Significant Difference In Fracture Load Research Articles

Effect of pulp-chamber lateral wall thickness and number on fracture resistance in endocrown-restored molars: An in vitro study

Background/purposeIt remains unclear how the thickness and number of pulp-chamber lateral walls (PCLWs) affects fracture resistance in endocrown-restored teeth. Materials and methods64 mandibular molars were collected and randomly divided into eight groups (n = 8). In group C (control group), the teeth were untreated. In groups T1, T2, and T3, the teeth were subjected to endodontic treatment and restored with nanoceramic endocrowns exhibiting different PCLW thicknesses (T1: 0.5 mm, T2: 1.0 mm, and T3: 1.5 mm). In groups N1, N2, N3, and N4, the numbers of missing PCLWs in prepared teeth were one (N1), two (N2), three (N3), and four (N4). All restored teeth were subjected to axial loading until fracture using a universal testing machine. The mean fracture loads were recorded and compared by one-way analysis of variance; the fractured samples were observed under a stereo microscope. ResultsThe results showed no statistically significant differences in fracture load among groups T1, T2, and T3 (P > 0.05). Although the fracture loads gradually decreased as the number of missing PCLWs increased, there were no statistically significant differences in fracture load among groups C, N1, N2, and N3, and N4 (P > 0.05). ConclusionBoth thickness and remaining number of PCLW does not affect fracture resistance in endodontically treated molars restored with nanoceramic endocrowns.

Fracture resistance and fracture modes in endodontically treated maxillary premolars restored using different CAD-CAM onlays.

To examine the fracture resistance and fracture modes of endodontically treated teeth (ETT) restored using onlays of different materials fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM). Sixty maxillary first premolars were randomly assigned to six groups (n=10). The first group comprised intact teeth (INT). The remaining premolars were prepared for mesio-occluso-distal cavity and root canal treatments. Group 2 was treated using polymer-reinforced zinc oxide-eugenol intermediate restorative material (IRM). Groups 3-6 were core build-up, prepared for onlay, and restored using resin nanoceramic (Cerasmart [CER]), polymer-infiltrated ceramic networks (Vita Enamic [VE]), lithium disilicate-based ceramic (IPS e.max CAD [EM]), or translucent zirconia (Katana Zirconia UTML [KZ]). All specimens were immersed in 37 °C distilled water for 24 h. Each specimen was loaded at 45° to the long axis until failure (crosshead speed, 0.5 mm/min). Fracture loads were analyzed using one-way analysis of variance and Tukey's post-hoc test (α=0.05). There were no significant differences in fracture load among the INT, CER, VE, and EM groups. The fracture load in the KZ group was significantly higher than those in the other groups (P < 0.05). Fracture load was the lowest in the IRM group (P < 0.05). The unrestorable failure rate was 70% in the KZ group and 10-30% in the other experimental groups. ETT restored using Cerasmart, Vita Enamic, or IPS e.max CAD onlays had fracture resistance and patterns comparable to those of intact teeth. Katana Zirconia UTML-restored ETT had the highest fracture load but also a higher unrestorable failure rate.

Impact of Polymerization Technique and ZrO2 Nanoparticle Addition on the Fracture Load of Interim Implant-Supported Fixed Cantilevered Prostheses in Comparison to CAD/CAM Material.

