Purpose: Bio-inspiration is an approach in engineering aimed at optimizing artificial systems by borrowing biological concepts from nature. This review sets out to summarize the fundamental aspects employed by nature to avoid premature dental failures. On the basis of these findings, it then defines and evaluates rules for 'post-modern' manufacturing processes to imitate or regenerate complex biological systems.

Study selection: A thorough literature search was conducted using PubMed, the Cochrane Library database and Google Scholar. Peer-reviewed articles and other scientific literature provided up-to-date information addressing two topics: (a) how natural dental tissues combine to create a structure as tough, strong and highly resistant to fatigue failure as tooth, and (b) how 'bio-inspiration' can be applied to the manufacture of dental restorations, taking into consideration the limitations of techniques currently used in dentistry.

Results: Bio-inspired concepts have already been successfully applied in a range of engineering fields to enhance the toughness and strength of artificial materials. The area of technology with greatest potential to unlock the development of these new approaches is additive manufacturing. Consequently, these technologies and concepts could be applied to dentistry to improve the mechanical properties of dental restorations. Three-dimensional (3D) printing technologies also offer a new and promising prospect of regenerating dental tissues.

Conclusions: Considering the limitations to both conventional and subtractive computer-aided design/ computer-aided manufacturing (CAD/CAM) methods, further research should focus on new, additive 3Dprinting techniques. This may open new research paths in dentistry that will enhance the clinical performance of artificial dental materials.

Purpose: To determine the effect of veneering material and framework design on fracture loads of implant-supported zirconia molar fixed dental prostheses (FDPs).

Methods: Sixty-six zirconia FDPs were manufactured onto two implants and classified as uniform thickness (UT) or anatomic design (AD). These framework design groups were then further divided into three subgroups (n = 11): feldspathic porcelain-veneered zirconia FDPs (PVZ), indirect compositeveneered zirconia FDPs (IVZ), and metal–ceramic FDPs (MC). The FDPs were luted on the implant abutments and underwent fracture load testing. Significant differences were assessed by the Kruskal– Wallis test and Mann–Whitney U-test (α = 0.05).

Results: For UT group, median fracture load was significantly higher for the IVZ (1.87 kN) and MC (1.90 kN) specimens than for the PVZ specimens (1.38 kN) (p < 0.05). In the AD group, the IVZ specimens had the highest median fracture load (4.10 kN) of the three groups tested. The AD group exhibited higher median fracture loads than the UT group in all subgroups.

Conclusions: Indirect composite appears to be a useful alternative to feldspathic porcelain as the layering material for implant-supported zirconia FDPs. The AD group had higher fracture loads than UT group. In addition, implant-supported indirect composite-veneered zirconia-based FDPs appear to be clinically feasible.

Purpose: The aim of this study was to evaluate the shear bond strength and durability of MMA-TBB resin to human enamel applied a self-etching primer with phosphoric acid etching.

Methods: A self-etching primer (Teeth primer, TP) containing 4-methacryloyloxyethyl trimellitate anhydride (4-META) and sodium sulfite and two etchants having different phosphoric acid concentrations (K-etchant gel, KE, 35–45%: Red gel, RG, 20–25%) were used as treatment agent, and MMA-TBB resin was used as luting agent. Enamel surfaces were treated with six methods which were as follow: KE, RG, TP, KE + TP, and RG + TP. After enamel specimens were bonded with MMA-TBB resin and stored in distilled water for 24 h, the shear bond strength test was done at 0 thermocycling or 20,000 thermocycling. These results were statistically verified with Steel-Dwass multiple comparisons and Man–Whitney U test.

Results: The shear bond strength of TP group, KE + TP group, and RG + TP group were significantly higher than KE group and RG group in pre-thermocycling. KE + TP group and RG + TP group were significantly higher than other groups in post-thermocycling.

Conclusions: Applying TP with phosphoric acid etching can increased shear bond durability despite difference of phosphoric acid concentrations (35–45% or 20–25%).

Purpose: To perform a comparative analysis of the microstructure, porosity, mechanical properties, corrosion, and tarnish resistance of Co–Cr alloys prepared by casting and three different computer aided designed/computer aided manufacturing (CAD/CAM) techniques.

