Miguel Gómez-Polo

A 10-year retrospective study of the survival rate of teeth restored with metal prefabricated posts versus cast metal posts and cores

OBJECTIVE The aim of this retrospective study was to compare the cumulative survival rate of teeth restored with prefabricated posts and with cobalt-chrome cast post-cores. METHODS 112 endodontically treated teeth restored with prefabricated post and cobalt-chrome cast post-and-cores were evaluated. Teeth were considered as failures when were objective or radiologic sign of endodontic failure, post or root fracture, or when they had been extracted at the moment of the evaluation. Kaplan-Meiers method was used to reconstruct the survival curves of the restorations and to test the variable type of post-and-core restoration. RESULTS 93 of the posts were still in function without clinical or radiographic signs of failure at the time of the examination resulting in a survival rate of 83.03% after a mean follow-up period of 10.08 years. When comparing the two techniques, prefabricated posts showed a slightly higher survival rate: 84.6% versus 82.6%.Focusing on tooth-type, maxillary premolars (n=30) had the highest failure rate (30%) and also the lowest mean lifetime, with 6-and-a-half years. Maxillary incisors (n=20) showed the highest success rate (5%) with only one case of failure. CONCLUSIONS The results showed no significant difference between both groups after a 10-year average follow-up.

Differences between the human eye and the spectrophotometer in the shade matching of tooth colour.

OBJECTIVES The aim of this work was to assess the agreement between instrumental and visual colour matching. METHODS Shade selection with the 3DMaster Toothguide (Vita-Zahnfabrik) was performed for 1361 maxillary central incisors and compared with the shade obtained with the EasyShade Compact (Vita-Zahnfabrik) spectrophotometer. RESULTS We observed a greater correlation between the objective method and the subjective one in the colour dimension of lightness (Kappa 0.6587), followed by hue (Kappa 0.4337) and finally chroma (Kappa 0.3578). CONCLUSION The colour dimension in which the greatest agreement is seen between the operator and the spectrophotometer is value or lightness. CLINICAL SIGNIFICANCE This study reveals differences between the measurement of colour via spectrophotometry and the visual shade selection method. According to our results, there is better agreement in the value or lightness colour dimension, which is the most important one in the choice of tooth colour.

A clinical study relating CIELCH coordinates to the color dimensions of the 3D-Master System in a Spanish population

STATEMENT OF PROBLEM The 3D-Master System comprises 26 physical shade tabs and intermediate shades. Determining the relationship among all the groups of lightness, chroma, and hue of the 3D-Master System (Vita Zahnfabrik) and the L*, C*, and h* coordinates is important, because according to the manufacturer, 2 Toothguide 3D-Master shades need to be mixed in a 50:50 ratio to create an intermediate shade. PURPOSE The purpose of the study was to relate the lightness, chroma, and hue groups of the 3D-Master System with the polar coordinates of the CIELAB chromatic space, L*, C*, and h*, and to quantify the shades tabs and intermediate shades of the 3D-Master System according to color coordinates. MATERIAL AND METHODS The middle third of the facial surface of a natural maxillary central incisor was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Spanish participants aged between 16 and 89 years. Natural tooth color was recorded in the 3D-Master nomenclature and in the CIE L*, C*, and h* coordinates system. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. RESULTS In the L* variable, the minimum was found at 47.0 and the maximum at 91.3. In the C* variable, the minimum was found at 5.9 and the maximum at 49.8, while for h*, the minimum was 67.5 degrees and the maximum 112.0 degrees. CONCLUSIONS Despite the limitations of this study, the 3D-Master System was found to be arranged according to L*, C*, and h* coordinates in groups of lightness, chroma, and hue. The corresponding groups of lightness, chroma, and hue can be estimated on the basis of L*, C*, and h* coordinates.

Marginal and Internal Discrepancies of Posterior Zirconia-Based Crowns Fabricated with Three Different CAD/CAM Systems Versus Metal-Ceramic.

PURPOSE The aim of this study was to analyze the marginal and internal fit of metalceramic and zirconia-based crowns. MATERIALS AND METHODS Forty standardized steel specimens were prepared to receive posterior crowns and randomly divided into four groups (n = 10): (1) metal-ceramic, (2) NobelProcera Zirconia, (3) Lava Zirconia, and (4) VITA In-Ceram YZ. All crowns were cemented with glass-ionomer agent and sectioned buccolingually. A scanning electron microscope was used for measurements. Kruskal-Wallis and Wilcoxon signed rank test (α = .05) statistical analyses were conducted. RESULTS Significant differences (P < .0001) in marginal discrepancies were observed between metal-ceramic and zirconia groups. No differences were found for the axial wall fit (P = .057). Significant differences were shown among the groups in discrepancies at the occlusal cusp (P = .0012) and at the fossa (P = .0062). No differences were observed between surfaces. CONCLUSIONS All zirconia groups showed better values of marginal discrepancies than the metal-ceramic group. Procera Zirconia showed the lowest gaps.

Natural Tooth Color Estimation Based on Age and Gender.

