Evaluation of the conventional method for establishing the posterior palatal seal

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King Saud University Journal of Dental Sciences (2012) 3, 61 67 King Saud University King Saud University Journal of Dental Sciences www.ksu.edu.sa www.sciencedirect.

Salloum Department of Removable Prosthodontics, Faculty of Dental Medicine, Damascus University, Syria Received 26 March 2011; accepted 21 June 2011 Available online 23 August 2012 KEYWORDS Complete

1 King Saud University Journal of Dental Sciences (2012) 3, King Saud University King Saud University Journal of Dental Sciences ORIGINAL ARTICLE Evaluation of the conventional method for establishing the posterior palatal seal Alaa a M. Salloum Department of Removable Prosthodontics, Faculty of Dental Medicine, Damascus University, Syria Received 26 March 2011; accepted 21 June 2011 Available online 23 August 2012 KEYWORDS Complete denture; Posterior palatal seal; Smear Abstract Objective: Providing sufficient posterior palatal seal (PPS) of a maxillary denture is necessary for retention. This research was designed to estimate the arbitrary scraping method used for establishing the PPS. Methods and material: Eight complete edentulous patients were selected. They received conventional complete dentures by using a scraping method for establishing the PPS. The posterior retention of the maxillary dentures was measured, the postpalatal area for each patient was visually estimated, and smears were made from the postpalatal areas at insertion appointment, 7, 30, and 90 days after denture placement. Result: The study revealed that the posterior retention of the maxillary dentures did not change during the stages of the study, and the epithelium of the postpalatal area converted gradually to a keratinized one. Conclusion: It is concluded that the scraping method used for establishing the PPS is an effective and safe technique. Ó2012 King Saud University. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license. 1. Introduction A successful complete denture treatment should meet patients functional needs and gain their acceptance. For achieving such goals patients should receive well retained dentures when in use [32]. The accuracy or fit of complete dentures is essential for providing retention [25]. But even with the presence of newly improved dental materials spaces may develop under address: drsalloum74@hotmail.com Peer review under responsibility of King Saud University. Production and hosting by Elsevier dentures. [12,15,19,22,28,24,31,2,30,9,10]. For this reason, a compensating mechanism is required. The posterior area of the maxillary denture is flat, so it does not restrict the release of internal stresses during processing of the acrylic base and cannot prevent the deformation occurrence [29,19]. Whereas the form of the anterior alveolar bone may resist the deformation when the denture is removed from its cast [9]. Providing sufficient posterior palatal seal (PPS) of a maxillary denture is necessary for retention [7,1]. The PPS area has been defined as the soft tissue area at or beyond the junction of the hard and soft palates on which pressure, within physiologic limits, can be applied by a complete denture prosthesis to aid in retention [26]. The functions of the PPS of the maxillary complete denture include improving retention, performing sealing of the denture base with the underlying tissue and decreasing the gag Ó 2012King Saud University. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license.

