Maxillary Occlusal Plane Research Articles

開こうを伴う骨格性下顎前突症患者の顎矯正手術後の硬軟組織変化‐上下顎移動術と下顎枝矢状分割術単独との比較‐

The purpose of this study was to evaluate hard and soft tissue changes in mandibular prognathic patients with open bite following different orthognathic surgery.Twenty adult patients who underwent orthognathic surgery to correct mandibular protrusion and open bite were selected for this study. The subjects were divided into the following two groups based on surgical method: 12 subjects who underwent mandibular setback osteotomy with the sagittal split technique (one jaw group) and 8 subjects who underwent mandibular setback osteotomy with the sagittal split technique and combination (Le fort I and horseshoe) osteotomy in bimaxillary surgery (two jaw group). A pair of pre- and post-operative lateral cephalograms was used for hard and soft tissue analysis. Statistical analysis using a paired t test was performed for comparative study.No significant differences were observed in the pre-operative anterior occlusion, dento-skeletal pattern and facial profile between the two groups. Anterior occlusion was improved in both groups following surgery and no significant differences were observed in the post-operative overjet and overbite between the two groups. However, significant differences were observed both in the dento-skeletal and facial profile changes between the two groups. The amount of mandibular up-backward movement, especially the chin portion in the two jaw group was significantly larger than that in the one jaw group due to the clockwise rotation of the maxillary occlusal plane following superior repositioning of the maxillary posterior portion. In accordance with this larger mandibular up-backward movement coupled with maxillary advancement in the two jaw group, more harmonized bimaxillary skeletal relationship as well as better facial profile were achieved in the two jaw group in comparison with that in the one jaw group. It is suggested that a combination of Le fort I and horseshoe osteotomy in bimaxillary surgery is a useful technique to treat mandibular prognathic patients with open bite.

Positional changes and stability of bone segments during simultaneousbilateral mandibular lengthening and widening by distraction

The purpose of this study was to analyse the skeletal changes and stability of the distracted segments during and after simultaneous widening and bilateral lengthening of the mandible in baboons with a miniaturized intraoral bone-borne osteodistractor. Distraction appliances were activated 5 days after vertical posterior body and midsymphyseal osteotomies at a rate of 0.9 mm/day for 10 days. The appliances were then stabilized for a period of 8 weeks, after which the animals were killed. The distraction gaps and gingival tissues were studied clinically and on standardized radiographs. The proportional movement of the distracted segments that we found supports the clinical use of the miniaturized intraoral bone-borne distraction appliance to widen and lengthen the mandible selectively. It also supports the concept of positioning the mandibular osteodistractors parallel to the common vector of distraction, which should parallel the corrected maxillary occlusal plane.

Treatment of a patient with a Class II malocclusion, impacted canine, and severe malalignment

A case report of the orthodontic treatment of a male adolescent with a unilateral dental Class II malocclusion, an impacted canine, severe maxillary malalignment, and a canted maxillary anterior occlusal plane. Treatment consisted of full fixed appliances, extraction of the maxillary right first premolar, and surgical exposure of the impacted canine. Treatment vastly improved the patient’s facial and dental esthetics. A Class I skeletal and dental relationship was established, along with a functional anterior guidance. The dental arches were coordinated and the dental midlines coincident with the midsagittal plane. This case report was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board. (Am J Orthod Dentofacial Orthop 2000;118:693-8)

Assessment of the relationships among posture, maxillomandibular denture complex, and soft-tissue profile of aesthetic adult Korean women.

