Management of teeth with necrotic pulps and open apices

28 Pages·2012·1.18 MB·English

EndodonticTopics2012,23,105–130 2012©JohnWiley&SonsA/S
Allrightsreserved
ENDODONTICTOPICS2012
1601-1538
Management of teeth with
necrotic pulps and open apices
MAHMOUD TORABINEJAD & IBRAHIM ABU-TAHUN
When the pulp of a tooth is irreversibly inflamed or necrotic and the apex is open, conventional root canal
treatment is difficult to perform and the outcome is uncertain. Traditionally, the apexification procedure has
consistedofmultipleandlong-termapplicationsofcalciumhydroxide[Ca(OH) ]tocreateanapicalbarriertoaid
2
theobturation.Recently,artificialapicalbarrierssuchasthosemadewithmineraltrioxideaggregate(MTA)have
been used in teeth with necrotic pulps and open apices. More recently, procedures referred to as regenerative
endodontics have received much attention as an option for these teeth. The purpose of this article is to provide
a comprehensive literature review from May 1952–May 2011 regarding the management of teeth with necrotic
pulpsandopenapices.Thisreviewcoversthearticlespublishedindentaljournalsandbookchaptersregardingthe
definition, history, materials used, animal and human studies, mechanisms of action, prognosis, as well as
advantages and disadvantages of apexification, apical plugs, and regenerative endodontics.
Received 27 October 2011; accepted 17 February 2012.
Introduction ment. The advantages of such a procedure lie in the
potential for reinforcement of dentinal walls by the
Pulpal necrosis in immature teeth results in the ces-
deposition of hard tissue, and for the development of
sation of root development, making endodontic
an apical morphology more appropriate to routine
treatment with conventional techniques and materials
root canal treatment procedures if future treatment
difficult because obtaining an adequate apical seal is a
becomes necessary (5,6).
major objective of root canal treatment (1). In addi-
Thepurposeofthisarticleistoprovideacomprehen-
tion, due to their thin walls, these teeth are suscep-
sive literature review from May 1952–May 2011
tible to fracture after treatment (2,3). Traditionally,
regardingthemanagementofteethwithnecroticpulps
apexification procedures have consisted of multiple
and open apices. This review covers the articles pub-
and long-term applications of calcium hydroxide
lishedindentaljournalsandbooksregardingthedefi-
[Ca(OH) ] in order to create an apical barrier before
2 nition, history, materials used, animal and human
obturation of the root canals. Because these proce-
studies, mechanisms of action, prognosis, as well as
dures might alter the mechanical properties of dentin
advantages and disadvantages of apexification, apical
and make these teeth more susceptible to root frac-
plugs, and regenerative endodontics to maintain
ture, developing artificial apical barriers using mineral
naturaldentition.
trioxide aggregate (MTA) has been suggested before
obturation of the rest of the root canal (3,4).
However, this procedure may not result in continued
Inclusion criteria
root formation and may leave the root susceptible to
fracture (4,5). The ideal outcome for a tooth with an All publications related to the treatment of teeth with
immature root and a necrotic pulp would be the necrotic pulps and open apices from peer-reviewed
regeneration in the canal of pulp tissue capable of journals and books published in English from May
promoting the continuation of normal root develop- 1952–May 2011 are included in this review.
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Torabinejad & Abu-Tahun
Search methodology development first proposed by Granath (13), who
describedtheuseofCa(OH) forapicalclosureorthe
2
AnelectronicsearchwasconductedinthePubMedand
establishment of an apical barrier.
Cochrane databases with appropriate MeSH headings
Although proper condensation of gutta-percha is
and key words related to the treatment of teeth with
almost impossible because the apical portion of the
necroticpulpsandopenapices.Toenrichtheresults,a
root is frequently wider than the coronal portion, a
manual search was conducted of the last two years’
number of authors described the use of custom-fitted
worth of issues in the following major endodontic
gutta-percha cones for the management of teeth with
journals:InternationalEndodonticJournal;Journalof
open apices (14).
Endodontics; and Oral Surgery, Oral Medicine, Oral
In 1961, Nygaard-Ostby hypothesized that the lac-
Pathology, Oral Radiology and Endodontology. The
erationoftheapicaltissuestopromotebleeding“may
process of cross-referencing continued until no new
result in further development of the apex” (15) and
articles were identified. In addition, materials from
Möller etal. (16) showed that infected necrotic pulp
textbooksrelatedtothesubjectswerealsoincluded.
tissue induces strong inflammatory reactions in the
apical tissues. Others proposed that instrumentation
Apexification may in fact hamper root development and that prepa-
ration of these canals should be done cautiously (17).
