Evaluation of Dental Status in Relation to Excessive Horizontal and Vertical Overlap in North Indian Population.

INTRODUCTION: Tooth wear (attrition) is a multifactorial entity, the pathogenesis of which involves many factors but the role of malocclusion cannot be undermined. Overjet and overbite play an important role in defining occlusion, hence they should also play an important role in causing attrition.
OBJECTIVES: This study aims to evaluate the relationship of dental health status between the vertical and horizontal overlap.
MATERIALS AND METHODS: This study was conducted on 600 patients selected randomly from rural population which were divided into three equal groups as per the predefined criteria, namely, horizontal overlap, vertical overlap, and control group. All patients were examined for the tooth attrition.
RESULTS: In Group 1 - 73 patients out of 200 showed one or more teeth attrition, in Group 2 - 38 patients out of 200 showed one or more teeth attrition, and in the control group, 22 patients out of 200 showed one or more teeth attrition.
CONCLUSION: It was concluded that both vertical and horizontal abnormal relationships of teeth play an important role in the etiology of attrition, with abnormal horizontal overlap being the more detrimental as compared to the vertical one. Copyright:

INTRODUCTION

Malocclusion is incorrect relationship of teeth when opposite arches come in contact with each other for the physiologic function. The major cause of malocclusion is misaligned teeth. Misaligned teeth pose many problems including aesthetic to function. Although what is physiologically acceptable occlusion has always been a topic of debate.

Horizontal and vertical overlap has always played a major role in deciding the occlusal relationship. Horizontal overlap is the projection of maxillary teeth over the mandibular teeth also termed as overjet and the vertical overlap is the leeway of the maxillary teeth over the mandibular antagonists in the vertical direction when the dentition is in centric occlusion also known as overbite.

Excessive overjet is seen as protruded maxillary teeth with v-shaped arch, the degree of which can vary. Although there is no consensus in the orthodontic societies still it is observed that this type of malocclusion is more prone to the damage of teeth due to trauma as they are protruded and hence gets maximum impact. The excessive overjet in extreme cases is seen as the mandibular teeth fully covered by the maxillary teeth, this kind of malocclusion is quite detrimental for the periodontium. Although all types of malocclusions have detrimental effects on the periodontium, excessive overbite is the one whose impact can be seen early.

When maxillary and mandibular teeth do not touch each other, it is known as open bite. This may occur in the front teeth (anterior open bite) or in the back teeth (posterior open bite).

The ideal overjet range for an average dentition is considered to be 1.5–2.5 mm and the ideal overbite range is considered to be 3–5 mm.

It is observed by many studies that the average overjet ranges in the 76-81% of the population while in 11.8%–16.7% this exceeds from 3 mm and edge-to-edge or negative overjet was observed to be in 5.5%–7.2% of the test population.[12]

Sundareswaran and Kizhakool,[2] also observed that the normal overbite was present in 70.5% and 27.5% patients examined had deep bite. The frequency of anterior and posterior open bites was 1.6% (25) and 0.4% (6), respectively.

According to the study conducted on NHANES III data, there is no relationship between the degree of anterior overlap and tooth condition, but no such data are available for the Indian population hence this study was conducted to study the relationship between excessive horizontal/vertical overlap and dental status in Rural Indian population.

MATERIALS AND METHODS

The study patients included aged between 13 and 50 years, in the North Indian Rural population near Patna city, Bihar. Regular examinations were conducted in the nearby Gram Panchayat area for the collection of data after taking prior permission from the local authorities.

Patients were then accessed for the vertical and horizontal overlap and tooth condition and were graded as per the predefined grades given below.

A total of 600 patients were included in the study. These were divided into three groups with 200 in each group. Group 1 included patients with abnormal horizontal overlap, in Group 2 patients with abnormal vertical overlap were included, and Group 3 served as control group in with individuals with normal dentition with no malocclusion was included in the study.

