The Impact of Implant Abutment Angle and Height on Peri-implant Tissue Health: Retrospective Analyses from a Randomized Controlled Clinical Trial.

PURPOSE: To examine the influence of abutment emergence angle and abutment height on marginal peri-implant bone stability in patients not considered susceptible to peri-implantitis. Furthermore, it was analyzed whether titanium-base (Ti-base) abutments lead to wider abutment emergence angles compared to one-piece abutments. MATERIALS AND METHODS: A total of 48 abutments (ie, 24 Ti-base and 24 one-piece abutments in 24 patients) were evaluated at abutment installation, after 1 year, and thereafter on a yearly basis for up to 5 years. Clinical and radiographic outcome variables were assessed. RESULTS: With regard to peri-implant marginal bone stability, only moderately negative, albeit significant, correlations were found on the mesial sides of the one-piece abutments after 4 and 5 years for an abutment emergence angle > 30 degrees. No statistically significant negative correlations were found for distances of ≤ 1.5 mm between the restoration margin and the crestal peri-implant bone level for either Ti-base or for one-piece abutments. Furthermore, abutments bonded to Ti-bases were not associated with larger emergence angles than one-piece abutments. CONCLUSIONS: For patients at low risk of developing peri-implantitis, it can be concluded that neither a larger abutment emergence angle (> 30 degrees) nor a distance of ≤ 1.5 mm between the restoration margin and the crestal peri-implant bone level are associated with marginal peri-implant bone loss. Furthermore, abutments bonded to Ti-bases are not associated with wider emergence angles than one-piece abutments.

Testing of Zirconia FPD Frameworks for Fixed Prostheses: Model Design and Evaluation of Fracture Load.

In our previous test model, the abutment teeth and the model base were printed with resin and bonded with a polyether material. Some abutment teeth fractured during the mechanical load test. Therefore, the aim was to develop and to evaluate a new model under mechanical loading until fracture with zirconia FPD frameworks. Up to a fracture load of 1636 N, neither the artificial abutment teeth nor the base model fractured. Furthermore, the artificial abutment teeth did not detach from the base model. Therefore, the model should be suitable for mechanical testing of most ceramic-based framework materials for three-unit FPDs.

The impact of implant abutment angle and height on peri-implant tissue health: Retrospective analyses from a randomized, controlled, clinical trial.

PURPOSE: Implant abutment design may influence the predisposition of peri-implant sites to develop peri-implant inflammation, especially peri-implantitis. Therefore, the objectives of the current study were to examine the influence of (1) abutment emergence angle and, (2) abutment height on marginal periimplant bone stability in patients not considered susceptible to peri-implantitis. Furthermore, it was analyzed (3) whether Ti-Base abutments lead to wider abutment emergence angles as compared to onepiece abutments. MATERIALS AND METHODS: 48 abutments (i.e., 24 Ti-base- and 24 one-piece abutments in 24 patients) have been at abutment installation, after one year, and thereafter on a yearly basis for up to five years. Clinical and radiographic outcome variables were assessed. RESULTS: With regard to peri-implant marginal bone stability, (1) only moderately negative, albeit significant, correlations were found on the mesial sides of the one-piece abutments after 4 and 5 years for an abutment emergence angle >30° and no statistically significant negative correlations were found between a distance of less than or equal to versus more than 1.5 mm between the restoration margin and the crestal peri-implant bone level, neither for Ti-Base nor for one-piece abutments. Furthermore, (3) abutments bonded to Ti-bases are not associated with larger emergence angles than one-piece abutments. CONCLUSION: For patients at low risk of developing peri-implantitis it can be concluded, that neither (1) a larger abutment emergence angle (>30°) nor (2) a distance of less than or equal to 1.5 mm between the restoration margin and the crestal peri-implant bone level are per se associated with marginal periimplant bone loss. Furthermore, (3) abutments bonded to Ti-bases are not as such associated with wider emergence angles than one-piece abutments. Int J Prosthodont 2023. doi: 10.11607/ijp.8138.

