Astra Tech AB Research Articles

Dental implant survival and success rate after sinus augmentation with deproteinized bovine bone mineral and platelet-rich plasma at one and five years: a prospective-controlled study

ABSTRACTThe aim of this comparative study was to evaluate, at one and five years, the implant success rate in the resorbed maxilla after sinus augmentation with platelet-rich plasma (PRP)/deproteinized bovine bone mineral (DBBM) versus DBBM/collagen membrane (CM). Using a split-mouth design, 10 patients with ≤5 mm of residual alveolar bone were treated with PRP/DBBM or DBBM/CM. After eight months, a total of 22 and 21 implants (Osseospeed™, Astra Tech AB, Sweden) were inserted in the PRP/DBBM and DBBM/CM sites, respectively. The implant success and survival rates, modified plaque and bleeding indices, probing depth and changes in bone level were all evaluated one year later, and again five years later. Only one implant was lost before the prosthetic rehabilitation of the PRP/DBBM group. There were no statistically significant differences in the evaluated parameters for the 1- and 5-year follow-up in the two groups (p > 0.05). After five years of loading, no further implants were lost, giving it an overall success rate of 83%. The clinical study showed that a high implant success and survival rate can be achieved at one year and maintained for up to five years, after a sinus-lift procedure utilizing both combinations.

Effect of implant number and distribution on load transfer in implant-supported partial fixed dental prostheses for the anterior maxilla: A photoelastic stress analysis study

Statement of problemThe 4-, 3- or even 2-implant-supported partial fixed dental prosthesis (PFDP) designs have been used to rehabilitate the anterior edentulous maxilla. PurposeThe purpose of this in vitro study was to compare the stress distribution in the supporting tissues surrounding implants placed in the anterior maxilla with 5 PFDP designs. Material and methodsA photoelastic model of the human maxilla with an anterior edentulous region was made with photoelastic resin (PL-2; Vishay Micro-Measurements), and 6 straight implants (OsseoSpeed; Astra Tech AB) were placed in the 6 anterior tooth positions. The 5 design concepts based on implant location were as follows: model 6I: 6 implants; model 2C2CI: 4 implants (2 canines and 2 central incisors); model 2C2LI: 4 implants (2 canines and 2 lateral incisors); model 2C1CI: 3 implants (2 canines and 1 central incisor); and model 2C: 2 canines. A load of 127.4 N was applied on the cingulum of 3 teeth at a 30-degree angle to the long axis of the implant. Stresses that developed in the supporting structure were recorded photographically. ResultsThe 6-implant-supported PFDP exhibited the most even and lowest distribution of stresses in all loading conditions. When the canine was loaded, the 2- or 3-implant-supported PFDP showed higher stresses around the implant at the canine position than did the 4- or 6-implant-supported PFDP. When the central incisor or lateral incisor was loaded, the two 4-implant-supported PFDPs exhibited similar levels of stresses around the implants and showed lower stresses than did the 2- or 3-implant-supported PFDP. ConclusionsImplant number and distribution influenced stress distribution around the implants in the anterior maxilla. With a decrease in implant number, the stresses around the implants increased.

Simultaneous or Delayed Placement of Surface Modified and Fluoridated Dental Implants into Autogenous Block Bone Grafts: A Histologic and Biomechanical Study in the Rabbit

A delayed approach is recommended for reconstruction of the jaws with autogenous bone grafts and dental implants. Experimental studies have shown stronger bone tissue responses to surface modified implants than to nonmodified ones. The aim of the study was to evaluate bone integration and stability of surface modified and fluoridated implants when placed with fresh or healed autogenous bone grafts. Six rabbits were used in this study. Each right rabbit tibia (control) received an autogenous bone graft, harvested from the calvarium. Eight weeks later, a second graft was harvested from the other side of the calvarium and placed on the left tibia (test) with an implant. Another implant was installed in the healed graft of the right tibia. TiO2-blasted and fluoridated OsseoSpeed(TM) implants (Astra Tech AB, Mölndal, Sweden), 3.5 mm in diameter and 9 mm long, were used. After additional 8 weeks, the rabbits were sacrificed and the implants were removed en bloc for light-microscopic analysis. Bone-to-implant contact (BIC) was registered as well as the amount of bone filling a rectangle indicating a region of interest (ROI). Resonance frequency analysis (RFA) was conducted both at the time of surgery and at the end of the experiment. There were no statistically significant differences either in BIC or ROI between the test and control sides. RFA showed higher implant stability for the control side at the time of the surgery, but the difference had leveled out at the time of the sacrifice. The present study showed similar bone tissue responses and stability for surface modified and fluoridated implants after 8 weeks of healing in fresh or healed autogenous bone grafts.