PURPOSE Assessment of the predictability of tooth color coordinates according to the CIELab system to estimate the color of the maxillary central incisor based on patient age and gender. MATERIAL AND METHODS The tooth color of one of the maxillary central incisors of 1361 Caucasian Spanish individuals aged 16 to 89 years, male and female, was measured using the Easyshade compact spectrophotometer. Color coordinates L*, C*, h*, a*, and b* were recorded according to age and gender. RESULTS The results obtained show that differences in age account for 45% of the total variation of the L (lightness) coordinate; 21% of the variation in coordinate a*, and 17% of the variation in coordinate b* is due to the same reason. At a confidence level of 95% it may be proposed that the mean estimated color difference (ΔEab *) between real natural color and that predicted by the linear regression model is between 6.4 and 6.9 units. CONCLUSIONS In this sample of Caucasians from Spain, teeth became darker yellow and more reddish with increasing age. The L* coordinate is most strongly related to tooth color in aging.

SEM evaluation of the precision of fit of CAD/CAM zirconia and metal-ceramic posterior crowns

The purpose of this study is to evaluate the precision of fit of posterior crowns made from three commercial CAD/CAM zirconia ceramics and conventional metal-ceramic technique. The external and internal marginal fit of the crowns was evaluated using direct SEM-based measurements. The data were subjected to Kruskal-Wallis, multicomparison post hoc analysis and Wilcoxon rank sum tests (α=0.05). Significant differences were observed for the external (p<0.002) and the internal (p<0.0001) marginal evaluation among the groups. No differences were observed between the buccal and lingual surfaces for the external (p=0.34) and internal (p=0.55) evaluations. No differences were showed between the external and internal measurements (p=0.37). The accuracy of fit was within the range of clinical acceptance. The lowest discrepancies corresponded to the NobelProcera group for external (39.3±11.81 μm) and internal (41.09±7.54 µm) marginal fit. The results confirmed that destructive methods are not required to assess the marginal fit of dental prosthetic crowns.

Study of the most frequent natural tooth colors in the Spanish population using spectrophotometry

PURPOSE To identify the most frequent natural tooth colors using the Easyshade Compact (Vita -Zahnfabrik) spectrophotometer on a sample of the Spanish population according to the 3D Master System. MATERIALS AND METHODS The middle third of the facial surface of natural maxillary central incisors was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Caucasian Spanish participants aged between 16 and 89 years. Natural tooth color was recorded using the 3D Master System nomenclature. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. RESULTS The results show that the most frequent dental color in the total sample studied is 3M1 (7.05%), followed by the intermediate shade 1M1.5 (6.91%) and 2L1.5 (6.02%). CONCLUSION According to the research methodology used, and taking into account the limitations of this study, it can be proposed that the most frequent color among the Spanish population is 3M1; the most common lightness group is 2; the most frequent hue group according to the 3D Master System is M and the most frequent chroma group is 1.5.

Clinical study on natural gingival color

The aims of the study were: to describe the gingival color surrounding the upper incisors in three sites in the keratinized gingiva, analyzing the effect of possible factors which modulate (socio-demographic and behavioral) intersubject variability; to study whether the gingiva color is the same in all three locations and to describe intrasubject color differences in the keratinized gingiva band. Using the CIELAB color system, three reference areas (free gingival margin, keratinized gingival body, and birth or upper part of the keratinized gingiva) were studied in 259 individuals, as well as the related socio-demographic factors, oral habits and the chronic intake of medication. Shadepilot™ spectrophotometer was used. Descriptive and inferential statistical analysis was performed. There are statistically significant differences between males and females for coordinates L* and a* in the middle and free gingival margin. For the b* coordinate, there are differences between males and females in the three locations studied (p < 0.05). The minimum and maximum coordinates in which the CIELAB natural gingival space is delimited are L* minima 28.3, L* maximum 65.4, a* minimum 11.1, a* maximum 37.2, b* minimum 6.9, and b* maximum 25.2*. Age, smoking, and the chronic intake of medication had no significant effect on gum color. There are perceptible color differences within the keratinized gingiva band. These chromatic differences must be taken into account if the prosthetic characterization of gingival tissue is to be considered acceptable. There are significant differences between the color coordinates of the three sites studied in the keratinized gingiva of men and women.

Clinical Study of the 3D-Master Color System among the Spanish Population

PURPOSE To study whether the shades of the 3D-Master System were grouped and represented in the chromatic space according to the three-color coordinates of value, chroma, and hue. MATERIALS AND METHODS Maxillary central incisor color was measured on tooth surfaces through the Easyshade Compact spectrophotometer using 1361 participants aged between 16 and 89. The natural (not bleached teeth) color of the middle thirds was registered in the 3D-Master System nomenclature and in the CIELCh system. Principal component analysis and cluster analysis were applied. RESULTS 75 colors of the 3D-Master System were found. The statistical analysis revealed the existence of 5 cluster groups. The centroid, the average of the 75 samples, in relation to lightness (L*) was 74.64, 22.87 for chroma (C*), and 88.85 for hue (h*). All of the clusters, except cluster 3, showed significant statistical differences with the centroid for the three-color coordinates (p <0.001). CONCLUSIONS The results of this study indicated that 75 shades in the 3D-Master System were grouped into 5 clusters following coordinates L*, C*, and h* resulting from the dental spectrophotometer Vita Easyshade compact. The shades that composed each cluster did not belong to the same lightness color dimension groups. There was no special uniform chromatic distribution among the colors of the 3D-Master System.

Interim restoration using dynamic abutments to re-treat a single-implant crown with a labial angulation: A clinical report

The cause of some peri-implant problems may be primarily attributable to the design of the prosthesis. A screw-retained interim implant may be advisable for reversibility and to avoid peri-implant cement, although screw retention may be difficult for maxillary anterior implants with a labial angulation. In the treatment described, a interim screw-retained crown was attached to a dynamic abutment with a lingual screw access hole to obtain a correctly fitting restoration.