiation markers and extracellular matrix components. Results showed that the surface topography may influence in vitro the phenotypical expression of human osteoblast-like cells. In particular the tested sandblasted-acid-etched titanium surface induced a significantly increased Co I deposition and α2-β1 receptor expression as compared to the relatively smooth surface, promoting a probable tendency of SaOS-2 cells to shift toward a mature osteoblastic phenotype. It is therefore likely that specific surface properties of sandblasted-acid-etched titanium implants may modulate the biological behavior of osteoblasts during bone tissue healing.

A review of dental implants and infection

Dental implants have become increasingly common for the management of tooth loss. Despite their placement in a contaminated surgical field, success rates are relatively high. This article reviews dental implants and highlights factors leading to infection and potential implant failure. A literature search identified studies analysing the microbial composition of peri-implant infections. The microflora of dental peri-implantitis resembles that found in chronic periodontitis, featuring predominantly anaerobic Gram-negative bacilli, in particular Porphyromonas gingivalis and Prevotella intermedia, anaerobic Gram-negative cocci such as Veillonella spp. and spirochaetes including Treponema denticola. The role of Staphylococcus aureus and coagulase-negative staphylococci that are typically encountered in orthopaedic infections is debatable, although they undoubtedly play a role when isolated from clinically infected sites. Likewise, the aetiological involvement of coliforms and Candida spp. requires further longitudinal studies. Currently, there are neither standardised antibiotic prophylactic regimens for dental implant placement nor universally accepted treatment for peri-implantitis. The treatment of infected implants is difficult and usually requires removal. In the UK there is no systematic post-surgical implant surveillance programme. Therefore, the development of such a project would be advisable and provide valuable epidemiological data.

Implant maintenance

Endosseous root-form implants have become an integral part of dental reconstruction in partially and fully edentulous patients. The long-term prognosis of an implant is related directly to routine assessment and effective preventive care. To maintain healthy tis-sues around dental implants, it is important to institute an effective maintenance regimen. Different regimens have been suggested, but it is unclear which are the most effective. This article evaluates the literature regarding implant maintenance. Factors affecting the soft tissue surrounding endosseous root-form implants are discussed, and procedures for assessment of the implant and the treatment of reversible disease in implant maintenance are outlined.

Growth factor delivery for oral and periodontal tissue engineering

The treatment of oral and periodontal diseases and associated anomalies accounts for a significant proportion of the healthcare burden, with the manifestations of these conditions being functionally and psychologically debilitating. Growth factors are critical to the development, maturation, maintenance and repair of craniofacial tissues, as they establish an extracellular environment that is conducive to cell and tissue growth. Tissue-engineering principles aim to exploit these properties in the development of biomimetic materials that can provide an appropriate microenvironment for tissue development. These materials have been constructed into devices that can be used as vehicles for delivery of cells, growth factors and DNA. In this review, different mechanisms of drug delivery are addressed in the context of novel approaches to reconstruct and engineer oral- and tooth-supporting structures, namely the periodontium and alveolar bone.

The Effect of rhBMP-2 Around Endosseous Implants With and Without Membranes in the Canine Model

BACKGROUND

Bone morphogenetic protein (BMP) is a potent differentiating agent for cells of the osteoblastic lineage. It has been used in the oral cavity under a variety of indications and with different carriers. However, the optimal carrier for each indication is not known. This study examined a synthetic bioabsorbable carrier for BMP used in osseous defects around dental implants in the canine mandible.

METHODS

Twelve canines had their mandibular four premolars and first molar teeth extracted bilaterally. After 5 months, four implants were placed with standardized circumferential defects around the coronal 4 mm of each implant. One-half of the defects received a polylactide/glycolide (PLGA) polymer carrier with or without recombinant human BMP-2 (rhBMP-2), and the other half received a collagen carrier with or without rhBMP-2. Additionally, one-half of the implants were covered with a non-resorbable (expanded polytetrafluoroethylene [ePTFE]) membrane to exclude soft tissues. Animals were sacrificed either 4 or 12 weeks later. Histomorphometric analysis included the percentage of new bone contact with the implant, the area of new bone, and the percentage of defect fill. This article describes results with the PLGA carrier.

RESULTS

All implants demonstrated clinical and radiographic success with the amount of new bone formed dependent on the time and presence/absence of rhBMP-2 and presence/absence of a membrane. The percentage of bone-to-implant contact was greater with rhBMP-2, and after 12 weeks of healing, there was approximately one-third of the implant contacting bone in the defect site. After 4 weeks, the presence of a membrane appeared to slow new bone area formation. The percentage of fill in membrane-treated sites with rhBMP-2 rose from 24% fill to 42% after 4 and 12 weeks, respectively. Without rhBMP-2, the percentage of fill was 14% rising to 36% fill, respectively.

