Prevalence of enamel projections and its co-relation with furcation involvement in maxillary and mandibular molars: A study on dry skull.

BACKGROUND: The objectives of this study were to investigate the incidence of cervical enamel projection (CEP) in molars of Indian dry human skulls and to evaluate its relationship with furcation involvement (FI).
MATERIALS AND METHODS: The material consisted of 944 upper and lower first, second and third permanent molars from 89 Indian dry human skulls. CEPs were investigated from the buccal aspect of the tooth and classified according to a system describeddescribed by Masters and Hoskins. FI was measured horizontally from the buccal aspect into the furcation with a graduated probe to the nearest millimeter. Any measurement ≥2 mm was considered to have positive FI.
RESULTS: The results showed that CEPs was found more frequently in the mandibular than in the maxillary molars (2:1). The highest incidence of CEP was found in the mandibular second molar (14.7%) followed by the maxillary second molar (14.6%). The mandibular third molar showed the lowest incidence (5.5%). The association between CEP and FI (87.5%) was statistically significant. This favors the view of the possible role played by such anomalies in the progression of periodontal diseases. CEP in male skulls (77.4%) was significantly more prevalent than in female skulls (20.4%). No significant difference was found between the right and left side of maxillary and mandibular teeth with CEP and FI.
CONCLUSION: The findings suggested the role of CEPs as a local contributing factor in localized chronic periodontitis and FI in molars. Detailed examination as well as early diagnosis of periodontal disease at the region of furcation is clinically very important.

INTRODUCTION

Periodontitis is primarily a bacterial-induced disease that can be modified by tooth related local factors. Enamel, which is normally restricted to the anatomical crown of human permanent teeth, may be found ectopically on the root either as enamel pearl[1] or enamel projections.[2] Among the anatomical factors cervical enamel projections (CEPs) are a common tooth anomaly that can act as a contributing factor in the development and progression of periodontitis.[3] CEPs are flat, ectopic deposits of enamel apical to the normal cemento-enamel junction (CEJ) level in molar furcation areas.[4] These enamel deposits usually have a triangular shape and a tapering form, extending apically into furcation areas. They are most commonly found at the buccal surfaces of mandibular molars.[5]

A possible relationship between CEP and periodontal breakdown was first indicated by Atkinson[6] in 1949. He suggested that the anatomy and location of CEP might act as probable causes for rapid pocket formation. The enamel covering the CEP prevents the formation of a connective tissue attachment. Instead, the gingival tissue adjoining the CEP is attached to the tooth by epithelial attachment, which is less resistant to the insult of bacterial plaque. Goldstein[7] described this attachment as a locus minori resistentcia. The morphology of CEP enables the adherence of dental plaque. This, together with a reduced access for oral hygiene measures and the proximity to the furcation dome, might enhance periodontal breakdown in the furcation.

The clinician must be aware of the presence of such aberrations and their importance in the etiology of local periodontal breakdown. Early diagnosis may improve the prognosis of the involved tooth. Although reports vary, about 15-24% of mandibular molars and 9-25% of maxillary molars have CEPs. Considering both arches, they are most likely to be found on buccal surfaces of second molars.[89]

Swan and Hurt,[10] in their study on Indian skulls, noticed a direct association between the contour of the marginal bone and the position of CEP. They also found widening of the periodontal ligament adjacent to the alveolar crest, which allowed the apical portion of the CEP to merge toward the furcation.[10] They concluded that it was the bone's excellent remodeling properties that enabled it to adjust to the varying tooth surface anatomy.

Masters and Hoskins[4] reported the incidence of CEPs in extracted human teeth and suggested their possible implication in isolated furcation involvement (FI). They feel that even a slight gingival inflammation could produce a deep constricted periodontal pocket almost overnight. This could explain why destruction of the periodontium occurs at one given location, while bypassing adjacent areas.

Grew et al.[8] examined 5000 extracted molars and reported a positive correlation between enamel projections and FI. However, an attempt by Leib et al.[11] to statistically associate these enamel extensions with FI was unsuccessful.

The purpose of this study is to re-evaluate the incidence and distribution of CEPs and to correlate their possible relationship with FIs present in dry human Indian skulls.

MATERIALS AND METHODS

A total of 944 upper and lower first, second and third permanent molars were examined from 89 dry human Indian skulls for the presence of CEP dipping into the root furcation area. CEPs were investigated from the buccal aspect of the tooth and classified according to a system given by Masters and Hoskins[4] [Figure 1].

Figure 1

Classification of cervical enamel projection

Grade I: The enamel projection extends from the CEJ of the tooth toward the furcation entrance.

Grade II: The enamel projection approaches the entrance to the furcation. It does not enter the furcation and therefore no horizontal component is present.

Grade III: The enamel projection extends horizontally into the furcation.

FI was measured horizontally from the buccal aspect into the furcation with a graduated probe to the nearest millimeter. Any measurement ≥2 mm was considered to have positive FI. The degree of involvement was not recorded. Male and female skulls were identified on the basis of the following anatomical landmarks:[12]

Male skulls typically have more prominent supraorbital ridges, a more prominent glabella and more prominent temporal lines.

Female skulls generally have rounder orbits and narrower jaws.

Male skulls on average have larger, broader palates, squarer orbits, larger mastoid processes, larger sinuses and larger occipital condyles than those of females.

Male mandibles typically have squarer chins and thicker, rougher muscle attachments than female mandibles.

The data collected were subjected to statistical analysis using a Chi-square test for determining the incidence of each variable and tabulated in Tables 1–5. The relationship of CEP and FI is shown in Figures 2–4.