Bending moments of zirconia and titanium implant abutments supporting all‐ceramic crowns after aging

To test the fracture load and fracture patterns of zirconia abutments restored with all-ceramic crowns after fatigue loading, exhibiting internal and external implant-abutment connections as compared to restored and internally fixed titanium abutments. A master abutment was used for the customization of 5 groups of zirconia abutments to a similar shape (test). The groups differed according to their implant-abutment connections: one-piece internal connection (BL; Straumann Bonelevel), two-piece internal connection (RS; Nobel Biocare ReplaceSelect), external connection (B; Branemark MkIII), two-piece internal connection (SP, Straumann StandardPlus) and one-piece internal connection (A; Astra Tech AB OsseoSpeed). Titanium abutments with internal implant-abutment connection (T; Straumann Bonelevel) served as control group. In each group, 12 abutments were fabricated, mounted to the respective implants and restored with glass-ceramic crowns. All samples were embedded in acrylic holders (ISO-Norm 14801). After aging by means of thermocycling in a chewing simulator, static load was applied until failure (ISO-Norm 14801). Fracture load was analyzed by calculating the bending moments. Values of all groups were compared with one-way ANOVA followed by Scheffé post hoc test (P-value<0.05). Failure mode was analyzed descriptively. The mean bending moments were 464.9±106.6N cm (BL), 581.8±172.8N cm (RS), 556.7±128.4N cm (B), 605.4±54.7N cm (SP), 216.4±90.0N cm (A) and 1042.0±86.8N cm (T). No difference of mean bending moments was found between groups BL, RS, B and SP. Test group A exhibited significantly lower mean bending moment than the other test groups. Control group T had significantly higher bending moments than all test groups. Failure due to fracture of the abutment and/or crown occurred in the test groups. In groups BL and A, fractures were located in the internal part of the connection, whereas in groups RS and SP, a partial deformation of the implant components occurred and cracks and fractures of the zirconia abutment were detected. The differently connected zirconia abutments exhibited similar bending moments with the exception of one group. Hence, the type of connection only had a minor effect on the stability of restored zirconia abutments. In general, restored titanium abutments exhibited the highest bending moments.

Comparison of two different restoration materials and two different implant designs of implant-supported fixed cantilevered prostheses: A 3D finite element analysis

Abstract Purpose: A key factor for the success or failure of a dental implant is the manner of stresses transferred to the surrounding bone. Parallel to this situation, cantilever extensions where it is not possible to place another implant, would cause greater stress and it should be avoided if possible. Manufacturers and clinicians try to develop new implant designs and superstructure materials to reduce the stresses around the implant and supporting bone tissue. This study analyzed the influence of superstructure materials and implant designs on stress distribution around dental implants supporting cantilever restoration under loading conditions. Materials and Methods: Three-dimensional finite element models of a 3-unit cantilever bridge were subjected to 150 N occlusal load to evaluate two different superstructure materials (conventional metal ceramic, fiber reinforced composite) and two different implant designs, cylinder type (Institut Straumann AG, Waldenburg, Switzerland) and cylinder type with micro threads around implant neck (Astra Tech AB, Mölndal, Sweden). To evaluate the distribution of stresses within the bone surrounding the implants, 3-dimensional finite element analysis was conducted using four mathematical models of unilateral 3-unit cantilever fixed partial dentures supported by two implants. Results: The stress distribution patterns and stress values were similar and stress concentrations were similar in both restoration materials. The highest stress concentrations were around the adjacent ITI implant, which supports the conventional metal porcelain restoration. Conclusions: Although, there was no significant difference in stress distribution between fiber reinforced composite (FRC) and conventional metal porcelain, stress values were lower in FRC restorations. The Astra-Tech micro-thread design reduced the stress that was distributed throughout the implant body, but it should be noted that the peak stress was still present on the implant neck.

