Maxillary interim obturator prosthesis fabrication for a patient with limited mouth opening with a digital approach: A clinical report.

Squamous cell carcinoma is a common malignant condition affecting the oral cavity and may involve the surrounding maxillofacial regions. Treatment commonly involves resection of the tumor, followed by prosthetic rehabilitation of the resection defect. This clinical report presents a 62-year-old Asian male patient who had previously undergone surgical resection, resulting in a post-surgical Aramany Class II maxillary defect. The patient's medical history included severe trismus, characterized by restricted mouth opening, as well as a diagnosis of maxillary sinus verrucous squamous cell carcinoma. This report provides a comprehensive account of the rapid fabrication of an interim obturator using digitally assisted dentistry techniques.

Mechanical properties of simulated dentin caries treated with metal cations and L-ascorbic acid 2-phosphate.

This pH cycling study aimed to investigate the effects of L-Ascorbic acid 2-phosphate (AA2P) salts of Mg, Zn, Mn, Sr, and Ba on the surface microhardness, compressive strength, diametral tensile strength (DTS), and solubility of root canal dentin. 186 cylindrical dentin specimens from 93 teeth were fortified with optimal concentrations of AA2P salts of Mg (0.18 mM), Zn (5.3 µM), Mn (2.2 × 10-8 M), Sr (1.8 µM), and Ba (1.9 µM). Saline was used as the control group. These dentin specimens underwent a 3-day cycling process simulating dentin caries formation through repeated sequences of demineralization and remineralization. Surface microhardness at 100 and 500 µm depths (n = 10/subgroup), scanning electron microscopy (n = 3/group), compressive strength (n = 10/group), DTS (n = 6/group), and solubility (n = 5/group) tests were performed to analyze the dentin specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA, and Post Hoc Tukey tests (p < 0.05). The control group had significantly lower microhardness at both depths (p < 0.001), reduced DTS (p = 0.001), decreased compressive strength (p < 0.001), and higher weight loss (p < 0.001) than all other groups. The Sr group had the highest compressive strength and microhardness among all the groups. The microhardness was significantly higher for the 500 µm depth than the 100 µm depth (p < 0.001), but the difference in microhardness between depths across groups was not significant (p = 0.211). All fortifying solutions provided some protection against artificial caries lesions. Therefore, these elements might have penetrated and reinforced the demineralized dentin against acid dissolution.

Effects of Diabetes on Elemental Levels and Nanostructure of Root Canal Dentin.

INTRODUCTION: This study evaluated the effects of diabetes mellitus (DM) on the nanostructure of root canal dentin using high-resolution transmission electron microscopy (HRTEM) and inductively coupled plasma mass spectrometry (ICP-MS). METHODS: Twenty extracted human premolars from diabetic and nondiabetic patients (n = 10 in each group) were decoronated and sectioned horizontally into 40 2-mm-thick dentin discs, with each disc designated for a specific test. ICP-MS was used to determine the different elemental levels of copper, lithium, zinc, selenium, strontium, manganese, and magnesium in diabetic and nondiabetic specimens. HRTEM was used to analyze the shape and quantity of the apatite crystals in diabetic and nondiabetic dentin at the nanostructural level. Statistical analysis was performed using Kolmogorov-Smirnov and Student t test (P < .05). RESULTS: ICP-MS revealed significant differences in trace element concentrations between the diabetic and nondiabetic specimens (P < .05), with lower levels of magnesium, zinc, strontium, lithium, manganese, and selenium (P < .05), and higher levels of copper in diabetic specimens (P < .05). HRTEM revealed that diabetic dentin exhibited a less compact structure with smaller crystallites and significantly more crystals in the 2500 nm2 area (P < .05). CONCLUSION: Diabetic dentin exhibited smaller crystallites and altered elemental levels more than nondiabetic dentin, which could explain the higher root canal treatment failure rate in diabetic patients.

Neural network approach to evaluate the physical properties of dentin.

