The International Journal of Prosthodontics, 04/2016

Purpose: This study aimed to evaluate the 10-year prosthodontic outcomes with splinted and unsplinted designs for maxillary overdentures on three implants opposing mandibular two-implant overdentures. Materials and Methods: Using two similar implant systems, 40 edentulous participants with existing mandibular two-implant overdentures were randomly allocated to two prosthodontic treatment groups (splinted design with bar units; unsplinted design with ball attachments). Participants had three narrow-diameter implants placed in their edentulous maxillae using a one-stage surgical procedure, and they were conventionally loaded with overdentures. Prosthodontic maintenance events were documented at 1-, 2-, 5-, 7-, and 10-year recalls. Results: Progressive attrition of the cohort resulted in 36 participants being seen for the 1-year recall, 31 participants for the 2-year recall, 30 participants for the 3-year recall, 28 participants for the 5-year recall, 26 participants for the 7-year recall, and 23 participants (nearly 60%) for the 10-year recall. Data showed no significant differences in prosthodontic maintenance or success associated with patrices, matrices, or other aspects of the overdentures using the different attachment systems and designs. Conclusion: Maxillary three-implant overdentures are a viable treatment option for edentulous patients wearing opposing mandibular two-implant overdentures. There were no differences in prosthodontic maintenance and success between the splinted (bar) and unsplinted (ball) designs.

The resin-bonded fixed partial denture (RB-FPD) is the first restorative treatment option to be considered in cases where one or more teeth are missing. The indications for implants, conventional FPDs, and adhesive FPDs, considering the general and dental conditions of the patient, are discussed in this article. When the RB-FPD is the chosen option, a direct or indirect technique, a cantilever-type or fixed-fixed design, and materials to be used need to be selected. The choice will depend on a variety of factors, such as interproximal space at the connector area, anterior or posterior location, the skills of the dentist, esthetics, and the patient's wishes. The RB-FPD can be made using various techniques and materials.

Purpose: This parallel randomized controlled trial (RCT) compared the efficacy of a computeraided design/computer-assisted manufacture (CAD/CAM) splint versus a conventional stabilization splint in patients with temporomandibular disorders (TMD). Materials and Methods: A sample of 48 age-matched TMD patients from the Ludwig Maximilian University Prosthodontic Department in Munich, Germany, were randomly allocated into groups 1 (CAD/ CAM splint) and 2 (conventional splint). The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was used for TMD Axis I (groups I, II, and III) and Axis II (chronic pain grade [CPG]) diagnoses. Numeric scales (TMD/NS, 10 cm) were used to measure headaches, face pain, jaw joint pain, jaw joint noises, mastication pain, neck pain, face tension, limitation of mouth opening, complaints during mastication, and teeth sensitivity at baseline and then monthly for 9 months (T1 to T10). Optical axiography was used to measure right and left condyle movements (mm) at baseline, 3 months, and 6 months (T1, T4, and T7). Results: A total of 32 patients (drop-out rate = 33%; 68.75% women; 28.51 ± 7.13 years old), 16 per group, completed the study. RDC/TMD Axis I showed the following diagnoses: 93.75% muscle disorders, 37.75% disc displacement with reduction, 3.12% disc displacement without reduction, and 56.25% arthralgia. There was a significant reduction in 10 out of 13 items of the TMD/NS in the CAD/ CAM splint versus 8 out of 13 in the conventional splint. However, no significant improvement in mandibular movements (ie, increase in range of motion and reduction in asymmetry between right and left condyles) was observed. Conclusion: Both treatments were equally efficacious and no difference was found between them.

Purpose: This study evaluated the vertical misfit of implant-supported frameworks made using different techniques to obtain passive fit. Materials and Methods: Thirty threeunit fixed partial dentures were fabricated in cobalt-chromium alloy (n = 10) using three fabrication methods: one-piece casting, framework cemented on prepared abutments, and laser welding. The vertical misfit between the frameworks and the abutments was evaluated with an optical microscope using the single-screw test. Data were analyzed using one-way analysis of variance and Tukey test (α = .05). Results: The one-piece casted frameworks presented significantly higher vertical misfit values than those found for framework cemented on prepared abutments and laser welding techniques (P < .001 and P < .003, respectively). Conclusion: Laser welding and framework cemented on prepared abutments are effective techniques to improve the adaptation of three-unit implant-supported prostheses. These techniques presented similar fit.

