The effect of Le Fort I maxillary impaction on nasal airway resistance

The effect of Le Fort I maxillary impaction on nasal airway resistance

The effect of Le Fort I maxillary on nasal airway resistance impaction Dr. Guenthner Terry A. Guenthner, D.D.S., A. Howard Sather, D.D.S., and Eugen...

3MB Sizes 0 Downloads 57 Views

The effect of Le Fort I maxillary on nasal airway resistance

impaction Dr. Guenthner

Terry A. Guenthner, D.D.S., A. Howard Sather, D.D.S., and Eugene 6. Kern, M.D. Rochester, Mm. To evaluate the effect of maxillary superior movement via Le Fort I osteotomy on nasal airway resistance, eleven Caucasian patients whose surgical orthodontic treatment included Le Fort I impaction (range 2 to 8 mm, mean 5.3 mm) were selected. Nasal airway resistance in these patients was determined a few days before and approximately 8 weeks after the Le Fort I surgical procedure. Nasal airway resistance was determined by means of a uninasal active mask rhinomanometric technique. Contrary to the predicted negative effects of maxillary superior movement on nasal airway function, there was a statistically significant improvement in nasal airway resistance (P < 0.01) after maxillary superior movement. This rather unexpected finding can be explained by examining the effect of maxillary superior movement on the nasal valve area in the anterior nose. The nasal valve area is a teardrop-shaped area bordered by the nasal septum, the caudal end of the upper lateral nasal cartilage, the floor of the nose, and the soft fibrofatty tissue on the lateral aspect of the nose. The apex of the teardrop-shaped area (the angle between the nasal septum and the upper lateral cartilage) is called the nasal valve. In the Caucasian type of nose, the nasal valve accounts for most of the inspiratory resistance to airflow. Maxillary superior movement increases the alar width. It is proposed that this increase in alar width is transmitted at least partially to the nasal valve angle, causing it to widen slightly, paradoxically reducing nasal airway resistance while reducing skeletal intranasal dimensions. Key words: Le Fort I impaction,

nasal airway resistance, nasal valve, rhinomanometry

I

n the past decade, the Le Fort I osteotomy has been used with increasing frequency in the correction of dentofacial deformities. Le Fort I osteotomy is particularly useful for the reduction of vertical facial dimensions in patients with vertical maxillary excess, long-face syndrome, or skeletal anterior open-bite deformity. The typical clinical findings are those of a mouth-breathing pattern with an anterior dental open bite, a high vaulted palate, a long narrow face, lips apart at rest with lip strain to achieve full lip closure, excessive exposure of maxillary incisors with lips at rest, exposure of excessive gingival tissue when smiling, reduced nasal width in the alar region, and excessive convexity of facial profile with chin retrusion. In the combined surgical-orthodontic correction of such a deformity, a Le Fort I osteotomy is frequently performed to produce superior maxillary movement. From the Departments of Dentistry and Otorhinolaryngology, Mayo Clinic and Mayo Foundation. Presented at the American Association of Orthodontists/American Association of Oral and Maxillofacial Surgeons Research Conference associated with the 1983 Clinical Congress on “Surgical Orthodontic Challenges: A Maturing Perspective” in New Orleans, La., Jan. 28-30, 1983. This article was based on work performed in partial fulfillment of the requirements for the Master of Science in Dentistry degree, Mayo Graduate School of Medicine, Rochester, Minn., December, 1982.

308

This superior maxillary repositioning improves the relationship of the upper lip to the upper incisor (eliminates the “gummy” smile) and allows the mandible to rotate upward and forward, thus improving the profile and reducing lip incompetence (Fig. 1, A). Additional mandibular surgical procedures (that is, mandibular advancement, genioplasty , or both) are also commonly used to help establish a proper anteroposterior molar relationship and to further improve chin contour (Fig. 1, B). In the years since use of the Le Fort I osteotomy has become more routine, various aspects of the procedure have been studied. Stoker and Epker’ demonstrated good skeletal stability in five subjects after simultaneous anterior and posterior maxillary osteotomies for superior movement of the maxilla. Schendel and associate2 evaluated stability and soft-tissue osseous relationships via computer morphometric analysis after superior maxillary repositioning by total maxillary osteotomy or combined anterior and posterior maxillary osteotomies. In a series of thirty patients with an average follow-up of 14 months, they found minimal postoperative maxillary movement, with the detectable movement occurring in the same direction in which the maxilla was moved surgically.

