Influence of a machined collar on crestal bone changes around titanium implants: a histometric study in the canine mandible

Background: It has been shown that peri‐implant crestal bone reactions are influenced by both a rough–smooth implant border in one‐piece, non‐submerged, as well as an interface (microgap [MG] between implant/abutment) in two‐piece butt‐joint, submerged and non‐submerged implants being placed at different levels in relation to the crest of the bone. According to standard surgical procedures, the rough–smooth implant border for implants with a smooth collar should be aligned with the crest of the bone exhibiting a smooth collar adjacent to peri‐implant soft tissues. No data, however, are available for implants exhibiting a sandblasted, large‐grit and acid‐etched (SLA) surface all the way to the top of a non‐submerged implant. Thus, the purpose of this study is to histometrically examine crestal bone changes around machined versus SLA‐surfaced implant collars in a side‐by‐side comparison. Methods: A total of 60 titanium implants (30 machined collars and 30 SLA collars) were randomly placed in edentulous mandibular areas of five foxhounds forming six different subgroups (implant subgroups A to F). The implants in subgroups A to C had a machined collar (control), whereas the implants in subgroups D to F were SLA‐treated all the way to the top (MG level; test). Furthermore, the MGs of the implants were placed at different levels in relation to the crest of the bone: the implants in subgroups A and E were 2 mm above the crest, in subgroups C and D 1 mm above, in subgroup B 3 mm above, and in subgroup F at the bone crest level. For all implants, abutment healing screws were connected the day of surgery. These caps were loosened and immediately retightened monthly. At 6 months, animals were sacrificed and non‐decalcified histology was analyzed by evaluating peri‐implant crestal bone levels. Results: For implants in subgroup A, the estimated mean crestal bone loss (± SD) was ?0.52 ± 0.40 mm; in subgroup B, +0.16 ± 0.40 mm (bone gain); in subgroup C, ?1.28 ± 0.21 mm; in subgroup D, ?0.43 ± 0.43 mm; in subgroup E, ?0.03 ± 0.48 mm; and in subgroup F, ?1.11 ± 0.27 mm. Mean bone loss for subgroup A was significantly greater than for subgroup E (P = 0.034) and bone loss for subgroup C was significantly greater than for subgroup D (P <0.001). Conclusions: Choosing a completely SLA‐surfaced non‐submerged implant can reduce the amount of peri‐implant crestal bone loss and reduce the distance from the MG to the first bone–implant contact around unloaded implants compared to implants with a machined collar. Furthermore, a slightly exposed SLA surface during implant placement does not seem to compromise the overall hard and soft tissue integration and, in some cases, results in coronal bone formation in this canine model.     

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 pilot study to assess the performance of a partially threaded sintered porous-surfaced dental implant in the dog mandible

PURPOSE: The purpose of this study was to compare patterns of crestal bone remodeling with 2 sintered porous-surfaced dental implant designs during a 14-month functional period. MATERIALS AND METHODS: Two root-form press-fit dental implants were evaluated in healed extraction sites in dog mandibles. The standard (control) design was a press-fit implant with a 2-mm machined collar; the remainder of the implant had a sintered porous surface. The test or "hybrid" design had 3 coronal machined threads instead of a machined collar; the remainder of the implant had a sintered porous surface. RESULTS: Standardized radiographs indicated significantly less crestal bone loss (0.82 to 0.93 mm versus 1.45 to 1.5 mm) with the hybrid design and a slower approach toward an apparent steady state (12 to 14 months for the hybrid versus 7 months for the standard design). Morphometric assessment of back-scattered scanning electron micrographs confirmed that crestal bone loss was significantly less for the hybrid design on all but the lingual implant aspect. CONCLUSION: The addition of coronal threads to an implant relying on a sintered porous surface geometry for its long-term osseointegration reduced the extent of crestal bone loss compared to a machined collar region.     