ZrO2 nanoparticles (ZNPs) have excellent physical properties. This study investigated the fracture load of implant-supported, fixed cantilevered prosthesis materials, reinforced with ZNPs and various polymerization techniques, compared with conventional and CAD/CAM materials. Sixty specimens were made from two CAD/CAM; milled (MIL) (Ceramill TEMP); and 3D-printed (NextDent Denture 3D+). Conventional heat-polymerized acrylic resin was used to fabricate the other specimens, which were grouped according to their polymerization technique: conventionally (HP) and autoclave-polymerized (AP); conventionally cured and reinforced with 5 wt% ZNPs (HPZNP); and autoclave reinforced with 5 wt% ZNPs (APZNP). The specimens were thermocycled (5000 cycles/30 s dwell time). Each specimen was subjected to static vertical loading (1 mm/min) using a universal Instron testing machine until fracture. Scanning electron microscopy was used for fracture surface analyses. The ANOVA showed significant fracture load differences between all the tested groups (p = 0.001). The Tukey post hoc tests indicated a significant difference in fracture load between all tested groups (p ˂ 0.001) except HP vs. HPZNP and AP vs. MIL. APZNP had the lowest mean fracture load value (380.7 ± 52.8 N), while MIL had the highest (926.6 ± 82.8 N). The CAD/CAM materials exhibited the highest fracture load values, indicating that they could be used in long-term interim prostheses. Autoclave polymerization improved fracture load performance, whereas ZrO2 nanoparticles decreased the fracture load performance of cantilevered prostheses.

Biomechanics of a cemented short stem: a comparative in vitro study regarding primary stability and maximum fracture load

PurposeIn total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation.MethodsIn this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics.ResultsReversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84).ConclusionPrimary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified.

Fracture Load of Veneered Telescopic Secondary Crowns Made of High-Performance Polymer on Zirconia Primary Crowns: Impact of Veneering Technique.

To analyze the impact of different veneering techniques on the fracture load of telescopic secondary crowns made of a high-performance polymer (Ultaire aryl ketone polymer [UAKP]). Zirconia primary crown models (taper of 0 degrees) were prepared (N = 48), polished, scanned, and divided into four veneering groups (n = 12 each): premanufactured, digital, full anatomical, and vestibular. For all groups except vestibular, a standardized telescopic secondary crown (thickness: 0.6 mm, circular margin: 1 mm) was constructed, adapted to the corresponding primary crown, milled from UAKP, and veneered. The veneered master crown was developed based on the premanufactured group. After surface polishing, all specimens were artificially aged in a chewing simulator (1.2 million cycles, 50 N, 1.1 Hz, between 5°C and 55°C). Fracture load was tested in a universal testing machine with a piston (Ø = 6 mm, 1 mm/minute). Fracture patterns were analyzed. For statistical analysis, Kolmogorov-Smirnov test and descriptive statistics followed by one-way ANOVA with post hoc Scheffé test were conducted (P < .05). Significant differences in fracture load were found between different veneering techniques (P < .001), with the highest values for the vestibular and digital groups, followed by the premanufactured group. Full anatomical veneering showed the significantly lowest fracture load (1,885 ± 397 N). For all specimens, cohesive brittle fractures with similar fracture patterns occurred, irrespective of the veneering technique. The veneering technique of telescopic secondary crowns made of high-performance polymer affects overall stability. All veneering techniques provided sufficient fracture load values for telescopic secondary crowns made of UAKP. Digital veneers seem the most recommendable.

Comparison study of bone strength of the proximal femur with and without hip osteoarthritis by computed tomography-based finite element analysis

Proximal femoral fractures are common in elderly osteoporosis patients; however, its prevalence is clinically rare in hip fracture patients with hip osteoarthritis (OA). This study aimed to evaluate bone strength of the proximal femur with or without hip OA and proximal femoral fracture risk using computed tomography (CT)-based finite element analysis (FEA). A retrospective analysis was done on CT data of 20 patients who underwent total hip arthroplasty for unilateral hip OA. Furthermore, the fracture load between OA and contralateral sides was compared and the association between fracture load and risk factor was analyzed. The fracture load was significantly higher in the OA side than that in the contralateral side (3819.5 ± 1557.8 N vs. 3224.5 ± 943.7 N, respectively; P = 0.0405). There was no significant difference in fracture load between OA and the contralateral side in Kellgren–Lawrence (KL)-3 and KL-4 grade, but the KL-4 fracture load tends to be high (P = 0.2461 and P = 0.0527, respectively). Moreover, there was no significant association between fracture load and OA severity or age. The study findings may assist in predicting bone strength and proximal femur fracture risk. The results of this FEA study indicate the bone strength of the proximal femur was affected by the severity of the osteoarthritis.