Soft and hard tissue alterations around implants placed in an alveolar ridge with a sloped configuration

The aim of this study was to evaluate soft and hard tissue alterations around implants placed in healed, sloped ridge sites. In this prospective multi-center study, 65 patients between 20 and 74years of age and with a need for a single tooth replacement were included. All patients presented with a recipient implant site demonstrating a lingual-buccal bone height discrepancy of 2.0-5.0mm and with a neighboring tooth on its mesial aspect. Implant placement (OsseoSpeed™ Profile implants; Astra Tech AB, Mölndal, Sweden) was performed using a non-submerged installation procedure. The implants were placed in such a way that the sloped part of the device was located at the buccal and most apical position of the osteotomy preparation. As the buccal rim of the implant was positioned at the crestal bone level, the lingual rim became situated either below or at the level of the lingual bone crest. Clinical assessments of bone levels at the buccal and lingual aspects of the implant were carried out immediately after implant installation and at a surgical re-entry procedure performed 16weeks later. Crowns were placed at 21weeks after implant placement. Radiographs were obtained immediately after implant placement, at 16 and 21weeks and at the 1-year re-examination. Clinical assessment of probing pocket depth and clinical attachment levels were carried out at 21weeks and at 1year of follow-up. The alterations of the bone levels that occurred between implant placement and the 16-week surgical re-entry were -0.02mm (lingual) and -0.30mm (buccal). The average change in interproximal bone levels between implant placement and the 1-year re-examination was 0.54mm. Clinical attachment level changes between the 21week and the 1-year examinations varied between 0.1mm gain and 0.1mm loss. Implant placement in an alveolar ridge with a sloped marginal configuration resulted in minor remodeling with preserved discrepancies between buccal and lingual bone levels.

Deviations between Placed and Planned Implant Positions: An Accuracy Pilot Study of Skeletally Supported Stereolithographic Surgical Templates

The aim of the present study was to evaluate deviations between virtually planned and placed implants by the use of skeletally supported stereolithographic templates. Ten consecutive patients were selected for virtual three-dimensional implant planning using the Facilitate(TM) software (Astra Tech AB, Mölndal, Sweden). Computer tomography images were obtained in the pre- and postoperative phase. Four deviation parameters (i.e. global, angular, depth, and lateral deviation) were defined and calculated between the planned and the placed implants, using the coordinates of their respective apical and coronal points. Deviations at the coronal positions appeared to be smaller (95% confidence interval: 0.15-1.0) as compared with apical positions (95% confidence interval: 0.14-1.1). But only the difference with regard to lateral measurements appeared to be statistically significant (p = .03). Except for depth (p = .01), no significant association between mesial or more distal locations could be detected concerning global (p = .07), lateral (p = .87), and angular (p = .56) values in mixed model analyses. Overall, there was a slight tendency for higher values for more distal locations. As slight deviations between planned and placed implants especially may occur even with skeletal-supported templates, the clinician should be aware not to overestimate advocated surgical safety by using static navigation tools.

Implants of 6 mm vs. 11 mm lengths in the posterior maxilla and mandible: a 1‐year multicenter randomized controlled trial

