Influence of different convergence angles and tooth preparation heights on the internal adaptation of Cerec crowns

An In Vitro Study of Retention and Marginal Adaptation of Endocrowns With Different Intracoronal Depths

BACKGROUND

Marginal adaptation and retention of endocrowns are crucial for the success and survival of endocrowns. This study aimed to investigate the effect of different materials and intracoronal depth on the retention and marginal adaptation of CAD/CAM fabricated all-ceramic endocrowns.

METHODS

Thirty-six mandibular premolar teeth with an average surface area of 64.49 mm2 were prepared to receive CAM/CAM fabricated endocrowns. Samples were divided randomly and equally into groups of lithium disilicate with 2 mm intracoronal depth (LD2), lithium disilicate with 4 mm intracoronal depth (LD4), polymer infiltrated ceramic network with 2 mm intracoronal depth (PICN2) and polymer infiltrated ceramic network with 4 mm intracoronal depth (PICN4). All endocrowns were cemented using ParaCore resin cement with 14N pressure and cured for 20 seconds. Fifty measurements of absolute marginal discrepancy (AMD) were done using a stereomicroscope after cementation. After 24 hours, all samples were subjected to thermocycling before the retention test. This involved using a universal testing machine with a crosshead speed of 0.5 mm/min and applying a load of 500N. The maximum force to detach the crown was recorded in newtons and the mode of failure was identified.

RESULTS

Two-way ANOVA revealed that the AMD for PICN was statistically significantly better than lithium disilicate (p=0.01). No statistically significant difference was detected in the AMD between the two intracoronal depths (p=0.72). PICN and endocrowns with 4 mm intracoronal depth had statistically significant better retention (p<0.05). 72.22% of the sample suffered from cohesive failures and 10 LD endocrowns suffered adhesive failures.

CONCLUSIONS

Within the limitations of this study, we found that different materials and intracoronal depths can indeed influence the retention of CAD/CAM fabricated endocrowns. Based on the controlled setting findings, PICN was found to have better retention and better marginal adaptation than similar lithium disilicate premolar endocrowns.

The effect of pre-ceramic soldering on marginal and internal fit of 4-unit zirconia frameworks and monolithic zirconia fixed dental prostheses

The aim of this study is to evaluate the effect of pre-ceramic soldering on the marginal and internal fit of 4-unit zirconia fixed dental prostheses (FPDs) that have two abutments and two pontics. 4-unit zirconia frameworks (Zirkonzahn ICE Translucent) (Z Group) and monolithic zirconia (Zirkonzahn Prettau) (M Group) FPDs were manufactured. Groups were divided into two groups (n = 10) control (ZC and MC) and soldering (ZS and MS). Samples of ZS and MS groups were cut into two pieces under cooling water and soldered with a bonding material (DCM Zircon HotBond). The marginal and internal fit of the restorations were measured from 36 points of each sample and cement space volume was calculated using reverse engineering software (Geomagic Design X). The mean and standard deviations were submitted to Generalized Linear Mixed Model (GLMM) analysis (α = 0.05). Statistical differences between groups before and after pre-ceramic soldering on point measurements were found. In total cement spacing measurements, a significant difference was found amongst all groups (P < 0.05). However, in premolars, a statistically significant difference was found between ZC and ZS groups and MC and MS groups (P < 0.05). All discrepancies after pre-ceramic soldering were found to be lower than before.

The Effect of a Digital Manufacturing Technique, Preparation Taper, and Finish Line Design on the Marginal Fit of Temporary Molar Crowns: An In-Vitro Study

The aim of this study is to investigate the combined effect of a digital manufacturing technique (subtractive vs. additive), preparation taper (10° vs. 20° TOC), and finish line (chamfer vs. shoulder) on the marginal adaptation of temporary crowns following cementation with a compatible temporary cement. Four mandibular first molar typodont teeth were prepared for full coverage crowns with standard 4 mm preparation height as follows: 10° TOC with the chamfer finish line, 10° TOC with the shoulder finish line, 20° TOC with the chamfer finish line and 20° TOC with the shoulder finish line. Each of the four preparation designs were subdivided into two subgroups to receive CAD/CAM milled and 3D-printed crowns (n = 10). A total of 80 temporary crowns (40 CAD/CAM milled and 40 3D-printed) were cemented to their respective die using clear temporary recement in the standard cementation technique. The samples were examined under a stereomicroscope at ×100 magnification following calibration. Linear measurements were performed at seven equidistant points on each axial surface and five equidistant points on each proximal surface. One-way ANOVA analysis and Tukey HSD (Honestly Significance Difference) were performed. The best marginal fit was seen in group 8, while the poorest fit was noted in group 2. Shoulder finish lines and 10° TOC resulted in higher marginal gaps, especially in CAD/CAM milled group. The selection of 3D-printed crowns may provide a better marginal fit within the range of clinical acceptability. Marginal gaps were within clinical acceptability (50 and 120 µm) in all groups except group 2.

Comparison of marginal and internal adaptation of three-unit fixed dental prostheses made using CAD/CAM metal-free materials

The aim of this study was to compare the marginal and internal adaptation of three-unit fixed dental prostheses (FDPs) fabricated from different metal-free materials using CAD/CAM methods. A total of 100 three-unit FDPs were produced from a cubic zirconia, a fiber-reinforced resin composite, a polyetheretherketone (PEEK), a polyetherketoneketone (PEKK), and a polymer composite material by the CAD/CAM method (n = 20 per material). The zirconia group was considered the control/reference material. Marginal and internal gap values of the produced FDPs were measured using the silicone replica method at ×40 magnification under a stereomicroscope. The obtained data were analyzed using one-way ANOVA and Tukey's HSD tests. The marginal and internal gap values for the cubic zirconia material were found to be statistically significantly lower than those seen for the PEEK, polymer composite, PEKK, and fiber-reinforced resin composite materials. While the marginal and internal adaptation of the cubic zirconia material was found to be better than the others, it should be noted that the marginal and internal gap values for all other materials tested were found to be within the clinically acceptable range.

