Meat eating and nutritional quality of lambs sired by high and low muscle density rams.

Intramuscular fat (IMF) content affects eating and nutritional quality of lamb meat. Muscle density measured by computer tomography is an in vivo proxy measure of IMF content that affects eating and nutritional quality of lamb meat. Lambs sired by high muscle density (HMD) or low muscle density (LMD) rams, selected for slaughter on commercial criteria were measured for meat quality and nutritional traits. A restricted maximum likelihood model was used to compare lamb traits. Additionally, regression analysis of sire estimated breeding value (EBV) for muscle density was performed for each meat quality trait. Muscle density EBV had a negative regression with IMF content (P < 0.001). For each unit increase in muscle density EBV, there was a significant decrease in loin (-1.69 mg/100 g fresh weight) and topside IMF (-0.03 mg/100 g fresh weight). Muscle density EBV had a negative regression with grouped saturated and monounsaturated fatty acids concentration (and monounsaturated proportion P < 0.001). Muscle density EBV had a negative regression with loin sensory traits tenderness, juiciness and overall liking and many novel tenderness sensory traits measured (P < 0.05). Selecting for LMD EBV increased IMF content and favourable meat eating quality traits. In contrast, sire muscle density EBV had a positive regression with loin polyunsaturated:saturated fat ratio and grouped polyunsaturated proportion traits (including total polyunsaturated proportion, total omega-6 (n-6) and total omega-3 (n-3) fatty acids (P < 0.001). This is explained by the fact that as sire muscle density EBV increases, polyunsaturated fatty acid proportion increases and the proportion of saturated and monounsaturated fatty acid content decreases. Muscle density EBV had a positive regression with shear force and the novel toughness sensory traits (P < 0.05). Selection for HMD EBV's increased shear force and toughness traits, which is unfavourable for the consumer. Low muscle density sired meat had higher meat colour traits chroma/saturation (+0.64, SD 2.30, P = 0.012), redness (+0.52, SD 1.91, P = 0.012) and yellowness (+0.31, SD 1.49, P = 0.08) compared to HMD sired meat. Selection for LMD could be used within a breeding programme to increase IMF content and enhance both meat colour and improve eating quality parameters.

Prediction of intramuscular fat in lamb by visible and near-infrared spectroscopy in an abattoir environment.

The study used visible and near-infrared spectroscopy (Vis-NIR) in a large commercial processing plant, to test a system for meat quality (intramuscular fat; IMF) data collection within a supply chain for UK lamb meat. Crossbred Texel x Scotch Mule lambs (n = 220), finished on grass on 4 farms and slaughtered across 2 months, were processed through the abattoir and cutting plant and recorded using electronic identification. Vis-NIR scanning of the cut surface of the M. longissimus lumborum produced spectral data that predicted laboratory-measured IMF% with moderate accuracy (R2 0.38-0.48). Validation of the Vis-NIR prediction equations on an independent sample of 30 lambs slaughtered later in the season, provided similar accuracy of IMF prediction (R2 0.54). Values of IMF from four different laboratory tests were highly correlated with each other (r 0.82-0.95) and with Vis-NIR predicted IMF (r 0.66-0.75). Results suggest scope to collect lamb loin IMF data from a commercial UK abattoir, to sort cuts for different customers or to feed back to breeding programmes to improve meat quality.

Prediction of intramuscular fat content and shear force in Texel lamb loins using combinations of different X-ray computed tomography (CT) scanning techniques.

Computed tomography (CT) parameters, including spiral computed tomography scanning (SCTS) parameters, intramuscular fat (IMF) and mechanically measured shear force were derived from two previously published studies. Purebred Texel (n = 377) of both sexes, females (n = 206) and intact males (n = 171) were used to investigate the prediction of IMF and shear force in the loin. Two and three dimensional CT density information was available. Accuracies in the prediction of shear force and IMF ranged from R2 0.02 to R2 0.13 and R2 0.51 to R2 0.71 respectively, using combinations of SCTS and CT scan information. The prediction of mechanical shear force could not be achieved at an acceptable level of accuracy employing SCTS information. However, the prediction of IMF in the loin employing information from SCTS and additional information from standard CT scans was successful, providing evidence that the prediction of IMF and related meat eating quality (MEQ) traits for Texel lambs in vivo can be achieved.