Effects of decontamination and implant surface characteristics on re-osseointegration following treatment of peri-implantitis

Background: Although considerable bone fill may occur following treatment of peri-implantitis, re-osseointegration appears to be limited and unpredictable.
Objectives: To evaluate the effects of various decontamination techniques and implant surface configurations on re-osseointegration of contaminated dental implants.
Material and methods: Three months after tooth extraction, implants consisting of a basal part and an exchangeable intraosseous implant cylinder (EIIC) were placed in the mandibles of dogs. The EIIC was machined (M), sandblasted and acid-etched (SLA), or titanium plasma sprayed (TPS). Ligature-induced peri-implantitis was initiated 8 weeks post-implantation and lasted until bone loss reached the junction of the two implant parts. Three treatment modalities were applied: (T1) the EIIC was exchanged for a pristine EIIC; (T2) the EIIC was sprayed in situ with saline; and (T3) the EIIC was removed, cleansed outside the mouth by spraying with saline, steam-sterilized, and remounted. A collagen barrier was placed over each fixture, and 3 months later, samples were processed for histology and histomorphometry.
Results: T2 revealed the highest bone-to-implant contact (BIC) level (significantly better than T1 and T3). T2 also yielded the highest bone crest level (significantly better than T1), followed by T3 (significantly better than T1). SLA showed the highest BIC level (significantly better than M), followed by TPS. There were no statistically significant differences in bone crest height between implant types.
Conclusions: Both SLA implants and in situ cleansing resulted in the best re-osseointegration and bone fill of previously contaminated implants.     

Clinical field trial examining an implant with a sand-blasted, acid-etched surface

BACKGROUND: Conventionally, endosseous dental implants have required 3 to 6 months of uninterrupted healing based on observations for dental implants that were characterized by a relatively smooth machined surface. Many studies have since demonstrated that implants with a roughened surface resulted in greater bone apposition, earlier bone contact, and a stronger bond between the implant and the bone, suggesting that implants with roughened surfaces could be loaded earlier than 3 to 6 months. Formal clinical studies confirmed that implants with rough surfaces can have abutments placed and be loaded occlusally as early as 6 weeks postplacement. The purpose of this prospective, human clinical investigation was to evaluate a large number of implants with a specific rough surface (sand-blasted acid-etched [SLA]) placed in everyday practice under routine private-practice conditions. METHODS: A prospective, multicenter, human clinical observational study was initiated with the goal of recruiting a minimum of 500 patients and 800 implants. The implants were to be placed and restored in predominantly private-practice settings around the world. Ninety-two practitioners in 16 countries agreed to participate, and 86 followed the study design. Patients had to be in good health, have sufficient bone to encase the implant, and agree to return for recall appointments. Exclusion criteria included heavy smoking (>10 cigarettes a day) and bone augmentation procedures at the implant site. All implants were two-piece (an abutment was to be placed after 6 weeks of healing) and were characterized by the presence of a transmucosal polished collar. Each implant had an SLA surface. All implants were positioned using a non-submerged (single-stage) surgical technique. Survival and success rates were calculated by life-table analyses. RESULTS: A total of 706 patients were enrolled and 1,406 implants were placed. In the final analyses, 590 patients with 990 implants (70.4% of those enrolled) met all inclusion criteria, including placement of an abutment and provisional restoration within 63 days of surgical placement. The majority of implants were 10 and 12 mm long (78.7%) and were placed in type II and III bone (87%). Seventy-three percent of the implants were placed in the mandible, and 27% were placed in the maxilla. The cumulative survival rate was 99.56% at 3 years and 99.26% at 5 years. The overall success rate was 99.12% at 3 years and 97.38% after 5 years. CONCLUSIONS: Under private-practice conditions, implants with an SLA surface could be placed and restored predictably within 6 to 8 weeks. Data from this prospective, multicenter, human observational study reinforced the results of more formal clinical studies and demonstrated that implants with the SLA surface can be restored in patients in approximately half of the time of conventional healing periods.     

