Key Topics in Restorative Dentistry

Weine 1969

Permanent Maxillary Molars

Barker, Parsons, Mills, Williams 1974

MB. The root is compressed mesiodistally broad at the cervix and heavily grooved longitudinally on its distal aspect. A single canal in this root is the exception->apart from very young subjects where apical division is more likely. A single canal may be partially subdivided by dentine partitions for much of the length although my terminate in a single foramen. Two separate canals may exit from the pulp chamber, reunite in the middle of the root and end in a single canal. More frequently there are two main canals in the mesiobuccal root and these may exit via discrete foramina and break up in to multiple channels.

P. Least complicated although bifurcation or bending of the canal apically may be encountered. Curving towards the buccal is common.

DB.  Frequently ‘S’ shaped in its apical extent when viewed from the buccal aspect.

Kulild Peters 1990

Showed that MB2’s were present in 96.1% of 1^st molars and 93.7% of 2^nd molars. 54 % were located with standard access preparation 31 % with careful use of a bur and the remaining with use of a microscope. If there was only one MB this increased the likelihood of forking at the apical 3-4mm. The first evidence of an orifice of the MB canal was an average distance of 1.82 mm lingual to the orifice of the MB canal. Its orgin is slightly distal to the MB but as it progressed apically it moved directly ML to the MB.

Difficulty in locating MB2’s 1. Shelf of dentine from palatal aspect covering orifice. 2. Smallest during normal development. 3. Often become pulpally involved during mesial caries therefore chronic irritation in this area and subsequent tertiary dentine formation.

The hypothesised a developmental pattern of MB1 MB2. Originally a ribbon shaped canal which conforms to external anatomy develops within the root. During maturation the isthmus between the MB and ML srea closes leaving a larger MB and a smaller ML canal. This is the proposal as to how these canals develop.

The need for excellent access highlighted.   MB1 and MB2 have thicker dentine on the mesial than the distal and MB canal is consistently larger than the ML.

Imura 1998

Vertucci 1984

100 maxillary 1^st molars. MB=51 had lateral canals.58.2 % in apical portion. DB=36 had lateral canals and 59.6%   in apical portion. P=48 had lateral canals and 61.3% in apical portion.

Pineda 1973

40.8 % had one canal. 29.8% had two independent canals with two apical foramina. 12.3% had two canals that merged apically and exited in a single foramen. 7.3% had just one canal that subsequently divided into two canals exiting through two separate foramina. 4.9% had two canals that merged into one and then bifurcated to exit through two foramina. 4.9% demonstrated reticular canals. There were 53.1% with just one apical foramen and 42 % with two canals and two foramen.

SINGLE CANAL: 1: Root may be wide buccolingually in a young patient and maybe narrow in a mesiodistal direction. 2.Slightly wider buccolingually than in the mesiodistal aspect. TWO CANALS TWO MAIN FORAMINA: In this aspect the canals are conical but slightly wider in a buccolingual direction. The two canals do not always terminate at the apical ends at the same level. The more buccally placed canal is always longer and wider whereas the more palatally situated canal is shorter and narrower and may end in the middle third of the root.

Eskoz 1995

92% had three roots and 8% had two roots. 60% of MBR had one canal. 21% had two separate canals that merged short of the apex. 16 % had 2 separate distinct canals and 3 % had one canal dividing mid root and forming to foramina at the exit.

NG 2001

Two canals in MBR of 1^st molars was 68% and in 2^nd molars 48%. In the two canalled MBR type II and IV were the most prevalent. Inter canal communications were most prevalent in MBcanals of 1^st molars. Apical 1/3 of all molars had highest prevalence of lateral canals.

Alavi 2002

Prevalence of MB1 and MB2 in 1^st molar   MBR was 68% was higher than in 2^nd molars (41.5%). In two canalled MBR tyoes II and IV were most prevalent. Intercanal communications were evident in about only 16%. Once again the apical 1/3 had highest prevalence of lateral canals.

Cleghorn et al. 2006

Smadi 2006

Rwenyonyi et al. 2007

To investigate the root and canal morphology of permanent maxillary molar teeth from a Ugandan population.