Patients those who have under gone any dental procedure within 6-month period were excluded from the study, patient's suffering from any other systemic disease and under some medication were excluded from the study, patient suffering from chronic periodontitis, pericoronitis or other infective dental conditions were also excluded from the study.

Horizontal and vertical overlap was defined as below:

Horizontal overlap

Overjet was evaluated in millimetres and was considered normal when it ranged between 1.0 and 3.0 mm[3] (Grade 0), increased when it was >3 mm[4] (Grade 1) and edge-to-edge when the upper and lower incisors at the same level[3] (Grade 2). Anterior crossbite when there were one or two lingually dislocated upper anterior teeth (Grade 3) and a reverse overjet was recorded when all four mandibular incisors were in front of the maxillary incisors (Grade 4).[5] When both upper and lower incisors were proclined with lip incompetence the term bimaxillary protrusion was used (Grade 5).[6]

Horizontal overlap was measured as the distance from the labial surface of the most prominent incisor to the labial surface of the mandibular incisor with the help of the periodontal probe.

Vertical overlap

The amount of overbite was measured using the periodontal probe vertically. It was considered normal between 1/3 and ½ overlap, (Grade 0).[7] Deep bite was registered when more the half overlap was observed (Grade 1), anterior open bite was considered when there was no overlap of incisors (Grade 2).[7]

Assessment of dental status

The assessment of dental status was done by recording the attrition of the teeth which was graded as

Grade 0: Sound tooth (score 0)

Grade 1: Defective margins (score 1)

Grade 2: Less than half of the crown is defective (score 2)

Grade 3: More than half but <2/3rd of the crown is defective (score 3)

Grade 4: Grossly fractured, mobile, or pulpal involvement (score 4)

Grade 5: Retained roots (score 5)

Grade 6: Missing tooth (score 6)

Randomization was done by random number selection method with the help of excel sheet. Very study participant was given numbers from 1 to 200 for each group and then a random number was allocated to each individual with the help of excel sheet random number allocation, then all the allocated numbers were arranged in descending pattern and top 200 patients were selected. For this process, regular surveys and village visits were conducted.

RESULTS

Table 1 shows the number of patients in each category with the maximum possible score, actual score, and percentage. Out of total 200 patients in the horizontal overlap group, 127 were in graded as 0. 28, 29, 11, 7, and 8 were graded as 1, 2, 3, 4, and 5, respectively.

Table 1

Number of subjects in each category with the maximum possible score, actual score, and percentage score

Group	Grade 0	Grade 1	Grade 2	Grade 3	Grade 4	Grade 5	Grade 6	Max score possible	Actual score	Percentage
1	127	28	19	11	7	8	0	1000	167	16.7
2	162	29	9	0	0	0	0	600	47	7.83
3	178	13	4	1	3	1	0	1200	41	3.41

Similarly in vertical overlap group, 162 were graded as 0 and 29, 9 were graded as Grade 1 and 2, respectively.

In the control group out of total 200, 178 had all sound tooth 13, 4, 1, 3,1, and 0 were graded as Grade 1, 2, 3, 4, 5, and 6, respectively. The total score for Group 1 was 167 when the maximum possible score was 1000. The percentage score was 16.7%.

Total score for Group 2 was 47 when the max possible score was 600 and the percentage score was 7.83.

For control group, the total score was calculated as 41 and the maximum possible score was 1200 with the percentage score was 3.41%.

Table 2 shows the comparison of Group 1 with the control group. A significant difference was observed when horizontal overlap group was compared with the control group suggesting that the patient's having abnormal horizontal overlap are more prone to attrition as compare to those with normal occlusion.

Table 2

Comparison of horizontal overlap with tooth condition

	Sound tooth	Affected tooth	Percentage score
Horizontal overlap	127	73	16.7
Control group	178	22	3.41

Chi-square test: P<0.00001. Significant at P<0.05

Table 3 shows the comparison of Group 2 with the control group. This comparison also suggests that the abnormal vertical overlap is significantly related to the attrition as compared to the normal occlusion.