Biomechanical effects of osteoplasty with or without Kirschner wire augmentation on long bone diaphyses undergoing bending stress: implications for percutaneous imaging-guided consolidation in cancer patients

BackgroundOsteoplasty has been discouraged in long bones. However, despite a substantial lack of pre-clinical biomechanical tests, multiple clinical studies have implemented a wide range of techniques to optimise long bone osteoplasty. The aim of the present study is to evaluate the biomechanical properties of osteoplasty alone and in combination with Kirschner wires (K-wires) in a cadaveric human diaphyseal model undergoing 3-point bending stress.MethodsThirty unpaired human cadaveric hemi-tibia specimens were randomly assigned to receive no consolidation (group 1, n = 10), osteoplasty alone (group 2, n = 10), or K-wires augmented osteoplasty (group 3, n = 10). Specimens were tested on a dedicated servo-hydraulic machine using a 3-point bending test. Fracture load was calculated for each specimen; two-sample Wilcoxon rank-sum tests were used to assess differences between groups.ResultsMedian volume of polymethyl methacrylate injected was 18 mL for group 2 (25th–50th percentile 15–21 mL) and 19 mL for group 3 (25th–50th percentile 17–21). There were no significant differences in fracture load between groups 1 and 2 (z = − 0.793; p = 0.430), between groups 1 and 3 (z = − 0.944; p = 0.347), and between groups 2 and 3 (z = − 0.454; p = 0.650). Fractures through the cement occurred in 4 of 30 cases (13.3%); there were no K-wires fractures.ConclusionsOsteoplasty with or without K-wires augmentation does not improve the resistance of diaphyseal bone to bending stresses.

An in vitro evaluation of fracture load of implant‐supported zirconia‐based prostheses fabricated with different veneer materials

The purpose of this in vitro study was to evaluate fracture loads of implant-supported zirconia-based prostheses fabricated with different veneer materials (resin-based material and lithium disilicate ceramics). Forty-four zirconia-based molar prostheses were fabricated on dental implants and divided into four groups (n=11): zirconia-based prostheses veneered with feldspathic porcelain (ZVF), zirconia-based prostheses bonded with the lithium disilicate glass-ceramic veneer (ZBD), zirconia-based prostheses veneered with indirect composite resin (ZVC), and zirconia-based prostheses bonded with composite materials fabricated from a CAD/CAM resin block (ZBC). The zirconia-based prostheses and abutments were adhesively bonded with a dual-polymerized resin-based luting material. Fracture load was determined using compression load to the prostheses with a universal testing machine. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey's HSD test (α=.05). The mean fracture load was significantly higher in the ZBC group (3.95 kN) than in the ZVC group (3.28 kN). No significant difference in fracture load was found among the ZVF (3.52 kN), ZBD (3.48 kN), and ZVC groups. The adhesively bonded veneering technique enhances fracture resistance of implant-supported zirconia-based prostheses fabricated with a resin-based material. All implant-supported zirconia-based restorations tested should resist physiologic masticatory forces in the oral environment.

Marginal adaptation, fracture load and macroscopic failure mode of adhesively luted PMMA-based CAD/CAM inlays

