EGYPTIAN Vol. 66, 1155:1162, April, 2020 DENTAL JOURNAL Print ISSN 0070-9484 • Online ISSN 2090-2360

Fixed , Dental materials, Conservative Dentistry and Endodontics

www.eda-egypt.org • Codex : 13/2004 • DOI : 10.21608/edj.2020.24156.1033

EVALUATION OF BITING FORCE FOR THREE DIFFERENT PARTIAL DENTURE MODALITIES IN BILATERAL DISTAL EXTENSION CASES (CROSSOVER STUDY)

Mohamed Abdel Hakim Abdel Aal* and Amr Mohamed Ismail Badr**

ABSTRACT

The purpose of the present study was to assess the magnitude of biting force in three different partial denture designs.

Methodology: A total of ten patients with mandibular bilateral free end saddles without modification (Unmodified class I) were included in this study. All patients received three successive partial denture designs (conventional, extra-coronal attachment and posterior implant with bar attachment successively). Each design was used for 4 months intervals. The mean biting force was measured at the time of insertion and after 4 months for each design.

Results: One way ANOVA followed by Post Hoc test was made to check the significance within each group and between groups of different designs for the biting force measurements. The data revealed that the magnitude of biting force at insertion was 44.425+6.21398, 84.1050+5.93779 and 129.1900+7.92749 for conventional, extracoronal attachment and implant bar attachment design respectively, while after 4 month it was 49.4900+5.41002, 90.1850+6.36713 & 142.5700+7.49098 for conventional, extracoronal attachment and implant bar attachment design respectively.

Conclusion: Within the limitation of this study it can be concluded that:

1. Using a posterior implant with bar supporting and retaining removable partial denture is a viable treatment option for free end saddle cases.

2. Significant improvement in biting force occurred by changing the design from conventional to extra-coronal attachment and from extra-coronal to implant bar attachment.

KEYWORDS: Distal extension base, Extracoronal attachment, Implant bar attachment, Biting force.

* Lecturer of Removable Prosthodontics, Faculty of Dentistry, Beni-suef University. ** Associate Professor of Removable Prosthodontics, Faculty of Dentistry, Minia University. (1156) E.D.J. Vol. 66, No. 2 Mohamed Abdel Hakim Abdel Aal and Amr Mohamed Ismail Badr

INTRODUCTION implants are significantly accepted than conventional Loss of posterior teeth can reduce oral function partial as it routinely improves the biting and affect nutritional status (1,2), prosthetic treatment forces thus enhancing the masticatory function, also options for partially edentulous patients includes patient satisfaction is high in comparison with the (12-15) fixed and removable (3). conventional dentures. Distal extension bases have a problem of The magnitude of the biting force act as a major support due to the absence of the distal abutment, indicator of the masticatory system functional the difference of compressibility between mucosa state. The efficiency of bite function depends on and the periodontal ligament thus increasing tempro-mandibular joint, muscles of mastication (16) torque forces on the distal abutments. Rotation of and dentition (whether natural or artificial) . the distal extension base in a tissueward direction Bite force and its measurement for occurs during function under occlusal force (4). rehabilitation may become an integral part of the Due to the mismatch of the viscoelastic responses complete oral examination and assessment. (17,18) between mucosa and the teeth this rotation potential Several techniques and devices are used to as- always exists, the rotation of the denture base under sess the biting force, from which are the bite fork[19], function determines the occlusal efficiency of the strain gauge transducers(20), portable hydraulic pres- (5) partial denture . sure gauges(21), force-sensing resistors(22), pressur- To protect the natural abutment from torqueing ized rubber tube(23), pressure-sensitive sheets(24), foil during function, resilient extracoronal attachment transducers(25) and the gnathodynamometer(26) may be used for distal extension bases allowing for The aim of this study was to assess the a limited degree of distal rotation (6).it also decrease magnitude of biting force in three different partial stresses transmitted to the abutments as the forces denture designs. are or near the long axis of the abutment (7) One of the most outstanding methods to control MATERIAL AND METHODS this rotation potential is to replace the missing A total of 10 patients were selected from the distal abutments by using strategically placed distal outpatient clinic of the removable prosthodontic implants to transform a Kennedy class I RPD into department of Beni-Suef University, Patient’s a tooth and implant assisted removable partial written informed consent was obtained before the denture(8,9) beginning of this study. Male patients with the age Replacing missing teeth by conventional partial ranging between 45-55 years were selected with denture is associated with decreased bite force the following inclusion criteria : Class I maxillary (10) and patient satisfaction , however, using dental mandibular relationship free from any systemic implants combined with removable partial dentures diseases that would affect the bone quality or post- enables the patients to have benefits from both operative healing, with no T.M.J. disorders, with the implant and the partial denture. In implant- completely edentulous maxillary arch opposed by supported partial dentures the destructive lever arm bilateral free end saddles in the mandible and the is minimized, bone is preserved, prosthetic retention ridge is well-moderately formed with healthy intact increases and unaesthetic prosthetic components mucosa. All patients have available inter-arch (11) can be eliminated . space and cases with abnormal habits as bruxism or Removable partial dentures supported by smoking were excluded. EVALUATION OF BITING FORCE FOR THREE DIFFERENT PARTIAL DENTURE MODALITIES (1157)

