[show abstract][hide abstract] ABSTRACT: Recombinant human bone morphogenetic protein-2 (rhBMP2) has been shown to induce both in vitro osteogenic differentiation and in vivo bone formation, with the capacity of rhBMP2 to elicit the repair of numerous bony defects (calvaria, spinal fusion, femora, and so on) well documented. In addition, rhBMP2 has been approved by the Food and Drug Administration (FDA) for selected human indications. Despite the fact that healing is often achieved, the challenge still remains to optimize the therapeutic use of rhBMP2. One avenue may be through the combination of rhBMP2 with stem cells capable of osteogenic differentiation. This study investigates the ability of rhBMP2 at various doses in combination with human adipose-derived stem cells (ASCs) to heal critical-sized rat segmental femoral defects. For this, different doses of rhBMP2 were incorporated with apatite-coated porous poly(l-lactide-co-dl-lactide) (70 : 30) (PLDLA) scaffolds, seeded with ASCs, and implanted into athymic rats. After 8 weeks, all implants were harvested and processed for bone formation using micro computed tomography (microCT) analysis and histology. Despite the findings that indicate no adverse effect of the apatite surface on ASC osteogenesis, no significant difference in bone formation could be qualitatively or quantitatively determined upon the implantation of ASC-seeded scaffolds absorbed to increasing doses of rhBMP2. Such results would suggest that the presence of ASCs within rhBMP2-absorbed scaffolds does not improve the bone-forming ability of the construct and that the formation of bone may be driven by the rhBMP2 alone. Based on these results, the addition of ASCs to rhBMP2-treated scaffolds may provide no significant advantage in terms of the ability to heal bone.
Connective tissue research 04/2011; 52(2):109-18. · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate the primary stability of dental implants placed with condensing-osteotome versus drilling-osteotome techniques and to explore peri-implant mircromorphologic consequences of lateral bone condensing.
The experimental model designed for the study comprised bilateral iliac crests from 3 fresh frozen human cadavers. Two AstraTech dental implants (AstraTech AB, Mölndal, Sweden) were consecutively placed with condensing- and drilling-osteotome techniques in bone with a 10-mm interimplant distance. Six experimental bone sites received a total of 12 implants. Installation torque values (ITVs) and implant stability quotients (ISQs) were measured to quantify primary implant stability. Bone specimens including implants were removed to quantify the peri-implant relative bone volume and bone microstructural parameters in the 1-mm circular vicinity of implants using desktop computed tomography (microCT). The Mann-Whitney U test was used to evaluate the differences in primary implant stability values and microCT data for the surgical placement techniques.
ITVs and ISQs were similar for both surgical placement techniques without statistical significance (P > .05). Relative bone volumes around implants placed with the condensing-osteotome technique were significantly (P < .05) higher than those around implants placed with the drilling-osteotome technique. Microstructural parameters, such as trabecular thickness, separation, and number, differed significantly between the 2 osteotome techniques.
Managing implant sites with the condensing-osteotome technique results in notable changes in peri-implant bone architecture but might not be as promising in improving primary implant stability compared with the drilling-osteotome technique.
Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 12/2007; 65(12):2487-91. · 1.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Osteoporosis may present a risk factor in achievement of osseointegration because of its impact on bone remodeling properties of skeletal phsiology. The purpose of this study was to evaluate micro-morphological changes in bone around titanium implants exposed to mechanical and electrical-energy in osteoporotic rats.
Fifteen 12-week old sprague-dowley rats were ovariectomized to develop osteoporosis. After 8 weeks of healing period, two titanium implants were bilaterally placed in the proximal metaphyses of tibia. The animals were randomly divided into a control group and biophysically-stimulated two test groups with five animals in each group. In the first test group, a pulsed electromagnetic field (PEMF) stimulation was administrated at a 0.2 mT 4 h/day, whereas the second group received low-magnitude high-frequency mechanical vibration (MECHVIB) at 50 Hz 14 min/day. Following completion of two week treatment period, all animals were sacrificed. Bone sites including implants were sectioned, removed en bloc and analyzed using a microCT unit. Relative bone volume and bone micro-structural parameters were evaluated for 144 mum wide peri-implant volume of interest (VOI).