CONCLUSIONS

After 4 weeks, the rhBMP-2-treated sites had a significantly higher percentage of contact, more new bone area, and higher percentage of defect fill than the sites without rhBMP-2. After 12 weeks, there was no significant difference in sites with or without rhBMP-2 regarding percentage of contact, new bone area, or percentage of defect fill. In regard to these three outcomes, comparing the results with this carrier to the results reported earlier with a collagen carrier in this study, only the area of new bone was significantly different with the collagen carrier resulting in greater bone than the PLGA carrier. Thus, the PLGA carrier for rhBMP-2 significantly stimulated bone formation around dental implants in this model after 1 month but not after 3 months of healing. The use of this growth factor and carrier combination appears to stimulate early bone healing events around the implants but not quite to the same degree as a collagen carrier.

Crestal Bone Changes Around Titanium Implants. Part I: A Retrospective Radiographic Evaluation in Humans Comparing Two Non-Submerged Implant Designs With Different Machined Collar Lengths

BACKGROUND

Experimental studies demonstrated that peri-implant crestal hard and soft tissues are significantly influenced in their apico-coronal position by the rough/smooth implant border as well as the microgap/ interface between implant and abutment/restoration. The aim of this study was to evaluate radiographically the crestal bone level changes around two types of implants, one with a 2.8 mm smooth machined coronal length and the other with 1.8 mm collar.

METHODS

In 68 patients, a total of 201 non-submerged titanium implants (101 with a 1.8 mm, 100 with a 2.8 mm long smooth coronal collar) were placed with their rough/smooth implant border at the bone crest level. From the day of surgery up until 3 years after implant placement crestal bone levels were analyzed digitally using standardized radiographs.

RESULTS

Bone remodeling was most pronounced during the unloaded, initial healing phase and did not significantly differ between the two types of implants over the entire observation period (P >0.20). Crestal bone loss for implants placed in patients with poor oral hygiene was significantly higher than in patients with adequate or good plaque control (P <0.005). Furthermore, a tendency for additional crestal bone loss was detected in the group of patients who had been diagnosed with aggressive periodontitis prior to implant placement (P = 0.058). In both types of implants, sand-blasted, large grit, acid-etched (SLA) surfaced implants tended to have slightly less crestal bone loss compared to titanium plasma-sprayed (TPS) surfaced implants, but the difference was not significant (P >0.30).

CONCLUSION

The implant design with the shorter smooth coronal collar had no additional bone loss and may help to reduce the risk of an exposed metal implant margin in areas of esthetic concern.

A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. I. Implant-supported FPDs

OBJECTIVES

The objective of this systematic review was to assess the 5- and 10-year survival of implant supported fixed partial dentures (FPDs) and to describe the incidence of biological and technical complications.

METHODS

An electronic MEDLINE search complemented by manual searching was conducted to identify prospective and retrospective cohort studies on FPDs with a mean follow-up time of at least 5 years. Patients had to have been examined clinically at the follow-up visit. Assessment of the identified studies and data abstraction was performed independently by two reviewers. Failure and complication rates were analyzed using random-effects Poisson regression models to obtain summary estimates of 5- and 10-year survival proportions.

RESULTS

The search provided 3844 titles and 560 abstracts. Full-text analysis was performed for 176 articles resulting in 21 studies that met the inclusion criteria. Meta-analysis of these studies indicated an estimated survival of implants in implant-supported FPDs of 95.4% (95 percent confidence interval (95% CI): 93.9-96.5%) after 5 and 92.8% (95% CI: 90-94.8%) after 10 years. The survival rate of FPDs supported by implants was 95% (95% CI: 92.2-96.8%) after 5 and 86.7% (95% CI: 82.8-89.8%) after 10 years of function. Only 61.3% (95% CI: 55.3-66.8%) of the patients were free of any complications after 5 years. Peri-implantitis and soft tissue complications occurred in 8.6% (95% CI: 5.1-14.1%) of FPDs after 5 years. Technical complications included implant fractures, connection-related and suprastructure-related complications. The cumulative incidence of implant fractures after 5 years was 0.4% (95% CI: 0.1-1.2%). After 5 years, the cumulative incidence of connection-related complications (screw loosening or fracture) was 7.3% and 14% for suprastructure-related complications (veneer and framework fracture).

CONCLUSION

Despite a high survival of FPDs, biological and technical complications are frequent. This, in turn, means that substantial amounts of chair time have to be accepted by the clinician following the incorporation of implant-supported FPDs. More studies with follow-up times of 10 and more years are needed as only few studies have described the long-term outcomes.

Oral rehabilitation with implant-supported fixed partial dentures in periodontitis-susceptible subjects. A 5-year prospective study

BACKGROUND

Comparatively few studies with at least 5 years of follow-up are available that describe the use of implants in prosthetic rehabilitation of partially edentulous patients. Randomized, controlled clinical studies that evaluated the effect of different surface designs of screw-shaped implants on the outcome of treatment are also sparse.

OBJECTIVE

To determine, in a prospective randomized, controlled clinical trial, the outcome of restorative therapy in periodontitis-susceptible patients who, following basic periodontal therapy, had been restored with implants with either a machined- or a rough-surface topography.