This study intended to evaluate the effects of inorganic trace elements such as magnesium (Mg), strontium (Sr), and zinc (Zn) on root canal dentin using an Artificial Neural Network (ANN). The authors obtained three hundred extracted human premolars from type II diabetic individuals and divided them into three groups according to the solutions used (Mg, Sr, or Zn). The authors subdivided the specimens for each experimental group into five subgroups according to the duration for which the authors soaked the teeth in the solution: 0 (control group), 1, 2, 5, and 10 min (n = 20). The authors then tested the specimens for root fracture resistance (RFR), surface microhardness (SµH), and tubular density (TD). The authors used the data obtained from half of the specimens in each subgroup (10 specimens) for the training of ANN. The authors then used the trained ANN to evaluate the remaining data. The authors analyzed the data by Kolmogorov-Smirnov, one-way ANOVA, post hoc Tukey, and linear regression analysis (P < 0.05). Treatment with Mg, Sr, and Zn significantly increased the values of RFR and SµH (P < 0.05), and decreased the values of TD in dentin specimens (P < 0.05). The authors did not notice any significant differences between evaluations by manual or ANN methods (P > 0.05). The authors concluded that Mg, Sr, and Zn may improve the RFR and SµH, and decrease the TD of root canal dentin in diabetic individuals. ANN may be used as a reliable method to evaluate the physical properties of dentin.

Functional role of inorganic trace elements in dentin apatite tissue-part III: Se, F, Ag, and B.

Dentin hydroxyapatite possesses a unique versatile structure which allows it to undergo ionic substitutions. Trace elements play pivotal roles within the oral cavity, especially in dentin apatite tissue. Therefore, it is critical to explore the role of these elements in dentin apatite structure. The roles of other inorganic elements in dentin apatite were discussed in part I (Mg, Sr, Zn, and Fe) and part II (Cu, Mn, Si, and Li) of these series. In the last part of the review series, the role of selenium, fluorine, silver, and boron in the regulation of dentin apatite structure and function was discussed. We evaluated how these elements affect the overall size, morphology, and crystallinity of dentin apatite crystals. Moreover, we investigated the importance of these elements in regulating the solubility of dentin apatite. An electronic search was performed on the role of these trace elements in dentin apatite from January 2010 to January 2022. The concentration of selenium in teeth has been explored only recently, particularly its incorporation into dentin apatite. Silver nanomaterials inhibit the growth of cariogenic microorganisms as well as arrest the degradation of collagen. Fluorine was found to have important roles in dentin remineralization and dentinal tubule occlusion, making it widely used for hydroxyapatite doping. Boron is critical for mineralized tissues like bone, dentin, and enamel, but its exact role in dentin apatite is unknown. Therefore, understanding the impact of these elements on dentin apatite is potentially transformative, as it may help to fill a significant knowledge gap in teeth mechanics.

Diabetes negatively affects tooth enamel and dentine microhardness: An in-vivo study.

OBJECTIVE: This study was performed to evaluate the effect of type 1 diabetes mellitus (T1DM) on the microhardness of tooth enamel and dentine in mice. DESIGN: Seventy male C57BL/6 J mice were used in this study. Thirty-five mice were rendered diabetic by administration of streptozotocin (STZ), and the remaining animals received citrate buffer (normal/non-diabetic). In each group, specimens were divided into 7 subgroups of 5 mice based on the time points 0, 1, 4, 8, 12, 20, and 28 weeks. The microhardness value (MHV) of the second molars' enamel and root dentine were tested with a Vickers microhardness tester. Five specimens from each subgroup were evaluated for dentinal tubular density by scanning electron microscope (SEM) and color dot map analysis to determine the color intensity of strontium (Sr) and magnesium (Mg) by using ImageJ software. RESULTS: The MHV of enamel was significantly reduced in STZ specimens in time points of 12 weeks (STZ: 274.39 ± 15.42, normal: 291.22 ± 15.28), 20 weeks (STZ: 247.28 ± 19.65, normal: 290.68 ± 11.52), and 28 weeks (STZ: 232.87 ± 15.07, normal: 282.76 ± 10.36) (P < 0.05). When comparing the MHV of dentine in subgroups of the normal group, after 20 weeks (169.1 ± 7.5) and 28 weeks (168.6 ± 7.81), the MHV increased significantly (P < 0.05). However, in the STZ group, a significant reduction of MHV was noticed between 28 weeks (131.69 ± 6.2) specimens with other subgroups (P < 0.05). CONCLUSIONS: T1DM negatively affected enamel and dentine microhardness, and enamel was influenced much more negatively and rapidly compared with dentine in diabetic groups.

The effect of diabetes on the tensile bond strength of a restorative dental composite to dentin.

