Effect of Cement Space Settings on the Vertical Marginal gap of Cement Retained - Implant Supported Crowns: An in vitro study

Document Type : Original Article


Department of Fixed Prosthodontics, College of Dentistry, Tanta University, Tanta, Egypt


Background: Several researches on tooth-supported crowns have shown that when cement space is increased, the marginal gap is reduced. However, there is no sufficient data measuring the effect of increasing the cement space on the vertical marginal gap of implant supported crowns.
Materials and methods: Thirty internal connection dummy implants and matching stock titanium abutments were coupled and implanted into auto polymerizing acrylic resin blocks. Three groups (n=10) of zirconia molar crowns with 3 different virtual cement space settings (40, 60, and 100 μm) were designed by using a CAD design software program. A digital microscope was used to measure the mean vertical marginal gap (MG) for each group, where a total of 120 measurements for each of the 3 groups (12 sites per crown and 10 crowns per group) were evaluated. all specimens were collected for thermomechanical aging which in this study simulated 3 months of chewing conditions. marginal gaps were remeasured as described before, One-way variance analysis and the post hoc Tukey pairwise comparison tests were used to analyze the data (α=.05).
Results: A significant difference (P<.001) was found between the MG values of the zirconia implant-supported crowns fabricated by using the 3 cement space settings. The smallest MG was obtained with the 60-μm setting as compared with the 40-μm and 100-μm settings.
Conclusion: The smallest MGs were obtained when a 60-μm cement space value was used (P<.001).


Main Subjects




Implant-supported fixed dental prostheses (FDP) represent a well-established treatment option that has evolved to become a standard of care in dental medicine over the past four decades. Dental implant systems composed of implant fixtures which implanted into the bone, implant abutment which attach to the fixture and support the final crown and the fixed restoration [1].

There are many types of abutments available for the dentists to choose from. One of these types is the prefabricated metal abutment which became one of the most used abutment types because these types of abutments are relatively easy to use. The dentist places an abutment of the correct size and length on the implant body in the mouth, attaches it with a screw [2].

A successful implant supported restorations should have some distinct properties as: biocompatibility, esthetics, mechanical strength [3], marginal adaptation and passive fit which ensure both mechanical and biological equilibrium and eliminates over loading of the abutment-screw-implant assembly and the supporting bone [4-6].

Marginal adaptation is especially important property for success of restoration as presence of any marginal discrepancies can increase plaque and food accumulation followed by adherence of oral bacteria[7] that may lead to inflammatory reaction in the peri-implant soft tissues (peri-implantities) followed by bone loss around the dental implant then eventual loss of the dental implant.[8-10] Mechanical complications may occur with crowns with marginal holes, in addition to biologic complications. If the strains inside the crown increase, veneering porcelain chipping may occur, particularly with zirconia crowns [11-13].

Computer-aided design/computer-aided manufacturing (CAD/CAM) Restorations are becoming more common because of their efficient manufacturing methods, better reported precision, and decreased laboratory expenses as compared to traditional fabrication processes. Furthermore, as compared to traditional restorations, CAD/CAM-fabricated restorations showed preferable marginal fit and integrity.[14] For fixed restorations, marginal gaps of 50 to 120 µm have been found to be clinically suitable in many studies, with the range narrowing to 50 to 100 µm for CAD/CAM restorations. Various methods of measuring marginal gaps have been identified, with direct microscopy, sectioning, and replica methods being the most widely used. Each approach has its own set of benefits and drawbacks [15, 16].

CAD/CAM systems offer a wide range of options for scanning, designing, and manufacturing restorations. The virtual die spacer (cement space) can be set to the desired thicknesses with these systems.[17-19] Die spacer thickness has been linked to the marginal fit of tooth-supported CAD/CAM restorations in several tests.[14, 17, 20-32] These digital technologies, which depend on precise dimensional predictions, are said to have better marginal adaptation.[26] Some CAD/CAM systems, however, have been confirmed to produce crowns with unacceptable marginal gaps due to poor scan quality and inaccurate design tools [20, 21].

