Title: Maxillary molars with two palatal roots. Report of two cases under the operating microscope

Author: A. Chaniotis1

1DDS, MSc, PhD Candidate, Department of Endodontics, Dental School of Athens, Greece

Keywords: Maxillary molars, palatal root, operating

microscope

Running title: Molars with two palatal roots

Maxillary molars have a highly variable root and canal anatomy. Among the

root canal anomalies of maxillary molars, the least frequent appears to be that of

the palatal root. Anomalous root morphology of maxillary molars, such as two

palatal roots and canals, is infrequently reported. Although most of the clinical

literature on the fourth canal concerns an additional mesiobuccal canal in

maxillary molars, the present article describes the diagnosis and clinical

management of a maxillary first molar and a maxillary second molar with two

separate palatal roots, drawing particular attention to radiographic

interpretation and access refinements.

The variability of the root canal system of maxillary molars poses a constant

challenge for the dentist who wishes to provide successful endodontic treatment.

Walton & Vertucci (1), introducing concepts of internal pulpal anatomy, stated that

lack of thorough knowledge of root canal morphology ranks second as a cause of

treatment failures, only to errors in diagnosis and treatment planning. This means that

having a working knowledge of the number of roots, number of canals per root and

their location, longitudinal and cross-sectional shapes, most frequent curvatures and

root outlines in all dimensions is essential in order to provide high standard

endodontic treatment.

The number, form and configuration of root canals present in maxillary first molars

have been thorough investigated in the literature for almost a century. They are the

largest teeth in volume and of the most complex in root and canal anatomy. The three

individual roots of the maxillary first molar form a tripod. The palatal root generally

is the longer, has the larger diameter and offers the easiest access. It often curves

buccally at the apical one third and can contain one, two or three root canals in

various percentages according to studies of apical canal configurations and case

reports (2). The distobuccal root is conical and may have one or two canals. The

mesiobuccal root may contain one, two or three root canals and is the most studied

root in the mouth. However, in rare cases, roots of maxillary first molars don’t form a

tripod because of the presence of an additional palatal root.

Furthermore, root and canal anatomy of maxillary second molars are similar to those

of first molars. The distinguishing morphologic feature of the maxillary second molar

is that its three roots are grouped closer together and are sometimes fused. They

usually have one canal in each root. Often they have two mesiobuccal canals and

infrequently they have two palatal canals. One study found a 1, 4% incidence of two

palatal roots and canals in maxillary second molars (3).

Although the morphological pattern of double palatal root canal in maxillary molars is

extremely infrequent, dentists should be aware of it when considering endodontic

treatment of these teeth.

Cases reported in this paper provide clues and hints about the predictable endodontic

management of maxillary molars with two palatal roots, drawing particular attention

to radiographic interpretation and access refinements.

Case Report A

A 38-years-old Caucasian female was referred from her general dentist to our

Endodontic Private Practice Clinic for endodontic treatment of her right maxillary

first molar. At the time of the appointment, she presented with signs and symptoms of

irreversible acute pulpitis. The patient’s medical history was noncontributory. As the

same patient had been subjected to endodontic therapy of her right maxillary second

premolar two months prior to her present appointment in our office, we used as

preoperative radiograph the one that was taken two months ago. This was done in

order to avoid unnecessary exposure to a new preoperative radiograph; hence the

diagnosis of irreversible pulpitis was straight forward. The preoperative radiograph

can be seen in figure 1. Thorough examination of the preoperative radiograph reveals

the image of a maxillary molar that appears to have only a mesial and a distal root. A

radiograph with buccolingual superimposition of this type may suggest an anatomy of

two separate palatal roots as stated by Christie et al (4). In addition, root canal space

seemed obliterated. This may be due either in true obliteration or in superimposition

of roots.

The patient was prepared for endodontic therapy and a rubber dam was placed.

Access to the pulp cavity was performed using a diamond bur. Once the pulp cavity

has been reached the completion of the access preparation was accomplished with a

carbide bur with blunt tip in order to keep the pulp floor intact. Irrigation of the pulp

chamber was performed using 5, 25% solution of NaOCl, until bleeding was

controlled. Original access preparation revealed three orifices located mesiobuccal,

distobuccal and distolingual. Although the pulp tissue had been totally removed from

the pulp chamber there was constant bleeding from a spot located mesiolingual to the

access preparation suggesting an extra palatal canal orifice. Access was made wider

on the lingual aspect of the preparation, taking a trapezoid shape rather than a

triangular outline and the existence of a mesiolingual canal orifice was confirmed.

