Bone augmentation at titanium implants using autologous bone grafts and a bioresorbable barrier. An experimental study in the rabbit tibia

Influence of wound closure on volume stability with the application of different GBR materials: an in vitro cone-beam computed tomographic study

PURPOSE

To assess the influence of using different combinations of guided bone regeneration (GBR) materials on volume changes after wound closure at peri-implant dehiscence defects.

METHODS

In 5 pig mandibles, standardized bone defects were created and implants were centrally placed. The defects were augmented using different combinations of GBR materials: xenogeneic granulate and collagen membrane (group 1, n=10), xenogeneic granulate and alloplastic membrane (group 2, n=10), alloplastic granulates and alloplastic membrane (group 3, n=10). The horizontal thickness was assessed using cone-beam computed tomography before and after suturing. Measurements were performed at the implant shoulder (HT0) and at 1 mm (HT1) and 2 mm (HT2) below. The data were statistically analysed using the Wilcoxon signed-rank test to evaluate within-group differences. Bonferroni correction was applied when calculating statistical significance between the groups.

RESULTS

The mean horizontal thickness before suturing was 2.55±0.53 mm (group 1), 1.94±0.56 mm (group 2), and 2.49±0.73 mm (group 3). Post-suturing, the values were 1.47±0.31 mm (group 1), 1.77±0.27 mm (group 2), and 2.00±0.48 mm (group 3). All groups demonstrated a loss of horizontal dimension. Intragroup changes exhibited significant differences in group 1 (P<0.001) and group 3 (P<0.01). Intergroup comparisons revealed statistically significant differences of the relative changes between groups 1 and 2 (P=0.033) and groups 1 and 3 (P=0.015).

CONCLUSIONS

Volume change after wound closure was minimized by using an alloplastic membrane. The stability of the augmented horizontal thickness was most ensured by using this type of membrane irrespective of the bone substitute material used for membrane support.

Alveolar ridge augmentation with maxillary sinus elevation and split crest: Comparison of 2 surgical procedures

The purpose of this study was to evaluate the clinical and radiological outcomes of 2 piezosurgical split techniques performed in conjunction with the sinus lift.The present retrospective study included 20 patients with edentulism of the posterior maxilla who had undergone the sinus lift and alveolar ridge split treatment separately or the sinus lift combined with the monoblock alveolar ridge split. Differences between these 2 techniques were analyzed.All the surrounding areas successfully produced an adequate bone volume for the insertion of implants. A clinical evaluation showed a mean vertical augmentation of 3.6 ± 0.4 mm in Group A and 3.2 ± 0.7 mm in Group B. With regards to the lateral augmentation, the clinical evaluation gives a mean gain of 5.2 ± 0.3 mm in Group A and 4.9 ± 0.5 mm in Group B. The mean vertical and horizontal bone augmentation recorded for both types of surgical procedures were comparable.The proposed surgical procedures enabled the tridimensional volume of the alveolar ridge to be recreated. This resulted in the creation of a natural contour of hard and soft tissues which enabled a functional and aesthetic rehabilitation of the edentulous posterior maxilla to be obtained.

Preserving the Bone Profile in Anterior Maxilla using an Equine Cortical Bone Membrane and an Equine Enzyme-treated Bone Graft: A Case Report with 5-year Follow-up

AIM

This study aimed to report a well-succeeded use of equine enzyme-deantigenic cortical membrane and bone granules for guided bone regeneration (GBR) in the esthetic zone concomitant with implant placement.

BACKGROUND

In the anterior maxilla, where patients typically have the highest expectations for implant-supported restorations, bone resorption in the wake of tooth loss often leads to a lack of soft tissue support and ultimately to unsatisfactory esthetic results. Buccal bone augmentation at the time of implant placement has thus become common. This is usually accomplished following GBR principles and employing membranes made from various materials to serve as a barrier between the soft tissue and graft material. One of the more recently introduced membrane materials is made from thin, flexible equine cortical bone, i.e., rendered nonantigenic in an enzymatic process that preserves native bone collagen.

