Fracture resistance of endodontically treated maxillary incisors restored with single or bundled glass fiber-reinforced composite resin posts.

Background: To compare the fracture resistance of endodontically treated maxillary incisors restored with single versus bundled glass fiber-reinforced composite resin posts (FRC). Material and Methods: Twenty-four maxillary incisors underwent root canal preparation (1.5-mm-diameter post spaces after canal obturation). Teeth were randomly divided into two groups (n = 12). Two different FRC groups were used for the intracanal post treatment. Single FRC (Rebilda Post system, 1.5 mm diameter) and bundled FRC (Rebilda Post GT, 12 fiber bundles, 1.4 mm diameter) were bonded to the prepared canals using dual-cure resin-based luting cement. Specimens were kept in humid at 37°C for one day. The fracture resistance testing was performed using universal testing machine by applying a compressive static load at a 135° angel to the axis of the teeth. The failure type after fracture was examined by visual inspection. Results: The fracture resistance of teeth with single FRC (Rebilda Post) and bundled FRC (Rebilda Post GT) were 787 ± 156 and 850 ± 166 Newton, respectively. There was no statistical significant difference between the two groups. Root fracture was the major failure type in both groups. Conclusions: The fracture resistance of endodontically treated maxillary incisors with bundled FRC (Rebilda Post GT) did not differ from incisors with single FRC (Rebilda Post). Key words:Endodontically-treated teeth, fracture resistance, glass fiber post, intracanal post.

Marginal and internal fit of crowns based on additive or subtractive manufacturing.

OBJECTIVE: To assess the marginal and internal fit of crowns manufactured by additive and subtractive manufacturing technique. MATERIALS AND METHODS: Twenty extracted teeth prepared for complete coverage crowns were scanned with an intra-oral scanner (Omnicam, DentsplySirona). For the subtractive manufacturing (SM) group, ten crowns were manufactured in a hybrid resin block (Vita Enamic, Vita Zahnfabrik). For the additive manufacturing (AM) group, the crowns were manufactured in a hybrid resin material (NextDent C&B, 3D systems). The design parameters were identical for the two groups. The marginal and internal fit (determined at the axial wall, the cusp tip and occlusally) was assessed before cementation with the replica technique and after cementation under stereomicroscope after sectioning of the crowned teeth. RESULTS: For the SM group, the marginal fit was 91 µm (±28 µm) before cementation and 85 µm (±18 µm) after cementation. In the AM group, the marginal fit was 75 µm (±29 µm) before cementation and 71 µm (±18 µm) after cementation. The differences were not statistically significant. As regards the internal fit, the fit at the axial wall was statistically significantly better in the SM group than in the AM group (p=.009 before cementation and .03 after cementation). Occlusally the fit in the AM group was significantly better than in the SM group after cementation (p<.001). CONCLUSION: Within the limitations of the current study, the marginal fit of additively manufactured crowns is comparable to crowns manufactured with chair-side subtractive technique and within the clinically acceptable range. As regards the internal fit no one technique was consistently superior.

Accuracy of Intra-Oral Scans Compared to Conventional Impression in Vitro.

AIM: The purpose of the present study was to assess the accuracy of intra-oral scans and conventional impression measured at various points on a single tooth preparation. METHODS: Ten conventional silicone impressions, and ten intra oral-scans using eight different digital intra oral digital scanners were taken of a prepared master tooth. The conventional impressions were directly digitised using a laboratory scanner. Each scan/impression was superimposed on a high-accuracy digital model of the prepared master tooth. For each superimposition, the deviation from the prepared master tooth was measured at six points on four two-dimensional cross-sections. Data was analysed using two-way analysis of variance (ANOVA). RESULTS: Most intra oral scanners had lower accuracy at the preparation margin compared to smooth surfaces. When only conventional impression and the latest intra oral scanners of various manufacturers are considered, the mean discrepancy at the preparation margin was 50µm (SD 16) for conventional impression, 15µm (SD 4) for trios 3, 26µm (SD 4) for LAVA TDS, 29µm (SD 7) for CEREC Omnicam, 30µm (SD 6) for CS 3600 and 64µm (SD 7) for GC aadva. The increased accuracy of trios 3 was statistically significant (p<0.05). CONCLUSIONS: At the preparation margin, Trios 3 performed significantly better than conventional impression and the other intra oral scanners. LAVA TDS, CEREC Omnicam and CS3600 showed similar accuracy at the margin, yet better than conventional impression and GC Aadva.

