Comparative in vitro evaluation of CAD/CAM vs conventional provisional crowns.

OBJECTIVE: This study compared the marginal gap, internal fit, fracture strength, and mode of fracture of CAD/CAM provisional crowns with that of direct provisional crowns. MATERIAL AND METHODS: An upper right first premolar phantom tooth was prepared for full ceramic crown following tooth preparation guidelines. The materials tested were: VITA CAD-Temp®, Polyetheretherketone "PEEK", Telio CAD-Temp, and Protemp™4 (control group). The crowns were divided into four groups (n=10), Group1: VITA CAD-Temp®, Group 2: PEEK, Group 3: Telio CAD-Temp, and Group 4: Protemp™4. Each crown was investigated for marginal and internal fit, fracture strength, and mode of fracture. Statistical analysis was performed using GraphPad Prism software version 6.0. RESULTS: The average marginal gap was: VITA CAD-Temp® 60.61 (±9.99) µm, PEEK 46.75 (±8.26) µm, Telio CAD-Temp 56.10 (±5.65) µm, and Protemp™4 193.07(±35.96) µm (P<0.001). The average internal fit was: VITA CAD-Temp® 124.94 (±22.96) µm, PEEK 113.14 (±23.55) µm, Telio CAD-Temp 110.95 (±11.64) µm, and Protemp™4 143.48(±26.74) µm. The average fracture strength was: VITA CAD-Temp® 361.01 (±21.61) N, PEEK 802.23 (±111.29) N, Telio CAD-Temp 719.24 (±95.17) N, and Protemp™4 416.40 (±69.14) N. One-way ANOVA test showed a statistically significant difference for marginal gap, internal gap, and fracture strength between all groups (p<0.001). However, the mode of fracture showed no differences between the groups (p>0.05). CONCLUSIONS: CAD/CAM fabricated provisional crowns demonstrated superior fit and better strength than direct provisional crowns.

Comparative in vitro evaluation of CAD/CAM vs conventional provisional crowns

ABSTRACT Objective This study compared the marginal gap, internal fit, fracture strength, and mode of fracture of CAD/CAM provisional crowns with that of direct provisional crowns. Material and Methods An upper right first premolar phantom tooth was prepared for full ceramic crown following tooth preparation guidelines. The materials tested were: VITA CAD-Temp®, Polyetheretherketone “PEEK”, Telio CAD-Temp, and Protemp™4 (control group). The crowns were divided into four groups (n=10), Group1: VITA CAD-Temp®, Group 2: PEEK, Group 3: Telio CAD-Temp, and Group 4: Protemp™4. Each crown was investigated for marginal and internal fit, fracture strength, and mode of fracture. Statistical analysis was performed using GraphPad Prism software version 6.0. Results The average marginal gap was: VITA CAD-Temp® 60.61 (±9.99) µm, PEEK 46.75 (±8.26) µm, Telio CAD-Temp 56.10 (±5.65) µm, and Protemp™4 193.07(±35.96) µm (P<0.001). The average internal fit was: VITA CAD-Temp® 124.94 (±22.96) µm, PEEK 113.14 (±23.55) µm, Telio CAD-Temp 110.95 (±11.64) µm, and Protemp™4 143.48(±26.74) µm. The average fracture strength was: VITA CAD-Temp® 361.01 (±21.61) N, PEEK 802.23 (±111.29) N, Telio CAD-Temp 719.24 (±95.17) N, and Protemp™4 416.40 (±69.14) N. One-way ANOVA test showed a statistically significant difference for marginal gap, internal gap, and fracture strength between all groups (p<0.001). However, the mode of fracture showed no differences between the groups (p>0.05). Conclusions CAD/CAM fabricated provisional crowns demonstrated superior fit and better strength than direct provisional crowns.

A preliminary evaluation of the structural integrity and fracture mode of minimally prepared resin bonded CAD/CAM crowns.

