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STUDY ON RELATIONSHIP BETWEEN ENAMEL LAMELLA AND DENTAL DECAY

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STUDY

ON RELATIONSHIP

BETWEEN

ENAMEL

LAMELLA

AND

DENTAL

DECAY

BY

YASUYUKI AWAZAWA*, HIROYASUYAMADA**, TAKASABURO SUGAYA**, IWAO AWAZAWA* and SHIN-HACHIRO KANO*

I INTRODUCTORY

Gottlieb1) and other scholars attached much importance to lamellae as being responsible for the occurrence of dental decay, regarding them as starting points and invasion road on the enamel smooth surface towards dental decay. But so far an exact extent of their possible influence has not been established or proved. The authors have attempted at looking into relationship between lamellae and dental decay by observations of susceptibility percentage of enamel caries in regard to the extracted permanent teeth with the first stage of dental decay in which the lamellae were observed to be the starting base.

II EXPERIMENTAL METHODS AND MATERIALS

For the purpose of this experiment, 40 human incisors, 24 canines, 51 premolars and 85 molars which had been extracted in such a manner as did not give any force upon their toothcrowns when a gradual power was applied in extractive pro cess, were employed. All of these teeth had spots of enamel caries more than one and the degree of this enamel caries rangedfrom the initial enamel caries to the stage where carious defect advanced as far as the amelo-dentinal junction. These ex tracted teeth were dyed by means of the differential staining invented by Y. Awazawa, one of the authors, which differentiates between genuine enamel lamellae and artificial splittings or pseud enamel lamellae, and following the mass-staining process the experimental teeth were placed in the solution of 10% HNO3 as a post-treatment for the purpose of decalcification. Care was excercised in the above decalcifying process to prevent any unnecessary excessive decalcification of enamel. Therefore, the decalcification should be conducted anywhere from ten to twenty minutes and a yardstick to be applied in this process is a stage at which the reduced silver filmsformed on the enamelsurface are sufficiently washed off. Following the above process, the experimental teeth were rinsed by water and then neutralized in the solution of 10% sodium to be washed and wiped clean and dry afterwards.

Black lines running almost parallel to tooth axis from the neck to the top of a tooth are observed on the white toothcrown, indicating the stained lamellae. as usual

*粟 沢 靖 之

,粟 沢 巖,鹿 野 紳 八 郎: Dept. of Pathology, ColLege of Dentistry, Nihon Univ.

**山 田 裕 保

,菅 谷 高 三 郎: Dept. of Legal Medicine,℃011ege of Medicine, Nihon IJniv. (Chief Prof, of Pathology: Yozo KOBAYAKAWA, College of Dentistry, Nihon Univ.)

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-47-Therefore, when a dental decay starts from the lamella as its base it is admittedly to be found along the black line. In the execution of the present observations, the number of decays on each of the experimental teeth and their localities together with other pertinent facts were carefully recorded to serve as reference in the final results.

III RESULTS

When the incisors, canines, premolars and molars under experiment were looked into in terms of the bases from which their enamel caries started. the majority of the cases has been found to have started from lamellae, the cases of enamel caries starting from other bases being far fewer.

As is shown on Table 1, the percentage of enamel caries in the incisors starting from lamellae as base is 100% and other cases of enamel caries are 5% in mesial and distal surface regions and 2% in the combined regions of labial, lingual and palatal sides.

TABLE 1 Incisors

The same can be said of the canines, as showh on Table 2, where the cases of enamel caries which started from lamellae give 91%, those of mesial and distal surfaces 10% and those of labial, lingual and palatal regions 12% respectively.

As for the premolars and molars, the cases of enamel caries starting from lamellae are by far the largest as in the case of incisors and canines above and the enamel caries originating from pits and fissures are second in frequency and those of outer surface of the tooth crown except those of occlusal and approximal surfaces are the least. As is indicated on Table 3, the enamel caries of the pre-molars starting from lamellae is 88%, those of pits and fissures are 45%,those of mesial and distal surfaces are 7%, those of occlusal surface are 11% and those of outer surface of the tooth crown except approximal surface are 9%.

As is known from Table 4, the nearly same is true of the molars in which the cases of enamel caries originating from lamellae as their base are 90%, those of

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TABLE 2 Canines

TABLE 3 Premolars

pits and fissures are 77 and those of other regions are decidedly small in per centages, those of mesial, distal and approximal surfaces being 7%, those of occlusal surface 2% and those of the outer surface of tooth crown except approximal surface 9% respectively.

