Effects of different implant surfaces and designs on marginal bone-level alterations: a review

Objective: The purpose of this review was to evaluate the effect of different implant surfaces and designs on marginal bone-level (MBL) alterations.
Material and methods: A MEDLINE search (PubMed) was performed to identify clinical, prospective and controlled studies using a sufficient sample size (>10 subjects) and with a follow-up time of ≥3 years.
Results: Ten publications fulfilled the inclusion criteria. Two studies evaluated the influence of implant surface characteristics and two studies reported on the effect of implant design on MBL changes. Six publications analyzed the combined effect of different implant surfaces and designs on MBL alterations. As revealed from available studies, there is no evidence that modified surfaces are superior to non-modified implant surfaces in marginal bone preservation. One study reported on significantly improved MBL preservation for implants with a conical and micro-threaded marginal collar than implants with a cylindrical and non-threaded marginal portion after 3 years in function. No implant system was found to be superior in marginal bone preservation.     

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.     

Clinical evaluation of dental implants with surfaces roughened by anodic oxidation, dual acid-etched implants, and machined implants

PURPOSE: The purpose of this study was the clinical and radiographic comparison of dental implants with surfaces roughened by anodic oxidation (TiUnite), dual acid-etched implants (Osseotite), and machined implants. MATERIALS AND METHODS: Seventy-four patients (mean age, 52.8 +/- 14.2 years; range, 23 to 80 years; 41 men and 33 women) received 198 dental implants-58 TiUnite implants (25 patients), 52 Osseotite implants (27 patients), and 88 machined implants (22 patients). Clinical measurements and radiographs were evaluated at the time of surgery, at the restorative phase, and 2 years postloading. To account for statistical correlation among multiple implants in the same subject, a "per patient" mode of analysis was conducted. A 1-way analysis of variance of bone loss was conducted by type of implant as well by area of the mouth. In addition, differences in mean bone loss were tested for bone density category, gender, and smoking status using Student t tests. RESULTS: Eighteen TiUnite implants (31.0%) were placed in the maxilla and 40 (69.0%) in the mandible. The Osseotite group included 29 maxillary implants (55.8%) and 23 mandibular implants (44.2%). The machined group included 49 maxillary implants (55.7%) and 39 mandibular implants (44.3%). All 198 implants were considered radiographically and clinically successful. No mobility, signs of infection, or inflammation were detected. DISCUSSION: Implant size, location, bone quality, gender, age, and smoking did not influence the comparative clinical outcomes of the 3 groups (P > .05). A trend toward greater coronal bone loss in the TiUnite group was detected. CONCLUSION: Within the limitations of the present study, TiUnite, Osseotite, and machined dental implants had similar short-term clinical outcomes. No statistically significant differences in bone loss could be detected among implant groups or among the different regions of the oral cavity. The present data underlined the significance of surgical and prosthetic treatment planning.     

Histologic evaluation of early human bone response to different implant surfaces

BACKGROUND: Studies have demonstrated that roughened dental implant surfaces show firmer bone fixation and an increased percentage of bone-to-implant contact (BIC%) compared to commercially pure titanium-surface (machined) implants. Therefore, the purpose of this study was to evaluate the influence of implant-surface topography on human bone tissue after 2 months of unloaded healing. METHODS: Fourteen subjects with a mean age of 46.87 +/- 9.45 years received two microimplants each (2.5 mm in diameter and 6 mm in length), one test (sandblasted acid-etched surface) and one control (machined surface), either in the mandible or in the maxilla. After a healing period of 2 months, the microimplants and surrounding tissues were removed with a trephine bur and prepared for histologic analysis. RESULTS: All microimplants, except for one of the controls, were clinically stable after the healing period. Histometric evaluation indicated that the mean BIC% was 23.08% +/- 11.95% and 42.83% +/- 9.80% for machined and rough microimplant surfaces, respectively (P = 0.0005). The bone area within the threads was also higher for sandblasted-surface implants (P = 0.0005). The mean percentage of bone density did not differ between the two groups (P = 0.578). CONCLUSION: Data from the present histological study suggest that the sandblasted acid-etched implant provides a better human bone tissue response than machined implants under unloaded conditions after a healing period of 2 months.     