PURPOSE: This study was a preliminary evaluation of two minimal preparation designs proposed for ceramic and composite resin bonded CAD/CAM crowns. It compared the structural integrity and fracture mode of teeth restored with traditionally and minimally prepared resin bonded CAD/CAM crowns fabricated from the same material hypothesizing that teeth restored with minimal resin bonded crowns would demonstrate the same fracture strength to teeth restored with traditional resin bonded crowns. MATERIALS AND METHODS: Forty intact maxillary molar teeth were used and divided in four groups. Two groups were prepared according to a traditional crown preparation design and two groups were prepared according to minimal preparation designs. A resin composite (Paradigm MZ100, 3M ESPE) and a leucite glass-ceramic (ProCAD, Ivoclar Vivadent) were used for the fabrication of the crowns using CEREC Scan. Crowns of ceramic were cemented using Variolink II (Ivoclar Vivadent) and crowns of composite with Rely X Unicem Aplicap (3M ESPE) and loaded until fracture. Load data was analysed using ANOVA comparing crowns of the same restorative material. The mode of fracture was also recorded and analysed (Kruskal-Wallis). RESULTS: For the composite system the mean fracture load and SD was 1682N (+/-315) for the traditional and 1751N (+/-338) for the minimal crowns. For the ceramic system the mean fracture load and SD was 1512N (+/-373) for the traditional and 1837 (+/-356) for the minimal crowns. No statistically significant difference was found between the two designs for each system. Nonparametric analysis (Kruskal-Wallis) of the fracture mode showed no statistical significant difference between designs for either material (p>.05). CONCLUSION: Within the limitations of this experimental design, it was found that minimally prepared resin bonded CEREC crowns demonstrated equal fracture resistance and mode of fracture to that of crowns bonded to traditionally prepared teeth.

Brittleness index of machinable dental materials and its relation to the marginal chipping factor.

OBJECTIVES: The machinability of a material can be measured with the calculation of its brittleness index (BI). It is possible that different materials with different BI could produce restorations with varied marginal integrity. The degree of marginal chipping of a milled restoration can be estimated by the calculation of the marginal chipping factor (CF). The aim of this study is to investigate any possible correlation between the BI of machinable dental materials and the CF of the final restorations. METHODS: The CEREC system was used to mill a wide range of materials used with that system; namely the Paradigm MZ100 (3M/ESPE), Vita Mark II (VITA), ProCAD (Ivoclar-Vivadent) and IPS e.max CAD (Ivoclar-Vivadent). A Vickers Hardness Tester was used for the calculation of BI, while for the calculation of CF the percentage of marginal chipping of crowns prepared with bevelled marginal angulations was estimated. RESULTS: The results of this study showed that Paradigm MZ100 had the lowest BI and CF, while IPS e.max CAD demonstrated the highest BI and CF. Vita Mark II and ProCAD had similar BI and CF and were lying between the above materials. Statistical analysis of the results showed that there is a perfect positive correlation between BI and CF for all the materials. CONCLUSIONS: The BI and CF could be both regarded as indicators of a material's machinability. Within the limitations of this study it was shown that as the BI increases so does the potential for marginal chipping, indicating that the BI of a material can be used as a predictor of the CF.

Evaluation of the marginal fit of three margin designs of resin composite crowns using CAD/CAM.

OBJECTIVES: To examine the marginal fit of resin composite crowns manufactured with the CEREC 3 system employing three different margin designs; bevel, chamfer and shoulder, by means of a replica technique and a luting agent. METHODS: Three master casts were fabricated from an impression of a typodont molar tooth and a full-coverage crown prepared with a marginal finish of a bevel, a chamfer and a shoulder. Each cast was replicated 10 times (n=10). Scanning of the replicas and crown designing was performed using the CEREC Scan system. The crowns were milled from Paradigm MZ100 composite resin blocks. The marginal fit of the crowns was evaluated with a replica technique (Aquasil LV, Dentsply), and with a resin composite cement (RelyX Unicem, Aplicap) and measured with a travelling microscope. Statistical analysis was performed using two-way ANOVA. RESULTS: For the replica technique the average marginal gaps recorded were: Bevel Group 105+/-34 microm, Chamfer Group 94+/-27 microm and Shoulder Group 91+/-22 microm. For the resin composite cement the average marginal gaps were: Bevel Group 102+/-28 microm, Chamfer Group 91+/-11 microm and Shoulder Group 77+/-8 microm. Two-way ANOVA analysis showed that there was no statistically significant difference between the three groups of finishing lines regardless of the cementation technique used. CONCLUSIONS: The marginal gap of resin composite crowns manufactured with the CEREC 3 system is within the range of clinical acceptance, regardless of the finishing line prepared or the cementation technique used.