User:Sedigheh Daneshvar/My Publications/Evaluation of ant.-post. changes of skeletal class II malocclusion through treatment with Twin block appliance

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Evaluation of ant.-post. changes of skeletal class II malocclusion through treatment with Twin block appliance

Contents

Introduction:

One of the most common abnormalities is class II malocclusion which has the most prevalence in human population after class I malocclusion. About 15-25% of Americans and north European are involved. According to researches, most class II abnormalities in USA are due to mandibular deficiency. So use of easy proper and effective treatment to remove this abnormality by Gpor specialist is important. The ideal solution to treat class II skeletal malocclusion is growth modification which should be done in growth spurt (Rapid growth period during mixed dentition before puberty) so that patient's growth potential exist.

This way we can remove the abnormality through changing growth pattern and velocity (speed) functional app. is a growth modification appliance.

By the definition a functional app. is an appliance is an appliance that can change mandibular position by keeping it open and forward. (1) The pressure produced from muscles safe tissue is transferred to teeth and skeleton and growth changes and movements.

Regarding this theory in this study we try to introduce Twin block functional app. (Designed by Mr. Clark) to evaluate the result of its application. Twin block functional app. which is made in 2 parts in comparison with other functional app. has extra advantages such as using at the same time or separately in upper or lower jaw, sloped occlusal surfaces in ant. and lat. movements give more freedom to the jaws also they have less interruption in natural movements.(2) This way we introduce one of the newest and most useful functional app. to dentistry world.

Method and material:

The material consisted of 10 patients including 5 girls and 5 boys ranging in age from 7 years and 7 months to 12 years and 6 months from private practice of Dr. E. Vahid Dastjerdi.

The criteria for case selection were as follows:

  1. All the patients were in involved in class II division I malocclusion.
  2. All of them were in mixed dentition age (7-13 years old).
  3. All the patients were Iranian and muslems and residing in Tehran.
  4. None of them had used orthodontic treatment before.
  5. None of the patients didn't have tooth extraction before or during treatment with Twin block App.

We used quasi experimental method: before and after clinical trial. After subscription and patient selection questionnaire was filled by them. The required records including study casts and lateral cephalometry and panorex radiographs were produced in 2 stages: before and after treatment with Twin block functional app. patients were advised to produce radiographs at the same special center. All the lateral cephalometry radiographs were studied on negatoscope in a dark room and cephalometric tracing was performed using acetate cellulose pad (cephalometric tracing pad) and ethod (0.5).The pired T-Test analysis was performed on cephalometric results by computer. It has to be mentioned the treatment duration for all patients took 12 to 17 months and during this period patients were visited and controlled every 4 to 6 weeks.

a) Independent index:

Malocclusion class II treating by Twin block functional app. (Designed by Mr.Clark).

b) Dependent variable:

Cephalometric index:

image:Cephalometric_index.jpg

c) Demographic variable:

  1. Age: All of the patients' age was between 7 years and 7 months to 12 years and 6 months.
  2. Sex: The patients were both male and female.
  3. Race: The patients were Iranian, Moslem and residing in Tehran, Iran.

d) Interventional variable:

  1. Patient cooperation: The patients who don't continue the treatment to the end of retention will be omitted of the samples.
  2. Duration of treatment: It was between 12-17 months.

Landmarks(references points):

1-N(Nasion), 2-S(Sella), 3-A(Point A), 4-B(Supramental, Point B), 5-P(Pogonion),6-Go(Gonion),7-Me(Menton),8-Ar(Articulare),9-PPOCC(Post. point of occlusal plane),10-IS or 1(Incisor Superius),11-Ap 1(Apical 1),12-Ii(Incisor Inferius).

Plans:

1-SN,2-Go-Me(Mandibular Plane),3-Occlusal Plane.

Results:

Sample's cephalometric skeletal changes in vertical direction and dental changes and also discrepancies of values, before and after treatment with Twin block app. (Designed by Mr. Clark) were statistically analyzed.

