Comparative Evaluation of the Surface Area of the Maxillary and Mandibular Denture Bearing Area According to Arch Shapes Obtained Through A Manually Molded Impression.

Objective: This study was done to compare the surface area of the maxillary and mandibular denture bearing area obtained through a manually molded impression in an open mouth selective pressure technique. Methodology: Final impression was made in 60 patients with zinc oxide eugenol impression paste, poured in dental stone to get master cast. Denture bearing area was marked with an indelible pencil. The number of squares were calculated which constituted the denture bearing area.
Results: Square arch form provides more surface area than ovoid and tapering which in turn increases the retention and support.
Conclusion: The variance and standard deviation of the surface area of square, ovoid, and tapering arch shapes of maxillary dentures were very much significant and in case of Mandibular dentures were less significant. Copyright:

INTRODUCTION

The success of complete denture depends upon the height and shape of the residual ridge, the nutritional condition and health of soft tissues, and maximum coverage of denture bearing area.[12] The preservation of the alveolar ridge ranks one of the foremost concerns for complete denture prosthodontics. It has been postulated that resorption of the residual alveolar ridge can be minimized through extending denture base as far as possible; in turn, the increased size of the denture base would reduce the occlusal load per unit area on the tissue under the denture.[3]

Increased size of the denture foundation increases both the retention and stability of the denture base as well as its support. Interfacial surface tension, adhesion, capillary attraction, and atmospheric pressure also affect the retention of complete denture.[4] Area of the basal seat covered by the denture is directly proportional to these factors. Retention and stability of the denture is affected by the form of ridge and palate. Thus, retention and stability proportionally increase with the increase in the size of the denture bearing area.[5] The purpose of this in vivo study was to compare and determine whether there was any relationship between basal seat area and different arch shapes in edentulous patients.

MATERIALS AND METHODS

Sixty patients twenty each for the alveolar arch shapes, square, ovoid, and tapering were chosen for this study. The patient information sheet and informed consent form were provided to each patient prior to proceeding with the study. Primary impression of each subject in various alveolar arch shapes was made with impression compound. Border molding of the special tray was accomplished using green stick compound (DPI PINNACLE). Final impression was done with ZOE impression paste (DPI impression). The impression was poured in dental stone to get master cast. Base plate was adapted, flasking, and dewaxing done. The flask was packed with addition silicone (photosil). The maxillary elastomeric base was divided into three parts, middle part is the palatal portion and the other two are ridge portions. Mandible elastomeric base was divided into two ridge portions.

The divided parts of the set rubber base impression were pressed on the graph paper. The outlines of each part were drawn on the graph paper and counted three times to minimize the counting error made by the same operator. The squares included in each outline were counted. The combined basal seat areas of the ridge and the palate constituted the total area of the basal seat. The master casts of each patient were grouped into square, ovoid, and tapering arch shapes. The surface area of the basal seat was measured in cm2 for each cast. The values were recorded, and it was statistically analyzed.

RESULTS

Table 1, Graph 1 shows that the mean value of the basal seat area of maxillary denture was 21.75 cm2 in ovoid arch, 25.26 cm2 in squared arch, and 21.12 cm2 in tapering arch. The mean value of the basal seat area is the largest in the square-shaped arch.

Table 1

Maxillary basal seat area

Maxillary Denture Arch Average Values (All Values in cm2)
Sl. No	Square	Ovoid	Tapering
1	25.62	22.72	19.89
2	23.47	21.69	20.34
3	24.07	21.95	17.52
4	25.58	20.67	21.36
5	25.27	20.27	22.76
6	25.53	21.81	20.94
7	25.05	21.18	21.52
8	25.29	22.26	21.46
9	25.3	20.92	22.49
10	24.96	21.55	21.39
11	24.88	20.61	21.06
12	25.49	21.75	21.15
13	26.21	20.93	21.02
14	26.27	22.35	21.33
15	25.5	21.68	21.84
16	25.21	21.74	21.48
17	25.11	22.1	21.32
18	25.28	22.87	22.33
19	25.69	23.53	20.31
20	25.47	22.32	20.9
Mean	25.26	21.75	21.12
Standard Deviation	0.63	0.82	1.1

Graph 1

Comparison of maxillary values of square, ovoid, and tapered basal seat areas

Table 2, Graph 2 shows that the mean value of the basal seat area of corresponding mandibular denture is 14.45 cm2 in ovoid arch, 14.63 cm2 in squared arch, and 13.70 cm2 in tapering arch.

