Comparison between conventional and computerised methods in the assessment of an occlusal scheme

Occlusal equilibration and muscle activity in fixed versus removable mandibular implant supported overdenture

OBJECTIVES

Single denture rehabilitated patients have negative appraisals regarding oral function, mostly associated by stability and retention issues regarding mandibular prosthetics. Therefore, this study assessed patients' occlusal equilibration, muscle activity, and oral health-related quality of life (OHRQoL) receiving milled removable or fixed mandibular implant retained prostheses.

MATERIALS AND METHODS

Twenty-two edentulous mandibular ridges patients were randomly distributed into two groups based on the definitive prosthesis received. Group I: Removable mandibular implant-supported overdenture, Group II: Implant retained fixed prosthesis. Occlusal equilibration was evaluated utilizing Occlusense, muscle activity via Electromyograph (EMG) at delivery, after one, and three months. The OHRQoL was evaluated by Oral Health Impact Profile questionnaire (OHIP-19) before delivery and after follow-ups. Data were collected, tabulated, and analyzed, utilizing independent t-test and One-way ANOVA followed Tukey`s post-hoc test. Significance level set at P ≤ 0.05.

RESULTS

Groups I &II showed significant improvement in occlusal equilibration, muscle activity and OHRQoL. Group II demonstrated significantly higher improvement than group I in occlusal equilibration associated with muscle activity after 1 month, and in functional limitations domain in OHRQoL questionnaire after 3 months.

CONCLUSION

Implant retained mandibular prosthesis showed improvement in occlusal equilibration, muscle activity, and OHRQoL regardless of prosthesis type employed. Fixed implant-supported prosthesis revealed better outcomes than removable mandibular implant-supported overdenture concerning occlusal equilibration, muscle activity, and OHRQoL regarding functional limitations.

CLINICAL RELEVANCE

Implant retained mandibular prosthesis is one of best treatment options for single mandibular completely edentulous patients, as dental implants improved occlusal equilibration, muscle activity, and OHRQoL.

Clinical analysis of CAD-CAM milled and printed complete dentures using computerized occlusal force analyser

BACKGROUND

Digital complete dentures (CDs) by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques (milling and three-dimensional (3-D) printing) have been evaluated clinically and provided satisfactory results. But clinical studies assessing occlusal forces by digital dentures are lacking.

OBJECTIVES

To compare the occlusal force parameters in complete dentures (CDs) fabricated by milling, 3-D printing and conventional techniques having 3 commonly used occlusal schemes, using computerized occlusal force analysis system (Tech-Scan III- T-Scan III).

METHODS

A total of 45 CDs were fabricated for 5 patients. Nine sets of CDs were made for each patient and were divided into 3 groups: Conventional CDs (CCD), Milled CDs (MCD), and 3-D printed CDs (3-DP CD). The CDs in each group were further divided into 3 sub-groups based on occlusion schemes - bilateral balanced (BBO), lingualized (LO) and mono plane (MP). Occlusal force analysis [percentage (%) of occlusal force applied on the right and left sides of the arch difference between them, centralization of forces and % of maximum occlusal/bite force] was done using computerized occlusal analysis system (T-Scan III) at the time of denture insertion. Univariate regression analysis and logistic regression analysis were performed (p< 0.05).

RESULTS

The intergroup comparison of force distribution on right and left side in CDs fabricated by various techniques showed insignificant differences (p> 0.05) but statistically significant differences (p< 0.01) were found in right-left side force difference, maximum bite force % and centralization of forces. The maximum force difference on right and left side was observed CCD with MO (37.48 ± 1.03 N) and maximum occlusal-bite force % was observed for 3-DPCD with LO (95.40 ± 1.30 N). In comparison to 3-DP CD, the chances of centre of force out of ellipse (centralization of forces) was 3.36 and 2.15 times more in CCD and MCD techniques made CDs respectively.

CONCLUSIONS

The occlusal parameters in CDs were affected by the fabrication techniques and occlusal schemes of CDs. The digital CDs retain adjusted occlusal schemes better and 3-DP CDs with BBO and LO occlusal schemes provided centralization of forces, better distribution and high maximum occlusal force % respectively.

