Peter M. Sinclair

Cephalometric effects of face mask/expansion therapy in Class III children: a comparison of three age groups.

The purpose of this investigation was to determine the skeletal, dental, and soft tissue effects of face mask/expansion therapy and to examine the effect of age on treatment response. Pretreatment and posttreatment cephalometric radiographs from 63 subjects (4 to 13 years) who had a Class III malocclusion were analyzed. Serial cephalometric tracings of 32 subjects with Class I occlusion made at 4, 6, 8, 10, 12, and 14 years were used as controls. Landmarks were digitized on each tracing and treatment effects were measured by using cranial base and maxillary superimposition techniques. Annual rate differences were compared with t tests for the combined treated group (N = 63) and between stratified treated groups (4 to 7 years N = 15, 7 to 10 years N = 32, 10 to 14 years N = 16). The treated group (N = 63) demonstrated significant (p < 0.001) hard and soft tissue changes that resulted from treatment. Skeletal change was primarily a result of anterior and vertical movement of the maxillae. Mandibular position was directed in a downward and backward vector. Orthodontic changes contributed to the correction, and soft tissue effects resulted in a more convex profile. Minimal significant differences were observed between age groups when comparing angular and linear measurements alone. However, when analyzing the algebraic sum of treatment effects (Johnston analysis), significantly (p < 0.01) greater differences were observed in apical base change (ABCH) and total molar correction (6/6) in the younger age groups. This study demonstrates that face mask/expansion therapy produces dentofacial changes that combine to improve the Class III malocclusion. Although early treatment may be most effective, face mask therapy can provide a viable option for older children as well.

Nonextraction orthodontic therapy: Posttreatment dental and skeletal stability

To assess the long-term stability of nonextraction orthodontic treatment, the dental cast and cephalometric records of 28 cases were evaluated. Thirty cephalometric and seven cast parameters were examined before treatment, posttreatment, and an average of almost 8 years postretention. Results showed overall long-term stability to be relatively good. Relapse patterns seen were similar in nature, but intermediate in extent, between untreated normals and four first premolar extraction cases. Significant decreases were seen in arch length and intercanine width during the postretention period despite minimal changes during treatment. Incisor irregularly increased slightly postretention; intermolar width, overjet, and overbite displayed considerable long-term stability. Mandibular incisor mesiodistal and faciolingual dimensions were not associated with either pretreatment or posttreatment incisor crowding. Class II malocclusions with large ANB values and shorter mandibular lengths showed increased incisor irregularity, shorter arch lengths, and deeper overbites at the postretention stage, suggesting that the amount and direction of facial growth may have been partially responsible for maturational changes seen during the postretention period.

The local use of vitamin d to increase the rate of orthodontic tooth movement

The purpose of the study was to determine if the rate and amount of orthodontic tooth movement in a sample of cats could be enhanced by the injection of a vitamin D metabolite 1,25-dihydroxycholecalciferol (1,25D) into the periodontal ligament. After 21 days of canine retraction with a light-wire retraction spring, the teeth that had received weekly intraligamentous injections of a solution of 1,25D in dimethylsulfoxide (DMSO) had moved 60% further than matched control teeth (P less than 0.05). At the histologic level, increased numbers of mononuclear osteoclasts were recruited and activated, resulting in greater amounts of alveolar bone resorption on the pressure side of the periodontal ligament. No obvious clinical, microscopic, or biochemical side effects were noted.

Soft tissue changes associated with double jaw surgery

The purpose of this study was to evaluate the amount, direction, and predictability of the soft tissue changes associated with simultaneous maxillary impaction and mandibular advancement surgery. The results suggested that the soft tissue responses were similar to those seen in single jaw procedures, with the exception of the changes seen in the nasolabial angle and in the area of the lower lip and chin. The type of soft tissue manipulation employed, in particular the use of the alar base cinch suture and V-Y closure techniques, were important factors in determining the response of the upper lip to the surgery. The maxillary soft tissues moved forward 90% of the hard tissue change and showed 20% shortening of the upper lip, with the changes in the nasolabial angle being due primarily to the degree of the maxillary rotation. A predictable progressive increase was seen in the horizontal movement of the mandibular soft tissues ranging from 73% of the hard tissue change at the lower lip to 100% at pogonion. The vertical movement of the mandibular soft tissue was greater than that of underlying hard tissues, particularly in the area of the lower lip as it was freed from the effects of the maxillary incisors.

A comparative study of Caucasian and Japanese mandibular clinical arch forms.

The purpose of this study was to clarify morphological differences between Caucasian and Japanese mandibular clinical arch forms in Class I, II, and III malocclusions. The study included 60 Class I, 50 Class II, and 50 Class III cases from each ethnic group. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and 2 proportional measurements were taken. The dental arches were classified into square, ovoid, and tapered forms to determine and compare the frequency distributions between the 2 ethnic groups. The Caucasian population had a statistically significant decreased arch width and increased arch depth compared with the Japanese population. When the subjects were regrouped by arch form, no statistically significant difference in arch dimension was observed between the 2 ethnic groups in any of the arch form samples. Our results suggest that there is no single arch form specific to any of the Angle classifications or ethnic groups. It appears to be the frequency of a particular arch form that varies among Angle classifications or ethnic groups.

