This position paper proposes a definition and naming standard for removable partial dentures (RPDs) using thermoplastic resin, and presents a guideline for clinical application. A panel of 14 experts having broad experience with clinical application of RPDs using thermoplastic resin was selected from members of the Japan Prosthodontic Society. At a meeting of the panel, "non-metal clasp denture" was referred as the generic name of RPDs with retentive elements (resin clasps) made of thermoplastic resin. The panel classified non-metal clasp dentures into two types: one with a flexible structure that lacks a metal framework and the other having a rigid structure that includes a metal framework. According to current prosthetic principles, flexible non-metal clasp dentures are not recommended as definitive dentures, except for limited cases such as patients with a metal allergy. Rigid non-metal clasp dentures are recommended in cases where patients will not accept metal clasps for esthetic reasons. Non-metal clasp dentures should follow the same design principles as conventional RPDs using metal clasps.

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Statistics play essential roles in evidence-based dentistry (EBD) practice and research. It ranges widely from formulating scientific questions, designing studies, collecting and analyzing data to interpreting, reporting, and presenting study findings. Mastering statistical concepts appears to be an unreachable goal among many dental researchers in part due to statistical authorities' limitations of explaining statistical principles to health researchers without elaborating complex mathematical concepts. This series of 2 articles aim to introduce dental researchers to 9 essential topics in statistics to conduct EBD with intuitive examples. The part I of the series includes the first 5 topics (1) statistical graph, (2) how to deal with outliers, (3) p-value and confidence interval, (4) testing equivalence, and (5) multiplicity adjustment. Part II will follow to cover the remaining topics including (6) selecting the proper statistical tests, (7) repeated measures analysis, (8) epidemiological consideration for causal association, and (9) analysis of agreement.

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Purpose: The aim of this study was to compare saliva flow and protein composition induced using five basic taste stimulations between natural and bioengineered salivary glands.
Materials and methods: We developed a mouse saliva secretion model using taste stimulation and analyzed the saliva secretion from natural and bioengineered salivary glands using an assay. The protein components and alpha-amylase in the natural and bioengineered saliva were analyzed by gel electrophoresis and Western blotting.
Results: The salivary flow responses induced by sour (citric acid) and bitter (quinine-HCl) stimuli were significantly high in the natural and bioengineered salivary glands. Although the protein concentrations in the natural and bioengineered saliva induced using five basic taste stimulations were similar, the protein composition and the amylase concentration in the natural saliva after taste stimulation had different profiles. Sympathetic and non-sympathetic nerves were observed around the acini and ducts in the natural and bioengineered salivary glands. However, the frequency of neuropeptide Y-positive sympathetic nerves in the bioengineered gland was relatively high compared to that in the natural gland.
Conclusions: These results suggest that the signal balance between the sympathetic and parasympathetic components of the efferent nerves in an engrafted bioengineered salivary gland may differ from that in a natural salivary gland.

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Purpose: A desideratum of oral health-related quality of life (OHRQoL) instruments – such as the Oral Health Impact Profile (OHIP) – is that they accurately reflect the structure of the measured construct(s). With this goal in mind, the Dimensions of Oral Health-Related Quality of Life (DOQ) Project was proposed to investigate the number and nature of OHRQoL dimensions measured by OHIP. In this report, we describe our aggregate data set for the factor analyses in the project, which consists of responses to the 49-item OHIP from general population subjects and prosthodontics patients from 6 countries, including a large age range of adult subjects and both genders.
Materials and methods: The DOQ Project's aggregate data set combines data from 35 individual studies conducted in Croatia, Germany, Hungary, Japan, Slovenia, and Sweden.
Results: The combined data set includes 10778 OHIPs from 9348 individuals (N = 6349 general population subjects, N = 2999 prosthodontic patients). To elucidate the OHIP latent structure, the aggregated data were split into a Learning Sample (N = 5173) for exploratory analyses and a Validation Sample (N = 5022) for confirmatory analyses. Additional data (N = 583) were assigned to a third data set.
Conclusion: The Dimensions of Oral Health-Related Quality of Life Project contains a large amount of international data and is representative of populations where OHIP is intended to be used. It is well-suited to assess the dimensionality of the questionnaire.

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Purpose: Several thermoplastic denture base resins have been introduced for the fabrication of non-metal clasp dentures. Although the surface of these materials is easily damaged, the surface roughness and characteristics of scratches created have not been evaluated. The purpose of this study was to evaluate the surface roughness of thermoplastic resins using a scratch test for the development of future materials.
Methods: Four thermoplastic (polyamide: Valplast^®; VLP and Lucitone FRS^®; FRS, polyethylene terephthalate: EstheShot^®; ES, and polyester: EstheShot Bright^®; ESB) and two conventional acrylic (Heat-polymerizing: Urban^®; HC, and Pour type auto-polymerizing: Pro-Cast DSP^®; PR) denture base resins were examined. Eight specimens, approximately 10 mm × 10 mm × 30 mm in size, of each material were fabricated. Scratch test was performed by a scratch tester with a diamond indenter of 10-μm radius and cone angle 90°, applying a constant load of 500 mN, and 2-mm-long scratches were made. The scratch marks were studied under 3D laser measuring microscope and cross-section profiles at approximately 0.5 mm, 1.0 mm, and 1.5 mm from the starting point were extracted and measured with analysis software. Data from 24 cross-section profiles in each denture base material were analyzed.
Results: The maximum depths of ES, ESB and FRS were greater than VLP, PR and HC, and the scratch widths of ES, ESB, FRS and VPL were greater than PR and HC.
Conclusions: The results showed that the surface of thermoplastic denture base resins was easily damaged compared to polymethyl methacrylate.