Prediction of intramuscular fat content using CT scanning of packaged lamb cuts and relationships with meat eating quality.

Novel, multi-object X-ray computed tomography (CT) methodologies can individually analyse vacuum-packed meat samples scanned in batches of three or more, saving money and time compared to scanning live animals. If intramuscular fat (IMF), as a proxy for meat quality, can be predicted with similar accuracies as in live lambs, this method could be used to grade on quality, or to inform breeding programmes. Lamb loin cuts from commercial carcasses (n=303), varying in fat and conformation grade, were vacuum-packed and CT scanned, then tested for meat quality traits and by a trained taste panel. Tissue density values measured by CT, alongside carcass and loin weights, predicted IMF with moderate accuracy (R2 0.36), but did not accurately predict shear force or sensory traits. Juiciness and flavour increased linearly with IMF, whilst texture and overall liking increased to an optimum between 4 and 5% IMF. Samples predicted by CT as having >3% IMF scored significantly higher for sensory traits, than those predicted as <3% IMF.

Prediction of intramuscular fat levels in Texel lamb loins using X-ray computed tomography scanning.

For the consumer, tenderness, juiciness and flavour are often described as the most important factors for meat eating quality, all of which have a close association with intramuscular fat (IMF). X-ray computed tomography (CT) can measure fat, muscle and bone volumes and weights, in vivo in sheep and CT predictions of carcass composition have been used in UK sheep breeding programmes over the last few decades. This study aimed to determine the most accurate combination of CT variables to predict IMF percentage of M. longissimus lumborum in Texel lambs. As expected, predicted carcass fat alone accounted for a moderate amount of the variation (R(2)=0.51) in IMF. Prediction accuracies were significantly improved (Adj R(2)>0.65) using information on fat and muscle densities measured from three CT reference scans, showing that CT can provide an accurate prediction of IMF in the loin of purebred Texel sheep.

Wear of enamel opposing low-fusing and conventional ceramic restorative materials.

PURPOSE: This study evaluated the wear area of human enamel opposing 2 conventional and 2 low-fusing dental porcelains, as well as abrasive wear, attrition, surface hardness, and fracture toughness for the 4 porcelain substrates. MATERIALS AND METHODS: Two low-fusing and 2 conventional metal-ceramic porcelains were used to form 15-mm-diameter disks (n = 10), which were fired according to manufacturer's recommendations. Enamel cusps (n = 40) were formed from extracted third molars. All ceramic and enamel specimens were finished to a 1000-grit silicon carbide surface. The Oregon Health Sciences University (Portland, OR) oral wear simulator was used to deliver a 20-N load from the cusps to the ceramic substrates through a food-like slurry. The sliding action of the cusps over an 8-mm linear path produced abrasive wear. A static 70-N load was applied at the end of the path to create attrition. This sequence was repeated at 1.0 Hz for 50,000 cycles. Ceramic wear was measured with a profilometer (+/-2 micrometers), and enamel wear was evaluated using optical scanning methods. After wear testing, the hardness and fracture toughness of the ceramic surfaces were determined, and scanning electron photomicrographs were made using representative ceramic and enamel specimens from each group. Enamel wear areas, abrasion and attrition depths, hardness, and fracture toughness values were subjected to analysis of variance and Tukey-Kramer post hoc tests to determine significant differences. RESULTS: Enamel wear was not significantly different for low-fusing and conventional porcelains (p =.29). The wear of conventional and low-fusing ceramic substrates was also not significantly different (p =.79). However, depth of porcelain wear caused by attrition was in general significantly greater than abrasive wear (p =.0004). Although no significant differences were found in the measured porcelain hardness values (p =.08), 1 conventional porcelain exhibited fracture toughness significantly greater than 1 low-fusing porcelain (p <.01). CONCLUSIONS: No differences in wear patterns were noted among low-fusing compared with conventional metal-ceramic porcelains, but static loading resulted in significantly greater attrition compared with the observed sliding abrasive wear. J Prosthodont 2001;10:8-15.

Adhesion testing of a denture base resin with 5 casting alloys.

