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Table of Contents   
ORIGINAL RESEARCH  
Year : 2012  |  Volume : 23  |  Issue : 6  |  Page : 814-818
An in vivo study to determine the range of posterior teeth disclusion on working side in canine-guided occlusion


Department of Prosthodontics, A.B. Shetty Institute of Dental Sciences, Deralakatte, Mangalore, India

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Date of Submission04-Jul-2010
Date of Decision11-Nov-2010
Date of Acceptance13-Jan-2011
Date of Web Publication3-May-2013
 

   Abstract 

Background and Objectives: This study was done with the objectives to determine the range of functional zone between the intercuspal positions and edge to edge position, the range of incomplete and complete disclusion of posterior teeth in canine-guided occlusion, and to have a gender comparison and comparison between right and left sides of the obtained values.
Materials and Methods: Thirty-five subjects showing canine-guided occlusion and Angle's class I canine and molar relation were chosen for the study.
Maxillary midline and a corresponding line on the mandible were marked in maximum intercuspation with marker pen in the patient's mouth. Lines from 1 to 5 mm were marked on maxillary central incisor with marker pen. A dental floss was looped around the distal surface of mandibular last molar and the subject was asked to make left lateral movement (working side) at 1-mm intervals. The point at which floss was freed posteriorly was considered as initial disclusion and the point at which edges of maxillary and mandibular canines contacted was considered as complete disclusion.
Results: Most of the male and female subjects in the study showed progressive disclusion on right side and delayed disclusion on left side. The range of complete disclusion was 3-4 mm in males and 2-3 mm in females irrespective of the side. The range of functional zone was 1-4 mm irrespective of side or gender.
Interpretation and Conclusion: There is a need to redefine canine guidance in terms of immediate disclusion, delayed disclusion, and progressive disclusion.

Keywords: Canine disclusion, complete disclusion, functional zone, incomplete disclusion

How to cite this article:
Narang P, Shetty S, Prasad KD. An in vivo study to determine the range of posterior teeth disclusion on working side in canine-guided occlusion. Indian J Dent Res 2012;23:814-8

How to cite this URL:
Narang P, Shetty S, Prasad KD. An in vivo study to determine the range of posterior teeth disclusion on working side in canine-guided occlusion. Indian J Dent Res [serial online] 2012 [cited 2020 Nov 28];23:814-8. Available from: https://www.ijdr.in/text.asp?2012/23/6/814/111269
Mutually protected occlusion, also known as canine protected occlusion or organic occlusion, has its origin in the work of D'Amico, Stuart, Stallard, and Lucia and the members of Gnathological society. According to D'Amico, the upper canine teeth, when in functional contact with lower canines, determine both lateral and protrusive movements of the mandible. Thus, canines prevent masticatory forces from being applied to the remaining teeth during functional movements of the mandible away from centric occlusion. Also, the proprioceptors of periodontal ligament of canines are far more responsive than those of any other teeth. Consequently, the proprioceptors of canines transmit desirable impulses to the muscles of mastication and occlusal trauma is thus prevented by reduced muscular tension and magnitude of applied force. [1]

Reported studies [2],[3] on the functional range of tooth contact in lateral gliding movements have determined the amount and nature of contact of natural teeth in working movement. However, quantified data of the functional range are lacking.

Hence, this study was planned to estimate the point of initial and complete disclusion, range of incomplete disclusion, complete disclusion, and the range of functional zone between maximum intercuspation and edge to edge position of canine in canine-guided individuals.


   Materials and Methods Top


A total of 35 subjects (18 males and 17 females) were selected with following inclusion criteria:

  • Subjects showing canine-guided occlusion [Figure 1].
    Figure 1: Canine-guided occlusion (a) on right side, (b) on left side

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  • Subjects with full complement of teeth with no morphological abnormality.
  • No history of orthodontic treatment.
  • Angle's class I molar and canine relation.
  • All subjects of 21-27 years of age as the dentition achieves complete occlusion and tooth wear due to aging is not seen in such age group.
Criteria for exclusion

  • Subjects showing group function type of guidance.
  • Severely attrited or compromised canines.
  • Subjects with fixed or removable prosthesis.
Maxillary midline and a corresponding line on the mandible were marked in maximum intercuspation with marker pen in the patient's mouth. Lines from 1 to 5 mm were marked on maxillary central incisor with marker pen (Faber-Castell, Germany) [Figure 2]. Subjects were given a face mirror and were trained to make 5-mm left lateral movement (working side) at intervals of 1 mm. When the subject mastered these movements, a dental floss (Colgate Total, India) was looped around the distal surface of mandibular last molar and was tucked in between canine and lateral incisor anteriorly (working side). The free end of dental floss was held with an artery forceps and the subject was asked to make left lateral movement (working side) at 1-mm intervals. The free end of the dental floss was withdrawn anteriorly with artery forceps at every 1 mm of lateral excursive position till edge to edge position of the maxillary and mandibular canine was achieved. If the floss would hold its position, it indicated absence of disclusion. The point at which floss was freed posteriorly was considered as initial disclusion [Figure 3] and the point at which edges of maxillary and mandibular canines contacted was considered as complete disclusion [Figure 4]. At both stages of initial and complete disclusion, the readings were recorded at a point where the previously marked lines on maxillary central incisor overlapped with marked mandibular line.
Figure 2: Midline and 5 lines marked at 1-mm interval on maxillary central incisor

