Tooth discoloration induced by endodontic materials: a laboratory study

Tooth discoloration induced by endodonticmaterials: a laboratory study P. Lenherr1*, N. Allgayer2*, R. Weiger2,3, A. Filippi3,4, T. Attin5 & G. Krastl2,3,61Clinic for Reconstructive Dentistry and Temporomandibular Disorders, University of Basel, Basel; 2Department of Periodontology,Endodontology and Cariology, University of Basel, Basel; 3Center of Dental Traumatology, University of Basel, Basel; 4Departmentof Oral Surgery, Oral Radiology and Oral Medicine, University of Basel, Basel; 5Clinic for Preventive Dentistry, Periodontology andCariology, Centre for Dental and Oral Medicine and Craniomaxillofacial Surgery, University of Zurich, Zurich, Switzerland; and6Department of Oral Surgery, School of Dentistry, University of Birmingham, Birmingham, UK 1 month (T3), 3 months (T4), 6 months (T5) andafter 1 year (T6). Colour change (DE) values were Lenherr P, Allgayer N, Weiger R, Filippi A, Attin T, Krastl calculated. A two-way analysis of variance was used G. Tooth discoloration induced by endodontic materials: a to assess significant differences between the endodon- laboratory study. International Endodontic Journal.
tic materials. The mean values of all groups were Aim To investigate the discoloration potential of compared using the Tukey multiple comparison test endodontic materials using a bovine tooth model.
Methodology Two hundred and 10 dentine-en- Results Significant differences were detected amongst amel cuboid blocks (10 · 10 · 3.5 mm) were pre- the experimental groups after 12 months (P < 0.0001).
pared out of the middle thirds of bovine tooth The lowest colour change values were observed in the crowns. Standardized cavities were prepared in the groups N (AH Plus, 3.2 ± 1.5), A (empty, 3.8 ± 1.4), L walls of the pulp chamber leaving 2 mm of enamel (PC, 4.1 ± 1.7), C (calcium hydroxide, 4.7 ± 1.5), E and dentine on the labial wall of the crown. The (Ultracal XS, 5.1 ± 1.9) and J (WMTA, 7.9 ± 6.7). The specimens were randomly assigned to 14 groups most discoloration was measured in groups G (3Mix, (n = 15). Endodontic materials were placed into the 66.2 ± 9.9) and F (Ledermix, 46.2 ± 11.6). PC showed cavities as follows: group A: empty, group B: blood, the best colour stability amongst the Portland cement- group C: calcium hydroxide, group D: ApexCal, based materials; however, when contaminated with group E: Ultracal XS, group F: Ledermix, group G: blood (group M), a significantly higher DE value (13.6 ± 4.2) was detected (P = 0.032).
MTA(GMTA), group I: GMTA + blood, group J: white Conclusion Materials used in endodontics may stain MTA (WMTA), group K: WMTA + blood, group L: teeth. Therefore, the choice of material should not rely Portland cement (PC), group M: PC + blood and solely on biological and functional criteria, but also group N: AH Plus. The cavities were sealed with take aesthetic considerations into account.
composite and stored in water. Standardized colour Keywords: bovine tooth model, discoloration, end- measurement (VITA Easyshade compact) was per- odontic materials, sealer, staining.
formed at the following intervals: prior to (T0) andafter placement of the filling (T1), 1 week (T2), Received 5 February 2012; accepted 15 March 2012 Correspondence: Gabriel Krastl, Center of Dental Traumatol-ogy, Department of Periodontology, Endodontology and Cari- Tooth discoloration induced by endodontic materials is ology, University of Basel, Hebelstrasse 3, CH-4056 Basel, a common finding and may impair the aesthetic Switzerland (Tel.: 0041 61 2672622; e-mail: gabriel.krastl@ outcome of endodontically treated teeth (van der Burgt et al. 1986a,b). A progressive discoloration is suggested *Both authors contributed equally to this study.
to be primarily a result of materials ingressing into Discoloration from endodontic materials Lenherr et al.
dentinal tubules (van der Burgt et al. 1986a,b). How- materials, which are used in endodontics. This study ever, it has been shown that a visible crown discolor- was undertaken to develop a new model for the ation may not necessarily be associated with tubule assessment of tooth discoloration and to investigate penetration and may be caused by material remnants the staining ability of endodontic materials.