Retentive Strength of CAD/CAM-Fabricated All-Ceramic Crowns Luted on Titanium Implant Abutments Using Different Ceramic Materials and Luting Agents: An In Vitro Study

Objectives: This study aimed to determine the retentive strength of monolithic hybrid-all-ceramic crowns luted on titanium implant abutments. Material and Methods: In total, 450 crowns (75 each of Mark II, Empress CAD, e.max CAD, Suprinity, Enamic, Celtra Duo) were milled using a CAD/CAM system. The crowns were cemented onto sandblasted titanium implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, Fujicem, and Panavia 2.0). After thermocycling was performed (5000 cycles: 5−55 °C, 30-s dwell time), the crowns were removed using a universal testing machine. The location of luting-agent residue on the abutment and inner crown surfaces was evaluated. Analyses of variance (ANOVA) with the Bonferroni correction were performed to evaluate differences of retentive strength depending on the crown material and the kind of the luting agent. Results: The retentive strengths for the different ceramic materials were Vita Mark II: 652N-759N (SD:134N-146N), Empress CAD: 681N-822N (SD: 89N-146N), e.max CAD: 784N-1044N (SD: 109N-176N), Vita Enamic: 716N-1177N (SD: 132N-220N), Vita Suprinity: 867N-1488N (SD: 202N-278N), and Celtra Duo 772N-1335N (SD:151N-229N). After the removal trials, the visual documentation showed different adhesive residue location depending on the ceramic materials. Furthermore, the pull-off force was dependent on the choice of adhesives. No significant differences were found between different luting agents and the ceramic material Vita Mark II and Empress CAD. EmaxCAD showed significant differences with Unicem and FujiCem compared to Panavia, as did VitaSuprinity, VitaEnamic, and Celtra Duo (p < 0.001). Conclusions: The ceramic material used seems to influence the retentive strength and the use of certain luting agents results in a higher retentive strength for some ceramic materials.

Effect of different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium crowns produced by computer-aided designing and selective laser melting processes

PURPOSE

To evaluate the impact of five different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium (CoCr) crowns produced by computer-aided designing (CAD) and selective laser melting (SLM) processes.

MATERIALS AND METHODS

Five preparation data were constructed, after which design crowns were obtained. Actual crowns were fabricated using an SLM process. After the data of actual crowns were obtained with structural light scanning, intaglio surfaces of the design crown and actual crown were virtually superimposed on the preparation. The fit-discrepancies were displayed with colors, while the root means square was calculated and analyzed with one-way analysis of variance (ANOVA), Tukey's test or Kruskal-Wallis test (α =.05).

RESULTS

The marginal or internal color-coded images in the five design groups were not identical. The shoulder-lip and sharp line angle groups in the CAD or SLM process had larger marginal or internal fit discrepancies compared to other groups (P < .05). In the CAD process, the mean marginal and internal fit discrepancies were 10.0 to 24.2 µm and 29.6 to 31.4 µm, respectively. After the CAD and SLM processes, the mean marginal and internal fit discrepancies were 18.4 to 40.9 µm and 39.1 to 47.1 µm, respectively. The SLM process itself resulted in a positive increase of the marginal (6.0 - 16.7 µm) and internal (9.0 - 15.7 µm) fit discrepancies.

CONCLUSION

The CAD and SLM processes affected the fit of CoCr crowns and varied based on the preparation designs. Typically, the shoulder-lip and sharp line angle designs had a more significant effect on crown fit. However, the differences between the design groups were relatively small, especially when compared to fit discrepancies observed clinically.

Assessment of Tooth Preparations Submitted to Dental Laboratories for Fabrication of Monolithic Zirconia Crowns

Purpose: The objective of this study was to assess the quality of posterior teeth prepared for monolithic zirconia crowns. Materials and Methods: A total of 392 STL-files of posterior preparations for monolithic zirconia crowns were evaluated in this study. Three-dimensional (3D) images were evaluated using a software (3D Viewer; 3Shape A/S, Copenhagen, Denmark) for finish line design, finish line width, occluso-cervical dimension, total occlusal convergence (TOC), intercuspal angulation, finish line quality, line angle form, and presence or absence of undercut at the axial wall and unsupported lip of enamel. The assessment was performed by two calibrated evaluators. Then, data were descriptively analyzed. Data for occluso-cervical dimension and TOC were descriptively analyzed according to their location. Results: Thirty-nine percent of premolars, 77% of first molars, and 91% of second molars had an average occluso-cervical dimension of less than 3 mm (premolars) and 4 mm (molars), with most of the preparations having a TOC of more than 20 degrees. More than 50% of preparations had undercut, unsupported enamel and/or unacceptable finish line quality. Conclusions: The quality of tooth preparation including finish line quality, absence of unsupported enamel and undercut at the axial wall should be evaluated when preparing monolithic zirconia crowns.

Effect of cement space on marginal discrepancy and retention of CAD/CAM crown

This research aimed to evaluate the effect of cement space on the marginal discrepancy and retention of computer-aided design/computer-aided manufacturing (CAD/CAM) crowns. A total of 30 premolar Frasaco teeth were machined to receive crowns with cement spaces of 70, 90, and 110 μm. The marginal discrepancy measurements were done before and after cementation. Pull-off test was conducted using universal testing machine (UTM). Data was analyzed using two-way mixed ANOVA with post-hoc Bonferroni test and Kruskal-Wallis test. The crowns with cement space of 70 μm showed a significantly higher absolute marginal discrepancy than those with 90 and 110 μm. No significant effect on the crown retention was found. Within the limitations of this study, modifying cement space to 90 μm and 110 μm may improve the marginal adaptation of CAD/CAM crown, whereas adjusting cement space from 70 to 110 μm did not significantly affect the crown retention.

Effect of Adhesive Gap Setting on Fracture Resistance of All-ceramic Crowns

Background:

Several factors might affect the fracture resistance of all-ceramic crowns, including cement thickness.

Aim:

To evaluate the influence of cement thickness on the fracture resistance.

Objective:

To determine the effect of varying the adhesive gap thickness on the fracture loads of all-ceramic CEREC 3D molar crowns.

Methods:

Standardized prepared epoxy resin molar dies (Viade Inc.) were fabricated. A standard molar crown was designed using a CEREC 3D machine (Sirona Dental Systems). Twenty-four crowns were milled from Vita Mark II blocks (Vita Zahnfabrik), using adhesive gap settings of 30, 60 and 90 µm (n=8). A dual-cure resin cement (PanaviaF 2.0, Kuraray) was used to cement the crowns to their respective dies, following manufacturer's recommendation. After 1 week of storage in distilled water at 37°C, each crown was loaded in compression until complete failure in a universal testing machine (Instron 8501) and fracture loads (N) were recorded. Fractured specimens were sectioned to determine cement thickness. Sections were examined using a traveling light microscope to measure cement thickness. Data were statistically analyzed using one-way ANOVA test and Pearson's correlation at (α=0.05).