The divergent apical architecture and the fragile root
Cooke & Robotham (18) stated that the remnants of
canalwallsinimmatureteethwithopenapicesmaybe
Hertwig’sepithelialrootsheath,underfavorablecon-
too weak to withstand the normal forces of mastica-
ditions, may organize the apical mesodermal tissues
tion, becoming more prone to fracture and making
into root structure. They advised avoiding trauma to
complete debridement and control of the obturation
the tissues around the apex, a theory supported by
materialnearlyimpossible(3,7).Theclinicalapproach
Vojinovic (19) and Dylewski (20).
for an immature permanent tooth with an open apex,
Removalofinfectedpulptissuetocreateanenviron-
pulp necrosis, and periapical disease consists of the
ment conducive to apical closure without the use of
long-term application of Ca(OH) for the apexifica-
2 medication has been described (16), but much of the
tion or “quick” placement of apical plugs such as an
earlyworkintheareaofinducedapicalclosurefocused
MTA barrier (4,8). The purpose of the apexification
ontheuseofantisepticandantibioticpastes(21).Many
procedureistoestablisharootcanalspacethatcanbe
techniques involving the removal of necrotic tissue
successfullyobturated.UsingCa(OH) hashistorically
2 followedbydebridementofthecanalandplacementof
been the standard treatment protocol in order to
amedicamenthavebeensuggestedfortheinductionof
induce apical closure (9).
apicalclosuretoproducemorefavorableconditionsfor
conventionalrootcanalfilling(22).
Definition A number of investigators (23,24) have demon-
strated apical closure using an antiseptic paste as a
Apexification is defined as “a method of inducing a
temporaryfillingmaterialfollowingrootcanaldebride-
calcified barrier in a root with an open apex or the
ment. Ball (25) successfully reproduced these results
continued apical development of an incompletely
using an antibiotic paste. The real breakthrough
formed root in teeth with necrotic pulp” (10).
occurred in 1964 when Kaiser (26), taking advantage
of the osteogenic potential property of Ca(OH) ,
History 2
described an apexification technique that involved
Before 1966, immature teeth with necrotic pulps the use of calcium hydroxide–camphorated parachlo-
were often extracted and the clinical management rophenol (CMCP), a technique that was popularized
of a “blunderbuss” canal usually required a surgical byFrankin1966(9).TheFranktechniquerequiredthe
approach for the placement of an apical seal into the replacementofCa(OH) every3monthsuntilabarrier
2
often fragile and flaring apex, a procedure that is fre- hadformed.Thiscouldtakeupto24monthsorlonger
quently difficult in uncooperative children (11,12). (9,27). In the 1970s, several investigators demon-
Becauseofproblemswiththeseprocedures,significant strated histological changes at the site of apexification
interest arose in the phenomenon of continued apical (28,29). McCormick etal. (30) hypothesized that
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Management of teeth with necrotic pulps and open apices
debridement of the root canal and removal of the apex (50). Apexification could occur without endo-
necrotic pulp tissue and microorganisms, along with dontic intervention. In these cases, complete pulpec-
a decrease in pulp space, are the critical factors in tomy followed by obturation against the already
apexification. formed apical barrier allowed periapical healing to
occur (51). Recently, apexification interest has cen-
teredontheuseofMTA,amaterialfirstintroducedin
Materials used
1993 that received Food and Drug Administration
Many procedures and materials have been recom- (FDA) approval in 1998 (52).
mendedandusedfortheinductionofroot-endbarrier
formation including no treatment (31), infection
Animal studies
control(32),inductionofabloodclotintheperiapical
tissues (33), antibiotic pastes (25), tricalcium phos- TheosteogenicpotentialofCa(OH) wasdocumented
2
phate (TCP) (34), collagen calcium phosphate (35), by Mitchell & Shankhwalkar (53) in 1958 by the
bone growth factors (36), osteogenic protein (37), implantation of Ca(OH) in rat connective tissues. A
2
surgery and retrograde sealing, gutta-percha obtura- calcifiedmaterialwasobservedeveninareaswhereno
tion, calcium hydroxide alone or mixed with various pre-existing hard tissue was present. In some of the
materials(11,19,38,39),and,morerecently,theplace- earlierstudiesonCa(OH) sustainedrelease,theteeth
2
ment of an apical plug of MTA (37). wereentirelyimmersedinsalineordistilledwater(54).
The short- and long-term sealing abilities are con- Althoughtheradiographicshapeofthe“cap”varies,
sideredtobetwoveryimportantpropertiesforallroot the most frequently seen closure seems to be a hori-
canalfillingmaterials(37).Amongtheavailableintra- zontalbridgespanningthetipsoftheflaredapex.The
canal dressings, Ca(OH) has been used in Dentistry histological studies of the “cap” generally describe a
2
foralmostacentury(22).Sinceitsintroductioninthe cementum-like material with underlying inclusions of
1920s, calcium hydroxide has been widely used in various minerals and organic substances (55). An
Endodontics as a short- or long-term intra-canal anti- experiment evaluated the effect of Ca(OH) injected
2
bacterial dressing (40,41). into the maxillary sinus cavity of monkeys. Sinusitis
ThecalciumhydroxidepasteusedinEndodonticsis was described as the initial inflammatory response of
composed of a powder, a vehicle, and an optional the sinus mucosa, but later the calcified mass acted as
radiopacifier (42). Various biological properties and a foreign body (56).
effects such as antimicrobial activity (41,43), tissue- DryTCPcondensedinastepwisefashioninthecanal
dissolving ability (44), inhibition of tooth resorption from the apex to within 4mm of the access opening
(45),andinductionofrepairbyhardtissueformation successfully induces apical closure in monkeys (57).