Immediate versus delayed loading of dental implants placed in fresh extraction sockets in the maxillary esthetic zone: a clinical comparative study

PURPOSE: The aim of this study was to report a clinical comparative assessment of crestal bone level change around single implants in fresh extraction sockets in the esthetic zone of the maxilla either immediately loaded or loaded after a delay. MATERIALS AND METHODS: Forty patients were included in a prospective, randomized study. All patients required 1 tooth extraction (ie, 1 tooth with a hopeless prognosis) and were randomized into either the test group or the control group. Implants were positioned immediately after tooth extraction and were loaded immediately in the test group (20 implants) and after 3 months in the control group (20 implants). The implant site was prepared, with at least 4 mm of sound apical bone below the implant apex, and the coronal margin of the implant was placed at the buccal level of the bone crest. All implants were 13 mm long; 30 implants had a diameter of 5 mm, and 10 had a diameter of 3.75 mm. Radiographic examinations were made at baseline, at 6 months, and at 24 months. To compare the mean values between test and control group, a paired t test was performed (considered statistically significant at P < .05). RESULTS: After a 24-month follow-up period, a cumulative survival rate of 100% was reported for all implants. The control group resulted in a mean mesial bone loss of 1.16 +/- 0.32 mm and a mean distal bone loss of 1.17 +/- 0.41 (mean bone loss, 1.16 +/- 0.51 mm). The test group resulted in a mesial bone loss of 0.93 +/- 0.51 mm and a distal bone loss of 1.1 +/- 0.27 mm (mean bone loss, 1.02 +/- 0.53 mm). No statistically significant difference between control and test groups (P > .05) was found. CONCLUSION: The success rate and radiographic results of immediate restorations of dental implants placed in fresh extraction sockets were comparable to those obtained in delayed loading group.     

Fully vs. partially rough implants in maxillary sinus floor augmentation: a randomized-controlled clinical trial

OBJECTIVES: To compare implants with a rough surface in their whole length (FR) with implants having a 2 mm coronal machined portion (PR) when used in association with a sinus-lift procedure. MATERIAL AND METHODS: Twenty-six patients with 2 mm< or =x< or =9 mm residual alveolar crest were prosthetically restored with implants after a staged sinus-lift procedure using osteotomes. In 13 randomly chosen patients, no more than one FR implant was placed (test group), while the rest were PR implants. The other 13 patients received only PR implants (control group). For comparisons, only one implant from each patient was used, i.e., from the test group only the 13 FR implants were used, while from the control group, one PR implant was randomly chosen. The presence/absence of plaque, BOP, PPD and REC were registered at the day of delivery of the restorations and after 1 year. Residual alveolar crest height and marginal bone levels around the implants were evaluated on standardized periapical radiographs taken at various stages. RESULTS: Four FR and two PR implants were lost, and the cumulative survival rate was 82.9% (six lost out of 35). There were no significant differences between the two groups. Implant type, residual alveolar crest height, time of osseointegration, time of implant loading and smoking did not seem to influence implant survival. CONCLUSIONS: FR and PR implants placed in augmented sinuses did not differ in their clinical performance.     

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.     

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. II: ridge alterations

Aims: To describe the early phases of healing at the alveolar ridge around dental implants placed into fresh extraction sockets and to study whether (i) the dimension of the socket and (ii) a new implant surface nano-topography may have any influence.
Materials and Methods: Sixteen beagle dogs received 64 test (new surface) and control implants randomly placed at the distal socket of 3P3 and 4P4. The implant shoulder was levelled with the marginal buccal bone crest. Animals were sacrificed at 4 h, 1, 2, 4 and 8 weeks for histological examination.
Results: Bone loss occurred at the buccal crest between the 4-h and 1-week healing intervals, being more pronounced at the third premolar site [vertical bone loss between day 0 and 8 weeks 1.1 (0.5) mm]. The corresponding loss at the fourth premolar site was 0.3 (0.5) mm. Test sites containing implants with discrete crystalline deposition nano-particles' surface exhibited less buccal bone resorption than control sites at 8 weeks.
Conclusion: Dimensions of the socket influenced the process of wound healing of implants placed into fresh extraction sockets, with more bone loss in the narrower sockets; however, the implant surface nano-topography seemed to have a limited effect in the healing of this implant surgical protocol.     

