Bone response to functionally loaded, two-piece zirconia implants: A preclinical histometric study.

OBJECTIVE: To evaluate the bone response to a two-piece zirconia implant in comparison with a control titanium implant in the canine mandible 4 and 16 weeks after restoration. MATERIAL AND METHODS: Zirconia and titanium implants were alternately placed bilaterally in healed mandibular molar and premolar sites of five canines. Full-ceramic single-tooth restorations were cemented after 6 weeks of transmucosal healing, allowing for full functional loading of the implants. Histologic and histometric analyses were performed on orofacial and mesiodistal undecalcified sections of the specimens obtained upon sacrifice after 4 and 16 weeks of functional loading. Bone-to-implant contact (BIC), multinucleated giant cells-to-implant contact (MIC), crestal bone level, and peri-implant bone density were histometrically assessed. RESULTS: All 60 implants and 60 restorations were still in function after 4 and 16 weeks of loading in both test and control groups. No implant loss, no implant or abutment fracture, and no chipping of the restorations could be detected. Histometric analysis showed no statistically significant differences between zirconia and titanium implants in BIC, crestal bone level, and peri-implant bone density at both time points. Between 4 and 16 weeks, the crestal bone level around zirconia implants showed a small but statistically significant increase in its distance from the implant shoulder. MIC was very low on both implant types and both time points and decreased statistically significantly overtime. CONCLUSION: The present two-piece zirconia implant showed a similar bone integration compared to the titanium implant with similar surface morphology after 4 and 16 weeks of loading.

Bone changes around early loaded chemically modified sandblasted and acid-etched surfaced implants with and without a machined collar: a radiographic and resonance frequency analysis in the canine mandible.

PURPOSE: The purpose of this study was to evaluate the radiographic bone level and stability changes around early loaded chemically modified sandblasted and acid-etched implants with and without a machined collar. MATERIALS AND METHODS: Seventy-two chemically modified sandblasted and acid-etched implants 4.1 mm in diameter and 8 mm in length were placed in six dogs. Thirty-six implants had no machined collar (NMC) and 36 had a 2.8-mm machined collar (MC). Resonance frequency measurements were obtained at placement and weekly for 3 weeks. All implants were loaded 21 days after surgery. Standardized periapical radiographs were obtained at baseline, at 3 weeks, and at 3, 6, 9, and 12 months. The radiographs were randomized and digitized, and linear measurements of the distance from the first bone-to-implant contact to the shoulder of the implant were performed at the mesial and distal aspects of each implant. For statistical analysis, mixed-model repeated-measures analysis of variance was used. RESULTS: All implants achieved hard and soft tissue integration clinically and radiographically and were clinically immobile. From placement to week 3, the mean implant stability increased for MC implants by more than 5 ISQs and for NMC implants by more than 7 ISQs. Radiographically, there were significant differences between treatment groups beginning at 3 months. After 12 months of loading, the MC implants presented a mean bone loss of 1.00 mm and the NMC implants presented a mean bone gain of 0.11 mm. CONCLUSIONS: Chemically modified sandblasted and acid-etched implants without a machined collar presented bone gain, and implants with a machined collar showed bone loss after a 1 year following early (21-day) loading. The tendency toward a coronal apposition of bone observed under these conditions may be attributed to the osteoconductive properties of the chemically modified surfaces of these implants and to the absence of the machined collar.

Bone response to loaded implants with non-matching implant-abutment diameters in the canine mandible.

BACKGROUND: One way to evaluate various implant restorations is to measure the amount of bone change that occurs at the crestal bone. The objective of this study was to histologically evaluate the alveolar bone change around a bone-level, non-matching implant-abutment diameter configuration that incorporated a horizontal offset and a Morse taper internal connection. METHODS: The study design included extraction of all mandibular premolars and first molars in five canines. After 3 months, 12 dental implants were placed at three levels in each dog: even with the alveolar crest, 1 mm above the alveolar crest, and 1 mm below the alveolar crest. The implants were submerged on one side of the mandible. On the other side, healing abutments were exposed to the oral cavity (non-submerged). Gold crowns were attached 2 months after implant placement. The dogs were sacrificed 6 months postloading, and specimens were processed for histologic and histometric analyses. RESULTS: Evaluation of the specimens indicated that the marginal bone remained near the top of the implants under submerged and non-submerged conditions. The amount of bone change for submerged implants placed even with, 1 mm below, and 1 mm above the alveolar crest was -0.34, -1.29, and 0.04 mm, respectively (negative values indicate bone loss). For non-submerged implants, the respective values were -0.38, -1.13, and 0.19 mm. For submerged and non-submerged implants, there were significant differences in the amount of bone change among the three groups (P <0.05). The percentage of bone-to-implant contact for submerged implants was 73.3%, 71.8%, and 71.5%. For non-submerged implants, the respective numbers were 73.2%, 74.5%, and 76%. No significant differences occurred with regard to the percentage of bone contact. CONCLUSIONS: Minimal histologic bone loss occurred when dental implants with non-matching implant-abutment diameters were placed at the bone crest and were loaded for 6 months in the canine. The bone loss was significantly less (five- to six-fold) than that reported for bone-level implants with matching implant-abutment diameters (butt-joint connections).