in the pulp chamber, which get darker over time and The tested hypotheses were (i) there is no difference transmit through the hard tissues (Davis et al. 2002).
in discoloration amongst the tested materials after The staining ability of several endodontic materials 12 months and (ii) all materials show a similar including Walkhoff’s paste, Grossman’s cement, zinc progression of discoloration over time.
oxide eugenol, endomethasone and N2 has beendemonstrated (Gutierrez & Guzman 1968, van der Burgt et al. 1986a,b). However, most of these materialsare no longer used.
Limited data are available on the staining ability of recent endodontic materials. Most studies that focused Two hundred and 10 bovine incisors were extracted, on root canal sealers concluded they stained teeth. This cleaned and stored in water at room temperature.
was shown in laboratory studies for AH26, Kerr Pulp Following the removal of the roots, the labial surface of Canal Sealer, Roth 801, Sealapex, Endofill, Tubliseal, each tooth was cleaned meticulously with scalers. A zinc oxide eugenol, Apatite Root Canal Sealer, Cavizol, cuboid enamel-dentine block (10 · 10 mm) was pre- AH Plus and EndoREZ (Parsons et al. 2001, Davis et al.
pared from the middle third of each crown using a 2002, Partovi et al. 2006, Elkhazin 2011). The discol- diamond-coated disc (Intensiv SA, Grancia, Switzer- oration potential of Ledermix has been evaluated ex land). The height of each block was standardized at vivo (Kim et al. 2000a,b) and in a recent clinical study 3.5 ± 0.1 mm, measured with a calliper (Iwanson, (Day et al. 2011). In the same three studies, calcium Ustomed, Tuttlingen, Germany). A cylindrical-shaped hydroxide pastes were used as controls. It was hole with the diameter of 2.5 mm was drilled with a concluded that, compared with Ledermix, calcium form-congruent bur (Dentsply Maillefer, Ballaigues, hydroxide may cause only minor but measurable Switzerland) in the middle of each specimen to leave staining. However, there are various formulations of 2 mm of the labial tooth structure (Fig. 1). The calcium hydroxide available with different constitu- specimens were placed in 1% sodium hypochlorite for ents, which have been added to the powder toimprove properties such as antibacterial action, radio-pacity, flow and consistency (Fava & Saunders 1999).
These additives may affect the staining ability of thepastes.
Several case reports reveal discoloration produced by MTA. However, there is only one study documentingsevere discoloration caused by MTA when the materialwas used as a pulpotomy agent in primary molars(Naik & Hegde 2005).
Although manufacturers such as Medcem GmbH (Weinfelden, Switzerland) claim that a better colourstability is achieved when using Portland cement (PC)instead of MTA, there are no studies available to provethat statement.
Discoloration after canal medication with triple antibiotic pastes (3Mix), as used in the field of regen-erative endodontics, has only been scarcely mentionedin the literature (Trope 2010). Only one laboratoryexperiment proved clear evidence of tooth discolorationafter use of the paste (Kim et al. 2010).
Figure 1 Schematic showing the tooth piece cut out of the In summary, no systematic approach has been used middle third of the crown of a bovine incisor. The spectro- to evaluate and compare the discoloration induced by photometer is held on to the tooth piece.
Lenherr et al. Discoloration from endodontic materials 30 min and, after drying with air, placed in 20% EDTA Polymerization was initiated with a LED curing light (lege artis, Detthausen, Germany) for two additional (Smart Lite PS Series, Dentsply International, York, PA, minutes to remove the smear layer. After a final 3 min in sodium hypochlorite, the specimens were stored in Every specimen was placed into a single tube with tap water (Standard Micro Test Tube 3810; Eppendorf The specimens were randomly assigned to 14 groups AG, Hamburg, Germany). The tubes were stored at (n = 15), and different endodontic materials (Table 1) room temperature and kept in the dark during the first were placed into the cavities. The materials were 3 months. During the following period and up to prepared as indicated by the manufacturer’s guidelines/ 12 months, the specimens were exposed to indirect recommendations. In group G, a triple antibiotic paste sunlight until the end of the experiment.
