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COMPARATIVE EVALUATION OF THE ACCURACY OF TWO METHODS OF OCCLUSAL REGISTRATION INVOLVING TERMINAL ABUTMENTS - AN INVIVO STUDY.

Byline: E. MANGALA DEIVANAI, SEYED ASHARAF ALI, SUMA KARTHIGEYAN, R.MADHAN, 5T.C.GIRI and S.CHENDIL MARAN

ABSTRACT

Purpose of the study was to evaluate the accuracy of interocclusal records made in the terminal abutment region by two recording techniques.

Ten partially edentulous patients planned for replacement of missing mandibular molars with fixed partial denture were selected. For each patient three sets of articulations were made.

Articulation I - Pre operative casts: Preoperative maxillary and mandibular casts mounted in an articulator. Measurements were made from the deepest part of the marginal gingiva in the maxillary and mandibular teeth using a travelling microscope.

Articulation II - Inter occlusal record with centric stop: Complete crown preparation was done for both mesial and distal abutments, preserving the centric stop in the distal abutment. Casts obtained were articulated using an inter occlusal record. Measurements between the maxillary and mandibular casts measured at the same area as the preoperative cast.

Articulation III - Inter occlusal record without a centric stop: The centric stop retained was reduced to complete the preparation and a third set of cast articulated with another inter occlusal record. Measurements between the maxillary and mandibular casts measured at the same area as the preoperative cast.

The values obtained were statically analyzed. Within the limitations of the study, presence of inter occlusal record in both the techniques showed an increase in vertical discrepancy.

Clinical Implication: Making interocclusal records with vertical stop shows increased vertical discrepancy.

Key Word: Interocclusal records, centric stop, distal abutment, terminal abutment.

INTRODUCTION

Accurate transfer of casts to the articulator is very critical in fabricating a restoration without occlusal errors. For the opposing casts to be held in a stable and reproducible manner, a tripod of vertical support and satisfied horizontal stability between the two casts are required. Interocclusal records are the means whereby the inter arch relationships are transferred from the mouth to the articulator1,2.

In spite of accurate records, problems exist in transferring the working cast to the articulator. Im- proper seating of condyles in the fossa, eccentric clo- sure by the patient due to loss of proprioception, mus- cular action, tissue changes within the joint, mandibu- lar position influenced by occlusal contacts are the factors that contribute to mounting errors.3 When the restoration involves the terminal tooth, then an interoc- clusal record becomes necessary. A unilatertal record is sufficient in those instances where a posterior sec- tion of one side of an arch alone is being restored.2

Though various techniques4,5,6 have been intro- duced to make accurate inter occlusal records in the distal abutment regions, none of them proved to be the most accurate. The purpose of the study was to com- pare the accuracy of inter occlusal records made in the terminal abutment tooth by two methods of recording technique, with centric stop and without centric stop using polyvinylsiloxane as the recording material.

METHODOLOGY

Ten partially edentulous patients who reported to the Department of Prosthodontics, Rajah Muthiah Dental College and Hospital, Annamalai University, Tamil Nadu, India for replacement of teeth were se- lected. The patients were explained about the different treatment options and only those interested in fixed partial dentures were selected for the study after their consent. Selection was done based on the following criteria:

i. One or two missing posterior teeth in the mandibular arch.

ii. The posterior abutment tooth, should be the terminal tooth (no teeth posterior to it).

iii.Braly's classification class I and II (3)

iv. Angle class I molar relationship.

v. No history of TMJ dysfunction or myofascial pain syndrome, crepitus facial muscle pain, or limitation of mandibular movement

For each patient three sets of articulations were made. Articulation I - Pre operative casts (reference group): Maxillary and mandibular preoperative impres- sions were made with polyvinyl siloxane impression material (Aquasil, Dentslpy). Preoperative maxillary and mandibular casts were mounted in an articulator in the maximum intercuspal position. Measurements were made from the deepest part of marginal gingiva of the proposed mesial and distal abutments, to their respective opposing teeth using a travelling micro- scope. The values obtained were used as the guideline measurement for that particular patient.

Articulation II - Inter occlusal record with cen- tric stop: The occlusal contacts in the patient were recorded using an articulating paper (Arti- fol) 8 microns thick (Fig 1). The cusp of the terminal abutment tooth that was in contact with the opposing tooth was considered as the centric stop. Complete crown preparations were done for both the mesial and distal abutments, pre- serving the centric stop in the distal abutment (Fig 2). Casts obtained were articulated using an inter oc- clusal record. The inter occlusal record was obtained using polyvinyl siloxane bite registration material (Bitrex, Equinox). The patient was guided to the maxi- mum intercuspal position and the bite registration material was injected between the prepared teeth. Measurements between the maxillary and mandibu- lar casts measured at the same area as preoperative cast.