It was shown in several studies concerning tooth supported crowns that the marginal gap is reduced when cement space is increased.[33-35] However marginal gap improvements were not observed for cement space greater than 120 µm, which may also significantly decrease the strength of ceramic restorations due to a large potential inner misfit as well as polymerization shrinkage of the cement.[14, 30-32, 35, 36] However the field of dentistry still remains without a clear agreement regarding the establishment of a clinically acceptable marginal gap value for implant supported crowns due to limitations of studies evaluating it.

The purpose of this study was measuring the marginal gaps of CAD/CAM zirconia crowns constructed using different cement space settings. The null hypothesis will be that there will be no difference in the mean marginal gaps between all the crowns constructed using three cement space settings.



Materials and Methods

Sample size calculation (power analysis):

The total sample size in this study will be 30 samples (10 in each group). The significance level was 0.05 and the power was 85% using a computer program G power version 3.


Z= z value (1.96 for 95% confidence level).

P=percentage picking a choice, expressed as decimal.

C=confidence interval, expressed as decimal.

N= community size.

Thirty implant analogs were vertically embedded in auto polymerizing acrylic resin (Vertex self-curing; Vertex Dental) with the aid of a dental surveyor to verify perpendicular placement. Thirty straight titanium stock implant abutments (s-Clean; Dentis Co, Ltd) were inserted into the implant analogs and tightened to 30 Ncm with the manufacturer’s torque driver Figure (1).


Figure (1) attaching the stock abutment to the dummy implant


The screw access channels were sealed with polytetrafluoroethylene tape and then covered with a flowable composite resin (Premise Flowable; Kerr Corp). The titanium abutments were sprayed with titanium dioxide spray (SILADENT Dr. Böhme & Schöps GmbH, Goslar, Germany) and scanned with an extraoral scanner (DOF Freedom HD, Seoul, Republic of Korea). Virtual replicas of each abutment were created on the software and used for designing the crowns for each abutment using the CAD/CAM system Figure (2).


Figure (2) designing the crowns using exocad software


This study involved 3 groups (n=10) according to the cement space setting used during the crown design, namely, group 40, group 60, and group 100, where the 30 specimens were divided according to the designed cement space settings into 3 groups of 10 crowns each.

Group : 10 crowns designed with cement space set to 40 µm and 1mm away from the margins.

Group 60: 10 crowns designed with cement space set to 60 µm and 1 mm away from the margins.

Group 100: 10 crowns designed with cement space set to 100 µm and 1 mm away from the margins.

Virtual model for the crowns were created on the software and transferred to milling CAD/CAM machine (imes-icore, GmbH, Eiterfeld, Germany) to start the milling process of pre-sinterd zirconia discs (Nacera Pearl, DOCERAM Medical Ceramics, Germany).

After milling was performed, the crowns were sintered to full density, cleaned in ultrasonic cleaner for 5 minutes in distilled water and then steam cleaned and were allowed to air dry and then polished with a special polishing kit for all-ceramic restorations available for dental laboratories.

The inner surface of all crowns was air-abraded with 110 µm aluminum oxide particles at a pressure of 2 bars for 5 seconds.

All crowns were collected, numbered and divided. Then they were tried-in onto their corresponding abutment to confirm proper seating and adequate marginal fit. The crowns were then cemented to the abutments with glass ionomer cement (Medicem, Promedica Dental Material GmbH, Domagkstrasse, Neumuenste, Germany)

Before cementation, the top of each abutment was covered with a cotton pellet to protect the abutment screw. The cement was mixed according to the manufacturer’s instructions. A thin uniform layer was applied to all internal surfaces of the crowns by using disposable brushes.

The crowns were then seated with finger pressure onto the abutment and were cemented using a uniform 3-kg load directed down the long axis of the implant for 10 minutes until the cement has set. Excess cement was removed from the margins using a probe and a plastic implant curette then the crowns were allowed to set for 24 hours.

Marginal gap distance:

Each specimen was photographed using USB Digital microscope with a built-in camera (Scope Capture Digital Microscope, Guangdong, China) connected with an IBM compatible personal computer using a fixed magnification of X45.  A digital image analysis system (Image J 1.43U, National Institute of Health, USA) was used to measure and evaluate the gap width.

