Investigation of color and physicomechanical properties of peek and pekk after storage in a different medium.

The aim of this study is to assess color stability, solubility, and water sorption on polyether ether ketone (PEEK) and polyether ketone ketone (PEKK) after immersion in different storage conditions. Material and Methods Ninety disc-shaped specimens (8 × 2) were obtained from CAD/CAM blocks [PEEK (n = 45) and PEKK (n = 45)]. Before immersion, baseline color value data were recorded with a spectrophotometer. The specimens were soaked in three solutions red wine, coffee, and distilled water at 37 °C for 28 days. Following immersion, color values were remeasured, and color-change values (ΔE) were calculated. Water sorption and solubility were assessed by mass gain or loss after storage in water for 28 days. The Kruskal-Wallis and the Mann-Whitney U test were used for analysis (P = 0.05). Results ΔE00 between PEEK and PEKK was significantly different statistically (P < 0.001). PEEK presented higher water sorption than PEKK (P = 0.005). The difference in solubility between PEEK and PEKK was not statistically significant (P = 0.163). The materials and storage medium types had a statistically significant impact (P = 0.100). In terms of staining potential, the solutions tested in this experiment were ranked as: coffee > red wine > distilled water. The results of this study demonstrated that PEKK was more successful in polymer-containing CAD/CAM materials as it exhibited less color change and water absorption.

Evaluation of the effects of different surface modification methods on the bond strength of high-performance polymers and resin matrix ceramics.

OBJECTIVES: The purpose of this in vitro study was to investigate the effects of various surface treatment methods on the shear bond strength of self-adhesive resin cement to polymer-infiltrated materials. MATERIALS AND METHODS: One hundred twenty-eight polymer-infiltrated specimens (n = 32) for four different computer aided design-computer-aided manufacturing (CAD-CAM) materials, polyether ether ketone (PEEK) (PE), polyether ketone ketone (PEKK) (PK), composite resin nanoceramic (Cerasmart) (CS), and polymer-infiltrated ceramic network (PICN) (VITA ENAMIC) (VE) were milled from CAD-CAM blocks. They were divided into two groups (n = 16) in terms of surface treatments: airborne-particle abraded (AA) or silica-coated (SC) and two subgroups (n = 8) according to adhesive application or no adhesive. The surface roughness, contact angle, and shear bond strength (SBS) values of specimens were measured. Data were analyzed with Shapiro-Wilk test, the generalized linear models' method, and Bonferroni corrected t test (α ˂ 0.05). RESULTS: No statistically significant differences were found between the groups in terms of surface roughness and SBS values (P > 0.05). A statistically significant effect of the main adhesive interaction on the bond strength was found independent of the material and surface treatments (P < 0.001). While the average bond strength of the non-adhesive was 4.9 MPa, the average of the adhesive applied was 9.1 MPa. On the other hand, there is a statistically significant difference between the means of the contact angle values (P ˂ 0.001). While the highest mean contact angle value was 117.1 ± 14.8° obtained from the non-adhesive PK in the AA group, the lowest mean contact angle value 22.6 ± 4.3° was obtained from the VE without adhesive in the SC group. CONCLUSIONS: Roughness and SBS values were similar between groups after surface treatments. Adhesive application increased the SBS values. Surface treatments were found to have an effect on the contact angle. CLINICAL RELEVANCE: Since the AA and SC surface treatments used in the study show similar bond strength values, the Cojet system, which is more practical and easier to use, can be preferred as an alternative to AA after restoration production with CAD-CAM as a chairside.

A comparison of the fracture resistance of premolars without a ferrule with different post systems.

