The International Journal of Prosthodontics, 01/2014

Reading good journals makes us better health professionals. It pushes us to develop new perspectives and see clinical challenges in a different light. It inspires us to pursue excellent patient treatment with passion-achievable through this compact and portable resource that never crashes or needs rebooting. Our International Journal of Prosthodontics (IJP) is a knowledge device that comes without wires, electric circuits, or batteries; it is also convenient, durable, and affordable. It reaches out to the global prosthodontic community by sharing both researched ideas and provocatively articulated ones. It continues to deserve its readers' appreciation and support while featuring acknowledged leaders' appreciation for our discipline. This issue's guest editorial is by one of the IJP's long-serving and gifted Associate Editors, the International College of Prosthodontists current Co-President, Dr Rhonda F. Jacob. Her leadership in maxillofacial prosthodontics, as a consummate clinical scholar, has just been recognized with the Ackerman Award from the American Academy of Maxillofacial Prosthodontics. She recently retired into private practice following a stellar 30-year clinical academic career at the MD Anderson Cancer Center at the University of Texas.

Purpose: This systematic review considers possible etiologic factors and definitions of peri-implantitis as reported in the recent literature. Materials and Methods: An electronic search of databases plus a hand search of the most relevant journals published between January 2005 and September 2012 were performed. Results: The electronic and manual searches yielded 640 and 14 titles, respectively. From the independent doublecheck of the titles and abstracts, 24 full texts were downloaded (18 clinical studies and 6 animal studies). After reading the full texts, 10 articles (4 clinical studies and 6 animal studies) were included in this review. None of the human articles selected provided sufficient evidence to address the research question, and no human clinical evidence is available to support a cause-effect relationship between peri-implantitis and bacterial accumulation and/or occlusal overload. The animal literature is also not unanimous regarding a specific peri-implantitis etiology. However, a correlation between periodontitis and smoking histories was cited as contributing to a higher incidence of peri-implantitis. Conclusion: The available scientific literature is characterized by an absence of a unanimous consensus regarding the etiology of peri-implantitis and its specific relationship to periodontitis. Furthermore, both the choice of the term peri-implantitis and its definition remain controversial. Int J Prosthodont 2014;27:15-25. doi: 10.11607/ijp.3785

Purpose: The aim was to evaluate the stress concentration caused by different cross sections of bar frameworks and clip materials used to retain overdentures. Materials and Methods: Three-dimensional models of a severely resorbed arch, an overdenture retained by two implants, and a bar-clip attachment system were made. A total of twelve models were made according to the cross section of the bar framework (round, oval, or Hader), clip material (gold or plastic), and presence of misfit. A vertical misfit of 100 μm between the implant and the bar framework was made on the right implant. Finite element models were obtained by importing the solid model into mechanical simulation software. The base of the mandible was set to be the fixed support, and a pressure of 100 MPa was applied to the right mandibular first molar. The analysis was made by means of von Mises stress for the prosthetic components and microstrain to the bone tissue. Results: Round bars led to lower values of stress in the clip and prosthetic screw of the ill-fitted component and lower microstrain values in the periimplant bone tissue. The lowest values of stress in the bar were observed in the Hader groups. Plastic clips reduced the stress concentration in all structures compared with gold clips. Conclusion: The clip material and the cross section of the bar framework influenced the stress distribution in overdentures retained by a bar-clip system presenting vertical misfit. Int J Prosthodont 2014;27:26-32. doi: 10.11607/ijp.3627

Purpose: This review aimed to evaluate the documented clinical success of zirconiabased crowns in clinical trials. Materials and Methods: Electronic databases were searched for original studies reporting on the clinical performance of tooth- or implant-supported zirconia-based crowns, including PubMed, Cochrane Library, and Science Direct. The electronic search was complemented by manual searches of the bibliographies of all retrieved full-text articles and reviews as well as a hand search of the following journals: International Journal of Prosthodontics, Journal of Oral Rehabilitation, International Journal of Oral & Maxillofacial Implants, and Clinical Oral Implants Research. Results: The search yielded 3,216 titles. Based on preestablished criteria, 42 full-text articles were obtained. While 16 studies fulfilled the inclusion criteria, only 3 randomized controlled trials were reported. Seven studies reported on tooth-supported and 4 on implant-supported crowns, and 5 studies reported on both types of support. Ten studies on tooth-supported and 7 on implantsupported crowns provided sufficient material for statistical analysis. Life table analysis revealed cumulative 5-year survival rates of 95.9% for tooth-supported and 97.1% for implant-supported crowns. For implant-supported crowns, the most common reasons for failure were technical (veneering material fractures). For tooth-supported crowns, technical (veneering material fractures, loss of retention) and biologic (endodontic/ periodontic) reasons for failure were equally common. The most common complications for implant-supported crowns were veneering material fractures and bleeding on probing. For tooth-supported crowns, the most common complications were loss of retention, endodontic treatment, veneering material fractures, and bleeding on probing. Conclusion: The results suggest that the success rate of tooth-supported and implant-supported zirconia-based crowns is adequate, similar, and comparable to that of conventional porcelain-fused-to-metal crowns. These results are, however, based on a relatively small number of studies, many that are not controlled clinical trials. Well-designed studies with large patient groups and long follow-up times are needed before general recommendations for the use of zirconia-based restorations can be provided. Int J Prosthodont 2014;27:33-43. doi: 10.11607/ijp.3647

