Showing papers in "Journal of Prosthodontics in 2011"

Epidemiology and etiology of denture stomatitis.

Abstract: Denture stomatitis, a common disorder affecting denture wearers, is characterized as inflammation and erythema of the oral mucosal areas covered by the denture. Despite its commonality, the etiology of denture stomatitis is not completely understood. A search of the literature was conducted in the PubMed electronic database (through November 2009) to identify relevant articles for inclusion in a review updating information on the epidemiology and etiology of denture stomatitis and the potential role of denture materials in this disorder. Epidemiological studies report prevalence of denture stomatitis among denture wearers to range from 15% to over 70%. Studies have been conducted among various population samples, and this appears to influence prevalence rates. In general, where reported, incidence of denture stomatitis is higher among elderly denture users and among women. Etiological factors include poor denture hygiene, continual and nighttime wearing of removable dentures, accumulation of denture plaque, and bacterial and yeast contamination of denture surface. In addition, poor-fitting dentures can increase mucosal trauma. All of these factors appear to increase the ability of Candida albicans to colonize both the denture and oral mucosal surfaces, where it acts as an opportunistic pathogen. Antifungal treatment can eradicate C. albicans contamination and relieve stomatitis symptoms, but unless dentures are decontaminated and their cleanliness maintained, stomatitis will recur when antifungal therapy is discontinued. New developments related to denture materials are focusing on means to reduce development of adherent biofilms. These may have value in reducing bacterial and yeast colonization, and could lead to reductions in denture stomatitis with appropriate denture hygiene.

Evidence-based guidelines for the care and maintenance of complete dentures: a publication of the American College of Prosthodontists.

Abstract: The current rates of edentulism have been estimated to be between 7% and 69% of the adult population internationally. In the United States, while the incidence of edentulism continues to decline, rapid population growth coupled with current economic conditions suggest that edentulism and conventional denture use will continue at current or higher numbers. Unfortunately, evidence-based guidelines for the care and maintenance of removable complete denture prostheses do not exist. In 2009, the American College of Prosthodontists (ACP) formed a task force to establish evidence-based guidelines for the care and maintenance of complete dentures. The task force comprised members of the ACP, the Academy of General Dentistry, American Dental Association (ADA) Council on Scientific Affairs, the American Dental Hygienists' Association, the National Association of Dental Laboratories, and representatives from GlaxoSmithKline Consumer Healthcare. The review process included the assessment of over 300 abstracts and selection of over 100 articles meeting inclusion criteria of this review. The task force reviewed synopses of the literature and formulated 15 evidence-based guidelines for denture care and maintenance. These guidelines were reviewed by clinical experts from the participating organizations and were published in February 2011 issue of The Journal of the American Dental Association for widespread distribution to the dental community. These guidelines reflect the views of the task force.

Impression materials in fixed prosthodontics: influence of choice on clinical procedure.

Abstract: The purpose of this article is to review impression materials used for fabricating fixed restorations in dentistry. Their compositions, properties, advantages, and disadvantages are presented and compared. How these properties influence clinical decisions is also described. This review helps the clinician choose which material is more suitable for a specific case. A broad search of the published literature was performed using Medline to identify pertinent current articles. Textbooks, the Internet, and manufacturers' literature were also used to supplement this information. It is limited to impression materials used in fixed prosthodontics. The review gives basic knowledge of ideal impression material properties and discusses traditional and, primarily, more recently developed products, such as polyethers, poly(vinyl siloxane), polysulfides, and condensation silicone materials. Clear advantages and disadvantages for these impression materials are provided along with the role that compositional variations have on the outcome of the impression. This should enable clinicians and technicians to easily identify the important physical properties of each type of impression material and their primary clinical indications.

Additive CAD/CAM Process for Dental Prostheses

Abstract: This article describes the evolution of a computer-aided design/computer-aided manufacturing (CAD/CAM) process where ceramic paste is deposited in a layer-by-layer sequence using a computer numerical control machine to build up core and fixed partial denture (FPD) structures (robocasting). Al(2)O(3) (alumina) or ZrO(2) (Y-TZP) are blended into a 0.8% aqueous solution of ammonium polyacrylate in a ratio of approximately 1:1 solid:liquid. A viscosifying agent, hydroxypropyl methylcellulose, is added to a concentration of 1% in the liquid phase, and then a counter polyelectrolyte is added to gel the slurry. There are two methods for robocasting crown structures (cores or FPD framework). One is for the core to be printed using zirconia ink without support materials, in which the stereolithography (STL) file is inverted (occlusal surface resting on a flat substrate) and built. The second method uses a fugitive material composed of carbon black codeposited with the ceramic material. During the sintering process, the carbon black is removed. There are two key challenges to successful printing of ceramic crowns by the robocasting technique. First is the development of suitable materials for printing, and second is the design of printing patterns for assembly of the complex geometry required for a dental restoration. Robocasting has room for improvement. Current development involves enhancing the automation of nozzle alignment for accurate support material deposition and better fidelity of the occlusal surface. An accompanying effort involves calculation of optimal support structures to yield the best geometric results and minimal material usage.

