Wednesday, November 30, 2011

Crowding: Timing of Treatment

Resident Name: Elliot Chiu

Article Info

Title: Crowding: Timing of Treatment

Author: Anthony Gianelly DMD, PhD, MD

Journal: The Angle Orthodontist 1994

Main Purpose: To describe the best time to treat mandibular incisor crowding.


Mandibular models of 100 pts in mixed dentition were analyzed. Average crowding of 4.5mm was found in 85/100 models. The sizes of permanent successors were estimated using the Moyer’s analysis.

“What would the incidence of crowding be if a lip bumper were used to move the first molars distally 1mm?”

Key Points

-Ample space for alignment can be achieved in 84/100 of these patients

-Distalization of over 1mm is associated with post-retention irregularity

-In the remaining 16/100 patients, the author prefers to extract the 1st premolars

-The key time to treat mandibular incisor crowding is in the late mixed dentition: after the eruption of the 1st premolars


The author’s conclusions are based on a theoretical treatment. This article would be stronger if actual treatment was done and the conclusions could be proved with evidence.

After 1mm of distalization with a lip bumper, what is done for retention?

Lower arch perimeter preservation using the lingual arch

Resident’s Name: Matthew Freitas
Author(s): Joe Robellato et al.
Journal: Journal of Orthodontics and Dentofacial Orthopedics
Year. Volume (number). Page #’s: 1997. 112:4. 449-455.
Major topic: Ortho

-To determine whether mandibular lingual arch maintained arch perimeter in the transition from mixed to permanent dentition and if so whether it was effective in preventing mesial migration of first permanent molars.

-30 patients randomly assigned to tx group (16) or control group (14).
-Study models, Ceph, and tomograms were taken of each patient at the beginning and end of tx.

-Lingual arch can helped to reduce arch primeter loss, but at the expense of slight mandibular incisor proclination.

-Take home: Lingual arch is a good tx option for patients that have early bilateral loss of 2nd primary molars, additional loss of adjacent primary teeth, and/or crowding of the anterior mandibular incisors. If your patient would benefit from proclination of the mandibular incisors then the lingual arch may help. However if they are edge to edge occlusion then maybe lingual arch is not ideal; if not, consider band and loop.

One-phase versus two-phase treatment

Kyung-Hong Cal Kim

One-phase versus two-phase treatment

Author: Anthony A. Gianelly, DMD, PhD, MD

American Journal of Orthodontics and Dentofacial Orthopedics Nov 1995

To determine the cost-effectiveness of 2-phase orthodontic treatment

Key Points:
-According to the Journal of Clinical Orthodontics survey, about 25% of the patients under orthodontic treatment receive 2-phase treatment (1/3 when excluding 20-25% adult patients).
-90% of all growing patients can be treated successfully with 1-phase treatment (not counting passive space maintainers and habit appliances) if the treatment begins at late mixed dentition stage (“all primary teeth have exfoliated except ‘E’s).
-The other 5-10% include crossbites with functional shifts and class III malocclusions
-Two of the most common orthodontic problems include crowding in class I or II malocclusions and class II malocclusions.

-Crowding can be resolved readily in up to 84% of all patients with treatment that need to be started no earlier than the late mixed dentition stage of development because the space necessary for alignment in most patients with crowding is gained principally by “E” space control.
-Main objective of the non-extraction approach is to gain intercanine width by actively or passively by expanding the arch through early intervention.
-Passive expansion of lower arch involves maxillary RPE & lip bumper, which, according to two studies by Sandstrom et al and Adkins et al, will yield no more than 1mm in intercanine width.
-Active expansion of lower arch is entirely in dental nature, and majority of investigations support that intercanine expansion in mandibular arch is not stable and will result in total relapse of the treatment gain over time.
-Serial extraction is a preferred method of treatment as its “diagnostic-observation phase” does not require active treatment involving appliance placement.

Class II malocclusion:
-If treatment is started in the late mixed dentition stage, at least 90% of all children with Class II malocclusion can be corrected with 1-phase treatment.
-One method of correction involves converting Class II malocclusion into Class I with spacing
-Molars can be moved distally at this age 1 to 2 mm per month, while sufficient mandibular growth occurs at this period of time to aid in correcting Class II malocclusion.
-Insufficient information supporting the effectiveness of early intervention to correct maxillary prognathism/mandibular retrognathism
-Treating Class II with mandibular retrognathism: age-dependent mandibular growth response study shows that there is a greater mandibular growth observed in patients AFTER 10.5 years of age.
-Treating Class II with maxillary prognathism: Little orthopedic effect by early intervention with extraoral appliances (~1mm), reappearance of corrected overjet during pause between phase I and phase II observed.

