Versatility and Importance of Bichat's Fat Pad in Dentistry: Case Reports of Its Use in Occlusal Trauma

INTRODUCTION

The knowledge of the anatomy surrounding Bichat's fat pad, as well as its clinical applications, is essential to indicate and to safely perform its removal. This surgery is indicated not only for esthetic purposes, but also for functional reasons. When used properly, Bichat's fat pad is composed of stem cells that have a similar phenotype to adipose stem cells, useful in the treatment of pathologies and/or complications, such as maxillary sinus membrane perforation, oroantral/oronasal communications, peri-implantitis, ulcers, fibrosis of the oral mucosa, soft tissue reconstruction, among others. Due to its location, it is prone to suffer clinically significant pathologies, as well as constant trauma.

AIM

The aim of this study is to report two clinical cases and subsequent follow-ups, where bichectomy was performed to avoid dental trauma to mucosal tissues during the masticatory function. Also, literature review on the application of Bichat's fat pad in dentistry is provided.

CASE REPORT

Two female patients (20 and 24 years) reported discomfort and constant pain in the oral mucosa caused by dental trauma. At the clinical examination, patient presented augmented and injured mucosa. The surgical sequence of Bichat's fat pad removal, as well as the extra-/intraoral photographic follow-up (8, 15, 30, and 180 days) of the patients is described.

CONCLUSION

In order to indicate and/or accomplish surgical procedures involving Bichat's fat pad, it is fundamental to know its anatomy and possible applications, not only for esthetic purposes, but also for functional purposes. The patients showed evident improvements following the removal of Bichat's fat pad.

CLINICAL SIGNIFICANCE

Application of Bichat's fat and its removal should be evaluated, being an alternative in patients who constantly undergo mucosal injury during masticatory function.

Quantitative assessment of morphological changes of dental pulp components of teeth affected by occlusal trauma

AIM

In the general economy of the stomatognathic system functionality, the occlusal function has an important role, meaning both the dental-dental reports and the dynamic reports interarch-interarch. Because of the interrelationships and inter-dependency that govern the functioning of the biological systems, a pathological change affecting a component of the stomatognathic system produces impaired functioning of the others. The aim of the present study is to assess the morphological changes occurred in the dental pulp components of teeth affected by occlusal trauma.

MATERIALS AND METHODS

Fragments of dental pulp coming from 45 patients with occlusal trauma were processed using classical histological techniques (formalin fixation and paraffin embedment) and stained with Hematoxylin-Eosin (HE), Masson's trichrome and anti-CD34 antibody immunostaining, in order to highlight the peripheral zone and central connective tissue of dental pulp morphological changes. A set of parameters namely thickness of peripheral zone components, calcifications, fibrosis and vascular density in the dental pulp were assessed individually and based on three topographical criteria namely the affected tooth, the position on the dental arches and the position according to sagittal plane.

RESULTS

There was no correlation between morphological changes of dental pulp and the topography of teeth with occlusal trauma. The size of the peripheral area of the dental pulp and that of its components evolved in the same sense, whether it was growth or decrease. Decrease of the peripheral area was associated with the increase of collagen fibers density, calcium deposits and density of the capillary network. The direct correlation between the amount of collagen fibers and vascular density seems somewhat paradoxical but it can be explained by the reemergence of chronic inflammatory events located in the dental pulp.

CONCLUSIONS

It seems that dental pulp morphological changes are not influenced by the teeth with occlusal trauma topography. With one exception (the components of peripheral zone), most of the correlations between the dental pulp morphological changes were only suggested but not validated statistically, which requires further studies on larger groups together with the introduction of inflammatory cell population studies.

Morphological changes of gums in occlusal trauma

AIM

Occlusal trauma causes major modifications of the coverage periodontium, which in turn reflect on the dental unit. The aim of the present study is to evaluate some of the morphological modifications occurred in the marginal periodontium surrounding teeth affected by occlusal trauma.

