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| Year : 2008 | Volume
: 19
| Issue : 4 | Page : 335-339 |
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| A study to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers: A pilot study |
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Vernie A Fernandes, Vidya Chitre, Meena Aras
Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa, India
Click here for correspondence address and email
| Date of Submission | 30-Oct-2007 |
| Date of Decision | 28-May-2008 |
| Date of Acceptance | 08-Jun-2008 |
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 Abstract | | |
Context: By convention, the posterior palatal seal area is located on the palate between the anterior and posterior vibrating lines. However, there are opposing views on whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion.
Aims: The study was carried out to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers. A second part of the study was formulated to evaluate whether the palpatory method correlated with the nose-blowing method in locating the anterior line of flexion
Materials and Methods: Twenty-three dental undergraduate clinical students were selected as observers. Twenty-three edentulous patients were randomly selected. The students were asked to record the anterior and posterior vibrating line on one patient each using two differently colored marking pencils. Also, the anterior vibrating line was marked by the palpatory method (using T burnisher) using a third colored marking pencil. The marked lines were then transferred onto the previously made impression of modeling plastic.
Results: Of the 23 recorders used in the study, 19 could locate separate anterior and posterior lines of flexion. In 4 cases, the anterior and posterior lines of flexion coincided and were not distinct. In 20 cases, the palpatory method produced a line anterior to the line located by the Valsalva maneuver.
Conclusions: The anterior and posterior vibrating lines could be located by the undergraduate students as two separate lines of flexion when the appropriate action was elicited for each of them; and the palpatory method produced a line slightly anterior to the anterior vibrating line located by the Valsalva maneuver. Keywords: Maxillary complete denture, peripheral seal, posterior palatal seal, vibrating line
How to cite this article:
Fernandes VA, Chitre V, Aras M. A study to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers: A pilot study. Indian J Dent Res 2008;19:335-9 |
How to cite this URL:
Fernandes VA, Chitre V, Aras M. A study to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers: A pilot study. Indian J Dent Res [serial online] 2008 [cited 2023 Mar 22];19:335-9. Available from: https://www.ijdr.in/text.asp?2008/19/4/335/44538 |
The role of the posterior palatal seal in the retention of the maxillary complete denture is very well established. [1],[2],[3] The posterior palatal seal may be defined as an area of soft tissue along the junction of the hard and soft palate on which pressure, within physiologic limits of the tissues, can be applied by a denture to aid in its retention.
The posterior palatal seal functions to provide retention, prevents food from getting under the denture base, diminishes gagging, makes the sunken border less conspicuous to the tongue, and provides a thick border to counteract denture warpage due to dimensional changes during the curing process [1],[2],[4],[5]
The location and preparation of the posterior palatal seal is a frequently neglected procedure. Most authors agree that this seal contributes significantly to the retention and stability of a maxillary complete denture. [6],[7],[8],[9] Determination of the posterior palatal seal is the responsibility of the dentist and should not be delegated to auxillary personnel. [4],[10],[11]
Location of the vibrating line relies on visual observation. The currently used techniques for determining the location of the vibrating line are based on:. [3],[12],[13],[14],[15]
- Phonation of 'ah' sound.
- The palpatory method.
- The nose-blowing method (Valsalva maneuver).
- The swallowing method.
Clinically, different methods may result in different locations of the vibrating line. The vibrating line in an individual observed by the nose-blowing method is located more anteriorly than the vibrating line observed by the phonation method. [10]
Ming-Sheh Chen et al, [10] conducted a survey on the methods taught in dental schools for determining the posterior palatal seal region in US and Canada. He concluded that
- A combination of clinical methods was most frequently taught for locating the vibrating line.
- The phonation of the 'ah' sound was the most popular single method taught for locating the vibrating line.
- Most of the dental schools taught that there is one vibrating line per person.
- The posterior flexion line was related to the distal termination of the maxillary denture by dental schools that teach the concept of two vibrating lines.
Most dental schools teaching the concept of two vibrating lines give no or little significance to the marking of the anterior vibrating line. It is either marked arbitrarily anterior to the posterior vibrating line or, most often, not marked at all.
In his original study, Silverman determined that the separation between the vibrating lines varies from 4-12 mm, with an average of 8.2 mm. [11] However, there are no subsequent studies that whether the anterior and posterior vibrating lines can actually be distinguished as two separate lines of flexion.A study was, therefore, designed to evaluate whether the posterior and anterior vibrating lines could be distinguished as separate lines of flexion by unbiased observers.
A second part of the study was formulated to evaluate whether the palpatory method (using a T-burnisher) correlated with the nose-blowing method (Valsalva maneuver) in locating the anterior vibrating line.
| Subjects and Methods | |  |
Fourth year, first semester students were selected as the observers. Students were selected after they answered the following questionnaire:
- Whether they had knowledge about the role and significance of the posterior palatal seal.
- Whether they were aware of the concepts of the anterior and posterior vibrating lines.
- Whether they knew what specific action carried out by the patient elicited movement at the anterior vibrating line and at the posterior vibrating line.
Those students who were aware of the concepts of the posterior palatal seal and the anterior and posterior vibrating lines, but were not certain of what specific action elicited movement at the anterior and posterior vibrating lines were selected to act as observers in the study. Of the 35 students questioned, 23 were selected. Twenty-three edentulous subjects were selected randomly. The students were asked to record the anterior and posterior vibrating lines on one patient each.
Preliminary impressions were made using modeling impression compound. Each subject was instructed by the study coordinator to rehearse the Valsalva maneuver until he/she became acquainted with it. The subject was then told to say 'ah' in a normal unexaggerated manner. He was then requested to perform the above maneuvers when required to do so.
