Twin block - Copy

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TWIN BLOCK Seminar by G.Rama krishna . CRI.


Introduction These are functional appliances designed to enhance forward mandibular growth in the treatment of distal occlusion by encouraging a functional displacement of mandibular condyles downards and forwards in the glenoid fossa. Repositioning creates a positive proprioceptive response in the muscles of mastication.

The occlusal inclined plane:

The occlusal inclined plane This is fundamental functional mechanism of habitual dentition occlusal forces transmitted through the dentition provide a constant stimulus to influence the rate of growth and trabacular structure of supporting bone this sensory feed back mechanism controls muscular activity and provides a functional stimulus or deterrent to mandibular bone growth.


Principle A technique that would maximise the growth response to functional mandibular protrusion by using an appliance system that is comfortable,simple and esthetically pleasing to the patient. The unfavourable cuspal contacts of a distal occlusion are replaced by favourable proprioceptive contacts on the inclined planes of the twin block to correct the malocclusion.

History :

History Evolved in response to a clinical problem when a young patient, son of a Dental collegue fell and luxated an upper incissor The first Twin block was fitted on september 7th 1977

Early Twin Blocks :

Early Twin Blocks

Standard Twin Block:

Standard Twin Block

standard twin blocks :

standard twin blocks

Angulation of the inclined plane:

Angulation of the inclined plane Initially the angulation between the blocks were made at 90 degrees since it was difficult to hold the mandible forward at this angle, the angulation was changed to a 45 degree one the angulation was changed to 70 degrees to the occlusal plane to apply a more horizontal force encouraging a more forward mandibular growth.

Ideal case selection:

Ideal case selection Angles class II Division I with proper arch form lower arch that is uncrowded or decrowded and aligned upper arch that is aligned or can be easily aligned an overjet of 10 - 12 mm and a deep over bite

Slide 11:

A full unit distal occlusion in the buccal segments a good buccal occlusion should result when the model is advanced Profile should improve clinically when the patient advances the mandible Patient should be in active growth phase.

Phases of treatment:

Phases of treatment Active phase a)Sagittal correction b)vertical correction c)correction of occlusion Support phase Retentive phase

Treatment time :

Treatment time Active phase : 6 -9 months Support phase : 3 -6 months Retentive phase: 9 months to reducing the wear time gradually Total time : Average 18 months inclusive of retention period

Diagnosis and Treatment planning:

Diagnosis and Treatment planning Essential orthodontic records supported by study models X-rays photographs along with a diagnostic report


CLINICAL GUIDELINES Improvement of facial profile when the mandible is advanced forward with the lips tightly closed indicates Twin block as the treatment of choice. This change is a preview of the anticipated result of functional treatment.

Functional Treatment objective:

Functional Treatment objective To predict the change in facial profile as a result of functional treatment. This can be done with the Photographs and by superimposition on a cephalogram.

Slide 17:

A template of the mandible and the lower teeth are drawn on a second tracing that also registers the cranial base for referance. The template is advanced to place the incisor teeth in correct contact with the lower incisor occluding with the base point of the upper incisor. lip outline is redrawn with the lips closed and the mandible forward. M ethod Pre treatment cephalogram taken in centric occlusion and tracing of the landmarks are done

Bite registration:

Bite registration The construction bite determines the degree of activation built into the appliance,aiming to improve jaw relationship Originally the bite registration for twin blocks was aimed for a single activation-edge to edge bite for an over jet of upto 10mm

Slide 19:

In an overjet of greater than 10mm initial advancement of 7 - 8mm and later further correction Patients with a vertical growth pattern find it difficult to protrude the mandible consistently due to a weak musculature in these cases activation has to be decreased by trimming the inclined planes The George Bite gauge is used to determine the protrusive position of the mandible and the amount of activation of the bite.

