Many treatment options are available to address the problem of missing second premolars. Extraction of retained deciduous second molars and subsequent space closure are often appropriate because this option alleviates the need for implants or other restorations. This article describes the conventional orthodontic closure of unilateral and bilateral congenitally missing second premolar spaces after the extraction of retained deciduous second molars.
Highlights
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An option for addressing the problem of missing second premolars is space closure.
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Space closure eliminates the need for implants or restorations if the deciduous tooth is lost.
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Space closure can reduce bialveolar protrusion.
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Careful attention to anterior anchorage preservation is needed.
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Mechanics can be challenging if anterior anchorage requirements are critical.
Various definitions that depend on the number of missing teeth are used to describe congenitally missing teeth: hypodontia, oligodontia, and anodontia. The absence of just 1 or a couple of teeth is hypodontia. , Features commonly associated with hypodontia are microdontia, peg lateral incisors, infraocclusion of primary molars, palatally impacted canines, lower mandibular plane angles, short anterior facial height, and a large freeway space.
After third molars, mandibular second premolars are the most common congenitally missing teeth. , The etiology of congenitally missing mandibular second premolars can be a consequence of a physical obstruction or disruption of the dental lamina, limited space, functional abnormalities in the dental epithelium, or failure of initiation of the underlying mesenchyme.
Retained deciduous second molars and congenitally missing second premolars can be managed by several treatment alternatives: (1) maintenance of the deciduous second molar, , (2) spontaneous space closure by extracting the deciduous second molar before the eruption of the first permanent molar, (3) space closure with controlled slicing and hemisection of the deciduous second molar, , , (4) orthodontic space closure following extraction of the deciduous second molar, , (5) autotransplantation, (6) implant replacement, (7) conventional fixed bridge, and (8) resin-bonded bridge.
Careful selection of the treatment plan is required when the second premolar is missing. Several factors should be considered during treatment planning, including the condition of the retained deciduous second molar, the patient’s age, space requirements for malocclusion correction, facial profile, patient’s treatment preference, and treatment time. , ,
Retaining healthy deciduous second molars has, for some patients, shown good prognosis and acceptable long-term clinical results, , , , but some risks should be considered. These risks include the deciduous tooth’s long-term prognosis due to root resorption, the acceptance of a Bolton tooth size discrepancy between the deciduous second molar and the permanent second premolar, pulpal pathology, crowding, ankylosis, and infraocclusion. These factors, for many patients, support extraction of the deciduous molar when a permanent second premolar is congenitally missing. , Infraocclusion is associated with permanent tooth agenesis and root resorption , and can be a critical factor in the decision to extract retained deciduous molars when the patient has the potential for more growth. , If the space that results from the extraction of the deciduous second molar is to be preserved for a dental implant after facial growth is complete, the width of the alveolar ridge will narrow, and the need for a bone graft will increase. , An ankylosed deciduous molar is related to infraoccluded teeth and could cause a vertical bone defect. Therefore, the extraction of ankylosed deciduous molars is recommended because the alveolar ridge moves occlusally as the adjacent teeth continue to erupt. ,
One risk with the extraction of the deciduous second molar can be flattening of the facial profile, especially in patients who present with flat or concave facial profiles. However, this risk can be mitigated with proper biomechanical planning and proper anterior anchorage control. , , This clinical article will describe the closure of both unilateral and bilateral spaces, which were created by the extraction of deciduous second molars when the second premolars were missing.
Patient 1
Facial photographs ( Fig 1 ) of this patient illustrated a mild protrusion of the lips. The casts ( Fig 1 ) revealed an Angle’s Class II “end on” molar occlusion with over-retained deciduous maxillary canines, deciduous mandibular second molars, and a deciduous mandibular left first molar. The panoramic radiograph ( Fig 2 ) revealed all permanent teeth to be present in the maxillary arch, but both mandibular second premolars were congenitally missing. The cephalogram and its tracing ( Fig 2 ) illustrated a low mandibular plane angle, proclined mandibular incisors, and a good ratio of posterior facial height to anterior facial height.
Because of the patient’s protrusive lips, the goal for facial esthetics was to reduce lip protrusion in order to achieve facial balance and harmony. Because of the missing mandibular second premolars, maxillary second premolars and the retained deciduous mandibular second molars were removed. All spaces were to be closed by retraction of anterior teeth and protraction of maxillary and mandibular right and left first and second molars.