MATERIAL AND METHODS

Fifty-one subjects (mean age, 59.5 years), 20 males and 31 females who, following treatment of moderate-to-advanced chronic periodontitis, required implant therapy for prosthetic rehabilitation were recruited. Seventeen of the patients were current smokers. Following the active treatment, all subjects were included in an individually designed maintenance program. A total of 56 fixed partial dentures (FPDs) and a total of 149 screw-shaped, and self-tapping implants (Astra Tech implants) -- 83 in the maxilla and 66 in the mandible -- were installed in a two-stage procedure. Each patient received a minimum of two implants and by randomization every second implant that was installed had been designed with a machined surface and the remaining with a roughened Tioblast surface. Abutment connection was performed 3-6 months after implant installation. Clinical and radiographical examinations were performed following FPD connection and once a year during a 5-year follow-up period. The analysis of peri-implant bone-level alterations was performed on subject, FPD and implant levels.

RESULTS

Four patients and four FPDs were lost to the 5 years of monitoring. One implant (machined surface) did not properly integrate (early failure), and was removed at the time of abutment connection. Three implants were lost during function and a further eight implants could not be accounted for at the 5-year follow-up examination. The overall failure rate at 5 years was 5.9% (subject level), 5.3% (FPD level) and 2.7% (implant level). Radiographic signs of loss of osseointegration were not found at any of the implants during the 5-year observation period. During the first year in function there was on average 0.33 (SD, 0.61) mm loss of peri-implant marginal bone on the subject and FPD levels and 0.31 (0.81) mm on the implant level. During the subsequent 4 years, the peri-implant bone-level alterations were small. The calculated annual change in peri-implant bone level was -0.02 (0.15) on subject and FPD levels and -0.03 (0.20) on the implant level. Thus, the mean total bone-level change over the 5-year interval amounted to 0.41 mm on all three levels of analysis. In the interval between baseline and 5 years, the machined and the Tioblast implants lost on average 0.33 and 0.48 mm, respectively (p>0.05).

CONCLUSION

The present randomized, controlled clinical trial that included partially edentulous periodontitis-susceptible subjects demonstrated that bone loss (i) during the first year of function as well as annually thereafter was small and (ii) did not vary between implants with machined- or rough-surface designs.

Submerged or non-submerged healing of endosseous implants to be used in the rehabilitation of partially dentate patients. A multicenter, randomized controlled clinical trial

OBJECTIVE

To evaluate bone-level alterations that occurred at implants of the Astra Tech(R) System that were placed in the load carrying, posterior parts of the dentition using either a submerged (two-stage) or a non-submerged (one-stage) installation protocol.

MATERIAL AND METHODS

Eighty-four patients that required 115 fixed partial dentures (FPDs or cases) entered the prospective study. All subjects were assigned one patient and > or =one case numbers. For the randomization of cases, a custom-made program based on balanced random permuted blocks was utilized. The cases were assigned to two treatment groups, namely one-stage installation procedure, non-submerged technique (group A) and two-stage installation procedure, submerged technique (group B). Several subjects contributed with cases to both groups A and B. Periodontal, endodontal and open caries lesions were treated prior to implant installation. All patients received careful oral hygiene instruction and training in self-performed plaque control measures. The surgical technique used for fixture installation followed the outline described in the manual for the Astra Tech System. The FPDs were placed 3 months (mandible) and 6 months (maxilla) following implant installation. Immediately following FPD placement, a baseline examination was performed that included assessment of plaque, soft-tissue inflammation and bone level. Clinicians who were otherwise not involved in the study performed the radiographic measurements. Clinical and radiographical examinations were repeated once a year after the baseline examination.

DATA ANALYSIS

The primary outcome variable was the change in the bone level at the implants from the time of placement of the bridge (FPD) to the 1- and 2-year reexaminations. Fisher's permutation test was used to test if differences existed between groups A and B, and between patients (men/women, smokers/non-smokers, age), sites (maxilla/mandible) and implants (length, diameter). Pitman's test was used to study correlations between bone shape and quality data and different radiographic bone-level data.

RESULTS

It was demonstrated that tissue healing following implant installation appeared to be independent of the surgical protocol, i.e. whether the marginal portions of the implants during surgery were fully or only partly submerged under the ridge mucosa. Thus, (i) in both treatment groups the number of implants that failed to osseointegrate (early failures) was small (<2%); (ii) at the end of the recommended periods of bone healing prior to loading, - in both groups, maxilla=6 months and mandible=3 months - the level of the marginal bone was close to the coronal rim of the fixture; group A: 1.54+/-0.92 mm, group B: 1.31+/-0.77 mm. The current study also demonstrated that irrespective of surgical protocol (two-stage, one-stage), implants supporting the FPDs exhibited only small amount of radiographic bone loss during the first year of function (group A: 0.02+/-038 mm, group B: 0.17+/-0.64 mm). Moreover, during the second year of function, the amount of additional bone loss that occurred in the two treatment groups was close to zero.

CONCLUSION

Periimplant bone-level change during function seemed to be unrelated to whether initial soft- and hard-tissue healing following implant installation had occurred under submerged or non-submerged conditions.