including metronidazole, minocycline and ciprofloxacinwas produced according to the composition and mixing instructions described by Trope (Trope 2008). Ingroups I, K and M, 1.5 lL of bovine blood was placed Colour measurements were taken in a dark room with on top of the material with a pipette (0.5–10 lL; a spectrophotometer (VITA EasyshadeÒ compact; VITA Eppendorf AG, Hamburg, Germany) to simulate a Zahnfabrik, Bad Sa¨ckingen, Germany) under standard- typical clinical situation in which calcium silicate- ized conditions in a custom-fabricated measuring based materials are in contact with vital and vascular- station (Fig. 2). The station consisted of a wooden ized tissue. This situation was not simulated for the root board with a fixed lamp, a carrier for the specimens canal dressings and sealers because their application and the VITA EasyshadeÒ Compact unit. The instru- implies that vital tissues have been removed from the ment was calibrated before the measurement in each The cavities were sealed with a self-adhesive resin Seven sessions of colour measurements were ob- material (RelyX Unicem; 3M ESPE, Seefeld, Germany).
tained at the following intervals: prior (T0 = baseline) Table 1 Materials used in the different experimental groups and their compositions Produits Dentaires, SA, Vevey, Switzerland Injectable calcium hydroxide paste containing Injectable calcium hydroxide paste containing Glucocorticosteroid-antibiotic root canal Riemser Arzneimittel, Greifswald, Germany Triple antibiotic mixture (ciprofloxacin, Grey mineral trioxide aggregate, containing White mineral trioxide aggregate (similar to GMTA, but lower amounts of iron, aluminium Portland cement (similar to MTA but absence of bismuth ions and presence of potassium Epoxy–amine resin-based root canal sealer, Discoloration from endodontic materials Lenherr et al.
The DE values at several time intervals are presented inFig. 3. The most severe discoloration after 12 monthswas caused by Ledermix and 3Mix. However, duringthe period of dark storage (first 3 months), Ledermixdid not reveal a significant difference compared withbaseline (P = 0.3057), whilst a highly significantdifference was observed for 3Mix (P < 0.0001). Pro-gressive discoloration in terms of a significant differencebetween baseline and 12 months was also observed forApexCal (P < 0.0001), WMTA + blood (P = 0.0146)and PC + blood (P = 0.0206).
Figure 2 Custom-built measuring station with VITA Easy- GMTA showed severe discoloration from the time of shadeÒ Compact instrument in the measuring position.
placement (T1). After a slight increase during the firstweek, the mean DE value seemed to remain stable at and after placement of the filling (T1), after 1 week (T2), 1 month (T3), 3 months (T4), 6 months (T5) and DE mean values and standard deviations after 12 months (T6). To prevent optical changes caused by 12 months are given in Table 2. At this time interval, dehydration, the excess water was removed briefly by PC caused the least discoloration amongst the Portland air-drying for 1 s. The entire measurement was com- cement-based materials when no blood was added, the pleted within 5 s for every specimen, and each speci- difference being statistically significant compared with men was measured once. The CIE L*a*b* data were GMTA (P < 0.0001) but not compared with WMTA For each specimen, colour change (DE) values were calculated with the following formula.
This study investigated the potential of endodontic DEà ¼ ððDLÃÞ2 þ ðDaÃÞ2 þ ðDbÃÞ2Þ1=2; DLà materials to induce discoloration in a new experimental ¼ Là À Là ; Daà ¼ aà À aà ; Dbà ¼ bà À bà : set-up using a bovine tooth model. The majority of For each group, the means of the DE values were previous studies have used human teeth to assess the calculated at the given time intervals.
degree of staining. However, the significant variability A two-way analysis of variance was used to assess in tooth morphology combined with small sample sizes significant differences between the tested endodontic may influence the results considerably. To overcome materials. The mean value of all groups were compared these limitations, the present laboratory model used using the Tukey multiple comparison test (a = 0.05).
standardized bovine tooth pieces with a similar shape Figure 3 DE values of the experimental groups at the different measurement points, directly after placement of the filling (T1), 1 week (T2), 1 month (T3), 3 months (T4), 6 months (T5) and after 1 year (T6). Each error bar is constructed using a 95% confidence interval of the mean. A time dependency is obvious for groups D, F and G.