Thermal aging:

After all marginal gaps were measured all specimens were collected for thermal cycling. In this study the number of cycles used was 2500 cycles to simulate the 3 months clinically. Dwell times were 25 s. in each water bath (Robota automated thermal cycle; BILGE, Turkey) with a lag time 10 s. The low-temperature point was 5 0C, the high temperature point was 55 0C.

Mechanical aging:

Mechanical aging was performed using a programmable logic-controlled equipment; the newly developed four stations multimodal ROBOTA chewing simulator (Model ACH-09075DC-T, AD-TECH TECHNOLOGY CO., LTD., GERMANY) integrated with thermo-cyclic protocol operated on servomotor

The specimens were embedded in chemical cured acrylic mold which in turn fixed by tightening screw to Teflon holder in the lower part of simulator. A weight of 5 kg, comparable to 49 N of chewing force was exerted. The test was repeated 37500 times to clinically simulate the 3 months chewing condition.




The results were analyzed using Graph Pad Instat (Graph Pad, Inc., USA) software for windows. A value of P < 0.05 was considered statistically significant. Continuous variables were expressed as the mean and standard deviation. After homogeneity of variance and normal distribution of errors had been confirmed, one-way ANOVA was done for compared cement spacegroups followed by Tukey’s pairwise if showed significant results. Student t-test was done between groups before and after thermo-mechanical aging. Two-way analysis of variance was performed for total effect of variables on gap results. Sample size (n=10/group) was large enough to detect large effect sizes for main effects and pair-wise comparisons, with the satisfactory level of power set at 80% and a 95% confidence level.

Marginal gap

Descriptive statistics showing mean values and standard deviation of Marginal gap test results measured in micrometer (µm) for all cement space groups as function of thermo-mechanical aging are summarized in table (1) and figure (3).


Table (1) Marginal gaptest results for all cement space groups as function of thermo-mechanical aging



Thermo-mechanical aging







95% CI



95% CI

t value











Cement space groups







































F value


F value




P value


P value





Different superscript capital letter in the same column indicating statistically significant difference between cement space groups (p < 0.05)

 Different subscript small letter in the same row indicating statistically significant difference between aged subgroups (p < 0.05)

 CI; confidence intervals                 *; significant (p < 0.05)              ns; non-significant (p>0.05)  


Figure (3): Bar chart of the mean values of marginal gap for all cement space groups before and after thermo-mechanical aging.


Before thermo-mechanical aging

The highest mean ± SD values of marginal gap were recorded for 100 group (55.78±3.09 µm) followed by 40 group mean ± SD values (34.43±4.61 µm) meanwhile the lowest mean ± SD value was recorded with 60 group (24.97±7.84 µm). The difference between groups was statistically significant as indicated by one-way ANOVA test followed by Tukey’s pair-wise post-hoc test (F=13.09, P<0.001).

After thermo-mechanical aging

The highest mean ± SD values of Marginal gap were recorded for 100 group (76.13±2.88 µm) followed by 40 group mean ± SD values (56.61±2.79 µm) meanwhile the lowest mean ± SD value was recorded with 60 group (44.36±2.79 µm). The difference between groups was statistically significant as indicated by one-way ANOVA followed by Tukey’s pair-wise post-hoc test (F=276.9, P<0.001).

Before vs. after thermo-mechanical aging

With 40 group; it was found that 40 group recorded higher mean ± SD value of marginal gap after aging (56.61±2.79 µm) than before aging group mean ± SD value (36.45±3.61 µm). This was statistically significant as indicated by paired t-test (t value =25.1, P <0.001)

With 60 group; it was found that 60 group recorded higher mean ± SD value of marginal gap after aging (44.36±2.79 µm) than before aging group mean ± SD value (26.95±7.64 µm). This was statistically significant as indicated by paired t-test (t value =7.8, P <0.001)

With 100 group; it was found that 100 group recorded higher mean ± SD value of marginal gap after aging (76.13±2.88 µm) than before aging group mean ± SD value (57.76±4.09 µm). This was statistically significant as indicated by paired t-test (t value =5.7, P <0.001).