The objective of this study was to assess the relationships among the posture, the maxillomandibular denture complex, and the soft-tissue profile of aesthetic adult Korean women. From an initial group of 346 women, the authors examined 28 beautiful adult Korean women who had normal vertical and sagittal skeletal relationships and normal occlusion. There were no differences in the inclinations of the incisors to the occlusal planes in the maxilla and the mandible in the data for Korean women vs. Arnett's data for white women. However, the overbite and overjet in Korean women were slightly smaller than in white women. AB to maxillary occlusal plane angle (MxOP) represented the anteroposterior denture base discrepancy to the occlusal plane. Angulation of the maxillary occlusal plane to the Frankfurt (FH) plane and the true vertical line at submasale (TVL) (Sn) was a little steeper in Korean women than in white women. The FH plane was almost parallel to the true horizontal line in Korean women who had normal vertical and sagittal skeletal relationships and normal occlusion. With regard to soft-tissue variables, the upper lip length (Sn-Stms), interlabial gap, upper incisor exposure, nasolabial angle, lip and nose tip projection value, and TVL (Sn)-to-upper lip line (UL) angle showed interracial differences. The results of this study can assist in the diagnosis and treatment planning of orthognathic surgery.

Comparison of three facebow/semi-adjustable articulator systems for planning orthognathic surgery

Our aim was to measure the steepness of the occlusal plane produced by three different semi-adjustable articulators: the Dentatus Type ARL, Denar MkII, and the Whipmix Quickmount 8800, and to assess the influence of possible systematic errors in positioning of study casts on articulators that are used to plan orthognathic surgery. Twenty patients (10 skeletal class II, and 10 skeletal class III) who were having pre-surgical orthodontics at Liverpool University Dental Hospital were studied. The measurement of the steepness of the occlusal plane was taken as the angle between the facebow bite-fork and the horizontal arm of the articulator. This was compared with the angle of the maxillary occlusal plane to the Frankfort plane as measured on lateral cephalometry (the gold standard). The Whipmix was closest to the gold standard as it flattened the occlusal plane by only 2 ° (P<0.05). The results of the Denar and Dentatus differed significantly from those of the cephalogram as they flattened the occlusal plane by 5 ° and 6.5 ° (P<0.01), respectively. Clinicians are encouraged to verify the steepness of the occlusal plane on mounted study casts before the technician makes the model.

Progression of facial asymmetry in hemifacial microsomia.

Hemifacial microsomia is a common craniofacial anomaly, variably affecting structures derived from the first and second pharyngeal arches. Correction of the skeletal deformity in children has been advocated to improve growth potential and reduce secondary deformity. However, contrary reports have suggested that facial asymmetry in hemifacial microsomia does not increase with growth; therefore, skeletal correction can be postponed, even until adolescence. The purpose of this study was to test the hypothesis that facial asymmetry in hemifacial microsomia is progressive. This is a retrospective evaluation of 67 patients with untreated hemifacial microsomia. The patients were categorized as: group I (mandible type I, IIa), n = 38, and group II (mandible type IIb, III), n = 29. Pretreatment posterior-anterior cephalometric radiographs were used to analyze asymmetry by measuring the angle between the true horizontal and the following planes: piriform rim, maxillary occlusal plane, and intergonial angle. Angular measurements were averaged for patients in the deciduous (<6 years), mixed (> or =6<13 years), and permanent dentition (> or =13 years). In group I, angle piriform rim, maxillary occlusal plane, and intergonial angle increased from 7.0, 4.3, and 4.4 to 8.4, 6.6, and 6.1 degrees, respectively [mean age, 4.1 (deciduous) to 8.6 (mixed) to 21.0 (permanent) years]. In group II, angle piriform rim, maxillary occlusal plane, and intergonial angle increased from 9.5, 6.2, and 5.3 to 11.7, 7.6, and 8.0 degrees, respectively [mean age, 3.4 (deciduous) to 8.0 (mixed) years]. These data demonstrate that hemifacial microsomia is progressive and underscores the importance of early surgical correction of mandibular asymmetry in this disorder.

The effect of sagittal orientation of the distractor on the biomechanics of mandibular lengthening.