MATERIALS AND METHODS

Fragments of marginal periodontium coming from 51 patients with occlusal trauma were processed using classical histological techniques (formalin fixation and paraffin embedment) and stained with Hematoxylin-Eosin (HE), Masson's trichrome and anti-CD34 antibody immunostaining, in order to highlight the epithelial and connective tissue changes of gingival mucosa. A set of epithelial and connective tissue morphological parameters were assessed individually and based on three topographical criteria concerning the affected tooth.

RESULTS

The epithelium and especially its superficial compartment presented changes depending on the tooth type and the dental arch. Epithelial thickness had the tendency to decrease as the fibrosis in both corium compartments and vascular density in the deep corium compartment were increasing. Leukoplakia present around the affected teeth but not always was related with the tooth type and was more obvious as the superficial compartment of the epithelium was thicker and as fibrosis was more reduced in the papillary compartment of the corium. Vascular density reduced when fibrosis process increased in the corium.

CONCLUSIONS

Lesions determined by occlusal trauma and their topography can and are influencing locally the different structures of the surrounding periodontium.

The effect of experimental occlusal interferences on nerve growth factor levels in periodontal tissues

OBJECTIVE

To test the hypothesis that experimental occlusal interferences increase the nerve growth factor (NGF) levels in periodontal tissues and cause an up-regulation of preprotachykinin-A (PPTA) mRNA.

BACKGROUND

NGF is related to hyperalgesia and inflammation. PPTA mRNA, a primer of substance P, is a possible factor in the aetiology of pain.

METHODS

Experimental interferences were created by placing inlays in the right maxillary molars of 15 dogs. The right side molars formed the experimental group. The left side molars served as controls. Three dogs with cavities prepared without changing the occlusion formed a sham group. The dogs in the first group were sacrificed, 3 at each time, after 3, 7, 14, 30, and 60 days. The sham group was sacrificed after 14 days. The levels of NGF in periodontal tissues and PPTA mRNA in the trigeminal ganglions were detected by ELISA and TR-PCR. Comparisons were made with paired t-tests and a multivariate MANOVA test.

RESULTS

On all measurement days, there were higher levels of NGF mRNA, PPTA mRNA, and NGF on the experimental than on the control side in 14 of 15 comparisons and in the sham group. NGF production in periodontium was time-dependent. No differences in NGF protein levels were observed between the control and the sham groups.

CONCLUSION

The results which need confirmation in further tests are of clinical interest. They indicate that occlusal experimental interferences may be an etiologic factor in oral facial pain by increasing mRNA and NGF protein levels in the periodontal tissues.

Incidence of noncarious cervical lesions and their relation to the presence of wear facets

PROBLEM

Noncarious cervical lesions are characterized by loss of tooth structure in the cervical area, compromising its integrity and resulting in esthetic problems for the patient.

PURPOSE

The purpose of this study was to assess noncarious cervical lesions in young patients in an attempt to establish a possible relationship to the presence of wear facets.

MATERIALS AND METHODS

First-year dental students of Bauru Dental School were studied to verify the prevalence of noncarious cervical lesions and their relationship to the presence of wear facets. After 3 years, the students were examined again to verify the incidence of new lesions, trying to establish a correlation to the previous existence of wear facets.

RESULTS

Of the 1,131 teeth analyzed, 129 had noncarious cervical lesions. Twenty-nine of the 40 students had at least one tooth with one lesion. After 3 years, the incidence of new lesions was 57. Mandibular first molars (22.3%), mandibular first premolars (13.2%), mandibular second premolars (13.2%), and maxillary first molars (12.4%) showed the highest prevalence of lesions. On final analysis, 86.8% of all teeth presenting lesions showed wear facets. The identification of new lesions associated with the presence of wear facets identified during the first exam 3 years earlier was statistically significant (p < 0.01).

CONCLUSIONS

The patterns of wear facets found in the study population examined were associated with an increased occurrence of noncarious cervical lesions.