There are several factors that affect marginal adaptation of the fixed restoration, one of them is the cement space that was set during designing the restoration. Several studies concerning tooth supported fixed restorations showed that the marginal adaptation of the restoration improved as the cement space increased. [37]

In this in vitro study ready-made titanium abutment were used to study the effect of the cement space settings on the marginal gap of implant supported fixed restorations as they ensure standardization for all samples, easy to use, widely available. These abutments were attached to dummy implants inserted straightly in acrylic blocks, their straight placement were checked using dental surveyor. This straight placement of the implants and the abutment attached to it allow ease of designing and insertion of the restoration and accurate measurement of the marginal gap.

Digital impression technique was used to scan the specimens as it provides similar accuracy as conventional impression techniques but more time efficient, simple and more comfortable for the patients [38-39], using the resulted images, zirconia crowns were designed using CAD/CAM software as it has the following advantages over the conventional techniques: application of new materials, reduced labor, cost-effectiveness, and quality control.[40]

In this study the material chosen for manufacturing the crowns is zirconia which was selected as it is becoming increasingly popular due to its excellent aesthetic properties and good color matching natural teeth, their biocompatibility and wear resistance. In addition, patients ' fears about the potential side effects of metal restoration on their health have increased demand for metal-free restorations. [41]

During designing the crowns using the software they were divided into 3 groups according to the cement space settings as follow:

Group 40: crowns designed with cement space of 40 µm, as the textbook rule for the best cement space dimensions ranging from 20 to 40 µm [42] and it is within the range of resin cements film thickness [43].

Group 60:crowns designed with cement space of 60 µm, the value of 60 µm was recommended by the authors of a study that evaluated the MG of CAD-CAM tooth-supported ceramic crowns.

Group 100: crowns designed with cement space of 100 µm, the value of 100 µm was selected as the median of the gap settings (0 to 200 µm) provided by the EXOCAD software program.

To standardize the forces applied to each crown during cementation uniform load of 3 kg applied to the crowns using cementation device until the cement was set, for this study glass ionomer cement was used for cementation of the crowns as it is widely available, has lower marginal discrepancy when used for cementation than other conventional cements and suitable for a semi-permanent cementation for implant supported crowns.

Regarding the marginal gap evaluation method, there is also no consensus on the best method for evaluation [44] the direct microscopy [45-46] cross sectioning and replica methods [47-48] are the most used.

The direct microscopy method was selected in this study because it is the most easily repeated, straightforward and time saving. The sectioning method was not used because it may be difficult to do cutting through titanium abutments. Although microcomputed tomography (micro-CT), is a powerful tool in evaluating the marginal gaps of restorations, one of its limitations is that the results may be affected by the radio opacity of the luting cement so it was not used in this study as the marginal gap was measured after cementation.

Laboratory simulations of clinical service are often performed because clinical trials are costly and time consuming. Thermal cycling is an in vivo process often represented in these simulations, but the regimens used vary considerably and, with few exceptions, are always proposed without reference to in vivo observations. Standardization of conditions is necessary to allow comparison of reports.

Temperature regimens previously used for in vitro tests. Thermal cycling is common in tracer penetration (leakage), shear bond strength and tensile bond strength tests of dental materials. The mean low-temperature point was 6.60C (range 0–360C, median 5.00C). The mean high-temperature point was 55.50C (range 40– 100 0C, median 550C). The majority of reports quoted used just hot and cold temperature points. The number of cycles used varied from 1 to 1 000 000 cycles, with a mean of about 10 000 and median of 500 cycles. Dwell times were sometimes not stated, but the mean stated dwell time was 53 s, the median 30 s, with a range of 4 s to 20 min. Sometimes a longer dwell time 23 s was used with an intermediate temperature of 37C, and a shorter dwell time 4 s for the temperature extremes, presumably in an attempt to mimic expected intraoral timings. [49]

In this study the number of cycles used was 2500 cycles to simulate the 3 months clinically. Dwell times were 25 s. in each water bath* with a lag time 10 s. The low-temperature point was 5 0C). The high temperature point was 55 0C. [50]

The results of the current study showed significant differences for all the groups tested, and so the null hypothesis was rejected.

The lowest mean MG of the CAD-CAM implant-supported zirconia crowns examined in this study was observed in group 60 (26.95 µm), and this value is within the range of MGs reported by Mohammed et al [51] and Wilson. However, this result is slightly less than half the mean MG value (56.09 µm) reported by Hassan Zadeh et al, [52] who used the same restoration material but a different software program to fabricate tooth-supported crowns. Shim et al [43] concluded that the MG value of CAD-CAM fabricated crowns may be influenced by the software program type and spacer settings.