CASE REPORT

This report describes the treatment of a patient who received an equine enzyme-deantigenic graft and membrane in conjunction with placement of an implant in the right maxillary lateral incisor site.

CONCLUSION

After 5 years of follow-up, the patient was very satisfied with her appearance. A cone-beam computed tomography scan showed that the peri-implant bone levels and ridge thickness had been maintained, and the cortical layer in the pristine ridge had also undergone remodeling.

CLINICAL SIGNIFICANCE

Guided bone regeneration with the concomitant use of enzyme-deantigenic membrane and graft is a valuable and suitable option for effective implant-supported prosthetic rehabilitation in the esthetic zone.

The effect of membrane exposure on lateral ridge augmentation: a case-controlled study

BACKGROUND

The effect of membrane exposure on guided bone regeneration (GBR) for lateral ridge augmentation has been poorly addressed. This case-controlled study aimed to investigate potential effect of membrane exposure lateral ridge augmentation and subsequent implant placement.

METHODS

A total of 14 patients that did receive lateral ridge augmentation procedure using allogeneic cancellous graft particulate in combination with an alloplastic bioresorbable matrix barrier were retrospectively selected for this study. Bone width was measured at the crest with a digital caliper before bone augmentation and at the reopening for implant placement 4 months later for all patients. Cases where primary flap closure was achieved and the barrier did not expose throughout the time until implant placement were assigned to the control group (n = 7). Cases where primary closure could not be achieved or a barrier exposure happened within the first week following the initial surgery were assigned to the test group.

RESULTS

The measured alveolar ridge width before surgery as well as after GBR procedure were not statistically significant different between the two groups (p > 0.05). Both groups showed a significant (p < 0.05) increase in their mean alveolar ridge width 4 months after later augmentation procedure, from 3.4 ± 1.2 to 6.0 ± 1.1 mm in the control group and from 3.6 ± 1.0 to 5.0 ± 1.4 mm in the test group. However, the mean alveolar ridge gain was significantly greater in the control group than in the test group (p < 0.05). Consequently, the reduction of the augmented alveolar ridge was significantly higher in the test group averaging to 4.7 mm than for the control group showing a loss of 3.1 mm after 4 months, respectively. However, in all 14 cases, successful implant placement was achieved after 4 months.

CONCLUSIONS

Within the limit of this study, it can be concluded that early exposure of a bioresorbable matrix barrier during lateral ridge augmentation may compromise the results of the GBR procedure but may still result in a favorable alveolar ridge width gain that allows for the placement of dental implants.

Alveolar Ridge Split Technique Using Piezosurgery with Specially Designed Tips

The treatment of patients with atrophic ridge who need prosthetic rehabilitation is a common problem in oral and maxillofacial surgery. Among the various techniques introduced for the expansion of alveolar ridges with a horizontal bone deficit is the alveolar ridge split technique. The aim of this article is to give a description of some new tips that have been specifically designed for the treatment of atrophic ridges with transversal bone deficit. A two-step piezosurgical split technique is also described, based on specific osteotomies of the vestibular cortex and the use of a mandibular ramus graft as interpositional graft. A total of 15 patients were treated with the proposed new tips by our department. All the expanded areas were successful in providing an adequate width and height to insert implants according to the prosthetic plan and the proposed tips allowed obtaining the most from the alveolar ridge split technique and piezosurgery. These tips have made alveolar ridge split technique simple, safe, and effective for the treatment of horizontal and vertical bone defects. Furthermore the proposed piezosurgical split technique allows obtaining horizontal and vertical bone augmentation.

Preliminary evaluation of a three-dimensional, customized, and preformed titanium mesh in peri-implant alveolar bone regeneration

Objectives

The purpose of this preliminary study is to evaluate the effectiveness of a customized, three-dimensional, preformed titanium mesh as a barrier membrane for peri-implant alveolar bone regeneration.