Treatment was initiated with full banding and bonding after the removal of all deciduous teeth and the maxillary second premolars. Initial archwires were 0.016 × 0.022-in stainless steel (SS). After leveling and alignment, the archwires were changed to 0.020 × 0.025-in SS. Closing loops with tie backs were used for space closure in the mandibular arch. Maxillary arch space closure was accomplished with an elastomeric chain. An elastomeric chain was also used in conjunction with the mandibular arch closing loops in the mandibular archwire. When the spaces were almost closed, the archwire size in both arches was increased to ideal 0.0215 × 0.0275-in SS for final space closure and tooth positioning.
The posttreatment facial photographs ( Fig 3 ) exhibit less protrusion and more facial balance. The posttreatment casts ( Fig 3 ) exhibit an Angle’s Class I canine and molar relationship and complete closure of all extraction spaces. The posttreatment panoramic radiograph ( Fig 4 ) shows total closure of the extraction spaces in both the maxillary and the mandibular arches. The roots of the teeth adjacent to the extraction sites are properly uprighted. The posttreatment cephalogram and its tracing ( Fig 4 ) illustrate maintenance of the vertical dimension, mild uprighting of the mandibular incisors to improve facial balance and harmony, and a reduction in the ANB angle. The pretreatment and posttreatment superimpositions ( Fig 5 ) confirm the incisor uprighting and mesialization of both maxillary and mandibular molars.
Patient 2
The facial photographs ( Fig 6 ) illustrate a very orthognathic and pleasing facial profile. Some would consider the profile to be a bit retruded, but the smile is full and pleasant. The casts ( Fig 6 ) confirm an end on molar relationship, but the deciduous second molars are still present. The maxillary lateral incisors are small. Overjet and overbite are relatively normal. The pretreatment panoramic radiograph ( Fig 7 ) reveals that all second premolars are missing. The 4 deciduous second molars have no permanent teeth to replace them. The cephalogram and its tracing ( Fig 7 ) confirm ideal cephalometric values with mild retrusion of the lips due to a large soft tissue chin.
If any patient ever needed nonextraction treatment, this is the patient. Had the maxillary and mandibular second premolars not been missing, this patient might not have needed orthodontic treatment. The general dentist could do cosmetic buildups for the lateral incisors, if indicated. Of course, this supposition is predicated on the fact that second premolars would erupt properly and there would be a shift of the mandibular molar forward into a nice Class I occlusion along with the proper eruption of all second molars. However, there was no chance for this to happen to this patient because of the congenitally missing second premolars. Options were discussed with the family. The option of leaving the dentition as it was until the patient was an adult and allowing the deciduous second molars to last as long as possible before considering orthodontics and replacements with implants or crowns was discussed at length. It was explained that this was probably the best option for the facial profile. The family was very concerned about the fact that there would be a considerable expense if the implant and crown restoration option became a reality during adulthood. They were not comfortable with this option and wanted to know if there was not some way that the problem could be eliminated during the patient’s adolescence. The option of removing the deciduous second molars and treating the patient with orthodontics to protract the posterior teeth was explained. The parent was told that this was going to be difficult, and if done, many practitioners would use mini-screws to protract the posterior molars. The family decided that this option would be the best for this patient.
The parent did not want to have the patient condemned to implants and crowns, should the deciduous second molars fail. The deciduous second molars were removed. The placement of temporary anchorage devices by an oral surgeon was eliminated because of a family financial issue. Conventional edgewise appliances were used. The archwires were fabricated so that there was third-order anchorage in the maxillary and mandibular anterior teeth as the molars were protracted. Initially, closing loops were used in the extraction sites. When maxillary and mandibular second molars erupted, these teeth were banded. The archwire was inserted into the buccal tubes, and protraction of first molars continued with the use of elastic chain as well as closing loops in the extraction sites.