The mean MG in group 40 (36.45 µm) was within the range of values reported by Shim et al [43] and Rahme et al,[53] and the mean MG in group 100 (57.76 µm) was within the range of the minimum vertical MG values reported by Carrilho et al. [54] The lower MG values recorded in this study, as compared with other studies, may be the result of using different restorative materials, which has been confirmed in a recent systematic review. [55]

The inverse relation between MG and the cement gap is supported by the results of group 40 and group 60 only, where the MG decreased from 36.45 µm to 26.95 µm when the cement gap increased from 40 to 60 µm. [56-57] However, the MG increased again to 57.76 µm when the cement gap was increased to 100 µm. Most of the studies reporting this inverse relationship were conducted on natural or artificial tooth-supported crowns that may have different taper and finish line configurations than implant abutments.

Moreover, unlike crown seating on a stock implant abutment, which is mainly circular and only has one minor flat area on one of its axial surfaces, crown seating on a natural tooth is usually well handled by tooth preparation features and non-circular circumference. As a result, growing the cement space above a certain point would result in a larger restoration that may or may not be properly seated on the implant abutment, resulting in an inaccurate MG measurement. The higher MG in group 100 may be attributed to a looser internal fit than in groups 40 and 60, allowing the crowns' virtual CAD design to change along their respective abutments.

Since the cement gap affects not only the MG but also the retention and fracture resistance of restorations, particularly with ceramics, the inverse relationship between the cement gap or die spacer and MG can only be valid to a level. [58] As a result, additional researches is needed to determine how various cement gap settings affect ceramic crown retention, fracture resistance, and marginal adaptation.

The current study just focused on the vertical marginal fit of crowns since, under the right laboratory conditions, the horizontal misfit can be corrected by reshaping. If the discrepancy is a vertical misfit, however, it can only be corrected with a new restoration. [59] All the MG values in this study were below 110 µm, which has been the highest reported MG value in CAD-CAM restorations. [60]

In this study, significant increase in the marginal gap after artificial aging as the degradative effect of thermocycling in an aqueous atmosphere on dental ceramics has been reported. [61] Reasonable explanation of this increase in marginal discrepancy suggests that it is related to the luting cement. Some portions of the cement film were washed out during the aging procedures, resulting in a clearer image under microscope and, thus, creating the possibility for increased measurements of the marginal discrepancy particularly, when using water-soluble cements such as glass-ionomer which deteriorate over time due to the deleterious effects of thermocycling. On contrary, found no significant effect on marginal discrepancy after aging was reported by others. This different finding can be due to the different ceramic systems and luting agents being evaluated as the insoluble resin cement they used decreased the potential of interfacial failure of the luting agent during thermocycling.


  • The evaluation of internal fit has been neglected.
  • The possible collapse of the luting cement layer and fracture or loosening of crowns may be increased by poor internal fit. [62]
  • Because of the use of a laboratory scanner, the results may not reflect the outcome in clinical situations, where the accuracy of CAD-CAM crowns may be adversely influenced by gingival bleeding, moisture, and limited mouth opening during intraoral scanning.
  • Differences in luting cement, materials for restoration, and CAD/CAM system used could also affect the results. So further research under different conditions is required.
  • The MG values reported in this study may be smaller than most of the studies in the literature, so a future study may be needed to verify these results by two different evaluation methods.




Within the limitations of this in vitro study, the following conclusions were drawn:

  1. The marginal fit of implant supported CAD/CAM zirconia crowns was significantly affected by the 3 cement space settings used.
  2. Up to 60 µm, the marginal discrepancy values decreased when the cement space increased.
  3. The optimal mean marginal adaptation of implant supported CAD/CAM zirconia crowns was obtained when the digital cement gap was set at 60 µm. 



Conflict of Interest

The authors declare that there is no conflict of interest


This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.



