POST-TREATMENT STABILITY IN CLASS II NON-EXTRACTION AND TWO-MAXILLARY

PREMOLAR EXTRACTION PROTOCOLS

G Janson, J Araki, L Camardella

It has been shown that the two-maxillary premolar extraction protocol has a greater

efficiency than the non-extraction treatment of Class II malocclusions (JANSON 2007)

Introduction

Nonextraction 2 premolar extractions

Studies comparing stability of Class II malocclusion treatment with 4- premolar extractions and non-extraction or 2-

premolar extractions have not found any significant difference in stability between

these protocols (UHDE 1983, LITTLE 1988, SADOWSKY 1982, ELMS 1996, JANSON 2004, PAQUETTE 1992, FIDLER 1995, ARTUN 1996, BIRKELAND

1997, JANSON 2009)

Introduction

Similar studies comparing the 2-maxillary premolar extraction protocol long-term

stability to the non-extraction approach have not been performed (MIHALIK 2003)

Recently, only one study showed similar occlusal stability when comparing non-

extraction and the 2-maxillary premolar extraction protocol (JANSON 2010)

Introduction

Introduction

Stability Class II malocclusions treated with 2-maxillary premolar extractions is

considered to be suspicious by some authors.(LOUGHLIN 1952; REITAN 1958; MAILANKODY 2004)

Objective

The purpose of this study was to compare the cephalometric stability of the overjet,

overbite, molar and canine relationships of Class II malocclusions treated with and

without extractions of 2-maxillary premolars.

Material

180 lateral cephalograms of 60 Class II patients evaluated at T1, T2 and T3, with matching characteristics and divided into

2 groups:

Group 1: non-extraction Group 2: 2-maxillary premolar extractions

MethodsSkeletal and dental relationship

measurements

Pretreatment cephalograms (T1)

Posttreatment cephalograms (T2)

Long-term posttreatment cephalograms (T3) – mean of 8.2 years after the end of treatment.

STABILITY EVALUATION =

Long-term posttreatment stage (T3)

MINUS

Posttreatment stage (T2)

The greater the difference, the greater the relapse.

Methods

Table 1 – INTERGROUP COMPARISON: Results of the intergroup compatibility tests (t and chi-square tests)

Group 1 (n=30)Non-extraction

Group 2 (n=30)2- extractions

Mean sd Mean sd pAGE1 (years) 12.14 1.36 12.87 1.49 0.05AGE2 (years) 14.82 1.55 15.40 1.71 0.17AGE3 (years) 21.98 3.38 24.65 4.05 0.01*Treatment time (years) 2.68 1.04 2.53 0.72 0.94Long-term post-treatment time (years) 7.15 3.26 9.25 3.52 0.02*

Sex distribution(Chi-square tests)

Male (n) Female (n) Male (n) Female (n)0.80

14 16 17 13

Results

Group 1 (n=30)Non-extraction

Group 2 (n=30)2- extractions

TREATMENT changes

Growth Pattern Mean sd Mean sd p

FMA -0.30 2.44 0.59 2.33 0.16SN.GoGn -0.43 2.30 -0.21 2.26 0.71SN.OcclPlane -0.11 6.11 -2.19 6.59 0.21

Table 2 – INTERGROUP COMPARISON: Intergroup comparison of treatment (T2-T1) and long-term post-treatment changes (T3-T2)

Results

Group 1 (n=30)Non-extraction

Group 2 (n=30)2- extractions

TREATMENT changes

Dental Relationships Mean sd Mean sd p

Overjet (mm) -5.01 2.85 -4.33 2.47 0.33Overbite (mm) -2.92 1.50 -2.73 2.53 0.73Molar relationship (mm) -4.44 1.20 0.44 0.69 0.00*Canine relationship (mm) -3.80 1.48 -6.02 1.56 0.00*

Table 2 – INTERGROUP COMPARISON: Intergroup comparison of treatment (T2-T1) and long-term post-treatment changes (T3-T2)

Results

Group 1 (n=30)Non-extraction

Group 2 (n=30)2- extractions

LONG-TERM POST-TREATMENT changes

Growth patternMean sd Mean sd p

FMA -0.78 2.61 -2.39 2.99 0.03*SN.GoGn -1.42 2.47 -2.14 2.92 0.31SN.OcclPlane -2.23 6.16 -1.29 6.00 0.55

Table 2 – INTERGROUP COMPARISON: Intergroup comparison of treatment (T2-T1) and long-term post-treatment changes (T3-T2)

Results

Group 1 (n=30)Non-extraction

Group 2 (n=30)2- extractions

LONG-TERM POST-TREATMENT changes

Dental Relationships Mean sd Mean sd p

Overjet (mm) 0.19 0.97 0.55 1.19 0.21Overbite (mm) 0.98 1.07 1.04 1.26 0.83Molar relationship (mm) 0.16 0.77 0.11 0.96 0.82Canine relationship (mm) 0.19 1.35 1.23 1.51 0.00*

Table 2 – INTERGROUP COMPARISON: Intergroup comparison of treatment (T2-T1) and long-term post-treatment changes (T3-T2)

Results

Table 3 – INTERGROUP COMPARISON: Comparison of long-term post-treatment changes (T3-T2) in subgroups with similar post-treatment canine relationship at T2

Results

Group 1 (n=17)Non-extraction

Group 2 (n=16)2- extractions

POST-TREATMENT stageMean sd Mean sd p

Overjet (mm) 3.06 0.88 3.34 0.66 0.31Overbite (mm) 2.26 1.29 1.97 0.99 0.47Molar relationship (mm) -1.24 0.98 4.04 0.65 0.00*Canine relationship (mm) -0.98 0.58 -1.50 0.92 0.06

Table 3 – INTERGROUP COMPARISON: Comparison of long-term post-treatment changes (T3-T2) in subgroups with similar post-treatment canine relationship at T2

Results

Group 1 (n=17)Non-extraction

Group 2 (n=16)2- extractions

LONG-TERM POST-TREATMENT changes Mean sd Mean sd p

Overjet (mm) 0.26 0.80 0.49 0.93 0.46Overbite (mm) 1.06 0.92 1.24 1.07 0.61Molar relationship (mm) 0.34 0.89 0.42 0.95 0.80Canine relationship (mm) 0.21 1.41 0.81 1.39 0.22

Conclusion

Treatment of Class II malocclusion with or without 2-maxillary premolar extractions have a similar long-term

posttreatment stability.