Durability of Resin Cement Bond to Aluminium Oxide and Zirconia Ceramics after Air Abrasion and Laser Treatment

Abstract: Purpose: The erbium laser has been introduced for cutting enamel and dentin and may have an application in the surface modification of high-strength aluminum oxide and zirconia ceramics. The aim of this study was to evaluate the durability of the bond of conventional dual-cured resin cements to Procera Al2O3 and zirconium oxide ceramics after surface treatment with air abrasion and erbium laser. Materials and Methods: One hundred twenty Al2O3 and 120 zirconia specimens measuring 3 × 3 × 0.7 mm3 were divided equally into three groups, and their surfaces treated as follows: either untreated (controls), air abraded with Al2O3 particles, or erbium-laser-treated at a power setting of 200 mJ. The surface of each specimen was then primed and bonded with one of two dual-cured resin cements (either SCP-100 Ceramic Primer and NAC-100 or Monobond S and Variolink II) using a 1-mm thick Tygon tube mold with a 0.75-mm internal bore diameter. After 24 hours and 6 months of water storage at 37°C, a microshear bond strength test was performed at a crosshead speed of 1 mm/min. Surface morphology was examined using a confocal microscope, and failure modes were observed using an optical microscope. The data were analyzed using the Kaplan-Meier nonparametric survival analysis. Results: In the case of zirconia, air abrasion and Erbium:yttrium-aluminum-garnet (Er:YAG) laser treatment of the ceramic surface resulted in a significant reduction in the bond strengths of both resin cements after 6 months water storage; however, when the zirconia surface was left untreated, the SCP-100/NAC-100 group did not significantly reduce in bond strength. In the case of alumina, no treatment, air abrasion and Er:YAG laser treatment of the surface led to no significant reduction in the bond strengths of the three SCP-100/NAC-100 groups after 6 months water storage, whereas all three Monobond S/Variolink II groups showed a significant reduction. Conclusion: Er:YAG laser treatment of the zirconia surface did not result in a durable resin cement/ceramic bond; however, a durable bond between a conventional dual-cured resin cement and Procera All Ceram and Procera All Zirkon was formed using a ceramic primer containing the phosphate monomer, MDP, without any additional surface treatment.

Marginal gap, internal fit, and fracture load of leucite-reinforced ceramic inlays fabricated by CEREC inLab and hot-pressed techniques.

Abstract: Purpose: This in vitro study was designed to evaluate and compare the marginal gap, internal fit, and fracture load of resin-bonded, leucite-reinforced glass ceramic mesio-occlusal-distal (MOD) inlays fabricated by computer-aided design/manufacturing (CAD/CAM) or hot pressing. Materials and Methods: Fifty caries-free extracted human molars were prepared for standardized MOD inlays. Impressions of each specimen were made and poured using type IV dental stone. Dies were randomly divided into two equal groups. Twenty-five ceramic inlays were fabricated by the hot-pressed technique using IPS Empress leucite-reinforced glass ceramics, and the other 25 ceramic inlays were produced by CAD/CAM technology using ProCAD leucite-reinforced ceramic blocks and CEREC inLab facilities. Inlays were bonded to the teeth using a dual-cured resin cement. The specimens were stored in distilled water at 37°C for 24 hours and then thermocycled for 5000 cycles. The marginal gap measurements were taken with a stereomicroscope. Specimens in each group of inlay systems were randomly divided into two subgroups of 10 and 15 specimens each. Ten specimens in each subgroup were sectioned mesiodistally for evaluation of the internal fit. The fracture load of specimens in the second subgroup (n = 15) of the two inlay systems was determined under compressive load in a universal testing machine. Data were analyzed using Student's t-test at a significance level of p < 0.05. Results: The mean marginal and internal gap size in both IPS Empress and ProCAD inlays were less than 100 μm; however, the marginal gap for the IPS Empress restorations was significantly higher than that of ProCAD restorations (p 0.05). Conclusions: The leucite-reinforced glass ceramic inlay restorations fabricated by CEREC inLab (CAD/CAM) and the hot-pressed technique provided clinically acceptable marginal and internal fit with comparable fracture loads after luting.

Implant-retained removable partial dentures: an 8-year retrospective study.

Abstract: Purpose: To evaluate the long-term outcomes of removable partial dentures (RPDs) retained (but not supported) by dental implants. Materials and Methods: We retrospectively evaluated 32 consecutive patients who received implant-retained RPDs. Each patient received one to four endosseus implants; the sample included a total of 64 implants. Follow-up was conducted for a minimum of 8 years, during which satisfaction, implant survival, and prosthetic success were evaluated. Results: Patient satisfaction systematically increased. The implant success rate was 93.75%, and 100% of the prostheses were successful. Conclusion: Implant-retained RPDs are a reliable intermediate solution that can reduce biological and economic costs while maintaining implant treatment benefits and the ease of RPD procedures.

