The effect of repetitive firings on the color of an alumina ceramic system with varying ceramic shade and thickness.

OBJECTIVE: The color of all-ceramic restorations is one of the main criteria to achieve esthetical success. Many factors such as ceramic thickness, condensation techniques, firing temperature, and numbers can affect the final color of restoration. The purpose of this study was to investigate the color changes in alumina-based ceramic system according to ceramic shade and thickness during the multiple firings. MATERIALS AND METHODS: Sixty disc-shaped specimens with two different veneering porcelain shades (A1 or A3), and with three different ceramic thicknesses (0.5, 1, or 1.5 mm), were fabricated from an alumina-based ceramic system. Multiple firings (3, 5, 7, or 9 firings) were performed, and color changes (ΔE00 ) were determined using a spectrophotometer. Repeated-measures ANOVA were used to analyze the data. The Duncan test was used for multiple comparisons (α = .05). RESULTS: The L*a*b* values of the specimens were affected by the number of firings (3, 5, 7, or 9), veneering ceramic shades (A1 or A3) and veneering ceramic thicknesses (0.5, 1, or 1.5 mm). Significant interactions were present between the number of firings, veneering ceramic shade, and veneering ceramic thickness for L* (p < .001), a* (p < .001), and b* (p < .001) values. CONCLUSIONS: No statistically significant color change was observed between 3rd and 9th firings. CLINICAL SIGNIFICANCE: Veneering ceramic shade, veneering ceramic thickness, and number of firings should be carefully considered to obtain an acceptable color match of the definitive restorations.

Effects of Low-Profile Stud Attachment Configurations on Stress Distribution Characteristics of Implant-Retained Overdentures.

PURPOSE: Implant-retained mandibular overdentures are a proven treatment modality for edentulous patients. Low-profile stud attachments may allow divergence between the abutments up to 40 degrees. The purpose of this study was to investigate load transfer characteristics of various locations and nylon male configurations of low-profile stud attachment-retained overdentures. MATERIALS AND METHODS: Three tapered dental implants were placed into three photoelastic mandibular models. The center implants were placed vertically onto the midline, and the distal implants were inclined 20 degrees corresponding to centralized implants. Three different distances (11, 18, and 25 mm) between the centralized and the distal implants were set on the models. Low-profile stud attachment (Locator)-retained mandibular overdentures were fabricated for each photoelastic model. Five different nylon male configurations of this stud attachment were established. The load transfer characteristics of the configurations were tested using a circular polariscope. RESULTS: The observed stress levels for the tested configurations were moderate except for group 25C (photoelastic model with 25-mm interimplant distances and clear nylon male), which illustrated a high stress level. For the 11-mm photoelastic model, little or no discernible stress was noted around the dental implants for group 11R (red nylon male), group 11G (green nylon male), and configurations of clear and red or green nylon males (group 11CR [clear and red nylon males] and group 11CG [clear and green nylon males]). CONCLUSION: The applied loads were distributed to the supported dental implants and denture-bearing areas for tested designs. Equitable load distribution and less stress may be gathered using nylon males for angulated implants (red and green) when dental implants are placed inclined.

Load Transfer Characteristics of Three-Implant-Retained Overdentures with Different Interimplant Distances.

PURPOSE: Implant-retained overdentures are the first choice of rehabilitation for edentulous mandibles. Bone morphology and anatomical landmarks may be influenced by the location and angulation of implants and distances between the implants. The purpose of this study was to investigate stress distribution characteristics and to compare stress levels of three different attachment designs of three-implant-retained mandibular overdentures with three different interimplant distances. MATERIALS AND METHODS: Three photoelastic mandibular models with three implants were fabricated using an edentulous mandible cast with moderate residual ridge resorption. The center implants were embedded parallel to the midline, and the distal implants were aligned at a 20-degree angulation corresponding to the center implants. Distances between the center and distal implants were set at 11, 18, and 25 mm at the photoelastic models. Bar, bar-ball, and Locator attachment-retained overdentures were prepared for the models. Vertical loads were applied to the overdentures, and stress levels and distribution were evaluated by a circular polariscope. RESULTS: The greatest observed stress level was moderate for the tested overdenture designs. The Locator attachment system showed the lowest stress level for the 11-mm and 25-mm photoelastic models. The bar attachment design transmitted less stress compared with the other tested designs for the 18-mm photoelastic model. CONCLUSION: Stresses were observed on the loaded side of the photoelastic models. The lowest stress was found with the Locator and bar attachments for the 11-mm photoelastic model, which transmitted little or no discernible stress around the implants.