Customized Titanium Mesh for Guided Bone Regeneration in the Posterior Mandible in a Patient Previously Treated with Bisphosphonates.

We describe the restorative treatment of an 86-year-old female patient who was referred to our specialist prosthodontics clinic. Due to secondary osteoporosis, she underwent oral antiresorptive therapy with ibandronic acid for 10 years. Although she was classified as a patient at increased risk of drug-induced osteonecrosis of the jaw, she eventually signed a consent form for fixed implant-supported prosthetic rehabilitation in her 4th sextant. However, after tooth extraction, the bone ridge was too small at the intended implant positions. Therefore, guided bone regeneration was performed with a computer-aided design/computer-aided manufacturing three-dimensional printed titanium mesh. Finally, a continuous augmented hard tissue ridge above 7 mm was found, and three implants were inserted. Eventually, after four months of submerged healing, the implants were loaded with single crowns. Now, the patient is seen regularly for supportive peri-implant therapy.

Long-term effects of titanium-base abutments on peri-implant health: A 5-year randomised controlled trial.

PURPOSE: Titanium bases are used frequently in daily practice for bonding to CAD/CAM abutments or crowns. Due to intimate contact between the adhesive gap of the titanium-base abutment and the peri-implant bone, the physical and chemical characteristics of the bonding material, or the gap itself, may affect peri-implant inflammatory reactions. The present study therefore aimed to examine the long-term effects of individualised abutments bonded to titanium bases on peri-implant health. MATERIALS AND METHODS: A total of 24 patients, each with one test and one control abutment, participated in the present prospective, single-blind, randomised controlled clinical trial. The test abutments were CAD/CAM titanium abutments bonded to titanium bases. As the control abutments were individualised, one-piece CAD/CAM titanium abutments were used. Clinical and radiographic parameters were assessed at abutment insertion and then on a yearly basis over the following 5 years. RESULTS: No significant differences in marginal bone level were observed between the titanium-base and one-piece abutments at any of the follow-up time points; however, when intragroup marginal bone levels were compared to the baseline values, significant differences were found at several follow-up time points. Intergroup differences were only found to be significant for pocket depth at the 4- (P = 0.006) and 5-year follow-ups (P = 0.024), favouring titanium-base abutments. CONCLUSIONS: Within the limitations of the present study, it appears that the peri-implant tissues of this specific patient cohort responded to titanium-base abutments in a rather similar manner to one-piece abutments over a 5-year period; however, no definitive conclusions can be drawn due to the low power of the present study.

Inflammatory effects of individualized abutments bonded onto titanium base on peri-implant tissue health: A randomized controlled clinical trial.

BACKGROUND: In implant prosthodontics, computer-assisted design and computer-assisted manufacturing (CAD/CAM) zirconia abutments bonded onto titanium bases are frequently used in prosthetic dentistry. Unpolymerized monomer of the bonding material or the adhesive gap itself may have a negative effect on peri-implant tissue health. However, evidence addressing this problem is not available. PURPOSE: The aim of the current trial was to study inflammatory effects of individualized abutments bonded onto titanium bases. MATERIAL AND METHOD: A total of 24 patients with one test abutment and one control abutment each participated in this prospective, double-blind, randomized controlled clinical trial. Thereby, test abutments were CAD/CAM titanium abutments bonded onto titanium abutments (Ti-Base). As control abutments individualized, one-piece CAD/CAM titanium abutments were used. At abutment installation as well as 6 and 12 months thereafter bone level changes, clinical parameters as well as Il-1ß levels were assessed. RESULTS: Neither for bone level or clinical parameters nor for Il-1ß levels, significant differences between test and control abutments could be found. However, in both groups Il-1ß levels were significantly elevated at both the 6 and 12 months follow-up compared to baseline. CONCLUSION: Within the limits of this RCT, it can be concluded that effects on the inflammatory state of peri-implant tissues do not differ between individualized abutments bonded onto Ti-Bases and individualized one-piece abutments.

