The International Journal of Prosthodontics, 02/2014

The following are the three best scientific posters that were presented at the 32nd International Congress of the Italian Academy of Prosthetic Dentistry held in Bologna on November 21-23, 2013.

Purpose: This before and after study evaluated the effects of a mandibular advancement device (MAD) on sleep bruxism (SB) activity and its associated signs and symptoms. Materials and Methods: Nineteen young adults (39.9 ± 12.9 years, 58% women) with a clinical history of SB without sleep or neurologic disorders and no spontaneous temporomandibular disorder pain were selected. SB activity was assessed after a habituation period of 2 weeks. The results of a 3-month treatment with a thermoplastic monoblock MAD were compared to baseline using electromyogram polysomnography and the BiteStrip, a portable EMG device. Sleep disorders were assessed and validated against the polysomnography sleep assessment questionnaire (SAQ). Additionally, common signs and symptoms of SB were evaluated with the research diagnostic criteria for temporomandibular disorders. Occlusal force was compared to baseline using a cross-arch force transducer. Results: There was a significant improvement in both SB activity and sleep scores (including SB episodes per hour) according to the BiteStrip and the SAQ, respectively. There was also a significant reduction in the signs and symptoms of SB, including grinding and/or clenching, temporomandibular joint (TMJ) sounds, muscle pain, and occlusal force. None of the SB subjects experienced MAD breakage, but in 24% of patients, the MAD treatment had to be interrupted due to TMJ/muscle pain and/or discomfort. Conclusion: The MAD treatment resulted in the reduction of SB activity, SB signs and symptoms, sleep disorders, and occlusal force. Int J Prosthodont 2014;37:119-126. doi: 10.11607/ijp.3675

Purpose: The objectives of this work were to systematically review the effect of bruxism on the survival of zirconia restorations on teeth and to assess the prevalence of nocturnal masseter muscle activity in a clinical sample. Materials and Methods: A Medline search was performed independently and in triplicate using the term "zirconia" and activating the filter "clinical trial." Furthermore, three other electronic databases were searched using the same term. Only papers published in English on prospective studies of veneered zirconia frameworks on teeth were included. To estimate the prevalence of sleep bruxism in clinical settings, subjects with no clinical signs of bruxism and who did not report grinding and/or clenching were examined by use of a disposable electromyographic device. Results: The initial search resulted in 107 papers, of which 22 were included in the analysis. Bruxers were excluded in 20 of these articles. In 1 study bruxers were not excluded, and 1 study did not provide information regarding this issue. The methods used to identify bruxers were heterogeneous/not described, and no study used reliable, valid methods. Of 33 subjects without clinical signs of bruxism, nocturnal muscle activity exceeded predefined muscle activity for 63.8% of the subjects. Conclusion: There is a lack of information about the effect of bruxism on the incidence of technical failure of veneered zirconia restorations because all available studies failed to use suitable instruments for diagnosis of bruxism. Nocturnal muscle activity without clinical symptoms/report of bruxism was observed for a relevant number of patients. Int J Prosthodont 2014;37:127-133. doi: 10.11607/ijp.3652

The use of new materials and computer-aided design/computer-aided manufacturing techniques can help dental practitioners efficiently treat dental erosion in a predictable manner. If the vertical dimension of occlusion has to be increased, the static and dynamic occlusion need to be reorganized. This article presents and documents a practical, digital approach to such treatment and discusses possible merits as they relate to treatment time, ease of treatment, and predictability. Int J Prosthodont 2014;27:134-136. doi: 10.11607/ijp.3768

Purpose: The aim of this study was to investigate if argon plasma cleaning increases the shear bond strength between zirconia and veneering ceramic surfaces. Materials and Methods: Ninety tablets of densely sintered yttriastabilized tetragonal zirconia polycrystal were divided into three groups according to cleaning treatment (steam cleaning or plasma of Argon for 375 or 750 seconds). Groups were divided into two subgroups according to the application of a ceramic liner (A = liner, B = no liner). Results: Within subgroup A, argon plasma cleaning significantly decreased shear bond strength. In subgroup B, the plasma treatment increased the shear bond strength, but the differences were not statistically significant. Subgroup A demonstrated lower shear bond strength compared to subgroup B. Conclusions: Argon plasma cleaning was suggested to improve the bond between ceramic and zirconia surfaces; however, when plasma cleaning was followed by a glassy liner application, the veneering ceramic/zirconia bond was significantly reduced. Int J Prosthodont 2014;27:137-139. doi: 10.11607/ijp.3722

Purpose: This clinical trial evaluated the influence of denture adhesive (DA) use on masticatory function in denture wearers according to their denture-bearing ridge status. Materials and Methods: Thirty edentulous subjects, wearing new well-fitting dentures, were classified as having either a normal or resorbed ridge. Mastication was evaluated in patients who completed chewing tests with and without two DA substances (cream or strips), which were randomly assigned. A chewing test with a sieve method analyzed masticatory performance. A kinesiographic device evaluated chewing cycle, and a visual analog scale measured masticatory ability. Data were submitted to Mauchly's sphericity test, and PROC MIXED procedures were conducted on repeated measures. Tukey-Kramer tests performed appropriate statistical comparisons (P ≤ .05). Results: DA use increased masticatory performance and ability in patients with both ridge types (P .05). Subjects with resorbed ridges showed the best masticatory performance (P .001) and lowest chewing cycle time (P .001) with DA cream, followed by DA strips and the nonadhesive trial. For normal ridge subjects, decreases in ×50 values were only significant with DA use (P .05), regardless of DA type. The denture-bearing ridge status alone did not alter masticatory function in any of the parameters evaluated. Conclusion: DAs improve mastication by shortening the chewing cycle and by enhancing chewing ability and performance. Int J Prosthodont 2014;27:140-146. doi: 10.11607/ijp.3674

The aims of this study were to determine the fracture origins and crack paths in the porcelain of clinically failed bilayer ceramic restorations and to reveal the correlation between the porcelain failures and material properties. Three clinically failed crowns of each material (bilayer zirconia crowns, galvano-ceramic crowns, and porcelain-fused-to-metal crowns) were collected and underwent failure analysis. The fractures found in porcelain veneers showed several characteristics including wear, Hertzian cone crack, chipping off, and delamination. The results indicated that the fracture origins and features of the porcelain in bilayer ceramic restorations might be affected by the rigidity of core materials and thickness of copings. Int J Prosthodont 2014;27:147-150. doi: 10.11607/ijp.3608

This retrospective report describes an individual prosthodontist's views regarding clinical factors that presumably influence the frequency of relining procedures (FRP) during the maintenance period of removable prostheses. Patient selection was composed of 60 removable prosthesis-wearing individuals who had been clinically monitored and maintained at 3-month intervals for periods ranging from 5 to 25 years. The FRP was designated as the dependent value, and the number of occlusal supporting areas, number of remaining teeth, sex, and age were designated as independent values using linear regression analysis (P .05). Factors influencing the FRP were the number of occlusal supporting areas and patient age; the period between relining procedures increased as occlusal supporting areas and age increased. Int J Prosthodont 2014;27:151-152. doi: 10.11607/ijp.3799