Clinical procedures: Trial insertion of the metal framework in the Intraoral visual and digital examination includ- patient’s mouth followed by jaw relation registration, ing checking the mucosa, inclination of the remain- mounting of the casts on semi-adjustable articulator, ing natural teeth, periodontal evaluation, adequate setting up of teeth, try-in of the waxed up partial lingual sulcular depth for placement of the major denture followed by processing of the final denture connector, presence of attached gingiva and mo- base.The partial denture was inserted into the bility of the remaining teeth were tested especially patient’s mouth and final occlusal adjustment was those that will be used as abutments. made. Preoperative periapical, panoramic radiographs, The biting force was measured bilaterally using as well as cone beam computed tomography (CBCT) occlusal force meter three times at the first molar was done to check the bone height and density as region by an occlusal force meter which involves a well as to help in implant placement orientation in hydraulic pressure device and a disposable polyvinyl relation to the inferior alveolar canal. cap (17 mm in width and 5.4 mm in height). The Pre-prosthetic procedures were performed measuring range was 0–1000 N with an accuracy for each patient including periodontal treatment, of ± 1 N (GM10, Nagano Keiki, Tokyo, Japan). The through supra and sub-gingival scaling and root instrument was placed such that all bite forces were planning; all conservative procedures were per- directed to the center. Fig (1) formed as fillings and root canal treatment. The patients were instructed to bite as powerful All patients received upper single denture con- as possible three times per side, with a rest time of structed with the conventional technique opposed 2 minutes in between. The maximum occlusal force by lower three successive different partial denture recorded in Newton (N) was recorded. The mean of designs. (Crossover study) the three records was considered to be the patient’s maximum biting force. Steps of construction of design I: The biting force was measured for each patient Preliminary impression followed by initial at the time of denture insertion and 4 month later. surveying of study cast was made to detect the amount of undercut on the terminal abutments and the most appropriate path of insertion followed by drawing the partial denture design. Intraoral mouth preparation was made according to the previously determined plane. The final impression was recorded using medium body rubber base (ImpregumTM F 3M ESPE, Deutschland Gmbh, 41453 Neuss-Germany) followed by surveying of the master cast. The master cast was modified and duplicated. On the duplicate cast the wax pattern was construct- Fig (1) Patient biting on the occlusal force meter ed, cast with cobalt-chromium alloy, finished and polished. (1158) E.D.J. Vol. 66, No. 2 Mohamed Abdel Hakim Abdel Aal and Amr Mohamed Ismail Badr

Steps of construction of Design II: After four months of using the skeleton type removable partial denture, the terminal abutments were prepared to receive a surveyed PFM crowns with an extracoronal OT attachment 1.8mm sphere (OT strategy/optional steady. Via E. Zago, Rhein83, Bologna, Italy) Fig (2) and a new skeleton-type re- movable partial denture was constructed with the same previous steps in addition to picking up the female nylon caps in the fitting surface of the den- ture by self-cure acrylic resin (Acrostone, England) Fig (2) PFM crowns with an extracoronal OT attachment Again biting force was measured for each patient at the time of denture insertion and 4month later.