Lenherr et al. Discoloration from endodontic materials Table 2 Mean colour change after 12 months (mean ± stan- and to provide optimal penetration of the endodontic materials into the dentinal tubules, the smear layer was Despite the standardized experimental set-up, the present model has limitations in fully imitating the clinical situation. Interaction of the endodontic mate- rial with salivary components and bacteria may occur if there is leakage at the restoration margins. This may lead to different staining mechanisms in vivo. Further- more, placing medicaments or sealers intentionally for up to 12 months inside the tooth crown may exagger- ate the clinical situation in which materials in the access cavity are removed before the final restoration is The present survey revealed significant differences between the endodontic materials with regard to their ability to discolour teeth. Furthermore, the materials Levels not connected by same superscript are significantlydifferent.
showed a different progression of discoloration overtime. Thus, both hypotheses had to be rejected.
and thickness. Furthermore, the colour analysis wasconducted under standardized conditions in a custom- Discoloration by Portland cement-based materials fabricated measuring station to ensure that the con-secutive measurements were taken at the same region Portland cement-based materials have gained much popularity in endodontics because of their biocompat- For colour determination, the Vita Easyshade Com- ibility and good sealing properties (Parirokh & Tora- pact Device was chosen because of its high data binejad 2010, Torabinejad & Parirokh 2010).
stability and excellent repeatability (Lehmann et al.
Amongst these materials, in the present study, the 2010). Even though deviations from the spectrophoto- best colour stability could be achieved with PC even metric reference may occur with most commercially though the difference was not significant compared available devices, this discrepancy may not be relevant with WMTA after 12 months. PC differs from the MTA for this study, because the assessment of colour by the absence of bismuth ions and presence of changes and not the determination of the exact tooth potassium ions (Song et al. 2006). According to Steffen and van Waes (2009), bismuth oxide, which has been Although bovine root dentine has a significantly added to PC to increase radiopacity, is a possible factor higher tubule density than human samples, coronal responsible for the discoloration of teeth treated with dentinal layers do not differ significantly in terms of MTA. After contamination of the specimens with blood, density or diameter of the tubules (Schilke et al. 2000).
all Portland cement-based materials showed an in- This suggests that bovine incisor crowns may represent creased discoloration. Namazikhah et al. (2008) dem- suitable substitutes for human teeth in laboratory onstrated that the microstructure of the materials studies dealing with tooth discoloration.
shows pH-dependent porosities. These porosities may The severity of tooth discoloration depends on uptake blood components and may be responsible for whether the smear layer is removed or not (Davis et al.
the observed discoloration. This is of clinical relevance 2002). It has been reported that the smear layer can because Portland cement-based materials are usually markedly reduce the permeability of dentine (White placed in direct contact to vital, vascularized tissue.
et al. 1987). In studies performed without the removal Thus, the development of biocompatible materials with of smear layer, tooth discoloration was less evident or a reduced porosity level may be beneficial.
took longer (Parsons et al. 2001, Davis et al. 2002).
Recent protocols for root canal irrigation recommend Discoloration by triple antibiotic pastes the removal of the smear layer to facilitate thedisinfection of the root canal system (van der Sluis The most severe discoloration was seen when the triple et al. 2007). To reproduce a realistic clinical situation antibiotic paste containing ciprofloxacin, metronidazole Discoloration from endodontic materials Lenherr et al.
