RESULT

Frequency Distribution of Tooth Loss due to Caries According to Tooth Type

A total of 1269 patients attended the clinic, 8741 patients under went extraction, 11546 teeth were extracted altogether and 6145 permanent teeth were extracted due to caries and its sequalae within the two years under review (Tables 1 and 2).

Table 1. Frequency distribution of tooth loss due to caries according to tooth type

Table 2. Frequency distribution of tooth loss due to caries according to tooth type.

Table 3. Sextant distribution of pre-molar extraction due to caries

X = 15.937 df = 3 P = 0.001

Table 4. Sextant distribution of molar extractions due to caries

X² = 204.036 df = 6 P = 0.000

The upper anteriors accounted for 194 (3.2%), upper pre-molars 475 (7.7%) and upper molars 1833 (29.8%). The lower anteriors accounted for 22 (0.4%), lower pre-molars 202 (3.3%) and lower molars 3419 (55.6%). It was observed that tooth loss due to caries tends to increase anterior-posteriorly in both arches. The table also shows that the upper anterior (3.2%) is eight times more vulnerable to caries attack when compared to their corresponding lower anteriors (0.4%).

Inter-jaw distribution of pre-molar and molar tooth losses due to caries.

Ninety four (43.3%) upper right and 80 (36.9%) upper left first premolar was extracted due to caries as against their corresponding lower right (11.5%) and left (8.3%) first premolar (Table 3). The same pattern was observed for the second upper and lower premolars. The rate of losses due to caries is significantly higher in the upper than in the lower premolars (p = 0.001). The trend in the molars were opposite to what was observed in the premolars. Eight hundred and eighty three (33.0%) lower right and 33.0% lower left first molar were lost due to caries as against their corresponding upper right 16.6% and upper left 17.4%. The same trend was observed for the second and third molars (Table 4, Figure 1).

The study further revealed that the upper second molar was the least vulnerable to caries attack of all the molars. The lower molar losses, due to caries, were significantly higher than for the upper molars (p = 0. 000).

DISCUSSION

The vulnerability of a tooth to caries and tooth mortality was the focus of interest in this study. Previously reported studies have shown that dental caries is the foremost reason for tooth extraction in Nigeria and other African countries^1,2,6 and the rest of the world.^7,8,9,10 This high prevalence may be due to transition from the customary fibrous African diet to western diet.^2,6. In this study, it was observed that the maxillary anteriors (3.2%) were more susceptible to caries attack when compared to 0.4% of mandibular anteriors. A related study reported that 31.9% of maxillary centrals were extracted due to caries compared to 12.9% of mandibular centrals.¹¹ Another study reported that the least frequently extracted tooth type due to caries were the lower anteriors⁷. The reason for this may be due to the close proximity of the submandibular and sublingual salivary glands duct to the lower anterior teeth, as their secretions help to buffer and cleanse the products of bacterial plaque.

The upper pre-molars accounted for 70.2% of all pre-molars extracted due to caries, compared to 29.8% of lower pre-molars. It has similarly been reported that maxillary second pre-molars were more commonly extracted in Singapore as a result of caries and its sequalae.¹¹ The reasons for the difference in the rate of extraction due to caries and its sequalae may partly rest on the morphological differences, as the upper pre-molars have well defined palatal cusps and therefore deeper pits and fissures. It may also be as a result of poor saliva distribution in and around the upper pre-molar region as the buffer and cleansing action of the saliva may be reduced in this areas.

In this study it was observed that the mandibular molars accounted for 65.1% of all molar extraction due to caries, compared to 34.9% of maxillary molars. In the Singapore study, 63.7% mandibular first molars were extracted due to caries as against 44.7% of maxillary first molars¹¹. The reason may largely be due to morphological differences since, the mandibular molars have more extensive pits and fissures present in them while the fissures of maxillary molars are limited by the presence of oblique ridge. The direct secretions from the parotid gland duct, which is buccal to the maxillary teeth, may also assist in reducing the pH around the maxillary molars. In this study the first molar accounted for 50.9% of all molar extractions due to caries irrespective of quadrant. A related study in Ile- Ife reported 41.6%¹ and West Indies 45.3%⁷. It may be argued that the time of eruption may largely be responsible; at age six, the child may not have imbibed the various methods of maintaining good oral health, and also lacks the dexterity necessary in the use of both toothbrush and chewing sticks. A related study in Glamorgan noted that more decayed or filled occlusal surface were present in the second molars and pre-molars of those quadrants and arch, which have lost their first molar¹². They extrapolated from the result of the study that whatever aetiological factors were operating to place the child in high-risk group early in life continues to operate in the early teenage years¹². It was observed that the maxillary second molar was the least extracted due to caries. The reason may be due to the opening of the Stenson?s duct (parotid gland duct), which helps to buffer and cleanse bacterial plaque products.

CONCLUSION

The morphology, time of eruption and position of each tooth type confers an inherent advantage/disadvantage to the various methods employed in plaque control and to naturally occurring defense factors. The result of this study showed that teeth with deep pits and fissure like the maxillary premolars and molars are most susceptible to dental caries and would benefit from the use of prophylactic pits and fissure sealants.

ACKNOWLEDGEMENTS

This work was supported by a research grant from the Regional Centre for Oral Health Research and Training Initiatives (RCORTI) for Africa in Collaborative with WHO. Our thanks go to the entire staff of Plateau State Government Dental Centre for their assistance during the period of data collection.