Results:

The mean fracture loads and standard deviation values in N were 1,267.57 (122.82), 1,225.20 (179.46) and 1,180.76 (161.77) for the crowns with 30, 60 and 90µm, respectively. ANOVA indicated no significant differences among mean fracture strength values (p = 0.55). All crowns failed in a catastrophic mode and were not repairable.

Conclusions:

Adhesive cement gap as achieved with three CEREC 3D settings from 30 to 90µm had no significant effect on fracture strength of crowns made from Vita Mark II blocks.

X-ray microtomographic evaluation of the absolute marginal fit of fixed prostheses made from soft Co-Cr and zirconia

STATEMENT OF PROBLEM

The absolute marginal fit of CAD-CAM presintered fixed partial dentures has been poorly documented.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal fit of presintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed partial dentures by using X-ray microcomputed tomography (μCT).

MATERIAL AND METHODS

A metal model was prepared from a typodont to receive fixed partial dentures (N=12). The maxillary first premolar and first molar were prepared with a circumferential 1.2-mm chamfer and 2-mm occlusal reduction. The dies were scanned and assigned to 1 of 2 groups to receive the prostheses made of presintered Co-Cr or presintered zirconia (n=6). Each framework was seated on its model without load application. The abutments were scanned by using μCT. A circle with 10 diameters, with a step of 18 degrees, was projected at the center of the obtained image. Absolute marginal discrepancy and marginal gap mean values were measured, and overextended and underextended margins determined. The data were analyzed by using the Levene t test and ANOVA (α=.05).

RESULTS

No statistically significant difference was found in the marginal fit between the materials tested (P=.939). The mean values were 66 ±14 μm for Co-Cr and 61 ±12 μm for zirconia. The absolute marginal discrepancy mean value for the premolar was 69 ±12 μm and 41 ±9 μm for the molar (P<.001). Overextension was predominant for both materials tested, with a higher percentage reported for the zirconia group.

CONCLUSIONS

Presintered alloys presented clinically acceptable adaptation with a predominance of marginal overextensions.

Clinical evaluation of the fit of lithium disilicate crowns fabricated with three different CAD-CAM systems

STATEMENT OF PROBLEM

The fit and performance of prostheses fabricated using various computer-aided design and computer-aided manufacturing (CAD-CAM) systems have been evaluated. However, most studies were conducted in vitro, and relatively few have addressed gingival parameters and prosthesis fit under clinical conditions.

PURPOSE

This clinical study aimed to compare the fit of lithium disilicate crowns produced using 3 CAD-CAM systems and evaluate clinical results up to 6 months after delivery.

MATERIAL AND METHODS

Forty participants requiring a single crown were recruited. Three monolithic lithium disilicate crowns were fabricated per participant by using 3 different CAD-CAM systems (intraoral scanners, CAD software, and milling machines): CEREC group (CEREC Bluecam, CEREC AC, CEREC MC); EZIS group (EZIS PO, EZIS VR, EZIS HM); and TRIOS group (TRIOS 3, EXO-CAD, ARUM-4X). The fit of the prostheses was assessed via a silicone replica technique, and the most acceptable crown was delivered; 12 were selected from the CEREC group, 16 from the EZIS group, and 12 from the TRIOS group. Follow-up clinical examinations were performed at 1, 3, and 6 months after delivery. The Kruskal-Wallis test with the post hoc Mann-Whitney U test was conducted to analyze significant differences in crown fit and periodontal conditions among the groups (α=.05).

RESULTS

The marginal gap of the CEREC group was significantly higher than that of the EZIS group, and the occlusal gap of the EZIS group was significantly lower than those of the CEREC and TRIOS groups (P<.05). Probing depth, bleeding index, and plaque index showed no intergroup differences at 6 months (P>.05).

CONCLUSIONS

The lithium disilicate crowns of all groups showed clinically acceptable fit. No significant differences were found among the groups in terms of periodontal conditions after 6 months.

[Influence of trueness for local finish lines of a full crown preparation on that of complete finish line]

OBJECTIVE

To investigate the factors affecting the trueness of finish lines of full crown preparations in digital impressions.

METHODS

A full crown preparation of the right maxillary molar was prepared on the standard resin dentition model, the trueness of the finish lines, the full crown preparation in the whole dentition and the isolated full crown preparation were measured respectively. Detection of scanning trueness of the finish lines of the full crown preparation in the whole dentition: (1) Using Imetric scanner to scan the full crown preparation, obtaining STL (Stereo lithographic) format data as the reference true value; (2) Using CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner to scan the full crown preparation, obtaining all the STL format data, import Geomagic Studio 2013 software, extraction of images and data of the complete finish lines or local finish lines (mesial, distal, buccal, lingual) of the full crown preparation, then using the data to 3D Compare Analysis with the reference true value, outputting RMS (root mean square) values which could evaluate the scanning trueness, the lower RMS value was, the lower the trueness was. The detection of scanning trueness of the finish lines of the isolated full crown preparation: (1) the anterior and posterior adjacent teeth of the preparation were removed to establish the model of the isolated full crown preparation; (2) CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner were used to scan the isolated preparations, and each group was repeated 6 times. Data collection and analysis were the same as the first part, that is, detection of scanning trueness of finish lines of the full crown preparation in the whole dentition.

