Soil Cementation

A theoretical approach was used to determine the distribution of a poly(methylmethacrylate) cement after its injection into a porous structure. The predictions of the model were then compared to experimental results obtained by injecting a polymethylmethacrylate cement into an open-porous ceramic filter. The goal was to define a model that could predict what factors affect the risk of cement extravasation and hence how the risk of cement extravasation can be minimized. The calculations were based on two important rheological laws: the law of Hagen-Poiseuille and the law of Darcy. The law of Hagen-Poiseuille describes the flow of a fluid in a cylindrical tube. The law of Darcy describes the flow of a fluid through a porous media. The model predicted that the extravasation risk was decreased when the cement viscosity, the bone pore size, the bone permeability and the bone porosity were increased, and when the diameter of the extravasation path and the viscosity of the marrow were decreased. Experimentally, the effect of the marrow viscosity and extravasation path could be evidenced. Therefore, the model was believed to be an adequate approximation of the experimental behavior. In conclusion, the experimental results demonstrated that the model was adequate and that the best practical way to decrease the risk of extravasation is to increase the cement viscosity. r

The identification of different dental implants and restorative components is difficult when dental records do not include an inventory of implant components. An implant record form is described. The form should be filled out and retained in the patient's chart for future use and implant maintenance visits.

This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives. r

W e have investigated the use of a conically-shaped cement plug made of Polyactive (PA), a biodegradable copolymer. The flexibility and hydrogel properties were thought to facilitate occlusion of the femoral canal even when it was oval or irregular in shape. The function of the plug was first compared with that of the Thackray polyethylene model in 16 artificial plastic femora.

Purpose: The aim of this study was to evaluate and compare the total color difference ( E) between natural teeth and fabricated crowns from three ceramic systems with different thicknesses. Materials and Methods: The color of ninety maxillary central incisors was measured from the middle third of the labial surface with a Vita Easyshade spectrophotometer. All-ceramic crown preparations with different thicknesses (0.8, 1.2, 1.5 mm) were done on selected teeth (n = 30). Prepared teeth were randomly divided into three equal groups to fabricate ceramic crowns from three ceramic systems, Duceram LFC (DLFC), In-Ceram SPINELL (ICS), and IPS Empress (IPSE). Colors of cemented crowns were measured and compared with their corresponding measurements before preparations. Data were statistically analyzed using two-way ANOVA at 5% significance level. Results: A significant difference of E was detected between natural teeth and different thicknesses of crowns constructed from the all-ceramic materials investigated. Comparing the three materials at 0.8 mm thickness revealed that the lowest E was recorded for DLFC, which was significantly different from the other ceramic systems while IPSE showed the highest E. At higher thicknesses there was no difference between natural tooth shade and crowns constructed from different ceramic materials. Conclusions: Reinforcement of ceramics by alumina for In-Ceram and leucite for Empress decreases color production. Level of acceptance between the different ceramic materials and thicknesses varied. DLFC showed the highest color matching at all thicknesses followed by ICS and IPSE in descending order. In general, increasing the thickness of fabricated crowns enhances color match.

The aim of this study was to compare the resistance of endodontically treated teeth with intraradicular retainer different amounts of remaining coronal structure. Fifty freshly extracted maxillary canines were endodontically treated and randomly assigned to five groups (n=10), as follows: group 1 (control) = teeth with custom cast post and core; group 2 = teeth without remaining coronal structure; group 3, 4 and 5 = teeth with 1 mm, 2 mm and 3 mm of remaining coronal structure, respectively. All specimens in groups 2 to 5 were restored with prefabricated post and resin core. The teeth were embedded in acrylic resin and the fracture strength was measured on a universal testing machine at 45 degrees to the long axis of the tooth until failure. Data were analyzed statistically by one-way analysis of variance and Tukey's test. There was no significant differences (p>0.05) between the control group and group 2, and between groups 3, 4 and 5 (p>0.05). Control group and group 2 had significantly higher resistance strength than groups 3, 4 and 5 (p<0.00001). The findings of this study showed that teeth without remaining coronal structure had significantly higher fracture strength than those with remaining coronal structure (1 mm, 2 mm and 3 mm). When the dental crown was not completely removed, the amount of remaining coronal dentin did not significantly affect the fracture strength of endodontically treated teeth with intraradicular retainer.

