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Notes: Purpose The purpose of this investigation was to measure and describe the lingual tissues of the anterior mandible to determine the acceptable boundaries of the zone of nonmovable tissue for placement of a lingual bar and to compare these to existing numerical guidelines.Materials and Methods Eighty subjects, grouped by age and gender, with clinically normal mandibular lingual gingival tissues from second premolar to second premolar were examined. The lingual sulcular depths (AB) and the distance from the gingival crest to movable tissue of the floor of the mouth (AC) were recorded. The zone of lingual nonmovable tissue was calculated (AC − AB) for each tooth.Results For all subjects, the mean value of the probing depth (AB) ranged from 1.22 mm (±0.33 mm) for central incisors to 1.66 mm (±0.43 mm) for second premolars. The mean distance from the gingival crest to movable tissue of the floor of the mouth (AC) ranged from 7.44 mm (±1.59 mm) for central incisors to 10.28 mm (±2.55 mm) for second premolars. The mean height of the lingual nonmovable tissue (the zone available for the lingual bar; AC − AB) ranged from 6.22 mm (±1.59 mm) for central incisors to 8.63 mm (±2.57 mm) for second premolars. Most subjects presented with the minimum zone of nonmovable tissue at the central incisors, but with increasing age more subjects presented with minimum values at the posterior teeth. The multifactorial analysis of variance (ANOVA) for males' available nonmovable tissue shows significance for both tooth (p 〈 0.001) and age (p 〈 0.001) factors. The multifactorial ANOVA for females' available nonmovable tissue shows significance for both tooth (p 〈 0.001) and age (p 〈 0.001) factors. Of all subjects, 85% (88% of males, 83% of females) had 4 mm or more of nonmovable tissue, sufficient for a lingual bar. The amount of available room decreased in older females.Conclusion Within the limits of this study, the use of actual measurements of lingual tissues versus existing numerical guidelines increased the percentage of patients for which the lingual bar can be used from approximately 6% to approximately 85%.

Notes: Purpose This study investigated the effects of implant proximity on inter-implant bone height, density, and osseointegration using digital radiography and histology.Materials and Methods After a feasibility study, a total of 80 endosteal implants were placed in 20 New Zealand White Rabbit tibias. With the aid of a surgical jig, four 8.5-mm implants were placed in the medial aspect of the tibial crest at inter-implant distances of approximately 1, 1.5, and 3 mm. Standardized digital radiographs using a paralleling device were made immediately after placement of implants. Implants were allowed to osseointegrate for 90 days. After this healing period, the animals were sacrificed, and the standardized radiographs were repeated. The tibias were harvested, processed, and invested in epoxy. Sagittal sections were made from each specimen for histologic evaluation. The initial and postmortem digital radiographs were evaluated for inter-implant distances, vertical bone height changes over time and between implant pairs, and bone density changes over time and between implant pairs using a computer image analysis program and computer statistics program.Results The actual inter-implant distances were consistent in a range of 0.2 mm. Bone height increased significantly from presurgical levels at all 3 locations (p 〈 .0005). Repeated measures analysis of variance comparing change in bone height at the 3 implant pair distances showed significant differences among the 3 (p= .002). Paired t tests showed that the amount of bone growth at the 1-mm separation site was significantly greater than the 1.5-mm site (p= .026) and the 3-mm site (p= .001), whereas bone growth at the 1.5- and 3-mm sites did not show significant differences (p= .162). A repeated measures analysis of variance comparing change in bone density showed no significant differences (p 〉 .05) among the 3 inter-implant distances for either the 8-mm position (approximately crestal bone height) or the 6-mm position (approximately 2 mm subcrestal).Conclusions Within the limits of this study, it seems placing implants closely together does not adversely affect bone height or density. Conversely, it seems that placing implants closer together may increase bone growth.