Purpose: This retrospective study investigated the frequency and time history of chipping and facing failures, recurrent caries (RC), periodontitis (PE), and loss of retention (LR) of porcelain-fused-to-metal (PFM) single crowns. Materials and Methods: A total of 997 PFM single crowns had been inserted according to a standardized treatment protocol from January 1984 to May 2009. The frequency and time history of chipping and facing failures were evaluated, as were possible risk factors from historical clinical data. Risk factors were bruxism, the type of antagonist, and the location of crowns (mandible, maxilla, anterior, posterior). The survival times of crowns were estimated using Kaplan-Meier (KM) analysis. Results: The median follow-up time calculated with the inverse KM method was 4.33 years. Anterior and posterior PFM crowns showed 5-year survival rates (time to crown replacement) of 96.4% and 97.5% and 10-year survival rates of 92.3% and 95.9%, respectively. Chipping was found in 17 (1.7%) of the 997 PFM crowns. According to the KM method, the 5- and 10-year free-of-event-rates for chipping of anterior crowns were both 98.9%, and the rates for posterior crowns were 98.2% for 5 years and 97.3% for 10 years. Thirteen patients showed RC (1.3%) and 144 (14.4%) PE. The 5-year free-of-event-rate for RC was 98.7% and the 10-year free-of-event rate was 97.2%. For PE, the 5-year free-of-event-rate was 85.8% and the 10-year free-of-event rate was 72.2%. The 5- and 10-year freeof- event-rates for LR were 92.2% each for anterior teeth and 97.1% each for posterior teeth. Conclusions: Patients with PFM crowns may expect long-term survival for their restoration. Clinical complications are rare. Chipping of the veneer or loss of retention may occur during the first few years. While chipping of the veneer may occur during the first few years, the frequency of caries or periodontitis increases with the length of oral service and with age. Int J Prosthodont 2014;27:153-160. doi: 10.11607/ijp.3440

Purpose: This study investigated the reliability of visual assessment of marginal gaps in relation to the use of magnification and the operator's profession. Materials and Methods: A titanium bar was notched, simulating 40 marginal gaps, and 35 operators performed a quantitative evaluation of the incisions. Results: Visual examination was neither sensitive nor specific, as an extreme variability of data was recorded. The precision of readers improved with magnification aids only for clinicians; technicians were significantly more accurate in evaluating the incision's width. Conclusion: The visual examinations were inadequate to decide the clinical acceptability of a restoration with regard to its marginal fit. Int J Prosthodont 2014;27:161-164. doi: 10.11607/ijp.3649

Purpose: To describe the survival, clinical rating, and patient satisfaction of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) ceramic singleunit cantilever crowns placed on hemisected molars and premolars after a follow-up of at least 12 months. Materials and Methods: Sixteen consecutive patients (mean age, 56.8 years) with 16 restored two-unit cantilever crowns (5 premolars and 11 hemisected molar abutments) were reevaluated after an observation period of at least 12 months. Tooth mobility, plaque and bleeding scores, and pocket probing depths were assessed on both the restored and contralateral untreated teeth. Patient satisfaction was evaluated using a visual analog scale. Results: The mean observation time was 25.7 ± 13.1 months. All restorations were in situ, and no significant biologic differences were observed between the treated and contralateral teeth. Clinical evaluation showed good performance, and patient satisfaction was recorded as excellent. Conclusion: The use of CAD/CAM ceramic single-unit cantilever crowns may be regarded as a conservative and cost-effective treatment modality with high patient acceptance in carefully selected patients. Int J Prosthodont 2014;27:165-168. doi: 10.11607/ijp.3514

Treatment of patients with microstomia due to scleroderma is complicated. Limited mouth opening and altered finger shape present difficulties at every step of the prosthetic rehabilitation. This article describes the prosthetic management of an edentulous patient with severe microstomia induced by scleroderma. From among the existing treatment options and according to the patient's ability and financial considerations, the authors provided a simple prosthetic design that effectively facilitated the patient's rehabilitation. To plan treatment for a patient with scleroderma, it is important to have knowledge about existing complications, alternative methods, and the patient's ability and comfort. Int J Prosthodont 2014;27:169-173. doi: 10.11607/ijp.3550

Chipping of the ceramic veneer is reported as a frequent occurrence when using zirconia-based fixed dental prostheses (FDPs). One possible cause of this complication is the inadequate support of the veneering ceramic by the zirconia substructure. In this article, early clinical observations from patients treated with 96 zirconia-based ceramic single- and multiple-unit FDPs on natural teeth and implants are presented. The FDPs were fabricated according to the aesthetic functional area protection concept of framework design for the prevention of ceramic chipping. Int J Prosthodont 2014;27:174-176. doi: 10.11607/ijp.3874