ObjectivesTo evaluate marginal adaptation, fracture load and failure types of CAD/CAM polymeric inlays. MethodsStandardized prepared human molars (48) were divided into four groups (n=12): (A) PCG (positive control group); adhesively luted glass–ceramic inlays, (B) TRX; CAD/CAM polymeric inlays luted using a self-adhesive resin cement, (C) TAC; CAD/CAM polymeric inlays luted using a conventional resin cement, and (D) NCG (negative control group); direct-filled resin-based composite restorations. All specimens were subjected to a chewing simulator. Before and after chewing fatigue, marginal adaptation was assessed at two interfaces: (1) between dental hard tissues and luting cement and (2) between luting cement and restoration. Thereafter, the specimens were loaded and the fracture loads, as well as the failure types, were determined. The data were analysed using three- and one-way ANOVA with post hoc Scheffé test, two sample Student's t-test (p<0.05). ResultsBefore and after chewing fatigue, marginal adaptation for interface 1 showed significantly better results for TRX and PCG than for TAC (p=0.001–0.02) and NCG (p=0.001–0.047). For interface 2, marginal adaptation for TAC was significantly inferior to TRX (p<0.001) and PCG (p<0.001). Chewing fatigue had a negative impact on the marginal adaptation of TAC and NCG. No significant differences in fracture load were found between all tested groups. SignificanceSelf-adhesive luted polymeric CAD/CAM inlays showed similar marginal adaptation and fracture load values compared to adhesively luted glass–ceramic inlays.

Fracture resistance of endodontically restored, weakened incisors

To test the fracture strength of weakened bovine incisors endodontically treated with mineral trioxide aggregate (MTA), calcium phosphate bone cement (CPBC) or fibre reinforced composite (FRC) posts, and to evaluate the fracture mode. Weakened bovine incisors (n = 75), standardized according to the dentinal wall thickness at the cervical area, were randomly assigned to one control group and three experimental groups. Unfilled teeth were assigned to group 1 (n = 20) and served as control group. Group 2 (n = 17) consisted of teeth filled with MTA. In group 3 (n = 18), the incisors were filled with CPBC and in group 4 (n = 20) with FRC posts. All specimens were subjected to load at a cross-head speed of 60 mm min(-1) until fracture occurred. The initial (IL) and final fracture (FL) loads (N) were recorded, and the failure mode among the different groups was evaluated. anova showed a statistically significant difference in fracture load among the groups. Tukey's test revealed a significant difference for the IL between the control group and the experimental groups with exception of the MTA group. The FL was not significantly different among the experimental groups. A high percentage of favourable fractures was seen in the FRC and CPBC groups. FRC posts and CPBC could be promising materials to strengthen non-vital structurally compromised teeth.

Effect of Framework Design on Fracture Resistance in Zirconia 4-unit All-ceramic Fixed Partial Dentures

The purpose of this study was to conduct static load-bearing tests on 4-unit Y-TZP all-ceramic fixed partial denture (FPD) frameworks with different cross-sectional areas and forms to evaluate the influence of connector design on fracture load. Each of the central, mesial and distal connectors was prepared with one of 2 different cross-sectional areas and one of 3 different forms (one circular and two oval forms) to give a total of 18 designs. Five frameworks were then prepared for each design, making a total of 90. Each framework was cemented to the test model with glass ionomer cement. Fracture load was measured with a universal testing machine at a cross-head speed of 1.0 mm/min. A three-way ANOVA revealed significant differences in fracture load depending on cross-sectional area, central connector cross-sectional form, or mesial/distal connector cross-sectional form (p<0.01). No interaction was observed, however, between any two connector design elements. The results of a Tukey analysis revealed a significant difference between the two connector cross-sectional areas investigated, with an increase in connector cross-sectional area resulting in an increase in fracture load. Fracture load decreased as the height of the mesial or distal connector decreased. Fracture load was significantly higher in frameworks in which the height of the central connector was greater than that of the distal or mesial connector. In conclusion, these results suggest that sufficient height needs to be maintained in the mesial/distal connector to secure a high fracture load in zirconia 4-unit all-ceramic FPDs. Moreover, even when this is not possible, a high fracture load may still be obtained by making the height of the central connector as great as possible. Furthermore, extending the connector cross-sectional area is effective in increasing fracture load.