State of the art in oral implants

Abstract. Uncontrolled oral implant devices are still being widely used. The documentation of most oral implant systems is poorly backed up or not followed up for an adequate time period. Success rates are being quoted without reference to any defined success criteria. Frequently used oral implant designs such as the Core-Vent, IMZ and Calcitek hydroxyapatite coated implants are in neither case supported by any adequate clinical reports from minimally 5-years of follow-up. Other implant systems such as the ITI, some subperiosteal designs and the Tubingen implant demonstrate well-controlled and acceptable 5-year data but are not followed up in a sufficient number or have demonstrated less good results in the 10-year evaluation. The Small transosteal staple has been adequately reported for more than 10 years of follow-up, whereas the Branemark implant is the only endosseous design that has demonstrated acceptable 15-year success rates.     

Preliminary 3-dimensional surface texture measurement and early loading results with a microtextured implant surface

PURPOSE: This investigation was conducted to obtain preliminary roughness data on a microtextured implant surface and to determine its ability to sustain a 1-stage surgical procedure and early full occlusal loading of single-tooth restorations in humans. MATERIALS AND METHODS: Three-dimensional (3D) vertical scanning interferometry was conducted on samples of the test surface (MTX) and 2 control surfaces (Osseotite and sandblasted/acid-etched [SLA]). Test implants were also placed in vivo, restored with fully occluding single-tooth restorations (n = 27) after 2 months of nonsubmerged healing, and clinically monitored for 48 months of follow-up. RESULTS: Microtexture was relatively uniform on the test surface and more random and irregular on the control surfaces. MTX and Osseotite were similar in some roughness parameters, but the MTX surface had a greater number of micropits that were spaced closer together (Stylus Y lambda q) and with higher slope values (Stylus Y delta q). Cumulative life table results were 100% for all MTX implants placed in maxillary and mandibular jaw locations, and no discernible marginal bone changes were observed. Overall implant success was 100% after 4 years of clinical functioning. DISCUSSION: The findings of this study appear promising but should be considered preliminary, because of the limitations in the number of locations measured on each product sample and the small number of implants clinically studied. CONCLUSION: Within the scope of the present study, MTX implants exhibited a uniform micropitted surface, as well as 100% survival and 100% clinical success after nonsubmerged placement, early loading with single-tooth restorations at 2 months, and 48 months of clinical functioning. (More than 50 references.)     

Oral implant surfaces: Part 1--review focusing on topographic and chemical properties of different surfaces and in vivo responses to them

PURPOSE: This article reviews the topographic and chemical properties of different oral implant surfaces and in vivo responses to them. MATERIALS AND METHODS: The article considers detailed mechanical, topographic, and physical characteristics of implant surfaces. Anchorage mechanisms such as biomechanical and biochemical bonding are examined. Osteoattraction and doped surfaces are discussed. RESULTS: Surface quality of an oral implant may be subdivided into mechanical, topographic, and physicochemical properties. Topographic properties are evaluated at the micrometer level of resolution. Moderately rough surfaces (Sa between 1.0 and 2.0 microm) show stronger bone responses than smoother or rougher surfaces. The majority of currently marketed implants are moderately rough. Oral implants permit bone ingrowth into minor surface irregularities-biomechanical bonding or osseointegration. Additional biochemical bonding seems possible with certain surfaces. Osteoattraction is a commercial term without precise biologic correspondence. Surfaces doped with biochemical agents such as bone growth factors have been developed. CONCLUSION: Moderately roughened surfaces seem to have some clinical advantages over smoother or rougher surfaces, but the differences are small and often not statistically significant. Bioactive implants may offer some promise.     

