Evaluating the Accuracy of Dental Restorations Manufactured by Two CAD/CAM Milling Systems and Their Prototypes Fabricated by 3D Printing Methods: An In Vitro Study

PURPOSE: This in vitro study was conducted to evaluate the marginal accuracy of all-ceramic onlay restorations and prototypes fabricated using additive and subtractive methods. MATERIALS AND METHODS: Ten typodont first molars were prepared and scanned two times using two different scanners: ARCTICA AutoScan (KaVo Dental) and CEREC Omnicam (Dentsply Sirona). The two groups of virtual models were used to design two groups of virtual onlay restorations using two different CAD software (n = 10 each group) and exported in STL files. Each group of STL files was converted to physical onlay restorations and prototypes by using three different methods; these included two additive manufacturing techniques, stereolithography apparatus (SLA) and digital light processing (DLP), and one subtractive technique, e.max milling using the KaVo Everest system and the Dentsply Sirona inLab MC X5. A digital microscope was used to evaluate the marginal fit around the onlay restorations or prototypes on the typodont teeth. RESULTS: All evaluated groups showed mean marginal gaps between 59 and 84 µm. No statistically significant differences were found when comparing the marginal accuracy of onlay restorations fabricated by the subtractive method and onlay prototypes from the two additive methods, SLA (P = .70) and DLP (P = .21). CONCLUSION: All the models evaluated produced marginal gaps within the reported acceptable clinical range. Thus, these subtractive and additive methods may be considered suitable for onlay restoration production.

Secondary caries in fixed dental prostheses: Long-term clinical evaluation.

OBJECTIVES: Even with excellent fixed dental prostheses (FDPs), there will be a substantial risk of biological complications, such as caries, if proper oral hygiene is not maintained. This study aimed to evaluate the risks of developing secondary caries with FDPs in relation to the patient oral hygiene status. MATERIAL AND METHODS: Clinical and radiographic examinations were performed for patients to collect data related to their FDP complications and oral hygiene status. The main clinical parameter analyzed was secondary caries. Complications such as a fracture, debonding, or the need for endodontic therapy were also analyzed. The interval survival rate and the cumulative survival rate of FDPs from the time of treatment to the time of follow-up were analyzed. RESULTS: A total of 423 patients (with a total of 1116 FDPs) were examined in this study, with a mean age of 43.7 years and a mean follow-up time of 7 years. Regarding complications, secondary caries was detected in 94 FDPs (8.4%), fracture (or chipping) in 85 (7.6%) cases, need for endodontic treatment in 42 cases (3.7%), and debonding in four (0.3%) cases. Secondary caries was found in nine out of 219 FDPs (4%) in patients with good oral hygiene, 35 out of 634 FDPs (5.5%) in patients with fair oral hygiene, and 50 out of 272 FDPs (18.4%) in patients with poor oral hygiene (p ≤ .001). CONCLUSIONS: Good oral hygiene has a great influence on reducing the risk of secondary caries in patients with FDPs. The occurrence of secondary caries is a common complication in patients with poor oral hygiene.

Uprighting a mesially tilted molar using customized titanium healing abutment of an adjacent osseointegrated implant.

This case report evaluates the use of a customized healing abutment of a dental implant to upright a mesially tilted molar using elastic separating rings. The external surface of the healing abutment was roughened by air particle abrasion, and a flowable composite was applied as a collar around it. The size of the resin collar was increased several times during the molar uprighting treatment by replacing the elastic ring. The uprighting procedure was evaluated after 2 months using radiographic and clinical evaluations. After treatment, the mesiodistal space above the implant was increased from 6 mm to 9 mm as follows: 2 mm by uprighting the second molar and 1 mm by mesial shifting the second premolar, and then a screw-retained zirconia crown was placed to restore the implant. The healing abutment of the implant can be modified by adding a resin collar and used as orthodontic anchorage for uprighting the adjacent tilted molar to facilitate the prosthetic procedure. Neither special instruments nor an orthodontic background are required for this minor tooth movement.

Effect of full arch two scanning techniques on the accuracy of overdenture conventional and CAD/CAM Co-Cr bars.

This work evaluates the internal and marginal adaptation of implant-assisted overdenture cobalt-chromium (Co-Cr) bars manufactured using conventional as well as CAD/CAM subtractive and selective laser melting (SLM) utilizing two scanning techniques. METHODS: An edentulous study model containing four dental implants placed at teeth sites 36, 33, 43, and 46 was used. The study cast was scanned and compared to the virtual casts developed from two scanning techniques, straight and zigzag motion, using the in silico superimposition process. Then, conventional techniques were used to produce full-arch bars that were compared to the bars fabricated using the two scanning techniques and CAD/CAM subtractive and additive techniques. RESULTS: The conventional impression and casting techniques had the smallest marginal gap among the groups (P-value < 0.05). The CAD/CAM subtractive milling techniques in groups II and III had significantly smaller marginal gaps than SLM technique used in groups IV and V (P-value < 0.05). The analysis of the internal gap within each group showed statistically significant differences between different implant sites in all groups (P-value < 0.001), except when using the conventional impression and casting techniques in group I (P-value = 0.20). CONCLUSION: The conventional impression and fabrication techniques were better than the digital impression and CAD/CAM subtractive and additive techniques for the fabrication of full-arch bars. However, both straight and zigzag scanning techniques and the CAD/CAM subtractive technique had marginal and internal gaps that were within clinically accepted ranges, and the SLM was found to be unsuitable for long-span framework fabrication with either scanning technique used.