(45) have been attributed to this strong alkaline sub- Nevins etal. (35) reported favorable outcomes using
stance, which has a pH of approximately 12.5. In an collagen–calciumphosphategel.Intradermalinjection
aqueous suspension, it has been recommended in ofBaSO intoanimalsisknowntocauseaforeign-body
4
severalclinicalsituationsandhasbeenusedaloneorin inflammatory reaction (58) and it has been shown to
combination with other materials (46,47). intensify the release of inflammatory mediators in
Its clinical applications have been well documented responsetopolymethylmethacrylate(PMMA)particles
in the scientific literature, including its use as an anti- (59). A remodeling and regeneration study in rabbits
microbial agent, controlling exudates from root withtibiadefectsfoundthatastandardNorianskeletal
canals, arresting inflammatory root resorption, induc- repairsystem(SRS)andSRSwithBaSO appearedtobe
4
ing calcific response, and also as a root canal sealer biocompatible and osteoconductive with no evidence
(46–48). The mixture of chlorhexidine gluconate and of either inflammation or fibrous tissue around the
Ca(OH) paste has been suggested in order to obtain implant materials or at the bone–material interfaces
2
a wide spectrum of antimicrobial action (49). (60).
Inthe1970s,TCPfortheinductionofapicalbarrier Teeth experimentally filled with Ca(OH) for 30
2
formation had some success (34). Locally induced days and re-obturated with MTA showed no signifi-
blood clots maintained the initial inflammatory state cant decrease in the strength of the roots during a
and did not result in hard tissue bridging of the open 100-dayobservationperiod(61).TheCa(OH) paste
2
107
Torabinejad & Abu-Tahun
with 2% chlorhexidine was significantly more effective the “cap” remain unresolved. The unexpected forma-
inkillingEnterococcusfaecalisindentinaltubulesthan tion of a mature apex demonstrates the possibility of
Ca(OH) with water in bovine incisors (62). This thisprocess,butnotitspredictability(14).According
2
synergisticantibacterialeffectduringendodontictreat- to Tronstad etal. (72), the mechanism of action of
mentinvivomightnotsignificantlyaffectosteoblastic Ca(OH) is attributed directly to its ability to dissoci-
2
cell biology (63). ate into calcium and hydroxyl ions and increase the
local pH. This apparently is responsible for the alka-
linization of the cavity, which is not conducive to
Human studies
bacterial growth. The importance of the alkalinizing
The routine, widespread use of Ca(OH) as an inter- effects of Ca(OH) when used as an intra-canal dress-
2 2
appointment, intra-canal medicament was promoted ing and its capacity to produce hydroxyl ions in the
by a series of articles documenting its antibacterial periapical environment has been extensively reported
efficacy in human root canals and subsequent studies (54,73). Ca(OH) mediates the neutralization of bac-
2
that substantiated these reports (64,65). Vehicles can terial lipopolysaccharide (LPS) and stimulates periapi-
also significantly prolong the duration of the drug cal hard tissue healing (74).
effect and improve the bioavailability of the material. In addition to acting as a physical barrier, the
In some of the earlier studies on the sustained release Ca(OH) dressingmaypreventrootcanalre-infection
2
ofCa(OH) ,theteethwereentirelyimmersedinsaline (75). The ability of Ca(OH) as an intra-canal medi-
2 2
or distilled water (66). Because of its increased anti- cationtoabsorbcarbondioxideintherootcanals(76)
microbial action, the intra-canal placement of a new disturbs nutritional supplies to the bacteria, thereby
paste made from Ca(OH) plus 2% chlorhexidine gel eliminating some bacteria and preventing the growth
2
hasbeenproposedforuseinclinicalpracticeasitdoes of others (77). Anaerobic Gram-negative bacteria
not affect the sealing ability of the root canal obtura- are more susceptible than facultative Gram-positive
tion (39). The results of this study are in agreement microorganisms to Ca(OH) pastes (46).
