Identification of a Sjögren's syndrome susceptibility locus at OAS1 that influences isoform switching, protein expression, and responsiveness to type I interferons

Sjögren's syndrome (SS) is a common, autoimmune exocrinopathy distinguished by keratoconjunctivitis sicca and xerostomia. Patients frequently develop serious complications including lymphoma, pulmonary dysfunction, neuropathy, vasculitis, and debilitating fatigue. Dysregulation of type I interferon (IFN) pathway is a prominent feature of SS and is correlated with increased autoantibody titers and disease severity. To identify genetic determinants of IFN pathway dysregulation in SS, we performed cis-expression quantitative trait locus (eQTL) analyses focusing on differentially expressed type I IFN-inducible transcripts identified through a transcriptome profiling study. Multiple cis-eQTLs were associated with transcript levels of 2'-5'-oligoadenylate synthetase 1 (OAS1) peaking at rs10774671 (PeQTL = 6.05 × 10-14). Association of rs10774671 with SS susceptibility was identified and confirmed through meta-analysis of two independent cohorts (Pmeta = 2.59 × 10-9; odds ratio = 0.75; 95% confidence interval = 0.66-0.86). The risk allele of rs10774671 shifts splicing of OAS1 from production of the p46 isoform to multiple alternative transcripts, including p42, p48, and p44. We found that the isoforms were differentially expressed within each genotype in controls and patients with and without autoantibodies. Furthermore, our results showed that the three alternatively spliced isoforms lacked translational response to type I IFN stimulation. The p48 and p44 isoforms also had impaired protein expression governed by the 3' end of the transcripts. The SS risk allele of rs10774671 has been shown by others to be associated with reduced OAS1 enzymatic activity and ability to clear viral infections, as well as reduced responsiveness to IFN treatment. Our results establish OAS1 as a risk locus for SS and support a potential role for defective viral clearance due to altered IFN response as a genetic pathophysiological basis of this complex autoimmune disease.

Brief Report: Patients With Primary Sjögren's Syndrome Who Are Positive for Autoantibodies to Tripartite Motif-Containing Protein 38 Show Greater Disease Severity

OBJECTIVE

Autoantibodies reactive with Ro52 (tripartite motif-containing protein 21 [TRIM21]) are detected in 70% of patients with primary Sjögren's syndrome (SS). TRIM21 belongs to a 34-member C-IV family of TRIM proteins. Although autoantibodies against other TRIM proteins within the C-IV family have been detected in the sera of patients with primary SS, their clinical relevance remains unclear. This study was undertaken to investigate the frequency of anti-TRIM38 in patients with primary SS and evaluate its association with various clinical measures of the disease.

METHODS

Serum samples from patients with primary SS (n = 235) and controls (n = 50) were analyzed for reactivity with in vitro-transcribed and -translated (35) S-methionine-labeled TRIM38 protein. The associations of anti-TRIM38 with various laboratory and clinical measures of primary SS were evaluated. Reactivity of anti-TRIM38 with different structural domains of TRIM38 was analyzed. Affinity-purified anti-TRIM38 antibodies were used to immunoprecipitate TRIM21.

RESULTS

TRIM38-reactive autoantibodies were detected in the sera of 24 of the 235 patients with primary SS and 2 of the 50 controls. Anti-TRIM38 positivity was significantly associated with the presence of anti-Ro60, anti-Ro52, anti-La, rheumatoid factor, and hypergammaglobulinemia. Clinically, anti-TRIM38 was associated with significantly higher ocular surface staining scores, lower Schirmer's test scores, and minor labial salivary gland biopsy focus scores of ≥3.0. Anti-TRIM38 antibodies mainly recognized the cortactin-binding protein 2 (CortBP-2; amino acids 128-238) and the B30.2/SPRY (amino acids 268-465) domains on TRIM38. Affinity-purified antibodies to TRIM38-CortBP-2 and TRIM38-B30.2/SPRY domains reacted with TRIM21.

CONCLUSION

Our data demonstrate that anti-TRIM38 specificity arising in a subset of patients with primary SS is associated with increased severity of the disease.

A histologic assessment of a HYBENX® oral tissue decontaminant in vital pulp therapy in dogs

The aim of this study was to assess HYBENX® Oral Tissue Decontaminant (HOTD) in treating vital pulp exposure in a canine model. The use of HOTD solution was compared to an accepted and standard regimen for vital pulp exposure, an application of a commercial calcium hydroxide product (Ca(OH)2). Both control and experimental treatments were followed by restoration with a commercial zinc oxide and eugenol obtundant intermediate restorative material and thermal insulator (ZOE). At 7 days there was 100% pulp vitality with HOTD and 50% with Ca(OH)2. New dentin formation was seen in 62.5% of the HOTD treated pulps and none of the Ca(OH)2 treatment group. The vital pulp exposures at day 21 post treatment with HOTD also showed significant improvement over Ca(OH)2 in the presence of odontoblasts, new dentin formation and pulp survivability. The presence of odontoblasts and new dentin was noted in 71% of the HOTD cases versus 50% of the survivable Ca(OH)2 cases. Furthermore, 100% of HOTD cases had vital pulps versus 62.5% of Ca(OH)2 cases. The 60-day specimens of both experimental and control techniques exhibited histologically similar appearances and were similar in outcomes. HOTD treatment at day 7 showed a significant positive difference, both in the formation of new dentin and tooth vitality. HOTD proved better for the post 21-day specimens and equivalent for the 60-day pulp specimens with no evidence of untoward tissue reactions or results.

A prospective, randomized, controlled, multicenter evaluation of extraction socket preservation comparing two bovine xenografts: clinical and histologic outcomes

The aim of this prospective, randomized, controlled, multicenter study was to evaluate and compare the histologic and histomorphometric aspects of extraction sockets grafted with two commercially available bovine bone xenografts: Endobon (test group) and Bio-Oss (control group). The study was designed to ensure that baseline variables between groups were as similar as possible to allow for a direct comparison of graft healing characteristics. Thirty-eight patients contributed 62 augmented extraction sites to the study. All sites were grafted with one type of bovine bone mineral and covered with a resorbable collagen membrane for 6 months of healing prior to implant placement surgery. The histologic outcomes between the two treatment groups are similar, with de novo bone (mean ± SD) for the test group at 28.5% ± 20% and for the control group, 31.4% ± 18%. Histologic specimens also include membrane remnants. All but two implants integrated successfully after 1 year of follow-up. This investigation provides support for the efficacy of bovine bone xenograft for socket preservation when subsequent implant placement is planned.

Bone grafting: history, rationale, and selection of materials and techniques

In the 100-year history of bone replacement in the human body for different purposes, a wide variety of surgical approaches and materials have been used. The techniques and materials selected significantly affect the outcome of bone replacement procedures in terms of bone formation volume and the quality and amount of vital bone. The choices facing the dental surgeon at the time of extraction, ridge augmentation, or sinus graft are wide-ranging. When choosing a bone graft material the surgeon should consider its ultimate effect on healing patterns in and around the alveolar bone at the endpoint of the procedure. As this article concludes, a better understanding of the materials and the results that can be predictably achieved with them can be valuable to the appropriately trained surgeon when preparing for these procedures.

Variants at multiple loci implicated in both innate and adaptive immune responses are associated with Sjögren's syndrome

Sjögren’s syndrome is a common autoimmune disease (~0.7% of European Americans) typically presenting as keratoconjunctivitis sicca and xerostomia. In addition to strong association within the HLA region at 6p21 (P_meta=7.65×10⁻¹¹⁴), we establish associations with IRF5-TNPO3 (P_meta=2.73×10⁻¹⁹), STAT4 (P_meta=6.80×10⁻¹⁵), IL12A (P_meta =1.17×10⁻¹⁰), FAM167A-BLK (P_meta=4.97×10⁻¹⁰), DDX6-CXCR5 (P_meta=1.10×10⁻⁸), and TNIP1 (P_meta=3.30×10⁻⁸). Suggestive associations with P_meta<5×10⁻⁵ were observed with 29 regions including TNFAIP3, PTTG1, PRDM1, DGKQ, FCGR2A, IRAK1BP1, ITSN2, and PHIP amongst others. These results highlight the importance of genes involved in both innate and adaptive immunity in Sjögren’s syndrome.

