Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2006  |  Volume : 24  |  Issue : 2  |  Page : 90--96

Loss of space and changes in the dental arch after premature loss of the lower primary molar: A longitudinal study


Padma Kumari B, Retna Kumari N 
 Dept. of Pedodontics, Govt. Dental College, Trivandrum, India

Correspondence Address:
Padma Kumari B
Dept. of Pedodontics, Govt. Dental College, Trivandrum
India

Abstract

The purpose of the study was to evaluate the space changes, dental arch width, arch length and arch perimeter, after the unilateral extraction of lower first primary molar in the mixed dentition period. A longitudinal study was conducted among forty children in the age group of 6-9 years, who reported for extraction of lower first primary molar in the department of Pedodontics, Govt. Dental College, Trivandrum. Study models were made from alginate impression taken before extraction and after extraction at the periodical intervals of two months, four months, six months and eight months. The mesiodistal width of lower first primary molar of the non-extracted side was taken as the control. The results of the study showed statistically significant space loss in the extraction side ( P value <0.01) and no significant space loss in the control side ( P value > 0.05). The rate of loss was greatest in the first four months. The arch width, arch length and arch perimeter had no significant change from initial to eight months follow up. The present study challenges the use of a space maintenance under the circumstances of premature loss of mandibular primary molar for preventing space loss.



How to cite this article:
Padma Kumari, Retna Kumari. Loss of space and changes in the dental arch after premature loss of the lower primary molar: A longitudinal study.J Indian Soc Pedod Prev Dent 2006;24:90-96


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Padma Kumari, Retna Kumari. Loss of space and changes in the dental arch after premature loss of the lower primary molar: A longitudinal study. J Indian Soc Pedod Prev Dent [serial online] 2006 [cited 2020 Feb 27 ];24:90-96
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Full Text

 Introduction



Pedodontists have traditionally accepted active supervision of the developing dentition as major responsibility. Management of space problems associated with the transitional stages from primary to permanent dentition is a routine component of pedodontic practice. The change from primary dentition to the permanent dentition is a complex phenomenon, which is composed of a variety of physiological adaptations of occlusion during this period. The exfoliation of the primary teeth, the permanent teeth eruption and the occlusion through independent, occur in a harmonious sequence.[1],[2] There are many morphogenetic and environmental influences, which manage the occlusal development and a disorder or deviation in any of these elements may influence the occlusion. Among these elements, there is the importance of the primary teeth because when they are physiologically exfoliated, there is a favourable alveolar growth and space for a better accommodation of the successor permanent teeth.[3] The permanent teeth dislocation occurs in the eruptive, pre functional and functional periods of the eruption, that are within the primary arch and in the mixed dentition stage.[4],[5],[6],[7]

Richardson[8] observed that the most severe space problems happen when the primary teeth, in particular the first primary molars are exfoliated before the eruption of the permanent molar. The premature loss of the primary molars that results in mesial positioning of the first permanent molar is of a great concern during the mixed dentition. Love and Adams[9] found a greater percentage of space loss by mesial migration of the posterior teeth than distal migration of the anterior teeth, especially in the mandible. In majority of children, the occlusion and space would be influenced by premature extraction of primary molars and canines.

Growth and development and drifting patterns of teeth are closely interdependent. In the field of pediatric dentistry much emphasis should be put on these factors in order to secure the optimal benefit of systematic dental care for the child. It is well known that after early loss of deciduous molars dental arch crowding arises in some cases, while in other cases it does not. It has been suggested that large jaws with normal spacing or over spacing are not influenced by the premature loss of the deciduous teeth. A tendency towards small jaws and space deficiency in the deciduous arch, on the other hand, will probably cause closure of the extraction gap resulting in crowding in the permanent dentition.[10] Premature loss of a primary tooth is of concern not only because of the loss of function, but also because of the increased possibility that the other teeth may drift. It would be useful in determining the treatment, if the dentist could predict the sequel of premature loss of primary teeth.