Effect of Le Fort I maxillary

Volume 85 Number 4

Fig. 1. Le Fort I osteotomy movement. A, Maxilla moved moved superiorly with removal and mandibular advancement zontal augmentation genioplasty.

to produce superior superiorly as one unit. of premolar osteotomy with vertical reduction

impaction

309

maxillary 6, Maxilla segment and hori-

When superiorly repositioned, the maxilla encroaches on the nasal cavity, therefore reducing its volume (Fig. 2). A proportional reduction in nasal airflow might be expected. In fact, early critics of Le Fort I osteotomy predicted a significant reduction in nasal airflow, which has prompted recommendation of other techniques ,3 such as total maxillary alveolar osteotomy , to avoid impingement on nasal airway space. Clinically, however, reduction in nasal airflow has not been a significant problem, even with the maxilla superiorly repositioned 8 to 10 mm. In an unpublished study, Graham4 measured expiratoty nasal resistance at fixed airflow rates before and 3 months after maxillary anterior osteotomy , posterior maxillary osteotomy , and Le Fort I osteotomy . In eleven of thirteen patients, an improvement in nasal resistance was achieved. The improvement, however, was not always correlated well with the patients’ subjective evaluation of their breathing patterns. Graham also stressed the need for proper surgical technique (grooving the maxillary nasal crest and reducing the nasal septum when necessary) to avoid buckling of the nasal septum or any other undesirable changes in nasal structures. A weak but variable linear correlation was found between superior maxillary movement and nasal resistance changes. Graham noted that patients whose presurgical nasal resistance was highest showed the most improvement in nasal resistance after surgery. He related this improvement to correction of nasal obstructions, for example, correction of nasal septal deviation, accomplished by adherence to proper Le Fort I surgical technique. The purpose of the present study was to determine the effect of maxillary impaction by total maxillary

Fig. 2. Superior

maxillary

movement

reduces

intranasal

di-

mensions.

osteotomy (Le Fort I) on nasal airway resistance and to evaluate the relationship between changes in anatomy and changes in nasal respiratory physiology. METHODS

Eleven white patients (seven females and four males) whose surgical-orthodontic treatment plans included superior maxillary repositioning were selected for participation in the study. The ages of the patients ranged from 13 to 29 years, with a mean of 21. All eleven osteotomies were performed by the Le Fort I down-fracture technique: six with no segmentalization of the maxilla and five with interdental osteotomies to achieve space closure or alteration of arch form (or both). Each patient also had simultaneous mandibular osteotomies. To determine the amount of superior maxillary movement, direct superimposition of the preoperative and 8-week postoperative cephalometric films was utilized. First, both films were placed on a high-intensity x-ray viewer in a darkened room. The two films were then positioned so that maximal numbers of cranial structures were superimposed, that is, sella, nasion, cranial outline, and so forth. Measurements were then taken perpendicular to the occlusal plane of the move-

310

Guenthner,

Sather,

and

Kern

Fig. 3. Technique used to measure the amount of superior maxillary movement from the cephalometric films.

ment of easily identifiable maxillary structures (dental fillings, orthodontic bands, bonded brackets) to determine the amount of superior maxillary movement (Fig. 3). If the posterior and anterior values differed, the mean of these values was taken. The measured amount of superior maxillary movement ranged from 2 to 8 mm, with a mean of 5.3. To assess the nasal airflow of each patient and to provide an objective quantification of nasal airway resistance, a technique known as uninasal anterior active mask rhinomanometry was utilized. This technique has been shown5 to be useful in clinical evaluation of nasal obstruction by providing objective data that can substantiate and quantitate the symptoms of nasal obstruction as well as evaluate the results of treatment. In each patient nasal airflow and pressure were measured a few days before surgery and again approximately 8 weeks after surgery. Nasal resistance was calculated from the measures of inspiratory nasal airflow and nasal pressure. Resistance refers to all factors that impede the flow of a fluid (air). Resistance reflects the functional status of the nasal airway. The techniques used in this study

