ABSTRACT
PURPOSE: To assess the histologic response of the periodontium, cementum, and pulp after intentional root injury with titanium screws. MATERIALS AND METHODS: Three female beagle dogs were used, and a total of 60 self-drilling/self-tapping miniscrews were manually inserted into the maxilla and the mandible with the intention of placement in close proximity or in direct contact with the roots. Digital radiographs were taken to select the sites with root injuries. After a 3-month period, the animals were killed and serial nondecalcified histologic sections were obtained with the miniscrew in place. RESULTS: Sixteen sites with significant root injury were identified. Four sites presented with cementum abrasion, 7 sites had dentin penetration up to 50% of the diameter of the screw, and 5 sites had miniscrew penetration into the pulp space with root fragmentation. At all damaged sites, continuous cementum repair could be observed. There was no evidence of external resorption or pulpal necrosis and/or inflammatory infiltrate. Point ankylosis was seen only in cases of severe injury with root fragmentation. Finally, woven bone was present along the miniscrew threads. CONCLUSION: When titanium screws penetrate root cementum or dentin, pulpal necrosis and/or inflammation was not observed at 12 weeks in an animal model. Cementum regenerates at every injury site, but ankylosis can occur with root fragmentation. Woven bone is present at the screw-bone interface even with root contact suggesting osteointegration.
Subject(s)
Bone Screws/adverse effects , Orthodontic Anchorage Procedures/adverse effects , Periodontium/injuries , Tooth Ankylosis/etiology , Tooth Injuries/etiology , Tooth Root/injuries , Alveolar Process/injuries , Alveolar Process/pathology , Alveolar Process/physiology , Animals , Dental Cementum/injuries , Dental Cementum/pathology , Dental Cementum/physiology , Dental Implantation, Endosseous/adverse effects , Dental Implantation, Endosseous/instrumentation , Dental Pulp/injuries , Dental Pulp/pathology , Dental Pulp/physiology , Dogs , Female , Mandible , Maxilla , Orthodontic Anchorage Procedures/instrumentation , Osseointegration/physiology , Periodontal Ligament/injuries , Periodontal Ligament/pathology , Periodontal Ligament/physiology , Periodontium/pathology , Periodontium/physiology , Titanium , Tooth Ankylosis/pathology , Tooth Injuries/pathology , Tooth Root/pathology , Tooth Root/physiologyABSTRACT
INTRODUCTION: The purpose of this study was to evaluate the effects on the pulp and supporting tissues when miniscrews severely abrade the root surface. METHODS: Sixty self-drilling and self-tapping miniscrews were placed between the premolars and molars of 3 beagles (20 miniscrews per dog). The miniscrews were placed according to the protocol suggested by the manufacturer, but with the intention of inflicting root damage. Radiographs were taken of all 60 interdental alveolar sites, 5 in each quadrant, and sites that evidenced root proximity were identified. The animals were killed at 12 weeks, and 20 of the most probable injury sites were selected for histologic analysis. Serial nondecalcified sections and microcomputed tomography scans were obtained with the implants in place. RESULTS: There was no histologic evidence of inflammatory response either at the root surface or in the pulp. Pulp necrosis, external resorption, and ankylosis were not found, but reparative cementum was seen at each injury site. The presence of woven bone along miniscrew threads lends evidence to support the osseointegration of miniscrews. CONCLUSIONS: Permanent damage to the pulp and supporting tissues is not a regular occurrence when miniscrews abrade or even enter the root surface.