Micro-morphologic changes around biophysically-stimulated titanium implants in ovariectomized rats

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>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 <it>en bloc </it>and analyzed using a microCT unit. Relative bone volume and bone micro-structural parameters were evaluated for 144 μm wide peri-implant volume of interest (VOI).</p> <p>Results</p> <p>Mean relative bone volume in the peri-implant VOI around implants PEMF and MECHVIB was significantly higher than of those in control (<it>P </it>< .05). Differences in trabecular-thickness and -separation around implants in all groups were similar (<it>P </it>> .05) while the difference in trabecular-number among test and control groups was significant in all VOIs (<it>P </it>< .05).</p> <p>Conclusion</p> <p>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.</p

Early-Loaded One-Stage Implants Retaining Mandibular Overdentures By Two Different Mechanisms: 5-Year Results

Purpose: To compare the biologic and prosthetic outcomes of implants loaded early to retain mandibular overdentures by means of two different attachment systems. Materials and Methods: Patients were screened according to specific inclusion/exclusion criteria and randomly allocated to treatment groups involving two-implant-supported early loaded mandibular overdentures retained by ball attachments or Locator attachments. Marginal bone loss, Plaque Index, peri-implant infection, Bleeding Index, prosthetic complications, and Kaplan-Meier survival estimates of the groups were assessed at the 5-year recall. Results: Among the 29 patients (58 implants) who completed the study, one implant was lost during healing; all implants survived after prosthesis delivery. Bone loss in the ball attachment group (0.77 +/- 0.05 mm) was significantly greater than that in the Locator group (0.59 +/- 0.03 mm). The Plaque and Bleeding indices of both groups were comparable, and peri-implant inflammation scores in both groups were zero for all implants. The frequencies of activation of the matrix, replacement of the matrix, and denture reline in the ball attachment group were significantly higher than those observed in the Locator group. While assessments for the absence of any complication showed that the 1- and 3-year Kaplan-Meier survival probabilities of both groups were comparable, when activation of the retainer was excluded, survival probabilities of the ball attachment group were higher. Conclusions: The biologic outcomes of early loaded mandibular overdentures retained by ball attachments or Locators were comparable. Although the frequency of prosthetic complications with ball attachments was higher, this did not decrease the survival probability for the treatment

EFFECT OF DIGITIZING TECHNIQUES ON THE FIT OF IMPLANT-RETAINED CROWNS WITH DIFFERENT ANTI ROTATIONAL ABUTMENT FEATURES

AKCA, KIVANC/0000-0003-3013-2533; ozcan, nihal/0000-0003-2022-6085WOS: 000335538900004PubMed: 24360015Statement of problem. The development of computer-aided design/computer-aided manufacturing technology has enabled the fabrication of implant-retained restorations. However, information on the marginal and axial accuracy of restorations fabricated by different digitizing techniques with different antirotational abutment features is not sufficient. Purpose. The purpose of this in vitro study was to evaluate the influence of digitizing techniques on the fit of implant-retained crowns with 2 antirotational features. Material and Methods. An experimental working cast housing a tissue-level dental implant was created. Resin-retained abutments with different antirotational features were connected to the implant. Optical impressions of 2 abutment types were obtained separately with 1 chairside and 2 laboratory approaches. Alumina silicate restorations were milled from chairside optical impressions, and ceramic oxide cores were milled from laboratory optical impressions. Restoration fit was evaluated from axial sections of restorations with silicone materials representing the marginal and axial gaps. Axial and marginal fits were measured on digital photographs of the sectioned specimens with a computer program. Two-way ANOVA was used to compare differences between abutments with 2 different antirotational features and digitizing techniques separately for the marginal and axial fits of single implant-retained crowns. A post hoc least significant difference test was used to compare digitizing techniques (alpha=.05). Results. Significant differences in the marginal fit of single-implant-retained crowns were found among digitizing techniques (P=.011) and between antirotational features (P<.001). No significant difference in the axial fit of single-implant-retained crowns was found among digitizing techniques (P=.905) or between antirotational features (P=.075). Conclusions. Within the limitations of this in vitro study, the marginal fit of single-implant-retained crowns was affected by antirotational abutment features. Furthermore, digitizing techniques were found to play an important role in the marginal fit of single-implant-retained restorations

Immediate Versus Conventional Loading Of Implant-Supported Maxillary Overdentures: A Finite Element Stress Analysis

