Minimally invasive sinus lift implant device: a multicenter safety and efficacy trial preliminary results

PURPOSE

In cases of advanced maxillary sinus atrophy of the bone (pneumatization), the sinus floor has to be augmented in order to obtain acceptable bone volume for implantation. The objective of the present study is to evaluate a new procedure and device, designed as a closed sinus lift using a dedicated dental implant that allows for Schneiderian membrane elevation and the placement of a flowable bone replacement graft.

MATERIALS AND METHODS

Eighteen patients (8 males, 10 females) underwent 23 procedures. All procedures were completed successfully, with elevation of the sinus membrane and insertion of bone graft and the dental implant at the planned site. No membrane tears were noted. No intraoperative or postoperative adverse events were observed in any of the cases. There were no postprocedural emergency or distress calls.

RESULTS

The patients' average age was 52 (range 38-72). The mean residual alveolar ridge height was 5.5 mm (range 4.0-7.0). The average bone gain was 11.2 mm (range 9-13) after an average healing period of 8.7 months (range 6.7-13.1). All implants achieved clinical stability and prosthetic rehabilitation was uneventful.

CONCLUSIONS

A closed sinus floor elevation procedure can be accomplished using a dedicated dental implant that allows for hydraulic elevation of the Schneiderian membrane and placement of a flowable bone replacement graft and dental implant placement all at the same time with minimal patient discomfort.

Osteoblast maturation and new bone formation in response to titanium implant surface features are reduced with age

The surface properties of materials contribute to host cellular response and play a significant role in determining the overall success or failure of an implanted biomaterial. Rough titanium (Ti) surface microtopography and high surface free energy have been shown to enhance osteoblast maturation in vitro and increase bone formation in vivo. Whereas the surface properties of Ti are known to affect osteoblast response, host bone quality also plays a significant role in determining successful osseointegration. One factor affecting host bone quality is patient age. We examined both in vitro and in vivo whether response to Ti surface features was affected by animal age. Calvarial osteoblasts isolated from 1-, 3-, and 11-month-old rats all displayed a reduction in cell number and increases in alkaline phosphatase-specific activity and osteocalcin in response to increasing Ti surface microtopography and surface energy. Further, osteoblasts from the three ages examined displayed increased production of osteocalcin and local factors osteoprotegerin, vascular endothelial growth factor (VEGF)-A, and active transforming growth factor (TGF)-β1 in response to increasing Ti surface roughness and surface energy. Latent TGF-β1 only increased in cultures of osteoblasts from 1- and 3-month-old rats. Treatment with the systemic osteotropic hormone 1α,25(OH)(2)D(3) further enhanced the response of osteoblasts to Ti surface features for all three age groups. However, osteoblasts derived from 11-month-old animals had a reduced response to 1α,25(OH)(2)D(3) compared to osteoblasts derived from 1- or 3-month-old animals. These results were confirmed in vivo. Ti implants placed in the femoral intramedullary canal of old (9-month-old) mice yielded lower bone-to-implant contact and neovascularization in response to Ti surface roughness and energy compared to younger (2-month-old) mice. These results show that rodent osteoblast maturation in vitro as well as new bone formation in vivo is reduced with age. Whether comparable age differences exist in humans needs to be determined.

Impact of recombinant platelet-derived growth factor BB on bone regeneration: a study in rabbits

The aim of this study was to test whether recombinant human platelet-derived growth factor BB (rhPDGF-BB) enhances bone regeneration in combination with Β-tricalcium phosphate (Β-TCP) granules or deproteinized bovine bone mineral (DBBM) compared to empty defects and Β-TCP granules alone. Four titanium cylinders were placed on the external cortical plates of seven rabbits' calvaria and randomly allocated to one of four groups: (1) empty, (2) Β-TCP, (3) Β-TCP + rhPDGF-BB, and (4) DBBM + rhPDGF-BB. The mean area of bone regeneration was 13.9% ± 8.4% (empty), 24.0% ± 14.8% (Β-TCP), 37.1% ± 8.9% (Β-TCP + rhPDGF-BB), and 64.4% ± 5.4% (DBBM + rhPDGF-BB), with the greatest bone regeneration noted for DBBM + rhPDGF-BB (P < .01). The fraction of bone substitute material varied between 48.3% ± 9.3% (DBBM + rhPDGF-BB), 53.1% ± 10.6% (Β-TCP + rhPDGF-BB), and 58.0% ± 14.8% (Β-TCP). rhPDGF-BB combined with DBBM showed the greatest potential to enhance bone regeneration.