and minocycline was used. The specimens in this group corticosteroid dressing may be a reasonable alternative became almost black after 12 months. Discoloration after canal medication with the triple antibiotic pastehas scarcely been mentioned in the literature (Trope 2010). Kim et al. (2010) identified minocycline as thecause for discoloration in vitro. Furthermore, the latter AH Plus, the only sealer tested in this study, seemed to study demonstrated that sealing the dentine wall with a exhibit satisfactory colour stability, presumably owing bonding agent prior to application of the paste could to the stable radiopacifier. Zirconium oxide has a high reduce the overall colour change, without being able to radiopacity but is not known to be involved in prevent it. Even though the triple antibiotic paste discoloration. However, the present results are in originally introduced by Hoshino et al. (1996) reliably contrast to the findings of Elkhazin (2011) who showed eradicates bacteria from infected root canals setting the distinct discoloration induced by AH Plus after conditions for subsequent re-vascularization in the field 6 weeks, which tended to decline after 8 weeks. The of regenerative endodontic procedures (Trope 2008), it present study also revealed a greater colour change may cause severe aesthetic problems. Thus, future during the first 3 months and declining DE values research should focus on alternative mixtures with a substitute for minocycline. Trope (2010) showed that with Arestin as a substitute discoloration could bemarkedly reduced but not prevented.
As a comparable alternative a prefabricated trianti- biotic mixture with cefuroxim as a substitute for The calcium hydroxide dressings varied in their discol- minocycline is available (TreVitaMix; Medcem GmbH).
oration ability. Pure calcium hydroxide and Ultracal XS However, there are no studies available neither regard- did not show any discoloration or difference to the ing the disinfection potential of the mixture in the root negative controls at any time. Interestingly, the Apex- canal, nor its discoloration ability.
Cal specimens showed an increase in their DE values inthe second half of the observation period. The differenceto all the other calcium hydroxide materials was statistically significant after 12 months. As bismuth Ledermix has regained attention in the field of dental carbonate is part of the chemical composition of traumatology. Placed as an intracanal medication ApexCal (22 weight per cent, according to the manu- after severe luxation injuries, it has the potential to facturers specification), a discoloration produced by inhibit inflammatory root resorption (Pierce et al.
bismuth ions may explain this finding.
1988, Bryson et al. 2002, Wong & Sae-Lim 2002).
A recently published randomized controlled clinical However, in the present study, severe and increasing trial on replanted teeth demonstrated that even Ultr- discoloration occurred in the Ledermix specimens acal XS produced measurable colour changes (DE especially after the specimens had been exposed to change in colour = 3.0) in a clinical situation. How- indirect sunlight. This is in accordance with other ever, only 1 of 12 patients was concerned about the laboratory (Kim et al. 2000a,b) and clinical studies colour of the tooth compared with 7 of 10 patients in (Day et al. 2011). From a clinical aspect, it may not be the Ledermix group (Day et al. 2011). In the laboratory possible to completely avoid contamination of the tests for this study, the mean DE change in colour for coronal dentine with the medicament or to meticu- the Ultracal XS group was 5.1. In a clinical situation, a lously clean the surfaces after placement. Thus, minor colour mismatch between DE 2.6 and 3.7 is alternative nonstaining alternatives are needed. This sufficient to be identified by a dentist. However, a may be Odontopaste (Australian Dental Manufactur- difference of DE 5.5–6.8 is needed to classify the ing, Kenmore Hills, Australia), a recently released discoloration as unacceptable and recommend further alternative with substitution of the tetracycline com- ponent by clindamycin (Athanassiadis et al. 2011).
Furthermore, as the inhibiting effect of Ledermix on external root resorption after severe dislocation inju-ries is primarily attributed to the corticosteroid com- Materials used in endodontics may stain teeth. There- ponent (Chen et al. 2008, Kirakozova et al. 2009), a fore, the choice of material should not rely solely on Lenherr et al. Discoloration from endodontic materials biological and functional aspects, but also take aes- Kim JH, Kim Y, Shin SJ, Park JW, Jung IY (2010) Tooth thetic considerations into account. Underlying mecha- discoloration of immature permanent incisor associated nisms of tooth discoloration by endodontic materials with triple antibiotic therapy: a case report. Journal of should be investigated in further research projects and Kirakozova A, Teixeira FB, Curran AE, Gu F, Tawil PZ, Trope M (2009) Effect of intracanal corticosteroids on healing of replanted dog teeth after extended dry times. Journal of Lehmann KM, Igiel C, Schmidtmann I, Scheller H (2010) Four The authors are very grateful to VITA Zahnfabrik (Bad color-measuring devices compared with a spectrophotomet- Sa¨ckingen, Germany) for providing the study with the ric reference system. Journal of Dentistry 38s, e65–70.
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