A laboratory investigation of the role of guide planes in the retention of cast cobalt-chromium alloy partial denture frameworks

Using a robot system to prepare guiding planes for removable partial dentures: An in vitro study

STATEMENT OF PROBLEM

Ensuring that guiding planes are parallel and that they maintain alignment with the path of insertion are essential for the success of a removable partial denture (RPD). However, freehand preparation and the use of digital guides have shortcomings, while the feasibility of using a robot system to prepare the guiding planes is unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of robot-assisted guiding plane preparation for an RPD.

MATERIAL AND METHODS

Fifteen mandibular typodonts, each without first molars bilaterally, were custom designed, and an indicator rod was placed on the lingual side of the anterior teeth. A split-mouth design was used, and the partially edentulous areas on the left and right sides of typodonts were randomly assigned to 2 groups based on the preparation technique: the robot or freehand. The guiding planes for the distal surface of the second premolar and the mesial surface of the second molar were prepared by a robot or freehand. For the robot group, the intraoral scan data of the typodonts were imported into a software program, and the trajectory of the handpiece was drawn in the edentulous area. The handpiece orientation in the software program was adjusted to align with the direction of the indicator rod on the typodont. Subsequently, a robotic arm equipped with a high-speed handpiece was used to perform the preparation procedures. For the freehand group, a dentist prepared the guiding planes by referring to the indicator rod with the naked eye. Postoperatively, the typodonts were scanned to evaluate the angles between the 2 guiding planes and the angular deviation between the guiding planes and indicator rod. The independent samples t test was used to analyze the angle between the 2 guiding planes, and 2-way analysis of variance (ANOVA) and the least significant difference (LSD) post hoc test were used to compare the angular deviation between the guiding planes and the indicator rod (α=.05).

RESULTS

The data are presented as mean ±standard deviation [minimum, maximum]. The angles between the 2 guiding planes prepared by the robot and freehand were 1.93 ±1.04 degrees (0.70 degrees, 3.93 degrees) and 13.41 ±8.86 degrees (2.91 degrees, 33.84 degrees), respectively (P<.001). The angular deviation between the guiding planes and indicator rod prepared by the robot in the second premolar and molar were 2.81 ±1.78 degrees (0.55 degrees, 5.70 degrees) and 2.48 ±2.21 degrees (0.28 degrees, 8.80 degrees), respectively (P=.715). The angular deviation of the freehand group in the second premolar and molar was 8.18 ±5.71 degrees (0.98 degrees, 25.53 degrees) and 15.37 ±8.55 degrees (3.26 degrees, 32.86 degrees), respectively (P<.001). The angular deviation between the guiding plane and indicator rod prepared by the robot was significantly lower than that of freehand (P<.001).

CONCLUSIONS

The robot system offers a feasible strategy for the preparation of parallel guiding planes for an RPD. The robot method prepared the guiding planes more accurately than the freehand method.

Digital design and fabrication of a template to prepare guiding planes in removable partial denture abutments

Guiding planes are essential to the success of removable partial dentures (RPDs). With computer-aided design and computer-aided manufacturing (CAD-CAM), this report presents a novel method of designing and fabricating preparation templates to precisely prepare guiding planes for RPD abutments.

In vitro comparison of guide planes for removable partial dentures prepared with CAD-CAM-assisted templates, guiding rod templates, and freehand

OBJECTIVES

This study aimed to evaluate the accuracy of computer-aided design and computer-aided manufacturing (CAD-CAM)-assisted templates (CCAT), guiding rod templates (GRT), and freehand (FH) preparation of guide planes.

METHODS

Forty-five identical maxillary resin casts were divided into three groups, in which the guide planes of the two abutment teeth were prepared using a CCAT (n=15), GRT (n=15), and FH (n=15). The CCAT and GRT were digitally designed on a digital cast of virtually prepared guide planes and fabricated using three-dimensional printing (3DP) technology. To assess the 3D trueness, the prepared guide planes were digitally scanned and compared to the virtually designed guide planes. The angle deviation was measured to assess the trueness of the direction of the guide plane preparation. Shapiro-Wilk and Levene's tests were used to check the normality and equivalence of the variance of the data. The data were compared by using the Kruskal‒Wallis H test (α=0.05).

RESULTS

The CCAT group exhibited significantly better 3D trueness (78.5±19.8 μm) than the GRT group (211.3±42.4 μm, p<0.05) and the FH group (198.9±44.3 μm, p<0.05). Additionally, the CCAT group (1.31±0.50°) showed significantly smaller direction trueness compared to the GRT (4.65±0.72°, p<0.05) and FH (5.64±0.70°, p<0.05) groups.

CONCLUSIONS

The novel CAD-CAM-assisted template significantly improved the quality of the guide planes compared with the GRT and FH procedures. This enhancement suggests that removable partial dentures can be predictably inserted immediately after guide plane preparation.

CLINICAL SIGNIFICANCE

CAD-CAM-assisted templates improve the quality of guide plane preparation.

Fabrication of an accurate guide plane template for removable partial dentures by using CAD-CAM

This technique enables the establishment of an accurate reciprocation distance to resist undesirable forces on abutments and ensure the parallelism of removable partial denture placement on the guide template by using computer-aided design and computer-aided manufacture techniques and to ensure accurate abutment preparation.

Preparing guiding planes for removable partial dentures: comparison between assisted CAD-CAM template procedure and freehand preparation: An in vitro study

OBJECTIVES

To compare the trueness of computer-aided design and computer-aided manufacturing (CAD-CAM) assisted procedure and freehand procedure for preparing guiding planes for removable partial dentures (RPDs).

METHODS

Forty identical mandibular resin casts were divided into two groups in which the guiding planes of two abutment teeth were prepared freehand (control group, n = 20) and using rigidly constrained templates (test group, n = 20). The template was designed on a digital cast of virtually prepared guiding planes and fabricated by selective laser melting using cobalt-chromium alloy. To assess the 3D trueness, all prepared guiding planes (Test data) were digitized using a laboratory scanner and compared to the virtually designed guiding planes (Reference data). The angle deviation between the Test data and the designed direction of the path of placement was measured for assessing the direction trueness of guiding plane preparation.

RESULTS

The 3D trueness of guiding plane preparation was significantly better in the test group (48.4 ± 12.9 μm) than in the control group (128.5 ± 37.6 μm, p < 0.01). The direction trueness of guiding plane preparation was also significantly better in the test group (1.20 ± 0.55°) than in the control group (7.68 ± 3.00°, p < 0.01).

CONCLUSIONS

The CAD-CAM template assisted procedure can significantly improve tooth preparation of the guiding planes compared to the freehand preparation. The CAD-CAM template could help clinicians prepare parallel guiding planes in a predictable manner.

A metal template for preparing guiding planes for removable partial dentures

Precise preparation of guiding planes is essential for removable partial dentures (RPDs). This report introduces a metal template fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) to help prepare guiding planes for RPDs.

Fabricating a reduction guide for parallel guiding planes with computer-aided design and computer-aided manufacturing technology

Preparing appropriate guiding planes is essential for the success of a removable partial denture. Owing to the difficulty of determining the location and dimension of proximal reduction, establishing optimal guiding planes may challenge even skilled clinicians. This article introduces a digital workflow for fabricating a reduction guide to establish parallel guiding planes.

Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method

Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement.