Murat Cavit Cehreli

The Significance Of Passive Framework Fit In Implant Prosthodontics: Current Status

The clinical and laboratory procedures employed for framework fabrication are inadequate to provide an absolute passive fit for implant-supported fixed superstructures. Although some prosthetic complications are attributed to the lack of passive fit, its effect on implant success is questionable. Nevertheless, the clinical results of increasing applications of advanced technology to improve framework fit seem promising. This article reviews the clinical significance of passive fit and the factors that affect the final fit of implant-supported frameworks.

The influence of functional forces on the biomechanics of implant-supported prostheses—a review

OBJECTIVES To evaluate published evidence related to the influence of functional forces on the biomechanics of implant-supported prostheses. DATA AND SOURCES The literature was searched for original research articles relating control of loads on dental implants, effects of early and late occlusal loads, the influence of bone quality, prosthesis type, prosthesis material, number of supporting implants, and engineering techniques employed for evaluating mechanical and biomechanical behavior of implants using MEDLINE and manual tracing of references cited in key papers otherwise not elicited. STUDY SELECTION Current literature on implant biomechanics as main focus and pertinent to key aspects of the review. CONCLUSIONS The outcome of implant treatment is often maximized when implants are placed in dense bone, number of supporting implants are increased, implant placement configuration reduces the effects of bending moments, and when a fixed prosthesis is delivered to the patient.

CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA) quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram® Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon® Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram® Zirconia (73%) and Cercon® Zirconia (80%) restorations, respectively. Slight color mismatch rate was higher for InCeram® Zirconia restorations (66%) than Cercon® Zirconia (26%) restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05). This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.

The effect of current bleaching agents on the color of light-polymerized composites in vitro

STATEMENT OF PROBLEM Bleaching agents may affect the color of existing composite restorations. PURPOSE The purpose of this study was to compare the effect of 10% carbamide peroxide and 10% hydrogen peroxide on the color of light-polymerized hybrid, macrofilled, and polyacid-modified composites. MATERIAL AND METHODS Two light-polymerized hybrid composites (3M Valux and Spectrum TPH), 1 macrofilled condensable composite (Solitaire), and 2 polyacid-modified composites (Dyract AP and Compoglass) were used. The hybrid composites served as controls. The color of 8 specimens of each material was analyzed by use of a spectrophotometer before bleaching. The specimens were then divided randomly into 2 subgroups (n=4). One group was immersed in 10% carbamide peroxide solution and the other in 10% hydrogen peroxide, for 8 hours each for 14 consecutive days. After bleaching, color changes (Delta E) were determined for each material and compared by use of the Kruskal-Wallis test, followed by the Mann-Whitney U test (P<.05). RESULTS After bleaching with carbamide peroxide, the color changes (Delta E) for Dyract AP (2.18; SD = 1.41), Compoglass (1.14; SD = 0.26) and Solitaire (1.56; SD = 0.89) were higher than the color changes recorded for 3M Valux (0.63; SD = 3.60), and Spectrum TPH (0.66; SD = 1.24). The differences between materials bleached with carbamide peroxide were not statistically significant. After bleaching with hydrogen peroxide, the color changes for Dyract AP (9.39; SD = 0.53) and Compoglass (5.15; SD = 0.52) were higher than the changes recorded for Spectrum TPH (4.53; SD = 1.53) and 3M Valux (3.41; SD = 4.40), whereas the color change of Solitaire (3.69; SD = 0.57) was significantly higher than that of 3M Valux (P=.01). The color changes for all restorative materials tested were clinically detectable after the application of 10% hydrogen peroxide. However, clinically noticeable discoloration was observed only for Dyract AP treated with 10% carbamide peroxide. CONCLUSION In comparison to 10% carbamide peroxide, 10% hydrogen peroxide caused more color changes in the composites tested.