In cases with limited bone height, short implants could be a good alternative to augmentation procedures. The aim of this randomized controlled trial was to compare the clinical performance of implants of 6 mm or 11 mm in length in the posterior region. In this multicenter trial (six study sites), 95 subjects were included. Subjects were randomly allocated to receiving implants with lengths of either 6 or 11 mm both with a diameter of 4 mm (OsseoSpeed(™) 4.0 S; Astra Tech AB; Mölndal, Sweden). In all cases, there had to be sufficient bone height to allow placement of an implant of at least 11 mm in length. Two or three implants were placed per subject using one-stage surgery with a 42-48 days' healing period before loading. They were restored with a screw-retained splinted fixed prosthesis. Clinical and radiographic examinations were performed preoperatively, postsurgery, at loading, and 6 and 12 months after prosthesis placement. A total of 208 implants were inserted in 49 subjects receiving 6-mm implants (test) and in 46 subjects receiving 11 mm implants (control). Two 6-mm implants failed before loading and one 6 and 11 mm implants failed before 1-year evaluation. From loading to the 12 months' follow-up, a mean marginal bone gain of 0.06 mm in the 6 mm group and 0.02 mm in the 11 mm group was found (P = 0.478). Soft tissue behavior was equal in both groups (Bleeding and plaque [P = 1.0] probing depth [P = 0.91]). One-year data indicate that treatment with the 6 mm implants is as reliable as treatment with the 11 mm implants. This provides a good treatment option in situations with limited bone height in the premolar and molar regions. Whether or not short implants provide a predictable treatment alternative to bone augmentation procedures remains to be investigated in the future randomized controlled clinical trials.

Longitudinal Changes in Tooth/Single‐Implant Relationship and Bone Topography: An 8‐Year Retrospective Analysis

To evaluate longitudinal changes in tooth/implant relationship and bone topography at single implants with a microthreaded, conical marginal portion (Astra Tech ST® implants, Astra Tech AB, Mölndal, Sweden). Thirty-one subjects with single implant-supported restorations in the esthetic zone were included. Radiographs obtained at crown installation and 1, 5, and 8 years of follow-up were analyzed with regard to changes in (1) bone level at the implant and adjacent teeth and (2) vertical position of adjacent teeth relative to the single implant. The mean marginal bone loss amounted to 0.1 mm at both implants and adjacent teeth during the 8 years of follow-up. Regression analysis failed to identify significant explanatory factors for observed variance in bone level change at the adjacent tooth surfaces. Vertical change in position of the teeth relative to the implants was more frequent and significantly greater in incisor compared with premolar tooth region but not associated with gender or age. The marginal bone level at teeth adjacent to single implants with a microthreaded conical marginal part was not influenced by horizontal and vertical tooth-implant distances. Continuous eruption of adjacent teeth may result in infraocclusal positioning of a single-implant restoration.

Three‐years clinical outcome of immediate provisionalization of single Osseospeed™ implants in extraction sockets and healed ridges

The purpose of this prospective multicenter clinical study was to compare 3years implant survival, bone and soft tissue changes following immediate loading using single Osseospeed(™) implants (Astra Tech AB, Mölndal, Sweden) installed in healed ridges or extraction sockets. Implants were provisionally restored the day of surgery using cemented acrylic crowns out of full occlusion. The provisional crowns were replaced after 12weeks by full-ceramic crowns. Implant survival, bone levels, soft tissue levels and peri-implant health were monitored up to 3years. 55 patients (22 men, 33 women; mean age 45) had the implant installed in extraction sockets and 58 patients (25 men, 33 women; mean age 42) received conventional implant treatment in healed ridges. Three implants failed in the extraction group and one implant failed in the healed group, all failures occurred before the final crown placement. No further losses occurred during 3years, giving a statistically comparable survival rate of 94.6% and 98.3%, respectively. The total bone loss after 3years, compared to implant placement was 0.4mm (SD 1.5) in healed sites, whilst the immediate sites showed a bone gain of 1.6mm (SD 2.4) due to bone fill in the alveolus. Papillae retracted with 0.3 and 0.0mm in the period of provisionalization, but grew back after final crown was placed with 0.3 and 0.5mm in extraction and healed sites respectively after 3years. Plaque and inflammation scores were very low throughout the study time, irrespective of treatment modality. Immediate implants restored at the day of surgery show comparable risk for implant failure, bone loss and midfacial soft tissue recession compared to conventionally installed implants. The 3-years results suggest both hard and soft tissue stability.