2
withthoseofprevioussimilarstudiesconductedunder In1982,Anthonyetal.(78)studiedtheeffectofthe
experimentally controlled conditions (67). paste vehicles on the pH of Ca(OH) with the use of
2
A few reports describe the accidental placement of normal saline, cresatin, and camphorated monochlo-
Ca(OH) into the maxillary sinus, with favorable rophenol.BecauseCa(OH) killsbacteriathroughthe
2 2
healing process and without the need for surgical release of hydroxyl ions, its efficacy depends largely
intervention (68,69). One case report described upon the availability of these ions in the solution,
gradually increasing, symptomatic swelling during a whichinturnisdependentonthevehicleinwhichthe
two-month period resulting from the unintentional Ca(OH) is carried (79). To be effective against bac-
2
extrusion of calcium hydroxide during a root canal teria located inside the dentinal tubules, the hydroxyl
treatment performed two years earlier (70). ions from Ca(OH) must diffuse into the dentin at
2
Studiesthatuseddyesforleakagemeasurementhave sufficientconcentrationsandshouldexceedthedentin
reported conflicting results regarding the influence of buffering ability, reaching pH levels sufficient to
intra-canal medication on the sealing ability of root destroy bacteria (46).
canal obturation (39,71). The sealing ability of the
coldlateralcompactiontechniquewithAH26asaroot
Prognosis
canal sealer is not adversely affected by the placement
of any previous intra-canal medicament tested (39). Even though a “Swiss cheese” porous callus bridge is
Long-term Ca(OH) use has been shown to decrease formedinCa(OH) apexificationcases,thislong-term
2 2
the fracture resistance of teeth in immature tooth traditionalapproachtofacilitateobturationoftheroot
models (61). canalspacestillcarriesasuccessrateofupto90%(80).
The need for a complete apical seal in apexification
casesisacontroversialissue(81).Thehealingproperty
Mechanism of action
oftheCa(OH) pastemighttakelongertoworkeffec-
2
The underlying mechanisms involved in controlling tively(42)andcontroversyexistsastowhetherorhow
notonlytheapexificationprocessbutalsotheshapeof often the Ca(OH) dressing should be changed
2
108
Management of teeth with necrotic pulps and open apices
Fig.1. (a)Pre-operativeradiographrevealsanimmaturerootwithanopenapexintheleftmaxillarycentralincisor.
(b)Afterplacementofcalciumhydroxideforseveralmonths,anapicalbarrierdeveloped.(c)Thecanalwasfilledwith
gutta-percha and sealer using a lateral condensation technique.
Fig.2. (a)Pre-operativeradiographrevealsthepresenceofperiapicallesionsandopenapicesinthemaxillarycentral
incisors. (b) The teeth were accessed, cleaned and shaped, and filled with calcium hydroxide several times. After 18
months,theteethdevelopedstopsandthecanalswerefilledwithgutta-perchaandsealerusingalateralcondensation
technique. (c) About one year later, both teeth fractured cervically and had to be extracted. Courtesy of Dr. Paul
Lovdahl.
(38,55).However,alongperiod(Fig.1)isrequiredto graphic interpretation of osseous healing has been
determine the clinical outcome in teeth with incom- reportedtobemoredifficultduetotheinabilityofthe
plete root development and open apices (80). A long bodytoabsorbinsolubleBaSO thathasbeenaddedto
4
healingperiodmightalsoberelatedtotheconsistency increasetheradiopacityofCa(OH) paste(28).
2
of the paste, together with the overflow and amount Concernshavebeenraisedthatlong-termCa(OH)
2
of extruded paste and the infection and/or the pres- therapymightalterthemechanicalpropertiesofdentin
ence of periapical disease. As well, the dimension of (32), leading to an elevated risk of fracture (Fig.2),
the lesion at the start of treatment and the patient’s even after treatment (84). The use of Ca(OH) as a
2
age may be inversely related to the time required for short-termintra-canalmedicationfollowedbyanapical
apical barrier formation (82–85). plug of MTA and the placement of a composite core
Theuseofantimicrobialagents,especiallythosethat mightincreasethelong-termprognosisforteethwith
have been shown to be irritating to periapical tissues necroticpulpsandopenapices(88).
with Ca(OH) , should be avoided (86). The time
2
needed for Ca(OH) to optimally disinfect the root
2 Advantages and disadvantages
canal system is controversial (87). Several recall
appointmentsarerequiredtopreventandidentifyearly Calcium hydroxide has been regarded as the best
caries lesions, especially in teeth more susceptible to option,andithasbeenwidelyrecommendedandused
cariessuchascaseswithinvaginations(88).Theradio- because of its proven antibacterial properties (89),
109
Torabinejad & Abu-Tahun
periapical tissue healing stimulation (50), biocompat- Apical barrier
ibility (90), anti-exudate activity (91), necrotic tissue
Thetreatmentofteethwithincompleterootdevelop-
dissolution property (92), and adequate periapical
ment is aimed at sealing a sizeable communication
healingfollowingthereductionofinfectionintheroot
between the root canal system and the periapical
canal system (81). Despite a long history of use in
tissues (102). Without creating a calcified apical
apexification procedures, calcium hydroxide-induced
barrier through apexification, obtaining an apical seal
apexification has several limitations and drawbacks
with gutta-percha and root canal sealer as obturation
(93).Becauseoftheselimitations,calciumhydroxide-
materialscannotofferagoodlong-termprognosisfor
inducedapexificationcannotbeconsideredauniversal
teeth with necrotic pulps and open apices (103).
procedure in teeth with necrotic pulps and open
To avoid the challenges associated with long-term
apices (46).