Osteonecrosis of the jaws has recently been associated with HIV infection and requires surgical and prosthetic intervention. The prosthetic management of an HIV patient with a maxillary lesion, as well as medical status-related treatment considerations, are discussed in this article.

This preliminary in vitro study evaluated the simulated retention force of O-rings used for mini-implant overdenture treatment and the effect of mechanical fatigue corresponding to 6 months of wear. A mandibular overdenture analog device was attached to two mini-implants and underwent a tensile strength test before and after the application of insertion-removal and simulated masticatory cycles. Insertion-removal cycles led to a retention loss of 24%, whereas masticatory cycles did not influence retention. Micro- CT scans showed minor deformation following mechanical cycling, but the changes were milder than those observed in similar clinical specimens. Both experimental loading methods led to physical changes in the O-rings, which explains in part the similar clinically observed wear.

This report describes the use of laboratory-fabricated crown intaglio replicas for extraorally prepared cementation of fixed restorations to implants. This technique minimizes excess cement and may therefore reduce the risk of cement-related marginal peri-implant bone loss. It is unclear whether the remaining thin layer of luting agent provides sufficient retention if low-adhesive zinc oxide (ZnO) cement is used. In 85 consecutive patients, 113 single crowns were cemented to implants using extraoral cementation technique (ECT) and ZnO cement. All patients were followed for 6 months and investigated for decementation. Seven events of decementation (incidence: 6.19%) were found in 7 patients (8.24%). ECT may represent a viable cementation technique for implant-supported single crowns, even using low-adhesion cements.

Purpose: The aim of this study was to assess quality of life (QoL) and obturator functioning in patients having undergone a maxillectomy as a tumor ablative resection and rehabilitation with a prosthetic obturator. Materials and Methods: The University of Washington Quality of Life scale version 4 (UW-QoLv4) and the Obturator Functioning Scale (OFS) were used to evaluate the self-reported QoL and obturator functioning. The effects of demographic and treatment variables on QoL were assessed using age, defect size, postoperative radiotherapy (RT), neck dissection, and dentition. Results: The study included 16 men and 13 women with a mean age of 48.8 years. Of the 29 patients, 16 had a Brown Class 2a or smaller defect and 13 had a Brown Class 2b or larger defect. The mean OFS score (P = .004) and the physical (P = .001) and social-emotional function scores (P = .001) of the patients who received postoperative RT were significantly lower than those who did not receive postoperative RT. The subscales for swallowing (P = .008), saliva (P = .001), pain (P = .001), and shoulder function (P = .002) correlated strongly with postoperative RT on the UW-QoL. The subscales for pronunciation (P = .007) and saliva (P = .002) correlated significantly with RT on the OFS. The mean OFS scores were significantly lower for the patients with a Brown Class 2a or smaller defect than for Brown Class 2b or larger (P = .005). Conclusion: Postoperative RT was the strongest variable affecting QoL in patients with maxillectomy and prosthetic obturator reconstruction. The size of the defect slightly influenced the obturator function; however, it did not influence the overall QoL.

Purpose: The aim of this study was to evaluate the fracture resistance of fatigued lithium disilicate pressed zirconia crowns versus other ceramic crowns. Materials and Methods: Lithium disilicate pressed zirconia, fluorapatite pressed zirconia, monolithic lithium disilicate, and monolithic zirconia crowns were fabricated. Cyclic and static loadings were applied to the mesiobuccal cusp tip after thermocycling and fracture strengths were recorded. Results: Fatigued lithium disilicate pressed zirconia crowns were found to have a fracture resistance of 9,117.81 ± 727.04 N, compared with 9,240.61 ± 887.21 N for monolithic zirconia crowns, 3,030.18 ± 1,505.83 N for fluorapatite pressed zirconia crowns, and 4,173.94 ± 877.46 N for monolithic lithium disilicate crowns (P = .001). Conclusion: This in vitro study shows that fatigued lithium disilicate pressed zirconia and monolithic zirconia crowns have better fracture resistance than fluorapatite pressed zirconia and monolithic lithium disilicate crowns.