Histological Analysis of the Ankylos Peri-implant Soft Tissues in a Dog Model

PURPOSE

The importance of the soft tissue-implant interface is enhanced by the presence of a microgap between the implant and the abutment, which represents a contamination site for bacteria. The aim of this study was to investigate the interface between the Ankylos gap-free implant system and the surrounding soft tissues in a dog model.

MATERIALS AND METHODS

Six Labrador dogs were included in the study and two Ankylos implants were inserted per dog. The dogs were killed 6 months after abutment placement without functional loading and without plaque control. The implants were analysed histologically by scanning electron microscopy, light microscopy, and histomorphometry.

RESULTS

Some sections exhibited histologic signs of a mild inflammation. The connective tissue between the most apical epithelial cells of the junctional epithelium and the alveolar crest was characterized by collagen fibers running from the periosteum and the alveolar crest toward the oral epithelium and, in front of the cone-shaped abutment, by a narrow zone of extracellular matrix with a few collagen fibers.

CONCLUSION

Compared with results obtained in other studies using different types of implant (Astra, Bränemark, ITI), the Ankylos implant showed a higher length and a larger width of connective tissue contact as well as a shorter epithelial downgrowth. The absence of a microgap in the Ankylos system could explain the histologic mild inflammation in the connective tissue.

Prevention. Part 5: Preventive strategies for patients requiring osseointegrated oral implant treatment

Prevention for patients requiring rehabilitation with oral implants is about preventing implant failure and biomechanical complications. This paper describes preventative strategies for the planning stage for implant treatment and the later maintenance period and indicates the level of scientific evidence supporting these strategies.

A systematic review of the incidence of biological and technical complications in implant dentistry reported in prospective longitudinal studies of at least 5 years

OBJECTIVE

To systematically review the incidence of biological and technical complications in implant therapy reported in prospective longitudinal studies of at least 5 years.

METHODS

A MEDLINE search was conducted for prospective longitudinal studies with follow-up periods of at least 5 years. Screening and data abstraction were performed independently by multiple reviewers. The types of complications assessed were as follows: implant loss, sensory disturbance, soft tissue complications, peri-implantitis, bone loss >or=2.5 mm, implant fracture and technical complications related to implant components and suprastructures.

RESULTS

The search provided 1310 titles and abstracts, out of which 159 were selected for full-text analysis. Finally, 51 studies were included. Meta analysis of these studies indicated that implant loss prior to functional loading is to be expected to occur in about 2.5% of all implants placed in implant therapy including more than one implant and when routine procedures are used. Implant loss during function occurs in about 2-3% of implants supporting fixed reconstructions, while in overdenture therapy >5% of the implants can be expected to be lost during a 5-year period. Few studies (41% of those included) reported data on the incidence of persisting sensory disturbance >1 year following implant surgery. Most of the studies that provided such data reported on the absence or a low incidence (1-2%) of this complication beyond this interval. A higher incidence of soft tissue complications was reported for patients treated with implants supporting overdentures. There is limited information regarding the occurrence of peri-implantitis and implants exhibiting bone loss >or=2.5 mm. Implant fracture is a rare complication and occurs in <1% of all implants during a 5-year period. The incidence of technical complications related to implant components and suprastructures was higher in overdentures than in fixed reconstructions.

CONCLUSION

Implant loss was most frequently described (reported in about 100% of studies), while biological complications were considered in only 40-60% and technical complications in only 60-80% of the studies. This observation indicates that data on the incidence of biological and technical complications may be underestimated and should be interpreted with caution.

Persistent acute inflammation at the implant-abutment interface

The inflammatory response adjacent to implants has not been well-investigated and may influence peri-implant tissue levels. The purpose of this study was to assess, histomorphometrically, (1) the timing of abutment connection and (2) the influence of a microgap. Three implant designs were placed in the mandibles of dogs. Two-piece implants were placed at the alveolar crest and abutments connected either at initial surgery (non-submerged) or three months later (submerged). The third implant was one-piece. Adjacent interstitial tissues were analyzed. Both two-piece implants resulted in a peak of inflammatory cells approximately 0.50 mm coronal to the microgap and consisted primarily of neutrophilic polymorphonuclear leukocytes. For one-piece implants, no such peak was observed. Also, significantly greater bone loss was observed for both two-piece implants compared with one-piece implants. In summary, the absence of an implant-abutment interface (microgap) at the bone crest was associated with reduced peri-implant inflammatory cell accumulation and minimal bone loss.

Treatment Planning for Implants Versus Root Canal Therapy: A Contemporary Dilemma

The predictability of implant fixtures as a long-term solution for edentulous areas has improved to the point where they have become the standard of care in many situations, in lieu of fixed prostheses. At the same time, the success rate of endodontically treated teeth, and those requiring retreatment, is very high as well. The dilemma presented to the clinician in treatment planning is when to retreat a tooth or extract and place an endosseous root-form implant. Risk assessment for prognostic evaluation plays an important role in the decision-making process. The clinical and systemic factors affecting the longevity of a tooth need be considered as well as location, bone quality and amount, and the condition of the patient's other teeth. This article attempts to provide a meaningful algorithm that will provide a basis for an appropriate choice of therapy.