RESULTS

In the whole dentition, (1) the RMS value [(44±7) μm] of CEREC Omnicam oral scanner scanning complete finish lines was greater than that of 3Shape TRIOS oral scanner [(35±6) μm](P < 0.05). (2) the RMS values of the mesial [(45±9) μm], buccal [(38±3) μm] and lingual [(40±3) μm] finish lines in CEREC Omnicam oral scanner scanning were all lower than that in distal [(63±7) μm](P < 0.05), and the RMS values in mesial were higher than that in buccal and lingual (P>0.05). The RMS values of 3Shape TRIOS oral scanner scanning mesial and distal finish lines were significantly higher than those of the buccal and lingual side (P>0.05), in which:(45±8) μm in mesial, (50±10) μm in the distal, (33±8) μm in the buccal and (33±6) μm in the lingual side. The RMS value of CEREC Omnicam oral scanner scanning distal finish line was greater than that of 3Shape TRIOS oral scanner (P < 0.05). Without adjacent teeth, (1) the RMS values of the complete finish lines of CEREC Omnicam oral scanner and 3 Shape TRIOS oral scanner were significantly reduced (P < 0.05), including CEREC Omnicam oral scanner (34±3) μm and 3 Shape TRIOS oral scanner (26±4) μm; (2) the RMS values of the buccal and lingual finish lines of CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner showed no significant changes (P>0.05), among which, CEREC Omnicam oral scanner buccal (44±7) μm, lingual (43±3) μm, 3Shape TRIOS oral scanner buccal (29±5) μm, lingual (40±7) μm. The RMS values of CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner were significantly reduced and there was no significant difference between them (P>0.05). CEREC Omnicam oral scanner (32±8) μm and 3Shape TRIOS oral scanner (32±6) μm. The RMS values of the distal finish lines of CEREC Omnicam oral scanner and 3 Shape TRIOS oral scanner also decreased significantly (P < 0.05), and CEREC Omnicam oral scanner (38±3) μm decreased more significantly, similar to 3Shape TRIOS oral scanner (36±1) μm, P>0.05.

CONCLUSION

When adjacent teeth exist in the full crown preparation, the mesial and distal parts of the finish line will be blocked by adjacent teeth, which will affect the trueness of the local finish line, and ultimately reduce the trueness of the complete finish line.

In Vitro Study of Comparative Evaluation of Marginal and Internal Fit between Heat-Pressed and CAD-CAM Monolithic Glass-Ceramic Restorations after Thermal Aging

The accuracy of newly developed ceramic materials is still being studied. Marginal and internal adaptation are known factors that have an essential impact on the long term success of dental restorations. The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling. Thirty-two crowns were studied and divided into four groups (n = 8), according to the ceramic material (feldspathic glass-ceramic (F) and zirconia reinforced lithium silicate glass-ceramic (ZLS)) and to their technological obtaining processes (milling (M) and heat-pressing (P)). A typodont preparation was scanned with a D2000 3D scanner to obtain identical 32 resin 3D-printed abutment teeth. Marginal and internal gaps were measured using the silicone replica technique under 40× magnification. The crowns were further cemented and thermally aged for 10,000 cycles After cementation and thermocycling of the samples, marginal and internal gaps were assessed using micro-CT (micro-computed tomography)) analysis. Data were statistically analyzed using statistical tests. Significant differences were found before and after cementation and thermocycling among the tested materials (p < 0.05). Related to technological processing, significant differences were seen in the marginal area between FP and FM (p < 0.05) Significant differences were also found in the axial and occlusal areas between the ZLSP and ZLSM. Thermocycling and cementation did not have a significant effect on the tested materials (p < 0.05). The technological processes influenced the marginal and internal fit of the crowns in favor of the CAD/CAM (computer aided design/computer aided manufacturing)technologies. Thermal aging had little effect on marginal adaptability; it increased the values for all the tested samples in a small way, but the values remained in their clinically acceptable range for all of the crowns.

Comparison of marginal adaptation and internal fit of monolithic lithium disilicate crowns produced by 4 different CAD/CAM systems

OBJECTIVES

To evaluate the marginal adaptation and internal space of crowns produced by 4 CAD/CAM systems using microcomputed tomography (μCT) and replica technique (RT).

MATERIALS AND METHODS

Monolithic lithium disilicate crowns were milled (Ceramill, Cerec, EDG, and Zirkonzahn) (n = 10). The cement film obtained with low viscosity silicone was scanned by the μCT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey's test were used for statistical analysis (α = 0.05). A uniformity index (UI) was idealized to describe the distribution of crowns' internal space and submitted to the Kruskal-Wallis and Tukey's test (α = 0.05). The correlation between μCT and RT was performed by Pearson's Correlation Coeficient (α = 0.05).

RESULTS

Marginal adaptation and internal space were statistically significant different between the experimental groups for the μCT and RT (p < 0.05). The medians of the 4 systems tested were within clinically acceptable range and the mean (± SD) highest marginal discrepancy was recorded in the Ceramill group at 133.0 ± 71.5 μm (μCT) and 90.6 ± 38.5 μm (RT). For internal fit, the UI disclosed a better distribution of the internal space for the Zirkonzahn group (p < 0.001). There was a strong correlation between the methods (p = 0.01 and r = 0.69).

CLINICAL RELEVANCE

Because of the variability of the CAD/CAM systems available, evaluating their accuracy is of clinical interest. The 4 systems are capable to produce restorations adaptated within clinically appropriate levels. The μCT and RT are efficient adaptation methodologies.

[Influence of preparation height and cement space on the fit and retention of computer aided design/computer aided manufacturing zirconia crown]

OBJECTIVE

To investigate the effects of preparation height and cement space on the fit and retention of computer aided design (CAD)/computer aided manufacturing (CAM) zirconia crown, and to provide reference for the clinical design and fabrication of CAD/CAM crowns.

METHODS

3D printing system was used to fabricate resin abutment teeth with convergence angle of 2° and height of 1-3 mm. The models' optical impressions were collected by the three-shape scanner. Then, the cement spaces were set by Cradle CAD/CAM system at 10-50 μm to create an all-ceramic zirconia crown. The fit of the crowns was measured by using silicone rubber interstitial impression method. The retention of the crowns was measured by pull-off test with uniaxial tensile force after the crown was bonded. The data were analyzed by SPSS 22.0 soft-ware.

RESULTS

When the preparation height was fixed, the fitness values of different cement space groups have statistical difference (P<
0.05), whereas the retention values of different cement space groups have no statistical difference (P>0.05). The fitness values of different preparation height groups have no statistical difference (P>0.05), and the retention values of different preparation height groups have statistical difference (P<0.05) when the cement space was fixed. No interaction was observed between the cement space and the preparation height (P>0.05).

CONCLUSIONS

When cradle CAD/CAM system is used to create a full crown in the clinic, the preparation height should be set to more than 3 mm, and the cement space should be set at 30 μm.

The effect of crown fabrication process on the fatigue life of the tooth-crown structure

OBJECTIVE

To compare the fatigue strength of lithium disilicate ceramic crowns when cemented as a compound structure, as a function of the manufacturing process and the type of ceramic variation.