This study was performed to evaluate the effect of diabetes mellitus (DM) on the tensile bond strength (TBS) of dental composite resin bonding to enamel and dentin of extracted human teeth. Thirty caries-free human premolar teeth (10 from type 1 DM (D1), 10 from type 2 DM (D2), and 10 from non-diabetic individuals (control)) were wet ground and polished to obtain flat surfaces of dentin (n = 10). 37% phosphoric acid was used to etch dentin specimens for 15 s. After the application of the adhesive system, the composite resins were applied and cured for 20 s. Then, specimens were subjected to TBS testing by Universal Testing Machine (1 mm/min). One specimen from each group was prepared and observed under a scanning electron microscope (SEM) and a dot map was generated. Data were analyzed by ANOVA and post hoc Tukey tests (α = 0.05). The TBS values were significantly higher in the control group compared to the D1 and D2 groups (P < 0.05). Between DM groups, D2 values were significantly higher than those in the D1 group. Unlike DM groups, the zigzag fracture pattern was only noticed in the control group. DM adversely affected the TBS of dental composite resins to dentin; this negative effect is more exaggerated by type 1 DM than type 2 DM.

Functional role of inorganic trace elements in dentin apatite tissue-Part 1: Mg, Sr, Zn, and Fe.

Many essential elements exist in nature with significant influence on dentin and bone apatite tissue. Hydroxyapatite (HAp) is the major inorganic crystalline structure of dentin that provides a site for various physiological functions such as surface layer ion exchange. Decades of apatite research have shown that enamel is a high-substituted crystalline apatite, but recent findings suggest that dentin apatite may play a more important role in regulating ion exchange as well as mineral crystallinity. This article is the first part of a review series on the functional role of inorganic trace elements including magnesium, strontium, zinc, and iron in dentin hydroxyapatite. The morphology, physiology, crystallinity, and solubility of these elements as they get substituted into the HAp lattice are extensively discussed. An electronic search was performed on the role of these elements in dentin apatite from January 2007 to September 2021. The relationship between different elements and their role in the mineral upkeep of dentin apatite was evaluated. Several studies recognized the role of these elements in dentinal apatite composition and its subsequent effects on morphology, crystallinity, and solubility. These elements are of great importance in physiological processes and an essential part of living organisms. Magnesium and strontium stimulate osteoblast activity, while zinc can improve overall bone quality with its antibacterial properties. Iron nanoparticles are also vital in promoting bone tissue growth as they donate or accept electrons in redox reactions. Thus, understanding how these elements impact dentin apatite structure is of great clinical significance.

The effect of diabetes mellitus on the shear bond strength of composite resin to dentin and enamel.

Diabetes mellitus might be linked to the deterioration of certain physical properties of dentin and enamel. This study aimed to determine the effect of two types of diabetes on the shear bond strength of enamel and dentin, by using the single bond universal bonding system. Sixty specimens [from 15 teeth; 5 from each group-non-diabetic (ND), Diabetic type I (D1), and Diabetic type II (D2)], were prepared with equal amounts of dentin (n = 5) and enamel (n = 5). Enamel specimens (E20) were etched with 37% phosphoric acid, for 20 s, and dentin specimens (D15) were etched for 15 s. A standard shear bond strength test was performed on all specimens. Their failure modes were also studied under a scanning electron microscope, and the data were analyzed by using ANOVA and Post Hoc Tukey's test (a = 0.050). For the enamel groups, significant differences were only noticed between the ND and D1 (P < 0.050) groups, and between the ND and D2 (P < 0.050) groups. In the dentin groups, there was a significant difference only between the ND and D1 (P < 0.050) groups. The micrographs showed that the ND group had the highest number of specimens with cohesive failure and D1 had the highest number of specimens with adhesive failure. It can be concluded that both types of diabetes reduce the shear bond strength of composite resin on dentin and enamel. However, it seems that the negative effect of diabetes on shear bond strength of dental composite resin is more drastic in individuals with type I diabetes as compared with type II.

Tissue reaction to novel customized calcium silicate cement based dental implants. A pilot study in the dog.