  1. Albrektsson T, Bra Nemark P, Hansson H, Lindstro M. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man. Acta Orthop Scand 1981;52:155-70.
  2. Christensen GJ. Selecting the best abutment for a single implant.  J Am Dent Assoc 2008;139:484-7.
  3. Karlsson S. The fit of Procera titanium crowns: an in vitro and clinical study. Acta Odontol Scand 1993;51:129-34.
  4. Abduo J, Bennani V, Waddell N, Lyons K, Swain M. Assessing the fit of implant fixed prostheses: a critical review. Int J Oral Maxillofac Implants 2010;25:506-15.
  5. Jemt T. Failures and complications in 391 consecutively inserted fixed prostheses supported by Brånemark implants in edentulous jaws: a study of treatment from the time of prosthesis placement to the first annual checkup. Int J Oral Maxillofac Implants 1991;6:89-102.
  6. Branemark P-I. Osseointegration and its experimental background. J prosthet Dent 1983;50:399-410.
  7. Sorensen JA. A rationale for comparison of plaque-retaining properties of crown systems. J Prosthet Dent 1989;62:264-9.
  8. Guichet DL, Caputo AA, Choi H, Sorensen JA. Passivity of fit and marginal opening in screw-or cement-retained implant fixed partial denture designs. Int J Oral Maxillofac Implants 2000;15:239-46.
  9. James RA. Periodontal considerations in Implant Dent. J Prosthet Dent 1973;30:202-9.
  10. Jansen VK, Conrads G, Richter E-J. Microbial leakage and marginal fit of the implant-abutment interface. Int J Oral Maxillofac Implants 1997;12:1-23.
  11. Georgakis G. An Investigation into the Integrity of Fit of Provisional Crowns made over a Dental Implant Analogue Using Two Current Proprietary Provisional Crown Materials Compared to a Proprietary'Snap On'Provisional Core. J Dent Health Oral Disord Ther 2014;24:50-7.
  12. Von Steyern PV, Carlson P, Nilner K. All‐ceramic fixed partial dentures designed according to the DC‐Zirkon® technique. A 2‐year clinical study. J Oral Rehabil 2005;32:180-7.
  13. Molin MK, Karlsson SL. Five-Year Clinical Prospective Evaluation of Zirconia-BasedDenzir 3-Unit FPDs. Int J Prosthodont 2008;21:223-7.
  14. Abdullah AO, Tsitrou EA, Pollington S. Comparative in vitro evaluation of CAD/CAM vs conventional provisional crowns.J Appl Oral Sci 2016;24:258-63.
  15. Nawafleh NA, Mack F, Evans J, Mackay J, Hatamleh MM. Accuracy and reliability of methods to measure marginal adaptation of crowns and FDPs: a literature review. J Prosthodont 2013;22:419-28.
  16. Sorensen JA. A standardized method for determination of crown margin fidelity. J Prosthet Dent 1990;64:18-24.
  17. Şeker E, Ozcelik TB, Rathi N, Yilmaz B. Evaluation of marginal fit of CAD/CAM restorations fabricated through cone beam computerized tomography and laboratory scanner data. J Prosthet Dent 2016;115:47-51.
  18. Beuer F, Korczynski N, Rezac A, Naumann M, Gernet W, Sorensen JA. Marginal and internal fit of zirconia based fixed dental prostheses fabricated with different concepts. Clin Cosmet Investig Dent 2010;2:5-11.
  19. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. Dent Mater J 2009;28:44-56.
  20. Terry DA. CAD/CAM Systems, Materials, and Clinical Guidelines for All’Ceramic Crowns and Fixed Partial Dentures. Compend 2002;23:637-52.
  21. Bindl A, Mörmann W. Marginal and internal fit of all‐ceramic CAD/CAM crown‐copings on chamfer preparations. J Oral Rehabil 2005;32:441-7.
  22. Pak H-S, Han J-S, Lee J-B, Kim S-H, Yang J-H. Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns. J Adv Prosthodont 2010;2:33-8.
  23. Borba M, Cesar PF, Griggs JA, Della Bona Á. Adaptation of all-ceramic fixed partial dentures. Dent Mater 2011;27:1119-26.
  24. Mously HA, Finkelman M, Zandparsa R, Hirayama H. Marginal and internal adaptation of ceramic crown restorations fabricated with CAD/CAM technology and the heat-press technique. J Prosthet Dent 2014;112:249-56.
