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Section 06 - Incisal Guidance   

 

Handout



Abstracts

001. Scaife, R. R. and Holt, J. E. Natural occurrence of cuspid guidance. J Prosthet Dent 22:225-229, 1969.

002. Schuyler, C. H. The function and importance of incisal guidance in oral rehabilitation.  J Prosthet Dent 13:1011-1030, 1963.

003. Dawson, P. E. Evaluation, Diagnosis, and Treatment of Occlusal Problems. C.V. Mosby, St. Louis, 1974, Chapter 11, Anterior Guidance, pp. 146-165.

004. Hobo, S. Twin-tables technique for occlusal rehabilitation: Part II. Clinical procedures. J Prosthet Dent 66:471-177, 1991.

005. Reynolds, J. M. The organization of occlusion for natural teeth. J Prosthet Dent 26:56, 1971.

006. Heinlein, W. D. Anterior teeth: Esthetics and function. J Prosthet Dent 44:389-393, 1980.

007. Broderson, S. P. Anterior guidance - The key to successful occlusal treatment. J Prosthet Dent 39:396-400, 1978.

008. DiPietro, G. J. and Moergeli, J. R. Significance of the Frankfort/mandibular plane angle to prosthodontics. J Prosthet Dent 36:624-635, 1976.

009. McAdam, D. B. Tooth loading and cuspal guidance in canine and group function occlusions.  J Prosthet Dent35:283-290, 1976.

010. Williamson, E. H. and Lundquist, D. 0. Anterior guidance: Its effect on electromyographic activity of the temporal and masseter muscles. J Prosthet Dent 49:816-823, 1983.

011. O'Leary, T.J., Shanley, D. B. and Drake, R.B. Tooth mobility in cuspid protected and group function occlusions. J Prosthet Dent 27:21-25, 1972.

012. Jemt, T. , Lundquist, S. and Hedegard, B. Group function or canine protection. J Prosthet Dent 48:719-724, 1982.

013. Kohno and Nakano. The measurement and development of anterior guidance. J Prosthet Dent 57:620-625, 1987.

014. Siebert, G. Recent results concerning physiological tooth movement and anterior guidance. Oral Health Rehabil 8:479-493, 1981.

015. Clements, W.C. Predictable anterior determinants. J Prosthet Dent 49:40-45, 1983.

016. Kahnm, A. E. The importance of canine and anterior tooth positions in occlusion. J Prosthet Dent 37:397-410, 1977.

Section 06: Incisal Guidance


(Handout)

Definitions:



Incisal guidance: 1. The influence of the contacting surfaces of the mandibular and maxillary teeth on mandibular movements. 2. The influence of the contacting surfaces of the guide pin and guide table on articulator movements. (GPT-6)

Incisal guide angle: 1. Anatomically, the angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation. 2. On an articulator, that angle formed in the sagittal plane, between the plane of reference and the slope of the anterior guide table, as viewed in the sagittal plane. (GPT-6)

Anterior guidance: 1. The influences of the contacting surfaces of the anterior teeth on tooth-limiting mandibular movements. 2. The influence of the contacting surfaces of the guide pin and the anterior guide table on articulator movements. 3. The fabrication of a relationship of the anterior teeth preventing posterior tooth contact in all eccentric mandibular movements. (GPT-6)

Mutually protected articulation: An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation, and the anterior teeth disengage the posterior teeth in all mandibular excursive movements. (GPT-6)

Anterior protected articulation: A form of mutually protected articulation in which the vertical and horizontal overlap of the anterior teeth disengage the posterior teeth in all mandibular excursive movements. (GPT-6).

Canine protected articulation, Canine guidance, Canine protection, A form of mutually protected articulation in which the vertical and horizontal overlap of the canine teeth disengage the posterior teeth in the excursive movements of the mandible. (GPT-6)

Group function: multiple contact relations between the maxillary and mandibular teeth in lateral movements on the working side whereby simultaneous contacts of several teeth act as a group to distribute occlusal forces. (GPT-6).