Implant stability and bone density: assessment of correlation in fresh cadavers using conventional and osteotome implant sockets

OBJECTIVE To compare the primary stability of implants placed in conventional and osteotome sites and to evaluate the level of correlation between cutting torque measurements, resonance frequency analysis (RFA), and bone density. MATERIALS AND METHODS Eight human femoral heads were scanned with computed tomography for bone density measurements as Hounsfield units (HU), and individualized computed tomography-based surgical stents were prepared for placement of implants. Five implant sockets were prepared in each collum (CoF), caput (CaF), and trochanter (Tr-MM) section of the femoral heads using the conventional drilling technique or by a combination of drilling and use of an osteotome. Cutting-torque values (CTV) of the implants were measured by a manual torque wrench, followed by determination of implant stability quotients (ISQ) by RFA. RESULTS The CTVs of implants were similar in the conventional group, but different in the osteotome group (P<0.05). There was a general tendency toward achieving higher CTV and ISQ values in CoF than CaF and Tr-MM (P<0.05), and measurements in CaF and Tr-MM were comparable (P>0.05). The mean HU of sites were similar, although CoF had higher HU values (P>0.05). CTV of implants in CaF and Tr-MM and ISQ values in CoF in the conventional groups were higher than those in the osteotome groups (P<0.05). The correlation between CTV and HU in Tr-MM was significant in the osteotome group, although no other correlations between CTV, ISQ, and HU could be detected (P>0.025). CONCLUSIONS Conventional placement led to higher implant stability than the drilling and osteotome technique used in the study. No correlation could be found between CTV, RFA, and bone density.

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

BackgroundOsteoporosis 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.MethodsFifteen 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 μm wide peri-implant volume of interest (VOI).ResultsMean 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).ConclusionBiophysical 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.

In vitro strain gauge analysis of axial and off-axial loading on implant supported fixed partial dentures.

The purpose of this study was to compare the in vitro strains on dental implants supporting cement-retained fixed partial dentures under axial and off-axial loading conditions. Ten implants incorporating strain gauges were placed in a certain configuration to simulate different clinical situations and were embedded in an experimental model. Two implant supported three-unit fixed partial dentures were fabricated on four groups of implants, and each group consisted of seven restorations. The prostheses were cemented with a temporary cement. Fifty N vertical load was applied on predetermined axial and off-axial loading locations on the prostheses. Strain indicator readings were re- corded at a standardized time following each loading sequence. The point of load transfer affected strains on implants. For all prosthetic designs, off-axial loading generated more strain than axial loading on implants (P < 0.05). In comparison with axial loading, off-axial loading causes bending of the implants that may affect bone loss around the implant collar. Axial loading of implants should be provided by using wide diameter implants, narrow occlusal tables, and proper occlusal contacts on implant restorations.

Marginal Bone Level Changes and Prosthetic Maintenance of Mandibular Overdentures Supported by 2 Implants: A 5‐Year Randomized Clinical Trial

BACKGROUND Documentation of early loading of mandibular overdentures supported by different implant systems is scarce. PURPOSE This study aimed to compare the biologic and prosthetic outcome of mandibular overdentures supported by unsplinted early-loaded one- and two-stage oral implants after 5 years of function. MATERIALS AND METHODS Twenty-eight consecutive patients were screened following an inclusion and exclusion criteria, and randomly allocated to treatment groups. Ball-retained mandibular overdentures were fabricated on two unsplinted Straumann (Institut Straumann AG, Basel, Switzerland) and Brånemark (Nobel Biocare AB, Göteborg, Sweden) dental implants and subjected to an early-loading protocol. During the 5-year period, prosthetic complications were recorded. At 5-years of function, plaque, peri-implant inflammation, bleeding, and calculus index scores were recorded, and standard periapical radiographs were obtained from each implant for measurement of marginal bone loss. RESULTS All implants survived during the observation period. The peri-implant inflammation, bleeding, and calculus index scores around Straumann and Brånemark implants were similar (p > .05). The marginal bone loss around Brånemark implants (1.21 +/- 0.1) was higher than Straumann implants (0.73 +/- 0.06) at 5 years of function (p = .002). Kaplan-Meier tests revealed that 1- and 5-year survival of overdentures on Straumann and Brånemark implants were similar (p = .85). Wear of the ball abutment in the Brånemark group was higher than in the Straumann group (p < .05). Complications regarding the retainer and the need for occlusal adjustments were higher in the Straumann group (p < .05). Chi-square test revealed that the frequency of retightening of the retainer was higher in the Straumann group than in the Brånemark group (p < .05). CONCLUSIONS Mandibular overdentures supported by unsplinted early-loaded Straumann and Brånemark implants lead to similar peri-implant soft tissue and prosthetic outcomes, although higher marginal bone loss could be observed around Brånemark implants after 5 years.