OBJECTIVES: The purpose of this study was to determine the level of periodontal tissue regeneration in a canine model following post-extraction placement of an implant molded from a composite material made from extracted tooth dentin and a calcium silicate cement (CSC) material. The investigation used autologous dentin in conjunction with a CSC material to form a composite implant designed for immediate tooth replacement. METHODS: Two (2) beagles had a periodontal and radiographic examination performed to rule out any pre-treatment inflammation, significant periodontal disease, or mobility. Then, ination eleven (11) teeth were extracted and polyvinyl siloxane molds were made to fabricate three different types of implants: Particulate Implant (Test Group 1, n = 4), Shell Implant Alone (Test Group 2, n = 2), Shell Implant with Emdogain® (Test Group 3, n = 3). Teeth in the control group were extracted, scaled (n = 2), and then re-implanted into their respective fresh extraction sockets. At 4 weeks, a clinical, radiographic, and histologic assessment was performed. RESULTS: Clinical evaluation revealed no mobility in any of the test or control implants and no radiographic evidence of significant bone loss or active disease. Based on the MicroCT analysis, direct bone to implant contact was observed in some areas with an apparent periodontal ligament space. Implant-related inflammation, on average, was similar among all groups, with low numbers of infiltrates. Implant-related inflammatory reaction was generally minimal and not interpreted to be adverse. CONCLUSION: The proposed novel composite materials revealed that not only do these materials demonstrate high biocompatibility, but also their successful integration in the alveolus is likely secondary to a partial ligamentous attachment. The current investigation may lead to the use of calcium silicate-based materials as custom dental implants. Further research on this novel composite's biomechanical properties is necessary to develop the optimal material composition for use as a load-bearing dental implant.

Evaluation of the accuracy of 2 digital intraoral scanners: A 3D analysis study.

STATEMENT OF PROBLEM: Evidence for the accuracy of a recently introduced intraoral scanner is lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the trueness (validity) and precision (reliability) of 2 intraoral scanners by scanning a quadrant and a sextant. MATERIAL AND METHODS: A maxillary typodont with plastic teeth made from a shade A3 polymethyl methacrylate was scanned (n=10) with each intraoral scanner (Planmeca Emerald and 3Shape TRIOS 3) to obtain sextant and quadrant scans. Control scans were made with an industrial optical scanner. The scans were analyzed with a 3D reverse engineering software program and an independent samples t test and general linear model 2-way analysis of variance (α=.05). RESULTS: The 3Shape TRIOS 3 scanner showed no significant difference between the sextant and quadrant scans in trueness (P=.118) or in precision (P<.285). The Emerald scanner had statistically significant higher trueness for the sextant scan (P=.007). The 3Shape TRIOS 3 scanner had better performance in trueness and precision when compared with the Emerald scanner. CONCLUSIONS: The 3Shape TRIOS 3 scanner was found to be more accurate than the Emerald scanner in terms of trueness and precision, regardless of the scanning field. The Emerald scanner's trueness decreased as the scanning field increased from a sextant to a quadrant.

Modification of denture teeth for improved occlusal stability of a maxillary removable complete denture opposed by a mandibular implant-supported fixed complete denture: A clinical report.

Wear of artificial teeth is the most common complication associated with an implant-supported fixed complete denture (ISFCD). This wear alters the occlusal scheme, with loss of eccentric occlusal balance and vertical dimension of occlusion (VDO). This clinical report describes the fabrication of a new maxillary removable complete denture opposing an existing ISFCD with occlusal modifications. Both prostheses received splinted zirconia crowns cemented with composite resin cement.

Evaluation of Mechanical Activation and Chemical Synthesis for Particle Size Modification of White Mineral Trioxide Aggregate.

Objective: Initial setting time is one of the most important properties of calcium silicate cements (CSCs) such as white mineral trioxide aggregate (WMTA). This study aimed to evaluate the effect of two methods used to reduce the particle size of WMTA, mechanical activation and chemical synthesis. Methods: WMTA without bismuth oxide (WMTA-B) was provided and divided into four groups (n=5) including: WMTA-B, WMTA-B+10 min milling, WMTA-B+30 min milling, and sol-gel. In groups 2 and 3, the milling was performed by using tungsten carbide balls in a ratio 1:15 (w/w) and a vibration frequency of 30 Hz together with absolute ethanol. For the fourth group, polyethylene glycol (PEG), calcium acetate (Ca(C2H3O2)2), SiO2, and aluminum oxide (Al2O3) were used for the sol-gel process. After preparation, sample powders were mixed with distilled water and placed in cylindrical molds, covered with water-moistened gauze, and incubated at 37°C for 24 hours. The Vicat needle test analyzed the initial setting time. Data were analyzed by ANOVA and Tukey tests at a significance level of P<0.05. The correlation between particle size and setting time was determined. Results: Initial setting time of the sol-gel and WMTA-B+30 min milling was significantly lower than in the other two groups (P<0.05). A significant correlation was noticed between particle size and initial setting time (P<0.05). Conclusion: Sol-gel process introduces a promising alternative strategy for the reduction of initial setting time of CSC materials. While both methods increased surface area, mechanical activation was not as successful in reducing surface area and initial setting time as effectively as the sol-gel process.