2 62 A.M. Salloum ging reflex [14,3,27] The PPS is performed by positioning the anterior and posterior vibrating lines [8]. [20,6] Stated that the one vibrating line concept for establishing the PPS is taught by 75 80% of schools. The palatal seal of the upper complete denture can be obtained by scraping the cast before denture processing, or by using physiologic impression technique or selective pressure impression technique [14]. [8] Stated that 87.5% of dental schools teach the method of carving the PPS arbitrarily in the maxillary cast. Whereas [20] found that 95% of schools teach this method. The random allocation and carving of the final cast can result in less effective posterior palatal seal of the upper dentures [3]. The research aimed to evaluate the conventional method (curving the cast before denture processing) for establishing PPS using a precise location of PPS area on the upper cast. The estimation included: fi Efficacy of this method in providing the posterior retention of the upper denture for a period of time. fi Maintenance of the integrity of mucous membrane in the PPS area. 2. Materials and methods 2.1. Sample Eight patients (6 males, 2 females) were selected for this study from the removable prosthodontic clinic at the College of Dentistry, Damascus University. The selection of patients included the following considerations: (1) all voluntaries were edentulous, (2) their ages ranged from years, (3) they were in good general health, (4) all patients had a middle alveolar bone resorption in the maxilla with absence of mechanical undercut, (5) the absence of irritated or abused mucosa, (6) the absence of temporomandibular joint (TMJ) symptoms, (7) the oral cavity of all patients was clinically healthy. The voluntaries participated in the study were informed about the study details and all patients approved to contribute in the study. The Ethics Committee in the Dental Faculty of Damascus University has accepted the research protocol Making complete dentures Conventional complete dentures were fabricated for patients according to academic steps. Heat-activated poly methyl methacrylate (PMMA) [RODEX, Mulazzano (LO), Italy] was used for making denture bases by using a compression-molding technique (dough technique). Heat-activated acrylic resins were polymerized by placing the flasks in a constant-temperature water bath [Hanau Curing Unit, Hanau Engineering Company Inc, Buffalo, USA] at 74 C (165 F) for 2 h then boiling at 100 C (212 F) for 1 h [2] Scraping the cast for establishing the PPS After an accurate and fully extended final impression had been made, boxed and poured, a well-adapted resin base was fabricated on the stone cast (the record base). A self curing acrylic resin [ResPal NF, Mulazzano(LO), ITALY] was used for making the base. By using the methods described by [23,3,27] anterior and posterior vibrating lines were positioned. A precise location of the PPS area on the upper cast was determined according to the technique illustrated by [6]. The patient was seated in an upright position and instructed to rinse with an astringent mouthwash to eliminate the stringy saliva that might preclude obvious transfer marking [5]. The PPS area was dried with gauze, a mouth mirror was glided along the crest posteriorly and anteriorly until it dropped into the pterygomaxillary notch. A line was drawn with an indelible pencil across the notch and extended 3 to 4 mm anterolateral to the tuberosity, approximating the mucogingival junction. The same procedure was then performed on the opposite side. The patient was asked to enunciate ah in a kind way not in a vigorous fashion. While observing the movement of the soft palate, the posterior vibrating line was marked with an indelible pencil [27]. By connecting the line through the pterygomaxillary seal with the line drawn demarcating the posterior vibrating line, the posterior denture extension was delineated. The patient was instructed to keep the mouth open to avoid distortion of the markings. The acrylic base was then put into the mouth and seated tightly to place. After removal from the mouth, the base returned to the master cast to determine the posterior border which had been transferred to the base. The base was returned to the master cast and the posterior border was determined. As stated by [6] the acrylic base was cut with a carbide bur to the posterior markings. [3,6] explained that the anterior vibrating line represents the anterior border of the PPS area. For locating this line the acrylic base was returned once more to the mouth, the palatal tissues anterior to the posterior border were palpated by using the T burnisher to determine their compressibility and the anterior outline of the PPS area (anterior vibrating line) [23]. Valsalva maneuver and visualization of the area while the patient said ah with short vigorous bursts were also used [3,27]. This line was marked in the mouth with an indelible pencil and transferred to the acrylic base. The base was trimmed to the markings, and it was put again on the master cast for transferring the anterior border of the PPS area [6]. A scraper was used to carve the cast. [3] Stated that the deepest points of the PPS area positioned between the hamular notch and the midline on each side, and at the junction between the posterior and middle thirds in antero-posterior direction. It was carved to the depth of approximately 1 to 1.5 mm. [1] sustained that the tissue covering the median palatal raphe has thin mucosa and cannot resist the same compressive force as the tissues lateral to it. So, [3] recommended to scrape this area to a depth of approximately 0.5 to 1.0 mm Evaluation of the posterior retention of the upper denture Measures for each patient were made by three clinicians. Each clinician performed his evaluation independently. The criteria used depended on the studies of [21] and [4]. Each patient was assessed by using a seven-point scale (1, 1.5, 2, 2.5, 3, 3.5 and 4) (Fig. 1). The evaluation was performed by applying direct force at the palatal surface of upper incisors. Each patient was evaluated at insertion appointment, 7, 30, and 90 days after denture placement.

Evaluation of the conventional method for establishing the posterior palatal seal 63 1. No retention: No posterior border seal. 2.

Strong retention: It is so difficult to break posterior border seal. Figure 1 Criterion for objective evaluation of the posterior retention of the maxillary denture. 1. No retention: No posterior border seal.