The stability of double jaw surgery: A comparison of rigid versus wire fixation***

The subjects of this study were 35 patients who underwent simultaneous surgery for superior repositioning of the maxilla and advancement of the mandible. They were studied cephalometrically for a comparison of the postsurgical stability of two commonly used fixation techniques: (1) rigid fixation with bone plates and (2) skeletal-wire fixation. One surgeon performed the operations on all 35 patients, and both groups were studied for an average of 15 months after surgery. Results showed that, although the maxilla remained relatively stable after surgery with both fixation techniques, rigid fixation tended to improve stability, primarily by eliminating relapse in excess of 2 mm. Mandibular stability was much greater with rigid fixation: the amount of relapse of the horizontal projection of B point with this method was 6%, while in the skeletal-wire sample it was 26%. Increased rotational stability between the proximal and distal segments of the mandible appeared to be a major factor in the improved overall stability of the rigid-fixation sample. The amount of mandibular relapse was found to be correlated to the amount of advancement in the wire-fixation sample, but not in the rigid-fixation sample.

A cephalometric, tomographic, and dental cast evaluation of Fränkel therapy

The purpose of this study was to evaluate the skeletal, dental, and condylar positional changes induced by Fränkel FR-2 therapy. The pre- and posttreatment cephalometric, tomographic, and dental cast records of 25 consecutively treated cases were evaluated. Results showed little Class II skeletal correction with no headgear-type restraining effect on the maxilla or mandibular growth stimulation noted. Significant amounts of maxillary incisor retraction and mandibular incisor proclination were observed. The maxillary intermolar width along with the mandibular intercanine and intermolar widths were significantly increased during treatment. No significant changes in condylar position were found during Fränkel therapy and only a small increase in mandibular plane angle was noted.

A comparison of the Ricketts and tweed-type arch leveling techniques☆

The purpose of this study was to compare the effectiveness and long-term stability of arch leveling and overbite correction carried out by the Ricketts and modified Tweed techniques. The sample comprised 60 Class II, deep bite, low-angle adolescent nonextraction cases, 30 each from the offices of Robert Ricketts and Fred Schudy, with cephalograms taken before and immediately after treatment and an average of more than 4 years after treatment. Both techniques were successful in overbite correction, producing only minimal increases in mandibular plane angle and anterior facial height. Mandibular incisors in the Ricketts group demonstrated more flaring and anterior bodily movement during treatment, with a greater amount of posttreatment uprighting and overbite relapse than the Schudy group. The Ricketts group demonstrated slightly more than 1 mm of true lower incisor intrusion; this change was relatively stable after treatment. Both techniques produced similar amounts of mandibular molar extrusion during treatment; these changes remained stable after treatment.

Predicting soft tissue changes in mandibular advancement surgery: a comparison of two video imaging systems.

The purpose of this study was to evaluate the accuracy of two video imaging systems, Prescription Portrait and Orthognathic Treatment Planner, in predicting the soft tissue profiles of 39 patients who underwent mandibular advancement surgery. Presurgical cephalograms and profile photographs were entered into a computer. Computerized cephalometric line and video image predictions were generated and compared with the actual postsurgical results. The results indicate that both programs were equally accurate clinically in their line drawing and video image predictions. In the line drawings, clinically acceptable accuracy was shown in approximately 80% of the upper lip and chin predictions and in less than 50% of the lower lip predictions. The video images produced by both programs received fair to good ratings from a panel of professional and lay judges. Orthodontists and surgeons rated all aspects of the images similarly, while lay people were most critical of the chin and submental areas and least critical in their overall evaluation.

The long-term stability of LeFort I maxillary downgrafts with rigid fixation to correct vertical maxillary deficiency

This study evaluated the long-term stability of LeFort I maxillary downgrafts with rigid fixation in 28 patients with vertical maxillary deficiency. Preorthodontic, presurgical, immediate postsurgical, and an average of 16 months postsurgical cephalometric radiographs were evaluated. The results indicated that overall vertical maxillary stability after downgraft was good with 80% of the cases showing superior relapse of 2 mm or less. The mean amount of postoperative relapse represented 28% of the surgical downgraft. No correlation was found between the amount of the maxillary downgraft and the subsequent postsurgical vertical stability of the maxilla. No difference was found in the vertical stability of the maxilla comparing one-jaw and two-jaw procedures. It was also found that there was no difference in the vertical stability of the maxilla between single-segment and multiple-segment maxillary procedures, and also when comparing standard and high LeFort I osteotomy techniques. In addition, occlusal plane rotation of surgery, as well as the type of presurgical orthodontic movement, were both found to have no influence on postoperative stability of the maxilla.