6.1 Need for the study: The main goal in comprehensive orthodontic treatment is to obtain optimal final occlusion, overbite and overjet. A coordinated proportion between the mesio-distal dimensions of the upper and lower teeth is necessary for good intercuspation. Without a proper intermaxillary mesio-distal tooth size ratio, proper coordination of arches would be difficult. The presence of a tooth size discrepancy prevents the achievement of an ideal occlusion. In some situations, tooth size discrepancy is not observed at the initial examination and could result in poor contacts, spacing, crowding and an abnormal overjet and overbite at the terminal stages of orthodontic treatment.
The clinician should be familiar with discrepancies in tooth size at the initial diagnosis and treatment planning stages, if excellence in orthodontic finishing is to be achieved. Bolton’s analysis, based on the ratios between the mesio-distal width of the mandibular and maxillary teeth, is the most popular and best known method for determining tooth size abnormality, and is also useful in aiding diagnosis in patients with severe tooth size discrepancy.1
There are tooth size discrepancies present in various types of malocclusions. Among various malocclusions skeletal class I is the most common followed by skeletal class II. The aim of my study is to compare the tooth size discrepancies between skeletal class I and skeletal class II malocclusion groups in Davangere population.
There are tooth size discrepancies present between skeletal class I and class II malocclusion groups.
There are no tooth size discrepancies present between skeletal class I and class II malocclusion groups.
6.2 Review of literature:
In 1989 a study was conducted on patients with class I and class II malocclusions. In this study occurrence of tooth size discrepancies among different malocclusion groups was
compared using Bolton’s method of tooth analysis. It was concluded that there was no significant difference in the incidence of tooth size discrepancies among these malocclusion groups, but there was a large number of tooth size discrepancies in each group.2
In 1999 a study was conducted on subjects with normal occlusion and patients with class I bimaxillary protrusion and class II malocclusions. A significant difference was found in anterior and overall ratios between the groups, the ratios showing that class I having ratios greater than class II malocclusions. It demonstrated that intermaxillary tooth size discrepancy may be one of the important factors in the cause of malocclusions, especially in class II malocclusions.3
In 2005 a study was conducted on Angle class I and class II malocclusion groups to compare the anterior and overall tooth size ratios (Bolton’s analysis). It was concluded that there were no significant differences among the class I and class II groups for the anterior and overall ratio. When tooth size ratios of class I and class II malocclusion groups were compared with the anterior and overall tooth size ratios of untreated normal occlusion subjects, a statistically significant higher overall ratio was found in the malocclusion patients than in the normal occlusion group.4
In 2006, a retrospective study was conducted on models of malocclusion groups class I and class II with the corresponding skeletal characteristics. The anterior and overall tooth size ratios were computed for each subject as described by Bolton. No statistically significant difference was found between the two types of class II malocclusion for anterior and overall ratios. The anterior and overall ratios of the class I group were significantly greater than those in the class II subjects.5
In 2009, a study was conducted on patient models prior to orthodontic treatment and comparison was done between tooth size discrepancies and malocclusions using Bolton analysis. The comparison of overall and anterior Bolton ratio revealed no statistically significant difference between class I and class II malocclusion groups.6
6.3 Objectives of the study:
1. To determine the tooth size discrepancies in anterior and the overall ratios for skeletal class I and class II malocclusion groups in Davangere population.
2. To compare the anterior and overall tooth size discrepancies among skeletal class I and class II malocclusion groups in Davangere population.
MATERIALS AND METHODS 7.1 Source of the data: Pretreatment study models of skeletal class I and class II malocclusions will be collected from the record section of the Department of Orthodontics and Dentofacial Orthopedics, Bapuji dental college and hospital, Davangere.
Sample Size Determination-
For the purpose of study, the probability of Type I error (α) is fixed at 5% and Type II error (β) at 20%.
So, the power of the study is 1-β=80%.
Based on the available information, Sample size is calculated by using the formula-
So, minimal sample size to be taken for class I and class II malocclusion is 30 each.
7.2 Method of collection of data: Criteria for selection of sample Inclusion criteria 1. Skeletal class I (ANB = 0 to 4 degrees ).
2. Skeletal class II (ANB > 4 degrees).
3. Good quality study models.
4. All permanent teeth (except second and third molars) erupted in both the upper and lower
1. Presence of any craniofacial and dental deformity or severe mesio-distal and occlusal tooth abrasion.
2. Any restorations extending to the mesial or distal surfaces, or enamel stripping of the anterior or posterior teeth.
Method of study:
The teeth on each model (both maxillary and mandibular casts), except the second and third molars, will be measured at the largest mesio-distal dimension. These measurements will be made with a digital caliper.
The anterior and overall tooth size ratios will be computed for each subject as described by Bolton :
Anterior ratio: sum of mandibular “6” × 100
sum of maxillary “6”
Overall ratio: sum of mandibular “12” × 100
sum of maxillary “12”
After the above calculations, tooth size discrepancies will be compared between skeletal class I and class II malocclusions.
The values obtained will be statistically analyzed using the student unpaired -t- test.
7.3 Does the study require any investigations or interventions tobe conducted on patients or other humans or animals? If so, please describe briefly.
Yes, patient’s study models will be used.
7.4 Has ethical clearance been obtained from your institution in case of 7.3?
Yes, the clearance of ethical committee is attached.
LIST OF REFERENCES:
1. Bolton WA.Disharmony in tooth size and its relation to the analysis and treatment of malocclusions. Angle Orthod 1958;28(3):113-30.
2. Crosby DFL, Alexander CG. The occurrence of tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop 1989;95:457-61.
3. Nie Q, Lin J. Comparison of intermaxillary tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop 1999;116:539-44.
4. Uysal T, Sari Z, Basciftci FA, Memili B.Intermaxillary tooth size discrepancy and malocclusion: is there a relation? Angle Orthod 2005; 75:208-13.
5. Fattah HR, Pakshir HR, Hedayati Z. Comparison of tooth size discrepancies among different malocclusion groups. Eur J Orthod 2006;28:491-5.
6. Lopatiene K, Dumbravaite A. Relationship between tooth size discrepancies and malocclusion. Stomatologija, Baltic \ dental and maxillofacial journal 2009;11(4):119-24.
I/We agree with the treatment plan and give my/our full consent for the treatment procedures and any modifications in the plan during treatment, as deemed necessary. I/We have been explained about the photographs, study models, x-rays, duration, maintenance of appliance, keeping of appointments and the financial commitments pertaining to the treatment. Further I/We have no objection for using my/our records as a teaching aid,scientific presentations, as a study subject or in academic journal for which I have no objection.
I/We have been informed about the treatment purpose, procedure, the benefits and risks in the language that I understand in a comprehensible manner.
I/We hereby grant to the Department of Orthodontics, Bapuji Dental College and Hospital Davangere, India all right to use the details.