Mean relative bone volume in the peri-implant VOI around implants PEMF and MECHVIB was significantly higher than of those in control (P < .05). Differences in trabecular-thickness and -separation around implants in all groups were similar (P > .05) while the difference in trabecular-number among test and control groups was significant in all VOIs (P < .05).
Biophysical stimulation remarkably enhances bone volume around titanium implants placed in osteoporotic rats. Low-magnitude high-frequency MECHVIB is more effective than PEMF on bone healing in terms of relative bone volume.
Head & Face Medicine 02/2007; 3:28. · 0.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: Osseointegrated implants can be applied to facilitate retention, stability, and support for facial and intraoral prostheses used to restore head and neck defects. At the University of California, Los Angeles, Maxillofacial Prosthetics Clinic, retrospective studies have indicated that in nonirradiated maxillectomy patients, implant survival rates are 82.6 percent. In mandibles reconstructed with fibula free flaps, survival rates are 94.6 percent. Similarly, high implant survival rates have been observed for most sites used to support facial prostheses. Cumulative six-year survival rates for auricular sites exceed 95 percent and for floor of nose sites, success rates exceed 87 percent. However, survival rates are low (53 percent) for implants placed in the frontal bone for retention of orbital prostheses and even lower for irradiated bone sites ranging from 63 percent in the maxilla to 27 percent in the orbit.
Journal of the California Dental Association 10/2006; 34(9):711-8.
[show abstract][hide abstract] ABSTRACT: The objective of this biomechanical study was to explore the effect of bone micro-morphology on initial intraosseous stability of implants with different designs.
Straumann and Astra Tech dental implants were placed into anterior and posterior regions of completely edentulous maxilla and mandible of a human cadaver. Experiments were undertaken to quantify initial implant stability and bone micro-morphology. Installation torque values (ITVs) and implant stability quotients (ISQs) were measured to determine initial intraosseous implant stability. For quantification of relative bone volume and micro-architecture, sectioned implant-bone and bone core specimens of each implant placement site were consecutively scanned and trabecular bone was analyzed in a micro-computed tomography (micro-CT) unit. Experimental outcomes were evaluated for correlations among implant designs, initial intraosseous implant stability and bone micro-structural parameters.
ITVs correlated higher with bone volume fraction (BV/TV) than ISQs, at 88.1% and 68.9% levels, respectively. Correlations between ITVs and micro-morphometric parameters were significant at the 95% confidence level (P<0.05) while ISQs were not. Differences in ITVs, ISQs and BV/TV data in regards to implant designs used were not significant at the 95% confidence level (P>0.05).
Bone micro-morphology has a prevailing effect over implant design on intraosseus initial implant stability, and ITV is more sensitive in terms of revealing biomechanical properties at the bone-implant interface in comparison with ISQ.
Clinical Oral Implants Research 09/2006; 17(4):465-72. · 3.43 Impact Factor
[show abstract][hide abstract] ABSTRACT: To compare the dimensional accuracy of implant framework castings from an argon vacuum casting machine with those from a centrifugal casting machine.
Three 4 x 10-mm external hex-type implants (3i/Implant Innovations) were embedded in an acrylic resin block 7 mm apart, with a 2 mm offset of the middle implant. Eight reference points were marked on the implant collars. Twenty implant bar frameworks were waxed with UCLA abutments, invested with a ringless system, and subjected to the same thermal cycle. Ten wax patterns were cast in gold alloy using an oxygen-propane torch and centrifugal casting system; 10 were cast using an argon vacuum casting machine (KDF; Denken). The White 1-screw technique was applied after sequentially tightening the mesial and distal abutment screws to 10 Ncm. Fit of the implant framework castings was evaluated by measuring the marginal opening between the casting and implant at the reference points. These measurements were averaged and statistically compared for differences.