It has been previously demonstrated that distractors placed parallel to the mandible in the transverse plane, without regard to the vector of distraction create lateral displacement tendencies at the appliance-bone interface, leading to potential clinical problems and complications. The purpose of this study was to evaluate the biomechanical effects of linear distractor orientation in the sagittal plane relative to the anatomic axis of the mandible (mandibular plane) and the maxillary occlusal plane. A 2-dimensional model of the human mandible was generated for computer simulation of osteodistraction. Positional changes of the distal mandibular segment were then analyzed during 10 mm of incremental lengthening based on distractor orientation relative to the maxillary occlusal plane. Distractors placed parallel to the inferior border of the mandible without regard to the maxillary occlusal plane created a vertical translation of the distal bone segment resulting in an anterior open bite. The magnitude of the anterior open bite was proportional to the angle between the vector of distraction and the maxillary occlusal plane, and to the amount of distraction. Placement of the distractors parallel to the maxillary occlusal plane eliminated the tendency for an anterior open bite. The orientation of the distractors relative to the maxillary occlusal plane is one of the important biomechanical parameters that must be included in preoperative planning for mandibular osteodistraction.

Intraoral widening and lengthening of the mandible in baboons by distraction osteogenesis

Purpose: The purpose of this study was to analyze the skeletal and dental positional changes and histomorphology of the distraction regenerates and mucogingival periosteal tissues that occurred after simultaneous widening and bilateral lengthening of the mandible in baboons by a miniaturized intraoral bone-borne distraction appliance. Materials and Methods: Distraction appliances were activated 5 days after vertical ramus and symphyseal osteotomies at a rate of 0.9 mm/d for 10 days. The appliances were then stabilized for 8 weeks, after which the animals were killed. The distraction gaps and gingival tissues were analyzed clinically, histologically, and by standardized radiographic studies. Results: Positional changes of the canines and incisor apices were proportional to the skeletal movements. Tipping of both incisors toward the center of the distraction gap was observed. Proportionate movement of the superior and inferior portion of the distracted segments was noted. Newly formed longitudinal trabecular columns parallel to the vector of distraction originated from the intact margins of alveolar bone contiguous with the adjacent teeth. Active histogenesis occurred in the stretched mucogingival periosteal tissues located in the distraction gaps. Conclusions: The results of this investigation support the clinical use of the miniaturized intraoral bone-borne distraction appliance to selectively widen and lengthen the mandible. The orientation of the mandibular distractors must be parallel to the common vector of distraction, which should be parallel to the maxillary occlusal plane. The formation of a bone regenerate in the alveolar region depends on the presence of an adequate bone interface on either side of the distraction gap.

Intraoral widening and lengthening of the mandible in baboons by distraction osteogenesis

Purpose: The purpose of this study was to analyze the skeletal and dental positional changes and histomorphology of the distraction regenerates and mucogingival periosteal tissues that occurred after simultaneous widening and bilateral lengthening of the mandible in baboons by a miniaturized intraoral bone-borne distraction appliance. Materials and Methods: Distraction appliances were activated 5 days after vertical ramus and symphyseal osteotomies at a rate of 0.9 mm/d for 10 days. The appliances were then stabilized for 8 weeks, after which the animals were killed. The distraction gaps and gingival tissues were analyzed clinically, histologically, and by standardized radiographic studies. Results: Positional changes of the canines and incisor apices were proportional to the skeletal movements. Tipping of both incisors toward the center of the distraction gap was observed. Proportionate movement of the superior and inferior portion of the distracted segments was noted. Newly formed longitudinal trabecular columns parallel to the vector of distraction originated from the intact margins of alveolar bone contiguous with the adjacent teeth. Active histogenesis occurred in the stretched mucogingival periosteal tissues located in the distraction gaps. Conclusions: The results of this investigation support the clinical use of the miniaturized intraoral bone-borne distraction appliance to selectively widen and lengthen the mandible. The orientation of the mandibular distractors must be parallel to the common vector of distraction, which should be parallel to the maxillary occlusal plane. The formation of a bone regenerate in the alveolar region depends on the presence of an adequate bone interface on either side of the distraction gap.