Am. J. Orthod. April 1984

provide a value for inspirarory nasal resistance, in contrast to Graham’s4 use of an expirutory nasal resistance value. Intuitively, nasal resistance during inspiration seems to provide a more reliable indication of true nasal airway function than does nasal resistance during expiration. In fact, in a population of 1,000 patients with rhinologic complaints,5 inspiratory nasal airway resistance correlated well with the side and severity of nasal obstructive symptoms. Bridger,6 in discussing his model of the nasal valve functioning as a Starling resistor during inspiration, described the effect of the air pressure differential during inspiration (higher pressure extranasally, lower pressure intranasally) on the nasal valve. He showed that this pressure differential collapses the nasal valve, thus limiting airflow. It is important to note that, during expiration, the transnasal pressure differential is reversed (higher pressure intranasally, lower pressure extranasally), thus producing an opening effect on the nasal valve. Therefore, the nasal resistance during expiration and inspiration may be very different. To provide the inspiratory nasal resistance values in the study, the following technique was used: 1. A snugly fitting pressure nozzle is inserted into one nostril, thus providing a means of measuring transnasal pressure on the contralateral side. 2. An airtight mask with an attached flowmeter is placed over the patient’s face (Fig. 4). 3. The patient is instructed to relax and breathe normally through the nose while sitting quietly for a few moments. 4. A dual-channel recorder allows visualization of recorded transnasal airflow (v) and pressure (P). 5. Once the depth and frequency of respiration have stabilized, a sequence of four similar breaths, as seen on the graph readout, is used to obtain average peak inspiratory airflow and pressure values during quiet breathing. 6. These peak transnasal airflow and pressure values are used to calculate the uninasal resistance by the following equation: Resistance= Transnasalpressuredifference = p Airflow v 7. To obtain a resistance value for the contralateral nostril, the pressure nozzle is transferred to the other nostril and steps 1 through 6 are repeated. Once the uninasal resistance values of the right and left sides have been obtained by the above sequence of steps, a topical vasoconstrictor (1% phenylephrine) is sprayed into each nostril. The 1% phenylephrine produces maximal nasal mucosal shrinkage and removes the influence of any transient mucosal changes from the

Volume 85 Number 4

of Le Fort

Effect

I maxillary

impaction

311

Amplmsr

Fig. 4. Rhinomanometric technique utilized in study. (From Kern EB: Rhinomanometry. In Coates GM, Schenck HP, Miller MV: Otolaryngology, Hagerstown, Md., 1979, Harper & Row, Publishers, vol. 2, pp. 1-18, by permission.) Table

I. Data on eleven patients undergoing Le Fort I osteotomy Total

Case

Sex

1 2 3 4 5 6 7 8 9 10 11 Mean

F F F M F F M M M F F

Difference

from

Amount of impaction (mm)

Age W-4 17-10 13-4 26-10 27- 1 24-O 29-10 20-5 24-6 19-1 16-3 15-9 21-4

zero (two-tailed

7 7.5 4 2 5 6.5 4.5 4 8 7 2.5 5.3

signed-rank

test): *0.05

Before Preop

Rntotal =

(R&i& O&d

X (Rnr,rJ + (Rnd

resistance

(cm H,OILis) After phenylephrine

phenylephrine Postop

Difference

7.0 4.1 1.9 8.7 3.8 8.6 4.8 10.1 7.4 3.2 2.7 5.7

4.6 3.7 2.2 2.1 3.1 6.0 3.5 3.9 4.3 3.7 5.4 3.9

< P < 0.10.

**P < 0.01.

resistance calculations, thus providing a value that is more reproducible and more useful for comparison purposes. After a lo-minute waiting period, steps 1 through 7 are repeated. After completion of these, the values for uninasal airway resistances of the right and left sides (Rn,ipht and Rnt,rJ are inserted into the following equation in order to calculate total nasal airway resistance (Rn,& before and after application of a topical vasoconstrictor:

nasal

-2.4 -0.4 +0.3 -6.6 -0.7 -2.6 -1.3 -6.2 -3.1 -to.5 f2.7 -1.8 (Median - 1.3)*

Preop

Postop

5.8 1.9 1.2 2.3 2.2 3.9 2.9 3.7 3.1 2.3 2.6 2.9

2.0 1.7 1.2 1.2 2.4 2.3 1.6 2.2 2.3 2.1 2.5 2.0

Di$erence -3.8 -0.2 0 -1.1 f0.2 -1.6 -1.3 - 1.5 -0.8 -0.2 -0.1 -0.9 (Median -0.8)**

RESULTS

Clinical symptoms of nasal obstruction usually occur when the total nasal resistance (after 1% phenylephrine) is greater than 3 cm H,O/L/s.j The preoperative resistances ranged from 1.2 to 5.8 cm H,O/L/s, with a mean of 2.9 (Table I). The postoperative resistance measures ranged from 1.2 to 2.5, with a mean of 2.0. More significant than the actual numerical values, however, is the observation that while four of the preoperative values were higher than 3, none of the postoperative values was higher than 3. Closer inspection of the changes in resistance for each patient reveals that