METHODOLOGY:

Maxillary first (n = 221) and second molar (n = 221) teeth were collected from patients attending dental clinics in Kampala. Teeth were prepared using a clearing technique: the pulp chambers were accessed and the teeth placed consecutively into 5% sodium hypochlorite, 10% nitric acid, then methyl salicylate. Indian ink was injected into the pulp chambers to demonstrate the canal system.

RESULTS:

In the first molars, 95.9% of the teeth had separate roots. The mesiobuccal root was fused with the palatal root in 3% of specimens and with the distobuccal root in 0.5% of teeth. In the second molars, 86% of the teeth had separate roots. The mesiobuccal rootwas fused with the palatal root in 6.3% of specimens and with the distobuccal root in 6.8% of teeth. Apical deltas were more frequent in the mesiobuccal root when compared with distobuccal and palatal roots of both the first and second molars. A type I canal configuration (>75%) was the most frequent in all the roots of both the first and second molars. Canal intercommunications and lateral canals were more frequent in the mesiobuccal root when compared with other roots.

CONCLUSIONS:

The mesiobuccal root tended to have more variations in the canal system followed by the distobuccal root, whereas the palatal root had the least. The findings in root and canal morphology of this Ugandan population were different from previous studies, which may partly be attributed to racial differences.

Pattanshetti et al. 2008

Soma et al. 2009

Thirty extracted intact human maxillary first molar teeth were selected for micro-tomographic analysis (SkyScan 1072, Aartselaar, Belgium) with a slice thickness of 38.0 mum. The following data regarding the MB root were analysed and recorded: number and type of root canals, prevalence of isthmuses, prevalence of intercanal connections, presence of accessory canals, presence of loops and number of apical foramina.

RESULTS:

The MB2 canal was present in 80% of specimens and was independent in 42% of these cases. When present, the MB2 canalmerged with the MB1 canal in 58% of cases. Communications between the two canals were found in all specimens, with isthmuses in 71% of the cases. These communications and isthmuses were respectively in 42% and 54% of the cases in the coronal third, in 59% and 79% of the cases in the middle third and in 24% and 50% of the cases in the apical third. A single apical foramen was found in 37% of specimens, two apical foramina were present in 23% of the cases, with three or more separate apical foramina occurring in 40% of the specimens.

Degerness et al. 2010

Uninstrumented MB roots from 153 teeth were imbedded, sectioned, and observed at 8x using a stereomicroscope for main canal numbers, isthmus presence, and dimensional size of canals and dentin walls.

RESULTS:

The number of canals observed in maxillary first and second molars was 20% and 38.1% for one canal, 79.8% and 60.3% for two canals, and 1.1% and 1.6% for three canals, respectively. The buccal canal was larger than lingual or middle canals at all levels of the root. The average distance between the two main canals was 1.2 +/- 0.6 mm in first molars and 1.78 +/- 0.6 mm in second molars. Isthmus tissue increased greatly at 3.6 mm from the apex, suggesting optimal root resection at this level. Little differences in thickness between mesial and distal canal walls were seen until reaching the coronal sections of the root where the average canal wall thickness was found to be thinner (33%) on the distal, suggesting a “danger zone” for maxillary molars at a level where the root joins the crown of the tooth.

Neelakantan et al. 2010

MAXILLARY FIRST (N = 220) AND SECOND (N = 205) MOLARS WERE COLLECTED FROM AN INDIGENOUS INDIAN POPULATION AND SCANNED BY USING A CBCT SCANNER AT A CONSTANT SLICE THICKNESS OF 125 ΜM/SLICE. VOLUME RENDERING AND MULTIPLANAR VOLUME RECONSTRUCTION WERE PERFORMED. THE NUMBER OF ROOT CANALS WAS EXAMINED, AND ROOT CANAL SYSTEM CONFIGURATIONS WERE CLASSIFIED BY USING HISTORICAL AND CONTEMPORARY CLASSIFICATIONS.