Load Transfer Characteristics of Various Designs of Three-Implant-Retained Mandibular Overdentures.

PURPOSE: Many different attachment systems (eg, bars, studs, magnets, telescopic copings) have been used to retain overdentures. The current study aimed to investigate the load transfer characteristics and to compare the stress levels of four attachment designs for mandibular overdentures retained by one central implant and two inclined distal implants. MATERIALS AND METHODS: Photoelastic mandibular models fabricated with three screw-type implants (Tapered Screw-Vent, 3.75 × 13 mm) were placed in the parasymphyseal area. The center implant was vertically oriented to the midline, and the other implants were embedded in the canine areas with a 20-degree angulation relative to the center implant. Four overdentures with different attachment designs (bar, bar/ball, bar/distally placed Rk-1s, and Locators) were studied in the context of this model. Vertical loads (100 N) were applied to the central fossa of the right first molar area of each overdenture. Stress levels that developed in the denture-bearing areas and around the implants were observed photoelastically and evaluated visually. RESULTS: The studied attachment designs showed low and moderate stress levels. The greatest stress was found with the bar/ball design, while the lowest stress levels were observed with the Locator attachment design. CONCLUSION: Stresses were concentrated on the loaded side for each design. All tested designs experienced moderate stress around the posterior edentulous area. None of the designs experienced more than moderate stress. The lowest stress was noted with the Locator attachments, which transmitted little discernible stress around the implants.

A technique for retrofitting a metal ceramic crown to an attachment-retained removable partial denture: a clinical report.

In dental applications, precision attachments have been used to retain removable partial dentures (RPDs) for several decades. Various types of extracoronal attachments are commonly used in combination with fixed partial dentures and RPDs to achieve retention and stability. Fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention are common reasons for a failed attachment-retained RPD. Another complication of metal ceramic crowns with precision attachment is decementation of the crowns. When fixed components of the attachment-retained RPD fail, the traditional treatment approach requires remaking both the fixed and removable components of the attachment-retained RPD. This technique describes retrofitting of a metal ceramic crown to a resilient attachment-retained RPD.

Microleakage of inlay ceramic systems luted with self-adhesive resin cements.

PURPOSE: To evaluate the microleakage of Cerec 3, IPS e.max Press, and Turkom-Cera inlays cemented with three self-adhesive resin cements. MATERIALS AND METHODS: Ninety standardized class III MOD cavities were prepared in intact human mandibular third molars. Ceramic inlays were fabricated according to the manufacturer's instructions and were cemented using three self-adhesive resin cements (RelyX Unicem, Smartcem 2, and SpeedCEM). The specimens were stored in distilled water at 37°C for 24 h and subjected to 1000 thermocycles in water between 5°C and 55°C with a dwell time of 30 s. Subsequently, the specimens were subjected to 100,000 cycles of mechanical loading of 50 N at 1.6 Hz in 37°C water. The specimens were immersed in 0.5% basic fuchsine for 24 h and were sectioned using a low-speed diamond blade. The percentage of dye leakage at the tooth/restoration interface was measured and compared by Kruskal-Wallis tests with Bonferonni correction and Mann-Whitney U-tests at a significance level of p<0.05. RESULTS: Microleakage at the RelyX Unicem interface was lower than that with Smartcem 2 and SpeedCEM resin cements (p<0.05). Microleakage of the Turkom-Cera system was higher than Cerec 3 and IPS e.max Press ceramic inlays (p<0.05). CONCLUSIONS: Regardless of the ceramic system and self-adhesive resin cement used, dentin margins were associated with higher microleakage than enamel margins.

Effects of implant angulations and attachment configurations on the retentive forces of locator attachment-retained overdentures.