Peri-implant bone regeneration using recombinant human bone morphogenetic protein-2 in a canine model: a dose-response study

The objective of this study was to evaluate the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) dose on alveolar ridge augmentation and dental implant osseointegration. Bilateral, 5 mm supraalveolar, peri-implant defects were surgically created in 6 beagle dogs. rhBMP-2 (0.05, 0.1 or 0.2 mg/ml) in an absorbable collagen sponge (ACS) carrier was molded around the fixtures and wounds were closed. Treatment variations were alternated between animals (incomplete block design). Animals were sacrificed at week 8 postsurgery. Nine of twelve jaw quadrants healed uneventfully. Two jaw quadrants exhibited wound failure by week 4 and one by week 8 postsurgery. Radiographic bone regeneration was observed in defects without wound failure from week 4 postsurgery. Radiolucent voids of variable size and shape were observed and regressed over time. In weeks 6 through 8, there was an apparent increase in bone density and trabecular structure, while bone height and volume decreased. Histometric analysis revealed limited differences in bone regeneration between experimental conditions. Bone regeneration area averaged (+/- SD) 1.0 +/- 0.5, 3.5 +/- 1.4 and 2.3 +/- 0.4 mm2 for the 0.05, 0.1 and 0.2 mg/ml dose, respectively. There were no significant differences in osseointegration. Osseointegration in newly formed bone averaged 19 +/- 4%, 18 +/- 10% and 21 +/- 6% for the 0.05, 0.1 and 0.2 mg/ml rhBMP-2 sites, respectively. Collectively, the data suggest that there are no dramatic differences in bone induction and osseointegration within the selected dose and observation interval.

The use of reduced healing times on ITI implants with a sandblasted and acid-etched (SLA) surface: early results from clinical trials on ITI SLA implants

ITI dental implants are available with two bone-anchoring surfaces, a titanium plasma-sprayed (TPS) surface, and a recently introduced sandblasted and acid-etched (SLA) surface. Cell culture and animal tests demonstrate that the SLA surface stimulates bone cell differentiation and protein production, has large amounts of bone-to-implant contact, and results in large removal torque values in functional testing of the bone contact. As a result of these studies, a prospective human clinical trial was initiated to determine whether the 4.1 mm diameter SLA ITI solid screw implants could be predictably and safely restored as early as six weeks after implant placement surgery. The protocol restricted the use of the reduced healing time to a) healthy patients with sufficient bone volume to surround the implant, and b) those patients who had good bone quality (classes I-III) at the implant recipient site. Patients with poorer bone quality (class IV) did not have restorations until 12 weeks after implant placement. The clinical trial is an ongoing multicenter trial, with six centers in four countries, and with follow-up over five years. The primary outcome variable was abutment placement with a 35 Ncm force, with no countertorque and no pain or rotation of the implant. A secondary outcome was implant success, as defined by no mobility, no persistent pain or infection, and no peri-implant radiolucency. To date, 110 patients with 326 implants have completed the one-year post-loading recall visit, while 47 patients with 138 implants have completed the two-year recall. Three implants were lost prior to abutment connection. Prosthetic restoration was commenced after shortened healing times on 307 implants. The success rate for these implants, as judged by abutment placement, was 99.3% (with an average healing time of 49 days). Life table analyses demonstrated an implant success rate of 99.1%, both for 329 implants at one year and for 138 implants at two years. In the 24-month period after restoration, no implant losses were reported for the 138 implants. These results demonstrate that, under defined conditions, solid screw ITI implants with an SLA endosseous surface can be restored after approximately six weeks of healing with a high predictability of success, defined by abutment placement at 35 Ncm without countertorque, and with subsequent implant success rates of greater than 99% two years after restoration.

Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible

BACKGROUND

Endosseous implants can be placed according to a non-submerged or submerged approach and in 1- or 2-piece configurations. Recently, it was shown that peri-implant crestal bone changes differ significantly under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of an interface (microgap) between the implant and abutment/restoration in 2-piece configurations. Several factors may influence the resultant level of the crestal bone under these conditions, including movements between implant components and the size of the microgap (interface) between the implant and abutment. However, no data are available on the impact of possible movements between these components or the impact of the size of the microgap (interface). The purpose of this study was to histometrically evaluate crestal bone changes around unloaded, 2-piece non-submerged titanium implants with 3 different microgap (interface) dimensions and between implants with components welded together or held together by a transocclusal screw.

METHODS

A total of 60 titanium implants were randomly placed in edentulous mandibular areas of 5 hounds forming 6 different implant subgroups (A through F). In general, all implants had a relatively smooth, machined suprabony portion 1 mm long, as well as a rough, sandblasted, and acid-etched (SLA) endosseous portion, all placed with their interface (microgap) 1 mm above the bone crest level and having abutments connected at the time of first-stage surgery. Implant types A, B, and C had a microgap of < 10 microns, approximately 50 microns, or approximately 100 microns between implant components as did types D, E, and F, respectively. As a major difference, however, abutments and implants of types A, B, and C were laser-welded together, not allowing for any movements between components, as opposed to types D, E, and F, where abutments and implants were held together by abutment screws. Three months after implant placement, all animals were sacrificed. Non-decalcified histology was analyzed histometrically by evaluating peri-implant crestal bone changes.

