AJODO 1993 mar 203-211 Taken from the AJO-DO on CD-ROM (Copyright 1997 AJO-DO), Volume 1993 Mar (203 - 211): CASE REPORT -

AJODO 1993 mar 203-211 Taken from the AJO-DO on CD-ROM (Copyright 1997 AJO-DO), Volume 1993 Mar (203 - 211): CASE REPORT - Popp, Gooris, and Schur--------------------------------

Nonsurgical treatment for a Class III dental relationship: A case report

Thomas W. Popp, DDS, MSD, Christel G. M. Gooris, DDS, MSD, and Jeffrey A. Schur, DDS, MSD

Seattle, Wash.

The purpose of this report is to review the orthodontic treatment of a patient with a Class III malocclusion who was treated nonsurgically with extraction of the mandibular first premolars. The basis for this treatment approach is presented, and the final treatment result reviewed. Important factors to consider when establishing a Class III molar relationship are discussed. (AM J ORTHOD DENTOFAC ORTHOP 1993;103:203-11.)

Edward H. Angle described a Class III malocclusion as one in which the lower first molar is mesially positioned relative to the upper first molar.1 This relationship may result from a normal maxilla and mandibular skeletal protrusion or a maxillary retrusion and a normal mandible or a combination of maxillary retrusion and mandibular protrusion. A Class III dental relationship could also exist in a patient with a normal maxillomandibular relationship. Patients with a Class III malocclusion usually have a concave facial profile, and the lower lip often is protruded relative to the upper lip. Sometimes a Class III relationship is caused by a forward shift of the mandible to avoid incisal interferences. This is a pseudo Class III malocclusion.2 The influence of environmental factors and oral function on the etiologic factors of a Class III malocclusion is not understood completely. However, there is a definite familial and racial tendency to mandibular prognathism.3 In the United States true skeletal Class III malocclusions are found in less than 1% of the general population.4,5 Most orthodontists therefore have much less experience treating patients with Class III malocclusions than they do in treating patients with Class I or Class II malocclusions. For many Class III malocclusions, surgical treatment is the best alternative. Depending on the amount of skeletal discrepancy, surgical correction may consist of mandibular shortening, maxillary lengthening, or a combination of mandibular and maxillary procedures. After surgical correction of the skeletal discrepancy, the occlusion usually can be finished orthodontically in a Class I relationship by using the same principals as in finishing a patient with a nonsurgical Class I relationship. However, if surgical treatment is not performed, and the final molar relationship is Class III, there are challenges specific to the static and functional Class III occlusion that must be considered. The following case report will illustrate some of these challenges and how to deal with them.

CASE REPORT

Patient history

Medical. The patient was examined initially at the University of Washington Orthodontic Department at age 12 years 4 months (Fig. 1). She was a healthy Asian girl with no history of significant medical problems.

Dental. The patient had received regular dental care. Her oral hygiene was poor. No caries were present, and all restorations were in good condition.

Growth. The patient had passed menarche, and in comparison with an older sibling and her parents, indicated that minimal growth remained.

Dental relationship

Fig. 1. Pretreatment photographs at age 12 years 4 months.

A full complement of permanent teeth were present (Fig. 2). All third molars were unerupted. In centric occlusion (CO) molar and canine relationships were Class III, and the incisors were in anterior crossbite with a negative overjet of 3 mm. In centric relation (CR) the incisors were in an end-to-end relationship. The maxillary midline was coincident with the facial midline. In CR the mandibular midline was 3.0 mm to the right of the maxillary and the facial midlines. A 1.5 mm left lateral shift from CR to CO placed the mandibular midline 1.5 mm to the right of the maxillary and the facial midlines in CO. The curve of Spee was moderate with a 7 mm overbite in CO. In CR the incisors contacted end to end resulting in no overbite and a posterior open bite. Both the maxillary and the mandibular arches exhibited moderate arch length deficiencies. No tooth size discrepancies were noted. The maxillary second molars were erupting buccally. Oral hygiene was poor, and the gingiva was mildly inflamed. All restorations were in good condition.