Table 3

Comparison of vertical overlap with tooth condition

	Sound tooth	Affected tooth	Percentage score
Vertical overlap	162	38	7.83
Control group	178	22	3.41

Chi-square test: P=0.025062. Significant at P<0.05

Table 4 shows the comparison of horizontal with the vertical overlap group. This comparison suggests that horizontal overlap is significantly more detrimental as compared to vertical overlap.

Table 4

The comparison of horizontal with the vertical overlap group

	Sound tooth	Affected tooth	Percentage score
Horizontal overlap	127	73	16.7
Vertical overlap	162	38	7.83

Chi-square test: P=0.000093. Significant at P<0.05

DISCUSSION

Vertical overlap/overbite is defined as the leeway of the maxillary teeth over the mandibular teeth, in the vertical plane, when the opposing teeth are in maximal intercuspation. Hence normally the incisal edges of the maxillary incisors overlap on one-third of the mandibular incisors. Increase in this interincisal distance increases calls for an abnormal condition which may range from mild to a severe abnormal vertical overlap.[8] Similarly, horizontal overlap/overjet is the protrusion of maxillary teeth beyond the mandibular antagonists but in the horizontal plane.[8]

There are studies indicating that severe overjet and overbite are responsible for the increased masticatory muscles load, leading to temporomandibular dysfunction.[9] It is also observed that increases horizontal overlap interfere with oral functions such as chewing, speech, and drink. It also leads to the rubbing of opposite teeth with one another causing attrition.

Increased overjet and overbite resulting in malocclusion also cause the reduction in alveolar bone height leading to periodontal conditions.[10]

Attrition, abrasion, and abfraction are considered to work synergistically in the etiology of noncarious lesions. Attrition is considered as wear of tooth material due to tooth to tooth contact. The major causes of attrition of teeth include temporomandibular disorder, bruxism and malocclusion.

Malocclusion also includes abnormal overjet and overbite. Hence, we conducted this study to observe the effects of these conditions on the tooth status, which was assessed by the attrition of tooth.

In our study, we developed a score as per the grading, which was later compared with the horizontal overlap, vertical overlap and the tooth status.

The score obtained for the horizontal overlap was 167 which was 16.7% indicating that out of total patients who suffered from excessive horizontal overlap the score for severity of dental attrition was 16.7%, similarly for vertical overlap, it was 47 and 7.83%.

The Chi-square test results were significant suggesting that there exists a relationship between excessive overjet, overbite, and attrition of the tooth. There are not many studies in the literature similar to our study, one such study was conducted by Grzegocka et al.[11] and our results find support in their study. As per their study which was conducted on polish adults, there was a high prevalence of attrition in the population affected by malocclusion, especially in Class II Division 2 cases. In our study also, we found that decreased overjet leads to tooth wear.

We also observed that the excessive horizontal overlap was more detrimental as compared to vertical one; again our findings are similar to that of Grzegocka et al.[11] They anticipated that anterior open bite, compensated Class III malocclusion and tightness of reverse overjet could result in dental wear. As per Grzegocka et al.[11] anterior open bite leads to the attrition of buccal segments hence validating our results.

There are studies which could not find any significant relationship between the overjet/overbite and tooth condition one such study was conducted by Koutnik[12] based on the NHANES III data. As per this study, no relationship exists between the degrees of tooth overlap and tooth condition. However, the study setup of this study was quite different from that of ours. They did a retrospective study based on the data collected not as per the well-defined study criteria and the tooth condition considered by them included the failed restoration mobile and missing teeth, etc., but our study took into account only one tooth condition which was attrition. Furthermore, the study criteria were well defined before recruiting the patients and starting the study.

CONCLUSION

We conclude that although the attrition is a multifaceted anomaly, with multiple processes and factors playing a role in its development the excessive vertical and horizontal overlap of anterior teeth do play an important role in the etiology of tooth wear.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.