Influence of Natural Killer Cells and Natural Killer T Cells on Periodontal Disease: A Systematic Review of the Current Literature.

Natural killer (NK) cells, as members of the innate immune system, and natural killer T (NKT) cells, bridging innate and adaptive immunity, play a prominent role in chronic inflammatory diseases and cancerogenesis, yet have scarcely been examined in oral diseases. Therefore, systematic research on the latest literature focusing on NK/NKT cell-mediated mechanisms in periodontal disease, including the time period 1988-2020, was carried out in MEDLINE (PubMed) using a predetermined search strategy, with a final selection of 25 studies. The results showed that NK cells tend to have rather proinflammatory influences via cytokine production, cytotoxic effects, dendritic-cell-crosstalk, and autoimmune reactions, while contrarily, NKT cell-mediated mechanisms were proinflammatory and immunoregulatory, ranging from protective effects via B-cell-regulation, specific antibody production, and the suppression of autoimmunity to destructive effects via cytokine production, dendritic-cell-crosstalk, and T-/B-cell interactions. Since NK cells seem to have a proinflammatory role in periodontitis, further research should focus on the proinflammatory and immunoregulatory properties of NKT cells in order to create, in addition to antibacterial strategies in dental inflammatory disease, novel anti-inflammatory therapeutic approaches modulating host immunity towards dental health.

Application of a standard autoclaving protocol does not harm structural integrity of two-piece zirconia abutments under detachment force testing.

OBJECTIVE: Aim was to assess the influence of a standard autoclaving protocol on the retention of zirconia abutments glued on titanium bases in two-piece implant abutments. MATERIALS AND METHODS: Twenty-four CAD/CAM-generated zirconia abutments were adhesively cemented on prefabricated titanium bases. Before mechanical and thermal aging, the specimens were divided into two groups. Group 1 was subjected to a standard steam autoclaving protocol and Group 2 remained untreated (control). The tensile strength in all specimens was evaluated by a standardized pull-off test limited to a maximum force of 1000 N. RESULTS: Eleven samples in both groups could be subjected to pull-off testing. Ten samples in Group 1 and three samples in Group 2 failed, while all others reached the maximum pull-off force. This difference was statistically significant. The mean retention values for the failed samples were 694.53 ± 369.10 N in Group 1 and 890.78 ± 25.90 N in Group 2. This difference was not statistically significant. CONCLUSIONS: A standard autoclaving protocol does not reduce detachment force of two-piece zirconia abutments. CLINICAL RELEVANCE: Clinical sterilization processes as recommended by regulatory authorities seem to be harmless to the structural integrity of two-piece zirconia implant abutments, at least with regard to the retention of the components.

Influence of Connector Diameter on Fracture Load of CAD/CAM-Processed Monolithic Lithium Disilicate Fixed Partial Dentures.

PURPOSE: To investigate the influence of connector diameter on the mechanical load to fracture in monolithic three-unit lithium disilicate fixed partial dentures (FPDs). MATERIALS AND METHODS: A total of 24 FPDs were designed and manufactured using computer-aided design/computer-assisted manufacturing (CAD/CAM) with connector diameters of 16 mm2, 12 mm2, or 9 mm2 (Groups A, B, and C, respectively; n = 8 for each group). After thermal and mechanical aging, the FPDs were subjected to mechanical load-to-fracture assessment. RESULTS: Fracture loads of Groups B (834 ± 105 N) and C (796 ± 41 N) were significantly lower compared to Group A (990 ± 65 N). CONCLUSION: Connector dimensions proved to be crucial for fracture resistance of monolithic lithium disilicate FPDs.

Correction to: human periodontal ligament fibroblasts stimulated by nanocrystalline hydroxyapatite paste or enamel matrix derivative. An in vitro assessment of PDL attachment, migration, and proliferation.

In the original published version of this article, the middle name for author Mirko H. H. Schmidt is missing.

Annual failure rates and marginal bone-level changes of immediate compared to conventional loading of dental implants. A systematic review of the literature and meta-analysis.