STATEMENT OF PROBLEM: Which type of post improves the performance of endodontically treated mandibular premolars without a ferrule remains unclear. PURPOSE: The purpose of this in vitro study was to compare the restoration of endodontically treated mandibular premolars without a ferrule by using different post systems. MATERIAL AND METHODS: Thirty extracted mandibular premolars were endodontically treated, and their crowns removed. They were divided into 3 groups with different post systems (n=10): zirconia ceramic posts (ZRPs), fiber posts (FPs), and bundled glass fiber-reinforced composite resin posts (GTPs). After post placement and core fabrication, computer-aided design and computer-aided manufacture (CAD-CAM) lithium disilicate crowns were cemented. The specimens were subjected to thermocycling and mastication simulation before a fracture test in a universal testing machine. The maximum load at which the fracture occurred was recorded, and the fractured specimens were examined by using an optical microscope. The data were analyzed for statistical differences with a 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05). RESULTS: No statistically significant difference in fracture strength was found among the groups (P=.970). From the light microscopy examination, catastrophic failure was observed in all specimens, and there was no failure of the ceramic crowns. CONCLUSIONS: Based on the findings of this in vitro study, the choice of post material with a low or high modulus of elasticity did not prevent catastrophic failures in endodontically treated teeth without a ferrule.

Evaluation of the effect of different polishing systems on the surface roughness of dental ceramics.

STATEMENT OF PROBLEM: How the finishing and polishing of ceramic restorations may affect their surface properties is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of different polishing systems on the surface roughness of dental ceramics by using a profilometer, an environmental scanning electron microscope (ESEM), and an atomic force microscope (AFM). MATERIAL AND METHODS: Sixty square specimens (2×14×14 mm) of 3 popular ceramic systems (monolithic zirconia and feldspathic-based ceramic containing feldspar and fluorapatite) were prepared, glazed, and assigned to 1 of the 5 groups: a control group with no additional treatment after the glaze; in the other groups, the glaze layer was removed, and the surfaces were polished by using 4 different ceramic polishing systems (OptraFine, Shofu, Meisinger, or Komet). The surface roughness was evaluated numerically by using a profilometer and visually by using an ESEM and an AFM. The data were interpreted by using 2-way ANOVA. A multiple comparison of averages was conducted by using the Tukey HSD (α=.05). RESULTS: The smoothest surface was obtained in the glazed group polished with the OptraFine kit, with no statistically significant difference (P=.95). The other groups showed a significant difference from the glazed one (P<.05); however, the difference among the other groups was not significantly different (P=.59). CONCLUSIONS: After the adjustment of dental ceramics and upon removal of the glaze, the OptraFine polishing kit and paste application can be used as an alternative to glazing for the 3 ceramic types tested. It was not possible to adequately polish the ceramic surface by using the Komet polishing kit.

Effect of MDP-Based Silane and Different Surface Conditioner Methods on Bonding of Resin Cements to Zirconium Framework.

PURPOSE: To determine the shear bond strength (SBS) between zirconium framework and resin cements after different surface conditioner methods and after application of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) based silane and a bonding agent mix. MATERIALS AND METHODS: 128 disc-shaped zirconium-oxide specimens were prepared. Specimens were placed in autopolymerizing acrylic resin. The bonding surface of specimens was smoothed consecutively with 600-, 800-, and 1200-grit silicon carbide papers under water cooling. Eight groups were prepared: CJ, Co-Jet; N, Nd-YAG laser; E, Er-YAG laser; NS, Nd-YAG laser + silane; ES, Er-YAG laser + silane; CJB, Co-Jet + bonding agent; NSB, Nd-YAG laser + silane + bonding agent; ESB, Er-YAG laser + silane + bonding agent. SEM analysis was performed under 2000× magnification. Dual- and self-cured resin cements were bonded to specimens, and shear force was applied. Data were analyzed with one-way ANOVA and Tukey's multiple comparison test (p < 0.05). RESULTS: The SBS values differed from each other among the groups. While the CJB group showed the highest values, the N group showed the lowest. The treatment with MDP-based silane and bonding agent mix increased SBS values of each cement belonging to each group. SB values of dual-cure resin cement were higher than those of self-cure resin cements. CONCLUSION: Different surface conditioner methods exhibit an important effect on the SBS of resin cements to zirconium. The application of MDP-based silane and bonding agent mix enhanced SB values.