The profile, very orthognathic at the outset, remains orthognathic at posttreatment ( Fig 8 ). The casts ( Fig 8 ) confirm the total closure of the deciduous maxillary and mandibular second molar extraction sites. The maxillary lateral incisors will be cosmetically bonded by the general dentist if it is desired by the family. The panoramic radiograph ( Fig 9 ) confirms the total space closure of all deciduous second molar extraction spaces. The posttreatment cephalogram and its tracing ( Fig 9 ) illustrate mild uprighting of the mandibular teeth from 94° to 90° and a change in the FMIA from 65° to 69°. ANB has been reduced to 1°. The Z angle, which was used to quantify the facial profile, has changed only 6° from 82° to 88°. The superimpositions of the cephalogram tracings ( Fig 10 ) confirm mild uprighting of mandibular incisors, a small amount of retraction of the maxillary anterior teeth with more third-order positioning, and considerable molar protraction.
The records of this patient have been incorporated into this short article because they represent the ultimate challenge of deciduous second molar extraction space closure. Rarely does the clinician have a patient who has all 4 of the second premolars missing. The treatment of this patient was not easy but not extraordinarily difficult. The overwhelming expense of implants with crowns during the patient’s adult life has been eliminated.
Patient 3
Facial photographs ( Fig 11 ) of this patient showed a relatively straight profile. The casts ( Fig 11 ) confirmed an Angle’s Class I molar relationship but an anterior open bite. The deciduous maxillary right second molar, the deciduous mandibular right second molar, and the deciduous mandibular left second molar remain in the arch. The panoramic radiograph ( Fig 12 ) confirmed a congenitally missing mandibular left second premolar. The cephalogram and its tracing illustrated a steep mandibular plane angle with an FMA of 32°, an incisor mandibular plane angle of 85°, and ANB of 4°.
Because of the patient’s soft tissue profile, the goal was to maintain the face as it was before treatment. Because of the missing mandibular left second premolar, it was decided both arches would be treated without removing any permanent teeth. The molars in the mandibular left quadrant would be protracted to close the space created by the missing mandibular left second premolar so that the patient would not need implant restoration. Although this was an ambitious treatment plan, patient cooperation was assured, and there was optimism that the plan would be successful.
The patient was banded and bonded with 0.022 standard edgewise appliance after the removal of all deciduous teeth. Initial archwires were 0.016 × 0.022-in SS. After leveling and alignment, archwires were changed to 0.019 × 0.025-in SS. A closing loop was placed in the deciduous mandibular left second molar extraction space. Anterior vertical elastics were used to help with open bite correction and to protect mandibular incisor position. Archwire sizes were changed to 0.0215 × 0.028-in SS and 0.020 × 0.025-in SS in the maxilla and mandible, respectively. Closing loop force in the mandibular left quadrant was continued, and Class II elastics from the mandibular left first molar to a hook on the maxillary archwire were initiated. Buccal and lingual power chains were also used in the mandibular left quadrant. The mandibular left first molar was brought forward. The second molar fully erupted during the first molar protraction. The archwire size was reduced to incorporate the second molar, but Class II elastics and power chain were continued from the first molar. Archwire size in the mandibular arch was increased back to 0.020 × 0.025-in SS once the second molar was leveled into the arch. Power chain and Class II elastics were continued on the left side until both mandibular left molars had been totally protracted. Finishing archwires (0.020 × 0.025-in SS) were placed in both arches, and the occlusion was finalized using cusp seating elastics.
The posttreatment facial photographs ( Fig 13 ) exhibit an unchanged facial profile. The posttreatment casts ( Fig 13 ) exhibit Class I canine and molar relationships on the right side, with a Class III molar relationship on the left side. The maxillary left second molar will have to be held in place by slight contact with the distal cusp of the mandibular left second molar until the mandibular left third molar eventually erupts to occlude with the tooth. The posttreatment panoramic radiograph ( Fig 14 ) exhibits adequate uprighting of the mandibular left first and second molars into the missing premolar extraction space. The posttreatment cephalogram and its tracing ( Fig 14 ) confirm the maintenance of the vertical dimension and mandibular incisor position. ANB has been reduced to 1°. The profile line to nose relationship was not changed during treatment. Superimpositions ( Fig 15 ) confirm excellent downward and forward growth, which is desirable for a high mandibular plane angle patient. The maxillary incisor position was not appreciably changed, but the mandibular left molar position was changed quite a bit because of molar protraction. The maxillary molars were held in their pretreatment positions.