CLINICAL SIGNIFICANCE

Occlusal factors, especially the presence of wear facets, should be considered in the management of noncarious cervical lesions.

[A study of calcitonin gene-related peptide-immunoreactive nerve fibers of rat molar pulp during traumatic occlusion and after removal]

OBJECTIVE

To study the effect of traumatic occlusion on CGRP-immunoreactive (CGRP-IR) nerve fibres in rat molar pulp and observe the recovery of CGRP-IR nerve fibres after removal of traumatic occlusion.

METHODS

To observe immunohistochemically the change of CGRP-IR nerve fibres in molar pulp during traumatic occlusion and after removal.

RESULTS

The increase of number, density and morphology of CGRP-IR nerve fibres in traumatic occlusion group was more than in control group, however, the changes of CGRP-IR nerve fibres in removal of traumatic occlusion group were less than in control group.

CONCLUSIONS

The changes of CGRP-IR nerve fibres in number, morphology, and density are induced by traumatic occlusion in rat molar pulp, however, the nerve fibres recover to normal by removal of traumatic occlusion.

Histological study of rat masseter muscle following experimental occlusal alteration

It has been suggested that occlusal interference results in masticatory muscle dysfunction. In our previous study, occlusal interference reduced the rat masseter energy level during masticatory movements. The purpose of this study was to investigate the histological alterations of rat masseter muscles following experimental occlusal alteration with unilateral bite-raising. A total of eight male adult Wistar rats were equally divided into control and experimental groups. The experimental rats wore bite-raising splints on the unilateral upper molar. However, 4 weeks after the operation, the anterior deep masseter muscles were removed and then stained for succinic acid dehydrogenase (SDH), haematoxylin eosin (HE) and myofibrillar ATPase. Most of the muscle fibres in experimental rats remained intact, although partial histological changes were observed, such as extended connective tissue, appearance of inflammatory cells in the muscle fibres and existence of muscle fibres with central nuclei and central cores. Moreover, the fibre area-fibre frequency histograms of experimental muscle indicated a broad pattern than that of controls. These results indicated that occlusal interference caused histological changes in masseter muscles and that this may be related to the fact that the masseter energy level was reduced during masticatory movements in unilateral bite-raised rats.

[Recurrence: mechanisms and treatments]

An original analysis by computer has been imagined. Etiological diagnosis in recurrence's cases is based on asymmetry. Different levels were investigated: dental arch, ridge, basal bone and mandibular position. Dental shift, deformed bone, eccentric mandibular and occlusal distortion were found. Each molar is independently moving. Mandibular basal bone is stabilized in the transverse dimension. Mandibular deviation induces compression or stretching in temporo-mandibular articulation. Occlusal interferences involve distortion of cuspal plans. To reach stable objectives, molars require symmetrical position below one millimeter discrepancy, molar locking is to be had for the disto-vestibular cusp and ovoid arch. A special anchor apparatus allows to correct every wrong position of each individual molar, in each three-directional space. Mini-positioner or mini-splint perfect anterior misalignment. Sometimes, thermical memory archs are required. Ten fundamental rules that regulate occlusal and mandibular stability have been checked after treatment.

The influence of controlled occlusal overload on peri-implant tissue: a histologic study in monkeys

This study examined the influence of controlled occlusal overload on an implant. An experiment was conducted on five crab-eating monkeys (Macaca fascicularis) in which overload with no inflammation in the peri-implant tissues was modeled. Two osseointegrated implants were placed into each monkey. After 3 months of osseointegration, superstructures that were excessive by about 100 microns were mounted on the implants, and a traumatic occlusal force was experimentally delivered to its implant from the lingual to the buccal side. This procedure was performed under conditions of good oral hygiene. The monkeys received an excessive occlusal force for 1 to 4 weeks and were then immediately sacrificed. The results showed that the implants remained firmly integrated with bone, and all of the subjects that received excessive occlusal force for 1 to 4 weeks showed an absence of gross bone loss. These results suggest that conditions of occlusal force created by excessively high implant-supported superstructures may not destroy the peri-implant tissues.

