More by the authors about Palatal Expansion (followed by relevant references):
From geometry you will remember that an increase in the radius of a circle results in an even larger increase in circumference. If there is crowding, it is because there is not enough space. If you widen the dental arch, you will create more space for the teeth, but you will be pushing them into the cheeks, lips, and muscles of the face. The literature demonstrates that widening the dental arch will not be stable. If the teeth are moved slowly, the teeth may move outward, through the bone, and conceivably off the bone.
The upper jaw is comprised of two pairs of bones joined along the midline by the palatine suture. This suture is malleable until a time shortly after puberty in most patients, and expansion can be done very predictably until then. The separation of the suture allows the boney halves to be moved apart. In order for this to happen, the appliance must be activated in a rather aggressive fashion. This rapid expansion is an orthopedic correction where force exceeds the levels suitable for normal tooth movement; the teeth receive such force that they act as the anchor device for the force to be delivered to the bone. They do not move within the bone, and their relationship with the muscles is not modified as the muscles are moved outward at the same time as the bone. The result is a stable widening of the upper jaw. This cannot be done in the lower jaw as there is no suture in the lower. There are surgical techniques that can be used if widening in the lower is desirable.
References:
Garib DG, Henriques JF, Janson G, Freitas MR, Coelho RA.
Rapid maxillary expansion–tooth tissue-borne versus tooth-borne expanders: a computed tomography evaluation of dentoskeletal effects. Angle Orthod. 2005 Jul;75(4):548-57.
The results showed that RME produced a significant increase in all measured transverse linear dimensions, decreasing in magnitude from dental arch to basal bone.
This study evaluated rapid maxillary expansion (RME) dentoskeletal effects by means of computed tomography (CT), comparing tooth tissue-borne and tooth-borne expanders. The sample comprised eight girls aged 11 to 14 years presenting Class I or II malocclusions with posterior unilateral or bilateral crossbite that were randomly divided into two treatment groups, palatal acrylic (Haas-type) and hygienic (Hyrax) expanders. All appliances were activated up to the full seven mm capacity of the expansion screw. The patients were subjected to a spiral CT scan before expansion and after a three-month retention period when the expander was removed. One-millimeter-thick axial sections were scanned parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure maxillary transverse dimensions and posterior teeth inclination by means of a computerized method. The results showed that RME produced a significant increase in all measured transverse linear dimensions, decreasing in magnitude from dental arch to basal bone. The transverse increase at the level of the nasal floor corresponded to one-third of the amount of screw activation. Tooth-borne (Hyrax) and tooth tissue-borne (Haas-type) expanders tended to produce similar orthopedic effects. In both methods, RME led to buccal movement of the maxillary posterior teeth, by tipping and bodily translation. The second premolars displayed more buccal tipping than the appliance-supporting teeth. The tooth tissue-borne expander produced a greater change in the axial inclination of appliance-supporting teeth, especially first premolars, compared with the tooth-borne expander.
Buccheri A, Dilella G, Stella R.
Rapid palatal expansion and pharyngeal space. Cephalometric evaluation. Prog Orthod. 2004;5(2):160-71.
Rapid Maxillary Expansion resulted in an increase in upper respiratory width that often coincided with a reported improvement in nasal respiration.
OBJECTIVES: the aim of this study was to evaluate cephalometrically the upper respiratory airway dimensions before and after rapid maxillary expansion. MATERIALS AND METHODS: rapid palatal expansion was performed on 24 5-9 year old children with adenotonsillar hypertrophy determined radiographically by means of lateral cephalographs. Also, the subjects were questioned concerning their ability to breath through their noses. RESULTS: there was an increase in upper respiratory width that often coincided with a reported improvement in nasal respiration. Adenoid volume was not reduced. CONCLUSIONS: the increase in pharyngeal space and improvement in nasal breathing resulted from an increase in pharyngeal lumen enlargement rather than a reduction in the volume of the adenoid tissue.
Lima AC, Lima AL, Filho RM, Oyen OJ.
Spontaneous mandibular arch response after rapid palatal expansion: a long-term study on Class I malocclusion. Am J Orthod Dentofacial Orthop. 2004 Nov;126(5):576-82.