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Figure 3: Initial disclusion on right side

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Figure 4: Complete disclusion on right side

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The point of initial and complete disclusion, range of incomplete disclusion, complete disclusion, and the range of functional zone between maximum intercuspation and edge to edge position of canine were recorded.

Same procedure was repeated on the right side, and values were recorded during right lateral movement (working side).

To avoid intraobserver error, three sets of reading were recorded initially and were subjected to intraclass correlation coefficient which was found to be 0.7 (values above 0.6 is considered reliable).

The frequency and percentage of range of incomplete disclusion and complete disclusion were calculated on right and left side separately for both male and female subjects. A value of P < 0.05 was considered statistically significant.


   Results Top


Fifty percent of males showed incomplete disclusion at 1-2 mm range of lateral movement on the right side and 55.6% at 0-1 mm range of lateral movement on left side; 47.1% of females showed incomplete disclusion at 1-2 mm range of lateral movement on right side and 41.2% at 0-1 and 1-2 mm range of lateral movement on left side. The comparison of range of incomplete disclusion between males and females was done using chi-square test for both sides and the P values were 0.416 and 0.312 on right and left side, respectively, which was statistically insignificant [Table 1] and [Table 2].
Table 1: Gender comparison of range of incomplete disclusion using chi - square test on right side (working side)

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Table 2: Gender comparison of range of incomplete disclusion using chi - square test on left side (working side)

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In all, 33.3% of males showed complete disclusion at 3-4 mm range of lateral movement on the right side and 27.8% at 3-4 mm range of lateral movement on left side; 23.5% of females showed complete disclusion at 3-mm lateral movement on the right side and 29.4% at 2-3 mm range of lateral movement on left side. The gender comparison of range of complete disclusion using chi-square test gives P values of 0.234 and 0.504 on right and left side, respectively, which is statistically insignificant [Table 3] and [Table 4].
Table 3: Gender comparison of range of complete disclusion using chi - square test on right side (working side)

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Table 4: Gender comparison of range of complete disclusion using chi - square test on left side (working side)

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In all, 66.7% of males showed a functional range of 1-4mm on right side and 55.6% showed a functional range of 1-4 mm on left side; 35.3% of females showed a functional range of 1-4 mm both on right and left side. A gender comparison of these findings was made using chi-square test and the P values were 0.130 and 0.408 for right and left side, respectively, which was statistically insignificant [Table 5] and [Table 6].
Table 5: Gender comparison of range of functional zone from intercuspation till canine contact using chi - square test on right side (working side)

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Table 6: Comparison of range of functional zone from intercuspation till canine contact using chi - square test on left side (working side)

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In males, the mean value of initiation of disclusion was found to be 2.78 ± 0.64 mm on right side and 2.44 ± 0.51 mm on left side. The values were subjected to paired t-test and the P value was found to be 0.029 which is statistically significant. The mean values of complete disclusion were 4.22 ± 0.54 mm on the right side and 4.00 ± 0.68 mm on left side. The values were subjected to paired t-test and the P value was found to be 0.104 which is statistically insignificant [Table 7].
Table 7: Mean and standard deviation of initial disclusion and complete disclusion on right and left side (working sides) and their analysis with paired t-test in male subjects

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In females, the mean value of initiation of disclusion was found to be 2.94 ± 0.74 mm on right side and 2.59 ± 0.79mm on left side. The values were subjected to paired t-test and the P value was found to be 0.111 which is statistically insignificant. The mean values of complete disclusion were 3.88 ± 0.92 mm on the right side and 3.82 ± 0.80 mm on left side. The values were subjected to paired t-test and the P value was found to be 0.718 which is statistically insignificant [Table 8].
Table 8: Mean and standard deviation of initial disclusion and complete disclusion on right and left side (working sides) and their analysis with paired t-test in female subjects

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   Discussion Top


Canine protection has been defined as "a form of mutually protected articulation in which the vertical and horizontal overlap of the canine teeth disengages the posterior teeth in the excursive movements of the mandible" according to Glossary of Prosthodontic terms 8.This definition fails to recognize the point of initiation of disclusion during the excursive movements. Some studies [3],[4] have identified canine disclusion only when immediate disclusion by canines was present on lateral movement and other study [5] has recognized intermediate phases between maximum intercuspation and extreme eccentric lateral movement. Hence, reliability of the defining canine guidance is unclear.