Purpose: To show the reliability of the Maltese translations of OHIP-14, GOHAI, and the Denture Satisfaction Questionnaire, define the reliability of the responses, and determine the correlation between OHIP-14 and GOHAI. Materials and Methods: The items of the three questionnaires (OHIP-14, GOHAI, and Denture Satisfaction) were translated into Maltese and back into English to compare with the original version. Specific sampling of a population well versed in Maltese and English was carried out to obtain a sample of respondents for each questionnaire. Data were gathered through self-administered questionnaires: first administering the Maltese version and following with the English version 1 week later. Results: Participation rates were high (98%). Cronbach's alpha for all three questionnaires was high (> 0.7), indicating satisfactory test-retest reliability of the instruments. Similarly, the Spearman correlation coefficients for both the English and Maltese versions of OHIP-14 and GOHAI were good (> 0.6). Conclusion: The Maltese versions of OHIP-14, GOHAI, and the Denture Satisfaction Questionnaire can be safely used as a valid alternative to the English versions in studies of patients who are limited in linguistic proficiency. Int J Prosthodont 2014;27:44-49. doi: 10.11607/ijp.3603

The aim of this study was to assess fear and anxiety in dental patients. Five hundred patients were evaluated using the Modified Dental Anxiety Scale and the Dental Fear Scale, along with a questionnaire. Oral health status was assessed using the Decayed, Missing, and Filled Teeth (DMFT)/Decayed, Missing, and Filled Surfaces (DMFS) index. Statistic al analysis was performed (P < .05). Sex significantly affected dental anxiety (P < .05), and sex, marital status, having children, and time elapsed since last visit to clinician affected dental fear (P < .05). DMFT/DMFS scores were not related to dental anxiety or fear (P > .05). Female sex alone was a significant predictor of dental anxiety; female sex, adulthood, marriage, having children, and time passed since last visit to a clinician are significant predictors of fear. Int J Prosthodont 2014;27:50-53. doi: 10.11607/ijp.3708

Purpose: To assess the relationships between occlusal tooth wear and occlusal conditions, chewing side preference, and occlusal guidance scheme. Materials and Methods: A total of 257 Chinese adult dental school patients were categorized according to a hierarchical functional classification system. Occlusal tooth wear was assessed using a modified Smith and Knight index. Occlusal tooth wear index (OTWI) scores were analyzed using multivariate regression models, including four specific occlusal conditions (≥ 10 teeth in each arch, complete anterior regions, sufficient premolar regions, and sufficient molar regions) adjusted for age and sex. Results: Occlusal tooth wear was observed in all participants; older participants and men had significantly higher mean OTWI scores. The occlusal condition of having fewer than 10 teeth in each arch was significantly associated with occlusal tooth wear; participants with fewer than 10 teeth in each arch had higher mean OTWI scores in anterior and premolar teeth. OTWI scores for the different tooth types were highly correlated with chewing side preference. OTWI scores for the molar region (including third molars) were significantly higher at the preferred chewing side. The same effect was seen for OTWI scores of all teeth combined. OTWI scores were not associated with occlusal guidance scheme. Conclusions: The occlusal condition of having fewer than 10 teeth in each arch appears to be a risk factor for increased occlusal tooth wear. Occlusal wear was more severe at the chewing side. Occlusal tooth wear was significantly associated with the nondental factors of age and sex. Int J Prosthodont 2014;27:54-60. doi: 10.11607/ijp.3642

Purpose: Tooth loss and its prosthetic rehabilitation significantly affect speech intelligibility. However, little is known about the influence of speech deficiencies on oral health-related quality of life (OHRQoL). The aim of this study was to investigate whether speech intelligibility enhancement through prosthetic rehabilitation significantly influences OHRQoL in patients wearing complete maxillary dentures. Speech intelligibility by means of an automatic speech recognition system (ASR) was prospectively evaluated and compared with subjectively assessed Oral Health Impact Profile (OHIP) scores. Materials and Methods: Speech was recorded in 28 edentulous patients 1 week prior to the fabrication of new complete maxillary dentures and 6 months thereafter. Speech intelligibility was computed based on the word accuracy (WA) by means of an ASR and compared with a matched control group. One week before and 6 months after rehabilitation, patients assessed themselves for OHRQoL. Results: Speech intelligibility improved significantly after 6 months. Subjects reported a significantly higher OHRQoL after maxillary rehabilitation with complete dentures. No significant correlation was found between the OHIP sum score or its subscales to the WA. Conclusion: Speech intelligibility enhancement achieved through the fabrication of new complete maxillary dentures might not be in the forefront of the patients' perception of their quality of life. For the improvement of OHRQoL in patients wearing complete maxillary dentures, food intake and mastication as well as freedom from pain play a more prominent role. Int J Prosthodont 2014;27:61-69. doi: 10.11607/ijp.3597