Combined maxillary and mandibulardistraction osteogenesis

Mandibular elongation by gradual distraction in patients with hemifacialmicrosomia is a simple and effective procedure to correct facial asymmetry. The changes in mandibular dimension result in changes in dental occlusion. These are minimal in children because of the rapid growth of the maxilla and can be corrected easily with minor orthodontic treatment. Mandibular distraction in adults with hemifacial microsomia produces good aesthetic results but leaves the patient with a severe alteration in the occlusion requiring complex orthodontic treatment over a long period of time. To avoid this problem, an incomplete Le Fort I osteotomy is performed simultaneously with the mandibular corticotomy. Intermaxillary fixation is placed on the fifth postoperative day, and distraction is initiated. This technique preserves the preexisting stable occlusion. After distraction, both the maxillary and mandibular occlusal planes become horizontal, and facial asymmetry is corrected.

Cephalometric parameters affecting severity of anterior open bite

One hundred and four patients with anterior open bite (AOB) were subdivided by statistical means into three distinctly separate groups with AOB of different severity based on the extent of separation of the incisors in the vertical plane. Cephalometric evaluation of all subjects was completed using 24 skeletal and 12 dentoalveolar measurements, and the results were compared between the mild, moderate and severe groups of AOB. The findings suggest that the palatal plane, mandibular occlusal plane, upper anterior dental height and upper posterior dental height correlate significantly with the severity of AOB. In contrast, skeletal jaw relationship in the horizontal plane correlated only weakly with severity. This study further highlighted the steep mandibular occlusal plane as an important indicator of AOB severity in contrast to the maxillary occlusal plane.

Timing for effective application of anteriorly directed orthopedic force to the maxilla

Class III malocclusion with retrusive maxilla can be orthopedically corrected in the deciduous and mixed dentition, with reverse-pull headgear in combination with rapid palatal expansion. The literature recommends this procedure be carried out before the patient is 8 years old to obtain the optimal orthopedic result. This statement, however, has not been supported by scientific data. The current study examined the treatment effects of patients younger than 8 years old (5 to 8 years) and patients older than 8 years old (9 to 12 years). Thirty patients treated with maxillary protraction and expansion in the Department of Children's Dentistry and Orthodontics, University of Hong Kong were included in this study. Cephalometric radiographs were taken 6 months before the initiation of treatment (T0), at the initiation of treatment (T1), and after 6 months of treatment (T2). In this way, (T2-T1) represented cephalometric changes during the treatment period and (T1-T0) represented 6 months of growth changes without treatment. Experimental subjects served as their own control in this study. A grid system consisting of maxillary occlusal plane (OL) and a line perpendicular to OL through sella (OLp) was used for linear measurements. A total of 15 linear and 3 angular cephalometric measurements were made. A multivariate analysis of variance (MANOVA), which used age and treatment time as its factors, was used to determine effect of age and/or treatment on each cephalometric parameter. Results indicated strikingly similar therapeutic response between the younger and older age groups. These data suggest that similar skeletal response can be obtained when maxillary protraction was started either before age 8 (5 to 8 years) or after age 8 years (8 to 12 years). (Am J Orthod Dentofac Orthop 1997;112:292-9.)

Geometric analysis of occlusal plane orientation using simulated ear-rod facebow transfer.

Ear-rod facebow techniques may position casts high or low between the upper and lower members on the articulator when using orbitale or nasion as anterior reference positions. This study assessed the effect of changing the anterior reference position on simulated mountings utilizing simulated ear-rod facebow. Tracings from latoral cephalographs made on seven subjects were superimposed with an outline model of a semiadjustable articulator. Three simulated mountings were performed for each subject in which the plane of occlusion was positioned (1) high, (2) midway, and (3) approaching the lower member (low). Maxillary and mandibular occlusal planes representing intercuspal position were determined from the cephalographs and positioned on the articulator model in a simulated centric relation position for each mounting. Condylar guidance was determined from a simulated protrusive position. Analysis of the three mounting positions demonstrated no change in intercuspal position within subjects; however, angles formed between upper member and condylar guidance were 14.9% smaller for the mid-distance mounting, 42.9% smaller for the high mounting, and 13.4% higher for the low mounting positions when compared with a standard Frankfort horizontal plane reference. The cephalographs showed extreme variability in the position of the ear piece to bony structures of the skull, but this deviation appeared to be compensated by a change in the horizontal condylar guidance relative to mounting. Results also suggest that casts may be mounted in a convenient mid-position for routine articulation.