The mean marginal openings at the most distant measuring locations from the tightened retaining screw at location 1 was between 44 to 48 microm for the centrifugal system compared to between 28 to 32 mm for KDF (P < .01). For screws tightened at location 3, the mean marginal openings at the most distant measuring locations were between 40 to 51 mm for the centrifugal system compared to between 27 to 29 microm for KDF (P < .01).
In comparison with the centrifugal casting and oxygen-propane system, the argon vacuum system was more accurate and user friendly and less technique-sensitive.
The argon vacuum casting machine tested produced more accurate, better fitting implant-supported prosthesis frameworks than a conventional centrifugal casting system. The "1-screw" method of evaluating casting fit was most effective when either of the prostheses' end screws were tightened.
The International journal of oral & maxillofacial implants 01/2006; 20(5):720-5. · 1.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Facial defects secondary to the treatment of neoplasms, congenital malformations, and trauma result in multiple functional and psychosocial difficulties. Prosthetic rehabilitation attempts to restore these facial disfigurements and may improve the level of function and self-esteem for these patients. However, a limited number of studies have evaluated the change in perceived quality of life after maxillofacial prosthetic rehabilitation.
The purpose of this study was to evaluate patients' perceptions of treatment with adhesive-retained and implant-retained facial prostheses and to assess differences in overall satisfaction with these 2 types of treatments.
In this study, a questionnaire with 28 items was administered for evaluation of perceptions of appearance, comfort, fit and irritation, reliability of retention, frequency of wear, ease of placement and removal, level of self-consciousness, and value of treatment. Subjects were categorized into 2 groups: adhesive-retained group (n=16) and implant-retained group (n=19). Comparisons were made for each item in the questionnaire using Fisher exact tests (alpha=.05).
The implant group reported higher positive ratings on all 28 questionnaire items when compared with the adhesive group. Statistically significant (P<.05) differences between the implant and adhesive groups were noted for ease of placement and removal, frequency of wear at home, and quality of retention during various activities, such as home chores and when perspiring or sneezing/coughing.
The implant-retained facial prosthesis offers significant enhancement over an adhesive-retained prosthesis with respect to ease of use and retention during a variety of daily activities, resulting in greater use of the prosthesis.
Journal of Prosthetic Dentistry 09/2005; 94(3):275-80. · 1.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: The mechanical behavior of bone is a critical factor in the attainment and maintenance of osseointegration. Current procedures and classifications in assessing bone quality have limitations. Micro-computed tomography (microCT) is a new method to image and quantify bone with very high resolution. This study was aimed to analyze cadaveric maxillary and mandibular trabecular bone with 3-D morphometric data acquired through microCT and correlate with conventional bone assessment methods. Moderately resorbed edentulous maxilla and mandible from a human cadaver were scanned in the conventional CT unit with opaque markers indicating specific anterior and posterior sites. These sites were then sectioned and standard periapical radiographs were obtained. Bone cores were harvested from the sectioned sites and scanned in the microCT unit. Bone density values based on the Hounsfield scale ranged from 51 to 529 in the mandible and 186 to 389 in the maxilla, anterior sites being higher in both. Periapical images did not yield distinct differences. 3-D morphometric analysis in microCT produced a range of values with anterior specimens being favorable: bone volume density (0.12-0.291), trabecular thickness (0.12-0.16 mm), trabecular separation (0.46-0.82 mm), trabecular number (1.08-2.071/mm) and structural model index (0.29-1.27). General agreement between bone density and microCT indices was noted; however, subtle differences have to be studied with larger samples. This preliminary study suggests that the understanding of mechanical competence of trabecular bone might reveal further information about the prognosis of implant therapy, advancements in implant design, surgical techniques and grafting.
Clinical Oral Implants Research 05/2004; 15(2):213-8. · 3.43 Impact Factor
[show abstract][hide abstract] ABSTRACT: An analysis of retrospective data was conducted to establish the survival rates of osseointegrated implants used to retain orbital, nasal, and auricular prostheses over a 14-year period and to recommend guidelines in the restorative treatment of such facial defects.
