Comparison of the Retention of Conventional and Polyvinyl Siloxane Matrix Materials with Different Patrices for Implant-Retained Overdentures: An In Vitro Study.

PURPOSE: To compare the retention forces of implant overdenture patrices (ball, bar, and TiSi.snap) to conventional (O-ring, metal housing, and clip) and polyvinyl siloxane (PVS)-based silicone (retention.sil 200, 400, and 600; Mucopren Soft; and GC Reline Soft) matrix materials. MATERIALS AND METHODS: Two implant analogs, in which the patrices were to be placed, were embedded parallel to each other in polyethylene blocks, and the matrices were placed in heatpolymerized acrylic blocks that were fabricated as overdentures. Ten samples were prepared for each attachment type, and 180 samples were obtained from 18 groups. All samples were placed in a chewing simulator for occlusal force application and for insertion and removal of the pieces. Retention measurements were performed with a universal testing device at the initial (10 cycles), simulated first-year (1,825 cycles), and simulated second-year (3,650 cycles) periods, assuming that the patients would insert and remove their overdenture five times daily. RESULTS: Loss of retention occurred in all the attachment systems at the end of 3,650 cycles (P < .05). The PVS matrix materials showed less retention than the O-ring and metal matrices when a ball patrix was used, while they had higher retention than bar clips when the Hader bar patrix was used (P < .05). Among the PVS matrix materials, retention.sil 200 produced the lowest retention values, whereas retention.sil 600 generated the highest. CONCLUSION: PVS matrix materials show higher retention than that achieved by yellow plastic bar matrices. However, these materials exhibit lower retention than with plastic and metal matrices of ball abutments.

Technique for Converting A Fractured Implant Locator Abutment to A Custom Implant Cast Post and Core.

This technique article describes an efficient, cost effective and time saving procedure using the fractured abutment as a custom cast post and core when an overdenture abutment is fractured and attempts to retrieve the fractured segment fail.

Reverse Torque Values of Abutment Screws After Dynamic Loading: Effects of Sealant Agents and the Taper of Conical Connections.

The purpose of this in vitro study was to evaluate the influence of taper angle in internal conical connections of implant systems and the application of chlorhexidine gel as an antibacterial agent or polyvinyl siloxane sealant on reverse torque values of abutment screws after dynamic loading. Four implant systems having different taper angles (5.4°, 12°, 45°, 60°) were tested in this study. Test specimens were divided into 3 groups: control (neither chlorhexidine gel filled nor silicone sealed), 2% chlorhexidine gel filled, and silicone sealed. The samples were subjected to a dynamic load of 50 N at 1 Hz for 500 000 cycles before reverse torque measurements. The taper angle of conical connections presented a quantitative positive correlation between the degree of the taper angle and the percentage of tightening torque loss. However, it was significant only between 60° angled connection and others except for the sealant applied groups (P = .013 for control groups and P = .007 for chlorhexidine groups). The percentages of decrease in torque values of silicon sealant-applied specimens were significantly higher than both the control and chlorhexidine groups (P values are .001, .002, .001, and .002, respectively, according to increasing taper angles), but the percentage of decrease in torque values due to chlorhexidine application was not statistically significant when compared with control groups. Gel form chlorhexidine application as an antibacterial agent does not significantly affect the implant-abutment connection stability under dynamic loads. Polyvinyl siloxane sealant may cause screw loosening under functional loads.

The Influence of the Gonial Angle on the Initial Biomechanical Stability of the Plate Osteosynthesis in Polyurethane Mandibles With Angle Fractures.

The aim of the present study was to examine the biomechanical stability of the mandibular angle fractures (MAF) fixated with standard titanium miniplates in polyurethane models with different gonial angles (GA). Three custom molds were prepared for 3-dimensional printed mandibles with low, normal and high GA. Twenty polyurethane replicas were cast per group and standard MAFs were created on each sample. Fractures were stabilized with 1 4-hole standard titanium miniplate inserted over the superior alveolar border. Half of the samples were subjected to molar loading and the other half to the incisal loading up until 150 N force magnitude. The load-displacement curves and the horizontal moment arms were recorded and analyzed. The samples with high GA demonstrated greater displacement than those with normal and low GA during molar loading (P < 0.05 for both). After correcting for the effects of the moment arm, the incisal loading also resulted in higher mean displacement in the high GA group than the others (P < 0.05 for both) and the normal GA samples showed higher displacement after 100 N level compared to those in low GA (P < 0.05). Within the limits of this in vitro study, it can be concluded that the MAFs of the polyurethane mandibles with high GA fixated with 1 standard monocortical plate are more likely to demonstrate higher displacement values under the effects of the molar and incisal loadings than do the mandibles with normal and low GA.