METHOD

A typodont maxillary first premolar was prepared for an all-ceramic crown in accordance with the manufacturer's guidelines for monolithic ceramic crowns (IPS e. max®; Ivoclar-Vivadent, Liechtenstein). 60 dies were duplicated in a polymer with a Young's Modulus closely matched to dentine (Alpha die, Schütz GmbH). Three different crown fabrication techniques were used (n = 20): (i) Manually applied wax spacer and pressed-crown; (ii) digitally scanned preparation, CAD-printed wax-pattern (D76PLUS, Solidscape Inc.) and pressed-crown; (iii) digitally scanned preparation and machined-crown (CEREC-inLab® v3.6 Sirona GmbH). Resin-based cement (Variolink-II®, Ivoclar-Vivadent, Liechtenstein) was employed with a standardised mechanised cementation technique to apply a controlled axial cementation pressure [Universal testing machine (Lloyd LRX®, Lloyd Materials Testing Inc)]. The samples were subjected to fatigue life testing with a cyclic impact load of 453 N for 1.25 × 10⁶cycles at 37C⁰ and 1 Hz frequency until the point of fracture.

RESULT

There was a significant difference in the resistance to fatigue loading between the three groups. Weibull probability analysis and the α and β Weibull parameters indicate that the teeth restored with a 'Manually-applied wax spacer and pressed-crown' are best able to resist cyclic fatigue loading. They also have the most uniform interface geometry.

CONCLUSION

Teeth restored with IPS e. max® crowns constructed by manually applied wax spacer and pressing, have a more uniform interface and a greater structural integrity than wax CAD-printed patterns or CAD-CAM crowns.

Influence of the Fabrication Technique on the Marginal and Internal Adaptation of Ceramic Onlays

This study aimed to evaluate the marginal and internal adaptation of partial coverage crowns (ceramic onlays) fabricated with Press, CEREC BlueCam, and CEREC OmniCam systems, using two preparation designs and evaluating the internal discrepancies at different locations. Two phantom maxillary premolars (master teeth) received different preparation designs, with (BX) and without (NB) a modified occlusal box with round internal angles. Sixty IPS e-max ceramic restorations were fabricated with three systems: Press (n=20), CEREC BlueCam (n=20), and CEREC OmniCam (n=20). Both marginal and internal discrepancy width were measured by using a stereomicroscope at ×25 magnification. The data were evaluated statistically using analysis of variance followed by Tukey's Honestly Significant Difference test (α=0.05). The ceramic restorations fabricated with the Press system presented significantly smaller marginal and internal disadaptations than the BlueCam and OmniCam CEREC systems (p&lt;0.0001). Regarding the preparation designs, preparation BX presented the smallest marginal discrepancies for all fabrication systems and larger internal discrepancies than for restorations fabricated with the Press system. The occlusal location presented a larger internal discrepancy compared with the axial locations. Although the three systems resulted in the fabrication of restorations within a clinically acceptable adaptation with marginal discrepancies below 100 μm, the Press system presented the smallest marginal and internal discrepancies. An improved marginal adaptation was observed in the preparation design with a modified occlusal box with rounded internal angles.

In vivo wear determination of novel CAD/CAM ceramic crowns by using 3D alignment

PURPOSE

To determine wear amount of single molar crowns, made from four different restoratives, and opposing natural teeth through computerized fabrication techniques using 3D image alignment.

MATERIALS AND METHODS

A total of 24 single crowns (N = 24 patients, age range: 18 – 50) were made from lithium disilicate (IPS E-max CAD), lithium silicate and zirconia based (Vita Suprinity CAD), resin matrix ceramic material (Cerasmart, GC), and dual matrix (Vita Enamic CAD) blocks. After digital impressions (Cerec 3D Bluecam, DentsplySirona), the crowns were designed and manufactured (Cerec 3, DentsplySirona). A dual-curing resin cement was used for cementation (Variolink Esthetic DC, Ivoclar). Then, measurement and recording of crowns and the opposing enamel surfaces with the intraoral scanner were made as well as at the third and sixth month follow-ups. All measurements were superimposed with a software (David-Laserscanner, V3.10.4). Volume loss due to wear was calculated from baseline to follow-up periods with Siemens Unigraphics NX 10 software. Statistical analysis was accomplished by Repeated Measures for ANOVA (SPSS 21) at = .05 significance level.

RESULTS

After 6 months, insignificant differences of the glass matrix and resin matrix materials for restoration/enamel wear were observed (P>.05). While there were no significant differences between the glass matrix groups (P>.05), significant differences between the resin matrix group materials (P<.05) were obtained. Although Cerasmart and Enamic were both resin matrix based, they exhibited different wear characteristics.

CONCLUSION

Glass matrix materials showed less wear both on their own and opposing enamel surfaces than resin matrix ceramic materials.

Convergence angles of all-ceramic full crown preparations performed in Dubai private practice

Background

This study aimed to determine the degree of taper and total occlusal convergence angles (TOC) for all-ceramic bonded crown preparations carried out by private practitioners in Dubai, UAE.

Material and Methods

A convenience sample of all-ceramic crown preparations carried out by private dental practitioners were scanned (Carestream CS 3500) from casts and the digital images assessed. The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated.

Results

A total of 154 dentists prepared a total of 206 crown preparations (72 anterior, 134 posterior). The mean convergence angles mesio-distally for all preparations was 24.6° (sd 11.8º), and for the bucco-lingual it was 32.6° (sd 15.3°). The mean TOC was 28.6°. In anterior preparations, the mean bucco-lingual convergence angle was 38.8° (sd 12.2°) compared to 29.3° (sd 15.5°) for posterior preparations (p<0.001). Mean mesio-distal convergence anteriorly was 20.6° (sd 10.18°) compared to 26.7° (sd 12.16°) posteriorly (p<0.001). Distal and buccal taper were significantly greater on posterior teeth (<0.001) compared to anteriors whereas lingual taper was greater on anterior teeth (p<0.001). Mesial taper was not different. Premolars had significantly lower convergence values compared to other teeth.

Conclusions

Bucco-lingual and mesio-distal convergence angles significantly exceeded the clinically acceptable convergence angle of between 10° and 22°. Greater axial taper is recommended for resin bonded all-ceramic crowns but reliance on adhesion in such preparations rather than parallelism may reduce retention and have increased biologic cost to pulp health.