Articulation III - Inter occlusal record without a centric stop: The centric stop retained was reduced to complete the preparation (Fig 3) and a third set of cast articu- lated with another inter occlusal record. Measure- ments between the maxillary and mandibular casts measured at the same area as preoperative cast.

Measurement phase: The articulated maxillary and mandibular cast were measured at three different areas (Fig 4).

Distance A-B: The distance between the gingival zenith of the terminal abutment tooth (A) to the gingi- val zenith of opposing tooth (B).

Distance C-D: The distance between the superior most portion of edentulous ridge (C) to the gingival zenith of the corresponding opposing tooth (D).

Distance E-F: The distance between the gingival zenith of mesial abutment tooth (E) to the gingival zenith of opposing tooth (F).

The measurements were made using a travelling microscope with the sensitivity of .001mm. This proce- dure was carried out for all ten patients. The average for the distance A-B, C-D, E-F, of all ten patients was calculated and statically analyzed.

RESULTS

The articulated casts were measured at three different points. The distance A-B was on terminal abutment teeth, the distance C-D was at edentulous area, the distance E-F was at mesial abutment tooth. These three measurements were carried out for all the three mounted maxillary and mandibular casts - refer- ence group (Articulation I), with centric stop plus Interocclusal records (Articulation II) , without centric stop plus Interocclusal records (Articulation III). The values obtained for each group are tabulated in Table No. 1, 2, 3 and statiscal analysis are tabulated in Table No. 4, 5 and 6.

TABLE 1: VALUES OBTAINED FOR 10 PATIENTS BELONGING TO GROUP I IN MILLIMETERS

Articulation I

S.No.###A-B###C-D###E-F

1###8.88###6.20###8.58

2###11.2###6.13###10.7

3###11.6###6.06###7.08

4###8.68###4.75###6.09

5###1.32###7.06###12.6

6###10.7###3.83###6.61

7###9.82###7.80###6.54

8###11.6###8.53###11.9

9###11.4###3.82###6.64

10###10.9###8.85###9.60

###10.6###5.79###8.64

TABLE 2: VALUES OBTAINED FOR 10 PATIENTS BELONGING TO GROUP II IN MILLIMETERS

Articulation II

S.No.###Mesial###Edentulous###Distal

Abutment###space###Abutment

1###9.60###11.2###9.27

2###11.8###7.66###11.9

3###8.37###6.08###8.04

4###12.2###5.32###8.15

5###14.2###11.3###16.1

6###11.6###5.90###8.45

7###13.9###10.4###10.3

8###12.7###11.0###11.4

9###11.8###5.90###8.50

10###11.2###9.52###10.1

11.8###8.43###10.2

TABLE 3: VALUES OBTAINED FOR 10 PATIENTS BELONGING TO GROUP III IN MILLIMETERS

Articulation III

S. No. Mesial Edentulous###Distal

###Abutment###space###Abutment

1###6.95###10.7###8.28

2###10.9###5.71###11.3

3###6.66###7.22###8.13

4###11.2###5.96###7.00

5###15.5###9.89###15.9

6###11.2###5.43###8.76

7###15.7###9.92###5.75

8###11.7###6.58###11.4

9###11.2###5.56###8.77

10###10.8###8.57###10.1

###11.2###7.56###9.54

Statiscal Analysis

TABLE 4: READINGS ON DISTANCE A-B BY ANNOVA REPEATED MEASURE ANALYSIS

Distance A-B###Mean###SD###F-ratio###P-value

Group I###8.64###2.43###6.735###.007

Group II###10.2###2.48###

Group III###9.54###2.85

TABLE 5: READINGS ON DISTANCE C-D BY ANNOVA REPEATED MEASURE ANALYSIS

Distance C-D###Mean###SD###F-ratio###P-value

Group I###6.30###1.80

Group II###8.43###2.50###8.397###.003

Group III###7.56###2.05

TABLE 6: READINGS ON DISTANCE E-FBY ANNOVA REPEATED MEASURE ANALYSIS

Distance E-F###Mean###SD###F-ratio###P-value

Group I###10.6###1.09

Group II###11.8###1.87###1.421###.267

Group III###11.2###2.94

Table 4 shows that for distance A-B, the average interocclusal space by Group I was found to be 8.64mm with standard deviation of 2.43mm, average interoc- clusal space for Group II was found to be 10.2mm with standard deviation of 2.48mm, and average interoc- clusal space for Group III was found to be 9.54mm with standard deviation of 2.85mm.