Methods: Four groups of metallic specimens were prepared, one each by conventional casting (CST), milling (MIL), selective laser melting (SLM), and milling soft metal (MSM). Ten samples were tested by X-rays, after which their microstructure and elemental composition were tested by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Martens hardness (HM) and elastic index (η_IT) were determined by instrumented indentation testing (IIT), while modulus of elasticity (E) was determined by three-point bending. Corrosion measurements were tested according to International Organization for Standardization (ISO) 10271. The electrolytes were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results were analyzed by one-way ANOVA and Holm–Sidak's multiple-comparison test (α = 0.05).

Results: The CST group illustrated internal flaws while all CAD/CAM group samples were found to be free of them. No statistically significant differences were identified among groups in their elemental composition. SLM showed the highest HM, followed by the MIL, CST, and MSM. Elastic index showed significant differences among all groups, with CST showing the lowest and SLM the highest values. SLM showed the highest elastic modulus values, followed by MSM, MIL, and CST. No significant differences were found in ionic release among groups. No surface deterioration after static and cyclic tarnish testing was determined.

Conclusions: The manufacturing procedure significantly affects the microstructure, porosity, and mechanical properties of Co–Cr alloys. In contrast, ionic release and tarnish resistance are independent of the manufacturing technique used.

Purpose: Elderly individuals with dry mouth wearing dentures require an appropriate denture adhesive. The purpose of this study was to evaluate the in vitro properties of a newly developed denture adhesive for patients with dry mouth and compare these with those of a currently available adhesive and oral moisturizing agent.

Methods: We developed a new gel-type denture adhesive with physical properties suitable for patients with dry mouth (DM). We subsequently performed in vitro comparisons among DM, New Poligrip (NP), and Biotene Oralbalance Gel (BT) with regard to the following properties: retention force, resistance to squeezing, and ease of removal. In accordance with the standards of the International Organization for Standardization (ISO10873:2010), the retention force was measured for dry samples (no water exposure, severe dry mouth model) and for samples exposed to water for 10 min (normal model) and 1 min (moderate dry mouth model). The resistance to squeezing was evaluated by pushing the samples out of syringes, while the ease of removal was evaluated by measuring the time required to wash the material from a polymethyl methacrylate plate.

Results: In the severe dry mouth model, DM exhibited greater retention force than did NP and BT. Moreover, the resistance to squeezing was significantly lower for DM than for NP. Both BT and DM showed better ease of removal than did NP. NP was the most difficult to wash out with water.

Conclusions: Our findings suggest that the newly developed denture adhesive DM is suitable for use in patients with dry mouth.

Purpose: This study aimed to clarify the influence of chewing on human β-defensin 2 (hBD-2) and secretory immunoglobulin A (SIgA) expression levels.

Methods: We included 15 healthy males with no missing teeth (mean age, 25.5 ± 2.5 years). Subjects were instructed to chew a piece of gum for 30 min. Saliva and skin-extraction samples were collected before and after chewing for 15 and 30 min. hBD-2 and SIgA concentrations in the samples were determined using enzyme-linked immunosorbent assay (ELISA). hBD-2 and SIgA expression levels before and after chewing were analyzed using the Mann–Whitney U test, following the Friedman test. The significance level was 0.05.

Results: The hBD-2 level in skin-extraction samples was significantly different before (99.4 ± 17.3 pg/mL) and after chewing for 30 min (142 ± 23.0 pg/mL). The SIgA level in skin-extraction samples was also significantly different before (2.39 ± 0.25 μg/mL) and after chewing for 30 min (3.61 ± 0.33 μg/mL). No significant difference was noted in either hBD-2 or SIgA secretion rate in saliva between before and after chewing.

Conclusions: Chewing gum for 30 min increased hBD-2 and SIgA expression levels in skin. Moreover, chewing gum could influence the secretion pattern of these two biomolecules on skin, but not in saliva.

Purpose: To assess the average full-arch scanning time, perception and likelihood of future adoption of technology by final-year dental students using three different Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) intraoral scanning systems.

Methods: Final-year undergraduate Dental Students (FDS), with no prior experience of intraoral scanning, full-arch scanned (IOS) a mannequin head-mounted model under supervision. Three scanning systems were used, TRIOS Colour (TRIOS); True Definition (TDef); and CEREC AC OmniCam (CEREC). Thereafter, FDS completed a questionnaire to assess their perception of IOS. Data were analysed by Generalized Estimating Equations, Fisher's exact tests and logistic regression.