Key words:All-ceramic crown preparations, convergence angles, axial taper.

Educational effects using a robot patient simulation system for development of clinical attitude

INTRODUCTION

The aim of this study was to assess the effectiveness of improving the attitude of dental students towards the use of a full-body patient simulation system (SIMROID) compared to the traditional mannequin (CLINSIM) for dental clinical education.

MATERIALS AND METHODS

The participants were 10 male undergraduate dental students who had finished clinical training in the university hospital 1 year before this study started. They performed a crown preparation on an upper pre-molar tooth using SIMROID and CLINSIM as the practical clinical trials. The elapsed time for preparation was recorded. The taper of the abutment teeth was measured using a 3-dimensional shape-measuring device after this trial. In addition, a self-reported questionnaire was collected that included physical pain, treatment safety and maintaining a clean area for each simulator. Qualitative data analysis of a free format report about SIMROID was performed using text mining analysis. This trial was performed twice at 1-month intervals.

RESULTS

The students considered physical pain, treatment safety and a clean area for SIMROID significantly better than that for CLINSIM (P < .01). The elapsed time of preparation in the second practical clinical trial was significantly lower than in the first for SIMROID and CLINSIM (P < .01). However, there were no significant differences between the abutment tapers for both systems. For the text mining analysis, most of the students wrote that SIMROID was similar to real patients.

CONCLUSION

The use of SIMROID was proven to be effective in improving the attitude of students towards patients, thereby giving importance to considerations for actual patients during dental treatment.

Marginal and internal fit of pre-sintered Co-Cr and zirconia 3-unit fixed dental prostheses as measured using microcomputed tomography

STATEMENT OF PROBLEM

Limited information is available on the precision of new metal processing technologies.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal and internal fit of pre-sintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed dental prostheses using x-ray microcomputed tomography.

MATERIAL AND METHODS

Three-unit fixed dental prostheses were prepared on metal dies (N=12) using a typodont model from the maxillary first premolar to the first molar. A standardized preparation with a 1.2-mm chamfer (360 degrees) and a 2-mm occlusal reduction was prepared on abutment teeth. The dies were scanned and divided into 2 groups to receive the fixed dental prostheses (n=6) made of pre-sintered Co-Cr and pre-sintered zirconia. Each framework was seated on its cast, and marginal and internal discrepancies were measured at 9 points, starting from the most distal point from the pontic for the maxillary first premolar and the first molar (points 1-4, mesial; point 5, occlusal; points 6-9, distal) of each abutment tooth using microcomputed tomography. The data were analyzed using the Levene test, t test, and ANOVA (α=.05).

RESULTS

When overall mean discrepancy values were compared, no significant difference was observed between pre-sintered Co-Cr and pre-sintered zirconia (P=.085). Discrepancy values for points 1, 2, and 3 were significantly different for pre-sintered Co-Cr and pre-sintered zirconia, with the lowest mean values for point 1 and the highest for point 5. On the abutment tooth basis, for the maxillary first premolar and the first molar, a significant difference was found only in points 6 (P<.001) and 8 (P<.003) for both materials. When the discrepancies for the maxillary first premolar were considered for pre-sintered Co-Cr and pre-sintered zirconia, the mean values were significantly different only at points 1 (P<.001), 2 (P=.007), and 3 (P=.003) and were smaller for pre-sintered zirconia. For the tooth the first molar, a significant difference was observed at point 2 (P=.002) and point 3 (P=.008) for both materials, where the mean values were higher for pre-sintered Co-Cr than for pre-sintered zirconia. The pairwise comparison between points showed a significant difference between measurement points within each material (P<.05). The increase in values between points 1 and 5 was evident for both pre-sintered Co-Cr and pre-sintered zirconia materials.

CONCLUSIONS

Three-unit fixed dental prostheses made of pre-sintered Co-Cr or zirconia showed similar marginal and internal discrepancy values, with the highest discrepancy values at the occlusal region in both the first premolar and first molar.

Comparison of digital intraoral scanners by single-image capture system and full-color movie system

BACKGROUND

The use of dental computer-aided design/computer-aided manufacturing (CAD/CAM) restoration is rapidly increasing.

OBJECTIVE

This study was performed to evaluate the marginal and internal cement thickness and the adhesive gap of internal cavities comprising CAD/CAM materials using two digital impression acquisition methods and micro-computed tomography.

METHODS

Images obtained by a single-image acquisition system (Bluecam Ver. 4.0) and a full-color video acquisition system (Omnicam Ver. 4.2) were divided into the BL and OM groups, respectively. Silicone impressions were prepared from an ISO-standard metal mold, and CEREC Stone BC and New Fuji Rock IMP were used to create working models (n=20) in the BL and OM groups (n=10 per group), respectively. Individual inlays were designed in a conventional manner using designated software, and all restorations were prepared using CEREC inLab MC XL. These were assembled with the corresponding working models used for measurement, and the level of fit was examined by three-dimensional analysis based on micro-computed tomography.

RESULTS

Significant differences in the marginal and internal cement thickness and adhesive gap spacing were found between the OM and BL groups.

CONCLUSIONS

The full-color movie capture system appears to be a more optimal restoration system than the single-image capture system.

Clinical Acceptability of the Internal Gap of CAD/CAM PD-AG Crowns Using Intraoral Digital Impressions

The purpose of this study was to compare the internal gap between CAD/CAM palladium-silver crowns and cast gold crowns generated from intraoral digital versus conventional impressions and to determine the clinical acceptability. Nickel-chrome master dies were made from the prepared resin tooth with the conventional impression method (n = 40). For ICC (Intraoral, CAD/CAM) group, 10 intraoral digital impressions were made, and 10 CAD/CAM crowns of a PD-AG (palladium-silver) machinable alloy were generated. For IC (Intraoral, Cast) group, 10 gold crowns were cast from ten intraoral digital impressions. For CCC (Conventional, CAD/CAM) group, 10 CAD/CAM PD-AG crowns were made using the conventional impression method. For CC (Conventional, Cast) group, 10 gold crowns were fabricated from 10 conventional impressions. One hundred magnifications of the internal gaps of each crown were measured at 50 points with an optical microscope and these values were statistically analyzed using a two-way analysis of variance (α = 0.05). The internal gap of the intraoral digital impression group was significantly larger than in the conventional impression group (P < 0.05). No significant difference was observed between the CAD/CAM group and the cast group (P > 0.05). Within the limitations of this in vitro study, crowns from intraoral digital impressions showed larger internal gap values than crowns from conventional impressions.