3 Evaluation of the conventional method for establishing the posterior palatal seal No retention: No posterior border seal. 2. Weak retention: There is a little resistance before breaking posterior border seal. 3. Medium retention: There is a moderate resistance before breaking posterior border seal. 4. Strong retention: It is so difficult to break posterior border seal. Figure 1 Criterion for objective evaluation of the posterior retention of the maxillary denture. 1. No retention: No posterior border seal. 2. Weak retention: There is a little resistance before breaking posterior border seal. 3. Medium retention: There is a moderate resistance before breaking posterior border seal. 4. Strong retention: It is so difficult to break posterior border seal Clinical evaluation of the PPS area The PPS area was evaluated visually. The evaluation included appearance and color of oral mucosa. It was done four times for each patient (at insertion appointment, 7, 30, and 90 days after denture placement). Table 1 Mean evaluation of the posterior retention of the maxillary dentures for each patient. Patient At insertion appointment After one week After one month After three months Mean Table 2 Results of statistical test. P At insertion appointment * After one week * After one month * After three months * * < Cytological study of the PPS area Wipes were made from the mucous membrane covering the PPS area by using a sterilized spatula. Samples were then spread on sterilized glass plates. The case number and the date of each sample were registered on the plates. For each case four samples were made at insertion appointment, 7, 30, and 90 days after placement of dentures. The samples were immediately fixed in 90% ethyl alcohol for min. After cleaning with water they were stained with hematoxylin and eosin stains. The stained slides were then subjected to microscopic study Statistical study The data of the posterior retention evaluation were collected. ANOVA test was applied to test for statistical significance between datasets with the level of significance P = Statistical analysis did not show a significant difference (P < 0.05). Figure 2 Mean evaluation of posterior retention at insertion appointment (A), one week after denture placement (B), one month after denture placement (C), and three months after denture placement (D). 3. Results 3.1. Results of the tests for posterior retention of the maxillary dentures Table 1 reveals mean evaluation of the posterior retention of the maxillary dentures for each patient. Table 2 reveals results of statistical test. Fig. 2 shows mean evaluation of posterior retention at the insertion appointment, 7, 30, and 90 days after denture placement Results of clinical evaluation of the PPS area The appearance and color of the palatal mucosa in the PPS area were normal throughout the study in six cases. An indentation appeared clearly in this region in the remaining two cases one month after denture placement (Figs. 3 and 4). Figure 3 Indentation located at the PPS area.

(Magnification Figure 6 Nonkeratinized stratified squamous epithelium.

3. Results of cytological study of the PPS area Smears made at

4 64 A.M. Salloum Figure 4 Positive relief located at the internal surface of the maxillary denture. Figure 7 Nonkeratinized stratified squamous epithelium with bacterial aggregation. (Magnification Figure 5 Nonkeratinized stratified squamous epithelium. (Magnification x 60). Figure 8 Parakeratinized stratified squamous epithelium with bacterial aggregation. (Magnification Figure 6 Nonkeratinized stratified squamous epithelium. (Magnification x 60). Figure 9 Flattened epithelial cells. (Magnification 3.3. Results of cytological study of the PPS area Smears made at insertion appointment revealed a nonkeratinized stratified squamous epithelium with absence of inflammatory percolation (Figs. 5 and 6). One week after placement of the upper dentures, the slides showed the same view. Only in two cases bacterial aggregation could be noticed (Figs. 7 and 8).

Evaluation of the conventional method for establishing the posterior

(Magnification Figure 13 Keratinized stratified squamous epithelium.

(Magnification Figure 12 Keratinized stratified squamous epithelium.

(Magnification After one month, the epithelium was still

9 and 10), and keratin granules were seen in cytoplasm clearly (Fig.

5 Evaluation of the conventional method for establishing the posterior palatal seal 65 Figure 10 Flattened parakeratinized epithelial cells. (Magnification Figure 13 Keratinized stratified squamous epithelium. (Magnification Figure 11 Parakeratinized epithelial cell contains keratin granules. (Magnification Figure 14 Keratinized stratified squamous epithelium. (Magnification Figure 12 Keratinized stratified squamous epithelium. (Magnification Figure 15 Keratinized stratified squamous epithelium. (Magnification After one month, the epithelium was still nonkeratinized but the cells became flattened (Figs. 9 and 10), and keratin granules were seen in cytoplasm clearly (Fig. 11). Three months after placement of the upper dentures, the epithelium was keratinized markedly (Figs ). Only one case showed nonkeratinized epithelium after one month

66 A.M. Salloum Figure 16 Parakeratinized epithelial cells. (Magnification The study included a precise location of the anterior and posterior vibrating lines.

