Histomorphometric and biomechanical analyses of Self-drilling Orthodontic Temporary anchorage devices (TADs)

Dr Mahfud Al-Atty BDS, MSc, PhDDepartment of Orthodontics

Faculty of DentistryUniversity of

BenghaziLibya

Dr Amer MaherBDS, MSc

Department of Orthodontics

Faculty of Dentistry Suez Canal University

Egypt

Histomorphometric and biomechanical analyses of Self-drilling Orthodontic Temporary anchorage

devices (TADs)

introduction Primary stability shows how much the screw is locked into

the bone that would be manifested as a stable anchorage for the various clinical applications (an indicator for success rates)

The stability of TADs has been attributed to mechanical (device design and dimensions) and biological factors including the nature of the surrounding bone particularly bone density.

introduction

Objectives

To evaluate: bone density torque resisting force In relation to two types of self-drilling miniscrews (TADs)

Tapered TADs Cylindrical TADs

The animal Six healthy adult mongrel dogs (1-3 years) were

selected and properly fed.Hosted in separate cages in the animal house of

Suez Canal University. All Dogs had their permanent teeth fully erupted.

Methods

Preparation of the animal Food was withheld overnight before the operation. Each dog was pre-medicated with intramuscular

injection of chloropromazine hydrochloride in a dose of 1 mg/Kg 10-15 minutes prior to the induction of general anesthesia.

General anesthesia was conducted with intravenous injection of thiopental sodium 2.5% until the main reflexes were abolished

Misr Co. Pharm. Industries, El-Matria, Cairo, Egypt Egyption International Pharm Industries Co. A.R.E.

Methods

The sample consisted of Group 1: Six tapered self-drilling TADs (1.4mm neck diameter and

1.3mm diameter near the apex)

Group 2: Six cylindrical self-drilling TADs (1.4mm neck diameter, 1.4mm diameter near the apex)

Sample

SH 1413-10, Dentos, Daegu, Korea

Group 1: Parallel to the occlusal plane, each TADs of group 1 screws was inserted in the right buccal side between the roots of the maxillary third premolar (P3); the threaded intra-bone part was 10mm long.

Group 2: Parallel to the occlusal plane, each of group 2 screws was inserted in the right buccal side between the roots of the maxillary first molar (M1); the threaded intra-bone part was 10mm long.

Methods

L-Shaped costume made acrylic guide stint was used to insure that TADs were inserted perpendicular to the cortical plate of maxilla.

Methods

• Swabbing the area with disinfectant.

• Infiltration local anesthesia,

• Drill-free TADs were one-step inserted in the designated sites.

• Force was manually applied using palm and thumb grip until the penetration of bone, then pen grasp grip was used to rotate the miniscrew till it was completely inserted, with only the its head exposed in the oral cavity.

Methods

• Immediate, constant and continuous load was applied using 8mm long, heavy short Nickel Titanium coil spring.

• It was ligated between the heads of the two types of TADs; the two heads were apart by a distance range of (20-26mm) .

a b

a b

Methods

a b

a b

• The load lasted for 12 weeks period, then TADs were removed by using a torque screwdriver .

(NT15-8H) , Dentos, Daegu, Korea (LHD-B-TG), Dentos, Daegu, Korea

Methods

Bone density assessment:For evaluation of bone density in the areas of interest, occlusal radiographic views were taken at different time intervals: pre-insertion, just after insertion (T0), after 4 weeks (T1) after 8 weeks (T2) and after 12 weeks (T3).

Methods

• Each dog was positioned in a supine position to the table of the x-ray machine.

• Radiographs were taken using an X-ray beam of 60kv-200ma.

• The distance between the cone and the table was fixed at about 55cm. The X-ray beam was centered using a light beam guide in the machine on the center of the film, and it was perpendicular to the occlusal plane .

Eureka, USA

Methods

Using IDRISI Kilimanjaro computer software, the peri-implant area surrounding the apical one third of miniscrew was studied measuring the amount of grey color. By applying the digitize effect of the program, special dots could be applied just over the thread interface of the TADs, and the area surrounding all the apical one third of the TADs. Then the program shades the selected area. Using this program, the area surrounding the implant in the digitized radiographs was divided into five zones with standardized width. The denso-metric analysis of five zones was measured in both groups.

Clark's labs, Clark's university, USA

Methods

Methods

Statistical analysis: Statistical analysis was carried out using SAS program. Independent T- test was run to compare the measurements of the bone density pre-insertion of TADs between roots of M1 and P3, and the bone density post-insertion of TADs in the cylindrical and tapered TADs groups (intergroup difference). Independent T-test was run also to compare the removal torque measurements for each TADs type.

SAS Institute, Cary NC, USA.

Statistics

Mean bone density in the five zones in relation the two types of TADs during the follow-up period

Results

126.54

157.67

111.07116.2

139.09

161.39

190.74

201.38

100

120

140

160

180

200

220

T01 T11 T21 T31

Tapered Cylindrical

The 1st Zone

Results

124.55

156.06

109.81115.13

136.62

160.26

189.85

200.7

100

120

140

160

180

200

220

T02 T12 T22 T32

Tapered Cylindrical

Statistics

The 2nd Zone

123.83

155.45

109.422114.74

135.88

159.75

189.23

200.39

100

120

140

160

180

200

220

T03 T13 T23 T33

Tapered Cylindrical

The 3rd Zone

Results

123.36

155.71

108.96114.32

135.5

159.33

188.88

200.36

100

120

140

160

180

200

220

T04 T14 T24 T34

Tapered Cylindrical

The 4th Zone

Results

100

120

140

160

180

200

220

T05 T15 T25 T35

123.11

108.73

133.64

188.55

155.18

114.05

158.91

200.32

Tapered Cylindrical

The 5th Zone

Results

Results

0

0.2

0.4

0.6

0.8

1

1.2

1.41.208

0.75

Cylindrical Tapered

The mean removal torque of both miniscrew types.

Conclusions

• Cylinderical TADs showed significantly higher peri-implant bone density in comparison with the tapered TADs immediately at insertion and after 8 weeks post-insertion.

• Both cylindrical and Tapered miniscrews showed no significance difference regarding peri-implant bone density after 4 weeks and 12 weeks post-insertion.

• Cylindrical TADs showed higher resistance to removal compared to tapered TADs after 12 weeks loading period.

• Both types of miniscrews showed stability during the whole 12 weeks period despite immediate loading.

Conclusions

Thank You!