Purpose: The aim of this study was to describe and analyze the restoration profiles of 5,491 implant-supported single crowns, fixed partial dentures (FPDs), and splinted restorations prescribed between January 2005 and December 2009. Materials and Methods: Dental clinicians qualified in or before December 2004, registered in Victoria, and placing and/ or restoring implants in private practice were invited to participate in the study. Data was extracted by two trained and calibrated research assistants from dental records. Crosstabulation was carried out in SPSS (IBM) to provide descriptive statistics on clinician profiles, patient demographics, and restoration information. Results: A total of 34 practitioners participated in the study: 25 general dentists and 9 specialists. Clinicians that graduated between 1970 and 1989 (16 to 40 years of experience) prescribed most of the prostheses (82.0%). Female patients were present in higher numbers across most age and restoration groups. Of the implant-supported prostheses, 5,491 fit the criteria for simple basic restorations and were included in this report. The majority of the prostheses (86.7%) were single-tooth restorations. Metal-ceramic was the material of choice for the majority of the restorations (3,382/5,491). The use of single implant-supported crowns in the anterior mandible was rare. More than 65% of the implant-supported restorations in this study were screw retained directly to the implant. The specialist clinicians in this study largely used the screw-retained method to retain single implant-supported crowns (82.0%). General dentists provided 1,066% more cement-retained single implant-supported crowns compared with other practitioners. Conclusion: This report showed that during the period of January 2005 to December 2009, private practice clinicians in Victoria, Australia favored porcelain-fused-to-metal material over all-ceramic for implant restorations. Most implant restorations were single crowns. More female patients received implant-supported restorations in the posterior region of the mouth. The clinicians included in this study, particularly the specialists, generally favored a retrievable design in choosing the retention method for the prostheses.

Purpose: This in vitro study evaluated the effect of biofilms on abutment torque loss and wear of implant internal connection surfaces. Materials and Methods: Morse taper abutments were torqued to corresponding implants and then the implant-abutment assemblies were immersed in a biofilm medium for 72 hours. After detorque evaluation, the abutments were removed and the inner implant surfaces were observed via scanning electron microscopy and profilometry. Results: The removal torque values and the implant damaged areas decreased after contact with biofilms. Conclusion: The lubricating effect of biofilms decreased the friction between contacting surfaces, negatively affecting the mechanical integrity of the implant-abutment connection.

Purpose: Various materials and systems for bonding lithium disilicate to the tooth substrate are available to clinicians, who can adapt the materials to each clinical situation to maximize the performance of indirect esthetic restorations. This study aimed to evaluate the degree of conversion (DC) and the microhardness (MH) of a dual-curing and a light-curing cement under lithium disilicate discs of different thicknesses. Materials and Methods: A total of 48 lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) samples were prepared and divided into three groups (n = 16) according to the thickness (group A was 0.6 mm; group B was 1.0 mm; group C was 1.5 mm). Each group was further divided into two subgroups (n = 8) according to the resin cement employed, NX3 (Kerr) or Choice 2 (Bisco). A standardized quantity of cement was placed on the sample, and DC was evaluated with an attenuated total reflectance Fourier transformed infrared spectrophotometer (Nicolet IS10, Thermo Scientific). Twenty-four hours after DC was established, Vickers test was performed on the cement with a microindentometer (Leica Microsystems). Results were statistically analyzed with analysis of variance test and significance set at P < .05. Results: Statistical analysis showed cement type had a significant influence (P = .005) on DC. MH results were influenced by thicknesses only between 0.6 and 1.5 mm when light-cured cement was employed. Conclusion: The light-curing and the dualcuring cements reached comparable DCs between 0.6 and 1.5 mm. However, the light-curing resin showed a higher DC and MH.