Table 5 shows that, for distance C-D, the average interocclusal space by Group I was found to be 6.30 mm with standard deviation of 1.80 mm, average interoc- clusal space for Group II was found to be 8.43mm with standard deviation of 2.50mm, and average interoc- clusal space for Group III was found to be 7.56 mm with standard deviation of 2.05mm.

Table 6 shows that, for distance-F, the average interocclusal space for Group I was found to be 10.61mm with standard deviation of 1.09mm, average interoc- clusal space for Group II was found to be 11.8mm with standard deviation of 1.87mm, and average interoc- clusal space for Group III was found to be 11.2mm with standard deviation of 2.94mm.

The results obtained to compare three methods by ANNOVA repeated measure infers significant result, this confirms that all three methods differs in assess- ing interocclusal space.

Bonferroni multiple comparision test infers Group I differs with Group II in distance A-B, and distance C-D. There was no significant difference between three groups in distance E-F.

DISCUSSION

Prosthetic rehabilitations frequently require an interocclusal record to fabricate a successful restora- tion. The ideal combination of material and technique for making interocclusal records allow the placement of indirectly made restorations in the patient's mouth without additional occlusal adjustments. In situation were the terminal tooth in the dental arch is used as distal abutment, an interocclusal record is of im- mense importance. An inaccurate transfer of such interocclusal records result in improper mounting of the casts in the articulator with concomitant treat- ment errors.5

The accuracy of an interocclusal record6, is influ- enced by the material properties, the recording tech- nique, the accuracy with which the recording materi- als fit on the working cast, and the reliability of the mandibular position which is influenced by the oc- clusal contacts, muscular action or tissue changes within the TemperoMandibular joints.

Various authors have described different tech- niques of making accurate Interocclusal records par- ticularly in situations when the distal most tooth is used as an abutment. but none of the techniques has been compared or analysed for its accuracy.

A method by Christensen7 has been selected for the study, to verify the accuracy of interocclusal record, as it is less time consuming and can be done along with routine clinical procedures. The other methods of mak- ing records has some clinical inconvinence like, (i) Yuji sato's method7 is the modification of Christensen, but it needs additional time to build up composite cone whereas (ii) Adams technique4 needs bite registration tray to make interocclusal records and (iii) Postol technique8 is a time consuming procedure to fabricate a resin coping and resin registration material is not dimensionally stable compared to other bite registra- tion materials.

Christensens preserved a cusp which is in maxi- mum occclusal contact as vertical stop to make the record. Yuji sato did a modification in christensens method, in situation where the maximum occlusal contact is not on the cusp tip, thereby its on the slope of the cusp, in that case he build up composite cone to provide stability for the vertical stop. Adam prepared shallow groove on the abutment tooth to stabilize the record. Postol fabricated a resin coping on terminal abutment tooth to transfer the record with accurate vertical dimension.

Choice of material is another important factor to transfer the record to the articulator. Plaster, model- ing compound, wax, acrylic resin, and elastomers are materials commonly used for making records. To se- lect an ideal material, the desirable properities of recording material with their merits and demerits has to be thoroughly evaluated.8 Among the various re- cording materials, elastomer was selected as, it has a brief working time with good elastic properties, mini- mum resistance to closure, can be stored for relatively long time , the most dimensionally stable and accurate with minimal vertical discrepancy.11,12

The device used for measuring vertical discrep- ancy is travelling microscope.13 Measurements were made on three positions in a imaginary vertical plane, in three regions of mesial abutment, edentulous space and distal abutment, similar to Muller, as he mea- sured in his study in three regions of anterior, premo- lar and molar region.14

When the results were compared the distance A-B, measured in Articulation II and III 10.2 and 9.53mm res- pectively were found to be greater than the distance A- B, of the reference group (Articulation I, 8.64mm). The distance C-D measured in Articulation II and III, 8.42 and 7.58mm respectively were found to be greater than distance C-D of reference group (5.78mm). The dis- tance E-F measured in Articulation II and III, 11.8 and 11.1mm respectively were found to be greater than distance E-F, of reference Articulation I (10.6mm).