Steps of construction of Design III: After four months of using the previous partial denture (design II), an implant 3.9 mm diameter and 12 mm in length (Dentis Implants, Dentis Co LTD. One Q-SL. Korea) were surgically placed at the 2nd molar area bilaterally (flapless technique) and implant abutments were screwed in place. The implant abutments were prepared to receive porcelain fused to metal crowns Fig (3). The previously made porcelain crowns with the OT attachment on the terminal abutments were removed and a rubber base impression (Durosill, President Fig (3) Implant abutments prepared to receive PFM crowns Dental, Munchen- Germany) was taken and poured followed by fabrication of the wax pattern for the implant crowns as well as the crowns on terminal abutment teeth previously prepared, a bar plastic pattern with oval cross-section bar (OT bar multiuse, system Rhein 83, Via E, Zago Bologna. Italy) was positioned between the implant crowns & terminal abutment wax patterns aligned parallel to the plane of by the aid of the parallelometer. The assembly was then sprued, invested, burnt-out and cast followed by metal try-in of the -bar assembly in the patient’s mouth. Porcelain was built-up on the metal crowns, fired, finished, glazed and placed in the patient’s mouth Fig (4) Final cementation of the crown-bar assembly in the followed by an overall rubber base impression; patient’s mouth EVALUATION OF BITING FORCE FOR THREE DIFFERENT PARTIAL DENTURE MODALITIES (1159)

the assembly was removed from the impression and significant level set at P ≤ 0.05. Data were presented finally cemented in the patient’s mouthFig (4). The as means and standard deviation (SD). impression was poured, and a duplicate cast was obtained for RPD construction. RESULTS After construction of the new skeleton removable One way ANOVA test was made to check the partial denture and at time of denture insertion, significance between the three designs followed direct pick-up of the retentive clip was done by self- by Post Hoc test to reveal the significance between cure acrylic resin (Acrostone, England) in the fitting different designs at different follow-up periods. surface of the denture. Fig (5) Table (2) & Fig (6) shows that the mean biting Again biting force was measured for each patient force for the conventional design at the time of at the time of insertion and 4month later. insertion was 44.4250+6.21398 and after four month was 49.4900+5.41002 and P-value was 0.158 (no Statistical analysis: significant difference). Statistical analysis performed with SPSS 20®, The mean biting force for the extra coronal Graph Pad Prism® and Microsoft Excel 2016 with a attachment design at the time of insertion was 84.1050+5.93779 and after four month was 90.1850+6.36713and P-value was 0.049 (significant difference). The mean biting force for the implant with bar-retained partial denture design at the time of insertion was 129.1900+7.92749 and after four month was 142.5700+7.49098and P-value was 0.00 (significant difference). The data also revealed a significant difference between the three designs at the time of insertion and after four months (P-value was 0.00) Fig (5) Final fitting of the skeleton RPD in the patient’s mouth

TABLE (1) Significance between different designs

Biting force

Sum of Squares df Mean Square F Sig.

Between Groups 161047.735 5 32209.547 735.827 0.000*

Within Groups 4990.151 114 43.773

Total 166037.886 119

*: Significant at P ≤ 0.05 (1160) E.D.J. Vol. 66, No. 2 Mohamed Abdel Hakim Abdel Aal and Amr Mohamed Ismail Badr

TABLE (2) Mean biting force between different designs at different periods

Biting force

Time N Extra-coronal attachment Implant with bar retained Conventional partial denture Significance retained partial denture partial denture