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).     

Vertical crestal bone changes around implants placed into fresh extraction sockets

BACKGROUND: The aim of this study was to analyze bone healing and vertical bone remodeling for implants placed immediately after tooth removal without guided bone regeneration techniques. METHODS: Twenty patients received 20 implants immediately after the removal of 20 teeth. All implants were placed within the undamaged alveoli confines, and the cervical portion of each implant was positioned at coronal bone level. The distance from implant shoulder and bone crest was measured for each implant at four sites (mesial, buccal, distal, and palatal/lingual). No membranes or filling materials were used. Primary flap closure was performed in all clinical cases. RESULTS: All peri-implant bone defects had healed completely 6 months after implant placement. The pattern of bone healing around the neck of the implants showed an absence of peri-implant defects. The vertical distance between the implant shoulder and bone crest ranged from 0 to 2 mm. CONCLUSIONS: The bone remodeling of implants placed in fresh extraction sockets showed a healing pattern with new bone apposition around the implant's neck and horizontal and vertical bone reabsorption. The vertical bone reabsorption, which has been observed at buccal sites, was not associated with any negative esthetic implications.     

Retrospective Evaluation of Crestal Bone Changes Around Implants With Reduced Abutment Diameter Placed Non‐Submerged and at Subcrestal Positions: The Effect of Bone Grafting at Implant Placement

Background: There is limited information regarding the effect of grafting of the osteotomy after subcrestal implant placement. The primary aim of this study is to retrospectively evaluate the effect of bone grafting of the defect between the bone crest and the coronal aspect of implants with reduced abutment diameter placed non‐submerged and at subcrestal positions. Methods: Records of 50 consecutive patients treated with subcrestally placed dental implants grafted with a xenograft (Group A) and 50 consecutive patients with subcrestally placed dental implants without any grafting material (Group B) were reviewed. For each implant, the radiographs after placement were compared to images from the last follow‐up visit and evaluated regarding the following: 1) degree of subcrestal positioning of the implant, 2) changes of marginal hard‐tissue height over time, and 3) whether marginal hard‐tissue could be detected on the implant platform at the follow‐up visit. Results: The mean marginal loss of hard tissues was 0.11 ± 0.30 mm for Group A and 0.08 ± 0.22 mm for Group B. Sixty‐nine percent of the implants in Group A and 77% of the implants in Group B demonstrated hard tissue on the implant platform. There were no statistically significant differences between the groups regarding marginal peri‐implant hard‐tissue loss. Conclusion: The present study fails to demonstrate that grafting of the remaining osseous wound defect between the bone crest and the coronal aspect of the implant has a positive effect on marginal peri‐implant hard‐tissue changes.     

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.     

Equicrestal and subcrestal dental implants: a histologic and histomorphometric evaluation of nine retrieved human implants

Background: Stability of peri‐implant crestal bone plays a relevant role relative to the presence or absence of interdental papilla. Several factors can contribute to the crestal bone resorption observed around two‐piece implants, such as the presence of a microgap at the level of the implant–abutment junction, the type of connection between implant and prosthetic components, the implant positioning relative to the alveolar crest, and the interimplant distance. Subcrestal positioning of dental implants has been proposed to decrease the risk of exposure of the metal of the top of the implant or of the abutment margin, and to get enough space in a vertical dimension to create a harmoniously esthetic emergence profile. Methods: The present retrospective histologic study was performed to evaluate dental implants retrieved from human jaws that had been inserted in an equicrestal or subcrestal position. A total of nine implants were evaluated: five of these had been inserted in an equicrestal position, whereas the other four had been positioned subcrestally (1 to 3 mm). Results: In all subcrestally placed implants, preexisting and newly formed bone was found over the implant shoulder. In the equicrestal implants, crestal bone resorption (0.5 to 1.5 mm) was present around all implants. Conclusion: The subcrestal position of the implants resulted in bone located above the implant shoulder.     