A treatment protocol that may lead to reduced mandibular posterior residual ridge resorption in patients with overdentures retained and supported by two interforaminal implants was investigated. The treatment included the addition of short implants in the posterior edentulous mandible for the presumed purpose of favorable provision of mechanical load stimulus to alveolar bone. Three-dimensional finite element analysis was used to model cited effective strains that may stimulate bone remodeling in two selected models. Based on this laboratory study, the addition of posterior short implants has a favorable effect in maintaining bone mass under implantretained overdentures. Int J Prosthodont 2014;27:70-72. doi: 10.11607/ijp.3425

Purpose: This study evaluated the materials used for tooth core restorations by dental students. Materials and Methods: The study included all patients treated with a single crown or fixed partial denture by undergraduate dental students during the years 1984 to 1986, 1994 to 1996, and 2004 to 2006. Results: More direct (62%) than indirect (38%) cores were prepared during the total time period evaluated. Conclusion: The complication rate of indirect cores compared with direct ones appeared to be higher in single crowns, but not in fixed partial dentures. Int J Prosthodont 2014;27:73-75. doi: 10.11607/ijp.3609

This study evaluated the effect of six screw-tightening sequences and two tightening methods on the screw preload in implant-supported superstructures. The preload was measured using strain gauges following the screw tightening of a metal framework connected to four implants. The experiment included six sequences ([1] 1-2-3-4, [2] 4-2-3-1, [3] 4-3-1-2, [4] 1-4-2-3, [5] 2-3-4-1, and [6] 3-2-4-1), two methods (onestep, three-step), and five replications. Significant differences were found between tightening sequences and methods. In the three-step method, a higher total preload was found in sequences 2 (312 ± 85 N), 3 (246 ± 54 N), and 4 (310 ± 96 N). In the one-step method, a higher total preload was found in sequences 1 (286 ± 94 N), 5 (764 ± 142 N), and 6 (350 ± 69 N). It is concluded that the highest total screw preload was achieved when anterior implants of the superstructure were first tightened in one step, followed by posterior implants. Int J Prosthodont 2014;27:76-79. doi: 10.11607/ijp.3306

Purpose: To examine whether electrical stimulation of the masseter muscle triggered by heart rate elevation preceding sleep bruxism (SB) can actively suppress SB. Materials and Methods: Ten volunteers who were aware of their SB habits participated in the study. Baseline electromyogram (EMG) activity of the unilateral masseter muscle and electrocardiogram (ECG) signal were recorded on the first night. The individual mean sensation and pain thresholds to electrical stimulation of the unilateral masseter muscle were determined in awake subjects before the experiment. On the second night, electrical stimulations at either of the two threshold intensities were automatically generated and delivered to the masseter muscle on the opposite side from where electrodes were placed immediately after the heart rate exceeded 110%. On the third night, electrical stimulations at the other threshold intensity were delivered. Results: The numbers of SB events per night and per hour, the number of EMG bursts per SB event, and the duration of SB events decreased significantly on the nights when stimulation was applied compared with the baseline data. There were no significant differences between cases where the sensation threshold was used as the stimulation intensity and those in which the pain threshold was used as the stimulation intensity. Conclusion: The results suggest that electrical stimulation of the masseter muscle triggered by heart rate elevation can significantly suppress SB. Int J Prosthodont 2014;27:80-86. doi: 10.11607/ijp.3330

Both causation and management of noncarious cervical lesions (NCCLs) (abfractions, wedge-shaped defects, stress-induced cervical lesions, and cervical erosion) remain debatable. A survey of clinicians' perceptions was therefore conducted at a recent professional meeting to determine optimal approaches to NCCL management. Examples of lesions differing in depth (1, 2, and 3 mm) were presented as being either sensitive or nonsensitive, and participants recorded their responses to the presented individual scenarios. This report provides information regarding correlations between increases in lesion depth, lesion sensitivity, and professionals' willingness to restore them. It was also noted that decisions to ensure mechanical retention positively influenced estimates for restoration longevity. Int J Prosthodont 2014;27:87-90. doi: 10.11607/ijp.3585