Ca(OH) apexification procedures, a non-surgical,
ThebiologicalactionofCa(OH) maynotbeenough 2
2
one-stepalternativebarriertechniquewithavarietyof
toeliminatewidespreadchronicapicallesionsofimma-
materials has been suggested (104–109). The ten-
tureteethatanearlyage,andthefragilityandporosity
dencytominimizethenumberofpatientvisitsandthe
of the calcified apical barrier during treatment might
need to provide a treatment that can ensure continu-
complicateandcompromisetheapexificationoutcome
ous hard tissue deposition in order to reinforce the
(94). The length of the treatment and the number of
fragile root canal walls have recently been reported
“dressings” necessary for barrier formation, which is
with a high rate of success for open-apex teeth (4).
reportedtotakeanywherefromthreeto24monthsor
longer,areoftentoolongforyoungpatients,leadingto
patientattritionasaresultoffatigueandpoorcompli- Definition
ance. Geographic relocation of the child during the
One-visit apexification has been defined as the non-
courseoftreatmentalsomakesitdifficulttoensurethe
surgicalcondensationofabiocompatiblematerialinto
integrityofthecoronalseal(27,95–97).
theapicalendoftherootcanalinordertoestablishan
Even if successful, apexification can only induce a
apical stop that would enable the root canal to be
hard tissue barrier at the apex; it cannot promote
immediately filled (105).
continued root development. Intra-canal Ca(OH)
2
dressing can also make the tooth brittle due to its
History
hygroscopic (61) and proteolytic (98) properties.
Filling the root canal with Ca(OH) creates an envi- Initially,teethwithopenapiceswereobturatedwithout
2
ronment that prevents migration of multi-potent firstinducinganaturalapicalbarrier(109).Becausethis
undifferentiated mesenchymal cells into the canal and procedure was associated with the extrusion of filling
regeneration of dentin on the lateral dentinal walls materials into the periapical tissues, various materials
(84). and methods were tested in order to avoid this extru-
Calciumhydroxide,withitshighpH,isknowntobe sion of filling materials during condensation in teeth
toxic to vital cells (30) and promotes necrotic and withimmatureapices(105–108,110,111).
degenerative changes in its contact at the apex (99). Theideaofasingle-visitapexificationisnotnewand
The toxicity of calcium hydroxide-induced apexifica- hasbeendiscussedandattemptedformanyyears(102).
tion is its biggest disadvantage and offsets advantages Early uses of an apical plug include the use of dentin
such as its antibacterial effect that promotes healing chipsin1972(112).In1975,Roberts&Brilliant(34)
(100). Several case reports have shown that direct described obturation of the canal with gutta-percha
contact of Ca(OH) with neurovascular bundles usingachlorosinlateralcondensationtechnique.
2
induces hyperesthesia and paresthesia of the inferior A technique using dentin filings obtained from the
alveolar, trigeminal, and infraorbital nerves (101). coronal aspect of the canal to form an apical plug or
The shorter treatment time with MTA as an apical matrix was popular for a time (113). Dentin chips
barrier and the lower dependence on patient compli- and Ca(OH) plugs (114) as well as hydroxyapatite
2
anceforsuccessfultreatmenthasminimizedtheuseof powder (107) were also used as apical plugs in teeth
Ca(OH) except as a temporary canal disinfectant with open apices. Because of the possibility of using
2
(102). infected dentin chips, an alternative, simpler, and
110
Management of teeth with necrotic pulps and open apices
quicker technique using Ca(OH) powder with suffi- diate apical barrier was quick, relatively easy, biocom-
2
cientstrengthtoresisttheapicalforcesofgutta-percha patible, and inexpensive, with no post-operative
filling procedures was later used (115). Recent treat- discomfort.Itgavepredictableresultsasanalternative
ment strategies include the creation of an artificial to multi-appointment apexification procedures
apical barrier using MTA (116,117). (108,132).