Effect of Diabetes on Tubular Density and Push-out Bond Strength of Mineral Trioxide Aggregate to Dentin.

INTRODUCTION: This study compared the tubular density and push-out bond strength of mineral trioxide aggregate (MTA) to dentin in diabetic and nondiabetic patients. METHODS: Ten extracted single-rooted human teeth from diabetic and nondiabetic patients (n = 5 in each group) were decoronated, prepared up to a #5 Gates-Glidden drill, and sectioned horizontally at the midroot area to prepare 3 dentin slices, each measuring 2 mm in thickness (1 slice for the push-out test and 2 slices for the tubular density test). MTA was prepared and packed into the root canal space followed by incubation for 3 days. The push-out bond strength values were determined using a universal testing machine. Specimens were viewed under a stereomicroscope and a scanning electron microscope to determine the failure types at the cement-dentin interface. Ten slice specimens in each group were evaluated under SEM at 3 different sites to determine the tubular density. Comparisons were performed using the Mann-Whitney U test (P < .05). RESULTS: Diabetic patients exhibited significantly lower push-out bond strength of MTA to root canal dentin (P < .05). The pattern of failure at the MTA-dentin interface was different between the 2 groups. The tubular density was significantly higher in diabetic patients (P < .05). CONCLUSIONS: The dentin in diabetic patients exhibited different physicochemical properties. The failure patterns and modes in diabetic patients might be explained by the changes in the push-out bond strength, the calcification mechanism of the dentin-pulp complex, a higher dentinal tubule density, and less peritubular dentin. These differences could explain the higher failure rate of root canal treatment in these patients.

Moderately Acidic pH Promotes Angiogenesis: An In Vitro and In Vivo Study.

INTRODUCTION: This study evaluated the effect of different pH values of 4.4, 5.4, 6.4, 7.4, 8.4, and 9.4 on angiogenesis. METHODS: Endothelial cells were isolated from the mice molar teeth and placed in 42 Matrigel (Corning, NY)-coated wells, which were prepared and divided into 6 groups (n = 7). Synthetic tissue fluid was prepared and divided into 6 parts, and their pH values were adjusted to 4.4, 5.4, 6.4, 7.4, 8.4, and 9.4. A 2-mL volume from each group was diluted in the growth medium at a ratio of 1:3 and used for tubulogenesis assay. Forty-two 6-week-old mice in 6 groups (n = 7) were used for choroidal neovascularization (CNV). A 2-µL volume from each group or saline (control) was delivered by intravitreal injection on the day of laser application and 1 week later. Data on the number of nodes, the total length of the branches, and CNV areas (µm2) were determined using ImageJ software (National Institutes of Health, Bethesda, MD) and analyzed with 1-way analysis of variance and post hoc Tukey tests. The correlation was assessed between the tested variables. RESULTS: The number of nodes decreased with changes in pH values as follows: 6.4 > 5.4 > 7.4 > 8.4 > 9.4 > 4.4. The total branch length decreased with pH value changes as follows: 6.4 > 4.4 > 6.4 > 7.4 > 8.4 > 9.4, and the CNV areas decreased with pH value changes as follows: 6.4 > 5.4 > 4.4 > 7.4 > 8.4 > 9.4. CONCLUSIONS: Moderately acidic pH values (5.4 and 6.4) enhanced angiogenesis, whereas moderately alkaline pH values (8.4 and 9.4) suppressed angiogenesis.

Effect of thermocycling on the surface texture and release of titanium particles from titanium alloy (Ti6Al4V) plates and dental implants: An in vitro study.