Results are decrypted as below:

  1. The mean of SNA angle is 78.8° SD= ±3.8 before treatment and 78.2° SD= ±1.3 after that. The mean discrepancy of values is -0.6° SD= ±1.3 which is not statistically significant.
  2. The mean of SNB angle is 72.3° SD= ±3 before treatment and 73.8° SD= ±3.6. The mean discrepancy of values is -2.1° SD= ±1 which is statistically significant.
  3. The mean of ANB angle is 64° SD= ±1.8 before treatment and 4.3° SD= ±1 after that. Mean of discrepancy of values is -2.1° SD= ±1 which is statistically significant.
  4. The mean of SN-Pog angle is 73.4° SD= ±3.5 before treatment and 74.7° SD= ±4.5 after that. The mean discrepancy of values is 1.3° SD= ±2 which is statistically significant.
  5. The mean of Witt's appraisal is 1.8° SD= ±2.6 before treatment and -0.5° SD= ±1.5 after that. The mean discrepancy of values is -2.3° SD= ±3.3 which is statistically significant.
  6. The mean of mandibular length (Ar-Pog) is 99.8° SD= ±7.9 before treatment and 105.8° SD= ±7 after that. The mean discrepancy of values is 6° SD= ±3 which is statistically significant.
  7. The mean of 7-SN angle is 104° SD= ±6.5 before treatment and 99.3° SD= ±5.4 after that. The mean discrepancy of values is -4.7° SD= ±5.7 that this decrease is statistically significant.
  8. The IMPA is 95.7° SD= ±8.8 before treatment and 95.7° SD= ±8.8 after that. The mean discrepancy of values is 0° SD= ±3.8 which indicate this landmark remained unchanged during treatment.
  9. The mean of interincisal angle is 121.3° SD= ±10.10 before treatment and 4.7° SD= ±6.7 after that. This increase is statistically significant.

Discussion:

Skeletal changes;

  1. As a result of treatment with Clark app. there was insignificant statistical decrease of SNA angle value which indicated the inhibition of ant. movement of point A resulting from the change in maxillary plan slope (inclination).

This insignificant head gearal effect matches Tumer(3), Mills and McCulloch's(4) et. al, Trenouth(5) and Mr. Ian Land(6) suggestions but has no adaptation to Mr. Illing(7) et. al suggestion.

  1. SNA angle had significant increase through treatment with Clark app. which indicates ant. movement of point B resulting from ant. Growth of mandible that matches Trenouth, Tumer et. al, Mills et. al and Ian Land et. al investigation. Sidhu(8) et. al concluded Herbst app. changed sagital position of mandible which is one of the factors to correct over jet, that presents desired insignificant ant. rotation of mandible. Mr. Devincenzo and Winn(9) have also reported significant statistical increase in SNB angle through treatment with funtional appliance.
  2. As a result of treatment with Clark app., significant statistical decrease in ANB angle resulting from increase of SNB value. This finding matches Mr. Illing's, Mr. Ian Land et. Al's, Mills's and McCulloch's and Tumer's and Trenouth's investigations.
  3. In SN-Pog angle, treatment with Clark app., shows significant statistical increase which indicates forward and downward movement of mandible. This result matches Mr. Illing et. al's findings.
  4. As a result of treatment with Clark app. significant statistical decrease was produced in Witt's appraisal indicating ant. movement of point B and correction of class II discrepancy and also creation of class I relationship.
  5. Whole mandibular size (Ar-Pog) had significant statistical increase through the treatment with Clark app. that matches Mr. Illing et. al's and Trenouth's and Mr.Ian Land et. al suggestions.