Insertion 20 44.4250+6.21398 84.1050+5.93779 129.1900+7.92749 0,00 *

4 Month 20 49.4900+5.41002 90.1850+6.36713 142.5700+7.49098 0.00 *

Sig. 0.158 0.049* 0.00 *

*: Significant at P ≤ 0.05

Mandibular bilateral distal extension cases were selected in this study as they are more common than the maxillary ones, due to the general pattern of tooth loss. Furthermore, mandibular distal extension cases are considered the most difficult to receive satisfactory and comfortable dentures due to support problems and smaller denture base area in relation to the functional load (29, 30) Osseointegrated implant is not mobile under occlusal forces compared to the natural teeth that possess at least 30μm physiologic mobility(31), Fig (6) Bar chart showing the biting force between different hence the displacement under the occlusal force designs at different follow-up intervals will be quite different, so rigid connection between implants and natural teeth is not recommended in DISCUSSION fixed bridges. The present study is a crossover study carried out to On the other hand; concerning partial overden- evaluate & compare the maximum biting force of three tures, connection between denture base and im- different partial denture designs rehabilitating mandib- plants are more flexible than that of fixed prostheses ular Kennedy class I partially edentulous cases. The because the only function of the distal implant is to three designs were conventional partial denture, Par- act as a vertical stopper to resist the rotation poten- tial denture retained by extra-coronal attachment and tial that occurs at the distal end of the denture base partial denture retained by implant with bar and clip during vertical loading, moreover the presence of attachment within the same subjects. resilient clip -bar connection allows for less stresses In all patients, mandibular RPDs are opposed on the distal implant. Thus, the overdenture would by in the maxilla with bilateral be quite safe. balanced occlusal scheme, which creates occlusal The distal support may prevent rotation of the harmony, standardizes the amount of force distal part of the saddle during functional loading; applied on the lower prosthesis from the opposing consequently, it maintains a continuous precised occlusion and improves load distribution. This also contact relationship between the opposing occlusal avoids potentiating parafunctional activity which tables during function. This may maintain the has been suggested to increase bone loss around masticatory force at a constant level, therefore the implants (27, 28) efficiency of food penetration is optimized. EVALUATION OF BITING FORCE FOR THREE DIFFERENT PARTIAL DENTURE MODALITIES (1161)

Bite force measurements are considered one of the four month. This improvement can be attributed to most important indicators for the assessment of masti- the effect of osseointegration of the implants which catory performance in different prosthetic designs. improves the biting force measurements. Moreover, the occlusal contact areas are significantly increased Biting force measurements within the three by the implant support due to the minimum different designs showed no significant difference displacement of the distal- extension RPD; both between the right and left side this can be attributed stronger occlusal force and the greater contact area to that all patients involved in this study don’t have may contribute to the improved chewing capacity of a preferable chewing side and all the patients used the implant-supported RPD. (33) both sides eventually during eating with their partial dentures. CONCLUSIONS The mean biting force within groups showed Within the limitations of this study, it can be that there was a significant difference between concluded that the three different partial denture designs in favor of the implant with bar and clip design giving the 1. Using a posterior implant with bar supporting higher mean values of biting force. The presence of and retaining a removable partial denture is a vi- posterior implant provides posterior support to the able treatment option for free end saddle cases. partial denture which allows for stabilization of the 2. Significant improvement in biting force occurred partial denture so consequently improves the biting by changing the design from conventional force in this design. This agrees with Ohkubo C et to extra-coronal attachment and from extra- (32) al who compared the masticatory movements, coronal to implant bar attachment. occlusal force, and patients’ preferences of implant- supported RPDs to conventional RPDs and REFERENCES recommended the use of distal implant to improve chewing by conventional distal- extension RPDs. 1. Dye, B. A., Thornton-Evans, G., Li, X., & Iafolla, T. J. (2015). Dental caries and tooth loss in adults in the United Meanwhile, the partial denture design with States, 2011–2012. Hyattsville, MD: US Department of extra-coronal attachment showed higher results Health and Human Services. than conventional partial denture design but lesser 2. Sheiham, A., & Steele, J. (2001). Does the condition of than that of implant bar supported design, this can the mouth and teeth affect the ability to eat certain foods, be explained by the presence of extra-coronal ball nutrient, and dietary intake and nutritional status amongst and socket attachment allowing for some degree of older people? Public Health Nutrition, 4(3), 797–803. resiliency protecting the torqueing action that can https://doi.org/10.1079/PHN2000116 be exhibited by the conventional partial denture on 3. Ribas, L.K., Montero, R.A., Willaert, Eva., Peraire, the terminal abutment . Also, the splinted effect of Maria. and Gomis, J. M.: Do implant-supported fixed the terminal abutments may be one of the reasons partial prostheses improve masticatory performance in that increase the biting force for this design and patients with unilateral posterior missing teeth? Clin Oral decreasing the torqueing action on these abutments. Impl Res. 2019;30:420–428.

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