We report on a prospective series of 201 primary uncemented total hip arthroplasties with a Bicontact prosthesis at a mean follow-up of 12.9 years. The mean Harris hip score improved from 41 before surgery to 89 at final follow-up. Two femoral stems, one each for infection and fracture, and 12 cups were revised. The mean number of years to revision post-primary surgery was 8.7 years (six months to 16 years). The cumulative survival of the prosthesis was 95.42% for any cause at ten years and 93.57% at 12 years. Survivorship for aseptic loosening of the femoral stem was 100%. In our series, the Bicontact uncemented total hip arthroplasty stem without hydroxyapatite coating showed excellent survival and the cup survival was comparable to other leading series.

All-ceramic crowns are subject to fracture during function, especially in the posterior area. The use of yttrium-stabilized zirconium-oxide ceramic as a substructure for all-ceramic crowns to improve fracture resistance is unproven. The aim of this study was to compare fracture strength and fatigue resistance of new zirconium-oxide and feldspathic all-ceramic crowns made with computer-aided design/computer-aided manufacturing (CAD/CAM). An ivorine molar was prepared to receive an all-ceramic crown. Using epoxy resin, 40 replication dies were made of the prepared tooth. Twenty feldspathic all-ceramic crowns (Vita Mark II) (VMII) and 20 zirconium-oxide crown copings (In-Ceram YZ) (YZ) were made using CAD/CAM technique (CEREC-3D). The YZ copings were sintered and veneered manually with a fine-particle ceramic (VM9). All crowns were cemented to their respective dies using resin cement (Panavia F 2.0). Ten crowns in each group were subjected to compressive fatigue loading in a universal testing machine (instron). The other ten crowns from each group were loaded to fracture at a crosshead speed of 1 mm/min. Data were statistically analyzed using independent t-test and Fisher&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s exact test at alpha= 0.05. There was a significant difference between the survival rates of the two materials during the fatigue test (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). All VMII crowns survived without any crack formation, while all YZ crowns fractured (40%) or developed cracks (60%). All the YZ crown fractures occurred within the veneering layer during the fatigue test. There was no significant difference in mean fracture load between the two materials (p= 0.268). Mean fracture loads (standard deviation) in N were: 1459 (492) for YZ crowns and 1272 (109) for VMII crowns. The performance of VMII crowns was superior to YZ crowns in the fatigue test. The premature fractures and cracks of the YZ crowns were attributed to weakness in the YZ veneer layer or in the core/veneer bond.

This article describes an alternative technique for the fabrication of interim restorations. A thermoplastic, vacuumformed template and translucent vinyl polysiloxane material are combined in the waxed diagnostic cast to fabricate a matrix in which the interim material can be placed. With this matrix, a variety of materials, such as dual-polymerized or light-polymerized resins, can be used in a predictable way. The major advantage of this technique is that it allows for the fabrication of accurate restorations with excellent reproduction of surface anatomy and for alterations of the tooth shape with light-polymerized materials

This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives. r

Periprosthetic fracture and infection are dreaded complications after total hip arthroplasty. We present the case of a 50-year-old man who suffered an early postoperative Vancouver B1 periprosthetic fracture, which was further complicated by concurrent infection after open reduction and internal fixation. We report the novel use of an antibiotic-impregnated cement coated locking plate during the staged treatment of concomitant periprosthetic fracture and chronic total hip arthroplasty infection. At 1-year follow-up, the patient is pain free and ambulating independently with full range of motion.

Using meta-analysis we compared the survival and clinical outcomes of cemented and uncemented techniques in primary total knee replacement. We reviewed randomised controlled trials and observational studies comparing cemented and uncemented fixation. Our primary outcome was survival of the implant free of aseptic loosening. Our secondary outcome was joint function as measured by the Knee Society score. We identified 15 studies that met our final eligibility criteria. The combined odds ratio for failure of the implant due to aseptic loosening for the uncemented group was 4.2 (95% confidence interval (CI) 2.7 to 6.5) (p < 0.0001). Subgroup analysis of data only from randomised controlled trials showed no differences between the groups for odds of aseptic loosening (odds ratio 1.9, 95% CI 0.55 to 6.40, p = 0.314). The weighted mean difference for the Knee Society score was 0.005 (95% CI -0.26 to 0.26) (p = 0.972).