Color Stability of Resins and Nylon as Denture Base Material in Beverages

Abstract: PURPOSE Staining of prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. This study aimed to determine the color stability of two heat-cured denture base acrylic (Lucitone 550, Vipi Cril) and one nylon denture base resin (Transflex) after immersion in beverages. MATERIALS AND METHODS Forty disks of each resin (20.0-mm diameter, 3.0-mm thick) were prepared and stored in distilled water for 24 hours at 37°C. During that time (T(0) ), the color of all specimens was spectrophotometrically measured. Each specimen was immersed in coffee, cola, red wine, and distilled water as a means of control. After 15-day (T(1) ) and 30-day (T(2) ) periods of immersion, the color of the specimens was measured again. The CIE (Commission Internationale de L' Eclairage) L*a*b* system was used to determine mean ΔE (color changes) values for each material and compared statistically with two-way ANOVA and Bonferroni intervals at 0.95. RESULTS In ΔET(0) T(1) and ΔET(0) T(2) the most severe staining was apparent with red wine (p < 0.001), followed by coffee (p < 0.01), when compared to the specimens stored in distilled water. Transflex also showed significant color change after immersion in cola (p < 0.01). In ΔET(1) T(2) only red wine promoted significant staining of all resins (p < 0.0001). CONCLUSION Chromatic changes were exhibited by specimens immersed in red wine, followed by coffee. For Transflex, cola also promoted color changes. The values of color changes converted to National Bureau of Standard units showed them to be perceivable to the human eye.

Effect of Implant–Abutment Connection Design on Load Bearing Capacity and Failure Mode of Implants

Abstract: Purpose: In this in vitro study, six implant–abutment connection designs were compared and evaluated regarding load bearing capacities and failure modes. Materials and Methods: Five implants of Astra Tech, Bego, Camlog, Friadent, Nobel Biocare, and Straumann were separately embedded in stainless steel tubes using polyurethane, for a total of 30 specimens. Specimens were statically loaded under an angle of 30° with respect to the implant axis in a universal testing machine using a test setup according to ISO 14801. Failure was indicated by a load drop of 100 N in force. Load–displacement curves were analyzed, and maximum force and force at which permanent deformation occurred were recorded. Statistical analysis was performed using one-way ANOVA with the level of significance set at 0.05. Results: Statistical analysis revealed that the type of implant–abutment connection design has a significant influence on load bearing capacity (p < 0.001). The mean maximum forces ranged between 606 N (Straumann) and 1129 N (Bego); the forces where plastic deformation set in ranged between 368 N (Friadent) and 955 N (Bego). Failure modes differed between the various implant–abutment connection types tested. Conclusions: Implant–abutment connection design has a significant influence on load bearing capacity and failure mode of implants; however, all implant–abutment connection designs tested would be expected to withstand clinically relevant forces.

Full zirconia fixed detachable implant-retained restorations manufactured from monolithic zirconia: clinical report after two years in service.

Abstract: The most frequently encountered problem with fixed detachable dental prostheses is loosening or fracture of the prosthetic screws Other problems include wear, separation or fracture of the resin teeth from the metal/acrylic prosthesis, chipping or fracture of porcelain from the metal/ceramic or zirconia/ceramic prosthesis, and fracture of the framework in some free-end prostheses For this type of prosthesis it is necessary to place the implants in a position that enables occlusal or lingual access so as not to impair the esthetics This clinical report describes the restoration of a patient with complete fixed detachable maxillary and mandibular prostheses made of monolithic zirconia with angled dental implants with buccal access The prostheses were esthetically pleasing, and no clinical complications have been reported after 2 years

Physical Properties of an Acrylic Resin after Incorporation of an Antimicrobial Monomer

Abstract: Purpose: This study evaluated the effect of the incorporation of the antimicrobial monomer methacryloyloxyundecylpyridinium bromide (MUPB) on the hardness, roughness, flexural strength, and color stability of a denture base material. Materials and Methods: Ninety-six disk-shaped (14-mm diameter × 4-mm thick) and 30 rectangular (65 × 10 × 3.3 mm3) heat-polymerized acrylic resin specimens were divided into three groups according to the concentration of MUPB (w/w): (A) 0%, (B) 0.3%, (C) 0.6%. Hardness was assessed by a hardness tester equipped with a Vickers diamond penetrator. Flexural strength and surface roughness were tested on a universal testing machine and a surface roughness tester, respectively. Color alterations (ΔE) were measured by a portable spectrophotometer after 12 and 36 days of immersion in water, coffee, or wine. Variables were analyzed by ANOVA/Tukey HSD test (α= 0.05). Results: The following mean results (±SD) were obtained for hardness (A: 15.6 ± 0.6, B: 14.6 ± 1.7, C: 14.8 ± 0.8 VHN; ANOVA: p= 0.061), flexural strength (A: 111 ± 17, B: 105 ± 12, C: 88 ± 12 MPa; ANOVA: p= 0.008), and roughness (A: 0.20 ± 0.11, B: 0.20 ± 0.11, C: 0.24 ± 0.08 μm; ANOVA: p= 0.829). Color changes of immersed specimens were significantly influenced by solutions and time (A: 9.1 ± 3.1, B: 14.8 ± 7.5, C: 13.3 ± 6.1 ΔE; ANOVA: p < 0.05). Conclusions: The incorporation of MUPB affects the mechanical properties of a denture base acrylic resin; however, the only significant change was observed for flexural strength and may not be critical. Color changes were slightly higher when resin containing MUPB was immersed in wine for a prolonged time; however, the difference has debatable clinical relevance.