Bone response to modified titanium surface implants in nonhuman primates (Papio ursinus) and humans: histological evaluation

The aim of this study is a comparative histological and histomorphometrical evaluation of the effect on early bone formation of 2 different implant surfaces: a machined and a new acid-etched implant surface (Leader, Milano, Italy). Ten screw-type microimplants were placed in 5 patients. Each patient received 2 microimplants (2 mm in diameter and 5 mm in length): 1 with a machined surface (control) and 1 with an acid-etched surface (test). The microimplants were retrieved after 60 days of healing with a 4-mm trephine bur and processed for histology. Moreover, 24 regular size implants--12 with a machined surface (control) and 12 with an acid-etched surface (test)--were placed in 2 adult nonhuman primates 3 months after the extraction of premolars and molars. Each animal received 3 machined implants (control) in the right hemimandible and 3 acid-etched implants (test) in the left hemimandible. The same animals received 3 control implants and 3 test implants in the rectus abdominis muscle. After 1 month, the implants were retrieved from the mandible and the rectus abdominis muscle and processed for histology. Histomorphometric evaluation demonstrated a higher bone-to-implant contact in the test implants compared with the controls in both primates (25.55% vs 15.8%) and humans (62% vs 45%). Moreover, in nonhuman primates after 1 month of healing, it was possible to observe a poor osseointegration in the control specimens, while newly formed bone in direct contact with test implants was evident. The rectus abdominis muscle specimens showed that the acid-etched surfaces can stimulate the formation and attachment of new connective and vascular tissues more than machined surfaces can. Implant surface geometry can speed up bone formation by the development of a special microenvironment that promotes angiogenesis. Long-term studies are needed to further test this new acid-etched implant surface.     

The single-tooth implant: a viable alternative for single-tooth replacement

BACKGROUND: The use of dental implants for single-tooth replacement cases introduces a challenge to the performance of these restorations. Clinical data suggest that single-tooth implant restorations do not benefit from lateral support from the surrounding dentition as do bridged implants, and that these restorations are subjected to greater masticatory forces. Therefore, single-tooth implants are exposed to an increased risk of failure. This prospective clinical trial was designed to evaluate the cumulative success rate of dual acid-etched single-tooth replacement implants in two clinical centers. METHODS: The study protocol included 59 patients between 19 and 73 years. Implants were evaluated for mobility, infection, and crestal bone loss from 30.9 to 60 months. RESULTS: Seventy-one (71) implants were placed in 59 patients, 20 male and 39 female. Forty-seven (47) were placed in the maxilla and 24 in the mandible. The percentages of anterior and posterior implants were 45.1% and 54.9%, respectively. A total of 13 (18.4%) implants were placed in soft, poor quality (Type IV) bone. Beginning 1 month post-implant placement, cases were followed for 30.9 to 60 months with a mean follow-up of 45.9 months. One implant failed (peri-implant infection) yielding an overall success rate of 98.6%. CONCLUSIONS: This success rate for single-tooth replacement dual acid-etched implants compares favorably with bridged implants and with success rates of other single-tooth implant studies. Dual acid-etched implants performed well even under conditions of poor quality bone, where concomitant bone augmentation was performed, and when used for immediate replacement of extracted teeth.     

Effect of modifications of dual acid-etched implant surfaces on peri-implant bone formation. Part I: organic coatings