Radiographs (Fig. 3) showed normal bone and tooth development. The third molars were developing, and all teeth exhibited normal root length. Although a functional shift was present from CR to CO, no signs of temporomandibular joint dysfunction were detected.

Fig. 2. Pretreatment study models, 12 years 4 months.

Fig. 3. Pretreatment radiographs.

Facial appearance

The patient's profile was concave in centric occlusion and straight in centric relation (Fig. 1). The lower lip was prominent, and lips were competent with no mentalis strain. Vertical facial proportions were normal, and there were no significant asymmetries.

Pretreatment cephalometric evaluation (Fig. 3)

The maxilla was slightly anterior to the cranial base (SNA 85), and in CO the mandible was significantly anterior to the cranial base and maxilla (SNB 87). The ANB ( 2) indicated a Class III skeletal relationship (Fig. 4). The maxillary incisors were slightly upright, while the mandibular incisors were retroclined (incisor-mandibular plane 80). The mandibular plane was slightly steep relative to cranial base (SN-MPA 35).

Etiologic factors

This malocclusion was primarily due to a skeletal discrepancy between the maxilla and the mandible. In CO the mandible was protrusive relative to the cranial base. The patient was unable to achieve normal function in CR and adapted with an anterior shift to a position where she could function. This shift resulted in an anterior crossbite and a negative overjet. Anterior dental tipping had resulted from this skeletal discrepancy.

Treatment objectives

1. To eliminate CR-CO discrepancy and anterior crossbite.

2. To establish Class I canine relationship.

3. To eliminate maxillary and mandibular arch length deficiencies.

4. To reduce overbite.

5. To align arches including midlines.

6. To establish a functional occlusion.

Treatment plan

Because of the functional shift and the end-to-end incisor relation in CR, this patient was treated with mandibular extractions instead of orthognathic surgery. The following treatment plan was established:

1. Extract mandibular first premolars.

2. Establish Class III molar and Class I canine relationship.

3. Maxillary and mandibular fixed appliances (standard edgewise 0.022).

4. Initial leveling and alignment with round arch wires.

5. Mandibular space closure using rectangular wire with lingual root torque in incisor region.

6. Class III elastics as needed.

7. Evaluate root alignment after space closure.

8. Extract maxillary second molars.

9. Finishing and occlusal equilibration.

10. Remove appliances.

11. Retention; maxillary circumferential, mandibular spring retainer.

12. Monitor third molar eruption.

Treatment progress

Fig. 4. Pretreatment cephalometric tracing, 12 years 4 months centric occlusion.

The appliances were cemented after extraction of mandibular premolars. Initial alignment and space closure proceeded smoothly and without complication. Class III elastics were used during space closure, and Class I canine and Class III molar relationships were established. Patient cooperation and compliance were good. Near the end of treatment the patient was involved in an automobile accident that displaced several maxillary and mandibular teeth. The appliances may have prevented some teeth from being totally avulsed. Several teeth required rebonding, and small, flexible round wires were placed in both arches. The displaced teeth returned to their preaccident position quickly and without further complication. Treatment time was probably extended 2 to 3 months because of the accident, but the final result was unaffected. Fixed appliance treatment was completed in 36 months. Occlusal equilibration was done before and after appliance removal to provide improved contact.

Treatment results

The treatment plan was a satisfactory nonsurgical alternative, and the treatment objectives were achieved (Figs. 5 and 6). A Class I canine relationship was established with good alignment. Some occlusal adjustment was needed to finalize the occlusion. All CR-CO shifts were eliminated, and centric occlusion and centric relation were coincident. A positive overjet was established, and overbite was reduced. Good torque control was maintained while the mandibular incisors were retracted resulting in better incisal inclination after treatment. The maxillary incisors were proclined significantly resulting in a better upper lip prominence and an improved facial profile. Growth was minimal, and correction of the malocclusion was accomplished with dental movement. The mandibular plane angle was opened minimally with an increase of only 1. Skeletally, the mandible is still prognathic, and the chin is slightly prominent (Figs. 7 and 8). A final panoramic radiograph shows all third molars are developing and may erupt into occlusion. The mandibular right second molar had a large carious radiolucency. The patient was referred for restoration of that tooth and a complete dental examination.