While Al Ansary et al. (133) questioned any reliable
evidencesupportingtheuseofeithercalciumhydrox-
Materials used
ide or TCP as effective apical plugs in immature ante-
The sealing ability of the filling material plays a rior teeth, Metzger et al. (134) recommended the
major role in improving endodontic success (118). condensationofcalciumhydroxideinwiderootcanals
In addition to eliminating the remaining viable bac- and advised discontinuing the addition of barium
teria unaffected by the chemomechanical prepara- sulfate because it has a residual radiopacity after
tion of the root canal, intra-canal medicaments have calcium hydroxide resorption.
been advocated to act as a physico-chemical barrier Comparing the sealing ability of a 5mm apical
(119). plug of SuperEBA, IRM, or laterally condensed
An ideal repair material should be non-toxic and gutta-percha and Roth’s sealer, SuperEBA produced
biocompatiblewithhosttissuesbecauseitisfrequently a significantly better seal (135). Dummer etal. (136)
placed in close contact with the periapical tissues. In compared lateral and automated thermaplastic con-
addition, it should have good sealing ability and mar- densation of gutta-percha with sealer to automated
ginal adaptation, resist dislocating forces, be dimen- thermaplastic condensation without sealer. The auto-
sionally stable, and be unaffected by the presence of mated thermaplastic technique without sealer pro-
tissue fluid (120,121). duced marginally better root fillings in teeth with
Materials such as gutta-percha, zinc oxide–eugenol- open apices than the other two methods.
basedcements(SuperEBAandIRM),compositeresin, MTA,whichsolidifiestoahardstructureinlessthan
glass ionomer cement, Cavit, gold foil, polycarbox- three hours (137), has a compressive strength equal
ylate cement, polyvinyl cement, amalgam, Vitremer, to intermediate restorative material (IRM) and
and MTA have been used to seal the communications SuperEBA. The use of MTA in the immediate obtu-
between the root canal system and periapical tissues ration of teeth with open apices has been advocated
(121–124). Unfortunately, most of them have shown (138). It is classified as a permanent-contact implant
variouslevelsofweaknessinbiocompatibility,leakage, device (139) and its use as an apical barrier (Fig.3)
solubility,handlingproperties,moistureincompatibil- has become the standard of care for the treatment of
ity, and cost (123,125,126). teethwithnecroticpulpsandopenapices(1).Astudy
Eventhoughtheuseofdentinchipplugsininfected byCampetal.(140)hasshownthepossibleadhesion
teeth is questionable due to the unfavorable response of human fibroblasts to MTA. Despite a favorable
of periapical tissues (127,128), Tronstad (129) found response to Geristore radiographically, it often shows
thatdentinchipplugsarewelltoleratedbythetissues chronic inflammation on histological examination
andmayactasaneffectivebarrierintheapicalpartof (141). Having features similar to calcium hydroxide,
the root canal. A similar result was obtained in 1972 MTA might well be used as an alternative to calcium
by Erausquin (112), who found that apical plugs hydroxide in Dentistry (142). Saghiri etal. (143)
formed by compressing radicular pulp and dentin advised the use of MTA with calcium phosphate
chips in rat molar teeth resulted in a favorable tissue cement (CPC) in situations where MTA comes into
reaction. Saunders studied the application of Nd:YAG direct contact with lesions, not only as a matrix to
pulsed laser to dentin chips, hydroxyapatite, and controltheplacementofrestorativematerials,butalso
low-fusing porcelain to produce a fused apical plug as a material that is more resistant to an acidic envi-
and found that this laser is unable to melt the dentin ronment. The interaction of MTA with phosphate-
chips (130). buffered saline (PBS) may result in apatite deposition
Demineralized freeze-dried bone compacted into that, over time, improves the seal of MTA apical
thecanalprovidesabiocompatibleapicalmatrix(131). plugs (144). Takenaka etal. (145) have described
Aone-appointmenttechniqueusingTCPasanimme- the properties of a new material formulated from
111
Torabinejad & Abu-Tahun
Fig.3. (a)Pre-operativeradiographrevealsthepresenceofperiapicallesionsandopenapicesinthemaxillarycentral
incisors. (b) The teeth were accessed, cleaned, and filled with MTA apical plugs after the initial use of calcium
hydroxidefor2weeks.(c)Apost-operativeradiographafter22monthsshowsresolutionoftheperiapicallesionsand
development of apical hard tissue in these teeth.
carbonate-containing apatite and collagen as an apical
barrier with osteoconductivity.
Animal studies
Theuseofapicallypackeddentininanimalstudieshas
been shown to be clinically effective and a tissue-
compatible means of filling roots with open apices
(112,129). In a dog model, Ariizumi et al. (128)
reported that the degree to which dentin chips are
infected can be a major factor in determining the
outcomes of this procedure. Holland et al. (146) Fig.4. (a) Lack of development of apical hard tissue in
studied the periapical response to dentin chips in adogtoothfilledwithcalciumhydroxidefornineweeks.
(b)Developmentofanapicalhardtissueinanotherdog
ferrets,monkeys,anddogswithgenerallygoodresults
tooth filled with MTA for nine weeks. Courtesy of Dr.
unless the dentin chips became contaminated with
Shahrokh Shabahang.
bacteria.
