Plaque-induced gingival inflammation in the absence of attached gingiva in dogs

The purpose of this experiment was to evaluate the effect of plaque infection on gingival units (1) with or without support of attached gingiva and (2) with different height of the attachment apparatus. 7 beagle dogs were used. Prior to the initiation of the study 4 different types of "dentogingival" units had been established in each dog by the use of excisional and grafting procedures, namely (1) normal non-operated free gingival units supported by a wide zone of attached gingiva and normal height of the attachment apparatus, (2) regenerated free gingival units supported by loosely attached alveolar mucosa and normal height of the attachment apparatus, (3) regenerated free gingival units supported by loosely attached alveolar mucosa and reduced height of the attachment apparatus and (4) regenerated free gingival units supported by a wide zone of attached gingiva and reduced height of the supporting apparatus. A baseline examination involved assessments of plaque, gingivitis, gingival exudate, probing depth, clinical attachment level, position of the "soft tissue margin" and width of attached gingiva. Following this examination 2 of the dogs were scheduled for biopsy and sacrificed. The remaining 5 dogs were for 40 days placed on a diet regimen which allowed plaque accumulation. The clinical examination was repeated and biopsies sampled at the end of this period. Following preparation the biopsy material was subjected to histometric and morphometric analysis. The results showed that the free gingiva which regenerated following surgical excision of the entire gingiva or following soft tissue grafting, was in most respects, clinically as well as histologically, similar to the "normal" free gingiva. The data obtained after 40 days of plaque accumulation did not reveal any differences between the various "dentogingival" units regarding size and apical extension of the infiltrated portion of the connective tissue. It was concluded that a free gingival unit which is supported by loosely attached alveolar mucosa is not more susceptible to inflammation than a free gingival unit which is supported by a wide zone of attached gingiva.