A Prospective Study on the Accuracy of Mucosally Supported Stereolithographic Surgical Guides in Fully Edentulous Maxillae

Flapless implant placement using guided surgery is widespread, although clinical publications on the precision are lacking. The purpose of this study was to evaluate the accuracy of mucosal-supported stereolithographic guides in the edentulous maxillae. Seventy-eight OsseoSpeed™ implants (Astra Tech AB, Mölndal, Sweden) of 3.5 to 5 mm width and 8 to 15 mm length were installed consecutively in 13 patients. Implants were functionally loaded on the day of surgery, and implant location was assessed with a computed tomography scan. Mimics 9.0 software (Materialise N.V., Leuven, Belgium) was used to fuse the images of the virtually planned and actually placed implants, and the locations, axes, and interimplant distances were compared. One implant was lost shortly after insertion because of abscess formation caused by remnants of impression material. Seventy-seven implant locations were analyzed. The deviation at the entrance point ranged between 0.29 mm and 2.45 mm (SD: 0.44 mm), with a mean of 0.91 mm. Average angle deviation was 2.60° (range 0.16-8.86°; SD: 1.61°). At the apical point, the deviation ranged between 0.32 mm and 3.01 mm, with a mean of 1.13 mm (SD: 0.52 mm). The mean deviation of the coronal and apical interimplant distance was respectively 0.18 mm (range 0.07-0.32 mm; SD: 0.15) and 0.33 mm (range 0.12-0.69 mm; SD: 0.28). These deviations are lower than the global coronal and apical deviations. The present study is the first to investigate the accuracy of stereolithographic, full, mucosally supported surgical guides in the treatment of fully edentulous maxillae. Clinicians should be warned that angular and linear deviations are to be expected. Short implants show significantly lower apical deviations compared with longer ones. Reasons for implant deviations are multifactorial; however, it is unlikely that the production process of the guide has a major impact on the total accuracy of a mucosal-supported stereolithographic guide.

Ten‐Year Retrospective Follow‐Up Study of the TiOblast™ Dental Implant

Long-term results in the clinical outcome of different implant systems, including high patient numbers and a long follow-up time, are rare. This retrospective study evaluated the cumulative survival rate of a self-tapping, cylindrical implant system with a conical implant-abutment connection after 10 years of prosthetic loading. A total of 516 TiOblast implants (Astra Tech AB, Mölndal, Sweden) were placed in 108 patients. The patients were treated in the Department of Oral and Maxillofacial Surgery, Johannes Gutenberg University, Mainz, Germany, between September 1994 and May 2005. The main indications for implantation were the treatment of edentulous mandibles (74%) and partial edentulism (15%). Twenty-three implants were placed postradiation, and a further 64 implants were irradiated after insertion. In 153 implants, a bony augmentation was conducted prior to implantation. The in situ rate was 89.7% after an average implantation time of 108 months. Eighty-three patients with 403 implants were available for investigation. Seventeen patients with 76 implants have died since 1994. Absence of osseointegration (n = 22), peri-implantitis (n = 18), fracture of the implants (n = 9), failing of primary stability (n = 2), and implants next to tumors (n = 2) were the reasons of explantation in 26 patients. Under analysis with different implant success-assessment criteria, the success rate showed results from 76 to 89%. With respect to the critical patient selection including a high number of patients with minor and major augmentations, the 10-year clinical use of the studied implant system showed acceptable results.

Stability Evaluation of Implants Integrated in Grafted and Nongrafted Maxillary Bone: A Clinical Study from Implant Placement to Abutment Connection