The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs.

BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.

Immediate and early loading of SLA ITI single-tooth implants: an in vivo study.

PURPOSE: The purpose of this investigation was to determine whether early and immediate loading of dental implants resulted in adverse consequences as determined clinically, radiographically, and histologically. MATERIALS AND METHODS: In a canine model, 48 sand-blasted, large-grit, acid-etched (SLA) surfaced implants were placed at 4 different times before definitive restoration and loading. These times were 3 months (group A), 21 days (group B), 10 days (group C), and 2 days (immediately) (group D) before loading. Each implant was restored at the same time with a single gold screw-retained crown. Immediately after restoration all crowns were placed in function. Standardized periapical radiographs were made 1, 2, and 3 months after restoration. At the end of the study, block sections were obtained for histologic examination. Changes in crestal bone height on the mesial and distal aspects of each implant and the change in bone density of the coronal 3 mm of crestal bone were recorded. Primary, secondary, and total bone-to-implant contact; bone marrow-to-implant contact; and connective tissue-to-implant contact were evaluated histologically. RESULTS: All implants were osseointegrated at the end of the study; no clinical failures of integration were noted. The changes in crestal bone heights for groups A, B, C, and D (means +/- SE) were 0.02 +/- 0.07 mm, 0.30 +/- 0.08 mm, 0.15 +/- 0.08 mm, and 0.35 +/- 0.18 mm, respectively. Total bone-to-implant contact for the 4 groups was 69.1%, 71.3%, 74.6%, and 75.2%, respectively (P > .57). DISCUSSION: Under the conditions of this study no statistically significant differences were noted between the 4 different loading protocols for any of the parameters recorded. This finding is consistent with other recent studies and case reports. CONCLUSION: The findings of this study indicate that early and immediate loading of single-unit SLA surfaced implants was possible in this model. (More than 50 references.)

Outcome analysis of implant restorations located in the anterior maxilla: a review of the recent literature.

PURPOSE: To document the literature regarding outcomes of implant restorations in the anterior maxilla to formulate consensus statements with regard to esthetics in implant dentistry, to provide guidelines to clinicians, and to articulate remaining questions in this area to be addressed by future research. MATERIALS AND METHODS: The following areas of the recent literature were scrutinized: treatment outcomes of implant therapy for partial edentulism (including maxillary anterior tooth replacement); anterior maxillary single-tooth replacement; effect of implant design, diameter, and surface characteristics; soft tissue stability/contours around anterior implant restorations; ceramic abutments; influence of surgical techniques; and finally, evaluation of patient satisfaction. RESULTS: The use of dental implants in the esthetic zone is well documented in the literature, and numerous controlled clinical trials show that the respective overall implant survival and success rates are similar to those reported for other segments of the jaws. However, most of the published studies do not include well-defined esthetic parameters. Currently, the literature regarding esthetic outcome is inconclusive for the routine implementation of certain surgical approaches, such as flapless surgery and immediate implant placement with or without immediate loading/restoration in the anterior maxilla. Considering anterior single-tooth replacement in sites without tissue deficiencies, predictable treatment outcomes, including esthetics, can be achieved because of tissue support provided by adjacent teeth. The replacement of multiple adjacent missing teeth in the anterior maxilla with fixed implant restorations is poorly documented. In this context, esthetic restoration is not predictable, particularly regarding the contours of the interimplant soft tissue. DISCUSSION AND CONCLUSIONS: This review has demonstrated that scientific documentation of esthetically relevant and reproducible parameters is rather scarce. Most of the reported outcome analyses primarily focus on implant survival. Elements of anterior implant success such as maintenance or reestablishment of harmoniously scalloped soft tissue lines and natural contours should be included in future studies.

Prosthetic management of implants in the esthetic zone.

The purpose of this article is to review and project treatment procedures for areas of esthetic concern. The authors were participants in a consensus conference sponsored by ITI and held in August 2003 in Gstaad, Switzerland. This article deals with the basic prosthetic/restorative aspects in implant esthetics. It is based on a literature review performed by 16 participants from Group 2 (Buser et al) in this section of the Journal.

Evaluation of the ITI Morse taper implant/abutment design with an internal modification.