  25. Grenade C, Mainjot A, Vanheusden A. Fit of single tooth zirconia copings: comparison between various manufacturing processes. J Prosthet Dent 2011;105:249-55.
  26. Gonzalo E, Suárez MJ, Serrano B, Lozano JF. A comparison of the marginal vertical discrepancies of zirconium and metal ceramic posterior fixed dental prostheses before and after cementation. J Prosthet Dent 2009;102:378-84.
  27. Gu X-H, Kern M. Marginal discrepancies and leakage of all-ceramic crowns: Influence of luting agents and aging conditions. Int J Prosthodont 2003;16:109-16.
  28. Prasad R, Abdullah Al-Kheraif A. Three-dimensional accuracy of CAD/CAM titanium and ceramic superstructures for implant abutments using spiral scan microtomography. Int J Prosthodont 2013;26:451-7.
  29. Euán R, Figueras-Álvarez O, Cabratosa-Termes J, Oliver-Parra R. Marginal adaptation of zirconium dioxide copings: influence of the CAD/CAM system and the finish line design. J Prosthet Dent 2014;112:155-62.
  30. Euán R, Figueras‐Álvarez O, Cabratosa‐Termes J, Brufau‐de Barberà M, Gomes‐Azevedo S. Comparison of the marginal adaptation of zirconium dioxide crowns in preparations with two different finish lines. J Prosthodont.: Implant, Esthetic and Reconstructive Dentistry 2012;21:291-5.
  31. Cho S-H, Schaefer O, Thompson GA, Guentsch A. Comparison of accuracy and reproducibility of casts made by digital and conventional methods. J Prosthet Dent 2015;113:310-5.
  32. Quintas AF, Oliveira F, Bottino MA. Vertical marginal discrepancy of ceramic copings with different ceramic materials, finish lines, and luting agents: an in vitro evaluation. J Prosthet Dent 2004;92:250-7.
  33. Rustum M, Gonzalez MAG, Kasim A, Hayaty N, Abu Kassim NL, Farook MS. Effect of operators' experience and cement space on the marginal fit of an in-office digitally produced monolithic ceramic crown system. Quintessence Int 2016;47:181-91.
  34. Beuer F, Naumann M, Gernet W, Sorensen JA. Precision of fit: zirconia three-unit fixed dental prostheses. Clin Oral Investig 2009;13:343-9.
  35. Aditya P, Madhav V, Bhide S, Aditya A. Marginal discrepancy as affected by selective placement of die-spacer: an in vitro study. J Indian Prosthodont Soc 2012;12:143-8.
  36. Vojdani M, Torabi K, Farjood E, Khaledi A. Comparison the marginal and internal fit of metal copings cast from wax patterns fabricated by CAD/CAM and conventional wax up techniques. J Dent 2013;14:118-29.
  37. Özçelik TB, Yilmaz B, Şeker E, Shah K. Marginal Adaptation of Provisional CAD/CAM Restorations Fabricated Using Various Simulated Digital Cement Space Settings. Int J Oral Maxillofac Implants 2018;33:1064-9.
  38. Berrendero S, Salido M, Valverde A, Ferreiroa A, Pradíes G. Influence of conventional and digital intraoral impressions on the fit of CAD/CAM-fabricated all-ceramic crowns. Clin Oral Investig 2016; 20:2403-10.
  39. Yuzbasioglu E, Kurt H, Turunc R, Bilir H. Comparison of digital and conventional impression techniques: evaluation of patients’ perception, treatment comfort, effectiveness and clinical outcomes. BMC oral health 2014;14:10-7.
  40. Gabor A-G, Zaharia C, Stan AT, Gavrilovici AM, Negruțiu M-L, Sinescu C. Digital Dentistry—Digital Impression and CAD/CAM System Applications. J Interdiscip Med 2017;2:54-7.
  41. Manicone PF, Iommetti PR, Raffaelli L. An overview of zirconia ceramics: basic properties and clinical applications. J Dent 2007;35:819-26.
  42. Boening KW, Wolf BH, Schmidt AE, Kästner K, Walter MH. Clinical fit of Procera AllCeram crowns. J Prosthet Dent 2000;84:419-24.