PURPOSE: This study compared denture base resin shear bond strengths to silicoated Au-Pd, Au-Pd-Ag, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys used to fabricate frameworks for hybrid implant prostheses. Microleakage between alloy and resin was also compared among groups after specimen fracture. MATERIALS AND METHODS: Twelve cylindrical specimens were cast for each alloy. Each specimen was made from a ring-shaped pattern (diameter [d] = 12 mm and height = 4 mm) and machined to achieve uniform hollow centers (d = 6.5 mm). Castings were abraded with 250-micron aluminum oxide and ultrasonically cleaned in distilled water before silicoating. Denture base resin was processed to the internal surfaces of the silicoated specimens. All specimens were thermocycled (1,000 cycles) between 4 degrees C and 50 degrees C, and placed in basic fuchsin dye for a week. A punch (d = 3.8 mm) driven at a cross-head speed of 0.5 mm/min was used to push out the resin specimens. The force required to cause failure was converted to the nominal shear bond strength for each specimen, and mean shear bond strengths for the 5 groups of specimens (N = 12) were compared using one-way analysis of variance and the Tukey-Kramer HSD multiple range test (alpha = 0.05). Six of the 12 debonded resin samples for each alloy were selected at random and evaluated for dye penetration. Using an 80-square grid, the percentage of dye penetration was evaluated with an optical microscope (x25) to determine the percentage of grid area penetrated by the dye. One-way analysis of variance was used to compare the degree of microleakage among groups. RESULTS: The mean resin-alloy shear bond strengths for the Au-Pd (9.6 +/- 3.7 MPa) and Au-Ag-Pd-Cu (9.2 +/- 1.5 MPa) alloys were significantly greater than mean resin-alloy shear bond strength for the Au-Pd-Ag alloy (5.6 +/- 1.9 MPa). No other significant differences in resin-alloy shear bond strengths were noted among the alloy groups. No significant differences were noted for dye penetration into the resin specimens bonded to any of the 5 alloys. The mean grid area penetrated by the dye was 25% when results for the alloys were pooled. CONCLUSIONS: Alloy type influences the shear bond strength of a denture base resin to silicoated alloys, but no difference in bond strength was found between Au-Pd, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys. In addition, under the conditions of this study, all groups showed a similar degree of microleakage, which penetrated approximately 25% of the bonded specimen surface area.

Solubility and sorption of resin-based luting cements.

This study compared the seven-day water sorption, water solubility and lactic acid solubility of three composite cements and three resin-modified glass-ionomer cements. Disc-shaped specimens measuring 15 mm x 0.5 mm were prepared according to each manufacturer's specifications and desiccated to a constant mass. Specimens were then placed in distilled water at 37 degrees C for seven days. Acid solubility was performed in 0.01 M lactic acid. The weight changes of the specimens after immersion in distilled water or 0.01 M lactic acid were measured using an electronic analytical balance. A one-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch (REGW) multiple range test was performed on all data. Significant differences (p < 0.05) were found among several cements tested for each of the properties investigated. Due to their hydrophilic nature, all resin-modified glass-ionomer cements showed significantly higher water sorption compared to composite cements.

Comparison of strains produced in a bone simulant between conventional cast and resin-luted implant frameworks.

Complete-arch implant prostheses continue to exhibit horizontal and vertical misfit between frameworks and abutments. It has been suggested that these gaps may be eliminated and that restoration-induced stresses may be reduced by luting frameworks to screw-retained abutments intraorally. This study measured and compared the strains generated by clinically acceptable, conventional frameworks were made from a single master cast representing a bone simulant model of an edentulous mandible with five Nobel Biocare implants and 4-mm abutments. Two strain gauges were also embedded in the bone simulant model to measure strains at two locations. Resin-luted frameworks were made by securing abutments to the clinical model with five gold slot screws tightened to 10 Ncm. Strain-indicator readings were recorded at a standardized time following the initial fastening of each prosthesis (n = 3). Mean principal strains were determined and compared using a one-way repeated measures analysis of variance. A statistically significant difference was found in the principal strains between the conventional cast and the resin-luted frameworks. Overall, there was a decrease in the magnitude of strain for the resin-luted frameworks. Intraoral luting of frameworks may decrease the strains produced in the bone around implants.