BACKGROUND: Immediate loading of dental implants appears to be a successful option. Questions still remain whether annual failure rates (AFRs) as well as annual marginal bone-level changes are comparable with conventionally loaded implants. HYPOTHESIS: Immediately loaded implants (≤24 h after implantation) do not show different annual survival rates or peri-implant bone-level changes as compared to conventionally loaded implants (≥3 months after implantation). MATERIAL AND METHODS: An electronic search in the National Library of Medicine and in Cochrane Central Register of Controlled Trials was performed for articles published up to November 2013. Only publications in English were considered. Additionally, the bibliographies of the full-text papers were searched. Primary outcome variable was percentage AFR; secondary outcome variable was annual radiographic bone-level change. RESULTS: Electronic search yielded 154 full-text articles; ten randomized controlled clinical trials were eventually meta-analyzed. Annual failure rates were 2.3% and 3.4% for conventionally and immediately loaded implants, respectively. No difference in implant failure rates was found (RR: 0.82). Regarding marginal bone-level changes, the weighted mean difference (WMD) between immediate and conventional loading amounted to 0.02 mm at 1 year (P > 0.05), to 0.08 mm at 2 years (P > 0.05), -0.10 mm at 3 years (P > 0.05) and -0.3 mm at 5 years (P < 0.05). The total WMD for the combined follow-up was 0.01 mm (P > 0.05). CONCLUSION: No clinically relevant differences regarding annual failure rates or radiographic bone-level changes between conventionally and immediately loaded implants can be found for up to 5 years of follow-up.

Tissue-engineered mandibular bone reconstruction for continuity defects: a systematic approach to the literature.

BACKGROUND: Despite significant surgical advances over the last decades, segmental mandibular bone repair remains a challenge. In light of this, tissue engineering might offer a next step in the evolution of mandibular reconstruction. PURPOSE: The purpose of the present report was to (1) systematically review preclinical in vivo as well as clinical literature regarding bone tissue engineering for mandibular continuity defects, and (2) to analyze their effectiveness. MATERIALS AND METHODS: An electronic search in the databases of the National Library of Medicine and ISI Web of Knowledge was carried out. Only publications in English were considered, and the search was broadened to animals and humans. Furthermore, the reference lists of related review articles and publications selected for inclusion in this review were systematically screened. Results of histology data and amount of bone bridging were chosen as primary outcome variables. However, for human reports, clinical radiographic evidence was accepted for defined primary outcome variable. The biomechanical properties, scaffold degradation, and clinical wound healing were selected as co-outcome variables. RESULTS: The electronic search in the databases of the National Library of Medicine and ISI Web of Knowledge resulted in the identification of 6727 and 5017 titles, respectively. Thereafter, title assessment and hand search resulted in 128 abstracts, 101 full-text articles, and 29 scientific papers reporting on animal experiments as well as 11 papers presenting human data on the subject of tissue-engineered reconstruction of mandibular continuity defects that could be included in the present review. CONCLUSIONS: It was concluded that (1) published preclinical in vivo as well as clinical data are limited, and (2) tissue-engineered approaches demonstrate some clinical potential as an alternative to autogenous bone grafting.

Long-term survival of calcium phosphate-coated dental implants: a meta-analytical approach to the clinical literature.