The effect of various occlusal reduction levels on postoperative pain in teeth with symptomatic apical periodontitis using computerized analysis: a prospective, randomized, double-blind study.

OBJECTIVE: The objective of this study was to evaluate the effect of various occlusal reduction levels on the postoperative pain in teeth diagnosed as symptomatic apical periodontitis by using a computerized analysis system. MATERIALS AND METHODS: Thirty-nine molar teeth with symptomatic apical periodontitis were included. After the root canal preparation and filling was performed, the subjects were divided into three groups according to the level of occlusal reduction determined by using T-Scan (T-Scan III for Windows, Tekscan Inc., South Boston, MA) as follows: (1) no reduction (control), (2) semi-reduction, and (3) full-reduction groups. Preoperative and postoperative pain levels using visual analogue scale, percussion pain, and analgesic intake were recorded for each subject. The data were evaluated statistically using two-way analysis of variance and Holm-Sidak post hoc tests at a 95 % confidence level (P = 0.05). RESULTS: There was no significant difference between the groups in terms of occlusal reduction (P > 0.005). CONCLUSION: Within the limitation of the present study, there were no significant differences among the no reduction, semi-reduction, and full-reduction groups at 1, 3, 5, and 7 days in terms of postoperative pain levels. CLINICAL RELEVANCE: Occlusal reduction, determined using a computerized analysis system, did not influence the postoperative pain in teeth diagnosed as symptomatic apical periodontitis.

The Bond Strength of Nanohybrid and Nanoceramic Composites to Feldspathic Porcelain.

BACKGROUND: Porcelain fracture is the most important problem in fixed prosthetic restorations. The replacement of fractured restoraions isn't often prefer by patients and dentists. Intraoral repair of fractured porcelain is a big alternative for patient and dentist. For this reason, dentists try to improve different surface treatments to increase the bond strength between porcelain and repair materials such as composite resins. AIMS: The aim of this study was to evaluate the shear bond strength (SBS) of nano-hybrid (Nh.com) and nano-ceramic composite resins (Nc.com) to this feldspathic porcelains (Vita and Ivoclar). SETTINGS AND DESIGN: 120 ceramic disc were fabricated from feldspathic porcelain. MATERIALS AND METHODS: The following surface treatment was applied on the ceramic surface: 1) Hydrofluoric acid+silane, 2) Air-abrasion+silane, 3) Air-abrasion=Control group. Nh.com and Nc.com was placed on the porcelain surface. Half of the specimens were stored in 37 ± 2oC distilled water and another half were subjected to thermocycling before SBS. The samples placed in an universal testing machine and applied shear force until seperation occured. STATISTICAL ANALYSIS USED: The data were analyzed by multi-way analysis of variance (ANOVA) and Duncan test (P <0.05). RESULTS: The results show that Ivoclar and Vita had almost equal fracture values. Nh.com showed high bond strength than Nc.com. In the Ivoclar porcelain, hydrofluoric acid etching had highest fracture values than other surface treatments, and in the vita porcelain air-abrasion had a little difference from hydrofluoric acid etching. CONCLUSIONS: Different surface treatments show different effect on SBS between feldspathic porcelain and composite resins.

Effect of sealer coating and storage methods on the surface roughness of soft liners.