The identification of different dental implants and restorative components is difficult when dental records do not include an inventory of implant components. An implant record form is described. The form should be filled out and retained in the patient&amp;amp;amp;#39;s chart for future use and implant maintenance visits.

Although several techniques exist for cementing the femoral component in TKA, no data are available on which is the best one to use. We therefore compared four cementing techniques in an anatomical open pore sawbone model (n = 20), in order to investigate the influence of cementation technique on overall cement penetration as well as length of the cement mantle over the different cuts. The technique which included cement application onto the anterior and distal bone surfaces, as well as the posterior flanges of the prosthesis, was statistically superior to the other techniques. We therefore advocate this technique as the standard for cementing the femoral component.

Introduction: This study evaluated the effects of three different endodontic sealers on the bond strength of a fiber post cemented with adhesive resin cement. Methods: Forty-eight extracted maxillary central incisors were prepared with the step-back technique and randomly divided into four groups (n = 12 for each group): group 1, control group (gutta-percha points only, no sealer); group 2, resin-based sealer (AH plus; Dentsply De Trey GmbH, Konstanz, Germany); group 3, zinc oxide-eugenol-based sealer (Endofill; Produits Dentaires SA, Vevey, Switzerland); and group 4, calcium hydroxide-based sealer (Sealapex; Kerr, Romulus, MI). The roots were obturated with gutta-percha using the cold lateral compaction technique. Fiber posts were cemented into the prepared post spaces with the adhesive resin cement Panavia F 2.0 (Kuraray Medical, Okayama, Japan). A push-out test was performed in a universal machine, and failure modes were observed. Morphologic changes of the root canal dentin surfaces were examined with scanning electron microscopy (SEM). Results: One-way analysis of variance revealed that sealers have significant effects on bond strength (p < 0.05). The control group had the highest mean pushout bond strength. No statistical difference was detected between the eugenol-based sealer group and the resin-based sealer group (p > 0.05). The root surfaces were covered with the smear layer and debris in all the groups after post space preparation in SEM analysis. However, some of the dentin tubules were partially open in the control and calcium hydroxidebased sealer groups after the application of the resin monomer. Conclusion: The results of this study showed that the type of canal sealer and chemomechanical preparation of the root canals affect the bond strength of a fiber post cemented with resin cement. (J Endod 2010;36:497-501)

This study aimed to identify factors that can affect the retention of glass fiber posts to intra-radicular dentin based on in vitro studies that compared the bond strength (BS) of GFPs cemented with resin cements. Searches were carried out in PubMed and Scopus until December 2013. Bond strength values and variables as type of tooth, presence of endodontic treatment, pretreatment of the post, type of bonding agent (if present), type of cement and mode of cement application were extracted from the 34 included studies. A linear regression model was used to evaluate the influence of these parameters on BS. The presence of endodontic treatment decreased the BS values in 22.7% considering the pooled data (p = 0.013). For regular cement, cleaning the post increased BS when compared to silane application without cleaning (p = 0.032), considering cleaning as ethanol, air abrasion, or phosphoric acid application. Applying the cement around the post and into root canal decreased the resistance compared to only around the post (p = 0.02) or only into root canal (p = 0.041), on the other hand, no difference was found for self-adhesive resin cement for the same comparisons (p = 0.858 and p = 0.067). Endodontic treatment, method of cement application, and post pretreatment are factors that might significantly affect the retention of glass-fiber posts into root canals mainly when cemented with regular resin cement. Self-adhesive resin cements were found to be less technique-sensitive to luting procedures as compared with regular resin cements.

Prostheses can be attached to implants or implant abutments by screw retention, cementation, or with the use of set-screws. The indications for non-screw-retained restorations are discussed with respect to implant body position and surgical limitations for implant placement. The advantages and disadvantages of each method are outlined. A technique that uses a screw threaded into the implant restoration to displace the cemented restoration is presented. Use of this technique will allow predictable removal of the cemented restorations without damage to the prosthesis or abutment.