Anterior protected articulation, canine protected articulation, or group function.

What do we use and why?

D. Blake McAdam summarized some similarities and differences in his article.

Similarities:

Both must provide a multiple posterior contact with intercuspal position (centric occlusion) located either coincident with centric relation contact position or within 1mm of protrusion in a straight sagittal direction. Where these positions are not coincident they should be joined by continuous bilateral contact of pairs of teeth as described by Beyron or a flat area or "long centric" as described by Schuyler in 1969.

There must be an absence of posterior contact during mediotrusion.

There should be no posterior contact during anterior incision whenever the anatomic arrangement permits.

There should be an anterior group-functional guidance during the protrusive movement accompanied by a posterior disclusion where the anatomic arrangement permits.

Both schemes try to keep horizontal forces to a minimum although they accomplish the task differently.



Differences:

The manner in which the teeth function in laterotrusion.

In canine guidance the horizontal forces are minimized by limiting the contact of the support cusp to their opposing fossa at or near their intercuspal position. All other lateral contacts are prevented by the steeper inclines of the canines. This results in the chewing stroke being more sagittal in a frontal view.

In group function the first contact is not made between the supporting cusp and opposing fossa, but instead at a lateral location followed by a slide to centric occlusion. This will exert some horizontal forces, but these forces can be minimized by the following:



  • Striking simultaneously as many working side contacts as possible.

  • Reduce the angle of the incline so the resultant force is more along the long axis of the tooth.

  • Reduce friction by removing any roughness or irregularities.

  • Slightly round the facial occlusal line angle.

A possible disadvantage for group function

Working group function occurring on relatively steep inclines can be damaging since it may generate excessive horizontal loading. This situation is usually seen in the transition between a worn occlusion with canine guidance and an early group function type of occlusion.



Tooth mobility in both types of occlusions?

It would seem that with more horizontal forces present in group function the teeth would exhibit more mobility. However, O'leary, Shanley, and Drake found just the opposite. They found that teeth in a group function occlusion had less mobility than teeth in cuspid protected occlusion. Siebert found that canine protected occlusion is necessary to limit tooth mobility. Why all the differing findings??



What is more common, Canine guidance or group function?

Scaife and Holt examined 1200 young people and observed that most North Americans under the age of 25 had canine guidance either bilaterally or unilaterally. However, clinical observation suggest that most people over 40 years of age have group function guidance. Weinberg found only 19 of 100 people had cuspid protected occlusion.

McAdam suggest that both occlusions are normal and a dentist restoring only a portion of an occlusion should not change the occlusal scheme. Obviously some qualifying remarks should be made with this statement now with the emergence of implant restorations.

Implants

Jemt, Lundquist, and Hedegard looked at group function v. canine guidance in implant restored patients and found the chewing cycles to be consistent with patients having a natural dentition. (i.e. more vertical chewing in canine protection)

How does this fit in with implant supported occlusion?

What about parafunction v. masticatory movement of the mandible?



Muscle Activity

Williamsom and Lundquist discussed the effects of anterior guidance on the temporal and masseter muscles and found that posterior disclusion reduced the elevating activity of the temporal and masseter muscles. This also makes us think about parafunction v. masticatory movement when deciding on an occlusion.



FMA

What effect does the FMA have on occlusion in prosthodontics and what arguments can be made for each type of occlusion in high or low FMA patients. Did DePietro and Moergeli ever look at FMA related to canine guidance or group function?



Occlusion

After reviewing some basic concepts about occlusion what type of occlusion does Reynolds suggest and why? This article was written one year prior to O'leary's.

Schuyler wrote that incisal guidance equals or surpasses the temporomandibular joints in its influence upon the functional occlusion of the dentition. How does incisal guidance relate to condylar guidance.

Kohno states the incisal path should equal the condylar path. When rotation of the condyle occurs; however, the incisal path may be increased, but not more than 25 degrees.

Schuyler discussed incisal guidance in oral rehabilitation. He incorporated freedom of movement in centric occlusion be the addition of a pin in the anterior guide table.