PURPOSE: The purpose of this study was to compare internal Morse taper connections in 2 separate modes: repeated torque/reverse-torque values and compressive bending at a 30-degree off-axis angle. MATERIALS AND METHODS: Three sample groups (n = 12 in each group)--a solid-screw implant paired with a 5.5-mm solid abutment (SSI), a synOcta implant with a 5.5-mm solid abutment (SOI), and a synOcta implant with a synOcta 5.5-mm solid abutment (SOSA)--were torqued to 35 Ncm, and the reverse torque to remove the abutment was recorded. This was repeated for 3 trials. Additionally, the sample groups were loaded 30 degrees off-axis, and the ultimate compressive values were recorded. RESULTS: There was a significant difference in the initial reverse-torque values. The SOSA setup showed significantly lower torque than the SOI and SSI setups (P < .05). In addition, the compressive bending test showed that the SOSA setup was significantly different (P < .05) from the SSI and SOI setups. Radiographic survey of the test groups following compressive bending revealed no implant fractures, but bending of the implant-abutment complex occurred. DISCUSSION: The alteration within the Morse taper did not reduce the strength of the implant-abutment connection, ie, the reduction in surface area did not significantly reduce the torque properties or tensile properties. The new 2-piece synOcta 5.5-mm solid abutment was shown to have a stronger implant-abutment connection when torqued down a second time. CONCLUSIONS: In this in vitro study, alteration of the Morse taper with an internal octagon indexing did not significantly reduce the strength of the implant connection. Sufficient strength was exhibited, which would indicate this implant-abutment design for anterior as well as posterior edentulous sites.

Biologic width adjacent to loaded implants with machined and rough collars in the dog.

Dental implant surface technology has evolved from a relatively smooth machined implant surface for osseointegration to more roughened osteoconductive surfaces. Recent studies suggest that peri-implant soft tissue inflammation with progressive bone loss (ie, peri-implantitis) is becoming a prevalent condition. One possibility that could explain such a finding is that more bacterial plaque forms on the roughened implant and abutment surfaces, which may result in the peri-implant inflammation in the soft tissues. This study compared 36 tissue-level implants with a machined transmucosal collar to 36 implants with a relatively roughened (SLActive) transmucosal surface in the dog. The implants were evaluated histologically and histomorphometrically after 3 and 12 months of loading. The results demonstrated that the connective tissue contact was similar between the two implant types but that the junctional epithelium and biologic width dimensions were greater around the implants with the machined collars. Interestingly, the amount of inflammation was similar between the two implant types. Slightly more bone formation and more mature collagen formation occurred around the implants with the roughened collars compared to the implants with machined collars. These results suggested that even if more plaque biofilm forms on the implants with the roughened SLActive surface compared to the machined surface, there is no biologic consequence related to the amount of inflammation or bone loss. In fact, the roughened surface promoted bone formation (was more osteoconductive) and more mature soft collagenous connective tissue.

Soft and hard tissue histologic dimensions around dental implants in the canine restored with smaller-diameter abutments: a paradigm shift in peri-implant biology.

PURPOSE: To evaluate the biologic width dimensions around implants with nonmatching implant-abutment diameters. MATERIALS AND METHODS: Five canines had their mandibular premolars and first molars removed bilaterally and replaced with 12 implants that had nonmatching implant-abutment diameters. On one side, six implants were placed in a submerged surgical approach, and the other side utilized a nonsubmerged approach. Two of the implants on each side were placed either 1 mm above, even with, or 1 mm below the alveolar crest. Two months later, gold crowns were attached, and the dogs were sacrificed 6 months postloading. Block sections were processed for histologic and histomorphometric analyses. RESULTS: The bone level, connective tissue length, epithelial dimension, and biologic width were not significantly different when the implants were initially placed in a submerged or nonsubmerged surgical approach. The bone level was significantly different around implants placed 1 mm above the crest compared to implants placed even with or 1 mm below the alveolar crest. The connective tissue dimension was not different for any implant level placement. The epithelial dimension and biologic width were significantly greater for implants placed 1 mm below the alveolar crest compared to implants placed even with or 1 mm above the alveolar crest. For five of six implant placements, connective tissue covered the implant/abutment interface. CONCLUSIONS: This study reveals a fundamental change in the biologic response to implants with nonmatching implant-abutment diameters. Unlike implants with matching implant-abutment diameters, the connective tissue extended coronally past the interface (microgap). This morphologic tissue alteration represents a significant change in the biologic reaction to implant-abutment interfaces and suggests that marginal inflammation is eliminated or greatly reduced in these implant designs.

A prospective noninterventional study to document implant success and survival of the Straumann Bone Level SLActive dental implant in daily dental practice.