Results: Forty-nine FDS participated. Average full arch IOS time varied significantly (p < 0.001) among the TRIOS, CEREC, and TDef, at 4 min (n = 48), 4 min 42 s (n = 33), and 7 min 32 s (n = 41) respectively. IOS using the TRIOS was significantly (p < 0.001) the quickest, while TDef was the slowest (p < 0.001). Seventy-one percent of FDS had positive overall IOS experience. FDS who reported intraoral scanning was timesaving compared with conventional impressions were more likely to adopt the technology after graduation (odds ratio (OR) = 11.91, 95% confidence interval (CI) = 2.56–55.45, p = 0.002).

Conclusions: Intraoral scanning performance of novice users varied significantly and was dependent on the scanning system used. The questionnaire showed that the overall IOS experience was positive amongst FDS. The perception of time-saving, when using IOS versus conventional impression methods, determined the likelihood of future adoption of the technology.

Purpose: To quantify and to compare a gravimetric and three-dimensional (3D) analysis of the removed tooth structure for different complete crown preparations.

Methods: A total of 80 molar resin teeth and 8 preparation finishing lines were chosen: 1 for metal ceramic crowns (MCC); 3 for zirconia all-ceramic crowns: knife edge (ZirKnE), chamfer (ZirCha), and shoulder (ZirSho); 4 for lithium disilicate: light chamfer (LDLCha), chamfer (LDCha), shoulder (LDSho) and table top. Teeth were individually weighed to high precision and then prepared following the preparation guidelines. The teeth were reweighed after preparation, and the amount of structural reduction was calculated. In addition, all teeth were scanned before and after preparation, and the 3D volume of removed dental tissue was calculated, superimposing the two.stl files, as a difference of the volumes before and after the preparation. Kruskal–Wallis statistical analysis was carried out to determine significant differences among the groups with a significance level of p < 0.05.

Results: Both analyses showed that LDLCha, ZirKnE and table-top preparations produced the smallest amount of removed structure, whereas the preparations for MCC, ZirSho and LDSho were more destructive. For MCC, 2.6 times more tooth structure must be removed than for table top. ZirKnE was 17.82% and LDLCha was 21.51% more conservative than MCC. The data obtained through the volumetric method were similar with those obtained by gravimetric analysis.

Conclusions: ZirKnE, LDLCha, and table-top preparations produced the least amount of tooth tissue removal. Three-dimensional volumetric analysis can be a possible alternative to gravimetric analysis.

Purpose: The purpose of this study was to examine the hypothesis that in the process from food ingestion to swallowing, intentional decrease in the muscle activity during mastication would affect the number of chewing strokes, and thus the occurrence of Stage II transport (St2Tr) or the number of swallowing.

Methods: Twenty adults with healthy dentition were instructed to make (1) normal mastication and (2) mastication with 50% muscle activity (50% mastication), controlled by visual feedback with electromyogram. Gummy jelly was selected as a test food. The oropharynx was observed during the sequence of events from the start of mastication until swallowing using a nasal endoscope. The number of chewing strokes was calculated by rhythmical masseter muscle activity on electromyogram.

Results: The number of chewing strokes increased with 50% mastication. There was a particularly noticeable increase in the number of pre-St2Tr strokes. No effect on the number of additional swallows was seen as a result of 50% mastication.

Conclusions: The present study supported the hypothesis that intentional decrease in the muscle activity during mastication affected the number of chewing strokes and the occurrence of St2Tr. Particularly, this tendency was noticeable during the mastication before the start of St2Tr. However, our results did not support a question as to the number of swallowing.

Purpose: To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics.

Methods: Layering and pressable ceramics without frames or on 0.8- and 1.2-mm-thick Y-TZP frames were fired with 5 schedules (normal and 4 customized conditions). The fracture toughness of the ceramics was measured at 0.5–2.5 mm from the frame by the indentation fracture method. Crystal structures at the measurement points were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Results: Under customized firing conditions, the fracture toughness of the layering ceramic significantly decreased, particularly near the frame. Use of a 1.2-mm-thick frame significantly decreased the fracture toughness of both layering and pressable ceramics compared to ceramics without the frame. The decreased fracture toughness only occurred close (0.5 and 1.0 mm) to the frame. XRD analysis showed identical diffraction patterns between points near and far from the frame, suggesting that the decreased fracture toughness was not due to crystal defects or impurities. SEM revealed many microcracks and large crystals in layering ceramic near the 1.2-mm-thick frame, possibly resulting from the thermal properties of the zirconia frame, such as large heat capacity and low thermal conductivity.