RESULTS:

SINGLE-ROOTED FIRST AND SECOND MOLARS COMMONLY SHOWED TYPES I, IV (0.5%) AND TYPE III (1%) CANAL SYSTEMS, RESPECTIVELY. BUCCAL ROOTS OF TWO-ROOTED FIRST MOLARS SHOWED 2 CANAL SYSTEMS, TYPE I AND TYPE IV, WHEREAS SECOND MOLARS WITH 2 ROOTS SHOWED WIDE VARIATIONS IN CANAL ANATOMY. THE MOST COMMON CANAL MORPHOLOGY IN THE MESIOBUCCAL ROOTS OF THREE-ROOTED FIRST AND SECOND MOLARS WAS TYPE I (51.8% AND 62%, RESPECTIVELY), FOLLOWED BY TYPE IV (38.6% AND 50%, RESPECTIVELY). THE DISTOBUCCAL AND PALATAL ROOTS OF FIRST AND SECOND MOLARS SHOWED PREDOMINANTLY TYPE I CANAL MORPHOLOGY. ADDITIONAL CANAL TYPES WERE IDENTIFIED IN 2.2% AND 9.3% OF THE FIRST AND SECOND MOLARS, RESPECTIVELY.

Verma & Love 2011

Twenty mesiobuccal roots were resected from randomly selected extracted human maxillary first molar teeth and prepared for scanning using a SkyScan micro CT scanner (SkyScan 1172 X-ray microtomograph, Antwerp, Belgium) at a slice thickness of 11.6μm. Three-dimensional images were produced and analysed to record the number and configuration of the canals, the presence of accessory canals, connections between the canals and number of canal orifices and foramina.

RESULTS:

The majority of roots had complex root canal systems with a second mesiobuccal canal present in 90% of the roots examined. Intercanal communications were observed in 55% of the roots. A single apical foramen was found in 15% of roots, two foramina were present in 20% and three or more foramina were present in 65%. In half of the roots, there were two orifices at the furcation level; 40% had one orifice and 10% had three orifices. Accessory canals were present in 85% of the roots. Only 60% of root canals could be classified using the classification of Weine et al. (1969) and 70% using the classification of Vertucci (1984).

Zhang 2011

A total of 269 patients with healthy, untreated, well-developed maxillary molars were enrolled, including those suffering facial trauma, and those who required a pre-operative assessment for implants. Radiographic examination by CBCT was conducted as part of their routine examination, diagnosis and treatment planning. Overall, 299 maxillary first and 210 maxillary second molar teeth were examined in vivo by CBCT. The number of roots, the number of canals per root, the canal configuration and the presence of additional mesiobuccal canals were recorded. Vertucci’s classification for root-canal configurations was utilized.

RESULTS:

All maxillary first molars had three separate roots; however, 52% of mesiobuccal (MB) roots had two canals with the remainder having one. All distobuccal and palatal roots had Vertucci Type I canal configurations. When the MB2 canal was present, 14, 69 and 16% of MB roots had Type II, IV and V canal configurations, respectively. The root canal system of the maxillary first molar teeth could be categorized into two variants: one with three separate roots with one canal in each of the distobuccal and palatal roots and two canals in the MB root, and the other with three separate roots with one canal in each root. Of 210 maxillary second molars, 10% had one root, 8% two roots and 81% three roots. Of the MB roots, 22% had two canals with the remainder having one. When the MB2 canal was present, 18%, 58%, 10% and 3% of MB roots had type II, IV, V and VI canal configurations, respectively. The root canal system of the maxillary second molar could be categorized into eight variants.

Kim et al. 2013

One hundred and fifty-four extracted human maxillary first molar MB roots were scanned by μCT (Skyscan) and their canals were reconstructed by 3D modeling software. Root canal configurations were categorized according to the classifications proposed by Weine and Vertucci. Canal configurations that did not fit into both classifications were categorized as non-classifiable.

RESULTS:

One hundred and thirteen (73.4 %) MB roots had multiple canals. The most predominant canal configuration was Weine type III (two orifices and two foramens). Thirty-three (29.2 %) and 20 (17.7 %) MB roots had non-classifiable configuration types that could not be classified by the Weine and Vertucci classification, respectively. Three configurations (types 1-3, 2-3-2-3-2, and 2-3-4-3-2) were first reported in maxillary first molar MB roots.