Objective: The aim of the present study was to test the hypothesis that peri-implant bone formation can be improved by modifying dual acid-etched (DAE) implant surfaces using organic coatings that enhance cell adhesion and osteogenic differentiation.
Material and methods: Ten adult female foxhounds received experimental titanium implants in the mandible 3 months after removal of all premolar teeth. Six types of implants were evaluated in each animal: (i) implants with a machined surface (MS), (ii) implants with a DAE surface topography, (iii) implants with an acid-etched surface coated with RGD peptides, (iv) implants with an acid-etched surface coated with collagen I, (v) implants with an acid-etched surface coated with collagen I and chondroitin sulphate (CS), (vi) implants with an acid-etched surface coated with collagen I and CS and recombinant human bone morphogenetic protein-2. Peri-implant bone regeneration was assessed by histomorphometry after 1 and 3 months in five dogs each by measuring bone implant contact (BIC) and the bone volume density (BVD) of the newly formed peri-implant bone.
Results: After 1 month, mean BIC was significantly higher in the coated implants group than in the MS group. There was no significant difference when mean BIC in the DAE group was compared with implants with any of the organic coatings, but the difference was significant when compared with the MS implants. Differences in mean BVD value did not reach significance between any of the surfaces. After 3 months, the same held true for the mean BIC of all the groups except for Coll I. Mean volume density of the newly formed bone was higher in all the surface modifications, albeit without statistical significance.
Conclusions: It is concluded that with the exception of Coll I, the tested organic surface coatings on DAE surfaces did not improve peri-implant bone formation when compared with the DAE surfaces but enhanced BIC when compared with the MSs.     

Immediate restoration of single-tooth implants in mandibular molar sites: a 12-month preliminary report

PURPOSE: The aim of this prospective clinical study was to evaluate the survival rates at 12 months of transmucosal implants placed in the posterior mandible and immediately restored with single crowns. MATERIALS AND METHODS: Thirty ITI dental implants with sandblasted, acid-etched surfaces were placed in 30 patients missing at least 1 mandibular molar and immediately restored if acceptable primary stability was attained. Primary stability was measured with resonance frequency analysis (RFA) using the Osstell device, and only implants with a stability quotient greater than 62 were included in the study. RFA measurement and radiographic assessment were made at baseline and 6 months after implant placement. Plaque Index, Bleeding Index, probing depth, attachment level, and width of keratinized tissue were measured at the 12 month follow-up examination. RESULTS: At 12 months, only 1 implant had been lost; it was removed because of acute infection. Radiographic as well as clinical examination confirmed osseointegration of all implants, with a survival rate of 96.7%. DISCUSSION: Interestingly, implant stability as measured using RFA did not increase significantly from baseline to 12 months (P > .05). CONCLUSION: The present study showed that immediate restoration of transmucosal implants placed in the mandibular area with good primary stability can be a safe and successful procedure. However, larger, long-term clinical trials are needed to confirm the present results.     

Bone-implant contact on machined and dual acid-etched surfaces after 2 months of healing in the human maxilla

BACKGROUND: Recent clinical studies indicate that an implant with a textured surface may be loaded sooner than traditional healing protocols have recommended. In a previous study, the 6-month bone-implant contact for dual acid-etched and machined implant surfaces was reported to be 72.96% and 33.98%, respectively. In 1991, a minimum of 50% bone-implant contact was considered necessary for loading to ensure long-term survival of the implant. This study evaluated the 2-month bone-implant contact for dual acid-etched and machined implant surfaces to determine if this criterion had been met. METHODS: Custom manufactured implants (2 mm diameter and 5 mm length), having on one side a machined surface and on the other side a dual acid-etched surface, were placed in the posterior maxilla of 11 patients, allowed to integrate for 2 months, then removed using a 4 mm internal diameter trephine with irrigation. Sections were processed and stained for histologic and histomorphometric analysis. The parameters calculated for each section were: bone volume (BV%), actual percent bone-implant contact (BIC%), and expected bone contact (EBC%) as determined from 3 implant images superimposed onto the adjacent bone 150, 500, and 1,000 microm lateral to the actual implant surface and representing the bone-implant contact expected on the day the implant was placed, based on the peri-implant bone volume. RESULTS: Histomorphometric analysis indicated that the mean BV% of 36.77% from all sections was closely matched to the mean EBC% of 34.36% (P<0.001). The analysis showed that after 2 months of healing, the 47.81% BIC% on the dual acid-etched side was statistically higher (analysis of variance, P<0.001) than the 19.00% BIC% on the machined side. In areas of low-density bone (<40% BV%), the difference between the BIC% for the machined and dual acid-etched sides was even greater. Nine of the 11 dual acid-etched sides had a higher BIC% than the EBC% value. In the machined group, 1 of the 11 sides had a higher BIC% value than the EBC% value. The bone surrounding the dual acid-etched surface was a woven bone with thin, connecting peri-implant bony trabeculae projecting into and between the threads. Bone on the machined side was observed mostly contacting the tips of the screw threads. CONCLUSIONS: At 2 months, the mean BIC% for the dual acid-etched group increased 39.14% compared to the EBC% value, while the mean BIC% for the machined group decreased 44.70%. Based on the histomorphometric results of this study, sufficient bone for functional loading of the implant exists on a dual acid-etched surface after 2 months of healing in the posterior maxillary arch.     