Tissue integration of collagen-based matrices: an experimental study in mice

OBJECTIVES

To test whether or not tissue integration, biodegradation, and new blood vessel formation in two collagen-based matrices depend on the level of chemical cross-linking.

MATERIAL AND METHODS

Two collagen matrices with high (CM1) and low (CM2) levels of chemical cross-linking were randomly implanted in two pouches in 14 athymic nude mice. Three and 6 weeks later, the animals were euthanized. Histologic and histomorphometric measurements were performed on paraffin-embedded sections.

RESULTS

Both collagen matrices integrated well into the surrounding soft tissues. The level of cross-linking and duration of implantation had an effect on the formation of new blood vessels. More blood vessels (n = in absolute numbers) were found in outer compartments compared to the central compartments of the matrices, reaching 5.6 (CM2) vs. 4.3 (CM1) at 3 weeks, and 5.3 (CM2) vs. 7.3 (CM1) at 6 weeks. Similarly, connective tissue formation increased for both matrices between 3 and 6 weeks, whereas the amount of remaining collagen network gradually decreased over time being more pronounced for CM1 (-50%) compared to CM2 (-15%).

CONCLUSIONS

The degree of cross-linking was negatively correlated for all outcome measures resulting in improved tissue integration, superior matrix stability and enhanced angiogenic patterns for the less cross-linked collagen matrix (CM2) in this experimental study in mice.

A 5-year prospective multicenter study of early loaded titanium implants with a sandblasted and acid-etched surface

PURPOSE

For dental implants to be successful, osseointegration must occur, but it is unknown how much time must pass for osseointegration to be established. Preclinical studies suggested that titanium implants with a sandblasted and acid-etched (SLA) surface were more osteoconductive and allowed more rapid osseointegration than machined or turned implant surfaces. The hypothesis of this study was that implants with an SLA surface could be loaded in half the conventional healing time of machined-surface implants and that, after loading, the implants would be successful for 5 years.

MATERIALS AND METHODS

A prospective multicenter clinical study was conducted with 439 implants placed in native bone in 135 edentulous and partially edentulous patients. Abutments were attached to the implant with 35 Ncm of torque without countertorque after 6 weeks in type I to III bone and after 12 weeks in type IV bone. The patients were carefully evaluated for 5 years.

RESULTS

Most implants were placed in nonsmoking, nondiabetic patients with a mean age of 55 years (range, 21 to 82 years). Eighty percent of the implants were 10 or 12 mm long, 96% had a diameter of 4.1 mm, and 78% were placed in type II or III bone. Patients maintained good oral hygiene and were satisfied with the restorations. Four implants failed, and one implant was deemed unsuccessful between surgery and the 1-year postloading visit. No implants failed or were unsuccessful in subsequent years. The cumulative survival and success rates for 385 implants in 120 patients after 5 years were 99.1% and 98.8%, respectively.

CONCLUSION

Implants with an SLA surface can be restored in 6 weeks for type I to III bone and 12 weeks for type IV bone. Furthermore, they can be maintained after loading for 5 years with very high success and survival rates.

Regeneration of periodontal tissues in non-human primates with rhGDF-5 and beta-tricalcium phosphate

The application of growth factors has been advocated in support of periodontal regeneration. Recombinant human growth and differentiation factor-5 (rhGDF-5), a member of the bone morphogenetic protein family, has been used to encourage periodontal tissue regeneration. This study evaluated the dose response of rhGDF-5 lyophilized onto beta-tricalcium phosphate (bTCP) granules for periodontal tissue regeneration in a baboon model. Periodontal defects were created bilaterally in 12 baboons by a split-mouth design. Plaque was allowed to accumulate around wire ligatures to create chronic disease. After 2 mos, the ligatures were removed, and a notch was placed at the base of the defect. Two teeth on each side of the mouth were randomly treated with bTCP only, 0.5, 1.0, or 2.0 mg rhGDF-5/g bTCP. Animals were sacrificed 5 mos post-treatment, with micro-CT and histomorphometric analysis performed. After 5 mos, analysis showed alveolar bone, cementum, and periodontal ligament formation in all treatment groups, with a dose-dependent increase in rhGDF-5-treated groups. Height of periodontal tissues also increased with the addition of rhGDF-5, and the amount of residual graft material decreased with rhGDF-5 treatment. Therefore, rhGDF-5 delivered on bTCP demonstrated effective regeneration of all 3 tissues critical for periodontal repair.