Monocytes: super cells for bone regeneration

Monocytes are progenitor cells that lead the inflammatory cascade reaction responsible for guiding revascularization and regeneration of tissue at injury sites. They do this by secreting inductive cytokines responsible for endothelial cell migration. When released into the peripheral blood, monocytes enter tissues and become macrophages. Monocytes also trigger the body's defense mechanism against microbial invasion by lysing and removing cell debris and dead tissue. The aim of this article is to explain the role of monocytes in the processes of bone healing and regeneration and describe their interaction with stem cells and other entities. Results of a pilot histomorphometric study in which concentrated monocytes were combined with demineralized allograft material to augment implant-placement sites in 2 patients also are presented.

Enhancing extraction socket therapy with a biphasic calcium sulfate

Studies have shown that tooth extraction results in loss of bone volume, which compromises dental implant placement. Prevention of site collapse at the time of extraction is recommended. In this 4-month case series, 40 patients were treated with an innovative biphasic calcium sulfate graft, demonstrating its ability to preserve or augment socket volume and resorb in the time period desired between extraction and implant placement. Some representative samples were retrieved at the time of implant placement and evaluated histologically and morphometrically for vital bone formation.

A comparison of screening methods in two early phase oral leukoplakia clinical trials

OBJECTIVES/INTRODUCTION

Clinical trial accrual for oral dysplasia is difficult in the United States and elsewhere. Patients with dysplastic oral leukoplakia progress to frank invasive carcinoma at a rate of 5-37% over 5 years. We compared two clinical trial screening efforts to hopefully devise better accrual strategies to these types of clinical trials.

METHODS

For the first trial, we identified 244 patients with dysplastic oral leukoplakia in our university database and a media campaign. Patients were notified and screened by examination and biopsy. For the second clinical trial, we established a preneoplastic lesions clinic and teaching and communications network with regional oral healthcare professionals.

RESULTS

Only one of 244 patients accrued to the first clinical trial through an organized screening effort based on database/medical records review. The second clinical trial accrued 16/30 screened patients through redirected efforts in teaching, communications, and a preneoplastic lesions clinic.

CONCLUSION

We conclude that significant difficulties resulted from medical record/database review of leukoplakia patients as a screening method for leukoplakia clinical trial entry. We feel that persistent direct contact and education of healthcare professionals who are likely to examine leukoplakia patients improved accrual to the second clinical trial.

Antral membrane elevation using a post graft: a crestal approach

The crestal approach to elevating the antral membrane by a resorbable StemVie post is a modification of the sinus lift technique. This technique can add 4-10 mm of bone height for severely atrophic ridges in areas that are difficult to access through a lateral window. The procedure is minimally invasive, simple, and predictable, and has less postoperative morbidity due to smaller flap design and minimal osteotomy. If sufficient alveolar bone is present for stabilization, an implant can be placed simultaneously with an antral elevation and graft. The StemVie post resorbs completely and is replaced by the patient's own bone. Healing is enhanced with the addition of bone marrow aspirate and/or peripheral venous blood to the StemVie post graft. The graft will absorb the blood or the marrow, allowing them to infiltrate through the porosity present in the graft. Bone marrow aspirate aids in healing with the addition of precursor osteoblastic stem cells, cytokines, and growth factors, while peripheral blood supplies mostly cytokines and growth factors.

Clinical and histomorphometric observations around dual acid-etched and calcium phosphate nanometer deposited-surface implants

PURPOSE

The objective of this study was to compare the clinical and histologic peri-implant parameters of a nano-calcium phosphate (CaP)-coated dual acid-etched (DAE) implant (n = 7) to those of an uncoated DAE implant (n = 7).

MATERIALS AND METHODS

The study included seven dogs who received implants bilaterally in edentulous mandibular areas; in the right side, procedures were performed 8 months after procedures in the left mandible. Clinical parameters were measured prior to euthanasia (8 months after the second set of implants was placed), followed by histologic nondecalcified processing for morphometric evaluation. Bone-implant contact (BIC), crestal bone resorption (CBR), intrabony defect (IBD), and bone area fraction (BAF) were measured. Analysis of variance with repeated measures and a two-tailed Pearson correlation test were applied.

RESULTS

Probing depth, Bleeding Index, and keratinized mucosal height were stable in both groups; there was a significant improvement in probing depths with time (P = .014). Morphometric measurements showed BIC from 75% to 89% in both groups at 8 and 16 months. The nano-CaP-coated group (n-CaP) showed a significant increase in BIC over time when compared to the DAE group (P = .02). Crestal bone level was maintained in both groups with average resorption of 1.4 to 1.5 mm at the n-CaP implants and 1.1 to 1.2 mm at the DAE implants at 8 and 16 months, respectively. Mean IBD values were 0.88 to 1.18 mm at the n-CaP implants and 0.65 to 0.66 mm at the DAE implants at the respective periods.

CONCLUSIONS

Within the limitations of this study, both the DAE and the n-CaP-surface implants showed successful osseointegration and functional soft and hard tissue adaptation. Except for the significant increase in BIC around the n-CaP implants over time, both showed similar clinical and histologic findings.

Beta-tricalcium phosphate/type I collagen cones with or without a barrier membrane in human extraction socket healing: clinical, histologic, histomorphometric, and immunohistochemical evaluation

The aim of this study was to investigate the healing of human extraction sockets filled with β-tricalcium phosphate and type I collagen (β-TCP/Clg) cones with or without a barrier membrane. Twenty patients were divided in two groups: (A) β-TCP/Clg non-membrane and (B) β-TCP/Clg + barrier membrane. Clinical examination and biopsies from the grafted sites were collected 9 months later. Bone samples were analyzed using histomorphometry and immunohistochemistry. The horizontal dimension of the alveolar ridge was significantly reduced 9 months after socket preservation in the non-membrane group. There was bone formation with no significant differences between the two groups in the areas occupied by new bone (A = 42.4%; B = 45.3%), marrow (A = 42.7%; B = 35.7%), or residual graft (A = 9.7%; B = 12.5%). Immunohistochemistry revealed osteonectin expression in both groups. Both groups demonstrated sufficient amounts of vital bone and socket morphology to support dental implant placement after the 9-month healing period. A future trial to evaluate the alveolar outcomes at an earlier 6-month time point rather than the 9 months used in this study would be of interest.

Simultaneous versus two-stage implant placement and guided bone regeneration in the canine: histomorphometry at 8 and 16 months

AIM

To compare the effect of timing of implant placement and guided bone regeneration (GBR) procedure on osseointegration and newly formed bone at 8 and 16 months.

MATERIAL AND METHODS

In seven dogs, four different sites were bilaterally established: (1) an implant placed in a 6-month healed (6m-GBR) bovine bone mineral (BBM) grafted site; (2) a simultaneously placed implant with the grafted BBM (Si-GBR) followed by a membrane coverage; (3) an implant placed in a membrane-protected non-grafted defect; and (4) an implant placement in a naturally healed site (Cont). Histomorphometry was obtained at 8 and 16 months post-implant placement. Bone-implant contact (BIC), crestal bone resorption (CBR), vertical intra-bony (VIB) defect, bone (BAF) and particle (PAF) area fractions, and osteoconductivity (CON) levels were measured.

RESULTS

In all sites, BIC ranged between 62% and 79% with no significant differences. PAF ranged from 17% to 27%, with no effect of time. At 8 and 16 months, BAF was significantly smaller at the Si-GBR site when compared with all other sites, CON was significantly greater at the 6m-GBR site, and CBR and VIB were significantly smaller at the 6m-GBR when compared with the Si-GBR sites.

CONCLUSIONS

The simultaneous and delayed techniques both showed a similar osseointegration level over time. However, the staged approach showed enhanced newly formed bone, higher osteoconduction around the grafted mineral, less CBR, and smaller vertical bone defect over time compared with the combined approach.

Histologic evaluation of recombinant human platelet-derived growth factor-BB after use in extraction socket defects: a case series

Recent advancements in the arena of therapeutic molecular enhancement have shown favorable clinical findings for periodontics. However, further studies to optimize clinical outcomes using this technology are warranted. Twelve premolar extraction sockets were assigned randomly for treatment with 0.3 mg/mL recombinant human platelet-derived growth factor (rhPDGF-BB) combined with either a collagen containing anorganic deproteinized bovine bone (xenograft) or beta-tricalcium phosphate (b-TCP). Histologic evaluation of extraction socket healing was performed at 3 months. Histologic findings were similar with b-TCP and the xenograft, having 21% and 24% vital bone, respectively. The use of rhPDGF-BB with either b-TCP or a xenograft resulted in uneventful socket healing. At reentry, all implants were placed without the need for further grafting, and 100% implant success was recorded at the time of final evaluation (restoration completion).

