Complete denture prosthodontics--the state of the art

In silico evaluation of the peripheral and inner seals in complete denture master impressions using a custom-developed 3D software

OBJECTIVES

Despite the complexity of the edentulous anatomy, little evidence exists as to what impression techniques and materials should be employed for an optimal result. The aim of this in silico study was to evaluate the trueness of peripheral and inner seals of different edentulous jaw impressions.

MATERIALS AND METHODS

Twelve maxillary edentulous participants (male = 8, female = 4; age 68.5 ± 11.7 years) participated in this study. Four different impression materials and techniques, irreversible hydrocolloid (Alginate; Blueprint X-Crème, Dentsply Sirona, PA, USA), polyvinyl siloxane impression (PVS; Aquasil Ultra+ Medium, Dentsply Sirona, PA, USA), and subsequently modified with ZnOE (PVSM) and an optical impression (Optical; 3Shape A/S, Copenhagen, Denmark), were tested against a control impression: low-fusing impression compound border molding (Kerr Corp., CA, USA) followed by a ZnOE impression (ZnOE; SS White impression paste, S.S. White Group, Gloucester, England). All impressions were scanned and analyzed using a custom-built 3D comparison software analyzing the vertical and horizontal trueness.

RESULTS

The vertical discrepancy (peripheral seal) of the impression surface was significantly more true for PVSM than Alginate (p = 0.001), PVS (p = 0.019), and Optical groups (p < 0.001). Where the horizontal discrepancy (inner seal) was compared, the impression surface was more true for PVSM than Alginate (p < 0.001) and Optical (p < 0.001). PVS group was also significantly more true than Optical (p = 0.015).

CONCLUSION

Impression techniques and materials may significantly influence the peripheral and inner seal of an edentulous jaw impression.

CLINICAL RELEVANCE

When using a polyvinylsiloxane impression material for master edentulous impressions, a selective inner seal reline with a conventional zinc oxide eugenol impression paste can improve the inner seal.

CAD/CAM: Applications for transitional bonding to restore occlusal vertical dimension

Objective

Explore the best technique for achieving stable and comfortable occlusion. This is critical for long‐term oral health and the foundation of durable esthetic, restorative, periodontal, and prosthodontic treatments.

Clinical considerations

Various techniques and therapies have been proposed for establishing, determining, and restoring ideal centric relation (CR) and vertical dimension of occlusion (VDO) in patients who require restorations and/or full‐mouth rehabilitation. An interim prosthesis phase can help establish and stabilize an enhanced esthetics and/or functional outcome for a limited period of time before the definitive dental restorations are placed. Transitional direct composite bonding and its additive nature have provided clinicians and patients with advantages when establishing a physiologic CR and VDO in interim restorations. However, it is time consuming, tedious, and challenging chairside. The author has been using additive CAD/CAM designed and milled restorations for over 10 years to make transitional bonding more efficient, manageable, and predictable.

Conclusion

Transitional bonded prostheses are significantly important to providing patients with an interim therapy to determine if the proposed esthetic outcome and occlusal scheme will function as expected, or if adjustments are needed prior to the delivery of the definitive long‐term restorations. CR and VDO are essential for establishing a functional and healthy occlusion, ideal restoration proportions and smile design, and treatment planning esthetic and prosthodontic restorations for long‐term durability.

Clinical significance

This article reviews CR, VDO, and the characteristics of a CAD/CAM transitional bonding technique in reversing the signs and symptoms of a compromised dentition and reestablishing an ideal esthetic and functional occlusal outcome. Transitional bonded prostheses are significantly important to providing patients with an interim therapy to determine if the proposed esthetic outcome and occlusal scheme will function as expected, or if adjustments are needed prior to the delivery of the definitive long term restorations.