Accuracy of crowns based on digital intraoral scanning compared to conventional impression-a split-mouth randomised clinical study.

OBJECTIVES: The aim of this prospective in vivo study was to evaluate the accuracy of the marginal and internal fit of crowns based on conventional impression (CI) or intraoral scan (IOS) in a randomised, split-mouth set-up. MATERIALS AND METHODS: Nineteen patients needing full coverage crowns, fitting a split-mouth design, were provided with two lithium disilicate crowns: one based on a CI and one based on an IOS. The marginal and internal accuracy of the crowns were assessed with the replica technique and clinically using a modified California Dental Association (CDA) quality evaluation system. RESULTS: At the preparation margin, the median gap was 60 µm for IOS and 78 µm for CI. For the other points, the median gap ranged from 91 to 159 µm for IOS and 109 to 181 µm for CI. The accuracy of the IOS was statistically significantly better at all point except at the cusp tip. All crowns where rated R or S at both the 6- and 12-month follow-up appointments. The results for the clinical evaluation with CDA for marginal integrity showed no statistically significant difference between the two impression methods at both the 6- and 12-month evaluations. CONCLUSIONS: Crowns based on IOS show statistically significantly better marginal and internal adaptation before cementation compared to conventional impression. However, the clinical evaluation showed similar marginal adaptation. CLINICAL RELEVANCE: Crowns based on a fully digital workflow can provide clinically acceptable marginal adaptation, comparable to crowns based on CI.

Effect of Software Version on the Accuracy of an Intraoral Scanning Device.

PURPOSE: To investigate the impact of software version on the accuracy of an intraoral scanning device. MATERIALS AND METHODS: A master tooth was scanned with a high-precision optical scanner and then 10 times with a CEREC Omnicam scanner with software versions 4.4.0 and 4.4.4. Discrepancies were measured using quality control software. RESULTS: Mean deviation for 4.4.0 was 36.2 ± 35 µm and for 4.4.4 was 20.7 ± 14.2 µm (P ≤ .001). CONCLUSION: Software version has a significant impact on the accuracy of an intraoral scanner. It is important that researchers also publish the software version of scanners when publishing their findings.

Evaluation of Operating Time and Patient Perception Using Conventional Impression Taking and Intraoral Scanning for Crown Manufacture: A Split-mouth, Randomized Clinical Study.

PURPOSE: To compare operating time and patient perception of conventional impression (CI) taking and intraoral scanning (IOS) for manufacture of a tooth-supported crown. MATERIALS AND METHODS: A total of 19 patients needing indirect full-coverage restorations fitting the requirements for a split-mouth design were recruited. Each patient received two lithium disilicate crowns, one manufactured from CI taking and one from IOS. Both teeth were prepared following the manufacturers' recommendations. For both impression techniques, two retraction cords soaked in 15% ferric sulphate were used for tissue management. CIs were taken in a full-arch metallic tray using one-step, two-viscosity technique with polyvinyl siloxane silicone. The operating time for each step of the two impression methods was registered. Patient perception associated with each method was scored using a 100-mm visual analog scale (VAS), with 100 indicating maximum discomfort. RESULTS: Median total operating time for CI taking was 15:47 minutes (interquartile range [IQR] 15:18 to 17:30), and for IOS was 5:05 minutes (IQR 4:35 to 5:23). The median VAS score for patient perception was 73 (IQR 16 to 89) for CI taking and 6 (IQR 2 to 9) for IOS. The differences between the two groups were statistically significant (P < .05) for both parameters. CONCLUSION: IOS was less time consuming than CI taking, and patient perception was in favor of IOS.