Observations recorded in the study were made by two observers, the study coordinator and the observer. The study coordinator first dried the posterior palatal seal area with a gauze sponge. The subject was asked to perform the first maneuver (saying 'ah' in an unexaggerated manner). The hamular notch was located by palpation and marked using a pointed lilac-colored pencil. The observer was then asked to mark the beginning of the line of motion of the soft palate with the lilac-colored pencil [Figure 1]. The dried impression was then placed in the mouth by the study coordinator to transfer the marking.
The lilac marking on the palate was then wiped off. The hamular notch was again located and marked with a pointed tip dipped in pink food color (Foster Clarks culinary essence, Foster Clarks Limited, Malta) and the subject was asked to perform the next maneuver (nose blowing). When the soft palate moved after gently pinching the subject's nose and having the subject attempt to blow air through the nose, the line of flexion was marked in violet color by the student [Figure 2]. The dried impression was again placed by the study coordinator in the mouth to transfer the second marking. The marking was wiped off the palate.
The anterior vibrating line was confirmed by the study coordinator by using the palpation method wherein a T - burnisher was used. This marking was done using a pointed tip dipped in green food color and the impression was repositioned in the mouth to transfer the third marking [Figure 3].
A comparison of the three colored lines was made on the impression [Figure 4] and [Figure 5].
| Results | | |
35 students were put forth the questionnaire on the posterior palatal seal before the study. Of the 23 students used in the study, 19 could locate separate anterior and posterior lines of flexion.
The anterior and posterior lines of flexion marked by the recorders correlated with the specific techniques described for the anterior and posterior vibrating lines in each of the 19 cases [Figure 6].
In 4 cases, the anterior and posterior lines of flexion coincided and were not distinct. In 20 cases, the palpatory method produced a flexion line anterior to that located by the Valsalva maneuver. [Figure 7] shows the relation between the palpatory method and the nose blowing method of recording the anterior vibrating line.
| Discussion | | |
It is accepted that the posterior border of the maxillary denture should end at the posterior vibrating line. Pressure within physiological limits can be placed in the area between the anterior and posterior vibrating lines to aid in the retention of the denture. [10] The anterior and posterior vibrating lines were first described by Silverman who also gave the techniques for recording the same. [3]
It has been agreed that the posterior palatal seal area lies between these anterior and posterior vibrating lines. In order to correctly locate these lines, careful observation and palpation of the tissue is necessary, as their locations vary with the contour of the soft palate. Also, the palatal tissues anterior to the posterior border need to be palpated with a blunt instrument to determine their compressibility in width and depth. The termination of the glandular tissues usually coincides with the anterior vibrating line. Thus, a combination of the palpatory and visual methods has been used in the present study. Although the dimension of the vibrating area was determined by Silverman as an average of 8.2 mm, it may vary depending on the configuration of the soft palate. Use of this average dimension for determining the palatal seal area can deprive the patient of up to several millimetres or more of tissue coverage, which can have a direct effect upon the retentive potential of the denture base.
For example, a class I soft palate configuration allows for a wide posterior palatal seal, but one that is not very deep. On the other hand, a class III soft palate allows for a smaller but deeper posterior palatal seal area. [13],[15]
The anterior vibrating line demarcates the zone of transition between no movement of the tissues overlying the hard palate and some movement of the tissues of the soft palate. It can be located by visualization and palpation of the hamular processes. The fovea palatine may be used as a guide in locating the anterior vibrating line but should not be used as a definite location to which the posterior border of the denture should be extended. The anterior vibrating line serves as the anterior border of the posterior palatal seal area. It is generally not a straight line between the hamular processes, but reflects the projection of the posterior nasal spine along the posterior border of the palatine bone.
The anterior vibrating line can be visualized by asking the patient to say 'ah' in short vigorous bursts or by asking the patient to perform the Valsalva maneuver.
The posterior vibrating line lies in the area of the junction of the aponeurotic portion of the soft palate and the muscular portion of the soft palate. It represents the area of maximum posterior extension of the posterior palatal seal. The posterior vibrating line can be visualized by instructing the patient to say 'ah' in a normal unexaggerated fashion. [3],[5]
The undergraduate students taking part in the study were not aware of the exact method that could elicit movement at the anterior and posterior vibrating lines. This eliminated the bias in locating the lines which could possibly have ensued from awareness of the same. Erasing each line previously marked before marking the next ensured that there was no subconscious attempt at separating the new line from the previous one.
The anterior vibrating line located by the palpatory method showed a general tendency to be slightly anterior to the line of flexion located by the Valsalva maneuver. This is so, because the palpatory method locates the anatomical junction of the hard and soft palate as opposed to the physiologic line of flexion at the junction of the movable and immovable parts of the soft palate located by the Valsalva maneuver.
As the sample size taken in the study was small (for the purpose of the pilot study), a statistical analysis was not done. However, graphical representations of the results have been illustrated below. This study may, therefore, be further extended by using a larger sample size and thus, achieving a more accurate outcome.
| Conclusions | | |
From the above study, the following conclusions were made:
- The anterior and posterior vibrating lines could be located by undergraduate students as two separate lines of flexion when the appropriate action was elicited for each of them.
- The palpatory method produced a line slightly anterior to the anterior vibrating line located by the Valsalva maneuver.
| Acknowledgment | | |
We like to thank the Dean, Goa Dental College and Hospital, Goa.
| References | | |
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Correspondence Address:
Vernie A Fernandes
Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0970-9290.44538
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7] |
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