The Williams appliance was developed by Dr. Jeff Williams who practices orthodontics and pediatric dentistry in Bartlett, Tennessee, USA. The appliance was originally designed to be used on the mandibular arch in the mixed dentition. The two basic objectives of the appliance are to develop the transverse width of the lower dental alveolar base, and to recover any lost mandibular arch length.
There is a great deal of controversy within the profession as to the success or failure of arch development, sometimes mistakenly referred to as arch expansion. It is this author’s opinion that this subject is well addressed in the text by Enlow and Hans entitled “Essentials of Facial Growth” published by Saunders, ISBN 0-7216-6106-8.
The following observations are clearly stated in this text:
- 1. The body of the maxilla, as well as the dental alveolar base upon the maxilla, is comprised of dermal bone which has developed from the ectoderm. Dermal bone growth is primarily driven by function, not by genes.
- 2. The body of the mandible is comprised of chondral bone which has developed from the mesoderm. Chondral bone growth is primarily driven by genes, not by function.
- 3. The dental alveolar base upon the mandible is dermal bone and thus effected by function not by genes.
These concepts form the foundation of functional orthopedic and orthodontic therapy. They also provide the clinician with the insight to diagnose and treat growth related malocclusions. For example, the orthopedic objective of the Williams appliance is to develop the transverse size of the mandibular dental alveolar base. The orthodontic objective of the appliance is to recover any mandibular arch length that may have been lost.
The Williams appliance is banded on the deciduous second molars in the “early” mixed dentition, and on the permanent first molars in the “late” mixed dentition. It consists of a special midline expansion screw, attachments contacting the lingual surface of all of the posterior teeth, and a nickel titanium arch wire that can be activated against the lower incisors. Separators are places on the patient while the appliance is being fabricated using the indirect banding technique.
A standard orthodontic button is bonded to the most instanding lower incisor or incisors. The lower arch is isolated for moisture control and the bands cemented using orthodontic glass ionomer band cement. If the appliance is banded on the deciduous second molars these teeth should be acid etched prior to cementation to enhance band retention. The lingual arch wire is activated by engaging it beneath the button on the incisor or incisors.
Protocol for Therapy:
The maxillary arch must always be developed at least one month in advance of the mandibular arch. This eliminates the “trapping effect” of the maxilla on the mandibular alveolar process which is in turn the underlying cause of the lower constriction. A maxillary Schwarz appliance is usually employed to obtain the upper arch development, and may be used in conjunction with a forward pull extra oral face mask.
The expansion screw in the Williams appliance is then activated by the parent using a special intra oral key. Both upper and lower arches are usually developed to the Schwarz-Korkhaus measurements.
The .014 lingual arch wire can be reactivated by replacing a longer new wire of the same gauge. The old wire is removed from the lingual tubes and used as a guide for cutting a new wire that is 2mm longer on each side. The new wire is then placed back into the lingual tubes and then flexed under the button on the incisor / incisors. The effect is to align the lower incisors and to use the reciprocal force to distalize the lower molars.
A very common modification of the Williams appliance is to use buccal tubes on the molar bands when the appliance is placed on the permanent first molars. Delta Force brackets can be placed on all of the permanent teeth that have erupted anterior to the permanent first molars. A .020 x .020 thermal activated, multi-gradient force, nickel titanium arch wire is used in conjunction with the Williams appliance to level, align, and torque the teeth as the arch is being developed.
The Williams appliance can be modified for treating a Class III patient by adding bilateral buccal arms with elastic hooks for intra-oral Class III elastics. This modification is usually employed in conjunction with a maxillary arch development appliance, and forward pull extra-oral traction.
Maxillary Williams Appliance:
The original mandibular Williams appliance was modified by Dr. Elliot Stevenson-Smith, a general dentist in London England, for use on the upper arch. His design utilizes a trans-palatal expansion screw and an ALF type palatal arch wire that can be activated to create a force for sagittal arch development.