The results showed that the presence of interoc- clusal records has increased vertical dimension in all three positions. Between the Articulations, the records made in the absence of centric stop was found to be in close approximation to the reference group (Articula- tion I).

The statiscal analysis showed that the values obtained at the distal abutment (distance A-B) and in the edentulous space (distance C-D) was statically significant, when comparing with Articulation I mod- els with Articulation II models. The values obtained for distance A-B and C-D showed no significance, when compared between Articulation I and III and between the Articulations i.e., Articulation II versus Articula- tion III. The values obtained for distance E-F showed no statically significant difference when comparing Articulation I, either Articulation II or Articulation III, and between the Articulation II and Articulation III.

The inaccuracies or change in measurements may be attributed to anyone of the following reasons,

i) Repositioning the record on cast could be a source of discrepancy, probably because im- prints of occlusal pits and fissures cannot ac- curately be repositioned onto occlusal surface of casts, which do not reproduce complete sur- face detail.3

ii) The mounting error can happen with every mounting. Breeding reported that, a mounting error of approximately .05mm can occur when casts are hand articulated.10

iii)The physiologic variation of mandibular posi- tion is influenced by occlusal contacts, muscu- lar action or tissue changes within joints.15

iv) The compressive force exerted on elastomeric material while making records, it has been reported in literature that elastomeric mate- rial become distorted as a result of compres- sive forces.16

CONCLUSION

Within the limitations of the present study, the following conclusions can be drawn: a) Presence of Interocclusal records results in an increase in vertical discrepancy. b) Presence of centric stop was found to cause greater discrepancy than without centric stop. Further studies has to be continued with more number of samples and with techniques to limit control of interoc- clusal materials to flow over the centric stop.

REFERENCES

1 Freilich, Principles for selection interocclusal records for articulation of dentate and partially dentate casts. J Prosthet Dent 1991; 68: 361-67.

2 Squier RS. Jaw Relation records for fixed prosthodontics. DCCNA 2004; 28: 471-86.

3 Vergos VK, Tripodakis AP: Evalluation of vertical accuracy of Interocclusal records. Int J Prosthodont 2003; 16: 365-68.

4 Adams HF: A technique for quadrant interocclusal records. J Prosthet Dent 1982; 47: 44-46.

5 Douglass GD: The cast restoration - why is it high? J Prosthet Dent 1975; 34: 491-95.

6 Berman MH: Accurate interocclusal records. J Prosthet Dent 1960; 10: 620-30.

7 Christensen LC, Preserving a cenric stop for Interocclusal re-cords. J Prosthet Dent 1983; 50: 558-60.

8 Postol: Interocclusal registration at the vertical dimension of occlusion using acrylic resin copings. J Prosthet Dent 1982; 48:39-43.

9 Yuuji S: creating a vertical stop for Interocclusal records. J Prosthet Dent 2000; 83: 582-85.

10 Breeding, DMD: Accuracy of three interocclusal recording materials used to mount a working cast. J Prosthet Dent 1994;71: 265-70.

11 Lassila V, McCabe JF: Properties of interocclusal registration material. J Prosthet Dent 1985; 53: 100-104.

12 Lassila Comparison of five interocclusal recording materials. J Prosthet Dent 1986; 55: 215-18.

13 Karthikeyan, Comparative evaluation of dimensional stability of three types of interocclusal recording materials: An in vitro study, JIPS 2007; 7: 24-27.

14 Millstein, DMD, MS, Differential accuracy of elastomeric recording materials and associated weight change, J Prosthet Dent 1994; 71: 400-03.

15 Berry DC, Singh BP: Daily variations in occlusal contact. J Prosthet Dent 1983; 50: 386-91.

16 Breeding: Compression resistance of four interocclusal recording materials. J Prosthet Dent 1992; 68: 876-78.

1 Senior lecturer, Prosthodontics, Raiah Muthiah Dental Ccollege and Hospital, Chidambaram, Tamil Nadu, India

2 Professor Prosthodontics,

3 Professor and Head of Department of Prosthodontics,

4 Reader, Prosthodontics,

5 Senior Lecturer, Prosthodontics,

6 Senior Lecturer, Orthodontics, Communicating author.

E.Mangala Deivanai, senior lecturer, department of prosthodontics, Raiah MuthiahDental Ccollege and Hospital, Chidambaram,India Email: drmangalamaran@gmail.com Received for Publication: February 4, 2013 Revision Received: March 1, 2013 Revision Accepted: March 7, 2013
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Publication:Pakistan Oral and Dental Journal
Date:Apr 30, 2013
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