Three methods were applied for locating the anterior vibrating lines: (1) visualization of the palatal tissues while the patient said ah with short vigorous bursts, (2) Valsalva maneuver, (3)

6 66 A.M. Salloum Figure 16 Parakeratinized epithelial cells. (Magnification The study included a precise location of the anterior and posterior vibrating lines. The posterior vibrating line was located visually while the patient said ah in short bursts in a kind manner. Three methods were applied for locating the anterior vibrating lines: (1) visualization of the palatal tissues while the patient said ah with short vigorous bursts, (2) Valsalva maneuver, (3) palpation of the palatal tissues anterior to the posterior boundary to determine their compressibility in width and depth. A method for providing a precise positioning of the PPS area on the upper cast was used. This method avoids the failed transfer of the markings. The scraping form was in the shape of Cupid s bow. This type of curving is widely spread ([8,20]). The depth of curving applied in the study was recommended by [3] and [16]. Results of the tests for posterior retention of the maxillary dentures revealed that the retention did not change throughout the study. It is referred that the recovery of soft tissues which compressed within certain limits by positive relief had no effect on the retention. The clinical evaluation showed normal appearance of PPS area. An indentation appeared clearly in this region in only two cases one month after denture placement. This might have been caused by exaggerated scraping of the master cast, but the cytological study did not appear with any evidence of inflammatory occurrence. The epithelium located at the PPS area is nonkeratinized. Smears made at insertion appointment and one week after denture placement revealed nonkeratinized stratified squamous epithelium with absence of inflammatory percolation, so they confirmed the tissue integrity. After one week bacterial aggregations were noticed in two cases only. These might be facilitated by the presence of debris beneath the denture at the PPS region due to poor oral hygiene. One month after denture placement, signs of keratinization appeared in the nonkeratinized stratified squamous epithelium. The cells became flattened with clear keratin granules in cytoplasm. The displacement of the supporting mucosa, which resulted in circulatory disturbances, could be probably the cause of these results. This is supported by other studies [18,17,13]. The epithelium became keratinized obviously 90 days after denture placement. The continuation of displacement of the supporting mucosa could be the reason of this outcome. After the dentures had been used for three months there was no evidence of inflammatory percolation. This result referred to the integrity of mucous membrane in the PPS area during the three months (the time of observation). Clinically, no bleeding site was left confirming the integrity of mucous membrane. 5. Conclusion Figure 17 Flattened parakeratinized epithelial cells. (Magnification (Fig. 16), and was still nonkeratinized after three months but the epithelial cells became flattened and some of them converted to keratinized cells (Fig. 17). 4. Discussion It appears from the present investigation that arbitrary scraping method used for establishing the PPS is intact and an acceptable method. It established a proper posterior retention of the maxillary denture for a period of time. The epithelial tissue at the PPS area had a natural reaction (conversion from nonkeratinized to keratinized type) and made it more resistant toward applied forces. References [1] Ansary IH. Establishing the posterior palatal seal during the final impression stage. J Prosthet Dent 1997;78: [2] Anusavice KJ. Phillips science of dental materials. 10th ed. Philadelphia: W. B. Saunders Company; 1996, [3] Appelbaum M. The posterior palatal seal. In: Winkler S, editor. Essentials of complete denture prosthodontics. St. Louis: Ishiyaku EuroAmerica; p [4] Burns DR, Unger JW, Elswick RK, Beck DA. Prospective clinical evaluation of mandibular implant overdentures: Part1-retention, stability, and tissue response. J Prosthet Dent 1995;73: [5] Calomeni AA, Feldmann EE, Kuebker WA. Posterior palatal seal locations and preparation on the maxillary complete denture cast. J Prosthet Dent 1983;49: [6] Chang BMW, Wright RF. Accurate location of postpalatal seal area on the maxillary complete denture cast. J Prosthet Dent 2006;96: [7] Chen JC, Lacefield WR, Castleberry DJ. Effect of denture thickness and curing cycle on the dimensional stability of acrylic resin denture base. Dent Mat 1988;4:20 4. [8] Chen MS, Welker WA, Pulskamp FE, Crosthwaite HJ, Tanquist RA. Methods taught in dental schools for determining the posterior palatal seal region. J Prosthet Dent 1985;53:380 3.

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