Purpose: The aim of this study was to investigate missing teeth and prosthodontic replacements in an institutionalized elderly population in China, and to assess dental functionality before and after the prosthodontic replacements based on a hierarchical dental functional classification (HDFC) system. Materials and Methods: A sample of 512 participants (9% aged 60-69 years; 29% aged 70-79 years; 62% aged ≥ 80 years) living in eight nursing homes in Qingdao were categorized by the HDFC with and without tooth replacements. A functional dentition in the HDFC meets all the following criteria: ≥ 10 natural teeth in each jaw; a complete anterior region; 3 or 4 posterior occluding pairs (POPs) in the premolar regions; and ≥ 1 POP bilaterally in the molar region. Participants with tooth replacements were reclassified. The score for effectiveness of replacements were as follows: 4 for ≥ 10 teeth in each jaw; 3 for a complete anterior region; 2 for 3 or 4 POPs in premolar regions; and 1 for ≥ 1 molar POP bilaterally. Results: Twenty percent of the participants had functional dentitions, but 42% met none of the functional criteria. In the branch '≥ 10 teeth in each jaw' the mean number of teeth present was 26.3 ± 2.9, and the mean number of POPs was 6.2 ± 2.0. In the branch '< 10 teeth in each jaw,' there were 13.4 ± 5.5 teeth and 1.1 ± 1.5 POPs. Of the 384 participants with natural teeth in each jaw, 44% had no replacements and 56% had fixed dental prostheses (FDPs), partial removable dental prostheses (PRDPs), or both. FDPs usually replaced 1 or 2 teeth, and PRDPs 3 or more teeth. On the basis of natural teeth plus artificial teeth (214 participants with replacements), 46% had functional dentitions while 18% met none of the functional criteria. In the promoted participants, the mean number of teeth added by FDPs was 3.6 ± 2.5, and for PRDPs it was 11.9 ± 6.5. FDPs had a significantly higher mean promotion value per tooth added than PRDPs. Conclusion: Approximately half the tooth replacements effectively met all criteria for a functional dentition.

Purpose: The partial removable dental prosthesis (PRDP) is used widely to replace missing teeth, but it can disturb the ecology of the mouth. In this retrospective cohort study, the null hypothesis was that there was no difference between tooth loss and the type of edentulous spaces in participants wearing PRDPs. Materials and Methods: Participants were selected from patients who were treated consecutively with PRDPs between January 2003 and December 2006 by undergraduate dental students at the University of British Columbia and attended the clinic for at least 5 years following placement of the PRDP. Clinical records were analyzed for 50 men and 52 women aged 19 to 85 years at baseline, before placement of the PRDP (mean age: 63.2 years). Baseline data were obtained from the records on missing teeth and edentulous spaces, and thereafter data were collected on teeth lost over the following 5-year period. Baseline data on age, sex, occlusal contacts, number of dental rests for the dentures, carious teeth, gingival attachment loss, and teeth with endodontic fillings were also obtained. Results: The presence at baseline of teeth with endodontic fillings significantly (P < .05) increased the prediction of tooth loss over the 5 years, but the type of edentulous space did not. Conclusion: The risk of tooth loss over a 5-year period was higher in the presence of endodontically treated teeth, but no higher in participants wearing PRDPs with distally extended edentulous spaces rather than tooth-bounded edentulous spaces.

Purpose: This study compared polyvinylsiloxane with polyether in handling dental impressions. Materials and Methods: Each participant (N = 39) made four impressions, each a combination of pickup and reseating techniques with polyether or polyvinylsiloxane, of one implant cast representing a specific clinical situation (tooth gaps, limited residual dentition, or edentulous jaw). Handling of impressions was subsequently rated by using a 12-item questionnaire with 100-mm visual analog scales. Results: While mean satisfaction scores were higher for polyvinylsiloxane than for polyether (69.5/63.0, P < .001), differences among subgroups were statistically significant only for pickup technique, limited residual dentition, and edentulous jaw. Conclusion: Implant impressions made with polyvinylsiloxane using a pickup technique seem to be the best option for most clinical situations.

Limited retrievability is a major disadvantage of cement-retained implant restorations. Despite great progress in locating the abutment screw within crowns, the existing techniques are based on prior data or prefabricated devices and require significant work. This study introduces a new procedure for fabricating a guide template to drill a screwaccess hole using a double-step superimposition technique that incorporates intraoral optical scanning, cone beam computed tomography, and dental design software. The double-step superimposition technique with computer-aided design/computer-assisted manufacturing technology can enhance the convenience and accuracy of drilling the screw-access hole.