Computerized occlusal forces analysis in complete dentures fabricated by additive and subtractive techniques

BACKGROUND

Fabrication of complete dentures by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques are now common. Subtractive and Additive are the two principal CAD-CAM techniques used for this purpose. However, studies that evaluated the occlusal forces by CDs manufactured by these techniques are lacking.

OBJECTIVES

To compare the occlusal forces in complete dentures fabricated by additive, subtractive and conventional techniques with different occlusal schemes, using computerized occlusal force analysis system [Tech-Scan III (T-Scan III)].

METHODS

Three groups (Gr) were made on the basis of techniques of fabrication of CDs: Conventional CDs (CCD), Subtractive CDs (SCD), and Additive CDs (ACD). Each group CDs were further divided into three sub groups based on occlusion schemes: bilateral balanced occlusion (BBO), lingualized occlusion (LO) and mono plane occlusion (MO). A total of 45 CDs were made: 15 in each group with 5 CDs of each occlusal scheme. For all samples, occlusal force analysis (percentage of occlusal force applied on the right and left sides of the arch, centralization of forces and percentage of maximum occlusal force) was done using computerized occlusal analysis system: T-Scan III. Univariate regression analysis and logistic regression analysis were used to find the effects of the technique of fabrication and occlusion scheme over the occlusal forces (p< 0.05).

RESULTS

The intergroup comparison revealed statistically significant differences (p< 0.01) in right-left side force difference, maximum bite force in CDs fabricated by various techniques and with different occlusion schemes. Though the effect of occlusion scheme was more than the technique of fabrication (according to effect size estimation). The maximum force difference between right-left side was observed in combination of CCD technique and MO scheme (36.88 ± 2.82 N). Furthermore, the maximum bite force was observed for SCD technique (89.14 ± 6.08 N) and LO scheme (92.17 ± 3.22 N). In comparison to ACD, the chances of centre of force out of ellipse was 2.53 time more in CCS and 0.75 times less in SCD techniques and in comparison to MO, the chances of out of ellipse was 0.298 times less in BBO and 0.396 times less in LO schemes, though these chances were not statistically significant (p> 0.05).

CONCLUSIONS

The digital CDs fabricated by subtractive technique were proved to be superior to additive technique in terms of occlusal force analysis on tested parameters. However, further research is needed on patients to determine the exact superiority of one technique over the other.

Automatic Digital Design of the Occlusal Anatomy of Monolithic Zirconia Crowns Compared to Dental Technicians' Digital Waxing: A Controlled Clinical Trial

PURPOSE

Reconstructing the occlusal morphology of posterior teeth in definitive dental prosthesis can be challenging. The use of the correlation technique enables replication of the information and occlusal anatomy of interim dental prostheses to the definitive ones. The purpose of this controlled clinical trial was to compare the static and dynamic contacts (SDC) of monolithic zirconia crowns designed with correlation and library techniques.

MATERIAL AND METHODS

Twenty-four patients were included in the study for a total of 28 molars. For each abutment tooth, an interim crown was fabricated and two digital scans, with and without the interim crown in place were made. Two single crowns were designed using correlation and library techniques. Fifty-six monolithic zirconia crowns were milled. The interim and definitive crowns were evaluated intraorally for SDC by using a 24-μm-thick blue articulating foil. After removing the interim and definite crowns, extraoral photographs were taken to calculate the SDC area using software (ImageJ) and analyzed by the Kruskal-Wallis test.

RESULTS

The average and ± standard deviation (SD) of area of the occlusal marks on interim crowns was 32.27 ± 3.45 mm² . Definitive crowns designed by using the correlation technique had an area of 31.01 ± 3.73 mm² ; the area in the library technique was 36.85 ± 5.78 mm² . No statistically significant difference was found (p = 0.091) between the occlusal mark areas of the interim and definitive crowns designed by using the correlation technique. Whereas, there were significant differences between the areas of occlusal marks of the interim and definitive crowns designed by using the library technique, and between the areas of occlusal marks of definitive crowns designed by using the correlation and library techniques (p < 0.001).

CONCLUSION

The average area of the SDC of monolithic zirconia crowns designed by using the correlation technique was similar to that of interim crowns. The library technique was less effective when replicating the SDC compared to the correlation technique.