Evaluation of implants coated with recombinant human bone morphogenetic protein-2 and vacuum-dried using the critical-size supraalveolar peri-implant defect model in dogs

BACKGROUND

Endosseous implants coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) in a laboratory bench setting and air-dried induce relevant bone formation but also resident bone remodeling. Thus, the objective of this study is to evaluate the effect of implants fully or partially coated with rhBMP-2 and vacuum-dried using an industrial process on local bone formation and resident bone remodeling.

METHODS

Twelve male adult Hound Labrador mongrel dogs were used. Critical-size, supraalveolar, peri-implant defects received titanium porous oxide surface implants coated in their most coronal aspect with rhBMP-2 (coronal-load, six animals), or by immersion of the entire implant in a rhBMP-2 solution (soak-load, six animals) for a total of 30 μg rhBMP-2 per implant. All implants were vacuum-dried. The animals were sacrificed at 8 weeks for histometric evaluation.

RESULTS

Clinical healing was unremarkable. Bone formation was not significantly affected by the rhBMP-2 application protocol. New bone height and area averaged (± SE) 3.2 ± 0.5 versus 3.6 ± 0.3 mm, and 2.3 ± 0.5 versus 2.6 ± 0.8 mm(2) for coronal-load and soak-load implants, respectively (P >0.05). The corresponding bone density and bone-implant contact registrations averaged 46.7% ± 5.8% versus 31.6% ± 4.4%, and 28% ± 5.6% versus 36.9% ± 3.4% (P >0.05). In contrast, resident bone remodeling was significantly influenced by the rhBMP-2 application protocol. Peri-implant bone density averaged 72.2% ± 2.1% for coronal-load versus 60.6% ± 4.7% for soak-load implants (P <0.05); the corresponding bone-implant contact averaged 70.7% ± 6.1% versus 47.2% ± 6.0% (P <0.05).

CONCLUSIONS

Local application of rhBMP-2 and vacuum-drying using industrial process seems to be a viable technology to manufacture implants that support local bone formation and osseointegration. Coronal-load implants obviate resident bone remodeling without compromising local bone formation.

Alveolar ridge augmentation using implants coated with recombinant human growth/differentiation factor-5: histologic observations

OBJECTIVES

In vitro and in vivo preclinical studies suggest that growth/differentiation factor-5 (GDF-5) may induce local bone formation. The objective of this study was to evaluate the potential of recombinant human GDF-5 (rhGDF-5) coated onto an oral implant with a purpose-designed titanium porous oxide surface to stimulate local bone formation including osseointegration and vertical augmentation of the alveolar ridge.

MATERIALS AND METHODS

Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in 12 young adult Hound Labrador mongrel dogs. Six animals received implants coated with 30 or 60 microg rhGDF-5, and six animals received implants coated with 120 microg rhGDF-5 or left uncoated (control). Treatments were alternated between jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at weeks 3, 4, 7, and 8 post-surgery when they were euthanized for histologic evaluation.

RESULTS

The clinical examination showed no noteworthy differences between implants coated with rhGDF-5. The cover screw and implant body were visible/palpable through the alveolar mucosa for both rhGDF-5-coated and control implants. There was a small increase in induced bone height for implants coated with rhGDF-5 compared with the control, induced bone height averaging (+/-SD) 1.6+/-0.6 mm for implants coated with 120 microg rhGDF-5 versus 1.2+/-0.5, 1.2+/-0.6, and 0.6+/-0.2 mm for implants coated with 60 microg rhGDF-5, 30 microg rhGDF-5, or left uncoated, respectively (p<0.05). Bone formation was predominant at the lingual aspect of the implants. Narrow yellow and orange fluorescent markers throughout the newly formed bone indicate relatively slow new bone formation within 3-4 weeks. Implants coated with rhGDF-5 displayed limited peri-implant bone remodelling in the resident bone; the 120 microg dose exhibiting more advanced remodelling than the 60 and 30 microg doses. All treatment groups exhibited clinically relevant osseointegration.

CONCLUSIONS

rhGDF-5-coated oral implants display a dose-dependent osteoinductive and/or osteoconductive effect, bone formation apparently benefiting from local factors. Application of rhGDF-5 appears to be safe as it is associated with limited, if any, adverse effects.

Evaluation of implants coated with rhBMP-2 using two different coating strategies: a critical-size supraalveolar peri-implant defect study in dogs

BACKGROUND

Implants coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) induce relevant bone formation but also resident bone remodelling.

OBJECTIVES

To compare the effect of implants fully or partially coated with rhBMP-2 on new bone formation and resident bone remodelling.

MATERIALS AND METHODS

Twelve, male, adult, Hound Labrador mongrel dogs were used. Critical-size, supraalveolar, peri-implant defects received titanium porous oxide surface implants coated in their most coronal aspect with rhBMP-2 (coronal-load/six animals) or by immersion of the entire implant in an rhBMP-2 solution (soak-load/six animals) for a total of 30 mug rhBMP-2/implant. All implants were air-dried. The animals were euthanized at 8 weeks for histometric evaluation.

RESULTS

Clinical healing was uneventful. Supraalveolar bone formation was not significantly affected by the rhBMP-2 application protocol. New bone height and area averaged (+/- SE) 3.4 +/- 0.2 versus 3.5 +/- 0.4 mm and 2.6 +/- 0.4 versus 2.5 +/- 0.7 mm(2) for coronal-load and soak-load implants, respectively (p>0.05). The corresponding bone density and bone-implant contact (BIC) recordings averaged 38.0 +/- 3.8%versus 34.4 +/- 5.6% and 25.0 +/- 3.8%versus 31.2 +/- 3.3% (p>0.05). In contrast, resident bone remodelling was significantly influenced by the rhBMP-2 application protocol. Bone density outside the implants threads averaged 74.7 +/- 3.8% and 50.8 +/- 4.1% for coronal-load and soak-load implants, respectively (p<0.05); bone density within the thread area averaged 51.8 +/- 1.2% and 37.8 +/- 2.9%, and BIC 70.1 +/- 6.7% and 43.3 +/- 3.9% (p<0.05).

CONCLUSION

Local application of rhBMP-2 appears to be a viable technology to support local bone formation and osseointegration. Coronal-load implants obviate resident bone remodelling without compromising new bone formation.

Alveolar ridge augmentation using implants coated with recombinant human bone morphogenetic protein-7 (rhBMP-7/rhOP-1): histological observations

BACKGROUND

Pre-clinical studies have shown that recombinant human bone morphogenetic protein-2 (rhBMP-2) coated onto purpose-designed titanium porous-oxide surface implants induces clinically relevant bone formation and osseointegration. The objective of this study was to examine the potential of rhBMP-7, also known as recombinant human osteogenic protein-1 (rhOP-1), coated onto titanium porous-oxide surface implants to support vertical alveolar ridge augmentation and implant osseointegration.

MATERIALS AND METHODS

Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in six young adult Hound Labrador mongrel dogs. The animals received implants coated with rhBMP-7 at 1.5 or 3.0 mg/ml randomized to contra-lateral jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at 3, 4, 7, and 8 weeks post-surgery when they were euthanized for histological evaluation.

RESULTS

Without striking differences between treatments, the implant sites exhibited a swelling that gradually regressed to become hard to palpation disguising the implant contours. The histological evaluation showed robust bone formation; the newly formed bone assuming characteristics of the contiguous resident bone, bone formation (height and area) averaging 4.1+/-1.0 versus 3.6+/-1.7 mm and 3.6+/-1.9 versus 3.1+/-1.8 mm(2); and bone density 56%versus 50% for implants coated with rhBMP-7 at 1.5 and 3.0 mg/ml, respectively. Both treatments exhibited clinically relevant osseointegration, the corresponding bone-implant contact values averaging 51% and 47%. Notable peri-implant resident bone remodelling was observed for implants coated with rhBMP-7 at 3.0 mg/ml.

CONCLUSIONS

rhBMP-7 coated onto titanium porous-oxide surface implants induces clinically relevant local bone formation including osseointegration and vertical augmentation of the alveolar ridge, the higher concentration/dose associated with some local side effects.