DiPietro [5] has stated that canine disclusion is not always immediate and may have immediate disclusion (immediate disclusion upon excursion), delayed disclusion (contact upto 1 mm followed by disclusion), or progressive disclusion (contact from 1 to 2 mm followed by disclusion).

Most of the males considered in the study showed progressive disclusion (contact from 1 to 2 mm followed by disclusion) on right side and delayed disclusion on left side (contact upto 1 mm followed by disclusion). Most of the females in the study showed progressive disclusion (contact from 1 to 2 mm followed by disclusion) on right side and progressive disclusion and delayed disclusion on left side (contact upto 1 mm followed by disclusion). The gender difference of range of incomplete disclusion was insignificant. Hence, within the study's sample consideration, a guideline can be drawn that 1-2 mm of working side lateral contacts are required irrespective of gender.

Most of the male subjects considered in the study showed the range of complete disclusion of 3-4 mm irrespective of the side and female subjects showed complete disclusion in the range of 2-3 mm irrespective of the side. The range of functional zone from maximum intercuspation till edge to edge position of canine was 1-4 mm irrespective of gender and side in majority of subjects.

Statistically insignificant results in both males and females were obtained when mean values of incomplete and complete disclusion were subjected to paired t-test to observe variation on left side when compared with right side.

The results verify the validity of classification used by DiPietro [5] and are in accordance with the results by Yaffe [2] who stated that lateral movement is a complex movement in which the nature of tooth contact is altered in location, direction, and number of teeth participating. The results are also in accordance to Ogawa [3] study who concluded that a new classification system of occlusal guidance is desirable. Hence, there is a need to redefine canine guidance in terms of immediate disclusion, delayed disclusion, and progressive disclusion.

The clinical significance of initial incomplete disclusion phase could be explained by gliding contacts which occur as the cuspal inclines pass by each other during the opening and grinding phase of mastication. Altering or reestablishing these values may change disclusion and hence should be recorded during the diagnostic phase either intraorally as in this study or on a programmed semiadjustable or fully adjustable articulator. Hence, these contacts should not be ignored in the process of selecting a scheme for occlusal reconstruction.

The above mentioned observations have been made on a smaller sample size. Therefore, future investigation is suggested on a larger scale in order to generalize the guidelines and quantify canine disclusion. Also, the observations were made intraorally. Such study can be done with either semi- or fully adjustable programmed articulator which would help in visualizing the nature, amount, and number of contacts at even smaller range of lateral movement.


   Conclusion Top


Within the limitations of the study, clinically significant conclusions can be drawn that many individuals exhibit intermediate phase between extreme lateral positions. Hence, canine disclusion must be clearly defined and should be categorized as immediate disclusion (immediate disclusion upon excursion), delayed disclusion (contact upto 1 mm followed by disclusion), or progressive disclusion (contact from 1 to 2 mm followed by disclusion). Most of the male and female subjects in the study showed progressive disclusion on right side and delayed disclusion on left side. The range of complete disclusion was 3-4 mm in males and 2- 3 mm in females irrespective of the side. The range of functional zone was 1-4 mm irrespective of side or gender.


   Acknowledgment Top


I would like to express my gratitude towards my alma mater A.B. Shetty Memorial Institute of Dental Sciences, Mangalore, which laid the foundation for my research and towards my esteemed guide Prof. (Dr.) N. Sridhar Shetty for his valuable suggestions during this research.

 
   References Top

1.Alexander PC. The periodontium and canine function theory. J Prosthet Dent 1967;18:571-8.  Back to cited text no. 1
    
2.Yaffe A, Ehrlich J. The functional range of tooth contact in lateral gliding movements.J Prosthet Dent 1987;57:730-3.  Back to cited text no. 2
    
3.Ogawa T, Ogimoto T, Koyano K. Pattern of occlusal contacts in lateral positions: Canine protection and group function validity in classifying guidance pattern. J Prosthet Dent 1998;80:67-74.  Back to cited text no. 3
    
4.McAdam DB. Tooth loading and cuspal guidance in canine and group-function occlusions. J Prosthet Dent 1976;35:283-90.  Back to cited text no. 4
    
5.DiPietro GJ. A study of occlusion as related to the Frankfort-mandibular plane angle. J Prosthet Dent 1977;38:452-8.  Back to cited text no. 5
    

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Correspondence Address:
Praful Narang
Department of Prosthodontics, A.B. Shetty Institute of Dental Sciences, Deralakatte, Mangalore
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9290.111269

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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