There was remarkable stability in lower arch width in response to the orthopedic effects of rapid palatal expansion in the early and mid-mixed dentition; this stability was maintained until adulthood.
The purpose of this study was to investigate the spontaneous mandibular arch response to rapid palatal expansion as the sole orthodontic intervention. Particular attention was paid to clinically significant effects and long-term (mean age, 11.3 years) posttreatment stability in 30 Class I malocclusion patients treated during the early and mid mixed dentition. Measurements were made directly on 120 dental casts obtained at 4 assessment stages: pre-expansion (A1), short-term follow-up (A2), progress (A3), and long-term follow up (A4). Comparisons between A1 and A2 showed statistically significant (P < .001) increases for intermolar widths (lingual and occlusal values). During the transition to the permanent dentition, a significant (P < .001) decrease occurred in arch length and arch perimeter. There was a 25% intermolar width (occlusal value) decrease from the initial net gain, whereas the lingual values remained unchanged. Comparisons between A2 and A4 showed an intermolar width (occlusal value) net gain of 50% and a significant (P < .001) decrease for the arch length and arch perimeter. There was remarkable stability in intermolar width (lingual value) and intercanine width (occlusal value), indicating that the increase in the mandibular arch width dimension was in response to the orthopedic effects of rapid palatal expansion in the early and mid-mixed dentition and that the stability was maintained until adulthood.
Cameron CG, Franchi L, Baccetti T, McNamara JA Jr.
Long-term effects of rapid maxillary expansion: a posteroanterior cephalometric evaluation. Am J Orthod Dentofacial Orthop. 2002 Feb;121(2):129-35.
Significant pretreatment deficiencies in maxillary width remained corrected at a mean age of about 20 years.
The aim of this study was to investigate long-term effects induced by rapid maxillary expansion (RME), followed by comprehensive orthodontic treatment, in a sample of 42 patients compared with normal growth changes in a sample of 20 subjects. Treated subjects underwent Haas-type RME with 2 turns a day (0.25 mm per turn) until the expansion screw reached 10.5 mm (about 21 days). The Haas expander was kept on the teeth as a passive retainer for an average of about 2 months. Immediately after the Haas expander was removed, fixed standard edgewise appliances were placed. Posteroanterior cephalograms were analyzed for each subject in both groups at T1 (pretreatment) and at T2 (long-term observation). The mean age at T1 was 11 years 10 months for both the treated and the control groups. The mean ages at T2 also were comparable (20 years 6 months for the treated group, and 17 years 8 months for the control group). The study included transverse measurements on dentoalveolar structures, maxillary and mandibular bony bases, and other craniofacial regions (nasal, zygomatic, orbital, and cranial). RME followed by edgewise appliance therapy appears to be an effective procedure to increase transverse facial dimensions in the long term, at both the skeletal and the dentoalveolar levels. Significant pretreatment deficiencies in maxillary width, maxillary incisor apex width, and maxillary first molar width remained corrected at a mean age of about 20 years. The initial deficiency in lateroorbital width was also eliminated.
Surgically assisted rapid maxillary expansion: a comparison of technique, response, and stability. Angle Orthod. 1997;67(4):309-20.
Rapid maxillary expansion can be accomplished and stable in patients who will not expand to orthopedic expansion, especially due to age, by using a relatively non-invasive surgical procedure.
The purpose of this study was to evaluate the differences in treatment effects between adult patients who underwent surgically assisted rapid maxillary expansion employing buccal corticotomies and those who had midpalatal splits as well. Responses and sequelae of these treated patients were compared with adults who were expanded orthopedically and adults who were treated orthodontically without expansion. The sample comprised 37 patients who were expanded and 5 controls. Dental study casts were taken prior to treatment, at debanding, and at the posttreatment follow-up. The results indicated that maxillary expansion in adults was predictable and stable, corrected crossbites remained corrected, palatal depth was reduced in SARME, palatal width increased (more dramatically in patients treated with a combined procedure), and tipping was controlled and stable. The long-term buccogingival condition was more acceptable in adults expanded with surgical augmentation than in those expanded orthopedically.
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