IV CONSIDERATIONS

The result of the above observations points out the fact that regardless of the position of teeth the percentage of enamel caries originating from lamellae is much

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TABLE 4 Molars

larger than that of other regions. Hitherfore, the general opinion has been that the most likely place for dental decay is the occlusal surface of molars with percentage as high as 80 or 90%, the approximal surface being the next likely spot. And pits and fissures on the occlusal surface of molars have been pointed out as base from which dental decay originates, the deeper the fissures the more susceptible they are. As a matter of fact, the authors themselves have ascertained that no dental decay is discerned on a tooth which has seen a full development of pits and fissures originating from there as base. On the other hand, as the front teeth have no occlusal surface there are no pits and fissures on them. Therefore, a different thinking is needed in regard to the susceptibility of the front teeth to dental decay and that of molars. When they are looked comparatively, it is known that the susceptibility of the teeth which have pits and fissures is much higher than those which are otherwise. The fact is indicative that pits and fissures are next possible spot for the generation of dental decay after enamel lamellae. As has been mentioned earlier, the authors have carried out another observation in regard to the teeth which were stained with the dye of Y. Awazawa's devise. The result of this observation shows that dental decay which has originated from pits and fissures is generally more advanced than that which has started from enamel lamellae as their base, however in the latter the penetration of decay is deeper. Of lamellae, some of them have been found to extend as far as the occlusal region, others connecting with other lamellae in the complicated networks and another being linked with pits and fissures. Also it is found that dental decay originating from lamella existing on the approximal surface is generally higher in frequency than other dental decays which generate from lamellae on the outer surface of tooth crown. This can be attributed to the fact that food stays longer on the approximal surface than on other

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surfaces, thus providing much possibility for the accumulation of various fermenta tions. That lamellae are an easy spot for caries is amply attested by the fact that caries makes its inroad along them in undermining manner.

V CONCLUSIONS

1. The susceptibility percentage to dental decay which originates from enamel lamellae is much larger than those which generatefrom pits and fissures or other enamel portions.

2. Therefore, it is decidedly established that lamllae are the most important base on the even surface of enamel from which dental decay is occasioned.

ACKNOWLEDGEMENT

The authors like to acknowledge their indebtedness to Prof. S. Sasaki, 1st Anatomy Dept., College of Medicine, Kumamoto University, and Prof. T. Nakayama, 1st Anatomy Dept., Kyushu Dental College, for their kindness in making it possible for them to carry out the present study.

REFERENCES

1) GOTTLIEB, B.: Atiologieund Prophylaxe der Zahnkaries, Z.Stomat., 19, 1921.

2)GOTTLIEB, B.: Caries prophylaxis by obstruction of the invasion roads, Amer.J. of Ortho-dont. and Oral Surg., Dec. 1947.

3)AWAZAWA, Y.: Staining method for differentiating enamel lamellae from artificial splittings, Act. Anat. Nippon., vol. 27, no. 3, 1952a.

4) AWAZAWA, Y.: Study on the cause of appearance of enamel lamellae, Act. Anat. Nippon., vol. 27 no. 3, 1952b.

5) AWAZAWA,Y.: About the abnormal histological structure of the dentine, especially the swelling of the dentinal canaliculi that are situated directly beneath the enamel lamellae,

Arch. Hist.Jap., vol. 4, no. 1,1952c.

6)AWAZAWA,Y: Comparative anatomical study on the superficial aspects of the enamel lamellae in the mammalian teeth, Act. Anat.Nippon., vol. 28, no. 3. 1953a.

7) AWAZAWA, Y.: On the histological nature of the enamellamellae and consideration of their appearance, Arch. Hist. Jap., vol. 5, no. 2, 1953b.

8)AWAZAWA, Y.: Comparative anatomical study on the nature of the so-called "Dentinanteil" of GOTTLIEB, Bulteno el la UnuaInstituto Anatomia de la Dentkuracada Facultato de Kjugu, no. 4, 1954.

9)UCHIDA,N. Comparative anatomical study on the superficial aspects of the enamel lamel lae in fishes, Kumamoto-igakkai-zassi, vol. 29, no 11. 1955.

TABLE  1  Incisors
TABLE  2  Canines
TABLE  4  Molars

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