Dental changes;

  1. Through treatment with Clark app. significant statistical decrease of 1-SN (-4.7) was observed, indicating retro inclination of maxillary incisors that matches Mr. Illing et. al's and Mr. Ian Land's et. al and Mill's and McCulloch's and Tumer's suggestions.
  2. IMPA angle remained constant during treatment with Clark app. that doesn't match Mr. Illing's et. al and Mr. Ian Land's et. al suggestions, because Mr. Illing et. al in their investigations have reported that among Bass, Bionator and Twin block appliances, treatment with Bass app. has the minimum retro inclination of IMPA angle, in which Bionator app. max proclination of lower incisors and Twin block app. had moderate change. Mr. Clark(10), also, have reported same movement in lower incisors through treatment with functional appliance.
  3. Through treatment with Clark app. significant statistical increase of interincisal angle was produced which indicates lingo version of lower incisors.
  4. Retroinclination of maxillary incisors with constant IMPA through treatment with Clark app. had been effective in the correction of over jet gathering with mandibular repositioning and forward growth caused noticable decrease in over jet.

Summary:

Skeletal changes after treatment with Twin block are as followed:

  1. Insignificant decrease in SNA angle shows inhibiting ant. movement of point A or the maxilla growth limitation.
  2. Significant increase in SNB angle shows ant. movement of point B which is because of ant. mandible growth.
  3. Significant decrease in ANB angle followed by insignificant decrease in SNA and significant increase in SNB. Shows repositioning and forward growth of mandible which ends in improving class II skeletal relation.
  4. Significant increase in SN-Pog angle shows ant. movement of point Pog and Witt's decrease shows decreasing dysplasia between the base of jaws.
  5. Significant statistical increase in mandible (Ar-Pog) about 6 mm, ends in improving of mandible retrusion.

Dental changes after treatment with Twin block are as followed:

1-Significant decrease in 1-SN angle and consistent of IMPA angle and significant increase in interincisal angle are position results of Twin block appliance. In act consistent of IMPA angle shows treating the class II skeletal deficiency.

2-Retroinclination of maxilla incisors and consistent of IMPA with forward growth and repositioning of mandible after treatment with Twin block results in noticeable increase in over jet.

References:

  1. Proffit W.R. and Fields H.W.,"Contemporary Orthodontics", Second Edition, 1993, Chapter 1, 2-22.
  2. Graber T.M., Rakosi T. and Petrovic A.G.,"Functional Appliance Diagnosis and Treatment", Second Edition, 1997, Chapter 13, 268-298.
  3. Tumer N."Comparison of the effects of monoblock and twin-block appliances on the skeletal and dentoalveolar structures", Am J Orthod Dentofacial Orthop 1999;116:460-8.
  4. Christine M. Mills and Kara J. McCulloch"Treatment effects of the twin block appliance: A cephalometric study", Am J Orthod Dentofacial Orthop 1998;114:15-24.
  5. Trenouth M.J."Cephalometric evaluation of the Twin-block appliance in the treatment of Class II division I malocclusion with matched normative growth data", Am J Orthod Dentofacial Orthop 2000; 117:54-9.
  6. Ian Land D., Medsio M. And Sandler P.J., "The Effect of Twin Block: A Prospective Controlled Study", American Journal Of Orthodontics And Dentofacial Orthopedics, 1998; 113: 104-110.
  7. Illing H.M., Morris E.O. and Lee R.T.,"A Prospective Avalution Of Bass, Bionator And Twin Block Appliance, Part 1, The Hard Tissue", European Journal Of Orthodontics, 1998; 20: 501-516.
  8. Sidhu M.S. and Sidhu S.S.,"Cephalometric Analysis Of Changes Produced By A Modified Herbst Appliance In The treatment Of Class II Division I Maloccusion", British Journal Of Orthodontics, 1995; 22: 1-12.
  9. Devincenzo J.P., Huffer R.A. and Winn M.W., "A Study In Human Subject Using A Device Designed To Mimic The Protrusive Functional Appliance Used Previously In Monkeys", American Journal Of Orthodontics And Dentofacial Orthopedics, 1987; 91: 213-224.
  10. Clark W.J."A Twin Block Techniques A Functional Ortnhodontics Appliance System", American Journal Of Orthodontics And Dentofacial Orthopedics, 1988; 93:1-18.
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