Comparison of extraction sites versus artificial defects with xenogenic bone substitute in minipigs

Preclinical Performance of a Novel Dental Implant Design Reducing Mechanical Stress in Cortical Bone

This animal study compared the healing performance of a novel implant design characterized by a shift in thread geometry and core diameter with two different surfaces with that of an apically tapered implant. Test Bioactive (n = 9), Test Porous (n = 7) and Control (n = 8) implants were placed in the mandibles of minipigs. Following healing, bone samples were harvested for determining bone-to-implant contact (BIC) and marginal bone loss (MBL). Comparative statistics were based on Levene's test, Shapiro-Wilk tests, the Kruskal-Wallis test and Wilcoxon tests with Holm correction (α = 0.05). The mean undersizing of the osteotomy was 0.15 mm for Control, while in the test groups 0.33 mm and 0.34 mm were calculated. Insertion torques ranged from 61.5 Ncm (Control) to 76.1 Ncm (Test Bioactive). Maximum BIC was seen in Test Porous with 55.83%, while Test Bioactive showed only 48.11%. MBL was 4.1 mm in Test Bioactive, while Test Porous and Control exhibited 2.8 mm. No significant differences between the implant groups were observed (p > 0.05). Despite greater undersizing, the novel implant type performed comparably to the established Control implants. The rougher surface of the bioactive implants increased the insertion torque and led to more MBL.

Histomorphometric Assessment of Non-Decalcified Plastic-Embedded Specimens for Evaluation of Bone Regeneration Using Bone Substitute Materials-A Systematic Review

With the implementation of bone substitute materials, regeneration strategies have inevitably evolved over the years. Histomorphometry is the optimal means of quantitative evaluation of bone structure and morphology. This systematic review focuses on determining study models, staining methods and histomorphometric parameters used for bone regeneration research on non-decalcified plastic-embedded specimens over the last 10 years. After being subjected to the inclusion and exclusion criteria, 118 studies were included in this review. The results establish the most commonly selected animal model is rat, followed by rabbit, sheep and dog. Strong preference for staining samples with toluidine blue was noted. With regard to histomorphometric parameters, terms related to bone were most frequently assessed, amounting to almost half of recorded parameters. New bone formation was the main descriptor of this category. Residual bone graft and non-bone tissue parameters were also often evaluated. With regard to dynamic histomorphometry, mineral apposition rate (MAR) was the parameter of choice for most researchers, with calcein green being the preferred dye for fluorochrome labelling. An overview of the contemporary literature, as well as weaknesses in the current research protocols have been discussed.

Regeneration of alveolar bone defects in the experimental pig model: A systematic review and meta-analysis

OBJECTIVE

Pigs are emerging as a preferred experimental in vivo model for bone regeneration. The study objective was to answer the focused PEO question: in the pig model (P), what is the capacity of experimental alveolar bone defects (E) for spontaneous regeneration in terms of new bone formation (O)?

METHODS

Following PRISMA guidelines, electronic databases were searched for studies reporting experimental bone defects or extraction socket healing in the maxillae or mandibles of pigs. The main inclusion criteria were the presence of a control group of untreated defects/sockets and the assessment of regeneration via 3D tomography [radiographic defect fill (RDF)] or 2D histomorphometry [new bone formation (NBF)]. Random effects meta-analyses were performed for the outcomes RDF and NBF.

RESULTS

Overall, 45 studies were included reporting on alveolar bone defects or extraction sockets, most frequently in the mandibles of minipigs. Based on morphology, defects were broadly classified as 'box-defects' (BD) or 'cylinder-defects' (CD) with a wide range of healing times (10 days to 52 weeks). Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 50% RDF (36.87%-63.15%) and 43.74% NBF (30.47%-57%) in BD, and 44% RDF (16.48%-71.61%) and 39.67% NBF (31.53%-47.81%) in CD, which were similar to estimates of socket-healing [48.74% RDF (40.35%-57.13%) and 38.73% NBF (28.57%-48.89%)]. Heterogeneity in the meta-analysis was high (I2 > 90%).

CONCLUSION

A substantial body of literature revealed a high capacity for spontaneous regeneration in experimental alveolar bone defects of (mini)pigs, which should be considered in future studies of bone regeneration in this animal model.

In Vitro Handling Characteristics of a Particulate Bone Substitute for Ridge Preservation Procedures

While particulate bone substitute materials are applied in a variety of augmentation procedures, standardized defects are being used for preclinical testing. This in vitro study evaluated the density and homogeneity of a particulate bone substitute in ridge preservation procedures. Premolars and molars were extracted in ten semimandibles of minipig cadavers. Light body impression material was used for determining the volume of the extraction sites followed by augmentation with particulate material, thereby weighing the graft material needed. Microradiographs and histologic sections were obtained for evaluating the homogeneity and density of the augmentation material. Statistical analyses were based on Shapiro-Wilk tests, Spearman's rho and one sample Wilcoxon test followed by Bonferroni-Holm correction for multiple testing (α = 0.05). Based on 103 single alveoli evaluated, the mean volume determined was 0.120 cm3 requiring a mean amount of graft material of 0.155 g. With only three exceptions, all parameters (volume, mass of augmentation material, density and homogeneity) correlated significantly (p < 0.020). The apical parts of the alveoli showed reduced density as compared to the middle parts (p < 0.001) and the homogeneity of the augmentation material was also lower as compared to the middle (p < 0.001) and cervical parts (p Collapse

Key Words

• alveolar ridge augmentation
• bone substitute materials
• ridge preservation

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Affiliation(s)

Samira Dahl
Virgilia Klär-Quarz
Annika Schulz
Matthias Karl
Tanja Grobecker-Karl Department of Prosthodontics, Saarland University, 66421 Homburg, Saar, Germany; (S.D.); (V.K.-Q.); (A.S.); (M.K.)

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Comparison of extraction sites versus artificial defects with xenogenic bone substitute in minipigs

Objectives

The preclinical evaluation of bone substitutes is frequently performed in artificially created defects. However, such defects do not reflect the predominant clinical application of bone substitutes for socket preservation. Hence, the goal of this animal study was to compare the performance of a xenogenic bone substitute in extraction sites versus artificial defects.

Material and Methods

Four study sites each were created in the mandibles of four minipigs in the region of the third premolars and first molars, respectively. On one side, fresh extraction sockets were established while contralaterally trephine defects were created in healed alveolar bone. All sites were augmented using a particulate xenogenic bone substitute, covered by resorbable membranes and allowed to heal for 12 weeks. The amounts of new bone, non‐bone tissue and remaining bone substitute granules were quantified through histological and micro‐CT analysis. Comparative statistics were based on t‐tests for two samples and ANOVA with the level of significance set at α = 0.05.

Results

Histomorphometric data from only two animals could be quantitatively analyzed due to difficulty with identifying the surgical sites. The percentage of newly formed bone ranged between 53.2% ± 5.6% for artificial defects and 54.9% ± 12.4% for extraction sites. With the exception of ANOVA indicating a greater amount of non‐bone tissue in extraction sites as compared to artificial sites (p = 0.047), no statistically significant differences were observed. Micro‐CT scans showed patterns similar to the ones observed in histomorphometry. As extraction sites could be identified only in two micro‐CT reconstructions, quantitative assessment was not undertaken.

Conclusions

Despite the comparable performance of bone substitute material in artificial defects and extraction sites found here, the data gathered with this experiment was insufficient for showing equivalence of both approaches.