Al-Fouzan et al. 2013

Silva et al. 2014

Patients referred for a CBCT radiographic examination for accurate diagnosis and treatment planning were enrolled in the study. A total of 620 healthy, untreated, fully developed maxillary first and second molars were included (314 first molars and 306 second molars). The following observations were recorded: (1) number of roots and their morphology, (2) number of canals per root, (3) fused roots, and (4) primary variations in the morphology of the root canal systems.

RESULTS:

First and second molars showed a higher prevalence of 3 separate roots, mesiobuccal, distobuccal, and palatal, with 1 canal in each root (52.87% and 45.09%, respectively). Two canals in the mesiobuccal roots represented 42.63% of teeth, whereas mesiobuccal roots of second molars presented 2 canals in 34.32%. The most common anatomic variation in the maxillary first molar was related to the root canal configuration of the mesiobuccal root, whereas the root canal system of the maxillary second molar teeth showed more anatomic variables.

Guo et al. 2014

Three hundred seventeen cases with bilateral maxillary first molars were included. All images from cone-beam computed tomography were carefully reviewed by 2 endodontists. Frequency of number of roots, presence of an additional mesiobuccal canal (MB2), and Vertucci canal type for each root were tabulated. Age, gender, and ethnicity differences were calculated with the χ(2) test. The intra-rater reliability was assessed by using the Cohen kappa statistic.

RESULTS:

The fused root rate was 0.9%. The occurrence of 3-rooted maxillary first molars differed between left and right sides (P = .03). MB2 occurrence only showed statistically significant differences among age groups (P = .005). In the mesiobuccal roots, the most common Vertucci classifications of canal types were type IV (2-2, 41.9%), type I (1, 28.3%), and type II (2-1, 26.3%). There was a statistically significant difference in Vertucci classification of canal type among 5 ethnic groups (African American, Asian, Hispanic, Other, and Non-Hispanic white, P < .001).

METHODS:

The root canal configuration, foramina, and accessory canal frequency of 179 maxillary first molars were investigated by means of micro-computed tomographic imaging and 3-dimensional software imaging. The root canal configuration and main foramina number are described from coronal to apical with a 4-digit system.

RESULTS:

The most frequent root canal configurations were 1-1-1/1 (45.8%), 2-2-2/2 (25.1%) and 2-2-1/1 (10.1%) in mesiobuccal roots and 1-1-1/1 in distobuccal (97.2%) and palatal (98.9%) roots. The first mesiobuccal (MB1) root canal had 1 accessory canal in 26.3% of the teeth, the distobuccal root canal had 12.3%, and the palatal root canal had 9.5%; in the second mesiobuccal root canal, there was rarely 1 accessory canal. There was 1 accessory canal in 26.3%, 12.3%, and 9.5% in the MB1, distobuccal, and palatal root canals, respectively. The MB1, distobuccal, and palatal root canals had 1 main foramen. The MB2 had 1 main foramen in 39.0% of the teeth and no main foramen in 61.0%.

Briseno-Marroquin 2015

The root canal configuration, foramina, and accessory canal frequency of 179 maxillary first molars were investigated by means of micro-computed tomographic imaging and 3-dimensional software imaging. The root canal configuration and main foramina number are described from coronal to apical with a 4-digit system.

RESULTS:

The most frequent root canal configurations were 1-1-1/1 (45.8%), 2-2-2/2 (25.1%) and 2-2-1/1 (10.1%) in mesiobuccal roots and 1-1-1/1 in distobuccal (97.2%) and palatal (98.9%) roots. The first mesiobuccal (MB1) root canal had 1 accessory canal in 26.3% of the teeth, the distobuccal root canal had 12.3%, and the palatal root canal had 9.5%; in the second mesiobuccal root canal, there was rarely 1 accessory canal. There was 1 accessory canal in 26.3%, 12.3%, and 9.5% in the MB1, distobuccal, and palatal root canals, respectively. The MB1, distobuccal, and palatal root canals had 1 main foramen. The MB2 had 1 main foramen in 39.0% of the teeth and no main foramen in 61.0