RESULTS

For implants in the laser-welded group (A, B, and C), mean crestal bone levels were located at a distance from the interface (IF; microgap) to the first bone-to-implant contact (fBIC) of 1.06 +/- 0.46 mm (standard deviation) for type A, 1.28 +/- 0.47 mm for type B, and 1.17 +/- 0.51 mm for type C. All implants of the non-welded group (D, E, and F) had significantly increased amounts of crestal bone loss, with 1.72 +/- 0.49 mm for type D (P < 0.01 compared to type A), 1.71 +/- 0.43 mm for type E (P < 0.02 compared to type B), and 1.65 +/- 0.37 mm for type F (P < 0.01 compared to type C).

CONCLUSIONS

These findings demonstrate, as evaluated by non-decalcified histology under unloaded conditions in the canine mandible, that crestal bone changes around 2-piece, non-submerged titanium implants are significantly influenced by possible movements between implants and abutments, but not by the size of the microgap (interface). Thus, significant crestal bone loss occurs in 2-piece implant configurations even with the smallest-sized microgaps (< 10 microns) in combination with possible movements between implant components.

Dental implants in periodontal therapy

Over the past 30 years, research has validated the success of osseointegrated implants as a viable alternative to fixed or removable prosthetic restorations. Periodontists are extensively trained in surgical procedures to treat and maintain patients with edentulous and partially edentulous arches. They also have a primary role in treatment planning and maintenance therapy. Thus, periodontists routinely integrate endosseous implants into periodontal therapy. This paper was prepared by the Research, Science and Therapy Committee of the American Academy of Periodontology and is intended to inform the dental profession regarding the utility of endosseous dental implants in the treatment of full and partial edentulism.

Crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible

BACKGROUND

Today, implants are placed using both non-submerged and submerged approaches, and in 1- and 2-piece configurations. Previous work has demonstrated that peri-implant crestal bone reactions differ radiographically under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of the interface (microgap) between the implant and abutment/restoration in 2-piece configurations. The purpose of this investigation was to examine histometrically crestal bone changes around unloaded non-submerged and submerged 1- and 2-piece titanium implants in a side-by-side comparison.

METHODS

A total of 59 titanium implants were randomly placed in edentulous mandibular areas of 5 foxhounds, forming 6 different implant subgroups (types A-F). In general, all implants had a relatively smooth, machined coronal portion as well as a rough, sandblasted and acid-etched (SLA) apical portion. Implant types A-C were placed in a non-submerged approach, while types D-F were inserted in a submerged fashion. Type A and B implants were 1-piece implants with the rough/smooth border (r/s) at the alveolar crest (type A) or 1.0 mm below (type B). Type C implants had an abutment placed at the time of surgery with the interface located at the bone crest level. In the submerged group, types D-F, the interface was located either at the bone crest level (type D), 1 mm above (type E), or 1 mm below (type F). Three months after implant placement, abutment connection was performed in the submerged implant groups. At 6 months, all animals were sacrificed. Non-decalcified histology was analyzed by evaluating peri-implant crestal bone levels.

RESULTS

For types A and B, mean crestal bone levels were located adjacent (within 0.20 mm) to the rough/smooth border (r/s). For type C implants, the mean distance (+/- standard deviation) between the interface and the crestal bone level was 1.68 mm (+/- 0.19 mm) with an r/s border to first bone-to-implant contact (fBIC) of 0.39 mm (+/- 0.23 mm); for type D, 1.57 mm (+/- 0.22 mm) with an r/s border to fBIC of 0.28 mm (+/- 0.21 mm); for type E, 2.64 mm (+/- 0.24 mm) with an r/s border to fBIC of 0.06 mm (+/- 0.27 mm); and for type F, 1.25 mm (+/- 0.40 mm) with an r/s border to fBIC of 0.89 mm (+/- 0.41 mm).

CONCLUSIONS

The location of a rough/smooth border on the surface of non-submerged 1-piece implants placed at the bone crest level or 1 mm below, respectively, determines the level of the fBIC. In all 2-piece implants, however, the location of the interface (microgap), when located at or below the alveolar crest, determines the amount of crestal bone resorption. If the same interface is located 1 mm coronal to the alveolar crest, the fBIC is located at the r/s border. These findings, as evaluated by non-decalcified histology under unloaded conditions, demonstrate that crestal bone changes occur during the early phase of healing after implant placement. Furthermore, these changes are dependent on the surface characteristics of the implant and the presence/absence as well as the location of an interface (microgap). Crestal bone changes were not dependent on the surgical technique (submerged or non-submerged).