Jaw displacement and F0 in contrastive emphasis.

This study examines the relationship between highest F0 (within the sonorant portion of the syllable) and maximum jaw displacement (lowest vertical position of the mandible in reference to the maxillary occlusal plane) in utterances with contrastive emphasis. Acoustic and articulatory recordings were made using the x-ray microbeam facilities at the University of Wisconsin [J. Westbury and O. Fujimura, J. Acoust. Soc. Am. Suppl. 1 85, S98 (1989)]. Three American English subjects produced question–answer sentences like ‘‘Is it 599 Pine Street? No, it’s 59FIVE Pine Street,’’ reading from a monitor display with a marking on the digit to be emphasized either in initial, middle, final position, or with no emphasis. The data showed positive correlation between jaw opening and F0 for syllables spoken with contrastive emphasis, but no correlation for nonemphasized syllables. One would expect two opposite biomechanical effects of jaw opening on F0: a positive effect by the action of jaw opening muscle on larynx elevation, and a negative effect by passive hyoid retraction due to jaw lowering. These findings suggest that prosodic contrast may be achieved by reorganization of interactive control of jaw opening and F0. Possible acoustical, physiological, and phonological ramifications of these findings are discussed. [Work supported by NSF SBR-951199B and ATR/ITL, Kyoto, Japan.]

Simultaneous Bimaxillary Orthognathic Surgery

Simultaneous bimaxillary orthognathic surgery, which can alter an occlusal plane, is employed for correction of varying maxillomandibular dentofacial deformities. Since positioning of the maxillary segment is inherently considerable to improve both facial esthetics and occlusion, a systematized and ensured procedure is needed to obtain stable results.The authors describe here the bimaxillary surgical procedures with special reference to a newly devised “Two-Step positioning” of the maxillary segment utilizing face bow transfer and an occlusal plane indicator.The Two-Step positioning technique is summarized as follows:1) An altered occlusal plane of the maxilla in model surgery is recorded in a Quick mount face bow (Whip-mix Co.). Beforehand the dental arch impression made with self-curing resin and small hooks at bilateral premolars is attached to the bite fork, which securely holds the mobilized maxillary segment on the bite fork during surgery.2) Step 1: After mobilizing the mandible and maxillary segment, the maxillary occlusal plane is transfered to the patient by means of face bow transfer. The maxillary segment is immobilized with two low profile miniplates (Leibinger Co.).3) Step: The occlusal plane indicator having an upper dental arch impression is applied to the dental arch, which enables easy assessment of the occlusal plane three-dimensionally. In case indicating additional correction of the plane, loosening some screws of the miniplate allows versatility in repositioning of the segment.This technique has been applied to 30 cases without incidence, and it has been our experience that positioning of the maxillary segment is ensured and the surgical procedures are systematized with this technique.

The headgear effect of the herbst appliance: A cephalometric long-term study

The short- and long-term effects of the Herbst appliance on the maxillary complex were evaluated in 45 patients who had Class II malocclusions. The patients were followed for 6.4 years (5 to 10 years) after treatment. Lateral cephalograms from before and after 7 months of treatment, 6 months, and 6.4 years after treatment were analyzed. During Herbst treatment the upper molars were distalized in 96% of the subjects (maximum 4.5 mm), and the upper molars were intruded in 69% of the subjects (maximum 3.5 mm). The maxillary occlusal plane was opened in 82% of the subjects (maximum 7.5 degrees). Sagittal maxillary jaw base position seemed unaffected by therapy. A downward tipping of the palatal plane was noted in 47% of the subjects (maximum 2 degrees). During the first 6 months after therapy most of the treatment changes reverted. During the following 5.9 years after treatment, normal growth developmental changes prevailed: the upper molars moved mesially, and the teeth extruded, the occlusal plane closed, the maxilla grew anteriorly, and the palatal plane tipped downward. In conclusion the Herbst appliance exhibited a pronounced high-pull headgear effect on the maxillary complex. Without proper retention, however, the effect seemed to be of a temporary nature.