Digital Image Capture and Rapid Prototyping of the Maxillofacial Defect

Abstract: Inordertorestoreanextraoralmaxillofacialdefect,amoulageimpressioniscommonly made with traditional impression materials. This technique has some disadvantages, including distortion of the site due to the weight of the impression material, changes in tissue location with modifications of the patient position, and the length of time and discomfort for the patient due to the impression procedure and materials used. The use of the commercially available 3dMDface TM System creates 3D images of soft tissues to form an anatomically accurate 3D surface image. Rapid prototyping converts the virtual designs from the 3dMDface TM System into a physical model by converting the data to a ZPrint (ZPR) CAD format file and a stereolithography (STL) file. The data, in conjunction with a Zprinter R 450 or a Stereolithography Apparatus (SLA), can be used to fabricate a model for prosthesis fabrication, without the disadvantages of the standard moulage technique. This article reviews this technique and how it can be applied to maxillofacial prosthetics.

The effects of adhesive type and thickness on stress distribution in molars restored with all-ceramic crowns.

Abstract: Purpose: This study investigated the effects of luting cement type and thickness on the stress distribution within all-ceramic crowns using finite element analysis. Materials and Methods: An all-ceramic crown restoration of the mandibular right first molar was prepared according to standard dental processes and scanned using micro-computed tomography. Eight 3D FE models were then developed that accounted for two adhesive systems, each with cement thickness of 60 μm, 90 μm, 120 μm, and 150 μm. The models were subjected to four loading conditions, and stresses in the veneer and core layers were evaluated. Results: The stress distribution and maximum stresses in the veneer, core, and cement are presented in corresponding loading conditions. The cement with higher elastic modulus resulted in lower tensile stresses in the veneer and core layers, and the shear strength of the cement was critical to the intactness of the all-ceramic crown. Conclusion: The cement thickness acts as a cushion between the crown and dentin substrate. Although there is an optimal thickness (approximately 90 μm) that can reduce the stress level in ceramic crowns, cement thickness is not very important to stresses in the core or veneer in most cases when compared to the influence of loading conditions or cement moduli.

Effect of Extraoral Aging Conditions on Mechanical Properties of Maxillofacial Silicone Elastomer

Abstract: Purpose: The purpose of this study was to investigate the effect of extraoral human and environmental conditions on the mechanical properties (tensile strength and modulus, elongation, tear strength hardness) of maxillofacial silicone elastomer. Materials and Methods: Specimens were fabricated using TechSil-S25 silicone elastomer (Technovent Ltd, Leeds, UK). Eight groups were prepared (21 specimens in each group; eight tensile, eight tear, five hardness) and conditioned differently as follows (groups 1 through 8): Dry storage for 24 hours; dry storage in dark for 6 months; storage in simulated sebum solution for 6 months; storage in simulated acidic perspiration for 6 months; accelerated artificial daylight aging under controlled moisture for 360 hours; outdoor weathering for 6 months; storage in antimicrobial silicone-cleaning solution for 30 hours; and mixed conditioning of sebum storage and light aging for 360 hours. The conditioning period selected simulated a prosthesis being in service for up to 12 months. Tensile and tear test specimens were fabricated and tested according to the International Standards Organization (ISO) standards no. 37 and 34, respectively. Shore A hardness test specimens were fabricated and tested according to the American Standards for Testing and Materials (ASTM) D 2240. Data were analyzed with one-way ANOVA, Bonferroni, and Dunnett's T3 post hoc tests (p < 0.05). Weibull analysis was also used for tensile strength and tear strength. Results: Statistically significant differences were evident among all properties tested. Mixed conditioning of simulated sebum storage under accelerated artificial daylight aging significantly degraded mechanical properties of the silicone (p < 0.05). Conclusions: Mechanical properties of maxillofacial elastomers are adversely affected by human and environmental factors. Mixed aging of storage in simulated sebum under accelerated daylight aging was the most degrading regime. Clinical significance: Accelerated aging of silicone specimens in simulated sebum under artificial daylight for 12 months of simulated clinical service greatly affected functional properties of silicone elastomer; however, in real practice, the effect is modest, since sebum concentration is lower, and daylight is less concentrated.