Sinus floor augmentation with simultaneous implant placement using Choukroun's platelet-rich fibrin as the sole grafting material: a radiologic and histologic study at 6 months

BACKGROUND

Sinus augmentation with simultaneous implant placement without bone graft material is a hotly debated technique. This technique could be improved and secured by the use of an autologous leukocyte- and platelet-rich fibrin (PRF) (Choukroun's technique) concentrate. The objectives of this study were to assess the relevance of PRF clots and membranes as the sole filling material during a lateral sinus lift with immediate implantation using radiologic and histologic analyses in a case series.

METHODS

Twenty-five sinus elevations with simultaneous implantation were performed on 20 patients with Choukroun's PRF as the sole filling biomaterial. For each patient, a presurgical exam and a 6-month post-surgical radiologic exam were performed with a panoramic x-ray and three-dimensional volumetric computed radiography (VCR) to evaluate the subsinus residual bone height and the final bone gain around the implants. In nine patients, 6 months after the sinus lift, bone biopsies were collected on the buccal wall of the alveolar ridge at the level of the osteotomy window, and evaluated by histomorphometry.

RESULTS

In this study, 41 implants from three different systems with different screw designs (Biomet 3I Nanotite, MIS Seven, Intra-Lock Ossean) were placed. All implants were inserted in residual bone height between 1.5 and 6 mm (mean +/- SD: 2.9 +/- 0.9 mm). The final bone gain was always very significant (between 7 and 13 mm [mean +/- SD: 10.1 +/- 0.9 mm]). No implant was lost. After radiologic analyses, the position of the final sinus floor was always in the continuation of the end of the implant. All biopsies showed well organized and vital bone.

CONCLUSIONS

From a radiologic and histologic point of view at 6 months after surgery, the use of PRF as the sole filling material during a simultaneous sinus lift and implantation stabilized a high volume of natural regenerated bone in the subsinus cavity up to the tip of the implants. Choukroun's PRF is a simple and inexpensive biomaterial, and its systematic use during a sinus lift seems a relevant option, particularly for the protection of the Schneiderian membrane.

Screw "tent-pole" grafting technique for reconstruction of large vertical alveolar ridge defects using human mineralized allograft for implant site preparation

PURPOSE

The purpose of this study was to evaluate the effectiveness of using titanium screws in combination with particulate human mineralized allograft, in a "tenting" fashion, to augment large vertical alveolar ridge defects for implant placement.

MATERIALS AND METHODS

This prospective case study evaluated augmentation in consecutive patients with large (>7 mm) vertical alveolar ridge defects. Vertical ridge augmentation was performed using mineralized allograft placed around titanium screws to tent out the soft tissue matrix. The ridges were clinically evaluated 4 to 5 months after augmentation, and implants were placed at that time. Bone cores were harvested from all patients for histologic evaluations.

RESULTS

Fifteen patients were treated in this prospective case study, and the mean vertical augmentation was 9.7 mm. Two patients had wound dehiscence resulting in loss of graft and requiring secondary grafting before implant placement. Five patients required 2-stage grafting procedures to achieve ideal ridge height before implant placement. Clinical evaluation of the grafted sites upon re-entry revealed uniform ridge anatomy. Histomorphometric analysis of 7 specimens revealed a mean bone content of 43%. A total of 32 implants were placed into grafted sites in 15 patients. All implants were integrated and successfully restored. Mean follow-up was 16.8 months after implant placement.

CONCLUSIONS

Tenting of the periosteum and soft tissue matrix with titanium screws maintains space and minimizes resorption of mineralized particulate allograft. This technique offers predictable functional and esthetic reconstruction of large vertical defects without the use of autogenous bone and is capable of osseointegration. More studies are needed to evaluate the stability of vertically grafted bone after long-term loading.

Sinus grafting with a natural fluorohydroxyapatite for immediate load: a study with histologic analysis and histomorphometry

The goal of this retrospective study was to evaluate the survival rates of dental implants placed in sinuses grafted with a 50:50 composite ratio of autogenous bone and a natural flourohydroxyapatite (FHA) combined with platelet-rich plasma (PRP) using an immediate-load protocol. The authors hypothesized that a 50:50 composite ratio of FHA and autogenous bone combined with PRP would permit immediate loading without compromising implant survival rates. Eleven patients with bilateral partial edentulism of the posterior maxilla were enrolled in this retrospective study. Autogenous bone used in the graft procedure was harvested from the tibia of the left lower extremity. Each patient was grafted with a 50:50 composite ratio of autogenous bone and FHA. Membranes were not used to cover the lateral wall osteotomy site. Platelet-rich plasma was added to the graft material to accelerate and enhance bone regeneration. Four to 6 months after the grafting procedure, 37 hydroxyapatite-coated dental implants were surgically placed and immediately loaded between 72 hours and 5 days later with custom titanium abutments and acrylic provisional restorations placed out of functional occlusion. Six months later, definitive ceramometal restorations were cemented on to the custom abutments. Patients were observed over a 52-week period. The overall implant survival rate was 97.3%. Histologic and histomorphometric analysis of core samples revealed formation of new vital bone in different graft specimens ranging from 23% to 34%. In each core bone sample, 100% of the bone sample was determined to be vital. In the grafted maxillary sinus, the natural FHA combined with autogenous bone in a 50:50 composite ratio with PRP is a suitable graft material permitting immediate load without compromising implant survival rates while decreasing the overall healing time.

Cementum, pulp, periodontal ligament, and bone response after direct injury with orthodontic anchorage screws: a histomorphologic study in an animal model

PURPOSE

To assess the histologic response of the periodontium, cementum, and pulp after intentional root injury with titanium screws.

MATERIALS AND METHODS

Three female beagle dogs were used, and a total of 60 self-drilling/self-tapping miniscrews were manually inserted into the maxilla and the mandible with the intention of placement in close proximity or in direct contact with the roots. Digital radiographs were taken to select the sites with root injuries. After a 3-month period, the animals were killed and serial nondecalcified histologic sections were obtained with the miniscrew in place.

RESULTS

Sixteen sites with significant root injury were identified. Four sites presented with cementum abrasion, 7 sites had dentin penetration up to 50% of the diameter of the screw, and 5 sites had miniscrew penetration into the pulp space with root fragmentation. At all damaged sites, continuous cementum repair could be observed. There was no evidence of external resorption or pulpal necrosis and/or inflammatory infiltrate. Point ankylosis was seen only in cases of severe injury with root fragmentation. Finally, woven bone was present along the miniscrew threads.

CONCLUSION

When titanium screws penetrate root cementum or dentin, pulpal necrosis and/or inflammation was not observed at 12 weeks in an animal model. Cementum regenerates at every injury site, but ankylosis can occur with root fragmentation. Woven bone is present at the screw-bone interface even with root contact suggesting osteointegration.

Clinical evaluation alveolar ridge preservation with a beta-tricalcium phosphate socket graft

PURPOSE

To determine the efficacy of an alloplastic graft material, consisting of a pure-phase beta-tricalcium phosphate (beta-TCP), in the preservation of ridge volume after tooth extraction and before dental implant placement. Histomorphometric analysis was completed on a few samples to determine the percentage of vital bone over a fixed healing period.

MATERIALS AND METHODS

Patients requiring tooth extraction and bone regeneration before implant placement were included in this study. Measurements of alveolar width were made at the time of extraction and the time of implant placement. The extraction sites were grafted with a pure-phase beta-TCP and covered with a barrier. Approximately 6 months after surgery, the sites were reentered for implant placement. Cores were taken of the regenerated material for histologic analysis, with a trephine used as the first bur in preparation for some of the osteotomies. Implants were placed according to the manufacturers' recommendations and loaded at the appropriate time.

RESULTS

The beta-TCP placed at the time of grafting extraction sockets was well tolerated in all sites with all of the barriers used. There were no incidences of postoperative infection or graft rejection. At the time of implant placement, much of the graft material had resorbed and been converted to vital alveolar bone. The implant recipient sites were dense and supported placement of endosseous dental implants that were fully stable. The width of the extraction sockets was preserved to 91% of the preoperative width.

