Long-term effectiveness of the continuous and the sectional archwire techniques in leveling the curve of Spee.

INTRODUCTION: The correction of a deep overbite with the subsequent achievement of long-term stability is a difficult problem for orthodontists. The role of leveling the curve of Spee (COS) in bite opening and the success of orthodontic treatment has been well documented in the literature. The aim of this study was to investigate whether leveling the COS, by using 2 orthodontic treatment techniques, produces stable results on a long-term basis. METHODS: We compared the long-term stability of leveling the COS with the straight-wire Alexander technique and the bioprogressive sectional-arch technique. The randomly selected subjects for this retrospective study were obtained from the private practices of Drs R. G. Alexander and Ruel Bench. Study models taken 2 months before treatment (T1), 2 months after treatment (T2), and after retention (T3) were evaluated. Measurements of the COS were made on the mandibular casts with a commercially available palatometer. Mandibular intercanine width, overbite, overjet, mandibular incisor irregularity, and mandibular arch length were also recorded. RESULTS AND CONCLUSIONS: Both techniques produced highly significant reductions in the COS (T1 to T2). Statistically significant, but clinically insignificant, postretention relapse of the COS occurred (T2 to T3). For both techniques, a statistically significant difference was seen in the incidence of the relapse of the COS between patients who were completely leveled posttreatment and those who were not. We did not find a correlation between pretreatment COS and relapse in any of the other occlusal traits studied.

Aspects of mandibular morphology, with specific reference to the antegonial notch and the curve of Spee.

The purpose of this investigation was to determine whether particular metrical traits of the mandibular antegonial notches are associated with specific mandibular growth patterns, and also with the mean depth of the curve of Spee. Thirty pre-treatment lateral cephalometric radiographs belonging to a randomly selected group of patients treated in the orthodontic clinic at the SUNY at Buffalo were digitized. The surface areas of the mandibular antegonial notches, as well as some sagittal facial dimensions were measured on each radiograph. The curve of Spee was measured directly from the pre-treatment mandibular study cast of each patient included in this study. An analysis of variance showed no statistically significant difference (p < 0.01) between the measurements recorded by the two examiners who conducted this study. The results of this study showed a statistically significant positive correlation between the surface areas of the antegonial notches and the lower anterior facial heights (r = 0.87, P < 0.001). At the same time a statistically significant negative correlation was found between the surface areas of the antegonial notches and the lengths of the mandibular bodies (r = -0.9, P < 0.001). A significant negative statistical relationship was shown to exist between the lower anterior facial heights and the lengths of the corresponding mandibular bodies, and also between the depths of the curves of Spee and the surface area of the respective antegonial notches (r = -0.85, P < 0.002). The results of this study indicate that an increase in the areas of the antegonial notches is associated with a tendency for greater vertical growth of the mandible. The results further suggest that the depth of the curve of Spee and the length of the mandibular body are decreased when there is an increase in the surface areas of the antegonial notches.

The effects of computer-aided anteroposterior maxillary incisor movement on ratings of facial attractiveness.

BACKGROUND: Before planning orthodontic treatment, it is necessary to understand societal preferences for facial esthetics. The anteroposterior (AP) position of the maxillary incisors affects the appearance of the soft tissue profile and can be manipulated by orthodontic techniques. To improve the ability to predict the most suitable maxillary incisor position, numerous cephalometric and profilometric measurements have been suggested. Among them are the Six Elements to Orofacial Harmony proposed by L. F. Andrews, whereby forehead angulation is used to dictate maxillary incisor sagittal position. Our aim was to evaluate differences in preference for the AP position of the maxillary incisor between orthodontic and lay panels. METHODS: A smiling profile photograph was taken of a female subject who best fit the chosen soft tissue normative values and whose maxillary incisors were in an Element II position. The photograph was manipulated to simulate maxillary protrusion and retrusion at 1-mm increments to a maximum of +/-4 mm. Panels of orthodontists and nonorthodontists scored the attractiveness of the photographic variations according to a 100-mm visual analogue scale. RESULTS: The 4-mm retrusive photograph was significantly less desirable than all others, which suggests that, from an esthetic standpoint, it is preferable to either leave a normally protrusive maxillary dentition where it is or advance rather than retract the maxillary anterior teeth. Orthodontic training did not significantly affect the magnitude of the ratings or pattern of preference in our sample. CONCLUSIONS: Andrews' Element II provides an additional useful method to evaluate attractiveness relative to the maxillary incisor position.

Prediction accuracy of computer-assisted surgical visual treatment objectives as compared with conventional visual treatment objectives.

PURPOSE: This present study used the conventional visualized treatment objectives (VTOs) as a tool to evaluate the predictive value of the Dolphin computer-assisted VTOs. MATERIALS AND METHODS: Presurgical cephalometric tracing predictions generated by oral and maxillofacial surgeons and the Dolphin Imaging software were compared with the postsurgical outcome as seen on lateral cephalometric tracings. Sixteen measurements of the predicted and actual postsurgical hard tissue landmarks were compared statistically. RESULTS: A paired Student's t test showed that 7 measurements had statistically significant differences for the conventional VTOs (facial angle, P < .0001; AOC, P < .0001; SNB, P = .003; ANB, P = .004; U1-NA-degrees, P = .01; U1-NA-mm, P = .02; and N perp Pog, P < .0001), while 9 measurements were statistically significant ( P = <.0001) for Dolphin (facial angle, P = .0001; AOC, P = .005; SNB, P = .001; ANB, I = .04; U1-NA-degrees, P = .003; PogNB, P = .04; U1-NA-mm, P = .002; N perp Pog, P = .0001; UFH, P = .03; and LFH, P = .03). CONCLUSION: From these data, it appears that both VTOs demonstrated good predictive comparative outcome and are equally precise.

Head posture and deprivation of visual stimuli.

INTRODUCTION: Natural head position (NHP) has been defined as the cranial position that is attained when individuals stand with their visual axes in the true horizontal plane. The visual axis is considered to be a key component in establishing, and maintaining NHP so that, in the absence of visual stimuli, gravitation and muscular proprioception chiefly control head position. SUBJECTS AND METHODS: In this study, the natural head positions of a group of normal sighted subjects were measured in a well-lighted room. The findings were compared to similar observations made in the same subjects when they were placed in a completely dark environment. Measurements of cranio-cervical angulation were made on adults (N = 30, males = 17, females = 13) by means of an electronic inclinometer. Sitting Head Position (SIHP), Standing Head Position (STHP), and Orthoposition (OP) were determined for each subject in a well-lighted room, and subsequently, in a completely dark room. RESULTS: The data indicate that there were statistically significant differences between Standing Head Position, and Orthoposition, measured in the light and in the dark. There were no statistically significant differences between Sitting Head Position measured in the light and in the dark. CONCLUSION: The results indicate that craniocervical angulation is more extended in the dark than it is in the light. This finding suggests that head position responds to visual stimuli, and that when this sensory input is not present, there is a tendency for subjects to extend their heads.