Soft tissue volume augmentation by the use of collagen-based matrices in the dog mandible -- a histological analysis

OBJECTIVES

The aim was to test, whether or not soft tissue volume augmentation with a specifically designed collagen matrix (CM), leads to ridge width gain in chronic ridge defects similar to those obtained by an autogenous subepithelial connective tissue graft (SCTG).

MATERIAL AND METHODS

In six dogs, soft tissue volume augmentation was performed by randomly allocating three treatment modalities to chronic ridge defects [CM, SCTG and sham-operated control (Control)]. Dogs were sacrificed at 28 (n = 3) and 84 days (n = 3). Descriptive histology and histomorphometric measurements were performed on non-decalcified sections.

RESULTS

SCTG and CM demonstrated favourable tissue integration, and subsequent re-modelling over 84 days. The overall mean amount of newly formed soft tissue (NMT) plus bone (NB) amounted to 3.8 ± 1.2 mm (Control), 6.4 ± 0.9 mm (CM) and 7.2 ± 1.2 mm (SCTG) at 28 days. At 84 days, the mean NMT plus NB reached 2.4 ± 0.9 mm (Control), 5.6 ± 1.5 mm (CM) and 6.0 ± 2.1 mm (SCTG). Statistically significant differences were observed between CM/SCTG and Control at both time-points (p < 0.05).

CONCLUSION

Within the limits of this animal model, the CM performed similar to the SCTG, based on histomorphometric outcomes combining NB and NMT.

The therapeutic potential of oxygen tension manipulation via hypoxia inducible factors and mimicking agents in guided bone regeneration. A review

Intraoral bone grafting is routinely employed for implant site development prior or simultaneously to implant placement. Bone graft consolidation is a complex biological process depending on the formation of blood vessels into the augmented area. It is highly regulated by the angiogenesis and osteogenesis coupling phenomenon. The vascular system apart from supplying nutrients and oxygen to the developing and regenerating bone, also delivers critical signals which stimulate mesenchymal cell differentiation towards an osteogenic phenotype. Hypoxia inducible factors (HIFs) and mimicking agents (HMAs) (or alternatively HIF stabilizing agents) are considered to act as key stimulators of blood vessel formation. Under normoxia, HIFs are rapidly degraded. However, their degradation is prevented under hypoxia, which in turn, triggers angiogenesis. Hence, the major role of HMAs is to prevent degradation of HIFs under normoxic conditions. Recent studies suggest that HIFs and HMAs trigger the initiation and promotion of angiogenic-osteogenic cascade events. In vitro and animal studies involving genetic manipulation of individual components of the HIFs and HMAs have provided clues to how angiogenic-osteogenic coupling is achieved. Evidence from preclinical studies further suggests that topical application of HMAs enhance angiogenesis in intraoral augmented sites. In this article, we review the current understanding of the cellular and molecular mechanisms responsible for angiogenic-osteogenic coupling. We also discuss the therapeutic manipulation of HIFs and HMAs in intraoral bone repair and regeneration. Such discoveries suggest promising approaches for the development of novel therapies to improve intraoral bone repair and regeneration procedures.

Inflammation and uncoupling as mechanisms of periodontal bone loss

Periodontal disease is characterized by both inflammation and bone loss. Advances in research in both these areas have led to a new appreciation of not only each field but also the intimate relationship between inflammation and bone loss. This relationship has resulted in a new field of science called osteoimmunology and provides a context for better understanding the pathogenesis of periodontal disease. In this review, we discuss several aspects of the immuno-inflammatory host response that ultimately results in loss of alveolar bone. A proposal is made that periodontal inflammation not only stimulates osteoclastogenesis but also interferes with the uncoupling of bone formation and bone resorption, consistent with a pathologic process. Furthermore, arguments based on experimental animal models suggest a critical role of the spatial and temporal aspects of inflammation in the periodontium. A review of these findings leads to a new paradigm to help explain more fully the impact of inflammation on alveolar bone in periodontal disease so that it includes the effects of inflammation on uncoupling of bone formation from resorption.