STATEMENT OF PROBLEM: A soft lining is applied under a removable prosthesis for various reasons. The porosity of the lining material may increase colonization by microorganisms and cause tissue inflammation. PURPOSE: The purpose of this in vitro study was to evaluate the effect of sealer coating on the surface roughness of soft lining materials under 4 different conditions. MATERIAL AND METHODS: A total of 125 specimens were prepared. One high-temperature silicone-based soft lining material and 2 room-temperature-polymerized soft lining materials (1 silicone-based and 1 methacrylate-based) were used. Twenty-five specimens of each room-temperature soft lining material were coated with 2 layers of surface sealer. Additionally, 5 specimens of each material were stored in either distilled water, Coca-Cola, denture cleanser, saliva, or air. The surface roughness was measured at baseline and after 1, 7, 14, and 28 days. Surface roughness values were analyzed with repeated measures analysis of variance, and the Bonferroni multiple comparison test was performed using time-dependent groups and storage methods. RESULTS: In the time-dependent groups, methacrylate-based sealer-coated soft liners exhibited a significant increase in roughness (1.74-2.09 µm, P<.001), and silicone-based sealer-coated soft liners exhibited a decrease in roughness, but it was not significant (2.16-2.02 µm, P>.05). Therefore, the sealer coating was not effective in reducing surface roughness. Among the time-dependent storage methods, the denture cleanser exhibited an almost significant increase in roughness (1.83-1.99 µm, P=.054). Coca-Cola and artificial saliva did not show a significant difference (P>.05). However, a significant decrease in roughness was found with distilled water (P=.02) and air (P<.001). CONCLUSIONS: Statistically significant differences in surface roughness were found among the different types of soft liners. The sealer coating had no significant effect, and denture cleanser slightly increased the surface roughness. Contrary to expectations, the roughness did not increase in all groups over time.

The Effect of Sandblasting, Er:YAG Laser, and Heat Treatment on the Mechanical Properties of Different Zirconia Cores.

OBJECTIVE: The purpose of this study was to evaluate the effect of surface and heat treatments on the mechanical properties and phase transformation of yttria-stabilized tetragonal zirconia (Y-TZP) materials. BACKGROUND DATA: Zirconia is exposed to several treatments during dental application process. Knowing the effect of applied treatments on zirconia is essential for clinical success. MATERIAL AND METHODS: Forty disk specimens of Zirkonzahn (Z) and DC-Zirkon (DC) materials were fabricated. The specimens were randomly divided into four groups according to surface [control, sandblasting, Erbium: Yttrium Aluminum Garnet (Er:YAG) laser irradiation] and heat (firing) treatments. The surface roughness (Ra, µm) was measured using a surface profilometer. The relative amount of the transformed monoclinic (m) phase was analyzed by X-ray diffractometry (XRD). Biaxial flexural strength was tested using piston-on-three-ball technique. The data were analyzed with the Kruskal-Wallis H test with Bonferroni correction, and the Mann-Whitney U test was used for pairwise comparisons. RESULTS: There were no significant differences in surface roughness among the treated groups (p > 0.05), whereas sandblasting showed higher surface roughness than other treatments for both materials. Scanning electron microscopic (SEM) analyses revealed changes in surface morphology after surface treatments, especially in laser groups with the formation of cracks, and in sandblasting groups with the formation of microretentive grooves. The greatest amount of the monoclinic phase was measured after sandblasting (8.13%) for Z and (19.8%) for DC. The monoclinic phase reverted to the tetragonal phase after heat treatment. Heat treatment groups showed significantly lower flexural strength than other treatments (p < 0.05). CONCLUSIONS: Heat and surface treatments influenced the mechanical properties of zirconia ceramic. The biaxial flexural strength and crystalline phase of materials decreased after heat treatments.

Effect of repair resin type and surface treatment on the repair strength of polyamide denture base resin.

The purpose of the present study was to evaluate the effects of different repair resins and surface treatments on the repair strength of a polyamide denture base material. Polyamide resin specimens were prepared and divided into nine groups according to the surface treatments and repair materials. The flexural strengths were measured with a 3-point bending test. Data were analyzed with a 2-way analysis of variance, and the post-hoc Tukey test (α=0.05). The effects of the surface treatments on the surface of the polyamide resin were examined using scanning electron microscopy. The repair resins and surface treatments significantly affected the repair strength of the polyamide denture base material (p<0.05); however, no significant differences were observed interaction between the factors (p>0.05). The flexural strength of the specimens repaired with the polyamide resin was significantly higher than that of those repaired with the heat-polymerized and autopolymerizing acrylic resins.