[Ultrastructure of the synovial membrane and the articular cartilage in the temporomandibular joint of the rabbits with occlusal trauma]

OBJECTIVE

To study the effect of occlusal trauma on the ultra structure of rabbits' temporomandibular joints (TMJ) synovial membrane and articular cartilage.

METHODS

TMJs from six rabbits with occlusal trauma and three control rabbits were studied by transmission electron microscopy.

RESULTS

Degenerative changes of TMJ tissues were found. The articular surface of the condyle was damaged, and the chondrocytes showed signs of degeneration. The synovial lining cell consisted of a number of vimentin intermediate filaments (IFs) which were especially prevalent in the processes as well as paranuclearly. Microvilli on the cell membrane were commonly seen. The vermiform body in the deeper interstitium was also found. Our finding of punctate adherens between synoviocytes was firstly reported in the study.

CONCLUSION

The occlusal trauma is really a factor inducing degenerative changes of the TMJ.

Occlusal contacts in maximum intercuspation in normal dentitions

A cross-sectional study of the contacts in maximum intercuspation was undertaken using a method to identify occlusal contacts, which is indicated as satisfactory by modern research. The aims were to describe in subjects with normal dentitions and normally functioning masticatory systems: (a) the general distribution of contacts; (b) the numbers in the various classes and types of occlusal contacts; (c) the numbers of teeth without contact. A randomized sample of 18 women and 20 men was used. Classical theoretical proposals for the numbers, distribution and nature of occlusal contacts were not supported. Wide variability was evident and asymmetry of distribution on the right and left sides of individual subjects was common. Contacts with stabilizing tendencies involved the mandibular supporting cusps in 79% of occurrences. Overall, the difference in the number of contacts with stabilizing effects was not significantly different from the number with unstabilizing tendencies. Contacts with mechanically unstabilizing effects did not produce clinically discernible, unfavourable sequelae in the dentitions. Because of the sparse number of stabilizing contacts, interventions involving the occlusal surfaces should maintain or improve on the number of such contacts in maximum intercuspation.

Symptoms and signs of temporomandibular disorders in girls with normal occlusion and Class II malocclusion

Mandibular function, headaches, and symptoms and signs of temporomandibular disorders (TMD) were studied in one group of girls with a well-defined normal occlusion (n = 60) and another group with class II malocclusion (n = 123). Frequent headaches and temporomandibular joint clicking, muscle tenderness to palpation, pain on mandibular movement, awareness of tooth clenching, and grinding were commoner in the class II malocclusion group. Awareness of tooth clenching had the largest influence on the odds for symptoms and signs of temporomandibular disorders (TMD) in a logistic regression analysis. Occlusal variables that increased the odds for symptoms and signs of TMD were large overjet, frontal open bite, few occlusal contacts, lateral sliding retruded-intercuspal contact position, crowding, and non-working side interferences. We concluded that normal occlusions have lower odds for symptoms and signs of TMD, whereas some occlusal characteristics, more frequently found in the class II malocclusion group, increased the odds for symptoms and signs of TMD.

[The effect of artificial traumatic occlusion on the pulp and periodontium in rat molars]

In order to study relationship between the period of occlusal trauma and pulpal and periodontal tissues, 44 rats were used in experimental occlusal trauma. The pulpal and periodontal tissues of rat molars were observed by histological examination and micrographic examination. The results showed that the damage of pulp became more serious as time went on, but periodontium appeared adaptive changes. The same changing area in periodontal tissues were observed between histological section and micrographic film. The results provide experimental evidences for the pathology and pathogeny of pulpitis and perioapical periodontitis caused by occlusal trauma.

