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5/29/2016 Influence of Functional Head Postures on the Dynamic Functional Occlusal Parameters

Repeated measures of analysis of variance with Greenhouse­Geisser values

Centre of occlusion and asymmetry of occlusion

Centre of Occlusion and Asymmetry of occlusion in supine head position was 4.80 (3.763), 24.821 (19.524) mm.
The Upright head posture and 30° forward head posture had a center of occlusion of 4.74 (3.702), 3.96 (3.680) mm
respectively. Asymmetry of occlusion for both the head posture was 25.20 (21.27) and 21.16 (18.253) mm
respectively. Repeated measures of ANOVA showed an F value of 1.710 for the center of occlusion and 1.192 for
asymmetry of occlusion. The respective P values were 0.190 and 0.308. Hence, the statistically insignificant
difference was observed among the groups.

Initial occlusal contacts

The initial occlusal contact was different for all groups. 30° forward head posture provided the initial contact
majority on anterior teeth 57.8% (30/50) followed by upright 33.3% (16/50) and supine posture 28.9% (14/50). The
initial contacts were significantly different among each head posture.

Discussion Go to:

Teeth contact patterns play a vital role in determining masticatory efficiency. The success of any restorative
treatment is largely dependent on its compliance with good occlusion parameters. Hence, restorations or tooth
replacement procedure cannot be initiated nor executed without the proper occlusal evaluation. Accurately
identifying and quantifying the occlusal contact, determining their relationships and interference is important in any
occlusal evaluation. The dynamic occlusal contacts during the mandibular movement are more important than the
static contacts. Knowing the acceptable baseline occlusal parameters are important for the restorative dentist, it will
enable him to detect and quantify the unacceptable deviations. The treatment approach like whether to follow
confirmative or reorganized approach can be selected depending on the findings. The digital evaluation by T Scan
III provides the multiple advantages such as quantification and sequence of occlusal contact. The other important
parameters such as occlusion and disclusion time can also be precisely determined.[7]

The studies have shown the influence of head postures on the occlusal contacts.[8] Various head postures are
utilized for better visibility and accessibility during routine dental treatments. The supine and upright head postures
are routinely used during diagnostic occlusion evaluation to final restorations. The head is flexed by average 30°
during the eating, existence of substantial change in occlusal contact between these head posture may be
detrimental to the teeth, restorations and their supporting structures. Hence, the dynamic tooth contact changes
during these head postures are critical for a dentist to understand.

Identifying the initial tooth contact (CR), premature contacts and slide from CR to maximum intercuspation is
important for the health of the teeth, supporting structure and TMJ.[9] Researchers observed the properly positioned
condyles in the articular fossae during CR has the least muscle activity.[10] The results of the study showed the
change in initial tooth contact position in all three head positions. An alert feeding position with 30° forward head
posture had the predominantly anterior initial contacts, while supine position only had few initial contacts on
anterior segment. The change on initial contact can be justified by the observation of Preiskel[11] and Goldstein et
al.[12] They demonstrated the relation between head position and mandibular position. The literature suggests[13]
the contraction of mandibular elevator muscles during alert feeding position shift the path of mandibular closure
slightly anterior to upright head position. Hence, the anterior teeth receive the heavy contact in this head posture
than upright position.

The time required by the anterior guidance to disengage all posterior teeth in protrusive and lateral movements is
known as disclusion time. The disclusion time more than 1.39 s reported to initiate the elevated muscular
contraction in masseter and temporalis.[14,15] The EMG study showed the resting state muscular activity was

http://www.st­va.ncbi.nlm.nih.gov/pmc/articles/PMC4160681/ 5/7