Fig. 5. Posttreatment photographs at age 15 years 6 months.

Fig. 6. Posttreatment study models, 15 years 6 months.

Fig. 7. Posttreatment radiographs.

Fig. 8. A, Pretreatment centric relation. B, Superimposition of pretreatment centric occlusion to posttreatment centric occlusion.

Secondary treatment

On completion of active treatment, further occlusal adjustment was performed, and a maxillary circumferential and a mandibular spring retainer were inserted. The patient was instructed to wear the retainers day and night for 1 year and then at night only.

DISCUSSION

Surgical correction would be another alternative to treat this malocclusion. Surgical alternatives included a bilateral sagittal osteotomy to retract the mandible, or a LeFort I procedure to advance the maxilla, or a combination of these. Current surgical techniques offer solutions in treating malocclusions and skeletal discrepancies that otherwise would be difficult, if not impossible, to achieve. However, there are still associated surgical risks and complications that must be considered, as well as the increased expense. If a nonsurgical treatment alternative can produce results comparable with those that could be achieved surgically, then it should be considered and may be the treatment of choice for some patients.

In this patient there was a significant skeletal discrepancy, but the presence of a functional shift and an end-to-end incisor relationship in CR made nonsurgical treatment a viable option. It was believed that an acceptable facial profile and functional occlusion could be achieved by treating this patient with mandibular extractions instead of orthognathic surgery. Although the jaws were not repositioned to correct the malocclusion, a reduction genioplasty procedure to reduce the prominence of the chin was discussed as a possibility. At the end of treatment, the chin was slightly prominent, but not enough to warrant the genioplasty procedure. The possibility of further mandibular growth was discussed, but it was thought that any remaining growth would be minimal.

The mandibular first premolars were extracted to allow for maximal retraction of the mandibular anterior teeth. Class III elastics were used during closure of the extraction spaces to maximize the retraction and to preserve mandibular posterior anchorage. The retraction allowed for the establishment of a Class I canine relationship. The molars were left in a Class III relationship. In this type of malocclusion the extraction of mandibular incisors may also be a possibility. This would reduce the arch circumference and provide positive overjet but would require substitution of canines for lateral incisors and first premolars for canines. That substitution might produce tooth size discrepancies and compromise the anterior esthetic result.

A Class III molar relation presents some unique occlusal contacts. The maxillary first molar occludes with the mandibular second molar so the maxillary second molar has no opposing tooth and does not provide any function. If not addressed, the maxillary second molar can overerupt and impinge on the mandibular gingival tissues. One alternative would be to hold the maxillary second molar, at the plane of occlusion while waiting for the possible eruption of the mandibular third molars to function with them. This would require a splint for several years with the possibility that the mandibular third molars may not erupt into occlusion. If the maxillary second molars are extracted, no maintenance is required, and both the maxillary and mandibular third molars may erupt into occlusion at a later time.

In a Class I molar relationship the mandibular first molar normally occludes with the maxillary second premolar and the first molar. In a Class III relationship the mandibular first molar occludes with the maxillary first and second premolars. The occlusal anatomy of these teeth can prevent good contact and interdigitation. Occlusal adjustment during and after treatment can improve the occlusion. The most prominent interference comes from the buccal of the mandibular molars occluding with the lingual inclines of the buccal cusps of the premolars. To eliminate this problem, a combination of tooth positioning and enamel recontouring is used. The mandibular molars should be positioned more to the lingual than in a Class I relationship, and the maxillary posterior teeth are positioned more to the buccal. Enamel recontouring usually involves the buccal of the mandibular molars and the lingual ridges of the buccal cusps of the maxillary premolars and first molar. Specific recontouring depends on the tooth anatomy of each individual patient. Although some may not consider this an ideal occlusion, balanced tooth contact can be obtained in a Class III relationship.

