A modification to the incisor classification of malocclusion.
The British Standards Institute classify the incisor relationship as Class I, Class II division I or division II, and Class III. Incisal relationship Class II Div. Class II malocclusion is extremely common in mixed dentition. including digit sucking, a lip trap or an underlying skeletal II base relationship. Being bullied was significantly associated with Class II Division 1 incisor relationship (P = 0·), increased overbite (P = 0·), increased overjet (P = 0· ).
A discrepancy in tooth size involving pegshaped or missing upper lateral incisors. Ectopic eruption, severe malpositioning, transposition, or exclusion of a lower incisor. Significant gingival recession or labial dehiscence of a lower incisor.
A Class I case with moderate lower-anterior crowding of as much as 5mm although a residual overjet may result. A moderate Class III malocclusion with an edge-to-edge occlusion or anterior crossbite tending toward anterior open bite.
Extraction of a lower incisor is contraindicated in the following clinical situations: Excessive overjet that would be worsened by the extraction. A deep bite that would be further deepened by closure of the extraction space.
A triangular lower incisor whose extraction could result in a loss of gingival papilla between the remaining incisors. A space requirement of less than 3mm, which would be better managed by interproximal enamel reduction than by extraction.
A lower-anterior tooth-size discrepancy in which extraction of a lower incisor could create a mandibular deficiency, making it difficult to obtain an ideal anterior occlusion. High insertion of the lower labial frenum, which could lead to gingival recession of a tooth moved into this region. Kokich and Shapiro strongly advocated the use of a diagnostic setup in lower-incisor-extraction cases to predict the precise occlusal result.
Case 1 A year-old female presented with the chief complaints of irregular front teeth and an inability to bite in the front because the lower teeth were ahead of the upper teeth. Clinical examination showed a Class III incisor relationship on a Class III skeletal base, with average lower-anterior facial height and a deficient Frankfort-mandibular plane angle Fig. The overjet was -2mm to the upper left lateral incisor; the overbite was reduced but incomplete, with an anterior open bite measuring 2mm at its worst point.
Invisalign Treatment of Class III Malocclusion with Lower-Incisor Extraction
We noted mild upper and moderate lower crowding, a lower midline shift to the left, and a bilateral buccal crossbite tendency. The panoramic x-ray demonstrated proper alveolar bone levels and root morphology, along with the presence of all permanent teeth except for the lower left lateral incisor, which had previously been extracted. Cephalometric analysis confirmed a Class III skeletal base with normally inclined upper incisors and retroclined lower incisors Table 1.
Because the patient did not want to wear visible appliances, treatment was planned with the Invisalign system. Space would be created in the upper arch by proclination of the upper incisors and a modest amount of expansion.
Extraction of the lower right central incisor, which was the most proclined and had the least satisfactory gingival contour of the remaining incisors, would provide space for relief of the lower crowding, while the incisor relationship would be corrected by minor retroclination. The objective was to maintain the Class III molar relationships and improve the overbite, accepting a lower midline discrepancy. Polyvinyl siloxane PVS impressions and a silicone bite registration were sent to Align Technology for the creation of pretreatment and projected end-of-treatment ClinChecks Fig.
We asked for slower staging to reduce the rate of tooth movement by half, to. Invisalign attachments are designed to provide 3D control of various tooth movements Table 2. In this case, to promote space closure and prevent tipping, vertical rectangular attachments 5mm high, 2mm wide, 1mm thick were bonded to the lower left central and right lateral incisors, and optimized rotation attachments were bonded to the upper canines Fig. Optimized rotation attachments were placed on the lower canines to provide a more acute activation angle between the aligner and the surface area of the attachments Fig.
Because the upper right central incisor, upper right lateral incisors, and upper left lateral incisor were lingually tipped compared to the upper left central incisor, optimized extrusion attachments were bonded to these teeth for. This ClinCheck programming would help close the anterior open bite and improve the smile line and incisor display. Beveled vertical rectangular attachments 5mm high, 2mm wide, 1.
Factors influencing orthodontic treatment time for non-surgical Class III malocclusion
A series of 29 aligners was fabricated, and the patient was instructed to wear each pair at least 20 hours a day for two weeks Fig. Activation angle of optimized attachments. After eight months of treatment. To promote root uprighting, sequential staging was performed on the teeth on either side of the extraction space were moved by the first three to four aligners, using the rest of the arch as anchorage, before the remaining teeth were repositioned. The Invisalign pontic system was used as a visual substitute for the extracted incisor Fig.
A bonding adhesive is applied to the inner surface of the aligner tray and let dry for 60 seconds before the tooth-colored PVS pontic is positioned in the aligner and allowed to set for five minutes.
