Influence of framework design on the cervical color of metal ceramic crowns.
BACKGROUND
The replication of natural teeth, especially for single tooth restorations in patients with high esthetic needs, represents a challenge.


OBJECTIVE
The purpose of the study was to analyze the color of the cervical portion of single metal ceramic crowns fabricated with different metal framework designs.


METHODS
The color, as measured on the CIELAB color scale, of 3 different groups of restorations (n=10) fabricated with a high noble metal alloy (V-Deltaloy) and feldspathic porcelain (Noritake Super Porcelain) was analyzed with a colorimeter. Conventional metal ceramic crowns with metal facial margins were compared to metal ceramic crowns with porcelain facial margins and a horizontal reduction of the metal framework (1.0 mm reduction) or an additional vertical reduction (1.0 mm reduction). In all specimens, the finish line was positioned at a subgingival or equigingival level. The 6 groups obtained by the combination of the levels of the 2 factors (framework extension and finish line location) were examined with an ANOVA Fisher's F-test and a post hoc Tukey's HSD test (α=.05).


RESULTS
The mean color difference for all the groups was clinically acceptable (ΔE<3.7). Conventional metal ceramic crowns showed higher differences in relation to finish line location (ΔE=2.34), while a vertical reduction of the framework was related to lower values (ΔE=0.96). Mean Lab* values were reported for all the groups of crowns. Statistically significant differences were present for L*, a*, and b* values when related to framework extension. Considering each value in relation to the interaction between framework extension and finish line location factors, significant differences were present only for L* and a* values.


CONCLUSIONS
No significant differences in base shade were present among the investigated crowns. Nevertheless metal ceramic crowns with vertical cut-back and porcelain facial margins presented more consistent results that tended to be closer to those of natural teeth.
School of Dental Medicine, Tufts University, Boston, MA, USA. panizg@hotmail.com
Gianluca
G
Paniz
Yongjeong
Y
Kim
Haythem
H
Abualsaud
Hiroshi
H
Hirayama
D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods; D003124:Colorimetry / Q000295:instrumentation; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D004955:Esthetics, Dental; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007180:Incisor; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry; D017797:Prosthesis Coloring; D019279:Resin Cements / Q000737:chemistry; D013053:Spectrophotometry; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods
D000538:Aluminum Silicates; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; D019279:Resin Cements; D003776:Dental Porcelain; C016447:feldspar; C103502:Variolink