Responses of periodontal nerve terminals to experimentally induced occlusal trauma in rat molars: an immunohistochemical study using PGP 9.5 antibody

The response of periodontal nerves to experimentally induced occlusal trauma in rat molars was assessed by immunohistochemistry for protein gene product 9.5 (PGP 9.5) at light and electron microscopic levels, and by computerized image analysis. The occlusal surface on the left upper first molar of 8-wk-old male Wistar rats was raised approximately 1 mm under ether anaesthesia. The rats were perfusion-fixed on d 1, 2, 3, 4, and 7 after bite-raising and then decalcified for 2-3 wk. Frozen sagittal cryostat sections were stained by the avidin-biotin complex method. By the second day after bite-raising many Ruffini endings were swollen and their outline unclear at the light microscopic level. Transmission electron microscopy disclosed PGP 9.5 reaction products within Ruffini endings that had unusually long cytoplasmic projections extending through enlarged slits of the Schwann sheaths and also diffuse extracellular PGP 9.5-immunoreactivity near the Ruffini endings. From d 2 to 4, thin nerve fibres on the pressure side of the periodontal ligament were orientated irregularly and had a prominent beaded appearance. An increase in beaded nerve terminals occurred at d 2-4 post elevation, and decreased later. These results suggest that occlusal trauma indices specific changes in the distribution and shape of nerve terminals in the periodontal ligament.

Periodontal ligament tissue reactions to trauma and gingival inflammation. An experimental study in the beagle dog

The aims of the present study were to analyze (i) which tissue changes may occur in the zone of co-destruction to better understand why trauma from occlusion may induce additional attachment loss, and (ii) whether changes occur in the periodontal ligament tissue when an inflammatory lesion (ICT) approaches the periodontal ligament space. 16, 1-year-old beagle dogs, were selected and divided into 2 groups, group A and group B, consisting of 6 and 10 dogs, respectively. In group A, on day 0, a bucco-lingual jiggling type movement was induced resulting in increasing tooth mobility at P3 (test tooth) by the application of an orthodontic elastic which traversed the buccal surface of the crown of the test tooth. The elastic was exchanged either in a buccal or in a lingual position 2x a week during a 3-month period. 3P served as non-jiggled control tooth. Tooth mobility measurements were recorded on days 0, 30, 60, 90. A plaque control regimen was maintained until the end of the experiment (day 90). On day 90, biopsies including P3 and 3P were harvested. The dogs representing group B, were divided into 2 subgroups of 5 each, group BI and group BII. On day 0, a 4-month period of experimental periodontal tissue breakdown was initiated by placing cotton floss ligatures submarginally around the mandibular fourth premolars (4P4) in group BI and around the mandibular third premolars GP3) in group BII. All ligatures were exchanged, replaced 1x every month, and on day 120 permanently removed. On the same day, biopsies included 4P4 were harvested. Following supragingival debridement 3P3 were allowed to accumulate plaque until the end of the study (day 225). On this occasion, biopsies including 3P3 were harvested. The results of the histological measurements revealed that in the most coronal portion of the periodontal ligament of teeth exhibiting increasing mobility, there was an increased width, a reduced % tissue volume of collagen, and an increased volume of vascular structures and leukocytes. Furthermore, the number of osteoclasts bordering this portion of the alveolar bone was increased and the number of collagen fibers inserting into the root cementum and into the alveolar bone was reduced. It was also demonstrated that in teeth with normal mobility, the position of the gingival ICT failed to influence the composition of the tissue within the coronal portion of the periodontal ligament.

[Effects of occlusal trauma on temporomandibular joints in rabbits: a scanning electron microscopic study]

Six rabbits with unilateral occlusal splints on the mandibular left molars for one month, three months or five months were examined to study the ultrastructure of the surface of the temporomandibular joint. Four rabbits were used as control. The results showed that the surface layer of the disk and articular cartilage were damaged. Severe fibrillation with sheets of fibers, collagen fibrils and collagen bundles inside fissures and craters were observed. These changes were seen in all rabbits with occlusal trauma and also in control rabbits for five months. The findings suggested that occlusal trauma could result in degenerative changes of the temporomandibular joint.