Comparison of strains transferred to a bone simulant between as-cast and postsoldered implant frameworks for a five-implant-supported fixed prosthesis.

PURPOSE: To measure and compare the strains transferred by screw-fastening one-piece full-arch prostheses as cast and after sectioning and soldering. MATERIALS AND METHODS: Photoelastic resin was applied directly to five 3.75 x 13-mm Brånemark implants, situated 7 mm apart, in a silicone mold of an edentulous mandible. Four strain gauge rosettes were also incorporated in the resin to allow strain measurements at four locations. Three frameworks were made from a single master cast produced from an impression of the five-implant model with 4-mm abutments. These frameworks were sequentially secured to the master model with five gold slot screws tightened to 10 N cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each prosthesis. The test was repeated three times. Each of the three castings were subsequently sectioned and soldered in two locations, mesial to the two terminal fixtures. After soldering, the three superstructures were returned to the master model for measurement of postsolder strains three times each. A one-way repeated-measures ANOVA was performed to determine differences between mean principal strains between the as-cast and postsoldered groups. RESULTS: A statistically significant difference was found in the principal strains between the as-cast and soldered frameworks. Overall, there was a decrease in the magnitude of strain for the soldered frameworks. CONCLUSIONS: Sectioning and soldering improved the as-cast accuracy as far as the amount of strain transferred to the bone simulant.

Comparison of strains transferred to a bone simulant among implant overdenture bars with various levels of misfit.

PURPOSE: To measure and compare strains transferred to a bone simulant by screw-fastening implant overdenture bars with various levels of fit or misfit. MATERIALS AND METHODS: Photoelastic resin was cast directly to two 3.75 X 13-mm Branemark fixtures (Nobelpharma USA Inc, Chicago, IL) situated 20 mm apart in a silicone mold of an edentulous mandible. Two strain-gauge rosettes were also incorporated in the resin to allow precise determination of principal stresses at two locations. Four groups of three overdenture bars with 0-, 180-, 360-, and 500-micrometer vertical gaps were fabricated. These bars were sequentially secured to the abutments with gold slot screws tightened to 10 N-cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each bar. The test was repeated three times for each overdenture bar. RESULTS: Mean principal stresses and strains at the location of the rosettes were determined. The magnitude of these stresses and strains increased significantly with each increase in gap size. Strains were several times larger mesial to the fixture than they were distal. CONCLUSIONS: Strains are transferred to the bone when misfitting prostheses were secured. Some of the strains mesial to the fixture appeared to be unfavorable for regions of lower bone density when the groups with designed gaps were secured. These data will be compared with those in ongoing animal studies regarding the cellular response to prosthesis misfit.

A three-dimensional finite element stress analysis of angled abutments for an implant placed in the anterior maxilla.

PURPOSE: A three-dimensional mathematical model of the maxilla was developed that was used to analyze the stresses and strains produced by an abutment system capable of three abutment angulations. MATERIALS AND METHODS: Computed tomography was used to derive the geometry and density values used for the maxillary model. A 3.8 x 10-mm cylindrical implant was embedded in the right central incisor position at a 35 degrees angle to the horizontal plane and parallel to the angulation of the bone site. All geometric and elastic properties for the fixture and the surrounding bone were included in the model. A simulated occlusal load of 178 N was applied along the long axis of 0 degrees, 15 degrees, and 20 degrees abutments. The mathematical models were solved by the Cray Y/MP Ohio Supercomputer (Cray, Eagan, MN) using the ABAQUS software program (Hibbitt, Karlsson, and Sorenson, Providence, RI). RESULTS: Numerical and graphic results were generated for the maximum (tensile) and minimum (compressive) stresses and strains. Principal stresses occurred predominantly in the cortical bone layers, whereas strains occurred mostly in the cancellous bone. CONCLUSIONS: In general, there was an increase in the magnitude of stress and strain as the abutment angulation increased. Reported stresses and strains for all three angles were within or slightly above the physiological zone derived from animal studies. A need to investigate the response of human bone to stress and strain was indicated.

Use of an axisymmetric finite element method to compare maxillary bone variables for a loaded implant.