As the premature loss of primary teeth is still a very common situation within the population, this study was undertaken using longitudinal cast data to investigate the changes after unilateral premature extraction of the mandibular first primary molar in the mixed dentition stage.

 Aim and Objectives



1. To evaluate the space changes in the extracted site.

2. To determine the changes in dental arch width.

3. To observe changes in the dental arch width.

4. To evaluate the changes in the dental arch perimeter.

 Materials and Methods



Forty children for the study. The patients were in the age group of 6-9 years, who had reported for extraction of lower first primary molar in the Department of Pedodontics, Govt. Dental college, Thiruvananthapuram for an evaluation of thirteen months. The selected patients were made as homogenous as possible. In the final stage of the study, the number of patients decreased to 30, as ten children did not come for further follow up and they were excluded from the study.

All the cases complied with the following criteria

1. The first permanent molars have erupted.

2. Patients indicated for unilateral extraction of mandibular first primary molar due to extensive decay and having an intact anterior tooth.

3. The anteroposterior and lateral arch relationships were acceptable.

4. Premature loss of the primary molar was defined as having an unerupted permanent predecessor for at least two years after extraction of the deciduous first molar.

5. Parents and guardians who were willing to overweigh the effects of not maintaining the extraction space.

Recordings

At the start of the study, the children were subjected to a clinical examination and the medical and dental history of the child was taken. Mandibular study models were prepared from alginate impressions before extraction and immediately after the impression procedure, the decayed first molar was extracted. No space maintaining appliance was advocated. Longitudinally, the procedure was repeated at each follow up after two, four, six and eight months after extraction. Thus each patient was subjected to evaluation at five stages. The opposite non-extraction side was taken as the control. Two dental arch models of each patient prior to extraction and four models after the extraction of lower first primary molar were used for the study.

Measurements on the casts

Four measurements concerning dental arch development were performed on the extraction space, arch width, arch length and arch perimeter using a measuring gauge.

Extraction space

The referent space was determined by measuring the distance between the mesial midpoint of the second deciduous molar and the distal midpoint of the primary canine [Figure 1][Figure 2].

Arch width

The arch width was measured between the central fossae on the occlusal surface of two second primary molars [Figure 3].

Arch length

The arch length was determined by the orthogonal distance of the median point between the central incisors until the tangent line to the distal face of the second primary molars or mesial surface of the first permanent molars [Figure 4].

Arch perimeter

The arch perimeter was the measurement of the arc from the mesial midpoint of the first permanent molar, through the cusp tip of the first permanent molars. It was measured by the brass wire method. Measurements were repeated three times using different caliper from which an average value of the measurement in millimeter was recorded and analysed [Figure 5].

Statistical analysis

The analysis was done with Statistical Package for Social Science Soft ware (SPSS) programme. Paired 't' test was used for the comparison of measurement of all parameters.

 Results



The present study, was undertaken to evaluate the loss of space and change in the dental arch after premature loss of lower first primary molar among thirty children in the age group of 6-9 years brought the results. The measurement of the mesiodistal width of lower first primary molar on both control and extraction side, before extraction and following 2, 4, 6 and 8 months after extraction are shown in table. It was observed that there was a space loss in the extraction side and no space in the control side. It was also noted that space loss was maximum during the first four months and consequently space loss was minimum during the period of six to eight months. The result showed statistically significant space loss in the extraction side ( P P >0.05).

Comparison of the space changes of the lower first primary molar between the initial and follow up examinations during 2 months, 4 months, 6 months and 8 months in both control and extraction side are shown in [Table 2] and [Figure 6]a-e. The first primary molar space of the extraction side during the follow up examinations after 2 months (7.72 0.56), 4 months (7.03 0.56), 6 months (6.62 0.56) and 8months (6.64 0.44), were significantly lesser than the control side. There are statistically significant difference between the initial and the follow up examination in the extraction side. No significant difference is noted between the control side and the extraction side in the initial first primary molar space.