Materials and Methods

Ten patients were recruited for this study. At the time of implant placement, all patients had fenestration or a dehiscence defect around the implant fixture. A mixture of particulate intraoral autologous bone and freeze-dried bone allograft was applied to the defect in a 1 : 1 volume ratio and covered by the preformed titanium mesh. A core biopsy specimen was taken from the regenerated bone four months postoperatively. Patients were followed for 12 months after the definitive prosthesis was placed.

Results

Satisfactory bone regeneration with limited fibrous tissue was detected beneath the preformed titanium mesh. Histologic findings revealed that newly formed bones were well-incorporated into the allografts and connective tissue. New growth was composed of approximately 80% vital bone, 5% fibrous marrow tissue, and 15% remaining allograft. All implants were functional without any significant complications.

Conclusion

The use of preformed titanium mesh may support bone regeneration by maintaining space for new bone growth through its macro-pores. This preliminary study presents the efficacy of a preformed titanium mesh as a ready-to-use barrier membrane around peri-implant alveolar bone defect. This preformed mesh is also convenient to apply and to remove.

Mechanisms of guided bone regeneration: a review

Post-extraction crestal bone resorption is common and unavoidable which can lead to significant ridge dimensional changes. To regenerate enough bone for successful implant placement, Guided Bone Regeneration (GBR) is often required. GBR is a surgical procedure that uses barrier membranes with or without particulate bone grafts or/and bone substitutes. There are two approaches of GBR in implant therapy: GBR at implant placement (simultaneous approach) and GBR before implant placement to increase the alveolar ridge or improve ridge morphology (staged approach). Angiogenesis and ample blood supply play a critical role in promoting bone regeneration.

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

In vivo behaviour of a biodegradable poly(trimethylene carbonate) barrier membrane: a histological study in rats

The aim of the present study was to evaluate the response of surrounding tissues to newly developed poly(trimethylene carbonate) (PTMC) membranes. Furthermore, the tissue formation beneath and the space maintaining properties of the PTMC membrane were evaluated. Results were compared with a collagen membrane (Geistlich BioGide), which served as control. Single-sided standardized 5.0 mm circular bicortical defects were created in the mandibular angle of rats. Defects were covered with either the PTMC membrane or a collagen membrane. After 2, 4 and 12 weeks rats were sacrificed and histology was performed. The PTMC membranes induced a mild tissue reaction corresponding to a normal foreign body reaction. The PTMC membranes showed minimal cellular capsule formation and showed signs of a surface erosion process. Bone tissue formed beneath the PTMC membranes comparable to that beneath the collagen membranes. The space maintaining properties of the PTMC membranes were superior to those of the collagen membrane. Newly developed PTMC membranes can be used with success as barrier membranes in critical size rat mandibular defects.

Histology and stability study of cortical bone graft influence on titanium implants

OBJECTIVE

The mechanisms for integrating titanium implants in recipient bone are still not well defined, and it is not known whether the process of bone formation around implants inserted into grafts is the same as that described for titanium implants in nongrafted cortical bone. This study compared the histology, stability, and osseointegration of titanium implants inserted in cortical bone with and without a simultaneous autologous cortical bone graft in an experimental animal model.

METHODS

Thirty titanium implants were inserted in 3 sheep. Half of the implants were inserted to fix the graft to the recipient bone, and the remainder were inserted in the distal part of the tibial metaphysis as controls. The animals were humanely killed at 2, 6, and 8 months after surgery. A stability test (unscrewing torque) was performed immediately on 12 fresh specimens (6 grafted implants and 6 control implants). The remaining unscrewed implants, both grafted and not grafted, were subjected to histomorphometric analysis.

RESULTS

After osseointegration, the unscrewing force exceeded the fracture limit of the titanium fixtures in both the grafted samples and controls, demonstrating their optimal stability but failing to demonstrate an improvement in the grafted bone. Histomorphometric analysis demonstrated newly formed tissue that extended from the contact area inside the graft, beginning at 6 months. At 8 months, the implant threads in the graft were surrounded by a large amount of newly formed bone mixed with necrotic fragments.