OBJECTIVES: Clinical studies to assess dental implants are common in implantology, but such studies are usually performed for specific indications and following a specific protocol with strict inclusion and exclusion criteria. The aim of the current study was to evaluate the Straumann Bone Level SLActive dental implant in a prospective, multicenter, noninterventional trial. METHOD AND MATERIALS: The implant could be used in whatever manner was deemed suitable by the clinician, within approved indications. No particular placement or loading protocol was specified. A total of 1,532 implants were placed in 852 patients in 123 centers in nine countries in the US and Europe. After exclusion of three countries due to patient enrollment and data issues, 759 patients with 1,355 implants were analyzed. RESULTS: Most patients received one or two implants (58.6% and 25.3% of patients, respectively), and 90% of cases were performed with a raised flap. A submerged healing protocol was significantly more prevalent in European centers, while transmucosal healing was significantly more prevalent in North American centers. After 1 year, 538 patients with 908 implants were available for evaluation. The cumulative implant survival and success rates were 98.5% and 96.0%, respectively. CONCLUSIONS: This prospective noninterventional study evaluated the use of Straumann Bone Level SLActive dental implants in a large number of patients. The cumulative survival and success rates were similar to those observed in controlled clinical trials, confirming this dental implant's clinical applicability in daily practice.

Effects of implant design on marginal bone changes around early loaded, chemically modified, sandblasted Acid-etched-surfaced implants: a histologic analysis in dogs.

BACKGROUND: A minimal marginal bone loss around implants during early healing has been considered acceptable. However, the preservation of the marginal bone is related to soft tissue stability and esthetics. Implant designs and surfaces were evaluated to determine their impact on the behavior of the crestal bone. The purpose of this study is to evaluate histologic marginal bone level changes around early loaded, chemically modified, sandblasted acid-etched-surfaced implants with a machined collar (MC) or no MC (NMC). METHODS: Three months after a tooth extraction, 72 sandblasted acid-etched chemically modified implants were placed in six dogs. Thirty-six implants had NMC, and 36 implants had a 2.8-mm MC. All implants were loaded 21 days after placement. For histologic analyses, specimens were obtained at 3 and 12 months. Assessments of the percentage of the total bone-to-implant contact and linear measurements of the distance from the shoulder of the implant to the first bone-to-implant contact (fBIC) were performed. Based on fBIC measurements, estimates of bone loss were obtained for each implant. A mixed-model analysis of variance was used to assess the effects of implant type and sacrifice time. RESULTS: All implants achieved osseointegration. The mean bone gain observed around NMC early loaded implants (at 3 months: 0.13 ± 0.37 mm; at 12 months: 0.13 ± 0.44 mm) was significantly different from the mean bone loss for MC early loaded implants (at 3 months: -0.32 ± 0.70 mm; at 12 months: -0.79 ± 0.35 mm) at 3 months (P = 0.003) and 12 months (P <0.001). No infrabony component was present at the marginal fBIC around NMC implants in most cases. There were no statistically significant differences among the means of total bone contact for implant types. CONCLUSIONS: Chemically modified, sandblasted acid-etched-surfaced implants with NMC presented crestal bone gain after 3 and 12 months under loading conditions in the canine mandible. The implant design and surface were determinants in the marginal bone level preservation.

A 5-year prospective multicenter clinical trial of non-submerged dental implants with a titanium plasma-sprayed surface in 200 patients.

BACKGROUND: Endosseous dental implants are a popular treatment to replace missing teeth. Although many advances have occurred and affected the macrogeometry and surface characteristics of dental implants, among other aspects, it is important to document how the implants perform in patients over time. Such evaluations are helpful not only to document the clinical survival of the implants but also patient satisfaction over an extended period. METHODS: A formal prospective multicenter human clinical was performed at five centers involving 200 patients and 626 implants. Specific inclusion and exclusion criteria were used and detailed data collected at specified times using case report forms. An independent study monitor reviewed all study data before entry into the study database. Two implant designs were used in two different clinical indications. A non-submerged titanium plasma-sprayed (TPS) hollow cylindrical implant with a smooth transgingival collar was evaluated in the maxillary anterior sextant and a non-submerged TPS solid screw implant with similar collar in the mandible. RESULTS: Over the course of the 5-year clinical trial, there was one early failure occurring before definitive prosthesis delivery. Three late failures were documented, one occurring at each of the 6, 12, and 18 months postoperative visits. Life table analysis at 5 years revealed a 99.4% survival rate and a 92.5% success rate. Patient satisfaction was rated as good to excellent for 96.1% of implants in regards to esthetics after 5 years; 98.8% for appearance; and 99.4% for prosthesis comfort, ability to chew and taste, fit, and general satisfaction. No serious adverse events were reported. CONCLUSIONS: Implant success and survival was over 92% and 99%, respectively, in a formal 5-year prospective multicenter clinical trial involving 200 patients and 626 non-submerged TPS implants. These implants included hollow cylinder implants in the anterior maxilla and solid screw implants placed in the mandible. These findings document the predictability and patient satisfaction of tooth replacement using a non-submerged surgical technique involving a tissue-level, rough surfaced endosseous dental implant.