Conclusions: Modification of the firing conditions from the manufacturer's instructions and inclusion of a thick Y-TZP frame decreased the fracture toughness of veneering ceramics at the interface, suggesting that a thick frame would pose a potent fracture risk in veneering ceramics used for zirconia-based allceramic restorations.

Purpose: To investigate the effect of sleep restriction on somatosensory sensitivity related to occlusion.

Methods: Twelve healthy participants participated in an experimental voluntary total sleep restriction (SR) study. In a study design, they were invited to sleep as usual, normal sleep (NS) or to restrict their sleep for four nights. Following the SR night, participants were followed for 3 consecutive days including the 2 sleep nights. In NS experiment, all participants were instructed to maintain NS both nights. During all nights, actigraphy data were collected and total sleep time was estimated. On days before and after sleep conditions, all participants underwent measurements of tactile detection threshold (TDT), interocclusal detection threshold (IDT), perception of unpleasantness (POU), and the Epworth sleepiness scale (ESS).

Results: As expected, total sleep time on the first night in SR experiment was significantly shorter than on the second night in SR experiment and on the first night in NS experiment (P < 0.05). ESS values on Day-2 following SR experiment were significantly higher than on Day-1 and Day-3 in SR experiment and Day-2 in NS experiment (P < 0.05). There were no significant differences in TDT and IDT between each day at each measurement point in both experiments. POU was significantly lower on Day-2 in SR experiment than on Day-1 and Day-3 in SR experiment and on Day-2 in NS experiment (P < 0.05).

Conclusions: The present results suggest that SR affects to occlusal sensation related to POU.

Purpose: The aim of this study was to clarify the effects of fitting palatal augmentation prosthesis (PAP) on the swallowing function for the patients in rehabilitation hospital.

Methods: The subjects included 18 elderly hospitalized patients whose body mass index was <18.5 kg/m². All subjects wore maxillary complete denture. During a videofluoroscopic examination in which the patients were asked to swallow, post-swallowing pyriform sinus residue was detected. The subjects' maxillary dentures were then modified into PAPs by recording tongue movement in the palatal region. The resulting swallowing dynamics were evaluated qualitatively and quantitatively before and after fitting the PAP.

Results: We found that fitting the PAP resulted in the resolution of aspiration in two patients and disappearance of pharyngeal residue in three. The pharyngeal delay and transit times were significantly shortened.

Conclusions: These results demonstrated that PAPs could be beneficial treatment devices that may reduce post-swallowing pharyngeal residue formation due to decreased muscle strength.

Purpose: Manual therapy has been used for the treatment of patients with temporomandibular disorders (TMD) with mouth-opening limitations. However, the curative effect of manipulation differs among researchers, and its necessity remains controversial. The purpose of this study was to confirm the efficacy of manipulation using a randomized controlled trial (RCT).

Methods: A total of 61 TMD patients who had mouth-opening limitation (upper and lower middle incisor distance ≤35 mm) were selected. They were divided into two treatment groups: conventional treatment (n = 30) and conventional treatment plus manipulation (n = 31). The conventional treatment included two types of self-exercise: cognitive behavioral therapy for bruxism and education. Mouth-opening limitation, orofacial pain, and temporomandibular joint (TMJ) sounds were recorded from baseline to 18 weeks after baseline. These parameters were statistically compared between the two treatment groups by using analysis of variance (ANOVA) and Scheffe's test to assess mouth opening distance and pain; TMJ sounds were compared using Mann–Whitney U test.

Results: No statistical difference was observed between the two treatment groups except for mouthopening limitation after treatment at the first visit. Subgroup analyses, stratified according to the pathological type of TMD, indicated a similar trend.

Conclusions: The efficacy of manipulation seems to be limited, in contrast to our expectations, and improved execution of therapeutic exercises has a similar effect to that of manipulation during long-term observation. The advantage of manipulation was observed only during the first treatment session. The RCT was registered in the University Hospital Medical Information Network in Japan (UMIN-CTR: 000010437).

Purpose: The relation between preference and the gaze for the test foods under unconsciousness using the eye-tracking system was investigated.

Methods: Participants consisted of 37 healthy volunteers. Test foods were steamed rice 150 g, grilled salmon approximately 45 g and slice cooked squash 60 g, all of which were served on a tray. Foods forms were regular food, chopped food, and blended food. After attached to the eye tracker, participants watched the each dish arranged in front of them freely for 10 s. And they ate test foods freely within 10 min. The gazing point was measured for 10 s from the time when the food was ordered and just before the eating. Preference levels were interviewed. The number of gaze point fixations and the total gaze point fixation time of the viewpoint during 10 s just before eating were analyzed. The analysis items were (1) the total number of gaze point fixations (2) the total gaze point fixation time (3) the amount of food intake and (4) the preference level details.