PURPOSE: The aim of this study was to evaluate the effects of different implant angulations and attachment configurations on the retentive forces of locator attachment-retained overdentures over a simulated time period of 6 months. MATERIALS AND METHODS: Two acrylic resin models (models 1 and 2) were fabricated to represent an edentulous mandible. In model 1, the midline implant (in the central region) was vertical and the other two implants (in the canine regions) were 20 degrees divergent from the midline, reaching a total divergence of 40 degrees. In model 2, all three implants were vertically oriented, perpendicular to the occlusal plane and parallel to each other. Three-point vertical pull-out forces were employed in a universal testing machine at a constant crosshead speed of 50 mm/min after overdenture construction and a simulation of 6 months of repeated insertions/removals of the overdenture. Locator attachments with different male combinations and bar and clip attachments were tested in model 1. Clear locator attachments and bar and clip attachments were tested in model 2 and served as controls. RESULTS: The initial retentive forces of all attachments in both models ranged from 26.58 to 62.05 N, whereas the initial retentive forces of the attachments for only model 1 ranged from 49.58 to 62.05 N. The highest retention value was recorded for clear green locator attachments and the lowest for hader bar yellow clip attachments. Locator attachments showed higher retention values than hader bar yellow clip attachments. CONCLUSION: All attachment systems demonstrated a decrease in retention over time. Locator attachments provided better retention than hader bar yellow clip attachments. The highest retention values were obtained when green male locators were used in combination with male attachments.

Effect of the number of supporting implants on mandibular photoelastic models with different implant-retained overdenture designs.

PURPOSE: The purpose of the study was to evaluate the effect of the number of supporting implants and different retentive mechanisms on load transfer characteristics of mandibular overdentures. MATERIALS AND METHODS: Two photoelastic models of edentulous mandibles were fabricated having two and four cylindrical implants (Calcitek, 4 × 13 mm) embedded in the parasymphyseal area. Four attachment systems were evaluated: single anchor attachment (ERA), bar-clip, bar with distally placed ball attachments, and bar with distally placed extracoronal rigid attachments (Easy Slot). A 133 N vertical force was applied unilaterally to the central fossa of the right first molar. The resulting stresses of the models were observed and recorded photographically in the field of a circular polariscope. RESULTS: The highest stresses were observed with the bar with distally placed extracoronal rigid attachment (Easy Slot) design, followed by bar-ball, bar, and the single anchor attachment (ERA) for both models. The lowest stress was observed with the single anchor attachment (ERA) design for both models. There were slight differences in stress values around implants in both models. CONCLUSIONS: For all tested attachments on both models, the stress was concentrated on the ipsilateral implant. The bar-clip system allowed the distribution of load to all supporting implants in both models. Although the highest stress level observed with all attachment systems was moderate, the bar-Easy Slot attachment showed the highest stresses. The lowest stress was observed with the single anchor attachment (ERA) design for both models. Varying the number of implants had no significant effect on stress values around supporting implants.

Comparison of internal fit between implant abutments and cast metal crowns vs laser-sintered crowns.

AIM: A common problem related to cemented single crowns is the internal misfit, which may cause inadequate retention, especially when seated on the implant abutment. The aim of this study was to compare the internal fit of Co-Cr crowns using a traditional lost-wax casting technique from laser-sintered Co-Cr alloy crowns. MATERIALS AND METHODS: Twelve metallic crowns per each technique were fabricated. The effect of the thickness of cement, originated internal gap was evaluated. Crowns were cemented on the implant abutments with resin cement, and the internal fit of crowns was measured at five areas with an optical microscope. The data were analyzed, and the means were compared with a t-test (p<0.05). RESULTS: The internal gap width measurements for the laser-sintered group (min. 52.19 ± 11.61 µm and max. 140.01 ± 31.84 µm) indicated the presence of a significantly closed internal gap compared to the crowns obtained through the lost wax method (min. 65.50 ± 9.54 µm and max. 313.46 ± 48.12 µm). CONCLUSION: The fit of the metal crown likely varies with the fabrication technique. The use of techniques that enable the adjustment of crown parameters, such as the laser sintering technique, maintains the desired fit between casting and implant abutments. CLINICAL SIGNIFICANCE: This study investigated which technique affects the internal fit of cemented implant-supported crowns, comparing the use of lost wax casting and laser-sintered metal dental alloys. The results of this study indicate that the use of laser-sintered crowns can improve for crown accuracy.

A simplified technique for solving the transfer problem of implant-supported fixed partial dentures for patients with microstomia.