Schuyler lists his objective of an occlusal rehabilitation to be:



  • A static centric occlusion in harmony with the centric maxillomandibular relation.

  • An even distribution of stress in centric occlusion over the maximum number of teeth.

  • Lateral and anteroposterior freedom of movement in centric occlusion.

  • Masticatory efficiency which involves uniform contact and an even distribution of stress on eccentric functional tooth inclines which are coordinated with the incisal guidance and normal functional condylar movements.

  • Reduction of the buccolingual width of the occlusal surfaces of the teeth

  • Reduction of the balancing incline contacts as a means for reducing a potentially traumatogenic load on the structures supporting the dentition.

Dawson discussed anterior guidance and firmly believes anterior guidance should be related to condylar guidance. Dawson does not believe in allowing the posterior teeth to share the load in eccentric movement stating "Even when anterior teeth are weakened by loss of supporting structure, it is preferable to have them carry the whole load during jaw excursions because by doing so we actually lessen the load on the anterior teeth because of reduction of elevator muscle contraction to only one actively contracting muscle on each side." His support for this statement may come from Williamson's article.

Dawson states maximum comfort and stability may be achieved if the following criteria are met:



  • Stable holding contacts for each anterior tooth

  • Centric relation contacts occurring simultaneously with equal intensity posterior tooth contacts.

  • Position and contour of anterior teeth in harmony with the envelope of function.

  • Immediate disclusion of all posterior teeth the moment the mandible leaves centric relation.

  • Position and contour of all anterior in harmony with the neutral zone and lip closure path.

How does Dawson "Harmonize the Anterior Guidance" ?

  • Lower anterior teeth reshaped and restored

  • Posterior equilibrated

  • Establish coordinated centric relation stops on all anterior teeth

  • Extend centric stops forward at the same vertical to include light closure from the postural rest position.

  • Establish group function (of the anterior teeth)in straight protrusion.

  • Establish ideal anterior stress distribution in lateral excursions.

After doing this Dawson will fabricate an anterior guide table.

Cusp angle as the occlusal determinant

Hobo will fabricate two guide tables and use cusp angle instead of condylar path or incisal path as a basis for the occlusion. This differs from any other technique we have studied. How does he do this and what are the advantages? What is his reasoning?

His steps are listed on the next page. His reasoning is cusp angle may be the most reliable factor to build an occlusion to. His basis for this is condylar guidance is influenced by occlusion, and therefore if you precisely simulate mandibular movement that is influenced by traumatic occlusion you will only duplicate that occlusion.

Steps for the twin stage procedure:



  • A cast with a removable anterior segment is fabricated.

  • Remove the anterior segment.

  • Set the condylar path and incisal guide table to 25 degrees. Set the Bennett angle at 15 degrees and the lateral wings of the guide table to 10 degrees. Wax the posterior teeth to a balanced occlusion. This will produce a 25 degree cusp angle.

  • Adjust the condylar path to 40 degrees and the sagittal inclination of the anterior guide table to 45 degrees, adjust the lateral wings to 20 degrees and wax the anterior guidance.

A standard amount of disocclusion will be obtained on the molars and a physiologic anterior guidance will be fabricated.

Hobo's limitations

Some limitations of this technique are if the condylar inclination of the patient is less than 16 degrees cuspal interferences will occur. (There is an 8% occurrence rate of condylar paths less than 16 degrees and Hobo states these interferences can be removed intraorally.)

Hobo's contraindications

The twin stage procedure is contraindicated in the following cases:


  • Abnormal curve of Spee

  • Abnormal curve of Wilson

  • Abnormally rotated tooth

  • Abnormally inclined tooth.

Helpful laboratory guide

If the anterior guidance is predetermined intraorally Clements describes an incisolingual index that will record the information for the lab tech to adapt wax or porcelain to. This technique was originally described by Fox.

A matrix of acceptable provisional restorations is also helpful in contouring the facial esthetics.

