Medicine JournalFeeds

Biological response to titanium implants coated with nanocrystals calcium phosphate or type 1 collagen in a dog model.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Alghamdi HS, A J A van Oirschot B, Bosco R, van den Beucken JJ, Aldosari AA, Anil S, Jansen JA

Abstract

OBJECTIVE: The current study aimed to evaluate the osteogenic potential of electrosprayed organic and non-organic surface coatings in a gap-implant model over 4 and 12 weeks of implantation into the dog mandible. MATERIAL AND METHODS: Sixteen Beagle dogs received experimental titanium implants in the mandible 3 months after removal of left premolars (P2, P3 and P4). Three types of implants were installed in each animal: non-coated implant, nano-CaP coated implant and implant with type 1 collagen coating. Both micro-CT and histomorphometry were used to evaluate peri-implant bone response after implantation periods of 4 and 12 weeks. The bone area percentage was assessed histomorphometrically in three different zones (inner: 0-300 μm; middle: 300-600 μm; and outer: 600-1000 μm) around the implant surface. Bone-bridging of the gap was also calculated for each sample. RESULTS: Four weeks after implantation, nano-CaP and collagen-coated implants showed significantly higher bone volume (BV) in the inner zone compared with non-coated implants (P < 0.05 and P < 0.01). After 12 weeks, histomorphometric analysis showed comparable amounts of BV between all experimental groups. Also, no significant difference was found in the BV, as measured using micro-CT, between the implant groups. Absolute bone ingrowth measurements were highest for collagen-coated implants, but these differences were not significant. CONCLUSION: The obtained data failed to provide a consistent favourable effect on bone formation of the collagen coating over 3 months of implantation. It is concluded that the source of the collagen as well as the limited osseous environment overshadowed a possible effect of the applied implant surface modifications. Similarly, the tested nano-apatite surface coating did not improve peri-implant bone ingrowth into a gap-implant model.

PMID: 22276577 [PubMed - as supplied by publisher]

Fractured zirconia implants and related implant designs: scanning electron microscopy analysis.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Osman RB, Ma S, Duncan W, De Silva RK, Siddiqi A, Swain MV

Abstract

OBJECTIVES: Two fractured one-piece experimental (commercially unavailable) zirconia implants were analyzed using scanning electron microscope (SEM) analysis to identify failure origins and aid in understanding the failure mechanisms. Modifications to the zirconia implant design are suggested to minimize such fracture incidences. MATERIALS AND METHODS: Two zirconia implants fractured during the final torquing in the maxillary ridge using the prescribed hand torque wrench. The implants were subsequently retrieved and prepared for optical and SEM evaluation. Critical attention was given to the fractography (crack morphology) of the fractured implants to identify the fracture origin. RESULTS: Events related to initiation and propagation of the crack front could be detected from the morphology of the fractured surfaces. Unfavorable torque and bending forces applied on the implant during surgical placement and the inherent flaws in the material may have resulted in crack initiation and implant failure. CONCLUSIONS: Caution must be exercised when placing zirconia implants in dense bone sites. Modification of surgical protocols for the intended implant site may be necessary. Improvement in design features specific to zirconia implants, and strict quality control during manufacture is essential to minimize the likelihood of fracture.

PMID: 22276596 [PubMed - as supplied by publisher]

Clinical use of alumina-toughened zirconia abutments for implant-supported restoration: prospective cohort study of survival analysis.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Kim SS, Yeo IS, Lee SJ, Kim DJ, Jang BM, Kim SH, Han JS

Abstract

OBJECTIVES: The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates. MATERIAL AND METHODS: From May 1998 to September 2010, 213 patients aged 18 years or older were recruited. The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments. During the follow-up, each restoration was coded as a dental event, which included loosening or fracture of abutment screws, and abutment fracture. From the coded data, the effects of the investigated clinical variables-restored area (anterior/posterior), number of prosthodontic units (one/two units or over), prosthesis type (single-unit/multiunit without pontic/multiunit with pontic), implant system, and patient gender-on the survival of the abutments were evaluated. Survival analysis using Kaplan-Meier method and Cox proportional hazard model was applied. The 5-year survival and complication rates of the abutments were assessed. RESULTS: The number of prosthodontic units and the type of prosthesis had a significant association with complication rates (P < 0.05). Kaplan-Meier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7%. Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9% and 3.8%, respectively. The 5-year survival rate of the abutments was more than 95%, regardless of the type of prosthesis. CONCLUSIONS: Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations. Single tooth replacement with the abutment at the molar region may require special care and extra attention.