CONCLUSIONS

Extraction socket grafting with the pure-phase beta-TCP tested in this study and covered with either a resorbable collagen or dense polytetrafluoroethylene barrier is a predictable method for preserving alveolar dimensions. The graft material resorbs to a high percentage in the timeframe desired between extraction and dental implant placement, as shown clinically, radiographically, and histologically. In addition, the regenerated material in the socket has enough density to support implant placement with subsequent loading in the 4- to 6-month period used in this study.

Histomorphometric evaluation of natural mineral combined with a synthetic cell-binding peptide (P-15) in critical-size defects in the rat calvaria

PURPOSE

The objective of this study was to histomorphometrically evaluate the synthetic peptide analog P-15 bound to anorganic bovine mineral (Pepgen/P15) in critical-size defects in the rat calvaria.

MATERIALS AND METHODS

A 5-mm-diameter critical-size defect was prepared in 48 rat skulls and divided into 4 equal groups: Pepgen/P15 particles covered by a membrane, Pepgen/P15 particles uncovered, nongrafted membrane-protected sites, and nongrafted uncovered control sites. At 12 weeks, histomorphometric measurements were made of the percentage area of newly formed bone and residual particles, the length of internal and external bone bridging, and linearly, the regenerated marginal and central total tissue augmentation height.

RESULTS

Nongrafted, membrane-protected sites gained 60.6% of newly formed bone, followed by 50.6% and 44.2% (P < .05 versus membrane only) at the grafted covered and uncovered sites, respectively. All experimental sites contained significantly (P < .005) more bone than did control sites (19.9%). In both types of grafted sites, the percentage area of Pepgen/P15 particles was similar. Mean internal and external length of bone bridging at nongrafted membrane-protected sites (76.7% and 71.2%, respectively) was significantly greater (P < .005) than that of the grafted covered (43.95% and 51.8%, respectively), grafted uncovered (28.7% and 23.9%, respectively), and control (28% and 25.5%, respectively) groups, except for internal bone bridging in the grafted covered sites. Regenerated marginal and central augmentation heights (0.92 mm and 1.02 mm, respectively) were greatest in the grafted covered group, followed by the non-grafted membrane-protected (0.88 mm and 0.51 mm, respectively), and grafted uncovered (0.89 mm and 0.12 mm, respectively) groups, all of which were significantly greater (P < .001) than the control group (0.63 mm and 0.04 mm, respectively).

CONCLUSION

While anorganic bovine mineral/cell-binding peptide contributes in volume, membrane application significantly increases the amount of bone regeneration.

Amelogenesis imperfecta, rough hypoplastic type, dental follicular hamartomas and gingival hyperplasia: report of a case from Central America and review of the literature

We report on a black male patient from Central America with amelogenesis imperfecta, rough hypoplastic type, dental follicular hamartomas, and gingival hyperplasia. Although previous reports have described this association of amelogenesis imperfecta with hyperplastic follicular hamartomas or central odontogenic fibroma-like lesions in blacks from South Africa, we have noticed non-black patients in the literature with similar findings.

Simple preservation of a maxillary extraction socket using beta-tricalcium phosphate with type I collagen: preliminary clinical and histomorphometric observations

Alveolar atrophy following tooth extraction remains a challenge for future dental implant placement. Immediate implant placement and postextraction alveolar preservation are 2 methods that are used to prevent significant postextraction bone loss. In this article, we report the management of a maxillary tooth extraction socket using an alveolar preservation technique involving placement of a cone of beta-tricalcium phosphate (beta -TCP) combined with type I collagen without the use of barrier membranes or flap surgery. Clinical examination revealed solid new bone formation 9 months after the procedure. At the time of implant placement, histomorphometric analysis of the biopsied bone showed that it contained 62.6% mineralized bone, 21.1% bone marrow and 16.3% residual beta -TCP graft. The healed bone was able to support subsequent dental implant placement and loading.

Impact of implant overloading on the peri-implant bone in inflamed and non-inflamed peri-implant mucosa

OBJECTIVE

To assess the impact of overloading on peri-implant bone level and the bone-to-implant contact (BIC) in the presence of healthy or inflamed peri-implant tissues.

MATERIALS AND METHODS

Four screw-shaped machined implants were placed bilaterally in the mandible of four beagle dogs and left submerged for 3 months. Prosthetic abutments were connected either in supra-occlusal contact with the opposite teeth (overloaded) or in infra-occlusal position (unloaded). In each dog, cotton floss ligatures were placed unilaterally around abutments to promote plaque accumulation; the contralateral side was brushed three times a week. There were four experimental sites, two implants in each: loaded uninflamed (LU), loaded inflamed (LI), unloaded uninflamed (UU), and unloaded inflamed (UI). Clinical and radiographic parameters were recorded at baseline and every 3 months throughout the observation period. At 12 months, the dogs were sacrificed and histomorphometric analysis was performed.

RESULTS

Implants with ligature-induced peri-implantitis presented high inflammatory indices throughout the observation period. Clinical parameters did not change from baseline for both LU and UU. Loading significantly increased the percentage of BIC (BIC%) (P<0.05) and slightly increased crestal bone resorption, but not apical to the implant neck. Both LI and UI groups showed significant peri-implant bone loss (P<0.01), mostly horizontal on the buccal aspect and angular on the lingual aspect, which exposed implant threads. Loading significantly (P<0.05) increased implant thread exposure due to buccal and lingual vertical bone resorption.

CONCLUSIONS

In the presence of uninflamed peri-implant mucosa, overloading of implants in the dog model increased BIC% and slightly reduced marginal bone level. However, resorption did not progress beyond the implant neck. Overloading aggravated the plaque-induced bone resorption when peri-implant inflammation was present.

Surface-etching enhances titanium implant osseointegration in newly formed (rhBMP-2-induced) and native bone

PURPOSE

The influence of surface modifications on osseointegration in newly formed bone is not well established. The purpose of this study was to compare osseointegration at acid-etched versus turned implants in newly formed and native bone.

METHODS

Supra-alveolar peri-implant defects were created in 8 hound/Labrador mongrel dogs. Titanium implants 10 mm long (2 turned and 1 dual acid-etched) were placed 5 mm into the surgically reduced alveolar crest, creating 5-mm supra-alveolar peri-implant defects. Recombinant human bone morphogenetic protein-2 (rhBMP-2; 0.4 mg) in a collagen carrier was used to induce new bone formation. A macroporous, expanded polytetrafluoroethylene device was used to delineate new bone formation. The animals were euthanized at 8 weeks for histometric analysis of the experimental sites.

RESULTS

There were no significant differences in rhBMP-2-induced bone density (mean +/- SD) at acid-etched versus turned implants (20.6% +/- 5.3% vs 23.8% +/- 4.7%; P = .232). However, there was a significant difference in bone-implant contact in favor of the acid-etched implants (12.3% +/- 6.8% vs 7.9% +/- 3.1%; P = .05). Native bone density averaged 63.9% +/- 7.5% and 64.5% +/- 9.0% for acid-etched and turned implants, respectively (P = .641). Nevertheless, bone-implant contact was significantly enhanced at acid-etched versus turned implants (59.7% +/- 11.3% vs 40.7% +/-21.2%; P =.005).

CONCLUSIONS

Surface dual acid-etching of titanium implants has a positive effect on osseointegration in newly formed and native bone. Significant differences in bone density do not appear to influence this effect.

Calcium sulfate–carboxymethylcellulose bone graft binder: Histologic and morphometric evaluation in a critical size defect

Calcium sulfate (CS) is widely used as a bone graft binder and expander. Recent reports indicate that carboxymethylcellulose (CMC) can improve the clinical properties of CS when used as binder for particulate bone grafts; however, limited information is available on the effects of CMC on bone regeneration. The purpose of this study was to evaluate the histologic and morphometric characteristics of bone formation in calvarial defects grafted with a CS-based putty containing 10% CMC in combination with allogeneic demineralized bone matrix (DBM). Bone formation and graft/binder resorption were compared with a surgical grade CS and DBM in paired critical-sized calvarial defects in 25 Wistar rats (350-450 g). Six animals each provided paired defects at 7, 14, 21, and 28 days postsurgery for nondecalcified processing and microscopic analysis. Defects grafted with CS or CS-CMC putty as the DBM binder exhibited similar patterns and proportions of bone formation, fibrous tissue/marrow, and residual DBM particles. Comparable mean +/- SD proportions of new bone formation (31.7 +/- 9.5 and 33.7 +/- 12.9), fibrous tissue/marrow (54.2 +/- 8.3 and 53.0 +/- 10.8), residual DBM particles (8.3 +/- 6.8 and 10.1 +/- 6.3), and residual binder material (5.5 +/- 4.6 and 3.7 +/- 3.5) were found at 28 days for defects grafted with CS and CS-CMC putty, respectively. Thus, CMC was found to improve the handling characteristics of CS and, when used in conjunction with DBM, supported comparable levels bone formation and patterns of binder/scaffold resorption as CS and DBM in a calvarial defect model.

