Non-extraction orthodontics via dental arch expansion - Can optimal esthetics, stability and preservation of periodontal health all be attained? by Robert Boyd Boyd's overall hypothesis is that, for moderate to severe malocclusions, two-phase orthodontic treatment (with expansion as needed) is more effective than single-phase treatment in the permanent dentition,. The two reasons Bob gave to validate this hypothesis are that there is less periodontal liability (apical root resorption, bone loss, and gingival recession) with two-phase treatment, and also better long-term esthetic results. Regarding facial esthetics, Boyd explained that he treats children and adolescents to the adult face, meaning that he leans towards a more full profile in his finished cases. He feels that by using a two-phase treatment, with expansion instead of extraction in borderline cases, he is able to achieve better long-term esthetic results, considering the aging effects of continued growth of the nose and the chin. He said that when he pushes the limits of expansion he does so to obtain a full smile. Bob stated that lip incompetence diminishes with age, citing a personal communication from Dr. Cetlin and also a study done by Vig and Brundo. Boyd's overall goal for the first phase of treatment is to minimize the amount of later treatment in the permanent dentition. His specific goals for the first phase are to: establish ideal or improved overjet/overbite, correct or improve skeletal problems, remove functional problems (functional shifts, etc), improve self-image (esthetics of a full smile), eliminate causes of malocclusion (habits, airways, etc), and develop a normal dimension of the arches (provide excess space of >2mmm per arch). Bob mentioned that fewer extractions are being presently performed than in the past, which indicates that "borderline" cases are now being treated non-extraction. He stressed that the benefits of two-phase treatment are the following: a decreased need for extractions of permanent teeth due to crowding (greater expansion of tissues possible without gingival recession), increased potential to favorably modify skeletal pattern because of longer treatment time during two growth periods, ability to remove functional problems (airways, habits, anterior cross-bite, functional shifts, etc), decreased liability for incisor damage in Class II patients, improved esthetics from greater ability to position anterior teeth ideally with less thinning of gingival tissue, enhanced self image at an earlier age, and decreased damage from palatal impingement with deep bite. Bob explained that in adults it is not advisable to move incisors labially because of the potential to develop bone dehiscences and gingival recession, particularly patients who have thin periodontal tissues. He stated that, in contrast, it is possible to move the lower incisors labially in the mixed dentition without damaging the labial tissues. He explained that thinning of the labial tissues may be minimized if intrusion of incisors into a wider portion of the ridge is combined with labial movement; that a 5mm forward and intrusive movement of the lower anterior teeth in the first phase can be done with no recession occurring. Bob stated that less gingival recession is observed, both short and long-term, around permanent teeth that have erupted through a widened alveolus from expansion in the mixed dentition. Bob explained that, based on the Moyers Michigan growth data of untreated individuals with excellent occlusions, the difference between crowded and non-crowded dentitions is not the size of the teeth but the narrowness of the arch. Thus, he said that the question is whether the width of the mandibular arch (basal bone) can be increased. Bob referred to longitudinal implant studies carried out by Baumrind, Useri, Gandini, all of whom documented increases in basal bone width of the mandible and the maxilla during the growth period. Boyd suggested that these studies support the concept of expansion in the lower arch. He asked how much arch perimeter may be gained for each millimeter of expansion. To answer this question Bob referred to a study, published by Germane, who determined that incisor advancement is nearly four times as effective at increasing arch perimeter as is molar expansion. To finalize this portion of his presentation Bob stressed that his main reason for pushing the limits of expansion is to obtain a full smile in order to anticipate the facial changes that will inevitably occur due to the aging process. Bob emphasized that one of the important reasons for doing two-phase treatments is that moderate and severe malocclusions increase in severity from mixed to adolescent permanent dentition; that crowding and ectopic eruption significantly increase as the succedaneous teeth erupt and that they are correlated with increased risk of periodontal damage. Boyd explained that patients with decreased vertical jaw relationships (Class II, Div 2) in the mixed dentition, generally have increased bite depth in the permanent dentition and potential palatal impingement associated with forward rotation of growth. Pertaining to the periodontal aspects of expansion, Bob explained that apical root resorption is not greater with expansion; that with extraction treatment root resorption may be aggravated due to the increased treatment time with fixed appliances, and also due to the bodily movement necessary during space closure. Bob mentioned that an advantage of two-phase treatment in regards to apical root resorption is that roots with developing apices are less at risk for root resorption. Reasons given for this fact are that the undeveloped apices have a better vascular supply and PDL cellularity associated with growth, and that they also have a better remodeling capacity and improved muscle adaptation. Bob explained that it has been documented that periodontitis begins in the teenage years; that, ideally, treatment with fixed appliances should be avoided, if possible, once the patient reaches the teen years. Another important fact stressed by Bob is that single-phase treatment increases the treatment time with fixed appliances, which can lead to increased loss of attachment when compared with two-phase treatment. Boyd cautioned that although there are many advantages of the two-phase treatment the clinician must be aware of the disadvantages. He cited the following disadvantages: longer treatment time may lead to increased cost of treatment, compliance "burn-out" may occur, patient expectations influence the clinician to spend too much time perfecting the first-phase alignment and occlusion, if the clinician does not achieve significant improvement of malocclusion the patient may elect not to have the second-phase of treatment, and that long-term stability is unknown especially with expansion of more than 4mm. To finish his presentation Bob summarized the many benefits of two-phase treatments: Potentially more beneficial for periodontal tissues (less apical root resorption, bone loss and recession) due to decreased susceptibility of children to periodontal problems and to root resorption during phase 1, and also due to decreased treatment time in phase 2 Eliminates functional problems earlier (habits) Decreases need for extractions Potential for better esthetics, earlier (fuller smile, improved lip incompetence) Ability to effect greater reduction of skeletal deformity (if treatment is not completely satisfactory there is an additional chance in the second phase) Lower risk of trauma to protruded front teeth Reduces likelihood of permanent teeth becoming impacted Better compliance in children than in adolescents Bob handed out a very extensive and useful summary of his presentation, which included all the references he used to prepare his highly informative lecture.