Rossmeisl et al. (109) found freeze-dried dentin to
be a biocompatible apical barrier against which gutta- (Fig.4), better structural integrity, better reparative
percha could be condensed. Hydroxyapatite cylinders periapical periodontal tissues (37,149), and less peri-
testedinguineapigmandibleswerenotresorbedover apical inflammation compared to zinc oxide–eugenol
the examination period, but Ca(OH)2 and collagen specimens (150) were found. Both calcium hydroxide
implantswerepartiallyortotallyresorbedandreplaced and MTA produced similar BMP-2 expression after
bybonytissue,indicatingthatcylindersmaybeuseful theuseofthesematerialsforapexificationinimmature
as apical plugs (147). In a recent study on dogs, monkeyteeth(151).ThereactionofMTAtobonein
Yamauchi etal. (148) found that the placement of guinea pigs was found to be most favorable, free of
2 mm plugs of either bonded composite or IRM over inflammation in every specimen (152).
gutta-percha as a filling material significantly reduces
periapical inflammation.
Human studies
A number of short-term animal studies have dem-
onstrated a more predictable healing outcome when Closureoftheflaringrootcanalspacewithhardtissue
MTAisusedtoobturatedogteethwithopenapices;a ingrowth in a child with a traumatically injured tooth
more consistent degree of hard tissue formation and an open apex was demonstrated in response to a
112
Management of teeth with necrotic pulps and open apices
resorbable collagen–calcium phosphate gel matrix pH values, the heat produced during material setting,
(153). Three successful cases using TCP as an apical and the production and release of pro-inflammatory
plugwerereportedbyHarbert(132,154). cytokinesduringtheproceduremightaccountforthe
Guiliani et al. (155) reported three clinical cases high inflammation (168).
using Ca(OH) therapy followed by MTA plugs with Rich in calcium oxide after setting, MTA generates
2
resolution of apical lesions at one-year recall. A man- calcium hydroxide upon contact with tissue fluid or
dibularcentralincisorthatwasdamagedinsurgerywas water (169). The resultant Ca(OH) produces the
2
treated as a tooth with an open apex using MTA; it high pH of this material and might contribute to the
remained asymptomatic after a two-year recall (156). early action of the material (170). Cellular and meta-
Using an MTA apical plug, a case of dens in dente bolic activity has the potential to induce periodontal
wastreatedsuccessfullywiththeresolutionofaprevi- ligament (PDL) cell attachment, and might stimulate
ous lesion (157). In a human outcome study that PDL fibroblasts to display the osteogenic pheno-
compared the clinical and radiographical results of type and promote the production of osteonectin,
apexification with either MTA or Ca(OH) , all of the osteopontin, and osteonidogen and increase alkaline
2
cases obturated with MTA were successful at the phosphatase levels (171).
12-month recall, whereas two of the 15 Ca(OH) MTAisabioactivesilicatecement,alkalineinnature
2
caseshadpersistentdisease(158).Inarecentstudyby byitself,andisabletoinduceprematureandenhanced
Pradhanetal.(159),MTAroot-endbarriersandlong- expression of alkaline phosphatase activity for fibro-
termCa(OH) apexificationwerecomparableinterms blastpopulations,whichmayhelpintheprocessofthe
2
ofhealingtimetoresolveperiapicalradiolucencies,but mineralizedareasobserved(171).Thisosteoinductive
there was a statistically significantly shorter treatment and cementogenic agent stimulates immune cells to
time for the MTA group. Follow-up healing after release lymphokines and stimulates bone coupling
usinganMTApluginincisorswithopenapices(160) factors necessary for the bioremineralization and
and in premolars with necrotic pulps supports the use healing of osseous periapical defects (172), inducing
of MTA as an apical plug in teeth with single or the regeneration of cementum and the PDL (173).
multiple canals (161). Recent prospective human The nature of the conductive and/or inductive
outcome studies of open apex teeth obturated with surface topography of cured MTA might provide a
MTA in one appointment demonstrate healing rates mechanism that modulates the osteoblastic pheno-
that ranged from 81–100% (9,118,138), with 94.1% type, which allows the promotion of various cells to
clinicalsuccessand76.5%radiographicalsuccesswhen attach, proliferate, and express proteins that are
MTAwasusedasanapicalpluginpermanentincisors involved in cementogenesis (174). The calcium ions
(116,162).AcombinationofMTAandenamelmatrix released from MTA can induce a reaction with envi-
derivative(EMD)promotessynergisticallymorerapid ronmental phosphorus. This leads to hydroxyapatite
odontoblastic differentiation in human dental pulpal crystal precipitation not only at the dentin–MTA
cells (HDPCs) than MTA alone (163). interface(164),butalsoonthesurfaceoftheroot-end
filling (175). Other investigators discuss the ability of
MTAtoreleasemajorcationiccomponentsandtrigger
Mechanism of action
surfaceprecipitatesthatarestructurallyandchemically
Afewstudieshaveshownthattheprofileofcytokines similar to hydroxyapatite (176).