Cystic variant of calcifying epithelial odontogenic tumor

Calcifying epithelial odontogenic tumor (CEOT) is a benign, locally aggressive odontogenic neoplasm characterized by sheets and nests of epithelial cells with deeply eosinophilic or occasionally clear cytoplasm, calcifications, and eosinophilic amorphous material that stains positive for amyloid. Although many cases of CEOT are associated with impacted teeth and occasionally appear radiographically as dentigerous cysts, a true cystic variant has not been previously reported. We report a 15-year-old white male with a large cystic maxillary lesion that filled most of the left maxillary sinus. It deformed the medial wall, the inferior orbital floor, and caused narrowing of the left inferior meatus. Histologically, the cystic lining showed characteristics of CEOT. An intraluminal component that featured histologic characteristics of CEOT was identified during surgery. The lesion was enucleated and the postsurgical course of the patient was uneventful. Because follow-up has been for less than 1 year, a meaningful long-term prognosis cannot be determined at present. However, the patient has not reported any symptoms or signs of recurrence during the follow-up period.

The critical-size supraalveolar peri-implant defect model: characteristics and use

OBJECTIVE

Novel implant technologies and reconstructive therapies for alveolar augmentation require pre-clinical evaluation to estimate their biologic potential, efficacy, and safety before clinical application. The objective of this report is to present characteristics and use of the critical-size, supraalveolar, peri-implant defect model.

METHODS

Bilateral extraction of the mandibular premolars was performed in 12 Hound Labrador mongrel dogs following horizontal surgical cut-down of the alveolar ridge approximating 6 mm. Each jaw quadrant received three custom-produced TiUnite, phi 4.0 x 10 mm threaded implants placed into osteotomies prepared into the extraction sites of the third and fourth premolars. The implants exhibited a reference notch 5 mm from the implant platform to facilitate surgical placement leaving 5 mm of the implant in a supraalveolar position, and to serve as a reference point in the radiographic, histologic and histometric analysis. The implants were submerged under the mucoperiosteal flaps for primary intention healing. Fluorescent bone markers were administered at weeks 3 and 4 post-surgery, and pre-euthanasia. The animals were euthanized following an 8-week healing interval when block biopsies were collected for analysis.

RESULTS

Healing was generally uneventful. The radiographic and histometric evaluations demonstrate the limited osteogenic potential of this defect model. Whereas lingual peri-implant sites exhibited a mean (+/-SE) bone gain of 0.4+/-0.1 mm, resorption of the buccal crestal plate resulted in a mean bone loss of 0.4+/-0.2 mm for an overall osteogenic potential following sham-surgery averaging 0.0+/-0.1 mm. Overall bone density and bone-implant contact in the contiguous resident bone averaged 79.1+/-1.1% and 76.9+/-2.3%, respectively.

CONCLUSION

The results suggest that the critical-size, supraalveolar, peri-implant defect model appears a rigorous tool in the evaluation of candidate technologies for alveolar reconstruction and osseointegration of endosseous oral implants. Limited innate osteogenic potential allows critical evaluation of osteogenic, osteoconductive, or osteoinductive technologies in a challenging clinical setting.

Experimental Intrabony and Periodontal Defects Treated With Natural Mineral Combined With a Synthetic Cell-Binding Peptide in the Canine: Morphometric Evaluations

BACKGROUND

A synthetic peptide (P-15) analog of collagen added to anorganic bovine bone mineral (ABM) has recently been used as an enhanced bone graft material (ABM/P-15). The objective of this study was to test the contribution of ABM/P-15 in a new putty form (PEP) in two experimental membrane-protected defects: periodontal and intrabony. Its efficacy as filler biomaterial in guided tissue regeneration (GTR) and guided bone regeneration (GBR) procedures was evaluated histologically and morphometrically.

METHODS

In the maxillary canines, a facial mucoperiosteal flap was raised bilaterally in nine dogs. Two circular defects, 5 mm in diameter and 2 mm in depth, were made on each side: a fenestrated periodontal on the canine root and an intrabony in the alveolar diastema, anteriorly. PEP particles filled both defects on one side; the contralateral side was blood filled (control). All surgical sites were covered with a bioabsorbable membrane. Histologically, at 4 months, tissue blocks were made using the cutting/grinding non-decalcification method followed by morphometric analysis. In the periodontal fenestration root surface, the linear percentage of new cementum (%CEM), area percentage of new bone (%NB), and residual biomaterial particles (%PEP) were calculated. These same measurements were calculated at the intrabony sites, except cementum. The amount of direct NB to PEP contact was measured to assess the osteoconductivity level (OSC). The Pearson correlation test was used to evaluate any significant relationship between the different measured parameters.

RESULTS

In the grafted and non-grafted fenestration root surface defects, %CEM averaged 59.5% and 73.9% (P <0.02), respectively; %NB averaged 36.1% and 31.4%, respectively; and %PEP averaged 20.6%. The mean percentage of OSC was 52.4%. In the intrabony grafted and non-grafted sites, %NB averaged 50.7% and 60.1%, respectively (P <0.02). Residual %PEP averaged 26.1%, and OSC averaged 35.6%. At the intrabony sites, higher %NB and lower %OSC were found compared to the fenestration sites (P <0.001 and P <0.03, respectively). Correlation analysis showed a negative correlation between %NB and %PEP at the fenestration defects. In between the two defect types, %OSC was significantly correlated (P <0.05).

CONCLUSIONS

ABM/P-15 putty showed osteoconductive and biocompatible qualities. However, at 4 months in this model, no enhanced regeneration was present compared to a higher CEM and NB growth detected at non-grafted membrane-protected sites.

Comparison of bone grafting materials in human extraction sockets: clinical, histologic, and histomorphometric evaluations

PURPOSE

Although there are a number of bone replacement graft materials that are currently available for clinical use, there are few studies that directly compare efficacy among graft treatments before implant placement. The purpose of this report was to compare 3 bone replacement graft materials (PepGen P-15 228 FLOW [DENTSPLY Friadent CeraMed, Lakewood, CO], Puros [Zimmer Dental, Carlsbad, CA], and C-Graft 228 [Clinician's Preference, Golden, CO]) for bone formation by clinical, histologic, and histomorphometric evaluation.

MATERIALS AND METHODS

In this prospective, intraoral pilot study, 13 maxillary sockets in 2 patients (both smokers) were grafted immediately after tooth extraction with C-Graft 228, Puros, or PepGen P-15 228 FLOW (containing additional PepGen P-15 228 particles; FLOW PUTTY). After 4 months, bone cores were retrieved and analyzed histologically.

RESULTS

PepGen P-15 228 FLOW PUTTY produced a significantly (P <0.01) higher amount of vital bone than C-Graft 228 or Puros. The amount of vital bone for FLOW PUTTY was 12-fold higher than for C-Graft 228 and 4-fold higher than Puros. Of 7 FLOW PUTTY treated sites, 7 showed >14% vital bone versus 0 of 3 C-Graft 228 and 0 of 3 Puros treated sites. FLOW PUTTY treated sites showed new vital bone between particles of residual graft. C-Graft 228 treated sites showed residual particles in a background of connective tissue with very little bone. Puros treated sites showed nonvital bone particles in a background of connective tissue, with some new vital bone forming around the nonvital bone.

CONCLUSION

PepGen P-15 228 FLOW PUTTY produced significantly greater vital bone as compared to Puros and C-Graft 228 after 4 months. A larger clinical study is required to confirm these results.

Bone-implant contact at calcium phosphate-coated and porous titanium oxide (TiUnite)-modified oral implants

BACKGROUND

Calcium phosphate (CP)-coated implants are usually referred to as having osteoconductive properties, whereas titanium implants with a native oxide layer are considered less osteoconductive. Often smooth titanium oxides (TOs) are compared to relatively rough CP structures. The objective of this study was to evaluate osteoconduction by comparing bone-implant contact at a relatively smooth, highly crystalline CP coating with a structured, porous TO (TiUnite)-modified surface.