Effect of Preparation Depth on the Marginal and Internal Adaptation of Computer-aided Design/Computer-assisted Manufacture Endocrowns

The aim of the study was to evaluate the effect of preparation depth and intraradicular extension on the marginal and internal adaptation of computer-aided design/computer-assisted manufacture (CAD/CAM) endocrown restorations. Standardized preparations were made in resin endodontic tooth models (Nissin Dental), with an intracoronal preparation depth of 2 mm (group H2), with extra 1- (group H3) or 2-mm (group H4) intraradicular extensions in the root canals (n=12). Vita Enamic polymer-infiltrated ceramic-network material endocrowns were fabricated using the CEREC AC CAD/CAM system and were seated on the prepared teeth. Specimens were evaluated by microtomography. Horizontal and vertical tomographic sections were recorded and reconstructed by using the CTSkan software (TView v1.1, Skyscan).The surface/void volume (S/V) in the region of interest was calculated. Marginal gap (MG), absolute marginal discrepancy (MD), and internal marginal gap were measured at various measuring locations and calculated in microscale (μm). Marginal and internal discrepancy data (μm) were analyzed with nonparametric Kruskal-Wallis analysis of variance by ranks with Dunn's post hoc, whereas S/V data were analyzed by one-way analysis of variance and Bonferroni multiple comparisons (α=0.05). Significant differences were found in MG, MD, and internal gap width values between the groups, with H2 showing the lowest values from all groups. S/V calculations presented significant differences between H2 and the other two groups (H3 and H4) tested, with H2 again showing the lowest values. Increasing the intraradicular extension of endocrown restorations increased the marginal and internal gap of endocrown restorations.

Are different generations of CAD/CAM milling machines capable to produce restorations with similar quality?

BACKGROUND

Different CAD/CAM machines' generation may impact the restoration overall quality. The present study evaluated the marginal fit of CAD/CAM restorations manufactured with different generations of CEREC milling unit systems.

MATERIAL AND METHODS

Sixteen typodont teeth were divided into two groups (n=8) according to the machine's generation assigned. These are control group (G1): Cerec AC with Bluecam/Cerec 3 milling unit and (G2): Cerec AC with Bluecam/MC XL Premium Package milling unit. Scanning of the preparation were performed and crowns were milled using the Vita Mark II blocks. Blocks were cemented using epoxy glue on the pulpal floor only and finger pressure applied for 1 min. Upon completion of the cementation step, misfits between the restoration and abutment were measured by microphotography and the silicone replica technique using light body silicon material on Mesial (M) and Distal (D) surfaces.

RESULTS

Mean and SDs of marginal gaps in micrometers were: G1/M: 94.90 (±38.52), G1/D: 88.53 (±44.87), G2/M: 85.65 (±29.89), G2/D: 95.28 (±28.13). Two-way ANOVA indicated no significant differences among different groups (P>0.05); surface area (P>0.05) and the interaction (P>0.05). Overall, G2 had greater margin gaps than G1, however, without statistical difference (P>0.05).

CONCLUSIONS

Difference in milling unit generation did not significantly affect the marginal fit. Marginal gap means were in the range of the clinical acceptance levels for both generations of Cerec milling units, regardless the teeth site area. Key words:CAD/CAM, margin, ceramics.

Influence of preparation design on fit and ceramic thickness of CEREC 3 partial ceramic crowns after cementation

OBJECTIVE

This study investigated the influence of preparation design on the marginal and internal gap and ceramic thickness of partial ceramic crowns (PCCs) fabricated with the CEREC 3 system.

MATERIALS AND METHODS

Sixteen extracted human mandibular molars were prepared according to two different preparation designs (n = 8): a retentive preparation design with traditional cusp capping (Group I) and a non-retentive preparation design with horizontal reduction of cusps (Group II). PCCs were fabricated from IPS Empress CAD with the CEREC 3 system. The parameters for luting space and minimum occlusal ceramic thickness were set to 30 μm and 1.5 mm, respectively. The fabricated PCCs were cemented to their corresponding teeth with self-adhesive resin cement and were then scanned by micro-computed tomography. The marginal and internal gaps were measured at pre-determined measuring points in five bucco-lingual and three mesio-distal cross-sectional images. The ceramic thicknesses of the PCCs were measured at the measuring points for cusp capping areas.

RESULTS

Group II (167.4 ± 76.4 μm) had a smaller overall mean gap, which included the marginal and internal gap measurements, than that of Group I (184.8 ± 89.0 μm). The internal gaps were larger than the marginal gaps, regardless of preparation design. Group I presented a thinner ceramic thickness in the cusp capping areas than the minimum occlusal ceramic thickness parameter of 1.5 mm. CONCLUSION. Preparation design had an influence on fit, particularly the internal gap of the PCCs. Ceramic thickness could be thinner than the minimum ceramic thickness parameter.

An open CAM system for dentistry on the basis of China-made 5-axis simultaneous contouring CNC machine tool and industrial CAM software

China-made 5-axis simultaneous contouring CNC machine tool and domestically developed industrial computer-aided manufacture (CAM) technology were used for full crown fabrication and measurement of crown accuracy, with an attempt to establish an open CAM system for dental processing and to promote the introduction of domestic dental computer-aided design (CAD)/CAM system. Commercially available scanning equipment was used to make a basic digital tooth model after preparation of crown, and CAD software that comes with the scanning device was employed to design the crown by using domestic industrial CAM software to process the crown data in order to generate a solid model for machining purpose, and then China-made 5-axis simultaneous contouring CNC machine tool was used to complete machining of the whole crown and the internal accuracy of the crown internal was measured by using 3D-MicroCT. The results showed that China-made 5-axis simultaneous contouring CNC machine tool in combination with domestic industrial CAM technology can be used for crown making and the crown was well positioned in die. The internal accuracy was successfully measured by using 3D-MicroCT. It is concluded that an open CAM system for dentistry on the basis of China-made 5-axis simultaneous contouring CNC machine tool and domestic industrial CAM software has been established, and development of the system will promote the introduction of domestically-produced dental CAD/CAM system.