CONCLUSIONS

Our results show that onlay cortical grafts on cortical bone enhance the osteogenic potential of the host bone, ensuring solid, viable bone tissue support that results in a high rate of integration of the titanium fixtures. The loading forces affect the bone-healing process after implant insertion; bone matrix was deposited unequally, being greater proximally (90% versus 40%), which is perpendicular to the maximal load tension lines when the sheep are standing. This implies that in the human jaw, where the tension lines parallel the axis of the implants, the implants can play an important role in guiding new bone formation during osseointegration.

A Comparison Between Enamel Matrix Derivative and a Bioabsorbable Membrane to Enhance Healing Around Transmucosal Immediate Post-Extraction Implants

BACKGROUND

This clinical report compares the use of an enamel matrix derivative (EMD) and bioabsorbable barrier membrane to enhance healing following the immediate placement of transmucosal implants into extraction sockets.

METHODS

Thirty-two adult patients scheduled for tooth replacement with dental implants agreed to participate. Following the insertion of a transmucosal implant into the extraction site, the subjects were assigned to one of two treatment alternatives of the remaining bone defects around the implants: 1) the residual bone defects were filled with EMD (EMD group) or 2) the residual bone defects were covered with a bioabsorbable membrane (membrane group). Flaps were then coronally positioned around implant cover screws. Patients followed weekly maintenance recalls for the first 6 weeks and then monthly recalls until the final prosthetic restoration was completed (after 6 months). The treatment outcome was evaluated after 12 months by the use of clinical variables. The null hypothesis of no treatment group differences was tested by the use of analysis of variance (ANOVA).

RESULTS

At a 12-month follow-up, all of the implants were completely osseointegrated and successfully functioning, showing a success rate of 100%. The membrane group showed a significantly lower mean probing attachment level than the EMD group at proximal (0.60 mm, standard deviation (SD) 0.37 versus 1.19 mm, SD 1.10), buccal (0.80 mm, SD 0.79 versus 1.77 mm, SD 1.16), and lingual sites (0.44 mm, SD 0.52 versus 1.48 mm, SD 1.46). The difference was statistically significant at all sites (P < 0.05). With respect to the position of the soft tissue margin around the implant shoulder, the membrane group showed a consistently higher value than the EMD group at, respectively, proximal (1.30 mm, SD 2.37 versus 1.16 mm, SD 1.0), buccal (0.90 mm, SD 1.29 versus 0.22 mm, SD 1.47), and lingual sites (1.12 mm, SD 1.10 versus 0.55 mm, SD 1.42).

CONCLUSIONS

The membrane group obtained more favorable results in terms of both the probing attachment level and peri-implant position of soft tissues compared to the EMD group. The use of a bioabsorbable membrane around immediately placed transmucosal implants enhanced soft and hard tissue healing and might be an advisable treatment choice particularly in areas with high esthetic demands.

Problems related to an intraoral approach for experimental surgery on minipigs

The purpose of the present study was to compare block and particulated bone grafts for jaw augmentation in combination with immediate implant placement. Bone defects measuring 10 mm x 10 mm x 30 mm were prepared on each side of the mandible of eight minipigs. After a healing period of 3 months, the defects in four animals were augmented with iliac crest grafts as a block or particulated graft, combined with immediate implant insertion. Clinical inspection was performed after 14 days. Complete exposure of grafts and implants was discovered. The surgical procedures were altered in the fifth animal. Inspection was made after 4 days showing no alterations. However, after another 7 days, grafts and implants were exposed. Consequently, the study was discontinued and all eight animals were killed. It is concluded that an intraoral approach is not applicable for this type of experimental surgery in minipigs. This paper describes some of the presumed reasons for the failure of the study.

