Diagnostic set up

Diagnostic Set-up

Prepared by : Ahmed Saeed BaattiahUnder supervision : prof . Maher Fouda

Mansoura UniversityFaculty of Dentistry

Orthodontics Department

INTRODUCTION

In 1953, Kesling, after developing a tooth positioner as an aid in finishing orthodontic treatments, suggested that cutting and repositioning the teeth in duplicate study models of the malocclusions would allow simulation of the results before startingorthodontic treatment.

Dental Press J Orthod. 2012 May-June;17(3):146-65

Diagnostic Set-up

INTRODUCTION

Pre treatment

Setup models


Diagnostic setup consists in cutting and realigning the teeth in plaster models, making it an important resource in orthodontic treatment planning.

Orthodontic setup procedure and analysis can provide important information such as the need for dental extractions , interproximal stripping , anchorage system.

Diagnostic Set-up

14-year-old , dark-skinned patient with Angle Class I malocclusion. Facial analysis revealed lip incompetence, convex profile, decreased nasolabial angle.

ORTHODONTIC SETUP PROCEDURE


She had a Class I skeletal pattern (ANB=3°), with a good maxillo-mandibular relationship (SNA=82؛ and SNB=79°). She had a Class I dental malocclusion, bimaxillary protrusion, upper and lower anterior crowding, with discrepancy of -11.2 mm and -5.5 mm, respectively.

Her incisors were in an edge-to-edge relationship, proclined (1-NA=28°, 1-NB=36°).

Initial panoramic X-ray, lateral cephalogram and cephalometric tracing.

STEPS OF ORTHODONTIC SETUP PROCEDURE

Step 1 : Models must be properly fabricated to faithfully reproduce the patient’s malocclusion, then duplicated , and polished to streamline the setup procedure.

Step 2 : Midline registration

Record of the initial upper and lower midlines using a ruler and 0.5mm mechanicalpencil

Coinciding the upper and lower dental midlines is one of the treatment objectives, be it for aesthetic and/ or functional purposes, be it to accomplish adequate dental intercuspation in the posterior region of the dental arches.


Grooves with 1 mm width and depth, made with a stylet.

In a front view of the patient at rest , and with lips slightly parted, one should imagine a line passing through the groove of the upper lip philtrum, and the distance from this line to a midpoint between the upper and lower central incisors should be estimated.

Midline grooves filled with heated wax in the lower and upper models

The grooves corresponding to the initial midlines should be filled with blue wax and heated in a dripper, and the registration of the correct midlines targeted by the orthodontic treatment should be performed using heated red wax.


Filled midlines with initial midlines in blue and the changes planned for the upper midline in red.

This information will guide the correct establishment of the midlines when mounting of the teeth.


This patient had a greater than 2 mm midline deviation to the right side while the lower midline coincided with the facial midline.

Step 3 : First molar registration

Record of the center of the upper molar mesiobuccal cusp and groove between the mesiobuccal cusp and the median cusp on the lower molar .

If the first molars are missing, the second or third molars can be used as reference.

Record of the molar positions should be extended to the base of the models using a ruler .


Tooth and base grooves filled with blue wax.


Recording the position of the upper and lower molars on the model bases is important to check for changes in the movement of these teeth in the anteroposterior direction, such as loss of anchorage, distalizations or correction of dental inclinations.

Step 4 : lower dental arch form registration

1) Record of the arch form with 0.021 x 0.026-in stainless steel wire showing its position on the incisal edges and buccal cusps of teeth .

2) Checking the symmetry chart.

To avoid relapses, studies recommend that the original form of the lower dental arch not be changed to ensure stability of the occlusion achieved with the orthodontic treatment.

Step 5 : lower incisor registration

Transfer of the midline of the model to the lingual area of the alveolar ridge by 0.5 mechanical pencil.

Record of the anterior posterior position of the lower incisors using condensation cure silicone.

Anterior and posterior incisor extensions of approximately 6 mm to facilitate planning the movement of these teeth.

The position of the incisors at the end of treatment clearly indicates that a successful, satisfactory occlusion and a balanced profile have been achieved.

Transfer of the midline marked on the model for the silicone. This line will serve as a reference to the median cutting of this guide.


Demarcation and removal of the silicone part in the lingual region of incisors to allow the simulation of the retraction of these teeth.