Effect of traumatic occlusion on CGRP and SP immunoreactive nerve fibre morphology in rat molar pulp and periodontium

Traumatic occlusion provides a trauma that affects the whole tooth and its supporting tissues. To study the effect of this trauma on CGRP and SP immunoreactive nerve morphology in pulp and periodontium, traumatic occlusion was induced in 2-months-old rats. The occlusal surface of the first maxillary molar in 30 rats were unilaterally raised 1 mm with a composite material. At different observation periods up to 30 days, the rats were transcardiacally perfused, the jaws demineralized, sectioned and processed for immunohistochemistry with the avidin-biotin-peroxidase method. Changes in nerve morphology, distribution and density in first and second molars and their supporting tissues were analyzed and compared in experimental (n = 30) and control rats (n = 14). Already after 5 days with traumatic occlusion, 22% of the experimental teeth had increased density of CGRP and SP immunoreactive nerves locally in gingiva, the periodontal ligament and the pulp, while in 15%, axonal proliferation and changed nerve morphology were found in the whole pulp (severe reaction). During a 20-day period, the pulpal nerve reactions progressed and included the whole pulp in 46% of the experimental teeth. The periodontal nerve responses were still localized only to the cervical and apical regions, and they remained local in these areas throughout the experimental periods. After 20 days the number of teeth with severe nerve changes seemed to decrease. The study shows that an unilateral change in occlusion of the first molar initiate nerve responses in the total molar dentition. In this experimental model the pulpal axons containing CGRP and SP reacted more serious to occlusal trauma than the nerves in the periodontium. The results indicate that the nerve changes in some cases might be transient.

Mandibular function in children with a lateral forced bite

Open-close-clench cycles have been studied in 12 children with a lateral forced bite in order to investigate how the neuromuscular system of the mandible adapts itself in the presence of occlusal interferences. The mandibular movements were registered in a frontal plane at the central incisors with an opto-electronic registration technique. Series of 35 cycles were recorded to intercuspal position, against flat occlusal splints constructed in intercuspal raised and retruded positions, and against splints with occlusal stops in a retruded position. Average lateral displacements of the mandible during cycle series against flat occlusal splints were measured relative to cycle series to intercuspal position and relative to series against splints with occlusal stops in the retruded position. The lateral mandibular displacements were registered at maximal tooth-tooth or tooth-splint contact and at 7, 14, and 21 mm mouth-opening. It was found that the mandible in the subjects investigated is displaced to the forced bite side both during cycle series into intercuspal position as well as when occlusal contacts are eliminated by the use of flat occlusal splints.

Relationship between clinical and radiologic findings of the temporomandibular joint in rheumatoid arthritis

The relationship between clinical findings in the craniomandibular system and radiologic findings in the temporomandibular joint was investigated in 101 adults with rheumatoid arthritis. Radiologic changes were correlated with duration and severity of temporomandibular joint symptoms and general joint disease. The radiologic changes were also associated with loss of occlusal support, anterior open bite, and occlusal interferences. Most joints with crepitus exhibited radiologic erosion. Joints with mutilating changes were silent.

Effect of occlusal (mechanical) stimulus on bone remodelling in rat mandibular condyle

Mechanical load influences the remodelling of skeletal tissues. In the mandibular condyle, occlusal alterations and the consequent mechanical stimulus induce changes in chondrocytes and cartilage mineralization. In the present study we quantified in the mandibular condyle the effect of occlusal interference on remodelling of the subchondral bone. Computerized histomorphometry after 5-21-day exposure to the influence of a unilateral occlusal splint revealed an increased rate of trabecular remodelling, consisting of enhancement in osteoblast and osteoclast numbers and activities. The bone formation parameters reached their high values on Days 5 or 9 and remained stable thereafter. Bone resorption showed a gradual increase throughout the experimental period. These results further characterize the temporomandibular joint reaction to occlusal alterations. It is suggested that the present increase in bone turnover together with the known enhancement in chondrogenesis are part of a process of functional adaptation in response to mechanical stimulus.