Subcrestal placement of two-part implants

Objective: The aim of the present experiment was to study the healing around two-part implants that were placed in a subcrestal position.
Material and methods: Five mongrel dogs, about 2 years old, were included. The mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later two test and two control implants (OsseoSpeed^™, 3.5 mm × 8 mm) were placed in one side of the mandible. The implants were placed in such a way that the implant margin was located 2 mm apical to the bone crest. In the test implants, the surface modification extended to the implant margin and, thus, included the shoulder part of the implant. Regular abutments with a turned surface (Zebra^™) were connected to the control implants, while experimental abutments with a modified surface (TiOblast^™) were connected to the test implants. A plaque control program that included cleaning of implants and teeth every second day was initiated. Four months later the dogs were euthanized and biopsies were obtained and prepared for histological analysis.
Results: The marginal bone level at the test implants was identified in a more coronal position than that at the control implants. In 40% of the test implants, the bone-to-implant contact extended coronal of the abutment/fixture (A/F) border, i.e. in contact with the abutment part of the implant. The connective tissue portion of the peri-implant mucosa that was facing the test abutments contained a higher density of collagen and a smaller proportion of fibroblasts than that at the control sites.
Conclusion: It is suggested that osseointegration may occur coronal to the A/F interface of two-part implants. Such a result, however, appears to depend on the surface characteristics of the implant components.     

Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs

Aim: To evaluate the influence of magnesium‐enriched hydroxyapatite (MHA) (SintLife^®) on bone contour preservation and osseointegration at implants placed immediately into extraction sockets. Material and methods: In the mandibular pre‐molar region, implants were installed immediately into extraction sockets of six Labrador dogs. MHA was placed at test sites, while the control sites did not receive augmentation materials. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. Results: After 4 months of healing, one control implant was not integrated leaving n=5 test and control implants for evaluation. Both at the test and the control sites, bone resorption occurred. While the most coronal bone‐to‐implant contact was similar between test and control sites, the alveolar bony crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 0.7 mm) compared with the control sites (loss: 1.2 mm), even though this difference did not reach statistical significance. Conclusions: The use of MHA to fill the defect around implants placed into the alveolus immediately after tooth extraction did not contribute significantly to the maintenance of the contours of the buccal alveolar bone crest. To cite this article:
Caneva M, Botticelli D, Stellini E, Souza SLS, Salata LA, Lang NP. Magnesium‐enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs.
Clin. Oral Impl. Res. 22 , 2011; 512–517
doi: 10.1111/j.1600‐0501.2010.02040.x     

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.     

Early functional loading of sand-blasted and acid-etched (SLA) Straumann implants following immediate placement in maxillary extraction sockets. Clinical and radiographic result

OBJECTIVES: To present the clinical and radiographic outcome of early loading of implants inserted into fresh extraction sockets and to present a treatment protocol for early loading of the implants by 'passively fitting' abutment-free permanent fixed complete dentures (implant FCDs). MATERIAL AND METHODS: The study included 19 dentate patients treatment planned for extraction of all remaining maxillary teeth. In all, 116 Straumann-implants with sandblasted, large grit and acid etched (SLA) surface were placed: 77 (66%) inserted in fresh extraction sockets and 39 (34%) in healed bone. At least six implants were placed in each maxilla. One hundred and ten implants were loaded by permanent FCDs within 10 days after placements and six after 14 days. The patients were reexamined clinically and radiographically after 2-3 years of clinical function. All FCDs were removed for control of implant stability and evaluation of the peri-implant status. RESULTS: Owing to framework fracture, two implants were lost, corresponding to a failure rate of 2%. The radiographic measurements after 2-3 years did not reveal any difference in bone height mesial and distal of the implants placed in extraction sockets vs. in healed bone. This was interpreted as a bone gain around the implants placed in extraction sockets and a slight bone loss around the implants placed in healed bone. CONCLUSION: Early functional loading of SLA-surfaced implants following immediate placement in maxillary extraction sockets by rigid and passively fitting permanent implant FCDs is a reliable treatment alternative.     