This graph paper will serve to quantify the extent to which the simulation of tooth movement is in accordance with the treatment plan, regardless of whether such movement is an intrusion, extrusion, proclination or retroclination.

Registration with silicone in the posterior region to maintain the vertical dimension of the models when mounting the setup model.


Step 6 : Tooth identification and cutting

Tooth identification using 0.5 mm mechanical pencil to prevent them from being confused when mounting the setup.


Demarcation of a guideline for cutting the teeth in the model base in both dental arches.

For the removal of the upper and lower teeth, a line must be drawn limiting the region of the alveolar ridge, approximately 5 mm from the cervical region of the teeth.


spiral saw

Drilling in the area of the lower alveolar ridge on the horizontal line near the midline for insertion of the thin spiral saw.

Horizontal and vertical sections in the lower alveolar ridge of the left quadrant using thin spiral saw mounted on the frame of a bow saw.

Explorer #5 being used to heighten the interdental limits

After separating the block of teeth from the model; some finger pressure should be applied to the stumps to separate teeth.

Stripping the tooth stumps with a steel bur, taking care to maintain the mesial-distal dimension of each tooth, without removing the dentogingival limit.

Making retentions in the stumps with a carborundum disk.

o Use of a digital caliper to check the mesiodistal dimension of each tooth after cutting, comparing it with the original value in the initial study model.

Leveling the lower alveolar base and making a central groove

Boring small holes (cavities) with a round bur #6 to create undercuts.

Removal of plaster residues using a compressed air syringe.

Step 7 : Tooth mounting

Filling the central groove of the alveolar ridge with red wax #7; a strip of utility wax is attached to the red wax to allow the teeth to be set in place.

Positioning the lower left central incisor in accordance with the proposed reduction of 3 mm in the treatment plan.

Mounting the remaining quadrant teeth

Step 7 : Tooth mounting

Checking for the correct tooth positions using the archwire from the arch form registration.

Setting the tooth stumps with heated red wax #7

Mounting of teeth on the upper and lower left side.

Checking to ensure maintenance of the vertical dimension, considering the total height of the bases (initial and setup); if necessary, use of posterior silicone record.

Mounting the left and right quadrants. The archwire registering the original archform should be used to check the shape and symmetry of the lower arch construction.

When mounting the teeth one should follow the guidelines and the six keys to a normal occlusion introduced by Andrews, whereas the arch form and intercanine and intermolar widths should be preserved.

Careful removal of the lower second molar, ensuring that the posterior cutting is done exactly on the distal surface of the tooth.

Once mounting is complete, the occlusion should be checked in its contact points, marginal ridge height and axial inclination of the anterior and posterior teeth.

Step 8: Waxing, carving and finishing

Adjustment and shaping of the gingival margins with a Hollemback carver.

wax plasticized with the aid of a Hannau lamp to ensure total smoothness.

Polishing of gypsum with silk fabric.

Washing in running water to remove residues

Finished setup model.

SETUP ANALYSIS

Once the setup is ready, much information is generated. The use of an evaluation form based on the model, first suggested by Cury-Saramago and Vilella14 is recommended.

The proposed method includes ten items: Extractions, changes in the basal bones, lower incisor position, leveling, midlines, dental arch form, molar and canine relationship, anchorage, interproximal stripping and cosmetic finishing.

Form used for setup analysis.

Finished treatment showing the treatment objectives were achieved according to plan.

Profile and panoramic radiographs, and final cephalometric tracing

The Importance of the Diagnostic Setup in theOrthodontic Treatment Plan

In the first case, three diagnostic setups were made in order to determine the treatment plan that best fitted the case and that would bring the best results and stability for this specific individual.

The importance of the diagnostic setup appear by examining the following two cases.

IJO. VOL. 23 .NO. 2. SUMMER 2012

In the second case, one diagnostic setup was made to verify whether the intended treatment plan would be able to be carried out resulting in harmonic intraarch and interarch relationships.

A healthy 11-year-old boy was brought by his parents for orthodontic treatment in Rio de Janeiro, Brazil. At the initial orthodontic evaluation he was already in the permanent dentition, with an Angle Class I malocclusion and a small mandibular arch-length discrepancy (-1.6 mm). The lateral cephalometric analysis showed a Class I skeletal malocclusion (ANB, 4)

Pretreatment extra oral photographs

First case

Pretreatment dental models of the first case.

Pretreatment cephalometricradiograph of the first case.