312

Guenthner,

Am. J. Orthod. April 1984

Sather, and Kern

1 A Rn

cm H,O/L/sec.

cm

-I

-

-2 -3 -

0 PreoP

POStoP

a. Before 1% Phenylephrine

PWOP

Postop

nine of the eleven demonstrated measurable improvement (decrease in resistance), with one patient showing no demonstrable change and another showing a slight increase in nasal resistance (from 2.2 to 2.4 but still well below 3). These improvements in nasal resistance to airflow were statistically significant (P < 0.01). There was a significant reduction in variability produced by the application of 1% phenylephrine (Fig. 5). The preoperative values before application of topical 1% phenylephrine ranged from 1.9 to 10.1, with a mean of 5.7 (Table I). The postoperative values ranged from 2.1 to 6, with a mean of 3.9. Both of these ranges are approximately twice as large as the corresponding ranges after application of 1% phenylephrine. After surgery, the individual responses (changes in resistance) before the application of 1% phenylephrine also showed more variability, with eight patients having decreases and three having increases. This suggests a tendency toward an overall decrease in resistance (0.05


superior maxillary movement and the change in nasal resistance. However, a negative relationship was noted between the initial nasal resistance values and the change after maxillary impaction. Thus, patients with higher initial resistance values (after the application of topical 1% phenylephrine) tended to show the most improvement in nasal resistance values after operation

1

2

Preoperative nasal 1% Phenylephrine

b. After 1% Phenylephrine

Fig. 5. Improvement (decrease in resistance) of nasal airway respiratory function observed after Le Fort I impaction. a, Note the greater range and variability of responses observed without using 1% phenylephrine to produce maximal nasal mucosal decongestion. Arrows indicate mean values. b, Use of 1% phenylephrine essentially eliminates the effects of nasal mucosal congestion, thus providing a reliable and reproducible measurement. When measured after administration of 1% phenylephrine, symptoms of nasal obstruction typically occur with nasal resistance greater than 3.0 cm H,O/LIs (dotted line) with the equipment and methods used in this study. See text for discussion and statistical analysis.

L.

r=-.93 99% C.I. -.99 to -.62

3

4

5

6

resistance (Rn) after (cm H,O/L/sec.)

Fig. 6. Negative correlation between the initial nasal value and the change brought about by maxillary (The higher the initial value, the greater the observed in resistance.) C.I., Confidence interval.

resistance impaction. decrease

(Fig. 6). The correlation coefficient between the actual change in resistance (in cm H,O/L/s) and the initial value was -0.93 (P < 0.001). The 99% confidence interval for the correlation coefficient ranged from -0.99 to -0.62. If the change in resistance was expressed as a percentage of the initial value and then plotted against the initial preoperative value (Fig. 7), the correlation coefficient was -0.77 (P < O.Ol), with a 99% confidence interval ranging from -0.96 to -0.11. The low P values associated with the correlation coefficients support the notion of a correlation between the initial preoperative resistance value and the observed postoperative change, but, because of the relatively small sample size, the 99% confidence intervals are somewhat large. Similar patterns of correlation were observed with the nasal resistance values taken without using 1% phenylephrine, but the variability was higher, as would be expected. DISCUSSION

The most significant finding was an objective improvement in the patients’ nasal airway function after superior maxillary movement via Le Fort 1 osteotomy (in basic agreement with Graham4). In addition, patients who initially had the highest nasal resistance values experienced the most improvement in their nasal airway after Le Fort I impaction surgery. At first glance, this improvement seems to be an unexpected finding. The finding that a patient who required Le Fort I superior movement because of excessive facial height (typically associated with a narrow nose, a deficient nasal airway, and a mouth-breathing tendency) actually showed improved nasal airflow after the maxilla was moved further up into the nasal cavities would seem to be difficult to explain. However, this improved nasal airway function associated with Le Fort I superior

Volume 85 Number 4

Effect of Le Fort I maxillary

Percentage change

impaction

313

1 -50

c

A

r=-.?? 99% C.I.

P= I

1

A

-96 to

-, 11

1

I

I

I

I

I

1

2

3

4

5

6

4

Preoperative nasal 1% Phenylephrine

resistance (Rn) after (cm H20/L/sec.)