Basic review of anterior guidance and esthetics

Heilein discusses how to establish anterior guidance. Incisal edge position is determined by phonetics and esthetics. His technique does not differ greatly from Dawson's.



  • Establish coordinated centric relation stops.

  • Centric stops in a postural position must have the same vertical dimension as those for centric relation.

  • Refine protrusive excursions.

  • Establish canine guidance in lateral border movements.

  • Check lateral protrusive movements.

  • Make sure there is a smooth transition to a cross over position.

- Abstracts –

06-001.  Scaife and Holt. Natural occurrence of cuspid guidance. J Prosthet Dent 22:225-229, 1969.



Purpose: To examine the natural occurrence of cuspid guidance in eccentric positions.
Materials and Methods: 1200 young men between the ages of 17 and 25 were examined. Subjects with multiple missing or carious teeth, missing maxillary first bicuspids or cuspids, or those who had restorations involving the occlusion of the maxillary or mandibular cuspids were not included in the study. An Angle classification was recorded for each subject. The presence or absence of gross wear facets was noted. The subject was instructed to close on their back teeth and side the teeth to protrusion, right and left laterotrusion. Contact was noted during the movements. Contact of the cuspids in centric occlusion was also noted.
Results: The results are displayed in two tables.
Conclusion: Cuspid protected occlusion in lateral movement was present bilaterally in 57% of the subjects, unilaterally in 16% and none in 26%. In protrusion, 99.4% lacked a cuspid protected occlusion. 91.5% had cuspid contact in centric occlusion.

06-002. Schuyler, C. H. The function and importance of incisal guidance in oral rehabilitation.  J Prosthet Dent 13:1011-1030, 1963.

abstract missing ........

06-003. Anterior Guidance. Evaluation, Diagnosis, and Treatment of Occlusal Problems. C. V. Mosby, St Louis, 1974, Chapter 16, Anterior Guidance, pp. 146-165.



     Posterior teeth that are not protected from lateral or protrusive stresses by the discluding effect of the anterior teeth will, in time, almost certainly be stressed or worn detrimentally.
     The anterior teeth are all forward of the closing muscle power, so to exert stress on the anterior teeth, the mechanical result of the closing muscles would be like trying to crack a walnut by placing it at the tips of the handles of a nutcracker and squeezing the handles back at the hinge. This is the unique position of the resistance to stress that the anterior teeth enjoy by virtue of their relationship to the condylar fulcrum and the source of muscle power.
     It is popular fallacy, that whatever path the condyles follow must be duplicated in the lingual surfaces of the upper anterior teeth so the lower anterior teeth can follow the same path. This is wrong. Condylar paths do not dictate anterior guidance, and there is no need or even advantage to try to make the anterior guidance duplicate condylar guidance. Advocates of such a concept have failed to recognize that the condyles can rotate as they move along their protrusive pathways. This allows the front end of the mandible to follow a completely different path without interfering with the condylar path.
     Patients may have the same outer limits of motion, but each may have a different envelope of function. Even though condylar guidance is the same, the anterior teeth would have to be contoured differently for each patient.
     Since functional movements occur within the envelope of motion borders, merely recording the outer limits of motion would not supply enough needed information for optimally restoring anterior teeth. The envelope of function that controls the anterior relationship must be treated as a separate entity.
     Anterior guidance cannot be determined on an articulator regardless of how perfectly the condylar path is duplicated. It is a separate entity and must be determined in the mouth where the determinants of anterior tooth position can be observed in function.
     Disclusion of all posterior teeth in eccentric jaw position reduces muscle contraction in two of the three elevator muscles.
     The moment any posterior tooth comes into premature excursive contact, not only the anterior guidance looses its capability for shutting off elevator muscle contraction, but also the elevator muscles are hyperactivated by the posterior contact.
      Because of our new understanding of muscle responses to posterior disclusion, we no longer attempt to bring posterior teeth into working side group function to help weak anterior teeth. Even when anterior teeth are weakened by loss of supporting structure, it is preferable to have them carry the whole load during jaw excursions because by doing so we actually lessen the load on the anterior teeth because of the reduction in elevator muscle contraction to only one actively contracting muscle on each side.