Clinical studies have shown a higher degree of implant failures in grafted bone compared with normal nongrafted maxillary bone. Additionally, a prolonged time for integration of titanium implants in grafted block bone has been shown by means of resonance frequency analysis (RFA). The aim of this prospective study was to compare the stability of implants placed in particulate bone, onlay block bone, interpositional bone, and nongrafted maxillary bone during the early phase of osseointegration using RFA and implant failure. Thirty-five patients with edentulism in the maxilla were included in the study. In all, 260 Astra Tech TiOblast implants (Astra Tech AB, Mölndal, Sweden) were installed. Twenty-five of these patients had severe maxillary atrophy and were treated with iliac bone grafts 5 to 6 months prior to implant placement, 19 with lateral onlay block grafts on one side (group A, 38 implants) and particulate bone for lateral augmentation on the other (group B, 38 implants). These 19 patients also got bilateral sinus floor augmentation with particulate bone (group C, 76 implants). Six patients had an unfavorable sagittal relation between the jaws and underwent a LeFort I operation with interpositional bone blocks grafted to the nasal and sinus floors (group D, 48 implants). The remaining 10 patients could be treated with implants without bone augmentation and served as control (group E, 60 implants). RFA was performed at implant placement and abutment connection 6 months later and an implant stability quotient (ISQ) value was given for each implant. Four implants (1.5%) were found mobile at abutment connection and removed (two in group A and two in group D). RFA showed a slight increase in stability from installation to abutment connection but the differences were not statistically significant in any of the groups (Wilcoxon signed rank test for comparison of paired data). Implants installed in group D had a significantly lower ISQ value at both measurements compared with the other groups (Wilcoxon Rank Sum test for comparisons of independent samples, p = .05). It is concluded that TiO(2)-blasted implants placed in nongrafted and grafted maxillary bone using a two-staged protocol show similar stability during the early phase of osseointegration. Patients reconstructed with interpositional bone graft after a LeFort I osteotomy showed lower implant stability values than nongrafted patients and other grafting techniques.

Clinical, Aesthetic, and Patient‐Related Outcome of Immediately Loaded Single Implants in the Anterior Maxilla: A Prospective Study in Extraction Sockets, Healed Ridges, and Grafted Sites

The objective of this prospective clinical study was to document the overall treatment outcome of immediately loaded single Astra Tech Osseospeed™ (Astra Tech AB, Mölndal, Sweden) implants placed in extraction sockets, healed ridges, and grafted sites. Forty-eight patients in need of a single implant in the anterior maxilla (15-25) were recruited. Patients were allocated to a conventional implant treatment (CIT) or immediate implant treatment (IIT) group on the basis of specific criteria. If the buccal bone plate was damaged or missing upon tooth removal, patients were allocated to a grafted implant treatment (GIT) group. Irrespective of the treatment concept, implants were immediately provisionalized. Hard and soft tissue alterations, aesthetic parameters (pink and white esthetic scores, [PES and WES]) and patient's opinion (Oral Health Impact Profile [OHIP-14] questionnaires) were registered at different time points. After 1 year of function, the overall implant survival rate was 98% with one failure following IIT. The mean bone level to the implant-abutment interface was 0.65 (SD 0.79), 0.85 (SD 0.64), and 0.56 mm (SD 0.44) for CIT, IIT, and GIT. Complete papilla loss was rare following either strategy. Mean midfacial recession amounted to 1.00 (SD 1.15), 0.12 (SD 0.78), and 0.49 mm (SD 0.82) for CIT, IIT, and GIT, respectively. The aesthetic outcome showed a mean PES of 10.30 (SD 1.89) and mean WES of 7.11 (SD 2.14), all patients considered. Patient's satisfaction showed a significant improvement after 1 year of function on all seven domains (p < .001). This prospective study showed that single implants clinically and aesthetically perform well under immediate non-occlusal loading conditions in the premaxilla. In this context, it is of pivotal importance to stress that patients were carefully selected for IIT and GIT.

Reliability of Circumferential Bone Level Assessment around Single Implants in Healed Ridges and Extraction Sockets Using Cone Beam CT