The uptake of horseradish peroxidase in monkey temporomandibular joint synovium after occlusal alteration

We conducted an electron microscopic study on the alterations in the temporomandibular joint (TMJ) synovium of the monkey after it was subjected to unilateral bite-raising, by means of a maxillary occlusal splint. The uptake of intravenously injected horseradish peroxidase (HRP) by type A cells was demonstrated in the disturbed TMJ. The uptake of HRP decreased three to six wk after occlusal alteration, and was the same as in normal type A synovial cells after 16 wk.

A 3-month study in monkeys of occlusal dysfunction and stress

A dysfunctional occlusal relationship was produced in six Macaca irus monkeys by insertion of occlusal splints in the maxilla which raised the vertical dimension of occlusion by 3-4 mm and incorporated interferences into the occlusion (test side). Cortisol levels of plasma and urine were measured by competitive protein binding analysis. At week 1 and week 3 after insertion of the splints there was a significant increase of 24 h urinary cortisol excretion rate and plasma cortisol concentration, indicating emotional stress. Furthermore, there was evidence of acute trauma from occlusion of the mandibular teeth of the test side, including a significant increase of tooth mobility and GI; radiographically there were signs of breakdown of margial and interradicular alveolar bone. One animal developed periodontal pockets of 4-5 mm adjacent to the teeth of the test side. At week 6 and week 12 urinary and plasma cortisol levels had declined to basal values whereas tooth mobility, GI and PI remained elevated. There was no clinical or radiographic evidence of further loss of bone or increase of pocket depth adjacent to the teeth of the test side during the latter part of the experimental period. The results suggest that emotional stress may be involved in periodontal reactions associated with acute trauma from occlusion.

The angular bone defect and its relationship to trauma from occlusion and downgrowth of subgingival plaque

Sixty-four sets of human teeth were collected with the aim of evaluating the role of trauma from occlusion in the etiology of destructive periodontal disease. Before the jaws were taken out, a careful bite analysis was carried out. After fixation of the jaws, impressions were taken and plaster of Paris models were made. Finally, a set of 14 radiographs were taken. On the basis of the "clinical" records postmortem, the study models and the radiographs, the jaws were sectioned. Only mesio-distal sections were included in the present analysis. The total number of interdental spaces examined was 106. The following observations were made: 1. Before any loss of periodontal fiber attachment has taken place, the configuration of the interdental septum is entirely dependent on the location of the cemento-enamel junction (CEJ) of the two neighboring teeth. The alveolar crest does not approach the apical border of the junctional epithelium closer than about 1 mm. Thus, if the CEJ is located at different levels on two neighboring teeth, the marginal termination of the interdental septum will be oblique, forming an acute angle with the "lowest" tooth. 2. Loss of periodontal fiber attachment could invariably be related to the apical growth of subgingival plaque, and downgrowth of plaque was always associated with an inflammatory process which involved lysis of the attachment fibers within a distance varying between 0.2 and 1.8 mm from the apical border of the plaque. Subsequently, the JE proliferated down to cover the denuded root surface. 3. Reduction in height of the alveolar crest could also be related to the downgrowth of plaque. The distance from plaque to bone was never found to be less than 0.5 mm and never more than 2.7 mm. The configuration of the interdental septum always seemed to be determined by the level of the plaque on the two neighboring tooth surfaces. Thus, if the plaque had reached the same level on both sides, the crest of the interdental septum assumed a horizontal outline; if plaque had proliferated down to different levels, the crest of the interdental septum was oblique and an angular defect hereby established. 4. In the present material no evidence was found to indicate that functional (traumatic) forces can act as a co-factor in the causation of angular defects. In fact, such defects were found equally often adjacent to "nontraumatized" as to "traumatized" teeth. 5. Infrabony pockets were invariably associated with downgrowth of subgingival plaque.