Modern molar endodontic access and directed dentin conservation

During patient treatment, the clinician needs to consider the operator needs, the restoration needs, and the tooth needs. This article discusses molar access and failures of endodontically treated teeth that occur not because of chronic or acute apical lesions but because of structural compromises to the teeth that ultimately render them useless. The authors believe that the current models of endodontic treatment do not lead to long-term success, and that the traditional approach to endodontic access is fundamentally flawed. This article introduces a set of criteria that will guide the clinician in treatment decisions to maintain optimal functionality of the tooth and help in deciding whether the treatment prognosis is poor and alternatives should be considered.

Influence of convergence angle and cement space on adaptation of zirconium dioxide ceramic copings

OBJECTIVE

The purpose of the present study was to evaluate the influence of total convergence angle and cement space on internal and marginal adaptation of posterior zirconium dioxide (zirconia) ceramic copings.

MATERIAL AND METHODS

Seventy-two standardized mandibular first molar zirconia copings were fabricated with nine parameters: three different total convergence angles (6 degrees , 12 degrees , and 20 degrees ) with three different computer-fixed cement spaces (10, 30, and 60 microm). Marginal adaptation was assessed to measure vertical discrepancy between the coping and abutment by direct viewing. Internal adaptation was evaluated using the cement replica technique with a laser microscope. The Kruskal-Wallis test and Wilcoxon rank-sum test were performed to test for differences in internal space and marginal discrepancy values (alpha=0.05).

RESULTS

The median of mean internal spaces/marginal discrepancies ranged from 54.0/27.4 to 128.1/77.8 microm. Statistically significant differences in the internal spaces were found between groups with 6 degrees and 20 degrees convergence angle, regardless of cement space. The different cement spaces did not have any significant influence on the 12 degrees and 20 degrees convergence angle groups. The 60-microm cement space group exhibited statistically smaller marginal discrepancies than the 10-microm cement space group in all the different convergence angles.

CONCLUSIONS

Within the limitations of the present study, the internal spaces of zirconia ceramic copings may decrease as the convergence angles of abutments increase. The computer-fixed cement space might influence the marginal adaptation of zirconia ceramic copings. The internal and marginal adaptation of zirconia ceramic copings obtained was within the range of clinical acceptance.

Developing meaningful systematic review of CAD/CAM reconstructions and fiber-reinforced composites

OBJECTIVE

Clinical literature was examined for evidence supporting use of CAD/CAM reconstructions and fiber-reinforced materials.

MATERIALS AND METHODS

Potential evidence was identified via databases [PubMed; EMBASE (R) Drugs & Pharmacology; Center for Reviews and Dissemination, University of York; Cochrane Library], hand search of non-indexed literature, secondary reference searches, and personal contacts with clinical trial PI's. Search terms included: dental restorations; CAD/CAM; CEREC; LAVA; CERCON; Procera; inlay/onlay; dental prosthesis; fiber-reinforced composite (FRC).

RESULTS

Two randomized-controlled clinical trials were identified as examined in one Cochrane Collaboration review relevant to CAD/CAM inlays. One systematic review of 15 CAD/CAM inlay studies was examined. Six studies were identified of three commercial FRC endodontic posts and eight reported on FRC use for fixed denture prostheses. Fifteen ongoing prospective trials were identified studying CAD/CAM fabricated zirconia-based prostheses. A total of 76 papers were referenced including those related to use of in vitro measures as evidence.

CONCLUSIONS

Review of the Cochrane analysis raised concerns that typical RCT protocols may prove insufficient for stratification of confounding variables (patient, practitioner, material) when treatment outcomes are primarily prosthesis- or material-based (not patient-based, e.g., as in fracture). RCT designs are most straightforward when treatment outcomes are patient-based (e.g., soft tissue changes). When treatment responses are material-based, controls also become difficult to define and studies become tests of equivalency/superiority; where well-stratified cohort designs are likely preferred. Large numbers of independent cohort studies support the use of CAD/CAM ceramic inlay/onlay restorations and crowns but many complications inhibit the application of high-level systematic review. Except perhaps for fiber-based endodontic posts, the clinical FRC literature appears insufficient for expert review. Single in vitro measures cannot currently serve as evidence for clinical practice, except in limited cases of simple function (e.g., impression material accuracy). Batteries of in vitro measures are often applied during materials development but cannot substitute for clinical study.

Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems

In this study, the hypothesis was tested that the marginal and internal fit of CAD/CAM fabricated all-ceramic three-unit fixed partial dentures (FPDs) can be as good as in metal-ceramic FPDs. Twenty-four all-ceramic FPDs were fabricated and randomly subdivided into three equally sized groups. Eight frameworks were fabricated using the Digident CAD/CAM system (DIGI), another eight frameworks using the Cerec Inlab system (INLA). Vita Inceram Zirkonia blanks were used for both groups. In a third group frameworks were milled from yttrium-stabilized Zirconium blanks using the Lava system (LAVA). All frameworks were layered with ceramic veneering material. In addition, six three-unit metal-ceramic FPDs served as control group. All FPDs were evaluated using a replica technique with a light body silicone stabilized with a heavy body material. The replica samples were examined under microscope. The medians of marginal gaps were 75 microm for DIGI, 65 microm for LAVA and INLA and 54 microm for the conventional FPDs. Only the DIGI data differed significantly from those of the conventional FPDs. Within the limits of this study, the results suggest that the accuracy of CAD/CAM generated three-unit FPDs is satisfactory for clinical use.

Quantitative evaluation of axial wall taper in prepared artificial teeth

The purpose of this study was to quantitatively evaluate the axial wall taper of prepared artificial teeth using a non-contact three-dimensional shape measuring system. A total of 54 artificial teeth prepared by pre-clinical dental students for complete cast restorations were evaluated. For quantitative analysis, five cross sections were computer-graphically placed perpendicularly to the z-axis. The surface coordinate values (x, y, z) of each cross section were converted into polar coordinate values (r, theta), which were then graphically rendered to a two-dimensional plane. At four points, each 90 degrees from the distal center point of the cross section, the axial wall taper was quantitatively calculated using a formula based on the differences in radius between the highest and lowest positions of the cross sections of the prepared tooth. The average calculated taper was 5.8 degrees in the distal region, 21.7 degrees in the buccal region, 14.9 degrees in the mesial region and 12.5 degrees in the lingual region. These results suggest that the axial wall taper of prepared teeth can be quantitatively evaluated using this measuring system.