Immunohistochemical comparison of lateral bone augmentation using a synthetic TiO2 block or a xenogeneic graft in chronic alveolar defects

OBJECTIVES

To evaluate osteogenic markers and alveolar ridge profile changes in guided bone regeneration (GBR) of chronic noncontained bone defects using a nonresorbable TiO₂ block.

MATERIALS AND METHODS

Three buccal bone defects were created in each hemimandible of eight beagle dogs and allowed to heal for 8 weeks before GBR. Treatment was assigned by block randomization: TiO₂ block: TiO₂ -scaffold and a collagen membrane, DBBM particulates: Deproteinized bovine bone mineral (DBBM) and a collagen membrane, Empty control: Only collagen membrane. Bone regeneration was assessed on two different healing timepoints: early (4 weeks) and late healing (12 weeks) using several immunohistochemistry markers including alpha-smooth muscle actin (α-SMA), osteopontin, osteocalcin, tartrate-resistant acid phosphatase, and collagen type I. Histomorphometry was performed on Movat Pentachrome-stained and Von Kossa/Van Gieson-stained sections. Stereolithographic (STL) models were used to compare alveolar profile changes.

RESULTS

The percentage of α-SMA and osteopontin increased in TiO₂ group after 12 weeks of healing at the bone-scaffold interface, while collagen type I increased in the empty control group. In the defect area, α-SMA decreased in the empty control group, while collagen type I increased in the DBBM group. All groups maintained alveolar profile from 4 to 12 weeks, but TiO₂ group demonstrated the widest soft tissue contour profile.

CONCLUSIONS

The present findings suggested contact osteogenesis when GBR is performed with a TiO₂ block or DBBM particulates. The increase in osteopontin indicated a potential for bone formation beyond 12 weeks. The alveolar profile data indicated a sustained lateral increase in lateral bone augmentation using a TiO₂ block and a collagen membrane, as compared with DBBM and a collagen membrane or a collagen membrane alone.

Osteocytes Influence on Bone Matrix Integrity Affects Biomechanical Competence at Bone-Implant Interface of Bioactive-Coated Titanium Implants in Rat Tibiae

Osseointegration is a prerequisite for the long-term success of implants. Titanium implants are preferred for their biocompatibility and mechanical properties. Nonetheless, the need for early and immediate loading requires enhancing these properties by adding bioactive coatings. In this preclinical study, extracellular matrix properties and cellular balance at the implant/bone interface was examined. Polyelectrolyte multilayers of chitosan and gelatin or with chitosan and Hyaluronic acid fabricated on titanium alloy using a layer-by-layer self-assembly process were compared with native titanium alloy. The study aimed to histologically evaluate bone parameters that correlate to the biomechanical anchorage enhancement resulted from bioactive coatings of titanium implants in a rat animal model. Superior collagen fiber arrangements and an increased number of active osteocytes reflected a significant improvement of bone matrix quality at the bone interface of the chitosan/gelatin-coated titan implants over chitosan/hyaluronic acid-coated and native implants. Furthermore, the numbers and localization of osteoblasts and osteoclasts in the reparative and remodeling phases suggested a better cellular balance in the chitosan/Gel-coated group over the other two groups. Investigating the micro-mechanical properties of bone tissue at the interface can elucidate detailed discrepancies between different promising bioactive coatings of titanium alloys to maximize their benefit in future medical applications.

DXA reference values of the humanoid sheep model in preclinical studies

Background

Merino land sheep are a popular pre-clinical large animal model in research on systemic skeletal diseases such as osteoporosis. Interpretation of studies is difficult because many reference parameters are missing or not established. This study aims to determine the reference parameters of the skeletal system (peak bone mass = PBM, T-Score). A defined standard allows an easier comparison of the study data of the animal model with human studies (T-Score).

Materials and methods

A total of 116 Dual Energy X-ray Absorptiometry DXA measurements were performed on 74 untreated sheep. The average age of the animals was 57 months. The BMD, BMC, and fat content of the sheep were determined by the relevant human region of interest (ROI). From this, the PBM and from this the T-score for each of the animals were calculated.

Results

Using 682 DXA measurements BMD and BMC were determined to provide an indication to PBM. For BMD a significant correlation to the age of the animals was observed (p = 0.043). A significant correlation was also seen for BMC (B) (p ≤ 0.001). In the age-dependent analysis, a widespread of values above the linear regression line was measured for both BMD and BMC between the 50th and 90th months of life. From an age of about 90 months, a wider spread of values below the linear regression line was found, although the average values continued to rise.

Discussion

The evaluation of the 116 DXA measurements allowed the determination of the PBM for merino land sheep. With the help of the PBM, a T-score was calculated for each animal. The statistical analysis shows significant differences in BMD values between the different animal groups in each of the four ROIs investigated. Individual control or sham groups per study are therefore not sufficient. To improve comparability, an independent reference group should be established.

Conclusion

An independent reference group for PBM and a T-score was established from four to six-year-old animals. The bone density increases with the age of the animals. Around the fourth year of life, a first peak could be observed. Also, after the seventh year of life, a further peak with the beginning plateau phase was observed. When compiling a group of animals for an osteoporosis model, animals from the age of seven years should, therefore, be used.

A New Clinically Relevant T-Score Standard to Interpret Bone Status in a Sheep Model

Background

Osteoporosis is diagnosed by bone loss using a radiological parameter called T-score. Preclinical studies use DXA to evaluate bone status were the T-score is referenced on bone mineral density (BMD) values of the same animals before treatment. Clinically, the reference BMD represents values of an independent group of healthy patients around 30 years old. The present study established a clinically similar T-score standard to diagnose osteoporosis in a sheep model.

Material/Methods

We used 31 female merino land sheep (average 5.5 years old) to study osteoporosis. The following groups were compared using DXA measurement: 1) control; 2) ovariectomized (OVX); 3) OVX combined with a deficient diet (OVXD); and 4) OVXD combined with methylprednisolone administration (OVXDS). Further, an independent group of 32 healthy sheep (4–6 years old) were measured as an independent baseline. BMD was measured at 0 months, 3 months, and 8 months after treatment.

Results

The same significance pattern between the treated groups and either baseline groups was seen. However, using an independent baseline changed the “clinical” interpretation of the data from an osteoporotic bone status (T-score <−2.5) after 3 months of OXDS treatment into an osteopenic bone status (T-score <−1.5 to −2.4).

Conclusions

Using an independent baseline enhanced the statistical significance and showed the clinical relevance. Furthermore, an independent baseline is a reliable alternative to use of a new control group for future experiments and thus reduces the number of animals needed by eliminating the need for a control and corresponding to clinical practice.