Enhanced implant stability with a chemically modified SLA surface: a randomized pilot study

PURPOSE: Chemical modification to a sandblasted, large-grit, acid-etched (SLA) implant surface has been shown to enhance the rate of osseointegration. The goal of the present study was to examine changes in stability for implants with a chemically modified SLA surface and to compare their outcomes to those of control implants. MATERIALS AND METHODS: A randomized controlled trial was conducted with 31 patients. Each patient received 2 implants with the same physical properties but with surfaces that were chemically different. The control implants had a standard SLA surface, while the test implants had a chemically modified surface. Resonance frequency analysis was assessed weekly over the first 6 weeks following implant placement. RESULTS: All implants proved clinically successful, allowing for restoration. Most implants were placed in the mandible (50 of 62). A shift in implant stability from decreasing stability to increasing stability (P < .001), occurred after 2 weeks for the test implants and after 4 weeks for the control implants. CONCLUSION: The findings from this pilot study provide clinical support for the potential for chemical modification of the SLA surface to alter biologic events during the osseointegration process and demonstrate levels of short-term clinical success similar to those observed for implants with an SLA surface.     

Surface analysis of machined versus sandblasted and acid-etched titanium implants

Initially, implant surface analyses were performed on 10 machined implants and on 10 sandblasted and acid-etched implants. Subsequently, sandblasted and acid-etched implant cytotoxicity (using L929 mouse fibroblasts), morphologic differences between cells (osteoblast-like cells MG63) adhering to the machined implant surfaces, and cell anchorage to sandblasted and acid-etched implant surfaces were evaluated. Results indicated that acid etching with 1% hydrofluoric acid/30% nitric acid after sandblasting eliminated residual alumina particles. The average roughness (Ra) of sandblasted and acid-etched surfaces was about 2.15 microns. Cytotoxicity tests showed that sandblasted and acid-etched implants had non-cytotoxic cellular effects and appeared to be biocompatible. Scanning electron microscopic examination showed that the surface roughness produced by sandblasting and acid etching could affect cell adhesion mechanisms. Osteoblast-like cells adhering to the machined implants presented a very flat configuration, while the same cells adhering to the sandblasted and acid-etched surfaces showed an irregular morphology and many pseudopodi. These morphologic irregularities could improve initial cell anchorage, providing better osseointegration for sandblasted and acid-etched implants.     

Radiologic follow-up of peri-implant bone loss around machine-surfaced and rough-surfaced interforaminal implants in the mandible functionally loaded for 3 to 7 years