PMID: 22276635 [PubMed - as supplied by publisher]

Ultrastructural study by backscattered electron imaging and elemental microanalysis of bone-to-biomaterial interface and mineral degradation of porcine xenografts used in maxillary sinus floor elevation.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Ramírez-Fernández MP, Calvo-Guirado JL, Maté-Sánchez Del Val JE, Delgado-Ruiz RA, Negri B, Barona-Dorado C

Abstract

OBJECTIVES: The aim of this study was to carry out an ultrastructural study of the biomaterial-to-bone interface and biomaterial mineral degradation in retrieved bone biopsies following maxillary sinus augmentation using collagenized porcine xenografts (Osteobiol(®) Mp3) in 15 clinical cases. MATERIALS AND METHODS: Nine months after sinus lifting, bone cores were harvested from the maxillary sinus. The specimens were processed for observation under a scanning electron microscope with backscattered electron imaging (SEM-BSE). In addition, chemical analysis and elemental mapping of the mineral composition were generated using a microanalytical system based on energy-dispersive X-ray spectrometry (EDX). RESULTS: No clinical complications were evident during surgery. Scanning electron microscopy revealed that newly formed bone had become closely attached to the xenograft. Statistical analysis showed a significantly high Ca/P ratio in the biomaterial (2.46 ± 0.16) and at the bone interface (2.00 ± 0.48) compared to bone (1.97 ± 0.36), which suggests that there may be a gradual diffusion of Ca ions from the biomaterial into the newly forming bone at the interface as part of the biomaterial’s resorption process. EDX analysis of the residual porcine biomaterial at different points showed some particle categories with different mean ratios of Ca/P according to size, pointing to different stages of the resorption process. CONCLUSIONS: The biomaterial proved to be biocompatible, bioreabsorbable and osteoconductive when used as a bone substitute for maxillary sinus elevation. SEM-BSE revealed that newly formed bone had become closely attached to the xenografts. EDX analysis monitored the resorption process of the porcine bone xenograft. Elemental mapping showed that there was a gradual diffusion of Ca ions from the biomaterial to the newly forming bone at the interface.

PMID: 22276656 [PubMed - as supplied by publisher]

Immediate single implant restorations in mandibular molar extraction sockets: a controlled clinical trial.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Atieh MA, Alsabeeha NH, Duncan WJ, de Silva RK, Cullinan MP, Schwass D, Payne AG

Abstract

BACKGROUND: In the replacement of missing teeth, a paradigm shift is currently observed with immediate implant placement and/or restoration, particularly in the aesthetic zone. In molar sites, however, anatomical, occlusal and biomechanical considerations remain deterrent factors influencing the outcome of this treatment paradigm. The aim of this report was to evaluate immediate placement and immediate restoration of strongly tapered wide-diameter implant in fresh mandibular molar extraction sockets. METHODS: Twenty-four 8- or 9-mm diameter implants were placed in either a fresh molar extraction socket or a healed site. All the implants received provisional crowns within 48 h. The provisional crowns were replaced with full ceramic crowns after 8 weeks of implant placement. RESULTS: The overall implant success rate after 1 year of service for the 24 implants in two treatment groups was 75%. Success rates were 83.3% and 66.7% for the delayed and immediate placement groups respectively, with no significant difference observed between the two groups (P = 0.35). Implant stability measurements identified the immediately placed implants to be more stable immediately after surgery than delayed placed implants. In contrast, the delayed placed implants were more stable after 8 week healing time. CONCLUSIONS: The rehabilitation of single missing mandibular molars by immediately placed and restored wide-diameter implants was associated with a relatively high failure rate.