Cracking of Porcelain Surfaces Arising from Abrasive Grinding with a Dental Air Turbine

Abstract: Purpose: The purpose of this in vitro study was to evaluate porcelain cracking induced by abrasive grinding with a conventional dental air turbine and abrasive diamond burs. Materials and Methods: Four commercially available porcelains were examined—Wieland ALLUX, Wieland ZIROX, IPS e.max Ceram, and IPS Empress Esthetic Veneering porcelain. Sixty discs of each porcelain type were fabricated according to manufacturer instructions, followed by an auto-glaze cycle. Abrasive grinding using fine, extra-fine, and ultra-fine diamond burs was carried out, using a conventional dental air turbine. The grinding parameters were standardized with regard to the magnitude of the force applied, rotational speed of the diamond bur, and flow rate of the water coolant. A testing apparatus was used to control the magnitude of force applied during the grinding procedure. The ground surfaces were then examined under scanning electron microscope. Results: Cracking was seen for all porcelain types when ground with the fine bur. Cracking was not seen for specimens ground with the extra-fine or the ultra-fine bur. Conclusion: Wet abrasive grinding with a conventional dental air turbine and fine grit diamond burs has the potential to cause cracking in the four porcelain types tested. Similar abrasive grinding with smaller grit size particles does not cause similar observable cracking.

Caries risk assessment and management for the prosthodontic patient.

Abstract: Prosthodontic patients are often at a high risk for caries, and assessing that risk prior to treatment is important. Historically, the nature of dental education and clinical practice has oriented clinicians toward recognizing and correcting the damaging effects of caries, rather than actively assessing and managing caries risk potential. New developments have led to better diagnostics and protocols for caries management, although one adapted to the specific needs of the prosthodontic patient has not been proposed. Our purpose is to outline caries risk assessment and management for the prosthodontic patient.

Volumetric Misfit in CAD/CAM and Cast Implant Frameworks: A University Laboratory Study

Abstract: Purpose: To compare the volumetric misfit between implant restorative platforms of implants and implant frameworks manufactured with two different technologies. One set of implant frameworks was made with a CAD/CAM protocol and a tactile probe; the second protocol consisted of frameworks made with the lost-wax technique and conventional casting technology. Materials and Methods: In this laboratory study, an acrylic resin model with five “inter-foraminal” implants was used as the “patient” model. Implant level impressions were made, and 10 definitive master casts were fabricated. The casts were verified using an index made on the patient model. Five cast high palladium noble alloy and five CAD/CAM titanium alloy frameworks were fabricated. The patient's implants and the frameworks’ implant restorative platforms were scanned with a tactile probe, and the data were digitized. The digitized implant restorative platforms of the frameworks were fit onto the patient's digitized implants via a software program, in a process called “lofting.” This computerized procedure simulated a 1-screw test; the process was performed on both sides. The volumetric misfit between the implant restorative platforms of the frameworks and the patient's implants were measured. A Welch's t-test was used to determine significant differences (p < 0.05) between the misfit of the two technologies. Wilcoxon Signed-Rank tests were used to evaluate differences between the right and left sides. Results: On average, the volumetric misfit of the CAD/CAM frameworks was 1.8 mm3 less than the volumetric misfit of the cast alloy frameworks (p 0.05). Conclusions: The scanning technology and computer software program used in this study demonstrated that the CAD/CAM implant frameworks had statistically significantly less volumetric misfit when compared with the cast implant frameworks. There were no significant differences between the right and left 1-screw tests within the same type of frameworks.

Assessment of optimal condylar position in the coronal and axial planes with limited cone-beam computed tomography.

Abstract: Purpose: No quantitative standards for the optimal position of the mandibular condyle in the glenoid fossa are yet available in the coronal and axial planes. We previously reported measurements of this position in the sagittal plane, using recently developed limited cone-beam computed tomography (LCBCT) capable of imaging the craniofacial structures with high accuracy. In this study, we assessed the optimal condylar position in the coronal and axial planes. Materials and Methods: The study included 24 joints in 22 asymptomatic patients (10 male, 12 female; age range 12–25 years, mean age 18 years) who had no disc displacement as confirmed by magnetic resonance imaging. Their joints had optimum function with the starting and end points of all functional jaw movements coincident with maximum intercuspation. Joint-space distances between the condyle and glenoid fossa were measured at the medial, central, and lateral positions in the coronal plane, and medial and lateral positions in the axial plane. Results: The mean coronal lateral space (CLS), coronal central space (CCS), and coronal medial space (CMS) were 1.8 ± 0.4 mm, 2.7 ± 0.5 mm, and 2.4 ± 0.5 mm, respectively. The ratio of CLS to CCS to CMS was 1.0 to 1.5 to 1.3. The mean axial medial space (AMS) and axial lateral space (ALS) were 2.1 ± 0.6 mm and 2.3 ± 0.6 mm, respectively. There were no significant sex differences in these measurements. Conclusions: These coronal and axial data, along with previously reported sagittal data, might provide norms for 3D assessment of optimal condylar position with LCBCT.

The effect of denture cleansing solutions on the retention of pink locator attachments after multiple pulls: an in vitro study.