Alveolar bone regeneration after removal of inflammatory and traumatic factors

In this investigation periodontal destruction was produced by a combination of inflammatory and traumatic factors. After the inflammation was resolved and the trama stopped, a significant amount of alveolar bone regeneration took place. The implications of these findings for the management of advanced periodontal disease are discussed.

Stresses created by occlusal prematurities in a new photoelastic model system

A new photoelastic model system incorporating a simulated periodontal ligament sleeve around an experimental first molar has been developed. The system was used to visualize internal compressive stresses created by various premature occlusal incline relationships in both buccolingual and mesiodistal dimensions. When prematurities were applied singly and observed buccolingually, both class 1 and and class 2 prematurities produced stresses along the lingual aspect of the root, whereas the class 3 prematurity produced stresses along the buccal aspect of the root. When viewed buccolingually, combinations of class 1 and class 2 prematurities resulted in stresses along the lingual aspect of the root. The stress pattern was similar to those created by the single class 1 or class 2 prematurities. A combination of class 2 and class 3 prematurities did not produce a well-defined indication of stress distribution. There was slightly more stress along the buccal aspect of the root. Comparison of this combination with individual class 2 and class 3 prematurities indicates that such a combination tended to diminish tipping of the tooth in any one direction. A combination of class 1 and class 3 prematurities showed slightly greater stress along the buccal aspect of the root surface. Again, the combination produced less tipping of the tooth in any one direction when compared with tipping caused by the individual prematurities. When all three prematurities were tested at the same time, the stress pattern was almost coincident with that achieved in the absence of prematurities. When prematurities were observed mesiodistally, the location of stresses was dependent on the mesial or distal placement of the prematurity, irrespective of its position buccolingually.

The effect of dexamethasone in traumatic changes of the periodontium of marmosets (Callithrix jacchus)

The systemic administration of steroid hormone (0.400 mg of Dexamethasone every 2 days), during a 28-day period in marmosets (Callithrix jacchus) produced modifications in the evolution of the experimental periodontal traumatism. The observed changes were osteoporosis and reduction of the periodontal fibers in quantity as well as a reduction of repair process, when compared to the control group that only received the action of the trauma from occlusion.

Lateral displacement of the mandible in Rhesus monkeys

Lateral displacement of the mandible was induced experimentally in five adult male Rhesus monkeys. Following from 2 1/2 weeks to 19 months, the animals were sacrificed and examined histologically. Two of the monkeys received H3 proline 4 months prior to sacrifice and radioautographs were prepared. The lateral displacement apparently caused great discomfort because the monkeys refused to eat and lost weight rapidly for a few months. After about 12 months, the monkeys could again eat their normal diet to the extent they started to gain weight slowly. The histological and radio-autographic findings indicated almost no changes of the articular surfaces of the temporomandibular joints. However, extensive reorganization of the neck of the condyles was observed. Severe periodontal trauma and extensive movements of the teeth occurred in spite of the fact that the teeth in each jaw were splinted firmly together.

Periodontal changes in distant teeth due to trauma from occlusion

The present investigation studies the changes that occur in periodontal supporting tissues of lower canine and premolar of marmosets (Callithrix jacchus), due to experimental modification of occlusal relationships in the region of the molar. For our purposes an extracoronal arch wire of 0.7 mm diameter was fixed into occlusal perforations of the upper third premolar and first molar, on both sides. Eight male marmosets weighing from 250 to 350 grams were used. After each experimental time interval of 7, 14, 21 and 28 days two animals were sacrificed. The results clearly showed areas of tension with stretch periodontal fibers in the distal region of the canine and areas of pressue with osseous and redicular resorption in the mesial region of the first premolar. The tissue changes may be considered to result from transmission of abnormal forces through the proximal contacts of teeth associated with displacements and minor modifications in their occlusal relationships. Similar changes may occur in a tooth distant from the teeth exposed to primary excessive occlusal forces.