Bárbara de Lima Lucas

Interalar Distance to Estimate the Combined Width of the Six Maxillary Anterior Teeth in Oral Rehabilitation Treatment

STATEMENT OF THE PROBLEM The faces architecture of dentate subjects has been studied to find a reliable guide for the selection of artificial anterior teeth. However, there is no consensus of data regarding a reference to estimate the width of artificial teeth. PURPOSE The purpose of this study was to analyze whether there is a consistent relationship between the interalar distance (IAD) and the combined mesiodistal width of the six maxillary anterior teeth. METHODS Standardized digital photographs of 81 dentate Brazilian subjects were included in the sample. They were 37 men and 44 women (age 17 to 33). Through image processing software, the IAD and the distance between the tips of the maxillary canines were measured when viewed from the frontal aspect. Accurate casts were made to quantify the distance between the distal surfaces of the maxillary canines on a curve, by use of a flexible millimeter ruler. Nonparametric statistics were performed to analyze the results (p < 0.05). RESULTS The IAD when compared with the width of the six maxillary anterior teeth, on a straight line and on a curve, presented a ratio of 0.914 and of 1.305, respectively. The Wilcoxon test showed no significant difference between the calculated width values and the mesiodistal width measured on a curve and on a straight line (p = 0.986). CONCLUSION The IAD, when increased by 31% of its value, can suggest the circumferential distance of the six maxillary anterior teeth. CLINICAL SIGNIFICANCE The width of the nose, when measured in digital photographs, can be utilized as a reliable guide for the selection of the maxillary anterior teeth width. It can improve the esthetic result of the oral rehabilitation treatment for the edentulous patient by offering a natural dentofacial relation.

Photoelastic Study of the Support Structures of Distal‐Extension Removable Partial Dentures

PURPOSE The double system of support, in which the distal-extension removable partial denture adapts, causes inadequate stress around abutment teeth, increasing the possibility of unequal bone resorption. Several ways to reduce or more adequately distribute the stress between abutment teeth and residual ridges have been reported; however, there are no definitive answers to the problem. The purpose of this study was to analyze, by means of photoelasticity, the most favorable stress distribution using three retainers: T bar, rest, proximal plate, I bar (RPI), and circumferential with mesialized rest. MATERIALS AND METHODS Three photoelastic models were made simulating a Kennedy Class II inferior arch. Fifteen dentures with long saddles, five of each design, were adjusted to the photoelastic patterns and submitted first to uniformly distributed load, and then to a load localized on the last artificial tooth. The saddles were then shortened and the tests repeated. The quantitative and qualitative analyses of stress intensity were done manually and by photography, respectively. For intragroup analyses the Wilcoxon test for paired samples was used, while for intergroup analyses Friedman and Wilcoxon tests were used to better identify the differences (p < 0.05). RESULTS The RPI retainer, followed by the T bar, demonstrated the best distribution of load between teeth and residual ridge. The circumferential retainer caused greater concentration of stress between dental apexes. Stress distribution was influenced by the type of retainer, the length of the saddle, and the manner of load application. CONCLUSIONS The long saddles and the uniformly distributed loads demonstrated better distribution of stress on support structures.

Correlation between the individual and the combined width of the six maxillary anterior teeth.

PURPOSE There is a consensus in the community of dental research that the selection of undersized artificial maxillary anterior teeth offers an unnatural appearance to the denture. Several methods to select the adequate width of these teeth are of questionable validity, and many dentures have an obviously artificial appearance. This article assessed the relationship between the individual and the combined width of maxillary anterior teeth. MATERIALS AND METHODS Impressions were made of the anterior dentition of 69 dentate undergraduate students with rubber impression silicon, and casts were formed. The individual widths of the maxillary anterior teeth were measured by using a digital caliper (SC-6 digital caliper, Mitutoyo Corporation, Tokyo, Japan), and the combined width was registered by both adding the individual width and using a flexible millimeter ruler. RESULTS Students t-test showed significant differences between the analogous teeth and different sides of the maxillary dental arch (p = 0.001), with the exception of the central incisor (p = 0.984). Pearsons product moment correlation coefficient showed significant positive correlation between all the measurements compared (p = 0.000). Linear regression analysis concluded three mathematical equations to obtain the individual tooth width after measuring the combined width of the six maxillary anterior teeth by using a flexible millimeter ruler. CONCLUSIONS The individual tooth width can be determined if the combined width of the maxillary anterior teeth is obtained by using a flexible millimeter ruler.

Distance between the medialis angles of the eyes as an anatomical parameter for tooth selection

During the construction of a removable prosthesis, the lack of pre-extractions records turns the selection of artificial maxillary anterior teeth into a complex procedure. The aim of this study was to identify a mathematical relation between the anterior dental segment and the distance between the medialis angles of the eyes, for selecting the suitable width of the six maxillary anterior teeth. Standardized digital images of 80 dentate Brazilian subjects were used to measure both facial and oral structures when viewed from the frontal aspect through an image processing program. Accurate casts were made to measure on a curve the distance between the maxillary canines. Parametric statistics was performed to analyse the results (P < 0.05). The distance between the medialis angles of the eyes showed no significant difference according to gender (P < 0.108). The Pearson Product Moment Correlation Coefficient showed significant positive correlation between the distance between the medialis angles of the eyes and all variables compared. After the linear regression analysis, mathematical formulae and biometric ratios were concluded to estimate the combined width of the six maxillary anterior teeth from the measurement of the distance between the medialis angles of the eyes. The distance between the medialis angles of the eyes measured through photogrammetry can be a reliable guide for tooth selection.

Impression Techniques for Multiple Implants: A Photoelastic Analysis. Part I: Comparison of Three Direct Methods

The purpose of this article was to compare through photoelastic analysis the stress distribution in 3 direct transfer techniques for implants with splinting. Three photoelastic resin blocks were made with 2 implants placed parallel to each other and 2 square transfer copings splinted. Both transfers were splinted with acrylic resin chemically activated in 3 different techniques: metallic sticks (T1), prefabricated acrylic bars (T2), or dental floss (T3). A circular polariscope was used, and the distortion energy (E) was calculated in 4 periods: 20 minutes and 3, 24, and 36 hours. Statistically significant differences were found among the 3 techniques (P < .05). The dental floss presented the greatest distortion energy values (T3 = 0.469 Kgf/mm(2)) and the metallic sticks the lowest values (T1 = 0.0 Kgf/mm(2)). Thus, the metallic sticks technique (T1) appears to be the most accurate protocol to be used for implant-supported prosthesis with multiple abutments.

Impression techniques for multiple implants: a photoelastic analysis. Part II: comparison of four acrylic resins.

Four commercial brands of chemically activated acrylic resin were compared through photoelastic analysis. Photoelastic resin blocks were made with 2 implants placed parallel to each other and 2 square transfer copings splinted. Both transfers were splinted with chemically activated acrylic resin: Dencrilay, Duralay I, Duralay II, and GC. Data were analyzed by 2-way analysis of variance and Tukey test (P < .05). Statistically significant differences were found among the 3 brands of chemically activated acrylic resin. Dencrilay showed greater dimensional alteration. Duralay I and GC are recommended for the transfer of the position of the multi-implants.