Accuracy of face-bow transfer: Effect on surgical prediction and postsurgical result

One of the most common errors in model surgery for orthognathic surgery is in the mounting of the models on the articulator. This study assessed the ability of one type of face-bow to transfer the maxillary model to the articulator. Twenty-five consecutive mountings were evaluated by calculating the angle made between the maxillary occlusal plane on the cephalogram and comparing it with the maxillary occlusal plane angle on the articulator. An accurate face-bow transfer should transfer this angle, making the two similar. It was found that a significant difference between the maxillary occlusal plane angle on the cephalogram and the articulator was found in the average case. The implications of such errors and a technique to avoid them are presented.

Cephalometrically predicted occlusal plane: Implications in removable prosthodontics

Although the determination of the occlusal plane is crucial in clinical removable prosthodontics, none of the existing methods gives sufficient guidelines for that purpose. The aim of this investigation was to check the hypothesis that the angulation of the occlusal plane is generally related to the skeletal base of the maxillae. Statistical analysis revealed (1) no strong linear correlation ( p > 0.05) between the following variables: (a) the length of Cook's plane to Cook's occlusal plane angle, (b) the length of the maxillary plane to the maxillary occlusal plane angle, and (c) the Po Na ANS angle to the occlusal Frankfort plane angle; (2) no parallelism between the occlusal and HIP plane with a mean angle of 4.57 degrees, SD 2.57 degrees, and range of 0 to 9.5 degrees; and (3) no correlation between the predicted and clinically determined occlusal planes ( r0.267, t1.797, p > 0.05).

骨格性反対こう合に対するチームアプローチ 上顎こう合平面の設定が困難であった２症例について

When the treatment of skeletal malocclusion is based on standardized profiles, the surgical field is expanded because of the individual morphological variations of the patients. Such an approach will not always permit functionally stable occlusion.To establish the functionally stable occlusion which we term desirable occlusion (D.O.), it is very important to set up the appropriate occlusal plane based on the fixed maxilla, and to establish the centric stop and anterior guidance. Therefore systematic treatment of the patient by a team approach is carried out with an oral surgeon, prosthodontists and orthodontists.In this paper, we report two cases of sagittal split osteotomy in which the maxillary occlusal plane was established by pre and post surgical prosthodontic treatments. In these cases it was not possible to apply orthodontic treatment for the improvement of maxillary occlusal plane because of many missing teeth.As the centric stop in the molar region were not sufficient, we utilized the resin bite splint. even after removal of intermaxillary fixation and maintained the centric stop. This stabilized the occlusion and intermaxillary relation during post surgical treatment. By applying this procedure, it is possible to maintain the centric stop throughout the post surgical treatment period and thus help in establishing desirable occlusion.

The relationships of upper facial proportions and the plane of occlusion to anatomic reference planes

A study was made of 28 dentulous Chinese (Singaporean) adults by using lateral skull radiographs. The dimensions of the maxillae and various craniofacial reference lines related to prosthodontic use were analyzed. The craniofacial reference angles that reflect the vertical height and horizontal depth of the maxillae in Chinese adults differed significantly from the norms obtained in a white North American adult population. By comparison, Chinese adults have a vertically high and horizontally receded upper face that could cause planes such as the Frankfort horizontal plane or an arbitrary axis-orbitale plane to assume a steeper anterior inclination, thus modifying the mechanical inclination of the maxillary cast and occlusal plane on the articulator.