Assessment of the Article:
I thought it was an interesting article to answer the question we often ask ourselves about whether to treat now or wait until later. I would like to have seen more evidence supporting the 2-phase group, especially since the author stated 1/3 of total growing patients under ortho tx receive 2-phase tx. I felt the article was somewhat biased towards 1-phase, extraction treatment (and the author didn’t seem to hide the fact). What I got out of the article was that the course of treatment should be case-specific considering its cost-effectiveness. If a specific case calls for an early intervention, knowing the limitation and likelihood of relapse in the long run, parents should be properly informed of what to expect from the treatment and begin the treatment as indicated with a realistic goal in mind.

Agenesis of mandibular second premolars. Spontaneous space closure after extraction therapy: a 4-year follow up

Authors: Mamopoulou, A., Hagg, U., Schroder, U. and Hansen, K.

Journal: Eurpoean Journal of Orthodontics, 1996 v. 18 589-600

Purpose: The purpose of the study was to determine space closure and occlusal changes in patients with agenesis of the mandibular second premolar after extraction of the mandibular second primary molar and maxillary second premolar on the side where agenesis was.

-11 subjects were in the study, followed over 4 years
-Treatment began when the first premolars came into occlusion
-Dental casts were taken at 1,2, and 4 years, Ceph x-ray taken at 2 and 4 years
-The following measurements were taken on casts:
space closure, sagittal movements, rotational movements, and tipping of the
first molars and first premolars and dental midline shift

-The following measurements were followed on ceph:
sagittal movement of the incisors

-Most of the extraction space closed during year 1 (Mx: 55%, Mn 46%)
-At year four, 89% (mean residual space= .9mm) of space closed in the maxilla, 80% (mean residual space=2mm) in the mandible
-Maxillary Movements were the following: distal movement, rotation, and tipping (during first year)
-Mandibular Movements were the following: mesial movement, rotation, tipping of the first molars and distal movement and tipping of the first premolars
-Unilateral extraction had no effect on the maxillary midline, but there was a statistically significant mandibular dental shift to the extraction side.
-In this study, extractions did not effect overbite, overjet, or incisor inclination

Overall, this study is applicable to patients who have a normal occlusion and a missing mandibular second premolar. In this situation extraction of the mandibular second primary molar and compensatory extraction of the maxillary second premolar can be recommended as a treatment plan. Nevertheless, as we see in this study, space closure is not 100%, therefore, as mentioned in the article, additional space closure -i.e. ortho treatment, may be necessary.

Changes in Soft Tissue Profile after Extraction Therapy

Resident: Swan
Article Title: Changes in the Soft Tissue Profile After Extraction Orthodontic Therapy
Authors: Darendeliler, et al.
Journal: Journal of Dentistry for Children, 73:3, 2006
Main Purpose: Evaluate effects of different growth pattern and the use/nonuse of headgear on the soft tissue profile in patients treated with fixed edgewise mechanics and 4 first premolar extractions.
Methods: 41 patients treated by the authors were selected according to mandibular plane angle (used to determine vertical growth pattern--either mesiodivergent 27-37 degrees, or hyperdivergent 38+ degrees). Mean age of patients=14.5. years.

Patients divided according to growth pattern and treatment type (use or nonuse of headgear to increase anchorage). Cervical headger used for mesiodivergent, high pull HG for hyperdivergent. The decision to extract was made with respect to total arch crowding (more than 7 mm). Mean tx time 2 yrs 10 months. Cephs taken before/after tx and data analyzed using ANOVA.

Steiner upper lip: hyperdivergent group; difference between HG/no HG stat. significant. headgear group; diff between mesio/hyperdivergent stat. significant

Steiner lower lip: hyperdivergent group; diff between HG/no HG stat. sig.

Vertical change in A': hyperdivergent group: difference bet. HG/no HG stat. sig.
headgear group; diff. between mesio/hyper stat. significant.

Sagittal change:
Studies indicate that effects on soft tissue profile seem to be influenced more by nose and chin growth than by extraction therapy. In this study, retraction of lips did not show sig differences between mesio and hyperdivergent growth nor between HG usage or none. Lips did show significantly greater retraction as a result of headgear usage with hyperdivergent growth pattern however. Avoid HG usage in hyperdivergent patients!
Vertical Change:
All groups showed increased vertical changes. Hyperdivergent group showed greatest increase.
Nasolabial angle:
No significant changes between groups
Labiomental angle:
No sig changes between groups

1. Avoiding premolar extractions based on potential detrimental soft tissue changes is not justified.
2. undesirable soft tissue changes are most often not a result of tx, but rather a result of growth
3. hyperdivergent profiles are subject to excessive changes. Avoid headgear use in these patients especially if lips are retruded at beginning of treatment.

Assessment: This study didn't use non-extraction controls to assess whether soft tissue changes were excessive. Those have been done and affirm that this shouldn't be a deciding factor when making the extraction/non-extraction decision. Dr. Brennan teaches that soft tissue retraction=about 1/2 insisor retraction. Take home from this study is to be careful with vertically sensitive patients.