Pulpal floor lines interconnecting the four canal orifices created an X-like formation.

The working length radiograph revealed the anatomy of the four canals (Fig 2). We

classified this case as in type I classification of maxillary teeth with two palatal canals

according to Christie’s classification (4). Routine endodontic treatment was

performed using engine –driven Hero 625 files ( Micro-Mega, Besançon, France)

according to the Hero protocol for medium canals. The whole procedure was

accomplished under the higher magnification provided by a Global entrée-plus

operating microscope ( Global surgicalTM corporation, St. Louis, USA) . The view of

the canal orifices after the completion of cleaning and shaping procedures can be seen

in figure 3.

Obturation was performed with thermoplasticised gutta-percha using the elements

obturation unit (Sybron Endo, Redmond WA, USA) and AH-plus sealer (Dentsply,

DeTrey, Germany). Postoperative radiograph can be seen in figure 4.

Case Report B

A 45-years-old Caucasian female was referred from her general dentist to our

Endodontic Private Practice Clinic for endodontic treatment of her left maxillary

second molar. The patient’s medical history was noncontributory. The tooth had

become symptomatic after preparing it to accept a bridge. The preoperative

radiograph can be seen in figure 5. Thorough examination of the preoperative

radiograph reveals an image of superimposed roots similar to that of the first case

reported. A diagnosis of irreversible pulpitis was made and the patient was prepared

for endodontic therapy. A rubber dam was placed and access was achieved using a

diamond bur. After initial access to the pulp chamber, a carbide bur with blunt tip was

used for the completion of access preparation. Irrigation of the pulp chamber was

performed using a 5, 25% solution of NaOCl. After initial bleeding control and pulpal

floor exploration three orifices were detected (mesiobuccal, distobuccal and

distolingual ). The three orifices were enlarged using the hero shaper orifice opener

(Micro-Mega, Besançon, France). The pulpal floor was dried with cotton pellets and

visualized under the higher magnification provided by a Global entrée-plus operating

microscope ( Global surgicalTM corporation, St. Louis, USA). The pulpal floor lines

interconnecting the three orifices seemed to extend mesiolingualy. Access

enlargement was performed at the mesiolingual aspect of the original access cavity

preparation using a non cutting tip carbide bur. Visualization of the pulpal floor

revealed an extra mesiolingual canal orifice. Pulpal floor lines created an X-like

formation. Routine endodontic treatment was performed using engine –driven Hero

625 files ( Micro-Mega, Besançon, France) according to the Hero protocol for

medium canals. The whole procedure was accomplished under the higher

magnification provided by a Global entrée-plus operating microscope ( Global

surgicalTM corporation, St. Louis, USA). The view of the canal orifices and

interconnecting pulpal floor lines after the completion of cleaning and shaping

procedures can be seen in figure 6. Obturation was performed with thermoplasticised

gutta-percha using the elements obturation unit (Sybron Endo, Redmond WA, USA)

and AH-plus sealer (Dentsply, DeTrey, Germany). Postoperative radiograph can be

seen in figure 7. We classified this case as in type II classification of maxillary teeth

with two palatal canals according to Christie’s classification

Discussion

The occurrence of maxillary molars with two palatal roots or two canals on the palatal

root is not frequent. It is speculated that maxillary molars with two palatal roots may

be encountered once every 3 years in a busy endodontic practice (4).

Thews et al. (5) reported two aberrations in palatal root of two maxillary first molars.

The first case had two totally separated palatal roots, with two distinctly eccentric

orifices, while the second case had two palatal orifices, centrally located, with two

root canals which joined at the apex. While, Wong (6) reported a case where final

radiograph revealed a trifurcation in palatal root and he ended up with a first

maxillary molar with three separated foramina in one palatal root.

Deveaux (7) found a second maxillary molar with two well-separated palatal roots

and pointed out the fact that unusual massive coronal morphology should attract

attention of dentist during clinical examination of any case.

Studies report an incidence between 0.4% and less than 2% of more than one palatal

canal in maxillary molars (8, 9). Libfeld and Rotstein (8) in a sample of 1200 teeth

reported an occurrence rate of 0.4% for the maxillary second molar. Stone et al. (9)

examined approximately 500 extracted upper first and second molars and reported a

low incidence of less than 2% cases, where more than one main palatal canal existed.

