Abstract
This report demonstrates the clinical use of a modified, truly anatomic, root-analogue zirconia implant for immediate replacement of a two-rooted, left first mandibular molar. A 50-year-old female patient with chronic apical periodontitis of the left mandibulary first molar was referred and the tooth was extracted. The mesial root had to be removed surgically due to a root fracture. A truly anatomical, root identical, roughened zirconia implant modified by macro-retentions was manufactured and placed into the extraction socket by tapping 7 days later. After 4 months a composite crown was cemented in place. No complications occurred during the healing period. A good functional and aesthetic result was achieved with minimal bone resorption and soft tissue recession at 30 months follow-up. This report describes the successful clinical use of an immediate, single stage, truly anatomical root-analogue zirconia implant for replacement of a two-rooted tooth. Significant modifications such as macro-retentions yielded primary stability and excellent osseointegration. This novel approach is minimally invasive, respects the underlying anatomy, aids socket prevention, is time- and cost-saving with good patient acceptance as there is no need for bone drilling, sinus lift, bone augmentation or other traumatic procedures.
Replacement of lost teeth using oral implants is an accepted treatment modality with well-documented, long-term success rates of 90–100% at 10-year follow-up. The time between extraction and implant placement varies from a few days (immediate) to several months (late). The main advantages of immediate implant placement are the decrease in treatment time and the reduction in the number of surgical interventions leading to improved quality of life for the patient and overall cost reduction. Irreversible alveolar bone resorption and soft tissue regression are avoided or significantly reduced, owing to early, albeit limited, functional load.
Over the past 40 years, screw- or cylinder-type implants have been used in most instances with no changes of the principle and only slight changes in design. The problem associated with immediate placement of these conventional implants is their incongruence with the extraction socket, necessitating the use of a barrier membrane and/or bone augmentation to prevent down growth of connective tissue or epithelium in between the implant and the socket.
The problem of incongruency was tackled by the use of custom-made root-analogue implants. The root was adapted to the extraction socket resulting in reduced bone and soft tissue trauma. At insertion and 1 month follow-up, a 100% primary stability rate was reported, but the failure rate was almost 100% at 1 year follow-up.
The authors selected root identical implants with significant modifications. These included the use of zirconia for its excellent biocompatibility, diminished plaque accumulation, improved aesthetic results (by preventing dark discoloration of the gum and display of titanium roots in case of gum recession), it has high compressive strength and bending forces, fracture toughness and high electrical resistance. The root surface was modified in two ways, by adding micro-retentions to the entire root surface and limiting macro-retentions to the interdental space. The implant diameter was reduced next to the thin cortical bone to avoid fracture and pressure-induced bone loss. A single stage implantation was used, resulting in immediate, albeit reduced, functional loading via the crown stump for prevention of bone resorption.
Case report
A 50-year-old woman with chronic apical periodontitis of the first mandibulary left molar was referred. The tooth had been treated previously for extensive caries ( Fig. 1 ). After informed consent was obtained the tooth was carefully extracted under local anaesthesia (Ultracain DS Forte, Aventis; Fig. 2 ). Owing to a fracture, the mesial root had to be removed surgically through a vestibular bone window keeping the alveolar border completely intact ( Fig. 2 b). The extraction socket and the area of the apical periodontitis were cleaned by curettage and an iodoform-soaked cotton gauze was placed in the fresh socket. The extraction socket and the vestibular window were closed by sutures ( Fig. 2 c). The extracted tooth was glued together with the fractured mesial root ( Fig. 3 a) . Macro-retentions, designed according to the study protocol, were strictly limited to the interdental space. On top of the root a stump was created for later connection to the crown. The modified root was laser scanned and a replica was then milled from a medical-grade zirconia block, the surface roughened by sandblasting and sintered for 8 h ( Fig. 3 b and c). The implant was cleaned in an ultrasonic bath containing 96% ethanol for 10 min, packaged and steam sterilized. On day 7 the sutures and the iodoform cotton gauze were removed, the alveolar socket was again curetted and flushed with sterile physiological saline solution. The custom-made individualized implant was placed into the socket under finger pressure and subsequent gentle tapping with a hammer and a mallet. Primary stability was achieved as checked by palpation and percussion. The patient was instructed to chew predominantly on the contralateral side and avoid hard food on the implant side for 8 weeks.
At the control visits, 3 and 10 days post-implantation, no postoperative pain, swelling, or bruising was reported ( Fig. 3 d). Over the entire follow-up period a clinically healthy marginal area was present with no bleeding on probing or wound infection. Owing to the surgical intervention during tooth extraction for the removal of the fractured root it was decided to wait for 4 months before the definitive prosthetic restoration was performed ( Fig. 3 e). At 24 months follow-up, the patient presented with a stable implant, unchanged peri-implant marginal bone level and complete apical peri-implant ossification with no signs of peri-implantitis as monitored by radiographs and soft tissue parameters and no bleeding on probing ( Fig. 4 ).