Soft tissue volume augmentation by the use of collagen-based matrices: a volumetric analysis

OBJECTIVES

The aim was to test whether or not soft tissue augmentation with a newly developed collagen matrix (CM) leads to volume gain in chronic ridge defects similar to those obtained by an autogenous subepithelial connective tissue graft (SCTG).

MATERIAL AND METHODS

In six dogs, soft tissue volume augmentation was performed by randomly allocating three treatment modalities to chronic ridge defects (CM, SCTG, sham-operated control). Impressions were taken before augmentation (baseline), at 28, and 84 days. The obtained casts were optically scanned and the images were digitally analysed. A defined region of interest was measured in all sites and the volume differences between the time points were calculated.

RESULTS

The mean volume differences per area between baseline and 28 days amounted to a gain of 1.6 mm (CM; SD+/-0.9), 1.5 mm (SCTG; +/-0.1), and a loss of 0.003 mm (control; +/-0.3). At 84 days, the mean volume differences per area to baseline measured a gain of 1.4 mm (CM; +/-1.1), 1.4 mm (SCTG; +/-0.4), and a loss of 0.3 mm (control; +/-0.3). The differences between CM and SCTG were statistically significant compared with control at 28 and 84 days (p<0.001).

CONCLUSION

Within the limits of this animal study, the CM may serve as a replacement for autogenous connective tissue.

A pilot experimental lateral ridge augmentation study using bone morphogenetic protein 2 in dogs

The loss of multiple teeth in the posterior mandible often results in deficient ridge width for prosthetic tooth rehabilitation. Multiple approaches have been used to regenerate lost bone; however, the outcomes are highly variable. Several approaches use combination therapy to make the procedure more predictable. In this experimental study in dogs, a chronic defect was created and then treated with one of four therapies: (1) autograft, (2) recombinant human bone morphogenetic protein 2 (rhBMP-2) in absorbable collagen sponge (ACS), (3) ACS wrapped around a collagen-ceramic matrix, and (4) rhBMP-2 in ACS around the collagen-ceramic matrix. Two metal screws were used for space maintenance. After 2 months, the metal pins were removed and an endosseous dental implant was placed in the regenerated bone. Two months later, the animals were sacrificed and specimens prepared for histologic evaluation. Only five animals were used, with each condition evaluated in each animal. With this low number of animals and with the observed variability, no quantitative differences were found between each of the four conditions evaluated. All conditions resulted in new bone growth. Dense native bone was found in the autograft sites and the sites treated with rhBMP-2 and ACS. Sites treated with the collagen-ceramic matrix with and without rhBMP-2 in the ACS had residual ceramic and large porous areas. Bone was found in varying degrees along the implant surfaces. These results suggest that multiple approaches can be used to augment bone horizontally in the posterior mandible of dogs. Interestingly, rhBMP-2 combined with a non-space maintaining collagen carrier yielded new bone densities similar to the autograft in this model.

The role of phospholipase D in osteoblast response to titanium surface microstructure