Recent studies report a 1.4% incidence of the maxillary molars to have second palatal

roots (3). Cleghorn et al. (10) , in a recent literature review regarding the root canal

system of maxillary first molars, came up with a percentage of 99% cases of one

distinct palatal root.

Anatomical variations of the double palatal root canal system in maxillary permanent

molars have been classified by Christie et al. (4) . They gathered 16 ended cases of

upper molars and 6 extracted molars with 2 palatal roots and came up with a

classification of three different types of molars with two palatal roots, according to the

root separation level and their divergences with some overlap between the groups.

Type I maxillary molars have two widely divergent palatal roots. Type II maxillary

molars have four separate roots also that are shorter and run parallel, while type III

maxillary molars have the double palatal root canal system encaged with the

mesiobuccal canals in a web of root dentin. Type III maxillary molars have three roots

and a double canal system in the palatal root. They also resumed that the incidence is

higher in second than in first maxillary molars.

Baratto-Filho et al. (11) reinforced the possibility of variations in internal anatomy of

human teeth and their importance in performing successful endodontic treatment by

reporting a root canal treatment in a first maxillary molar with two separated palatal

roots and two extracted second molars, one with two palatal roots and one with one

palatal root and two distinct root canals. They suggested a IV category in witch the

second canal of the palatal root fused with the mesiobuccal root up to the apical level.

Whatever type of double palatal canal system is encountered, the location and

management of all anatomy is imperative to endodontic success. In the present paper

we reported two cases of double palatal canal system in maxillary molars, drawing

special attention to radiographic interpretation and access preparation.

Indistinct images of palatal roots in preoperative radiographs should alert the clinician

for the possibility of a double palatal canal system. Sometimes four separate root

apices can be seen on an angled preoperative radiograph. In a type II maxillary molar,

such as the one reported in the second case, a radiograph with buccolingual

superimposition makes the molar appear as having only a mesial and distal root.

The distobuccal root in preoperative radiographs of type III variation has been stated

to stand alone or even diverge to the distobuccal. These are radiographic clues that

should alert the clinician.

Clinically, the distance between the lingual cusps of a maxillary molar with double

palatal canal system have been stated to be greater than usual. Periodontal and root

probing in these cases will often help in determining the root trunk.

In both cases presented here, access preparation was made wider on the lingual aspect

taking a rather trapezoid than a triangular outline. The conservation of tooth structure

must be kept in mind when establishing an endodontic access. The traditional

triangular access opening is often too constricted to allow straight-line access in

maxillary molars. Thomas et al. (12) found that 81% of the maxillary first molars they

studied had a trapezoidal pulp chamber and that the use of a trapezoidal access cavity

was warranted. Christie and Thomson (13) have recommended modifying the outline

to a rather ovoid one. They believe that this outline provides better access for the

detection of all additional canals.

Visualization of the pulp floor under magnification also facilitates the detection of

extra canals. In both cases, the interconnecting pulpal floor lines of the orifices,

visualized under magnification, created an X-like formation. This formation of pulpal

floor lines in maxillary molars should alert the clinician for the existence of a double

palatal canal system.

In the first case report, constant bleeding from the pulp floor led us to the detection of

the mesiolingual canal orifice. This finding may often help the detection of extra

canals when teeth with vital pulp are subjected to endodontic procedures. In the

second case report, visualization of the pulpal floor lines that extended mesiolingualy

led us to the detection of the extra mesiolingual palatal canal.

Both case reports contribute to our understanding of the complexity of the root canal

morphology found in maxillary molars. Although such cases occur infrequently,

clinicians must be aware of them. Clinical and radiographic aids are provided for the

detection of such aberrations in palatal root canal morphology. Knowledge of possible

variations in internal anatomy of human teeth is important for successful endodontic

treatment.

Fig 1. Preoperative radiograph of the right maxillary first molar

Fig 2. Working length determination radiograph of the right maxillary first molar

Fig 3. Pulp floor photograph of the right maxillary first molar after the completion of the cleaning and shaping procedure (Original magnification x16, Global entrée plus microscope)

Fig 4. Postoperative radiograph of the right maxillary first molar

Fig 5. Preoperative radiograph of the left maxillary second molar

Fig 6. Pulp floor photograph of the left maxillary second molar after the completion of the cleaning and shaping procedure (Original magnification x16, Global entrée plus microscope)

Fig 7. Postoperative radiograph of the maxillary molar

References

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