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Purpose: The purpose of this study was to use cortisol awakening response (CAR) to investigate the differences in daily life stress experienced by individuals wearing either a long-term (LT) or a short-term (ST) dento-maxillary prosthesis following head and neck cancer (HNC) resection. Also we used the University of Washington Quality of Life (UW-QOL) version 4 questionnaire to evaluate the differences in quality of life (QOL) scores between ST and LT wearers of a dento-maxillary prosthesis.
Methods: Salivary samples were collected from 11 LT and 10 ST prosthesis wearers on two consecutive days at two time points, immediately after waking up (T0) and 30 min later (T30), by passive drool collection. Cortisol levels were measured using a high sensitivity salivary cortisol enzyme immunoassay kit (Salimetrics, LLC, State College, PA, USA) and CAR (the differences between the cortisol levels at T0 and T30) was compared between LT and ST prosthesis wearers. In addition, both the groups completed the UW-QOL questionnaire and the scores were compared.
Results: A significant difference was observed in CAR between the two groups. CAR of the ST prosthesis wearers was significantly lower compared with that of the LT prosthesis wearers; moreover, the ST prosthesis wearers revealed significantly lower total UW-QOL scores and there were significant differences in appearance, activity, recreation, speech, and anxiety.
Conclusion: Within the limitations of this study, the findings suggest that individuals wearing ST dento-maxillary prostheses following HNC resection experience some sort of daily life stress and complicated socio-demographic factors may influence their QOL.

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Purpose: We investigated the influence of chewing time on salivary stress markers.
Methods: Participants performed arithmetic calculations for 30 min as stress loading, followed by chewing for 0, 5, 10, or 15 min. All experiments finished at 25 min after stress loading. With 0-min chewing, saliva was collected before stress loading (BS), immediately after stress loading (R0), and at 5, 10, 15, and 25 min after stress loading (R5, 10, 15 and 25). With 5, 10, or 15 min chewing, saliva was collected at BS and R0, immediately after chewing (Ch5, 10 and 15, respectively), and 25 min after stress loading (Ch5R25, Ch10R25 and Ch15R25, respectively). Salivary alpha-amylase activity and cortisol levels were measured to evaluate stress. Change in stress markers between R0 and Ch5, 10 and 15 or R25, Ch5R25, Ch10R25 and Ch15R25 were calculated.
Results: No significant differences were observed in rate of change in alpha-amylase activity among the chewing conditions. Rate of decrease in cortisol levels was significantly greater at 15-min chewing than at 5-min chewing. Rate of decrease in cortisol levels was significantly greater at 10 and 15-min chewing than at 0-min chewing.
Conclusion: The present results indicate that chewing time affects the reaction of the endocrine system to mental stress, and that continuous chewing for more than 10 min is effective in reducing stress.

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Purpose: The purpose of this study was to confirm the effectiveness of LEB irradiation onto the polymer powder for improving the mechanical properties of self-curing acrylic resin.
Methods: The polymer powder of self-curing acrylic resin was irradiated with total LEB doses of 25, 50, 75 or 100 kGy. Non-irradiated powder was used as a control. After LEB irradiation, ESR measurement, weight-average molecular weight measurement and three-point bending test were performed.
Results: ESR spectrum of control had no peaks. After LEB irradiation, nine peaks were observed in each ESR spectrum, which indicates the presence of free radicals from main polymer chain. The quantity of free radicals increased linearly up to 100 kGy. Calibrated weight-average molecular weights were as follows: control, 960,000; 25 kGy, 500,000; 50 kGy, 440,000; 75 kGy, 410,000; and 100 kGy, 390,000. Molecular weight decreased with increasing LEB irradiation dose. The mean values of flexural strength (MPa) were as follows: control, 61.5 ± 3.0; 25 kGy, 68.1 ± 4.0; 50 kGy, 73.0 ± 1.9; 75 kGy, 70.4 ± 3.6; and 100 kGy, 67.7 ± 2.3. The flexural strength of the specimens cured with the LEB-irradiated powder was significantly higher than that of control (p < 0.01). These results indicate that flexural strength of polymer materials cured with the LEB-irradiated powder increases because of increase in cross-linking structure.
Conclusion: It is confirmed that LEB irradiation onto the polymer powder of self-curing acrylic resin improves the flexural strength.

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Introduction: Auricular defects present reconstructive challenges, especially if they are bilateral. Surgical reconstruction provides effective results for defects; however for some patients surgical intervention is contraindicated. This case report describes an easy clinical technique to rehabilitate a patient with auricular defects. The prime purpose of this treatment rendered was to restore the lost auricular structure to the patient's satisfaction in an elegant, comfortable and cost effective manner.
Patient: A thirteen year old female patient, who had bilaterally missing ears, was referred with a chief complaint of discomfort caused due to her existing hair band prosthesis and unsatisfactory esthetics. There was constant formation of ulcers at the site where the prosthesis came in contact with the skin. Considering the patient's age, ease of use and economic status, hair band retained ear prosthesis was selected. Silicone ear prostheses were fabricated on acrylic substructure to ensure fit, esthetics. Beneath the acrylic plates, a thin layer of soft silicone material was attached. The ear prostheses of both sides were connected with a metal hair band to retain.
Discussion: The newly fabricated prosthesis overcame the limitations of the existing one. The patient and her parents were satisfied with the results.
Conclusion: The hair band retained silicone ear prosthesis is esthetic, economical and easy to use as a facial prosthesis. The addition of soft liner provided a cushion-like effect, thus reducing the formation of any ulcers due to pressure.

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