Clinical results of alveolar ridge augmentation with mandibular block bone grafts in partially edentulous patients prior to implant placement

A group of 15 partially edentulous patients who needed alveolar ridge augmentation for implant placement, were consecutively treated using a two-stage technique in an outpatient environment. A total of 18 alveolar segments were grafted. During the first operation bone blocks harvested from the mandibular ramus or symphysis were placed as lateral or vertical onlay grafts and fixed with titanium osteosynthesis screws after exposure of the deficient alveolar ridge. After 6 months of healing the flap was re-opened, the screws were removed and the implants placed. Twelve months after the first operation implant-supported fixed bridges could be provided to the patients. Mean lateral augmentation obtained at the time of bone grafting was 6.5 +/- 0.33 mm, that reduced during healing because of graft resorption to a mean of 5.0 +/- 0.23 mm. Mean vertical augmentation obtained in the 9 sites where it was needed was 3.4 +/- 0.66 mm at bone grafting and 2.2 +/- 0.66 mm at implant placement. Mean lateral and vertical augmentation decreased by 23.5% and 42%, respectively, during bone graft healing (before implant insertion). Mandibular sites showed a larger amount of bone graft resorption than maxillary sites. All the 40 implants placed were integrated at the abutment connection and after prosthetic loading (mean follow-up was 12 months). No major complications were recorded at donor or recipient sites. Soft tissue healing was uneventful, and pain and swelling were comparable to usual dentoalveolar procedures. A visible ecchymosis was present for 4 to 7 days when the bone was harvested from the mandibular symphysis. From a clinical point of view this procedure appears to be simple, safe and effective for treating localised alveolar ridge defects in partially edentulous patients.

The titanium surface texture effects adherence and growth of human gingival keratinocytes and human maxillar osteoblast-like cells in vitro

The adhesion, orientation and proliferation of human gingival epithelial cells and human maxillar osteoblast-like cells in primary and secondary culture were studied on glossy polished, sandblasted and plasma-sprayed titanium surfaces by scanning electron microscopy and in thin sections. The primary cultured explants of human gingival epithelial cells attached, spread and proliferated on all titanium surfaces with the greatest extension on the polished and the smallest extension on plasma-sprayed surfaces. In secondary suspension cultures of gingival keratinocytes, attachment spreading and growth was only observed on polished and plasma-sprayed surfaces, but not on sandblasted surfaces. Moreover, the attachment of these cells depended on the seeding concentration as well as on the coating with fetal calf serum. Cells on polished surfaces developed an extremely flat cell shape, but on sandblasted and plasma-sprayed surfaces a more cuboidal shape. In contrast human maxillar osteoblasts seeded as secondary suspension cultures attached very well to all three differently textured titanium surfaces and showed identical growth patterns independent of the titanium surface structure. These findings suggest that cell morphology, orientation, proliferation and adhesion of human gingival epithelial cells in primary or secondary culture are dependent on the texture of the titanium surface whereas no such differences were observed for maxillar osteoblast-like cells. In conclusion, the soft tissue integration and response is more influenced by the surface texture than the process of osseointegration.

Long-term evaluation of osseointegrated implants inserted at the time or after vertical ridge augmentation. A retrospective study on 123 implants with 1-5 year follow-up

The purpose of the present study was to evaluate retrospectively, after 1 to 5 years of prosthetic loading, 123 implants consecutively inserted at the time of vertical ridge augmentation in 4 clinics. At the time of the implant surgery, 3 different techniques were used: the implants were allowed to protrude 2 to 7 mm from the bone level and a titanium reinforced expanded-polytetrafluoroethylene (e-PTFE) membrane was positioned to protect either the blood clot (Group A, 6 patients), or an allograft (Group B, 11 patients), or an autograft (Group C, 32 patients). The annual implant evaluation was carried out according to a standard protocol utilized for long term studies with endosseous implants inserted in non-regenerated bone. Only 1 implant failed immediately after the second stage surgery and after 1 month it was substituted with a new implant. All the remaining implants appeared clinically stable, no signs of radiolucency were present at the bone-implant interface, therefore, they could be defined successfully osseointegrated. The radiographic analysis showed stable bone crest levels with a mean bone loss of 1.35 mm for the Group A, of 1.87 mm for the Group B and of 1.71 for the Group C during the period of observation. Only 2 implants demonstrated an increased crestal bone loss of 3.5 mm and 4 mm respectively at the first year examination. On the base of these results, we can confirm previous long term studies on regenerated bone and we can conclude that vertically augmented bone with GBR techniques responds to implant placement like native, non-regenerated bone.