title: Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep.
abstract: OBJECTIVE
  The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time.
  
  
  METHODS
  In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group).
  
  
  RESULTS
  Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5).
  
  
  CONCLUSIONS
  Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found.
authors.affiliation: Musculoskeletal Research Unit, Equine Hospital, Vetsuisse Faculty ZH, University of Zurich, Zurich, Switzerland; Center of Applied Biotechnology and Molecular Medicine (CABMM), Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Stübinger
authors.forename: Jasmin
authors.initials: J
authors.lastname: Waser
authors.forename: Thomas
authors.initials: T
authors.lastname: Hefti
authors.forename: Anika
authors.initials: A
authors.lastname: Drechsler
authors.forename: Michéle
authors.initials: M
authors.lastname: Sidler
authors.forename: Karina
authors.initials: K
authors.lastname: Klein
authors.forename: Brigitte
authors.initials: B
authors.lastname: von Rechenberg
authors.forename: Falko
authors.initials: F
authors.lastname: Schlottig
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis; D008422:Materials Testing; D011091:Polyesters; D012756:Sheep; D014025:Titanium
chemical_list: D015921:Dental Implants; D011091:Polyesters; C009495:titanium dioxide; C033616:poly(lactide); D014025:Titanium
keywords: bone welding; dental implants; insertion torque; osseointegration; primary stability; removal torque test; resonance frequency; sheep