Predicting time-dependent remodeling of bone around immediately loaded dental implants with different designs

The purpose of this study was to predict time-dependent biomechanics of bone around cylindrical screw dental implants with different macrogeometric designs under simulated immediate loading condition. The remodeling of bone around a parallel-sided and a tapered dental implant of same length was studied under 100N oblique load by implementing the Stanford theory into three-dimensional finite element models. The results of the analyses were examined in five time intervals consisting loading immediately after implant placement, and after 1, 2, 3 and 4 weeks following implantation. Maximum principal stress, minimum principal stress, and strain energy density in peri-implant bone and displacement in x-(implant lateral direction with a projection of the oblique force) and y-(implant longitudinal direction) axes of the implant were evaluated. The highest value of the maximum and minimum principal stresses around both implants increased in cortical bone and decreased in trabecular bone. The maximum and minimum principal stresses in cortical bone were higher around the tapered cylindrical implant, but stresses in the trabecular bone were higher around the parallel-sided cylindrical implant. Strain energy density around both implants increased in cortical bone, slightly decreased in trabecular bone, and higher values were obtained for the parallel-sided cylindrical implant. Displacement values slightly decreased in time in x-axis, and an initial decrease followed by a slight increase was observed in the y-axis. Bone responded differently in remodeling for the two implant designs under immediate loading, where the cortical bone carried the highest load. Application of oblique loading resulted in increase of stiffness in the peri-implant bone.

Comparative assessments, meta-analysis, and recommended guidelines for reporting studies on histomorphometric bone-implant contact in humans.

PURPOSE To evaluate factors that have an influence on histomorphometric bone-to-implant contact (BIC) of dental implants in humans. MATERIALS AND METHODS Using inclusion/exclusion criteria, eligible studies were searched in five databases and handsearched in 11 journals. A total of 351 articles were assigned to full text analysis. The extracted data were assigned to comparative statistical assessments and meta-analysis. RESULTS A total of 55 articles were included in the analysis. The mean BIC found in comparative assessments and meta-analysis of implants in the mandible (70.97 and 69.744 ± 3.304, respectively) was higher than those in the maxilla (53.24 and 56.692 ± 3.598; P = .000 and P = .008, respectively). The mean BIC in the anterior mandible (79.42) and maxilla (74.19) were higher than the posterior mandible (69.14) and maxilla (36.68) (P < .05). Differences were detected in BIC of commercially available implants and experimental micro-implants (P < .05). Comparative assessments and meta-analysis showed that conventionally loaded implants (75.70 and 75.786 ± 4.889, respectively) had higher BIC than unloaded (54.07 and 53.24 ± 4.971, respectively) and immediately loaded implants (58.53 and 68.831 ± 4.972; P = .000 and P = .004, respectively). CONCLUSIONS Based upon a meta-analysis of the literature the following conclusions can be made: The BIC in the mandible is higher than the maxilla. The BIC is higher in the anterior than the posterior regions. The implant design coupled with the anatomical region affects the amount of BIC. Placement of experimental micro-implants with different surfaces in the posterior region always result in low and almost comparable BIC. The loading state and healing period seems to have an influence on BIC. Specific reporting guidelines are required to improve reporting of studies on human BIC.