MATERIAL AND METHODS

Ten adult Hound Labrador mongrel dogs were used. Four titanium implants (Nobel Biocare) with CP-coated (2) or TO-modified (2) surfaces were installed 12 weeks following mandibular premolar and molar teeth extraction. The implants were alternated within and between jaw quadrants in consecutive animals. Mucosal flaps were advanced and sutured leaving the implants in a submerged position. The animals were injected with fluorescent bone labels at 3 and 4 weeks postsurgery, and pre-euthanasia to monitor progress of bone formation. The animals were euthanized at 8 weeks postsurgery and block biopsies were prepared for histologic and histometric analysis.

RESULTS

There were no remarkable differences in bone formation and apparent bone-implant contact comparing the TO-modified and CP-coated surfaces. However, the measured average bone-implant contact was 71% and 57% (P=0.027) for TO-modified and CP-coated implants, respectively.

CONCLUSIONS

We conclude that the TO surface exhibits osteoconductive properties exceeding that of the CP surface. One or several of the chemical and physical properties of the TO surface may result in the remarkable bone formation along its surface. This study indicated that crystallinity and/or chemistry may be important.

Clinical, Histologic, and Histomorphometric Evaluation of Mineralized Solvent-dehydrated Bone Allograft (Puros) in Human Maxillary Sinus Grafts

Demineralized freeze-dried bone allografts (DFDBA) have been successfully used alone or in composite grafts for many decades. Little research has been done on the effect of retaining the mineral content of bone allografts. This study histologically and histomorphometrically evaluated a new mineralized bone allograft material placed in human atrophic maxillary sinuses. Seven partially edentulous patients requiring sinus grafts before implant placement were selected for this study Their age range was 56 to 81 years (mean 67.7 years). Test grafts consisted of a mineralized solvent-dehydrated cancellous bone allograft, and control grafts were a composite of DFDBA and deproteinized bovine bone xenograft (1:1). Bilateral cases (n = 3) received both test and control grafts on opposite sides, and unilateral cases received either a test (n = 3) or control (n = 1) graft only. At 10 months, core biopsies were taken from each graft site, and dental implants were placed into the augmented bone. All bone grafts resulted in new bone formation and all implants osseointegrated. Test grafts resorbed and were replaced by newly formed bone significantly faster and in greater quantities than were control grafts. No complications with grafts or implants were noted. Both test and control grafts achieved excellent results. The faster bone formation observed with the test graft may be due, in part, to its smaller particle size compared with the bovine portion of the control graft. Test grafts were either replaced by new bone or displayed new bone-to-particle surface contact in higher percentages than did control grafts. No differences in osseointegration or graft stability were noted 2 years after the study.

The use of a mineralized allograft for sinus augmentation: an interim histological case report from a prospective clinical study

A prospective clinical research study of various graft materials used for the augmentation of human maxillary sinuses is currently in progress at New York University Department of Implant Dentistry. This interim case report describes the healing response after a sinus augmentation procedure using a new mineralized cancellous bone allograft. The results after 9 months of healing demonstrated a vital bone content of 25.2% in the grafted sinus, as ascertained from a trephine core taken from the superior aspect of the lateral window area. Although the vital bone requirement for implant survival in an augmented sinus is unknown, the 25.2% vital bone demonstrated in this case compares favorably with that reported in the literature for other augmentation materials, including xenografts, alloplasts, and autogenous bone.

Histologic evaluation of bone-implant contact of immediately loaded transitional implants after 6 to 27 months

PURPOSE

Transitional implants (TIs) were developed as a method of providing fixed provisional restorations for the implant patient who wishes to avoid removable temporary restorations during implant healing. Success of TIs depends on achieving sufficient osseointegrated bone-to-implant contact (BIC) during the provisional prosthesis phase. To date, little data are available on the degree of BIC of these implants in function. The purpose of this study was to histologically evaluate the BIC of TIs following various periods of loading.

MATERIALS AND METHODS

Histologic analysis of 33 immediately loaded implants from 21 patients was performed. All TIs had turned machined surfaces and were made of commercially pure titanium (grade 1). These transitional implants were in function for an average of 10.8 months (range: 6 to 27 months). Before the definitive restoration was provided, all of the TIs were removed with trephine drills and sent for hard tissue histomorphometric analysis.

RESULTS

The average percentage of BIC was 52.9% +/- 13.81% (range 25.1% to 83%).

DISCUSSION

Although TIs are traditionally removed when the definitive implants are restored, the BIC and clinical integration of the TIs in the present study may suggest a change in TI protocol. Studies are indicated to examine long-term use of TIs as sole support or in conjunction with definitive implants in definitive implant-supported restorations.

CONCLUSION

The percentage of BIC achieved with TIs was similar to that documented in the literature for conventional turned, machine-surfaced implants.

rhBMP-2 significantly enhances guided bone regeneration

BACKGROUND

Previous studies have shown a limited potential for bone augmentation following guided bone regeneration (GBR) in horizontal alveolar defects. Surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in such defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained. The objective of this study was to evaluate the potential of rhBMP-2/ACS to enhance GBR using a space-providing, macro-porous expanded polytetrafluoroethylene (ePTFE) device.

METHODS

Bilateral, critical size, supra-alveolar, peri-implant defects were surgically created in four Hound Labrador mongrel dogs. Two turned and one surface-etched 10-mm titanium dental implant were placed 5 mm into the surgically reduced alveolar ridge creating 5-mm supra-alveolar defects. rhBMP-2/ACS (rhBMP-2 at 0.2 mg/ml) or buffer/ACS was randomly assigned to left and right jaw quadrants in subsequent animals. The space-providing, macro-porous ePTFE device was placed to cover rhBMP-2/ACS and control constructs and dental implants. Gingival flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks postsurgery for histologic and histometric analysis.

RESULTS

Bone formation was significantly enhanced in defects receiving rhBMP-2/ACS compared to control. Vertical bone gain averaged (+/- SD) 4.7 +/- 0.3 and 4.8 +/- 0.1 mm, and new bone area 10.3 +/- 2.0 and 8.0 +/- 2.5 mm2 at turned and surface-etched dental implants, respectively. Corresponding values for the control were 1.8 +/- 2.0 and 1.3 +/- 1.3 mm, and 1.8 +/- 1.3 and 1.2 +/- 0.6 mm2. Bone-implant contact in rhBMP-2-induced bone averaged 6.4 +/- 1.4% and 9.6 +/- 7.5% for turned and surface-etched dental implants, respectively (P=0.399). Corresponding values for the control were 14.6 +/- 19.4% and 23.7 +/- 9.7% (P=0.473). Bone-implant contact in resident bone ranged between 43% and 58% without significant differences between dental implant surfaces.

CONCLUSIONS

rhBMP-2/ACS significantly enhances GBR at turned and surface-etched dental implants. The dental implant surface technology does not appear to substantially influence bone formation.

Biomaterial resorption rate and healing site morphology of inorganic bovine bone and beta-tricalcium phosphate in the canine: a 24-month longitudinal histologic study and morphometric analysis

PURPOSE

An inorganic xenograft (inorganic bovine bone [IBB]) and a porous alloplast (beta-tricalcium phosphate [beta-TCP]) material were compared at different healing periods in experimental bone defects in dogs.

MATERIALS AND METHODS

Six round defects, 5 x 4 mm, were made on the lateral bony mandibular angle in 8 dogs at different times. Two defects were randomly filled with IBB, 2 with beta-TCP, and 2 were left to blood clot. A bi-layer collagen membrane covered 1 defect of each type. Four specimens per treatment group were obtained for each treatment group at 3, 6, 12, and 24 months postoperatively. Morphometric analysis of decalcified (Donath technique) histologic slides was conducted using the measured areas of regenerated bone, grafted particles, and remaining concavity.