Table 1

Distribution of cervical enamel projections in relation to maxillary and mandibular molars

Table 5

Distribution of CEP with furcation according to the side of the arch

Figure 2

Correlation of cervical enamel projection and furcation involvement

Figure 4

Presence of cervical enamel projection without involving the furcation

Presence of furcation involvement without presence of cervical enamel projection

RESULTS

The incidence of CEPs was found to be 11.9% (112 out of 944 molars examined). CEP and furcation were present on 98 (10.3%) of the 944 molars examined. A total of 308 (32.6%) of the 944 molars examined, were with FI. CEP without furcation were present on 14 (1.4%) of the 944 molars examined. CEPs were found almost twice as frequently in the mandibular molars as in the maxillary molar, which was found to be highly significant (P = 0.000) [Table 1]. Tooth with grade III CEP shows the highest number (82) of FI as compared with Grade II and Grade I CEP, which was found to be highly significant (P = 0.000) [Table 2]. Number of molars with CEP and FI were 98 out of 944 (10.3%) which was statistically significant (P = 0.000) [Table 3] CEP with FI was significantly more in male skulls as compared with female skulls (P = 0.001).[Table 4] There was no significant difference between the right and left maxillary and mandibular teeth with CEP and FI (P = 0.751) [Table 5].

Table 2

Distribution of CEP with furcation involvement according to their grade

Table 3

Number of cervical enamel projections and furcation involvements in study sample

Table 4

Distribution of molars involving CEP & furcation according to the sex

DISCUSSION

Periodontitis is primarily a dental plaque induced inflammatory disease but the local factors that facilitate the accumulation of bacteria may contribute to the progression of the disease.[13] Factors such as tooth anatomy and restorative/endodontic considerations have been linked to gingival inflammation and attachment and tooth loss. Of all anatomic factors, the CEP is probably the most common and associated with attachment loss in the molar furcation area.[3]

This study investigated the incidence and distribution of CEP and attempted to correlate their possible relationship to FIs present in dry human Indian skulls. CEP were present on 112 (11.9%) of the 944 molars examined (224 maxilla, 720 mandible). In previous reports,[4811] the incidence of CEP ranged from 15% to 30%. A possible explanation for the low incidence in the present investigation may be the difference in racial origin of the specimens.

As shown in Table 1, CEPs were found almost twice as frequently in the mandibular molars as in the maxillary molars. The predominance in the mandibular molars is in general agreement with previous reports.[2141510]

The incidence of CEP varied between the first, second, third molars [Table 1]. Mandibular second molars showed the highest incidence (14.7%), followed by maxillary second molar (14.6%). The lowest incidence was seen in the mandibular third molar (5.5%). This pattern of frequency is in accordance as that reported by Swan and Hurt,[10] and Bissada et al.[15]

We found that 87.5% of molars with enamel projections (98 of 112) had an associated FI. Such a high percentage of association between the enamel projection and FI supports the view of a possible relationship, which may lead to the progression of periodontal disease.

Whether or not, there is a cause and effect relationship, requires further investigation. A total of 14 molars out of 112 molars (2.5%) with CEP had no associated FI. This was to be expected since there are a number of factors such as the presence of occlusal facets (trauma from occlusion), thickness of alveolar housing, variations in the root-trunk length and severity and extension of gingival inflammation which can contribute to periodontal breakdown in these areas.

Master and Hoskins,[4] suggested a classification system based on the extent of CEP into the furcation area. They used the adjacent CEJ and the furcation area as reference points to classify CEP as Grade I, II and III [Figure 1]. Hou and Tsai[16] and Swan and Hurt,[10] reported CEP Grade III to be the most commonly found CEP. In the present specimens, Grade III was the most prevalent (83.7%) and was associated with FI which shows the maximum potential of Grade III CEP for the FI. This can be explained by the mechanism that connective tissue cannot form an attachment to enamel.[14] Instead the junctional epithelium is present in these areas and consists of hemidesmosomes and basal lamina. As a result, when enamel forms on roots (more in Grade III), it may predispose the area to increased probing depth in the presence of gingival inflammation. Together with its plaque retentive nature, ectopic enamel might enhance periodontal breakdown.

One more new result found in the present study was the significantly more prevalence of CEP in male skulls (77.4%) than in female (20.4%). No significant difference was found between the right and left maxillary and mandibular teeth with CEP and FI. Exact reason behind this finding is unclear, but the possible role of genetics should be ruled out in future studies as bilateral occurrence of CEP was reported by one case report.[17] These results are not comparable as none of the previous studies have evaluated this aspects of CEP.

Since Bissada et al.[15] had experienced great difficulty in detecting selected teeth with CEP radiographically, in the present study the authors have not included such an identification in this manner; in fact, through clinical examination is more reliable for their detection.

CONCLUSION

A total of 944 maxillary and mandibular molar teeth present in Indian human dry skulls were examined for the incidence and location of CEP. Under the limitations of the present study, we have drawn the following conclusions:

The prevalence of CEPs in molars was 11.9%

CEPs were found more frequently in the mandibular than in the maxillary molars (2:1)

The highest prevalence of CEP was found in the mandibular second molar (14.7%) followed by the maxillary second molar. The mandibular third molar showed the lowest incidence (5.5%)

The association between CEP and FI (87.5%) was statistically significant. This favors the view of the possible role played by such anomalies in the progression of periodontal diseases

CEP in male skulls (77.4%) was significantly more prevalent than in female skulls (20.4%)

No significant difference was found between the right and left maxillary and mandibular teeth with CEP and FI.