Abstract: Purpose: The effect of denture cleansing solutions and multiple pulls on the retention of pink Locator patrices was studied. Materials and Methods: Five groups of pink Locator attachments (3.0 lb. Light Retention replacement patrix attachments; five in each group) were soaked for the equivalent of 6 months of clinical use in the following solutions: water (control), Efferdent, Polident Overnight, 6.15% sodium hypochlorite (NaOCL, 1:10 dilution), and Listerine mouthwash. A universal testing machine set at a 2 in/min crosshead speed was used to perform 548 pulls (548 cycles of insertion and removal). The reduction in load to dislodgement (retention) after the initial pull and the final pull and the percent reduction in retention after 6 months were compared between the groups using a one-way ANOVA followed by Tukey's Honestly Significant Difference (HSD) Test (α= 0.05). Results: Denture cleansing solutions significantly reduced the retentive values of pink Locator attachments after the initial pull (F = 17.435, p < 0.0001). The retentive values of Efferdent, Listerine, Polident Overnight, and water were significantly higher than the retentive value of the attachments soaked in NaOCl. After 6 months of simulated use (548 pulls), the four denture cleansing solutions had significant effects on the retentive values of pink Locator attachments (F = 5.855, p = 0.003). The retentive values for attachments soaked in NaOCl (7.29 ± 1.0 N) were significantly lower than those of attachments soaked in Listerine (15.82 ± 4.7 N) and in Polident Overnight (14.41 ± 3.6 N). These cleansing solutions also had a significant effect on the percentage of retention lost (F = 3.271, p = 0.032). The loss of retention in attachments soaked in Listerine (29 ± 9%) was significantly lower than attachments soaked in water (53 ± 12%). The loss of retention in attachments soaked in Efferdent was 49 ± 9%; in Polident Overnight, 34 ± 18%; and in NaOCl, 42 ± 11%. There was no significant difference in the percentage of retention loss between water, Efferdent, NaOCl, and Polident Overnight. There was also no significant difference in the percentage of retention loss between Efferdent, NaOCl, Polident Overnight, and Listerine. Conclusion: NaOCl significantly decreased the retentive value of Locators. Therefore, it should not be routinely recommended for use as a denture cleanser. Listerine significantly increased the retention of the Locator attachments; however, it is premature to recommend Listerine for use as a denture cleanser.

A Technique for Repairing a Loosening Abutment Screw for a Cement‐Retained Implant Prosthesis

Abstract: Prostheses may be attached to implants or implant abutments using screw retention or cementation. With the increased use of cement-retained, implant-supported restorations for the replacement of missing teeth, clinicians may choose to use a definitive cement to lute the definitive restoration. Loosening of an abutment screw is a challenging complication of cement-retained, implant-supported prosthetic restorations. Often, the abutment screw becomes loose from the implant body, whereas the crown remains cemented to the abutment. In such situations, separating the cemented crown from the underlying abutment or locating the abutment-screw access for removal of the restoration is a difficult task. The purpose of this report is to describe a simple technique for locating the abutment-screw access in the event of its loosening. The advantage of this technique is that it can facilitate easy location of the abutment screw, thus minimizing damage to the existing restoration and allowing it to be reused.

Treatment of Maxillary Jaws with Dental Implants: Guidelines for Treatment

Abstract: Maxillary implant prosthetic treatments may be considerably more difficult to accomplish when compared to the corresponding treatments for patients with edentulous or partially edentulous jaws. The objectives of this article include descriptions of diagnostic records and their impact on treatment success, and criteria clinicians should use to determine whether fixed or removable prostheses are the treatment of choice in any given situation. Specific criteria and clinical guidelines will be identified for use in the treatment planning process. Determination of optimal tooth positions and their relationships to residual ridges or extraction sites are one of the critical factors in determining designs for maxillary implant prostheses. Prosthetic designs (fixed or removable) should be determined by clinicians prior to placing implants; removable prostheses should not be considered to be the "fall-back" treatment option if fixed treatments become unavailable secondary to loss of implants or other clinical complications. Inherent differences between fixed and removable prosthetic treatments are critical for clinicians to understand, as they often include key points for clinicians explaining the features of fixed/removable-implant prostheses to patients. Appreciation of the differences between fixed and removable prostheses is critical for patients and clinicians to make informed decisions.

Effect of Surface Treatment on Shear Bond Strength of Zirconia to Human Dentin

Abstract: Purpose: The effect of surface treatment using tribochemical silica coating/silane coupling on the shear bond strengths of (1) a glass-infiltrated, zirconia-reinforced alumina (In-Ceram Zirconia) and (2) a yttria-stabilized zirconia ceramic (YZ Zirconia) to human dentin was studied. Materials and Methods: Twelve specimens of each ceramic were randomly assigned to one of three surface treatments: (1) no surface treatment (control group); (2) a chairside tribochemical silica coating/silane coupling system (CoJet group); and (3) a laboratory tribochemical silica coating/silane coupling system (Rocatac group). The mode of failure of each specimen was determined under magnification. Results: The shear bond strengths (mean ± SD) of In-Ceram Zirconia of the control, CoJet and Rocatec groups were 5.7 ± 4.3 MPa, 11.4 ± 5.4 MPa, and 6.5 ± 4.8 MPa, respectively. The corresponding figures for YZ Zirconia were 8.2 ± 5.4 MPa, 9.8 ± 5.4 MPa, and 7.8 ± 4.7 MPa. Two-way ANOVA revealed significant differences in bond strength due to the difference in surface treatment (p= 0.02), but the bond strengths between the two ceramics were not significantly different (p= 0.56). Post hoc tests showed that In-Ceram Zirconia treated with CoJet had significantly higher shear bond strengths than those untreated (p 0.05). Conclusion: The bonding of In-Ceram Zirconia can be improved by the chairside surface treatment system.