Table 2

Mandibular basal seat area

Mandibular Denture Arch Final Values (All Values in Cm2)
Sl. No	Square	Ovoid	Tapering
1	14.79	15.15	14.73
2	14.47	14.56	14.77
3	14.74	13.84	12.73
4	15.26	14.46	14.31
5	14.43	13.65	13.31
6	14.1	14.2	12.87
7	15.02	14.31	13.03
8	14.76	15.09	12.81
9	14.41	14.82	13.13
10	14.36	13.9	13.43
11	14.33	14.32	13.85
12	14.37	14.34	14.18
13	14.77	14.31	13.37
14	14.93	15.49	13.3
15	14.99	14.34	14.34
16	14.62	14.39	13.62
17	14.67	14.61	14.53
18	14.35	14.6	14.15
19	14.33	14.29	13.95
20	14.85	14.31	13.56
Mean	14.63	14.45	13.7
Standard Deviation	0.3	0.44	0.64

Graph 2

Comparison of mandibular values of square, ovoid, and tapered basal seat areas

Table 3 shows that the maxillary and mandibular basal seat ratio is 1.50 in ovoid arch, 1.73 in squared arch, and 1.54 in tapering arch.

Table 3

Mean and standard deviation of maxillary and mandibular of arch shapes

Arch Shapes/Basal Seat Area	Mean±SD
	Square (cm2)	Ovoid (cm2)	Tapering (cm2)
Maxillary	25.26±0.63	21.75±0.82	21.12±1.10
Mandibular	14.63±0.30	14.45±0.44	13.70±0.64
Maxillary/Mandibular	1.73	1.5	1.54

Table 4 shows ANOVA analysis results for maxillary with two factors with replication.

Table 4

ANOVA for maxillary: two factor with replication

Summary	Square	Ovoid	Tapering	Total
Count	20	20	20	60
Sum	505.23666	434.90333	422.42	1362.56131
Average	25.26183	21.74516	21.121	22.70933
Variance	0.39423	0.67741	1.20985	4.113595
Standard Deviation	63%	82%	110%	203%

Table 5 shows ANOVA analysis results for mandibular with two factors with replication.

Table 5

ANOVA for mandibular with two factors with replication

Summary	Square	Ovoid	Tapering	Total
Count	20	20	20	60
Sum	292.53333	289	273.97333	865.5067
Average	14.62666	14.45	13.69866	14.25844
Variance	0.08857	0.19465	0.41514	0.38952
Standard Deviation	30%	44%	64%	62%

Table 6 shows ANOVA values. As a result of analysis of variance, the relationship between basal seat areas in maxillary dentures with different arch shapes was significant at P ≤ 0.01, whereas it was less significant at P ≤ 0.01 in case of mandibular dentures.

Table 6

ANOVA table

Source of Variation	SS	df	MS	F	P	F crit
Sample (Maxillary/Mandible)	2142.52569	1	2142.526	4313.982	1.94E+92	3.92433
Columns (Square, ovoid, tapering)	137.4192757	2	68.70964	138.3471	3.23E+31	3.075853
Interaction (Maxillary/Mandibular * Type of Arch)	71.64689796	2	35.82345	72.13062	5.70E-21	3.075853
Within (Relations between square, ovoid, tapering)	56.61774333	114	0.496647
Total	2408.209607	119

DISCUSSION

Impression making is one of the important and crucial steps in denture construction.[6] Accurate impressions will not solve all the denture problems that are inherent to denture fabrication. If all subsequent steps are followed but still denture is loose or does not fit well, then maximum coverage of the denture bearing area should be kept in mind.[7]

An extensive review of literature revealed not much clinical studies, in which comparison has been done between the surface areas of the basal seat of maxillary and mandibular denture bearing area obtained through different open mouth impression techniques.[89] This study was done to compare the surface area of different arch shapes of the maxillary denture bearing and corresponding mandibular denture bearing area obtained through a manually manipulated impressions in an open mouth selective pressure technique.

We found that the mean values of the surface area of maxillary square arch shape is 25.26 cm2, ovoid arch shape is 21.75 cm2, and tapering shape is 21.12 cm2. The mean values of the surface area of mandibular square arch shape is 14.63 cm2, ovoid arch shape is 14.45 cm2, and tapering shape is 13.70 cm2. The maxillary and mandibular denture surface area seat ratio is 1.73 in square shape arch, 1.50 in ovoid shape arch, and 1.54 tapering arch shape types. Logan M[10] stressed the importance of utilization of maximum coverage of the basal seat to better distribute the forces of mastication and development of an effective border seal around each denture for providing stability, retention, and resistance to displacement.

CONCLUSION

The variance and standard deviation of the surface area of square, ovoid, and tapering arch shapes of maxillary dentures were very much significant and in case of mandibular dentures were less significant.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.