The Use of Light/Chemically Hardened Polymethylmethacrylate, Polyhydroxyethylmethacrylate, and Calcium Hydroxide Graft Material in Combination With Polyanhydride Around Implants in Minipigs: Part I: Immediate Stability and Function

Abstract

Background The present study is designed as a proof-of-concept study to evaluate light/chemical hardening technology and a newly formulated polymethylmethacrylate, polyhydroxyethylmethacrylate, and calcium hydroxide (PPCH) plus polyanhydride (PA) (PPCH-PA) composite graft material as a bone substitute compared to positive and negative controls in a minipig model. Methods PPCH-PA (composite graft); PPCH alone (positive control), PA alone (positive control), and no graft (negative control) were compared. Four mandibular premolar teeth per quadrant were extracted; a total of 48 implants were placed into sockets in three minipigs. Abutments were placed protruding into the oral cavity 4 mm in height for immediate loading. Crestal areas and intrabony spaces were filled with PPCH-PA, PPCH, or PA using a three-phase delivery system in which all graft materials were hardened by a light cure. In the negative control group, implant sites were left untreated. At 12 weeks, block sections containing implants were obtained. Evaluations included periodontal probing, pullout-force load, and stability measurements to determine implant stability, radiographs to examine bone levels, and scanning electron microscopy (SEM)–energy-dispersed spectroscopy to determine bone-to-implant contact. Results Probing measurements did not reveal any pathologic pocket formation or bone loss. Radiographs revealed that immediate implant placement and loading resulted in bone at or slightly apical to the first thread of the implant in all groups at 12 weeks. Stability test values showed a relative clinical stability for all implants (range: −7 to +1); however, implants augmented with PPCH-PA exhibited a statistically significantly greater stability compared to all other groups (P <0.05). The newly formed bone in PPCH-PA–treated sites was well organized with less marrow spaces and well-distributed osteocytes. SEM revealed a tighter implant–socket interface in the PPCH-PA group compared to other groups with reduced microfissures and implant–bone interface fractures during pullout testing, whereas implants treated with PA or no graft showed ≈10-μm microfissures between the implant and bone with fractures of the intrathread bone. Conclusions The newly formulated chemically hardened graft material PPCH-PA was useful in immediate implant placement after tooth extraction and resulted in greater stability and a well-organized implant–bone interface with immediate loading, especially in those areas where cancellous bone was present. The results of this proof-of-concept study warranted further research investigating different healing times and longer durations.

The Use of Light/Chemically Hardened Polymethylmethacrylate, Polyhydroxylethylmethacrylate, and Calcium Hydroxide Graft Material in Combination With Polyanhydride Around Implants and Extraction Sockets in Minipigs: Part II: Histologic and Micro‐CT Evaluations

“…The results of this present study confirm the previous report 23 by showing that the newly formulated light/chemically hardened graft material PPCH+PA was beneficial in immediate implant placement after tooth extraction and resulted in greater BIC and histologic bone formation in quality and quantity during 3 months. In addition, the PPCH+PA resulted in crestal bone augmentation over extraction sockets, preventing the soft‐tissue migration, and acted within the same context as socket preservation.…”

“…Results of the clinical and radiologic evaluations were reported in Part I of this study 23 . All sites treated with implants with or without augmentation materials healed without major complications.…”

“…Surgical and postoperative procedures were described previously 23 and are summarized in Figure 1. Briefly, parallel‐wall, screw‐type, 3.25‐mm‐diameter, 11.5‐ or 13‐mm‐long titanium implants §§ were placed after atraumatic extractions of four premolar and first molar teeth in each quadrant using the surgical drill system ‖‖ under general anesthesia.…”

“…Clinical outcome, stability, and function by visual inspection, periodontal probing of peri‐implant sulcus, radiology, pull‐out force test, and mobility were evaluated and reported in Part I of this study 23 . Soft‐tissue evaluations showed no adverse reaction, abscess, or impaired wound healing at all sites, including implants and sockets 23 . Assessments described below were made at 12 weeks on bone sections both around implants and from the sockets.…”

“…Assessments described below were made at 12 weeks on bone sections both around implants and from the sockets. The radiographs were taken with a digital x‐ray ## before histology and evaluated by counting the implant threads covered by the crestal bone (reported previously 23 …”