Avinoam Yaffe

Skeletal and functional effects of treatment for unilateral posterior crossbite

Unilateral posterior crossbite (UPXB) is a common malocclusion, frequently presenting a lower midline deviation, accompanied by Class II subdivision relationships in final closure and a very high prevalence of the reverse sequencing (RS) pattern of jaw movement. These features often persist even after the elimination of the crossbite. The purpose of the present study was to examine in detail the morphologic, skeletal, and functional effects of the treatment for this malocclusion category. The experimental group consisted of 24 children in the mixed dentition stage with UPXB who were treated with removable expansion plates and a control group of 10 age-matched children with normal occlusion. Longitudinal follow-up revealed a stable dental maxillary arch expansion of at least 1.5 mm but a complete elimination of crossbite in only 50% of the cases. The frequent persistence of Class II subdivision relations and lower midline deviation that were not due to functional mandibular shift was striking. The pretreatment posteroanterior (P-A) cephalograms indicated reduced facial and maxillary widths. After treatment, the achieved maxillary width increase was greater than expected with normal growth. Longitudinal assessment of the mandibular movement response revealed by the electrognathograph showed a high prevalence of RS, which was reduced after treatment. In conclusion, (1) a higher than expected prevalence of skeletal transverse aberrations at the maxillary and zygomatic levels were found in the UPXB group; (2) the removable expansion appliance induces transverse growth of the maxilla; and (3) an inherent pattern of jaw movement is characteristic to the UPXB and does not change significantly with orthodontic treatment.

The functional range of tooth contact in lateral gliding movements

The dynamic contact pattern of teeth in lateral glide movement was recorded in 72 individuals, 19 to 35 years of age, with normal tooth alignment and Angle class I molar and canine relationship. The lateral glide movement was divided into three stages to simulate the total range of events in lateral glide movement naturally demonstrated by the patient. This study has shown that lateral glide movement is a complex movement in which the nature of tooth contact is altering in location, direction, and number of teeth participating. Consequently the restoration of an occlusion in accordance with a given concept does not always apply to all patients.

Re-attachment of periodontal ligament by collagen in experimentally-induced alveolar bone dehiscence in dogs.

Fifty-four bone dehiscences were made in nine dogs by reflecting mucoperiosteal flaps on the labial aspect of lower and upper incisors and premolars and removing alveolar bone. One half of the dehiscences were treated with native enriched collagen solution (ECS) prepared from acid-soluble dog-skin collagen. Six weeks later, histologic sections were prepared from both the ECS-treated and untreated control sites. Re-attachment was promoted by the ECS preparation; there was arrest of epithelial migration apically and formation of new bone and cementum, as well as proliferation of fibrous connective tissue that became attached to the newly-formed cementum. This effect could be due to an influence of ECS on the chemotaxis of connective-tissue cells and to an anti-migratory (barrier) effect on gingival epithelium.

Fiberotomy enhances orthodontic tooth movement and diminishes relapse in a rat model

OBJECTIVES Accelerated orthodontic tooth movement is triggered by procedures that include mucoperiosteum flap surgery and surgical scarring of cortical bone. Our aim was to test whether fiberotomy by itself will accelerate orthodontic tooth movement and diminish relapse. MATERIALS AND METHODS In 34 Wistar rats, alveolar bone resorption and molar tooth movement were measured after fiberotomy, apical full-thickness flap without detachment of gingiva from the roots, or no surgery. Orthodontic appliance was installed at time of surgery and activated for 14 days, generating movement of the first maxillary molar buccal and then removed. RESULTS Percent of sections in which alveolar bone resorption was detected was significantly higher (p < 0.05) after fiberotomy (27%) in comparison with apical flap surgery (12%) or no surgery (6%), after 30 days. Also, at the end of active phase, the molar moved significantly faster (p < 0.01) and twice the distance after fiberotomy (0.54 ± 0.33) in comparison with apical surgery (0.26 ± 0.12) or no surgery (0.3 ± 0.09). Sixteen days after the appliance was removed, only 12% relapse was recorded in the fiberotomy group, while almost total relapse in other two groups. CONCLUSION We conclude that fiberotomy solely accelerated orthodontic tooth movement and diminished relapse.

Splinting: A retrospective 17-year follow-up study

A retrospective 17-year, longitudinal study monitoring 66 patients with fixed partial denture and removable partial denture restorations revealed that perceptive splinting was beneficial and enhanced the longevity of the restoration. The study discussed the advantages and disadvantages of splinting, the survival rate of splints and splinted teeth, and the importance of oral hygiene and a periodic maintenance program.