Cone beam computerized tomography (CBCT) provides three-dimensional information and could absolutely be useful for evaluating circumferential implant bone levels. However, the accuracy and precision of the technique has not been described. The aim of the study was to assess the accuracy and precision of CBCT (i-CAT®, Imaging Sciences International®, Hatfield, PA, USA) using periapical radiographs (PA) as a reference and to evaluate the circumferential bone level on CBCT around immediately loaded single implants placed in healed ridges (CIT, conventional implant treatment) and extraction sockets (IIT, immediate implant placement). PA and CBCT radiographs were obtained from 26 single Astra Tech Osseospeed™ implants (Astra Tech AB, Mölndal, Sweden) 1 year after loading in respectively healed ridges (CIT) or extraction socket (IIT). For accuracy analysis, the three mesial and three distal interproximal levels obtained by CBCT were pooled to enable a comparison with PA. Precision was analyzed by intra- and interexaminer reliability calculation from mesial and distal sites on CBCT. The circumferential bone level considered all eight positions assessed on CBCT. Accuracy of CBCT was low (R = 0.325/p = .019) given the fact that bone level of the total group was 0.70 mm (standard deviation [SD] 0.78, range 0.00-3.20) on PA and 0.23 mm (SD 0.27, 0.00-1.20) on CBCT (p < .001) with only 42% of the measurements showing deviation within 0.2 mm. However, intra- and interexaminer reliability were favorable (R ≥ 0.611/p < .001, ≥ 83%). The mean circumferential bone level on CBCT was 0.21 mm (SD 0.30) and 0.26 mm (SD 0.18) for IIT and CIT, respectively. The impact of the treatment strategy was not significant. PA should be the standard technique to assess interproximal bone level but correlates poorly with the CBCT measurements. However, the precision of CBCT was high. CBCT requires further improvements of hardware and/or software. Within the limitations of the study, there is an indication that the buccal bone 1 year after implant treatment is evenly preserved when implants are immediately loaded in extraction sockets or in healed bone.

Reconstruction of Severely Atrophied Alveolar Ridges with Calvarial Onlay Bone Grafts and Dental Implants

Severely atrophied alveolar ridges are most commonly reconstructed with free autologous bone grafts from the iliac crest. The use of these grafts, however, is frequently associated with bone resorption as possible late complication after implant surgery and prosthetic loading. Other donor sites, especially intraoral donor sites, show limited availability. The aim of this present study was to evaluate the clinical and radiographical outcome of alveolar ridge reconstruction with bone from the calvarium and subsequent implant rehabilitation. Reconstruction was performed by using calvarial split grafts in case of severe and complex alveolar ridge defects induced by trauma or bone atrophy. Fifteen patients were treated at 19 different intraoral recipient sites (15 sites in the maxilla, four in the mandible). Autologous block grafts were used for combined vertical and horizontal grafting. After a 3-month healing period, patients received dental implants. A total of 99 dental implants (OsseoSpeed™, Astra Tech AB, Mölndal, Sweden) were inserted and left to heal in a submerged position for 3 months before the prosthetic implant-based rehabilitation was performed. No donor site complications occurred during or after surgery. At the intraoral recipient sites two infections occurred, leading to partial loss of the grafts. Implant placement, however, was possible in all cases. Two of 99 implants were lost in two patients prior to prosthetic loading. Patients were followed up clinically and radiographically for an average observation period of 28 months. Implant survival rate and success rates were 97.85 and 95.7%, respectively, and a minimal marginal bone loss was documented. The low morbidity at the donor sites and the good marginal bone stability in the reconstructed regions indicate that calvarial bone grafts represent a viable treatment alternative to grafts from the iliac crest.

Long-Term Follow-Up of the Sinus Membrane Elevation Technique for Maxillary Sinus Implants Without the Use of Bone Grafts or Bone Graft Substitutes in Order to Facilitate Bone Formation

Long-Term Follow-Up of the Sinus Membrane Elevation Technique for Maxillary Sinus Implants Without the Use of Bone Grafts or Bone Graft Substitutes in Order to Facilitate Bone Formation

Mandibular Overdentures Supported by 6‐mm Dental Implants: A 1‐Year Prospective Cohort Study

ABSTRACTBackground: The extremely resorbed edentulous mandible, with a bone height of 8 mm or less, is still a challenge in implant dentistry. Recently, dental implants of 6 mm in length have been developed.Purpose: The purpose of this 1‐year prospective cohort study was to evaluate treatment outcome of mandibular overdentures supported by four 6‐mm dental implants.Materials and Methods: Twelve edentulous patients with a mandibular height between 6 and 8 mm participated. The patients were treated with an overdenture supported by four 6‐mm OsseoSpeed™ dental implants (Astra Tech AB, Mölndal, Sweden). Clinical and radiographic parameters were evaluated 1 year after completion of the prosthetic treatment. Patients' satisfaction was scored before implant surgery and 1 year after prosthetic treatment.Results: One‐year implant survival rate was 96% (two implants were lost). One patient had a fracture of the mandible in the region of one of the implants 3 weeks after implant surgery. Mean scores for plaque, calculus, gingiva, bleeding, and pocket probing depth were low. Patients' satisfaction was high.Conclusion: One‐year follow‐up data revealed that four 6‐mm dental implants inserted in an extremely resorbed edentulous mandible provided a solid basis for a bar‐retained overdenture.

