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Missing anterior teeth

How to deal with missing anterior teeth. Take stock of the situation

28.01.2019
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Dental implant therapy is considered a safe and predictable treatment to replace missing teeth. Nonetheless, implant rehabilitation in the anterior maxilla is still a challenge because of esthetic concerns.

Prof. Lin Ye | China, Dr. Jiang Xi | China

High predictability and low risk of complication with optimal esthetic outcome is the primary objective for implant therapy in the esthetic zone.1 To achieve this goal, an understanding of biology, clinical principles and technique is fundamental. 

Evaluation of esthetics

Objective methods for qualitatively assessing implant esthetics are crucial for evaluating outcomes, recording clinical data, comparing different studies and associated follow-up periods, and, last but not least, training and education. Three indices have been developed (Fig. 1):

  1. The Pink Esthetic Score (PES), which involves only the peri-implant soft tissue.2
  2. The modified PES to comprehensively assess the esthetic outcome of implant reconstruction of both soft tissue and restoration,3
  3. The White Esthetic Score (WES), which specifically focuses on the clinical crown supported by implant.3

The esthetic indices have been developed mainly on the basis of clinical results, without involving the patient’s opinions. Nevertheless, the concept of oral health care should integrate the patient’s needs with the professional’s point of view, and, therefore, it is important to consider both subjective and objective esthetic outcomes.

Key to success: Correct 3-dimensional position of the implant

From both the biological and technical point of view, the 3-dimensional implant positioning, and especially the implant shoulder, is one of the most important factors influencing the final esthetic result. Successful 3-dimensional positioning needs to be performed in relation to the following measures:

  • Mesio-distal,
  • Apico-coronal, and
  • Orofacial.

According to Buser et al., to obtain an optimal esthetic result the implant shoulder should be placed within the “comfort zones,” without invading the “danger zones,”4 which are defined mesio-distally, orofacially, and apico-coronally. (Fig. 2)

In the orofacial dimension, implant placement is particularly crucial, and improper application of this principle often leads to detrimental esthetic results (e.g., gingival recession and esthetics problems). Therefore, the orofacial positioning guidelines should always be followed whether dealing with a healed ridge or extraction socket. In healed sites, physiological ridge remodeling after tooth loss is characterized by more pronounced bone resorption on the buccal rather than the palatal aspect, resulting in a ridge with adequate bone height only at the palatal side of the implant. Hence, the implant should always be “palatally” placed in the anterior maxilla. However, in case of immediate implants, the extraction socket can be deceptive. Orofacial implant placement in the middle of the extraction socket often intrudes into the facial boundary. Following the rule of correct orofacial dimension, the implant position should be at the palatal wall of the extraction socket. (Fig. 3)

Timing of implant placement

The timing of implant placement is clinically relevant for treatment duration, surgical strategy, esthetics and patient perception. In 2004 a consensus statement classified the timing of implant placement into four categories. (Table 1)

With the evolution of our understanding of socket healing biology, the indication of the four types of implant timing needs to be updated, especially for type 1. Indeed, the concept of immediate implant placement developed in 1978 has been a controversial topic for more than 30 years, especially in the esthetic zone.  

The immediate implant placement involves two biological processes: (1) the healing/ remodeling of the extraction socket, and (2) the osseointegration of the implant. Clinical studies with large cohorts and long-term follow-up have demonstrated that the survival rate of immediate implants is comparable to implants placed in the healed ridge.5 A recent animal study revealed no differences in the establishment of bone-implant interface at the cellular level when comparing immediate and delayed implant placement.6 Therefore, we can conclude that the microenvironment of an extraction socket does not jeopardize the osseointegration of dental implants. Meanwhile, both animal and clinical studies have proved that placing a titanium implant into the socket does not alter the features and processes of socket remodeling.7,8 Therefore, the two biological processes are independent of one another, and they both influence the basic principle of immediate implant placement. 

To obtain favorable esthetic outcomes with long-term stability, immediate implants in the esthetic zone should include consideration of the following:  

Implant position. The implant neck should not protrude through the future buccal bone plate after bone remodeling. 

Augmentation/ preservation of the ridge profile. According to previous studies, spontaneous socket healing results in the loss of 50% of ridge width. Therefore, the residual bone may not be able to surround the implant circumferentially or maintain enough facial bone thickness. The most commonly used and evidence-based strategy for ridge preservation is intra socket grafting, which preserves 80% of ridge width. With immediate implant placement, the gap between the buccal bone and the implant surface should be filled with a low-substitution rate grafting material (DBBM) to compensate/ counteract socket remodeling, leading to higher bone formation at the buccal-coronal region.9,10 

Immediate provisionalization. Due to the resorption of bundle bone, extraction sockets tend to lose buccal bone within a month, jeopardizing bone volume stability. Pressure from the labial soft tissue can cause gingival collapse into the gap and compromise new bone formation. Therefore, besides the grafting material, a rigid socket sealing system (e.g., an implant-supported temporary crown) supporting the buccal soft tissue can provide additional volume stability.11  Clinical studies have revealed that immediate implant placement combined with immediate provisionalization (IIPP) insures better clinical outcomes than immediate implant placement alone.12  

IIPP using flapless technique. A gingival flap is usually raised to facilitate GBR and to achieve better new bone formation buccally. However, cost-effectiveness must be taken into consideration. Besides disturbing the natural gingival form, bone resorption and post-surgery discomfort can also be drawbacks. Current clinical evidence suggests that a reasonable thickness of buccal bone and predictable soft tissue levels over the long-term can be obtained by using intra socket grafting combined with implant supported provisional crowns. (Fig. 4)

The indication for immediate implant placement is controversial. Previous studies suggest immediate implant placement in the esthetic zone only with a thick buccal bone wall phenotype (> 1 mm) and a thick gingival biotype.1 These conclusions were reached by studying CBCT results, which indicated that thin bone phenotypes, exhibiting a facial bone wall thickness of 1 mm or less, produced progressive bone resorption with a vertical loss of 7.5 mm; whereas thick bone phenotypes produced only minor bone resorption with a vertical loss of 1.1 mm.13 The results of these studies are in agreement with our work.14 However, the deduction that immediate implant placement may not be considered with thin phenotypes is not always appropriate. Indeed, even if arresting the resorption of thin buccal bone, which is mostly comprised of bundle bone, is not achievable, by using appropriate methods we can regenerate new bone between the buccal bone and the implant surface. Regeneration potential is the key to success for immediate implants.  

Summary

  1. Implant esthetics should be evaluated both objectively (professionally) and subjectively (through patient opinions).
  2. Correct 3-dimensional implant positions (mesio-distal, apico-coronal and orofacial) are key to successful esthetics.
  3. Hard tissue augmentation is often needed in the esthetic zone. Different clinical situations require different reconstruction methods. Soft tissue management is used to guarantee long-term results and enhance esthetics.
  4. Timing of implant placement is a decision-making process relevant for esthetics. IIPP is an evidence-based technique that provides better esthetic results and patient satisfaction.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Prof. Lin Ye

Prof. Lin Ye | China

Peking University School and Hospital of Stomatology

Department of Oral Implantology

Beijing

Dr. Jiang Xi

Dr. Jiang Xi | China

Peking University School and Hospital of Stomatology

Department of Oral Implantology

Beijing

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