The purpose of Dr. Southard’s presentation was two-fold: First, to examine the application of evidence-based clinical decision-making in orthodontics and second, to promote critical thinking in the practice of orthodontics.

Dr. Southard stated that by its very nature, a talk like this will challenge what is considered conventional wisdom by most of us.

How do we use evidence-based decision-making in orthodontics?

Traditional models of health care, including the delivery of orthodontic treatment, are largely experience based, not evidence based. Evidence-based health care involves making diagnosis, recommendation of therapies and assessment of cost benefits based on identification, evaluation and application of relevant information from the best studies and science available. This is a goal desired by all orthodontists, according to Dr. Southard.

Evidence-based clinical decision-making requires careful definition of the question, or the problem, followed by identification of the most relevant and valid literature looking for the facts or truth. Defining the question can be easy, but identifying the most valid literature can be difficult. The methodology of studies is important. What type of study is it? Was the methodology sound? What statistical methods were used, and at what confidence levels? It is necessary to hone our critical thinking skills. Dr. Southard provided several examples of the process of evidenced-based clinical decision-making.

Example #1:

It has been stated that the magnitude and direction of mandibular jaw growth contributes significantly to the success or failure of orthodontic treatment of adolescent patients.

How do we predict jaw growth? One method accepted by many is with radiographic analysis of mandibular morphological characteristics defined by Skieller and Bjork in 1984. In this classic work, Skieller and Bjork determined an 86% predictability of mandibular growth rotation.

In a follow up study, Dr. Laurel Leslie assessed the Skieller/Bjork method with the subjects from the Iowa growth study. A 7% predictability was found assessing the defined morphologic characteristics using multiple regression analyses.

Why the difference? Dr. Leslie ran random numbers with the Monte Carlo analysis that mimicked the analysis used in the Skieller/Bjork study and determined that the results simply capitalized on chance. Dr. Southard provided this pearl for evaluating articles in the AJO. In a perfect relationship, r = 1 and r2 = 1 in correlation analysis, or the relationship between "x" and "y".

However, with studies involving humans a correlation of r = . 7 explains about ½ variance, and r >. 7 is clinically significant. Therefore, he advises that before using information from a study for clinical application a correlation should be at least r = . 7. It should also be kept in mind that the information may be statistically significant, but not necessarily clinically significant.

Example #2:

Studies are in our literature by McNamara, Woodside and Pancherz supporting the theory that it is possible to accelerate the growth of the mandible through condylar joint remodeling. The question Dr. Southard asked was whether or not this growth is significant over the long term and suggests that we "read between the lines" in these studies with critical thinking.

Dr. Southard reviewed several studies in this area. A study done by Dr. John Divincenzo on monkeys showed that mandibular length increases at a highly significant level at the age of two years, a significant level at three years, and there was no difference from the control group at four years.

Vislander’s study of functional appliances showed that mandibular change was insignificant, but the maxillary change held up (head gear effect). A long-term study done by Pancherz showed that a Herbst acted like high pull head gear, and that "no long-term effect on mandibular morphology could be verified.

In summary, Dr. Southard stated that functional appliances do have value in orthodontic therapy. Dentoalveolar changes have been verified (the headgear effect on the maxilla). Measured mandibular changes are average. Large changes can occur in individual patients, but some patients get no measurable growth, therefore a significant increase in mandibular length cannot be measured over the long term.

Example #3:

It is one role of the orthodontist’s to provide recommendations and answer to patients, parents and oral surgeons regarding third molars. The belief that third molars cause lower incisor crowding has been around since the beginning of dentistry.

Why do we continue to buy into this belief? What are the facts?

Fact #1: There is a marked increase in crowding through the teen years without retainers. Intercanine width decreases and crowding increases. This continues on into adulthood, long after the third molars have erupted.

Fact #2: Extraction of impacted third molars allows second molars to drift posteriorly and laterally. However, It is a local effect, and no effect on the lower anterior teeth.

Dr. Southard quoted a study that demonstrated crowding of 1mm or greater when third molars are present than in controls without third molars. Other studies show no difference between these groups.

In summary, Dr. Southard stated that there ae many valid reasons for extraction of third molars such as associated oral pathology, a communication with the oral cavity, or recurrent infection. However, extraction of third molars to decrease or prevent lower incisor crowding cannot be supported through current literature and evidence-based clinical decision-making.

Traditionally orthodontic treatment has been based on expert opinion. Dr. Southard feels we (orthodontists) rely too much on authority figures. A recent statement in the JADA supports this: "Dental education leaves a student willing to accept the views of a perceived authority figure without demanding to know the science supporting these views. " Dr. Southard's talk encourages orthodontists to evaluate studies and literature available to make scientifically based decisions in providing clinical care.

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