Fig. 7. Negative correlation between the initial nasal resistance value and the change brought about by maxillary impaction. (Change in resistance values expressed as a percentage of the initial value.) C.I., Confidence interval.

movement is explainable on plausible and rational bases. The nasal septum can be divided into several areas (Fig. 8). From a functional standpoint, the narrowest portion of the nasal passage serves as a flow-limiting segment and is an important determinant of nasal airflow resistance. In black people (with platyrrhine noses), the narrowest portion of the nasal passage is the area between the nasal septum and the anterior part of the inferior turbinate. Thus, the inferior turbinate probably is the most important inflow regulator (turbinal valve) in blacks. In white people (with leptorrhine noses), the narrowest portion of the nasal passage is the nasal valve area (area 2 in Fig. 8), which is probably the most important inflow regulator, accounting for most of the inspiratory resistance to airflow.6-s The nasal valve urea is a teardrop-shaped area (Fig. 9) bounded by the nasal septum, the caudal ends of the upper lateral cartilage, the soft fibrofatty tissue overlying the pyriform aperture, and the floor of the nose. The nasal valve is the apex of the nasal valve area and is bounded by the nasal septum and the caudal end of the upper lateral cartilage. Normally, the angle between the nasal septum and the upper lateral cartilage is 10” to 15”. Fig. 10 shows a clinical view of the nasal valve. The sensitivity of the nasal valve and the ability of small changes in the nasal valve to produce significant changes in nasal airflow can be demonstrated by a selfadministered Cottle test (Fig. 11). Even in the absence of significant nasal valve disease, a slight lateral pull on the cheek can produce a noticeable improvement in nasal airflow on the test side, even though the actual change in the nasal valve is very small. Le Fort I superior maxillary movement produces changes in external nasal dimensions, most commonly

Fig. 8. Areas of the nose. Area 7 (vestibular area) is the region of the caudal end of the nasal septum and its relationship to the anterior naris. Area2 (nasal valve area) is bounded by the nasal septum, the caudal end of the upper lateral cartilage, and soft fibrofatty tissue overlying the pyriform aperture and the floor of the nose. Thii area is shaped like a teardrop, the slitlike apex of which is the nasal valve. Area 3 (attic area) of the nasal septum is under the bony vault of the nasal bones. Area 4 (anterior turbinate area) of the nasal septum is in the region of the turbinates. Area 5 (posterior turbinate area) of the nasal septum is in the region of the choanae. (From Kern EB: Surgery of the nasal valve. In Sisson GA, Tardy ME Jr: Plastic and reconstructive surgery of the face and neck, New York, 1977, Grune & Stratton, vol. 2, pp. 43-59, by permission.)

an increase in the alar base width.3 This change can be undesirable in patients with good presurgical nasal esthetics. However, the typical candidate for Le Fort I superior movement frequently has a deficiency in alar width; therefore, the increase in alar width produced by Le Fort I impaction is esthetically desirable. This increase in alar width also may befunctionally desirable and may provide a mechanism for the reduction in nasal airway resistance observed after Le Fort I superior maxillary movement. The increase in alar width also presumably increases the width of the basal portion of the nasal valve area. In addition, this widening of the basal portion of the nasal valve area might increase the nasal valve angle, thus reducing the nasal airway resistance to airflow in a manner similar to the Cottle test by opening the nasal valve (Fig. 12). Thus, the increase in alar width produced by Le Fort I superior movement may open the nasal valve, paradoxically reducing nasal resistance, while the maxilla is moved superiorly into the nasal cavity. Although this study did not measure nasal width, the data did show that patients with high preoperative nasal resistance (which is likely associated with a narrow nose and a narrow nasal valve) tended to obtain the greatest reduction in nasal airway resistance

. 314

Guenthner,

Sather,

and

Kern

Fig. 9. Nasal valve area is bounded by nasal septum, caudal ends of upper lateral cartilage (UC), and soft fibrofatty tissue overlying the pyriform aperture and floor of the nose. This area is shaped like a teardrop, the slitlike apex of which is the nasal valve. Inset: Nasal valve is slitlike triangular opening at apex of nasal valve area (cross-hatched) and is bounded by the caudal end of the upper lateral cartilage and the nasal septum. The nasal valve angle represents the angle between the upper lateral cartilage and the nasal septum and is normally lo” to 15”. (From Kern EB: Surgery of the nasal valve. In Sisson GA, Tardy ME Jr: Plastic and reconstructive surgery of the face and neck, New York, 1977, Grune & Stratton, vol. 2, pp. 43-59, by permission.)