Included in this study were all patients who received implant-retained prostheses for auricular, nasal, or orbital defects from 1987 to 2001 in the Maxillofacial Clinics at the UCLA and City of Hope Medical Centers. Data were obtained from patient charts. Two methods were used to determine survival rates: (1) the percentage of the total exposed implants that survived was determined, and (2) life table analysis was used to calculate cumulative survival rates at different time intervals.
A total of 207 implants were placed in 72 patients, and 182 implants had been uncovered. During the study period, 35 implants failed to integrate, and the survival rate for all exposed implants was 80%. Auricular implants showed the highest survival rate (95%), and orbital implants showed the lowest survival rate (53%). The life table analysis demonstrated a cumulative 6-year survival rate of 92% for auricular implants and 87% for piriform/nasal implants. In contrast, the survival rate for orbital implants showed a steady downward trend and reached 59% at 66 months.
It is possible to achieve high survival rates of implants in the auricular and piriform/nasal sites through careful presurgical and radiographic planning. The less favorable long-term survival of implants in the orbital rim, especially at irradiated sites, requires further study.
The International journal of prosthodontics 15(4):325-32. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The capability of micro-computed tomography (microCT) for quantitative analysis of peri-implant bone has not been previously addressed. This study aimed to establish and validate a method to use this technique for 3-dimensional bone-implant integration profiling.
Unthreaded cylindric implants with a dual acid-etched surface were placed into the right femurs of 7 Sprague-Dawley rats. Two weeks postimplantation, the femurs were harvested and measured with a desktop micro-tomographic scanner with an isotropic resolution of 8 microm. To validate the microCT outcome, ground histologic sections and corresponding CT slices were compared with respect to bone morphometry.
Bone-implant integration profiles assessed by microCT revealed that the percentage of cancellous bone gradually increased with proximity to the implant surface, while the percentage of cortical bone was not affected by proximity to the implant. Using the optimized segmentation threshold, the bone configuration in the microCT images corresponded to that observed in the histologic sections. The correlation between microCT and histology was significant for cortical (r = 0.65; P < .05) and cancellous bone (r = 0.92; P < .05) at distances of 24 to 240 microm from the implant surface, but no significant correlation was found for the area from 0 to 24 microm from the surface.
The results support the usefulness of microCT assessment as a rapid, nondestructive method for 3-dimensional bone ratio measurements around implants, which may provide new perspectives for osseointegration research. Further study is necessary, however, to address the inherent metallic halation artifact, which potentially confounds peri-implant bone assessment.
The International journal of oral & maxillofacial implants 21(5):687-95. · 1.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: The published literature describing clinical evidence used in treatment decisionmaking for the management of tooth loss continues to be characterized by a lack of consistent outcome measures reflecting not only clinical performance but also a range of patient concerns. Recognizing this problem, an international group of clinicians, educators, and scientists with a focus on prosthodontics formed the Oral Rehabilitation Outcomes Network (ORONet) to promote strategies for improving health based on comprehensive, patient-centered evaluations of comparative effectiveness of therapies for oral rehabilitation. An initial goal of ORONet is to identify outcome measures for prosthodontic therapies that represent multiple domains with patient relevance, are amenable to utilization in both institutional and practice-based environments, and have established validity. Following a model used in rheumatology, the group assessed the prosthodontic literature, with an emphasis on implantbased therapies, for outcomes related to longevity and functional, psychologic, and economic domains. These systematic reviews highlight a need for further development of standardized outcomes that can be integrated across clinical and research environments.