Evaluation of recombinant human bone morphogenetic protein-2 in oral applications including the use of endosseous implants: 3-year results of a pilot study in humans

BACKGROUND

This study evaluated patients who had been treated with recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded in an absorbable collagen sponge (ACS) in human extraction sites or in sites that required alveolar ridge augmentation. An earlier report on the same patients revealed that after 4 months, implantation of rhBMP-2/ACS was safe, as determined by clinical, radiographic, systemic, and immunological analyses. In this longer-term follow-up, eligible patients were restored with endosseous dental implants in the area treated with rhBMP-2/ACS and bone biopsy samples were taken for histological analysis of the treated human bone tissue. The primary objective was to monitor the long-term safety of patients treated with rhBMP-2/ACS. Another objective was to evaluate the dental implants placed in the sites treated with rhBMP-2.

METHODS

Patient safety was evaluated by clinical examinations, periapical radiographs, and occurrence of adverse experiences. Dental implants were evaluated by radiographic and clinical examination. All 12 patients have been followed for 3 years.

RESULTS

Two years following surgical implantation of rhBMP-2/ACS, no serious or unexpected adverse experiences occurred. The adverse experiences that did occur were mostly benign and compatible with the dental implant surgeries performed in these patients. No adverse experiences were deemed as related to the rhBMP-2/ACS. Furthermore, no safety concerns in the local area of rhBMP-2/ACS placement were noted, based on oral wound examinations. In the 10 patients (6 extraction socket patients and 4 augmentation patients) who received endosseous implants, all implants were clinically stable at all assessments and all 10 patients have been functionally restored. Histological evaluation of the human bone core biopsies revealed normal bone tissue formation identical to the surrounding native bone. Three-year follow-up clinical examinations revealed that all implants had stable marginal bone levels and healthy peri-implant tissues.

CONCLUSIONS

These 3-year results demonstrate that rhBMP-2/ACS can be used safely in human patients. Human bone biopsies reveal normal bone formation in areas treated with rhBMP-2/ACS. Endosseous implants placed in these areas were all stable with no radiographic or clinical complications. The results from this study suggest that rhBMP-2/ACS (0.43 mg/ml) can be safely used in tooth extraction sites and in local ridge augmentation procedures and that endosseous dental implants placed in bony areas treated with rhBMP-2/ACS are stable and can be functionally restored without complication.

Aspartate aminotransferase activity in crevicular fluid from dental implants

BACKGROUND

Aspartate aminotransferase (AST) is an enzyme normally confined to the cytoplasm of cells, but released to the extracellular environment upon cell death. Its levels are associated with the severity of experimental gingivitis and the loss of periodontal attachment. The aim of the present study was to investigate the presence and activity levels of AST in peri-implant crevicular fluid (PCF) from healthy and diseased endosseous implants in order to assess if AST in PCF can be further studied as a possible objective diagnostic aid in oral implantology.

METHODS

Eighty-one fixtures from 81 systemically healthy subjects were divided into 3 groups, 27 healthy implants (HI), 27 implants with mucositis (MI) and 27 implants affected by peri-implantitis (PI) according to well-defined clinical and radiographic criteria. PCF was collected by the insertion of a #40 standardized endodontic paper point to the base of the crevice or pocket for 30 seconds. AST activity was determined spectrophotometrically at 25 degrees C. The results were expressed as AST Units/ml in PCF.

RESULTS

An AST activity was detected in each sample from HI, MI and PI. The mean AST activity in HI was 0.26 +/- 0.16 U/ml; in MI, 0.38 +/- 0.27 U/ml; in PI, 0.62 +/- 0.29 U/ml. ANOVA showed that the difference among HI, MI, and PI was statistically significant at P <0.01 level. Post-hoc tests demonstrated that a significant difference in AST activity existed between HI/PI (t = 5.14; P<0.01) and MI/PI (t = 3.09; P<0.01). No statistically significant difference was found between HI/MI (t = 1.07; P >0.1) AST activity was significantly (P <0.01) associated with probing depth (r = 0.55), the amount of bone loss (r = 0.60) and bleeding on probing (r = 0.67). When the threshold for a positive AST test was set > or =0.4 U/ml, a sensitivity = 0.81 and a specificity = 0.74 were found in the detection of peri-implantitis; the positive predictive value was 61% and the negative predictive value was 88%.

CONCLUSIONS

Within the limits of this study, our results may suggest that PCF analysis could be further investigated in longitudinal studies as a suitable diagnostic strategy in the evaluation of dental implants.

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.

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.

Comparison of bioactive glass to demineralized freeze-dried bone allograft in the treatment of intrabony defects around implants in the canine mandible

BACKGROUND

The purpose of this study was to evaluate and compare the healing of different bone grafting materials adjacent to titanium plasma-sprayed (TPS) endosseous dental implants.

METHODS

Implant osteotomy sites were prepared and standardized 3-walled intrabony defects (3 mm x 5 mm x 5 mm) were created at the mesial of each implant site. Thirty-two TPS implants were placed in edentulous mandibular ridges of the 4 dogs. Periodontal dressings were placed in the defect sites so as to create a defect simulating bone loss around an implant. After 3 months, the periodontal dressing was removed, the defect sites debrided and evaluated for size, and intramarrow penetration performed. The graft materials tested were 1) canine demineralized freeze-dried bone allograft (cDFDBA); 2) bioactive glass granules of a broad size range 90 to 710 microns (BRG); and 3) bioactive glass granules of narrow size range 300 to 355 microns (NRG). One site on each side of the mandible was not filled and served as a control. Dogs were sacrificed 4 months after graft placement.