Purpose: To compare biomechanical outcomes of immediately and conventionally loaded bar-retained implant-supported maxillary overdentures using finite element stress analysis. Materials and Methods: Finite element models were created to replicate the spatial positioning of four 4.1- x 12-mm implants in the completely edentulous maxillae of four cadavers to support bar-retained overdentures with 7-mm distal-extension cantilevers. To simulate the bone-implant interface of immediately loaded implants, a contact situation was defined at the interface; conventional loading was simulated by "bonding" the implants to the surrounding bone. The prostheses were loaded with 100 N in the projected molar regions bilaterally, and strain magnitudes were measured at the buccal aspect of bone. Results: The amplitude of axial and lateral strains, the overall strain magnitudes, and the strain magnitudes around anterior and posterior implants in the immediate loading group were comparable to those seen in the conventional loading group, suggesting that the loading regimens created similar stress/strain fields (P > .05). Conclusions: Conventional and immediate loading of maxillary implants supporting bar-retained overdentures resulted in similar bone strains.Wo

Predicting bone remodeling around tissue- and bone-level dental implants used in reduced bone width

The objective of this study was to predict time-dependent bone remodeling around tissue- and bone-level dental implants used in patients with reduced bone width. The remodeling of bone around titanium tissue-level, and titanium and titanium-zirconium alloy bone-level implants was studied under 100 N oblique load for one month by implementing the Stanford theory into three-dimensional finite element models. Maximum principal stress, minimum principal stress, and strain energy density in pen-implant bone and displacement in x- and y- axes of the implant were evaluated. Maximum and minimum principal stresses around tissue-level implant were higher than bone-level implants and both bone-level implants experienced comparable stresses. Total strain energy density in bone around titanium implants slightly decreased during the first two weeks of loading followed by a recovery, and the titanium-zirconium implant showed minor changes in the axial plane. Total strain energy density changes in the loading and contralateral sides were higher in tissue-level implant than other implants in the cortical bone at the horizontal plane. The displacement values of the implants were almost constant over time. Tissue-level implants were associated with higher stresses than bone-level implants. The time-dependent biomechanical outcome of titanium-zirconium alloy bone-level implant was comparable to the titanium implant

Occlusal adjustment of 3-unit tooth-supported fixed dental prostheses fabricated with complete-digital and -analog workflows : A crossover clinical trial

Aim: This prospective crossover clinical trial aimed to compare the complete-digital and -analog workflows in terms of occlusal adjustment of 3-unit tooth-supported fixed dental prostheses, operator, and patient preferences. Materials and method: This study included twelve patients receiving fourteen 3-unit posterior FDPs. 2 FDPs were made for each restoration site: one fabricated in complete-digital workflow comprising intraoral scan with static bite registration (Trios 3) and a monolithic zirconia FDP (test); the other fabricated in complete-analog workflow comprising conventional impression/face-bow transfer and a porcelain-fused-to-metal FDP (control). The FDPs (n=28) were intraorally/provisionally fixed, and quadrant-like intraoral scans were taken for every FDP before &amp; after their occlusal adjustments. Pre- and post-adjustment scans of each FDP were then superimposed using best-fit alignment (GOM Inspect) to measure the volumetric occlusal adjustment amount (mm3) (3Matic) (Mann Whitney U, α=0.05). The patient and operator experience for digital and analog workflows were evaluated using visual analog scales (Wilcoxon test, α=0.05). Results: Mean occlusal adjustments were 7.63 mm3[±7.02] and 25.95 mm3[±39.61] for test and control groups, respectively. The volumetric adjustment difference was clinically noticeable but not significant (P=0.12). The impression and digital workflow adjustment were perceived more favorably by both operator (P=0.003, P=0.046, respectively) and the patients (P=0.003, P=0.002, respectively). Conclusions: Within the limitations of this clinical study, the complete digital workflow with digital static bite-registration provided high occlusal accuracy for short-span tooth-supported FDPs. In addition, the patient and operator preferences significantly favored the digital workflow. Clinical significance: Complete-digital workflow employing intraoral scanning and model-free fabrication of monolithic-Zr short-span tooth-supported FDPs offers an effective treatment modality with sufficient occlusal accuracy. Therefore complete-digital workflow is a valid alternative for complete-analog workflow comprising conventional impression, face-bow transfer, and use of a semi-adjustable articulator.</p

Fabricated custom-made device to deliver PEMF stimulation on osteoporotic rats

<p><b>Copyright information:</b></p><p>Taken from "Micro-morphologic changes around biophysically-stimulated titanium implants in ovariectomized rats"</p><p>http://www.head-face-med.com/content/3/1/28</p><p>Head & Face Medicine 2007;3():28-28.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1947957.</p><p></p