Dental Tribune United Kingdom Edition

Fig. 1 Pre-op Fig. 2 Pre-op peri-apical X-ray Fig. 3 Resin-bonded provisional restoration Fig. 4 Lingual view Fig. 5 Twelve weeks post-extraction Fig. 6 Following implant placement Fig. 8 Immediate provisionalisation Fig. 9 Modification of provisional restoration Fig. 10 Eight weeks post-implant placement Fig. 7 Peri-apical X-ray at implant insertion Fig. 11 Friction-fit impression caps Fig. 12 Working cast Fig. 13 Top view Fig. 14 Final prosthesis Fig 9 the mandibular anterior region can be challenging due to: 1Insufficient facio-lingual bone volume 2Insufficient mesio-distal space between adjacent teeth 3Insufficient height of re- maining alveolar bone 4 The presence of mento- labial depression, which limits the facio-lingual angulation of implants 5The preservation or recre- ation of the inter-dental papilla being an extremely delicate procedure One of the prerequisites for the successful placement of an implant is the presence of adequate bone volume. Tarnow et al. stated that a submerged implant, following the delivery of the prosthesis, will create circumferential or horizontal bone resorption of 1.3 to 1.4mm. Grunder et al. also stated that at least 2mm of lateral alveolar bone must be present beyond the body of the implant to compensate for the effects of bone remodelling. If this amount of bone is not present, part or all of the facial or buccal bone plate will be lost after remodelling, with the subsequent risk of soft-tissue recession. This amount of bone around an implant rarely exists in the mandibular anterior re- gion. Therefore, ridge augmen- tation procedures are often re- quired to create adequate bone volume to maintain a 2mm al- veolar thickness following im- plant placement. Another prerequisite for successful implant treatment is sufficient interdental space. The creation of a natural-look- ing implant restoration largely depends on the appropriate placement of the implant dur- ing surgery. In order to achieve this goal, careful planning and precise implant placement are essential. An implant requires a minimum distance of 1.5mm between the implant and ad- jacent tooth to maintain inte- proximal bone and interdental papilla. Standard diameter im- plants of 4mm or greater there- fore require a mesio-distal space of at least 7mm to place an implant. For an interdental papilla between two adjacent implants to be established, the inter-implant distance should be more than 3mm. Thus, a minimum mesio-distal space of 14mm is required to place two standard-diameter implants adjacent to each other. Implant manufacturers have introduced narrow- diameter implants (3.0 to 3.5mm) in an attempt to solve these problems. However, these implants still require a minimum mesio-distal space of 6.0 to 6.5mm to allow adequate implant-to-tooth distance. With the exception of mandibular incisors, narrow-diameter im- plants present a solution for the aforementioned requirements of adequate bucco-lingual bone volume and proper implant spacing. For missing man- dibular incisors, it would be beneficial to use implants with an even smaller diameter than narrow-diameter implants. Mini-diameter implants (MDI) are not synonymous with narrow-diameter implants. MDIs are smaller in diameter than narrow implants and have a diameter of 2.7mm or less. Because of their smaller diam- eters, MDIs require minimal interdental space while pre- serving more of the alveolar bone following the osteotomies for implant placement. MDIs were initially developed to sup- port transitional prostheses and were ultimately intended to be removed. However, these implants exhibited a bone-to- implant contact similar to that of implants with conventional diameters. Numerous studies have in- dicated that MDIs appear to be an effective treatment op- tion for missing mandibular incisors. Nevertheless, one of the primary disadvantages of MDIs is the reduced resistance to occlusal loading. The reten- tion of an implant, however, is correlated to the length of the implant and not the diameter. This implies that MDIs may be used in situations where ex- cessive occlusal loading is not present. MDIs of less than 3 mm in diameter are fundamen- tally challenged as two-piece designs due to the insufficient strength of their component parts. When the diameter of an implant approaches 3mm or less, either the abutment screw becomes too small or the inter- nal axial walls of the implant become too thin to withstand the functioning load. These concerns can be overcome with a one-piece design. One piece implants have recently received substantial attention in implant dentistry; yet, one- piece implants are not new to implant dentistry. While the use of one-piece implants has been controversial, they have been used for decades with reasonable clinical success. Recent variations from early designs have created a renewed interest in this old, but not ob- solete concept. Most one-piece implants are composed of three portions — the bone-anchoring (fixation thread) portion, trans- mucosal portion and prosthetic abutment portion. The primary disadvantage of one-piece implants is related to the fact that these implants must be placed with a one-stage protocol. Therefore, the angu- lation of the abutment cannot be altered and only minimal 23ClinicalSeptember 12-18, 2011United Kingdom Edition page 24DTà Fig 1 Fig 2 Fig 3 Fig 4 Fig 5 Fig 6 Fig 7 Fig 8 ‘Another prerequisite for successful implant treatment is sufficient interdental space’ Fig 10 Fig 11 Fig 12 Fig 13 Fig 14