Pretreatment cephalometrictracing of the first case.

Protruded maxillary and mandibular incisors (1.NA= 27, 1.NB= 27; IMPA= 91). The lower left central incisor showed some gingival recession. The facial profile was convex. There was a tooth discrepancy with a mandibular excess of 1.7 mm. Total discrepancy of the lower arch was calculated by adding up the arch-length discrepancy and the cephalometric discrepancy (-5,6 mm).

In order to visualize the treatment results and to establish a treatment plan with confidence, three diagnostic setups were made with three alternative treatments :

The treatment objectives for this patient were to enhance theprofile, align the teeth and maintain the Class I relationship. Thereally small mandibular discrepancy made it difficult to decide forextraction of either a mandibular incisor or of four first premolars.

It is important to consider that this protrusion could worsen both the facial profile, and the gingival recession on the left central incisor, leading to an unfavorable result.

1) No extraction and mild protrusion of incisors

2) Extraction of four premolars with retraction of the anterior teeth and mesialization of the posterior teeth

The lower incisors were retracted 3 mm to their ideal position and the lower first molars migrated mesially 3.5 mm each. In this alternative of treatment, the facial profile would be altered, improving esthetics and making the face of the patient more harmonious. Additionally, since the left lower central incisor would be retracted, the gingival recession would tend to diminish.

3) Extraction of a mandibular incisor (the one with gingival recession).

The lower incisors were minimally retracted (1 mm). The upper incisors were submitted to a stripping process to eliminate tooth discrepancies created

by the extraction. The facial profile would be just slightly altered by the minimal retraction provided in this treatment alternative, but the gingival recession would no longer be a problem, since the affected tooth would be extracted.

Superimposition of the original tracing (black)

and of the tracings of thetreatment options for the first case:

1) No extraction (blue)

2) Four premolars extraction (green)

3) One lower incisor extraction (red)

Discussiono In all of them, it is likely that a good occlusion be achieved, as

foreseen in the setups.

However, only the option comprising the extraction of four premolars would allow a retraction of the incisors and their correct positioning on the basal bone.

According to Tweed, mandibular incisors must be upright over the basal bone if balance and harmony of facial proportions are to be achieved in orthodontic treatment. This concept is confirmed in Strang’s description of normal occlusion.

Consequently, this was also the only option of treatment that would affect the facial profile favorably. If this is an important aspect for the patient and his parents, this should be the alternative chosen.

Second caseA healthy 21-year-old woman came looking for orthodontic treatment in Rio de Janeiro, Brazil. At the initial orthodontic evaluation she presented an Angle Class I malocclusion and a mandibular arch-length discrepancy of -2.4 mm. The lateral cephalometric analysis showed a Class I skeletal malocclusion (ANB, 1), a harmonious facial growth.

Pretreatment extraoral photographs

Pretreatment dental models of the second case.

Pretreatment cephalometricradiograph of the second case.

Pretreatment cephalometric tracing of The second case.

Protruded maxillary and mandibular incisors (1.NA=35; 1.NB= 25; IMPA= 93). There was a transposition between the lower right lateral incisor and the lower right canine. The facial profile was slightly convex. There was no tooth discrepancy. Total discrepancy of the lower arch was calculated by adding up the arch-length discrepancy and the cephalometric discrepancy (-8.4 mm).

Two treatment alternatives were considered:

1) Extraction of four premolars with retraction of the anterior teeth and mesialization of the posterior teeth.

2) 2) Extraction of a mandibular incisor (the transposed one).

Setup models of the second case: simulation of treatment with extraction of one lower incisor.

Superimposition of theoriginal tracing (black)

and of the tracings of the treatment options forthe second case:

1) One lower incisorextraction (red)

2) Four premolarsextraction (green).

The treatment cephalometric simulation showed that the extraction of four premolars and retraction of the anterior teeth would provide a concave profile with retruded lips, which might accentuate the already prominent nose of the patient.

Therefore, the option of extraction of one lower incisor (the transposed one) seemed more reasonable with the advantage of favoring the mechanics by eliminating the need of correction of the transposed incisor.

However, this alternative would require a considerable amount of stripping in the upper incisors and canines. A setup was helpful to determine the amount of stripping necessary for each tooth and the final best possible occlusion.

Discussion

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Presented by:

Dr. Ahmed Saeed Baattiah

E-mail :[email protected]

Diagnostic set up

Health & Medicine

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