Quantity of space loss in millimeter after the premature loss of lower first primary molar is shown in [Table 3]. Space reduction in the analyzed dental arch were measured to be 1.31 mm, 1.69 mm, 1.41 mm and 1.22 mm during the monitoring in 2 months, 4 months, 6 months and 8 months respectively. Shows the mean changes of space reduction in control side and extraction side during the period from initial to eight months.

Measurements of arch width were analysed and the results showed no significant change in the arch width between the initial and the follow up examinations at 2, 4, 6 and 8 months intervals.

The measurements of arch length from initial and follow up examinations reveal no statistically significant change.

No statistically significant changes observed in the arch perimeter in the initial examination to follow up examinations.

 Discussion



Research dealing with space changes in the dental arch is difficult to perform accurately because of the multifactorial variance influencing the results. Most of the reports of research studies were based on cross sectional data, limited sample size and crude methodology that had led to misconceptions of space changes of the dental arch in maxillary or mandibular arch. The present study tried to minimize the errors conducting a longitudinal study by using strict homogenous samples and focusing on unilateral extraction of the mandibular first primary molar.

The present study was carried out to find out the space loss due to the unilateral premature extraction of the lower first primary molar. There is statistically significant space loss in the extraction side ( P value P value>0.05). The space changes in the extraction side measured by the first primary molar space after eight months (6.4 0.44 mm) have shown significant space loss compared to the initial first primary molar space (8.23 0.52 mm) and the control side (8.31 0.52 mm).

The result of the present study confirm with the conclusion of the studies of Helm, Owen and Yng-Tzer J, Lin and Li-Ching Chang.[11],[12],[14] They reported that space loss was more common in the mandibular arch after the premature loss of first primary molar. The results of the present study partly support the conclusions that space in the mandible is lost by both mesial migration of posterior teeth and distal movement of anterior teeth as reported by Osmar Aparecide Cuoghi et al .[13]

The mean changes of space loss in the present study are 1.31 mm after 2 months, 1.69 mm after 4 months, 1.41 mm after 6 months and 1.22 mm after 8 months. It is noted that space loss is maximum during the first four months and minimum is last four months. Concerning the rate of space change, the greatest space loss occurred in the first four months. The study reveals significant space loss during the average eight months of experimental period.

It appears in the present study that the space loss in the mandible is mostly due to distal movement of primary cuspid during the following eight months. The possible explanation is that the erupting anterior incisors pushed the primary cuspid towards the distal more than the erupting first permanent molar did on the second primary molar towards the mesial. The findings of the present study support the findings to Johnsen[15] that the space changes occurred mainly by the distal migration of primary cuspid in the intial stage.

The present study also investigated the changes in the arch width, arch length and arch perimeter. No significant change in the arch width, arch length and arch perimeter from initial and the follow up examinations at 2 months, 4 months, 6 months and 8 months was observed. Lundstrom[16] emphasized the importance of inheritance of dental arch, the exfoliation period, occlusal developmental stages and influences in the dental arch perimeter.

Briefly, the space loss is mainly, by movement of the primary cuspids distally and by a lesser degree by movement of the first permanent molar and second primary molar mesially, depending on the period of the referred tooth absence.

The following conclusions are drawn from the present study

1. The premature loss of the lower first primary molar in the mixed dentition resulted in statistically significant space loss in the extraction side than in the control side.

2. The early space change of the mandibular dental arch after premature loss of the mandibular primary first molar is mostly by distal movement of the primary cuspid towards the extraction space.

3. There is significant space change during the average eight months of experimental period. The greatest space loss is observed in the first four months after the premature extraction.

4. There is no significant space change in arch width, arch length and arch perimeter in the mandibular arch after premature loss of the primary first molar during the experimental period of eight months after extraction.

The present study challenges the use of a space maintenance under the circumstances of premature loss of mandibular primary molar for preventing space loss.

Further studies are needed to be done, regarding not only on space problems of primary first molars, but also involving the second primary molars in either the maxillary or mandibular arch.

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