Effect of Smoking Habits on Accuracy of Implant Placement Using Mucosally Supported Stereolithographic Surgical Guides

Smoking is considered as a factor for implant survival and peri-implant bone loss of dental implants. Several studies revealed the negative effect of smoking on osseointegration and its dose-related effect. To evaluate the effect of smoking habits on accuracy of implant placement using mucosally supported stereolithographic surgical guides. Six OsseoSpeed™ implants (Astra Tech AB, Mölndal, Sweden) were inserted into the maxilla in 13 patients. Patients were excluded if they suffered from any systemic disease or if they were actually taking any kind of medication. Software (Mimics® 9.0) was used to fuse images of the virtually planned and actually placed implants, and locations and axes were compared between the nonsmoking and smoking subgroups. As the mucosal biotype could probably influence accuracy data, 12 reference points were defined within each patient to define a mean mucosal thickness value. In the smoking subgroup, 36 implants were placed compared with 42 in the nonsmoking subgroup. Mean coronal deviation was 1.04mm (range: 0.29-2.45mm) among the smokers compared with 0.80mm among the nonsmokers (range: 0.29-1.67mm). At apical point, mean deviation was 1.26mm (range: 0.39-3.01mm) among the smokers compared with 1.02mm among the nonsmokers (range: 0.32-2.59mm). Mean angular deviation was 2.64° (range: 0.41-6.81°) among the smokers compared with 2.57° among the nonsmokers (range: 0.16°-8.86°). Significant differences were found when comparing global coronal and apical deviation between the smokers and the nonsmokers (p<.05). Evaluating mucosal thickness, mean value was 3.19mm (range: 2.39-4.01mm) among the smokers compared with 2.43mm among the nonsmokers (range: 1.44-3.03mm). Statistically significant differences were found when comparing the accuracy of dental implant placement of the smokers with the nonsmokers. Smokers have significant thicker supporting mucosal tissues compared with nonsmokers, which may explain inaccuracy due to less stability of the surgical guide or the scanning prosthesis.

Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta-Analysis

It is important that peri-implant bone breakdown caused by, for example, undue load and/or peri-implantitis, is prevented or minimized. Some continuous loss of marginal bone is generally accepted, but the question remains as to what extent it must occur. The purpose of this study was to compile and compare data on peri-implant marginal bone level changes from prospective studies that have registered the peri-implant marginal bone level radiographically at the time of prosthetic loading, and after 5 years of follow-up for implant systems currently available on the market. A literature search was carried out to identify prospective studies on peri-implant marginal bone level changes around dental implants. To be included in a meta-analysis, the implant systems should have been subjected to at least two independent studies. Copycats without documentation were not accepted. Forty prospective studies that presented with a 5-year data were identified. Three implant systems met the inclusion criteria of having at least two independent studies; Astra Tech Dental Implant System® (Astra Tech AB, Mölndal, Sweden), Brånemark System (Nobel Biocare AB, Göteborg, Sweden), and Straumann Dental Implant System (Institute Straumann AG, Basel, Switzerland). The pooled mean marginal bone level change amounted to -0.24 mm (95% CI -0.345, -0.135) for the Astra Tech Dental Implant System, 0.75 mm (95% CI -0.802, -0.693) for the Brånemark System, and 0.48 mm (95% CI -0.598, -0.360) for the Straumann Dental Implant System over 5 years, with a statistically significant difference (p < .01) between the systems. The identified implant systems showed an annual bone loss below or much below what hitherto has been set up as a limit for success. A careful documentation of marginal bone level changes should be mandatory for all implant systems before being marketed. It is also time for revision of existing success criteria to refine the basis for clinical quality judgment of implant treatment.