RESULTS

In IBB sites, complete bone healing was evident at 12 and 24 months, but grafted particles dominated the sites. In beta-TCP sites, only particle remnants remained at 12 months. At 24 months, particles had completely resorbed in both membrane-protected (MP) and uncovered (UC) defects. Data were combined for final analysis since there were no statistically significant differences within each graft material group (MP or UC). Mean bone area fraction increased from 3 to 24 months at all sites. In bone area fraction a statistically significant difference was found between 3 and 6 months in the IBB and beta-TCP groups. IBB sites also showed such significance between 6 and 12 months. A statistically significant difference was found between MP ungrafted sites (42.9%) vs IBB (24.7%) and vs the control (24.8%) at 3 months. At 6 months, beta-TCP bone area fraction (68.8%) was significantly greater than IBB (47.9%) and control (37.5%) sites. At 12 months, beta-TCP bone area fraction (79.0%) was significantly greater than the control (42.5%). At 24 months, beta-TCP bone area fraction (86.5%) was significantly greater than IBB (55.6%) sites. Mean particle area fraction of beta-TCP sites decreased gradually until complete resorption at 24 months. IBB sites showed a significant decrease only between 3 (38.7%) and 6 (29.4%) months.

DISCUSSION AND CONCLUSION

Complete bone healing was established in all grafted defects. IBB and beta-TCP are both excellent biocompatible materials. However, at 24 months beta-TCP particles were completely resorbed, whereas IBB particles still occupied a remarkable area fraction without significant resorption beyond 6 months. (More than 50 references.)

Repair of the perforated sinus membrane with a resorbable collagen membrane: a human study

PURPOSE

The purpose of this study was to evaluate the results of the repair of perforated sinus membranes with resorbable collagen membrane.

MATERIALS AND METHODS

A split-mouth design was followed. Twelve subjects requiring bilateral sinus grafting were included in the study; one site had been accidentally perforated during sinus augmentation and the other site had not been perforated. The perforated sites were repaired with a resorbable collagen membrane. Dental implants were placed during a second surgery, and biopsy samples were harvested from both sinuses during implant placement. New bone formation was measured for all sites. Implant survival was recorded at second-stage surgery. Panoramic radiographs were taken before and after sinus grafting and after implant placement.

RESULTS

Nonperforated sites demonstrated significantly more bone formation (33.58% +/- 7.45%) than perforated sites (14.17% +/- 7.06%) (P < .0001). Perforated sites demonstrated significantly more soft tissue formation (63.58% +/- 12.96%) than nonperforated sites (48.5% +/- 12.57%) (P = .006). In nonperforated sites, residual graft particles had more of their surface in contact with bone (40.17% +/- 14.92%) than perforated sites (14.5% +/- 12.03%) (P < .0001). The implant survival rate at second-stage surgery was superior for nonperforated sites (100%) in comparison to perforated sites (69.56%) (P = .0028).

DISCUSSION

This study suggested that repairing the perforated site of the sinus membrane with a resorbable collagen membrane may result in reduced bone formation and implant survival rate. A different technique and/or materials than those used in the current study may offer better results for the repair of the perforated sinus membrane.

CONCLUSION

The study demonstrated that perforation and repair of the sinus membrane may compromise new bone formation and implant survival.

Clinical, radiographic, histologic, and histomorphometric comparison of PepGen P-15 particulate and PepGen P-15 flow in extraction sockets: a same-mouth case study

PURPOSE

Although the efficacy of PepGen P-15 particulate has been conclusively demonstrated in two multicenter clinical studies, the effect of a new hydrogel formulation containing PepGen P-15 on bone repair has not been previously demonstrated.

MATERIALS AND METHODS

PepGen P-15 Flow contains PepGen P-15 particulate in a biocompatible hydrogel, which provides spacing between the particles. In this case study, bone repair of both PepGen P-15 particles and PepGen P-15 Flow was compared to natural bone in same-mouth extraction sockets.

RESULTS

The radiographic, histologic, and histomorphometric evaluations showed enhanced bone formation and faster particle resorption with PepGen P-15 Flow compared to the PepGen P-15 particulate.

CONCLUSION

The accelerated bone formation by PepGen P-15 Flow may provide faster implant placement.

Space-Providing Expanded Polytetrafluoroethylene Devices Define Alveolar Augmentation at Dental Implants Induced by Recombinant Human Bone Morphogenetic Protein 2 in an Absorbable Collagen Sponge Carrier

BACKGROUND

Surgical implantation of recombinant human bone morphogenetic protein 2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in horizontal alveolar defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained.

PURPOSE

The objective of this proof-of-principle study was to evaluate the potential of a space-providing macroporous expanded polytetrafluoroethylene (ePTFE) device to control volume and geometry of rhBMP-2/ACS-induced alveolar bone augmentation.

MATERIALS AND METHODS

Bilateral critical-size supra-alveolar periimplant defects were created in four Hound-Labrador mongrel dogs. Two turned and one surface-etched 10 mm titanium dental implants were placed 5 mm into the surgically reduced alveolar ridge creating 5 mm supra-alveolar defects. rhBMP-2/ACS (0.4 mg rhBMP-2) was placed around the exposed dental implants. Additionally, one jaw quadrant in each animal was randomly assigned to receive the dome-shaped macroporous ePTFE device. Mucoperiosteal flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks post surgery for histometric analysis.

RESULTS

The space-providing macroporous ePTFE device defined the volume and geometry of rhBMP-2/ACS-induced bone formation, whereas bone formation at sites receiving rhBMP-2/ACS alone varied considerably. Vertical bone gain at turned dental implants averaged (+/-SD) 4.7 +/-0.2 mm at sites receiving rhBMP-2/ACS and the ePTFE device compared with 3.5 +/-0.9 mm at sites receiving rhBMP-2/ACS only. The corresponding values for rhBMP-2/ACS-induced bone area were 9.6 +/- 0.7 mm2 and 7.5 +/-6.2 mm2. There was a highly significant correlation between induced bone area and the space provided by the ePTFE device (p <.001). There was no difference in induced bone density or bone-implant contact between the two technologies. These observations were consistent with those observed at surface-etched dental implants.

CONCLUSIONS

The data from this study suggest that a space-providing macroporous ePTFE device defines rhBMP-2/ACS-induced alveolar augmentation to provide adequate bone quantities for implant dentistry. The dental implant surface technology does not appear to substantially influence bone formation.

Qualitative and Quantitative Expression of Bovine Bone Mineral in Experimental Bone Defects. Part 1: Description of a Dog Model and Histological Observations

BACKGROUND

The purpose of this study was to evaluate histologically the contribution of inorganic bovine bone biomaterial in a new experimental bone defect in dogs at different healing periods and to examine newly formed bone around the grafted mineral particles and their relationship in membrane-protected (test) and non-protected intrabony (control) defects.

METHODS

Four round intrabony defects, 5 x 4 mm were made bilaterally (at different times) on the lateral bony mandibular angle in eight dogs. Two defects were filled with bovine bone mineral (BBM) particles and two remained non-grafted but were blood clotted. A collagen membrane covered each defect type (n = 4). This procedure was repeated on the contralateral side at a different given time to obtain two different healing periods in each dog. Thus, four specimens were obtained at 3, 6, 12, and 24 months postoperatively for each healing period. The non-decalcification method (Donath technique) with Stevenel's blue and van Gieson's picro fuchsin staining was used for histological examination.

RESULTS

Newly formed bone was observed at all examined defect types. The BBM particles were clearly evident regardless of the healing period. At 3 and 6 months, newly formed bone, woven in nature, was incorporated with the grafted particles. High cellular bone with occasional osteoclasts was noted towards the surface of the mineral particles. No substantial difference was observed between the protected and the non-protected defects except for higher ossified centers around the membrane-protected defects. At the non-grafted sites, the membrane-protected defect showed newly formed bone near the bony walls, and particularly under the membrane, establishing a bony bridge over the defect at the healing periods. The non-grafted unprotected defect (control) showed bone formation only at the base and close to the bony walls leaving a healed concave configuration. At 1 and 2 years, the grafted sites showed full bone healing configuration. However, the grafted particles still dominated the previous defect area and were completely surrounded by the newly formed bone. Osteons and lamellar bone arrangement were established but the bone was still highly cellular and osteoclasts could still be identified. The non-grafted membrane-protected sites showed excellent bone healing although areas of non-mineralized soft tissue were often seen. The control sites healed but still presented with a concave surface configuration.

CONCLUSIONS

BBM biomaterial is a highly osteoconductive material. In a 4-wall bony defect, newly formed bone was well evident in establishing excellent bone healing configuration with or without a regenerative biological barrier. The grafted material dominated the experimental sites with no substantial resorption at any healing period up to 2 years observation.