Comparison of Retention and Strain Energies of Stud Attachments for Implant Overdentures

Abstract: Purpose: The retentive forces and the strain energies absorbed during dislodging of implant overdenture stud attachments are useful parameters to consider in the selection of attachments. The purpose of this study was to compare the retentive forces and strain energies of the Nobel Biocare standard ball, Nobel Biocare newer generation ball (Yorba Linda, CA), Zest Anchor, Zest Anchor Advanced Generation (Escondido, CA), Sterngold-Implamed ERA white, and Sterngold-Implamed orange attachments (Attleboro, MA) on an implant-retained in vitro overdenture model. Materials and Methods: The attachments were tested using two permanently placed Branemark system implants on a test model attached to an Instron machine. Each attachment had one part embedded in a denture-like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with six specimens of each attachment. Retentive forces generated and strain energies absorbed during displacement were determined. A 1-way ANOVA followed by the Tukey studentized range test was used to determine groups that were significantly different at the p < 0.05 level. Results: The Zest Anchor Advanced Generation attachment had significantly the highest retentive vertical and oblique forces [37.2 (5.5) N and 25.9 (3.2) N, respectively]. The Zest Anchor had the lowest vertical force [10.8 (4.2) N], and Nobel Biocare Standard had the lowest oblique retentive force [10.6 (3.0) N]. The Nobel Biocare Standard Ball attachment had the highest strain energies [29.7 × 10−3 (11.9 × 10−3) J, 30.3 × 10−3(14.3 × 10−3) J, respectively, in the vertical and oblique directions]. The Sterngold-Implamed ERA White and Zest Anchor had the lowest strain energies [5.3 × 10−3 (3.2 × 10−3) J and 4.5 × 10−3 (1.1 × 10−3) J, respectively, in the vertical and oblique directions]. Conclusion: The retentive forces and strain energies of implant overdenture stud attachments are different and should be considered during prosthesis selection.

Effects of Horizontal Misfit and Bar Framework Material on the Stress Distribution of an Overdenture-Retaining Bar System: A 3D Finite Element Analysis

Abstract: Purpose: To evaluate the influence of horizontal misfit change and bar framework material on the distribution of static stresses in an overdenture-retaining bar system using finite element (FE) analysis. Materials and Methods: A 3D FE model was created including two titanium implants and a bar framework placed in the anterior part of a severely resorbed jaw. The model set was exported to mechanical simulation software, where horizontal displacement (10, 50, 100, and 200 μm) was applied simulating the settling of the framework, which suffered shrinkage during laboratory procedures. Four bar materials (gold alloy, silver–palladium alloy, commercially pure titanium, and cobalt–chromium alloy) were also simulated in the analysis using 50 μm as the horizontal misfit. Data were qualitatively evaluated using von Mises stress, given by the software. Results: The misfit amplification presented a great increase in the stress levels in the inferior region of the bar, screw-retaining neck, cervical and medium third of the implant, and cortical bone tissue surrounding the implant. The higher stiffness of the bar presented a considerable increase in the stress levels in the bar framework only. Conclusion: The levels of static stresses seem to be closely linked with horizontal misfit, such that its amplification caused increased levels of stress in the structures of the overdenture-retaining bar system. On the other hand, the stiffness of the bar framework presented a lower effect on the static stress levels.

Pilot Evaluation of Four Experimental Conditioning Treatments to Improve the Bond Strength between Resin Cement and Y-TZP Ceramic

Abstract: Purpose This study evaluated the bond strength between resin cement and Y-TZP ceramic (Yttrium-stabilized Tetragonal Zirconia Polycrystalline) submitted to different surface conditionings. Materials and methods Fifty Y-TZP ceramic discs (O= 10 mm) were allocated into five groups: Gr1 (control)-no conditioning; Gr2-tribochemical silica coating (30-μm SiO(2)) before sintering; Gr3-air abrasion with 50-μm Al(2)O(3) before sintering; Gr4-air abrasion with 110-μ Al(2)O(3) before sintering; Gr5 - air abrasion with 50-μm Al(2)O(3) after sintering. After specimen preparation, cylinders of composite resin were prepared and immediately cemented onto the ceramic. A shear test was performed. Results One-way ANOVA indicated a statistically significant difference among the groups (p= 0.0019). The mean shear bond strengths (MPa) were: Gr1 = 4.7 ± 0.8,(b) Gr2 = 4.6 ± 0.9,(b) Gr3 = 6.4 ± 1.0,(a) Gr4 = 6.5 ± 1.8,(a) Gr5 = 6 ± 1.3(ab) (same superscript letter indicates statistical similarity). Adhesive fracture between the ceramic and resin cement was the most common failure. No complete cohesive fracture at the ceramic or composite cylinders was noted. Conclusion Within the limitations of this study, additional surface treatment with air abrasion before and after sintering provided a significant increase in bond strength. Tribochemical silica coating before sintering was not effective as a surface treatment.