Threaded versus porous-surfaced implants as anchorage units for orthodontic treatment: three-dimensional finite element analysis of peri-implant bone tissue stresses

PURPOSE: A 3-dimensional finite element model was developed to investigate the cause of different crestal bone loss patterns observed around sintered porous-surfaced and machined (turned) threaded dental implants used for orthodontic anchorage in a previously reported animal study. MATERIALS AND METHODS: Twenty-noded structural solid elements with parabolic interpolation between nodes were used for modeling the bone-implant interface zone. A 3-N traction force acting between either 2 porous-surfaced or 2 machined threaded implants placed in canine premolar mandibular sites and bone profiles observed at initiation and 22 weeks of orthodontic loading were modeled. RESULTS: Higher maximum stresses in peri-implant bone next to the coronal region of the implants were predicted with the machined threaded implants at both the initial and final time points, with the values 20% greater than those predicted after the 22-week loading period. These values were approximately 200% greater than those predicted for the porous-surfaced implants, for which a more uniform stress distribution was predicted. DISCUSSION: The finite element model results indicated that the observed greater retention of crestal bone next to the porous-surfaced implants was attributable to lower peak stresses developing in crestal peri-implant bone with this design, which decreased the probability of bone loss related to local overstressing and bone microfracture. CONCLUSION: The predicted lower stresses were a result of the more uniform transfer of force from implant to bone with the porous-surfaced implants, which was a consequence of the interlocking of bone and implant possible with this design.     

Scalloped dental implants: a retrospective analysis of radiographic and clinical outcomes of 17 NobelPerfect implants in 6 patients

Background: The scalloped dental implant (NobelPerfect^TM, Nobel Biocare, Yorba Linda, CA, USA) is designed to biologically guide and facilitate interproximal bone remodeling during healing and to maintain bone height and papillae during functional loading. The design features of the scalloped implant include hard and soft tissue apposition areas, which are parallel to each other and mirror the cementoenamel junction. The hard tissue surface area is intended for osseointegration. The soft tissue surface area is meant to support the connective tissue zone and to provide a space for the subgingival margin of the restoration. Current literature on the clinical performance of the scalloped dental implant is limited. Purpose: The aim of this study was to evaluate whether the scalloped dental implant maintains interproximal bone and the overlying soft tissue. Materials and Methods: Radiographs for six patients (mean age 40.5 years) treated with 17 implants (NobelPerfect) were reviewed for an 18‐month follow‐up evaluation of bone response. Orthodontic movement and/or autogenous bone augmentation had been provided to obtain the best possible soft and hard tissue dimensions prior to implant placement. A surgical guide was used for an optimal implant placement. No surgical flap was reflected, and implants were placed a minimum of 2 mm and a maximum of 3 mm apical (midbuccally) to the most apical portion of the surgical guide. Final optimal rotational alignment was achieved in all cases by not exceeding 45 Ncm. Implants were immediately restored with provisional crowns. Photographic documentation provided the basis for analysis of papillary response. Radiographic change in the interproximal bone level was obtained by computer analysis (ImageJ for Windows, National Institutes of Health, Bethesda, MD) by measuring the distance from the interproximal shoulder of the scalloped implant to the crest of the bone. Results: When the scalloped implants were placed adjacent to existing natural dentition, the average bone level at placement and at 6, 12, and 18 months was ?1.7, ?3.5, ?3.8, and ?3.9 mm, respectively, compared with ?1.0, ?3.6, ?4.3, and ?4.4 mm respectively, when placed adjacent to other scalloped implants. Papillae formation exhibited no differences from the configuration that typically results after placement of conventional dental implants. Moreover, bone loss around the scalloped implants was notably greater than that expected after traditional implant placement. Conclusion: This chart review of 17 scalloped implants, followed for 18 months, determined that the scalloped implant design resulted in bone loss that was more severe than that associated with properly placed conventional dental implants. Further, the design showed no evidence of exceptional capacity to increase or maintain soft tissue height.