Morphological Investigation of Residual Ridge in Japanese Edentulous Elderly for Fabrication of Edentulous Stock Tray

The objective of this study was to determine the size of the residual ridge in edentulous elderly Japanese persons for preparation of edentulous stock trays and clarify any correlations among the items measured. The participants comprised 74 patients requesting construction of a complete denture for the maxilla, mandible, or both. The length, width, and anterior and posterior height of the maxillary and mandibular residual ridge was measured on a prepared working model using a caliper. For each of the maxillary and mandibular edentulous residual ridges, correlations among measurement items were analyzed employing Pearson's correlation coefficient. In participants who were edentulous in both the maxilla and mandible, correlations between the maxillary and mandibular measurement items were analyzed employing Pearson's correlation coefficient. The results revealed that the mean maxillary length of the residual ridge was 55.21±4.07 mm, while mean mandibular length was 56.03±4.04 mm. The mean posterior width of the maxillary jaw was 48.79±4.14 mm, while that of the mandibular jaw was 57.33±3.24 mm. A strong correlation was found between the length and width of the residual ridge in both the maxilla and mandible, but no strong correlation was detected between the height in the anterior tooth region and any other item measured. These findings suggest that the size of any given item can be estimated by measuring either the length or width of the residual ridge when selecting a stock tray. We also propose that it is necessary to prepare stock trays with several different heights in the anterior tooth region, regardless of the length and width of the tray, or to adjust the length of the tray.

The position of the occlusal plane in natural and artificial dentitions as related to other craniofacial planes

PURPOSE

This study aimed at determining the most reliable ala-tragus line as a guide for the orientation of the occlusal plane in complete denture patients by use of cephalometric landmarks on dentate volunteers.

MATERIALS AND METHODS

Analysis was made for prosthodontically related craniofacial reference lines and angles of lateral cephalometric radiographs taken for 47 dentate adults. Variables were determined and data were analyzed using SPSS (SPSS, Inc., Chicago, IL).

RESULTS

Occlusal plane angle formed between the occlusal plane and Camper's plane had the lowest mean value in the angle formed with Camper's I, which represents the measure taken from the superior border of the tragus of the ear with a score of 2.1°. The highest was measured in the angle formed with Camper's III with a score of 6.1°, while the angle formed with Camper's II was 3.2°. The differences between the three planes in relation to the occlusal plane was significant (p < 0.001).

CONCLUSION

The superior border of the tragus with the inferior border of the ala of the nose was most accurate in orienting the occlusal plane.

Influence of the buccolingual position of artificial posterior teeth on the pressure distribution on the supporting tissue under a complete denture

The buccolingual position of artificial teeth is one of the important factors affecting denture stability, chewing efficiency, and pressure distribution on the supporting tissue under a denture. This study compared the pressure values on the supporting tissue under a denture during chewing in denture wearers, each of whom tried three different setting positions of artificial posterior teeth. The pressure on supporting tissue was greater on the working side that on the non-working side during chewing. The difference in mean pressure was found among the buccolingual positions of artificial posterior teeth. When the posterior teeth were set on the crest, the total pressure was the smallest. This strongly suggests that the setting position of artificial teeth should be considered not only for denture stability but also for the avoidance of high pressure on the supporting structures.

Role of muscle function in mandibular prosthetics

The various effects of muscle function on mandibular prosthetics have been categorized and discussed. For obvious reasons, specifics such as muscle origins and insertions have not been included. This has been done most capably in the past. Many obvious and superficial facts have been presented to examine the depth and pervasiveness of muscle function in mandibular prosthodontic service. A similar case can be made for the maxillary denture, but to a lesser degree. The dictum of Martone calls attention to the fact that biologically inert prostheses are constructed for patients who are in state of minimal functional activity. When customary day-to-day activity resumes, those prostheses must serve harmoniously with the oral environment into which they are thrust.

The case against the edentulous ridge--and an alternative

Loss of alveolar bone height frequently occurs when all teeth have been extracted, and many consider this loss irreversible. Retaining teeth under complete and partial dentures is a way of preventing bone loss; this type of treatment should be considered more often to prevent the handicapping condition of edentulism.

Arranging artificial teeth according to anatomic landmarks

A system for arranging artificial teeth that satisfies three goals is desirable. These goals are accuracy, speed, and a facility for communication. Such a system, based upon certain anatomic landmarks that can be identified on an edentulous dental cast, has been described in detail. The dentist with the patient present records the anterior determinant of occlusion by placing the four central incisors according to phonetics and esthetics. All remaining teeth are placed at the laboratory according to anatomic landmarks. Then the dentist returns the trial dentures to the patient for verification, personalization, and perfection. It is the responsibility of the dentist to prescribe requirements of tooth placement in detail if he uses the services of a dental laboratory technician.