The International Journal of Prosthodontics, 02/2017

The following were selected as the three best scientific posters presented at the 35th International Congress of the Italian Academy of Prosthodontic Dentistry held November 17-19, 2016.

This article describes the digital fabrication of a surgical obturator (SO) using only computed tomography (CT) data from the tumor area. This procedure is a departure from the traditional method of making an impression and obtaining a patient cast prior to surgery to allow for SO fabrication. The present approach allows for a virtual resection based on the patient's CT image; the SO is digitally designed with animation software and fabricated by 3D printing. The SO is relined with a denture reliner at the time of surgery to complete the obturation of the maxillectomy defect.

Purpose: The aim of this study was to evaluate the effect of a computer-aided design/ computer-assisted manufacturing (CAD/CAM) guide on drilling the screw-access channel for lingually placed implants. Materials and Methods: Screw-channel drilling guides were fabricated on lingually placed implant models using CAD/CAM technology. The screw channels were prepared with guided or freehand drilling by 20 dental graduates. The accuracy of each screw channel was assessed for drilling entry point, channel volume, and angulation (α = .05). Results: The guided drilling group showed smaller deviations than the freehand drilling group, and prosthesis position influenced the guide effect (P .001). Conclusion: The CAD/CAM guide facilitated the screw channel preparation of cement-retained prostheses supported by lingually placed implants.

Purpose: The introduction of computer-aided design/computer-assisted manufacture (CAD/ CAM) technology into removable denture prosthodontics enables denture adaptation in fewer patient visits, an advantage that appeals to dentists and patients. Since manufacturers follow very different approaches, an evaluation of the different clinical CAD/CAM complete denture fabrication protocols is desirable. The aim of this article is to assess and evaluate the different clinical fabrication protocols of currently available CAD/CAM denture systems to provide decision support for dental practitioners. Materials and Methods: The information for the present article was gathered by questionnaires from (in alphabetical order) Global Dental Science, Merz Dental, Wieland Dental + Technik, Ivoclar Vivadent, VITA Zahnfabrik, and Whole You, and complemented with results from the authors' clinical experience. Results: Wieland Digital Denture involves four patient visits. Both AvaDent digital dentures and Whole You Nexteeth enable denture fabrication in three (including a try-in session) or two (without try-in) visits. Baltic Denture System stipulates complete denture fabrication in two visits, and VITA VIONIC material system is an open system enabling choice between different treatment protocols. It can be combined with several open scanners, CAD software options, and milling machines. Conclusion: The available CAD/CAM denture fabrication systems provide a variety of advantages, and the decision on a system should depend on the dentist's prosthodontic expertise, patient throughput rate, and requirements regarding denture individualization.

Bruxism is a common phenomenon involving repetitive activation of the masticatory muscles. Muscle-stretching exercises are a recommended part of several international guidelines for musculoskeletal disorders and may be effective in management of the jaw muscle activity that gives rise to bruxism. However, most studies of muscle-stretching exercises have mainly focused on their influence on performance (eg, range of motion, coordination, and muscle strength) of the limb or trunk muscles of healthy individuals or individuals with sports-related injuries. Very few have investigated stretching of the human masticatory muscles and none muscle-stretching exercises in the management of (sleep) bruxism. This article reviews the literature on muscle-stretching exercises and their potential role in the management of sleep bruxism or its consequences in the musculoskeletal system.

Purpose: The aim of this study was to determine the influence of selected cements, abutment heights, and aging on the retention of zirconia crowns on zirconia abutments. Materials and Methods: Zirconia crowns and abutments (height: 4.0 or 5.5 mm) were sandblasted and retained using five different cements. Axial pull-off tests were performed after thermocycling or 3 days of water storage. Results: An increase in abutment height was associated with an increase in decementation force when permanent cementation was tested. The aging protocol showed that temporarily cemented crowns showed a significant retention decrease, while use of a permanent cement led to a moderate increase. Conclusion: Only use of permanent cements ensures clinically adequate decementation forces.

Purpose: The aim of this study was to evaluate the marginal accuracy and mechanical behavior of implant-supported crowns restored with original stock abutments and nonoriginal computer-aided design/computer-assisted manufacture laser-sintered abutments. Materials and Methods: A total of 26 implants were divided in two groups (n = 13 each) as follows: implants connected to original stock abutments (OS) and implants connected to nonoriginal laser-sintered abutments (LS). Of these, 10 samples were cross-sectioned to measure the marginal accuracy under a scanning electron microscope. In addition, 16 samples were used to study the mechanical behavior. Two tests were performed: (1) static load and (2) dynamic load after thermocycling with artificial saliva. Results: OS exhibited the best marginal accuracy; however, the LS gap was within the clinically acceptable range of marginal discrepancy. No significant differences were found in the mechanical tests. Conclusions: Both abutments are acceptable alternatives to restore implants, although the original abutments showed better fit than nonoriginals.