PURPOSE: This study determined the effect of various bone models on the stresses and strains generated under occlusal loading of a dental implant. MATERIALS AND METHODS: A two-dimensional finite-element model was created for stress analysis. The geometric and elastic properties of a 3.8 x 10-mm Steri-Oss implant embedded in a segment of premaxilla were modeled. Computed tomography scanning of a dried maxilla half was used to determine representative geometry and density of this region. Material properties for bone were varied to simulate the following: all-cancellous bone, cancellous bone with a thin (1.5-mm) crestal isotropic cortical layer, cancellous bone with a thick (3-mm) crestal isotropic cortical layer, and cancellous bone with a thick (3-mm) layer of transversely isotropic (orthotropic) cortical bone. RESULTS: Low stresses and high strains surrounded the fixture apex for the all-cancellous bone model. When a layer of cortical bone was added, higher crestal stresses and lower apical strains were observed. The thicker layer of isotropic cortical bone produced stresses at least 50% less than the thinner layer. The assumption of transverse isotropy (orthotropy) increased stresses and strains by approximately 25% compared with isotropic bone. CONCLUSIONS: Crestal cortical layer thickness and bone isotropy have a substantial impact on resultant stresses and strains. Clinical assessment of these parameters is recommended.

A photoelastic and strain gauge analysis of angled abutments for an implant system.

This study was conducted to determine the effect of abutment angulation on the stress field near a specific dental implant. Photoelastic resin was cast directly to five 3.8 x 10-mm Steri-Oss implants in 50 x 70 x 13-mm molds. One additional model was fabricated with a strain gauge rosette embedded in the resin to allow precise determination of normal stresses. Zero-degree, 15-degree, and 20-degree abutments were assembled on each of the six implants, subjected to 178 N load, and viewed with a circular polariscope. Observed fringe patterns were photographed for all six models, and strain indicator readings were recorded for the strain gauge model. Numerical data from the strain gauges produced results that agreed with the visual interpretation of the isochromatic fringes. Strain gauge data were also used to calculate the principal stresses and strains. Although a statistically significant increase in stress and strain was found for each increase in abutment angulation, all three abutments produced principal strains that appear to be within the physiologic zone for bone. All values for stress and strain were determined at the location of the rosette, approximately 4 mm from the implant. Higher stresses and strains exist in regions closer to the fixture.

The effect of abutment angulation on stress transfer for an implant.

PURPOSE: This investigation compared the stress production characteristics of five abutment angulations for a specific implant system. MATERIALS AND METHODS: Photoelastic resin was cast directly to a 3.75 x 10-mm Branemark fixture (Nobelpharma USA, Inc, Chicago, IL) in a 50 x 70 x 13-mm mold. A strain gauge rosette was also incorporated in the resin to allow precise determination of normal stresses at a specific point. Each 4-mm abutment (15 degrees, 25 degrees, and 35 degrees from Implant Innovations (West Palm Beach, FL) and 0 degree and 30 degrees from Nobelpharma) was assembled on the fixture, subjected to 178N load, and viewed with a circular polariscope. Observed fringes were photographed and strain indicator readings were recorded. RESULTS: Mean observed fringe order and mean principle stress and strain at the location of the rosette were determined. CONCLUSION: At the location of the rosette, all five of the abutments produced principal strains (compressive and tensile) within the physiological zone for bone. The rosette was located approximately 4 mm away from the fixture. Higher stresses and strains can be expected in regions closer to the implant.

Three-dimensional finite element stress analysis in and around the Screw-Vent implant.

The three-dimensional finite element stress analysis method was used to determine the pattern and concentration of stresses within the Screw-Vent endosseous implant and its supporting tissues. For this commercially pure titanium implant, maximum stresses were located within the implant collar immediately below the bony crest. These stresses were at least 18 times less than the endurance limit of commercially pure titanium (259.90 MPa). Maximum stresses (19.57 MPa) in the bone were lingual to the superior portion of the collar. Previous longitudinal radiographic studies of a similar implant have revealed bone loss mesial and distal to the implant. For the Screw-Vent, mesial and distal stresses (maximum 0.38 MPa) were much lower than those buccal and lingual to the implant. The clinical significance of the stress transfer to the bone buccal and lingual to the implant has yet to be determined.