The relationship between milling a new silica-doped zirconia and its resistance to low-temperature degradation (LTD): a pilot study

The aim of this study was to determine the machinability of new silica-doped Y-TZP by CAD/CAM and the resistance to low temperature degradation of the milled sample by comparing with a commercial HIP type Y-TZP material. The copings could be milled from silica-doped Y-TZP blocks without chipping, and there was no significant difference between the two types of Y-TZP materials in either the marginal or the inner gap between the abutment and the coping. After aging, the monoclinic content in the commercial Y-TZP copings increased from 25% before testing to 65%, while that of silica-doped Y-TZP copings slightly increased from 23% to 30%. The silica-doped Y-TZP copings did not have any significant difference in fracture load in a comparison between the control group and the aging group, while the commercial Y-TZP copings had a significantly lower fracture load for the aging group than for the control group.

The effect of E-glass fibers and acrylic resin thickness on fracture load in a simulated implant-supported overdenture prosthesis

Implant overdenture prostheses are prone to acrylic resin fracture because of space limitations around the implant overdenture components. The purpose of this study was to evaluate the influence of E-glass fibers and acrylic resin thickness in resisting acrylic resin fracture around a simulated overdenture abutment. A model was developed to simulate the clinical situation of an implant overdenture abutment with varying acrylic resin thickness (1.5 or 3.0 mm) with or without E-glass fiber reinforcement. Forty-eight specimens with an underlying simulated abutment were divided into 4 groups (n=12): 1.5 mm acrylic resin without E-glass fibers identified as thin with no E-glass fiber mesh (TN-N); 1.5 mm acrylic resin with E-glass fibers identified as thin with E-glass fiber mesh (TN-F); 3.0 mm acrylic resin without E-glass fibers identified as thick without E-glass fiber mesh (TK-N); and 3.0 mm acrylic resin with E-glass fibers identified as thick with E-glass fiber mesh (TK-F). All specimens were submitted to a 3-point bending test and fracture loads (N) were analyzed with a 2-way ANOVA and Tukey's post hoc test (α=.05). The results revealed significant differences in fracture load among the 4 groups, with significant effects from both thickness (P<.001) and inclusion of the mesh (P<.001). Results demonstrated no interaction between mesh and thickness (P=.690). The TN-N: 39 ±5 N; TN-F: 50 ±6.9 N; TK-N: 162 ±13 N; and TK-F: 193 ±21 N groups were all statistically different (P<.001). The fracture load of a processed, acrylic resin implant-supported overdenture can be significantly increased by the addition of E-glass fibers even when using thin acrylic resin sections. On a relative basis, the increase in fracture load was similar when adding E-glass fibers or increasing acrylic resin thickness.

Elastomer femoroplasty prevents hip fracture displacement: In vitro biomechanical study comparing two minimal invasive femoroplasty techniques

The purpose of this study was to test femur strength and the ability to prevent fracture displacement of two minimal invasive Elastomer femoroplasty techniques. MethodsA total of sixteen fixed human cadaveric femur pairs were used. From each pair one femur was randomly assigned for Elastomer femoroplasty. In these femora we drilled a 3.5mm entrance in the lateral cortex. Cavities for the Elastomer were created by: group A, balloon and group B an excentric drill. All femora were fractured by simulating a fall on the greater trochanter. Neck-shaft-angles on plain anterior posterior radiographs were measured to determine fracture displacement. FindingsThere was no significant difference in fracture load between controls and treated femora for group A, 2904N (SD 1091) versus 2803N (SD 627) and group B, 2773N (SD 747) versus 2597N (SD 834). In group A the mean displacement was 35° (SD 14) for the control femora and 3° (SD 2) for the treated femora (P<0.001). In group B the mean displacement was 38° (SD 10) for the controls and 8° (SD 13) for the treated femora (P<0.001). InterpretationThe results of this study show that minimal invasive Elastomer femoroplasty prevents fracture displacement of the proximal femur. We found no significant compromise in load-to-fracture after minimal invasive balloon or excentric drill femoroplasty.

Effect of Connector Design on Fracture Resistance of Zirconia All-ceramic Fixed Partial Dentures

The purpose of the present study was to determine the relationship between cross-sectional design and fracture load using a static load bearing test in yttria-stabilized tetragonal zirconia polycrystal ceramic frameworks on a molar fixed partial denture. The test framework was designed as a 3-unit bridge with two abutment teeth at the second premolar and second molar of the mandible. The cross-sectional area of the connector was 9.0, 7.0, or 5.0mm(2). In terms of shape, the cross-section was either circular or oval, with a height/width ratio of 1:1, 3:4, or 2:3. For each of the 9 combinations of cross-sectional area and shape, 5 frameworks were prepared (45 in total). Frameworks were cemented to a metallic test model with adhesive resin cement. After fracture load was measured, the percentage of fracture sites was determined and the fracture surfaces observed. In terms of cross-sectional area, there was a statistically significant difference in fracture load between 9.0, 7.0, and 5.0mm(2). No significant difference in fracture load was observed between any two shapes of connector (p>0.05). The fracture load of all frameworks with a cross-sectional area of 9.0 or 7.0mm(2) was over 880 N, which was recognized as parafunctional occlusal force. Fracture occurred at the distal connector in 82.2% of all frameworks on average. Fracture load decreased as cross-sectional area of the connector became smaller. The cross-sectional shape used in the present study was less influential on fracture load. It appears to be clinical possible to apply a connector with a cross-sectional area of 7.0mm(2). Fracture often occurred at the distal connector between the pontic and the abutment, corresponding to the second molar.

An evaluation of the fracture resistance of class 2 amalgam restorations with different cavity designs on maxillary premolars

Aims and Objectives: The aim of this work was to compare the fracture resistance values of Mesio-occlusal preparation, slot preparation with conventional grooves, box-only, and MOD preparation. Materials and Methods: A total of 60, noncarious extracted maxillary premolars were selected and divided into four groups, consisting of 15 teeth each -- group A: Mesio-occlusal preparation, group B: slot preparation (conventional grooves), group C: box-only preparation (long grooves), group D: MOD cavity preparation. All the specimens were subjected to compressive axial load in triaxial testing machine at a cross head speed of 1.2 mm/min at an inclination of 13.5°. Results: Group A (Mesio-occlusal) preparation had the least fracture resistance value and group D (MOD) cavity preparation had the highest fracture resistance. There was a significant difference in fracture load found between groups B and C. Conclusion: Amalgam restorations with Mesio-occlusal preparations had the least fracture resistance. Amalgam restorations with slot preparations had better fracture resistance than box-only preparation. Amalgam restorations with MOD preparations had the highest fracture resistance.

Effect of Intermediate Fiber Layer on the Fracture Load and Failure Mode of Maxillary Incisors Restored with Laminate Veneers

This study evaluated the fracture load and failure mode of various veneer materials cemented with or without the addition of a fiber-reinforced composite (FRC) layer at the adhesive interface. Sixty intact incisors were randomly divided into three groups. Group 1 was fabricated with the heat-press technique (IPS Empress 2); Group 2 with the copy milling technique (ZirkonZahn); and Group 3 with the direct or indirect composite technique (Z250)--and specimens were cemented either with or without FRC at the adhesive interface. The specimens were thermocycled and tested with a universal testing machine. No significant differences in fracture load (p>0.05) were found among the various veneer materials. The addition of FRC at the adhesive layer did not lead to significant differences in the fracture load (p>0.05) but resulted in differences in the failure mode. Laminate veneers made of composite, zirconia, and Empress 2 showed comparable mean fracture loads. However, the use of FRC at the interface changed their failure modes.