PMID: 22276690 [PubMed - as supplied by publisher]

Effects of nicotine on guided bone augmentation in rat calvarium.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Saito Y, Sato S, Oginuma T, Saito Y, Arai Y, Ito K

Abstract

OBJECTIVE: A limited number of experimental animal studies and in vitro studies have confirmed that nicotine impairs bone healing, diminishes osteoblast function, causes autogenous bone graft morbidity, and decreases graft biomechanical properties. The aim of this study was the histomrphometric assessment of the effect of nicotine on guided bone augmentation in a rat model. MATERIAL AND METHODS: Twenty-four male Wistar rats were randomly divided into a nicotine group and a control group. All animals received either nicotine (3 mg/kg) or saline 4 weeks before the surgical procedure and continued to receive nicotine or saline from surgery until death at 12 weeks. Two plastic caps were placed in the exposed calvaria of rats. Images of bone augmentation within the plastic caps were then taken using microfocus computed tomography (micro-CT). Histological sections were cut along the same plane as that used for micro-CT images. RESULTS: Bone augmentation beyond the skeletal envelope occurred in both the nicotine and control groups. However, the nicotine group showed significantly smaller increases in bone volume and bone height than the controls. CONCLUSION: Nicotine jeopardized, but did not prevent, the process of guided bone augmentation in a rat model.

PMID: 22276738 [PubMed - as supplied by publisher]

Horizontal alveolar distraction osteogenesis for dental implant: long-term results.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Yamauchi K, Takahashi T, Nogami S, Kataoka Y, Miyamoto I, Funaki K

Abstract

OBJECTIVES: The aim of the present study was to present the results of patients followed for at least 3 years who underwent horizontal distraction osteogenesis DO and a final implant prosthesis. MATERIAL AND METHODS: A total of 13 sites in 12 patients (three men, nine women; mean age 45.4 years, range 21-63 years) who presented with severe horizontal atrophy of a partially edentulous maxilla or mandible were treated using horizontal DO. The horizontal distraction device was set on the transport bone which was osteotomized as bone splitting method and fixed to the segment using microscrews. RESULTS: The median of latency period was 9 days (range: 7-17); the median of amount of device activation was 5.6 mm (range: 4.4-9.6); the median of distraction period was 14 days (range: 8-24); and the median of consolidation period, from the end of activation until implant placement, was 13 weeks (range: 11-20). The median of actual gain in bone width at the end of the consolidation period was 3.6 mm (range: 1.1-5.6). A total of 35 implants were inserted in the augmented area with primary implant stability. The median of follow-up from the start of prosthetic loading was 5.4 years. Consequently, the implant survival and success rates were 100% and 94.2%, respectively. CONCLUSION: This article reports the long-term results of horizontal alveolar DO using a mesh device for patients with an atrophic alveolar region. Our results confirm that this technique is a predictable and effective regenerative procedure for implant preprosthetic treatment in patients with severe horizontal atrophy of the alveolar ridge.

PMID: 22276776 [PubMed - as supplied by publisher]

Sinus augmentation using rhBMP-2/ACS in a mini-pig model: relative efficacy of autogenous fresh particulate iliac bone grafts.

Clin Oral Implants Res. 2012 Jan 26;

Authors: Lee J, Susin C, Rodriguez NA, de Stefano J, Prasad HS, Buxton AN, Wikesjö UM

Abstract

BACKGROUND: Implant dentistry in the posterior maxilla often requires bone augmentation. The gold standard, autogenous bone graft, requires additional surgery with associated morbidity, while bone biomaterials may not support relevant bone formation. Recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge (ACS), however, induces significant, clinically relevant bone formation in several settings including the maxillary sinus floor. OBJECTIVE: The objective of this study was to compare local bone formation and osseointegration following maxillary sinus augmentation using rhBMP-2/ACS or a particulate autogenous cancellous bone graft obtained from the iliac crest in conjunction with immediate placement of dental implants. MATERIALS AND METHODS: Bilateral sinus augmentation using an extraoral approach including rhBMP-2 (0.43 mg/ml)/ACS or the autogenous bone graft, alternated between left and right sinus cavities in five adult male Yucatan mini-pigs, was performed. Two 12-mm dental implants were inserted into the sinus wall protruding approximately 8 mm into the sinus cavity. Surgical sites were closed and sutured in layers; block biopsies collected for histometric analysis at 8 weeks. RESULTS: rhBMP-2/ACS induced bone of significantly greater and consistent quality compared with the iliac crest autogenous bone graft; bone density averaging 51.9 ± 3.0% vs. 32.9 ± 2.5% (P = 0.01). However, there were only numerical differences in augmented bone height (9.3 ± 0.5 vs. 8.6 ± 0.7 mm) and bone-implant contact (37.4 ± 3.0% vs. 30.7 ± 5.9%) between treatments. CONCLUSION: rhBMP-2/ACS induces bone of superior quality compared with an iliac crest particulate autogenous cancellous bone graft when used for maxillary sinus augmentation, and should perhaps be considered the new standard for this indication.