Biomaterial surface properties such as microtopography and energy can change cellular responses at the cell-implant interface. Phospholipase D (PLD) is required for the differentiation of osteoblast-like MG63 cells on machined and grit-blasted titanium surfaces. Here, we determined if PLD is also required on microstructured/high-energy substrates and the mechanism involved. shRNAs for human PLD1 and PLD2 were used to silence MG63 cells. Wild-type and PLD1 or PLD1/2 silenced cells were cultured on smooth-pretreatment surfaces (PT); grit-blasted, acid-etched surfaces (SLA); and SLA surfaces modified to have higher surface energy (modSLA). PLD was inhibited with ethanol or activated with 24,25-dihydroxyvitamin-D(3) [24R,25(OH)(2)D(3)]. As surface roughness/energy increased, PLD mRNA and activity increased, cell number decreased, osteocalcin and osteoprotegerin increased, and protein kinase C (PKC) and alkaline phosphatase specific activities increased. Ethanol inhibited PLD and reduced surface effects on these parameters. There was no effect on these parameters after knockdown of PLD1, but PLD1/2 double knockdown had effects comparableto PLD inhibition. 24R,25(OH)(2)D(3) increased PLD activity and the production of osteocalcin and osteoprotegerin, but decreased cell number on the rough/high-energy surfaces. These results confirm that surface roughness/energy-induced PLD activity is required for osteoblast differentiation and that PLD2 is the main isoform involved in this pathway. PLD is activated by 24R,25(OH)(2)D(3) in a surface-dependent manner and inhibition of PLD reduces the effects of surface microstructure/energy on PKC, suggesting that PLD mediates the stimulatory effect of microstructured/high-energy surfaces via PKC-dependent signaling.

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

PURPOSE

The purpose of this study was to evaluate the radiographic bone level and stability changes around early loaded chemically modified sandblasted and acid-etched implants with and without a machined collar.

MATERIALS AND METHODS

Seventy-two chemically modified sandblasted and acid-etched implants 4.1 mm in diameter and 8 mm in length were placed in six dogs. Thirty-six implants had no machined collar (NMC) and 36 had a 2.8-mm machined collar (MC). Resonance frequency measurements were obtained at placement and weekly for 3 weeks. All implants were loaded 21 days after surgery. Standardized periapical radiographs were obtained at baseline, at 3 weeks, and at 3, 6, 9, and 12 months. The radiographs were randomized and digitized, and linear measurements of the distance from the first bone-to-implant contact to the shoulder of the implant were performed at the mesial and distal aspects of each implant. For statistical analysis, mixed-model repeated-measures analysis of variance was used.

RESULTS

All implants achieved hard and soft tissue integration clinically and radiographically and were clinically immobile. From placement to week 3, the mean implant stability increased for MC implants by more than 5 ISQs and for NMC implants by more than 7 ISQs. Radiographically, there were significant differences between treatment groups beginning at 3 months. After 12 months of loading, the MC implants presented a mean bone loss of 1.00 mm and the NMC implants presented a mean bone gain of 0.11 mm.

CONCLUSIONS

Chemically modified sandblasted and acid-etched implants without a machined collar presented bone gain, and implants with a machined collar showed bone loss after a 1 year following early (21-day) loading. The tendency toward a coronal apposition of bone observed under these conditions may be attributed to the osteoconductive properties of the chemically modified surfaces of these implants and to the absence of the machined collar.

Osteogenesis in an in vitro coculture of human periodontal ligament fibroblasts and human microvascular endothelial cells

BACKGROUND

Periodontal bone healing is a complex process involving many cells and processes that must function flawlessly for proper healing to occur. The exact progenitor cells that contribute to this process are not fully characterized. Periodontal fibroblasts and pericytes were postulated to be potential osteoprogenitor cells. This study describes a viable coculture model for the in vitro study of osteogenesis.

METHODS

Human microvascular endothelial cells (HMVEC) and human periodontal ligament (HPDL) fibroblasts were cocultured in a layered model and monitored for the development of runt-related transcription factor 2 (runx2) and desmin expression by real-time polymerase chain reaction. Conditions shown to be osteogenic (bone morphogenetic protein [BMP]-2 and enamel matrix derivative [EMD]) were compared to a control coculture that was unstimulated.

RESULTS

The HMVEC migrated into a layer of collagen containing only HPDL cells as monitored by fluorescent labeling. runx2 and desmin expressions were increased in stimulated cocultures in week 2 compared to controls. At week 3, the unstimulated control cocultures developed the expression of runx2 and desmin, and the cocultures that were stimulated with EMD and BMP-2 achieved significantly higher levels of these factors than any of the other conditions.

CONCLUSIONS

Signs of osteogenesis were present in the cocultures in unstimulated and stimulated conditions. However, in the stimulated condition, osteogenic markers were increased at earlier time points. As such, this model may provide a good method for the study of specific cellular processes that may lead to osteogenesis and eventually for understanding the regeneration of periodontal bone in vivo.