Results: For foods with higher preference levels, the number of gaze point fixations increased significantly and the total gaze point fixation time significantly increased. In both groups, maximum food intake was observed for food forms with a high preference level. Most of the participants' selected regular foods as their most preferred food form among the food forms.

Conclusions: The results suggested that subjects gazed at regular food which had high preference level.

Purpose: The purpose of this study was to evaluate the incidence of peri-implantitis and to identify potential associated risk indicators.

Methods: This longitudinal study included 477 patients treated with 1420 implants. Medical and dental histories were evaluated in all patients. The location, size, connection type, surgical protocol, use of prosthesis splinting and fixation type were evaluated for each implant. In peri-implant evaluation, minimum keratinized tissue width around implants, peri-implant probing depths, peri-implant bleeding and peri-implant suppuration were assessed. Bone resorption around implants was evaluated with intraoral radiographs at baseline and at follow-up examinations. The study endpoint was periimplantitis, which was defined as the presence of bleeding on probing and/or suppuration with bone resorption >1 mm, in accordance with previous studies. Data were analyzed with mixed-effects Cox models.

Results: Peri-implantitis occurred in 15.3% of patients and 9.2% of implants. The overall 5- and 10-year cumulative implant survival rates were 0.95 (95% confidence interval [CI]: 0.93–0.96) and 0.83 (95% CI: 0.8–0.87), respectively. Age (hazard ratio [HR] = 0.94, 95% CI: 0.90–0.98, p < 0.01), plaque control record >20% (HR = 2.61, 95% CI: 1.02–6.67, p = 0.04), maxillary placement (HR = 1.90, 95% CI: 1.11–3.23, p = 0.02) and number of occlusal supports (HR = 0.87, 95% CI: 0.77–0.99, p = 0.03) were significantly correlated with peri-implantitis development.

Conclusions: Within the limitations of this longitudinal study on risk indicators for peri-implantitis, age, inadequate plaque control, insertion in the maxilla and less occlusal support of natural teeth correlated with peri-implantitis development.

Purpose: Immersion tests in purified water were conducted to evaluate the leaching behaviors of filler elements contained in computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin.

Methods: Four commercial CAD/CAM resin composite blanks were tested: Shofu block HC 2 layer, Cerasmart, Katana Avencia block, and KZR-CAD HR Block 2. The specimens in the size of 10.0 × 12.0 × 2.0 mm were immersed in a 50-mL conical tube containing 40 mL of purified water, and then placed in a constant-temperature oven set at a temperature of 37, 60, 70, or 80°C and stored statically for 30 days. After storage, the concentrations of leached elements in the immersion solution were measured with an inductively coupled plasma atomic emission spectrometer. To characterize the surface of the specimen after the immersion test, secondary electron images were obtained.

Results: The immersion test resulted in the leaching of Si, the main component, from all materials tested. Some materials were found to have leached high amount of Ba or Sr in addition to Si, and remarkable surface degradation was observed. The amount of leached elements increased with increased immersion temperatures.

Conclusions: Filler elements in CAD/CAM composite resins used in this study leached into purified water. The leached elements and its quantities greatly differed among materials and depend on the types of the oxides composing the filler. The amounts of leached elements varied in a temperature-dependent manner.

Purpose: Clinical failures of teeth restored with post-and-core are critical issues for the survival of teeth and maintenance of oral functions. A tooth with post-and-core restoration is a complex structure. Cement adhesion is believed to be the weakest component, and breakage in this component leads to changes in stress distribution in the complex structure. The tested hypothesis was that cement breaking processes of prosthetic treated teeth were affected by elastic properties of post-and-cores.

Methods: Finite element analysis focused on sequential adhesion failure between the dentin and cement; the penalty function method was used to analyze stress during each stage of bonding conditions. Failure patterns of adhesion and stress distribution within dentin under load of different materials of post-andcore was observed.

Results: Although, an initial failure of cement was observed at the palatal crown margin regardless of the material. Different patterns of adhesion failure between dentin and post-and-cores were observed by different elastic properties of post-and-cores. Stress concentration was observed at the corresponding areas of interface between adhesion failure and continued elements using both post-and-cores.