The International journal of prosthodontics 26(4):319-22. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Purpose: A systematic literature review was conducted to identify the types of economic measures currently used in implant prosthodontics and determine the degree to which cost of care is considered in the context of any positive outcome of the care provided. Materials and Methods: A literature search was conducted using the following set of terms plus some additional hand searching: "dental implants" (Mesh) AND ("cost") OR "maintenance" OR "healthcare policy" OR "access to care" OR "third party" OR "economic") AND (("1995/01/01"[PDat]:'2009/12/31"[PDat]) AND (Humans[Mesh]) AND (English[lang])). Results: After a review of the 466 titles and abstracts identified by the search, 18 articles were accepted for further consideration, as some attempt at economic outcome measures was made. An additional four articles were identified by hand searching. The 22 accepted articles were grouped into four basic categories: (1) measure of costs of treatment (direct, indirect, and maintenance costs), (2) cost-effectiveness mathematical modeling applied to simulate the lifetime paths and cost of treatment, (3) cost-effectiveness analysis/cost minimization, and (4) willingness-to-pay, willingness-to-accept. Attempts at determining the costs of treatment varied widely. When the OMERACT filters were applied to the various measures it was felt that discrimination and/or feasibility was a problem for most of the current economic outcome measures. Conclusions: Measures of cost-benefit, cost-effectiveness, and cost-utility are currently the gold standard; however, feasibility of such analyses is an issue. Collaboration with health economists to guide future research is highly recommended.
The International journal of prosthodontics 26(5):465-469. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Oral Rehabilitation Outcomes Network (ORONet) Longevity Working Group undertook a search of the literature from 1995 to 2009 on randomized controlled trials related to longevity of osseointegrated implants. Outcomes measures used in these studies were identified and subjected to the OMERACT component criteria of truth, validity, and feasibility. Through this process, it was a challenge to identify clinical outcomes measures that fully met the criteria. An attenuated version of the component criteria was applied, and clinical measures were identified for implant outcomes, prosthetic outcomes, and indices. A recommendation on standardized reporting periods was also presented for future consideration. The endpoint of the evaluation process is to develop consensus on clinical outcomes measures that can be applied across broad populations for osseointegrated implant care. The present ORONet initiative represents a beginning toward continual improvement and consensus development for clinical outcomes measures for osseointegrated implants.
The International journal of prosthodontics 26(4):323-30. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The functional outcomes related to treating patients afflicted with tooth loss are an important hallmark in substantiating prosthodontic intervention. The Oral Rehabilitation Outcomes Network (ORONet) conducted two international workshops to develop a core set of outcome measures, including a functional domain. The process followed the general format used in the Outcome Measures in Rheumatology (OMERACT) workshops to develop consensus for clinical outcome measures in arthritis research, which included: developing a comprehensive list of potential outcomes in the literature; submitting them to a filter for validity, clinical discrimination, and feasibility; and ranking those measures meeting all the filter criteria for relative value. The search was conducted to include functional assessments of speech, swallowing, mastication, nutrition, sensation, and motor function as they relate to dental implant therapies. This literature review surveyed 173 papers that produced some result of these descriptors in the functional domain. Of these, 67 papers reported on functional assessments and further defined objective and subjective outcomes. Many of these results were patient-perceived improvements in function, while others were objective assessments based on established methodologies and instruments. Objective evaluations of masticatory function and speech may meet criteria for validity and discriminability for selected interventions, but are generally not feasible for routine use in clinical care settings. The current recommendation is to employ a well-validated survey instrument that covers mastication and speech, such as the Oral Health Impact Profile (OHIP-14, short form), recognizing that patient perceptions of function may differ from objective ability.
The International journal of prosthodontics 26(5):411-418. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Consensus regarding outcomes of the treatment of tooth loss, especially the psychologic outcomes, is needed to guide discovery of best practices and enable a better understanding of patient management for this chronic condition. This paper presents the findings of the ORONet Psychological Working Group for prosthodontics and aims to identify psychologic outcomes with properties deemed critical to meet clinical trial and clinical practice needs for the future. References obtained using a PubMed/Medline search were reviewed for clinical outcomes measures of interest. Clinical outcomes measures were judged relative to the criteria of truth, discrimination, and feasibility. Of the psychologic outcome measures identified in this systematic review, only the OHIP-14 was thought to be suitable for use in general practice and multi-institutional outcome registries and clinical trials. Development of clinically useful psychologic outcomes for future use could benefit from developmental methods and tools outlined in the patient-related outcomes field of clinical care.
The International journal of prosthodontics 26(5):429-434. · 1.63 Impact Factor