6-004.  Hobo, S. Twin-tables Technique for Occlusal Rehabilitation: Part II - Clinical Procedures. J Prosthet Dent 66:471-477, 1991.

     The deviation of the incisal path in an individual is less than that of the condylar path. The incisal path influences disocclusion at the second molar twice as much as that of the condylar path during a protrusive movement, three times as much on the non-working side and four times as much on the working side during lateral movement. The cusp angle is considered to be the most reliable reference for occlusion. The standard cusp angle values were determined to be 25 during protrusive movement, 15 on the working side, and 20 on the non-working side during lateral movement.
     In order to provide disocclusion, the cusp angle should be shallower than the condylar path. To make a shallower cusp angle, it is necessary to produce balanced articulation so the cusp angle becomes parallel to the cusp path of a opposing teeth during eccentric movement. The twin stage procedure uses a cast with a removable anterior segment and fabricates the posterior teeth in a balanced occlusion. The anterior segment is replaced and anterior guidance is established.( 1mm during protrusive movement)
     In Hobo’s article a description is given to create a custom incisal guide table, and a technique to simulate the protrusive movement on the articulator is detailed. In his text book, values have been determined and can be programmed into a semi-adjustable articulator.
     Stage I: The sagittal condylar path inclination 25 ; Bennett angle 15 ; sagittal inclination of the incisal guide table 25 ; and the lateral wing angle 10 .The anterior segment of the maxillary and mandibular casts are removed using dowel pins and the casts are adjusted so they do not disclude during eccentric movements. Wax the occlusal morphology of the posterior teeth so the maxillary and mandibular teeth contact during eccentric movements (balanced articulation).
     Stage II: The sagittal condylar path inclination 40 ; Bennett angle 15 ; sagittal inclination of the incisal guide table 45 ; and the lateral wing angle 20 .The anterior segment of the maxillary and mandibular casts is replaced. Wax the palatal contours of the maxillary anterior teeth so the incisors contact during protrusive movement, and the canines on the working side contact during a lateral movement. Anterior guidance is established and disclusion is produced.
     If the sagittal condylar path of the patient is steeper than the articulator adjustment value (40 ), disclusion increases. If the path is less than 40 , then the amount of disclusion decreases. If the patient has less than 16  (only about an 8% occurrence rate), cuspal interferences will occur.
     If the incisal path is more than 5 steeper than the condylar path, patients complain of discomfort( Mc Horris 1979).

06-005. Reynolds, J. M. The organization of occlusion for natural teeth. J Prosthet Dent 26:56, 1971.

abstract missing......

06-006. Heinlein, W. D. Anterior teeth: Esthetics and function. J Prosthet Dent 44:389-393, 1980.

abstract missing.........

06-007. Broderson, S. P.: Anterior Guidance-The Key to Successful Occlusal Treatment. J Prosthet Dent 39: 396-400, 1978.



Purpose: To show that the relationship between the maxillary and mandibular anterior teeth is the most important factor in the restoration and maintenance of the ideal occlusion. Ideal in this case is characterized by minimal wear, a healthy periodontium and temporomandibular joint, and maintains a quiet neuromuscular mechanism.
Materials & Methods: This literature review focused on the gnathologic approach for the treatment of anterior teeth by C. E. Stuart, who stated that the lingual surfaces of the maxillary anterior teeth are entirely controlled by condylar border movements, and the Pankey-Mann-Schuyler philosophy which stated that the lingual surfaces of anterior teeth are independent from condylar border movements and are dictated by a need for long centric.
Results: The author discussed the determinants of anterior guidance as being:

1. esthetics


2. phonetics
3. condylar border movements
4. positional relationship of the maxillary and mandibular anterior teeth.

Without the boundaries of the anterior teeth and the neuromuscular system the masticatory apparatus would destroy itself or muscle dysfunction would occur.

The functions of anterior guidance are:

1. to incise food


2. to aid in speech
3. to aid in esthetics
4. to protect the posterior teeth, by directing the teeth together in centric occlusion so that the closing forces will be vertically directed onto the posterior teeth.

The anterior teeth must also allow the Bennett movement to occur so that the final closure forces will be directed along the long axis of the posterior teeth. This is of particular importance for the restoration of the canines. As more Bennett movement is introduced and the angle of the eminence is reduced more lingual concave curvature is needed. In contrast a steep eminence will be in harmony with a small amount of lingual curvature.


Discussion: Regardless of philosophical approach to restoring the dentition, anterior guidance must be developed to restore and maintain a healthy masticatory system. Diagnostic casts and wax-ups, protrusive registrations, pantographs, functionally generated paths, resin provisional restorations, all contribute to fabricating a final restoration which maintains the harmony between the anterior teeth and the condylar movements.
Conclusion: Anterior guidance is an important component of occlusal treatment designed to protect the posterior teeth from eccentric forces, and allowing the posterior teeth to protect the anterior teeth by absorbing the vertical forces in centric position.

06-008. DiPietro, G.J. Significance of the Frankfort-mandibular plane angle to Prosthodontics. J Prosthet Dent 36:624-635, 1976.

     The FMA is an angle formed by the intersection of the Frankfort horizontal plane and the mandibular plane. Normal FMA ~25 plus or minus 5 degrees, high angle ~ 30 degrees or more (open bite skeletal patterns), and low angle ~ 20 degrees or less (closed bite skeletal patterns) and not to be confused with open or closed bite dental patterns.
     Clinically open bite skeletal type is associated with decreasing biting force and a low FMA (deep bite skeletal patterns) are associated with increased biting forces. "Sassouni" believed that with a deep bite molars are directly under the impact of the masticatory forces and that in the open bite patient the posterior vertical chain of muscles is arcuate, and the masseter is posterior to the molars and the premolars and therefore the patient had less powerful masticatory muscles.
     In the attempt to increase VDO, it is contraindicated in the low FMA patient as they tend to return to their former occlusion. Additionally, these teeth are more susceptible to abrasion. A prime importance in deciding to render a patient edentulous with a low FMA is that the increased biting forces and resorption may further complicate stability and retention and may also result in fractured resin dentures.
     With a high FMA, the glenoid fossa is situated superiorly and posteriorly and the low FMA patient, it is situated anteriorly and inferiorly. Constancy of the relationship between the position of the glenoid fossa and the FMA can be used in modifying the location of a particular arbitrary center of rotation ( Beyron, Bergstrom, and Gysi) for face bow mountings. Therefore using the Bergstrom point as a standard, the position of this arbitrary center can be modified superiorly and posteriorly for high FMA and anteriorly and inferiorly for low FMA. Additionally, the types of face bows using ear rods and anatomic averages can be modified to reflect the variation in position of the condyles as determined by the FMA.

06-009. McAdam, D. B. Tooth loading and cuspal guidance in canine and group function occlusions.  J Prosthet Dent35:283-290, 1976.

abstract missing ...........

06-010.  Williamson and Lundquist, Anterior guidance: Its effect on electromyographic activity of the temporal and masseter muscles. J Prosthet Dent 49:816-823, 1983.



Purpose: To determine the effect of anterior guidance or posterior contact in excursive movements on the temporal and masseter muscles.
Materials and Methods: Five women were selected, four had previous symptoms of dysfunction or pain associated with the TMJ. Maxillary acrylic resin splints were made that allowed for anterior guidance. Surface electrodes from a Teca EMG unit were attached to the right and left temporal and masseter muscles. The subject was instructed to close firmly and maintain pressure against the splint while moving into right laterotrusion, back to retruded contact position, into left laterotrusion, back to retruded contact position, and the into protrusion. Recording were printed with a paper speed of 10 cm/sec and a microvoltage of 500 microvolts. After the recording were made the anterior guidance was eliminated from the splint and the recording were repeated.
Results: The electromyogram strips are copied in the article. When the anterior guidance was eliminated from the splint more muscle activity was recorded.
Conclusion: This study showed the elimination of posterior contacts will exhibit less muscle activity than an occlusion that allows posterior contacts. However; the altered splint allowed bilateral posterior contacts that are not consistent with group function and possibly less drastic results may have been obtained without balancing contacts.

06-011. O'Leary, T. J., Shanley, D. B. and Drake, R. B. Tooth mobility in cuspid protected and group function occlusions. J Prosthet Dent 27:21-25, 1972.

abstract missing .......

06-012. Jemt, T. , Lundquist, S. and Hedegard, B. Group function or canine protection. J Prosthet Dent 48;719-724, 1982.

D’Amico - states that canine protection favors a vertical chewing pattern and prevents wear of teeth.
Beyron - states group function, implies contact and stress on several teeth in lateral occlusion and indicates abrasion as a positive and inevitable adjustment.

- Angle of departure was steeper than the approach angle, and these angles were slightly greater with group function than with canine protection.


- Lateral displacement and total displacement of the mandible, was greater with group function.
- Mandibular velocity was greater with group function.
- Duration of chewing cycle was stable between the two.

All results indicate that the chewing pattern may be influenced by the type of occlusion.

06-013.  Kohno and Nakano. The Measurement and Development of Anterior Guidance. J Prosthet Dent 57:620-625, 1987.

Purpose: To describe a method of measuring condylar and incisal angles in developing a criteria for anterior guidance in clinical practice.
Methods and Materials: 35 subjects were measured using a specific apparatus to record the jaw movements. A metal splint was attached to the lower teeth.
     A facebow with three small light bulbs was used with cameras to record the path of jaw movements.
Results: The average inclination of the incisal path was 46 . The average condylar path was 38.
Conclusion: The inclination of the incisal path should be equal to the inclination of the condylar path. The incisal path should not be more than 25 steeper than the condylar path. A jerky condylar movement will result from an incisal path that is flatter than the condylar path. If the incisal path is shallower than the condylar path, the condyle rotates in a reverse direction during protrusive movements.

06-014. Siebert, G. Recent results concerning physiological tooth movement and anterior guidance. Oral Health Rehabil 8:479-493, 1981.

abstract missing .......

06-015. Clements, William G. Predictable anterior determinants. J Prosthet Dent 49:40-45, 1983.



Purpose: To describe a method to predictably fabricate anterior restorations.
Materials and Methods: Author's description of a clinical and lab technique.
Results: None
Conclusion: Prior to make the tooth preparations on the anterior teeth resin composite restorations are placed that will determine the size and shape of the final crowns. Diagnostic cast are made when the patient is comfortable and pleased with the resin composite restorations. Provisional restorations are made from this cast in the laboratory. At the following appointment the teeth are prepared and provisional restorations are placed. A face bow transfer and centric relation record are made at the next appointment. The provisional restorations are evaluated and an impression is made of the provisional restorations. A face bow transfer and centric relation record are made with the provisional restorations in place. A custom incisal guide table is fabricated from the articulated provisional and lower opposing cast to reconfirm the excursions in the completed restorations.
     When the case is forwarded to the laboratory an incisolingual index is fabricated. To fabricate the incisolingual index the maxillary cast with the provisional restorations is attached to the upper member of the articulator and a new mounting plate is attached to the lower member. Boxing wax is wrapped around the lower mounting plate one inch short of the maxillary cast. The cavity is filled with mounting stone and the exposed surface roughened to create undercuts. Lab putty is placed over the mounting stone, catalyst is placed on the maxillary cast to act as a separating medium. The centric lock is engaged and the articulator is then closed. The putty gives an index to which the wax pattern or porcelain can be compared with.

06-016. Kahnm, A. E. The importance of canine and anterior tooth positions in occlusion. J Prosthet Dent 37:397-410, 1977.



abstract missing .....


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