The fixation of cemented and uncemented PCA modular cruciform-stemmed tibial components was examined 6 weeks after operation using roentgenstereophotogrammetric analysis in 26 randomly selected patients. Physiological external forces were applied in external~internal rotation and eccentric posterior loading generated by squatting. All cases showed inducible displacement, but there were no statistically significant differences between the 2 groups in inducible displacement or in the initial migration, except for subsidence between the lying and standing position. In some, the greatest movement was found when changing from resting to standing, or during rotational stress; in others, the greatest movement was found during squatting. There was a statistical difference in subsidence on squatting which was greater in the uncemented group. The design of the cruciform stem and the use of an internally cooled saw may explain this small differences between the 2 groups.

Clinical success of ceramic laminate veneers depends on material selection, bonding procedures, controlled laboratory steps, and enamel preservation. Enamel preservation is the most critical because excessive tooth preparation can expose dentin reducing bond strength, which is a factor that can cause a decrease in long-term clinical success. The proposed technique based on carefully treatment planning developed between clinician and dental technician helps to maximize enamel preservation, which is an important element for clinical success.

Cementation is an effective process that meets the requirements of process cleanliness. The performance of the cementation reaction is dictated by a number of variables. In this study, the effects of various parameters on the yields of copperiron cementation (wire and powder) were investigated. Statistical full factorial designs were used to produce appropriate mixture models for the yields. The experimental designs were done at three different levels of three operating variables, namely initial concentration, temperature, and pH. The optimization studies were carried out with MATLAB 7.0 software. The optimum yields obtained from the predicted models were found to be 0.9916 and 0.9088 for iron wire and powder, respectively, under optimized conditions, and these were in accordance with the experimental observations.

d e n t a l m a t e r i a l s 2 5 ( 2 0 0 9 ) 121-128 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a a b s t r a c t Objectives. With this in vitro study the fracture strength of zirconia-based crown copings being veneered with a CAD/CAM generated high-strength ceramic cap by sintering is compared with anatomically identical zirconia-based crowns, which were either overpressed or veneered by the layering technique for completion. Methods. A 1.2 mm, 360 • chamfer preparation was performed on a second maxillary molar and was dublicated 15 times in a cobalt-chromium-alloy. A sample of 45 zirconia copings was produced and divided into three groups. In the first group (VT) zirconia copings received conventional veneering in layering technique, in the second group the veneering porcelain was pressed over the zirconia coping (PT), and for the third group (ST) a CAD/CAM-fabricated high-strength anatomically shaped veneering cap was sintered onto the zirconia coping. All crowns were cemented conventionally onto their dies and tested in the universal testing machine until clinical failure. The fracture load data were compared by a one-way analysis of variance and a multiple comparison posthoc test (˛< 0.05).

The aim of this in vitro study was to evaluate the effects of different preparation designs on the fracture resistance of single-crown zirconia frameworks. To this end, maxillary molar dies of CrCo alloy were fabricated with five different preparation designs: shoulderless, slight and pronounced deep chamfer, beveled and non-beveled shoulder. Ten zirconia copings with a wall thickness of 0.4 mm were fabricated for each type of preparation. After cementation by glass ionomer cement, they were loaded until fracture. There were significant differences in the breaking load of the experimental groups (ANOVA, p<0.01). The shoulder preparation had a mean breaking load of 2286 N, the shoulderless preparation 2041 N, the beveled shoulder 1722 N, the pronounced deep chamfer 1752 N, and the slight chamfer 1624 N. Based on the results of this study, a shoulder preparation is highly recommended whenever possible. Moreover, for endodontically treated teeth that are structurally compromised or which have anatomically limited areas, the slight chamfer preparation is an optimal recommendation.

