Comparison of the flexural and surface properties of milled, 3D-printed, and heat polymerized PMMA resins for denture bases: an in vitro study.

PURPOSE To compare the flexural properties and the adhesion of Lactobacillus salivarius (LS), Streptococcus mutans (SM), and Candida albicans (CA) on heat-polymerized (CV), CAD-CAM milled (CAD), or 3D-printed (3D) Poly (methylmethacrylate) (PMMA). METHODS Ultimate Flexural Strength (UFS), Flexural Strain (FS) (%) at Flexural Strength, and Flexural Modulus (FM) of specimens (65.0×10.0×3.3 mm) from each PMMA group (n=6) were calculated by using the 3-point bending test. The surface roughness profiles (R) were measured before and after polishing with a contact profilometer. LS, SM, and CA adhesion on PMMA specimens (n=18) (10 mm in diameter, 3 mm in height) was assessed after 90 minutes and 16 hours by using scanning electron microscopy. The Kruskal-Wallis test with post hoc analysis was performed to compare the groups (alpha=0.05). RESULTS Mean UFS values were 80.79±7.64 MPa for CV, 110.23±5.03 MPa for CAD, and 87.34±6.39 MPa for 3D. Mean FS values were 4.37±1.04% for CV, 4.71±0.62% for CAD, and 6.19±0.13 % for 3D. Mean FM values were 2542±301 MPa for CV, 3435±346 MPa for CAD, and 2371±197 MPa for 3D. CAD had the lowest average R value (0.29±0.16 µm) before polishing, and bacterial adhesion after 90 minutes of incubation. R value and microbial adhesion were not different amongst groups after polishing and 16 hours of incubation, respectively. CONCLUSION The CAD group displayed the best flexural properties, except for FS, the lowest roughness before polishing and bacterial adhesion after 90 minutes of incubation. All tested PMMAs had similar surface roughness after polishing, and microbial adhesion after 16 hours of incubation

Validity of Italian version of the child perceptions questionnaire (CPQ11-14)

BACKGROUND: The Child Perceptions Questionnaire (CPQ(11-14)) is the most commonly used indicator of child oral health-related quality of life (OHRQoL), and its validity and reliability have been studied both in English and in other linguistic contexts. The aim of this study was to develop a CPQ(11-14) for use in Italy and to test its validity in a random sample of fourteen year-old Italian adolescents. METHODS: Once the CPQ(11-14)was translated into Italian and adapted for an Italian public, five hundred sixty-one adolescents were recruited for testing. Parents rated their social status; the children/adolescents were administered the questionnaire and underwent a dental examination during which their dental status was taken and recorded. Cronbach's alpha was used to assess the questionnaire’s internal consistency. Spearman's correlation coefficients were calculated to assess construct validity between the total and subscale scores and the respondents’ global ratings on oral health and well-being. Discriminant validity was analysed using the Kruskal-Wallis or Mann–Whitney tests in groups defined by gender, social position, caries experience and previous or no orthodontic treatment. RESULTS: The mean score on the CPQ(11-14) was 15.4 (SD=11.9), and the scores on all the domains were found to be highly skewed. Cronbach's alpha ranged from 0.85 to 0.90. The global ratings on oral health and well-being were correlated to the total score and to the sub-scores except for those regarding the functional limitations. There were significant differences in the two genders, in the groups that had already or had not yet undergone orthodontic treatment, and in the social classification groups, while the difference between those who had and those who did not have caries experience did not reach statistical significance. CONCLUSIONS: The Italian version of the CPQ(11-14) appears to be a reliable, valid instrument for Italian children/adolescents

Precision of the Connection Between Implant and Standard or Computer-Aided Design/Computer-Aided Manufacturing Abutments: A Novel Evaluation Method

Purpose: The aim of this in vitro study was to verify whether or not stock and computer-aided design/ computer-aided manufacturing (CAD/CAM) abutments show similar precision in the connection with the respective implants. Materials and Methods: Ten CAD/CAM titanium abutments were compared with 10 stock titanium abutments. Each abutment fit a regular-platform implant (Institute Straumann). Implants and abutments were measured independently and then connected. During the connection procedure, the torque was measured using a six-axes load cell. Then, outer geometric features of the implant-abutment connection were measured again. Finally, the assembly was sectioned to provide the analysis of inner surfaces in contact. The geometric measurements were performed using a multisensored opto-mechanical coordinate measuring machine. The following parameters were measured and compared for the CAD/CAM and stock titanium abutment groups, respectively: width of interference and interference length between the conical surfaces of the implant and abutment; and volume of material involved in the implant-abutment connection. Results: Interference width mean \ub1 SD values of 18 \ub1 0.5 and 14 \ub1 0.5 \u3bcm were calculated for the stock and CAD/CAM titanium abutment groups, respectively. The difference was statistically significant (P = .02). Furthermore, the interference length mean \ub1 SD values of 763 \ub1 10 and 816 \ub1 43 \u3bcm were calculated for stock and CAD/CAM titanium abutment groups, respectively. The difference was also statistically significant (P = .04). Finally, the volume of material involved in the implant-abutment connection was compared between stock and CAD/CAM titanium abutment groups; the mean \ub1 SD values of 0.134 \ub1 0.014 and 0.108 \ub1 0.023 mm3 were significantly different (P = .009). Conclusion: Both standard and CAD/CAM abutment groups showed a three-dimensional (3D) seal activation after the screw tightening. Nevertheless, stock titanium abutments showed a significantly higher volume of material involved in the implant-abutment connection compared with that of CAD/CAM titanium abutments

In Vitro Implant Impression Accuracy Using a New Photopolymerizing SDR Splinting Material

PURPOSE The study aims to evaluate three-dimensionally (3D) the accuracy of implant impressions using a new resin splinting material, "Smart Dentin Replacement" (SDR). MATERIALS AND METHODS A titanium model of an edentulous mandible with six implant analogues was used as a master model and its dimensions measured with a coordinate measuring machine. Before the total 60 impressions were taken (open tray, screw-retained abutments, vinyl polysiloxane), they were divided in four groups: A (test): copings pick-up splinted with dental floss and fotopolymerizing SDR; B (test): see A, additionally sectioned and splinted again with SDR; C (control): copings pick-up splinted with dental floss and autopolymerizing Duralay® (Reliance Dental Mfg. Co., Alsip, IL, USA) acrylic resin; and D (control): see C, additionally sectioned and splinted again with Duralay. The impressions were measured directly with an optomechanical coordinate measuring machine and analyzed with a computer-aided design (CAD) geometric modeling software. The Wilcoxon matched-pair signed-rank test was used to compare groups. RESULTS While there was no difference (p = .430) between the mean 3D deviations of the test groups A (17.5 μm) and B (17.4 μm), they both showed statistically significant differences (p < .003) compared with both control groups (C 25.0 μm, D 19.1 μm). CONCLUSIONS Conventional impression techniques for edentulous jaws with multiple implants are highly accurate using the new fotopolymerizing splinting material SDR. Sectioning and rejoining of the SDR splinting had no impact on the impression accuracy