Three interfaces of the dental implant system and their clinical effects on hard and soft tissues.

Anatomically, the human tooth has structures both embedded within and forming part of the exterior surface of the human body. When a tooth is lost, it is often replaced by a dental implant, to facilitate the chewing of food and for esthetic purposes. For successful substitution of the lost tooth, hard tissue should be integrated into the implant surface. The microtopography and chemistry of the implant surface have been explored with the aim of enhancing osseointegration. Additionally, clinical implant success is dependent on ensuring that a barrier, comprising strong gingival attachment to an abutment, does not allow the infiltration of oral bacteria into the bone-integrated surface. Epithelial and connective tissue cells respond to the abutment surface, depending on its surface characteristics and the materials from which it is made. In particular, the biomechanics of the implant-abutment connection structure (i.e., the biomechanics of the interface between implant and abutment surfaces, and the screw mechanics of the implant-abutment assembly) are critical for both the soft tissue seal and hard tissue integration. Herein, we discuss the clinical importance of these three interfaces: bone-implant, gingiva-abutment, and implant-abutment.

Influence of Connections and Surfaces of Dental Implants on Marginal Bone Loss: A Retrospective Study Over 7 to 19 Years.

PURPOSE: This retrospective study compared the long-term outcomes of dental implants according to type of connection and surface. MATERIALS AND METHODS: Multiunit restorations were classified as follows: an external connection with a turned surface, an external connection with an anodized surface, or an internal connection with a fluoride-modified surface. Patients who were followed up for longer than 7 years after implant loading were included in the study. Cumulative implant survival rates and the amounts of marginal bone loss were calculated by reviewing dental records and radiographs. Only implants that survived until the last follow-up visit were included in the analysis of marginal bone loss. Statistical analyses were performed to detect between-group differences at the significance level of .05. RESULTS: Sixty-nine patients with 261 bone-level implants were included. The average follow-up duration was 15.2 years in the external turned group, 10.6 years in the external anodized group, and 9.9 years in the internal fluoride-modified group. There was no significant between-group difference in the cumulative survival rate (P = .439) despite eight implant failures (six in the external turned group and two in the internal fluoride-modified group). The mean (SD) marginal bone loss values at the last follow-up were 0.47 mm (0.67), 0.87 mm (1.07), and 0.23 mm (0.58) in the external turned, external anodized, and internal fluoride-modified groups, respectively. After adjusting for follow-up duration, there was significantly less marginal bone loss in the external turned group than in the external anodized group (P < .001) and in the internal fluoride-modified group than in the external anodized group (P < .001). No significant difference in marginal bone loss was found between the external turned and internal fluoride-modified groups (P = .44). CONCLUSION: The implant-abutment connection structure is an important contributor to the maintenance of the level of marginal bone surrounding the implant. Implant surface characteristics are another contributor to marginal bone resorption.

Biological Responses to the Transitional Area of Dental Implants: Material- and Structure-Dependent Responses of Peri-Implant Tissue to Abutments.

The stability of peri-implant tissue is essential for the long-term success of dental implants. Although various types of implant connections are used, little is known about the effects of the physical mechanisms of dental implants on the stability of peri-implant tissue. This review summarizes the relevant literature to establish guidelines regarding the effects of connection type between abutments and implants in soft and hard tissues. Soft tissue seals can affect soft tissue around implants. In external connections, micromobility between the abutment and the hex component of the implant, resulting from machining tolerance, can destroy the soft tissue seal, potentially leading to microbial invasion. Internal friction connection implants induce strain on the surrounding bone via implant wall expansion that translates into masticatory force. This strain is advantageous because it increases the amount and quality of peri-implant bone. The comparison of internal and external connections, the two most commonly used connection types, reveals that internal friction has a positive influence on both soft and hard tissues.