Influence of pigments and opacifiers on color stability of an artificially aged facial silicone.

Abstract: Purpose: The aim of this study was to evaluate the influence of two pigments (ceramic powder and oil paint) and one opacifier (barium sulfate) on the color stability of MDX4–4210 facial silicone submitted to accelerated aging. Materials and Methods: Sixty specimens of silicone were fabricated and divided into six groups-–colorless (G1), colorless with opacifier (G2), ceramic (G3), ceramic with opacifier (G4), oil (G5), oil with opacifier (G6). All replicas were submitted to accelerated aging for 1008 hours. The evaluations of chromatic alteration through visual analysis and reflection spectrophotometry were carried out initially and after 252, 504, and 1008 hours of aging. The results were submitted to ANOVA and Tukey's test at 5% level of significance. Results: All groups exhibited chromatic alteration (ΔE > 0); however, this color alteration was not perceptible through visual analysis of the color. The pigmented groups with opacifier presented the lowest ΔE values, with a statistical difference from the other groups. For the groups without opacifier, the group pigmented with oil paint exhibited the lowest ΔE values in the different aging periods, with a statistical difference. Accelerated aging generated significant chromatic alterations in all groups after 252 hours, except for the colorless and oil groups, both with opacifier (G2 and G6). Conclusions: The opacifier protects facial silicones against color degradation, and oil paint is a stable pigment even without addition of opacifier.

Influence of zirconia base and shade difference on polymerization efficiency of dual-cure resin cement.

Abstract: Purpose: The aim of this study was to investigate the polymerization efficiency of dual-cured resin cement beneath different shades of zirconia-based feldsphathic ceramic restorations. Materials and Methods: Five translucent zirconia (Zirkonzahn) discs (4.0-mm diameter, 1.2-mm height) were prepared. Feldsphathic ceramic (1.2 mm) (Noritake Cerabien Zr) in 5 shades (1M2, 2M2, 3M2, 4M2, 5M2) was applied on the zirconia discs. Twelve dual-cure resin cement specimens were prepared for each shade, using Panavia F 2.0 (Kuraray) in Teflon molds (4.0-mm diameter, 6.0-mm height), following the manufacturer's instructions. Light activation was performed through the zirconia-based ceramic discs for 20 seconds, using a quartz tungsten halogen curing device (Hilux 200) with irradiance of 600 mW/cm2. Immediately following light curing, specimens were stored for 24 hours in dry, light-proof containers. Vickers hardness measurements were conducted using a microhardness tester with a 50-g load applied for 15 seconds. The indentations were made in the cross sectional area at four depths, and the mean values were recorded as Vickers hardness number (VHN). Results were statistically analyzed with one-way ANOVA and Tukey HSD test (p < 0.05). Results: A statistically significant decrease in VHN of the resin cement was noted with increasing depth and darkness of the shade (p < 0.05). Conclusion: Curing efficiency of dual-cure resin cement is mainly influenced by the lightness of the shades selected.

Influence of irrigant, dowel type, and root-reinforcing material on fracture resistance of thin-walled endodontically treated teeth.

Abstract: Purpose: Unresolved controversy exists concerning the optimum restorative material to reinforce the thin-walled roots of endodontically treated teeth to improve their fracture resistance under occlusal load. This study evaluated the effectiveness of irrigant, dowel type, and root-reinforcing material on the fracture resistance of thin-walled endodontically treated teeth. Materials and Methods: The root canals of 140 maxillary central incisors were enlarged and equally divided into seven groups according to the canal irrigant: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Within each group, root canals were lined with composite resin (PermaFlo) or glass ionomer cement (Fuji II LC). A light-transmitting plastic dowel (Luminex) was used to create space for a quartz fiber-reinforced dowel (Aestheti Post) or a titanium alloy dowel (ParaPost XH) and to cure the restorative materials. Following dowel cementation and restoration of the roots with composite core, the teeth were submitted to fracture resistance testing, and data were analyzed with 3-way ANOVA followed by Ryan-Einot-Gabriel-Welsch Multiple Range Test (α= 0.05). Results: Fracture resistance values were significantly different among irrigants, restorative materials, and their interaction (p < 0.001); however, the dowel type was not significantly different (p= 0.51). Conclusions: Thin-walled roots that had the smear layer removed with lactic acid and that were then lined with composite resin had a higher fracture resistance.

Effect of chemical disinfection and accelerated aging on color stability of maxillofacial silicone with opacifiers.

Abstract: UNESP Univ Estadual Paulista, Fac Dent Aracatuba, Dept Dent Mat & Prosthodont, BR-16050050 Sao Paulo, Brazil