BACKGROUND: Calcium phosphate ceramic coatings have the potential to compensate for challenging bone conditions such as delayed or impaired bone healing and low bone quantity or density. Thus, the increasing universal prevalence of subjects with such challenging bone conditions might be paralleled by an enhanced global use of calcium phosphate ceramic-coated dental implants. However, it is speculated that the long-term clinical survival of calcium phosphate-coated dental implants might be adversely affected by coating delamination. OBJECTIVE: The aims of the current review were (1) to systematically appraise and (2) to meta-analyse long-term survival data of calcium phosphate-coated dental implants in clinical trials. MATERIALS AND METHODS: An extensive search in the electronic databases of the National Library of Medicine (http://www.ncbi.nlm.nih.gov), The Cochrane Central Register of Controlled Trials and the ISI Web of Knowledge, was carried out for articles published between January 2000 and November 2011 to identify randomized controlled clinical trials, prospective clinical trials as well as retrospective analysis of cases (RA) presenting survival data on the topic of calcium phosphate-coated dental implants. Only publications in English were considered, and the search was narrowed to studies in humans with a follow-up of at least 5 years only. Furthermore, the reference lists of related review articles and publications selected for inclusion in this review were systematically screened. The primary outcome variable was percentage annual failure rate (AFR), and the secondary outcome variable was percentage cumulative survival rate (CSR). RESULTS: The electronic search in the database of the National Library of Medicine, The Cochrane Central Register of Controlled Trials and the ISI Web of Knowledge, resulted in the identification of 385 titles. These titles were initially screened by the two independent reviewers for possible inclusion, resulting in 29 publications suitable for further consideration. Screening the abstracts led to 20 full-text articles. From these articles, 15 reports were excluded. Finally, five of these original research reports could be selected for evaluation. No additional publications were identified by manual search. Thus, a total of five articles were included for analysis. Meta-analysis revealed that neither AFRs of calcium phosphate-coated dental implants increased progressively nor that long-term CSRs for calcium phosphate-coated dental implants were inferior to survival rates of noncoated implants. CONCLUSION: We conclude that (1) published long-term survival data for calcium phosphate-coated dental implants are very limited, (2) AFRs of calcium phosphate-coated dental implants do not increase progressively, and (3) long-term CSRs for calcium phosphate-coated dental implants are comparable to survival rates of noncoated implants.

Bone regeneration related to calcium phosphate-coated implants in osteoporotic animal models: a meta-analysis.

BACKGROUND: Osteoporosis is a frequent human metabolic bone disorder. Prospectively, global ageing of populations will lead to a major increase of subjects being diagnosed with osteoporosis and in need for dental rehabilitation. However, as local osteoporosis of the jaws affects bone quantity and quality of edentulous regions, osseointegration of dental implants might be hampered. Consequently, calcium phosphate ceramic-coated implants have been suggested to compensate for low bone quantity/density and for impaired bone healing in osteoporosis. Nonetheless, up to now no meta-analytical assessment of the relevant preclinical literature to quantify such a possible positive effect has been undertaken. MATERIALS AND METHODS: PubMed search, limited to animal models, to identify a possible positive effect of calcium phosphate-coated implants on bone regeneration, was carried out. Further, the reference lists of related review articles and publications selected for inclusion in this review were systematically screened. The primary outcome variables were bone-to-implant contact percentage as assessed histomorphometrically and mechanical stability testing. RESULTS: The electronic search in the database of the National Library of Medicine resulted in the identification of 2704 titles. These titles were initially screened by the two independent reviewers for possible inclusion, resulting in further consideration of 51 publications. Screening the abstracts led to 22 full-text articles. From these articles, 16 reports were excluded. Finally, six of these original research reports could be selected for evaluation. Additionally, eight publications were identified by manual search. Thus, a total of 14 articles were included for analysis. CONCLUSIONS: It was concluded that (1) in osteoporotic animal models calcium phosphate ceramic-coated implants are associated with improved bone-to-implant healing as compared to noncoated implants. Moreover, (2) essentially due to quality characteristics of the analyzed original research articles a negative impact of osteoporosis on bone-to-implant healing could not be confirmed. Besides, (3) the established positive bone-to-implant healing effect of calcium phosphate ceramic coatings does not differ between osteoporotic and nonosteoporotic, healthy animal models.

Effect of implant surface properties on peri-implant bone healing: implant stability and microcomputed tomographic analysis.