Effects of tongue movements on lingual sulcus depth while border molding in mandibular complete dentures.

BACKGROUND: In general, people speak and swallow frequently in their daily lives rather than making exaggerated tongue movements. AIM: The aim was to compare the effect of tongue movements on lingual sulcus depth, during the border molding process of impression making of mandibular complete dentures. SETTINGS AND DESIGN: In total, 32 double master impressions were made. One of these pairs was obtained by allowing the patient to swallow and the other by enabling the tongue to make excessive movements. MATERIALS AND METHODS: Measurements were taken from different regions of the lingual sulcus by determining the length of the parallel lines drawn from fixed points marked on the residual ridge crest to the deepest point of the alveolingual sulcus. These measurements were performed using a RMI three-dimensional measurement system. STATISTICAL ANALYSIS USED: Data were compared using the paired t-test (alpha = 0.05). RESULTS AND CONCLUSION: The high value found in casts with border molding, while swallowing was statistically significant in vertical and horizontal directions of the anterior lingual sulcus region (<0.001), vertical direction of the middle lingual sulcus region (MLSR) (<0.05) and horizontal direction of the retromylohyoid and MLSR (<0.05). According to the paired t-test, the mean differences between the 32 casts were statistically significant (<0.001). Within the limitations of this study, the swallowing in the vertical and horizontal directions provided higher values compared to the excessive movement of the tongue.

Evaluation of the flexural strength of dual-cure composite resin cements.

The aim of this study was to evaluate of flexural strength of some adhesive resin cements. Three dual-cure composite resin cements (Nexus 3; Variolink II, Panavia F) were prepared. The manufacturer's mixing directions for the cements were followed. Adhesive resin cement was mixed, placed in the rectangular portion of the mold. Fifteen specimens were prepared for each cements. The cements were light-activated with light lamp for 40 s on both and top and bottom surfaces. The each cement specimens were divided into three groups according to time of storage and stored in distilled water for 24 h, 15, and 30 days. Total 45 specimens were stored at 37°C (98.6 0F) in distilled water for 24 h, 15, and 30 days prior to tests. The flexural strength was tested with a universal testing machine at a crosshead speed of 0.5 mm/min (0.02 in.) The maximum load was recorded as MPa. The results were analyzed by Analysis of Variance and Duncan test. The Panavia F resin cements content Bisphenol A was showed the highest flexural strength (80.80 MPa) (11.71 ksi) for 24 h. The lowest flexural strength was observed in Nexus 3 (51.00 MPa) (7.39 ksi). It was found significant interaction of material and time (p < 0.05). The types of cement and time of storage was statistically significant on the flexural strengths (p < 0.001).

The effect of staining solutions on the color stability of provisional prosthodontic materials.

OBJECTIVES: The aim of this study was to evaluate the effects of staining solutions on the color stability of self-cure provisional resin materials. METHODS: The specimens were prepared for each of three auto-polymerized bis-acryl resin and auto-polymerized methyl methacrylate provisional resin material. The baseline color values were measured with a colorimeter according to the CIE L(*)a(*)b(*) color scale. After the first measurement (T(0)), specimens were placed in staining solutions (coffee, coca-cola, burn and distilled water for control group) and the other measurements were taken after 24h (T(1)), 1 week (T(2)) and 4 weeks (T(3)). RESULTS: Data were analyze statistically by (a) repeated measures (ANOVA), (b) one and two way ANOVA, and (c) Tukey HSD multiple comparison tests. At the 24h immersion period, the post hoc analysis indicated that AccessCrown-coffee revealed the highest ΔE(*) values (4.4). At the second immersion period (1 week), Structur2 SC-coffee had the highest ΔE(*) values compared with other materials (5.4). CONCLUSIONS: The degrees of discoloration were increased with immersion time. The methylmethacrylate resin was more resistant to discoloration than bis-acryl resins. After immersion for 30 days, the coffee solution resulted in unacceptable discoloration for all the tested materials.