This study&#39;s purpose was to investigate microleakage and marginal discrepancies in stainless steel crowns (SSCs) placed using conventional and Hall techniques and cemented with three different luting agents. Seventy-eight human primary maxillary second molars were randomly assigned to two groups (N=39), and SSCs were applied either with the Hall or conventional technique. These two groups were further subgrouped according to the material used for crown cementation (N=13 per group). Two specimens in each group were processed for scanning electron microscopy investigation. The extent of microleakage and marginal fit was quantified in millimeters on digitally photographed sections using image analysis software. The data were compared with a two-way independent and a two-way mixed analysis of variance (P=.05). The scores in the Hall group were significantly worse than those in the conventional technique group (P&lt;.05). In both groups, resin cement displayed the lowest extent of mi...

The clinical longevity of indirect restorations made of ceramics or indirect composite resins depends on their successful treatment and cementation. The cementation technique is determined by the type of restorative material—ceramics or indirect composite resins; thus, their intaglio surface treatment should be performed according to their particular compositions. The aim of this literature review was to define surface treatment protocols of different esthetic indirect restorative materials. A PubMed database search was conducted for in vitro studies pertaining to the most common treatment protocols of tooth-colored materials. Articles that described at least the surface treatment procedure, its effects on adhesion, its relationship with the material's composition, clinical aspects, and expected longevity were selected. The search was limited to peer-reviewed articles published in English between 1965 and 2004 in dental journals. Sandblasting, etching techniques, and silane coupling agents are the most common procedures with improved results.

Loss of tooth structure related to crown preparations can be reduced for composite resin crowns, if a small total convergence angle is combined with a 0.5-mm chamfer finish line and adhesive cementation. Statement of problem. Although composite resin materials are used for posterior crown restorations, the influence of preparation design, material thickness, convergence angle, and method of cementation on fracture resistance remains unclear.

This systematic review aimed to identify different prosthodontic outcomes between screw- and cement-retained implant prostheses. The relevant articles were retrieved from the following electronic databases: MEDLINE, EMBASE, PubMed (using medical subject headings), and the Cochrane Central Register of Controlled Trials (CENTRAL). The search was performed up to December 31, 2013, and was restricted to studies on human subjects reported in English. A further search was conducted through the reference lists of the articles found as well as from early online articles. Reviewed studies were those on fixed implant prostheses using different retention mechanisms such as screws or cement. Information on types of screws and mechanisms of preloading, as well as different luting cements, was collected in correlation with prosthodontic maintenance/complication issues seen in the clinical studies. Sixty-two papers met the review criteria. There were only six randomized controlled trials and none ...

PURPOSE: To compare the effect of implant abutment modification on the amount of cement extruded at the crown-abutment margin and to evaluate the vertical discrepancy after cementation.MATERIALS AND METHODS: Access openings of titanium abutments were modified with an opening (open) and placement of two vent holes 3 mm from the occlusal edge and 180 degrees apart (internal vent). Access openings were filled with resin material (closed) and used as controls. Each abutment was secured to an implant analog. Eugenol-free zinc oxide cement (TempBond NE) was selected to cement the cast crowns (n = 9) onto test abutments. The amount of cement extruded out of the margin was calculated, and vertical seating discrepancies were determined with a linear transducer device before and after cementation. Differences among groups were analyzed statistically.RESULTS: The mean amount of extruded cement ranged from 36% to 90% of the total cement placed within the crowns. The order, from least to greatest amount of excess cement extrusion at the margins, was internal vent, open, and closed; significant differences were observed between test groups. The net vertical discrepancies of tested specimens ranged from -7 μm to +6 μm (mean, 0 μm). No statistically significant differences in vertical discrepancy were found between the groups.CONCLUSIONS: Venting the hollow abutment resulted in the least amount of cement extrusion when compared to closing off the screw access channel or leaving it open. Within the limitations of this study, it may be concluded that the use of two, 0.75-mm radius vent holes placed 3 mm apical to the occlusal area of the abutment and 180 degrees apart will limit the amount of cement extruded into the gingival sulcus of implant-retained crowns.

The use of zirconia is an esthetic alternative to metal for implant-supported frameworks, and it has increased primarily for its high biocompatibility, low bacterial surface adhesion, high flexural strength and high mechanical features. The zirconia frameworks in fixed prosthetic restorations that are supported by implants is commonly covered with hand-layered overlay porcelain. This technical procedure is highly esthetic but it can cause some complications, such as porcelain fractures. The purpose of this article is to introduce an innovative approach to create an esthetic fixed ceramic implant restoration to minimize and facilitate the repair of the mechanical complications, by combining the adhesive-cementation of lithium disilicate full coverage restorations on implant screw-retained zirconia frameworks.

Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups (n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2 mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequ...

To investigate the influence of preparation design and mouth motion fatigue on the marginal accuracy of press-ceramic veneers bonded to human maxillary central incisors. Forty-eight extracted human maxillary central incisors divided in three groups of 16 specimens each, received veneer preparations. In Group WP a window preparation (WP) was performed. Specimens in Group IOP were prepared with an incisal overlap (IOP) of 2 mm without palatal chamfer. For Group CVP, specimens received a complete-veneer preparation (CVP) of 3 mm incisal reduction and 2 mm palatal extension. Veneers were fabricated with IPS Empress and bonded adhesively with dual polymerizing composite Variolink II. The discrepancies of marginal fit were examined on epoxy replicas before and after mouth motion fatigue at x200 magnification. The mean (geometrical) (95% confidence limits) marginal accuracy after cementation was recorded as follows: WP-46 (43-49) microm, IOP-46 (44-49) microm and CVP-54 (51-58) microm. Fat...

The purpose of this study was to present a new laboratory technique for cementable implant-supported restorations and to evaluate its efficacy in reducing chair time for both patients and clinicians, while maintaining the precision of an indirect procedure for crown fabrication. The technique consisted of the duplication of the implant portion of a working cast prepared using double-pour or plastic base die systems for single or multiple crowns. For this purpose, a flask previously intended for the production of ceramic inlays and onlays was used. Duplication was obtained using a high-precision addition silicon material and a low-shrinkage polyurethane resin. The duplicated implant abutment was used to finalize the fixed partial denture restorations after the originals were delivered to the patients. Fifty abutments were tested consecutively. The castings (19 single crowns, 31 fixed partial dentures) produced on the original abutments were seated on the duplicate abutments and evalu...

It has been recognized that liquefaction resistance of sand increases with age due to processes such as cementation at particle contacts and increasing frictional resistance resulting from particle rearrangement and interlocking. As such, the currently available empirical correlations derived from liquefaction of young Holocene sand deposits, and used to determine liquefaction resistance of sand deposits from in situ soil indices ͓standard penetration test ͑SPT͒, cone penetration test ͑CPT͒, shear wave velocity test ͑V s ͔͒, are not applicable for old sand deposits. To overcome this limitation, a methodology was developed to account for the effect of aging on the liquefaction resistance of old sand deposits. The methodology is based upon the currently existing empirical boundary curves for Holocene age soils and utilizes correction factors presented in the literature that comprise the effect of aging on the in situ soil indices as well as on the field cyclic strength ͑CRR͒. This paper describes how to combine currently recorded SPT, CPT, and V s values with corresponding CRR values derived for aged soil deposits to generate new empirical boundary curves for aged soils. The method is illustrated using existing geotechnical data from four sites in the South Carolina Coastal Plain ͑SCCP͒ where sand boils associated with prehistoric earthquakes have been found. These sites involve sand deposits that are 200,000 to 450,000 years in age. This work shows that accounting for aging of soils in the SCCP yields less conservative results regarding the current liquefaction potential than when age is not considered. The modified boundary curves indicate that old sand deposits are more resistant to liquefaction than indicated by the existing empirical curves and can be used to evaluate the liquefaction potential at a specific site directly from the current in situ properties of the soil.

The Poza Rica trend of the Tampico embayment, Mexico, will ultimately produce more than 2.3 x lo9 barrels of oil from Mid-Cretaceous (Albian-Cenomanian) basin-margin deposits. Bioclastic grainstone, packstone, and wackestone are interbedded with polymictic lime breccia and dolomitized debris; all were deposited by sediment gravity flow. Indigenous sediment was pelagic lime mud. Typical reservoir porosities are about 10%; permeabilities average 2 md and rarely exceed 100 md. Porosity is largely the result of selective dissolution of rudist fragments, which were originally aragonite.