Slide 20:

Functional activation within normal physiologic limits should not exceed 70 % of the protrusive path Class II Division I cases usually have a protrusive path of 13 mm and will tolerate activation of upto 10 mm

Vertical activation:

Vertical activation It is imperative that the bite blocks be made thick enough so that the bite is opened beyond the freeway space Average thickness is 5mm in the premolar region or an inter- incisal clearence of 2 mm in a class II Division I case with a deep bite In Class II Division II edge to edge bite is sufficient

Slide 22:

In the treatment of anterior open bite cases it is necessary to have greater inter-incisal clearance of 4 -5 mm Twin Blocks may be activated unilaterally to correct postural mandibular displacements


Technique 1. The centric occlusial position is checked 2.Lines are marked on the upper and lower incissors 3.The patient is asked to bite in a different occlusial position with the mandible in a protruded position 4. At this position there must be at least 6 mm of interocclusial space at the premolar region

Slide 24:

5.The patient is asked to bite in this manner for a couple of times to get used to the new bite 6.Construction bite is taken with a red base plate wax heated in a hot water bath and moulded to appropriate the arch 7. A minimum of 2 -3mm vertical clearance between the incisors is a must 8.Mandible is advanced depending on the degree of over jet 9.Models with the bite is articulated

Appliance design and construction:

Appliance design and construction These appliances are tooth and tissue borne The appliance is designed to to link teeth together as anchor units to limit individual movement and to maximise the orthopedic response to treatment

Parts of Upper bite block:

Parts of Upper bite block 1.The delta clasp 2.Ball end interdental clasps 3.C-clasps 4.Labial Bow 5.Screws I) Midline screws 2) Anterior sagittal screw 3)Three dimensional screws

Parts Of Lower Bite Block:

Parts Of Lower Bite Block Delta Clasps c-clasps Ball end clasps

Base plate &Bite blocks:

Base plate &Bite blocks Appliances are made in heat cure or cold cure acrylic cold cure has the advantage of speed and convenience but the strength is poor preformed bite blocks made of heat cure acrylic can be used with cold cure base

Heat cured Bite Blocks:

Heat cured Bite Blocks

Lower Heat Cured Bite Block:

Lower Heat Cured Bite Block

Inclined plane &extension of the upper bite block:

Inclined plane &extension of the upper bite block Angulation of 70 degrees Buccolingual thickness Vertical thickness

Inclined plane angulation & Lower bite block:

Inclined plane angulation & Lower bite block Angulated at 70 degrees Buccolingual thickness

Modification of standard Twin block:

Modification of standard Twin block In class II Div I cases with deep bite Combination Twin blocks with fixed appliance therapy &management in mixed dentition For transverse arch development”SCHWARTZ TWIN BLOCKS” Twin Block for the treatment of adult cases-”CROZAT APPLIANCE”

Slide 34:

Twin block for sagittal arch development For both anteroposterior and transverse development For anterior open bite Reverse Twin blocks With Orthopedic traction with intra oral elastics-class II elastics With attracting or repelling magnets For correction of facial assymetry For TMJ therapy Fixed Twin blocks

Mixed Dentition treatment:

Mixed Dentition treatment

Mixed dentition trt-cont’d:

Mixed dentition trt -cont’d

Magnetic Twin Blocks:

Magnetic Twin Blocks

Treatment of class II Div II:

Treatment of class II Div II



During treatment:

During treatment

Alligning after therapy:

Alligning after therapy

Treatment of Class III cases:

Treatment of Class III cases

Edge to Edge bite:

Edge to Edge bite

End of Twin Block therapy:

End of Twin Block therapy

Advantages of Twin Blocks:

Advantages of Twin Blocks Comfort Aesthetics Function Patient Compliance Facial appearance Speech Clinical management Arch development

Slide 49:

Mandibular repositioning Vertical control Facial assymetry Safety Efficiency Age of treatment Integration with fixed appliance Treatment of TMJ Dysfunction


Conclusion Facial balance and harmony are of equal importance to Dental Occlusal perfection.One cannot ignore the importance of Orthopedic techniques in achieving these goals by Growth guidance during the formative years of Facial and Dental development In the new millienium,the integration of Orthodontic &Orthopedic techniques offer a new initiatiye in restoring facial balance.

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