Effects of different solutions on the surface hardness of composite resin materials.

In this study, the surface hardness of five light-cured composite resins were evaluated, namely: filled (Estelite), nanofil (AElite), unfilled (Valux Plus), hybrid (Tetric ceram), and Ormocer-based (Admira) composite resins. The microhardness values of composite specimens were measured at the top and bottom surfaces after 24 hours or 30 days of immersion in different solutions (tea, coffee, Turkish coffee, mouthwash, cola, and distilled water). Comparisons were made with univariate analysis of variance and Duncan's multiple range test. It was found that rough specimens of reinforced nano-hybrid composite material immersed in cola for 30 days had the lowest surface hardness (33.20), whereas rough specimens of hybrid composite material immersed in cola for 24 hours had the highest surface hardness (156.00). In both tea and coffee, the top surfaces tended to be harder than the bottom ones. In conclusion, the five different materials exhibited different hardnesses, and that the hardness values of composite materials were statistically different in different immersion solutions.

Radiological evaluation of changes in the gonial angle after teeth extraction and wearing of dentures: a 3-year longitudinal study.

OBJECTIVE: The aim of this study was to evaluate the gonial angle measurements of 20 adult patients made from panoramic radiographs and to assess differences from dentate state to edentate state-with dentures. STUDY DESIGN: A total of 100 panoramic radiographs of 20 patients were evaluated, and gonial angle sizes were measured. Panoramic radiographs were made while the patients were dentulous and in the first month, sixth month, first year, and third year after tooth extraction and wearing dentures after a 2-3-month healing period. All radiographs used in this study were made with the same panoramic machine by the same person. Gonial angles were measured by tracing a line on panoramic radiographs tangential to the most inferior points at the gonial angle and the lower border of the mandibular body and another line tangential to the posterior borders of the ramus and the condyle. RESULTS: Difference in size of the gonial angle was found for both sides between continuous measurements. The gonial angle values tend to increase in both sides after tooth extractions. After the third measurement for both sides, the values start to decrease. CONCLUSION: After wearing denture for 3 years, a statistically significant decrease was found in the gonial angle values according to the edentulous state (P < .05).

A comparison of the fracture resistance of core materials using different types of posts.

OBJECTIVE: The purpose of this in vitro study was to determine the fracture resistance of 3 core materials (silver amalgam, resin composite, glass-ionomer cement) supported by 1 custom cast post (nickel-chromium alloy) and 2 prefabricated posts (Radix and Safix posts). METHOD AND MATERIALS: A sum of 45 recently extracted single-rooted human incisors and canines were placed in 0.5% sodium hypochlorite. Before the experiments, the anatomic crowns of teeth were removed below the cementoenamel junction to obtain a standard root length. The roots were endodontically treated by the manual condensation method. The teeth were randomly divided into 9 groups with 5 samples per group. The posts were luted in the corresponding root canals with zinc polycarboxylate cement. Each core reconstruction was prepared with diamond instruments, and the height of cores formed was 6.0 mm. The tooth and post-core combinations were mounted in acrylic resin blocks. Each tooth and post-core combination was placed in a special jig at a 45-degree angle to the buccal/lingual axis and then subjected to a load on an electronic pull-tension-compression testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed using one-way analysis of variance. RESULTS: The resistance to fracture for prefabricated posts was significantly higher for resin composite core than for the other post-core combinations (P <.001). For prefabricated posts, the composite core and amalgam core materials were significantly stronger than the glass-ionomer core material (P <.001). The differences between the core materials were statistically significant (P <.001). CONCLUSION: The glass-ionomer core with custom post was the weakest post-core system, while the prefabricated posts (Safix and Radix) with resin composite and amalgam cores were the strongest post-core systems.

