Effects of printing orientation and artificial ageing on martens hardness and indentation modulus of 3D printed restorative resin materials.

BACKGROUND: Three-dimensional (3D) printing is increasingly used to fabricate dental restorations due to its enhanced precision, consistency and time and cost-saving advantages. The properties of 3D-printed resin materials can be influenced by the chosen printing orientation which can impact the mechanical characteristics of the final products. PURPOSE: The objective of this study was to evaluate the influence of printing orientation and artificial ageing on the Martens hardness (HM) and indentation modulus (EIT) of 3D-printed definitive and temporary dental restorative resins. METHODS: Disk specimens (20 mm diameter × 2 mm height) were additively manufactured in three printing orientations (0°, 45°, 90°) using five 3D-printable resins: VarseoSmile Crownplus (VCP), Crowntec (CT), Nextdent C&B MFH (ND), Dima C&B temp (DT), and GC temp print (GC). The specimens were printed using a DLP 3D-printer (ASIGA MAX UV), while LavaTM Ultimate (LU) and Telio CAD (TC) served as milled control materials. Martens hardness (HM) and indentation modulus (EIT) were tested both before and after storage in distilled water and artificial saliva for 1, 30, and 90 days at 37 °C. RESULTS: 90° printed specimens exhibited higher HM than the other orientations at certain time points, but no significant differences were observed in HM and EIT between orientations for all 3D-printed materials after 90 days of ageing in both aging media. LU milled control material exhibited the highest HM and EIT among the tested materials, while TC, the other milled control, showed similar values to the 3D printed resins. CT and VCP (definitive resins) and ND displayed higher Martens parameters compared to DT and GC (temporary resins). The hardness of the 3D-printed materials was significantly impacted by artificial ageing compared to the controls, with ND having the least hardness reduction percentage amongst all 3D-printed materials. The hardness reduction percentage in distilled water and artificial saliva was similar for all materials except for TC, where higher reduction was noted in artificial saliva. SIGNIFICANCE: The used 3D printed resins cannot yet be considered viable alternatives to milled materials intended for definitive restorations but are preferable for use as temporary restorations.

Dimensions of Maxillary Lateral Incisor on the Esthetic Perception of Smile: A Comparative Study of Dental Professionals and the General Population.

AIM: To evaluate the effect of the differences in the dimensions of maxillary lateral incisor on the esthetic perception of smile among dental professionals and the general population. MATERIALS AND METHODS: Two sets of photographs where the maxillary incisor dimensions were modified using computer software (Adobe Photoshop) were created. In the first set, six images were included where the maxillary lateral incisor width was modified. The second set included five images where only the maxillary lateral incisor length was modified keeping the gingival margins same. Three groups of participants formed the sample. Hypodontia patients formed the first group, non-hypodontia patients formed the control group, while the dentists constituted to the third group. A total of 156 participants were recruited, 36 patients with radiographically confirmed hypodontia out of which 22 were female and 14 were male, 54 non-hypodontia "control" patients out of which 29 were female and 24 were male, and 66 dentists out of which 39 were female and 27 were male. Every participant had 15 seconds to view each photograph along with 30 seconds at the end for confirmation. RESULTS: The "most attractive smile" was the ones with 77% lateral incisor to central incisor width proportion according to 25.0% of the hypodontia group and 40.8% of the dentist's group, while only 4.2% of the control group agreed that it was the most attractive. However, the "least popular" was the 52% lateral incisor to central incisor width proportion according to 40.0% of patients who are hypodontic, 20.8% of participants from control group, and 49.0% of dentists. CONCLUSION: The golden proportion was not considered as the most attractive among all groups. The esthetic perceptions of the patients might not be same as that of the dentists. In general, reductions in the maxillary lateral incisor width were not all acceptable. CLINICAL SIGNIFICANCE: This study will help us understand the different perceptions of the patients and the dentists on esthetics, which would further help us in planning the treatment accordingly.