Conclusions: Using failure criteria for cement adhesion, sequential changes of adhesion failure between dentin and post-and-cores were observed. Local stress concentrations leading to severe destruction of dentin were caused by not only materials of post-and-cores but their adhesive conditions to dentin. Nonlinear finite element analysis (FEA) using complex structure model which deals with alterations of interfacial condition between components could provide the simulation for the clinical failure of teeth restored with post-and-cores.

Purpose: The aim of this study was to evaluate the influence of indirect restorative material type and thickness on the transmission of different wavelengths from a broad-banded dental curing light.

Methods: Four dental indirect restorative materials for computer-aided design and computer-aided manufacturing (CAD/CAM) were evaluated: [RC] resin/ceramic hybrid material (Lava Ultimate), [FC] feldspathic ceramic (VitaBlocs), and two zirconia-based ceramics ([ZK] Katana; and [ZL] Lava). Total loss of irradiance (TL) was measured for blue (W_B, 425–490 nm) and violet (W_V, 350–425 nm) wavelengths. Specimens of 15 × 15 mm with varying thicknesses (0.5, 1.0, 1.5, and 2.0 mm) were fabricated (n = 5). A plasma-arc dental light-curing unit was used (Arc Light-II). To assess TL as a function of wavelength, a software (Spectra Suite v5.1) connected to a spectroradiometer (USB2000) and an integrating sphere (CTSM-LSM-60-SF) was used. Data was subjected to statistical analysis (two-way ANOVA and post-hoc Tukey test, α = 0.05).

Results: A 0.5 mm interposition resulted in TL from 50.5 to 67.2%, depending on material. Increased thickness resulted in higher TL for all materials. FC showed less TL compared to ZK. In general, W_V showed higher TL than did W_B, and W_V/W_B proportion decreased with increasing thickness.

Conclusions: Indirect materials significantly reduced TL, and this effect is greater with increasing thickness. W_V showed lower penetration compared to W_B.

Purpose: Computed tomography (CT) imaging for three-dimensional (3D) printed models may improve the quality of surgical preoperative plans. Although metal objects can cause artifacts in CT images, integration of CT and digital dental arch imaging may solve this problem. The present study aimed to evaluate effects of the number of metal restorations and mandibular position during CT imaging on accuracy of reproduced models.

Methods: Stereolithography datasets from three sets of dental models having different numbers of metal restorations were obtained using a laboratory digitizing device (control) and CT equipment (nonintegrated data). CT scanning was performed under two conditions: intercuspal position (closed) and separated using paraffin wax (open). Nonintegrated data after metal artifact removal were separated into maxillary and mandibular dentition groups. The occlusal part of the control dentition and nonintegrated data were superimposed and integrated (integrated data). The root mean square (RMS) between the control and stereolithography data was calculated and analyzed with three-way analysis of variance and t-test with Bonferroni correction.

Results: Increasing numbers of metal restorations resulted in increase in metal artifacts and RMS values. Moreover, the RMS of the closed dataset was significantly greater than that of the open dataset because of the creation of artificial occlusal surfaces. The RMSs of the integrated datasets were significantly smaller than those of the nonintegrated datasets, except for the open model without metal restorations.

Conclusions: Accuracies of reproduced maxillary and mandibular models decreased with increasing numbers of metal restorations and in the closed mandibular position during CT scanning.

Purpose: To clarify the effect of denture treatment on masticatory movement in patients with complete dentures.

Methods: Forty eight patients who required new complete dentures and 20 patients who were satisfied with their original complete dentures (control: C group) participated in this study. Subjects were asked to chew a gummy jelly on their habitual chewing side. The movement of mandibular incisal point was recorded using a mandibular kinesiograph. First, average path and overlap of the movement path were displayed for the ten cycles between the fifth cycle and the fourteenth cycle. The movement path was classified into one of seven patterns and the frequency of each pattern was calculated and investigated the relationship between treatment and masticatory path pattern. Next, opening distance and masticatory width (spatial parameter) and cycle time (temporal parameter) were calculated and compared between the before treatment group (BT group) and after treatment group (AT group), and between the AT and C groups.

Results: The BT group showed various patterns of masticatory path, whereas the majority of subjects in the AT and C groups showed path patterns that were representative of healthy dentate subjects. The opening distance and masticatory width increased, and the cycle time was shortened after wearing new complete denture, and there were no statistically significant differences between AT group and C group.

Conclusions: From these results it was suggested that the masticatory movement of patients with complete dentures improved greatly after wearing new denture.