Commentary on: periodontally accelerated osteogenic orthodontics (PAOO) - a clinical dilemma.

It is apparent that tooth movement is enhanced by procedures that elevate the remodeling of alveolar bone, and of periodontal and gingival fibrous tissues. The periodontally accelerated osteogenic orthodontics (PAOO) also termed as Wilckodontics, involves full-thickness labial and lingual alveolar flaps accompanied with limited selective labial and lingual surgical scarring of cortical bone (corticotomy). Most of the authors suggest that the RAP is the major stimulus for alveolar bone remodeling, enabling the PAOO. However, we propose that detachment of the bulk of dentogingival and interdental fibers from coronal part of root surfaces by itself should suffice to stimulate alveolar bone resorption mainly on its PDL surfaces, leading to widening of the periodontal ligament space which largely attributes to accelerated osteogenic orthodontics. Moreover this limited fiberotomy also disrupts transiently the positional physical memory of dentition (PPMD), allowing accelerated tooth movement. During retention period, a new biological and physical connectivity is generated that could be termed as new positional memory of the dental arch.

Influence of bone-derived matrices on generation of bone in an ectopic rat model

Most bone regeneration experimental models that test bone‐derived matrices take place in conjunction with the native bone. Here, we compared the relative effectiveness of bone matrix components on bone‐marrow‐directed osteogenesis in an ectopic model. Cortical bone cylinders consisted of diaphysis of DA rat femurs. They were either demineralized (DBM), deproteinized (HABM), or nontreated (MBM). Fresh bone marrow was placed into cylinders and implanted at subcutaneous thoracic sites of 2‐month‐old DA rats. At designated times the cylinders were surgically removed from the animals. Microradiographs of DBM and histology of DBM and MBM cylinders demonstrated progressive increase in mineralized bone volume and its trabecular configuration. Bone filled the inner volume of DBM and MBM cylinders within 4 weeks, while in HABM cylinders mostly granulation tissue developed. In the DBM cylinders cartilage deposited within 10 days, while in the MBM cylinders bone was directly deposited. As early as day 3 after marrow transplantation, marrow cells interacting with DBM increased significantly the genes that express the cartilage and the bone phenotype. In conclusion, organic components of bone are needed for marrow‐directed osteogenesis.

Various methods in achieving anterior guidance

The anterior teeth are essential for esthetics, phoentics, and mastication and are equally involved in protecting posterior teeth. A 10-year longitudinal study of treatment modalities was conducted for overbite-overjet occlusal relationships. Comprehensive treatment combining orthodontics, occlusal adjustment, and selective restorations minimized the need for extensive restorative dentistry. The treatment of selected patients with a 10-year postoperative evaluation was discussed.

One-year follow up for the use of collagen for biological anchoring of acrylic dental roots in the dog

Second premolars in both upper and lower jaws of 6 dogs were extracted and acrylic resin replicas were made of the roots. Horizontal channels were drilled across the root replica perpendicular to the long axis. Before implantation, the prepared root replicas were immersed in a solution of native collagen. One year after implantation, proliferation of connective tissue and newly-formed viable bone were observed within the channel as well as surrounding the treated implants. All control implants without collagen treatment were rejected leaving chronically inflamed implantation sites.

Cytoskeletal disease: a role in the etiology of adult periodontitis

All cells and organisms across the evolutionary spectrum, from the most primitive to the most complex, are mechanosensitive. As the cytoskeleton is a key in controlling the normal basal prestress of cells and therefore is involved in virtually all physiological cellular processes, abnormalities in this essential cellular characteristic may result in diseases. Indeed, many diseases have now been associated with abnormalities in cytoskeletal and nucleoskeletal proteins. We propose that adult periodontitis is, at least in part, such a cytoskeletal disease. It is well established that adult periodontitis starts by bacterial invasion at the interface between the tooth surface and marginal gingiva that induces a local inflammatory response. The inflammatory cells release metalloproteinases which degrade gingival collagenous fibrous tissue and loss of local tissue integrity that reduces the normal prestressed cell-extracellular matrix network. This is a major signaling trigger that induces a local and rapid release of ATP, which then activates P2X receptors and stimulates a calcium influx, further activating osteoclastic resorption of the alveolar bone. As periodontitis is a chronic disease, it seems reasonable to suggest that agents that maintain cytoskeletal tensegrity, for example, inhibitors of ATP receptors, may diminish the bone loss and may have a role in future periodontal therapy.