PURPOSE: In this retrospective study, marginal peri-implant bone height around machined and sandblasted/acid-etched interforaminal implants in the mandible was evaluated radiologically at least 3 years after functional loading. MATERIALS AND METHODS: Fifty-one patients, each with 4 interforaminal screw-type implants placed between 1994 and 1998, were included in this study. Of these, 36 patients (70.6%) with a total of 144 implants (76 machined Mk II implants and 68 sandblasted/acidetched Frios implants) were available for follow-up studies. Interforaminal marginal bone loss was evaluated by extraoral rotational panoramic radiographs. In addition, predictive factors such as patient age and sex, nicotine use, implant position, implant life, and site of measurement were recorded, as well as bone loss at surgery (ie, baseline bone loss). Analysis of covariance for repeated measurements was used for statistical analysis. Between-group differences were expressed as least square means +/- standard error. RESULTS: Sandblasted/acid-etched implants showed significantly less marginal bone loss than machine-surfaced implants (2.4 +/- 0.23 mm vs 1.64 +/- 0.27 mm). Implants placed in the anterior of the arch showed significantly more peri-implant bone loss than implants placed in the posterior (P = .0001). DISCUSSION AND CONCLUSIONS: Significantly less long-term peri-implant bone loss was observed for rough implant surfaces compared to machine-surfaced implants. However, it was also demonstrated that both types of implants, in combination with bar-supported overdentures, can produce excellent long-term results in the atrophic edentulous mandible. Mesially placed implants showed more bone resorption than distally positioned implants, independent of surface roughness.     

Long-term observation of porous sapphire dental implants

We used porous sapphire dental implants made of alumina clinically for 4 years 1 month, commencing September, 1984 until September, 1988. Subjects consisted of 18 men and 42 women 20-71 years old (mean age: 35 years). Sixty-five implants were inserted in 60 patients. Of these, 20 were clinical cases of an implant connected with natural teeth and 45 were free-standing cases. We conducted a follow-up study on these patients over a 23-year period. One implant in 1 patient had to be removed because of postoperative infection and 8 implants in 7 patients had to be removed because of fracturing or detachment of the porous-part. This paper reports 3 cases where implants remained in place for 21-23 years. These cases have all shown good long-term clinical progress.     

The role of surface roughness in promoting osteointegration

Scientific evidence that has been gathered in the past 20 years established that certain endosseous dental implants--primarily screw-type implants made of commercially pure titanium can be successfully utilized as anchorage for dental prostheses. In recent years, an effort has been made to simplify the surgical procedure, in order to modify clinical treatment modalities. One of the trends is to increasingly utilize microrough titanium implants. Roughened implant surfaces have a long history in implant dentistry, and the most prominent surface is titanium plasma-sprayed (TPS). In recent years new implant surfaces have emerged, so-called microrough titanium surfaces produced with reducing techniques such as grit-blasting with Al2O3 or TiO2 particles, sandblasting and acid-etching, or acid-etching alone. These different titanium surfaces have been tested in numerous in-vivo studies utilizing different animal models. Summarizing the results of these studies, it can be concluded that there is currently sufficient evidence that titanium implants with a microrough surfaces achieve a faster bone integration, a higher percentage of Bone implant Contact (BIC), and a higher resistance to shear documented with higher Removal Torque Values (RTV) when compared with titanium implants with a polished or machined surface. In order to understand the mechanism through which surface roughness modulates its effects mentioned above, recent studies used in-vitro experimental methods to study cell response to implant surface topography. These studies have shown that osteoblasts are sensitive to surface roughness, exhibiting decreased proliferation and a more differentiated phenotype on rougher surfaces. PGE2 production is enhanced on rough surfaces, as is the production of TGF beta 1, suggesting that surface roughness can mediate autocrine and paracrine regulation of osteogenesis. Moreover, surface roughness was found to modulate the effect of systemic hormones like 1,25-(OH)2D3 on osteoblasts. The clinical advantages of implants with rough surface were observed in recently conducted clinical trials. It was found, in humans, that roughened titanium implants need shorter healing period before loading, 6-8 (SLA and Osseotite respectively) weeks instead of 12 weeks. The clinical advantages of shorter healing periods are obvious. Moreover, it was found that certain roughened implants can be used in shorter sizes (6-8 mm) then accepted today. The utilization of shorter implants offers the avoidance of extensive surgical procedures such as nerve lateralization in the mandible or sinus grafting in the maxilla. However, sufficient long term documentation is still lacking, and the predictability of such modalities has yet to be examined in long term prospective clinical trials.     

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.     

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.