The functional excursions are usually not a problem because Class I canines and good overbite-overjet relations are established. Incisal and canine guidance can be achieved. Group function in lateral excursions can also be achieved but is more difficult because of the molar-premolar occlusion. The Class III molar occlusion usually does cause increased balancing interferences.

In addition to retraction of the mandibular anteriors, some proclination of the maxillary incisors is usually required to establish good overjet relations. This proclination can also add prominence to the upper lip and produce a better esthetic relationship between the upper and lower lips. If correction can not be achieved without excessive proclination an alternative treatment plan should be considered. Surgical treatment may allow correction while maintaining ideal root and crown positions. Proclination of the maxillary incisors can also increase root proximity. When proclined, the incisal edges are in an arc of greater circumference than are the root apices. Therefore the roots must taper together to fit in the smaller arc and will not be parallel. If the teeth are upright and the incisal edges and root apices occupy the same circumferential arc, the roots will have more interproximal bone between them. It is not clear whether either of these positions is more desirable than the other, but extremes in either direction should be avoided.

The health of the periodontium should always be considered in developing a treatment plan. Minimal attached gingiva in the mandibular incisor region is often seen. This can be a problem if proclination of those teeth is considered. Grafting procedures are sometimes done before orthodontic treatment. However, when lower premolars are extracted and the incisors are retracted, the amount of attached tissue is usually not a concern. Proclination of maxillary incisors may be dependent on gingival health and contour in that area and must also be considered before deciding on this treatment choice.

If this nonsurgical approach to treating a Class III malocclusion is used, consideration must be given to the orthodontic appliance to produce the best occlusal and esthetic results. A straight wire appliance may not be the best choice in this situation. The tips, torques, and offsets built into the brackets may not produce the desired tooth positions. Compensatory bends in the wire may be required to produce ideal cosmetic and functional results.

SUMMARY

Treatment of a Class III patient with extraction of mandibular first premolars was reported. The basis for this treatment approach was presented, and the final treatment result was reviewed. Some important factors to consider when establishing a Class III molar relation were discussed to provide the clinician with a better understanding of this treatment alternative.

We express our sincere gratitude to Dr. Vincent Kokich for his valuable assistance in preparing the manuscript for this report and Mr. Jim Clark for his photographic assistance.

Eur J Orthod 1996 Jun; 18-3- 227-235 - A molecular mechanism of integrin regulation from bone cells stimulated by orthodontic forces

R. S. Carvalho*, A. Bumann**, C. Schwarzer**, E. Scott*** and

E. H. K.Yen****

Department of Preventive Dental Science, University of Manitoba, Canada, **Department of Orthodontics, University of Kiel, Germany; ***Departments of Anatomy and Oral Biology, University of Manitoba and ****Faculty of Dentistry, University of British Columbia, Canada

SUMMARY The purpose of this paper is to discuss a molecular mechanism in the signal transduction pathways of the regulation of integrin genes taking place in bone cells as a result of orthodontic or mechanical stimulation. Human osteosarcoma (HOS) TE-85 cells were cultured in Dulbecco's modified Eagle's medium (DMEM)/F-12 and grown to confluency in Flexercell type I dishes and orthodontic forces were applied to the cells via an intermittent strain of 3 cycles/minute using the Flexercell Strain Unit System for periods of 15 and 30 minutes, 2 and 24 hours and 3 days. Antibodies against B, and integrins were immunolocalized in strained and unstrained cultures. Total RNA was extracted and cDNA probes were used to measure at various mRNA expression of B| (1.2 kb) and