Techniques for treating a fully or partially edentulous patient with microstomia have been developed to overcome the challenge of accessing the oral cavity. Management of the problems associated with providing implant-supported fixed partial dentures for patients with microstomia has not been well reported. This article describes a solution for the transfer problem that occurs when making an impression of an implant-supported fixed partial dentures for patients with microstomia.

A technique for constructing a new maxillary overdenture to a nonretrievable implant connecting bar.

The most frequent mechanical complications of the bar-implant-retained overdentures are loosening of the bar screws and the need to reactivate the retentive clips. This article describes a technique to construct a new maxillary overdenture to a nonretrievable round-profile implant connecting bar with 2 distally placed attachments. The retainer round-profile bar was nonretrievable due to a worn retaining screw head. Attachment transfer analogs are used to transfer the position of the attachments to the master cast. The technique allows the clinician to construct new overdentures without the need for removal of the implant connecting bar. Reduced chairside time, reduced treatment cost, and increased patient satisfaction are the major advantages of the technique.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations.

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera(™) [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations.

Retention characteristics of different attachment systems of mandibular overdentures retained by two or three implants.

PURPOSE: The purpose of this study was to quantify and compare the retentive forces of five different prosthetic attachment designs on mandibular overdentures retained by two or three implants. MATERIALS AND METHODS: Two photoelastic acrylic resin models of an edentulous mandible were cast. In one model, three implants were aligned parallel to each other and oriented perpendicular to the occlusal plane. The distal implants were placed in the canine regions, with an interimplant distance of 22 mm. In the other model, two implants were placed using the same approach, with an interimplant distance of 22 mm. Five retention mechanisms were studied on both models: a bar with yellow clips, a milled galvanoformed bar, a bar with two clear distal locator attachments, a bar with two distal Ceka attachments, and a bar with clear locator attachments. Ten dentures were fabricated in clear acrylic resin. The specimens were loaded in tension at a crosshead speed of 50 mm/min in a universal testing machine. Five hundred forty cycles of repeated insertions and removals were performed to simulate 6 months of clinical function. RESULTS: Initial retention forces ranged from 23.33 to 54.32 N. Retentive values of the clear locator attachments on the three-implant model were higher than those for other attachments. CONCLUSION: All designs demonstrated a decrease in retention from the initial testing to the final pull-out test. This decrease was significant for all designs.

Fabrication of a fractured mandibular bar-retained implant overdenture without implant-level impression making: a clinical report.

The most frequent mechanical complications of bar-retained implant overdentures (IODs) are fracture of the dentures, loosening of the bar screws, and the need to reactivate the retentive clips. When a bar-retained IOD with an acrylic resin base fractures, the existing bar attachment should be removed to fabricate a new overdenture. So far, no method has been previously described for remaking a fractured mandibular bar-retained IOD without removing the existing bar attachment. This article describes fabrication of a fractured mandibular bar-retained IOD with distally placed ball attachments using attachment transfer analogs. The described technique allows the patient to use the existing overdenture temporarily until the new overdenture is delivered.

A technique for fabrication of an extracoronal attachment-retained removable partial denture to fit an existing fixed partial denture.

Precision attachments have been used for many years to retain removable partial dentures (RPDs). Common reasons for a failed attachment-retained RPD are fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention. When an RPD framework major connector has been fractured, it should be remade. This article describes a technique to remake a fractured mandibular RPD using cast round profile attachment analogs without the need for replacement of the fixed partial denture.

Replacement of a lost removable partial dental prosthesis using ball-attachment analogs: a clinical report.

Attachment-retained removable partial dental prostheses (RPDPs) may be lost. Although in such situations, the RPDP should be remade, no method has yet been described for replacing lost attachment-retained RPDPs. This report describes a method for fabrication of a replacement for a lost maxillary RPDP using ball-attachment analogs.

An alternative impression technique for implant-retained overdentures with locator attachments.

Locator attachments are commonly used for mandibular implant-retained overdentures. This case report presents an alternative mandibular overdenture impression technique that is pressure free.

An alternate pressure-free functional impression technique for implant-retained overdentures.

Overdenture treatment provides an esthetic and functional result that allows proper access for hygiene and maintenance. For implant-retained overdentures to be successful, functional loads must be distributed optimally to the mucosa and the abutments. For this purpose, impressions must record the soft tissue supporting areas simultaneously with accurate registration of the implant components. Usually, finger pressure is used to make functional impressions. This article describes an alternate pressure-free functional impression technique for implant-retained overdentures.