RESULTS

Histologically, differences in percent bone-to-implant contact in the defect area were observed between the treatment groups. cDFDBA>control=BRG=NRG with statistical significance found between cDFDBA and control (P = 0.0379), but no statistically significant difference between control or either bioactive glass material. When comparing percent bone height fill of the defect in the grafted area, cDFDBA (65.7%) was significantly better than the control (48.9%; P < or = 0.05) with no statistically significant difference between control, broad range bioactive glass (57.3%) and narrow range bioactive glass (56.6%). When total bone area was measured, the percentage of new bone in the grafted area was cDFDBA (42.1%), broad range glass (33.1%) and narrow range glass (22.6%) with significance found between cDFDBA and NRG (P = 0.0102). The content of residual graft particles in soft tissue was significant (P = 0.0304) between cDFDBA (1.4%) and NRG (11.4%) with no significant difference between graft material for residual particle content in bone tissue.

CONCLUSIONS

The results of this study indicate that percent bone-to-implant contact and percent bone height fill in an intrabony defect around titanium plasma-sprayed implants are statistically significantly higher with the use of DFDBA when compared to bioactive glass material.

Recombinant human bone morphogenetic protein-2 stimulation of bone formation around endosseous dental implants

BACKGROUND

Successful endosseous implant placement requires that the implant be stable in alveolar bone. In certain cases, the implant can be stabilized in native bone but some part of the implant is not covered by bone tissue. This often occurs during placement of implants into extraction sites or in areas where bone resorption has occurred and the ridge width is not sufficient to completely surround the implant. In those cases, the clinician usually employs a procedure to encourage bone formation. These procedures typically include a bone graft and/or membrane therapy. Recent advances have led to the isolation, cloning, and production of recombinant human proteins that stimulate bone formation. One of these bone morphogenetic proteins (rhBMP-2) has been extensively studied in animal models and is currently being tested in human clinical trials.

METHODS

In this study, rhBMP-2 was tested using a collagen sponge carrier to stimulate bone formation in defects in the canine mandible around endosseous dental implants. Six animals had a total of 48 implants placed. rhBMP-2 with the collagen carrier was implanted around 24 of these, the remainder having only the collagen carrier placed. Half the sites were covered with a nonresorbable expanded polytetrafluoroethylene membrane. Histologic analysis was performed after 4 and 12 weeks. The area of new bone formed, percentage of bone-to-implant contact in the defect area, and percentage fill of the defect was calculated.

RESULTS

The addition of rhBMP-2 resulted in significantly greater amounts of new bone area and percentage of bone-to-implant contact and with more percentage fill after 4 and 12 weeks of healing. The area of new bone formed was reduced after 4 weeks when a membrane was present but after 12 weeks, there was no significant difference between membrane and non-membrane treated sites. In some specimens, new bone was found coronal to the membranes, with rhBMP-2-treated sites having greater amounts than non-rhBMP-2-treated sites.

CONCLUSIONS

These data demonstrate that a bone differentiation factor significantly stimulates bone formation in peri-implant bone defects in the canine mandible. In addition, bone-to-implant contact was significantly enhanced along the rough implant surface. Membrane-treated sites had less new bone formation after 4 weeks of healing but were similar to non-membrane sites after 12 weeks. These results demonstrate that rhBMP-2 can be used to stimulate bone growth both around and onto the surface of endosseous dental implants placed in sites with extended peri-implant osseous defects.

The soft tissue response to osseointegrated dental implants

The use of dental implants in the treatment of fully edentulous patients has become an important addition in oral/dental rehabilitation. The fact that these implants penetrate the oral mucosa can lead to the assumption that peri-implant tissues, similar to the periodontal tissues, are fulfilling an important function as a barrier to protect the bony anchorage underneath. It has been shown that insufficient plaque removal may lead to peri-implant tissue disease with bone loss similar to teeth. However, it is unclear how important this cause is as a source of implant failure compared with other factors, such as inadequate bone healing, unfavorable quantity and quality of bone, or (bio)mechanical and functional problems. It is also not understood if peri-implant epithelium and connective tissue are equally needed and/or qualified to slow down or prevent tissue breakdown as their periodontal counterparts. The scientific work focusing on peri-implant soft tissues has dramatically increased in the past few years. Most studies to date have examined and described their structure but little data exist on their true biologic function. This review analyzes the current understanding of morphologic and clinical features of the peri-implant soft tissues. Furthermore, evidence shall be provided that peri-implant soft tissues do not interfere with the current favorable results obtained when treating the edentulous patient with osseointegrated implants.

Evidence-based periodontal treatment. Highlights from the 1996 World Workshop in Periodontics

State-of-the-art periodontal therapy involves a wide range of diagnostic and treatment options. The 1996 World Workshop in Periodontics used an evidence-based approach to assess the efficacy of many of these options. This article describes the evidence-based approach and summarizes the findings of the workshop in the areas of diagnosis and nonsurgical and surgical periodontal therapy as well as dental implants.