produced by cells in contact with the material (164)
originates from the physico-chemical reactions with
Prognosis
dentin (165), but the biological calcified tissue-
conductive mechanism still remains unclear. Variables The treatment of immature pulpless teeth presents
such as temperature, pH, and electrolyte and protein both an endodontic and restorative challenge and the
concentrations can change the crystalline nucleation, success of these cases is influenced by the extent of
latticegrowth,andrateofhardtissueformation(166). the lesion (118) and the extrusion of material beyond
The formation of a biocompatible inorganic layer is theapex(177).Bothanimalandhumaninvestigations
the basis for the observed biological properties in have confirmed the encouraging role of an MTA
other ceramic studies as well (167). The initial high apexification procedure followed by an internal
113
Torabinejad & Abu-Tahun
bondingtechnique(141).Thesestudiesshowafavor- ahigherlong-termsuccessratebecauseitavoidsmany
able long-term prognosis (1) with an overall success of the challenges associated with traditional apexifica-
rate of 88.8% (111). tion procedures, including a reduction in treatment
Yang etal. (178) reported apical barrier formation time and the number of patient visits, timely restora-
accompaniedbyaseparatedisto-apicallygrowingroot. tion of the tooth that results in a lower likelihood
In the separate newly formed part of the root, pulp to fracture (4,133), decreased patient attrition, and
tissue, odontoblasts, predentin, cementum, and an increased patient compliance (185). Complete or
apical foramen can be identified. Selden (12) suggests partialobturationoftherootcanalsystemusingMTA
that, for continued root development to occur, the is a viable option for teeth that exhibit extensive root
area of calcific scarring must not extend to Hertwig’s resorption, open apices, and selected cases that show
root sheath or the odontoblasts in the apical area. anatomical variations including dens evaginatus, “C”-
Orthograde positioning of MTA in the apical third shaped canals, and fusion or germination (186,187).
exhibitsexceptionaloutcomeswhenusedforcomplete While the objective of apexification is to stimulate
or partial canal obturation, providing an adequate apicalbarrierformation,expectingthatcontinuedroot
apicalsealinallpartsoftherootincasesofapicesthat formationwillnotoccur,thereareanumberofreports
are wide, resorbed, or irregular in shape (102). It has of continued apical development despite the presence
been questioned whether a moist cotton pellet over ofanecroticpulp(11).Inarecentstudy,whenmixed
theMTAoratwo-visitprocedureisneededwhenused MTA was compacted against dentin, a dentin–MTA
as an apical barrier with an open apex (179). interfacial layer formed in the presence of phosphates
The reinforcing effect and higher resistance to frac- (173), exhibiting higher fracture resistance than
ture was demonstrated by using a flowable, self-cured untreated counterparts (188).
intra-canal composite (180), a resin glass ionomer The hydrophilic nature of the particles from MTA
(177),aspecialtechniqueleavingapatentchannelfor powder allows its usage even in the presence of mois-
Ca(OH) replacement and subsequent obturation ture contamination, specifically blood, and does not
2
of the canal (145), and a technique described by affect its sealing ability (4), which is often a problem
Katebzadehetal.(181),whocomparedanMTAplug with other materials typically used in apexification
backfilled with gutta-percha and sealer. (36). MTA not only fulfills the ideal requirement of
Byvaryingthethicknessofthebarrier,techniqueof being bacteriostatic, but by the formation of a miner-
delivery (1), and application of non-setting Ca(OH) alized interstitial layer, it also provides a challenging
2
to neutralize the pH in an acidic environment (182), environment for bacterial survival with good antifun-
a number of investigators have attempted better gal susceptibility (142), resulting in less persistent
adaptation and denser compaction of the material in disease (138), even when the material is extruded
ordertowithstandgreaterforcesofcondensationand (189). Smear layer removal does not appear to affect
provideenoughdepthtoresistdisplacement.Whilede the sealing ability of MTA, and its presence might
Leimburgetal.(183)showednosignificantdifference actually improve the seal over time (190).
between1mm,2mm,and3mmthicknessesofMTA The disadvantage of MTA (in addition to the fact
apical barriers, another investigation demonstrated that it is sometimes difficult to handle when it is too
that only a 5-mm-thick MTA apical barrier can wet) is the long setting time required on clinical
adequately prevent bacterial penetration (1). The application, with a reported range from 75 minutes
method of insertion might play an important role in to 72 hours for an initial set (126) and 21 days for
bacterial penetration. A recent bacterial leakage inves- complete curing (191). Gray MTA can discolor teeth
tigationshowedsignificantlylowerEnterococcusfaeca- over time if the material is placed in the coronal
lis penetration after the use of ultrasonically activated structure or near the cemento–enamel junction
MTA as an apical barrier (184). (CEJ) in anterior teeth (192). Another potential
problem with the material can be elective removal
after placement and curing. Although removal can be
Advantages and disadvantages
accomplished with the aid of ultrasonic instruments,
Compared with calcium hydroxide-induced apical MTA obturation in curved canals can pose a dilemma
closurefollowedbycompactedgutta-percha,MTAhas (193).
114