In vitro Evaluation of the Marginal Fit and Internal Adaptation of Zirconia and Lithium Disilicate Single Crowns: Micro-CT Comparison Between Different Manufacturing Procedures

Abstract

Background:Prosthetic precision can be affected by several variables, such as restorative materials, manufacturing procedures, framework design, cementation techniques and aging. Marginal adaptation is critical for long-term longevity and clinical success of dental restorations. Marginal misfit may lead to cement exposure to oral fluids, resulting in microleakage and cement dissolution. As a consequence, marginal discrepancies enhance percolation of bacteria, food and oral debris, potentially causing secondary caries, endodontic inflammation and periodontal disease.Objective:The aim of the present in vitro study was to evaluate the marginal and internal adaptation of zirconia and lithium disilicate single crowns, produced with different manufacturing procedures.Methods:Forty-five intact human maxillary premolars were prepared for single crowns by means of standardized preparations. All-ceramic crowns were fabricated with either CAD-CAM or heat-pressing procedures (CAD-CAM zirconia, CAD-CAM lithium disilicate, heat-pressed lithium disilicate) and cemented onto the teeth with a universal resin cement. Non-destructive micro-CT scanning was used to achieve the marginal and internal gaps in the coronal and sagittal planes; then, precision of fit measurements were calculated in a dedicated software and the results were statistically analyzed.Results:The heat-pressed lithium disilicate crowns were significantly less accurate at the prosthetic margins (p<0.05) while they performed better at the occlusal surface (p<0.05). No significant differences were noticed between CAD-CAM zirconia and lithium disilicate crowns (p>0.05); nevertheless CAD-CAM zirconia copings presented the best marginal fit among the experimental groups. As to the thickness of the cement layer, reduced amounts of luting agent were noticed at the finishing line, whereas a thicker layer was reported at the occlusal level.Conclusion:Within the limitations of the present in vitro investigation, the following conclusions can be drawn: the recorded marginal gaps were within the clinical acceptability irrespective of both the restorative material and the manufacturing procedures; the CAD-CAM processing techniques for both zirconia and lithium disilicate produced more consistent marginal gaps than the heat-pressing procedures; the tested universal resin cement can be safely used with both restorative materials.

Comparison of marginal adaptation of fixed ceramic restorations prepared with the ceramic heat-pressed technique and CAD/CAM technology – review of literature

“…The results of the three presented studies indicate a better marginal adhesion to the abutment tooth made in the CAD/CAM system. 14,16,17 However, only the studies by Yϋksel et al show statistically significant results. 17 Another study proved the statistically significant superiority of the Cerec system over ED4; however, the difference in marginal seal of restorations made of IPS E.max CAD for CEREC and IPS E.max Press ceramics has not been shown to be statistically significant.…”

“…For crowns made by the heat-pressed technique, the maximum marginal width of this gap was set at 45-120 μm, while for crowns performed in the CAD/CAM system it was 40-90 μm. 14 Björn et al believe that the clinically acceptable marginal width size is 200 μm. 15 Despite many controversies, scientists and clinicians are trying to determine which method of making permanent restorations is the most accurate one to achieve long-term clinical success.…”

“…Dla koron wykonanych metodą tłoczenia maksymalna szerokość tej szczeliny została ustalona na poziomie 45-120μm, natomiast dla koron wykonywanych w systemie CAD/CAM wynosi 40-90μm. 14 Björn i wsp. uważają iż klinicznie akceptowalna wielkość szczeliny wynosi 200μm.…”

“…Restorations made in the CAD/CAM system showed better marginal adaptation (65μmfor zirconium dioxide, 69μm -for lithium disilicate) than those made by means of the heat-pressed technique (85μm). 14 Other researchers prepared sixty extracted human molars for crowns with a 90° shoulder (Group 1) and a 135° chamfer preparation (Group 2). The marginal integrity of crowns made in the Sirona inLab MC XL Computer Aided Design and Manufacturing (CAD/CAM) from Feldspar porcelain (Vitablocs Mark II) (Group A) and aluminum oxide (In-Ceram 2000 AL) was compared (Group B).…”

“…Uzupełnienia wykonane w systemie CAD/CAM wykazały lepszą adaptację brzeżną (65μm -tlenkowo-cyrkonowe, 69μm -dwukrzemowo-litowe) niż te wykonane metodą tłoczenia (85μm). 14 Inni badacze opracowali 60 usuniętych ludzkich zębów trzonowych pod korony ze stopniem shoulder 90° (Grupa 1) oraz chamfer 135° (Grupa 2). Porównywano szczelność brzeżną koron wykonanych w systemie Cerec Sirona inLab MC XL Computer Aided Design and Manufacturing (CAD/CAM) z porcelany skaleniowej (Vitablocs Mark II) (Grupa A) oraz tlenkowo glinowej (In-Ceram 2000 AL) (Grupa B).…”