Purpose: A cohort of Japanese patients diagnosed with occlusal dysesthesia (OD) was clinically analyzed for psychosomatic background, management, and treatment outcome. Materials and Methods: The study group comprised 61 patients (17 men and 44 women) who met the OD criteria. Treatment outcomes were categorized as improvement, interruption, and transfer to another department. Results: The diagnosed OD was resolved in 25 patients (41%), 20 patients (33%) discontinued treatment, 13 (21%) were referred or transferred to other specialties such as psychiatry, and 3 (5%) continued to receive treatment following an engagement period of 3 months, 2 years, and 5 years, respectively. Among the 20 patients who discontinued treatment, complaints persisted for 10 and they did not comply with treatment, 1 had immodithymia characterized by adherence to symptoms, 3 had depressive states, 2 were suspected to have schizophrenia, and 2 were suspected to have so-called phantom bite syndrome. Conclusion: This study suggests that OD treatment should take into account the underlying psychiatric disorder manifesting as physical complaints.

Purpose: The aim of this study was to evaluate the feasibility and accuracy of using an intraoral scanner to digitize edentulous maxillectomy defects. Materials and Methods: A total of 20 maxillectomy models with two defect types were digitized using cone beam computed tomography. Conventional and digital impressions were made using silicone impression material and a laboratory optical scanner as well as a chairside intraoral scanner. The 3D datasets were analyzed using 3D evaluation software. Results: Two-way analysis of variance revealed no interaction between defect types and impression methods, and the accuracy of the impression methods was significantly different (P = .0374). Conclusion: Digitizing edentulous maxillectomy defect models using a chairside intraoral scanner appears to be feasible and accurate.

Purpose: This study aimed to correlate micromotion and gap measurements at the implantabutment interface. Materials and Methods: A total of 10 implant-abutment assemblies were subjected to micromotion measurements under cyclic loading and subsequently quartered and inspected under a light microscope to measure vertical and horizontal gaps between implant and abutment. Statistical analysis was based on Pearson productmoment correlations (α = .05). Results: Micromotion varied from 8.03 μm to 100.32 μm, while horizontal gaps ranged from 8.72 μm to 59.93 μm and vertical gaps ranged from 3.93 μm to 30.82 μm. No significant correlations were found (P > .05). Conclusion: Simplistic gap measurements at the implant-abutment interface are inadequate for predicting micromotion.

Purpose: The aim of this study was to clinically monitor the progression of tooth wear over a period of 1 year in a cohort of referred tooth wear patients through the use of a computer-aided design/ computer-assisted manufacture (CAD/CAM) scanner and a standardized scanning/assessment methodology. Materials and Methods: Polyether impressions were made of 11 participants (130 teeth) at baseline and at 1 year. Impressions were poured in type IV dental stone and the anterior teeth were 3D scanned. A surface-matching software was used to compare 1-year and baseline scans and identify any dimensional differences. Results: Parafunctional habits were reported by all patients. All participants exhibited tooth wear ≥ 140 μm in depth and extending to ≥ 280 μm in at least one tooth. Maxillary central incisors were the most commonly and severely affected teeth. Conclusion: The ability of the developed CAD/CAM scanning methodology in clinical monitoring of tooth wear was demonstrated. Further research is needed to assess its practicality in largescale epidemiologic tooth wear studies.

Purpose: This study investigated the influence of tooth color on patients' satisfaction with the esthetics of their smiles. Materials and Methods: A shade guide was used to determine the color of the maxillary anterior teeth in 671 participants. Self-reported satisfaction was assessed through five criteria: tooth appearance, color, shape, and position and appearance of the gingiva. The Psychosocial Impact of Dental Aesthetics Questionnaire and an Oral Impact on Daily Performances questionnaire were also used. Results: The predictors of higher patient satisfaction were lower chroma, higher lightness, and uniform color of all maxillary anterior teeth. These are significant but weak predictors of satisfaction with smile esthetics. Conclusion: Color has a low level of influence on satisfaction with a smile's esthetics.

Purpose: The aim of this study was to evaluate the efficacy of a structured communication protocol between dentists and dental laboratory technicians. Materials and Methods: A total of 112 single metal-ceramic crowns, fabricated by four different dentist-dental technician pairs, were evaluated at the clinical try-in appointment. Subsequently, each professional pair produced another 112 crowns using a checklist. Results: The scores showed a statistically significant improvement in clinical outcomes with the use of a checklist by reducing adjustment times for contact area, fit, and occlusion and number of appointments. Conclusion: The use of a checklist improved crown quality.