Microleakage of ceramic inlays luted with different resin cements and dentin adhesives.

STATEMENT OF PROBLEM: Despite recent advances in adhesive dentistry, resin cement/dentin adhesive combinations are not able to prevent microleakage in ceramic inlays. Marginal quality of tooth-colored restorations in large Class II cavities is satisfactory in enamel margins, but microleakage in dentin margins remains a concern. PURPOSE: The purpose of this study was to evaluate the microleakage of all-ceramic inlays luted with 2 dual-polymerizing resin cements or 1 autopolymerizing resin cement in combination with different dentin adhesives. MATERIAL AND METHODS: One hundred and twenty extracted human mandibular third molars were used in this study. Teeth were prepared to receive Class II MOD inlays with enamel gingival margins on 1 proximal surface and dentin gingival margins on the other surface. One hundred and twenty prepared teeth were divided into 3 groups of 40; 1 group for each resin cement: RelyX ARC, Variolink II, or Panavia 21. Each of the 3 groups were further divided into 4 dentin adhesive groups; Single Bond, ExciTE DSC, ED Primer, or Admira Bond. Each of the resin cements were used in combination with the 4 dentin adhesives, and IPS Empress ceramic inlays were placed with 12 different cement/adhesive combinations. After 1000 thermal cycles in a 5 degrees -55 degrees C water bath with a dwell time of 30 seconds, all specimens were subjected to cyclic axial mechanical loading. Then the restored teeth were stored in 0.5% basic fuchsin solution for 24 hours. The extent of dye penetration along the margins was measured with a stereomicroscope at x40 magnification. The data were evaluated statistically using repeated-measures ANOVA and Duncan tests (alpha=.05). RESULTS: Microleakage at dentin margins was greater than that at enamel margins (P<.05) for all groups. Variolink II and RelyX ARC resin cements showed significantly lower microleakage results than Panavia 21 with all dentin adhesives in enamel margins. For dentin margins, Variolink II/Admira Bond combination showed the lowest microleakage value in dentin (P<.05). CONCLUSIONS: The overall microleakage at the enamel margins was significantly less than at the dentin margins (P<.05). Panavia 21 showed higher microleakage values than Variolink II and RelyX ARC in enamel margins.

The effect of ceramic thickness and number of firings on the color of two all-ceramic systems.

STATEMENT OF PROBLEM: All-ceramic restorations have been advocated for superior esthetics, and various materials have been used to improve ceramic core strength, but there is a lack of information on how color is affected by different core substructures and fabrication procedures. PURPOSE: The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of lithium disilicate glass-ceramic (IPS e.max Press) and zirconium-oxide (DC-Zirkon) all-ceramic systems. MATERIAL AND METHODS: Thirty disc-shaped specimens, 4 mm in diameter with a 1-mm core thickness, and 0.5-, 1-, or 1.5-mm dentin ceramic thicknesses, were made from each of 2 ceramic systems (n=10). Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade), and data were expressed in CIELAB system coordinates. Repeated measures ANOVA was used to analyze the data (number of firings, ceramic composition, and ceramic thickness) for significant differences. The Tukey HSD test and paired 2-tailed tests were used to perform multiple comparisons (alpha=.05). RESULTS: L*a*b* values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (P<.001), ceramic composition (DC-Zirkon or IPS e.max Press) (P<.001), and ceramic thickness (0.5, 1, or 1.5 mm) (P<.001). Significant interactions were present in L*a*b* values between the number of firings and ceramic composition (P<.001) and between the number of firings and ceramic thickness (P<.001). Significant interactions were present between the number of firings and ceramic thickness and ceramic composition (P<.05) in L* and b* values, but not for the a* value (P=.068). As the ceramic thickness increased, significant reductions in L* values (P<.01) were recorded for IPS e.max Press and DC-Zirkon specimens. For IPS e.max Press specimens, there were significant increases in a* and b* values (P<.01). For DC-Zirkon specimens, significant increases in a* values were observed; however, no significant differences were recorded for b* values. CONCLUSIONS: The analysis revealed that there were significant changes in L*a*b* color data as the number of firings increased, which resulted in perceptual color changes in L*a*b* color parameters.