Impact of abutment material and soft tissue thickness on mucosa discoloratio

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Impact of abutment material and soft tissue thickness on mucosa discoloration: A spectrophotometric in vitro study Peter Gehrke 1, Kai-Peter Zimmermann 1, Carsten Fischer 2 Dr. med. dent., Private Practice, Ludwigshafen, 2 MDT, Frankfurt - Germany

Abstract Objectives: To evaluate the discoloration of the peri-implant mucosa caused by titanium (Ti), titanium nitride (TiN), and zirconia (ZrO2) with and without ceramic veneering and to establish the influence of mucosal thickness on the resulting color. Material and Methods: For the present in vitro investigation a pig maxilla was used. In the region disto-palatally to the last molar on the right side of the palate a partial-thickness trap-door-type flap was prepared with a thickness of 0.5 mm and dimension of 5 x 5 mm (width x length). To simulate different mucosa thicknesses, multiple connective tissue grafts (CTG) with a thickness of 0.5 mm were harvested on the left side of the palate. To provide grafts of uniform thickness, a mucotome instrument (GB270, Aesculap, Tuttlingen, Germany) was used for the harvesting process. Thus, test-mucosa-layers with a thickness of 1.5, 2.0, or 3.0 mm resulted. To test a variety of clinical situations, different abutment and crown materials were evaluated. The following test specimens were prepared in dimensions of 5 x 5 mm and a thickness of 1.0 mm (Non-veneered) to 2.0 mm (Veneered): titanium (Ti alloy, Dentsply Sirona Implants, Mannheim, Germany), titanium veneered with veneering ceramic (Color A3), (GC Initial Ti, Leuven, Belgium), titanium nitride (GoldHue, Dentsply Sirona Implants, Mölndal, Sweden), titanium nitride veneered with veneering ceramic (Color A3) (GC Initial Ti, Leuven, Belgium), zirconia (Zirlux, Henry Schein Dental, Langen, Germany), and zirconia veneered with veneering ceramic (Color A3) (GC Initial Zr-FS, Leuven, Belgium). Color differences (ΔE values) were measured and calculated comparing the measurements of the native tissue, and the measurements with ascending mucosal thickness by spectrophotometric assessment (ShadePilot, Dentsply DeguDent, Hanau, Germany). Three consecutive images were captured to be used for data analysis. The ΔE E values were compared to the clinically visible ΔE threshold of 3.1 for intraoral color distinction as perceived by the bare eye (Sailer et al. 2014). Result: The results of the in vitro study confirm that all tested restorative materials lead to a discoloration of the mucosal tissue, diminishing with increasing mucosal thickness. In terms of metal-based abutment materials, the results indicate that in cases of thin soft tissues of 1.5 mm, the use of titanium nitride (mean ΔE 1.93) was superior compared to titanium alloy (mean ΔE 4.07), and revealed comparable ΔE values to the tested zirconia material (mean ΔE 2.13). At 3 mm mucosa thickness overlying the tested material, the differences in ΔE values became negligible.

Statistical Analysis

Methods and Materials

Titanium (Ti)

Titanium veneered (Ti-v)

Titanium Nitride (TiN)

Differences were calculated between the spectrophotometric values of tissues with and without test specimen interposition for each material group. The ΔL, Δa, Δb, and ΔE values of the three measurements were averaged, and this value was used for further analysis. The ΔE values were compared to the critical ΔE threshold of 3.1 for intraoral color distinction (Sailer et al. 2014). For statistical analysis of the differences between the ΔL, Δa, and Δb values, the onesample t test was used. A p-value < 0.05 indicated a significant result. The null hypothesis was that no visible changes occurred.

Zirconia (ZrO2)

Titanium Nitride Zirconia veneered (TiN-v) veneered (ZrO2-v)

Results Mucosa thickn.

Threshold of intraoral color dis/nc/on ΔE= 3.1

Delta E Mean Value

1

Ti

Ti;v

TiN

TiN;v

ZrO2

ZrO2;v

Tab.1: Mean ΔE values as a func8on of material and mucosa thickness

All tested materials lead to a mucosa discoloration, diminishing with increasing mucosal thickness. In cases of thin soft tissues of 1.5 mm, the use of TiN (mean ΔE 1.93) was superior compared to Ti alloy (mean ΔE 4.07), and revealed comparable ΔE values to ZrO2 (mean ΔE 2.13). Mucosa thickness

Ti

Ti-v

TiN

TiN-v

ZrO2

4,1

2,4

1,9

2,1

2,1

ZrO2-v 2,2

p = 0.002

p <0.001

p = 0.004

p = 0.001

p = 0.022

p = 0.002

2,6

2,2

2,0

2,2

1,9

1,8

p = 0.005

p = 0.005

p = 0.002

p < 0.001

p = 0.002

p = 0.004

1,5

1,0

1,4

1,9

1,9

1,3

p = 0.002

p = 0.042

p < 0.001

p = 0.004

p = 0.021

p = 0.013

in mm

1.5 mm 2 mm 3 mm

Tab.2: Mean ΔE values with 95%2confidence interval and t2test as a func8on of material and mucosa thickness

Background and Aim

Conclusions

Implant abutments made of pure titanium have been reported to cause a greyish discolouration of the surrounding soft tissues, compromising the esthetic outcome in the anterior region. This discoloration is most apparent in patients with a thin mucosal biotype (Lops et al. 2016; Ioannidis et al. 2016). Ceramic abutments have been promoted to achieve better mucogingival esthetics. Nevertheless, the esthetic benefit of all-ceramic abutments needs to be carefully balanced against the reduced fracture resistance. Recent studies have reported promising esthetic results with surface modifications of titanium such as coatings of CAD/CAM abutments with titanium nitride (TiN) (Ferrari et al. 2017). The aim of the current in-vitro study was to evaluate the discoloration of the periimplant mucosa caused by different metal-based and zirconia materials with and without ceramic veneering and to establish the influence of mucosal thickness on the resulting color.

In cases of thin peri-implant mucosa zirconia and titanium nitride as an abutment material lead to the least discoloration.

References 1.

Sailer I, Fehmer V, Ionnidis A, Hämmerle CH, Thoma DS. Threshold value for the perception of color changes of human gingiva. Int J Periodontics Restorative Dent. 2014 Nov-Dec; 34(6):757-62.

2.

Lops D, Stellini E, Sbricoli L, Cea N, Romeo E. Bressan E. Influence of abutment material on peri-implant soft tissues in anterior areas with thin gingival biotype: a multicentric prospective study, Clin Oral Implants Res, 2016 Oct. [Epub ahead of print].

3.

Ioannidis A, Cathomen E, Jung RE, Fehmer V, Hüsler J, Thoma DS. Discoloration of the mucosa caused by different restorative materials - a spectrophotometric in vitro study. Clin Oral Implants Res. 2016 Jul [Epub ahead of print].

4.

Ferrari M, Carrabba M, Vichi A, Goracci C, Cagidiaco MC. Influence of abutment color and mucosal thickness on soft tissue color. Int J Oral Maxillofac Implants. 2017 Mar/Apr; 32(2):393–399.


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