Evaluation of the solubility of dental cements in artificial saliva of different pH values.

The aim of this study was to determine the solubility of dental cements in artificial saliva of different pH values. A total of 180 specimens--20 specimens (20 mm diameter x 1.5 mm thickness) for each dental cement-were prepared. After the specimens were weighed, they were set in the media with different pH values. After 24 hours, 72 hours, seven days, and 28 days, the specimens were taken out, dried in a desiccator, and re-weighed. Percentage of solubility at each time period was calculated as 100 per cent times weight loss divided by the initial weight of the specimen. Analysis of variance and LSD multiple comparison test were applied. It was found that cement type, storage time, and medium pH exerted statistically significant (p<0.001) effects on solubility. Among the tested cement types, zinc phosphate cement (Adhesor Carbofine) presented the highest solubility. In terms of medium pH, the cements seemed to be most stable in the medium with pH 7.

The investigation of solubility values,water sorption and bond strength of auto-polymerising and heat-polymerising acrylic resin materials.

In this study the solubility, water sorption and the bond strength of auto-polymerising and heat-polymerising acrylic resins were investigated. Two auto-polymerising and five heat polymerising acrylic resin materials were used for this study. Thirty-five specimens were prepared (50 mm in diameter and 0.5 +/- 0.01 in thickness) for water sorption and solubility tests. In order to examine bond strength, specimens were prepared in 2.5 x 10 x 64 mm dimensions. These specimens were repaired with QC and major repair acrylic. Some specimens were kept in distilled water for 50 hours, and others for 30 days. The strength of the bond was measured by a Pull-Compress device. As a result of the variance analysis; water sorption, solubility and the bond strength between acrylic resins were identified as statistically significant (P < 0.001). The water sorption of the major acrylic resin specimens were lower than the other materials (P < 0.001).

The effect of different solutions on the bond strength of soft lining materials to acrylic resin.

In this study, we investigated the effect of different solutions--coffee, tea, Turkish coffee, artificial saliva, mouthwash, denture cleanser, and distilled water--on the bond strength of soft lining materials (one acrylic- and three silicone-based) to acrylic resin. Acrylic specimens (40x10x10 mm) were prepared for the bond strength test. The specimens were stored in different solutions and tested after 24 hours, seven days, and 30 days. Using analysis of variance, the bond strength of soft lining materials to acrylic resin was found to be related to the type of material, storage time, and storage solution. Visco-gel had the lowest bond strength to cured acrylic resin, where its strength ranged from 0.149 MPa to 0.784 MPa. The bond strength of Visco-gel was also found to increase with time. Molloplast-B and Ufi Gel P demonstrated better bond strength than Visco-gel and Mollosil.

Determination of the occlusal vertical dimension: use of maxillary and mandibular posterior teeth measurement in edentate subjects.

Determination of the occlusal vertical dimension (OVD) is one of the most important steps in making dentures. Various techniques have been used to make these measurements. Unfortunately, there is no universally accepted method available for clinical use. The aim of this study was, therefore, to develop a technique to determine OVD for complete dentures by using parameters obtained from natural posterior dentition. The silicon impressions were made from the posterior region of the mouth from dentate patients in maximum intercuspation. The measurements were made to determine the distance between the depth of maxillary and mandibular mucobuccal reflections and the relations of the posterior teeth to the mucobuccal reflections. The mean distance between the mucobuccal reflections was 36.14 mm. in the first premolar region, 35.57 mm. in the second premolar region and 32.44 mm. in the first molar region for the right side. The findings of this study can be used as a guide for the construction of record bases and occlusal rims and for establishing the occlusal vertical dimension in edentulous patients.