  43. Shim JS, Lee JS, Lee JY, Choi YJ, Shin SW, Ryu JJ. Effect of software version and parameter settings on the marginal and internal adaptation of crowns fabricated with the CAD/CAM system.J Appl Oral Sci 2015;23:515-22.
  44. Att W, Hoischen T, Gerds T, Strub JR. Marginal adaptation of all‐ceramic crowns on implant abutments. Clin Implant Dent Relat Res 2008;10:218-25.
  45. Presotto AGC, Bhering CLB, Mesquita MF, Barão VAR. Marginal fit and photoelastic stress analysis of CAD-CAM and overcast 3-unit implant-supported frameworks. J Prosthet Dent 2017;117:373-9.
  46. Lopez-Suarez C, Gonzalo E, Pelaez J, Serrano B, Suarez MJ. Marginal Vertical Discrepancies of Monolithic and Veneered Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Dental Prostheses. The Int J Prosthodont 2016;29:256-8.
  47. Bayramoğlu E, Özkan YK, Yildiz C. Comparison of marginal and internal fit of press-on-metal and conventional ceramic systems for three-and four-unit implant-supported partial fixed dental prostheses: An in vitro study. J Prosthet Dent 2015;114:52-8.
  48. Kim K-B, Kim J-H, Kim W-C, Kim H-Y, Kim J-H. Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two-and three-dimensional replica techniques. J Adv Prosthodont 2013;5:179-86.
  49. Gale M, Darvell B. Thermal cycling procedures for laboratory testing of dental restorations. J Dent 1999;27:89-99.
  50. Morresi AL, D'Amario M, Capogreco M, Gatto R, Marzo G, D'Arcangelo C, et al. Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature reviews. J Mech Behav Biomed Mater 2014;29:295-308.
  51. Al Amri MD, Al-Johany SS, Al-Qarni MN, Al-Bakri AS, Al-Maflehi NS, Abualsaud HS. Influence of space size of abutment screw access channel on the amount of extruded excess cement and marginal accuracy of cement-retained single implant restorations. J Prosthet Dent 2018;119:263-9.
  52. Hasanzade M, Sahebi M, Zarrati S, Payaminia L, Alikhasi M. Comparative evaluation of the internal and marginal adaptations of CAD/CAM endocrowns and crowns fabricated from three different materials. Int J Prosthodont 2020.
  53. Rahme HY, Tehini GE, Adib SM, Ardo AS, Rifai KT. In vitro evaluation of the “replica technique” in the measurement of the fit of Procera crowns. J Contemp Dent Pract 2008;9:25-32.
  54. Vaz IMCB, Carracho JFPCL. Marginal fit of zirconia copings fabricated after conventional impression making and digital scanning: An in vitro study. J Prosthet Dent 2020;124:223-9.
  55. Papadiochou S, Pissiotis AL. Marginal adaptation and CAD-CAM technology: a systematic review of restorative material and fabrication techniques. J Prosthet Dent 2018;119:545-51.
  56. Rinke S, Fornefett D, Gersdorff N, Lange K, Roediger M. Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings. Dent Mater J 2012;31:601-9.
  57. Grajower R, Lewinstein I. A mathematical treatise on the fit of crown castings. J Prosthet Dent 1983;49:663-74.
  58. Juntavee N, Millstein PL. Effect of surface roughness and cement space on crown retention. J Prosthet Dent 1992;68:482-6.
  59. Martinez-Rus F, Ferreiroa A, Özcan M, Pradies G. Marginal discrepancy of monolithic and veneered all-ceramic crowns on titanium and zirconia implant abutments before and after adhesive cementation: a scanning electron microscopy analysis. Int J Oral Maxillofac Implants 2013;28:480-7.
  60. Baig MR, Tan KB-C, Nicholls JI. Evaluation of the marginal fit of a zirconia ceramic computer-aided machined (CAM) crown system. J Prosthet Dent 2010;104:216-27.
  61. Blatz MB, Oppes S, Chiche G, Holst S, Sadan A. Influence of cementation technique on fracture strength and leakage of alumina all-ceramic crowns after cyclic loading. Quintessence Int 2008;39:23-32.
  62. Korkut L, Cotert H, Kurtulmus H. Marginal, internal fit and microleakage of zirconia infrastructures: an in-vitro study. Oper Dent 2011;36:72-9.