Wear resistance and microhardness of various interim fixed prosthesis materials.

The aim of the present study is to evaluate the wear resistance and microhardness of various interim fixed prosthesis materials with different chemical compositions and curing methods. One heat-cured and four self-cured acrylic resins, and three self-cured, one light-cured, and one dual-cured composite-based materials were tested. For microhardness, samples from each group were tested after storing either at 37°C in artificial saliva for 7 days, followed by thermocycling, or in distilled water solution at 37°C for 24 h. For the evaluation of wear, the remaining samples were evaluated using a 3D scanner and a surface analysis program before loading in the chewing simulator and after every 10,000 cycles. There was a significant difference in wear behavior among the materials tested at both 10,000 and 20,000 cycles (P < 0.001). Microhardness and wear resistance were significantly different between acrylic and composite materials.

A Comparison of the Color Stability of Conventional and CAD/CAM Polymethyl Methacrylate Denture Base Materials.

OBJECTIVE: The aim of this study was to evaluate the color stability of a heat polymerized resin, an auto-polymerizing resin, a urethane dimethacrylate resin and a CAD/CAM PMMA block resin stored in different storage media. MATERIALS AND METHODS: 60 disc-shaped specimens (15×2 mm) were fabricated for each group. A total of 240 disc-shaped specimens were thermal-cycled for 5,000 cycles. Then specimens were randomized into 4 groups (n= 15) according to storage media: coffee, coke, red wine and distilled water (control group). The color measurement of each sample was performed using a spectrophotometer before and after storage (after 7 and 30 days), and color changes (ΔE) were calculated. RESULTS: All the denture base materials demonstrated dissimilar color changes after stored in the different storage media in both evaluation stages. In all storage media, CAD-CAM denture base resins showed the minimum in color change. In all denture base resins, red wine showed a higher degree of color change than coke or coffee. CONCLUSION: The color stability of CAD-CAM denture base resins is better than any of the other kind of denture base resins. The color change values of all groups except Eclypse stored in red wine had clinically detectable values.

Effects of Denture Base Thicknesses and Reinforcement on Fracture Strength in Mandibular Implant Overdenture with Bar Attachment: Under Various Acrylic Resin Types.

OBJECTIVE: This study aimed to assess the effect of reinforcement, denture base thickness, and acrylic resin types on dynamic and static fracture strength in mandibular implant overdentures with bar attachment. MATERIALS AND METHODS: One hundred and eight experimental mandibular implant overdentures with bar attachments were fabricated in three main groups, namely unreinforced (control: C), reinforced with unidirectional glass fibers (FR), and Co-Cr cast metal (MR). Each group included denture bases of 2-, 3-, and 4-mm thicknesses and produced with conventional (CA) and high-impact acrylic (HIA) resins. Specimens were thermocycled (5,000 times, 5-55°C) then subjected to a 400,000 cyclic load regime. Unbroken specimens were then loaded until fracture by a universal testing machine. Differences in mean fracture resistance among the groups were compared using the one-way analysis of variance (with post hoc Tukey's honestly significant difference test) and Student's t-tests (α = 0.05). RESULTS: Fracture strength increased significantly when the denture base thickness was increased (p = 0.001). The 2-mm denture base thickness was not enough for reinforcement. The fracture strength of the FR groups was significantly higher than other groups for 3- and 4-mm thicknesses (p = 0.001). The fracture strength of the HIA resin was significantly higher than CA resin in FR groups (p = 0.029 and p = 0.001). MR groups showed the weakest fracture strength. CONCLUSIONS: The 2-mm denture base thickness had sufficient fracture strength without reinforcement and a positive relationship between acrylic resin thickness and fracture resistance was found.

The influence of steam cleaning procedures on the surface roughness of commonly used type III dental stone for the fabrication of removable dentures.