Am. J. Orthod. April 1984

Fig. 11. Cottle test. Cheek is pulled away from midline, carrying upper lateral cartilage away from septum; thus, slitlike angle is opened. (From Kern EB: Surgery of the nasal valve. ln Sisson GA, Tardy ME Jr: Plastic and reconstructive surgery of the face and neck, New York, 1977, Grune & Stratton, vol. 2, pp. 43-59, by permission.)

’ Septum Wow ofnose

Fig. 12. This illustrates the proposed mechanism to explain the paradoxical decrease in nasal resistance after superior maxillary movement via Le Fort I osteotomy. As the maxilla is moved superiorly a predetermined amount (cross-hatched area), the nasal floor is raised. Raising the nasal floor increases the alar base width. It is postulated that the increase in alar base width (lower black arrow in inset) produces a similar width increase in the nasal valve angle (upper black arrow ininset), thus opening the nasal valve and reducing nasal resistance to airflow. (By permission of Mayo Foundation.) Fig. 10. Clinical view of nasal valve. (From Kern EB: Surgery of the nasal valve. In Sisson GA, Tardy ME Jr: Plastic and reconstructive surgery of the face and neck, New York, 1977, Grune & Stratton, vol. 2, pp. 43-59, by permission.)

after the operation, which may be associated with an increased alar width and increase in the nasal valve angle. The specific relationship between nasal alar width changes and nasal resistance changes needs clarification by further research. SUMMARY

1. Superior maxillary movement via the Le Fort I osteotomy is a useful, effective, and stable procedure

as part of the overall surgical-orthodontic treatment to reduce vertical facial dimensions in patients with longface syndrome, vertical maxillary excess, skeletal open bite, or other dentofacial deformities involving excessive facial height. 2. The data demonstrated a statistically significant (P < 0.01) reduction in total nasal airway resistance after superior maxillary movement by the Le Fort I osteotomy. Also, a negative correlation was found between the initial nasal resistance value and the amount of postoperative resistance decrease; that is, the higher the initial resistance, the larger the postoperative decrease in nasal airway resistance. This correlation was

lJotume 85 Number

Effect of Le Fort I maxillary

itnpaction

315

4

demonstrated when the change in resistance was expressed as the actual value in cm H,O/L/s (r = -0.93, P < 0.001) and when the resistance change was expressed as a percentage of the initial value (r = -0.77, P < 0.01). 3. The decrease in nasal airway resistance after superior maxillary movement probably can be explained on the basis of nasal physiology, especially that of the nasal valve, and the positive influence of increase in alar width on nasal valve function. 4. This study involved only white patients, and the results and discussion would apply only to persons with a leptorrhine nasal configuration. Significant differences in basic physiology have been demonstrated to exist between the white (lepton-hine) nose and the black (platyrrhine) nose.

3.

4.

5. 6. 7.

8. 9.

sitioning of the maxilla: stability and soft tissue osseous relations. AM J ORTHOD 70: 663-674, 1976. Bell WH, Proflit WR, White RP Jr. (editors): Surgical correction of dentofacial deformities, Philadelphia, 1980, W. B. Saunders Company, ~01s. 1 and 2. Graham CR: The effect of superior repositioning of the maxilla on nasal airway resistance and airflow: a short term study. Master’s Thesis, 1977, University of North Carolina. McCaffrey TV, Kern EB: Clinical evaluation of nasal obstruction: a study of 1,000 patients. Arch Otolaryngol 105: 542-545, 1979. Bridger GP: Physiology of the nasal valve. Arch Otolaryngol92: 543-553, 1970. Kern EB: Surgery of the nasal valve. In Sisson GA, Tardy ME Jr. (editors): Plastic and reconstructive surgery of the face and neck, New York, 1977, Grune & Stratton, vol. 2, pp. 43-59. Van Dishoeck HAE: Inspiratory nasal resistance. Acta Otolaryngol (Stockh) 30: 431-439, 1942. Van Dishoeck HAE: The part of the valve and the turbinates in total nasal resistance. Int Rhino1 3: 19-26, 1965.

Reprint requests ro. REFERENCES 1. Stoker NG, Epker BN: The posterior maxillary ostectomy: a retrospective study of treatment results. Int J Oral Surg 3: 153-157, 1974. 2. Schendel SA, Eisenfeld JH, Bell WH, Epker BN: Superior repo-

Dr. T. A. Guenthner Department of Dentistry Mayo Clinic 200 First St. SW Rochester, MN 55905