A young female patient suffering from Satoyoshi syndrome had the first characteristic signs and symptoms of hair loss and progressive spontaneous intermittent painful spasms of limb muscles at age 6.5 years. Thereafter, she developed chronic diarrhea, amenorrhea, and skeletal deformities. In the orofacial region, she suffered from painful spasms of the masseter (jaw closing) muscles, progressive tooth loss, and degeneration of the mandibular condyles. Treatment with steroids and provision of complete dentures improved the signs and symptoms. Early diagnosis and timely provision of multidisciplinary care can minimize complications in these patients and improve their orofacial functions and quality of life.

Purpose: The aim of this critical review was to assess the survival and success rates of allceramic single crowns manufactured using different ceramic materials with a mean follow-up time of 5 years or longer. Materials and Methods: An electronic search of studies published between 1980 and 2014 complemented by manual searching was conducted in Medline and Scopus. The terms ceramic, crown, survival, success, longevity, and complications were selected as keywords. Predetermined inclusion and exclusion criteria guided the search. Data were extracted and assessed by two independent reviewers. The results were statistically analyzed according to the type of material, and survival/success rate was calculated by assuming a Poisson-distributed number of events. Results: The initial search yielded 972 articles. After subsequent filtering, 14 studies were selected. The inter-reviewer agreement was rated as good (κ = 0.65) and very high agreement (κ = 0.93) during the identification and screening phases, respectively. No studies on densely sintered zirconia or feldspathic crowns satisfied the minimum follow-up time. Only one study of each of the following materials satisfied the inclusion criteria: lithium disilicate, leucite reinforced, pressed Al2O3, and sintered Al2O3. Meta-analysis of the included studies on other materials resulted in the following estimated survival and success rates: for densely sintered alumina crowns, 93.8% and 92.75%, respectively; for fluoromica reinforced, 87.7% and 87.7%, respectively; and for glass-infiltrated alumina core, 94.4% and 92%, respectively. Crown fracture was considered the most frequent complication. Conclusion: Based on the present critical review, there was no evidence to support the superior application of a single ceramic system or material. Further long-term prospective studies are required.

Purpose: The aim of this study was to evaluate the effect of the build orientation/build angle on the dimensional accuracy of full-coverage dental restorations manufactured using digital light-processing technology (DLP-AM). Materials and Methods: A full dental crown was digitally designed and 3D-printed using DLP-AM. Nine build angles were used: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. The specimens were digitally scanned using a highresolution optical surface scanner (IScan D104i, Imetric). Dimensional accuracy was evaluated using the digital subtraction technique. The 3D digital files of the scanned printed crowns (test model) were exported in standard tessellation language (STL) format and superimposed on the STL file of the designed crown [reference model] using Geomagic Studio 2014 (3D Systems). The root mean square estimate (RMSE) values were evaluated, and the deviation patterns on the color maps were further assessed. Results: The build angle influenced the dimensional accuracy of 3D-printed restorations. The lowest RMSE was recorded for the 135-degree and 210-degree build angles. However, the overall deviation pattern on the color map was more favorable with the 135-degree build angle in contrast with the 210-degree build angle where the deviation was observed around the critical marginal area. Conclusions: Within the limitations of this study, the recommended build angle using the current DLP system was 135 degrees. Among the selected build angles, it offers the highest dimensional accuracy and the most favorable deviation pattern. It also offers a self-supporting crown geometry throughout the building process.

Purpose: The aim of this study was to report the distribution of patients with early implant failures after implant treatment in the edentulous jaw with regard to age at surgery and association with patient mortality over a 15-year period. Materials and Methods: All consecutively treated patients treated in the edentulous jaw at a single specialist clinic from 1986 to 1997 were included and followed up for 1 year for implant failures and for 15 years with regard to patient mortality. Patients were arranged into age groups, and life tables for patients and reference groups of patients with comparable age (based on national population data) were calculated. Log rank test was used to test differences in patient survival between those with reported early implant failures and those with no early failures. Mantel-Haenszel chi-square test was used to test association between proportions of implant failures and age groups. Results: A total of 55 patients were excluded because they were not living in Sweden (nonresidents/emigrated). Altogether, 2,566 patients were included, with a mean age of 65 years (SD: 11). Of these, 988 patients were deceased during the 15 years of followup (38%), and 291 presented an early implant failure (11.3%), most of them before prosthesis placement (72%). Patients with early implant failures presented higher mortality rates than patients with no failures (P .05), and failure rates decreased consistently from younger to higher age groups (P .05). Conclusion: Patients in the younger age groups showed an increased mortality compared with the reference group (P .05) and a higher prevalence of early failures compared with older patients (P .05). Older patients showed an opposing pattern of lower mortality compared with reference groups of comparable age (P .05), but both younger and older patients with early failures showed a higher mortality compared to patients with no failures (P .05).