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- Lower-Incisor Extractions
In the final stages, as the lower-incisor extraction space was closed, the pontic was omitted. Toward the end of treatment, composite buttons were bonded to the upper first molars and lower canines, and the aligner trays were modified for attachment of Class III elastics for finishing.
Three refinement aligners were required. After a total 16 months of treatment, upper and lower fixed retainers were bonded, and vacuum-formed retainers were delivered to be worn at night. The arches were well aligned, with positive overjet and improved overbite Fig. Patient after 16 months of treatment. A good esthetic result was achieved after closure of the lower-incisor extraction space.
The panoramic radiograph confirmed bodily tooth movement, with the roots of the remaining lower incisors almost completely parallel. A periapical radiograph showed no apical pathology of the lower right lateral incisor, as was suggested by the panoramic x-ray.
Case 2 A year-old male presented with the chief complaint of irregular front teeth and an almost edge-to-edge bite. No significant association with treatment duration was found. These data would be also indispensable for future investigations on treatment types and effectiveness of results.
Previous reports evaluating adult patients 16 showed that the amount of missed appointments is the factor that affects treatment duration These findings are supported by our findings This is a valuable information for orthodontists, since the patient also assumes some of the responsibility for the treatment time and it can persuade the patient into having good compliance.
Increments in treatment duration might be due to the necessity of returning to a lighter arch wire or the impossibility of treatment evolution in that month. Our findings indicate that patient cooperation appears to have a greater effect on duration of orthodontic treatment in Class III patients.
This might occur since it is known that moderate to severe Class III malocclusions can have a considerable impact on patient's aesthetics and quality of life, keeping them more motivated and easy to handle.
Clinically, this motivation should be increasingly utilized toward a shorter treatment duration. A previous study 1 reported that missed appointments and appliance repairs explained A different study 20 also shows that total brackets or bands breakage affects orthodontic treatment duration in teenage patients; however, no significant influence was found by the authors regarding missed appointments.
Maybe this could be explained by the fact that adolescents are more likely to accept parent control; therefore more assiduous than older adolescents or young adults.
Furthermore, intermaxillary elastics 24 are quite often required in Class III compensatory treatment, demanding good patient compliance. Peer Assessment Rating PAR was used to quantify the severity of the malocclusion given that it is a valid and reliable method: A possible explanation for this is the high PAR T1, which reflects poor patient compliance.
When the requirement of continuously using elastics is not met, the establishment of good occlusal relationship is affected, influencing the final PAR index. No statistical difference was found among patients who missed zero to two appointments and patients who missed more than two appointments during treatment regarding the final PAR index.
Age had no influence on treatment time in this study at the beginning of Class III treatment, differing from previous investigations examining Class I and Class II malocclusion 620 Therefore, other pretreatment or external factors, not included in this study, might be the reason why patients are skipping appointments.
When comparing only fixed treatment length, the literature shows no difference among patients treated for Class II malocclusion in one and two phases 9 as our findings. However, this does not mean that the first phase of the treatment is unnecessary. Most Class III patients who seek for treatment in a younger age have more severe malocclusion 14 Usually, the first phase includes an orthopedic expansion and maxillary protraction.
Consequently, most of the time, second phase involves only a compensatory treatment with fixed appliance. Differently from our findings concerning Class III malocclusion, some reports on Class II patients describe an association between overjet and treatment duration 12 Initial positioning of upper and lower anterior teeth and mandibular growth are not favorable to non-surgical Class III treatment 13 Frequently, the upper incisors show compensatory protrusion while the lowers have lingual inclinations, limiting the amount of negative overjet that can be treated without surgery.
Nevertheless, Class II division 1 patients have proclined upper incisors 25which is favorable for compensatory treatment. Treatment involving extractions and missing teeth before treatment had no statistically significant influence on treatment duration. Space closure can be a time-consuming treatment phase 23 ; however, extractions can increase treatment efficiency when they are correctly indicated.
This study had some methodological limitations, such as using a retrospectively selected unicenter sample. However, it is a consecutively treated sample, which decreases the risk of bias.
Another limitation of our study is the non-inclusion of surgical patients in the sample, leaving out a large number of Class III cases available in the office files. Evaluating this variable, it would have been important to verify the impact of conducting surgical treatment on treatment duration in Class III patients. Failure to meet the estimated treatment time frequently damages the doctor-patient relationship by decreasing the patient's trust.
Biologically, elongated treatment time have been related to increased probability of root resorption 17 Therefore, the awareness of the factors contributing to treatment overtime can help orthodontists to control some of these variables and perform a more efficient treatment for Class III malocclusion, having smoother relationship with patients and greater practice success.
Our findings showed that duration of orthodontic treatment in Class III dental malocclusion patients is mainly influenced by patient compliance. Thus, it seems crucial to inform patients about their role in the treatment progress and provide scientifically sound data to stimulate patient's cooperation.