Biomechanics of a new short-stemmed uncemented hip prosthesis: An in-vitro study in human bone

The migration pattern, cyclic motion, system stiffness and failure load of a new short-stemmed hip prosthesis were compared to a clinically successful shaft prosthesis during the initial loading phase. The influence of implant-sizing on mechanical stability was also investigated for the new stem, in particular with relation to the bone quality. Prostheses were implanted in paired human femora and loaded cyclically up to 3515 cycles. Relative displacements between prosthesis and bone were measured using a 3D-camera and reflective marker system. Migration of the new stem was predominantly into varus and was higher than for the shaft prosthesis. The test set-up was proposed to simulate a worst-case loading scenario since muscle forces, which tend to reduce bone deformation, were not simulated. It could therefore be expected that clinical migration of the implants would be less pronounced than that observed in this study. Cyclic motion for the new stem was similar to that for the clinically successful shaft prosthesis, suggesting that bone ingrowth could be expected for the new stem. No significant difference in fracture load was observed between the implants. The system stiffness with the new stem was lower than for the shaft prosthesis, indicating more physiological load transfer. Smaller implant sizing with 'cancellous' fixation seems favourable, as it led to similar migration and smaller cyclic motion values than with 'cortical' fixation. A trend for higher cyclic motion and migration was observed in femora with poor bone quality. Hence, sufficiently good bone stock is necessary, when implanting the new short-stemmed prosthesis.

Biomechanics of a New Short-Stemmed Uncemented Hip Prosthesis: An In-Vitro Study in human Bone

The migration pattern, cyclic motion, system stiffness and failure load of a new short-stemmed hip prosthesis were compared to a clinically successful shaft prosthesis during the initial loading phase. The influence of implant-sizing on mechanical stability was also investigated for the new stem, in particular with relation to the bone quality. Prostheses were implanted in paired human femora and loaded cyclically up to 3515 cycles. Relative displacements between prosthesis and bone were measured using a 3D-camera and reflective marker system. Migration of the new stem was predominantly into varus and was higher than for the shaft prosthesis. The test set-up was proposed to simulate a worst-case loading scenario since muscle forces, which tend to reduce bone deformation, were not simulated. It could therefore be expected that clinical migration of the implants would be less pronounced than that observed in this study. Cyclic motion for the new stem was similar to that for the clinically successful shaft prosthesis, suggesting that bone ingrowth could be expected for the new stem. No significant difference in fracture load was observed between the implants. The system stiffness with the new stem was lower than for the shaft prosthesis, indicating more physiological load transfer. Smaller implant sizing with 'cancellous' fixation seems favourable, as it led to similar migration and smaller cyclic motion values than with 'cortical' fixation. A trend for higher cyclic motion and migration was observed in femora with poor bone quality. Hence, sufficiently good bone stock is necessary, when implanting the new short-stemmed prosthesis.

No conclusive evidence favouring cast over direct post and core preparations

Data sources English, French or German articles were identified in Medline and EMbase, and in the reference lists of retrieved articles. Study selection The in-vitro studies were of single rooted teeth (no resin analogues) and load angles of 130–135°. In-vivo studies were of ⩾3 years’ duration. These included teeth that could be identified separately with complete crown restoration including fixed partial denture abutments and detectable information regarding success or failure. Data extraction and synthesis For in-vitro studies, primary outcome was load-to-failure. For in-vivo studies, failure was defined as a need for recementing, a new restoration of any kind, or tooth extraction. A qualitative synthesis of all included in-vitro and in-vivo studies was performed along with a meta-analysis of four in-vitro studies. Results Ten in-vitro and six in-vivo studies were included. The meta-analysis of four in-vitro studies revealed no significant difference in fracture load. There was also little difference in the mode of fracture across the 10 in-vitro studies. For three of the in-vivo studies it was possible to construct a life table that indicated the survival rate for cast posts was between 87 and 88% and for direct posts was 86% at 72 months. Conclusions There is no conclusive evidence favouring cast over direct post and core preparations or vice versa. The literature on the clinical success of post-retained cores is scare and randomised controlled trials are needed.