STATEMENT OF PROBLEM: The release of titanium (Ti) particles from the surface of endosseous dental implants is not well understood. PURPOSE: The purpose of this in vitro study was to evaluate the effect of thermocycling on the surface texture and release of Ti particles from the surface of dental implants. MATERIAL AND METHODS: Three MSI dental implants and 3 Ti alloy (Ti6Al4V) plates were divided into 6 subgroups (n=3). Specimens in each group were subjected to 0 (control group), 100, 200, 500, 1000, and 2000 thermocycles. After each cycling process, artificial saliva was collected, and the concentrations of released Ti particles were quantified by inductively coupled plasma-mass spectrophotometry (ICP-MS). The surfaces of the dental implants and Ti plates were evaluated before and after thermocycling by scanning electron microscopy (SEM), and SEM images were analyzed by using the ImageJ software program. Data were analyzed by mixed-model ANOVA and post hoc Tukey tests (α=.05). RESULTS: The greatest Ti release was seen after 2000 thermocycles. After increasing the number of cycles, additional Ti particles were released. SEM images of the surfaces of the dental implants and Ti plates displayed significant changes in surface texture. CONCLUSIONS: Thermocycling continuously removed the protective TiO2 layer on the surface of dental implants, resulting in the release of Ti particles. The surface treatment and texture did not affect the release of Ti particles.

Effect of length of LOCATOR abutment and cement type on retention to intraradicular dentin in overdentures.

STATEMENT OF PROBLEM: Limited information is available on the effect of LOCATOR abutment length and luting cement type on retention to intraradicular dentin in overdentures. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the length of a commercially available LOCATOR abutment and cement type on retention in the root canal. MATERIAL AND METHODS: Eighty LOCATOR abutments with a standard length of 6 mm were obtained. Half of them were shortened to 3 mm. Eighty recently extracted single-rooted teeth were divided into 2 groups. The post space was prepared to 6 mm in the first group and 3 mm in the second. After preparation, the LOCATOR abutments were luted with one of the following cements: dual-polymerized glass-reinforced resin cement (Parapost Paracore), dual-polymerized resin cement (Variolink II), self-adhesive resin cement (RelyX Unicem), and conventional cement (zinc phosphate). The tensile force required for the removal of the LOCATOR abutments from their corresponding roots was recorded. Data were statistically analyzed with 2-way ANOVA and the Tukey multiple comparison test. RESULTS: Both the cement type (P<.001) and the length of the LOCATOR abutment (P<.001) significantly affected the mean tensile forces. Dual-polymerized glass-reinforced resin cement (Parapost Paracore) presented significantly higher mean tensile forces for the LOCATOR abutment retention among all cements (P<.05). CONCLUSIONS: Regardless of the length, LOCATOR abutments luted with Parapost Paracore resin cement presented higher mean resistance to tensile forces compared with those luted with the other cements. LOCATOR abutments of 6 mm in length were more resistant to tensile forces than those of 3 mm in length in combination with all cements.

Retentive strength and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent: An in vitro pilot study.

STATEMENT OF PROBLEM: Information on the properties of a relatively new luting agent with a unique formulation (ceramic-reinforced calcium phosphate) is limited. PURPOSE: The purpose of this in vitro study was to compare the retentive strengths and marginal discrepancies of a ceramic-reinforced calcium phosphate luting agent (CM) with a self-adhesive resin luting agent (RX) and to determine and compare the mode of failure of dislodged cemented copings. MATERIAL AND METHODS: Forty extracted human molar teeth were prepared to receive zirconia copings. After cementation, the specimens were divided into 4 subgroups (n=10): CM A (axial loading), CM OA (off-axis loading), RX A (axial loading), and RX OA (off-axis loading). For each subgroup, 9 of the specimens received experimental treatment (thermocycling and dynamic loading), and the tenth received no experimental treatment. Eight copings were pulled off in a universal testing machine (MTS Insight; MTS). The ninth specimen was treated experimentally but was not pull tested. The marginal discrepancy and the dentin interface of the specimens that were not pull tested were analyzed with scanning electron microscopy and energy dispersion spectroscopy. The mode of failure of the dislodged copings was also subjectively evaluated. RESULTS: The mean retentive strengths were 5.92 MPa for CM A, 5.81 MPa for CM OA, 5.75 MPa for RX A, and 5.69 MPa for RX OA. The marginal discrepancy recorded for both CM and RX ranged from 30 to 45 µm, (mean, 36 ±4.6 µm). Energy dispersion spectroscopy analysis showed the presence of calcium, phosphorus, silicon, and aluminum for the CM marginal discrepancy and the presence of aluminum in the dentinal tubules adjacent to the CM. Calcium and phosphorus were detected in lesser amounts adjacent to the RX marginal discrepancy. The mode of failure for CM was primarily adhesive to the tooth preparation, and, for RX, the failure mode was predominantly adhesive to the coping. CONCLUSIONS: CM had statistically significantly higher mean retentive strength compared with RX. Subgroups loaded axially had statistically significantly higher retentive strengths compared with those loaded off axis.