PURPOSE: The present study aimed to evaluate and compare two types of implants: grit-blasted and acidetched implants (SLActive) and nanometer-scale hydroxyapatite-modified implants (NanoTite). MATERIALS AND METHODS: Twenty-two SLActive and 22 NanoTite implants were inserted into the mandibles of 11 beagle dogs. The animals were divided into three groups according to healing time (group A, 2 weeks; group B, 4 weeks; group C, 8 weeks). Resonance frequency analysis (RFA) was performed immediately after implant placement and after 2, 4, and 8 weeks of healing. Two, 4, and 8 weeks after implantation, the animals were sacrificed and the amount of bone surrounding the implants was assessed using microcomputed tomography. RESULTS: For SLActive and NanoTite implants, the RFA values decreased after 2 weeks and increased after 4 and 8 weeks of healing. After 8 weeks, the mean RFA value for SLActive implants was significantly higher than the mean RFA value for NanoTite implants. For the different healing periods, no significant differences in bone volume were seen for SLActive and NanoTite implants. CONCLUSIONS: SLActive and NanoTite implants evoked a similar bone response after implantation for 2, 4, and 8 weeks in a nonsubmerged position in the mandibles of dogs. In addition, the data confirmed that RFA is a reliable and noninvasive method to determine dental implant stability and the bone formation process at the clinical level.

Human periodontal ligament fibroblasts stimulated by nanocrystalline hydroxyapatite paste or enamel matrix derivative. An in vitro assessment of PDL attachment, migration, and proliferation.

We determined the effects of soluble or coated nanocrystalline hydroxyapatite paste (nano-HA) and enamel matrix derivative (EMD) on proliferation, adhesion, and migration of periodontal ligament fibroblasts (PDLs). Cultured PDLs were stimulated with nano-HA paste or EMD in a soluble form or were coated to the surface of cell culture dishes. Proliferation of PDLs on coated nano-HA and EMD was quantified by various methods including bromodeoxyuridine (BrdU) incorporation and Western blot. Cell migration was investigated in a modified Boyden chamber. The surface integrin profile of PDLs was determined using an integrin-specific ELISA, and integrin-specific signaling was measured by immunoblotting of phosphorylated focal adhesion kinase (FAK). Coated nano-HA stimulated PDL proliferation to a larger extent as compared with coated EMD. PDL migration towards a nano-HA or EMD gradient was more efficiently mediated by soluble EMD as compared with nano-HA but vice versa, adhesion of PDLs to compound-coated dishes was more effectively mediated by nano-HA as compared with EMD. Mechanistically, majorly integrin α5ß1-mediated adhesion of PDL and both coated compounds mediated a significant increase in FAK activation though to a different extent. Current findings offer two different modes of action for EMD and nano-HA paste. EMD efficiently acts as a chemoattractant in its soluble form, while nano-HA paste effectively serves as a synthetic extracellular matrix component in its coated form. Our findings suggest that EMD and nano-HA paste display different molecular characteristics and apply alternative routes to mediate their beneficial effects on periodontal tissues.

Effect of implant surface properties on peri-implant bone healing: a histological and histomorphometric study in dogs.

AIM: The present study aimed to evaluate and compare two types of implants, i.e. grit-blasted and acid-etched implants (SLActive(®)) with nano-meter-scale hydroxyapatite surface-modified implants (NanoTite™). MATERIAL AND METHODS: For histological and histomorphometrical evaluation, 22 SLActive(®) and 22 Nanotite™ implants were inserted in eleven Beagle dogs. The animals were divided into three groups of healing (A: 2 weeks; B: 4 weeks and C: 8 weeks). Two, 4 and 8 weeks after implantation, the animals were sacrificed and bone-to-implant contact (BIC %), first implant-bone contact (1st BIC) as well as amount of bone (BV) were assessed. RESULTS: For SLActive(®) and Nanotite™ implants, BIC% increased significantly over time. No statistically significant differences in BIC% were found between SLActive(®) and Nanotite™ at all the respective implantation times. Moreover, for the different healing periods, no significant differences for BV between SLActive(®) and Nanotite™ implants were found. CONCLUSIONS: The present study showed that SLActive(®) and NanoTite™ implants induce a similar bone response after implantation for 2, 4 and 8 weeks in a non-submerged position in the mandible of dogs.

Influence of different biomaterials on the viability of Aggregatibacter actinomycetemcomitans.