PMID: 22276816 [PubMed - as supplied by publisher]

Alterations in intraoral manipulation and splitting of food by subjects with tooth- or implant-supported fixed prostheses.

Clin Oral Implants Res. 2012 Jan 24;

Authors: Svensson KG, Grigoriadis J, Trulsson M

Abstract

OBJECTIVES: Sensory information provided by the periodontal mechanoreceptors (PMRs) is used by the nervous system to optimize the positioning of food, force levels, and force vectors involved in biting. The aim of this study was to describe motor performance during a novel manipulation-and-split task and to assess the extent to which control of this performance involves information from the PMRs. MATERIALS AND METHODS: A total of 10 subjects with natural teeth, 10 with bimaxillary tooth-supported fixed prostheses (TSP) and 10 with bimaxillary implant-supported fixed prostheses (ISP) (61-83 [mean 69] years of age) were asked to perform an intraoral manipulation-and-split task that involved positioning a spherical chocolate dragée between the front teeth and then splitting it into two parts of equal size. The vertical jaw movement, sound of food cracking and masseter muscle activity were monitored during this task and the accuracy of the split was evaluated. RESULTS: The group with natural teeth was significantly better than the other groups at splitting the candy with high precision. The jaw movements were similar between groups, but the contact phase prior to the split was significantly longer for those with natural dentition. CONCLUSIONS: The present findings support the conclusion that the nervous system collects rich information about contact between the teeth and food from the PMRs prior to powerful jaw action. Impairment (TSP) or absence (ISP) of this information alters motor behavior and impairs performance during the natural biting task employed here.

PMID: 22272657 [PubMed - as supplied by publisher]

The reliability of cone-beam computed tomography to assess bone density at dental implant recipient sites: a histomorphometric analysis by micro-CT.

Clin Oral Implants Res. 2012 Jan 17;

Authors: González-García R, Monje F

Abstract

OBJECTIVES: The aim of this study was to objectively assess the reliability of the cone-beam computed tomography (CBCT) as a tool to pre-operatively determine radiographic bone density (RBD) by the density values provided by the system, analyzing its relationship with histomorphometric bone density expressed as bone volumetric fraction (BV/TV) assessed by micro-CT of bone biopsies at the site of insertion of dental implants in the maxillary bones. MATERIAL AND METHODS: Thirty-nine bone biopsies of the maxillary bones at the sites of 39 dental implants from 31 edentulous healthy patients were analyzed. The NobelGuide™ software was used for implant planning, which also allowed fabrication of individual stereolithographic surgical guides. The analysis of CBCT images allowed pre-operative determination of mean density values of implant recipient sites along the major axis of the planned implants (axial RBD). Stereolithographic surgical guides were used to guide implant insertion and also to extract cylindrical bone biopsies from the core of the exact implant site. Further analysis of several osseous micro-structural variables including BV/TV was performed by micro-CT of the extracted bone biopsies. RESULTS: Mean axial RBD was 478 ± 212 (range: 144-953). A statistically significant difference (P = 0.02) was observed among density values of the cortical bone of the upper maxilla and mandible. A high positive Pearson’s correlation coefficient (r = 0.858, P < 0.001) was observed between RBD and BV/TV, with the regression equations: (1) Axial RBD = -19.974 + 10.238·BV/TV; (2) BV/TV = 14.258 + 0.72·Axial RBD. RBD was also positively correlated with the trabecular thickness (Tb.Th) and trabecular number (Tb.N), but negatively correlated with trabecular separation (Tb.Sp), structural model index, and inverse connectivity (Tb.Pf). Density values upper than 450 were associated with BV/TV upper than 50%, mean Tb.Th upper than 0.2 mm, mean Tb.Sp lower than 0.3 mm, and mean Tb.N upper than 2. CONCLUSION: RBD assessed by CBCT has a strong positive correlation with BV/TV assessed by micro-CT at the site of dental implants in the maxillary bones. Pre-operative estimation of density values by CBCT is a reliable tool to objectively determine bone density.

PMID: 22250839 [PubMed - as supplied by publisher]