Prospective randomized clinical trial evaluating the effects of two different implant collar designs on peri-implant healing and functional osseointegration after 25 years.

OBJECTIVES: Evaluate the effects of two different machined-collar lengths and designs on peri-implant healing. MATERIAL AND METHODS: An implant with a microtextured surface and 3.6mm-long internal-connection machined collar was compared to two implants that had an identical 1.2mm-long external-connection machined collar, but one had the microtextured surface while the other's was machined. Participants received the three implants, with microgap at the crest, alternately at five sites between mental foramen, and a full-arch prosthesis. Peri-implant bone levels were measured after 23 to 26 years of function. Keratinized tissue height, plaque, probing depth, bleeding, and purulence were also evaluated. Descriptive and mixed models for repeated\measures analyses were used, with Bonferroni correction for pairwise comparisons. RESULTS: Twenty-two participants (110 implants) were evaluated at the 25-year examination. Microtextured implants with the longer machined collar had significantly greater mean marginal bone loss (-1.77mm ± 0.18, mean ± SE) than machined (-0.85mm ± 0.18, p < .001) and microtextured (-1.00 ± 0.18mm, p < .001) implants with the shorter machined collar. Keratinized tissue height was greater for internal-connection (0.74mm ± 0.10) versus external-connection (0.51 ± 0.08, p =  0.01) microtextured implants. No differences were observed for plaque (p = 0.78), probing depth (p = 0.42), bleeding (p  = 0.07), and purulence (p = 1.00). Implant survival rate was 99%. CONCLUSIONS: Implants with the 1.2mm machined collar limited bone loss to 1mm, while those with the longer machined collar showed > 1.5mm loss after 25 years of function with microgap at the crest. Internal-connection design and fixture surface microtexturing did not result in greater bone preservation. ClinicalTrials.gov Identifier: NCT03862482.

Axolotl as a Model to Study Scarless Wound Healing in Vertebrates: Role of the Transforming Growth Factor Beta Signaling Pathway.

SIGNIFICANCE: The skin is our largest organ, with the primary role of protection against assaults from the outside world. It also suffers frequent damage, from minor scrapes to, more rarely, complete destruction such as in third-degree burns. It is therefore, by its nature, an organ that would benefit tremendously from being able to regenerate itself. RECENT ADVANCES: This review highlights the axolotl, a less well-known model organism capable of scarless wound healing and regeneration. Axolotls are salamanders with unsurpassed healing and regenerative capacities. Understanding how these animals can regenerate their tissues could help identify the pathways that need to be activated or inhibited in humans to improve wound healing. CRITICAL ISSUES: Presently, there are no therapies leading to skin regeneration or scarless wound healing. Various animal models have thus been developed for use in research, such as mice and pigs, to help us understand how wound healing could be improved or stimulated. However, these more common models cannot regenerate and, consequently, cannot direct us toward a solution to regenerate damaged tissues. Axolotls, on the other hand, can regenerate perfectly and therefore may offer avenues to identify molecular targets for therapeutic intervention. FUTURE DIRECTIONS: Identifying signaling pathways regulating tissue regeneration in vertebrate models is important. The use of animals such as axolotls, which hold the secret of full regeneration, will likely play a significant role in helping us achieve scarless wound healing for humans.

Preservation of posterior mandibular extraction site with allogeneic demineralized, freeze-dried bone matrix and calcium sulphate graft binder before eventual implant placement: a case series.

OBJECTIVE: This case series reports short- and long-term healing, before and after placement of an implant, in posterior mandibular extraction sites grafted with demineralized, freeze-dried bone matrix (DFDBM) allograft mixed with calcium sulphate graft binder. METHODS: Three patients who underwent surgical extraction of a posterior mandibular molar experienced partial loss of the buccal bone plate at the extraction site. Alveolar bone reconstruction with a DFDBM allograft mixed with calcium sulphate graft binder was performed immediately. The graft was covered with a biodegradable regenerative membrane. For each of the 3 patients, the implant and healing abutment were placed after 6, 9 and 12 months, respectively, followed by crown placement 3, 5 and 5 months later, respectively. The implants were periodically re-evaluated, both clinically and radiographically, between 10 and 39 months after final insertion of the crown. An implant stability device was used to evaluate the long-term biological and functional stability of the implants. RESULTS: Upon exposure and implant placement, the grafted alveolar ridge in all patients presented appropriately sized, dense and well-vascularized bone, wide enough to receive the planned wide-platform implant. The long-term interface stability quotient ranged from 87 to 90. CONCLUSIONS: Posterior mandibular extraction sites with compromised buccal alveolar bone may be effectively managed by immediate alveolar augmentation using a mixture of DFDBM allograft and calcium sulphate graft binder. This approach provides ideal alveolar form and consistency for eventual placement of the implant.