OBJECTIVES: The aim of the present in vitro study was to evaluate the effects of different biomaterials used for regenerative periodontal surgery on the growth of the periodontopathogen Aggregatibacter actinomycetemcomitans. METHODS: Three commercially available biomaterials of synthetic origin (hydroxyapatite/beta-tricalcium phosphate, nanostructured hydroxyapatite paste, oily calcium hydroxide suspension), a bovine-derived xenograft as well as an enamel matrix derivative (EMD) were added in different concentrations to calibrated suspensions of A. actinomycetemcomitans ATCC 43718/33384 (serotype b/c). Equal aliquots (0.1 ml) for the viability assay were taken after 5 min, 1h, 3h, 8h and 24h, plated on blood agar and incubated in an anaerobic environment for 48 h at 37°C. Viable cell counts were expressed as colony forming units (cfu)/0.1 ml. RESULTS: The results demonstrated that none of the investigated biomaterials could inhibit the growth of A. actinomycetemcomitans serotype b. A marked growth reduction of A. actinomycetemcomitans serotype c was observed in the presence of oily calcium hydroxide suspension and nanostructured hydroxyapatite. In contrast, no significant growth inhibition could be observed in the presence of hydroxyapatite/beta-tricalcium phosphate, enamel matrix derivative and bovine-derived xenograft. CONCLUSIONS: The results of the present study suggest that none of the investigated biomaterials possesses antimicrobial properties against A. actinomycetemcomitans serotype b. Therefore, the use of these biomaterials for regenerative procedures should be weighted critically in the presence of A. actinomycetemcomitans serotype b.

Study of the osseointegration of dental implants placed with an adapted surgical technique.

OBJECTIVE: To study the osseointegration of dental implants placed with a modified surgical technique in Beagle dogs and to compare it with the conventional method. MATERIALS AND METHODS: Dental implants were placed bilaterally in the mandible of Beagle dogs using the press-fit as well as undersized implant bed preparation technique. Micro computer tomography (micro-CT) and histometric methods were used to analyze the bone implant contact and bone volume (BV) around the implants. RESULTS: The bone-to-implant contact percentage (BIC: expressed as %), first BIC (1st BIC: expressed in mm), sulcus depth (SD: expressed in mm) and connective tissue thickness (CT: expressed in mm) were analyzed for both groups. The BIC percentage was significantly higher for the undersized installed implants (P=0.0118). Also, a significant difference existed between the undersized and press-fit installed implants for the first screw thread showing bone contact (P=0.0145). There were no significant differences in mucosal response (SD and CT) for both installation procedures. Also, no significant difference was found in the BV, as measured using micro-CT, between the implants placed with an undersized technique (59.3 ± 4.6) compared with the press-fit implants (56.6 ± 4.3). CONCLUSION: From the observations of the study, it can be concluded that an undersized implant bed can enhance the implant-bone response.

Carbon nanotubes in animal models: a systematic review on toxic potential.

Amongst the engineered nanomaterials, especially carbon nanotubes (CNTs) have received considerable attention for application in tissue engineering scaffolds. CNTs are considered promising on behalf of their physicochemical properties, yet such nanomaterials also have been associated with potentially hazardous effects on human health. To gain insight into the toxicity aspects of CNTs in vivo, the present study presents a systematic review of literature. After screening of literature through defined inclusion and exclusion criteria, and subsequent data extraction, it can be concluded that pulmonary administered CNTs have the capacity to induce toxicity in the lung area. However, conclusions for other organs, or on systemic toxicity, are yet premature. In addition, the carcinogenic potential of CNTs is also still ambiguous, because contradictive results are presented. Intrinsic factors, such as material characteristics, and associated distribution and agglomeration patterns influence the toxic potential of CNTs. Similarly, environmental factors such as the exposure route, preexisting allergies, pathological infections, or air pollutant exposure are significant. Despite the many reports published currently, more studies will be required to gain full understanding of the toxic potential of CNTs and especially the underlying mechanisms. For this end, development of standardized protocols and reliable nanodetection techniques will form prerequisites.