OBJECTIVE: This study investigated the possible detrimental effects of steam treatment on the surface of type III dental stone, which is a common laboratory material used for the construction of removable dentures. MATERIAL AND METHODS: Forty dental stone specimens were prepared and divided into four groups (A, B, C and D), and group A was used as the control group. The other groups were treated with steam from a standard distance for varying durations (30, 60 and 120 s). RESULTS: The duration of steam cleaning significantly increased Ra values (F = 63.150, p = 0.000). Similarly, the duration of steam application was directly correlated with the weight changes (F = 17.721, p = 0.000). A significant amount of dental stone can be removed from the surface while treating with steam. CONCLUSION: These studies demonstrated that expanded periods of steam cleaning cause weight loss and abrade the surface of type III dental stones; therefore, these devices should be used with caution during denture fabrication procedures.

Flexural properties of a light-cure and a self-cure denture base materials compared to conventional alternatives.

PURPOSE: A new light curing urethane dimethacrylate and a cold curing resin with simpler and faster laboratory procedures may have even improved flexural properties. This study investigated the 3-point flexural strengths and flexural moduli of two alternate base materials. MATERIALS AND METHODS: A cold curing resin (Weropress) and a light curing urethane dimethacrylate base material (Eclipse). Along with Eclipse and Weropress, a high impact resin (Lucitone199) and three conventional base materials (QC 20, Meliodent and Paladent 20) were tested. A 3-point bending test was used to determine the flexural strengths and flexural moduli. The mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations for each group were analyzed by means of one-way analysis of variance (ANOVA) (with mean difference significant at the 0.05 level). Post hoc analyses (Scheffe test) were carried out to determine the differences between the groups at a confidence level of 95%. RESULTS: Flexural strength, displacement and force maximum load values of Eclipse were significantly different from other base materials. Displacement values of QC 20 were significantly different from Lucitone 199 and Weropress. CONCLUSION: The flexural properties and simpler processing technique of Eclipse system presents an advantageous alternative to conventional base resins and Weropress offers another simple laboratory technique.

Reliability and comparison of two facial measurements to detect changes of occlusal vertical dimension in complete denture wearers.

BACKGROUND: Facial measurements are frequently used to determine OVD. However, the reliability of neither the method nor the chosen landmarks has been cleared yet. OBJECTIVE: This study compares the reliability of two facial measurements, subnasal (SN) to chin (C) and tip of the nose (TN) to C, for determining occlusal vertical dimension (OVD). MATERIALS AND METHODS: Thirty edentulous subjects with adequate neuromuscular co-ordination, without signs and symptoms of temporomandibular disorders and who had been wearing complete dentures for at least 5years were enrolled. A modified central bearing device was used to alter the OVD and facial measurements were made with a digital caliper. Student's t-test was used to compare the two measurements. Interobserver and intraobserver reliability were evaluated with Spearman's rho correlation test. RESULTS: TN-C distance had an improved correlation with the changes in intraoral alterations than SN-C distance. While the means of the changes in facial measurements were in good agreement with the intraoral alterations, the ranges were wide. Both interobserver and intraobserver reliability of the measurements were high. CONCLUSION: While facial measurement is not a good predictor of OVD, TN-C distance appears to be more reliable than SN-C distance.

An adult case of temporomandibular joint osteoarthritis treated with splint therapy and the subsequent orthodontic occlusal reconstruction.

Herein we report treatment for a 19-year-old female patient with severe osteoarthritis of the temporomandibular joint. The patient had severe open bite with a Class II molar relationship. She had limited mouth opening and pain. Clinical examination and magnetic resonance imaging revealed that she had anterior disc displacement without reduction. By splint therapy, limited mouth opening and pain was eliminated, but an anterior open bite developed after the treatment. By orthodontic treatment, an acceptable occlusion was achieved with a Class I molar relationship.

Prosthetic rehabilitation of a Crouzon patient: A case report.

Crouzon syndrome is a rare genetic disorder, which can be defined as a variation of craniofacial dysostosis caused by the premature obliteration and ossification of two or more sutures. The growth pattern results in pseudoprognathism and malocclusions including an overcrowded or a widely spaced dentition. Specifically maxillary arch is narrow, high, and V-shaped. Cleft palate and bifid uvula are other possible features in the oral cavity. This report describes a non-surgical treatment model to overcome the remaining significant Class III intermaxillary relation and excessive tooth loss to recover function and aesthetics for a 25-year-old Crouzon patient.